【作者】 马莉骍；

【导师】 李之达；

【作者基本信息】 武汉理工大学 ， 工程力学， 2012， 博士

【摘要】 道路沥青及沥青混合料作为目前最为重要的路面工程材料,同时又是一种复杂的粘弹性材料,在其长期的使用过程中,由于受到行车荷载、环境、人为等因素的影响会导致沥青路面的性能劣化,减少路面的使用寿命。对沥青及沥青混合料在老化过程中的粘弹性能进行研究,对掌握路面变形规律,预测沥青路面的使用寿命,掌握老化机理有十分重要的意义。本文采用试验室模拟老化和室外自然老化的方法,研究沥青及沥青混合料在老化过程中的粘弹性能、动态粘弹特性和疲劳性能,并结合热力学理论,建立沥青及沥青混合料的本构模型。本文首先采用动态剪切试验研究了老化方式、温度及作用荷载频率等因素对基质沥青和改性沥青的复数剪切模量、相位角等粘弹参数的影响规律。研究结果表明,老化作用使基质和改性沥青的复合剪切模量增大,而相位角降低,沥青呈现出较强的弹性,但改性沥青复数剪切的增加幅度小于基质沥青,说明改性剂可改善沥青的抗老化性能,采用时-温等效原理得到复数剪切模量主曲线,老化可增大沥青的复数剪切模量,使沥青变硬；与基质沥青对比,低温(高频)条件下改性沥青可以改善沥青的低温抗裂性,高温(低频)条件下改性沥青可以改善沥青的高温稳定性。第二,采用动态剪切蠕变试验研究了基质和改性沥青的蠕变特性,并选择合适模型对其粘弹特性进行描述。研究结果表明,基质沥青在各种老化方式后,蠕变总变形和永久变形都随着老化程度的加深而减小,改性剂的掺入一方面能降低沥青加载过程的总蠕变变形,同时又能提高沥青总变形中的弹性变形和可恢复弹性变形成分,使沥青承受外加荷载时产生的永久变形降低；沥青的劲度模量随时间的变化关系可以由幂函数S(t)=Bt(-m)的形式来表征,并建立了沥青的劲度模量与加载时间的函数关系；基于连续介质热力学中的Biot理论,导出了广义Kelvin蠕变型的粘弹性本构方程,采用Burgers模型能有效的描述基质沥青和改性沥青在老化过程中的粘弹特性,拟合曲线与实测曲线相关系数良好。第三,采用动态模量试验对基质沥青混合料和改性沥青混合料老化前后的动态力学参数进行对比研究。研究结果表明,沥青混合料的动态模量随着温度的升高和频率的减小而降低,而相位角在低温时随着频率增大一直减小,在高温时则出现先增加后减小的变化规律；改性剂的掺入使沥青混合料的动态模量增大而相位角降低；用时温等效原理得到不同老化方式下的沥青混合料的动态模量主曲线,结果表明老化使沥青混合料的动态模量在整个频率(或温度)范围内增大。采用间接拉伸疲劳试验评价沥青混合料在老化过程中的疲劳性能,建立5℃和15℃下沥青混合料老化过程中的疲劳寿命方程,在应力控制模式下,随着老化程度的加深,混合料的疲劳寿命增加。最后采用静载压缩蠕变试验对沥青混合料在老化过程中的蠕变特性进行研究,结果表明,温度升高使加载时总变形和卸载后的永久变形增加,老化使沥青混合料的总变形和永久变形减小,混合料的劲度模量和沥青的模量表现出一致的规律,都随着温度的升高而降低,随着老化程度加深而增加,劲度变化速率m值随着温度升高而增大,而随着老化时间的延长而降低；修正Burgers模型能很好的描述沥青混合料在老化过程中的粘弹特性,模型拟合结果与实测数据相关系数达到0.978以上,该模型拟合的结果显示,老化后沥青混合料的弹性系数E1和E2增加,在20℃和40℃下,粘性系数η1增大,而在低温时粘性系数η1减小,这表明老化使沥青混合料高温的抗变形能力增强而低温抗裂性能变差。更多还原

