The Effect of NaOH Molarity on The Performance of Geopolymer Concrete Using Fly Ash From North Sumatera and Aceh

Geopolymer concrete is green concrete that uses fly ash and alkali activator substituting Portland cement. The use of Fly Ash from different sources produces different concrete characteristics. This study used three different fly ashes obtained from three different coal-fired power plants in Aceh and North Sumatera: Nagan Raya, Labuhan Angin, and Pangkalan Susu, as geopolymer concrete material. The 10 Molar and 12 Molar Sodium Hydroxide (NaOH) solutions were used as a variable in this study. Then, the concrete was tested with a compressive strength test, splitting tensile strength test, flexural tensile strength test, and elasticity modulus test. The specimen for the compressive strength test was 100×100×100 mm cube which was tested at 7, 14, and 28 days. The splitting tensile strength test and modulus elasticity test specimen was 150×300 mm cylinder tested at 28 days. The specimen for the flexure test was 100×100×500 mm beam tested at 28 days. Based on the result, it was found that geopolymer concrete using Pangkalan Susu fly ash and 12 M of NaOH had higher performance than geopolymer concrete using Nagan Raya and mixed fly ashes. Geopolymer concrete made from fly ash is promising to be applied as a construction material for both structural and non-structural elements.