Evaluating Subgrade Soil Stabilization using Cement and Lime, Their Cost and Damage Progression Analysis

Abstract

This research study evaluates subgrade soil stabilization using cement and lime and their cost and damage progression analysis. Since treatments to soil are generally classified as processes of soil stabilization or soil modification. Specifically purpose of subgrade stabilization is to enhance the subgrade soil strength. This increased strength is then taken into account in the pavement design process. In this research cement and lime being easily available material has been selected as stabilizing agents with their proportions as 2%, 4% and 6% of the dry weight of soil in the mixture. Parameters considered for analysis of results were Dry Density, California Bearing Ratio (CBR), Unconfined Compressive Strength (UCS), and moisture susceptibility. A low plastic clay (CL), A-6 soil from Karachi Lahore Motorway (KLM) Hyderabad-Sukkur section near Nawabshah has been used in the research. Methodology adopted entails characterization of physical and chemical properties of soil material, determination of optimum stabilizer contents (for cement and lime), specimen preparation and testing for California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS) test in dry and moist condition. This research also determine cost effectiveness of easily available soil stabilizers like cement and lime and cost comparison with conventional methods used to increase the strength and CBR of unsuitable subgrade material. It is observed that cement works well to stabilize any type of soil, except soils with organic content greater than 2% or having pH lower than 5.3. Other significant effects of cement-soil stabilization process are reduction in shrinkage and swell potential with increase in strength. Moreover soil treatment with lime produced significant increase in strength of soil. The immediate increase in strength results from flocculation-agglomeration reaction and results increased workability, whereas long-term strength gain is due to pozzolanic reactions. Results indicate that under the defined test conditioned and site specific soil, cement and lime treatment can be 25% to 30% cost effective compared to the current practice of replacement of poor subgrade soil, besides enhancing the long term durability of the pavement.