Long-term research into the characteristics of high alumina cement concrete

Abstract

Synopsis The paper describes a research programme started in 1964 to study the characteristics of high alumina cement (HAC) concrete up to an age of 20 years. Experimental details are given of the main and two suhsidiary programmes together with test results up to 8·5 years. Four test series were undertaken to establish: (1) the strength development of a wide range of concrete mixes stored continuously in water at 18°C and at 38°C for long periods; (2) the effect of changes in curing regime during the first 24 h upon the subsequent strengths up to 1 year; (3) the effectiveness of an immediate conversion curing regime to give minimum strengths at 5 days instead of 3 months; (4) the modulus of elasticity of HAC concrete, both unconverted and converted. This research includes the quantitative measurement of the degree of conversion, factors influencing it and its relation to the reduction in compressive strength. The results show that the strength after long periods of storage in water at 18°C is extremely sensitive to the water/cement ratio, and that the temperature conditions during the first 24 hare highly criticalfor strength at later ages. The modulus of elasticity of high alumina cement, converted or unconverted, is related to the compressive strength of the concrete.