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The detection of the fracture of autoclaved aerated concrete during autoclave curing process by acoustic emission
39522 Satoshi Teramura; Koichi Tsukiyama; Hideaki Takahashi. The detection of the fracture of autoclaved aerated concrete during autoclave curing process by acoustic emission Journal of Acoustic Emission, Vol. 6, No. 4, pp. 261-266 ( O c t . - D e c . 1987) Autoclaved Aerated Concrete (AAC) occasionally fractures during the autoclave curing in the production process. To study the cause of the fracture, acoustic emission (AE) activities, during autoclave curing, were investigated. When AE events were detected during both temperature rise and fall periods in the autoclave operation of an AAC, the concrete contained a number of microcracks. When AE events were detected only during temperature fall period of an AAC, it was free of microcracks. AE activities during temperature rise period are indicative of the macrocracking. The macrocracking is influenced by the strength of the material just prior to the autoclave curing process. From these results, a procedure for the prevention against fracturing is proposed. 39517 Titus, R.N.K.; ReddY, D.V.; Dunn, S.E.; Hartt, W.H. Acoustic emission crack monitoring and prediction of remaining life of corroding reinforced concrete b e a m s Proceedings of the 4th E u r o p e a n Conference On Non-Destructive Testing, L o n d o n (United Kingdom), 13-17 Sep. 1987. Vol. 2, pp. 1031-1040. P e r g a m o n Press, 3173 pp. (1988) Maintenance of reinforced concrete structures requires the detection and characterization of corrosion damage through a diagnostic method. Acoustic emission (AE) testing has proven to be an effective procedure, and possesses the ability to detect the corrosion cracking damage process at an incipient stage. The paper describes the use of acoustic emission for crack monitoring, and prediction Of failure life for reinforced concrete members, subjected to varying periods of corrosion. Test beams were subjected to accelerated corrosion by partial submergence in seawater and impressed currents, with the bottom rebars as the anodes, a stainless steel plate as the cathode, and seawater the electrolyte. Piezoelectric ceramic type transducers were glued to the specimen surface at the mid-span top edge. Counts and amplitude distribution of the acoustic emission were monitored at 12 hour intervals. Plots of the amplitude distribution (cumulative and linear) were made just before the memory reached saturation. Correlation studies between AE counts and flexural strength indicated a 95% confidence that the variations in these parameters are interdependent. Correlation studies for other strength characteristics, such as durability and fatigue life, are anticipated to indicate similar trends. 39481 Gordon, C.M.; Peters, C.W. A fast-neutron probe for tomography and bulk analysis Transactions of the A m e r i c a n Nuclear Society, Vol. 56, Supplement No. 3, p. 63-65 (Conference on Industrial and Radioisotope M e a s u r e m e n t Applications, Pinehurst, North Carolina, 7-9 Sep. 1988) A new industrial tomographic method is described in this paper which combines three techniques, associated particle neutron time-of-flight (TOF) spectroscopy, inelagtic gamma-ray spectroscopy and a recently developed sealed tube neutron generator (STNG). A fast collimated neutron beam is used to probe the material. Inelastic gamma rays, produced by interactions with the neutrons are detected and analyzed. Spatial production of gamma rays is used to provide imaging information. This technique is especially useful for nondestructive tomographic analyses of solids or inaccessible spaces. The STNG used in the TOF system is described, and results from tests with coal, concrete and steel are mentioned. 39478 Minato, S.; Fukaya, M. Cosmic-ray radiographic image of large structural materials Transactions of the A m e r i c a n Nuclear Society, Vol. 56, Supplement No. 3, p. 63 (Conference on Industrial and Radioisotope Measurem e n t Applications, Pinehurst, North Carolina, 7-9 Sep. 1988) Gamma, X-ray, or neutron radiography is widely used in various fields at present for nondestructive testing. In analogy to those techniques, the feasibility of cosmic-ray radiography is reported in this paper. If the cosmic rays were effectively applied, quite large objects could be inspected because of the rays' extremely great penetrating quality. In this study, a temple gate is used which is made of concrete approx 20 m high as a test piece. The measurements of cosmic-ray intensities under the gate were made at 30 x 39 = 1170 points at every 1.275 m at ground level, corresponding to approx 1800 m 2 in area. The cosmic-ray radiographic image of the temple gate is shown. The plane figure of the roof is also given by solid lines in the figure. Here, the intensity values from minimum to maximum levels are divided into six groups for simplicity. Although the pattern looks to some extent out of focus, it seems enough to consider that it reflects well the structure of the temple gate. 39473 Kunz, C. Experience with testing prestressed concrete structures by radiography Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, L o n d o n (United Kingdom), 13-17 Sep. 1987. Vol. 2, pp. 1024-1030. P e r g a m o n Press, 3173 pp. (1988) Along navigable waterways the waterway and shipping administration of the Federal Republic of Germany maintains prestressed concrete structures, whose tendons are radiographically tested by exception. Imperfections of the mortar filling grade of the tendons, ensuring protection against corrosion, appear as different contrasts of the exposed film-negative. The contribution represents and evaluates experience gained with radiography from a civil engineering aspect. Future main points for working with radiographic testing of structures are discussed here.
