Evaluation of Cold Weather Performance of Rubber Modified Asphalt Placed in Ontario
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Canada has close to 900,000 km of roads, which are key to supporting the Canadian economy as they enable for efficient transportation of goods and services. The Canadian road network should be well maintained and perform to a high standard to ensure the function and growth of the economy and the Country. It is also important to consider sustainability, and more specifically, recycling, when designing the roads. In order to improve on the performance while being sustainable, research is being conducted on the feasibility of using recycled materials in asphalt pavements. One of these materials is crumb rubber, obtained from recycled rubber tires, used as an additive to conventional Hot Mix Asphalt (HMA) to produce Rubber Modified Asphalt (RMA). These tires would otherwise end up in landfills, which is undesirable when considering sustainability. The Ontario Tire Stewardship (OTS), along with the Centre for Pavement and Transportation Technology (CPATT), the Ontario Ministry of Transportation (MTO), and the Ontario Hot Mix Producers Association (OHMPA) have combined their efforts in order to carry out a pilot study on paving roads in Ontario with crumb tire rubber. Three highways, Highway 7, Highway 35, and Highway 115, have been paved using RMA, along with a section paved with conventional HMA to conduct a comparative study on the performance of the RMA sections. During the paving, samples were collected from the pavers in order to conduct laboratory testing on the materials to determine their performance. The material was used to test the performance using the Thermal Stress Restrained Specimen Test, which introduces a stress in the sample material by cooling it to the point of failure while restraining the specimen, preventing it from relaxing. The specimen is cooled until failure, and the temperature at failure, along with the stress in the specimen is recorded for comparison. This test was conducted to determine the ability of the mixes to withstand the low temperatures that pavements in Ontario would have to endure. A structural evaluation was also carried out on the pavement mixes using the AASHTOWare software (formerly the Mechanistic Empirical Pavement Design Guide, MEPDG). Although there are limitations to the software, it was still important to determine the structural capacity of the mix within a pavement structure to withstand the stresses of traffic and climate. The results of the AASHTOWare software determines the performance of the rubber mixes, as compared to the conventional mixes, to ensure that utilizing the rubber mixes does not hinder the performance of the pavement.