Improvement of Gypsiferous Soils Properties by Hydrated Lime in the Najaf City, Middle of Iraq

Abstract

This study includes the effect of lime addition on the engineering properties of gypseous soil taken from a part of the Najaf- Karbla plateau (52, 48, 72% gypsum). Also this study shows increase in the proportion of gypsum in the soil in the northwest direction of the study area. Maximum dry density and optimum moisture content (2.065, 2.025 and 2.003) at 15%, 14% and 15% respectively for the three samples. The maximum dry density decrease while optimum moisture content increases with increasing ratio of hydrate lime. The results show that the gypscous soil becomes non - plastic when treated by > 3 % of hydrated lime. Cohesion Force, with the increase in the percentage of lime from 3% to 6%, after which it decreases as the percentage addition of lime to reach zero when the addition became 9%. The reason for this is that the lime increases the cohesion strength between molecules to the limit of adding 6%, then the cohesion decreases to zero when 9% is added lime. The results of a liquid limits are changed and the soil becomes more liquidity limit when it's treated due to the hydrated lime increases liquid limits significantly, and it becomes clear that the limit of liquidity. After which the lime molecules work to separate the molecules from each other, and the cohesion force decreases. It is also noted that the internal friction angle decreases with the increase in the percentage of lime.