Impact of Wheat Fiber on Warm Mix Asphalt and Stone Matrix Asphalt Mechanical Properties and Moisture Damage

This study conducted a comparative laboratory analysis to assess the influence of natural wheat fibers (WFs) as reinforcements on the mechanical characteristics and moisture resistance of warm mix asphalt (WMA), an environmentally sustainable paving technology, and stone matrix asphalt (SMA), a surface layer noted for its durability under traffic loads and superior skid resistance. The WF fibers were included into the dry mix at concentrations of 0.1%, 0.3%, and 0.5% by weight of a 1200‐g asphalt mixture. The research aimed to evaluate the cracking resistance and moisture damage vulnerability of WF‐reinforced WMA and SMA mixtures by employing the indirect tensile strength (ITS) test, tensile strength ratio (TSR) analysis across different freeze–thaw cycles, and the semicircular bending (SCB) test at low and moderate temperatures. The findings indicated that mixtures with 0.3% WF exhibited optimal performance regarding moisture sensitivity for both WMA and SMA mixtures. Moreover, the TSR values for the WF‐reinforced samples markedly exceeded those of the control samples. The enhancement in moisture damage resistance was ascribed to the strengthened link between the asphalt binder and aggregates, alongside the formation of a fiber network inside the asphalt mixture, which resulted in augmented tensile strength and diminished moisture sensitivity. Moreover, the mixtures with 0.3% WF demonstrated superior performance against cracking and failure compared to other reinforced samples. Specifically, in WMA mixtures, an increase of 40% and 42% in fracture energy was observed at −18 and 25°C, respectively, contrasted to the control mixture. Similarly, for SMA mixtures, the corresponding increases in fracture energy were 35% and 29% at the same temperatures. The findings emphasize the superior tensile properties of WF fibers and their capability to establish a bridging effect between aggregates and the asphalt binder. Accordingly, it can be inferred that incorporating WF fibers into WMA and SMA mixtures substantially enhances both their mechanical properties and resistance to moisture damage. Nonetheless, the enhancement in performance of WMA mixtures was found to be more pronounced than that of SMA mixtures.