Experimental investigations on early-age tensile creep of internally cured high strength concrete under different initial stress/strength ratios

Abstract

High strength concrete (HSC) with high strength and low permeability has been widely utilized in the reinforced concrete structures recently. However, the water-to-cement ratio of HSC is low, marked self-desiccation will occur, and autogenous shrinkage is induced. The autogenous shrinkage causes tensile stress in the restrained concrete, and the tensile creep (TC) counteracts the autogenous shrinkage as a stress relaxation mechanism. Although the TC of internally cured HSC (ICHSC) with super absorbent polymers (SAPs) under fully restrained conditions has been studied, research on the early-age TC of ICHSC under constant tensile loading remains insufficient. Therefore, the effect of initial stress/strength (s/s) ratio (ranged from 20% to 35%, 50%, and 65%) on the TC behavior of ICHSC at early age was experimentally investigated by Temperature Stress Test Machine in this research. Experimental results and corresponding analysis showed that: (1) the early-age basic TC, basic TC coefficient, and specific basic TC of ICHSC at 7 days of loading was 37, 66, 95, and 148 με, 2.26, 2.31, 2.30, and 2.76, and 52, 53, 53, and 72 με/MPa, respectively, and increased as the initial s/s ratio increased; (2) the early-age basic TC rate of ICHSC at 1 day of loading was 0.57, 1.01, 1.70, and 3.04 με/h and increased as the initial s/s ratio increased; (3) the nonlinear basic TC of ICHSC occurred when the initial s/s ratio ranged from 50% to 65%; (4) a prediction model for the TC of ICHSC considering initial s/s ratios was proposed based on Østergaard model.