Assessing the performance of internal cured concrete using pre-saturated fine lightweight aggregates manufactured from coal combustion ash

Abstract Internal curing has emerged as an effective strategy for mitigating shrinkage and enhancing long-term concrete performance. This study evaluates the suitability of fine lightweight aggregates manufactured from waste coal combustion ash (WCA-FLWA) as an internal curing agent for concrete and compares their performance with commercial expanded slate fine lightweight aggregates (ES-FLWA) and conventional concrete. Experimental investigations included fresh, mechanical, durability, and microstructural characterization. Results showed that WCA-FLWA provided superior internal curing efficiency, resulting in higher compressive strength, reduced shrinkage, lower sorptivity, enhanced hydration, increased calcium hydroxide formation, and a refined pore structure characterized by a greater proportion of gel pores. Isothermal calorimetry confirmed prolonged hydration and higher cumulative heat release in WCA-FLWA concrete. The findings demonstrate that WCA-FLWA can simultaneously improve concrete performance and provide a sustainable reuse pathway for coal combustion ash waste.