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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 12 Abstracts search results
Document:
SP112-03
Date:
January 1, 1989
Author(s):
M. A. Taylor
Publication:
Symposium Papers
Volume:
112
Abstract:
Gamma-ray absorption techniques were used to determine the amounts of each component in a system of mixtures (such as concrete). The technique uses photons of several energies in contrast to previous applications where only one energy was employed. The use of multiple energies provides more information than the single-beam system, and thus more properties can be determined. Several possible models for cementitious materials are discussed and compared. The paper presents the experimental determination of the initial data set needed prior to prediction experiments. One predictive technique is evaluated by comparison with blind tests.
DOI:
10.14359/2362
SP112-10
T. J. Parson
Reports results of an investigation into the use of maturity for predicting early-age concrete strengths. Prediction models were developed from cylinder-test results obtained from twelve concrete mixtures cured under three constant curing conditions. A datum temperature of 25 F (-4 C) was used as it appeared to produce the best results. A prediction model based on estimated ultimate concrete strength was used and found to be independent of curing temperature. However, the estimated ultimate concrete strength value appeared to be dependent on curing temperature. The model was verified by using it to predict concrete strengths obtained from cylinders and slabs cured outdoors.
10.14359/2372
SP112-02
A. Alexander and H. T. Thornton
A new improved prototype ultrasonic pitch-catch (two-transducer) and pulse echo (one-transducer) system has been developed for concrete. Signal generation and detection is done with piezoelectric crystals. A literature search revealed that no piezoelectric pulse-echo system had been developed for the ultrasonic range ( > 20 kHz) and that pitch-catch measurements needed further development. No commercial system could be found on the market for making pitch-catch measurements. Research by the U.S. Army Engineer Waterways Experiment Station 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 reduced significantly from the prior state-of-the-art system. The WES system works well for thickness measurements of portland-cement concrete pavement and can indicate the presence of voids.
10.14359/3655
SP112-04
M. Ohtsu
On the basis of the acoustic emission (AE) measuring technique, a diagnostic method for nondestructive evaluation of cracks in concrete is proposed. The diagnostics consist of a mechanical criterion of crack initiation, a quantitative waveform analysis of AE, the evaluation of deterioration by a test of core specimens, and the ultrasonic spectroscopic investigation of cracked members. Results of basic studies on these methods are summarized. Results of basic studies confirm the feasibility and the usefulness of the proposed method as diagnostics of cracks in concrete structures.
10.14359/2840
SP112-05
A. K. Maji and S.P. Shah
The fracture process of a composite material involves crushing or slippage of adjacent particles, microcracking, etc., resulting in changes in the load-versus-displacement behavior. A study of the fracture process is necessary to develop a rational material model. Laser holographic interferometry was applied to study the whole field deformation pattern. Speckle photography was used to measure quantitatively 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 algorithm was used to calculate the locations of the AE events. Specimens were made with different aggregate and void sizes to study their effect on crack patterns and load-displacement behaviors.
10.14359/2846
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