Asphalt concrete modification to improve flexible pavement performance in cold regions

加拿大的公路网是世界上第七大公路网，总长113万公里，其中40%是铺设的公路，60%是未铺设的公路。加拿大路网中90%以上的铺砌道路由沥青路面组成。在加拿大等寒冷地区，路面结构在道路的生命周期中受到极低的气温和季节性冻融循环的影响，导致路面破损、恶化和使用寿命缩短。在高温和低温范围内提高沥青路面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，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困扰，导致沥青路面修复的大量经常性支出。近年来，纳米颗粒等创新材料作为沥青混凝土的改性剂越来越受到沥青行业的关注。多年来，纤维也被用于改性沥青路面；然而，在沥青混合料中掺入纤维以提高抗热裂性的关注较少。拟议的研究包括进行实验室调查，以了解纳米材料和纤维的添加对沥青混合料在不同温度和冻融条件下的性能的影响。实验室将对未改性和改性的沥青水泥进行测试，以研究纳米材料掺入对所得沥青水泥流变特性的影响。此外，将使用一系列制备好的沥青混合料样品——用纳米材料改性、用纤维改性和未改性——来确定各种沥青混合料在不同条件下和冻融循环下的物理和机械性能。这些综合试验数据将用于开发预测改性沥青混合料蠕变顺应性的模型，这是预测沥青路面低温性能在力学经验路面设计中的关键输入。该模型如果得到验证，将允许预测含有类似添加剂的沥青混合料的低温特性，使其成为交通部门在设计使用改性沥青混合料的路面时的有用工具。这项研究将为建立道路建设新材料的长期研究计划奠定基础。它还将通过改进设计、耐久性和在寒冷气候下用于道路建设的沥青材料的使用寿命，为加拿大提供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.