Investigating the Laboratory Performance of Crumb-Rubber-Modified and High-Float Polymer-Modified Asphalt Emulsions in Chip Sealing

Chip sealing is a widely popular pavement maintenance treatment because of its low initial cost and convenient construction process. Bleeding, loss of aggregate, reduced skid resistance, and aging have been identified as the most common type of distress that lead to the failure of chip sealing. The objective of this study was to evaluate the laboratory performance of a crumb-rubber-modified asphalt emulsion and a high-float polymer-modified asphalt emulsion in chip sealing and to evaluate the effects of crumb rubber as a modifier as well as its utilization as part of the aggregate stone. To achieve this objective, four types of emulsion were evaluated, namely a crumb-rubber-modified asphalt emulsion (CRS-2TR), a high-float polymer-modified emulsion (CHFRS-2P), a polymer-modified emulsion (CRS-2P), and a conventional unmodified emulsion (CRS-2). Based on the results of the experimental program, it was concluded that the aggregate retention properties of polymer-modified and crumb-rubber emulsions were superior to the unmodified emulsion. In addition, the granite aggregate performed better than the granite–crumb-rubber blends regardless of the type of emulsion used. However, a small percentage of crumb rubber may be used in chip sealing without significantly affecting its performance. According to the rheological and physical test results, CHFRS-2P showed the highest useful temperature interval (92.7), followed by CRS-2P (87.8), CRS-2TR (82.6), and CRS-2 (76.7). Based on Fourier transform infrared spectroscopy and saturate, aromatic, resin, and asphaltene test results, both CRS-2TR and CHFRS-2P showed lower carbonyl indices growth as compared to the other emulsions, indicating superior resistance to aging.