NDT International April 1990
39468 Russ, J. C. Differential absorption three-dlmemtcaol m k r o t o m z g r u p h y Transactions of the A m e r i c a n Nuclear Society, Vol. 56, Supplement No. 3, p. 14 (Conference o n Industrial and Radioisotope Measurement Applications, Pinehurst, North Carolina, 7-9 Sep. 1988) Beam hardening in x-ray tomographic reconstruction of internal structure in materials samples can be overcome using balanced filters. Pairs of filters made from adjacent or nearby elements in the periodic table are thickness adjusted to equalize their absorption coefficients over most of the energy range, except for the region between the absorption edge energies of the component elements. Here the very large difference in absorption is used to detect the presence of elements whose emission lines fall in this region. Resolution of a few micrometres can be achieved using a microfocus x-ray source for studying the fine-scale internal structure of complex materials such as sintered ceramics, composites and cements. The two dimensional far beam projections are reconstructed in series to produce quasi tomographic images for interactive viewing or generating a transparency. 39424 Hillger, W. Inspection of concrete by ultrasonic testing Proceedings of the 4tli E u r o p e a n Conference on Non-Destructive Testing, L o n d o n (United Kingdom), 13-17 Sep. 1987. Vol. 2, pp. 1003-1012. Pergamon Press, 3173 pp. (1988) This article reports the investigations to enhance the informative value of the ultrasonic NDT of concrete. The object of the investigations was the defectoscopy, i.e. the monitoring of homogeneity and detection of localized faults. The testing technique was further developed with regard to amplitude evaluation. A US-inspection system "Sonograf 1000" was developed for this purpose. This new flaw detector automatically evaluates the amplitude with a gated digital logarithmic peak detector, the time of flight and the frequency spectrum of the received signal, so that it became possible to record C-scans of precast concrete components by fully automatic procedure. C-scans clearly show the artificially introduced defects and the homogeneity of the material. 39423 Berthaud, Y. Damage measurement via ultrasonic method Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, L o n d o n (United Kingdom), 13-17 Sep. 1987. Vol. 2, pp. 1013-1023. Pergamon Press, 3173 pp. (1988) A special ultrasonic testing method has been developed to measure damage in concrete structures. This technique, which is closely related to the presence of microcracks and/or micropores, takes account of the particular micro-structure of concrete. The first part of this study demonstrates the great influence of the particular nature of undamaged concrete on wave propagation. The second part consists in the analysis of the effects of mechanical damage and specially of its anisotropy. 39392 Bungey, J.H. A review of the assessment of in.situ strength of concrete Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, L o n d o n (United Kingdom), 13-17 Sep. 1987. Vol. 2, pp. 1048-1057. P e r g a m o n Press, 3173 pp. (1988) Methods available for assessing in situ strength of concrete are reviewed and classified. These include cores, non-destructive, and partially destructive near-to-surface techniques as well as maturity measurement and temperature matched curing. Emphasis is placed upon the limitations to the accuracies possible, and the importance of estabfishing reliable correlations between measured property and strength. The advantages of combinations of test methods are identified, and guidance is given about the selection of the must appropriate techniques. Attention is also paid to variability of concrete properties, and the influence of this upon the interpretation and use of test results in practical situations. 39389 Bungey, J.H. The most effective use of NDT of concrete Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, L o n d o n (United Kingdom), 13-17 Sep. 1987. Vol. 2, pp. 963-970. Pergamon Press, 3173 pp. (1988) The most worthwhile appfications of NDT to concrete are identified and discussed with emphasis on practical limitations. These include testing during and after construction, assessment of deterioration, and testing of repairs. The importance of careful test selection and planning taking into account practical features of the test site as well as features of individual test methods is considered. Particular attention is paid to the value of sequential investigations with ongoing interpretation using combinations of test methods. This offers flexibility, which is essential with an inherently variable material such as concrete. 39367 Teramura, S.; Tsukiyama, K.; Takahashi, H. Evaluation of fracture toughness of autoclaved lightweight concrete by means of acoustic emission technique Journal of Acoustic Emission, Vol. 7, No. 1, pp. 1-8 (Jan./Mar. 1988) The quality of an autoclaved aerated concrete has usually been evaluated by the mechanical strength, such as compressive strength and bending strength. These mechanical properties, however, are not appropriate for the evaluation of the fragility of the concrete, because the fragility depends strongly upon the crack nucleation and the crack propagation. The aim of this investigation is to determine the fragility of the autoclaved aerated concrete in term of J-integral
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NDT International April 1990
