Effect of Salt Solutions on Rheological Properties and Water Retention of Soils

Currently, the concept of a double electric layer in soil colloids is often used to explain the effect of the ionic strength of soil solutions on soil properties. It is known that when the ionic strength increases, the double electric layer contracts. The aim of the work is to study the effect of increasing the ionic strength of a soil solution on the rheological properties and soil water retention curve. Loamy soils were studied: sod-podzolic, gray forest, and leached chernozem. The rheological characteristics of the soil pastes were determined on a vibrating viscometer, the soil water retention curve by the method of equilibrium centrifugation. The particle size distribution in the suspensions was determined using a laser diffractometer. In the course of experiments, it was found that an increase in the ionic strength of the dispersion medium in pastes leads to a sharp increase in the viscosity of pastes. From the perspective of double electric layer compression, the viscosity should decrease. In addition, it was found that in soil pastes prepared with 1 N potassium chloride, the amount of rheopexy decreases. At the same time, there is no influence of the ionic strength of solutions on the soil water retention curve, although from the standpoint of double electric layer, it was assumed that the soil water retention curves would shift to the left. The experiments conducted to study the swelling of soil pastes suggest that periodic colloidal structures of a local type exist in soils. Thus, the concept of a double electric layer does not allow us to explain changes in all soil properties.