Effect of Soil Stabilization on Subgrade Soil Using Cement, Lime and Fly Ash

Subgrade soil plays an important role in road structural design; therefore, poor subgrade soil may cause insufficient support for the pavement and may reduce its life.The poor properties subgrade soil should be replaced with a strong soil to improve the pavements properties and this cost a lot.Considering that, improving the poor subgrade soil properties by mixing it with different additive materials in site and stabilize it may be a better solution.This study was carried out to improve sample subgrade soil properties by stabilizing it using three different additive materials with different properties and quantities.For this purpose (ordinary portland cement), (limestone powder) and (fly ash) with percentages of (3%, 6% and 10%) were utilized.The modified mixture test results of (proctor test), Unconfined Compression Strength (UCS) and California Bearing Ratio (CBR test) showed that stabilization of the subgrade soil using different percentages of those additives improved the mechanical properties of the subgrade soil.Utilizing the above additive percentages, the CBR values improved from (5.25%) to (44.3%, 71%, 102.5%) while cement was utilized and to (8.75%, 9%, 10.2%) when fly ash was utilized and to (9.95%, 10.94%, 12.6%) with lime used.