【作者】 汤寄予；

【导师】 高丹盈；

【作者基本信息】 郑州大学 ， 结构工程， 2013， 博士

【摘要】 通过矿质混合料堆积性能、不同类型纤维沥青混合料高低温性能、水稳定性能和损伤自愈性能的系列试验,对矿质混合料堆积状态组成规律与级配性能、纤维沥青混合料配合比设计方法、路用性能以及损伤自愈性能进行了系统的理论分析,得到以下主要结论：(1)二元矿料颗粒体的密实填充状态和最优骨架状态分别对应不同的组成,最密填充时大小矿料的质量比为6：4,最优骨架状态时大小矿料的质量比为7：3；二元体的密实填充状态和最优骨架状态的组成规律同样适用于对矿料级配的设计和评价。(2)提出了直接测试矿质混合料骨架内摩阻力的方法—塑模试件抗压强度试验方法,所测抗压强度可作为反映矿质混合料骨架内摩阻力大小的力学指标；摩阻力与矿料级配中粗集料的含量具有正相关性；对公称最大粒径为13.2mm的矿料级配,应以4.75mm作为粗细集料的分界点。(3)提出了纤维沥青混凝土最佳油石比的预估方法。可将沥青膜厚度法计算的有效沥青用量和矿料开口孔隙吸入多余沥青含量之和作为沥青混合料的最小沥青用量,将马歇尔试模击实级配矿料所得的沥青用量作为最大沥青用量。(4)采用传统经验法优选SMA的矿料级配时,依据马歇尔试件的体积指标不足以做出合理评价,而塑模试件的摩阻力测试是更为适宜的方法；在确定SMA的最佳油石比时,马歇尔试件的体积指标宜采用合成矿料的有效密度计算。(5)提出了“主骨架间隙体积优化填充法”的骨架型纤维沥青混合料配合比设计方法。将矿料级配设计和沥青混合料的配合比设计相统一,使骨架型沥青混合料的配合比设计过程成为性能可控的对矿料级配、最佳油石比和纤维掺量的组成优化过程。与经验法相比,采用该方法设计SMA和OGFC沥青混合料是一种更经济可行的方法,可有效避免矿料级配选择和最佳油石比确定存在的盲目性,减少试验工作量。(6)矿料级配对沥青混合料的路用性能具有重要影响,密级配沥青混凝土具有更好的低温性能和水稳定性,而骨架结构的SMA和OGFC沥青混合料具有更好的高温稳定性。(7)纤维对沥青混合料的高温稳定性、低温抗裂性和水稳定性均有不同程度的改善效果,但只有在纤维掺量和相应沥青增加量达到最佳组成时才能发挥最佳改性效果。综合考虑,取得最佳改性效果时,密级配沥青混凝土中钢纤维和聚酯纤维的吸附沥青经验系数K分别取0.07和0.95；SMA和OGFC沥青混合料中添加木质素纤维的吸附沥青经验系数分别取1.7和1.7-2.0,添加玄武岩纤维时吸附沥青经验系数取1.1。(8)纤维可明显改变密级配沥青混凝土的低温破坏形态,由脆性破坏变为带有屈服特征的韧性破坏。纤维掺量越高对密级配沥青混凝土的破坏强度和变形的提高幅度越大。虽然采用劲度模量指标评价纤维沥青混凝土的低温抗裂性能有局限性,但劲度模量能反映纤维对沥青混凝土强度和变形的相对改善幅度。以临界弯曲应变能密度评价纤维沥青混凝土的低温破坏特性更为合理。(9)相同条件下,复合掺入两种纤维比单一纤维更能改善沥青混凝土的各项路用性能,展现出纤维复合改性的“叠加效果”,但不具“线性叠加”规律。(10)马歇尔方法确定的高纤维掺量密级配沥青混凝土的最佳油石比偏高；采用本文提出的“主骨架间隙体积优化填充法”设计的SMA沥青混合料比传统经验法设计的SMA沥青混合料具有更好的路用性能。(11)根据对试验结果的统计分析,建立了考虑纤维和沥青综合影响的弯拉强度和临界弯曲应变能密度预估模型、动稳定度预估模型和浸水马歇尔残留稳定度(或冻融劈裂抗拉强度比)预估模型,可供实际工程应用时参考。(12)纤维对温度裂缝的发展形态有重要影响,并对沥青混凝土裂缝自愈能力具有显著改善,其改善机理来自对抗裂能力的提高。自愈能力以能量的恢复率表示更为合理。自愈期的引入和纤维的复合作用对沥青混凝土裂缝修复的影响显著。根据对试验结果的统计分析,建立了考虑温度及纤维综合影响的裂缝自愈能力预估模型。更多还原

