PERFORMANCE EVALUATION OF COLD IN-PLACE RECYCLING (CIR) MIXES FOR ONTARIO

Cold In-Place Recycling (CIR) is a conventional rehabilitation technique which uses 100% Recycled Asphalt Pavement (RAP). In common practices in Ontario for CIR, emulsified asphalt cement (AC) is added to the milled recycled pavement before placing it back onto the roadway. The pavement is also allowed to cure for 14 days before letting traffic back on. It is important to determine the strength of such a pavement technique in order determine how long the pavement will perform before any deteriorations occur. Varying percentages of added asphalt emulsion also affect the strength and workability of the mixtures. Furthermore, the curing time is also important to the whole process. The 14-day curing time might not be ideal for this technology but further laboratory investigation is encouraged. In this study, five different percentages of AC were used varying from 1.2% to 3.2% of the mass of the recycled aggregate. The workability and strength of each of these percentages were determined using dynamic modulus material testing. Along with varying percentages of AC, there was a duration test carried out using 1.2%AC in order to determine the optimal curing time for the mixture, before and after compaction, for laboratory test purposes. Using AC extraction, it was observed that the Southern Ontario RAP contained 4.77% of existing AC. Adding an additional 3.2%AC to this RAP, gave a mixture that performed best in terms of strength gain and rutting resistance. The duration tests determined that a time of 0 to 2 days before compaction and 7 to 14 days after compaction allowed for the best strength gain for the mixes, at different frequencies. Having a set %AC in accordance to the type and location of the obtained RAP causes a big change in the strength gain of the final mix. The curing time of the mix before and after compaction also controls the strength gain. Curing it properly allows it to resist fatigue cracking under higher frequency of loading and rutting at lower frequencies.