【作者】 刘小明；

【导师】 吴少鹏；

【作者基本信息】 武汉理工大学 ， 建筑材料与工程， 2007， 博士

【摘要】 沥青混凝土已被广泛应用于道路和桥梁的铺面层。通过掺入适量的导电相材料，能显著地改善其导电性能，并具有高度灵敏的机敏特性。可利用导电沥青混凝土的机敏特性来实现对外部应力及其产生的应变，甚至内部结构损伤的自诊断。这将会对沥青路面损坏检测、交通流量和车辆载荷进行监控和调配等公路交通智能化管理等产生深远的影响。采用连续级配AC-20和间断级配Superpave12.5均可获得同时具有优异电学性能和路用性能的沥青混凝土。马歇尔残留稳定度，四点弯曲疲劳试验，间接拉伸模量试验和车辙试验表明石墨导电沥青混凝土的抗水稳定性能力强，抗疲劳开裂能力较佳，弹性模量高，高温稳定性能良好，可作为新型路面使用。电阻率与空隙率之间遵从一定的指数关系。由于沥青与石墨的膨胀系数不一致，导致其电阻率随温度变化而发生变化。对于间接拉伸疲劳试验，四点弯曲小梁疲劳试验和车辙疲劳试验，导电沥青混凝土对外加应力所产生的应变具有良好的诊断能力。其电阻率变化呈现负压阻效应，石墨相材料掺量相对较低时(在阈值范围内)，单位应变对应的电阻率变化值也越大，也就是说对应变的响应越明显。当施加更高的应力荷载时，每单位应变所引起的电阻率变化值也更高。导电沥青混凝土对其内部损伤也有良好的自诊断能力，在试件遭到破坏的过程中，电阻率输出变化存在三个明显的阶段：首先由于导电沥青混凝土试件受到追密作用后导致导电颗粒接触更加紧密，表现为输出电阻率急剧下降；第二阶段，沥青混凝土电阻率变化处于平稳变化阶段；最后阶段，由于沥青混凝土的微细裂缝逐渐发展，最终导致试件的完全破坏和裂开，导电通路遭到严重破坏，表现为电阻率急剧增大。当导电沥青混凝土作为器件只占试件体积分数的一部分时，其路用性能与完全导电沥青混凝土相比有了大幅度的提高，而且仍然具有良好的机敏特性。当压阻效应从负开始转变为正压阻效应的时候，这时对应的车辙深度10mm就是影响舒适性和安全性的车辙深度临界值，因而车辙变形的自诊断具有特别重要的意义。导电沥青混凝土具有良好的机敏特性，机理可用载流子的浓度变化来解释，其电阻率与载流子浓度成反比。当试件受压时，总应变小于零，而且随着荷载的增加变的越来越负，受压后载流子浓度大于受压前，而且随着加载时间的延长越来越大，导致电阻逐渐减小。当试件受拉时，总应变大于零，导致受拉后载流子浓度小于受压前，而且随着加载时间的延长越来越小，电阻逐渐增大。采用CT破损识别能够证实电阻率的变化是由材料内部结构变化所引起的，疲劳破坏过程中电阻率出现下降或上升是由于材料内部空隙率下降或上升所导致的。更多还原

【Abstract】 Asphalt concrete has been widely applied in the pavement of highway and bridge. The conductive behavior of asphalt mixture can be improved with the addition of conductive materials, thus the self-monitoring material can be obtained. The monitoring of strain is valuable for structural control and dynamic load monitoring for traffic control; the monitoring of damage is valuable for structural health monitoring and service life prediction. The combined ability to monitor both reversible strain and damage is particularly valuable in real-time fatigue damage monitoring under dynamic loading, because the strain cycle and the point within the cycle at which damage occurs can be identified.The continuous mixture proportion such as AC-20 and discontinuous mixture proportion such as Superpave 12.5 are all can be employed to prepare electrically conductive asphalt concrete (CAC). Experimental results of Marshall Remnant Stability Test, Four Point Bend Fatigue Test, Indirect Tensile Modulus Test and Rutting Test show that graphite modified CAC possesses of high resistance to moisture damage and resistance to fatigue damage, high resilient modulus and excellent high-temperature stability, which is expected to apply as new-type pavement. It is exponential relation between the resistivity and air voids of asphalt mixture. The resistivity varied with temperature because the expansion coefficient of asphalt and graphite are repugnant.By using Dynamic Indirect Tensile Test, Four Bend Fatigue Test and Rutting Test, the use of CAC containing graphite and carbon fibers for strain monitoring was investigated and shown to be effective. The electrical resistivity increases reversibly with increasing strain under the test. It has higher self-monitoring ability when the graphite content is lower (beyond the value of threshold) and higher load. CAC for interior damage monitoring was investigated and shown to be effective too. The resistivity change can be divided into three phases through fatigue process: The resistivity is deceased with the specimen was more compressed in the first phase, and then it changed little in the second phase because the specimen was in a steady state after compressed. Finally the resistivity is increased with the specimen was destructed gradually. The increase or decrease of resistivity can be thought is begot by the variation of internal structure of asphalt concrete. Compression action can form more conductive paths and the resistivity is decreased. In the meanwhile, material failure can cut conductive path and the resistivity is increased.When the conductive concrete was embedded into common asphalt concrete specimen as a partial structure function, the road performances were greatly improved compared with completely CAC and it still has excellent piezoreisitivity character. When the piezoresistivity from negative turn into positive, it is 10mm rutting depth critical value that influence driving comfortably and safely, therefore the deformation self-monitoring has specially important significance.CAC has highly sensitive piezoresistivity and the mechanism can be explained by the number variation of electronic carrier. When the loading is compressive stress, the strain becomes smaller and smaller, so the number of carriers higher than that of previous load, therefore the resistivity is decreased. When the loading is tensile stress, the strain becomes bigger and bigger, so the number of carriers lower than that of previous load, as a result, the resistivity is increased. It can be identified that the structure variation of CAC was responsible to the resistivity change by Computer Tomography damage detecting.更多还原