【作者】 易军艳；

【导师】 冯德成；

【作者基本信息】 哈尔滨工业大学 ， 道路与铁道工程， 2012， 博士

【摘要】 在今年初国家制定的十二五规划中,提出绿色发展的概念,即建设资源节约型、环境友好型社会,促进资源的循环利用,加强生态和环境保护。在这种背景下,由于具有抗滑、降噪、雨天行驶安全、有效补充地下水资源、合理利用废旧轮胎材料等诸多优点,多孔沥青路面已经成为道路工程界路面铺装的研究热点。但是,由于结构组成与常规密级配沥青混合料不同,强度仅靠内摩阻力与相对更弱的粘聚力提供,耐久性问题一直是制约多孔沥青混合料进一步应用的瓶颈,尤其在季节性冰冻地区使用规模更小。国内外对多孔沥青混合料在季冻区耐久性的研究主要关注带钉轮胎导致的磨损与过度撒布除冰盐带来的经济与环保问题,而对于不利季节的冻融耐久性,由于研究目标与方法不一致,仍然有许多问题亟待澄清。因此结合理论分析与试验验证,探讨多孔沥青混合料冻融损伤特性,通过界面行为分析,提出改善冻融耐久性的技术对策,将对多孔沥青混合料在季冻区的应用提供理论支撑。首先,对多孔沥青混合料的冻融损伤特点进行了分析,由于材料属性、外部冰冻荷载以及损伤模式的复杂性,具体研究过程应做适当简化。由此提出宏微观结合的分析手段。宏观层面涉及冻融力学试验,全面分析了试验条件对冻融结果的影响,确定了包含不同饱水条件与加载模式的两种试验方法。微观上以沥青与集料界面性能为研究目标,提出了评价界面性能的试验系统,基于界面受力分析明确了研究界面性能的关键在于沥青薄膜厚度的选择。进一步采用真实集料模拟混合料中沥青与集料的粘结状态,试验结果表明相对于铝制夹具,集料与沥青之间有着更强的界面粘结性能。其次针对多孔沥青混合料抗冻性能的内外影响因素进行了全面的研究。基于不同空隙率沥青混合料的强度与物理特性衰减规律,总结出沥青混合料冻融损伤的三阶段,明确沥青与集料界面性能对于冻融耐久性的重要影响。结合空隙率在实际路面以及室内混合料试样内部的不均匀分布现象,提出多孔沥青混合料的冻融损伤临界位置在其结构内部。以空隙率与渗水系数间的关系为基础,初步提出满足多孔沥青混合料冻融耐久性的渗水系数要求。而后对影响室内混合料抗冻性能评价的因素进行了分析,提出单轴压缩模式更适合开级配磨耗层抗冻性能的评价。并根据多次冻融循环试验中的沥青硬化规律,借助混合料动态模量预测模型,建立了室内冻融试验结果的修正公式。基于增量型本构方程,构建了多孔沥青混合料的粘弹塑性损伤模型。以此对近似冻融温度下(-10~20℃)多孔沥青混合料单轴压缩试验的应力-应变曲线进行了拟合,并重点针对粘弹模型、塑性模型以及损伤因子中相应参数随温度与加载速率的变化规律加以分析,验证了该理论模型用于描述多孔沥青混合料力学性能的合理性。进而采用上述模型对冻融作用后的多孔沥青混合料力学行为进行了分析。理论模型中的参数变化规律揭示了多孔沥青混合料冻融损伤特点,即宏观模量下降,松弛时间变长,内摩阻角增大,材料体积变形加大,混合料内部粘聚力丧失,集料与沥青间界面性能也随之迅速衰减。随后重点针对沥青与集料界面性能开展了大量的试验研究。选取2种沥青(3种老化状态)与2种集料分别组合成为界面试验系统,首先以温度循环荷载为研究目标,对界面系统施加了低频疲劳荷载,根据提出的疲劳损伤模型,对疲劳寿命进行了预估。结果表明橡胶沥青与集料间有着更好的界面疲劳寿命。在0℃以上时,温度越低,沥青与集料间界面疲劳寿命越长。除长期老化橡胶沥青外,老化可以有效改善沥青与集料间界面疲劳性能。此外相对于花岗岩,玄武岩与沥青间具有更佳的界面疲劳性能。进一步提出了界面系统单向加载开裂试验,基于时温等效原则建立了不同温度下的界面开裂临界应变能密度主曲线,并对较低温度下(0℃以下)的开裂行为进行了预测。综合对比界面疲劳与开裂性能,分析疲劳试验中单次加载循环应变峰值,借助统计分析手段明确了两者之间存在着较强的相关性,由此可采用1剪应变率下的开裂试验临界应变能密度评价冻融循环荷载下的界面性能。不同温度与加载速率下的开裂试验结果同样表明橡胶沥青具有更大的临界应变能密度,老化的作用规律也基本同疲劳试验,但在较低温度下,长期老化不利于界面粘结性能。在上述研究基础上,提出更为简便的低温粘附性试验,并对3种集料与3种沥青及胶浆在低温状态下的粘结性能进行了分析。改性沥青,尤其是橡胶沥青,有助于提高集料与沥青间的界面粘结性能。同时,根据低温粘附性试验中破坏特征分析可知,沥青薄膜与集料间的粘结性能是低温下混合料破坏的主要诱因。选用2种典型的材料组合成型多孔沥青混合料,综合分析宏观冻融性能演化规律,并结合微观界面性能试验数据,提出沥青与集料界面系统临界应变能密度越大,界面疲劳性能越好,低温下界面粘结性能越佳,选用该材料组合成型的多孔沥青混合料也具有更好的抗冻融破坏能力。最后,就自愈性对沥青与集料界面粘结性能的影响进行了初步研究,提出沥青类材料良好的自愈性有助于混合料抗冻融耐久性的提高。更多还原

