Durable High Early Strength Concrete via Internal Curing Approach using Saturated Lightweight and Recycled Concrete Aggregates

Concrete pavements tend to degrade at joints when concrete gets exposed to freeze-thaw cycles in the presence of moisture. In Kansas, U.S., one common repair method for deteriorated concrete pavement involves patching with high early strength concrete (HESC). For heavily trafficked routes and intersections, this is often done at night, so that the pavement can be opened to traffic next morning. Often, patched concrete shows poor durability lasting for just few years. HESC mixtures often include high cement content and low water-to-cement ratio. These factors lead to shrinkage that creates cracks which, in turn, facilitate the ingress of detrimental substances that eventually degrade patches. Internal curing (IC) has been explored in this study to improve the durability of HESC repair materials. Saturated lightweight aggregates and recycled crushed concrete were used to replace a portion of the virgin fine aggregates. Both mixtures were compared with a control mixture. These three mixtures were replicated for low and high cement contents. The test program focused on assessing two main performance indicators-strength development and durability. Durability testing included autogenous and drying shrinkage, and freeze-thaw cycling where relative dynamic modulus of elasticity, expansion, and mass change were measured. Target strengths were achieved in all mixtures. Autogenous shrinkage test results showed that IC significantly improves shrinkage potential and durability. For these mixtures, low cement content also appears to improve durability.