Effect of a novel spherical tailings aggregate on the macro- and mesoscopic properties of pervious concrete

Iron tailings have caused serious potential environmental risks with the massive accumulation. This study developed pervious concrete using novel spherical tailings aggregates (STA) synthesized from tailings sand, and explored the mechanism of the effect of STA on macro- and mesoscopic properties. Pervious concrete with natural coarse aggregate and STA replacement up to 100% were prepared. Compressive strength, splitting tensile strength, water permeability and porosity were tested. The thickness and distribution of cement paste at the top, middle and bottom of the specimens were analyzed. The uniformity of the pore distribution was quantified. The economic and environmental benefits are evaluated. The results showed that no more than 50% STA had little effect on the mechanical properties and permeability of the pervious concrete, and high contents of STA led to a decrease in mechanical properties and a significant increase in permeability. The porosity increases with the STA content and linear relations with the mechanical properties and permeability are observed. STA reduced the percentage of paste with thickness below 0.6 mm and increased that above 0.9 mm, and increased the average paste thickness. The aggregate particle interference phenomenon has been proven both theoretically and practically to cause non-uniform distribution of paste and pores, which affects macroscopic properties and water permeability. This study improves the fundamental understanding of the effect of aggregates on the properties of pervious concrete and contributes to the alleviation of environmental stress.