EFFECT OF MAGNESIUM OXIDE AND CARBONATION ON COLLAPSE POTENTIAL OF COLLAPSIBLE GYPSEOUS SOIL

Abstract

Gypseous soils are known as problematic soils from an engineering point of view. Many studies deal with collapsible soils and how to reduce the sudden collapse when the soil is soaked in water. The objective of this paper is to investigate the collapse potential when the collapsible gypseous soil is mixed with different percentages of Magnesium Oxide (0, 5, 10, and 15%) and carbonated with different carbonation periods (0, 1, 3, and 24 hours). The adequate Magnesium Oxide percentage was found to be 10% because its effect is close to that of 15% and the optimum carbonation period time is 3 hours. The 10% Magnesium Oxide used in treating the gypseous soil of relative density 35% without carbonation resulted in a reduction in collapse potential by 76% as compared with the natural soil. When the natural soil is carbonated at the relative density of 35% without adding Magnesium Oxide, the collapse potential decreased about 65% from no carbonation to 3-hour carbonation, but it decreased only 9% between the carbonation period of 3 hours and 24 hours. As for samples prepared at the relative density of 75%, the collapse potential decreased more than 77% from no carbonation to 3-hour carbonation, but it decreased only 8% between 3 hours and 24 hours.