Dispersion and stability of fine-grained soils under different pretreatments based on the particle size distribution

Abstract

Particle size distribution (PSD) has been extensively used to evaluate the properties of the soil. The PSD curve is influenced by soil pretreatments. This study intends to evaluate the quantitative effect of sample pretreatment on the PSD of the soil. In this study, the sieving-hydrometer method was employed for determining the mass PSD of soils. Four different soil pretreatment methods were adopted, i.e., non-treated, boiling only, sodium hexametaphosphate only, and a combination of boiling and sodium hexametaphosphate. The implications of the sample pretreatments were evaluated based on the fine fractal dimension (Df). The samples treated using boiling and sodium hexametaphosphate exhibited the highest Df among all the samples. The Df of the sample was obviously enhanced after it was pretreated using sodium hexametaphosphate (p 0.01). Regardless, the results obtained via a pretreatment in which boiling and sodium hexametaphosphate were both used denoted that the dispersion effect of sodium hexametaphosphate could be enhanced by boiling; furthermore, boiling and sodium hexametaphosphate improved the fitting degree of the power law function (p < 0.01). The results of this study prove that sodium hexametaphosphate is an efficient dispersant, which would promote the dispersion effect when used in combination with boiling. The mechanisms responsible for the dispersing and stabilizing effects of sodium hexametaphosphate are verified based on the behaviors of ion exchange and micelle formation in the suspensions.