Influence of soil texture on matrix densification and structural integrity of RHA-stabilized sustainable masonry units

Abstract The growing research on sustainable and low-carbon construction materials has driven the development of Greencrete blocks incorporating Rice husk ash (RHA) and ordinary Portland cement (OPC) as eco-efficient binders. This study investigated the influence of soil texture on the physical, mechanical, and microstructural characteristics of Greencrete blocks stabilized with varying proportions of RHA (5–15%) and OPC (8–12%) within distinct soil matrices. Bulk density, water absorption, and compressive strength were evaluated following relevant standards, while matrix densification was examined using SEM–EDS analysis. Experimental results indicated that clayey soil blocks, optimized with 5% RHA and 12% OPC, achieved the highest compressive strength (3.67 MPa) and the lowest water absorption (32%). In contrast, sandy soil specimens exhibited significantly lower structural performance, which can be attributed to coarser particle arrangement and suboptimal binder–soil interfacial bonding. SEM–EDS analysis confirmed matrix densification resulting from hydration and pozzolanic reactions, thereby establishing the synergistic role of RHA and OPC in enhancing soil stabilization. Overall, these findings highlight the necessity of texture-responsive mix design for producing resilient, low-carbon masonry units suitable for sustainable construction.