Performance of Asphalt Mastics and Mixtures Incorporating Recycled Fibers from Wind Turbine Blades

To facilitate the high-value recycling of composite materials from decommissioned wind turbine blades, three recycled fiber products, RFA, RFB, and RFC, were investigated. Their macro- and micromorphological characteristics were examined, and their effects on asphalt mastic and asphalt mixtures were evaluated. A three-factor Box–Behnken design (BBD) considered mastic fiber content, mixing speed, and mixing time. The reported RFC candidate setting was 3.45% fiber by total mastic mass, 600 r/min, and 40 min; the BBD preparation temperature was not documented. Mixtures were evaluated separately at 0.3% fiber by total mixture mass and formulation-specific Marshall optimum asphalt–aggregate ratios. RFC had a dynamic stability of 2266 cycles/mm, 53.2% above the fiber-free reference, a flexural tensile strain at failure of 2651 με, and a freeze–thaw tensile strength ratio (TSR) of 91.46%. BF had the highest reported dynamic stability and residual Marshall stability; RFC had the highest reported flexural strain and TSR. At the stated prices, RFC added CNY 1.71/t in fiber-material expenditure. Incomplete preparation and specimen-level records limit reproducibility and uncertainty assessment. These laboratory observations concern complete formulations and do not establish statistical superiority, long-term durability, environmental safety, or lower total production costs.