Concrete, Materials & ConservationSTRUCTURAL FAULTS & REPAIR-2014

15th International Conference9th – 10th July 2014

Edinburgh, ScotlandISBN No: 0-947664-75-10

Editor: Professor M C Forde, PhD, FREng, FRSE, FACI, CEngCarillion Chair, University of Edinburgh

m.forde@ed.ac.uk

Keynote Papers

1190 TOWARDS THE ESTABLISHMENT OF “INFRA-DOCK” FOR CONCRETE STRUCTURES, M Ohtsu, Kumamoto Univ, Japan

Toward the sustainable society, the long service-life of infrastructure is going to be an evolutional target. Aging problems and damages due to natural disasters in concrete structures have updated the urgent demand for continuing maintenance of the structures in service. Because this issue is critical for the sustainable infrastructure, a variety of techniques and evaluation methods for diagnosis and prognosis are under development in concrete engineering. For the purpose of maintenance, these techniques are to be practically applicable to on-site measurement.

With respect to human body, the medical checkup system for prognosis is developed as “a ward for detailed medical checkup, requiring short-term hospitalization” in Japan and is known as “the ningen dock”. In order to extend the service life of the concrete structure, “the infra-dock”, so-called as referring to “the ningen dock”, is in urgent demand to be established. Recent achievements related to this issue are summarized, including updated non-destructive testing (NDT) techniques for maintenance and prognosis, and research activities of technical committees in RILEM and JCI.

K Plemic USE OF NON-DESTRUCTIVE TECHNIQUES INEVALUATION AND REPAIRS OF STRUCTURES

P Plemic, P L. Popovic, & N Rende,Wiss, Janney, Elstner Associates, Inc., Northbrook, Illinois, USA

Non-destructive testing is an essential and effective tool in evaluation and repairs of structures. Different techniques used in several actual projects are reviewed and presented in this paper. Testing methodologies and associated testing techniques for the assessment of structural concrete include reflective ultrasonics (impact-echo (IE), shearwave tomography, through-transmission ultrasonics (ultrasonic

pulse velocity (UPV), and geophysical/electromagnetic methods (ground-penetrating radar (GPR), infrared thermography (IR) and accelerometers (resonant frequency measurements). These techniques can be used to identify and assess a variety of internal conditions, including embedded elements (reinforcing steel, prestressing strand, conduit, cables etc.), as-built conditions, internal flaws or distress, material degradation, support conditions, repair and overlay integrity, and member dimensions. Although this article is not intended to provide a comprehensive list or thorough description of each technique, several techniques are described introduced in the project examples provided below.

Asset Management & Structural Investigation

1197 EXAMINATION & TESTING OF RC STRUCTURE SUBJECTED TO SEVERE FIRE

K Sharobim, Suez Canal Univ, Ismailia, Egypt

Steam turbine generator at a thermal power plant has been exposed to severe fire. The extent of the fire affected the concrete surfaces. As a result, spalling and cracking on the sides and underside of the generator support beams. In addition, vertical and horizontal reinforcing steel are exposed in some areas. The extent of fire affected the steel structure supporting the operating floor. Nondestructive and destructive tests were carried out to check the strength and the integrity of the concrete. These tests includes rebound test according to ASTM C805, ultrasonic test as per ASTM C597, pullout test, core test as per ASTM C42, and petrographic examination as per ASTM C856. In addition, tension test was carried out on three reinforcing steel samples removed from existing reinforcing bars. Structural steel elements including beams and columns and their connections were investigated to define member's distortion such as deflection, wrapping and buckling, damages of bolts and welds, and separation between the steel deck and the beams underneath. Nondestructive tests such as hardness test and liquid (dye) penetration test were carried out on steel elements. In addition, steel sample was cut and tested in tension to determine the mechanical properties of structural steel subjected to fire. After testing and examination, structural analysis was carried out on RC beams, which the most affected parts by the fire and the methods of repair and strengthening were proposed. According to analysis of test results, replacement of two steel tension posts was recommended.

Early Age Testing of Concrete

1167 EARLY AGE TESTING OF SELF-COMPACTING CEMENT PASTE AND CONCRETE FOR STRUCTURAL REPAIR,

G Barluenga, J Puentes, I Palomar, Univ of Alcala,Madrid, Spain

Structural repair requires building materials compatible with the existing materials and able to improve the mechanical performance of the existing structural members and joints. Cement based materials (CBM) with self-compacting ability, as slurries and Self-Compacting concretes (SCC), are good candidates because they can be used both as consolidating materials and as reinforcing layers in thin sections or complex configurations without vibration.Although the hardened performance of self-compacting CBM is similar to conventional CBM, their composition is different. In order to achieve large fluidity, fine-particle mineral additions and water reducing admixtures are commonly used. These components modify the early age microstructural development and, therefore, material hardened and long term performance. As far as most of the microstructural changes take place in CBM during early age, an experimental procedure to monitor early age material characteristics is required in order to identify the key points of the setting process.

An experimental program on SCC at early ages, combining a limestone filler with several active mineral additions (AMA), Metakaolin (MC), microsilica (MS) and nanosilica (NS), was carried out in order to assess the temporal relations among hydration, microstructure changes and drying shrinkage and their influence on early age cracking risks. The relationships between cement reaction and microstructural changes were investigated by monitoring temperature and UPV propagation. The risk of early age cracking due to drying shrinkage was evaluated, monitoring water evaporation, capillary pressure and shrinkage and measuring cracking on double restrained slabs subjected to an air flow of 3 m/s during the first 6 hours. Profiles of the reaction process, the microstructural evolution and the physical effects of water movement and evaporation were obtained. In order to compare the results obtained for different compositions, the early age measured parameters were related to a reaction index (Ir,24), defined as the fraction of heat produced (accumulated plus released) with regard to the total heat at 24 hours. Several relationships among the EA parameters were identified.These parameters were evaluated considering the early age cracking due to drying shrinkage. It was observed that the cracking risk increased when some events occurred simultaneously. The simultaneous monitoring of several parameters allowed a better understanding of the mechanisms involved during SCC early ages.

NDT of Concrete

1216ADVANCED INSPECTION TECHNIQUE FOR EMBEDDED STEEL WITHIN CONCRETE USING ULTRASONIC GUIDED WAVES

N Lee & K Tuncbilek, TWI, Cambridge, UK

This paper is based on work carried out during the CROSS-IT project, which was a collaborative project for small-to-medium sized enterprises, funded by the European Union under the FP7 framework, under grant agreement no 286981. The project is being co-ordinated by TWI, It began in November 2011 and will finish at the end of January 2014. The inspection technologies that have been researched in CROSS-IT are a hybrid between GPR (Ground Penetrating Radar) and GUW (Guided Ultrasonic Waves). This paper covers the GUW technology involved in the inspection of embedded steel using the Long Range Ultrasonic(LRU) technique that has been extensively used for screening pipes for corrosion.In the CROSS–IT project we have shown that this system of low frequency guided ultrasonic waves can be used to detect flaws and corrosion within the embedded steel tendons and reinforcement. A new design of transducers and array design has been designed based on the results of extensive computational modelling and this has enabled the use of preferred wave modes to be generated to maximise the propagation of the ultrasonic wave in the embedded steel components within the concrete structure.

1245NON-DESTRUCTIVE EVALUATION METHODS FOR SOUNDNESS OF ADHESIVE PORTION AROUND ANCHOR BOLTS IN CONCRETE BY ELASTIC-WAVE SIMULATION ANALYSIS-BASED ELECTROMAGNETIC PULSE

H Miyata & K Tanaka , West Nippon Expressway, Osaka, Dr S Uchida & T Kimura, Ritsumeikan Univ, Prof T Kamada & X Liu, Osaka Univ, Osaka, Japan

In general, highway concrete structures are maintained by appropriate investigations based on a visual test or hammering test by inspectors. Furthermore, introducing non-destructive inspection techniques is required in order to improve the reliability of those investigations. Electromagnetic pulse method is one of the non-destructive inspection techniques that can vibrate the magnetic body in concrete without contact by the electromagnetic force. And when a vibration sensor which is arranged on the surface of the target member captures the elastic wave due to the vibration of the magnetic body, this method can evaluate the state of adhesion and defects at the interface of magnetic body without damage by analyzing the waveform obtained. The

purpose of this study is to establish measurement method by electromagnetic pulse in order to evaluate soundness of adhesive portion around anchor bolts in concrete. To this end, specifically, two cases where the input method of elastic wave is different were examined by analysis so that the applicable properties of elastic wave were revealed for evaluating soundness in each case. Additionally, in order to verify the results of analysis, the specimens which reproduced the situation of adhesive portion around anchor bolts in concrete were measured by electromagnetic pulse method.

1336 DAMAGE ASSESSMENT OF CONCRETE STRUCTURES BY USING ULTRASONIC Q-VALUE

T Shiotani, Y Takada & K Ishitusuka, Kyoto Univ, S Momoki, Tobishima Corporation, Chiba, Japan

In the conventional elastic wave technique, several parameters such as frequency and velocity have so far been used to relate the damage of materials; however, these are the parameter to be readily influenced by the propagation distance or the frequency excited so that they could not quantify the damage/ degradation of the materials. This research studies the promising damage index being applicable for the quantification of damage of heterogeneous materials as concrete by using the frequency response characteristics of elastic waves. In this research Q-value being regarded as normalized attenuation-parameter which is not dependent on the propagation distance as well as the frequency excited is focused. Several types of mortar specimens, containing different volume of styrene material simulating false cavity, were prepared for the test where elastic waves were excited and propagated through the specimen. As a result, it was clarified that the quantitative damage evaluation of heterogeneous materials, mortal with different volume of artificial damages in this paper, could be performed by the Q-value.

1157 ULTRASONIC COUPLING POWDER FOR CONCRETE MATERIALS,

K Mori, Kumamoto Univ, T Mori, Ryoyu System Engineering, Kobe, Japan

A new ultrasonic coupling powder has been developed where the gel of conventional contact mediums is replaced with powder. In this method, ultrasonic testing is carried out while compressing the powder between probes and concrete surfaces by applying pressure to the probes. Even though the powder usually prevents the transmission of elastic waves, they can be transmitted through it under pressurized conditions. In addition, the acoustic impedance can be matched to that of mortar or concrete by controlling the pressure applied to the powder. In this paper, this ultrasonic coupling powder was applied to the testing of mortar test specimens with varying surface roughness. The results were that the amplitudes of the back reflection increase as the pressure of the powder increases. These results were compared to those from grease coupling. The problem with the coupling powder is the necessity of high pressure applied to the powder. Our solutions to this problem are outlined in the last section.

1225 3-D AE-TOMOGRAPHY WITH ACCURATE SOURCE LOCATION TECHNIQUE,

Y Kobayashi, K Oda, Nihon Univ, Tokyo, T Shiotani, Kyoto Univ Japan

The authors introduce a new algorithm of three-dimensional AE-Tomography with accurate source location technique in this paper. This algorithm aims to estimate locations and occurrence times of AE events and elastic wave velocity distribution from arrival time of elastic wave at receivers and locations of the receivers in three-dimensional manner. It is noteworthy that the three-dimensional algorithm considers effect of inhomogeneity of elastic wave velocity distribution in volumes of interest on the estimation of the source informations and elastic wave velocity distribution by using a ray-trace technique with relay points. The ray-trace technique is adopted to obtain ray-paths that give minimum travel time between two points in the volume and rise accuracy of the estimation of source informations of AE events. This algorithm has a capability to carry out the estimation on the mesh in which the volume is subdivided into tetrahedral or hexahedral cells, and it is an advantage to applying the

algorithm for structures of irregular shape. The present algorithm was verified by carrying out a series of numerical investigations in simple models, and it was confirmed that the algorithm gives reasonable result.

1182ULTRASONIC INVESTIGATION OF EXTENSION OF PLASTIC SHRINKAGE CRACKING IN MORTAR & CONCRETE SPECIMENS,

JM Carelli & RCA Pinto, Federal Univ of Santa Catarina, Brazil

Plastic shrinkage cracks may occur when water evaporated from the surface of a freshly placed concrete is not replaced by bleed water. The cracking pattern and its extension depend on the rate of water evaporation. At higher rates of evaporation, it is expected that plastic shrinkage cracking develops in a more extensive pattern, and therefore might impair the durability and serviceability of the concrete structure. The analysis of the extension of such cracking can be performed by nondestructive methods such as visual analysis or using stress wave parameters given by ultrasonic testing. While the ultrasonic pulse velocity is usually the most common wave parameter used in the inspection of concrete structures, there are other lesser used wave parameters that might be more sensitive to distributed damage given by plastic shrinkage cracks. This research explores different stress wave parameters such as group velocity, accumulated energy, amplitude decay and their relationship to the extent of plastic shrinkage cracking in mortar and concrete specimens. It is concluded that the stress wave parameters investigated here are better indicators of the extent of a plastic shrinkage cracking than the common ultrasonic pulse velocity.

1360 DEVELOPMENT OF INPUT-OUTPUT DEVICE FOR ON-SITE MEASUREMENT OF SIBIE,

Y Nagai & M Ohtsu, Kumamoto Univ, T Sonoda & S Shimozono, Nippon Koei Co. Ltd, Tokyo, Japan

The impact-echo method, well known as one of nondestructive testing (NDT) techniques for concrete structures, is improved as the SIBIE procedure by visualizing a cross-sectional image, instead of identifying peak frequencies in the frequency spectra. In the current SIBIE procedure, elastic waves are generated by shooting an aluminum bullet and detected by using an accelerometer. The frequency responses of the input-output system are studied quantitatively, by applying Lamb’s solution.After clarifying the responses of the input device by shooting an aluminum bullet, a new device consisting of an impactor-head of titanium alloy and a spring system is developed. As a result, it has come out that the new device is practically able to cover the high frequency range and to drive a good impact to detect ungrouted tendon ducts in situ. Thus, the SIBIE procedure is improved as applicable to on-site measurement.

1193 ASSESSMENT OF SULPHATE ATTACK IN SILICA FUME MORTARS USING ELECTRICAL TECHNIQUES,

MC Williams, Waldeck Consulting, London & J.M Ortega, I Sanchez, M Climent, Univ of Alicante, Spain

Two electrical techniques (Wenner resistivity and A.C. Impedance Spectroscopy) were employed for the non-destructive testing of mortars with 0%, 5% and 10% silica fume, in order to assess the effect of exposure to three different sulphate solutions (15% sodium sulphate, 15% magnesium sulphate and mixed sulphate). The results were compared with compressive strength and mercury intrusion porosimetry results, and showed that that the loss of compressive strength in OPC samples resulting from exposure to sodium sulphate was not reflected in the electrical results. However, the observed visual deterioration and loss of compressive strength in silica fume samples exposed to the solutions containing magnesium correlated well with the electrical measurements. The Mercury Intrusion Porosimetry results did not correlate well with others, possibly due to intrinsic limitations of the technique. While both electrical techniques appeared unsuitable for the assessment of expansion type deleterious reactions such as sulphate attack, a good assessment of damage due to dissolution type reactions such as magnesium attack was made. In OPC samples, the presence of magnesium appeared beneficial, independent to the concentration of sulphate ions present. The fact that extensive deterioration was observed in the mixed sulphate solution suggests a complex decay mechanism in silica fume samples.

