indian journal of science and technology, vol 10(26), doi

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Indian Journal of Science and Technology, Vol 10(26), DOI: 10.17485/ijst/2017/v10i26/115874, July 2017ISSN (Print) : 0974-6846

ISSN (Online) : 0974-5645

Case Study on the Repair and Rehablitation of G+3Residential Appartment Located Near Sea Shore,

Tamil Nadu, IndiaR. Vijayalakshmi1*, S. Ramanagopal1, R. Sathia2 and R. Arvindh Raj1

1Department of Civil, SSN College of Engineering, Kalavakkam – 603110, Tamil Nadu, India; [email protected], [email protected], [email protected]

2Department of Civil, Jeppiaar College of Engineering, Chennai – 600119, Tamil Nadu, India; [email protected]

AbstractObjectives: In this paper we have discussed about the case study of repair and rehabilitation work carried out for a G+3residential apartments located very close to sea shore, Besant Nagar, Tamil Nadu, India. Methods/Analysis: The Repair strategy involved, removal of delaminated concrete cover, anti corrosive coating, polymer modified mortar, injectionof epoxy grout for the repair of beam column junction and masonry crack, self sacrificial anode to prevent corrosionof reinforcement, micro concrete for slab and column, additional reinforcement with anti corrosive coating, glass fibrewrapping for column to increase ductility, and polymer modified mortar for repair of RCC and Masonry cracks. Findings: Though reinforced concrete structures are designed using the code provisions and standards, enough care should be takenduring the construction process. During the service life of the building, proper maintenance and care should be taken toavoid corrosion of reinforcement and further environmental effects. Novelty/Improvement: A study of some modernconcreting techniques and different types of special concrete used in the repair and rehabilitation process.

Keywords: Corrosion Coating, Epoxy Grout, Polymer Modified Mortar, Repair and Rehabilitation

1. Introduction

The deterioration of typical concrete structure starts fromthe time it is exposed to the elements of nature, primar-ily under high humidity, high temperature conditions andvariation in temperatures; thus certain parts of structuresincluding roofs and structural elements directly exposedto weather condition, are more susceptible to deterio-ration. The deterioration of materials such as concreteand reinforcement reduce the strength of the structuralmembers. While elements such as temperature variations,pollution, wind, rains, floods etc. contribute towardsdeterioration; sometimes changes in environment afterconstruction and changes in functional requirement also

contribute towards premature deterioration. Corrosionof embedded steel is the prime cause of damages to thereinforced concrete structures. It progresses with slowdeteriorating process and if neglected or not attended intime, may spread over a large area and cause extensive dis-integration/deterioration of structural elements. It mayeven lead to catastrophic structural failure, in the absenceof timely remedial measures. Various causes which cre-ate conducive conditions to accelerate/propagate rate ofcorrosion are Inadequate cover to reinforcement, Useof inadequate grade of concrete for the purpose, Use ofrusted steel, Workmanship/workability/compaction,thus leaving concrete porous, Poor Unsuitable ingredi-ents (both coarse and fine aggregate), Use of high W/C

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Case Study on the Repair and Rehablitation of G+3 Residential Appartment Located Near Sea Shore, Tamil Nadu, India

ratio resulting in fine hairline cracks in concrete during drying, Use of water containing high incidence of salts/sulphates, Wave action (alternate wetting and drying pro-cesses), Presence of harmful gases in the air, Contact with acids/fumes, Exposures to relatively high humidity.

