摘要 车辙是在大多数柔性路面表层的反复加载引起的永久变形的累积和增长。动态蠕变试验与路面荷载和变形的响应关系相一致，易用于评价沥青路面的抗车辙性能。沥青路面分析仪 (APA)也是加速荷载车辙试验仪的一种，它让热拌沥青混合料（HMA）试件在可控温度和湿度条件下受到累积移动车轮荷载。本研究中会用到这两种试验方法。 本研究考察了三种沥青面层混合料AC-13, SMA-13 and OGFC-10在试验室测试的永久变形。通常情况下，SBS改性沥青在改善沥青混合料的抗车辙性能上为人所知。在本研究中，SBS改性沥青用于设计这三种沥青混合料，研究每种混合料在受到不利条件如高温、高外加荷载和潮湿环境下的行为，并作出相互比较。 动态蠕变试验的结果显示温度效应在三种混合料的永久变形中起重要作用。在所有的试验参数固定之下，全部试件疲劳之前，每增加15℃都会增加永久应变并显著降低荷载循环。本研究也表明永久变形（蠕变曲线通过图表描绘了该结果）在所施加荷载方面上的依赖度。 湿度通过促成增加永久应变而表明其作用。通过比较AC-13 和OGFC-10，动态蠕变试验也表明SMA即使在极高的应力水平下都表现出良好的抗永久变形能力。试验结果分析使用了蠕变应变斜率、正切蠕变刚度模量、蠕变刚度模量等参数。 在沥青路面分析仪（APA）试验中，SMA最初在40℃（干燥环境）下有很高的动稳定度值，但在20℃的温度增量下，动稳定度水平下降明显，超过一半。在60℃温度条件下集料颗粒之间的内摩擦损失导致动稳定度的显著下降。这表明，SMA特别依赖粒料之间的内摩擦，正是高比例的内摩擦在抗车辙性能上起了最主要的作用。 关键词：动态蠕变；永久变形；正切蠕变刚度模量；动稳定度；抗车辙性能。 ABSTRACT Rutting is the result of repeated loading which causes accumulation and increase of permanent deformations in mostly the uppermost layers of flexible pavements. Dynamic creep test which accords with the response relationship of pavement load and deformation has been readily proposed to evaluate the rutting resistance of asphalt pavements. Asphalt Pavement Analyzer (APA) also is one of the accelerated loaded wheel testers which allow for the hot mix asphalt (HMA) specimens to be subjected to simulated moving wheel loads under controlled temperature and moisture conditions. These two methods of testing were carried out in this research. The study examines the permanent deformation behavior of three types of asphalt surface course mixtures AC-13, SMA-13 and OGFC-10 tested in the laboratory. In general, SBS modified bitumen is known to improve rutting resistance properties of asphalt mixtures. In this study SBS modified bitumen was used in the design of all three asphalt mixtures to see how each of these mixtures behave and compare with each other when subjected to adverse conditions such as high temperatures, very high applied loadings and moist conditions. The results for dynamic creep testing showed that the effect of temperature plays a major role in permanent deformation behavior of all three mixtures. With all other test variables fixed, an increase of 15oC increased permanent strain and significantly shortens the loading cycles just before failure for all specimens. The investigation also demonstrates the dependence of permanent deformation on the magnitude of applied loading (creep curves graphically depict this outcome). Moisture proved its effect by contributing to increases in permanent strains. The dynamic creep test also show that SMA provided excellent resistance to permanent deformation even at very high stress levels, followed by the AC-13 and OGFC-10 in comparison. The parameters, creep strain slope, secant creep stiffness modulus (SCSM), creep stiffness modulus (CSM) were used in the analysis of test results. In the APA tests, SMA initially at 40oC (dry condition) had a high Dynamic Stability (DS) value but at a temperature increment of 20oC the DS level dropped significantly by more than half. The loss of internal friction between aggregate particles at high temperature of 60oC resulted in the significant DS value drop. This shows that SMA relies heavily on internal friction between particles and it is this high proportion of internal friction that plays a main role in its rut-resistance performance. Key Words: Dynamic Creep, Permanent Deformation, Secant Creep Stiffness Modulus, Dynamic Stability, Rut-Resistance. |
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