1229 EFFECT OF PIBEM ANALYSIS WITH AE FOR REBAR CORROSION TOWARD ON-SITE MEASUREMENT,

Y Kawasaki, K Masuda, S Uchida & K Izuno, Ritsumeikan Univ, Shiga, Japan

The mechanisms of corrosion-induced cracks and evaluation methods for diagnosis are under development in concrete engineering. In order to develop AE techniques to be applicable to on-site measurement for infrastructure, hybrid nondestructive evaluation (NDE) is under investigation. Thus, an accelerated corrosion test of reinforced concrete (RC) specimens was conducted.To monitor the corrosion process, AE measurement was applied, along with measuring half-cell potentials and polarization resistances at the surface of the RC specimen. Here, in order to identify the corroded area in rebar, the potential inversed BEM (PiBEM) analysis was developed and applied. Toward practical on-site measurement using NDE, damage identification of rebar corrosion due to salt attack was demonstrated.

1226 HYBRID NDE FOR EVALUATION OF CORROSION-INDUCED CRACKS,

Y Kawasaki, T Wakuda, Y Tomoda & M Ohtsu, Kumamoto Univ, Japan

For on-site measurement of the corrosion in reinforced concrete, hybrid nondestructive evaluation (NDE) is in progress. Here, AE measurement is conducted, along with measuring half-cell potentials and polarization resistances at the surface of the slab. In order to identify the corroded area along rebar, the potential inversion by BEM (PiBEM) analysis is developed and applied. It is demonstrated that the hybrid NDE is practically applicable to on-site evaluation of the corrosion in rebar. Further the mechanisms of corrosion-induced cracks are investigated. Based on the prediction of chloride-ion concentration, stress distribution around rebar due to expansion of corrosion product is analyzed by BEM. Accelerated corrosion tests of reinforced concrete (RC) slabs were conducted. The mechanisms analyzed are compared with micrograph observation of cross-sections. As a result, the applicability of the hybrid NDE for rebar corrosion is confirmed.

1273 TARGET RESOLUTION USING VERY HIGH FREQUENCY GPR E Carrick Utsi, Utsi Electronics Ltd, Cambridge, UK

For on-site measurement of the corrosion in reinforced concrete, hybrid nondestructive evaluation (NDE) is in progress. Here, AE measurement is conducted, along with measuring half-cell potentials and polarization resistances at the surface of the slab. In order to identify the corroded area along rebar, the potential inversion by BEM (PiBEM) analysis is developed and applied. It is demonstrated that the hybrid NDE is practically applicable to on-site evaluation of the corrosion in rebar. Further the mechanisms of corrosion-induced cracks are investigated. Based on the prediction of chloride-ion concentration, stress distribution around rebar due to expansion of corrosion product is analyzed by BEM. Accelerated corrosion tests of reinforced concrete (RC) slabs were conducted. The mechanisms analyzed are compared with micrograph observation of cross-sections. As a result, the applicability of the hybrid NDE for rebar corrosion is confirmed.

1271 DATA FUSION – WHY WE NEED IT AND HOW TO DO IT RIGHT,

M Lim, Proceq Technical & Application Services, Gurnee, IL, USA & M. Nagi, American University in Dubai

With the onset of technology today, it has become a simple and relatively quick process to obtain data from a single nondestructive testing method. Many manufacturers offer individual equipment that provides results based upon a specific testing principle. These instruments have been proven to provide reliable data to assist in the evaluation of a structure, but may not provide the complete picture associated with the deterioration process. There have also been many standards written on these testing methods. However, in the evaluation of a structure, the deterioration phenomenon is typically a result of a

series of complex issues and not just associated with a single one deterioration phenomenon. The complexity of the deterioration phenomenon usually requires several testing methods to obtain the relevant information to uncover the underlying cause of the deterioration.

Fusing the data obtained from different nondestructive testing method together requires an understanding of the testing principles of each test method and the significance of the role of the testing results in relation to the particular deterioration. Having a large amount of data does not automatically provide the correct solution. This paper will discuss the need for combining data from different testing methods based upon field testing experience, especially the added importance of structuring the data obtained from different testing principles. The author will also discuss the advantages and disadvantages associated with data fusion, and how a one size fits all solution cannot be applied to every evaluation. In addition, the author will discuss the value associated with field sampling for correlation of the testing data, and how laboratory testing can be useful to complete the evaluation process.

1298 NDE OF CONCRETE STRUCTURES WITH INTERNAL FLAWS

J D Nelson & CC Ferraro, Univ of Florida, Gainesville, FL, USA & D Algernon, Nuclear Inspectorate, Zurich, Switzerland

Nondestructive Evaluation (NDE) systems for use in qualitative evaluation of concrete structures have traditionally relied on the manual application of a single instrument of a particular NDE method for each instance of an inspection. More recently, there have been advances in NDE technology and methodology that embrace the use of multiple techniques as well as more sophisticated data processing available to the operator in the field. Moreover, the NDE industry is rapidly adopting automation practices that allow dense, systematic data collection using multiple NDE techniques. This paper investigates the usefulnessand functionality of such an automated NDE system for validation of flaw detection via field-deployable NDE instruments. The use of an automated NDE system shows great potential for field use as a tool for both quality control and forensic applications. Treated strictly as an automated data collection tool, this system offers the most rapid and repeatable method available for collecting large numbers of data points in extremely dense grids. Furthermore, and most importantly, the automated method of data collection reduces the potential for operator error and produces data that is dense, detailed, repeatable, and defensible.

1260 NDT MEASUREMENTS ON DURABILITY OF HYDROPHOBIC TREATMENTS,

U Antons, O Weichold, M Raupach, RWTH Aachen Univ, Germany

The paper deals with investigations on the durability of hydrophobic layers in concrete specimens by using single-sided nuclear magnetic resonance (NMR) measurements. With this measuring technology the amount and distribution of water as well as of hydrophobic agents below the concrete surface can be detected non-destructively and changings over time can be visualised. To observe changings in hydrophobic layers specimens were measured before, during, and after exposure to different attacks. Measurements on specimens affected by UV radiation, carbonation or hydration show the impact of each attack. The results show, that the effect of the UV radiation is limited to the roll-off behaviour on the concrete surface. While after accelerated carbonation at 2 vol.-% CO2 structural changes caused by carbonation of blast furnace slag cement based concrete decrease the hydrophobic layer thickness. In contrast the carbonation of Portland cement concrete had no influence. Hydrophobic treatments applied in an early concrete age show major degradation depending on the hydration state during application.

1250 AE & 3D IMAGE ANALYSIS FOR DAMAGE ESTIMATION OF HEAVY CRACKED CONCRETE DUE TO FREEZE-THAW, T Suzuki, Niigata Univ, & M Ohtsu, Kumamoto Univ, Japan

As a detailed inspection of a concrete structure in service, core samples are usually drilled out and then physical properties are measured. In this study, damage estimation of structural concrete from concrete-core samples is developed, applying elastic wave method. By the authors, the quantitative damage evaluation of concrete has been proposed, by applying acoustic emission (AE) and damage mechanics in the compression test. In this study, concrete-core samples taken from reinforced concrete of an existing canal were tested. These samples are strongly influenced by freezing and thawing process.The crack distributions of concrete-core samples were inspected with helical CT scans. After helical CT scan, damage of freeze-thawed samples was evaluated, based on fracturing behavior under unconfined compression with AE. AE behavior of the concrete under compression is dependent on the local distribution of cracks, and could be approximated by applying damage parameter and P wave velocity.These experiments suggest that the decrease in physical properties could be evaluated by AE generation behavior in core test. These values are affected by the internal actual cracks. Thus, the damage of concrete could be quantitatively evaluated by damage parameters based on detected elastic waves.

1148 FRACTURE MODE OF TEXTILE REINFORCED MORTAR LAMINATES USING AE

DG Aggelis J Blom, M El Kadi, J Wastiels, Vrije Univ Brussel (VUB), Belgium

The bending behavior of textile reinforced cement (TRC) laminates is examined using the acoustic emission (AE) technique. TRC is a combination of inorganic phosphate cement (IPC) matrix with randomly distributed glass fibres. IPC has a neutral pH meaning that glass fibers are not chemically attacked. During bending, stresses lead to the activation of damage mechanisms like matrix cracking, fiber pull-out and delaminations being in succession or overlapping in time. AE records the transient waves from the damage propagation events and allows the monitoring of the fracture behavior from the onset to the final stage. The effect of the bottom span in three-point bending tests is targeted, which is varied to create different stress fields. Parameters like duration and frequency of AE waveforms reveal information about the mode of the damage sources relatively to the span. Results show that as the span decreases, the dominant damage mode shifts away from bending and acquires more shear characteristics by increasing the interlaminar shearing events.

1158 DEVELOPMENT OF HAMMERING TESTER AT HEIGHT, S Tokuomi, K Mori, K Tateishi, Kumamoto Univ, Japan

A hammering tester which is called “Concrete Pecker I” has been developed for testing concrete walls at height as well as other fastening devices such as bolts that might have deteriorated over time. This hammering tester consists of a long extendable pole with a very light tapping device attached on top. The total length of the pole is 3.1 m and the pole weights 3.2 kg. The upper limit of testing is about 4 m depending on the operator. The hammering tester taps concrete on the surface once a second like a woodpecker. The weight of the hammer is 0.16 kg and the maximum impact speed is 2.2 m/s. Therefore, the impact power of the device is comparable to the power of workers’ hammering. The hammering testing device has a sound acquisition system. The system has four microphones and the noise is reduced by averaging the sound signals collected through them. The sound signals are transmitted to the operator’s head set and simultaneously converted into frequency spectrums displayed on a monitor. The new apparatus is able to detect a defect with a diameter of 200 mm and at a depth of 25 mm in a concrete wall. The detectable depth of the defect is limited to be 100 mm or less.

1372 NDT OF CONCRETE - BEYOND EU & USA GUIDELINES MC Forde, Univ of Edinburgh

Clients worldwide face increasing pressure to obtain best value for money from NDT surveys. Yet this gives rise to the dilemma of whether a high quality survey and analysis is being undertaken.

ACI 228 Committee provides documentation on the available NDT test methods, but stops short of giving advice on the interpretation of data. RILEM TC Committee on the NDT of Concrete does give advice – but the Committee has a fixed term of operation.

This paper discusses progress towards international standards of NDT of concrete.

1373 FREQUENCY REDUCTION OF GPR SIGNALS IN SURFACE CONTACT WITH CONCRETE

IJ Padaratz, Federal Univ of Santa Catarina + MSA Hardy, A Giannopoulos & MC Forde, Univ of Edinburgh

Issues of coupling effects between radar antenna and various surfaces have been reported elsewhere in relation to both geophysical applications and structural applications.

Experimental work is reported using 900 MHz antenna coupled to concrete. The experiment was designed using tiles. The work was undertaken in the transmission mode using a multi-channel digital radar system. The data was analysed in both the time and frequency domains. The results from the laboratory experiment using 900 MHz antenna showed that signal distortion affects travel time measurements, and thus different references on a wave in the time domain (signal peaks) can produce variable results for the wave's velocity. The coupling effect between an antenna and concrete surface will happen for any moisture condition: oven dried, air dried or saturated.

Although the receiving antenna may indicate a loss of frequency component, the transmitted signals actually retain most of their original frequency components when transmitted into a medium different from air. This phenomenon was more evident for the dry tiles, where the centre frequency of the recorded signals reached values over 850 MHz. This latter value is equivalent to the nominal centre frequency for the 900 MHz antennae in air. However when the materials contain moisture, then amplitude attenuation and shape distortion will occur. High conductivity will increase these problems further. The practical consequences of the work are clarified.

The shape of the GPR radar pulse generated in air is related to the design of the antenna box, which is usually shielded. Once the antenna is then coupled to a surface such as concrete the antenna and the concrete combine in the near field to form an antenna of different frequency.This work will be analysed in relation to future field surveys.

1374 INTERPRETATION OF NDT OF THICK CONCRETE R De Bold, Dr A Giannopoulos, and Prof MC Forde, Univ of Edinburgh & K Pareemamun, Mauritius Standards Board

Construction of modern structures requires good quality concrete with adequate strength and durability. Certain structures require the use of very thick concrete either for for load bearing purposes or for retainment structures, or both. Examples where very thick concrete may be utilised includes bridge abutments, structural components of buildings and nuclear waste containment structures. With the construction of these more complex structures, combined with the need to test ageing infrastructure, this paper focuses on available NDT techniques.

Concrete Structural

Behaviour

1187 CRACKING BEHAVIOUR OF FRC FLEXURAL BEAMS WITHOUT STIRRUPS,

F Micelli, Univ of Salento, Lecce, E Vasanelli, CNR-IBAM, Lecce, M Leone & A Aiello, Univ of Salento, Lecce, , Italy

Distortion-induced fatigue affects a large number of bridges in the US highway system. This type of damage is commonly observed at connections between cross-frames and steel girders. Differential displacements between adjacent girders caused by bridge traffic induce forces in the cross frames which impose out-of-plane distortions on the girder webs. These secondary forces also induce highly localized stresses at the welds of the connection plates that tie cross frames to the bridge girders.

This paper describes the results of an experimental program to evaluate the use of composite materials to prevent and repair distortion-induced fatigue damage in web-gap regions of steel girders. In this method of repair, a composite block is cast in place in the area surrounding the cross-frame to girder connection to provide an alternate load path and reduce the stress demands in the welds of the connection.

Two full-scale bridge girders were subjected to dynamic loading under a constant force range and allowed to develop fatigue cracks. The girders were subsequently repaired using composite blocks and subjected to several million fatigue cycles. Test results showed that the repair method was effective in halting the propagation of fatigue cracks in the bridge girders, and that it was particularly effective when anchor bolts were attached to the girder flange.

1362 STRENGTH AND LOAD-DEFORMATION RESPONSE OF CORRODED COLUMNS D Coronelli, Politecnico di Milano, Milan, Italy

This study investigates the ultimate strength and deformations of R/C columns corroded by chloride attack, subject to axial force and cyclic bending moments. A database of tests from the literature is selected and analysed, highlighting the main effects of the deterioration. Artificial and natural corrosion are compared for the effect of corrosion cracking. A strategy is proposed for the prediction of the response on the basis of quantities that can be estimated through in situ testing i.e. geometry of the members, concrete strength, corrosion crack width and reinforcement cross-section. Strength and moment-curvature relations for corroded members are determined modifying the material properties and the cross-sections of concrete and steel. The modelling approach is applied both in cases when the corroded reinforcement cross-section or the corrosion cracks have been measured. The results show that artificially corroded laboratory specimens for a given corrosion crack width have much higher reinforcement corrosion than naturally corroded specimens; thus the latter may suffer less deterioration than shown in laboratory tests. The approach in the future needs to be compared with naturally corroded specimens with high deterioration levels.

1164NUMERICAL & EXPERIMENTAL INVESTIGATION FOR BI-DIRECTIONAL FLEXURAL STRENGTHENING OF TWO-WAY SPANNING RC SLABS USING FRP MATERIALS

M Tavallaee & T Donchev, Kingston Univ, London, UK

ABSTRACT:This paper deals with strengthening of two-way reinforced concrete (RC) slabs with fiber reinforced polymer materials (FRP).

Experimental investigations have been performed in order to determine the effectiveness of this strengthening solution.The experimental program involves tests on four medium scale slabs. The first slab is control sample without strengthening while in each of other three slabs a different type of strengthening is applied. Deflections, strains and crack patterns are monitored during the loading process until destruction. The experimental results are analysed and the most important conclusions as the result of investigation are offered.

