Unconfined compressive strength of compacted fly ash and CL class clay mixture at standard and modified proctor energy levels

In this study, the unconfined compressive properties of variable mixtures of CL type clay and fly ash, which is a waste product of thermal power plants, have been studied. The mixtures were prepared at different fly ash percentages of 5%, 10%, and 20% by total weight of fly ash and CL clay, using fly ash supplied from 13 different power plants. Four main investigations were made in this study. These are; the effect of different types of fly ashes on unconfined compressive properties, the effect of different amount of fly ash on unconfined compressive properties, the curing period?s effect on unconfined compressive properties and the effect of compaction energy?s level on unconfined compressive properties. By performing standard and modified Proctor experiments, optimum water contents and maximum dry unit weights of the pure clay, which have been used in this study, were determined. All of the fly ash and clay mixtures were prepared by using with these determined values of optimum water contents and maximum dry unit weights. Three pieces of identical specimens were prepared for each type of mixture, and the results were evaluated by the obtained average value of unconfined compressive strength. Curing periods were one day and 28 days. Within the scope of this experimental study, unconfined compression tests have been applied on 480 pieces of specimen. The strength of CL type of clay tripled by increasing compaction energy level from Standard Proctor to modified Proctor level. The value of unconfined compressive strength has risen with the increased curing period and fly ash content. When the effect of curing period is evaluated; the maximum strength increase at standard Proctor energy level with increased curing time was reached with %20 Kemerköy fly ash (approximately quadruple of the first value). Similarly, the maximum strength value increase at modified Proctor energy level with increased curing time was reached with %20 Yatağan fly ash (approximately double of the first value). The specimens which include 20% of Soma fly ash with 28 days-curing time reached the highest average strength value, among all of fly ash and clay mixtures (approximately 7 MPa at standard Proctor level and approximately 12 Mpa at modified Proctor level).