Abstract
Globally, cement is the highest utilized pozzolanic material in construction. Consequently, yearly ordinary Portland cement is manufactured in enormous amounts worldwide. Manufacturing of cement is a natural resource and energy consuming process which involves greenhouse gas CO2 release in the air in vast amount. The utilization of ordinary Portland cement in construction can be lessened by replacing it with some other by-product cementitious material having equal or higher mechanical strength and durability. This paper discusses the impact of cement manufacturing on the environment and gives the background to the requirements for the invention of alternate binders over conventional binders like cement. Many researchers attempted to produce an environmentally friendly binder, "Geopolymer". This paper aims to present an overview of past and recent studies on the utilization of flyash and other waste materials in developing geopolymer as a sustainable construction material. Description of the production of geopolymer, the chemistry of geopolymerization, microstructural analysis, and its relationship with mechanical strength and durability of geopolymer are reviewed. Moreover, the influence of the inclusion of calcium-based waste material in geopolymerization is reviewed and reported. Many researchers reported higher strength of a flyash-based geopolymer composite than the conventional cement composite.