Concrete & Mortar Behaviour

1338 INFLUENCE OF RUBBER FILLERS ON THE HYDRAL BEHAVIOUR OF CLAYEY CELLULAR CONCRETES

N Madjoudj, RM Dheilly, A Goullieux, M Queneudec, Univ of Picardie Jules Verne, Amiens, France,

Previous work has shown that clayey sludges of the aggregates industry could be transformed into lightweight concrete of cellular type by proteinic foaming. The protein used was haemoglobin from blood waste recovered from slaughterhouses. It is an excellent foaming agent for clay-cement pasta both by its foaming ability and stability of the formed foam. Cellular structure remains away from the water invasion through the protein film that causes a slowing of water transfers. However, the presence of clay, even stabilized with cement, maintains sensitivity to water.To remedy this problem, the authors performed an addition of rubber fillers obtained by aspiration during the granulation of waste of the automotive industry. The amount of additions was limited to 10 % in weight to not modify significantly the viscosity of the mixture.It has been observed that the addition of rubber powders decreases air entrainment, probably by interfering with the diffusion of the protein in the medium. Extreme dimensional variations are reduced. Sorptivity, which reflects the ability of a material to absorb water by capillarity, is reduced from 1.5% of ground rubber. The presence of these rubber fillers decreases the humidity setting and slows the kinetics of sorption.From the environmental point of view, it can be seen also the interest of such material that allows to enhance both the waste of aggregates industry, food industry and automotive industry.

1290 COMPARISON OF CONTINUOUS AND CYCLIC SULFATE ATTACK ON CONCRETES CONTAINING FLY ASH

N Ghafoori, H Diawara, M Najimi & S Islam, Univ of Nevada Las Vegas, USA

This investigation evaluates the influence of sodium sulfate immersion types and fly ash replacement levels on the ettringite-based expansion and gypsum formation (strength reduction and mass loss) of fly ash contained concretes. To this aim, a control concrete was made with cement content of 374 kg/m3 having a water-to-cementitious materials ratio of 0.45. Fly ash contained concretes were designed by replacing 15, 20, 25 and 30% by weight of cement with fly ash. An experimental program was designed including cyclic and continuously-immersed sulfate exposure conditions. The sulfate medium consisted of 5% sodium sulfate solution. Length change, mass loss, and compressive strength were monitored for a period of 360 days to evaluate the performance of the test specimens exposed to “very severe” sulfate attack. The results of this study revealed improvements in concretes’ resistance to sulfate attack by replacing a portion of cement with fly ash. When applying the failure criteria against the ettringite-based expansion results, the studied fly ash contained concretes performed remarkably well. The selected fly ash concretes can be classified as having “high sulfate resistance.” Additionally, they showed no signs of material loss during the 12-month continuous and cyclic immersion in a sulfate-rich environment. The compressive strengths of samples under cyclic immersion condition were marginally lower than those of continuously immersed samples, whereas an

opposite trend was observed for ettringite-based expansion. The studied mixtures produced lower expansion under cyclic immersion than continuous immersion.

1339VALORIZATION OF LEAFLETS STEMMED FROM MAINTENANCE OF DATE PALM TREES IN CEMENTITIOUS PASTES,

K Harrat, Univ Badji Mokhtar, Annaba, Algeria, LB Mboumba-Mamboundou & M Queneudec, Univ of Picardie Jules Verne, Amiens, France

The need to find alternatives to fossil-based materials has led for several decades to consider the use of plant resources. This strategy is even more interesting that the agricultural resources are co-products or waste. It is the case for dry palms stemmed from the maintenance of date palms.In Algeria, date palm is the fundamental element of the oasis ecosystem of Sahara. The annual tonnage of dry palms issued from maintenance can be estimated to 210,000tons in Algeria and about 2 million worldwide what constitute a significant deposit of waste, renewable annually. Leaflets from dry palms are rich in fibers which appear performing. Studies about these fibers are recent and limited: literature reported essentially fibers of the stipe and its surface.Therefore, it was interesting to examine the potential use of these fibers in cementitious materials. Geometric factors of fibers and their proportion can influence their dispersal in the matrix with an impact on the mechanical performances of materials. This work was therefore attached to optimize the size of the fibers and their proportion on the basis of mechanical criteria in the case of cement paste. Examination of the results showed satisfactory properties. Improvement of flexural strength is recorded for the volume fraction of 15% - for example, 24% for 40mm length and 14% for 50mm. Compressive strength are little affected. Thermo physical determinations were conducted for various proportions of 40mm length fibers.

1289STRENGTH AND TRANSPORT PROPERTIES OF ALKALI-ACTIVATED FLY ASH MORTARS HAVING DIFFERENT CONCENTRATIONS OF SODIUM HYDROXIDE

N Ghafoori, K Sierra and M Najimi, Univ of Nevada Las Vegas, USA

Alkali-activated fly ash binders have been recognized as a promising solution in the development of a sustainable alternative binder to ordinary Portland cement (OPC). The goal of this study was to evaluate fresh, strength, and transport properties of alkali-activated fly ash mortars as affected by activator concentration and curing age. As such, alkali-activated fly ash mortars were made with various sodium hydroxide concentrations of 5, 7.5, 10, and 12.5M and tested for slump flow, setting times, compressive strength, flexural strength, density, absorption, void content, chloride migration, and resistivity to rapid chloride ion penetration. The produced samples were sealed cured for 3 hours at 60°C prior to de-molding and cured at 80°C until time of testing. The results of this study revealed increases in compressive and flexural strengths with increases in alkaline activator concentration. There were also increases in the density of alkali-activated mortars with increases in activator concentration, while contrary results were found for absorption, and void content. The depth of penetrated chloride and the passed through charge were reduced with increases in activator concentration. The findings of this study suggest that a strong binder using fly ash and sodium hydroxide can be developed as a sustainable substitution for OPC.

1207 IMPROVING DURABILITY OF CONCRETE BY EARLY CARBONATION

Y Shao, V Rostami, McGill Univ, Montreal, Canada & H El-Hassan, American Univ at Dubai

A carbonation process was developed to reduce steam duration, improve durability performance and sequester carbon dioxide emitted from cement production. It was found that early carbonation introduced after an initial two-hour steam curing could yield a carbon uptake of 9% based on dry cement content. This chemical modification had significantly improved the concrete

resistance to sulphate attack and chloride ion penetration, while maintaining the pH of the pore solution above the corrosion threshold. The durability improvement is attributed to the elimination of hydroxyl ions and precipitation of calcium carbonate on the surface layer.

1154 FUNDAMENTAL RESEARCH ON CARBONATION CONTROL EFFECT BY COATING MATERIALS, M Sugiyama, Hokkai Gakuen Univ, Sapporo, Japan

This research applied three kinds of coating materials to the concrete and examined the carbonation performance. Three kinds of coating materials are silicate system surface impregnation material, the silicon system surface impregnation material, and polymer cement. As a result, the covering material of polymer cement had the largest carbonation control performance.

1282 ALKALI SILICA REACTION MITIGATION USING HIGH VOLUME CLASS C FLY ASH

WJ Phillips, RA Deschenes,, WM Hale, Univ of Arkansas Fayetteville, AR, USA

Akali Silica Reaction (ASR) in concrete has been found in increasing quantities in Arkansas as shown by the Interstate Highway system in the I-540 barrier wall near Fayetteville, AR. The purpose of this research is to determine the required amount of Class C fly ash to prevent ASR in the concrete. The research will study three regional, Class C fly ashes. The research will include two fine aggregate sources. One fine aggregate has been found to be the source of reactive silica in the ASR occurring in the I-540 barrier wall. The other fine aggregate has been well researched and certified as a source of reactive silica. Class F fly ashes have been previously is typically prescribed for impeding ASR (ACI Comm. 221 1998). However, the availability of Class F fly ash in Arkansas is somewhat limited compared to the availability of Class C fly ash. This paper examines the use Class C fly ash for preventing ASR in Arkansas.

Chloride Content

1357 EFFECT OF SPACERS ON CONCRETE TRANSPORT PROPERTIES AND CHLORIDE PENETRATION

S Alzyoud, HS Wong, NR Buenfeld, Imperial College, London, UK

There is a lack of research to establish the influence of reinforcement spacers on the mass transport properties of concrete despite concerns over their effect on the durability of concrete structures. This paper presents an extensive experimental investigation on the effects of three types of reinforcement spacer (concrete, plastic, and steel) on gas diffusion, gas permeation and water absorption (sorptivity) in the concrete cover. Concrete specimens containing embedded reinforcement spacers were made and subjected to different curing and drying regimes to simulate site conditions. The transport properties were then measured and selected specimens were pressure impregnated with fluorescent epoxy to study the extent and spatial distribution of epoxy intrusion. µXRF was utilised to study the distribution of chloride ingress, particularly near the interface between spacers and concrete matrix. Concrete samples containing plastic spacers consistently gave the least resistance to transport, followed by samples with concrete spacers, then steel spacers. The control samples (samples without spacers) had the highest resistance to transport in all cases. This behavior is attributed to drying-induced cracking and the presence of a porous interface between spacer and concrete.

1256BASIC STUDY FOR IMPROVEMENT OF ESTIMATION ACCURACY CONTENT OF CHLORIDE ION USING ELECTROMAGNETIC WAVES METHOD

J Nojima, M Uchida, T Mizobuchi, Hosei Univ, Tokyo, Japan

Chloride induced corrosion is one of the cause of deterioration reinforced concrete structures. In generally, as one of

evaluation method of deteriorated situation caused by reinforcement corrosion in the concrete, drawing cores and chemical analysis are carried out. It is possible to perceive chloride content in the neighborhood of reinforcing bars. However, it is not possible to perceive only chloride ions at the position drawn cores and difficult to perceive about any corrosion of reinforcement unless corrosion induced cracks appear on the surface. Then, if it is possible to estimate the chloride ions in concrete using electromagnetic waves as non-destructive method, it is possible to perceive the chloride ions in concrete without giving any damages. In addition, it is possible that this method conveniently evaluate the condition of degradation in respect of the wide area.From past studies, it was confirmed that the amplitude value of the electromagnetic waves decreases with increasing chloride ions within concrete. It is possible to estimate chloride ions by utilizing this characteristic.In this report, in order to improve the accuracy of this method, Simulation of Attenuation Electromagnetic waves (SAE) of concrete are constructed, by applying the basic equation and attenuation theory of the electromagnetic waves.As the results, it is possible that the attenuation characteristics to electromagnetic waves by material changes of properties of concrete and to obtain the basic equation which contribute to improve in ac-curacy of estimation of chloride ions in concrete using electromagnetic waves.

1355SERVICE LIFE EXTENSION AND ENVIRONMENTAL IMPACT DUE TO REPAIRS BY SILANE TREATMENT ON CONCRETE STRUCTURES EXPOSED TO TIME-DEPENDENT CHLORIDE ATTACK

A Petcherdchoo, King Mongkut's University of Technology North Bangkok, Thailand

As a detailed inspection of a concrete structure in service, core samples are usually drilled out and then physical properties are measured. In this study, damage estimation of structural concrete from concrete-core samples is developed, applying elastic wave method. By the authors, the quantitative damage evaluation of concrete has been proposed, by applying acoustic emission (AE) and damage mechanics in the compression test. In this study, concrete-core samples taken from reinforced concrete of an existing canal were tested. These samples are strongly influenced by freezing and thawing process.The crack distributions of concrete-core samples were inspected with helical CT scans. After helical CT scan, damage of freeze-thawed samples was evaluated, based on fracturing behavior under unconfined compression with AE. AE behavior of the concrete under compression is dependent on the local distribution of cracks, and could be approximated by applying damage parameter and P wave velocity.These experiments suggest that the decrease in physical properties could be evaluated by AE generationbehavior in core test. These values are affected by the internal actual cracks. Thus, the damage ofconcrete could be quantitatively evaluated by damage parameters based on detected elastic waves.

1192REPAIRS BY FLY ASH CONCRETE TO EXTEND SERVICE LIFE OF CHLORIDE-EXPOSED CONCRETE STRUCTURES CONSIDERING ENVIRONMENTAL IMPACT

A Petcherdchoo, King Mongkut’s Univ of Tech North Bangkok, Thailand

This paper presents numerical assessment of corrosion-free service life (or period) and environmental impact in terms of CO2 due to repairs by replacing cover concrete with fly ash concrete on chloride exposed concrete structures. The mechanism of chloride diffusion based on the partial differential equation (PDE) of the Fick’s second law is used in computation. After repairs, the PDE cannot simply be solved. The difficulty is encountered in solving nonlinear chloride profile and space-dependent diffusion coefficient after repairs. Moreover, if both surface chloride and diffusion coefficient are time-dependent, the difficulty is even more. To remedy the difficulty, the Crank-Nicolson based finite difference approach is introduced. Using the approach, the diffusion of chloride ions can be calculated and presented as chloride profiles in terms of the chloride

content with concrete depth and time. From these profiles, the service life and the time of repairs for corrosion-free condition of concrete structures can be predicted. At the predicted time of repairs, the environmental impacts in terms of CO2 dealing with producing concrete and processing cover concrete replacement also occurs, and can be predicted using a CO2 emission model developed in this study. From the study, it is found that repairs by concrete with more amount of fly ash lead to not only lower CO2 in each repair, but also lower cumulative CO2 because of longer extension of corrosion-free period after repairs. If the threshold ratio or the ratio of the diffusion coefficient of original concrete to that of repair concrete is larger than two, deeper depth of cover concrete replacement causes shorter extension of corrosion-free period. The increase of the amount of fly ash in concrete by 15% leads to the reduction of the cumulative CO2 from cover concrete replacement by as high as 58% at the design lifetime.

Concrete Surface, Interfaces & Bonding

1215 INTERPRETING FIELD DATA FOR ADHESION STRENGTH OF BONDED OVERLAYS,

P Robery, R Baldwin, P Segers, N Ferreira, CH2M HILL, Birmingham, UK

European Standard EN 1504 has been fully in place since 31 December 2008 and in the UK is published by British Standards Institution as BS EN 1504. UK industry continues to adapt and integrate the ten parts of BS EN 1504 into the repair process, mandated through the Construction Products Regulations.

In the authors' experience, one common area of potential dispute is interpretation of site adhesion test data when this is used as a quality control tool. Guidance on suitable techniques for adhesion testing of repair products and systems is given in BS EN 1504 10, covering quality control of the works on site. BS EN 1504 contains no guidance on how to interpret the adhesion test values generated by bond strength testing, based on the method of BS EN 1542 and adapted for site use. This test method requires partial coring through the bonded material and into the substrate, bonding a steel dolly to the surface and then testing by direct tension pull-off. Our evidence from many projects shows that field test values are consistently much lower than the values quoted by manufacturers for testing to BS EN 1542 under laboratory conditions.

This paper presents field data on typical test results from pull-off adhesion testing of concrete repair overlays based on several projects carried out over the past few years. Some of the causes of high variation and low values from adhesion testing on site are then discussed and compared with laboratory testing. A proposal is tabled for selecting the frequency of site pull-off testing and guidance is given on acceptability criteria for adhesion test results obtained for concrete repair mortars and concretes tested on site, including sprayed concrete overlays and overlays that are part of a cathodic protection system.

