就地热再生过程中老化沥青混合料性能评价

摘要

In order to improve the utilization efficiency of the aged asphalt mixture in hot-in-place re⁃cycling, a study was conducted to evaluate the performance of the aged mixture. By extraction and siev⁃ing, the aged asphalt binder and aggregate were separated and submitted for property inspection. It was found that the loss of asphalt was limited, the degradation of binder′s ductility and penetration were more than 50 percent and the coarse aggregates were refined. Then three kinds of asphalt mixtures were prepared:A, aged asphalt mixture;B, new asphalt mixture (the same gradation with A);C, new asphalt mixture (the same gradation with the initial construction) and the respective performance indicators were tested. Dynamic modulus test indicated adverse effect of aged binder and degraded gradation on the viscoelasticity mechanical responses of asphalt mixture; the freeze and split test result of A was only 51.9 percent, indicating the remarkable reduction of water damage resistance of A;A was matching with C in light of high temperature performance, revealing the stable condition of high temperature perfor⁃mance;the flexural tensile strength, failure strain and strain energy density of A were 62.5 percent, 32.3 percent and 13.2 percent of those of B, suggesting sharp reduction of low temperature performance of A. According to the test results, both the aged binder and degraded aggregate gradation influence the prop⁃erties of hot-in-place recycled mixtures:water damage and low temperature crack resistance of asphalt mixture are significantly impacted while the high temperature performance is less influenced; but the specific qualitative relationships need further investigation.%为了提高沥青路面就地热再生过程中老化混合料的利用效率，对老化混合料性能进行研究。对老化混合料进行抽提筛分试验，发现沥青损失量较少，但针入度和延度衰退超过50%，粗集料明显细化。制备了三种混合料，包括路面回收旧料A、与旧料级配一致的新料B和与旧料初始级配一致的新料C，分别对其进行性能评价。动态模量试验结果显示，沥青老化和级配衰减对沥青混合料黏弹性力学响应产生不利影响；A的冻融劈裂强度比仅为51.9%，表明抗水损害能力严重下降；A与C的高温稳定性接近，表明旧料高温稳定性保持稳定；A的抗弯拉强度、破坏应变、应变能密度分别是B的62.5%、32.3%和13.2%，表明旧料低温抗裂能力显著下降。上述试验结果表明，沥青老化和级配衰变皆对就地热再生沥青混合料性能产生影响：对水稳定性和低温抗裂性影响显著，对高温稳定性影响较小；但两因素的具体贡献比例有待进一步研究。