Effect of Superplasticizers on Slump, Strength, and Degree of Conversion of High-Alumina Cement Concrete

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Title: Effect of Superplasticizers on Slump, Strength, and Degree of Conversion of High-Alumina Cement Concrete

Author(s): D. H. H. Quon and V. M. Malhotra

Publication: Special Publication

Volume: 68

Issue:

Appears on pages(s): 173-188

Keywords: aluminate cements and concretes; consistency tests; high-alumina cements; me mix proportioning; plasticizers; slump test cement ratio; water-reducing agents. compressive strength; chanical properties; s; specimens; water-

Date: 1/1/1981

Abstract:
The introduction of superplasticizers, or high-range water reducers as these are sometimes called, has made it possible to achieve very high slumps in normal portland cement concrete at very low water-to-cement ratios. It was considered that perhaps a similar approach may help to overcome the problems associated with concrete made with high-alumina cement. This report gives results of a brief investigation undertaken to determine the effect of superplasticizers on the consistency, compressive strength and degree of conversion of high-alumina cement concrete. Three commercially available superplasticizers were added to high-alumina cement concrete mixtures with a water-to-cement ratio of 0.36. The slump test was used as a measure of consistency. Compressive strength was obtained on 102 x 203~mm cylinders and the degree of conversion was determined using differential thermal analysis. In spite of dosages of 3% or more by weight of cement, concrete having flow characteristics was not obtained. In addition, there was extremely rapid slump loss, the concretes, reverting to their original slump in less than 20 minutes. At the ages of 10 hours, 1 and 2 days, the compressive strength of concrete incorporating superplasticizers was considerably lower than the strength of the control concrete. At 180 days 9 the strengths of the superplasticized and the control concretes were comparable, reaching a value of the order of 80 MPa. The addition of the superplasticizers to high-alumina cement concrete did not affect the rate of conversion of the high-alumina cement; the degree of conversion values for the superplasticized and the control concretes was less than 30% at 180 days.