Concrete Maturity Method Using Variable Temperature Curing for Normal-Strength Concrete Mixes. II: Theoretical Study

Variable curing temperatures were used to simulate the condition of how mass concrete cures and how temperature affects strength development. For normal-strength portland cement concrete, higher curing temperature during the early age yields lower strength at a later age compared with an initial lower early-age curing temperature. Experimental work in all phases of this research clearly shows a crossover effect. However, results for maturity analysis indicated that the strength-maturity relationship does not reflect the strength result at a later age—this is related to one of the stated limitations of the existing ASTM C 1074 maturity method. Therefore, a modified equivalent age equation was developed, which takes into account the effect of the early-age concrete temperature on the long-term ultimate strength. The modified equation includes both the effect of the water diffusion through layers of hydrates and the effect of the chemical reaction (nucleation and growth) in forming new hydrates due to the combination of unhydrated cement with free water.