Browsing by Author "Covenant Unversity, Dissertation"

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    INVESTIGATION OF INFLUENCE OF CALCINED CLAY AND RICE HUSK ASH ON THE PROPERTIES OF SELF COMPACTING CONCRETE
    (Covenant University, Ota, 2026-06) AREMU, Ayodeji Emmanuel; Covenant Unversity, Dissertation
    The growing need for environmentally friendly building materials has led to the research on supplementary cementitious materials (SCMs) as substitutes for the ordinary Portland cement (OPC) used in concrete. This research explores the impact of calcined clay (CC) and rice husk ash (RHA) on the fresh, mechanical and durability characteristics of self-compacting concrete (SCC). This research aims to assess the potential of these readily available materials for improving sustainability without compromising the performance of SCC. Different mixes of SCC were prepared with varying percentages of cement replaced by calcined clay (0-30%) and rice husk ash (0-20%). The rheology of the concrete was measured using standard SCC tests such as slump flow, V-funnel, and L-box tests, to evaluate the filling ability, stability and passing ability of the concrete, respectively. The hardened properties were assessed by compressive strength at various ages and the durability of the concrete was investigated by water absorption and abrasion tests. The findings suggest that using calcined clay at reasonable replacement levels enhances cohesiveness and stability of SCC while maintaining workability. But the addition of rice husk ash adversely affected workability due to the increased specific surface and demand for water. Specimens with an RHA content greater than 5% showed poor workability and did not meet the criteria for SCC. When it came to strength, compressive strength decreased as the amount of calcined clay and rice husk ash increased. However, SCC with up to 20% calcined clay showed a significant portion of the control compressive strength, suggesting the possibility of using the calcined clay as a cement replacement. Moreover, higher rice husk ash content caused considerable loss of strength, due to higher porosity and reduced effectiveness of hydration. In terms of durability, water absorption showed a progressive increase with increasing replacement, suggesting increased permeability. Abrasion resistance also dropped with higher SCM levels, indicating a loss of surface quality. However, the durability of the mixes with moderate calcined clay content and low rice husk ash content showed satisfactory results, indicating a compromise between sustainability and performance. The research concludes the best results for SCC with calcined clay and rice husk ash is with around 20% CC and 5% RHA recording a 28-day compressive strength of 19.69MPa (77.2% Strength Retention) compared to the control mix which achieved a 28-day compressive strength of 25.49MPa. Here, the concrete retains xviii satisfactory workability, strength and durability, and minimises cement use. The study underscores the need for proportionate material replacement, and offers guidelines for the eco-efficient design of SCC with local materials. This study contributes to sustainable construction by showing the viability of using calcined clay and rice husk ash as supplementary binders in SCC. It also offers guidelines for optimising mix designs and suggests future research directions, such as long-term behaviour and microstructure studies.