Incorporation of CFBC ash in sodium silicate-activated slag system: Modification of microstructures and its effect on shrinkage

Abstract

Circulating fluidized bed combustion (CFBC) ash was applied in sodium silicate-activated slag system as a secondary activator and/or for the substitution of commercialized expanding admixtures. To understand the effects of this ash on such alkali-activated slag (AAS) system, a series of experiments relating to hydration kinetics, hydration products and microstructure, and engineering properties were performed. It was found that the introduction of the ash resulted in different types of hydration products in AAS, leading to increases in both the size and volume of the pores. Although the setting time was retarded, the autogenous and dry shrinkages of the AAS decreased by the increase in the ash content. The shrinkage and strength of AAS affected by the external moisture conditions during curing could be controlled by substituting the slag with the ash.