Upcycling of construction spoil powder as partial cement replacement for sustainable cement-based materials: Properties and modification

Abstract

Construction spoil accounts for the main part of construction and demolition waste, the effective recycling of which has been paid less attention to by previous investigations. This work investigated the feasibility of utilizing waste spoil powder (WSP) ground from construction waste as partial cement replacement for preparing sustainable mortar, and a 800–1200 °C heat treatment was employed to modify the properties of WSP. The WSP with an irregular particle shape contains massive inert quartz, anorthite and kaoline, and mixing WSP reduces the hydration reaction and enlarges the pore structure of cement-based materials. However, new metakaolin and amorphous components are generated in heat-treated WSP, and heat-treated WSP has higher activity than untreated WSP; besides, the paste with heat-treated WSP has finer pore size than the paste with untreated WSP. The drying shrinkage of mortar increases by intermixing WSP; but the mix of heat-treated WSP reduces the drying shrinkage, and the maximum shrinkage of mortar with 30% WSP after 1200 °C treatment is 25.0% lower than that of plain mortar. Incorporating WSP reduces the mechanical strength and meanwhile increases the water absorption of mortar, but the mortar including heat-treated WSP has higher strength and lower water absorption than the mortar with untreated WSP. Decreasing WSP particle size further improves the properties of WSP blended mortar. It is noticed that incorporating heat-treated WSP together with active mineral admixture can prepare sustainable mortar with similar mechanical strength and lower water absorption than plain mortar without WSP.