Internal curing, as a means of retaining moisture from within the concrete during the maturation process, can increase the durability properties of concrete but may decrease its mechanical properties, like modulus of elasticity and tensile strength. This study introduces a Mineral Enriched Internal Curing (MEIC) strategy using Na2SiO3 and Ca(OH)2 mineral enrichment to transform lightweight expanded clay aggregate (LECA) from a passive water reservoir into an active chemical particle. Fourier Transform Infrared (FTIR) spectroscopy confirmed this enrichment created a pre-reacted C-S-H gel layer and residual Ca(OH)2, providing the mechanistic basis for enhanced performance. MEIC successfully overcame the 41.3 % compressive strength loss (14.88 MPa) compared to the control specimen seen in the standard internal curing process (L30: 30 % sand replacement by fine LECA); the mix that has 30 % replacement of enriched LECA (L30-E30) regained strength by 77.3 % to 26.39 MPa, ultimately surpassing the Control strength. Furthermore, volume stability was dramatically improved: while the control mix exhibited 2375.14μϵ shrinkage, the L30-E30 mix achieved 111.89 % effectiveness with a net compensating expansion of −282.65μϵ. The enhanced microstructure also conferred superior thermal resilience; at the catastrophic failure point of 900°C, the L20-E30 mix maintained the highest measurable structural integrity with 9.53 % UPV retention. The optimal L20-E30 formulation, achieving an fc of 27.16 MPa (up 13.3 % from Control), promises progress of a breakthrough in internal curing technology by successfully balancing strength, volume stability, and durability.