1224RELATIONSHIP BETWEEN BOND STRENGTH & SURFACE CRACK WIDTH IN R.C. SUBJECT TO CHLORIDE INDUCED CORROSION,

TCK Molyneaux, D Law, RMIT Univ, Melbourne, & DL Tang, Dept of Infrastructure, Energy & Resources, Tasmania, Australia

Concrete infrastructure is vulnerable to the corrosion of the steel reinforcement which can lead to deterioration, loss of functionality, major maintenance, remediation and, in the worst cases, loss of structural integrity and consequent replacement of the asset. Once corrosion has commenced the corrosion products result in pressure and complimentary tensile stresses

which lead to cracking that eventually progresses to the surface and eventually to spalling. This paper reports on a long running series of pullout tests on rectangular concrete specimens that have been subject to an applied current to accelerate corrosion. The concrete mix incorporated sodium chloride in order to facilitate this process. Corrosion was monitored and related to pullout strength. Results are reported for specimens with and without stirrups and relate pullout force and extent of corrosion up to first visible crack.

1246A STUDY ON BONDING PROPERTY OF CFRP STRAND SHEETS USING POLYUREA SOFT LAYER AT ELEVATED TEMPERATURES

T Arai & S Yamanobe, Kajima Corporation, Tokyo, M Arazoe & A Kobayashi, Nippon Steel and Sumikin Materials, & Chuo-ku, Y Sato, Hokkaido Univ, Japan

In previous study, it was found out that polyurea soft layer, which has low Young’s modulus and high elongation, improves the bonding property between CFRP (Carbon Fiber Reinforced Plastic) strand sheets and concrete surface. In this study, in order to evaluate the bonding property of CFRP strand sheets using polyurea soft layer quantitatively, a series of bond strength test and FE analysis were carried out. Especially to verify the applicability of the bonding method with polyuria soft layer at elevated temperature for structure such as chimney, bond strength test at different temperature (23 degree Celsius (deg C), 50 deg C, and 70 deg C) were selected. As a result, it was found out that sufficient bonding property can be obtained at elevated temperature around 50 deg C, while can be lowered at 70 deg C. It was also found out that the bonding properties can be predicted by FE analysis with bilinear bond stress- slip model which was developed based on the experimentally observed bond stress-slip curves.

Corrosion and Cathodic Protection

1221 ASSESSMENT OF STRUCTURAL PERFORMANCE IN NATURALLY CORRODED R.C.,

M Tahershamsi, Hokkaido Univ, K Zandi, CBI Swedish Cement & Concrete Research Institute, Borås, K Lundgren & M Plos, Chalmers Univ of Tech, Gothenburg, Sweden

Reinforcement corrosion is one of the main causes of deterioration in reinforced concrete (RC) structures. The structural behaviour of deteriorated (RC) members have been studied by many researchers. Nevertheless, the knowledge obtained is mostly based on experimental investigations of artificially corroded specimens. Earlier studies have shown that artificial corrosion may affect the structural behaviour differently than natural corrosion. Therefore, it was important to gain a better understanding of these differences by conducting experiments on naturally corroded reinforced concrete members. The aim of this study was to investigate the remaining bond capacity of naturally corroded bars. The bond behaviour of naturally corroded reinforcement was monitored in the anchorage region. The test specimens were taken from concrete edge beams of a 30-year old bridge, the Stallbacka Bridge in Sweden. The specimens were grouped into three categories differentiated by the levels of observed corrosion damage: Reference specimens with no visible damage, Medium damaged specimens with splitting cracks and Highly damaged specimens with spalling of the concrete cover. The tests were carried out using an indirectly supported four-point bending test set-up. The failure mode consisted of a splitting-induced pull-out failure. It was observed that the specimens with cracking and cover spalling had 6 to 9 % lower load-carrying capacity respectively in comparison with the reference specimens. Bond stresses in the anchorage zones showed a reduction of 12 to 20 % in the bond strength for the specimens with cover spalling and cracking respectively in comparison to that of Reference specimens. The decrease in bond capacity and its relationship to the crack widths documented were studied for both the naturally corroded specimens and artificial corrosion tests from the literature. A reduction of bond strength with increasingly maximum crack widths was observed. However, the bond strength in the naturally corroded specimens was considerably higher than that of the artificially

corroded specimens. Furthermore, the provisions given in Model Code 2010 in terms of the reduction in bond strength compared with crack width remained on the safe side.

1181IMPRESSED CURRENT CATHODIC PROTECTION AT HALF-JOINTS OF A PRESTRESSED CONCRETE BRIDGE – CASE STUDY,

A Sharifi, S Das, G Jewell, Amey,Birmingham, UK

Although Impressed Current Cathodic Protection (ICCP) systems have used successfully to mitigate on-going corrosion and concrete deterioration at bridge half joints, most of these half joints do not have pre-stressing or post tensioned elements. ICCP has not been widely used for the protection of highway structures with pre-stressing or post-tensioned elements. Generally this is due to the concerns that ICCP can cause hydrogen embrittlement in pre-stressing steel. The likelihood of hydrogen embrittlement is greatly reduced by good design, advanced electronic monitoring, and control procedures. ICCP has been applied to Bridstow Bridge where there has been concrete deterioration in the vicinity of the half joints The design concept and the performance of a system in which MMO/Ti mesh and a cementitious overlay are applied to post tensioned half joints are discussed. The performance data for the cathodic protection installation to the half joints of this structure demonstrates that the installed CP system is operating effectively and efficiently and has no detrimental effect on the post tensioning. This paper may allow a wider application of ICCP to structural elements containing pre-stressing or post tensioning.

Concrete Repair

1319 REGENT STREET DISEASE - INVESTIGATION & REPAIR OF WELLCOME BUILDING, LONDON,

M Tahershamsi, Hokkaido Univ, K Zandi, CBI Swedish Cement & Concrete Research Institute, Borås, K Lundgren & M Plos, Chalmers Univ of Tech, Gothenburg, Sweden

Steel-frame building construction was initially employed in Chicago and subsequently used in most major western cities around the turn of the 20th century. However, unless the steelwork is adequately protected from moisture, corrosion can occur and the resulting expansion of the corrosion products on the steel can disrupt concrete or masonry cladding, causing serious consequences with respect to serviceability, safety, and aesthetics. Most notably, the identification of “Regent Street Disease” in the United Kingdom in the late 1970s first highlighted the problems of steel-framed corrosion. Many of the grand, high profile, and often protected structures in the centres of many cities have been affected, notably in Regent Street, London, but also in Manchester, where the problem is referred to as “Deansgate Disease.”

This paper details the investigation carried out by Sandberg at the Wellcome Trust building in the Euston Road, London to determine the cause of cracking to stonework in the historic building. The investigation included a detailed visual survey of the whole structure using abseiling, to identify defects, and a combination of non-destructive methods including rest-potential, corrosion rate studies, ground probing radar, endoscope and exploratory core sampling. Following the investigation, Sandberg prepared a tender for the works based on the NBS form of tender with additions to deal with the Cathodic Protection.

The paper concludes with details of the cathodic protection system and repairs that were installed to deal with the problems identified. This was especially challenging as colour matching of repairs was required for the architectural stonework.

1166 INVESTIGATION, REPAIR, & LOAD TESTING OF A 2-WAY SLAB WITH CONSTRUCTION DEFICIENCIES,

F Calabrese, P Popovic, FD Heidbrink, Wiss, Janney, Elstner Associates, Inc, Northbrook, IL, USA

As a firm that specializes in forensic engineering, we are often asked to evaluate structures in which errors have occurred during design or construction. In this case study, we will discuss errors made in the construction of a reinforced concrete parking garage and plaza structure. These errors led to calculated strength deficiencies, excessive cracking, and increased deflections. This paper includes a description of repairs proposed by the original structural designer and a description of an alternative repair approach as well as of load testing of the repaired slab. Load testing of the slab utilized hydraulic rams and shoring frames reacting against the plaza slab structure above.

1210 A MODELLING STUDY OF DRYING SHRINKAGE DAMAGE IN CONCRETE REPAIR SYSTEMS

M Lukovic, B Savija, E Schlangen, K van Breugel, TU Delft, G Ye, Ghent University, The Netherlands

Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems (Martinola, Sadouki et al. 2001, Beushausen and Alexander 2007). Magnitude of induced stresses depends on many factors, for example the amount of restraint, moisture gradients caused by different curing and drying conditions, type of repair material, etc. Once stresses exceed the strength, two damage mechanisms may take place: debonding (curling) of the repair material or/and cracking inside the repair material or concrete substrate.

Numerical simulations combined with experimental observations can be of great use when determining the influence of governing parameters and predicting the performance of a repair system. In this work, a lattice type model is used first to simulate moisture distribution inside a repair system in time, and then to model cracking caused by resulting shrinkage. The influence of substrate surface preparation, bond strength between the two materials, thickness of the repair material, and different types of repair materials is investigated. One of the promising materials which was developed recently and showed to have promising properties for application in a concrete repair is a strain hardening cementitious composite - SHCC. Benefits of applying either SHCC or concrete as a repair material over non-reinforced repair mortar are discussed.

1145EXPERIMENTAL AND ANALYTICAL STUDIES OF STRENGTHENING USING DRILLED-IN BONDED SHEAR REINFORCEMENT

M Fiset & J Bastien, Univ Laval, Quebec & D Mitchell,McGill University, Montréal, Canada

In order to study means of improving the behaviour of thick slabs without shear reinforcement a series of large-scale beams representing thick slabs was constructed and tested. Companion specimens were strengthened using drilled-in reinforcing bars to study the effectiveness of this repair technique. The behaviour of these beams, before and after strengthening, is compared. An additional experimental program using pull-out specimens enabled a study of the bond characteristics of drilled-in reinforcement having different embedment lengths. An analytical model to predict the bond-stress versus slip relationshipenabled the development of a method for predicting the influence of the added shear reinforcementin improving the shear strength. These predictions are compared with the experimental results and providea practical means of assessing the influence of post-installed shear reinforcement.

1238THE LABORATORY INVESTIGATION OF EFFICIENCY OF NONCONVENTIONAL METHOD OF REPAIR CRACKED REINFORCED CONCRETE BEAMS

E Michalak, Rzeszow Univ of Technology, Poland

In order to study means of improving the behaviour of thick slabs without shear reinforcement a series of large-scale beams representing thick slabs was constructed and tested. Companion specimens were strengthened using drilled-in reinforcing bars to study the effectiveness of this repair technique. The behaviour of these beams, before and after strengthening, is compared. An additional experimental program using pull-out specimens enabled a study of the bond characteristics of drilled-in reinforcement having different embedment lengths. An analytical model to predict the bond-stress versus slip relationship enabled the development of a method for predicting the influence of the added shear reinforcement in improving the shear strength. These predictions are compared with the experimental results and provide a practical means of assessing the influence of post-installed shear reinforcement.

1265DEVELOPMENT OF CRITERIA FOR THE SELECTION OF REPAIR MORTARS IN ESTIMATING THE SERVICE LIFE OF REPAIRED REINFORCED CONCRETE COMPONENTS

Prof R Nsambu, Agostinho Neto Univ, Luanda, Angola & Prof. A M Gomes, TU Lisbon, Portugal

Carbonation induced corrosion of steel in concrete is one of the causes for deterioration of reinforced concrete structures and can lead to the need for repairs. This paper presents results of an extensive experimental program on repair mortars. The behavior of a set of three pre-dosed and three laboratory formulated repair mortars was studied. Important properties of these repair mortars were determined in an extensive experimental program that evaluated the mechanical properties, sorptivity, total immersion, permeability, electrical resistivity and carbonation penetration. Of the three commercially available predosedformulations one was based on a Portland cement mortar and the other two on polymer modified cementitious mortar. The three laboratory formulated repair mortars included one polymer modified and two cementitious mortars; these were used for comparison to the three pre-dosed mortars. Based on the results derived from the study of the carbonation rate and depth, sorptivity and compressive strength, the requirements for minimum reinforcement cover thickness of the mortar was evaluated for two exposure classes and the expected service life of concrete. From this information, a criteria for the selection ofrepair mortars was proposed based on the degree of sorptivity and compressive strength of the mortar.

1304 PERFORMANCE OF SHCC WITH BACTERIA FOR CONCRETE PATCH REPAIR,

M. G Sierra-Beltran, H.M.Jonkers, E.Schlangen, TU Delft, Netherlands

The overall performance of concrete patch repair systems depends on the durability of and compatibility between the concrete substrate and the repair material. This paper investigates the performance of a new type of SHCC material with embedded bacteria as a repair material. The bacteria are a healing agent to enhance the durability of the repair system. The bonding strength between the repair material and the concrete was studied by means of both pullout tests and flexural tests. Restrained shrinkage was measured in layered systems with the concrete substrate, whereas the durability of the layered systems was measured by means of rapid chloride migration tests and thermal compatibility tests. Detailed results reported in this paper show the potential of SHCC with bacteria as a concrete patch repair material with improved bonding and durability.

FRP Repair of Concrete

1172 STRENGTHENING BY CFRP GRID FOR RC SLABS APPLIED WITH PCM & ADHESIVES,

A Komori & T Abe, Nihon Univ, Narashino City & M Arazoe, Nippon Steel, Tokyo, Japan

The fatigue life of bridge road Reinforced concrete (RC) slab decreases with the repetition of movements caused by heavy vehicles due to formation of cracks in two directions. It is necessary to strengthen such structures with appropriate techniques in order to restore their full performance so as to ensure its safety and durability. This study evaluates the reinforcing methods of RC slabs using Carbon Fiber Reinforced Polymer-Grid (CFRP-Grid) applied with PCM on bottom surface of the slab, especially the effect of epoxy adhesive applied on CFRP-Grid and concrete surfaces. CFRP-Grid has several advantages such as high strength, high stiffness, lightweight, easy application, and excellent corrosion resistance when compared to the steel reinforcing bar. The reinforcing effects were evaluated as fatigue resistance of the RC slabs examined under the load carrying wheel tracking machine. Six types of RC slab specimens were investigated with different reinforcing conditions and the results were compared with each other in terms of equivalent number of cycles, deflection of slab, crack patterns etc. It is found that the existence of adhesive and effective height improves the fatigue resistance of the slabs greatly. In this paper, the effects of effective height of additional tension members and the epoxy adhesives will be discussed.

1162DYNAMIC IMPACT BEHAVIOUR OF REINFORCED CONCRETE BEAMS EXTERNALLY STRENGTHENED WITH CARBON FIBRE REINFORCED POLYMER (CFRP)

M Al-Farttoosi, M Y Rafiq, J Summerscales & C Williams, Plymouth Univ, UK

Reinforced concrete (RC) structures can be exposed to impact loading from various sources. They include ocean waves, earthquakes, tornados, crashing vehicles, explosions, and missiles. Carbon Fibre Reinforced Polymer (CFRP) matrix composites are widely used nowadays for strengthening and repairing of the structures. Our study aims to investigate experimentally the impact behaviour of RC beams externally strengthened with CFRP strip using near surface mounted technique (NSM). A new heavy drop weight impact test machine has been designed and manufactured. Four reinforced concrete (RC) beams were tested under drop weight. Two of the tested beams were considered as control beams without any strengthening, while; the other two beams were externally strengthened with CFRP strip. The impact response of the beams was compared in terms of impact energy, maximum and residual deflection, reaction force and mode of failure. There was a significant improvement the impact resistant of the beams strengthened with CFRP compared to unstrengthened beams. The experimental maximum and residual deflections were also significantly reduced using CFRP to externally strengthen the beams.

