The effects of alumina-leached coal fly ash residue on magnesium oxychloride cement.

Effects of alumina-leached coal fly ash residue (ACFAR) on magnesium oxychloride (MOC) cement are comprehensively investigated. The results show that the addition of ACFAR delayed the setting time of MOC paste. The compressive strength, the flexural strength and the water resistance of MOC are improved by the incorporation of ACFAR. Furthermore, the improvement effects of ACFAR are compared with those of raw coal fly ash (RFA) on MOC cement. Scanning electron microscopy analysis of MOC cement reveals that ACFAR decreases the interspaces in MOC cement and facilitates the radial growth of 5Mg(OH)·MgCl·8HO. X-ray diffraction analysis of MOC cement with ACFAR indicates that the addition of ACFAR promotes the production of magnesium silicate, which can improve the compactness of 5Mg(OH)·MgCl·8HO and the water resistance of MOC cement. [ABSTRACT FROM AUTHOR]