基于氧气扩散和消耗机理的沥青路面老化预测模型

Asphalt aging results in different distresses, such as cracking, raveling, and pothole. The distresses not only have a negative effect on traffic safety, passenger comfort, and pavement maintenance costs but also significantly reduce the service life of asphalt pavement. Asphalt aging has been studied for decades and has gained plenty of findings, but it is still not clear how to quantify the effect of oxygen diffusion and consumption on asphalt pavement aging, especially for the mechanism of oxygen diffusion and consumption in asphalt pavement. In the applicant’s Ph.D. thesis, a newly developed method was developed to measure the oxygen diffusion coefficients of compacted asphalt mixtures and was used to model oxygen flows in field pavement. In the proposed research, the developed method will be further improved to measure and calculate the oxygen diffusion and consumption coefficients of compacted asphalt mixtures prepared with different design formulas. The coefficients will be used to model oxygen flows and consumption in field pavements and will be used to characterize the asphalt aging in field pavement as a function of time and depth. Additionally, the effect of oxygen diffusion and consumption on asphalt pavement aging will be investigated and the mechanism of oxygen diffusion and consumption in field pavement will be further discussed based on the above outcomes. Finally, a new oxidative aging model of asphalt pavement will be built according to the combination of the above studies, pavement temperatures, and material properties. Furthermore, the aging model will be calibrated to enhance the accuracy and robustness of the prediction procedure by using the asphalt aging results from different types and service life of asphalt pavements. The outcomes are anticipated to help develop more aging-resistant asphalt mixture designs and improve pavement structural design and maintenance strategies.

沥青老化引发沥青路面出现裂缝、松散、坑槽等病害，不仅影响行车安全及舒适性、增加路面维修成本，而且严重缩短路面的寿命。研究人员虽对沥青老化开展了大量研究，但现有研究无法量化孔隙形貌对沥青路面老化的影响，尤其是氧气在沥青路面内消耗和扩散的机理尚不明确。项目申请人已通过自主研发的设备测定了沥青混合料的氧气扩散系数，并初步探讨了氧气扩散与沥青混合料老化之间的关系，为解决以上不足提供了新的研究思路。本项目拟借助自制的氧气扩散和消耗设备来表征氧气在沥青路面中扩散和消耗的规律，使用自制的老化装置来模拟氧气在沥青路面中扩散和消耗过程并研究沥青老化随时空变化规律。基于以上研究成果，本项目将阐明氧气在沥青路面中扩散和消耗的机理，量化孔隙形貌对沥青路面老化影响，进而建立新的沥青路面老化预测模型。本项目的研究成果在提高沥青路面耐久性、减少路面维修、提升路面服务水平、节约资源等方面具有重要的社会效益和经济效益。

沥青路面的老化引发多种路面病害，严重影响其路用性能和使用寿命。现有的沥青老化研究主要针对沥青本身，而沥青混合料老化才更贴近实际路面老化，沥青混合料老化试验又存在试验条件与实际情况严重不符的情况。此外，沥青路面老化因素很多，空间深度上的老化梯度变化往往被忽略，作为沥青老化反应关键的氧气扩散因素并未受到应有的重视。因此，本项目基于自制老化容器提出了新的沥青混合料室内老化方法，探究了沥青混合料老化随时空演变的规律，研发了沥青混合料氧气扩散系数测定装置，建立了沥青混合料空隙特性参数与氧气扩散之间的关系，探明了沥青混合料中氧气扩散机理，建立了基于氧气扩散系数的沥青混合料老化预测方程。具体研究结果包括：（1）随着老化时间增加，沥青混合料的高温性能变好，但疲劳性能下降，且老化速率随时间在逐渐减小，空间层面上，老化随着深度的增加存在明显梯度，越靠近表层老化程度越重；空隙率增大以及老化温度升高都会加快沥青混合料的老化进程。（2）温度升高和空隙率增大均会加速氧气扩散，其中空隙率对扩散的影响最大，氧气扩散速率随时间的增长逐渐减小，且氧气浓度在沥青混合料内部呈梯度变化。（3）将氧气扩散系数作为指标建立了沥青混合料老化预测模型，验证了氧气扩散规律评价沥青混合料老化的合理性。沥青混合料时空老化研究提供了更为贴近沥青路面实际老化的室内试验方法，着重考虑了老化深度这一影响因素，得到了时间和空间多个维度下的老化规律，对沥青道路设计优化有着指导意义。扩散试验验证了实验室测试氧气扩散系数的可行性，为后续氧气扩散规律的研究提供了思路和方法，也为沥青混合料老化的评价提供了新参考指标。