Statistical study was carried on the repair and strength-ening methods of 114 RC buildings damaged after the 1985 earthquake in Mexico City. The most commonly used techniques were the addition of shear walls and the RC jacketing of columns1. The present state of con-crete structures & the major areas where improvement is needed during its service life stage for sustainable devel-opment were highlighted & also the method of carrying out Repair, Rehabilitation &Retrofitting was discussed2. A case study was carried out in 3 no. (G+8) multi sto-rey building damaged due to bhuj earth quake (2001) and rehabilitation of the same was carried out during 2003 and discussed about the repair and rehablitation methods adopted in the building3 . In this paper we have discussed the repair and rehabilitation work carried out in a G+3 residential building located very close to sea shore. The

building is severely damaged due to salt water and chlo-ride attack, suffer with corrosion of reinforcemnt, spalling of concrete in floor and roof slabs, major cracks at stair-case landing and cracks in RCC and Masonry strucutres. Repair strategy involved, removal of delaminated concrete cover, anti corrosive coating, polymer modified mortar, injection of epoxy grout for the repair of beam column junction and masonry crack, self-sacrificial anode to pre-vent corrosion of reinforcement, micro concrete for slab and column, additional reinforcement with anti corrosive coating, glass fibre wrapping for column to increase duc-tility, and polymer modified mortar for repair of RCC and Masonry cracks.

2. Preliminary Investigation

A detailed visual observation was made on all the col-umns, beams and slabs of the above said location and the following observations were made, excessive spalling was noticed in few of the columns and beams in the ground floor(Figure 1a), Excessive spalling was noticed in all

. Figure 1(a) Figure 1(b). Figure 1(c)

Figure 1(d). Figure 1(e). Figure1(f).

Figure 1. Preliminary Investigation at Site.

R. Vijayalakshmi, S. Ramanagopal, R. Sathia and R. Arvindh Raj

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the stair case landing slab portion (Figure 1b), in manyplaces the slab portions has dampness (Figure 1c), andcorrosion traces (Figure 1d), cracks were noticed at theconcrete and brick work joints (Figure 1e), major cracksseen in masonry wall (Figure 1f).

3. Detailed Investigation

The non destructive testing carried out at the site are• Ultrasonic pulse velocity test (UPV)• Rebound hammer test• Core smapling and testing• Carbonation level• Half cell potential survey• Chloride content in concrete samples

Ultrasonic and rebound hammer test were carried outto assess the condition of concrete in the column, beamand slab at various locations. Test for chloride and car-bonation was carried out for verifying the present statusof the cover concrete. Half cell potential survey was car-ried out to identify the extent and severity of corossionactivity . The extraction of core sampling and testingfor compressive strength was carried out to assess thehomogenity and actual insitu strength of concrete.

3.1 Ultrasonic Pulse Velocity TestUPV test was carried out at various points of beams andcolumns to assess the quality of concrete, integrity ofconcrete and honey combing. To carry out the test thesurface of the selected column beams and slab locationswere marked with grid lines at a regular spacing of 300mm on vertical and 300 mm on horizontal face. The areaaround the grid points was smeared with grease, so thata smooth plain concrete surface was available for hold-ing the transducer. The transit time of the ultrasonicpulse velocity was read from the digital indiactor. It wasfound from the result of UPV test that the values in theslab portion of ground floor and first floor are very low,it has maximum value of 2.59 and minimum value of 1.39 and average of 1.99 and falls in the category of poorto satisfactory. The UPV reading for beams varies from 3.99 maximum to 3.37 minimum and average of 3.17which falls with in the category of satisfactory to good.For slabs the UPV values varies from 4.11 maximum to 3.2 minimum and average of 3.74 which also falls within the category of satisfactory to good.

3.2 Rebound Hammer TestSchmidt rebound hammer test was carried out to mea-sure the quality of near surface concrete. The hammerwas used only to compare the quality of concrete indifferent locations of a concrete member. The reboundhammer test was carried out on all the location wherethe UPV test was conducted and also at the additionalpoints in between for the slelected location of the col-umn, beams and slabs. All the locations were preparedand cleaned to ensure complete removal of laitance andloose particles.

3.3 Concrete Core Sampling and TestingCore sampling test is the most appropriate method toassess the strength of insitu reinforced concrete construc-tion. Concrete core samples of diameter 77 mm and ofsufficient length were extracted using an electrically oper-ated core drilling machine and diamond core drill bitsfrom different members of the structure to asses the qual-ity/ strength of insitu concrete. The locations were chosenso that they were representative of good concrete as wellas the badly affected portions. The extracted core sampleswere subjected to compressive strenght tests after neces-sary trimming and capping.

