SOAKED CBR AND MICROSTRUCTURAL ASSESSMENT OF FLY ASH-RICE HUSK ASH-LIME STABILIZED SANDY PODZOL

Abstract

Within tropical areas experiencing regular rainfall and seasonal wetness, pavement support under soaked conditions can be significantly reduced. It is primarily attributed to the weakened sandy Podzol subgrade soil due to moisture. To stabilize the sandy Podzol subgrade soil in South Kalimantan, Indonesia, this study examined the soaked performance of a ternary binder involving three components: (i) fly ash, (ii) rice husk ash, and (iii) lime. The untreated soil was classified as well-graded sand (SW) with less than 5% non-plastic fines. At the optimal moisture content determined using the Standard Proctor method, various specimens were compacted, cured for seven days, and soaked for four days prior to California bearing ratio (CBR) testing. The F15LR (15% FA + 5% RHA + 2.5% lime) specimen revealed the highest CBR improvement (4.30% to 7.50%, 74% increase). Fourier transform infrared spectroscopy analysis indicated chemical changes associated with stabilization-related reactions. A more densely bonded matrix was observed in the optimal mixture through scanning electron microscopy analysis. In sandy Podzol subgrade soil, soaked performance was influenced more by binder dosage efficiency and granular packing than by binder quantity alone. Overall, in enhancing pavement subgrade in wet conditions using locally available by-products, this study suggested that the proposed ternary system had high potential.