Evaluating the potential of high free-CaO fluidized bed boiler ash as a cement admixture

Abstract

This study investigates the feasibility of utilizing ash from circulating fluidized bed combustion (CFBC) boilers as a cement admixture. Two types of CFBC ash, distinguished by their free-CaO contents, are examined to evaluate their impact on the hydration reactions and mechanical properties of cement. The incorporation of CFBC ash with elevated free-CaO content into cement facilitates a hydration reaction, which results in accelerated setting and reduced compressive strength. To effectively utilize CFBC ash as a cement admixture, it is necessary to reduce the free-CaO content to an appropriate level, and carbonation curing is found to be an efficient method. It is confirmed that even CFBC ash with a high free-CaO content can effectively be utilized as a cement admixture through pretreatment with carbonation curing. This study may have valuable implications for the ability of CFBC ash to reduce carbon dioxide via mineral carbonation and its potential use as a cement admixture.