The effect of cement and fly ash mixture variations on clay soil as a subgrade layer of road pavement

Soil stabilization is a process to improve soil properties by adding additives to increase soil strength. Clay soil is a type of soil that has a small bearing capacity; therefore, stabilization is needed to increase its bearing capacity value. The majority of Indonesia's territory tends to have a clay soil type, for example, the Green Rollo area of West Koya, Papua. This research aims to determine the characteristics of the soil and to ensure the effectiveness of the addition of cement and fly ash on the value of unconfined compressive strength. In this study, the stabilization process involved mixing original soil with cement + class F fly ash in any variations, which are 8% cement + 10% fly ash, 8% cement + 15% fly ash, and 8% cement + 20% fly ash. The soil sample can be classified as clay with high plasticity, namely A-7-6, according to AASHTO. The addition of cement + fly ash affects the value of unconfined compressive strength, the original soil has a compressive strength value of 11.73 kg/cm2 after stabilization with 8% cement and fly ash content with varying levels of 10%, 15% and 20% UCS values obtained are 24,29 kg/cm^2, 26,85 kg/cm^2, dan 27,12 kg/cm^2. In addition, the results show that the addition of cement and fly ash with varying percentages can increase the soaked CBR value to 11.89% with the optimum percentage at 15% fly ash content.