Evaluation of Leaching Behavior of Treated and Untreated Gypseous Soil

Abstract

Leaching is defined as the removal of salts and soluble materials from soil by water percolation and water table fluctuation. The physicochemical and mechanical properties of the soil are changed with the removal of soluble salts and dissolved matter. The process takes place under a hydraulic gradient or by diffusion. Gypseous soils undergo several changes in their characteristics due to the continuous loss in their mass and due to the alteration in properties of the material constituents during leaching and removal of cementation between soil particles. Some experiments on natural gypseous soil and soil treated with magnesium oxide and carbonated magnesium oxide with two relative densities (35 and 75%) are carried out in this research. Oedometer permeability leaching test and modified permeability leaching test are used to investigate the effect of the behavior of soil during leaching. The results illustrate that the coefficient of permeability in oedometer permeability shows results less than the modified leaching, and the coefficient of permeability in the modified permeability test is more believable results than the oedometer permeability test. The results showed that magnesium oxide and carbonated magnesium oxide are good treatment materials that can be used to improve gypseous soil. Using 10% of 3 hours carbonated magnesium oxide reduces the coefficient of permeability compared with untreated soil more than 100% for the samples of two relative densities and for the two types of tests.