Improvement in Bearing Capacity of a Soft Soil by Addition of Fly Ash

Soft soils are not suitable for use in runway and highway construction due to their undesirable characteristics such as poor grading, low strength, and excessive plasticity, tendency to shrink or swell. By stabilizing such soils with appropriate agents, their engineering properties can be improved. One of the stabilizing agents is Class C fly ash. The paper aimed to study the bearing capacity improvement of a soft soil (from Elmadağ area) by using Class C fly ash (from Soma Thermal Power Plant). In the experimental study, index properties of soft soil and fly ash stabilized samples are determined. Then modified Proctor compaction, soaked California Bearing Ratio, and Unconfined Compressive Strength characteristics of the samples are investigated. During the study, the stabilized soil samples are prepared at different fly ash contents, i.e., 0%, 3%, 5%, 7%, and 10%. The samples are subjected to soaked California Bearing Ratio tests after 0, 7, and 28 days of curing. In addition to California Bearing Ratio tests, Unconfined Compressive Strength tests with 0, 7, and 28 days of curing are performed. In order to observe microstructures of samples, Scanning Electron Microscope-Energy Dispersive X-ray analysis are performed. The results of the study show that bearing capacity of Elmadağ soft soil can be improved substantially and swell can be reduced significantly by using Class C fly ash.