ABSTRACT
Subgrade soil is a critical element in the pavement system and can be considered as one of the major challenges for civil engineering applications. This paper investigates the efficiency of geopolymer material in sandy silt soil stabilization in terms of the strength and durability. Various proportions of the kaolinite (5, 10, 15, 20, 25, and 30%) by weight were used as a raw material to produce the geopolymer. The alkaline liquid consists of the NaOH at 8M and Na2SiO3 liquid, at 1.5 ratio of the NaOH:Na2SiO3. Laboratory investigation involves the compaction and mechanical properties of the natural and stabilized soil mixtures. The results showed a great improvement in the strength of the soil in terms of the unconfined compressive strength (UCS) and the indirect tensile strength (ITS). The optimum content of the kaolinite was 15%, which achieved the maximum UCS and ITS values. The CBR index of the soil significantly increased with the kaolinite-based geopolymer. Specimens stabilized using the optimum content of the kaolinite-based geopolymer did not pass the durability test in terms of the weight loss and volume change. The microstructural analysis of the stabilized specimens showed a poor distribution of the geopolymer binder. Moreover, pores were clear in the structure and this may indicates the poor behavior during the durability test.
