Expansive soils swell when wet and shrink when dry, causing differential settlements that can lead to structural failures in roads and buildings. In cases where these soils cannot be avoided, improving their stability is essential. This study investigates the use of two binders, ground granulated blast-furnace slag (GGBS) and bagasse ash (BA), byproducts of steel and sugarcane processing, respectively, to reduce soil swelling and enhance stability by assessing the mechanical behavior of reinforced expansive soil. To evaluate the behavior of reinforced expansive soils, tests such as Atterberg limits, compaction, swelling potential, and direct shear were conducted. Results indicated that as reinforcement levels increased to an optimal threshold (3 % GGBS and 12 % BA), the optimum moisture content rose, while maximum dry unit weight generally decreased. A 15 % increase in moisture content and a 3.16 % decrease in maximum dry unit weight were observed with reinforcement. Cohesion decreased by 27 % in soaked conditions and 31 % in unsoaked, while the angle of internal friction rose by 106 % and 111 %, respectively, at the maximum reinforcement threshold. These additives also improved shear strength, reduced swelling potential, and lowered plasticity index, shifting the soil behavior from clay-like to silty. The results show that bagasse ash and GGBS effectively enhance soil properties and provide a sustainable solution for soil stabilization in construction.

The United States' top provider of long-grain rice is Arkansas. The burning of the outer shell of paddy under controlled circumstances generates rice husk. A significant portion of the ash created during the rice-milling process is silicate, which is a pozzolanic substance that may enhance the strength of poor soils. By examining two local subgrade soils from Arkansas, the primary goal of this study is to determine the optimal amounts of hydrated lime, Rice Husk Ash (RHA), and RHA + lime. Various tests, including the Atterberg Limits, Modified Proctor, Unconfined Compressive Strength (UCS), California Bearing Ratio (CBR), pH, and Free Swell (FS), were performed on the treated soils. The findings of the tests indicate that the maximum dry density and plasticity of the soil are decreased by both RHA and lime. On the other hand, adding either RHA or lime improved the treated soils' strength characteristics. According to the FS results, the soil's swelling was decreased by both RHA and lime. But it was shown that lime was more successful than RHA in lowering the FS of soils. RHA has no discernible impact on soil pH; however, lime causes a significant rise in pH. It was found that the best dosages for treating both soils were 6% RHA and 3% lime. The swelling potential may be decreased, and the strength properties could be enhanced by the combination of RHA and lime. Based on laboratory test findings, it is recommended to stabilize poor subgrade soils using 4% RHA + 1% lime.

The mechanical properties of shallow expansive soil are crucial to expansive soil engineering. However, few effective test methods have been available to measure the in-situ mechanical properties of shallow expansive soil. This paper attempts to test the effects of water content and fissures on the mechanical properties of shallow expansive soil under a natural state by in-situ CBR and resilience modulus tests. The evolution characteristics of shrinkage fissures in expansive soil were recorded and observed. The fissure connectivity coefficient is used to express the degree of fissure development and the integrity of soil structure. The CBR strength and resilience modulus of expansive soil increase first and then decrease with the decrease of water content and the increase of fissure development degree, and reach the peak near the optimal water content. It is effective to use the inverse hyperbolic sine function to fit the relationship between soil mechanical parameters, water content, and fissure connectivity coefficient. When the water content is higher, the influence of water content on soil mechanical properties is great. When the water content is lower, fissures are more developed, and the influence of fissures on soil mechanical properties is dominant.