3.4 Carbonation Test on Concrete CoreSample

When any concrete structure is exposed to atmosphere,the surface of concrete comes in contact with carbon-di-oxide present in the atmosphere. The calciumpresent in the concrete will react with the carbondioxide forming calcium carbonate resulting in reduc-tion of alkalinity in concrete. Whenever the concrete isdense and impervious to atmospheric agents the carbo-naation will be restricted to the surface only. Howeverif the concrete is previous the carbonation reactioncontinues inward and reaches the concrete surround-ing the rebars, thus reducing the alkalinity of concreteand causing initiation of corrosion. Carbonation testwas conducted immediately on all the core samples thatwere extracted from the column, beam and slab. Thetest was conducted using phenolphthalein indicatorin dilute alcohol. The uncarbonated portion will turnpink, while the carbonated portions remain colourless.The measured depth of change in colour indicated thecarbonation level of concrete.



3.5 Half Cell Potential MeasurementHalf cell potentiometer works on the principle of measur-ing the voltage in the circuit of reinforcement and cover concrete using copper sulphate half cell. This method con-sist of measurment of the absolute potential of the concrete with reference to the reference electrode.Half Cell Potential Measurement Test (HCPT) was carried out on the RC col-umn, beams and slabs of the slected locations.

3.6 Chloride Determination TestChloride determination test was carried out on concrete powder smaples that were extracted from the tested cores. The presence of higher amount of chlorides in concrete surrounding the reinforcement will result in corrosion of rebars. The quantity of chlorides in concrete is deter-mined by chemical analysis and is expressed in terms of weight of concrete.

3.7 Observations from NDTBased on the non destructive testing conducted in few loca-tions of the column, beam and slab in the referred structural elements following recommendations were made:

• During visual examination, it was observed that the concrete cover portions has spalled very badly and also cracks were noticed in the same area where the treatment was already carried out.

• It was also noticed that the rebars were not treated with suitable system to take care of the corrosion since no traces of such systems was noticed

• Corrosion cannot be stopped and with the present chloride level immediate care must be taken to avoid the rebar corrosion. Also there is no proven cost effec-tive method to remove the chloride from the core concrete.

• Hence repair need to be done with sacrificial anode.

4. Reapir and Rehablitation Methodology

The quality of concrete in most of the columns and beams are found to be satisfactory to good as the UPV values are reasonable. However the amount of chlorides is quiet considerable. Many of the columns and beams which have undergone damage due to corrosion are to be strengthened to regain their original load carrying capacity. Before taking up the strengthening procedure,

proper supporting scheme has to be provided to prevent damage of the building by affecting the transfer of load from column to the temporary supports. This is essential to ensure safety aspects during the rehablitation. It may be noted that before rehablitating the RC beams, RC col-umn in which the beams are spanning have to be suitably strengthened from the point of view of ensuring safety.

4.1 Prepration of Surface At the places where the concrete cover had already spalled, (column corner, slab,step landing, beams) loose concrete was removed 25 cm more than the length of spall. For the other areas hammer sounding method was used to locate delami-nated concrete and marked with paint. The beam and slab portions were supported with props before the removal of damaged concrete. The surface to which polymer modified concrete has to be applied was cleaned off all loose materials by means of wire brush (Figure 2 a,b). All the loose particles were removed by washing with water under pressure.

a. Roof sLab b. column

Figure 2. Surface Preperation of Roof Slab and Columns.

