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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 13 Abstracts search results
Document:
SP259-02
Date:
February 1, 2009
Author(s):
M. Ozawa, S. Uchida, T. Kamada, and H. Morimoto
Publication:
Symposium Papers
Volume:
259
Abstract:
Drying shrinkage cracking can occur in concrete due to volumetric changes caused by temperature and moisture gradients. The purpose of this study is to acquire fundamental data on the relationship between internal relative humidity and drying shrinkage cracking. The detection of drying shrinkage cracking was performed using the Acoustic Emission method. It was found that the AE measurement technique was successful at detecting drying shrinkage cracking.
DOI:
10.14359/56534
SP259-06
R. Henkensiefken, G. Sant, T. Nantung, and J. Weiss
The propensity for early-age shrinkage cracking in low w/c concretes has spawned the development of new technologies that can reduce the risk of cracking. One such technology is internal curing. Internal curing uses saturated lightweight aggregate to supply ‘curing water’ to low w/c paste as it hydrates. Significant research has been performed to determine the effects of internal curing on shrinkage and stress development in sealed samples. However, relatively little detailed information exist about how water is released from the lightweight aggregate to the surrounding cement paste. This study examines the timing of moisture release from saturated lightweight aggregate (LWA). Specifically this paper focuses on fluid transport around the time of set. X-ray absorption is used to trace the time at which water moves from the lightweight aggregate to the paste. X-ray observations are compared with results from the Vicat needle, autogenous shrinkage, and acoustic emission tests. These results are contextualized in terms of structure formation and vapor space cavitation in the cement paste.
10.14359/56538
SP259-11
J. Abel, R.C.A. Pinto, and K.C. Hover
A simple but challenging experiment was carried out to measure concrete temperature, air content, unit weight, slump, setting (penetration resistance), heat release, maturity, and compression strength over a 28-day period beginning with discharge from the chute of a concrete truck. It was thus demonstrated that concrete’s transition from liquid to solid is represented continuously by maturity and by heat release, but it is more commonly recorded in terms of three phases in concrete development: slump loss, setting, and strength gain. The paper describes how these phases overlap each other and are related to concrete temperature, heat release, and maturity.
10.14359/56543
SP259-01
C. Chung, J.S. Popovics, and L.J. Struble
Ultrasonic wave reflection (UWR) has been used to monitor hydration and strength development of concrete. UWR measures the changes in reflected ultrasonic waves at the interface between a buffer material and hydrating cement paste. To monitor the subtle changes during early hydration it is necessary to use a buffer with low acoustic impedance, close to that of cement paste. In this research, UWR measurements on hydrating Type I portland cement are performed using a high impact polystyrene (HIPS) buffer. Both S-waves and P-waves are analyzed simultaneously to develop and extend the use of UWR to monitor early stiffening of cement paste. The penetration resistance test (ASTM C 403) and temperature rise of cement paste are used to correlate stiffening characteristics. The UWR responses show good correlation with results from temperature rise and penetration resistance. The onset of stiffening is the same for penetration resistance and both P- and S-wave UWR, and nearly the same for temperature rise. It is found that the HIPS buffer can provide sensitive measurement on the early age stiffening of cement paste.
10.14359/56533
SP259-08
R.P. Ferron, C. Negro, and S.P. Shah
Structural build-up that occurs during the induction period is of particular interest to users of self-consolidating concrete (SCC) since it can affect the workability of concrete. A novel experimental device based on scanning laser microscopy was used to directly monitor particle flocculation in SCC cement pastes. This is one of the few studies in which this experimental method has been used to study flocculation in concentrated suspensions. This paper discusses the results from a study that was carried out to investigate the flocculation and floc properties in SCC cement pastes. Results show that the floc network is immediately broken down by superplasticizers and that the rate of reflocculation decreases when the water-to-cement (w/c) ratio is decreased. An increase in w/c ratio resulted in a reduction in floc strength. Results show that viscosity modifying agents can induce flocculation due to different flocculation mechanisms.
10.14359/56540
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