Abstract
This study examines effects of mixing municipal solid waste incineration bottom ash (MSWI-BA) with reddish laterite clay (RLC), evaluating factors such as vertical stress, mixing ratio, curing period, and the addition of lime. A total of 153 direct shear tests were conducted to thoroughly assess the mixture's strength characteristics. Vertical stress levels of 85.5 kPa, 172.4 kPa, and 259.3 kPa were used to simulate varying stress conditions, while mixing ratios of 40 %, 80 %, 100 %, and 120 % were applied to explore potential applications of recycled MSWI-BA with clayey soils. A fast-curing approach was employed, with curing periods of 24, 48, and 72 h, to investigate the time-dependent strength development under controlled conditions. A three-way ANOVA analysis confirmed that mixing ratio, curing period, and vertical stress significantly impacted both peak and residual shear strength. The 100 % MSWI-BA mixture, with or without 1 % lime, exhibited optimal performance, providing the pronounced shear strengths and dilative behavior. The study found that MSWI-BA significantly improved shear strength ratios compared to the RLC, with improvement ratios ranging from 1.439 to 2.460 across stress levels. Additionally, upper and lower bound equations for peak and residual strength ratios were developed, providing predictive tools for mixture design. Cohesion values in the range of 8.3-128.9 kPa and friction angles from 40.6° to 44.1° were achieved, surpassing or matching those reported in similar research. The study employed Bolton's (1986) dilatancy model, finding α values between 0.61 and 0.71, comparable to those in studies of granular materials. These results highlight the effectiveness of adding MSWI-BA and lime in enhancing reddish laterite soil stabilization through both chemical and mechanical means, making it a sustainable and cost-effective approach for civil engineering projects by improving material strength, reusing local soils, recycling waste, and reducing carbon footprints.