Asphalt concrete modification to improve flexible pavement performance in cold regions

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Canada's road network is the seventh largest in the world, with a total length of 1.13 million km. The network is composed of 40% paved roadways and 60% unpaved roadways. More than 90% of the paved roads in Canada's network are composed of asphalt pavement. In cold regions such as Canada, pavement structures are subject to extremely low air temperatures and seasonal freeze-thaw cycles over the life cycle of the roadway, resulting in pavement distress, deterioration, and decreased service life. One promising possibility for increasing the performance of asphalt pavements at the high and low temperature ranges is modification of the asphalt to alter the physical properties of the asphalt mix. It is particularly important in the Canadian context to increase the resistance of asphalt mixes to thermal cracking. Low temperature cracking is the most prevalent distress in asphalt pavements in cold climates, resulting in substantial recurring expenditures for the rehabilitation of asphalt pavements. Recently, innovative materials such as nanoparticles have attracted increasing attention in the asphalt industry for use as asphalt concrete modifiers. Fibers have also been used to modify asphalt pavements for many years; however, there has been less attention to the incorporation of fibers in asphalt mixes to improve resistance to thermal cracking. The proposed research involves conducting laboratory investigations to understand the effects of the addition of nanomaterials and fibers on the properties of asphalt mixes at various temperatures and under freeze-thaw conditions. Laboratory testing will be done on unmodified and modified asphalt cement to investigate the impact of incorporation of nanomaterial on the rheological properties of the resulting asphalt cement. In addition, a series of prepared asphalt mix samples - modified with nanomaterials, modified with fibers, and unmodified - will be used to determine the physical and mechanical properties of the various asphalt mixes at different conditions and under freeze-thaw cycles. This comprehensive test data will be used to develop a model to predict creep compliance of modified asphalt mixes, which is a critical input for predicting the low temperature performance of asphalt pavements in mechanistic-empirical pavement design. This model, when validated, will allow the low temperature properties of asphalt mixes containing similar additives to be predicted, making it a useful tool for transportation authorities when designing pavements using modified asphalt mixes. The research will form the foundation for the establishment of a long--term research program in novel materials for road construction. It will also provide immediate economic and social benefits to Canada by improving the design, durability, and longevity of the asphalt materials used in roadway construction in cold climates.