Autogenous shrinkage reduction in concrete using eco-efficient hybrid internal curing (WAPB and LWA)

Autogenous shrinkage concrete is a critical issue related to self-desiccation during hydration. This study investigates the effectiveness of internal curing using water-absorbing polymer balls (WAPB), pre-wetted lightweight pumice aggregate (LWA), and a hybrid system combining both methods. Autogenous deformation was monitored up to 7 days at two-gauge locations (100 mm and 200 mm) under restrained conditions. The reference mixture exhibited the highest autogenous deformation, while all internally cured mixtures showed noticeable reductions. The full LWA mixture achieved the greatest shrinkage mitigation (≈40%), followed by the 50% LWA and hybrid mixtures, whereas WAPB alone provided limited improvement. Although internal curing led to reductions in compressive strength and density, partial LWA and hybrid mixtures offered a balanced performance between shrinkage control and mechanical properties. These findings highlight the potential of LWA-based internal curing as an effective approach for reducing autogenous shrinkage in concrete.