Effect of Asphalt Pavement Compaction on Interlayer Bonding and Tensile Strength of Asphalt Concrete under Low Temperatures and Temperature Cycling

The maintenance and rehabilitation of highway network systems are major road agency expenditures. The combined effects of environmental conditions, traffic loading, moisture, construction quality, and maintenance contribute significantly to rates of pavement deterioration and the length of asphalt pavement life. One of the important performance parameters for asphalt concrete pavements, particularly in cold regions, is the capability to withstand cyclic temperature changes. Such temperature cycles, especially those that alternate above and below freezing, lead to mechanical stresses that can cause failure. This research presents the results and major findings of an experimental investigation performed on rectangular asphalt slab samples extracted from newly constructed pavements of actual highway projects, rather than gyratory-compacted samples that are created in the laboratory. The first phase (Test Series A) studied the effects of temperature cycles and compaction equipment on interlayer bonds by using a custom-made temperature cycling testing machine that allows the reproduction of several temperature cycles over a relatively short time (7-10 days). The second phase (Test Series B) focused on resistance to tensile stresses under cold temperatures. During Test Series B, a custom-made direct tensile strength test was employed to estimate the tensile strength of slab samples at different temperatures (i.e., 0°C, -10°C, or -20°C) for single- and double-layer samples. Test Series B included 171 asphalt samples 300mm long by 100mm wide, with thicknesses of 50mm for single layers and 100mm for double layers. The results of Test Series A showed that samples compacted with an Asphalt Multi-Integrated Roller (AMIR) had superior interlayer bonding in comparison with the samples compacted with a Conventional Compacting Method (CCM). Those latter samples were shown to experience debonding during cyclic temperature changes, which would cause the different layers to act independently and have lower resistance to thermal stresses. The results of Test Series B showed that construction-induced cracking affects the tensile strength of asphalt pavements. This research and its related laboratory tests explain how different types of equipment used for compacting asphalt can affect the tensile strength and interlayer bonding of asphalt pavement.