Geopolymer has been developed as an alternative material to Portland cement. Geopolymer is based on the polymerization of alkaline activation and oxide of silicon and aluminium. These oxides can be found in many pozzolanic materials such as metakaolin and the wastes from industries and agricultures in Thailand, e.g., fly ash, bagasse ash and rice husk ash.Pozzolanic materials were selected as source materials for making geopolymers into 4 different types. Sodium hydroxide concentration of 10 Molar (10MNaOH) and sodium silicate (Na 2 SiO 3 ) solutions were used as alkaline activators by the mass ratio of Na 2 SiO 3 /NaOH at 1.5. The mixtures were cast in 25×25×25 mm. cubes. After casting, the geopolymers were cured at 80 ๐ C for 24 hrs. in an oven and then at room temperature for 7 days. The pozzolanic materials effects, the Si/Al molar ratio and the Na/Al molar ratio were studied and characterized.An X-ray fluorescence (XRF) was chosen to determine the percentages of silica and alumina in order to verify the proper ratio of the fly ash, Rice husk ash, Bagasse ash and Metakaolin.The study also included the impact on mechanical and physical properties such as compressive strength, water absorption, density and porosity.
1.IntroductionGeopolmer was first originated by Davidovits (1979) to designate a new class of three dimensional silico-aluminate materials [1]. The geopolymer is produced by totally replacing the ordinary Portland cement. Hence, the use of geopolymer concrete to replace the cement is to reduce the CO 2 emissions by the cement industries [2]. Geopolymerization can be applied to utilize solid wastes and by-products containing silica and alumina which are called 'Pozzolans'. A geopolymer is environmentally friendly [3] which is attractive to increase attention in various research fields as a construction material [4]. Pozzolans from industrial and agricultural by-products such as fly ash, bagasse ash and rice husk ash were used to produce geopolymers in this research.An industrial by-product, from power plants, which is now being used quite extensively as a pozzolan for replacing cement is fly ash. Bagasse ash is a by-product from sugar refinery whereas rice husk is a by-product from rice mill. When they are burnt both bagasse ash and rice husk ash contain around 80% of silica, silica in amorphous form suitable for use as a pozzolan [5]. Furthermore, the geopolymerization can be reacted with metakaolin, obtained by burning kaolin from Ranong province in Thailand, normally, at temperature higher than 600°C [6].The main alkali solutions activated with pozzolans were sodium silicate and sodium hydroxide. In this research, the fly ash, bagasse ash, rice husk ash and metakaolin were used as the starting materials. They were studied the effects of pozzolanic materials, the Si/Al molar ratio, the Na/Al molar ratio and Na/Si molar ratio for mechanical and physical properties such as compressive strength, water absorption, density and porosity.
