【作者】 薛连旭；

【导师】 张肖宁；

【作者基本信息】 华南理工大学 ， 结构工程， 2011， 博士

【摘要】 环氧沥青是将环氧树脂加入沥青中,经与固化剂发生硬化反应,形成不可逆的固化物,这种固化物从根本上改变了普通沥青和其他热塑性的改性沥青的热塑性质。由于其良好的路用性能,已经在大跨径桥梁,特别是钢箱梁桥桥面铺装中得到了广泛的应用。我国对环氧沥青混凝土钢箱梁桥桥面铺装的研究与应用时间起步较晚,对于环氧沥青的研究除生产商规定的一些技术指标外,多关注环氧沥青的粘温曲线。对环氧沥青的流变学特性则研究较少;对于环氧沥青混合料的配合比设计以马歇尔试验为主,最佳油石比的确定一般由体积指标最终控制,即多以满足目标空隙率要求的油石比作为最佳油石比;对铺装层疲劳开裂的机理、部位、发展规律有比较一致的认识,但对于环氧沥青混合料的疲劳特性、疲劳方程研究不够深入,特别是对于影响混合料疲劳性能的油石比、级配等因素缺乏系统的研究。本文在现有研究的基础上,通过技术调研、理论分析、室内试验相结合的方式,对环氧沥青混凝土在大跨径钢桥面铺装的应用进行了以下几个方面的研究:国内目前对环氧沥青和环氧沥青混合料的的研究主要集中在其低温疲劳、高温稳定性、马歇尔指标等路用性能方面,对其粘弹特性的研究则较少。本文应用动态粘弹力学的理论和方法,对环氧沥青进行了不同应力、应变、温度和时间条件下的流变学性能试验研究。试验结果表明,与普通改性沥青相比,其蠕变柔量小约4个数量级;复数模量随频率降低(温度升高)而降低并与贮存模量共同趋于定值,而在高频(低温)条件下则显示出一定的粘性特征;各项粘弹性参数远远大于改性沥青和普通沥青,具有很好的抵抗流动变形能力。分别对环氧沥青混凝土的主要力学参数模量和强度进行了试验、分析和讨论。动态弯曲模量由于其试验加载方式和铺装层实际受力状态基本一致,而且测试方式模拟了荷载作用下材料应力和应变的实际过程,相对而言更适合作为桥面铺装力学分析时的模量。对于常温下的环氧沥青混凝土铺装,其力学分析计算的模量值变化幅度应为500～15000Mpa。从安全取值、破坏模式的一致性考虑,推荐采用15℃弯拉破坏最大拉应变εB作为其极限拉应变。通过频率扫描的方法得到环氧沥青混合料的40℃主曲线,其形状与普通沥青混合料同样近似呈“S”型,但环氧沥青混合料主曲线跨越的数量级要比普通沥青混合料窄,说明环氧沥青混合料的松弛范围相对较小,粘弹区间窄。通过有限元计算,分析了大跨径钢桥钢桥面铺装的受力特点和使用技术要求,研究了桥面系统各项参数对铺装层的敏感性。通过对钢桥面铺装层间剪应力分析,铺装层模量在500~15000MPa时,铺装层与桥面板间粘结层剪应力在0.5~1.6MPa之间,环氧沥青无论在高温还是常温下均可满足粘结层抗剪强度的要求,应为铺装粘结层的首选材料。对铺装层模量分析表明,铺装层模量变化对铺装层横向应变影响并不成线性关系,铺装层模量从500MPa增加5000MPa,铺装层横向应变水平显著降低;当铺装层模量增加到5000~6000MPa后,铺装层模量对铺装层横向应变得影响水平已经不显著,较为典型的环氧沥青混凝土钢桥面铺装结构其表面最大拉应变约为300～400με。这个应变水平在重复车辆荷载反复作用下会发生疲劳破坏。因此,必须通过混合料的设计来解决环氧沥青混凝土的疲劳耐久性问题。桥面板厚度对铺装层顶面的影响比加劲肋的厚度影响显著,应进行桥面板厚度、加劲肋厚度的经济和技术两方面比较优化的组合设计。依据断裂力学理论与能量原理,提出用冲击韧性(冲击荷载作用下的荷重-位移曲线下的面积),作为评价环氧沥青混合料疲劳性能的指标。冲击韧性值越大,疲劳性能越强;通过用矿料主骨料空隙体积填充法进行了环氧沥青混合料配合比设计,并在控制混合料体积指标的情况下,改变混合料沥青用量,从而考察混合料在各种油石比条件下的冲击韧性及疲劳性能。研究发现冲击韧性与表征材料疲劳性能的指标疲劳剩余模量基本成线性关系,且相关性非常好。环氧沥青混合料的冲击韧性可以作为评价疲劳性能的指标。在冲击荷载作用下小梁三点弯曲试验可以作为评价混合料疲劳性能的试验方法。更多还原

