Utilization of micronized recycled polyethylene waste to improve the hydrophobicity of asphalt surfaces

Abstract Super-Hydrophobic (SH) surfaces possessed low free energy and are highly resistant to wetting. These properties of SH surfaces made them suitable for engineering applications like waterproofing, anti-corrosion coatings, anti-icing finish etc. Asphalt binder that is widely adopted as civil engineering material for waterproofing application is only hydrophobic, not SH. In this study, recycled Low Density and High Density Poly-Ethylene (rLDPE & rHDPE) were employed to transform asphalt surface from hydrophobic to SH. Micronized rLDPE and rHDPE powders were obtained by grinding and sieving. The morphologies, thermal characteristics, and particles distributions of the various powders were analyzed using Scanning Electron Microscope (SEM), Differential Scanning Calorimetry (DSC); Thermogravimetric Analysis (TGA), and laser diffraction method respectively. The asphalt surfaces were modified by thermally fusing the micronized rLDPE and rHDPE at 100 °C for 15, 30, and 45 min curing durations. Roughness and Water Contact Angle (WCA) of the rLDPE and rHDPE treated asphalt surfaces were analyzed using 3D optical profilometer and sessile drop video contact angle system, respectively. The bonding at asphalt-rLDPE/rHDPE interfaces, and surface morphologies of the rLDPE and rHDPE asphalt surfaces were studied using SEM. Surface roughness decreases with increase in curing duration due to settling and thermal shrinkage of rLDPE/rHDPE particles. The WCA of the asphalt was increased by at least 35% for just 15 min curing duration. However, longer curing duration was found to yield a more resilient treated surface. The increase in WCA transformed the asphalt surfaces from hydrophobic to SH. Due to the elongated and fuzzy morphology of the rLDPE powder, in addition to its higher thermal sensitivity, it was able to form a better surface texture that facilitate higher WCA than the rHDPE. Statistical analysis of variance was conducted to assess the extent at which the micronized powder types and curing duration affect the surface roughness and WCA.