Utilizing Rice Hull Ash as Partial Replacement for Cement in Producing Soil-Cement: Materials for Deep Mix Soil Stabilization

Civil Engineering Department, University of Mindanao, 8000 Davao City, Philippines

^* Corresponding author: daarol_michelle@umindanao.edu.ph

Abstract

Stabilization of residual soils is studied chemically using cement and Rice Hull Ash (RHA). The investigation includes the evaluation of the physical properties of the soil and its classification. Furthermore, changes in the unit weight, the specific gravity of non-treated and treated with 5-25% RHA partially replacing soil-cement samples, and the moisture content of non-treated and treated soil before and after curing (21 days) were also examined. Moreover, ultimately, an investigation as to what percentage of RHA in partially replacing cement would produce the largest compressive strength and shear strength has also been done in this study. Tests showed that the soil was CL (Low Plasticity Clay) and that it has been found out the unit weight increases as the treatment of percentage increases. The specific gravity also increases with the further addition of cement but decreases when the amount of RHA is noticeable in the mix. As to moisture content, it has been found that there were always changes in the water content before and after curing for hydration. Moreover, the Unconsolidated Undrained Triaxial test was also employed to determine the changes in the strength of non-treated and untreated soil. It has been found that the maximum deviator stress peaked at 20 % RHA replacement, as do the internal friction angle and cohesion value, hence the maximum shear strength, for all confining pressures. These parameters have proved that RHA 20% partial replacement has the potential to Deep Mix Method (DMM) in strength and economics.