Internal Curing to Mitigate Cracking in Rapid Set Repair Media

Abstract

Abstract Rapid hydration and high early strength portland cement and calcium sulfoaluminate (CSA) concretes are commonly used as pavement repair media. Field trials reveal a tendency to crack along the longitudinal axis of the repair. The authors hypothesized that internal curing with saturated lightweight aggregate would prevent or delay restrained shrinkage cracking in the rapid repair media. The fresh properties (slump, setting time), mechanical properties (elastic modulus, compressive and tensile strength), and volume stability (autogenous shrinkage, drying shrinkage, restrained ring shrinkage, creep) of the rapid repair media were evaluated with and without internal curing with saturated lightweight aggregate. Despite delayed hydration and reduced early-age strength, internally cured concretes could retain the requisite minimum 4-hour compressive strength of 4,000 psi. Significant improvements in volume stability were also noted. Drying and autogenous shrinkage were reduced by factors up to 20 % and 50 %. However, detrimentally, creep shrinkage was increased by factors up to 45 %, respectively. The time to cracking in restrained ring shrinkage tests was increased by factors up to 60 %. These results indicate that internal curing can successfully improve volume stability and mitigate restrained shrinkage cracking in rapid repair media without compromising fresh properties or ultimate mechanical strength.