Improvement of Gypseous Soil by Compaction and Addition of Cement

Abstract

The engineering problems faces civil engineer in building and construction, is almost foundation problems results from the properties of the beneath soil. One of the effected problems is the presence of gypseous soil. The presence of gypsum in some regions reaches up to 70%. Gypsum salts is one of highly dissolved salts in water. The solubility depends on temperature degree, atmospheric pressure, PH of the dissolved liquid. There are many treatments for such soils, some of them are physical like earth reinforcement, compaction. The others are chemical like the addition of lime, asphalt emulsion, oil products…etc(1).The aim of this study is to investigate the ability of improving gypseous soil by reducing the collapsibility during wetting with water, by the addition of Portland cement with different percentages:( 1.5%, 4%, 6%,7.5%, 10%), to gypseous soil with at different densities14 kN/m3 and 11 kN/m3.A laboratory model test consists of a cylindrical plastic container of 250 mm diameter and 400mm height. The soil was artificially prepared by mixing natural soil brought from a location near the Civil Engineering Department building in Diyala University, and mixed with 70% gypsum. The density of the soil was controlled by placing the required weight inside the container of known volume, to the required height. A rectangular footing 25mm*40mm made from steel was used. The stress was applied from a fix loading system designed especially for model tests and applying 46kPa stress. The aim of this setting is to control stress and to ensure keeping the dial gauges dry during tests.The results of laboratory test on model samples shows a considerable reduction in collapsibility for gypsiferous soil models treated with cement and compaction, during soaking with water. The reduction percent in collapsibility was (95%) for treated model by (10%) of cement addition and with increasing soil density up to (14 kN/m3).