Synergistic effect of expansive agent and internal curing on the performance of UHPC

The challenge of autogenous shrinkage in ultra-high performance concrete (UHPC) arises from the scarcity of expansive hydration products and insufficient water for cement hydration, which jeopardize structural stability. This study investigates a novel approach that combines expansive agent (EA) with water-saturated perforated cenospheres (WPCs) to mitigate this issue. Individually, increasing EA dosage reduces autogenous shrinkage but negatively impacts compressive strength due to accelerated water consumption. Meanwhile, WPCs as internal water reservoirs, enhancing hydration. When used together, these materials exhibit a synergistic effect, reducing autogenous shrinkage to below 100 με and maintaining compressive strength comparable to the control sample. The additional water from WPCs can mitigate the quick drop in internal relative humidity (IRH) caused by EA, promoting expansive product formation and mitigating shrinkage. This study highlights the effectiveness of combining EA and WPCs to enhance UHPC performance by simultaneously addressing shrinkage and strength retention.