determined, crack orientations can be decided from the directions of eigenvectors. The procedure developed was applied to a pull*out test of anchor bolt and a cylindrical tension test. The results confirm the applicability of the procedure to inspecting internal c r acksby the quantitative AE waveform analysis based on the moment tensor inversion.

47640 Limaye, H.S.; Krause, R.J. Nondestructive evaluation of concrete with impact-echo and pulse- velocity techniques Materia ls Evaluat ion, Vol. 49, No. 10, pp. 1312-1315 (Oct. 1991)

The paper describes the applications of two nondestructive techniques, impact echo and pulse velocity, to evaluate the condition of concrete structures. The power plant case histories describe the evaluation of a concrete foundation, a tunnel slab, and turbine pedestal columns. In the impact-echo method, the response of a concrete structure to mechanical impact is monitored and analyzed. The impact induces longitudinal, shear, and surface waves that reflect off internal discontinuities as well as the backs and sides of the concrete members. These reflections, or echoes, can be analyzed with a fast-Fourier transform (FFT) analyzer to determine the condition of the concrete. The pulse-velocity method involves measurement of transit time of an acoustic wave through a concrete structure. Significant changes in transit time are associated with the internal makeup of the structure. This method can be used to determine uniformity of concrete and to detect internal faults such as cracks, voids, or honeycombing.

47627 Gaydecki, P.A.; Burdekin, F.M.; Damaj, W.; John, D.G.; Payne, P.A. An u l t r a s o n i c i n spec t ion system capable of detecting voids and corroded steel components embedded in prestressed concrete structures Col loquium on Measurements , Model l ing and Imag ing for Non-Dest ruct ive Testing, London (United Kingdom) , 27 Mar. 1991. pp. 4/1-4/3. IEE (1991) Digest No. 1991/054

The strength of reinforced prestressed concrete structures critically dependent upon the integrity of the steel reinforcing cables. Catastrophic failure can occur in bridges for examples where cables break, corrosion occurs or defective concrete is present. This article describes an ultrasonic nondestructive inspection system which aids the location and identification of problem regions and can thus be used as a aid to bridge maintenance and repair. The system investigates changes in frequency bands as the signal travels through the concrete as these will change depending upon the size, geometry and acoustic impedance of the defect encountered.

47622 Kim, Y.H.; Lee, S.; Kim, H.C. Attenuation and dispersion of elastic waves in multi-phase m a t e r i a l s Journal o f Physics D. Appl ied Physics , Vol. 24, No. 10, pp. 1722-1728 (14 Oct. 1991)

The attenuation and dispersion of elastic waves in multi-phase materials such as granite, cement, mortar and concrete have been evaluated by the point-source/point- receiver technique with glass capillary breaking as an ideal source and a calibrated pin-type transducer as an ideal detector. The magnitude and phase spectrum from the Fourier analysis of the velocity signal gave attenuation and dispersion of the materials respectively, and the frequency dependence was also obtained in a single experiment. The sequence for attenuation was mortar, cement, granite and concrete; however, that for dispersion was cement, mortar granite and concrete in increasing order. The difference in resonant frequency spectra of mortar and concrete blocks was explained in terms of the measured attenuation and dispersion.

47524 Ohtsu, M. R a t e p roce s s a n a l y s i s of AE activity in u n i a x i a l compression test of core sample Progress in Acoust ic Emiss ion V. The 10th Internat ional Acoust ic Emiss ion Sympos ium, Sendal (Japan), 22-25 Oct. 1990. pp. 311-316. Edited by K. Yamaguchi , H. Takahashi and H. Nii tsuma. The Japanese Society for Non-Dest ruct ive Inspect ion (1990)

A rate process analysis of acoustic emission (AE) during uni-axial compression tests of core samples is proposed to evaluate the deterioration degree of concrete due to microcracking. When concrete contains a number of critical microcracks, AE events occur actively from low stress level. In contrast, AE activity of sound concrete is observed just prior to final failure. The discrepancy of AE generating behaviors is quantitatively evaluated, introducing the rate process analysis. To gauge the applicability of AE rate process analysis, experiments on newly cast concrete and core samples are performed. The correlation with the strength, the age, and the damage levels of concrete is clarified. Thus, AE rate process analysis shows a great promise for providing quantitative information on the deterioration of concrete in the uniaxial compression test of core samples.

47523 Nomura, N.; Mihashi, H.; Suzuki, A.; Izumi, M. Aspects of fracture process zone of concrete Progress in Acoust ic Emiss ion V. The 10th International Acoust ic Emiss ion Sympos ium, Sendal (Japan), 22-25 Oct. 1990. pp. 317-324. Edi ted by K. Yamaguchi , H. Takahashi and H. Nii tsuma. The Japanese Society for Non-Destruct ive Inspect ion (1990)

In this paper, three dimensional acoustic emission technique (3-D AE) is applied to observe the phase of the fracture process zone of concrete. The results show that the fracture process zone is widely created at the peak load and then the zone with active AE events moves towards the bottom of the specimen.

