Abstract:Using expansion energy during hydration of free calcium oxide contained in high calcium fly ash creatively, a kind of expansion agent with the advantage of saving energy and utilizing industrial waste was produced in this research. The mixture of high calcium fly ash and proper proportion of S activator made by ourselve can be added into concrete directly. Compared with commercial UEA expansion agent, the cost of concrete with high calcium fly ash added is very low when producing the concrete with same properties.