Engineering Properties of Treated Clay by Kaolin-Rice Husk Ash Geopolymer Activated with Sodium Hydroxide Solution

Thailand's highway development project and expansion of the main road are currently being built or planned. The development of stabilizing techniques in soils with various agents has been adopted since the early days due to the insufficient availability of local materials and their unsatisfactory engineering properties. Rice husk ash's (RHA) partial replacement of geopolymers in road-based applications received less attention. This study examines the engineering properties of clay (C) treated by kaolin-rice husk ash geopolymer (K-RHAGP). The ordinary clay is activated by sodium hydroxide solution. The appropriate proportion of kaolin:rice husk ash (K:RHA) of 70:30 stimulated by a sodium hydroxide solution of 8 molars exhibits the highest unconfined compressive strength (qu). Clay is treated by kaolin-rice husk ash geopolymer (K-RHAGP) with various ratios of C:K-RHAGP by weights of 90:10, 80:20, 70:30, 60:40, and 50:50. The results showed that the optimal C:K-RHAGP proportion of treated clay is 70:30, which yielded the highest qu at 7 days under curing temperatures of 70 degrees C and 50 degrees C, resulting in values of 9352 and 4557 kN/m2, respectively. The highest split tensile strength under 70 degrees C and 50 degrees C curing temperatures was 1182 and 576 kN/m2, respectively. The relationship between the modulus of elasticity at 50% strength, E50, and qu is expressed as E50 = 4.531qu. After wet and dry processes, the samples with the C:K-RHAGP ratio of 70:30 exhibit the highest strengths of 2445.89, 1670.55, and 1218.68 kN/m2 for 3, 9, and 12 wet-dry cycles corresponding to the lowest weight loss. The C:K-RHAGP weight loss of 70:30 in cycles 1 to 12 was 1.5 to 7.2%. The authors believe that the proposed K-RHAGP stabilization could be used as an effective replacement for cement-based soil stabilization in road-based construction.