【Abstract】 Through a series of tests on the packing characteristics of mineral aggregates, high temperature stability, low-temperature crack resistance, water stability and self-healing capability of different type of fiber reinforced asphalt mixture, A systematically theoretical analysis on the packing component laws and gradation properties of mineral aggregates, mix design method, road performances and self-healing capacity of fiber reinforced asphalt mixtures was carried out, conclusions obtained are as follows:(1)The closely packing status and the optimal skeleton status of a binary system correspond to different composition of the two aggregates respectively, the volume ratio of6:4corresponds to closely packing status of the two aggregates, nevertheless, the volume ratio of7:3corresponds to the optimal skeleton status of the two aggregates. The component laws on closely packing status and optimal skeleton status derived from binary system can also be applied for design and evaluation on aggregate gradation.(2) A direct method to measure the inner frictional resistance of aggregate skeleton using plastic mould sample compression test was developed, and the measured compressive strength can be taken as a indicator of inner frictional resistance of the aggregate skeleton, the friction resistance has a positive correlation with coarse aggregate content.4.75mm can be regarded as the dividing point between coarse aggregates and fines for aggregate gradation with the nominal maximum size of13.2mm.(3) A prediction method on the optimal asphalt content of fiber reinforced asphalt concrete is proposed, the sum of effective asphalt caculated by asphalt film thickness and excess asphalt inhaled by opening pores of aggregates could be as the minimum asphalt content, and the amount of asphalt obtained by compacting grading aggregates with Marshall test mould as the maximum asphalt content.(4) It is not enough to make a reasonable assessment on the optimal gradation of SMA using traditional method based on the volume indexes of Marshall specimens, however, friction resistance test with plastic mould samples is a more suitable method. The optimal asphalt content of SMA could be determined accurately by effective synthetic density of aggregates.(5) A mix design method for skeleton fiber reinforced asphalt mixture, named as "Skeleton Clearance Volume Optimization Packing Method", was put forward based on predecessors’researches, which turns the mix design process of skeleton asphalt mixture into an optimization process of aggregate gradation, optimal asphalt content and fiber content. This design method has obvious advantages over traditional design method when designing SMA and OGFC asphalt mixtures.(6) Aggregate gradation has important influence on road performances of asphalt mixture, dense-graded asphalt concrete has better low temperature performance and water stability, while skeleton asphalt mixtures such as SMA and OGFC have better high temperature stability.(7) Fibers have different improving effects on high temperature stability, low temperature crack resistance and water stability of asphalt mixtures, however, the improving effect is restricted by the correspondingly increased asphalt content. Comprehensive consideration, asphalt adsorption coefficient K for steel fiber and polyester fiber playing their best improving effects on dense-graded asphalt concrete are0.07and0.95respectively, K for cellulose fiber added to SMA and OGFC should be1.7and1.7to2, and it should be1.1for basalt fiber added to SMA and OGFC.(8) Fiber can significantly change the failure mode of dense-graded asphalt concrete at low temperature, from brittle failure mode to failure with somewhat yield characteristics, the higher the fiber content, the greater the improving ranges of the failure stress and strain of dense-graded asphalt concrete. Though the stiffness modulus has limitation to evaluate low temperature performance of fiber reinforced asphalt concrete, which can reflect the relative improving effects of fibers on strength and deformation of asphalt concrete, on the country, it is more reasonable to evaluate the failure characteristics of fiber reinforced asphalt concrete using critical bending strain energy density.(9) Under the same conditions, the improving effects of combined fibers on road performances of asphalt concrete are much better than that of a single kind of fiber, which shows the superimposed effect of the combined fibers, but not a linear superposition rule.(10) The optimal asphalt content determined by Marshall method of dense-graded asphalt concrete with larger fiber content is higher than it needs. The road performances of SMA asphalt mixtures designed by the Skeleton Clearance Volume Optimization Packing Method are better than that designed by traditional method.(11) Prediction models such as bending strength, critical bending strain energy density, dymamic stability, residual Marshall stability(or freeze-thaw splitting strength ratio) considering the interaction influence of fiber and asphalt were established according to the test results, which could be a reference for practical engineering application.(12) Fiber has an important impact on the form of temperature cracks and has significant improving effects on cracking self-healing capacity of asphalt concrete, in fact, the improving mechanism of fiber on self-healing capacity of asphalt concrete derives from the improvement on anti-cracking ability of asphalt concrete. It is more reasonable to characterize the self-healing capacity by the energy recovery rate. The interaction of introduced rest period and fiber affects the self-healing capacity of asphalt concrete evidently. The prediction model of crack self-healing capacity was established considering the influences of temperature and fiber.更多还原