1176LONG-TERM BEHAVIOR OF FIBER REINFORCED POLYMER (FRP) REINFORCED CONCRETE PANELS WITH SECONDARY REINFORCEMENT

W Wang & JJ Myers, Missouri Univ of Science & Technology, Rolla, MO, USA

An experimental program was developed to investigate the effects of concrete shrinkage and secondary reinforcement ratio on concrete crack development and crack widths in panels reinforced with glass fiber reinforced polymer (GFRP) reinforcement. Six panels were constructed and exposed to exterior seasonal conditioning for approximately seven years: one steel reinforced concrete (RC) control specimen using the ACI 318-02 lower limit for secondary reinforcement, and five subsequent GFRP RC panels reinforced at varying reinforcement ratios. The final crack patterns of the six panels are discussed in this paper, and the maximum crack widths and the total average crack widths are compared in the six panels. At the same time, a finite element analysis (FEA) was also undertaken to analyze the crack patterns of the six panels at specific times and further

investigate the effects of concrete shrinkage on the panels. The results confirm that the GFRP panels yielded greater crack widths than a panel reinforced with mild steel bars. From FEM analysis, crack patterns demonstrated good correlation with similar crack distributions at earlier age to field observed data. However, the FEM analysis did not correlate at late ages in terms of crack rate growth to what was observed in this long-term experiment study.

1191 PREDICTING EFFECTIVENESS OF FRP IN CORROSION REPAIR,

C Khoe, CKPE LLC, Land O Lakes, R Sen & VR Bhethanabotla, Univ of South Florida, Tampa, FL, USA

Several independent studies have confirmed that fiber reinforced polymers (FRP) used for repairing corrosion-damaged concrete structures slow down the corrosion rate of steel in concrete. This suggests that in this application, FRP serves as a barrier to the ingress of moisture and oxygen critically important for sustaining electrochemical corrosion of steel in concrete. Since oxygen molecules are smaller than both water and chloride molecules they diffuse faster and therefore their permeation through FRP is more critical. This paper provides an overview of the findings from a comprehensive research study in which the oxygen permeability of epoxy, FRP, concrete and FRP-concrete systems was experimentally determined. This finding was subsequently used to develop a model that may be used to predict the long term performance of FRP used for corrosion repair and also to conduct parametric studies to identify FRP-concrete combinations most favorable for such repair.

1219 TEXTILE REINFORCED CONCRETE LAYERS FOR A DURABLE PROTECTION OF BUILDING SURFACES, C M Cruz, M Raupach, ibac, Aachen, Germany

Textile reinforced concrete (TRC) is a new composite material consisting of cement mortar and textile reinforcement. Extensive studies at the Technische Universität Dresden (University of Technology) and the RWTH Aachen University in the past decade have led to innovative solutions for both, new structures and for the conservation of existing structures. As an alternative to steel reinforced concrete, TRC is used for slender lightweight, filigree load carrying structures such as the pedestrian bridge in Albstadt, Germany (Hegger et. al., 2010).At the Institute of Building Materials Research (ibac) of the RWTH Aachen University, DURTEX, a durable, waterproof, and crack-bridging protective textile reinforced concrete layer, was developed for restoring concrete, steel reinforced concrete or natural stone structures. Pilot applications include the repair of the “Octagon vault” of the Aachener Dom (UNESCO World heritage site) and a pillar of the “Weir Horkheim” in Heilbronn-Horkheim. Both structures are permanently monitored to examine the conditions regarding cracking.Recent research addresses the further development and evaluation of the crack-bridging properties. Various textile reinforced layers are being tested with optical 3D-Video deformation analysis using the Aramis® system. Furthermore, studies will investigate the change in the crack-bridging properties of the DURTEX-layer under cyclic load and permanent load combined with rear water pressure.This paper provides an overview of the function principle of DURTEX and presents this principle for the surface repair of waterway engineering structures. A comprehensive paper describing the implementation of the DURTEX concept and results appeared in (Büttner et. al., 2013).

1232STUDY ON BEHAVIOUR OF CORRODED RC BEAM STRENGTHENED WITH CFRP ROD, AN EXPERIMENTAL AND FINITE ELEMENT MODELLING STUDY

B Almassri, A Kreit, F Al Mahmoud & R Francois Univ de Toulouse, F Al Mahmoud, Nancy Université, France

The near surface mounted reinforcement technique (NSM) is one of the promising techniques used nowadays to strengthen RC structures. In the NSM technique, the Carbon Fibre Reinforced Polymer (CFRP) rods are placed inside pre-cut grooves

and are bonded to the concrete with epoxy adhesive. This paper investigates the effectiveness of repair technique with Near Surface Mounted (NSM) carbon fiber-reinforced polymer (CFRP) rods to restore the mechanical performance of corrosion-damaged RC beams; it also studies the failure mode of the repaired corroded RC beam according to experimental and numerical modeling results. Experimental results and numerical modeling results of finite element FE model using ABAQUS software are obtained on two beams: one corroded beam which was exposed to a natural corrosion for 25 years and one control beam with no corrosion; both beams were 3 meters long. The two beams were repaired in flexion with one 6-mm-diameter NSM CFRP rod and then they were tested in three-points bending test up to failure. Overall stiffness and crack maps before and after repairing were studied. Ultimate capacity, ductility and failure mode are also discussed. The experimental results showed that the NSM technique increases the overall capacity (ultimate load capacity and stiffness) of control and corroded beams and allows restoring a sufficient ductility for repaired corroded elements and then restoring safety margin despite a non-classical mode of failure with the separation of concrete cover which happened in the corroded beam due to damage induced by corrosion. Finally some comparisons were made between experimental and FE numerical modeling results in order to study the specific mode of failure of corroded beam which happened by the separation of concrete cover.

1344 REPAIR OF REINFORCED CONCRETE T BEAMS WITH WEB OPENING IN SHEAR BY FRP SHEETS, N M Kassem & E E Etman, Tanta University, Egypt

The T-shaped cross section is favored because it adequately simulates the slab-on-beam construction method. However, the presence of opening in the web of a reinforced concrete beam resulted to many problems in the beam behavior. So an experimental study was carried out to investigate the shear behavior and the performance of FRP sheets in repairing simply supported reinforced concrete T-beams with web opening in the shear span. Four different orientations of FRP sheet vertically, horizontally, perpendicularly and inclined glued around the opening were used in the repairing operation. Also the effect of the size and location of the opening on the beam shear capacity were examined. Seven reinforced concrete T-beams with an opening, were constructed and tested under four-point loading. The experimental results of the tests in terms of crack patterns, load deflection relationship, steel strain and FRP strain are presented. The proposed technique for repairing T-beams with opening by FRP sheets was found very effective in upgrading the shear strength and enhancing the toughness which is important to improve the brittle shear failure.

1180 MECHANICAL PERFORMANCE EVALUATION OF FIBER REINFORCED CONCRETE THROUGH INDEX TESTS H-Y Jeon, Inha Univ, Nam-Gu, Korea

Effect of add of PVA fiber and carbon fiber on the mechanical properties of the fiber reinforced cement has been studied. The experimental variations were fiber length (3, 6, 9mm) and fiber weight fraction (0.25, 0.5, 0.75, 1.0 wt %). The compressive, tensile and flexural strength of the PFRC (PVA Fiber Reinforced Cement) and CFRC (Carbon Fiber Reinforced Cement) tend to increase with add of the fiber. The compressive strength of PFRC was the highest when the length of PVA fiber was 3mm, and that of CFRC was the highest when the length of carbon fiber was 6mm. The tensile and flexural strength of PFRC and CFRC were increased with increase of the fiber length and fiber content.

FRP Bars & Cable

1240 DEVELOPMENT & CHARACTERIZATION OF BASALT FRP BARS FOR CONCRETE,

M Hassan, HM Mohamed & B Benmokrane,,Univ of Sherbrooke, Canada

Recently, there has been a rapid increase in using non-corrosive fiber-reinforced polymers (FRP) reinforcing bars as alternative reinforcement for concrete structures, especially those in harsh environments. A new developed product, namely basalt FRP (BFRP) bars, has been introduced to be used as internal reinforcement for concrete structures. These bars have acceptable mechanical properties in normal environmental condition. However, to increase the worldwide interest in utilizing BFRP composites for civil infrastructure applications, short and long-term durability characteristics should be investigated. This paper presents preliminary laboratory test results on the physical and mechanical properties of newly developed 16-mm-diameter BFRP bars. Tensile test, transverse and interlaminar shear strength test and bond strength test (pullout test) were conducted on these bars. In addition, the durability performance of the mechanical properties for 1.5 months exposure time at 60oC was addressed. The test results indicated that the physical and mechanical properties fulfill the minimum requirements of CSA S807-10 and ACI 440-2008 to be used as non-prestressed reinforcement. More experimental tests, however, for short and long-term durability issue of the BFRP bars under different environments and exposure conditions are needed.

1209 BEHAVIOUR OF FRP UNDER EFFECTS OF FIRE, P Stepanek, D Horak, M Zlámal, & D Cairovic, Brno Univ of Technology, Czech Republic

New type of composite FRP reinforcement has been developed in recent years at Brno University of Technology, which can be used for reinforcing, strengthening and prestressing of concrete structures. Advantage of FRP reinforcement is namely resistibility against aggressive environment and therefore possibility to use smaller cover of reinforcement. High demands on durability and resistibility against outer (often extreme) influences as well are required in modern construction. Hence the next part of the research is focused on resistibility of FRP reinforced structures under effects of fire.

The paper deals with experiments oriented to observing the behaviour of prestressed and non-prestressed FRPRC panels subjected to fire effects as well as behaviour of FRP reinforcement itself. Results of experiments proved resistibility of FRP reinforced panels to fire effects and subsequently they were used for mathematical models.

The results of the tests performed on the FRPRC panels provide proof of the importance of understanding the behaviour of composite reinforcing bars alone and their behaviour along the anchoring zone in concrete members exposed to fire. In the tests providing a sufficient anchorage length (and thus enabling the transfer of load from the reinforcement into the concrete) proved to be a key feature enabling a structure to function over much longer time periods and even under surprisingly high temperatures.

Beside the test results commenting the resistibility of FRPRC panels, the first results covering the behaviour of FRP bars under effect of fire (and high temperatures in general) will be presented in the paper.

1239 LONG TERM TENSILE PROPERTIES OF CARBON FRP CABLE,

B Benmokrane, A H Ali & H M Mohamed, Univ of Sherbrooke, Quebec, Canada & A El-Safty, Univ of North Florida, Jacksonville, FL, USA

This paper presents the physical, mechanical, and durability characterization of Tokyo Rope carbon-fiber composite cables (CFCCs). Specimens were exposed to alkaline solutions for 1000, 3000, 5000, and 7000 hours at elevated temperature (60°C) to accelerate the effect of the concrete environment. The alkali exposure condition was based on CSA S806 and ACI 440. The durability performance of the Tokyo Rope assessed by conducting tensile tests on the specimens after different exposure periods.

The test results revealed that the average tensile-strength retentions of the conditioned CFCCs could be affected with accelerated time and temperature in alkaline solutions. While some experimental work on characterizing the durability of CFCC has been completed, other studies are still ongoing at the University of Sherbrooke, such as the effect of alkaline conditioning under prestressing load.

NDT of Composites

1253 PROBABILISTIC ANALYSIS OF STEEL FIBER R.C. BEAMS UNDER TORSION BY AE,

A Behnia, HK Chai & MZ Jumaat, Univ of Malaya, Kuala Lumpur, Malaysia & T Shiotani, Kyoto University, Japan

This paper presents the physical, mechanical, and durability characterization of Tokyo Rope carbon-fiber composite cables (CFCCs). Specimens were exposed to alkaline solutions for 1000, 3000, 5000, and 7000 hours at elevated temperature (60°C) to accelerate the effect of the concrete environment. The alkali exposure condition was based on CSA S806 and ACI 440. The durability performance of the Tokyo Rope CFCC tendons was assessed by conducting tensile tests on the specimens after different exposure periods. The test results revealed that the average tensile-strength retentions of the conditioned CFCCs could be affected with accelerated time and temperature in alkaline solutions. While some experimental work on characterizing the durability of CFCC has been completed, other studies are still ongoing at the University of Sherbrooke, such as the effect of alkaline conditioning under prestressing load.

1306INNOVATIVE LABORATORY INVESTIGATION OF PROBLEMATICS IN CERAMIC TILINGS BY MEANS OF ACOUSTIC AND ELECTROMAGNETIC NON-DESTRUCTIVE TECHNIQUES

C Colla, E Gabrielli & F Ubertini, Univ of Bologna, Italy

Ceramic materials are assuming a pre-eminent role as elements of external claddings in buildings, for floorings, wall linings and other diversified uses thanks due their characteristics of strength and durability. With respect to traditional ceramic tilings, their use is widely spread in many Countries but the assessment of the health state of existing tilings or the preventive conservation of historic tilings has not yet been properly addressed. The durability of ceramic tilings in real environments is strictly connected to problems which may arise at the time of laying or later in their life-cycle. Most common problematics are cracks or insufficient strength of support, discontinuities at tile/support interface, moisture below the tiles, detachment between adhesive and tiles or between adhesive and support, all of which may occur during or after tile installation. It is evident a lack of appropriate non-destructive testing (NDT) approach for the investigation of these issues on site and the reliability of testing techniques for these purposes has still to be assessed. A laboratory experimental campaign was carried out in Bologna University on several on purpose built ceramic tiling specimens, simulating 7 of the above mentioned defects. The data acquisition was undertaken via acoustic (sonic and impact-echo tests) and electromagnetic (IR thermography and GPR radar) non-destructive diagnostic techniques. A comparison of the outcome from the different techniques was foreseen. In this paper, selected results are presented. One of the aims of the work is to develop a diagnostic procedure to be further used on-site for the verification of the conditions of new or existing tilings.

Sustainable & Recycled Materials

1231 SUSTAINABLE CONCRETE IN QATAR – A CASE STUDY,K E Hassan, TRL QSTP-B, Doha, Qatar, JM Reid, TRL, Wokingham, UK, & MS Al-Kuwari, Qatar Standards, Doha, Qatar

A major construction programme is underway in Qatar to develop state-of-the-art infrastructure for hosting the World Cup in 2022. One of the main challenges facing the rapidly developing infrastructure is the four-fold increase in aggregate supply needed to meet the demand for the proposed construction programme. Qatar has a shortage of natural aggregate and the industry relies on imported aggregate for use in concrete and asphalt. Varying quality of imported aggregate and limited port capacity are the reasons for considering other options. Recycled aggregates are potentially available in large quantities in Qatar but have had limited use in construction to date.This paper presents a leading building trial on the use of recycled materials in concrete applications. The main identified waste streams of excavation waste, construction & demolition waste and incinerator bottom ash were subjected to extensive testing to optimise their use in concrete blocks and structural C40 concrete. Selected mixtures were used for the construction of three trial buildings to demonstrate application in practice. Laboratory and site testing indicated at least similar strength and durability-related properties of the concrete made with recycled aggregate and imported aggregate. The results are being used to update the Qatar Construction Specification.

