Laboratory evaluation of poor subgrade modified using lime

Abstract

The subgrade of a pavement system deteriorates and sub sequentially reaches its failure due to an excess amount in water moisture, load fatigue, aging, and temperature variations affecting the material used in the system. Road success lies in the strengthening of its foundation, also known as the subgrade material, by the addition of chemical additives. The effectiveness of using mixtures of lime in poor soil stabilization was investigated by mean of laboratory testing to evaluate the California Bearing Ratio (CBR) value. In this study, two weak soil types were extracted from two construction sites in Tripoli, Lebanon in order to evaluate the modifications of the physical properties of these subgrade materials with the aim of strengthening by means of laboratory modification using local materials. A chemical reaction between the lime and clayey fraction is supposed to take place leading to higher strength and lower plasticity. The laboratory testing done in this study was to determine the physical properties of poor subgrade material stabilized with lime. These tests include Particle Size Distribution, Specific Gravity, Atterberg Limit, Moisture Content, Compaction Characteristic and Natural Moisture Content. For Soil Type 1 the best results were from an addition of 6% lime while as for Soil Type 2, 5% and 6% of lime yielded the best results. The results of this study show an improvement in the mechanical properties of the soil type 1 and soil type 2 but not enough to be used as approved sub-grade material in Lebanon. As a result, lime stabilization technique can be used to enhance poor subgrades. Furthermore, this can be an approach for solving disposal problems and moving towards a green environment.