determined. In investigations by the combined method of rebound and ultrasound velocity measurement the new procedure is outlined. It performs equally well with different related equations.

47204 Carino, N.J.; Sansalone, M. Flaw detection in concrete using the impact-echo method Bridge Evaluation, Repair and Rehabili tation. Edited by A.S. Nowak. pp. 101 - 118. Kluwer Academic Publishers (1990)

A technique called the impact-echo method has been developed for flaw detection in concrete. This paper discusses the theoretical basis of the method and gives representative examples of the results of analytical and experimental studies. A procedure called spectral peak plotting is described which simplifies interpretation of data from scans across a structure. By using this procedure a profile view of the interior of the test object can be constructed.

47178 Tarricone, P. Inspection goes high tech Civi l Engineering, Vol. 61, No. 5, pp. 38-41 (May 1991)

The author argues that progress towards the ready acceptance of nondestructive testing (NDT) for large public structures such as building bridges has been unnecessarily slow. New construction is less likely that reconditioning of existing structures in the stringent financial climate of the 1990s, so appropriate use of NDT makes sound economic and safety sense. Particular attention is drawn to the use of radar and thermography for assessing concrete bridge-decks, and of ultrasonics impact-echo for concrete arch bridges. NDT of wood and steel as cracks and penetrant, magnetic particle, and eddy current testing are all used as well as radiography and ultrasonics.

47013 Nomura, N.; Mihashi, H.; Izumi, M. C o r r e l a t i o n of fracture process zone and tens ion sof ten ing behavior in concrete Cement and Concrete Research, Vol. 21, No. 4, pp. 545-550 (Jul. 1991)

Relation of fracture process zone to tension softening behavior of concrete has been studied using an acoustic emission (AE) source location technique and a simulation of tension softening behavior in double cantilever beam specimens. AE source distribution along ligament at three loading levels and visible cracks on the surfaces of specimens were related to tension softening phase simulated by means of a fictitious crack model.

46657 Berthaud, Y. Damage measurements in concrete via an ultrasonic technique Part H m o d e l i n g Cement and Concrete Research, Vol. 21, No. 2-3, pp. 219-228 (Mar . -May 1991)

It has been shown in Part I that the state of stress in elastic undamaged concrete has a great influence on the propagation of elastic waves. In the load direction (for the compression test) the elastic modulus decreases whereas the longitudinal wave is not perturbed. To explain this discrepancy, in this paper the damaged medium is considered as an homogeneous microcracked material. The solutions of the wave equations are used to identify the the different parameters such as the crack density or the shape factor of the cracks.

46630 Bungey, J.H. Ul t rason ic t es t ing to iden t i fy a lka l i - s i l i ca r eac t ion in concrete British Journal of Nondestructive Testing, Vo133, No. 5, pp. 227-231. (May 1991)

Deterioration of concrete structures in the United Kingdom due to alkali-silica reactions has caused considerable concern. This paper describes a pilot programme to consider the feasibility of using ultrasonic testing to assess and monitor the condition of concrete in buildings and structures known to be suffering from this so called "Concrete Cancer'. The presence of moisture while the concrete is in service shown to effect the degree of expansion and cracking caused by alkali-silica reactions. Pulse velocity and attenuation methods were both successful for expansions up to 0.3% but access to rear faces remains a problem with ultrasonic testing.

46560 Mindness, S. Acoustic emission methods CRC Handbook on Nondestructive Testing of Concrete. Edited by V.M. Malbotra and N.J. Carino. pp. 317-333. CRC Press (1991)

This review deals with the parameters affecting acoustic emissions from concrete, including discussions of the Kaiser effect, specimen geometry, and concrete properties. There follows an extensive discussion of the use of AE to monitor cracking in concrete, whether due to externally applied loads, drying shrinkage, or thermal stresses. AE studies on reinforced concrete are also described. It is concluded that while AE is a very useful laboratory technique for the study of concrete properties, its use in the field remains problematic.

46553 Muravin, G.B.; Shcherbakov, E.N.; SnezhnitskiL ES.; PaleL EM. An investigation of the structural and mechanical characteristics and formation of the structure of concrete by the acoustic emission method Soviet Journal of Nondestructive Testing, No. 26, VoL 6, pp. 391-398 (Feb. 1991)

On the basis of a composite method of investigations developed an analysis was made of the combination of properties of concretes of different compositions and method of preparation. The optimum composition for operation under conditions of nonsteady and dynamic loads was selected.

