EFFECTS OF FLY ASH AND RICE HUSK ASH MIXING WITH BANJARMASIN SOFT CLAY SOIL ON CBR, SWELLING AND SHEAR STRENGTH VALUE

Abstract

Soil stabilization using admixture is one way to improve the mechanical properties of soil. Several studies have shown that the use of fly ash and rice husk ash can have an effect to increasing the CBR value and suppressing the expansion of soil volume (swelling), as well as increasing the shear strength value. However, the research cannot explain the effectiveness of mixing fly ash and rice husk ash as a soft clay soil stabilizer, especially soft clay soil in Banjarmasin, South Kalimantan Province. The fly ash used comes from the Asam-asam PLTU, while the rice husk ash is taken from the Cempaka sub-district. The percentage of fly ash used in the mixture is 15%, 20% and 25% of the dry weight of the original soil, while the percentage of the rice husk ash used is 5% and 10% of the dry weight of the original soil. Each sample that has been compacted is cured for 3, and 7 days before performing the CBR test. On the samples that will be subjected to the immersion CBR test, a numerical analysis will be performed on shear strenght. Samples that have been tested for immersion CBR will be molded using a ring for testing direct shear. The maximum CBR value resulting from this research was in soil conditions mixed with 25% fly ash and 5% rice husk ash. When the curing time reached 7 days, the CBR changed to be 1,72%. The cohesion and friction angle of the soil also change depending on the percentage of admixture used. However, chemical stabilization uses fly ash and rice husk ash requires water on the process of stabilization so that the water content in the sample keep decrease during of curing time.