Effect of Alkaline Activator Ratio to Mechanical Properties of Geopolymer Concrete with Trass as Filler

Abstract

This paper describes the effect of alkaline activator ratio (Na 2 SiO 3 /NaOH) to mechanical properties of geopolymer concrete. The mechanical properties of geopolymer concrete were assessed by setting time, split tensile strength and porosity. Fly ash was used as a cement substitute, and trass used as filler. While, Natrium hydroxide (NaOH) and Sodium Silicate (Na 2 SiO 3 ) was applied as alkaline activator. In this study, NaOH concentration eight and ten molar with an alkaline activator ratio Na 2 SiO 3 / NaOH by mass: 0.5, 1, 1.5, 2 and 2.5 were used. The test result showed that setting time, porosity and split tensile strength of geopolymer concrete were hardly influenced by NaOH concentration and the alkaline activator ratio. The alkaline activator ratio of Na 2 SiO 3 /NaOH has an optimum value at 2 and 2.5. Test result showed that the fastest setting time was 25 minute, the highest amount of closed porosity was 9.035 % and the highest split tensile strength was 2.86 MPa.