Stabilization of muscat’s expansive soil using bottom ash from medical waste incineration

Expansive soils are inherently known for exhibiting significant volumetric change in response to slight variation in the moisture content. In this study, medical waste material in the form of bottom ash (BA) was investigated as a potential stabilizer for expansive soil. The unique characteristics of BA, such as its cost-effectiveness and availability as a residue, establish it as a potent stabilizer for expansive soils compared to other alternatives. The locally collected expansive soil from Muscat was identified to be of poorly clay type with high plasticity (CH) based on the USCS, and A-6 according to AASHTO classification. The BA was obtained from the medical waste treatment plant of the Be’ah Company in Oman. Samples were prepared by treating the expansive soil with BA in percentages of 6%, 8%, 10%, and 12% by mass. It was found that the pH level of the treated soil continued to reduce with increasing BA content, which was indicative of the reaction between the expansive soil and BA particles. The unconfined compression strength (UCS) test yielded a 57.63% increase over that of untreated expansive soil at 28 days of curing. Similarly, the California Bearing Ratios (CBR) of the treated soils were up to two times higher than the untreated soil, both in its unsoaked and soaked conditions. Based on the results of the UCS, CBR and linear shrinkage tests, the optimum quantity of BA required for treating the expansive soil was determined to 10%, beyond which no further enhancement in the UCS, CBR or shrinkage attributes of the soil was observed. Overall, the outcomes of this research highlight the potential of medical waste material, specifically bottom ash, as a sustainable stabilizer for expansive soil in construction applications.