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

The main objective of this paper presents a study of the effect of engineering properties of expansive soil as subgrade when stabilized by using different percentage of hydrated lime on thickness of 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 also mechanical tests in term of 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 behavior of expansive soil as subgrade on thickness of 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 45cm, 35cm, and 35 cm when using 2%, 4%, and 6% percentages of lime respectively in stabilization of expansive soil as subgrade. The results suggest that the lime content 6% is optimum percentage were that given a highly strength, lowest swelling and small thickness of pavement.