Evaluating mechanical properties of cement-fly ash-stabilized laterite soil under different curing conditions

The use of industrial by-products in soil stabilization has gained considerable interest in recent years as the construction industry seeks more sustainable alternatives to conventional binders. While cement-fly ash systems have been widely studied, the extent to which different curing environments influence the mechanical performance of stabilized laterite soil (LS) remains unclear. In this study, LS was treated with a fixed cement content of 10% (ratio of cement/(LS + fly ash)) and varying fly ash (FA) contents of 0%, 10%, 20%, and 30% (ratio of FA/(LS + FA)) to evaluate the combined effects of binder composition and curing condition on strength development for pavement subbase applications. Specimens were subjected to sealed, air-dry curing, and water-saturated environments, and their unconfined compressive strength (UCS) and splitting tensile strength (STS) were measured over a curing period of up to 28 days. The experimental results showed that the curing environment had a more pronounced effect on strength development than the FA replacement level. Across all mixtures, specimens cured in air-dry consistently achieved the highest strengths, followed by those under sealed curing, whereas water-saturated specimens produced the lowest values. Incorporating FA further improved the mechanical performance of the stabilized soil, with the C10FA20 mixture (10% cement and 20% FA) delivering the best overall results. After 28 days of air curing, this mixture reached a UCS of 2.292 MPa and an STS of 0.244 MPa, corresponding to increases of approximately 26.4% and 40.2%, respectively, compared with the cement-only control. In addition, UCS showed a clear inverse relationship with moisture content ( R 2 = 0.90), emphasizing the important role of moisture conditions in governing strength development. Overall, the findings suggest that combining 10% cement with 20% FA offers a practical and sustainable approach for stabilizing LS and represents a promising option for pavement subbase construction in tropical environments.