Effect of curing on the tensile strength of medium to high strength concrete

Curing effects upon the tensile strength of medium- and high-strength concrete are reported. Five concrete grades, with 28-day compressive cube strengths ranging from 40 N/mm(2) to 110 N/mm(2), were cured in two environments: air, and in water. Tensile strengths were measured using three indirect tests (flexural strength, split cylinder and torsional tensile). Strengths were measured at 28, 84 and 365 days. The objective of the study was to investigate the relative effects of curing on the indirect tensile strength measurement. Various strength-modifying mechanisms are identified, which are related to the observed results. The flexural and torsional surface failure tests exhibit air-cured strengths that approach and in some instances surpass their water-cured comparisons. This is thought to occur because of positive (drying moisture gradient prestressing) and negative (swelling gradient, self-desiccation) effects on the measured air-cured and water-cured strengths respectively The split cylinder air-cured/water-cured ratio (0(.)78) compared well with other compressive strength studies (0(.)81).