Analysis of expansive clay mixed with pumice for soil stabilization

Abstract

Expansive clays pose a recurring problem in geotechnical engineering due to the deformations they undergo when moisture levels fluctuate. These changes in volume negatively affect the performance of pavements, foundations, and civil engineering structures, causing cracks and differential settlement, as evidenced by countless studies around the world. Soil expansion is directly related to the presence of active minerals capable of absorbing water and altering its crystalline structure. Various studies have aimed to reduce expansion in this type of soil, yielding favorable results that have helped mitigate negative effects.  The central objective of the research was to find the optimal mixture of clay and pumice to achieve effective stabilization, that is, to reduce expansion by lowering parameters such as the soil plasticity index, among others. To achieve this, three mixtures with different percentages of pumice added to the natural clay soil were prepared, and for each mixture, laboratories measured the physical, chemical, mechanical, and morphological characteristics that indicate stabilization patterns through the measurement of key indices. Among the notable results, it was found that the mixture containing 25 percent pumice exhibited a 30 percent decrease in the plasticity index, a reduction in free expansion of more than 45 percent, and a reduction in volumetric potential from very critical to marginal. Morphological analyses confirmed the change in the mineralogical and chemical composition of the treated soil, showing a reduction in the concentration of expansive minerals and the formation of new mineral phases. These findings suggest that pumice can be used as an effective, sustainable stabilizer for clay soils with high expansion potential.