【Abstract】 Epoxy asphalt is asphalt mixed with resin. The hardening reaction occurs with the resin to form irreversible agent which fundamentally changes the thermoplastic performance of the conventional asphalt and other thermoplastic modified asphalt. Epoxy asphalt was applied extensively on long-span bridges, especially on deck paving of steel box girder bridges due to its advanced performance. The research and application on epoxy-asphalt deck paving of steel box girder bridges started late in China and most of the work was mainly conducted on viscosity-temperature curves of asphalt epoxy. While few studies were conducted on its rheology properties. The design of epoxy-asphalt mixture was mainly based on Marshall tests and the optimum asphalt content was determined by volume parameters. There has been a consistent understanding on mechanism, location, development law of fatigue cracking inside the pavement. However, there is no further research conducted on the fatigue performance and fatigue equations of the epoxy-asphalt mix. Moreover, it lacks systematic research on the factors of the asphalt content and grading. Based on current research accomplishments, the following researches were conducted as for the application of epoxy-asphalt mixture on the deck paving of long-span steel bridges through the combination of technology research, theoretical analysis and laboratory tests.The research was mainly conducted on the pavement performance of epoxy mix such as the low-temperature fatigue, high temperature stability, Marshall parameters and so on. While it is lack of viscoelastic property research. The Rheology property research was conducted as for different stresses, strains and time based on dynamic viscoelastic mechanics. The results revealed the creep compliance of the epoxy-asphalt is about 4 orders of magnitude lower than that of the traditional asphalt. Complex modulus decreased with decreasing frequency (the temperature is increasing) and tend to be stable together with storage modulus. While it exhibited some characteristics of viscosity for high frequency (low temperature). Each viscoelastic parameter was far larger than that of the traditional asphalt and modified asphalt and it has good capacity to resist flow and deformation.The main mechanical parameters of epoxy-asphalt mix such modulus and strength gained through experiments were analyzed and discussed. As for dynamic modulus test, the loading test mode was similar to the real state, and the real material stress and strain process under loading was simulated under through dynamic loading test. It was a more suitable modulus for the mechanical analysis on the deck paving comparatively. As for the epoxy-asphalt mix paving under the common temperature, the modus values for mechanical analysis vary between 500～15000Mpa. The maximum tensile strainεB under 15℃was recommended as its limited tensile strain considering the consistency of safety and failure mode. Epoxy-asphalt mixture is a viscoelastic material which is totally different from the traditional asphalt and modified asphalt. The master cure of the epoxy-asphalt mix was got for 40℃and its shape tends to be an“s”style just like the traditional asphalt. However, the magnitude level span was more narrow than the traditional asphalt which indicated relaxation range of epoxy-asphalt mix was relatively lower and its viscoelastic span was more narrow.Based on Finite Element Method (FEM), the mechanical performances and application requirements were analyzed as for deck paving of long-span steel bridges and the sensitivity analysis was conducted on the systematic parameters. The shearing stress within the steel bridge deck paving was analyzed and the results revealed the shearing strength around the paving/bonding layer interface was around 0.5~1.6MPa when the paving modulus varied between 500 and 15000MPa. The epoxy-asphalt could meet the shearing strength requirements of the bonding layer either for high or low temperatures which should be taken for an optimum choice. The results from the paving modulus analysis revealed the modulus change was not in a linear relationship with the horizontal strain change. When the paving modulus was increased from 500MPa to 5000MPa, the horizontal strain was decreased obviously. However, when the paving modulus was around 5000~6000MPa, the paving modulus had an insignificant impact on the horizontal strain. The largest tensile strain inside the structure surface of deck paving with epoxy-asphalt mix was around 300～400μεand the fatigue failure wouldn’t occur under such strain levels. Therefore, mix design should be conducted to solve the fatigue problems confronted with epoxy-asphalt mix. The effect of deck depth on the pavement surface is more significant than the stiffener depth. The integrated optimum design should be conducted economically and technically on the deck depth and stiffener depth. Impact toughness (the area of the load-displacement curve under the impact loading) was proposed as the parameter to evaluate the fatigue performance of the epoxy-asphalt mix based on principles of fracture mechanics and energy. The fatigue performance increased with impact toughness value. The epoxy-asphalt mix design was conducted based on the volume parameters. The asphalt contents were changed while controlling the mix volume indices to observe its pavement performances. The analysis revealed the impact toughness had a linear relationship with residual fatigue modulus which indicated the fatigue performance and the correlation was very good. The impact toughness of the epoxy-asphalt mix can be used for the parameter to evaluate its fatigue performance. The three bending test can be applied for evaluating the mix fatigue performance under the impact loading.更多还原