1201 CEMENT COMBINATION CONCRETES: WHERE LESS CEMENT IS MORE,

D Dunne, AECOM, Birmingham, P McKenna, CH2M Hill, Glasgow, Dr M Newlands, Univ of Dundee, A Waite, CH2M HILL, Worcester, UK

Concrete finds application in every economy around the world, making it a vitally important construction material. Based on 2012 figures, its production is estimated to be in the region of 3.8 billion tonnes per year worldwide. In the UK, it is estimated that 22.5 million m3 is produced alone (MPA, 2006). Concrete is a sustainable construction material however, the material has drawbacks. The primary issue is where producing one tonne of Portland cement (CEM I), is reported to release an equivalent quantity of carbon-dioxide (CO2) into the atmosphere (BCA, 2007). Hence, methods of reducing CO2 emissions and embodied CO2 (CO2e) values are essential. This is required to ensure that concrete remains competitive and continues to contribute to sustainable development. This paper will demonstrate the advantages that can be achieved when the total PC (CEM I) contents of concrete are reduced, and replaced with a percentage of additions material. This paper will discuss cement and addition materials blended as binary blended cement in ternary blended cement combination concretes. Concrete durability performance will be shown to improve whilst overall CO2e values attributed to these concretes can be reduced.

1214FLY ASH CONCRETE MADE OF HIGH QUALITY RECYCLED AGGREGATE PRODUCED BY PULSED POWER TECHNIQUE

E Arifi & M Shigeishi, Kumamoto Univ, Japan & A Zacoeb, Brawijaya Univ, Malang, Indonesia

Recently, Kumamoto University has developed pulsed power technique which has been proven to reproduce high quality recycled aggregate. It is well known that fly ash as a by-product of the combustion coal in thermal power plant has been widely used as supplementary material in concrete production. Therefore, to promote sustainable construction which has been increasingly developed, the use of fly ash as cement replacement in concrete made of high quality recycled aggregate produced by pulsed power technique was investigated. Results showed that concrete made from recycled coarse aggregate by pulsedpower technique had similar strength and drying shrinkage to natural coarse aggregate concrete, while fly ash concrete made of high quality recycled aggregate produced by pulsed power technique indicated to reduce drying shrinkage. Furthermore, two-stage mixing approach (TSMA) for making recycled aggregate concrete was applied to improve its compressive strength and tensile splitting strength.

1228 RECYCLING OF POST WAR DEMOLISHED BUILDING WASTES FOR CONCRETE INDUSTRY IN LIBYA, M Tughar, KA Harhour, Al Mergeb Univ, Garaboli, Libya

After end of the liberation war of Libya in Oct. 20th. 2011, and as a result of that, a huge amounts of demolished building waste materials has been recorded. These represent wastes of destruction materials which cause a storage and environmental problems. Environmental problems are always considered as a national priorities to the local authority of the Libyan Interim Government (LIG) to find a rapid and safe solutions to this case. A global research program is initiated to study recycling building waste materials in manufacturing of concrete. The first part of this on going research program is devoted to buildings waste materials or products of destruction; crushed granite, marbles, and crushed concrete are recycled as concrete coarse aggregate. A large number of concrete mixes manufactured using the pre-mentioned waste materials was tested under compressive strength, flexural and splitting tensile strength, the workability of concrete mixes was also tested. The modulus of elasticity of the tested concrete mixes was estimated. Encouraging recycling and use of building waste materials in the production of normal-strength concrete (NSC), and thereby preserve natural resources and reduces the environmental pollution in new Libya is the main feature of the paper.

1308 DESIGN OF NEW RECYCLED CONCRETES WITH CERAMIC WASTE,

C Medina Martínez, Univ of Extremadura, Cáceres, M Frías & M I Sánchez de Rojas, Eduardo Torroja Institute, C Thomas & JA Polanco, Univ of Cantabria, Santander, Spain

The durability and leachability of concrete in contact with public drinking water are among the properties of this material with the greatest impact on human safety, particularly when manufactured with recycled materials. These properties also have economic and environmental implications. The research reported here aimed to assess the effect of aggregates made from ceramic sanitary ware on the leachability of the elements present in concrete made with these materials, as well as on the durability of the concrete itself. Permeability to water and gas (O2 and CO2) and the leachability of these new recycled concretes, in which 25 % of the natural coarse aggregate was replaced with recycled ceramic coarse aggregate, were compared to the same parameters in a reference concrete. Their physical and mechanical properties were likewise compared. Recycled ceramic aggregates were found to have no adverse effect on concrete durability, while none of the leached elements exceeded the thresholds specified in the existing legislation on water for human consumption.

1263 PROPERTIES OF GREEN ENGINEERED CEMENTITIOUS COMPOSITES INCORPORATING VOLCANIC MATERIALS,

KMA Hossain & MS Anwar, Ryerson Univ, Toronto, Ontario, Canada

This paper presents fresh, mechanical and durability properties of new form of engineered cementitious composites (ECCs) produced by incorporating volcanic ash as replacement of Portland cement. Fresh state properties were determined by slump flow, flow time, heat of hydration, initial and final setting time tests. Mechanical, transport, and durability properties were determined by measuring compressive/flexural strengths, water porosity, water absorption, rapid chloride-ion permeability and freezing-and-thawing resistance. The use of volcanic ash does not adversely affect fresh and strength properties as well as strain hardening and multi-cracking characteristics of ECC. The study demonstrates the viability of producing greener, sustainable and cost effective ECCs using volcanic materials having satisfactory fresh, mechanical and durability properties.

Masonry Structures

1159 ANALYSIS AND CLASSIFICATION OF HISTORIC CONSTRUCTION WITHIN THE NORTH-EAST OF ENGLAND

M Corradi, AI Osofero, K Coventry, A Richardson, C Udeaja & T Vo, Northumbria Univ, Newcastle upon Tyne

Utilising a numerical index, developed to classify the condition of historic masonry buildings in the Umbrian region of Italy, a clear description of the typological and morphological characteristics of historic masonry structures in the North East of England, is presented in this paper. This description facilitates the understanding of the mechanical behavior of historic masonry typologies and assists in determining the most suitable analysis and design strategy to inform approaches to the conservation and preservation of historic buildings. This paper describes the method adopted and applies the approach to wall sections selected throughout the county of Northumberland. On the basis of this preliminary investigation, a comprehensive research program has been recently carried out at the University of Northumbria at Newcastle.

1335TEXTILE REINFORCED MORTAR SYSTEM AS A MEANS FOR CONFINEMENT OF MASONRY STRUCTURES EXPOSED TO ELEVATED TEMPERATURES.

T Krevaikas, Xi’an-Liverpool University, Suzhou, China

The present paper demonstrates the initial results of an ongoing experimental and analytical research programme on masonry structures confined with Textile Reinforced Mortars (TRMs). The application of externally bonded TRM as a means of masonry confinement, a subject never addressed before, is investigated in this experimental programme. In the present experimental stage three series of uniaxial compression tests, were conducted on small scale masonry columns having as the only variable the ambient temperature. The purpose of this experimental investigation was to examine the performance of TRM jackets exposed to elevated temperatures. All specimens had rectangular 240*240 mm2 cross-sections with a corner radius of 20 mm and were strengthened with one layer of Carbon fiber textile having a weight of 220 g/m2 and a tensile strength of 8.40 MPa. The carbon fiber textiles were externally bonded to masonry using mortar-as a binder-that contained polymeric additives. A total of 15 specimens were divided into three groups comprising three, three and six specimens, respectively. The first two groups each comprising three specimens were tested after 8 hours of exposure to 100 oC and 200 oC degrees respectively. The six specimens in the third group were tested under room temperature conditions. In addition three unreinforced control specimens were prepared (one for each group) and tested under the same environmental conditions. From the results obtained, the performance of the TRM jacket proved to be unaffected by the exposure to elevated temperatures and this gives an initial advantage as compared with the FRP strengthening technique. Further experimental and analytical investigations will be made in the future in order to examine the behavior of TRM confined masonry axially loaded under elevated temperatures and/or real fire conditions.

1173

STRESS STATE ANALYSIS & IDENTIFICATION OF LOAD-BEARING CAPACITY OF BRICK MASONRY COLUMNS WITHOUT AND WITH INITIAL CRACKS REINFORCED WITH COMPOSITES BASED ON HIGH-STRENGTH FABRICS LOADED BY CONCENTRIC COMPRESSION

J Witzany, R Zigler, & J Kubat, Czech Tech Univ in Prague, Czech Republic

The experimental research completed to-date (NAKI DF12P01OVV037, 2012-2015) has manifested that the efficiency of the reinforcement of masonry columns by wrapping in “non-prestressed” fabrics of high-strength fabrics depends on the mechanism applied in the masonry failure process due to loading in concentric compression and on the deformation (strain) characteristics of the masonry. In the case of masonry loaded by compression, the failure mechanism characterised by the

appearance and development of tensile cracks passing in the direction of compressive trajectories, accompanied by a progressive growth in horizontal deformations, may be assumed (Witzany et al., 2011). By its tensile strength, the fabric (composite) prevents the development of horizontal deformations x and vertical tensile cracks thus contributing to the increase in the load-bearing capacity in compression. The fabric is activated by the forced deformation effect caused by transverse (horizontal) deformations of compressed masonry. In the area of the column’s wrapping in high-strength fabrics, the multiaxial stress state of masonry is significantly applied after the ultimate load-bearing capacity of wrapped masonry columns has been reached.The paper presents the results of experimental research (NAKI DF12P01OVV037, 2012-2015) of masonry columns without initial cracks wrapped in composites based on carbon fibres and masonry columns partially degraded by tensile cracks, additionally wrapped in composites based on carbon fibres applied along the whole column’s length.

1230 DETECTING DEGRADATION IN REINFORCED MASONRY WALLS BY ELECTROCHEMICAL NDT,

SR Cillán, I Martinez, Instituto Ciencias de la Construcción Eduardo Torroja, Madrid, Spain

Existing buildings decay with the passage of time, and as a result, continually require maintenance and rehabilitation. When considering existing reinforced masonry structures, testing is often necessary to complete structural analysis in preparation for rehabilitation or repair.

The corrosion of reinforcements has resulted to be one of the most frequent causes of their premature failures. Monitoring the corrosion rate, assuming the uniform corrosion and the loss in diameter decreases linear with the corrosion rate, allows calculating the remaining load carrying and the safety of the structure. The main investigation of corrosion researchers is detection and measuring of defects in the initial stage of corrosion process. Even though there are a few methods of measuring true, instantaneous rate of corrosion, based on electrochemical methods, no references about its application to masonry structures are found.This paper proposes a new methodology to evaluate reinforced masonry structures advanced electrochemical techniques. These non-destructive techniques can be used as an efficient tool to contribute to the diagnosis of the conservation state of reinforced masonry wall and to monitor the restoration treatment.

The experimental work is carried out pioneering a study of the durability of these reinforcements through on site evaluation by non-destructive electrochemical techniques. Some preliminary results in the application of the proposed evaluation methodology to different masonry constructive systems are presented.

1220 STRUCTURAL ANALYSIS OF MASONRY HISTORICAL CONSTRUCTION: RIBBED-VAULT CASE STUDY

T Parent, N Domede, A Sellier, Univ de Toulouse, C Dujarrier, Ginger CEBTP, Elancourt, France

The aim of the research, carried out in association with Ginger CEBTP, was to understand the causes of structural pathologies observed on a historic heritage monument. The edifice studied is a gothic church built in the centre of Paris during the 13th century using the ribbed-vaults technique. The first step of the research consisted of on-site investigations. Secondly, laboratory tests were performed and structural pathologies identified. Then FEM modelling was used to identify the mechanical behaviour of one bay of the church. An orthotropic damage model featuring a localized crack reclosure approach implemented in the finite element code CAST3M© was used. The loading history of the structure was simulated from its

construction to the present day. The comparison of cracks and displacements measured on site and those obtained by the numerical structural analysis gives an understanding of the mechanical behaviour of this monument dating from the Middle Ages.

1186EXPERIMENTAL TESTS ON FULL SCALE FRP/FRCM CONFINED MASONRY COLUMNS SUBJECTED TO AXIAL LOAD

F Micelli, A Aiello, Univ of Salento, Lecce, M Di Ludovico, A Prota, G Manfredi, Univ of Naples, R Angiuli, CETMA, Brindisi, Italy

The results of an experimental program performed on full-scale masonry columns strengthened with different composite systems are provided in the present paper. The same kind of study has been previously performed by the authors on medium scale masonry columns, using the same materials for both the masonry core and for the FRP systems. Masonry was formed by prismatic block of calcareous stone and joints were made by using a lime/pozzolan based-mortar, with a thickness of 10 mm. The experimental program involved six full scale masonry columns with a square cross section having a side length of 40 cm, and 210 cm height. The following test schemes were studied: control unconfined columns; column with continuous wrapping by using unidirectional Glass FRP (GFRP) sheets; column with discontinuous wrapping by using GFRP unidirectional sheets; column with continuous GFRP wrapping and internal carbon FRP (CFRP) bars bonded in the transverse directions with an epoxy resin; column wrapped with continuous alkali resistant GFRP grid and steel spikes bonded together in lime based matrix. The experimental results are presented and discussed in the paper; failure modes, strength and ductility are discussed by comparing the different strengthening techniques that were tested. The results confirmed that FRP-confinement may be considered an effective technique able to increase the load-carrying capacity and at the same time the axial deformability of the compressed columns. A ductile behaviour was observed in confined columns as also expected from the previous results available for small and middle scale columns. A comparison between experimental data and theoretical predictions provided by the new analytical model found in the guidelines of the CNR-DT 200/2012 technical document is also illustrated.

1346 AN EXPERIMENTAL INVESTIGATION OF MASONRY WALL ON A STEEL PLATE-MASONRY COMPOSITE BEAM

DH Jing, T Wu, SY Cao, Southeast University,Nanjing, China & JF Chen, Queen’s University Belfast, UK

This paper presents an experimental study on the seismic behaviour of steel plate-masonry composite (SPMC) columns consisting of irregular masonry columns with steel plates attached to all sides using a combination of tie bolts and epoxy adhesive. The study included the test of four L shaped and four T shaped SPMC column specimens under combined axial force and cyclic lateral loading. The effects of axial loading level and bolt spacing were also investigated. Test results including the ultimate lateral strength, ductility and energy-absorption capacity are presented. This study adopted cold-formed steel plates, avoiding weld fracture which occurred in previous studies. Test results also show that L shaped columns offer substantial post-buckling strength and stiffness, which are not evident in most T shaped columns.

1294EVALUATION OF EFFICIENCY OF AIR ABRASIVE CLEANING ON OLD MASONRY BUILDINGS USING GREYSCALE IMAGING ANALYSIS

H Reza, N Gupta, Edinburgh Napier Univ, B Zhang, Glasgow Caledonian Univ, UK

The stone cleaning and restoration of historic buildings is a crucial strategy for maintaining the aesthetic appearance, integrity and quality of the fine art, construction method and architecture of previous civilisations. In this study, advanced greyscale imaging analysis was conducted using Adobe Photoshop 6 on the surfaces of masonry stones, taken from old buildings, to accurately assess the efficiency of building cleaning. Five commonly used masonry stones for those buildings were selected,

including granite, limestone, marble, yellow sandstone and red sandstone. Seven abrasives were adopted for air abrasive (sandblasting) cleaning, including steel plant by-product slag (coarse, medium and fine), recycled glass (coarse, medium and fine) and natural abrasive. Also the reductions in thickness were also monitored for assessing the cleaning efficiency. The cleaning degrees at different stages were evaluated using greyscale image photos, converted from original colour ones, together with reductions in thickness, where a lower greyscale value normally corresponded to a darker and dirtier surface and a higher greyscale value to a brighter and cleaner surface. In general, greyscale continuously increased with the cleaning time and tended to be stable when the surface became fully cleaned. Thickness reduction monotonically increased with the cleaning time, which could also be used to assess the cleaning efficiency in combination the cleaning time. The most efficient building cleaning case would be the one with the shortest cleaning time and smallest thickness reduction. The harder abrasives with smaller particles sizes were confirmed to be more effective, e.g. the medium or fine slag and glass in this study.

