道路沥青老化评价方法研究进展

沥青是路面工程中常用的筑路材料之一,被广泛应用于中国高速公路和城镇道路中。在路面服役过程中,沥青材料会出现硬化变脆等老化现象,显著影响了路面的运营品质及服役寿命。为了进一步促进道路沥青老化评价方法研究的发展,以宏观性能测试、微观结构探测和数值模拟技术等老化评价方法为脉络,比较了各类评价方法的所属尺度和应用优劣。研究结果表明:现行的沥青热氧老化室内研究方法并不能很好地反映沥青的长期服役耐久性,而紫外老化的室内研究方法更加亟需标准化和规范化;紫外老化和热氧老化的差异在于化学键断裂机制不同,热氧老化主要是由于高温热分解导致化学键断裂,而紫外老化的引发是由于分子内所含的基团吸收了具有能量的紫外线,导致化学键发生断裂;宏观性能测试是构建沥青老化与性能衰退联系的直接研究途径,2类老化类型的宏观性能测试方法和评价指标不能完成等同和替换;荧光显微镜、原子力显微镜、傅里叶红外光谱等微观探测技术能够定性或者定量分析沥青的老化过程和改性剂的老化响应;采用分子动力学模拟和细观力学模型既能继承利用微观研究的精确结论,又可与宏观力学试验建立关联性,对沥青的老化过程进行数值表征,其研究结果能够为其微观演化规律和宏观性能特性提供参考;在实际沥青路面使用中,紫外老化和热氧老化是并行存在的,基于室外沥青路面老化监测的多因素复合老化应是沥青室内老化模拟研究的重点;融合多层次老化评价指标和数值模拟技术,建立多尺度沥青老化动态仿真模拟是沥青材料与数值模拟交叉应用的主要研究方向。

The State-of-the-art Review on Evaluation Methods of Asphalt Binder Aging

The asphalt binder is one of the most commonly used construction materials in pavement engineering, and is widely used in highways and urban roads in China. During pavement maintenance, asphalt materials exhibit aging behavior, such as hardening and brittleness, which significantly affects the operational quality and service life of the pavement. To promote the development of asphalt binder aging evaluation methods, this paper considers aging evaluation methods such as macroscopic performance testing, microscopic structure detection, and numerical simulation techniques. The macro- and micro-mechanisms that drive asphalt binder thermo-oxidative aging and ultraviolet aging were analyzed multidimensionally. The scales and application advantages of various evaluation methods were compared. The results show that current laboratory investigation methods for the thermo-oxidative aging of asphalt binders fail to accurately determine the long-term service durability. Thus, there is a great need for standardized laboratory research methods on ultraviolet aging. Thermal-oxidative aging is mainly due to high-temperature thermal decomposition that causes chemical bonds to break. Ultraviolet aging is triggered by the absorption of energetic UV light by groups in the molecule and their conversion from the ground state to the excited state, which leads to the breaking of chemical bonds. Macroscopic performance testing is a direct way to establish a link between asphalt binder aging and performance deterioration. The macroscopic performance testing methods and evaluation indicators for the two types of aging cannot be equated or replaced. Microscopic detection techniques, such as fluorescence microscopy, atomic force microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, and transmission electron microscopy, can be used to qualitatively or quantitatively analyze the microscopic evolution process of asphalt binder aging and the aging response of modifiers. The results of molecular dynamics and micromechanical models correspond to the precise conclusions of microscopic investigations, and establish correlations with macroscopic mechanical tests to numerically characterize the aging process of asphalt binders. The results of this study can provide a reference for the microscopic evolution law and macroscopic performance properties of asphalt binders. In actual asphalt pavement maintenance, ultraviolet aging and thermal-oxidative aging occurs simultaneously. Multifactor composite aging simulations based on outdoor asphalt pavement aging monitoring should be the focus of laboratory asphalt binder aging simulation. The establishment of a multiscale asphalt aging dynamic simulation, which combines multilevel aging evaluation indicators and numerical simulation techniques, is the main research direction for the cross-applications of asphalt binder materials and numerical simulation.