Recycling of waste glass powder as paste replacement in green UHPFRC

Abstract

Featured by a high cement content and a large consumption of quartz sand, ultra-high performance fiber reinforced concrete (UHPFRC) encounters hindrance in the pursuit of carbon neutralization and extensive application. Recycling materials (e.g., waste glass) may lower the performance of UHPFRC when used as cement/aggregate substitution. To conquer this problem, an innovative paste replacement method, i.e., adding waste glass powder (WGP) to substitute an equal volume of paste without altering the paste composition, was employed. An optimum amount of WGP was revealed for remarkably enhancing the workability, compressive strength, bending strength and microstructure of UHPFRC. Meanwhile, cement content was reduced by 18.8% to 365 kg/m3, whilst the strength was remarkably increased to exceed 150 MPa. To explore the mechanism, the wet packing density and slurry film thickness (SFT) of the paste were determined, whereby empirical models were established based on SFT and fiber factor (FF) for workability. Lastly, certain synergistic effects between the combined use of WGP and steel fibers on the properties of green (low carbon) UHPFRC were identified.