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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
Document:
SP135-06
Date:
December 1, 1992
Author(s):
C. X. Ling, K. T. Lin, and W. F. Chang
Publication:
Symposium Papers
Volume:
135
Abstract:
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.
DOI:
10.14359/2279
SP135-05
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.
10.14359/2268
SP135-02
J. J. Brooks and A. Neville
Paper reviews the influence on creep and shrinkage of water reducers, retarders and accelerators, and superplasticizers. Few generalizations can be made. Partial replacement of cement fly ash or blast furnace slag leads to reduced creep except for early age loading. Specific properties of the materials used affect creep. Data on the use of microsilica suggest that it increases creep. Because of the paucity of data available, reliable deductions about the influence of various materials cannot be made and, in important cases, experimental determination of creep and shrinkage of concrete with the actual mix ingredients may be necessary.
10.14359/2241
SP135-01
H. S. Miller
The Comite Euro-International du Beton (CEB) has prepared a new model code for the design and analysis of concrete structures (CEB-FIP Model Code 1990) which includes new prediction models for creep and shrinkage of concrete. These models have been derived and optimized on the basis of a computerized data bank. For the prediction of shrinkage, a diffusion theory-type model has been chosen. The prediction of creep is based on a simple product-type approach. Though the new creep model resembles some of the features of the model presented by ACI 209, various basic improvements could be achieved. The coefficients of variation for shrinkage and creep have been found to be approximately 33 and 20 percent, respectively. The developed prediction models, both for creep and shrinkage, represent a reasonable compromise of accuracy and simplicity. They meet the requirements for presentation in a code. In this paper, both models are presented and some comparisons with test data are shown.
10.14359/3152
SP135
Editors: Marwan A. Daye and C.C. Fu
SP135 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.
10.14359/14167
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