STABILIZATION OF EXPANSIVE SUBGRADE SOIL BY USING ADDITIVES

Abstract

Expansive soils refers to a particular type of soils – almost clayey soils - that expand as they absorb water and shrink when they dry out. The process of swelling generates pressures that can cause lifting, or heaving of structures whilst shrinkage process can cause differential settlement. A large number of buildings and roads are placed on such soil and exposed to the danger from this swelling and shrinkage processes. In order to avoid the previous mentioned risk from the expansive soil, a technique of soil stabilization should be made for this type of soil to enhance some of its properties. In this study, we experimentally treated a particular type of an expansive soil as a subgrade material by adding three different types of chemical additives which are (Addicrete P), (Addibond 65) and (Glass Fibers) at different mixing ratios 2, 4, 6% to maintain an enhanced subgrade layer according to its swelling and bearing behavior. A series of laboratory-coded tests were conducted on the native soil. Tests are Atterberge limits, Modified proctor, and California bearing ratio test. The same tests are also conducted on each soil-additive mixed sample. Results showed that there is a tendency from the soil to stabilize by these additives. California bearing ratio was increased from 4.7% to 8.05% and the expansion after the 96 hours soaking time was eliminated from 4.95 millimeters to 0.35 millimeter. This is considered the best effect and was a result from mixing the native soil with a percent of 6% Addicrete P.