Historic Conservation

1307 STABILIZATION OF BAROQUE WALL USING WIDENING OF FOUNDATIONS & VERTICAL PRESTRESSING

L Klusáček, Z Bažant & R Mitrenga, Brno Univ of Tech,Czech Republic

Declined baroque wall with pillars built in 1673 was stabilized by widening of the foundations and vertical post-tensioning using protected cables (monostrands). The post-tensioning was used not only in the vertical direction but also in the horizontal direction to rich reliable connection between the widening and the old basement strip.

1234THIN CONCRETE VAULT OF THE PARABOLOIDE OF CASALE, ITALY. INNOVATIVE METHODOLOGIES FOR SURVEY, STRUCTURAL ASSESSMENT & CONSERVATION INTERVENTIONS

C Bertolini, S Invernizzi & F Chiabrando, Politecnico di Torino, Italy

The former clinker warehouse, also known as the “Paraboloide” of Casale is an architectural symbol of the concrete Italian industrial heritage. The constructive technology and the structural shape of the thin concrete vault are comparable to the outstanding realizations achievements of the beginning of the XXth century, as for examples the works of E. Torroja and of P.L. Nervi. The metric survey has been achieved using high resolution terrestrial laser scanning technology (TLS), in order to obtain an accurate 3D model with uniform level of detail and precision, in addition to a continuous metric information for each portions and elements of the structure. This procedure allowed a proper reading of the structural typology of the building and the recognition of possible design and construction principles, essential for the conservation project. The laser survey was carried on both intrados and extrados of the huge parabolic vault, performing a high number of scan positions, located inside and along the outer limit of the building. The model processing has been mainly directed to the evaluation and control of geometrical features of the reinforced concrete membrane. The image texturing of the complex surfaces has been performed by the Focus 3D Faro integrated camera, with principal axis coaxial with laser ray. Some other photogrammetric stripes, focused on interesting portions of the structure, enabled to accomplish the detailed inquiries of the shape model with a materials decay analysis. The structural assessment combined a detailed finite element analysis. The analysis was performed with the software Diana (TNO, The Netherlands), accounting for smeared cracking and the presence of reinforcements. Finally, the paper summarizes the main criteria for interventions, according both to structural safety requirements and conservation prescriptions, enhancing the extraordinary innovative value of this particular cultural heritage.

1178DETERMINATION OF PROPERTIES OF SELECTED NANOTEXTILES – RESISTANCE TO UV RADIATION AND DIFFUSION EQUIVALENT AIR LAYER THICKNESS

K Kroftova, M Smidtova, Czech Technical Univ in Prague, Czech Republic

The paper presents partial results of experimental testing of nanotextiles applied on historic plasters implemented at the Faculty of Civil Engineering, CTU in Prague* as part of the project “Progressive non-invasive methods of the stabilisation, conservation and strengthening of historical structures and their parts with composite materials based on fibres and nanofibres”. The study is focused on the development of a methodology for the conservation of historic plasters by nanotextile-based coatings preserving their characteristic material properties so that their service life may be extended. The current experimental research dealing with historic plasters will continue by investigating timber and stone test specimens. The paper deals with the determination of the resistance of nanotextiles to UV radiation and the comparison of the diffusion equivalent air layer thickness of several types of historic plasters fitted with nanotextiles.

1184 STRENGTHENING INTERVENTIONS OF THE ROMAN TEMPLE OF SAN TOMÈ IN BERGAMO C Rossi, PP Rossi, R.Teknos s.r.l., Bergamo, Italy

The Temple of San Tomè near Bergamo is one of the most singular Romanesque structure. The church has a circular plan and it was built in the first centuries of the Christian Era. A diagnostic investigations campaign was carried out in 1980 in order to analyse the structural characteristics of the stones masonry and to check the property of the soil foundation. In the same period a monitoring system was installed to observe the deformation behaviour of the walls interested by important vertical cracks. During the observation period of about 27 years (from 1984 to 2012) a progressive opening of the cracks was observed. A strengthening intervention was designed in order to restrain the radial deformations of the structure. The effect of the strengthening interventions was analysed by means of a finite element mathematical model of the whole structure. The paper describes the design criteria and the execution of the strengthening interventions that were completely covered by the stone slabs of the roof.

1259 IN-SITU LOAD TEST OF AN HISTORIC STAIR RAIL MADE OF LIME STONE

M Gutermann, W Malgut, Univ of Applied Science Bremen, Germany

The building of the Hessian State Museum in Darmstadt, Germany, has been built in the late 19th century and is under monument protection. Since 2007 the museum is closed for reconstruction measures. Unfortunately the height of the handrail was assessed too low for modern utilization. It was planned to add an additional handrail on top of the old construction. Since neither construction details nor static calculation could be found, the proof of sufficient load carrying safety had to be proven by load tests. By assessing experimentally the existing load carrying capacity using load tests, the allowed live loads were identified. This article deals with the problem analysis, the development of a load and measurement concept and the eventful execution of the tests.

1312 DYNAMIC MONITORING FOR POST-EARTHQUAKE ASSESSMENT OF A MASONRY TOWER Prof C Gentile & Prof A Saisi, Politecnico di Milano, Italy

After the earthquakes of Spring 2012, an extensive research program had been performed to assess the state of preservation of the Gabbia Tower, the tallest historic tower in Mantua. The post-earthquake investigation (including direct survey, historic

and documentary research, testing of materials and ambient vibration tests) highlighted the poor state of preservation of the upper part of the building and suggested the installation of a dynamic monitoring system, with seismic and structural health monitoring purposes. After a brief description of the investigated tower and its state of preservation, the paper summarizes some results of the long-term dynamic monitoring.

1248 SIGNIFICANCE OF DETAILED SURVEY FOR ADEQUATE GROUTING

A Miltiadou-Fezans, J Dourakopoulos, P Giannopoulos, Hellenic Ministry of Culture & Sports, Athens, Greece, A Manzo, Politecnico di Milano, Italy

Grouting constitutes one of the most common techniques applied for the repair and strengthening of masonry structures or fissured architectural members, when interconnected voids in adequate percentage are present. This technique can also be appropriate for the in situ consolidation of detached and cracked mosaics and wall paintings. Although grouting is a non-reversible technique, it is well accepted even in monuments of high historical and architectural value, since it has the advantage to retrieve the continuity, cohesion and strength of the damaged structures without altering their morphology, geometry and load-bearing system. To achieve this goal, the design of the grout composition should satisfy a series of performance requirements involving injectability, strength and durability aspects. Nevertheless, the careful design of the grout composition cannot by its own ensure the successful completion of the grouting intervention. Evidently, particular care has to be taken for the execution of the whole intervention in situ. One of the major parameters affecting the adequate application of the technique is the installation of the grout entrance and exit tubes so as to reach the internal voids, fissures and discontinuities present between masonry leafs or between leafs and infill material. In this paper, the importance of a detailed geometrical survey of all masonry faces and their pathology will be presented, together with the methodology to be followed in order to design the grid of grouting tubes to be installed. Furthermore, the type of tubes and the way of their installation will be described. This procedure consists of different phases, which need a detailed design and programming and constitute a prerequisite for achieving strength increase and improvement of the monolithic behaviour of the damaged masonry. The whole procedure will be highlighted using as an example the case of the piers of the drum of the Katholikon of Daphni Monastery.

1363THE TIBURIO OF THE CATHEDRAL OF MILAN: STRUCTURAL ANALYSIS OF THE CONSTRUCTION AND 20TH CENTURY FOUNDATION SETTLEMENTS

D Coronelli, C di Prisco & F Pisanò Politecnico di Milano, Italy, S. Imposimato, FEAT, The Netherlands, S. Ghezzi & M. Pesconi, Politecnico di Milano, Italy

The history of the construction of the tiburio of the Cathedral of Milano is studied in relation to the load-bearing system and the foundation soil of the whole building. The structure is analysed by preliminary limit analysis. The characteristics of the tiburio and supporting piers are shown. The load path is studied, considering the construction of the supporting arches in the 15th century and the final configuration of the 18th century. An analysis of the foundation settlements caused by lowering of the water table in the 20th century is carried out by 3d finite element analysis, and compared to results from the monitoring started since the 1950s. An elastic model of the soil under the whole cathedral and the nearby buildings is used first, followed by nonlinear analyses of the soil beneath one of the main piers. The results provide an interpretation of the damage caused by the differential settlements at the end of the 20th century. The models are a basis for the prediction of future events in the structural history of the Duomo di Milano.

1334 CONSEQUENCES OF A WRONG DECISION: CASE STUDY OF CHILADAR MONASTERY GREAT FIRE,

N Kurtovic Folic, University of Novi Sad, V Milanko, High technical school, Novi Sad, A Bogdanov, Ministry of Finance, Tax & Administration, Novi Sad, Serbia

In this paper we analyze the causes and consequences of the Great Fire, which occurred on March 4th 2004. The fire destroyed much of the complex of the Serbian Orthodox monastic community on Mount Athos in Greece. Serbian Orthodox monastery of Chilandar was founded in 1198. It was developed and expanded over the years. Today, Chilandar is the spiritual and religious centre of the Serbian people and since 1988 is part of the World heritage. The fire originated in a dormitory built in 1814, in the upper area, around one of the chimneys. These quarters were conserved and partly rebuilt in the late twentieth century. Due to the lack of any masonry partitions in the attic, the fire spread rapidly, scorching the wooden elements of the roof and floor structures. After extinguishing the fire, all the wooden elements have disappeared; only parts of the outer walls were partly preserved.Lessons to be learned from this example, in which the desire to preserve as much of original fabric as it could be done, without introducing fire protection walls, results in dramatically loss of historical building, are important for all entities that are responsible for fire protection and preservation of cultural heritage in Serbia. Original building materials and construction of huge part of the Chilandar monastery are permanently lost, not to mention a huge financial loss incurred by investing in building that not so long ago was conserved and partially restored.

Timber Structures

1146 JOINTS IN HISTORICAL TIMBER STRUCTURES, P Fajman & J Máca, CTU Faculty of Civil Engineering, Prague, J Kunecký, ITAM AS, Prague, Czech Republic

Traditional joints used in the restoration of historical timber structures are not designed according to standards. The forces in the most common vertical splice skew joint with a bolt are not known. Only their relations or limits may be derived analytically, even this, however, is very valuable for practice. In this way, practising engineers get some easy assistance for their designs employing joints. Accurate values may be obtained from measurements or experiments.

1143 HARDENING LIGHT FRAME TIMBER STRUCTURES FOR COASTAL HAZARDS,

A Lamanna, S A Arias, Eastern Kentucky Univ, Richmond, USA

A wealth of forensic information has been gathered on the damage caused by coast hazards. The average annual normalized damage from hurricanes in the United States is about $10 billion. Resistance to storm surge and hurricane and tropical storm level winds is addressed in new structures by the building codes; however, changes in building codes are not reflected in existing structures. This paper presents an overview of mitigation techniques applicable to light frame timber structures that are based upon the requirements for new structures in the recent International Building Code.

Increasing the resistance of existing structures to storm surge and high winds can decrease the damage in an extreme event, thereby decreasing the cost to repair the structure. A cost analysis will be performed in order to determine the hardening cost. The estimated cost for individual methods of hardening 210 m2 (2,260 ft2) and 80 m2 (861 ft2) model light timber frame buildings will be discussed. These model homes reflect the average size homes for the United States and for the United Kingdom.

Metallic Structures

1211 TENSILE TEST OF STEEL PLATE BONDED WITH JOINTED CFRP STRAND SHEETS

T Miyashita & M Nagai, Nagaoka Univ of Technology, Y Okuyama, Nagano National College of Technology, Y Hidekuma & A Kobayashi, Nippon Steel, Tokyo, A Kudo, Metropolitan Expressway Co. Ltd Japan

The objective of this study is to determine the reinforcing effect and strength characteristics of the bonding method using carbon fiber sheet in joints for steel members. A uniaxial tensile test of steel plates bonded with CFRP strand sheets with joints was carried out. The results indicate that there was no fracture or delamination of the sheets until reaching the yield stress of Steel for Bridge High-performance Structures 700, which is a grade of high-strength steel, when the gap length of the joint was greater than or equal to 20 mm. In test pieces whose strengths were below the yield stress of the steel, cohesive failure of the adhesive occurred at the edge of the joint, and cracks propagated in the joints. Moreover, numerical analyses were conducted to investigate stress distribution.

1241 REPAIRING METHOD FOR STEEL CROSS SECTION LOSSES BY CFRP

Y Hidekuma & A Kobayashi, Nippon Steel & Sumikin Materials Co, Ltd, Tokyo, T. Miyashita & Y Okuyama, Nagaoka Univ of Technology, T Ishikawa, Kyoto Univ, Japan

Steel structures are often corroded by various mechanisms, and their performance decreases dramatically due to corrosion. As a repairing method for corroded steel members, a method to bond the carbon fiber sheets with resin to the steel member had been developed. Commonly, for steel members on which axial force is applied, the carbon fiber sheet having the tensile stiffness equal to or greater than that of the cross-section loss is bonded to the steel member. However, in the case of such repairing method, it has been reported that the reinforcing effect may not be sufficient. Therefore, in this study, a new repairing method was proposed for the steel member having cross-section defects. In this newly designed method, the carbon fiber sheets, having the inverse number times tensile stiffness of the residual ratio at the defected parts of the steel, are bonded. In order to confirm the validity of proposed method, the tensile test and the numerical analysis were carried out. The result showed that the tensile stiffness at the cross-section defected part is recovered by equal to or greater than the original tensile stiffness by bonding the carbon fiber strand sheet.

Coastal Structures

1153 INVESTIGATIONS & REPAIRS TO GOREY PIER, JERSEY, S Hold, Arup, Cardiff, UK

This paper describes how a long period of desk study and research, monitoring the structure over several years in conjunction with using new surveying technology using virtual modelling has enabled a very complicated and difficult marine structure to be saved. The use of these new technologies has also refined the focus, or costs, for repairs to be narrowed down to only one section of the breakwater at the pierhead. The original 400 year old Heritage structure had a partial collapse at the head in 1964 and in the past decade there has been an acceleration of the visible signs of damage reoccurring close to the original failure. Detailed investigation and modelling of the breakwater and pierhead has allowed an understanding of the behaviour of the structure and a concept for strengthening and repair to be achieved.

1351 STRUCTURAL CAPACITY REDUCTIONS DUE TO RE-BAR CORROSION IN COASTAL CONCRETE,

SMD Aguiar, Edinburgh Napier Univ & MJ McCarthy,Univ of Dundee, UK

Global sea levels are rising due to climate change and reinforced concrete coastal structures are essential components of defence against associated effects including, flooding and coastline erosion. The high chloride content of these environments is a major cause of reinforcement corrosion and consequently potential structural capacity reduction. In this paper, real-size reinforced concrete walls under both sustained loading and continuous exposure to chloride-laden conditions were investigated. The experimental programme was carried out mainly by destructive tests made periodically over 24 months. These enabled the effects of loading and subsequent flexural cracking (intersecting cracks) on corrosion propagation, and structural capacity and stiffness to be quantified. The results showed that corrosion was greater when flexural cracks were present and that reductions in structural capacity and stiffness increased as the process developed. Design calculations based on reinforcement losses and concrete strength reductions during exposure tended to over-estimate damage occurring.

