The Study of The Kinetic Effect of Aluminosilicate Gel Formation on Fly Ash Based Geopolymer

Fly ash based Geopolymer is a type of concrete based that can act as the basic building materials which is utilized in construction of roads, buildings and infrastructures and it is expected to be widely used in foreseeable future. It is formed through the reaction of fly ash with have high content of silica and alumina and alkaline solution. It is a potential alternative to Ordinary Portland Cement (OPC) in cement industry as it is not only minimizing CO2 emission, but also contributes toward recycling waste material, fly ash which is economically feasible. Geopolymer also showed good properties such as low creep, low shrinkage, high compressive and tensile strength and good acid resistance. This research is to study the effect of kinetic formation of aluminosilicate gel formation in geopolymer. The kinetic formation is measured before setting time of the solidification of fly ash geopolymer based on 3 parameters. The parameters are type of alkaline solution, concentration of alkaline solution and process temperature. First, four different alkaline solution is tested; the mixture of sodium silicate and sodium hydroxide, the mixture of sodium silicate and potassium hydroxide, sodium hydroxide and potassium hydroxide. Second, the concentration of alkaline solution which is varied at 5, 8, 10 and 15M. Third is the process temperature where the geopolymerization is conducted at room temperature, 270c and at 900C. The fly ash based geopolymer paste would be tested using Vicat needle and the result of this study would be analyzed and explained based on the Avrami’s Kinetic Theory. It was found that the addition of sodium silicate into alkaline solution will produce shortest time for solidification geopolymer at 60min followed by sodium hydroxide (NaOH) solution at 90min and potassium hydroxide (KOH) solution at 100min. The increase in concentration of alkaline solution and process temperature shortens the setting time for solidification of geopolymer at 57min for 15M at 900C reaction temperature and at 55min for 10M at 900C. From the Avrami Kinetic Theory’s perspective, the growth form of crystal in the geopolymerization process exhibits mixed structure