Performance regulation of construction waste-based pervious concrete through paste film thickness: Mechanical...

Using construction waste to prepare pervious concrete provides a low-carbon route for developing sponge cities. However, the complex constituents lead to a technical bottleneck in controlling fresh properties of paste. By regulating the paste film thickness (PFT) of recycled micropowder-ground granulated blast furnace slag-cement (RSC) paste, this study prepares recycled aggregate concrete with balanced strength and permeability (RSC-RAPC). Water reducer effects on flowability, PFT and rheology are investigated, establishing a PFT-performance relationship that is more applicable to aggregates of 4.75-9.5 mm. Compared with pure cement paste, RSC paste exhibits 17.1% higher PFT and 10% higher initial yield stress, while average fluidity decreases by 5.26%. Within a water reducer dosage of 0.11%, adjusting the PFT of the recycled aggregates in RSC paste from 0.20 mm to 0.57 mm yields RSC-RAPC with 13.5%-24.7% of connected porosity, 1.38-2.59 mm/s of permeability, and 6.1-28.8 MPa of 28-day compressive strength. Three interfacial transition zones are identified in RSC-RAPC, where the new paste-old paste interface exhibits 10.66% higher microhardness than the weakest interface due to carboaluminate reaction densification. A target porosity of 15%-17% is recommended, as it can maintain excellent permeability and mechanical strength while cutting both carbon emissions and economic costs per unit strength by over 43% and 45%, respectively.