Combined use of natural Pozzolan powder and aggregates in lightweight, high-ductility ECC with enhanced self-healing properties

While natural pozzolan (NP) provides many beneficial properties in concrete, a clear research gap exists in exploring its use as an aggregate, or as both a binder and aggregate, in lightweight engineered cementitious composites (ECC). This study investigates the combined use of NP aggregates (NPA) and powders (NPP) to develop sustainable, lightweight, and self-healing ECCs, offering an eco-friendly alternative to silica sand (SS) and ground granulated blast-furnace slag (SG). Mixtures were prepared using 100% NPP, with 25–100% replacement of SS by NPA, alongside control ECCs with SS and SG or NPP. Key sound and self-healing performance characteristics evaluated include compressive and flexural strength, deflection capacity, density, chloride permeability, cracking behavior, and recovery efficiency, supported by microstructural analysis. Replacing SG with NPP and SS with NPA resulted in reductions in compressive and flexural strengths. However, these reductions were accompanied by approximately 28% density reduction and over 100% increase in deflection capacity at sound state. Furthermore, after pre-cracking, enhanced self-healing and greater C–A–S–H formation were observed, confirming NPP and NPA as sustainable and cost-effective alternatives.