Performance evaluation of cold in-place recycling asphalt mixtures prepared using different recycling agents, curing processes, and compaction levels

The main objective of this study was to determine the impact of recycling agent, compaction level, and curing process on the rutting and cracking performance of cold in-place recycled (CIR) mixtures prepared using a balanced mix design approach. Eight CIR mixtures were prepared using two binding agents (CSS-lh emulsion and PG 64-22 foamed asphalt), two levels of compaction (30 and 70 gyrations), and two curing temperatures (50 and 140°F). These mixtures were designed at constant dosages of cement (1%) and water (3%). Laboratory performance tests were then conducted on balanced CIR mixtures to evaluate the impact of the recycling agent, compaction level, and curing temperature on CIR rutting performance measures using the Asphalt Pavement Analyzer (APA) and dynamic complex modulus (|E∗|) and cracking performance measures using the indirect tensile strength (ITS) and semi-circular bend (SCB) tests. Statistical analysis was also performed on CIR performance measures using ANOVA to evaluate the impact of recycling agent, gyration level, and curing temperature on APA rut depth, dynamic modulus, ITS, and SCB-FE. The performance of these mixtures was then evaluated in terms of rutting susceptibility and cracking resistance. Results showed that the higher compaction level or/and higher curing temperature led to increasing the ability of both emulsion and foamed asphalt CIR mixtures to resist rutting. With regard to cracking, SCB-FE results showed that emulsified asphalt CIR mixtures were better at resisting cracking than foamed asphalt CIR mixtures.