Working and mechanical properties of waste glass fiber reinforced self-compacting recycled concrete

Glass fiber reinforced plastics (GFRP) have been widely used in the field of civil engineering infrastructure, while it also generating a large amount of waste glass fibers simultaneously. This paper uses waste glass fiber in self compacting recycled concrete (SCRC), forming a kind of waste glass fiber reinforced self-compacting recycled concrete (RGF-SCRC). The effects of recycled coarse aggregate (RCA) replacement ratio, water to binder (W/B) ratio, the content and type of glass fiber on the working and mechanical properties of RGF-SCRC were investigated. The results showed that the specimens could meet the requirements of self-compacting concrete (SCC) in terms of working performance, but the addition of RCA and glass fiber could reduce the workability of RGFSCRC, when RCA is replaced with 100 % and the fiber content reaches 10 kg/m3, the slump expansion is reduced by 9.5 % and 12.4 %, respectively. The mechanical properties of RGF-SCRC decreased as the growing value of RCA replacement ratio and the W/B ratio, among them, the elastic modulus decreased the most, by 40.4 % and 30.0 %, respectively. Compared with the results of the control specimen, the properties could be improved significantly under an appropriate content of waste glass fiber: the cube compressive strength, splitting tensile strength, flexural strength, and elastic modulus of RGF-SCRC were increased by 1.3-9.6 %, 13.5-59.4 %, 17.8-40.9 %, and 3.3-13.4 %, respectively. However, excessive fiber content showed a negative effect on the mechanical properties. Specimens with the 7.5 kg/m3 alkali resistant glass fiber content showed the best mechanical properties. Moreover, the X-ray CT and scanning electron microscope (SEM) techniques were applied to explore the influencing mechanism of waste glass fibers on RGF-SCRC. The results showed that after adding an appropriate content of waste glass fiber, the porosity and the number of large pores decreased, and the pore size and distribution became more reasonable, which enhanced the compactness of RGF-SCRC to some extent. The mechanical force and friction force anchored at the fiber end at the interface with the concrete matrix increase the bonding strength, thereby enhancing the mechanical properties of RGF-SCRC. This study achieve the resource utilization of waste glass fiber and improve the mechanical properties of concrete and the research results can provide a reference for the practical application of RGF-SCRC in civil engineering.