DEVELOPMENT OF COCOA POD HUSK ASH (CPHA) BASED CEMENT MATRIX FOR LOW-COST HOUSING

Abstract

The persistent housing deficit in Nigeria, coupled with the escalating cost of Portland Cement (PC), necessitates the development of sustainable and cost-effective alternative binders. This study investigates the combined use of Cocoa Pod Husk Ash (CPHA) and Calcium Carbide Waste (CCW) as supplementary cementitious materials (SCMs) for low-cost housing, in comparison with established agro-waste SCMs such as Rice Husk Ash (RHA) and Palm Oil Fuel Ash (POFA). Laboratory analyses were conducted to evaluate the physicochemical and mechanical properties of CPHA and CCW in accordance with ASTM C618 standards. Results indicate that both materials satisfy key physical requirements, with fineness of 10% passing 45 μm and normal consistency values of 33.3% (CPHA) and 34% (CCW). Blended CPHA–CCW mortars exhibited decreasing workability with increasing CCW content, while setting times increased progressively due to higher lime concentration. Among the mix ratios investigated (60:40 to 35:65), the 55:45 CPHA–CCW blend demonstrated the most balanced performance, exhibiting adequate workability (65 mm slump flow), moderate setting time (135 min initial; 273 min final), and superior compressive strength development over curing periods. Comparatively, this optimal ratio performs competitively with conventional SCM systems at 20–30% replacement levels, highlighting the synergistic interaction between silica-rich CPHA and calcium-rich CCW. However, the relatively low silica content of CPHA suggests the need for improved calcination to enhance reactivity. Overall, the study establishes that a 55:45 CPHA–CCW blend is the most effective proportion, offering a viable, eco-friendly alternative to PC while supporting sustainable construction and circular economy practices in Nigeria.