Recycling waste fiber-reinforced polymer composites for low-carbon asphalt concrete: The effects of recycled glass fibers on the durability of bituminous composites

Waste Fiber-Reinforced Polymer (FRP) composites have become an environmental issue in China, Europe, and the United States. However, recycling waste FRP composites poses sustainability challenges in the long term because their predominantly cross-linked structure (thermoset matrices coating) typically cannot be re-used or re-processed. Here, for the first time, we studied the merits of introducing recycled glass fibers (rGF) to bitumen to enhance bitumen's durability as measured by resistance to aging and resistance to moisture damage. We compared the reinforcement efficacy of recycled glass fibers (rGF) with recycled glass fibers after the polymer coating was removed (rGFWP) and with virgin glass fibers (vGF). After aging, compared to the bitumen with rGFWP, the bitumen containing rGF showed enhanced resistance to oxidative aging, as evidenced by lower values of two indexes of chemical aging (a 64.5% lower carbonyl index and a 94.5% lower sulfoxide index), a 47.10% lower increase in the ratio of large molecular size, and a 61.41% lower rheological aging index. Moreover, bitumen containing recycled glass fiber demonstrated noticeably improved resistance to moisture damage as compared to base bitumen, particularly for rGFWP, as demonstrated by energy ratio (ER) values that were 478% higher. The resistance to moisture damage of bitumen containing rGF was also significant improved, as evidenced by a 72.78% increase in surface energy, the better MISTI value (the least variation from a value of one), and a 213% higher ER value compared to base bitumen. This indicates that recycled glass fibers have positive effects on the durability of bitumen composites. The outstanding durability of bitumen with recycled glass fibers highlights the feasibility of adding recycled glass fibers to bitumen as a practical application that provides an economic and environmentally friendly solution for waste glass fibers.