47522 Uomoto, T.; Kato, H. Drying shrinkage of concrete and acoustic emission Progress in Acoust ic Emiss ion V. The 10th International Acoust ic Emiss ion

Sympos ium, Sendal (Japan), 22-25 Oct. 1990. pp. 325-330. Edited by K. Yamaguchi , H. Takahashi and H. Nii tsuma. The Japanese Society for Non-Dest ruct ive Inspect ion (1990)

This paper is aimed to clarify how drying shrinkage starts through experiment, measuring both length change and acoustic emission after concrete prisms are stored in dry atmosphere. The results show that the initiation of drying shrinkage is directly after the concrete is revealed to dry atmosphere, and acoustic emission (AE) monitoring show good correlation with drying shrinkage of concrete.

47521 Niiseki, S.; Satake, M.; Gohke, M. Quick detection of alkali-aggregate reaction by AE monitoring Progress in Acoust ic Emiss ion V. The 10th International Acoust ic Emiss ion Sympos ium, Sendal (Japan), 22-25 Oct. 1990. pp. 331-336. Edi ted by K. Yamaguchi , H. Takahashi and H. Nii tsuma. The Japanese Society for Non-Dest ruct ive Inspect ion (1990)

In the early stage of alkali-aggregate reaction, the expansion pressure of reaction product is considered to give rise to microcracking and AE is extremely sensitive to microcracking in specimens. From such a point of view, in this paper, we propose a new method quickly detecting the alkali-aggregate reaction by monitoring AE in mortar-bar specimens under the same storage condition as the mortar-bar test of JASS.

47520 Muravin, G. Determination of concrete behaviour in structures on the basis of acoustic emission data Progress in Acoust ic Emiss ion V. The 10th International Acoust ic Emiss ion Sympos ium, Sendal (Japan), 22-25 Oct. 1990. pp. 337-344. Edited by K. Yamaguchi , H. Takahashi and H. Nii tsuma. The Japanese Society for Non*Destructive Inspect ion (1990)

We have studied the acoustic emission (AE) nature while concrete deformation and emission parameters are identified with the material structure state characterized by the reference point of the microcrackformation beginning, non-linear creep and develop- ment of main cracks. A method of toughness evaluation of concrete deformation by the way of its hydrodynamic or tared local shot load combined with synchronous AE measuring against microcracks formation in the fracture zone has been worked out for structural engineering exposed to dynamic and impact loads. The data is compared with AE parameters measured at the time of traditional bend test of the samples. The functional connection between mechanic and acoustic energy while concrete samples deformation, in the range of work load, microcrackformation and fracture development is proved.

47519 Yuyama, S.; Nagataki, S.; Okamoto, T.; Soga, T. Several AE sources observed during fracture of repaired reinforced concrete beams Progress in Acoust ic Emiss ion V. The 10th International Acoust ic Emiss ion Sympos ium, Sendal (Japan), 22-25 Oct. 1990. pp. 345-353. Edited by K. Yamaguchi , H. Takahashi and H. Nii tsuma. The Japanese Society for Non-Dest ruct ive Inspect ion (1990)

Bending tests were carried out on large repaired reinforced concrete beams. Fracture process was monitored by AE, visual observation and displacement measurement. It was found that distinctive AE signals were produced by the initiation of early tensile microcracks, local slips, main tensile crack and large-scale slips between the original part and the repaired part. All these different AE sources and their amplitude levels could be clearly discriminated by comparing the AE data with the results of visual observation and displacement measurement. Concrete beam integrity (CBI) ratio, the ratio of the load at onset of AE and the maximum prior load, is proposed as an effective criterion to measure the severity of damages induced in repaired concrete beams.

47484 Taylor, M.; Leaird, J.D. Acoustic emission from concrete NDE: The Next Decade and Beyond. 1990 A S N T Spring Conference, San Antonio, Texas (United States), 19-23 Mar. 1990. pp. 147-149. A S N T (1990)

Evaluation of large amounts of a concrete is obviously a major undertaking and the industry has long felt the need for an accurate in- place test for such qualities as strength and durability (against freeze-thaw, chemical attack, weathering) of concrete. There is no well established nondestructive test (NDT) for any of these qualities. This paper reports the results of three pilot investigations which indicate that acoustic emission (AE) techniques offers real promise as a NDT test for the future.

47350 Mihashi, H.; Nomura, N.; Niiseki, S. Influence of aggregate size on fracture process zone of concrete detected with three dimensional acoustic emission technique Cement and Concre te Research, Vol. 21, No. 5, pp. 737-744 (1991)

Three dimensional acoustic emission technique is applied to observe the phase of the fracture process zone of concrete which is created ahead of the crack tip and significantly influences the tension softening behaviour of concrete. The results show that the fracture process zone is already created at the peak load and then the active AE event zone moves towards the bottom of the specimen. It is also revealed that the fracture process zone may expand as the crack grows and the expanding rate of the process zone is influenced by the aggregate size.

47222 Voiczek, G. Nondestructive testing of concrete in buildings (In German: Eng l i sh Abstract) Mater ia lprufung, Vol. 33, No. 9, pp. 269-271 (1991)

The nondestructive determination of the strength of concrete in buildings becomes as precise as the destructive testing when correction factors are experimentally

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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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