161 / 2022-04-30 08:09:33

Application of Elaborately Recycled Fiber and Powder from Waste Glass Fiber Reinforced Plastics in Cement-Based Materials

Recycled GFRP,Fiber Reinforced Concrete,Mechanical Properties,Microstructure

Glass fiber reinforced polymer (GFRP) is a type of composite material made of resin matrix, glass fiber, and auxiliary materials. The wide application of GFRP in wind turbine blades, storage tanks, ship hull and other products leads to enormous production. Exceeding 10 million tons of GFRP is produced globally, with which 5~40% of wastes are generated, due to the high proportion of offcuts (3~5%) and frequent retirement (15-20 years’ service life). To alleviate the pressure to environment, waste GFRP is increasingly disposed with mechanical recycling technique and reused as fillers in concrete. However, due to diverse sources, nonuniform sizes and complex properties, the recycled GFRP presented disparate, even detrimental influences on the physical and mechanical performance of concrete, limiting the further reuse and application.



To solve this problem, the mechanically crushed GFRP from three sources were elaborately separated through sieving and water-air selection to select fibers with different sizes and powder to investigate their physicochemical properties of recycled GFRP fibers and GFRP powder were carefully studied. The influence of contents, GFRP sources and physicochemical properties of fibers on the mechanical properties, shrinkage, micromorphology and porosity of mortars were investigated. Results indicated that the fine selected GFRP fibers apparently enhanced the mechanical properties and reduced the shrinkage of mortars, with the highest value of 47.3 MPa and 9.83 MPa, respectively. These mechanical improvements of mortars were mainly attributed to (i) the increased fiber uniformity that ameliorated the porosity of mortar; (ii) the rough and hydrophilic surface of recycled GFRP fibers, which increased fiber-cement bonding strength; and (iii) the resin coating that protected recycled GFRP fibers from alkali corrosion (Fig. 1).



On the other hand, recycled GFRP powder introduced dramatical expansion of concrete at the fresh state, leading to the significant decrease of mechanical properties. The expansion mechanism and the effectiveness of five types of modification treatments were comprehensively investigated by testing the physical and mechanical properties, microstructure and hydration kinetics of recycled GFRP powder (rGP) filled mortar. The gas of H₂, NH₃ and CH₄ produced by the reaction between rGP and alkaline pore solution was the main cause for the expansion. This expansion can be significantly reduced by adding silica fume and fully eliminated by presoaking rGP in NaOH. Using this method, the compressive and flexural strength of rGP filled mortar were increased by 67%~100% and 25%~60%, respectively (Fig. 2).



The findings in this study would provide solid experimental foundation for further modification and application of recycled GFRP in cement-based materials.