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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 7 Abstracts search results
December 1, 1992
Editors: Marwan A. Daye and C.C. Fu
This Special Publication contains six papers covering the areas of prediction models, effects of admixtures and cement replacement materials, relationship between creep and thermal stresses, effects of fly ash and silica fume, characteristics of carbon fiber reinforced composites, and cement-phosphogypsum mixtures.
S.K. Hirata, D.M. Smith and M.I. Hammons
Thermal-related cracking in mass concrete structures can significantly increase maintenance and repair costs and decrease service life. Incremental construction thermal-stress analyses performed on a critical section of a navigation lock chamber monolith provided the basis for a study of the relationship between creep of concrete and thermal stresses during construction. Two concrete mixtures with high proportions of fly ash to portland cement (up to 50 percent fly ash) were selected for a full complement of thermal and mechanical properties testing at ages from 16 hours to 14 days. A general purpose heat-transfer an structural analysis finite element code was used in the analyses. The code incorporated a time-dependent material model as an integral part of the analysis effort. Material and mechanical properties test results were incorporated into the analyses for each mixture.
H. M. Marzouk
In recent years, considerable attention has been given to the use of silica fume as a partial replacement for cement to produce high-strength concrete. The use of silica fume high-strength concrete offers great promise for marine structures and offshore platforms. Preliminary results of creep strain measurements for 24 specimens at temperatures of 20, 10, 0, -10, and -20 C are presented. At room temperature, three stress levels were applied to the concrete specimens ranging from 25 to 75 percent of the 28-day strength at room temperature. For specimens at temperatures of 10, 0, -10, and -20 C, one stress level of 50 percent of the 28-day compressive strength of the reference specimens was applied. The results of creep at low temperatures were compared to the corresponding results at room temperature. In general, the relation of creep to stress-strength ratio at room temperature was found to be linear for silica fume concrete as the case for ordinary portland cement concrete. Test results revealed that low temperature had a minor effect on the magnitude of creep strains at temperatures between -10 and -20 C. Based on the experimental results, a basic expression for creep of silica fume concrete is suggested. Discussion of a hypothesis of the creep mechanisms is presented.
C. X. Ling, K. T. Lin, and W. F. Chang
The huge quantity of phosphogypsum which has been stockpiled in Florida has caused increasing concerns with respect to its possible environmental impacts. Many research projects on utilization of phosphogypsum as construction materials have been sponsored by the Florida Institute of Phosphate Research. It was found that phosphogypsum-based materials possess valuable strength sufficient for use in building and road construction after compaction. The aim of the tests in this paper is to investigate the shrinkage properties of phosphogypsum-cement mixtures and the influence of thefactors, such as moisture content (MC), phosphogypsum/cement ratio (P/C), curing conditions, the relation between shrinkage and moisture loss, comparison of shrinkages of the compacted and vibrated specimens, and ambient humidity. A standard 1 x 1 x 11.25-in. (25 x 25 x 285-mm) bar, of which the net length between the two contact points at the two ends is 10 in., was used to measure the linear shrinkage. The specimens covered 14 to 22 percent MC, 10:90-95:5, three 28 days' curing, and 50 to 70 percent ambient humidity. Effect of these factors on the development of drying shrinkage over time is described, and the relationship between drying shrinkage and loss of water is given for each factor involved. The volume change of the specimen in the air is a swelling-shrinkage process with loss of moisture. Shrinkage of compacted specimen is much less than that of vibrated specimen. Curing conditions and ambient humidity are significant to the shrinkage. There is a maximum shrinkage at about 25:75 P/C, and an empirical formula to predict effect of P/C is obtained, using a program which fits least-squares polynomials to bivariate data.
P. Soroushian, M. Nagi, and E. Mustata
An experimental study was conducted to assess the effect of carbon fiber reinforcement on drying shrinkage strains in cementitious matrixes. Composites with different fiber lengths and volume fractions were considered in this investigation. Results indicated that shorter fibers at relatively low volume fractions tend to reduce drying shrinkage strains. The increase in fiber volume fraction does not necessarily produce further reductions in shrinkage movements, possibly due to the corresponding increase in water requirements for maintaining fresh mix workability. Longer fibers may not be as effective as the shorter ones in reducing shrinkage strains. This observation also can be attributed to the increase in water requirement with increasing fiber length. The large scatter in shrinkage test results makes it difficult to statistically derive reliable conclusions based on the limited test results generated in this investigation.
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