Engineering Performance of Fly Ash Stabilized Çatalağzı Clay

Abstract

Stabilizing of soils can be done with physical, chemical and hydraulic methods. Chemical stabilization is one of the most widely used method among them. In this study, low plasticity Çatalağzı clayey soil is chosen as a research material. F type of fly ash are used as a chemical additive. Soil is mixed with various amount (0%, 10%, 20% and 30%) of fly ash. Index tests (hydrometer, specific gravity, liquid limit, plastic limit and standard compaction) were performed on clayey soil. Then samples prepared with optimum water content obtained from standard compaction test were exposed to unconfined compressive strength (UCS), moisture condition value (MCV) and California bearing ratio (CBR) tests. Curing time are selected as 0, 7 and 28 days for UCS test. Curing for CBR test includes 28 days air curing and 4 days full soaking. MCV has no curing time. Addition of fly ash increase the UCS of untreated soil. UCS of samples for S10FA, S20FA and S30FA having 7 day of curing time is 1.46, 1.51 and 1.53 times of the Çatalağzı clay of having no curing time. Rate of increase in UCS gets slow down after 7 days. MCV of S10FA is 18.3 while it is 12.2 for Çatalağzı clay which means 50% increase. Fly ash content after 10% have no significant change and even decrease slightly. CBR values are increased with an addition of fly ash also. It has been concluded that this type of fly ash increases the engineering performance of untreated clay but it is not suitable to be a subgrade for highway when taking into account of CBR value