Effect of Steel Wool Fibre Addition on Self-Healing Capability and Marshall Characteristics of Rehabilitated Asphalt Concrete Wearing Course (AC–WC)

This study investigates the effect of steel wool fibre addition on the self-healing capability and Marshall performance of Asphalt Concrete Wearing Course (AC–WC). The concept of induction-activated self-healing is introduced to prolong pavement service life by restoring mechanical integrity after microcracking. Four fibre dosages (0%, 1%, 1.5%, and 2%) were evaluated through Marshall testing and controlled induction-healing cycles. The Marshall results revealed a decreasing stability trend with increasing fibre content, from 1870 kg at 0 % to 1717 kg, 1367 kg, and 1038 kg at 1%, 1.5%, and 2%, respectively. Flow increased to 4.3 mm at 1.5% before slightly decreasing at 2%, while VIM rose significantly from 3.82% to 13.85% with increasing fibre dosage. The Marshall Quotient declined from 558 kg/mm at 0% to 276 kg/mm at 2%, indicating reduced stiffness at high fibre contents. Healing performance, assessed via three-point bending before and after induction, showed the highest recovery at 1–1.5% fibre content, confirming the role of conductive fibres in enabling localized binder regeneration. These findings demonstrate that a 1% fibre dosage offers a practical balance between structural stability and healing capability. The results support the potential use of conductive-fibre-modified asphalt as a cost-effective smart pavement strategy in tropical regions while highlighting the need for further field validation and standardization before large-scale implementation.