Comparative performance of SBR and recycled GFRP in modified asphalt binders and mixtures

End-of-life glass-fiber-reinforced polymer (GFRP) components require practical recycling routes, while recycled GFRP (RGFRP) can reduce the low-temperature flexibility of asphalt. This study evaluated whether styrene-butadiene rubber (SBR) could offset this limitation in a pre-blended binder route. Twelve binder formulations were screened by storage stability and conventional property tests. The 1.5/2 formulation (1.5 wt% SBR solids and 2 wt% RGFRP) was selected using a minimum-modifier rule that balanced ductility, softening point, and penetration. SEM and AFM observations, exploratory BBR and MSCR tests on as-prepared binders, un-notched SCB tests, and wheel-tracking tests were then used for comparative evaluation. Relative to the 0/2 mixture, the 1.5/2 mixture had a 22.5% higher mean fracture energy at 0 °C (3,437 versus 2,805 J/m 2 ) and a 1.4% lower mean dynamic stability at 60 °C (3,341 versus 3,387 cycles/mm). These descriptive comparisons indicate an improved low-temperature response without a clear change in rutting resistance. The microscopy results are consistent with interfacial association between SBR and RGFRP but do not establish a chemical interaction. Because standardized binder aging was not applied, residual water was not quantified, and the laboratory pre-blending route differs from common dry-mixing practice, the findings are restricted to the tested preparation conditions and within-study comparisons.