The use of various fibers in asphalt mixes has been developed and applied to enhance pavement performance. The conventional asphalt mixture can be improved by including steel fibre as an additive in the asphalt mixture. However, the use of steel fibre in SMA mixtures was not widely studied. Consequently, the objective of this study was to evaluate the effect of steel fibre on the volumetric properties and characterize the performance of steel fibre in SMA mixture. Different steel fiber proportions of 0%, 0.3%, 0.5%, and 0.7% by the total weight of the mixture were used in this study. The test conducted includes the Marshall stability and Flow test, and the Resilient Modulus Test. Response Surface Methodology (RSM) from Design Expert Software was then performed to determine the most optimum properties from the experimental data. The test results revealed that adding steel fiber greatly improved the SMA mixture’s resistance to deformation while also increasing its stability, reducing the abrasion loss, and increasing the stiffness of the SMA mixture. Optimized performance was observed at 0.3% steel fiber content and 1598 MPa of resilient modulus. The relative error results show acceptable agreement between the prediction and the experiment which is considered tolerable and acceptable. This demonstrates that the software optimization of the specific SMA with steel fiber characteristics by the RSM technique has the desired precision for laboratory tests.

Recycling waste materials, such as partial replacement of WCA for natural aggregates in hot-mix asphalt, could be an option for addressing problems such as environmental pollution and the increasing demand for natural resources. Due to continual development and renovation in the construction industry, the generation of concrete waste has become one of the major challenges. Consequently, the purpose of this study was to develop an asphalt mix design utilizing waste concrete aggregate (WCA) as a partial substitute for natural aggregates (NA). The ratios of WCA10:NA90 and WCA30:NA70 are utilised to design the asphalt mixtures. In this study, asphalt mixtures containing 10 and 30 percent WCA are referred as WCA10 and WCA30, respectively. The density-voids analysis enables the determination of the optimum asphalt content that satisfies the criteria of the Malaysian Public Works Department (PWD). Results indicates that the criteria and design parameters of both mix conforms to the PWD specifications. The optimum asphalt content determined for both WCA10 and WCA30 asphalt mix is 5.7 and 5.8 percent respectively. The moisture sensitivity test is then performed on both WCA10 and WCA30 asphalt mixtures to determine how susceptible these mixtures are to moisture-induced damage. The tensile strength ratio (TSR) for WCA10 and WCA30 asphalt mixtures is 83.6 and 97.4 percent, respectively, which is greater than the minimal requirement of 80%. This investigation revealed that the use of WCA in hot-mix asphalt satisfies the moisture susceptibility requirements.