CIRCULAR ECONOMY AND SUSTAINABLE CONSTRUCTION: DEVELOPMENT OF ECO‑FRIENDLY WALLING MATERIALS USING LATERITIC SOIL AND AGRO‑WASTE COMPOSITES IN RURAL SOUTHWEST NIGERIA

Abstract

The construction sector in Nigeria faces growing pressure to deliver affordable housing while reducing environmental impact and material waste. This study investigates the development of eco-friendly walling materials using lateritic soil blended with selected agro-waste composites — rice husk ash (RHA), cassava peel ash (CPA), and sawdust ash (SDA) — within a circular economy framework for rural Southwest Nigeria. Laboratory-based experiments were conducted to evaluate the chemical, mechanical, physical, thermal, durability, and cost performance of various composite mix ratios. Results show that RHA-stabilised lateritic blocks achieved the highest compressive strength and durability, exceeding minimum requirements for non-load-bearing walls, while CPA composites offered balanced strength and moisture resistance. SDA composites demonstrated superior thermal insulation and the lowest production cost, albeit with reduced durability under wet–dry cycles. Compared with conventional cement blocks, all composite materials achieved cost reductions of over 25% and significantly lower embodied material intensity. The findings confirm that lateritic–agro-waste composites can provide structurally adequate, thermally efficient, and affordable walling solutions while valorising agricultural waste. The study contributes empirical evidence to support circular construction practices and sustainable rural housing policy in Nigeria and similar developing-country contexts.