4.2 Reinforcement Cleaning and Anti Corrosive Coating

All the concrete sticking to the rebar was removed by hammering and manual chipping. Rust remover coating was applied on the reinforcement steel bars and care was taken that the backisde of the bars also get coated. It was allowed to act for 24 hrs. wire brush were used to remove the rust from the steel bars followed by washing with water jet for the complete removal of rust. Anti corrosive zinc primer coating was applied completely surrounding the periphery of the reinforcing steel and allowed it to dry for 4 hrs. second coat of primr was applied after 4 hrs and care was taken to cover all the steel area without leaving a small portion of the steel uncovered (Figure 3). The rein-


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forcing steel which were highly corroded were replacedwith additional reinforcement by welding with existitingbars or drilling holes into concrete and inserting addi-tional steel bars with epoxy mortar.

Figure 3. Anti Corrossive Coating.

4.3 Application of Bonding Coat toSubstrate

All the concrete surface were thoroughly inspected andmade free from oil dust dirt etc. the surface was wellsaturated with water and after natural drying, a bond-ing agent of cement and acryliyc polymer in the ratioof 1:1 by volume was prepared to a lump free creamyconsistency. The bonding slurry was aplied into the sur-face of parent body using a stiff brush and allowed it todry. A second coat was applied at right angle to the firstcoat and ensured complete coverage and no pin holesare visible. Care was taken to apply cement based poly-mer concrete as soon as possible after the application ofbonding coat.

4.4 Application of Polymer ModifiedMortar

The polymer modified mortar was prepapred such thatit has a minimum compressive strength of 25MN/m2

. The proportion of cement, sand and acrylic polymerby weigth was 50Kg: 150Kg: 20-25% of cement content.The water cement ratio was kept as 0.4 (by weight).Masonry surface with polymer modified mortar isshown in Figure 4. After the application of polymermodified mortar and proper drying of surface, cur-ing compound was sprayed on the concrete surface

(Figure 5). Concrete surfaces must be clean and drywith all stains, oil, grease, dust, and dirt removed priorto applicationof curing compound. The concrte sur-face was cleaned with degreaser. Curing compoundwas sprayed when surface water has completely disap-peared and the concrete surface will not be marred bywalking workmen.

Figure 4. Polymer Modified Mortar.

Figure 5. Application of Curing Compund.

4.5 Rehablitation of ColumnsPlace suitable supporting system in position. The supportshould be as close to the column as possible ( atleast overa distance of effective depth of beam from column, wheremaximum shear present) and should be designed to with-stand the floor loading coming on the column and shallbe placed on a firm ground, without any settlement. Thestrengthening should be carried out on alternate columnsin the first stage.



4.5.1 Micro/Self Compacting Concrete for Jacketing the Column

Strengthening was done using micro/self compacting concrete jacketing technique. The micro/self compacting concrete used in the jacketing should be free flow, no shrink and should have atleast M40 grade. Remove the damaged concrete portion of the column completely, till the rein-forcement is exposed. Spray phenolphthalein to check the alkalinity of the concrete. On spraying the phenolphthalein if the concrete does not turn to pink colour, continue the chipping further. Drill holes of 16mm dia and 75mm deep into the column. The positioning of the holes has to be stag-gered along the perimeter and height of the column. The vertical spacing of shear connector should be not more than 250mm for all four sides of the column. Clean the holes with a jet of water and clean the same thoroughly. Use chemical polyester anchor resin for anchoring the shear connector. The reinforcement in the column should consist of longi-tudinal bars and transverse direction bars. The longitudinal bars in the jacket portion are to be taken into the top of the first floor column through the floor beams. Apply the epoxy based jointing compound for the columns surface to have a better bonding between the old concrete and the new micro concrete. Water tight shuttering to be provided so that the micro concrete should not leak. Cure the micro concrete as per standard practice. After the concrete in the jacket portion of the columns has attained its strength, the props placed for supporting the corresponding floor beam are to be removed. The rehablitation of the future floors can be taken up, once the repair of the ground floor column is completed.

