The comparison of adding fly ash and Sinabung ash to limestone towards the soil improvement via CBR value

Fly ash is categorized as pollutant produced from coal combustion, where the waste produced is around 4% of the total coal usage. This will be extremely dangerous since this waste is produced continuously. Mount Sinabung, which is located in North Sumatera, Indonesia, has erupted since 2010 and released a lot of ash pollution. Sinabung and fly ash can cause environmental and health problems for the people who live near the area. In the other hand, limestone is one of the building materials that can be used for soil improvement. When limestone with clay minerals reacts, it forms a strong and hard gel namely calcium silicate which can coat and bind clay particles and close the pore pores, so that it can reduce the soil plasticity index. This research analyzes the optimum CBR value and the optimum mixture. Variation of the mixture used was 2% and 4% limestone with the addition of 2%, 4%, 6%, 8%, 10%, 12% and 14% fly ash and 2% and 4% limestone with the addition of 2%, 4%, 6 %, 8%, 10%, 12% and 14% of Sinabung ash. The result shows that the mixture of limestone and Sinabung ash indicates the bigger value of CBR compared to the limestone and fly ash mixture. Furthermore, the largest CBR value was found in the mixture of 2% limestone and 8% Sinabung ash with 9.01%.