Autogenous Shrinkage of Internally Cured Conventional, Latex-Modified, and Very High Early Strength Latex-Modified Concrete and Mortar

Abstract

Abstract Internally cured concrete has been shown to help mitigate early-age cracking and to provide improved durability performance in concrete elements. The increased absorptive capacity of lightweight aggregates (LWA) facilitates delivery of moisture to concrete internally during the curing process. In this study, a range of concrete mortar mixtures representative of mortar contained in bridge deck and pavement concrete mixtures were batched and tested for autogenous shrinkage. Two significantly different LWAs were utilized in this study: one LWA with an absorption typical of most manufactured LWA and one with a relatively low absorption for a manufactured LWA. Autogenous shrinkage test results clearly demonstrated the impact of use of prewetted LWA for internal curing. Reductions in autogenous strain ranged from 30 to 56 % depending on the type of LWA used as well as the percentage replacement of prewetted LWA for normal-weight fine aggregate. The reduction in autogenous shrinkage correlated with LWA replacement rate, and shrinkage was even further reduced for mixtures that included fly ash. Findings indicated that the lower-absorption LWA provides internal curing benefits when used at suitable replacement levels, which may exceed those currently specified by some state highway agencies. Use of the approach to computing LWA substitution rate provided in ACI (308-213)R-13, Report on Internally Cured Concrete Using Prewetted Absorptive Lightweight Aggregate, should provide adequate moisture delivery to support reduction in autogenous shrinkage and internal curing benefits and is suitable for proportioning of both the typical and lower absorption LWA to support internal curing. In addition to reduced autogenous shrinkage, use of prewetted LWA in very high early strength latex-modified concrete mixtures provided workability and work-time advantages.