Asphalt concrete modification to improve flexible pavement performance in cold regions

加拿大的公路网是世界第七大公路网，总长度为113万公里。该网络由40%的已铺装道路和60%的未铺装道路组成。加拿大路网中90%以上的铺装道路由沥青路面组成。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，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使用性能的一个有希望的可能性是对沥青进行改性，以改变沥青混合料的物理性质。在加拿大的情况下，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普遍的病害，导致大量经常性支出用于沥青路面的修复。 近年来，纳米颗粒等创新材料作为沥青混凝土改性剂在沥青行业引起了越来越多的关注。纤维也被用于改性沥青路面已有多年；然而，在沥青混合料中掺入纤维以提高抗热裂性的研究较少。拟议的研究包括进行实验室调查，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，以调查纳米材料的掺入对所得沥青水泥的流变性的影响。此外，制备了一系列纳米材料改性沥青混合料、纤维改性沥青混合料和未改性沥青混合料样品，用于测定各种沥青混合料在不同条件下和冻融循环下的物理力学性能。这些综合试验数据将被用来建立一个预测改性沥青混合料蠕变柔量的模型，该模型是在力学-经验路面设计中预测沥青路面低温性能的关键输入。该模型经过验证后，将能够预测含有类似添加剂的沥青混合料的低温性能，使其成为交通部门使用改性沥青混合料设计路面时的有用工具。这项研究将为建立用于道路建设的新型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，为加拿大带来立竿见影的经济和社会效益。

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.