Evaluating the impact of polymer and fiber modifiers on mechanical performance of asphalt mixtures across a wide temperature range

In this research, the effects of using different fiber modifiers and bitumen additives on the mechanical and performance properties of asphalt mixtures across a wide temperature range, including high-, moderate-, and low-temperature conditions (specifically - 6 °C and - 12 °C for low-temperature testing), were investigated. The main objective of this study was to improve the durability and extend the service life of asphalt mixtures using combinations of polymeric modifiers and fibers, with particular emphasis on clarifying the influence of fiber tensile strength and length on overall performance. Seven types of asphalt mixtures were prepared, including mixtures modified with Styrene-Butadiene-Styrene (SBS) and RW Elast polymers, as well as fibers such as Forta and Parafiber, and combinations of 6AR and 12AR fibers with Low-Density Polyethylene (LDPE). Various mechanical tests, including resilient modulus (RM), four-point bending fatigue (FPBF), three-point bending fracture (TPB), and the wheel tracking test (WTT) tests were conducted under controlled laboratory conditions. The results showed that the 6AR+LDPE mixture achieved the highest resilient modulus (≈ 7100 MPa), followed by 12AR+LDPE (≈ 6100 MPa), compared to the control mixture (≈ 4200 MPa). Forta fibers provided the highest fatigue life (> 140,000 cycles), significantly exceeding the control mixture (~ 80,000 cycles). In the rutting test, mixtures containing Forta and Parafiber exhibited the lowest rut depth, indicating improved resistance to permanent deformation.