Sulfate and Sulfuric Acid Resistance of Geopolymer Mortars Using Waste Blended Ash

This paper presents the chemical resistance of geopolymer mortars prepared from the combination of palm oil fuel ash (POFA) and pulverized fuel ash (PFA) from agro-industrial waste as cement replacement and activated by alkaline solution. Alkaline solution was prepared by combining sodium silicate and sodium hydroxide. The concentration of alkaline solution used was 14 Molar. The optimum mix proportions of geopolymer mortars with PFA: POFA mass ratio of 70:30 was used together with alkaline solution. The ratio of sodium silicate solution-to-sodium hydroxide solution by mass was 2.5:1. The mass ratio of sand to blended ashes was 3:1. Test specimens 70×70×70 mm cube were prepared and cured at room temperature (28 ℃) for 28-d and heat-cured at 90 ℃for 24 h, respectively. Then specimens were exposed to 5% sodium sulfate solution and 2% sulfuric acid solution for 28-d, 56-d, 90-d, 180-d and 365-d .The evaluation was done by visual observation, mass change, and loss of compressive strength. The test results revealed that geopolymer mortars showed higher resistance to acids as compared to ordinary Portland cement mortar due to the elimination of cement in the mixture.