Effect of surface-modified fly ash on compressive strength of cement mortar

Abstract

This paper presents the experimental results on the impact of modified coal fly ash on mechanical performance of cement materials. Fly ash used in the experiments was received from Burshtyn thermal power plant (Ukraine). The surface modification was carried out by the acidic treatment in order to increase its pozzolanic activity. The impact of raw fly ash and surface-modified fly ash on the cement mortar strength have been compared. It was found in the experiments that the replacement of cement by 5% (wt) of modified fly ash increase the compressive strength value from 61.3 MPa to 63.2 MPa compared to unmodified fly ash at age 28 days. The mineral phase formation, structure and chemical compositions of the modified fly ash/cement composites were analyzed by XRD, SEM and EDS. This research is of great importance and opens a new way for the future investigation and utilization of coal fly ash.