Multi-scale Evaluation of Moisture Susceptibility of HMA Containing UHMWPE Based on Adhesion, Bond Strength, and Morphology

Moisture damage is a prevalent failure in asphalt pavements, which is directly linked to stripping and bitumen-aggregate adhesion. Also, it can lead to other main damages. This research aims to evaluate the adhesion and moisture susceptibility of asphalt mixes containing a new polymer additive namely ultra-high-molecular-weight polyethylene (UHMWPE) with 2 and 4% bituminous weight was performed. Moreover, the tensile strength ratio (TSR), boiling water test by the image processing of coating ratio ((CR) index), and surface free energy (SFE) were conducted and compared. The results indicated that adding 4% UHMWPE to the base bitumen (B-B) increased the 27% TSR index and 31% CR index compared to the base mixtures (without additive). The best performance in the mixture of limestone (LS) and bitumen was associated with 4% UHMWPE (LS-B-UHMWPE4), in which both TSR and CR indices had the highest values. The results of SFE components indicated that the free cohesion energy in modified bitumens has increased substantially by 65% compared to B-B. Additionally, the free adhesion energy in modified bitumens with limestone and granite has demonstrated higher values. The highest increase in TSR, CR, and SFE indices was observed in the modified mixture with LS-B-UHMWPE 4.