Cementitious properties and hydration mechanism of circulating fluidized bed combustion (CFBC) desulfurization ashes

Self-cementitious properties and pozzolanic reactivity of CFBC desulfurization ashes (CFBCA), modified CFBCAs (MCFBCAs) and pulverized fuel fly ash (PFA) are investigated. The results show that CFBCA and MCFBCAs are self-cementitious, but PFA is not self-cementitious. Self-cementitious strength of MCFBCAs is influenced by the grinding mode and modifiers. Compared with CFBCA and PFA, the pozzolanic reactivity index of MCFBCAs is increased by 23-37% and 15-28.8%, respectively. A higher strength of the cement with the intergrinding MCFBCAs is attained, which is comparable to that of the pure cement paste (C-O) at 28 days. Moreover, MCFBCAs have higher pozzolanic reactivity and can be used as an admixture in cement. By means of XRD, SEM and FT-IR, the main hydration products of the CFBCA and MCFBCAs samples are hydrated calcium silicate (C-S-H), ettringite, gypsum and some portlandite, but no obvious hydration products are detected in the PFA. (C) 2012 Elsevier Ltd. All rights reserved.