Improving strength development of wastepaper sludge ash by wet-milling

Wastepaper sludge ash (WSA) requires relatively higher proportions of water than Portland cement (PC) when used as a single binder. This high water demand may be reduced by the addition of secondary binders such as ground granulated blastfurnace slag (GGBS), which improves the hydration properties of the mixes. Based on the already determined physico-chemical properties of WSA a new method of paste preparation is introduced which also enhances the cementitious properties of WSA. The method utilises a wet-grinding stage prior to mixing. Pre-treatment of WSA prior to the addition of GGBS enhances effectively the strength development of the blended binder. Higher compressive strengths are obtained for the paste cube samples made using the new method of paste preparation than those achieved by conventional dry mixing methods.