Properties of high-volume slag cement mortar incorporating circulating fluidized bed combustion fly ash and bottom ash

This study investigates the incorporation of circulating fluidized bed combustion (CFBC) fly ash as an activator and CFBC bottom ash as fine aggregate in high-volume slag cement mortar. A series of investigations were carried out to analyze the influence of CFBC ash products on the properties of mortar. For comparison, control specimens of ordinary Portland cement and high-volume slag cement were considered. The results obtained from X-ray diffraction and thermogravimetric analyses revealed that the addition of CFBC fly ash activated the hydration of the slag and improved the initial strength of the mortar. Additionally, a pore size distribution test showed that the introduction of CFBC fly ash resulted in decrease of the critical pore diameter and the porosity of the high-volume slag mixes up to 28 days of curing. Similarly, it was found that the compressive strength of high-volume slag mortar manufactured with CFBC fly ash and CFBC bottom ash was improved. Furthermore, the enhanced hydration of high-volume slag mortar due to CFBC ash products resulted in decreased water absorption and fewer total voids. However, inferior resistance to chemical attack was also observed.