Impact of Polypropylene Application Method on Long-Term Aging of Polypropylene-Modified HMA

The effect of polypropylene application method on long-term aging of hot mix asphalt (HMA) was investigated. Three different application methods were considered within this paper, namely, the coating method (where aggregate surface was coated with polypropylene), the dry method, and the wet method. Constant polypropylene content of 0.7% by weight of total mix was adapted. Laboratory aging program was set up to simulate the aging process of asphalt pavement occurred in the field. The mechanical properties of aged and unaged mixtures prepared using the three different polypropylene application methods were evaluated based on Marshall quotient, the indirect tensile strength, fracture energy, and unconfined compressive strength. Experimental testing has revealed the enhancement in the mechanical properties of HMA when polypropylene was added. The polypropylene additive has managed to counteract the effect caused by long-term aging of HMA. A comparison between the three polypropylene application methods indicated that the coating method has caused a considerable improvement in the indirect tensile strength and fracture energy of HMA under aged and unaged conditions. Marshall quotient and compressive strength of tested mixtures have shown less dependency on the polypropylene application method.