The effects of fly ash addition on the geotechnical properties of clay

Improvement of clayey soils with poor bearing capacity, high swelling and shrinkage potential is one of the current research topics of geotechnical engineering. Different methods have been used to improve this kind of soils. In recent years, studies on the improvement of clayey soils by using waste materials such as marble dust, rubber clippings and fly ash have accelerated. In this thesis, the effect of fly ash obtained from the thermal power plants waste on the geotechnical properties of high plasticity clayey soil has been investigated. Pursuant to this goal, fly ash from Çatalağzı Thermal Power Plant was added to the clay samples taken from Bartın Kutlubey region in 5%, 10%, 15% and 20% by weight, respectively. Compressed at optimum water contents, the mixture of clay-fly ash and pure clay samples were subjected to consolidation test, then the swelling percentages related to fly ash ratio and the consolidation statement of these samples under vertical loads have been examined. Compressed at optimum water contents, the samples were cured for 1, 8, 16 and 32 days, then cured with CBR for 1, 8, 16, 32, 120 and 360 days and unconfined compression test was performed. As a result of the experiments, significant increases in CBR and unconfined compression strength were observed depending on the curing time and fly ash content in the mixture. Fly ash added to clay soils up to 10% induced an enhancement in unconfined compressive strength, and after 10%, increase in fly ash ratio decreased the unconfined compressive strength.