Effect of Hydrated Lime on Behavior of Expansive Soil as Subgrade of Flexible Pavement Structural System

Abstract

The main objective of this paper is to present a study of the effect of the engineering properties of expansive soil as subgrade when stabilized by using different percentages of hydrated lime on the thickness of the pavement structural system. A series of physical tests in terms of sieve analysis, liquid limit, plastic limit and plasticity index as well as dry density, moisture content relationship and also mechanical tests and CBR test was conducted before and after adding three percentages of lime (2%, 4% and 6%) by weight of expansive soil with curing time of 24 hour to evaluate the effect of hydrated lime on the behavior of expansive soil as subgrade on the thickness of the flexible pavement structural system. The results shows that the lime provides better physical properties in term of liquid limit, plastic limit and plasticity index and shows that the lime increases the CBR value to 52%, 27% and 44% when adding 2%, 4% and 6% percentages of lime, respectively, for untreated soil (CBR=1%). Also, the lime decreases swelling from 4% in untreated soil to 1.20%, 0.01% and 0.20% when adding 2%, 4% and 6% lime percentages, respectively. The design of pavement thickness shows that the adding of lime decreases the thickness from 92.5 cm when using untreated expansive soil as subgrade to 45 cm, 35 cm, and 35 cm when using 2%, 4%, and 6% percentages of lime, respectively, in the stabilization of expansive soil as subgrade. The results suggest that the lime content 6% is the optimum percentage that will give a high strength, lowest swelling and small thickness of pavement.