Mechanistic approach for polypropylene-modified flexible pavements

The present study investigates the benefits of modifying the asphalt and stone matrix asphalt (SMA) mixture in flexible pavement. Fifty/sixty penetration grade asphalt cement and four proportion of pyrolisis polypropylene (PP) were selected. Unmodified and modified asphalt binders were subjected to rheological and homogeneity tests. The performance tests including, Marshall stability, tensile strength and compressive strength were conducted on unmodified and modified SMA mixtures. The regression relationships between the performance tests were obtained. A mechanistic-empirical design approach was used for estimating the improvement in service life of the pavement or reduction in thickness of SMA and base layer for the same service life due to modification the SMA mixtures. The analyses of test results show that the performance of PP-modified asphalt mixtures are better when compared to conventional mixtures. The temperature susceptibility can be reduced by the inclusion of PP in the asphalt mixture. A PP content of 5% by weight of asphalt is recommended for the improvement of the performance of asphalt concrete mixtures similar to that investigated in this study. The results of multi-layer elastic analysis presented herein indicate that the pavement consisting of PP-modified SMA as a surface layer is beneficial in reducing the construction materials. Actual savings would depend upon the option exercised by the designer for reducing the thickness of an individual layer.