Resistance of Chloride and Sulfate of Geopolymer based on fly ash and silica fume as alternative raw materials.

Concrete durability to salt resistance is the main factor affecting the service life of concrete used in acid or salt environment. This project aims to develop the concrete composition for salt resistance of chloride and sulfate at 50,000 mg/L as the simulated salt solution in this project. Geopolymer consisted of 10%wt 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). The various parameters which were type and content of the alternative raw materials, plasticizers content, liquid to powder ratio, etc, were studied for developing the compressive strength of geopolymer after soaking in the simulated salt solution for 14 days as comparison with those in the normal water and the ordinary Portland cement. The results found that geopolymer consisted of fly ash and silica fume with the mixture of NaOH (10M): Na2SiO3 in a ratio of 24:16 (wt./wt.) could improve the compressive strength of geopolymer cement after soaking in the simulated sulfate salt solution for 14 days as compared to the ordinary Portland cement type 1 and type 5. Moreover, this geopolymer showed low density which was beneficial for use in the engineering structure in the high salt area. In addition, the change of chemical reaction and phases after setting of geopolymer in high concentrations of chloride and sulfate solution were studied to understand the mechanism of salt resistance of geopolymer and to develop the concrete composition for salt resistance in the future.