Asphalt concrete modification to improve flexible pavement performance in cold regions

加拿大的公路网位居世界第七，总长度达113万公里。路网由40%的铺面道路和60%的未铺面道路组成。在加拿大的道路网中，90%以上的铺装道路是由沥青路面组成的。在加拿大等寒冷地区，路面结构在道路的整个生命周期中会受到极低的气温和季节性冻融循环的影响，从而导致路面损坏、劣化和使用寿命缩短。提高沥青路面在高温和低温范围内的性能的一种有希望的可能性是对沥青进行改性以改变沥青混合物的物理性质。在加拿大，提高沥青混合料的抗热裂性尤为重要。低温开裂是寒冷气候下沥青路面最常见的病害，导致沥青路面修复的大量经常性支出。 最近，创新材料如纳米颗粒在沥青工业中用作沥青混凝土改性剂引起了越来越多的关注。多年来，纤维也被用于改性沥青路面;然而，很少有人关注在沥青混合料中掺入纤维以提高耐热开裂性。拟议的研究涉及进行实验室调查，以了解在不同温度和冻融条件下添加纳米材料和纤维对沥青混合料性能的影响。将对未改性和改性沥青水泥进行实验室测试，以研究掺入纳米材料对所得沥青水泥的流变性能的影响。此外，一系列制备的沥青混合料样品-用纳米材料改性，用纤维改性，和未改性-将用于确定在不同条件下和冻融循环下的各种沥青混合料的物理和机械性能。这一全面的测试数据将被用来开发一个模型来预测改性沥青混合料的蠕变柔量，这是一个关键的输入预测沥青路面的低温性能的机械经验路面设计。这个模型，验证后，将允许含有类似的添加剂的沥青混合料的低温性能进行预测，使其成为一个有用的工具，为交通运输当局设计路面时，使用改性沥青混合料。该研究将为建立道路建筑新材料的长期研究计划奠定基础。它还将通过改善寒冷气候下道路建设中使用的沥青材料的设计、耐久性和寿命，为加拿大带来直接的经济和社会效益。

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.