Effect of Pore Structure Changes on Cyclic Swell-Shrink Behavior of Nanomaterial Treated Expansive Soil

Abstract In an effort to mitigate the volumetric instability of Black Cotton soil, this study explores the effectiveness of Nano Rice Husk Ash (NRHA) treatment. The research focuses on evaluating the cyclic swell-shrink response of NRHA-treated soil through multiple wetting-drying cycles. To assess the impact of NRHA, the pore structure was analyzed using the Brunauer, Emmett and Teller (BET) test along with the Barrett, Joyner and Halenda (BJH) method. The results demonstrate that NRHA significantly modifies the pore structure of Black Cotton Soil. Among the tested samples, soil treated with 0.4% NRHA exhibited the lowest specific surface area and pore size distribution compared to untreated soil and soil treated with 1% NRHA. Adsorption isotherms confirmed a transformation in soil microstructure, characterized by a reduction in mesopore and macropore volumes, which contributed to improved soil stability. After fifth cycle, the pore size distribution analysis showed a decline in mesopore and macropore volume for the 0.4% NRHA-treated soil, corresponding to the lowest specific surface area. This reduction is likely responsible for the overall decrease in swell-shrink potential compared to untreated Black Cotton Soil. The findings confirm that NRHA is a durable and effective stabilizer for enhancing the swelling-shrinkage characteristics of Black Cotton Soil.