Cement accounts for approximately 7% of global CO2 emissions. Carbon dioxide, which causes global warming, threatens the environment. All efforts have been made to reduce CO2 emissions, yet cement hasn't been substituted. Fly Ash (FA) based concrete reduces construction cement consumption. This study discusses using FA concrete in building to improve two environmental problems: thermal power stations' disposal of vast volumes of FA in big landfills and the cement industry's excessive carbon dioxide emissions. FA is a coal-burning byproduct. It's one of the most complicated human-made materials, and improper disposal wastes resources and harms the environment. The FA must be recycled urgently. This review discusses FA's physical and chemical characteristics and worldwide risks. It discusses its current and prospective users in the construction industry. The merits and downsides of various uses, how FA is used globally, and future research prospects are discussed.