Flyash Based Geopolymer Concrete – A State of t he Art Review

Abstract

Concrete usage around the world is second only to water. Ordinary Portland Cement (OPC) is conventionally used as the primary binder to produce concrete. But the amount of carbon dioxide released during the manufacture of OPC due to the calcinations of lime stone and combustion of fossil fuel is in the order of 600 kg for every ton of OPC produced. In addition, the extent of energy requires to produce OPC is only next to steel and aluminum. On the other hand, the abundant availability of fly ash worldwide creates opportunity to utilize (by ‐ product of burning coal, regarded as a waste material) as substitute for OPC to manufacture concrete. Binders could be produced by polymeric reaction of alkali liquids with the silicon and the aluminum in the source materials such as fly ash and rice husk ash and these binders are termed as Geopolymer. In Geopolymer Concrete, fly ash and aggregates are mixed with alkaline liquids such as a combination of Sodium Silicate and Sodium Hydroxide. United Nation’s Intergovernmental panel on Climate Change (IPCC) prepared a report on global warming during April 2007 which enlists various methods of reduction of CO2 emissions into atmosphere. As per that report, unmindful pumping of CO2 into the atmosphere is the main culprit for the climate change. Large volume of fly ash is being produced by thermal power stations and part of the fly ash produced is used in concrete industry, low laying area fill, roads and embankment, brick manufacturing etc. The balance amount of fly ash is being stored in fly ash ponds. Hence it is imperative on the part of Scientists and Engineers to devise suitable methodologies for the disposal of fly ash. Disposal of fly ash has the objective of saving vast amount of land meant for ash pond to store fly ash. Further, use of fly ash as a value added material as in the case of geopolymer concrete, reduces the consumption of cement. Reduction of cement usage will reduce the production of cement which in turn cut the CO2 emissions. Many researchers have worked on the development of geopolymer cement and concrete for the past ten years. The time has come for the review of progress made in the field of development of geopolymer concrete. Consequently 102 papers pertaining to the ingredients and technology of geopolymer concrete have been reviewed in this state of the art paper.