Sub-Soil & Geotechnical Structures

1217CASE STUDY: STABILISATION OF A GRADE II LISTED CHURCH STEEPLE USING JACK DOWN PILES AND AN INNOVATIVE LOAD TRANSFER PLATFORM

J Ball, Roger Bullivant Piling, Burton Upon Trent & J Hull, Roger Bullivant Piling, Burton Upon Trent, Preston, UK

Using a vibrationless jack in piling system, a 19th century grade II listed preservation structure has been stabilised. This case study outlines the benefits of using a jack down system and describes the design and installation of jack down piles 17m into founding strata. The paper also describes the implementation of a novel method of load transfer using a lattice work of reinforcement in order to minimise point loading when compared with more traditional methods.

1160APPLICATION OF GROUND PENETRATING RADAR (GPR) IN INSPECTION AND MONITORING OF DEEP BURIED TRUNK CONCRETE SEWER SYSTEMS

A Sadri, WL Ying & J Armitage, Hatch Ltd., Mississauga,ON, Canada

In the North America’s municipalities, every year there are many deep trunk sewer systems that are approaching or exceeding their design service life. Inspection and monitoring of urban waste water infrastructure which is mostly buried underground is difficult and complicated resulting in infrequent maintenance visitations and costly sewer system rehabilitations. The alternative to crisis management is continuous condition monitoring, data analysis, modeling and planning. Hatch has designed, developed and commissioned a sewer inspection system based on the ground penetrating radar (GPR) technology to evaluate the condition of deep trunk sanitary sewer systems. The system is capable of inspecting both cast-in-place and pre-cast concrete sewers and has been successfully tested in both brand new and under operation sewers.

This paper describes our GPR based sewer inspection and monitoring system and demonstrates its capabilities through the two case studies.

1337AUTOMATIC CABLE-FREE SYSTEMS OF GEOTECHNICAL MONITORING FOR CONSTRUCTION OF UNDERGROUND TRANSPORT INFRASTRUCTURE PROJECTS

Dr. A Baukov & S Pavlov, ZAO “Triada-Holding”, Moscow, Russia

The authors consider geotechnical monitoring techniques utilized in the course of underground transport infrastructure projects construction in big cities. Special attention is paid to TBM-driven metro tunnels when many buildings and utility mains are influenced by the construction process.One of the crucial tasks to be solved is to minimize risks of emergency situations while maintaining designed construction rates. The authors suggest to use modern cable-free systems to monitor various parameters, such as deformations, vibrations, tilt of buildings located close to construction sites as well as hydrological and geological conditions, soil movements, etc.Special emphasis is put on design considerations and operational principles of such systems for urban environment.

1252 CONSERVATION OF CORRODED STEEL SHEET PILE USING CONCRETE COATING,

T Suzuki, Niigata Univ, SI Kobayashi, Mizukura Construction Co.Ltd, Niigata, Japan

A large number of the steel sheet pile canal has been widely used in Japan. In recent years, the relationship between the durability and the corrosion of the steel sheet pile has been discussed as a technical problem. In this study, development of conservation method for corroded steel sheet pile in canal structure is going to be performed, applying steel sheet pile - concrete composite. The experiments were conducted as a bending test by the model samples. In the monitoring, the bendingproperties of composite are evaluated based on displacement measurement and AE. Thus, the mechanical properties of composite could be evaluated by comparing a moment with a maximum displacement. The AE generation behavior is correlated with fracture process in load-displacement characteristics. The experimental result, the covering effect of concrete is quantitatively evaluated.

1331CONSOLIDATION OF SOIL UNDERLYING THE EXISTING METRO TUNNEL IN THE COURSE OF A NEW UTILITY TUNNEL CONSTRUCTION

Prof A Shilin & Dr M Kurgansky,ZAO “Triada-Holding”, Moscow, Russia

The author considers feasibility and efficiency of soil consolidation under the existing metro tunnel located not far from a new utility tunnel being constructed at the moment. TAM injections from the TBM access pit were chosen for the purpose.Calculations performed as well as comprehensive analysis of design solutions confirmed the author’s considerations that TAM injections could be used as an effective technique capable of preventing soil settlements and metro tunnel subsidence, thus allowing laying a new utility tunnel underneath the metro line not impeding regular train traffic.

1288PREDICTION OF ASBESTOS CEMENT WATER PIPE AGING & REPLACEMENT SCHEDULING USING MONTE CARLO SIMULATION,

W Punurai, Mahidol Univ, Nakhonpathom, Thailand, D Paul, & G Scott, CSIRO Land & Water, Highett, Vic, Australia

With the infrastructure deficit in Thailand and other ASEAN countries climbing along with the changing economy, there is a real need for municipalities and utility's to take a hard look at the way they manage their infrastructure assets. The effective management of water distribution pipes is no exception. Asbestos cement water pipes are among the oldest assets in many water supply networks in ASEAN countries. For a buried AC pipe in service, internal and external surface degradation can occur by dissolution or leaching of cement-based components leading to loss of pipe strength. Since water quality and soil

environment cannot be completely specified along a pipeline, it is to accept that uncertainty in pipe failure exist as pipe ageing proceeds. The paper presents the results of comprehensive studies into the AC water pipe management in Thailand. The studies are conducted in three parts. First, the predicted failure rates are computed from aggregated independent pipe segments residual strength test data taken from 400 mm AC pipes used in various Thai water utilities locations during condition assessments using core samples. Second, the lifetime probability functions (discrete Weibull probability density functions) of AC pipes are estimated using Monte Carlo simulation in conjunction with the physical failure state formulations. Output from the Monte Carlo simulation provides a number of failures recorded over time, which then allows the lifetime distribution to be estimated. All is described in the third part. The results of studies can be used for water utilities to allocate government funds for pipe maintenance and pipe replacement activities in the future.

Civil Structures

1205 USE OF FLY ASH IN CONCRETE DAM TO REDUCE CALCIUM IONS LEACHING DAMAGE, Z He, X Cai & H Sun, Wuhan Univ, China

Ca2+ leaching is one of the prevalent deterioration problems of concrete dam. The loss of calcium leads to a decrease in strength and an increase in porosity. It has been a threat to the structural integrity of the dam. This research studied the Ca2+ leaching mechanism in concrete dam and the effect of fly ash on the reduction of its associated damage. An accelerated electrochemical leaching test was devised using concrete prism specimens. The fly ash was added to replace cement at a fly ash to cement ratio of 0, 30, 50 and 70%. Leaching tests were performed up to age of 90 days and 360 days after 28 days and 90days initial curing respectively. The leachate was analyzed using XRD and XRF and the C-S-H structure of concrete after exposure of leaching was examined by XRD, TG, 29Si NMR and FTIR. It was found that the strength reduction of plain concrete due to leaching was 20% in 90 days. However, the reduction was only 5% when fly ash was applied. Fly ash addition decreased porosity, increased condensation polymerization of C-S-H and increased Q1/Q2 ratio, leading to a more stable gel structure. When fly ash to cement ratio reached 50%, concrete exhibited the best resistance to Calcium ion leaching. Fly ash concrete shall be considered as both construction and repair materials for concrete dams.

Seismac Analysis & Repair

1353 RECOMMENDATION FOR SEISMIC UPGRADING OF DAMAGED RC STRUCTURES

R Folic, Univ of Novi Sad, Serbia & D Zenunović, Univ of Tuzla, Bosnia & Herzegovina, A Liolios, Democritus Univ of Thrace, Xanthi, Greece

Serious earthquakes, including recent events cause large stresses in structures and serious damage to their elements and foundations, even the collapse of the structures. The observation of building structures’ condition after seismic events showed that the cause of the most significant damages is inappropriate design and construction. The focus of this paper is on reinforced concrete (RC) buildings. Different classification of damage in vital structural elements and structure is discussed. Post-earthquake assessment and analysis of seismic strength and structural conditions are analysed. Different classification of damage and its influence on stability of structures is discussed. The system aspects related to: lack of strength and deformation capacity; vertical irregularity; horizontal irregularity; inadequate diaphragms; interaction with non-structural elements; previous modifications and damage; pounding of adjacent buildings; pancake failure; inadequate stiffness and resulting damage to non-structural elements and foundation inadequacies. After evaluation of damage degree and determination required and available seismic resistance of structures a redesign must performed.

In seismic rehabilitation, analyses are made to estimate the safety and performance of the building prior to and after rehabilitation. The structure must provide adequate capacity and acceptable deformation according to recommendations given in the current Code. Modern European codes – CEN EN 1998-1 and EN 1998-3, provide the rules for seismic design of new and existing damaged structures, respectively. Federal emergency management agency (FEMA) work very actively in assessing conditions of structures after seismic events and for its retrofitting. The current seismic design of structures is based on the presumed ductile response and yielding probability of some part of a structure, without transforming the structure into a mechanism or brittle failure. Design techniques of repair/strengthening focus on the building displacement, as the primary parameter for the characterization of seismic performance. Review and comparison of international recommendations (Eurocode), CEB (fib) and some provisions of the US Code related to the topic of this paper are discussed as well. General and technical criteria for the choice of structural intervention are discussed, also.

1107STRUCTURAL FAULTS AND INNOVATIVE REPAIR TECHNIQUES IN THE BUILDINGS DAMAGED IN THE L'AQUILA 2009 EARTHQUAKE

A Salvatori, Univ of L’Aquila, Italy

L'Aquila city was struck down by a 6.3 Mw earthquake in 2009 April 6th. Its historical centre and all the surrounding suburbs were severely damaged, causing 309 casualties, and more than 1500 people injured. L'Aquila has been the first Italian important city directly destroyed by a near fault earthquake since Messina earthquake (1908). Many buildings collapsed completely, both in masonry structure and in reinforced concrete ones. This work analyse the most relevant collapses of many buildings, the relevant causes of the collapse, the lack in design, construction and maintenance of the buildings (both of public interest or private ones), and the impact the collapses have caused to the urban centre. Many important buildings and structures have not been totally collapsed, and the application of the most innovative repair and seismic retrofitting techniques are applied in order to restore them, especially those with historical and artistic relevance. The first Italian application of seismic isolation to masonry and monumental buildings have been studied, and a combination of both seismic isolation and tunnelling techniques are analysed and developed in order to repair and seismically retrofit some important monumental building in the historical centre of the city. Several application of retrofitting seismic isolation to existing and severely damaged buildings are shown, concerning building uplifting, pillar cut and underpinning structures. Energy dissipation techniques are applied as an alternative tool to seismic isolation in those particular buildings where energy dissipation has been coupled with displacement control. A particular reference has been made for the monumental buildings with stone masonry where the need to preserve the historical environment results in difficult agreement with seismic safety.

1349DEFORMATION RESPONSE OF ADHESIVE ANCHORS IN RETROFITTED MASONRY STRUCTURES DURING THE 2010/2011 CANTERBURY, NEW ZEALAND EARTHQUAKES

A Schultz, University of Minnesota, Minneapolis, USA, D Dizhur & JM Ingham, Univ of Auckland, New Zealand

Between September 4, 2010 and December 23, 2011, a series of earthquakes struck the South Island of New Zealand including the city of Christchurch producing heavy damage. During the strongest shaking, the unreinforced masonry (URM) building stock in Christchurch was subjected to seismic loading equal to approximately 150-200% of code values. Post-earthquake reconnaissance suggested numerous failures of adhesive anchors used for retrofit connection of roof and floor diaphragms to masonry walls. A team of researchers from the Universities of Auckland (NZ) and Minnesota (USA) conducted a field investigation on the performance of new adhesive anchors installed in existing masonry walls. Variables included adhesive type, anchor diameter, embedment length, anchor inclination, and masonry quality. Buildings were selected that had been slated for demolition but which featured exterior walls that had not been damaged. A summary of the deformation

response measured during the field tests are presented.

1204ASSESSMENT OF INFILL WALL TOPOLOGY CONTRIBUTION IN THE OVERALL RESPONSE OF FRAME STRUCTURES UNDER SEISMIC EXCITATION

N Nanos & D Begg, Univ of Portsmouth, UK

Due to the increasing pressure for leaner construction and reduced carbon footprint structures, the contribution of “non-structural” elements to the structural response of steel frame structures, is once more under the spotlight. This paper identifies the effects of infill wall existence and arrangement in the seismic response of steel frame structures. Despite their non-structural nature quantifiable differences have been recorded in the overall seismic behaviour, with different infill wall arrangements, highlighting their potential seismic design significance. This paper advocates the use of infill walls as a light method of seismic rehabilitation intervention that can provide considerable structural benefit without the traditional difficulties associated with seismic upgrade. To demonstrate the above, a methodology based on the utilisation of overall seismic response indicators was followed. This post processing enables a straightforward comparative statistical distillation of the complex structural response. The overall structure damage index after Park/Ang (OSDIPA) and the maximum inter-story drift ratio (MISDR) have been selected as widely utilized structural seismic response parameters. A set of 225 spectrum compatible accelerograms, based on EC8 and the Greek national compendium provisions, have been created and a series of non-linear dynamic analyses have been executed on an indicative steel frame structure with 5 different infill wall topologies. Results indicate the significant overall contribution of infill walls. Response reduction in the range 35-47% of the maximum and 74-81% of the average recorded OSDIPA values followed by an overall reduction of 64-67% and 58-61% for the respective maximum and average recorded MISDR values, demonstrates the relative benefits of infill wall presence. Similar reductions were also observed in 1st level damage indicators.

1161COMPARISON OF DIFFERENT TECHNIQUES FOR SEISMIC STRENGTHENING OF EXISTING REINFORCED CONCRETE FRAME STRUCTURES OF SCHOOL BULDINGS IN BULGARIA

M Traykova & T Chardakova, Univ of Architecture, Civil Engineering & Geodesy,Sofia, Bulgaria

In this paper the need of seismic strengthening of existing school buildings in Bulgaria is addressed. The purpose of the study is to propose the most appropriate technique for seismic strengthening of such buildings with reinforced concrete frame structure.For the purposes of the study, first, the most popular techniques for seismic strengthening in the Bulgarian construction practice are discussed: addition of new reinforced concrete or steel elements, reinforced concrete or steel jacketing, FRP wrapping and covering. Analysis of the advantages and the problems of these techniques with respect to their application for seismic strengthening of schools is done.Then a numerical example based on an actual case is solved. An existing school building with typical for the Bulgarian architectural and structural practice is considered. Using the finite element technique, an analysis of the building is done, first for the as-built structure, then for the structure, strengthened with picked techniques. A comparison of the global behavior of the different models is done. Finally, some general conclusions are made and the most appropriate approach for seismic strengthening.

1347 EARTHQUAKE PERFORMANCE OF STEEL PLATE-MASONRY COMPOSITE (SPMC) COLUMNS,

YX Pan, DH Jing, SY Cao, Southeast University, Nanjing,China & JF Chen, Queen’s University Belfast

This paper presents an experimental study on the seismic behaviour of steel plate-masonry composite (SPMC) columns

consisting of irregular masonry columns with steel plates attached to all sides using a combination of tie bolts and epoxy adhesive. The study included the test of four L shaped and four T shaped SPMC column specimens under combined axial force and cyclic lateral loading. The effects of axial loading level and bolt spacing were also investigated. Test results including the ultimate lateral strength, ductility and energy-absorption capacity are presented. This study adopted cold-formed steel plates, avoiding weld fracture which occurred in previous studies. Test results also show that L shaped columns offer substantialpost-buckling strength and stiffness, which are not evident in most T shaped columns.