Valorization of quartz powder for drying shrinkage and carbonation resistance of alkali-activated slag cement.

Abstract

Alkali-activated slag (AAS) cement is one type of alkali-activated binders free from Portland cement. The main problems of this type of cement are its high drying shrinkage and low carbonation resistance that hinder its wide use. In the current paper, the authors tried to suppress this high drying shrinkage and enhance the carbonation resistance of this type of binder by incorporating quartz powder (QP). For that reason, slag was partially replaced with QP at ratios of 10-30 wt%. The flowability of each mixture was measured using a hand-driven flow table. The initial reading of drying shrinkage was monitored after 24h from casting and continued up to 90days. After initial curing, some specimens were exposed to atmospheric natural carbonation for one year, whilst the remaining specimens were sealed and used as references. Different techniques such as thermogravimetric analysis and its derivative (TGA/DTG), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) were used to analyze the results. The results showed that the incorporation of QP in the matrix increased the flowability and compressive strength, decreased the drying shrinkage, increased the carbonationresistance, and refined the microstructure.