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Evaluation of the factors that affect the fracture resistance of asphalt mixtures at low temperatures using mechanical testing and acoustic emission methods.

机译：使用机械测试和声发射方法评估在低温下影响沥青混合料抗断裂性的因素。

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摘要

This dissertation investigates the use of mechanical testing and acoustic emission to study microstructural phenomena and the corresponding effects on macroscopic fracture behavior of asphalt mixtures tested at low temperature. The fracture resistance of 28 asphalt mixtures, which represent a combination of factors such as binder type, binder modifier, aggregate type, asphalt content and air voids, was evaluated by performing semi-circular bending fracture tests at three low temperatures. Two parameters, fracture energy and fracture toughness, were calculated from the experimental data. The statistical analysis indicated that fracture resistance is strongly dependent on temperature and significantly affected by type of aggregate and air void content. The results of the analysis also confirmed the significance of binder grade and modifier type with relation to cracking resistance of asphalt mixtures. Asphalt content was also found to be significant for fracture energy but not a significant factor affecting fracture toughness. It was found that loading rate and initial notch length significantly affect the testing results at the highest test temperature, but the influence gets diminished with the decreasing of the test temperature.; An acoustic emission system with eight channels of recording was used to monitor the failure process during testing. The analysis of the accumulated AE events illustrated the relationship between the micro damage and macroscopic behavior at different loading levels. Results showed that the load level corresponding to the localization played a critical role in the damage process of the material. The accumulative AE energy was found to be related to the fracture energy at the two lower temperatures. A method to obtain the fracture process zone was proposed by using the event locations that corresponds to 95% of total AE energy before peak. Comparison results showed that the size of the process zone significantly depends on air voids and aggregate type, but is less depend on the asphalt content. The length of the process zone is strongly affected by the initial notch length and temperature. No obvious difference was found with the size of fracture process zone for different loading rates. (Abstract shortened by UMI.)
机译：本文研究了利用机械测试和声发射研究低温下沥青混合料的微观结构现象及其对宏观断裂行为的影响。通过在三种低温下进行半圆形弯曲断裂试验，评估了28种沥青混合物的抗断裂性，这些混合物代表诸如粘结剂类型，粘结剂改性剂，集料类型，沥青含量和气孔等因素的组合。从实验数据计算出两个参数，断裂能和断裂韧性。统计分析表明，抗断裂性在很大程度上取决于温度，并且受骨料类型和空隙含量的影响很大。分析结果还证实了粘合剂等级和改性剂类型对沥青混合料抗裂性的重要性。还发现沥青含量对于断裂能是重要的，但不是影响断裂韧性的重要因素。已经发现，在最高测试温度下，加载速率和初始切口长度会显着影响测试结果，但是随着测试温度的降低，影响会减小。具有八个记录通道的声发射系统用于监视测试过程中的故障过程。对累积的AE事件的分析说明了在不同载荷水平下微观损伤与宏观行为之间的关系。结果表明，相应于局部化的载荷水平在材料的损伤过程中起着至关重要的作用。发现在较低的两个温度下，累积的AE能量与断裂能有关。通过使用对应于峰值前总AE能量的95％的事件位置，提出了一种获得断裂过程带的方法。比较结果表明，加工区的大小在很大程度上取决于空隙和集料的类型，而对沥青含量的影响则较小。加工区域的长度受初始缺口长度和温度的强烈影响。对于不同的加载速率，断裂过程区的大小没有发现明显差异。 （摘要由UMI缩短。）

著录项

  • 作者

    Li, Xinjun.;

  • 作者单位

    University of Minnesota.;

  • 授予单位 University of Minnesota.;
  • 学科 Engineering Civil.
  • 学位 Ph.D.
  • 年度 2006
  • 页码 103 p.
  • 总页数 103
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 建筑科学;
  • 关键词

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