Application of Maturity to Estimate the Strength Development of High-Early-Strength Concrete Mixtures Using Isothermal Calorimetry.

Repair materials for concrete infrastructure applications are designed to minimize closure time and subsequent effect on traffic. Available material choices are typically limited to expensive prepackaged materials or high-early-strength (HES) concrete mixtures. HES concrete mixtures are often designed with high paste content and limited inclusion of supplementary cementitious materials so to promote higher early-age strengths. The traditional approval for HES concrete mixtures has relied on testing the strength of concrete cylinders cured at room temperature. This practice has often resulted in the overdesign of these HES mixtures, primarily because it fails to consider the higher temperatures that typically develop during the in situ curing. Moreover, as highlighted in several reports by state agencies, the high cement content and the near absence of proper curing practices have likely contributed to the premature failure of some of these mixtures. In this study, isothermal calorimetry was explored as a potential tool to quickly evaluate HES concrete formulations in terms of early-age mechanical performance. It was found that this test method, when combined with maturity, can provide reasonable estimations of the concrete strength development for isothermal and nonisothermal curing conditions up to 8 h after the initial mix. The proposed test method can be used as a first step in the optimization of HES concrete mixtures and can help predicting the time to reopening for in situ conditions. [ABSTRACT FROM AUTHOR]