Toughening mechanisms in polypropylene fiber-reinforced asphalt mastic at low temperature

Abstract

Low temperature cracking is a prevalent mechanism of failure in hot mix asphalt (HMA) pavements. Prolonged cold temperatures can lead to premature cracking and subsequent failure of pavements. It has been previously shown that fibers as additives can improve the mechanical properties of asphalt mastic (asphalt binder and filler material passing the 75 μm sieve). However, the success of any effort to evaluate the low-temperature behavior of the fiber-reinforced asphalt mastic is based on the understanding of the fracture and toughening mechanisms. The objective of this study was to develop an asphalt mastic with enhanced resistance against cracking with the use of small amounts of fiber. Here, the effects of fiber length and content in the asphalt mastic were studied to create an asphalt mastic with enhanced fracture toughness. The Single Edge Notched Three-point Bending (SENB) test was performed at low temperatures to measure the strength and fracture toughness for polypropylene fiber-reinforced asphalt mastic. The major conclusions were that both fiber length and content improved the fracture properties of mastics significantly, and crack bridging and fiber pull-out were the two main toughening mechanisms in these materials.