基于核壳结构缓释剂和抗氧化剂的新型复合沥青抗老化剂研究

Development of Long-lasting Antiaging Additives for Recycled Asphalt Binders

我国每年的沥青路面回收料已经接近亿吨,同时回收料的使用率不断提高。沥青旧料回收利用的关键步骤是老化沥青的再生过程,而其中添加剂的选择和使用是影响再生后沥青混合料工程性质和沥青路面路用性能的关键因素。传统的沥青再生剂可以得到瞬时的沥青还原效果,但是无法延长再生后沥青的使用寿命。相较而言,用于回收沥青的长效抗老化剂是提高再生沥青路面耐久性的有效解决方案,但目前鲜有抗老化剂在沥青再生工艺中的实验室研究和实际应用。本研究探索了利用一种抗氧剂和一种缓释剂作为复合抗老化添加剂,通过实验室模拟沥青长期老化,评价其对典型回收沥青的抗氧化老化效果。选用的抗氧化剂分别为Irganox和木质素磺酸盐,同时合成的缓释剂分别为包裹食用植物油和商业再生剂油的聚苯乙烯微胶囊。未改性的基础回收沥青和四种抗氧化剂改性沥青通过压力反应釜进行60 h的长期高温高压老化,并利用动态流变剪切仪(DSR)对未改性沥青和抗老化剂改性沥青老化前后的粘度、衍生延度和SHRP流变指标进行分析。结果表明,本研究采用的四种复合抗老化剂均可以有效控制沥青老化过程中的物理性质变化。商业再生剂微胶囊和木质素磺酸钠的复合添加剂表现出最好的效果,可以减缓22.4%的沥青老化硬化速率和27%的延度下降速率,而商业再生剂微胶囊和Irganox的复合抗老化剂次之,可以减缓21.3%的沥青老化速率和19.5%的延度下降速率。相比之下,由植物油再生剂微胶囊和抗氧化剂组成的抗老化剂只减缓了10%的沥青粘度上升速率并且加快了沥青延度的下降趋势,但可以提供相对较高的车辙因子。最后,通过对沥青老化过程中红外光谱的变化研究,发现抗老化剂对羰基和亚砜产物的生成控制是抑制沥青物理老化的驱动力,四种抗老化剂均显示了瞬时的亚磺酰基氧化反应控制作用。本工作所建议的抗老化剂方案解决了以往沥青抗老化剂缺乏长效性的缺点,能够有效延长再生后沥青路面的路用寿命。同时本研究提供的复合抗老化剂组成思路可以选用其他环保材料,以帮助推广新型抗老化剂在沥青回收路面可持续再生过程中的应用。

In China,about one hundred million of reclaimed asphalt pavement(RAP)are produced every year.Worldwide,the length of asphalt pavements and amount of recycled asphalt pavement also grow continuously.Additives have been used to improve the performance of asphalt pavements with high RAP content,such as rejuvenation agent and antiaging agent.Compared with the rejuvenators,antiaging modifiers receive little attention in current asphalt recycling industry because the conventional antiaging agents provide limited anti physical hardening performance and are usually cost-intensive.Therefore,there is a great need to develop effective and long-lasting antiaging additives for recovered asphalt binders.This study aims to develop new complex asphalt antiaging agents that contain both antioxidants and microcapsules in order to prevent the physical hardening of asphalt binder by both obstructing the chemical oxidation reaction and sustainably releasing the rejuvenation oil.The antioxidants involve the commercial antioxidant Irganox and sodium lignosulfonate.The microcapsules are prepared by polystyrene-shell and two type of oil-core materials:cooking vegetable oil and commercial rejuvenation oil using phase separation method.SEM shows that the microcapsules are successfully synthesized.The base asphalt binder and modified asphalt binders are treated by a pressure aging vessel(PAV)to simulate the long-term aging of asphalt binder,then measured by the dynamic shear rheometer(DSR).Results show that the four antiaging additives developed can effectively slow down the physical hardening of asphalt binders.Overall,the additive with microcapsules containing rejuvenation oil and sodium lignosulfonate demonstrates a superior antiaging performance,which reduces 22.4%of the asphalt hardening rate and 27%loss rate of asphalt ductility.The second ranked antiaging additive includes the microcapsules with commercial rejuvenation oil core and Irganox antioxidant,which results in a 21.3%reduction of physical hardening and 19.5%reduction of losing durability.By comparison,the aging additives containing cooking vegetable oil microcapsules present a lower performance in reduction the viscosity of asphalt binder and conversely increase the loss rate of asphalt ductility.On the other hand,the two antiaging additives containing rejuvenation oil microcapsule provide a better fatigue resistance but a lower rutting stabi-lity,which is opposite to the antiaging additives containing cooking oil.By analyzing the change of functional groups during oxidation process,results indicate that the control of carbonyl and sulfoxide products is the key to the physical anti-aging of asphalt binder,and the prevention of physical aging is more relied on controlling the production of sulfoxides.The design of antiaging agents in this study is proved to provide sustainable softening and rejuvenation effects to recycled asphalt binder,and has high potential to be developed into mature technologies that benefit the road and highway construction industry as well as environmental conservation.