Geopolymer is alumino-silicate material which can apply for many applications due to that geopolymers have several attractive properties of high strength, low permeability, high acid resistance, hazardous materials, and immobilization of toxic materials. This chapter presents synthesis of the dense and the porous structures of geopolymer by using fly ash and industrial waste as the raw materials. Aluminum hydroxide waste (Al-waste) and fly ash (FA) were used to synthesis the dense geopolymers for cement materials. The Al-waste based geopolymer influenced the geopolymer strength, when sodium hydroxide (NaOH) concentration was changed at different curing temperatures. As preliminary microwave oven was exposed in the lower NaOH paste of geopolymer, the successful synthesis of geopolymer cement was obtained. In addition, porous fly ash geopolymers was achieved using a household microwave oven. The geopolymer paste was cured within 1 min by using a microwave oven at different output power. Porous geopolymers were formed immediately as ued at 850 W power of the microwave oven.
TopIntroduction
Geopolymers are known as sustainable materials with eco-friendly process, since these simply can use wastes for raw materials, and have excellent mechanical properties (Kumar & Kumar, 2011; Nazari & Sanjayan, 2015). Usually, the geopolymer materials are activated in a high alkali solution (Davidovits, 2008) because alumino silicate geopolymers consist of tetrahedral AlO4 and SiO4 units that occur easily in a polycondensed polymer framework in high-alkali conditions (Davidovits, 1991). In geopolymer materials prepared at low temperatures with high alkali solutions, generally alumino-silicate materials such as slag (Karakoç et al., 2014), metakaolin (Rovnaník, 2010a), and fly ash (Ryu, Lee, Koh, & Chung, 2013) were mixed with alkaline solution. For example, sodium or potassium hydroxide is necessary for dissolving silicon and aluminium atoms from raw materials of natural minerals or industrial waste. The silicate alkaline solution includes:
- •
A binder,
- •
Alkaline activator, and
- •
A dispersant or plasticizer (Abdullah, Jamaludin, et al., 2012a; Nazari, Bagheri, & Riahi, 2011; Somna, Jaturapitakkul, Kajitvichyanukul, & Chindaprasirt, 2011).
The basic forms of the chemical structure have silicon-aluminate 3D structures with cross-linked chain bonds together in the geopolymer matrix (Songpiriyakij, Kubprasit, Jaturapitakkul, & Chindaprasirt, 2010). The condensation reaction of geopolymers proceeded greatly at room temperature (Puertas, Martı́nez-Ramı́rez, Alonso, & Vázquez, 2000). At elevated temperatures of 40–95 °C, geopolymerization is improved in the strength of specimens (Bakharev, 2005; Chindaprasirt, Chareerat, & Sirivivatnanon, 2007; Panias, Giannopoulou, & Perraki, 2007; Swanepoel & Strydom, 2002). Dense geopolymer materials having apparent density higher than 1 g/cm3 were applied for construction materials (Andini et al., 2008). Several reports described the use of metakaolin and fly ash as starting materials in geopolymerization (Duxson, Fernández-Jiménez, Lukey, et al., 2007; Komnitsas & Zaharaki, 2007). Moreover, industrial wastes of various types were used to synthesize geopolymers materials such as:
- •
Aluminum slag,
- •
Grey cast iron slag, and
- •
Blast furnace slag.
Among them, the use of etching surface waste, aluminum hydroxide, is interesting in the raw material for geopolymers. The Al-waste has high aluminum contents, making it suitable for the synthesis of better Al-source of geopolymers. Therefore, it is extremely attractive to investigate the geopolymerization of fly ash and Al-waste as a sustainable source for cement substitute materials.