【Abstract】 As the main high-grade construction materials, while at the same time is a complex viscoelastic materials, through a long period of usage, due to the impact of traffic load, natural and human factors will result in the deterioration of asphalt pavements and reduce the service life of the road. The research on the viscoelastic properties of asphalt and asphalt mixtures in the ageing are very important for understanding the deformation law, predicting the service life of asphalt pavement and understanding the aging mechanism. Based on the dynamic mechanical, creep and fatigue damage, the viscoelastic constitutive model of asphalt and asphalt mixtures are establish by combining thermodynamics theoretical in this pape.Firstly, the viscoelastic characteristics of asphalt are study by dynamic shear rheology test in this paper. The effects of ageing type, temperature and loading frequency on the complex shear modulus and phase angle of base asphalt and modified asphalt are investigated. The findings indicate that the complex modulus was increased, while the phase angle was decreased by aged, which suggests that asphalt became more elastic in the process of ageing, which results in the enhancement of resistance to deformation. The complex modulus was increased by aged, but it grew more slowly than base asphalt. Modifier improved the resistance of asphalt, whereas the complex modulus of modified asphalt grew more slowly than base asphalt. Adopting the Time-Temperature equivalence principle, the complex modulus master curves of asphalt in the ageing can be obtained. It suggests that the complex modulus is increased in the whole working frequency or temperature range. In contrast with base asphalt, the modified asphalt in the enhancement of resistance to deformation at a high temperature or low frequency and in the reduction of resistance to crack at a low temperature or high frequency.Secondly, the viscoelastic characteristics of base asphalt and modified asphalt are investigated by the Dynamic Shear Test, and suitable models are selected to describe such viscoelastic characteristics. Results demonstrate that the total and permanent deformation of base asphalts are decreased during loading period. Due to the modifier, the deformation of asphalt is decreased, and the elastic and retardant elastic deformations are increased, which result in the reduction of irrecoverable deformation for asphalt. The relationship of creep stiffness modulus and loading time can be characterized by a power function for asphalt, and a relationship between the stiffness and loading time can be established for asphalt. The elastic strain and inelastic strain are both chosen as state variables. On the basis of Biot theory and by introducing a dissipation potential. Burgers model can be used to describe the viscoelastic characteristics for base and modified asphalt in the process of ageing.Thirdly, the Dynamic Modulus Test is applied to study the dynamic viscoelastic characteristics of base and modified asphalt mixtures. This Study Shows That the dynamic modulus of asphalt mixtures is increased with frequency decreasing and temperature increasing. The phase angle is decreases at a low temperature with the frequency increasing, while the phase angle increases firstly and then decreases with the frequency increasing at a high temperature. Due to modifier, the phase angle is decreased of asphalt mixtures and the dynamic modulus is increased. Adopting the Time-Temperature equivalence principle, the dynamic modulus master curves of asphalt in the ageing can be obtained. It suggests that the dynamic modulus are increased in the whole working frequency or temperature range. An indirect tensile test was used to evaluate the fatigue resistance of the modified asphalt mixtures in the process of ageing, and fatigue predictive equations were found at two temperatures. Results indicate that the fatigue life of asphalt mixtures is increased with the ageing in the stress control mode.Finally, the viscoelastic characteristics of asphalt mixtures in the process of ageing are studied by compression creep test, and suitable viscoelastic models are exerted to describe such properties. It indicates that the total deformation and irrecoverable deformation of mixtures are increased as temperature rise, while the total deformation and permanent deformation are decreased as ageing deepen. The relationship of creep stiffness modulus is decreased as temperature rise, and modulus are increased as ageing deepen. The revised Burgers model is more appropriate to the viscoelastic characteristics research of asphalt mixtures in the process of ageing, and the correlation coefficient reached over0.978. The model demonstrate that the coefficient of elasticity of asphalt mixtures increases, and coefficient of viscosity increases at20℃and40℃and decreases at a low temperature, which result in the enhancement of resistance to deformation at a high temperature and in the reductiont of resistance to crack at a low temperature for asphalt mixtures.更多还原