基于应力-应变关联变化的沥青混合料低温抗裂性能研究
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作者:万里 陈军
摘 要:沥青混合料低温性能的好坏直接关系到沥青路面的耐久性。现行规范主要以小梁低温弯曲试验结果评价沥青混合料的低温性能,但该评价方法的有效性存疑,且可操作性不强。基于此,该研究在分析沥青混合料低温性能传统评价方法不足的基础上,基于沥青混合料在承载过程中应力和应变的关联变化特征,提出采用断裂能指标评价沥青混合料的低温性能。结合基质沥青混合料和SBS改性沥青混合料小梁试件浸水损伤前后的应力和应变变化,分析采用断裂能指标评价沥青混合料低温性能的有效性。结果表明,不同于传统评价方法,断裂能指标能正确区分和反映出不同种类沥青及环境因素(水、温度)对沥青混合料低温性能的一般影响规律。说明采用断裂能指标评价沥青混合料的低温性能更科学、可靠性更高。
关键词:应力;应变;断裂能;沥青混合料;低温抗裂性能
中图分类号:V445 文献标志码:A 文章编号:2095-2945(2022)24-0069-04
Abstract: The low-temperature performance of asphalt mixture is directly related to the durability of asphalt pavement. The current specification mainly uses the low-temperature bending test results of beam specimens to determine the low-temperature performance of asphalt mixture, but the effectiveness of this evaluation method is questionable and the operability is also not strong. Therefore, after analyzing the insufficiency of the traditional evaluation method for the low-temperature performance of asphalt mixture, the fracture energy index was proposed to evaluate the low-temperature performance of asphalt mixture in this research based on the correlation change of stress and strain during the bearing process of asphalt mixture. Based on the changes of stress and strain of the beam specimens of the base asphalt mixture and the SBS modified asphalt mixture before and after water immersion damage, the effectiveness of using fracture energy to evaluate the low-temperature performance of asphalt mixture was analyzed. The results show that, different from the traditional evaluation methods, the fracture energy index can correctly distinguish and reflect the general influence of different kinds of asphalt and environmental factors (water and temperature) on the low temperature performance of asphalt mixture. It is shown that the use of fracture energy index to evaluate the low temperature performance of asphalt mixture is more scientific and reliable.
Keywords: stress; strain; fracture energy; asphalt mixture; low temperature crack resistance
半性基层沥青路面是在我国高等级公路建设中普遍采用的道路结构形式,其由半刚性基层和沥青面层组合而成[1]。沥青面层直接暴露于服役环境中,承受温度、水分及交通荷载等因素的多重作用[2-3],因而沥青面层耐久性的好坏是决定整个道路结构能否安全服役的前提。沥青面层由沥青混合料铺筑而成,骨料和沥青是沥青混合料的主要构成[4]。沥青是一种温敏性材料,因而沥青混合料的温度敏感性是沥青路面耐久性的重要组成部分,主要包括高温抗变形性能和低温抗开裂性能。
目前在评价沥青混合料低温性能时,主要遵从《公路工程沥青及沥青混合料试验规程》[5]中的沥青混合料弯曲试验标准方法(T0715)。该方法虽然同时考察了沥青混合料试件的破坏强度、破坏应变及破坏劲度模量,但在《公路沥青路面施工技术规范》[6]中仅按照气候类型和沥青种类对沥青混合料的低温应变应达到的水平进行了规定,即主要依赖沥青混合料低温下能承受的最大弯拉应变这一单一指标来决定其低温抗裂性能,这显然比较片面。虽然在《公路沥青路面施工技术规范》中同时也提到,最大弯拉应变并不是太满意的低温性能评价指标,沥青混合料的低温性能要结合试件的破坏强度、破坏应变、破坏劲度模量及对应的应力-应变曲线形状进行综合评价。而在实际操作中,因缺乏量化的标准或规定,这一评价方法的可操作性不强,主观因素对评价结果影响较大。
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