The effect of nanoclay as bitumen modifier on rutting performance of asphalt mixtures containing high content of rejuvenated reclaimed asphalt pavement

Using some kinds of rejuvenators to restore the characteristics of aged binder in reclaimed asphalt pavement might lead to reduction in rutting resistance. In this research, nanocaly was used as virgin bitumen modifier to compensate for the negative effect of rejuvenator in asphalt mixtures containing high percentages of reclaimed asphalt pavement. For this purpose, dynamic creep test was conducted on the mixtures containing 2%, 4% and 6% modified NC and 25%, 50%, 75% RAP. Laboratory test results indicated that the reduction of flow number due to adding rejuvenator in the mixture can be compensated by using nanoclay modified virgin bitumen.     

沥青稳定基层路面结构的理论研究

根据国内外研究经验,对沥青稳定基层设置、选取不同的基层模量,应用理论方法对不同情况下的沥青路面结构进行计算,结果表明：增加基层模量有利于降低基层底和土基顶的应变,增加底基层厚度能降低基层层底拉应变和表面弯沉,增加土基模量能减小表面弯沉。     

Rutting behavior and androgen variation in reindeer (Rangifer tarandus L.)

The rutting behavior of captive reindeer was studied during three rutting seasons. Blood samples from three males were taken for androgen analysis before, during, and afterthe rut. The amount of androgen increased at the end of August to a peak during late September-early October and decreased thereafter. Flehmen, urinating on the hindlegs, and two different low-stretch displays emerged during the prerut period. The preorbital gland enlarged and secretion occurred at the rim of the pocket. A conspicuous breath odor appeared very abruptly during the most intense period of rutting. A few days later a strong odor also appeared in the urine. The urination behavior and the two odors were confined to a brief period during the rut, while other behavior persisted afterwards.     

基于动力问题的高等级公路沥青路面车辙预估方法

基于运动车辆与不平整路面的相互耦合作用,建立车辆动力作用下沥青路面车辙计算与预估方法。提出一种更加符合实际的汽车动载模型;采用室内蠕变试验确定不同级配、不同温度和不同油石比下的沥青面层混合料Burgers黏弹性模型参数;提出以车辙等效的轴载换算及轴载累加作用时间tt计算方法;通过路面温度场观测,综合相应温度场路面材料动稳定度,建立一种新的路面代表温度的计算方法;针对重复与累加作用时间加载的不同,在理论计算基础上,提出不同沥青路面结构加载修正系数;结合有限元方法分析动力轴载累加时间作用下沥青路面车辙及加载修正系数,获得最终车辙预估值。通过邯郸—长治高速公路试验路车辙预估值与实测值对比,误差仅为8%～9.5%。表明沥青路面车辙预估方法的合理性,并具有较高的精度。     

高等级公路车辙形成机理与防治措施

对沥青路面车辙按形成原因进行了分类,根据沥青路面车辙形成的过程,分析了车辙形成的机理,针对车辙形成的机理,探讨了影响车辙的因素,并提出了一些有效防治沥青路面车辙产生的措施,以期延长路面的使用寿命,提高道路承载力。     

基于严重程度和性能衰变的独立车辙养护优先排序

为适应未来精细化的车辙养护作业及资金有限情况下的车辙路段养护选择,并充分考虑车辙严重程度及性能衰变,针对路段中的独立车辙,提出了严重程度指标(车辙深度、车辙长度)和性能衰变指标(车辙深度增加量、车辙长度增加量),基于组合赋权法对多条独立车辙进行养护优先排序.3 km路段2年车辙数据分析结果表明,利用本文所提方法自动判断得到的排序结果与基于行车安全和性能衰变的分析结果相符.因此,考虑独立车辙的严重程度和性能衰变,利用组合赋权法对独立车辙进行养护优先排序,节约了大量的时间和人力,对于公路养护和管理部门在有限资金情况下进行车辙养护决策具有一定的指导作用,为未来精细化的车辙养护作业提供了有效的决策方法.     

高模量橡胶改性沥青及其混合料性能研究

高模量沥青及其混合料是解决沥青路面重载交通及长大陡坡路面车辙等问题的重要工程材料。采用活化橡胶颗粒制备的橡胶改性沥青具有优异的高低温性能及抗车辙性能。本文分析了克炼30#A级和克炼50#A级低标号硬质沥青、克炼70#A级沥青及橡胶改性沥青性能,并采用两种级配类型（ATB-25和SUP-20）来评价其高低温性能及水稳定性能。结果表明,橡胶改性沥青PG分级为76-28,在相同温度下,橡胶改性沥青复数剪切模量及车辙因子最大;随着温度的降低,四种沥青的蠕变劲度均显著增大,但橡胶改性沥青的增大趋势最慢,橡胶改性沥青的m值最大;两种级配类型下,橡胶改性沥青具有最大的动稳定度及弯曲劲度模量,同时有较好的水稳定性能。     

高温重载条件下沥青混合料的蠕变试验研究

在4种应力水平、3种温度水平和2种空隙率水平下进行了沥青混合料的重复加载动态蠕变试验,得出了其永久变形与荷载作用次数关系曲线及竖向和横向流动数、竖向塑性应变、竖向塑性弹性应变比等永久变形参数.研究表明,重载车辆对沥青路面产生的高接触应力加剧了其横向流动失稳变形的发展,加速了车辙的产生;车辆轴载增大对沥青路面产生车辙的影响要大于温度变化的影响.     

基于多应力蠕变回复试验的沥青结合料高温性能评价

为了更好地评价沥青结合料的高温路用性能, 基于动态剪切流变仪(DSR)的应用, 选用基质沥青和SBS改性沥青, 在通过震荡试验确定沥青PG高温等级的基础上, 采用多应力蠕变回复(MSCR)试验对比分析和评价了沥青结合料的高温抗车辙性能.结果表明, 现有规范中的震荡试验得到的车辙因子指标G^*/sinδ可以很好地评价基质沥青的高温性能(不适用于改性沥青);而MSCR试验得到的回复率R能很好地表征改性沥青的延迟弹性, 蠕变柔量J_nr则可以考虑取代车辙因子作为沥青结合料高温性能评价的新指标.此外, SBS改性沥青的应力敏感性问题比基质沥青更为显著.     

Laboratory evaluation of the effect of SBS and Lucobite on performance properties of bitumen

In this research, the effects of two additives namely SBS (3, 5%) and Lucobite (3, 5%) on the performance properties of binder were evaluated. The binder fatigue and rutting performance was evaluated through linear amplitude sweep (LAS) and multiple stress creep and recovery (MSCR) test, respectively. Results indicated that 3% SBS modified binder has the highest percent recovery value and the lowest Jnr value, but had the highest sensitivity to a sudden increase in the stress level inside the asphalt mixture. The LAS test results demonstrated that the fatigue behavior of asphalt binders modified with 3% Lucobite, is the highest one.