Utilization potential of waste residue and dust powder from C&D waste

The by-products generated during the recycling of construction and demolition (C&D) waste, namely waste residue (WR) and dust powder (DP), are typically regarded as low-quality waste and subjected to landfill disposal. These by-products account for approximately 20% of the C&D waste, thereby occupying a large landfill capacity. This paper explores the utilization potential of WR and DP obtained from C&D waste. The physical and chemical characteristics of WR and DP were analyzed and their effects on cementitious composites were studied. The flowability, mechanical properties, and microstructural characteristics of the WR or DP contained mortar were evaluated. To enhance DP's practical applications, diverse alkali activators were adopted. The results showed that WR has potential to be used as a replacement for fine aggregates, and replacing less than 20% of natural sand by WR will not significantly affect the strength of mortar. Substituting cement with DP will significantly decrease the mortar strength, but the strength can be improved by activating the DP with an alkali activator. The activator with the best effect is Ca(OH)2, which can increase the mortar activity index to 69.0% with 4% addition. The current study provides valuable information for C&D waste management and can significantly improve the reuse value of low-quality C&D waste product, which contributes to reducing the amount of landfilled C&D waste.