Interest in in-situ testing of hardened concrete has increased considerably since the 1960s, and significant advances have been made in techniques, equipment, and methods of application since publication of the fu'st edition of this book in 1982. This has largely been a result of the growing number of concrete structures, especially those of recent origin, that have been showing signs of deterioration. There is also an increasing awareness of the shortcomings of control or compliance tests which require a 2g-day wait before results are available. Even than, such tests reflect only the adequacy of the material supplied rather than overall construction standards. The principal aim of this book is to provide an overview of the subject for non-specialist engineers who are responsible for the planning of test programmes. The scope is wide in order to comprehensively cover as many aspects as possible of the testing of hardened concrete in structures. In addition to established methods, new techniques which show potential for future development are outlined, although in many cases the application of these to concrete is still at an early stage and of limited practical value at present. Emphasis has been placed on the reliability and limitations of the various techniques described, and the interpretation of results is discussed from the point of view both of specification compliance and application to design calculations. A number of illustrative examples have been included with this in mind.

42347 Anon I n - p l a c e m e t h o d s f o r d e t e r m i n a t i o n o f s t r e n g t h o f c o n c r e t e ACI Mater ia ls Journal , Vol. 85, No. 5, pp. 447-471 (Sep . -Oct . 1988)

The state of the at~ in the use of methods for determining the in-place compressive strength of concrete is reported. The methods covered include the rebound hammer, probe penetration, pullout, ultrasonic pulse velocity, maturity, and cast-in-place cylinder. The underlying principles and inherent limitations of each method are discussed. Repeatability of test results is reviewed, and recommendations are given for developing the correlation relationship relationship for each test method, recom- mendations are given for the number of tests, and statistical techniques for interpretation of test results are described.

42340 Ohtsu, M. Diagnostics of cracks in concrete based on acoustic emission Nondest ruct ive Testing, SP 112, pp. 63-82. Edi ted by H.S. Lew, Amer i can Concre te Institute, Detroi t (1988)

The stress intensity factor Ktc of linear elastic fracture mechanics is considered as the mechanical criterion of crack initiation. The critical value was determined from AE observation and numerical solutions by the boundary element method (BEM). A quantitative waveform analysis is developed for source characterization of AE. A new procedure for determining crack locations, crack types, and orientations is proposed. The deterioration of a concrete structure is examined by the test of core specimens under uniaxial loading. Existing cracks are evaluated nondestructively by ultrasonic spectroscopy. Results of basic studies confirm the feasibility and the usefulness of the proposed method as diagnostics of cracks in concrete structures.

42339 Marl, A.K.; Shah, S.P. Application of acoustic emission and l a s e r h o l o g r a p h y to study mierofracture in concrete Nondes t ruc t ive Testing, SP 112, pp. 83-110. Edi ted b y H.S. Lew, Amer ican Concre te Institute, Detroi t (I 988)

Model concrete specimens with cylindrical limestone aggregates were used to simulate concrete and ease efforts of analysis. Laser holographic interferometry was applied to study the whole field deformation pattern in real time. Cracks could be detected as discontinuities in the fringe pattern corresponding to discontinuities in the displacement field. Sensitivity of about 0.3 microns was obtainable. Speckle photography was used to quantitatively measure displacement discontinuities at bond cracks at various stages of loading. Acoustic Emission (AE) techniques were applied to monitor microseismic activities resulting from the various fracture phenomena. The rate of microfracture was measured from the AE event rates. A source location aigorithin was used to calculate the locations of the AE events.

42197 Sansalone, M.; Carino, N.J. Laboratory and field studies of the impact-echo method for flaw detection in c o n c r e t e . Nondes t ruct ive Testing, SP 112, pp. 1-20. Edited by H.S. Lew, Amer ican Concre te Institute, Detroi t (1988)

A nondestructive test method has been developed for locating defects in concrete. The technique is referred to as the impact-echo method and is based on monitoring surface displacements resulting from the interactions of transient stress waves with internal discontinuities. This paper describes the technique and presents results of laboratory studies designed to evaluate the capabilities of the method. These laboratory studies were carded out on 500-mm thick slabs which contained a variety of artificial flaws embedded at known locations. Frequency analysis of recorded time-domain waveforms is explained and shown to be a quick and simple signal processing technique. Finally, results are presented from a field study in which the impact-echo method was used to investigate a 150-ram thick slab believed to contain voids.

42196 Alexander, A.M.; Thornton, H.T., Jr. Developments in ultrasonic pitch-catch and pulse-echo for m e a s u r e - m e n t s in concrete Nondest ruct ive Testing, SP 112, pp. 21-40. Edi ted by H.S. Lew, Amer i can Concre te Institute, Detroi t (1988)

Research by the U.S. Army Engineer Waterways Experiment Station (WES) has resulted in the development of a 200-kHz pitch-catch system with a signal to noise ratio of 18 and a pulse-echo system with a SNR of 8. The mass and dimensions of the improved system have been significantly reduced from the prior state-of-the-art system. The WES system has the lowest Q (shortest ringing time and widest bandwidth) and therefore the shortest pulse length on record. This system works well for making thickness measurements of portland-cement concrete pavement and can indicate the presence of voids.