4.5.2 GFRP Wrapping of ColumnsCompression load carrying capacity of column increases once confined with FRP sheets. The FRP wrap stiffness plays a major role in the column jacket design. In order to develop appropriate confinement forces, the jacket must be stiff enough at a relatively low axial strain in the column. For eccentrically loaded columns, smaller enhancement factor should be considered in design of FRP-wrapped concrete columns. Corrosion damage to deficient RC col-umns can be reduced or completely prevented by applying unidirectional fiber composite sheet along the longitudinal direction to increase flexural capacity, and by wrapping the columns in the lateral direction to improve their ductility and energy absorption capacity. To withstand impact load-ings, concrete columns should be properly strengthened to achieve adequate level of energy absorption capacity and

ductility. The FRP repair of corrosion damaged RC col-umns not only provides strength and ductility, but also could slow down the rate of the corrosion reaction. The process of applying primer to the column is shown in Figure 6 and wrapping of column with glass fibre rein-forced polymer (GFRP) sheets is shown in Figure 7. After proper bonding of GFRP sheets sand pellets were sprinkled (Figure 8) around the column for proper curing.

Figure 6. Application of Primer.

Figure 7. Glass Fibre Wrapping.

Figure 8. Sand Pellets Sprinkled Post Curing of the Glass Fibres.


Indian Journal of Science and TechnologyVol 10 (26) | July 2017 | www.indjst.org

4.6 Rehablitation of RC Beams /SlabsSupport the slab which is contributing the load for thebeam under rehablitation. Continue the operation asper the column procedure like providing additional barsusing shear connectors as required. Provide cores fromthe salb of about 77mm diameter to facilitate the pouringof micro/self compacting concrete. Cement grouts wereinjected through the holes drilled in the slab (Figure 9).

Figure 9. Injection of Cement Grouting.

4.7 Cathodic ProtectionCathodic protection of steel in concrete is a technique thathas been demonstrated to be successful in appropriateapplications in providing cost effective long term corrosioncontrol for steel in concrete. Cathodic protection is theonly known means of mitigating the corrosion of reinforc-ing steel, which is caused by the presence of the chlorideion in existing structures. It is a technique that requiresspecific design calculations and definition of installationprocedures in order to be successfully implemented. Insubmerged or buried areas discrete zinc anodes are posi-tioned adjacent to the structure where the low resistivity ofthe soil or water allows the current to pass readily from theanode to the steel reinforcing. In atmospherically exposedconcrete it is necessary to distribute the zinc anode moreclosely in the areas to be protected, as the resistivity of con-crete is substantially higher than soil or water. Provision ofsacrificial anode is shown in Figure 10 a and Figure 10 b

a. Near reinforcement b. Roof slab

Figure 10. Self Sacrificial Anode.

4.8 Cracr Repair and Protective Coating Acid wash and water wash the entire repaired surface aswell as the existiting good members. Apply acrylic asphal-tic based protective coating to the members to prevent thedamage in future.

Plasticized expanding grout admixture with acrylicpolymer modified mortar was used for sealing of allmasonry and RCC cracks. The external masonry crackswas filled with polymer modified grout which is shownin Figure 11.

Figure 11. External Patch Work with Polymer ModifiedMortar.

5. Reference1. Aguilar J, Juarez H, Ortega R, Iglesias J. The Mexico earth-

quake of September 19, 1985. Statistics of damage andretrofitting techniques in reinforced concrete buildingsaffected by the 1985 earthquake. Earthquake Spectra. 1989February; 5(1):145-51. Crossref

2. Bhattacharjee J. Repair, rehabilitation and retrofitting ofRSS for sustainable development with case studies. CivilEngineering and Urban Planning: An International Journal(CiVEJ). 2016 Jun3; 3(2):33-47. Crossref

3. Varinder K Singh. 2013, Structural repair and rehabilita-tion of 3 no. (G+8) multi storeyed residential buildings,at ONGC colony at chandkheda, Ahmadabad, Gujarat.Procedia Engineering. 2013; 5:55-64.

https://doi.org/10.1193/1.1585516

https://doi.org/10.5121/civej.2016.3203

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