Study of the Effect of Organic Geopolymer for Soil Stabilization Materials as Main Road Subgrade

Soil stabilization is an effort to improve soil properties, increase soil carrying capacity and soil shear strength by mixing it with chemicals or other additives. Stabilizing the soil aims to increase soil density, replace inactive materials to increase cohesion and friction resistance that arises, adding it to change soil's chemical and/or index, reduce the soil drainage, replace bad soil so that it has technical specifications as subgrade for highway pavement. The most commonly used and best-considered soil chemical stabilization material for soil is cement but it has a negative impact so organic geopolymer used instead of it. The organic geopolymer forming material derived from oil palm shell ash and alkali activator are NaOH. Based on the results of soil index properties, the initial PI soil test results was 22.92% and after the addition of organic geopolymer become 15.70%. Soil engineering properties test in the form of standard compaction testing, CBR laboratory and unconfined compression test (UTC). The initial standard compaction test for the soil maximum dry density soil was 14,00 kN/m3 , and the optimum water content was 29.39%, after adding organic geopolymer the weight become 14,80 kN/m3 , and optimum water content become 25.35 % (qualify). The initial CBR soil test results were 6.9%, but after the addition of CBR organic geopolymer become 8.7% (qualify). The initial soil UCT results were 59,87 kPa, after the addition of UCT organic geopolymer become 90,91 kPa (qualify).