Comparative Study of Self-Curing Concrete Using Lightweight Aggregates and Hydrogel (SAP) as Internal Curing Agents

Self-curing concrete, also known as internal curing concrete, has been developed to overcome the limitations of conventional external curing, particularly in situations involving water scarcity and inadequate curing conditions. In this study, M45 grade concrete incorporating two internal curing systems—(i) 50% lightweight aggregate (LWA) replacement combined with 2.5% polyethylene glycol (PEG-400), and (ii) 0.2% superabsorbent polymer (SAP) by weight of cement—was experimentally investigated. The performance of these mixes was evaluated through workability, compressive strength, split tensile strength, and scanning electron microscopy (SEM) tests conducted at curing ages of 7, 14, and 28 days. The results indicated that although both self-curing systems exhibited reduced workability compared to conventional concrete, they achieved a significant improvement in compressive strength of approximately 15–20% at 28 days. SAP-based concrete showed enhanced split tensile strength, while the LWA + PEG system exhibited a marginal reduction. SEM analysis further confirmed improved hydration and microstructural densification due to the sustained internal moisture supply. Overall, the findings demonstrate that self-curing concrete, particularly when incorporating SAP, offers a viable and effective solution for improving strength and durability in conditions where conventional curing practices are difficult to implement.