46526 Shimizu Construction Co Ltd.; (Kuramochi, M.; lmai, M.) Ultrasonic measuring apparatus including a damped transducer p r o b e

Brit ish Patent No. 2,232,487 (12 Dec. 1990) A metallic casing contains a low-frequency resin damper; to its front is fitted a

transducer and there is a connection for an ultrasonic measuring apparatus which supplied electrical pulses to the transducer; the resuRant high-damping probe is useful for measurement of thickness, voids and compressive strength of concrete; the damper absorbs unnecessary low frequency vibrations of the transducer so that the transmission and received waves are clearly separated. One or more such probes can be connected to a signal conversion (eg a fast Fourier transform) means, signal processing means (a low-pass filter) and a second signal converting means (an inverse fast Fourier transformKto obtain the signal waveform of the shear wave component of the reflected wave, for measurement of the thickness.

46458 Berthaud, Y. Measurement of mechanical damage to concrete by ultrasound. (In French) Proceedings of the 1st International Congress held by RILEM, Palais des Congres, Versailles (France), 7-11 Sep. 1987. Vol. 1, pp. 123-126. Edited by J.C. Maso. Chapman and Hall (1987)

46457 Kadlecek, V.; Dohnalek, J. Spectral analysis of u l t r a son ic s ignals in the testing of concrete Proceedings of the 1st International Congress held by RILEM, Paiais des Congres, Versailles (France), 7-11 Sep. 1987. Vol. 1, pp. 127-130. Edited by J.C. Maso. Chapman and Hall (1987)

The possibilities of the use of ultrasonic spectroscopy in the testing of concrete are investigated. The equipment for instantaneous analysis of the spectrum of the ultrasonic signal is described and also the technique of measurements. Further, the criteria for a quantitative evaluation of the obtained spectra are suggested. For testing of the suitability of the technique finally chosen, concrete test specimens with different structure, length and also with different state of deterioration were used. The results obtained represent the shape changes on the amplitude-frequency spectrum envelope.

46456 Galan, A. St reng th and e las t ic i ty cha rac t e r i s t i c s of gas concrete in the structure determined by non-destructive methods Proceedings of the 1st International Congress held by RILEM, Palais des Congres, Versailles (France), 7-11 Sep. 1987. Vol. 1, pp. 167-170. Edited by J.C. Maso. Chapman and Hall (1987)

The main purpose of the study was to develop nondestructive methods for determining the compressive strength of gas concrete in the structure and elements which are possible except its strength changes due to technology factors in the production and to note also the strength changes owing to different moisture contents in various points of the structure. The author has developed two methods of one parameter and five combined multiparameter nondestructive methods. The author has developed the method for measuring the time of pulse propagation of the transversal ultrasonic waves. This fact makes possible to establish these elasticity characteristics of the gas concrete in the structure by means of the real nondestructive way without the calibration samples.

46455 Samarai, M.A.; Raouf ZA.; Alshawaf A.K. C h a r a c t e r i z a t i o n of porous ferrocement plates by ul t rason ics Proceedings of the 1st International Congress held by RILEM, Palals des Congres, Versailles (France), 7-I 1 Sep. 1987. Vol. 1, pp. 171-178. Edited by J.C. Maso. Chapman and Hall (1987)

An experimental investigation was carried out in order to characterize lightweight ferrocement plates by ultrasonic pulse velocity. The reduction in weight of the plates was achieved by using foamed polystyrene beads in the matrix. The results of ultrasonic tests have been correlated with other properties such as flexural moments, resilience, ductility, and thermal conductivity. The dynamic modulus and the stiffness constants were found to decrease as the polystyrene beads to mortar ratio was increased. The Poisson's ratio was determined. The coefficient of thermal conductivity was considerably decreased depending on the polystyrene and steel wire contents. Relationships were found between the stiffness constants and the thermal conductivity of the plates.

46454 Limaye, H.S. Applications of impact.echo technique Proceedings of the 1989 SEM Spring Conference on Experimental Mechanics, Cambridge, Boston (United States), 29 May - 1 Jun. 1989. pp. 683-688. The Society for Experimental Mechanics (1989)

Impact-echo is a recently developed nondestructive test technique to detect significant flaws in concrete such as honeycombing, delaminations, cracks, cold joints and voids. The method is also capable of measuring thickness of various structural members or depths of piles or drilled piers. After describing the impact-echo technique, various applications of the techniques are presented in this paper.

46438 Naik, T.R.; Malhotra, V.M. The u l t r a son ic pulse veloci ty m e t h o d CRC Handbook on Nondestructive Testing of Concrete. Edited by V.M. Malhotra and N.J. Carino. pp. 169-188. CRC Press (1991)

The ultrasonic pulse velocity method has been used successfully to evaluate the quality of concrete for over 50 years. This method can be used for detecting internal structure changes in mortar and concrete such as deterioration due to aggressive chemical environment, cracking, and changes due to freezing and thawing. By using the pulse velocity method it is also possible to obtain the dynamic modulus of

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