Impact of Volcanic Ash and Lime Adding on Expansive Soil for Subgrade Layer

Abstract

Pavement performance is significantly affected by the mechanical properties and composition of soil subgrade. The mechanical properties of such soil are rigidity, strength, deformation and stability of subgrade material. Expansive clay is the soil with a low bearing capacity when used as the subgrade. The effort taken to improve the strength and rigidity of subgrade is represented by  volcanic ash and lime stabilization. Volcanic ash is the non-widely used local material originated from Merapi and Kelud volcanoes. This research observes the value of subgrade rigidity and the changes in expansive soil morphology occurring due to the addition of volcanic ash and lime to increase the value of soil bearing capacity and stiffness. The tests are compaction, CBR, and SEM (Scanning Electron Microscopy) tests. The results show that, with the addition of volcanic ash and lime, there is an increase in the CBR value of soil, dry density and a decrease in optimum water content. The increased CBR value occurs due to the pozzolanic reaction between volcanic ash and lime and clay that results in mixed inter-particle bonding and changes in clay fraction morphology into the sand fraction, making  sand stronger and more rigid.
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