【作者】 孟美丽；

【导师】 王复明；

【作者基本信息】 郑州大学 ， 水工结构工程， 2014， 博士

【摘要】 路面材料如沥青混合料、水泥混凝土均是由几种不同材料组成的复合材料，复合材料介电常数与其组成成份介电常数及体积率有关，还与电磁波频率、环境温度等因素有关。通常将描述复合材料介电常数与其成份介电常数及体积率、频率和温度等参数之间的函数关系式，称为介电模型。若能建立复合材料介电模型，即可根据电磁无损检测技术测试的介电常数计算各成份的体积率，从而实现沥青混合料空隙率、沥青含量、压实度、和水泥混凝土配比、厚度、含水量等质量指标的检测。由此可见，水泥混凝土和沥青混合料介电模型的建立是应用电磁波技术进行路面材料质量检测的前提和基础。国内外学者先后对各种不同复合材料的介电特性进行研究，建立了多种介电模型，但针对水泥混凝土和沥青混合料的研究较少，鉴于这两种材料有各自的结构特点，已有模型是否适用有待研究和验证。此外，大多已有介电模型没有考虑温度和频率的影响，这样会造成使用不同频率的仪器在不同时间不同温度条件下测试出来的数据不能共享和对比。若忽略，势必会造成一定的误差。针对上述存在的问题，本文根据两种复合材料不同的介电特性，通过研究介电常数与组成成份之间的关系，确立了各自的介电模型；在分析频率、温度对介电常数影响的基础上，基于试验建立了综合考虑频率、温度的水泥混凝土和沥青混合料介电模型；结合试验数据，对两种复合材料的综合介电模型进行了验证；将综合介电模型应用于工程实践，进行了水泥混凝土结构层厚度、含水量的计算，以及沥青混合料含水量、沥青体积率、骨料体积率和空隙率的计算。本文主要研究成果和结论如下：1.以电磁波理论的Maxwell方程为基础，根据水泥混凝土、沥青混合料各自特点，理论推导了水泥混凝土和沥青混合料介电模型，因考虑了各自特点，与其他模型相比，本文模型更适合描述水泥混凝土和沥青混合料介电特性。2.基于理论和试验研究分析了影响两种复合材料介电常数的因素，两种复合材料的介电常数不仅与其成份的介电常数和体积率有关，还与测试频率和温度相关。研究表明：水泥混凝土的介电性能受温度和频率影响较大，随温度升高呈线性规律减小，随频率增加大致呈指数规律减小；而沥青混合料的介电特性随温度变化较小，随频率增加大致呈线性减小。3.鉴于频率和温度对介电常数的影响，建立了综合考虑频率、温度在内的水泥混凝土和沥青混合料介电模型，并根据试验数据进行了检验，确定了模型中的待定常数。4.结合相关文献的数据，基于综合介电模型，分别进行了水泥混凝土结构层厚度、含水量的计算，以及沥青混合料含水量和各成份体积率的计算，计算结果与实测数据较为接近，满足相关规范检测精度的要求，进一步验证了介电模型的适用性和精确度，也进一步说明应用电磁无损检测技术进行质量指标检测是行之有效，可为工程应用提供参考。论文主要创新点：1.在分析了组成成份对介电常数影响的基础上，研究了频率和温度对介电特性的影响，建立了综合考虑频率、温度影响的水泥混凝土介电模型。采用理论和试验相结合的方法分析了影响水泥混凝土介电特性的因素，建立了含频率、温度等因素的水泥混凝土的介电模型，并进行了试验验证。研究结果显示：水泥混凝土具有明显频散特性，随测试频率的增加，介电常数大致呈指数规律减小，且频率越大，降幅越小；随温度升高大致呈线性规律下降；与其他模型相比，所建模型比较适合描述水泥混凝土介电性能。2.分析了组成成份、频率和温度对沥青混合料介电特性影响，建立了综合考虑频率、温度的沥青混合料介电模型。根据沥青混合料的介电特性，通过研究介电常数与组成成份之间的关系，确立了介电模型的基本形式；在分析频率、温度对介电特性影响的基础上，建立了综合考虑频率、温度沥青混合料介电模型；结合试验数据，进行了介电模型验证。试验验证结果表明：介电常数随频率的增加大致呈线性减小；随着温度升高介电常数呈线性略有升高；所建模型比较适合描述沥青混合料介电性能。3.基于综合介电模型，建立了结构层厚度、含水量和成份体积率的计算方法，并在工程实践中得到检验。基于水泥混凝土介电模型，建立了由介电常数计算结构层厚度和含水量的关系式；以沥青混合料介电模型为基础，发展了由介电常数计算含水量和骨料、沥青以及空隙率的关系式；并结合相关文献的试验数据，分别根据实测介电常数进行了水泥混凝土结构层厚度和含水量的计算以及沥青混合料含水量、沥青体积率、骨料体积率和空隙率的计算，计算结果与实测结果较为接近，满足检测精度要求，进一步验证了模型的实用性、准确性和其工程实用价值。更多还原