42185 Yamada, K.; Tsuchiya, H., Kosaka, Y. Q u a l i t y evaluation of concrete exposed to high temperature by u l t r a s o n i c s p e c t r o s c o p y ( In J a p a n e s e : E n g l i s h abstract) Journal o f the Society o f Mater ia ls Science, Japan, Vol. 38, No. 431, pp. 959-965 (Aug. 1989)

In this study, the ultrasonic spectroscopy was applied to evaluate the quality of concrete exposed to high temperature conditions, as the first step to establish a new non-destructive testing technique for concrete and mortar. The main results obtained in this study are summarized as follows: (1) compressive and flexnral strengths of concrete decreased according to temperature rise. Especially the flexural strength of mortar was sensitively affected by temperature rise; (2) the ultrasonic pulse velocity, maximum amplitude and energy of measured ultrasonic pulse waves decreased according to temperature rise; (3) the maximum amplitude and energy of frequency transfer function of concrete decreased with increasing temperature, and these decreasing rates were not affected very much by the water-cement ratio and heating duration; (4) the local maximum amplitude and energy of the frequency transfer function in the frequency ranges of 50-100 kHz and 200-250 kHz were closely related to the change of internal structure of concrete exposed to high temperature.

42159 Aggour, M.S. Non-destructive tests of concrete in s t r u c t u r e s Depar tment o f Civil Engineer ing, Mary land Univers i ty (United States) PB89-136238 , 55 pp. (Mar. 1987)

The state-of-the-art report is based on a brief critical literature review of nondestructive test methods for determining the in-place strength of concrete. The report describes test methods and techniques, and lists their limitations. The methods discussed are surface hardness methods, penetration resistance methods, pullout, pulloff and hreakoff methods, pulse velocity techniques, and the combined methods approach. To date no single nondestructive evaluation method is entirely satisfactory for predicting the quality and strength of concrete in situ. A combination of methods that respond to different factors may give the needed information. It is the recommendation of the report that a combination of pullout techniques and the pulse velocity method might provide an acceptable method for determining both the relative and absolute quality of concrete in a structure.

42152 Yun, C.H.; Choi, K.R.; Kim, S.Y.; Song, Y.C. Comparative evaluation on nondestructive tes t m e t h o d s for in-place s t r e n g t h determination Nondest ruct ive Testing, SP 112, pp. 111-136. Edited by H.S. Lew, Amer i can Concre te Institute, Detroi t (1988)

This paper presents an investigation to determine the within-test variability of various nondestructive test (NDT) methods and the correlation between NDT test results and the corresponding compressive strength of cores. The size effects of coarse aggregate on the variability and correlation were also evaluated. The NDT test methods evaluated in the test series include: rebound hammer; pulse velocity; probe penetration; pullout; and CAPO (Cut and Pullout). Companion tests of field-cured standard cylinders and cores were also made at the ages when the NDT tests were made. The tests were performed on plain concrete slabs, at different ages. The test variables included the size of coarse aggregate (sand only, 25 nun and 40 mm) and the compressive strength of concrete (210,280 and 350 kg/sq cm).

42151 Teodoru, G.V. T h e use of simultaneous nondestructive tests to predict the compressive strength of concrete Nondest ruct ive Testing, SP 112, pp. 137-152. Edited by H.S. Lew, Amer i can Concre te Institute, Detroi t (1988)

The aim of the present work is to analyze the correlations between several nondestructive measured values (ultrasonic velocity and attenuation, rebound number) and the compressive strength of concrete. A computational program performs a general multiple correlation of the values of the results obtained from the non-destructive tests. The utility of this concept of multiple correlation for concrete quality control especially for a plant for precast elements, is evident both directly by means of the transformation of non-destructive testing values into the compression strength of concrete, as well as for the utilization of this transformation for statistical quality analysis.

42140 Leaird, J.D.; Taylor, M.A. Acoustic emission investigation into some concrete construction prob- lems Journal of Acoust ic Emission, Vol. 8, Nos. 1-2, pp. 5322-5325 ( Jan . - Jun. 1989) Special Supplement - Extended Summar ies o f Papers to be presented at the World Meet ing on Acoust ic Emission, Charlotte, Nor th Carol ina, USA, 20-23 Mar. 1989

The construction industry would benefit greatly from a cost effective method of increasing the crack resistance of structural concrete and for the early detection of reactive aggregates. One method proposed to achieve the first objective is to add polypropylene fibers to the concrete. A series of beams were manufactured with polypropylene fibers added and a series without the fibers. These beams were tested in four point loading and the acoustic emission activity from each beam was measured during the load test. The plain concrete beams had 2 to 3 times the acoustic emission activity of the fiber reinforced beams. The results of tests to detect the presence of reactive aggregates are also reported.

41956 Ohtsu, M.; Sakimoto, T.; Kawai, Y.; Yuji, S. E v a l u a t i o n of concrete structure d e t e r i o r a t i o n via A E observation of core tes ts Journal o f Acoust ic Emiss ion, Vol. 7, No. 4, pp. 167-172 (Oct-Dec. 1988)

An AE technique is proposed to evaluate the deterioration of concrete structures by means of tests of core-drilled samples. AE activity during a uniaxial compressive test is

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