RESISTANCE OF CHLORIDE AND SULFATE OF GEOPOLYMER MORTAR BASED ON FLY ASH AND SILICA FUME AS ALTERNATIVE RAW MATERIALS

The durability of concrete in acid or salt environments greatly influences its service life. This paper aims to develop the mortar composition for chloride and sulfate salt resistance at 50,000 mg/L as the simulated salt solution. Geopolymer mortar in this study consisted of 10%weight ordinary Portland cement (OPC type 1) with the other alternative raw materials which were pozzolanic materials and wastes (fly ash, silica fume and rice husk ash). Several parameters were investigated, including the type and content of the alternative raw materials, liquid to powder ratio, to enhance the compressive strength of the geopolymer mortar after a 14 -day immersion in the simulated salt solution as comparison with those in the normal water and the ordinary Portland cement. The results demonstrated that geopolymer mortar composed of fly ash and silica fume, with the mixture of NaOH (10M): Na2SiO3 in ratio of 24:16 (wt/wt), exhibited the improvement of the compressive strength as compared to ordinary Portland cement type 1 and type 5 after the 14 -day exposured in salt environment. Moreover, this geopolymer mortar provided low density, making it suitable for engineering structures in high -salt areas. Furthermore, this paper investigated the chemical reactions and phases that occur in the geopolymer mortar upon setting in high concentrations of chloride and sulfate solutions by XRD and FESEM-EDS techniques. XRD and FESEM-EDS results indicated that the change of chemical reaction and phases after setting of geopolymer mortar in high concentrations of chloride and sulfate solution provided the protection of Mg and Cl ions penetration inside the samples better than the Ordinary mortar. These findings provide insights into the salt resistance mechanism of geopolymer and lay the groundwork for developing concrete compositions with improved salt resistance in the future.