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International Concrete Abstracts Portal

Showing 1-5 of 7 Abstracts search results

Document: 

SP135-03

Date: 

December 1, 1992

Author(s):

S.K. Hirata, D.M. Smith and M.I. Hammons

Publication:

Symposium Papers

Volume:

135

Abstract:

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.

DOI:

10.14359/10032


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


Document: 

SP135-02

Date: 

December 1, 1992

Author(s):

J. J. Brooks and A. Neville

Publication:

Symposium Papers

Volume:

135

Abstract:

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.

DOI:

10.14359/2241


Document: 

SP135

Date: 

December 1, 1992

Author(s):

Editors: Marwan A. Daye and C.C. Fu

Publication:

Symposium Papers

Volume:

135

Abstract:

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.

DOI:

10.14359/14167


Document: 

SP135-04

Date: 

December 1, 1992

Author(s):

H. M. Marzouk

Publication:

Symposium Papers

Volume:

135

Abstract:

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.

DOI:

10.14359/2259


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