Solidification of Bangkok clay by fly ash-based geopolymer

Portland cement, an essential material for infrastructures like building and bridge construction is said to discharge about 1 ton of carbon dioxide (CO2) to produce 1 ton of cement. Lime which is also essentially used to improve an agricultural soil and is also a construction material, discharges huge amount of CO2 in the production process. An effort is desired to find and to make an effective use of an alternative construction material which enables the decrease in the use of cement and lime, and hence lowers CO2 emissions, being a major source of environmental concern. Geopolymer which is a term covering a class of synthetic aluminosilicate materials has recently been developed to use predominantly as a replacement for Portland-based cement and to solidify sludge polluted by heavy metals. Geopolymer is generally formed by reaction of an aluminosilicate powder with an alkaline silicate solution at roughly ambient conditions and is solidified by polymerization as the metal ion (Msup(m+)) liquidated out from the filler, bonds with the acetic acid silicate by the reacting with the components of water glass (Si, O, H). Sodium silicate is used as an alkaline silica and the fly ash is used as the filler. Fly ash which is known to be pozzolanic in nature and reacts with calcium hydroxide (Ca(OH)2) and alkali to form calcium silicate hydrates (CaSi) and other cement like compounds. The fly ash-based geopolymer is developed by mixing fly ash with an activator which is a solution made by sodium silicate (law of water glass) and caustic soda. In this paper, the development of the fly ash-based geopolymer is described and the mechanical and chemical characteristics of the stabilized Bangkok clay by the geopolymer are clarified. The fly ash is an industrial waste material from power station. This paper aims to propose an effective use of fly ash as a resource.