39468 Russ, J. C. Differential absorption three-dlmemtcaol m k r o t o m z g r u p h y Transactions of the A m e r i c a n Nuclear Society, Vol. 56, Supplement No. 3, p. 14 (Conference o n Industrial and Radioisotope Measurement Applications, Pinehurst, North Carolina, 7-9 Sep. 1988) Beam hardening in x-ray tomographic reconstruction of internal structure in materials samples can be overcome using balanced filters. Pairs of filters made from adjacent or nearby elements in the periodic table are thickness adjusted to equalize their absorption coefficients over most of the energy range, except for the region between the absorption edge energies of the component elements. Here the very large difference in absorption is used to detect the presence of elements whose emission lines fall in this region. Resolution of a few micrometres can be achieved using a microfocus x-ray source for studying the fine-scale internal structure of complex materials such as sintered ceramics, composites and cements. The two dimensional far beam projections are reconstructed in series to produce quasi tomographic images for interactive viewing or generating a transparency. 39424 Hillger, W. Inspection of concrete by ultrasonic testing Proceedings of the 4tli E u r o p e a n Conference on Non-Destructive Testing, L o n d o n (United Kingdom), 13-17 Sep. 1987. Vol. 2, pp. 1003-1012. Pergamon Press, 3173 pp. (1988) This article reports the investigations to enhance the informative value of the ultrasonic NDT of concrete. The object of the investigations was the defectoscopy, i.e. the monitoring of homogeneity and detection of localized faults. The testing technique was further developed with regard to amplitude evaluation. A US-inspection system "Sonograf 1000" was developed for this purpose. This new flaw detector automatically evaluates the amplitude with a gated digital logarithmic peak detector, the time of flight and the frequency spectrum of the received signal, so that it became possible to record C-scans of precast concrete components by fully automatic procedure. C-scans clearly show the artificially introduced defects and the homogeneity of the material. 39423 Berthaud, Y. Damage measurement via ultrasonic method Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, L o n d o n (United Kingdom), 13-17 Sep. 1987. Vol. 2, pp. 1013-1023. Pergamon Press, 3173 pp. (1988) A special ultrasonic testing method has been developed to measure damage in concrete structures. This technique, which is closely related to the presence of microcracks and/or micropores, takes account of the particular micro-structure of concrete. The first part of this study demonstrates the great influence of the particular nature of undamaged concrete on wave propagation. The second part consists in the analysis of the effects of mechanical damage and specially of its anisotropy. 39392 Bungey, J.H. A review of the assessment of in.situ strength of concrete Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, L o n d o n (United Kingdom), 13-17 Sep. 1987. Vol. 2, pp. 1048-1057. P e r g a m o n Press, 3173 pp. (1988) Methods available for assessing in situ strength of concrete are reviewed and classified. These include cores, non-destructive, and partially destructive near-to-surface techniques as well as maturity measurement and temperature matched curing. Emphasis is placed upon the limitations to the accuracies possible, and the importance of estabfishing reliable correlations between measured property and strength. The advantages of combinations of test methods are identified, and guidance is given about the selection of the must appropriate techniques. Attention is also paid to variability of concrete properties, and the influence of this upon the interpretation and use of test results in practical situations. 39389 Bungey, J.H. The most effective use of NDT of concrete Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, L o n d o n (United Kingdom), 13-17 Sep. 1987. Vol. 2, pp. 963-970. Pergamon Press, 3173 pp. (1988) The most worthwhile appfications of NDT to concrete are identified and discussed with emphasis on practical limitations. These include testing during and after construction, assessment of deterioration, and testing of repairs. The importance of careful test selection and planning taking into account practical features of the test site as well as features of individual test methods is considered. Particular attention is paid to the value of sequential investigations with ongoing interpretation using combinations of test methods. This offers flexibility, which is essential with an inherently variable material such as concrete. 39367 Teramura, S.; Tsukiyama, K.; Takahashi, H. Evaluation of fracture toughness of autoclaved lightweight concrete by means of acoustic emission technique Journal of Acoustic Emission, Vol. 7, No. 1, pp. 1-8 (Jan./Mar. 1988) The quality of an autoclaved aerated concrete has usually been evaluated by the mechanical strength, such as compressive strength and bending strength. These mechanical properties, however, are not appropriate for the evaluation of the fragility of the concrete, because the fragility depends strongly upon the crack nucleation and the crack propagation. The aim of this investigation is to determine the fragility of the autoclaved aerated concrete in term of J-integral
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