【作者】 庞凌；

【导师】 吴少鹏；

【作者基本信息】 武汉理工大学 ， 材料学， 2008， 博士

【摘要】 沥青在使用过程中的老化,导致沥青路面性能劣化,影响了路面的使用寿命。太阳光中的紫外光辐射是引起沥青在路面服务期间发生老化的主要自然因素之一,尤其在海拔较高的强紫外光辐射地区。对沥青在紫外光老化过程中的老化机理、流变特性、路用性能及残余疲劳寿命进行深入系统的研究,可以为评价和预测沥青的抗紫外光老化性能提供理论基础和技术指导。(1)应用红外光谱分析和流变学方法相结合,研究了紫外光辐射强度、温度、沥青试样膜厚、老化时间等因素对室内沥青加速紫外光老化模拟试验结果的影响规律,优化了室内加速紫外光老化模拟试验条件。研究发现,紫外光辐射强度越高,沥青的羰基指数增加速度越快,即沥青的氧化速度越快;紫外光老化主要发生在沥青的表层,当沥青膜厚小于200μm时,紫外光老化对沥青流变性能和老化特征官能团的影响较大。(2)采用四组分、红外光谱等现代分析技术,研究沥青在紫外光老化过程中发生的化学组成变化。研究结果表明:紫外光老化后沥青的羰基和亚砜基指数显著增加,产生了更多的极性官能团,导致形成了更多的分子量相对较大的沥青质,其胶体结构更趋凝胶型;SBS改性沥青中,紫外光老化除了导致其基质沥青中含氧极性官能团的增加外,还使得丁二烯官能团含量减少,SBS改性剂裂解,这两种反应过程决定了SBS改性沥青紫外光老化后的化学组成结构。(3)核磁共振氢谱研究发现,沥青在紫外光老化过程中发生了异构化、脱烷、裂解等化学反应。(4)沥青的原子力显微镜图显示,沥青在老化过程中的化学组成结构的变化引起了沥青表面微观结构形态的改变;老化使基质沥青中沥青质缔合结构增大,SBS改性沥青的网络结构消失,SBS改性沥青的表观形态向基质沥青靠近;SBS改性剂的引入,可以部分的改善老化沥青中沥青质的分布状况;沥青的原子力显微镜测试结果与沥青的四组分分析、傅立叶红外光谱分析及核磁共振氢谱分析结果具有很好的相关性。(5)利用美国SHRP研究成果推荐的布氏粘度、动态剪切流变仪等技术手段,研究紫外光老化对沥青流变性能、路用性能的影响。研究结果表明:紫外光老化使沥青粘度增加、温度敏感性降低,在低温情况下,老化的增粘效应较高温条件下明显;紫外光老化作用显著增大了沥青复合剪切模量G~*并降低了相位角δ,使沥青变硬;紫外光老化使SBS改性沥青的相位角平台区逐渐向高温方向移动,最后消失。(6)通过对沥青试样反复施加恒定应变,进行DSR时间扫描疲劳试验,测试其残余疲劳寿命。试验结果表明,紫外光老化使沥青的残余疲劳寿命急剧降低,且紫外光老化对沥青疲劳性能的影响比其他技术性能的影响大。(7)SBS改性沥青对基质沥青路用性能的改良作用随着紫外光老化时间的延长逐渐降低,但在各老化条件下其路用性能仍好于基质沥青。(8)沥青老化前后技术指标变化幅度研究结果表明:短期的紫外光老化就比PAV老化严酷;与PAV老化试验相比,室内加速紫外光老化与自然暴露紫外光老化试验之间具有更好的对应关系。更多还原

【Abstract】 Oxidation degradation causes hardening of asphalt and, consequently, may make a contribution to the deterioration of asphalt pavements. The principal reason of asphalt oxidation and embrittlement during service period is ultraviolet radiation in sunlight, especially in the high elevation areas where there is intensive ultraviolet radiation. The profound researches on the mechanism of photooxidation, rheological properties, service performance and retained fatigue life of asphalt binder, under the condition of ultraviolet radiation, are important for evaluating and forecasting the photooxidation resistance of asphalt.(1) Fourier Transform Infrared (FTIR) and Dynamic Shear Rheometer (DSR) were used to investigate the dominant effect factors in the indoor accelerated ultraviolet radiation (UV) ageing test, including ultraviolet radiation intensity, temperature, sample thickness and ageing time. Based on the estimation of the environmental conditions, a suitable ultraviolet radiation ageing condition was chosen for UV test. The higher the ultraviolet radiation intensity was, the faster the speed of carbonyl index increased. The effect of UV radiation was dominant, in particularly when the film thickness was smaller than 100μm.(2) By methods of four components analysis and FTIR, the influences of ultraviolet radiation ageing on chemical structural evolutions of asphalt binders were investigated. Results indicated that the carbonyl and sulphoxide indices of asphalt increased remarkably, resulting in more polar groups and the fraction of asphaltenes after ultraviolet radiation ageing as well as the formation of gels. With respect to the aging of SBS modified asphalt, there were more carbonyl and sulphoxide groups but less chain segments of butadiene. The analysis of FTIR spectra demonstrates that oxidation of base asphalt and degradation of SBS modifier occurs in parallel during ageing, which contribute to the changes on the chemical structure of SBS modified asphalt after ageing.(3) By ~1H Nuclear Magnetic Resonance (~1H NMR), test results show that during the ultraviolet radiation ageing process, several chemical reactions were occurred including isomerization, dealkylation and dissociation.(4) Using Atomic Force Microscopy (AFM), test results indicate that the distinct changes of asphalt in surface morphology occurred as a result of chemical structure changes during ageing. Due to ageing, asphaltene aggregates in base asphalt become larger, and network structure in SBS modified asphalt was disappeared and the surface morphology of SBS modified asphalt became close to base asphalt. The existence of SBS can only partly improve the dispersion of asphaltenes in bitumen after ageing, in consistence with the results of four components analysis, FTIR and ~1H NMR analysis.(5) Based on Brookfield viscosity and DSR tests, the effects of ultraviolet radiation ageing on the rheology and pavement performances of asphalt were investigated. Results indicate that viscosity of asphalt was enhanced, particularly in low temperature when compared to high temperature. The temperature sensibility was weakened after ultraviolet radiation ageing. The complex modulus was increased, while the phase angle was decreased, and the aged asphalt became hard. The flat area of phase angle of SBS modified asphalt was moved to high temperature area and then disappeared with the extension of the ageing time.(6) DSR time sweep fatigue test in constant strain was conducted to study the fatigue life of asphalt. Results indicate that ultraviolet radiation ageing caused the decrease of fatigue performance distinctly, and the influence of ultraviolet radiation on fatigue life of asphalt was the greatest among other factors.(7) SBS modifier improved the performance of base asphalt, while the improvement effect reduced gradually with the ageing time, whereas the property of SBS modified asphalt was still better than that of base asphalt.(8) The short-term ultraviolet radiation ageing may be stronger than PAV ageing that is recommended to assess the long-term ageing effect. It is especially true in the high latitude regions where the solar radiation is expected to be very strong. At the same time, compared with the PAV experiment, the UV test has a better corresponding relationship with the outdoor Natural Exposure Ageing (NEA) test.更多还原