耐久性沥青路面湿度弱化效应演化过程与表征方法研究

Moisture in asphalt pavement structures penetrates asphalt film and weakens the adhesion and cohesion of asphalt binders, which we define as the moisture weakening effect. Compared to the acute damage from hydrodynamic pressure, the moisture weakening effect slowly and continuously undermines asphalt pavement, which is like a chronic disease for asphalt pavement. Thus it is necessary to discuss if moisture damage resistance of asphalt mixtures is able to meet the durability demand of a long-term pavement. Based on the achievements of the previous National Natural Science Foundation of China (Micro-cracking Mechanism of Asphalt-aggregate System Based on Surface Energy Theory 50908175), this project studies the moisture weakening effect on multi-scales. First, this project characterizes the sorption procedure of moisture to asphalt thin film using Dynamic Vapor Sorption (DVS). Second, a model is built for measuring the process of the moisture weakening effect on intact and damaged asphalt binders using Pneumatic Adhesion Tension Testing Instrument (PATTI). Third, through freeze-thaw cycles to simulate the damage of asphalt film and using modified Lottman test and indirect tensile fatigue test etc., this study builds a durability evaluation model for transferring the moisture weakening effect to the freeze-thaw cycle damage. Finally, based on the results from in-situ moisture measurement system and in-field sample in urgency parking strip, the evaluation model is tested and improved. Outcomes of this experimental study can potentially improve the durable asphalt pavement design method.

沥青路面内部存在的水汽经扩散侵蚀沥青粘结性能，产生湿度弱化效应。与动水损坏相比，湿度弱化如“慢性病症”，持续损害路面耐久性。因此需要探讨沥青混合料抗水损性能是否满足耐久性(50年)沥青路面需求。以结题自然基金《基于表面能理论的沥青－集料体系界面微观开裂机理研究50908175》研究理论和实验为基础，本项目先通过动态气体吸附仪测试沥青膜吸湿时间过程，用PATTI实验测试沥青-集料界面有损和无损两种情况经水侵蚀后的拉拔强度；建立基于Fick理论沥青膜水汽扩散方程，从微观上获得湿度弱化时间与沥青-集料粘结强度演化关系；然后，利用不同冻融循环次数的改进Lottman实验和间接拉伸疲劳试验获得沥青混合料湿度弱化宏观性能衰减规律。通过强度衰减将湿度弱化时间效应转化为冻融次数，进而获得湿度弱化表征方法。最后，通过现场路面湿度监测和停车带沥青路面芯样性能测试进行验证。研究成果可完善耐久性沥青路面设计方法。

沥青路面内部存在的水汽经扩散侵蚀沥青粘结性能，产生湿度弱化效应。与动水损坏相比，湿度弱化如“慢性病症”，持续损害路面耐久性。因此，本文从环境中水汽向沥青路面的扩散过程出发，按照“扩散→弱化→开裂”的研究逻辑，首先对水汽穿透沥青膜的过程进行试验与建模，之后基于不同含水量沥青砂浆试件的半圆弯曲试验及有限元模拟结果，提出湿度弱化演化方程，将沥青混凝土内部黏结/附力下降定义为水分含量的函数，量化湿度对沥青混凝土性能的弱化作用。在此基础上，利用有限元多物理场耦合方法对长期湿度与荷载共同作用下沥青混凝土的开裂行为进行了模拟与分析。本文初步探究了水分对沥青混凝土耐久性侵蚀破坏的演化过程与影响程度，揭示了沥青路面在长期服役过程中的性能衰变规律。