沥青混合料抗反射裂缝试验参数的优化

Optimizing basic test parameters for reflective crack evaluation in asphalt mixtures

Overlay Tester(OT)是美国德州交通研究所(TTI)新开发的、用来评价沥青混合料抗反射裂缝性能的试验方法.它有效地模拟了沥青路面反射裂缝的基本特性,通过施加周期荷载并以荷载循环次数来评价沥青混合料的抗反射裂缝性能;其试验参数包括试件厚度38 mm、初始裂缝宽度2 mm、加载频率0.1 Hz、最大拉伸位移0.625 mm等.目前的试验方法中,这些试验参数并没有经过有效的对比分析和评估,而是根据经验武断地选取.结合我国沥青路面实际情况,通过对OT的各个试验参数进行对比试验,分析了各个试验参数的不同取值对试验结果所产生的影响,最终对该试验方法的基本试验参数做出了优化.试验结果表明:试件的厚度可以采用40 mm,加载频率采用0.2 Hz,初始裂缝宽度参考德州交通部规定值为2 mm;对于最大拉伸位移,应当结合当地的温度情况、路面结构和材料类型,进行分析计算选取.

The Overlay Tester(OT) is a recently developed test method at the Texas Transportation Institute(TTI) that is used to evaluate and characterize the reflective cracking resistance potential of asphalt mixtures.The OT loading configuration and test conditions can effectively simulate the basic characteristics of reflective cracking in the asphalt pavement by applying cyclic loading and using the number of repetitive load cycles to evaluate and quantify the reflective cracking performance of asphalt mixtures. The basic OT loading parameters include specimen thickness of 38 mm, gap opening of 2 mm, loading frequency of 0.1 Hz, maximum tensile displacement of 0.625 mm and so on. These OT test parameters were derived and selected based on the experience, but no sensitivity evaluation has been conducted. In consideration of the different conditions and pavements in China, this laboratory study was undertaken to assess the influence of varying the OT test parameters on the cracking performance of the Chinese asphalt mixtures. An extensive laboratory testing was completed,including a comprehensive sensitivity evaluation of the basic OT test parameter. For optimization of the reflective cracking performance, the corresponding study results indicate that the optimum OT specimen thickness should be 40 mm, and the optimum loading frequency should be 0.2 Hz, while the recommended TTI gap opening of 2 mm is found to be satisfactory; the maximum tensile displacement should be selected and calculated according to the Chinese local temperature conditions, pavement structure and material type.