【Abstract】 The twelfth five-year guideline of the China presents the idea of Green which relates with the establishment of resource saving and environmental friendly society, keeping the recycle and protection of resource and environment. Due to the exceptional performance of porous asphalt mixture on drainage, skid resistance, noise reduction, complementarities of ground water etc., the application of porous asphalt mixture in pavements has gradually become an important technology trend. However, due to its different structure from conventional dense-graded asphalt mixtures, that is strength only provided by internal friction angle of coarse aggregate and weak bounding from less binder between aggregates, durability problem has been a big issue for the further application of porous asphalt mixtures, especially for cold regions. Until now, on the durability of porous asphalt in cold regions, researchers at home and abroad mainly focus on the excessive wear caused by tires with nails, as well as the economical and environmental issues by spreading much de-icing salt. But due to the inconsistent research purposes and methods in the past, there are still many issues to be clarified for freeze-thaw durability in adverse seasons. In this paper, theoretical analysis and experimental verification are combined to study the freeze-thaw properties of porous asphalt mixture; furthermore, based on the analysis of interface behaviors, technical measures are proposed to improve freeze-thaw durability. The whole study can provide a theoretical support for its application in seasonal frozen regions.Firstly, damage characteristics of porous asphalt mixtures under freeze-thaw cycles were analyzed. For the complexity of material properties, frozen loading and damage mode, the research methods were determined by a simpler mode. Consequently, the micro-macro analytical methods and corresponding test procedures were proposed. For the macroscopic freeze-thaw mechanical test, a comprehensive analysis on the influence of test conditions on freeze-thaw durability was presented, and two kinds of testing process including different water-saturated conditions and test time were developed at last. For micro level, test method on evaluation of interfacial adhesion performance is provided based on analysis of the asphalt and aggregate interface state. Through the analysis of interfacial system, it was found that the thickness of asphalt film affected interfacial performance badly. And then, the effectiveness of evaluating interfacial performance between asphalt and aggregate with proposed interface system is verified.Secondly, factors affecting on frost resisting performance and evaluation of porous asphalt mixtures were discussed. Based on the attenuation rule of strength and physical properties, the freeze-thaw damage process could be divided into three phases, and among that the interfacial performance would behave rather important. Considering the asymmetrical distribution characteristics of percent of air voids, it is believed that the critical location of porous asphalt mixtures in freeze-thaw cycles lie in the inner structure. Reasonable permeability coefficient considering frost resisting performance in cold region was proposed based on the relationship between the permeability coefficient and porosity of porous asphalt mixture. Then, factors which influence the indoor frost resistance evaluation were analyzed. It was found that uniaxial compression mode is more suitable to the evaluation on frost resistance of porous asphalt pavement in China. Based on the asphalt hardening law during freeze-thaw test, correction method for indoor freeze-thaw test results was established.A viscous-elastic-plastic damage model of porous asphalt mixtures was constructed, and then the stress-strain curves under uniaxial compression modes at freeze-thaw temperature (-10~20℃) were fitted. The rationality of model was validated through parameter analysis including elastic modulus, relaxation time, shear modulus and bulk modulus etc.. The attenuation behavior under multiple freeze-thaw cycles was analyzed with the model. It was concluded that the freeze-thaw will cause to decrease of modulus, enlarge of relaxation time and internal friction angle, increase of bulk volume, and debonding between asphalt and aggregate.To further, the interface bonding performance between two kinds of asphalt and aggregate was discussed. Firstly fatigue loading with low frequency was applied to interfacial system to simulate the effect of temperature cycling. Interface fatigue damage model was established and used to predict fatigue lives. The final test results indicated that rubber asphalt exhibit better fatigue lives. The decrease of temperature and use of basalt could improve the fatigue lives above the 0℃. Aging had an important effect on the fatigue performance. Furthermore, the monotonic test was introduced. And the critical strain energy density (CSED) was determined based on the stress-strain curve. The master curve of CSED at different temperature could be got based on time temperature correspondence, and so the fracture behavior at lower temperature could be predicted. Comparison and analysis of the results from fatigue and cracking tests show that there is a good relationship between these two tests, and a simpler critical strain energy density in cracking test is proposed to evaluate interface performance under the freeze-thaw load. Meanwhile, the CSED results at different temperature and load rates show the same change trend on the effect of rubber asphalt and aging. However, it is found that long-term aging had negative effect on the interfacial performance at lower temperature.Based on the above experiment results, a simpler low-temperature adhesion test was proposed, and interfacial bonding properties between different aggregate and binder at low temperatures were studied. The modified asphalt, especially rubber asphalt had a good effect on the interfacial performance. It was also found that the adhesion between asphalt film and aggregate determined the damage mode. The feasibility of replacing mechanical test with it was analyzed compared to mechanical properties of the interface bonding. Then two kinds of typical asphalt and aggregate combinations were chosen to prepare porous asphalt mixtures, and the freeze-thaw durability was studied. Preliminary analysis shows that freeze-thaw durability of porous asphalt mixtures can be characterized by the interface bonding properties between asphalt and aggregate. Finally, the effect of healing on the interfacial bonding performance was investigated. It is believed that healing of viscoelastic materials has a positive effect on the freeze-thaw durability of asohalt mixtures.更多还原