沥青混合料氧化老化微观力学模型的研究

In recent years, more and more evidences show that oxidative aging exists in asphalt pavement and oxidative aging of asphalt mixture occurs through the entire life of asphalt pavement. Although the chemistry of asphalt oxidation has been well characterized, there is still limited information explaining the mechanism of oxidation in asphalt mixtures based on the microstructure. Three-dimensional microstructure of asphalt mixture will be reconstructed and incorporated into FEM software. The oxygen diffusion process will be simulated using Fick’s second law. Fourier transform infrared spectroscopy test and chemistry kinetics are combined to determine the carbonyl formation rate model. The correlation between carbonyl area and viscoelastic material properties of asphalt binder and the corresponding asphalt mastic will be established based on Dynamic Mechanical Analyzer and Dynamic Shear Rheometer. Information of diffused oxygen resulting from the previous stage is used in conjunction with a chemical kinetics model to determine the carbonyl area that is being created at every element within the asphalt mastic through time. The amount of carbonyl area is used to assign different viscoelastic material properties to each location within the asphalt mastic. Virtual dynamic modulus test and indirect tensile test will be conducted towards the micro-mechanical model to characterize the impact of oxidation on the overall mechanical response of the mixture through time. The research results will help understand the mechanism of oxidative aging in asphalt mixtures, predict asphalt pavement oxidative aging behavior and optimize asphalt pavement design.

近年来越来越多的事实证明沥青路面中存在氧化老化，沥青混合料氧化老化贯穿于沥青路面整个寿命周期。现阶段对沥青老化的化学机理研究得比较透彻，但基于微观结构沥青混合料氧化老化行为与机理的研究却非常有限。本项目拟构建沥青混合料的三维微观结构，将模型导入有限元软件，利用菲克第二定律模拟氧气的扩散过程。基于傅立叶变换红外光谱试验和化学动力学建立羰基的生成速率模型。通过动态力学分析仪和动态剪切流变仪建立羰基面积与沥青粘结料粘弹特性、沥青玛蹄脂的粘弹特性的关系模型。利用每一年的氧气扩散结果，结合羰基生成速率模型计算得到沥青玛蹄脂中各个单元的羰基面积，从而赋予沥青玛蹄脂中每个单元不同的粘弹特性。对沥青混合料进行虚拟动态模量测试和间接拉伸测试，研究氧化老化对沥青混合料整体力学响应的影响。研究成果为探索沥青混合料氧化老化机理,预测沥青路面的氧化老化行为、优化沥青路面的设计奠定基础。

本项目通过X-射线计算机断层扫描技术，重构沥青混合料的三维结构，基于菲克第二定律模拟氧气在沥青混合料内的扩散，然后利用氧气扩散的结果，通过化学动力学模型来计算沥青玛蹄脂内每一点随着时间生成的羰基面积。最后基于羰基数量信息修改沥青玛蹄脂的材料特性，并分析材料力学特性随着时间的变化对沥青混合料整体力学响应的影响。沥青混合料氧化老化微观力学模型有助于揭示氧气在混合料微观结构内的扩散现象及路面深度方向的扩散规律，从微观角度观察破坏的发生及演变，以完善基于氧气扩散-反应原理的路面结构氧化老化模型，更深入地理解氧化老化导致的破坏行为和机理。