Evaluation of the impacts of basalt fibers and hydrothermal liquefaction bio-oil on the fracture properties of asphalt mixtures at intermediate and low temperatures
Mohammad Hossein Hassanjani, Mahyar Arabani, Fereidoon Moghadas Nejad, Mohammad Mahdi Shalchian
Abstract
Cracking remains one of the most critical distresses in asphalt pavements, with aging-induced embrittlement accelerating crack initiation and propagation under repeated loading. Although bio-oils offer rejuvenation potential and fibers provide mechanical strengthening, previous studies have not combined these mechanisms within reclaimed asphalt binder systems under thermo-mechanical fracture conditions. This gap limits the development of more sustainable and durable pavement technologies. This study presents an integrated approach that couples the viscoelastic restoration offered by hydrothermally derived bio-oil with the reinforcement provided by basalt fibers to enhance crack resistance at intermediate and low temperatures. Asphalt mixtures incorporating reclaimed binder were prepared with increasing bio-oil contents and varying fiber dosages and then conditioned through standardized short- and long-term aging procedures. Fracture behavior was assessed using the semi-circular bending method under both opening-mode and shear-dominated loading across temperature and notch configurations representing a wide range of fracture severities. Mixtures containing a balanced level of bio-oil and a dense fiber network demonstrated the most stable and effective fracture response. Performance gains stem from two complementary mechanisms: viscoelastic rejuvenation of the aged binder, where bio-oil improves molecular mobility and energy-dissipation capacity, and structural strengthening by fibers, which form a continuous bridging network that redistributes stresses and delays crack initiation. Mixtures with the highest bio-oil dosage combined with the greatest fiber content also exhibited enhanced deformation capacity at low temperatures due to intensified molecular relaxation and crack-tip blunting promoted by the fiber phase. Overall, the combined use of hydrothermal bio-oil and basalt fibers substantially enhances crack resistance, suppresses micro-crack coalescence, and provides a practical, sustainable strategy for improving the performance of high-reclaimed asphalt mixtures while reducing reliance on virgin binder and maintaining favorable environmental and economic outcomes.