Examining Fresh Properties of Ternary Blended Cement Concrete Containing Rice Husk Ash and Metakaolin for Sustainable Construction Practices in Nigeria

Cement production in Nigeria is substantially contributing to its Gross Domestic Product. However, its production is adversely impacting the environment due to excessive exploration. This study examined the effect of combining Rice Husk Ash (RHA) and Metakaolin (MK) as partial replacement for cement on fresh properties of ternary blended concrete as a sustainable material. Therefore, a mixed-method experimental research approach involving laboratory experiment was adopted for the study. Concrete and paste samples (1:1.6:2) were prepared with binary (RHA or MK) individually and ternary (RHA + MK) replacement levels ranging from 10% to 30% and cured at 7, 28 and 90 days. Fresh properties including consistency, setting time, and workability were evaluated in accordance with relevant international standards. Findings indicate that a 15% ternary blend (RHA + MK) accelerated the setting time by 44 minutes relative to a 15% RHA binary blend, while exhibiting a 45-minute delay compared to a 15% MK binary blend. At 20% replacement level, the ternary blend increased water demand by 1.5% compared to MK binary paste but reduced it by 3.5% when compared with 20% RHA binary paste. All ternary blends up to 30% replacement satisfied standard limits for initial and final setting times. Although ternary mixes required more water than MK binary blends, their water demand was lower than that of RHA binary mixes. The study concludes that combining RHA and MK in ternary cement systems enhances the fresh performance of concrete and provides a sustainable alternative for producing durable cementitious materials suitable for Nigeria’s construction industry.