【Abstract】 Pavement materials, such as asphalt concrete and cement concrete, are composedof several different materials and named as composite materials. The dielectricconstant of the composite material is related not only to the dielectric constant and thevolume ratio of each component but also to the test frequency and the environmentalfactors such as temperature. Usually it is called the dielectric model that the functionis used to describe the relationship between composite dielectric constantand thepermittivity, the volume ratio of each component, the frequency and temperature. Ifdielectric model is established, the volume of each component can be calculatedbased on the dielectric constantwhich is tested by the electromagnetic non-destructivetesting techniques. It is possible that the porosity, water content/asphalt content,degree of compaction and other important quality indicators are detected. Therefore,the dielectric model establishment of cement concrete and asphalt concrete is thepremise and foundation technology for quality testing of pavement materials.Domestic and foreign scholars have conducted research on dielectric propertiesof different composites and established many various dielectric models. But the studyon the cement concrete and asphalt mixture is relatively less, because the twomaterials have their own structure characteristics. The existing models are to bestudied and verified if they are suitale to the two materials respectively. In addition,most of the existing dielectric models do not contain the effects of temperature andfrequency factors. Thus, it will cause the data not to be shared and contrasted whichare tested by the different instruments using different frequency in different time anddifferent temperature conditions. If ignored, it is bound to cause some error.In view of the above problems, based on the dielectric properties of two differentcomposites and through the study of the relationship between the dielectric constantand dielectric of components, the models are established respectively in this paper.On the basis of the frequency and temperature influence on the dielectric constant, thedielectric models of asphalt mixture and cement concrete are established consideringthe frequency and temperature. Combined with experimental data, the comprehensivedielectric models of the two kinds of composites were verified. The dielectric models are applied to calculate cement concrete layer thickness, water content and asphaltmixture water content and the volume ratio of asphalt, aggregate and void in theengineering practice.The main results and conclusions are as follows:1. On the basis of the Maxwell equation in electromagnetic theory andaccording to the respective characteristics of cement concrete and asphalt mixture,dielectric models are derived in theory. Compared with other models, these modelsare more suitable to describe the cement concrete and asphalt mixture dielectricproperties respectively.2. The dielectric influence factors of two composite materials are studiedtheoretically and experimentally. The dielectric property is related not only to thepermittivity and the volume ratio of the component but also to the test frequency andtemperature. Research shows that cement concrete dielectric properties are affectedby temperature and frequency significantly. The dielectric constant linearly decreaseswith the temperature rising and exponentially decreases with the frequency increase.The dielectric properties of asphalt mixture increase slightly with the temperature andlinearly decrease with the increase of the frequency.3. Considering the frequency and temperature effects on the dielectric constant,dielectric models of cement concrete and asphalt mixture are established andexamined ccording to the test data. In addition, the undetermined constants aredetermined in the model.4. Combined with the data in these literatures and based on the comprehensivedielectric models, the structure of cement concrete layer thickness and moisturecontent are calculated as well as the asphalt mixture water content and the volumefraction of each component. The calculated results are close to the measured data andmeet the relevant standard detection accuracy requirements. The applicability and theaccuracy of dielectric model are further verified. It is illustrated that the qualityindex detection is effective using electromagnetic wave nondestructive testingtechnology to provide reference for engineering application.更多还原