Feasibility analysis of treating recycled rock dust as an environmentally friendly alternative material in Ultra-High Performance Concrete (UHPC)

Quartz sand is a kind of advanced aggregate and can be utilized to produce Ultra-High-Performance-Concrete (UHPC). However, its production process always create environmental risks, such as dust pollution, noise pollution, and soil pollution. Therefore, to overcome the problems mentioned above, this study try to decrease the quartz sand content in UHPC by utilizing recycled rock dust with different replacement ratio (20%, 40%, 60%, 80%, and 100% by weight), and produce a green UHPC. This cleaner product is designed based on modified Andreasen and Andersen (MAA) particle packing model. Then, its properties are evaluated and discussed, including workability, dimensional stability, mechanical properties, durability, hydration kinetics and pore structure. The obtained experimental results show that the added rock dust has limited effect on UHPC flowability and hydration process. The compressive strength of the mixture containing 80% rock dust achieve 154.1 MPa, which is even larger than that of reference sample (141.3 MPa). The micro-hardness and backscatter electron results demonstrate that the interfacial transition zone (ITZ) of UHPC can be improved when quartz sand is replaced by rock dust. Ultimately, the environmental and economical analysis prove that the raw cost per unit volume of UHPC can be reduced by 42% without sacrificing its performance, meanwhile, the dust pollution, soil pollution, noise pollution and land waste problems can also be correspondingly solved.