Soil stabilization application using geopolymerization method

Abstract

Soft soils such as clay and silt have been associated to countless problems especially in engineering field. The main concern is to search for the best soil stabilizers to overcome the aroused problems. The purpose of soil stabilization is not only to achieve the required soil engineering properties, in fact the cost and the effect towards the environment also should be considered. Continues studies are done by numerous researchers in order to find alternative methods for soil stabilization and geopolymerization is one of the method that can fulfill those requirements. This study has been conducted to investigate the geopolymerization method for soil stabilization application, by mixing the soils directly with alkaline solutions, producing soil based geopolymer. This method was conducted towards three types of soil; kaolin, Soil 1 and Soil 2. The soils were analyzed in terms of soil classification, Atterberg Limits, chemical composition, phase and morphology for geopolymer fabrication. Meanwhile, for the design of soil based geopolymer, the parameters involved were NaOH concentration, solid/liquid ratio and Na2SiO3/NaOH ratio. The optimum mixing ratio (solid/liquid ratio) of soil based geopolymers were obtained based on the highest strength values in Unconfined Compressive Strength (UCS) test and California Bearing Ratio (CBR) test. The highest strength value for kaolin based geopolymer was 436 kPa for UCS test and 46% for CBR test. Both values were at the same optimum solid/liquid ratio of 1.5. The optimum mixing ratio for Soil 1 based geopolymer was 2.0, with highest strength value of 500 kPa for UCS test and 55% for CBR test. Soil 2 based geopolymer also indicated the same optimum mixing ratio, 2.0, with highest strength value of 620 kPa and 62% for UCS test and CBR test, respectively. The soil based geopolymers were not effective for soil stabilization application according to ASTM D4609 specification and did not comply the minimum value specified in the Design Guideline for Alternative Pavement Structures (Low Volume Roads) of Malaysia Public Work Department (PWD). Kaolin based geopolymer indicated reduction of plasticity index up to 11.24%, meanwhile Soil 1 and Soil 2 based geopolymers indicated reduction up to 3.08% and 4.31%, respectively. The characterization of soil based geopolymers; phase analysis and morphology analysis were conducted at optimum mixing ratio. The increment of strength values and changes in the characterization of soil based geopolymers proved that geopolymerization method can be used for soil stabilization application.