Properties of ultra-high-performance concrete with recycled macro fibers: Effects of fiber coating with graphene oxide

Use of macro fibers processed from waste glass fiber-reinforced polymer (GFRP) composites as discrete reinforcements offers a cost-effective solution in the production of ultra-high-performance fiber reinforced concrete (UHPFRC) and a value-added routine for recycling waste GFRP. Despite its benefits in improving the tensile properties of UHPFRC, the incorporation of recycled macro fibers leads to a decrease in the compressive strength of the UHPFRC mainly due to the weak interfacial transition zone (ITZ) between recycled macro fibers and UHPFRC matrix. In the present study, the effects of coating recycled macro fibers (RMF) with graphene oxide (GO) were examined on the properties of UHPFRC. The macro fibers were first characterized using the morphological characterization and Fourier transform infrared (FTIR) spectrometer. The effects of fiber coated by GO on UHPFRC were evaluated by investigating the fluidity, permeability, mechanical properties as well as autogenous shrinkage of UHPFRC. The results indicated that the GO coating had a negligible effect on the fluidity and autogenous shrinkage of UHPFRC while increasing the 28-day cubic compressive strength and flexural strength by up to 6.6 % and 32.4 %, respectively. These findings have demonstrated the feasibility of coating RMF with GO to improve the mechanical properties of UHPFRC.