Upcycling of Construction Waste Powder for Sustainable Ultra-High Performance Engineered Cementitious Composites: Effects of Waste Powder Source and Content

Utilizing construction waste powder (CWP) as cement replacement for sustainable ultra-high performance engineered cementitious composites (UHP-ECC) provides a value-added approach to recycling construction waste. The effects of CWP sources and replacement levels on the micro-characteristics and mechanical strength of CWP incorporated UHP-ECC were examined in this study. The results demonstrate that CWP has good nucleation effect and micro-aggregate filling effect; the mix of CWP decreases the new hydration products, and mixing high-volume CWP in UHP-ECC brings about a loose micro-structure. Incorporating CWP reduces the compressive strength of UHP-ECC; when the CWP replacement level is equivalent, the compressive strength of UHP-ECC with CWP ground from brick waste is higher than that of UHP-ECC with CWP ground from concrete and mortar waste. Under three-bending loading, the mix of 10-30% CWP brings about a slight decrease in the ultimate load and an increase in the ultimate displacement of UHP-ECC. However, the ultimate load and displacement of UHP-ECC both significantly decrease when 50% CWP is incorporated. Under uniaxial tensile load, the ultimate stress of UHP-ECC with 30% CWP is slightly lower than that of plain UHP-ECC, but mixing 30% CWP in UHP-ECC elevates the ultimate strain. Furthermore, UHP-ECC incorporated with CWP from clay brick waste has better uniaxial tensile performance than UHP-ECC incorporated with CWP from concrete and mortar waste. Optimizing CWP type and replacement level can prepare sustainable UHP-ECC with good strength and ductility, and 30% replacement level of CWP is recommended.