Physical Properties of Gypseous Soil after Gypsum Removal using EDTA Solution


The main structural problem in construction on gypseous soils is due to the melting of the gypsum when exposed to water. This may be creating voids in the soil leading to rearrangement of the soil structure and moving the soil particles to more stable positions. This can cause excessive settlement which directly affects superstructures. This study, investigates the influence of gypsum removing on granular soil classification. Four gypsum soil specimens were taken from Al-Qadisiyah district in Tikrit at different depths from the natural ground surface. The depths adopted were 0.75, 1.10, 2.00 and 3.30 m. The corresponding gypsum content was 42.23%, 32.50%, 8.75% and 19.82%, respectively. The EDTA solution was used to disassemble and remove the gypsum particles by washing using distilled water. The results showed that EDTA solution and washing with distilled water was an effective method to remove gypsum from granular soils. Gypsum ratio was reduced to less than 2% in all tested specimens. The percentage of organic matter was not affected, and the specific gravity of the specimens increased between 2% and 12%. The gypsum removal process affected the granular distribution curves of the soil specimens and led to a decrease in the rate of soil grain diameters. In general, classification process of the soil before and after the washing of gypsum from the soil was not affected.