【作者】 磨炼同；

【导师】 吴少鹏；

【作者基本信息】 武汉理工大学 ， 材料学， 2004， 硕士

【摘要】 沥青混凝土广泛应用于高等级公路和机场跑道。沥青混合料的电阻率约为10~7～10~9Ωm，属于绝缘体材料。通过掺入适量的导电相材料，改善沥青混合料的电学性能，可望获得多功能的沥青混凝土，将会对沥青路面冬季融雪化冰、路面损坏检测、公路交通智能化管理等产生深远的影响。 导电沥青混凝土的级配设计采用Superpave设计方法，合成曲线尽可能远离禁区，提供足够的矿料间隙率来填充高掺量的导电相材料。导电粉末可作为一部分填料，但与矿粉的密度差异大，需折算成当量矿粉质量。通过掺入炭黑、石墨和碳纤维可改善沥青混凝土的导电性能。炭黑的吸油性、石墨的润滑性及碳纤维的分散性分别限制其在导电沥青混凝土的应用。石墨单位体积对沥青混凝土导电性能改善效果良好，与其它导电相材料复合改性时改善作用显著，可作为导电沥青混凝土的主要导电相材料，少量碳纤维作为辅助导电相，同时炭黑代替部分矿粉既可起增强作用。掺入少量短切碳纤维可明显改善导电粉末填充沥青混凝土的导电性能，发挥碳纤维大的长径比所具有的导电桥梁作用和导电通路短接作用，改善电子的导电机制。 导电沥青混凝土中导电率与石墨掺量依赖性可用渗流理论解释其导电通路的形成。导电沥青混凝土的导电行为则可用隧道效应进行分析，交变电场中的导电行为可等效为电阻R和电容C并联，非线性V-I特性产生于隧道效应时粒子间的非线性导电和高电场时诱发额外的导电通路，二者是粒子间隙的函数，与电子跃迁能力有关。 石墨对沥青的吸收能力强，评价导电沥青混凝土的体积性能指标必须考虑吸收沥青。马歇尔残留稳定度试验、冻融劈裂试验和车辙试验表明石墨导电沥青混凝土的抗水损害能力强，高温稳定性能良好，可作为新型路面使用。通过控制沥青用量和石墨用量，增加沥青混凝土的压实度，可获得稳定的导电性能。压敏产生的原因是导电沥青混凝土试件的压缩邻近效应、微裂纹和石料间的剪切力使部分导电通路错位。而温敏产生的原因则为沥青的体积膨胀、石墨和沥青的热膨胀系数差异、内部应力和沥青温度敏感性共同作用的结果。更多还原

【Abstract】 Asphalt concrete has been extensively applied in expressway and runway of airfield. It belongs electrical insulating material with a resistivitvy of 107~109om. The conductive behavior of asphalt mixture can be improved with the addition of conductive materials, thus a multifunctional Asphalt concrete can be obtained, which would have a profound effect on pavement deicing, damage testing, highway traffic monitoring and so on.Superpave design method was employed to design the mix proportion of electrically conductive asphalt concrete (ECAC). The curve of mix proportion kept away from the restricted zone in order to provide enough voids in mineral aggregate (VMA) to fill the high content of conductive materials. Conductive powder can regard as a part of filler in asphalt concrete. But they need to make a conversion for equal quality of limestone powder because of the deference of the density. The conductive behavior of asphalt mixture can be improved by adding carbon black, graphite and carbon fiber. The absorbing oil nature of carbon black, the lubricated effect of graphite and the bad dispersion of carbon fiber limit their application in ECAC respectively. The improving effect of graphite on the resistivity of ECAC is excellent, and the composite modification with other conductive materials also is obvious. Graphite was used as main component, and a few carbon fibers were added as assistant component. Carbon black replaced a part of limestone powder, which has an enforcement effect on asphalt concrete. The conductive performance of conductive powder filling asphalt concrete is improved by adding a few chopped carbon fibers. Carbon fibers play a role of the conductive bridge effect and the short circuit effect because of high long/ diameter ratio, improving the conductive mechanism of electron.Percolation Theory can explain the formation of conductive passages under the dependence of the conductivity and graphite content in ECAC. The conductive behavior of ECAC was analyzed by tunnel effect. So the conductive behavior in AC field was equivalent with the parallel connection of a resistor and a capacitor, the nonlinearity of V - I characteristics originate from a combination of the implication of the nonlinear contribution of tunnel conduction between graphite particles and the production of additional conducting pathways under sufficiently strong local fields, which is the function of the gap between graphite particles andhas a relation with the transition ability of electrons.Graphite absorbs asphalt in liquid state strongly. The evaluation of volume performance of ECAC must take absorbed asphalt into account. Experimental results of Marshall Remnant Stability Test, Water Susceptibility Tensile Strength Ratio (TSR) Test and Rutting Test show that graphite modified ECAC possesses of high anti-water damage ability and excellent high-temperature stability, which is expected to apply as new-type pavement. Stable conductive performance can be achieved by controlled graphite content and asphalt content and increasing the compact degree. Piezoresistivity of ECAC may involve proximity effect, microcrack and the staggered arrangements of conductive pass-ways due to shear strength of aggregates. The T-R characteristics may originate from the total function of volume expansion and temperature susceptibility of asphalt, the deference of volume expansion coefficient with heat between asphalt and graphite, and internal stress.更多还原