Moisture Susceptibility of Asphalt Mixtures Modified by Recycled Polypropylene

Moisture damage is the most commonly occurring problem, causing layers of asphalt pavements to break apart, reducing the serviceability of roads. The utilization of recycled polymer in asphalt mixtures has become popular because it may offer environmental benefits. The present study aims to investigate how the use of recycled polypropylene (RPP) can reduce the moisture susceptibility of hot mix asphalt (HMA). Asphalt binders were modified with three different concentrations of recycled polypropylene: 1%, 3%, and 5% by weight of the bitumen. The Marshall mix design method was utilized to establish the optimal asphalt content for the specific aggregate gradation both the control and modified mixtures were tested for moisture damage. Tensile and compressive strength tests were conducted to assess the moisture damage in asphalt mixtures. In the results, an optimal amount of RPP was found in asphalt mixtures, which improved Marshall properties. The same goes for their resistance to any moisture damage, which was also able to be considerably improved with this addition. The maximum tensile strength ratio (TSR) was 86.45% at 3% RPP, and the index of retained strength (IRS) of up to 81.99% by addition of 5% RPP, while the control mixture exhibited 80.25% for TSR and 75.82% for IRS. These results have shown the viability of applications with RPP in asphalt mixtures towards improved pavement performance and sustainability.