蓖麻基生物油对不同老化程度沥青的再生作用

Rejuvenation effect of castor-based bio-oil on asphalt with different aging levels

为探究蓖麻基生物油对不同老化程度沥青的再生作用,首先,制备了TFOT 2.5 h(T2.5)、TFOT 5.0 h(T5.0)和PAV 20 h(P20)这3种老化沥青,以针入度恢复至未老化水平为依据,确定了不同老化沥青再生所需的生物油最佳掺量;然后,分析了老化及再生沥青的基本路用性能与流变特性;最后,借助傅里叶变换红外光谱(FTIR)与原子力显微镜(AFM),分析老化及再生沥青的特征官能团及微观结构特性,阐述了蓖麻基生物油对老化沥青的再生机理。研究结果表明:3种老化沥青针入度和软化点指标均可恢复至未老化水平,但延度偏小且黏度、活化能偏大;在流变特性方面,与未老化沥青相比,在保证高温性能的前提下,生物油再生沥青具有较低的蠕变劲度S和较高的蠕变速率m;其中,P20老化沥青经生物油再生后,低温等级降至PG-28,表现出良好的低温柔韧性;生物油对老化沥青疲劳性能同样具有较强的再生及恢复能力,其中,P20经生物油再生后的疲劳寿命已显著大于未老化沥青的疲劳寿命。生物油中的脂肪酸含有大量羰基,因此,FTIR羰基指数无法用于评价生物油对老化沥青的再生作用;生物油富含的轻质组分会有效溶解和稀释沥青中的老化产物,使沥青胶体结构重新稳定,从而使得老化沥青的性能得到有效恢复。

To investigate the rejuvenation effect of castor-based bio-oil on asphalt with different aging levels,firstly,three aged asphalts,i.e.,TFOT 2.5 h(T2.5),TFOT 5.0 h(T5.0),and PAV 20 h(P20)were prepared.Based on the recovery of the penetration degree to the non-aging level,the optimal mixture of bio-oil required for the regeneration of different aged asphalt was determined.Secondly,basic pavement performance and rheological properties of aged and rejuvenated asphalts were analyzed.Finally,functional groups and microstructure characteristics of aged and rejuvenated asphalts were analyzed by Fourier-transform infrared spectroscopy(FTIR)and atomic force microscopy(AFM),and thus the rejuvenation mechanism of castor-based bio-oil on aged asphalt was revealed.The results show that bio-oil rejuvenated asphalts have the same softening point and penetration as that of the unaged asphalt,but have lower ductility and higher viscosity as well as activation energy.In terms of rheological properties,compared with unaged asphalt,bio-oil regenerated asphalts have lower creep stiffness S and higher creep velocity m on the premise of ensuring high-temperature performance.Among them,the low-temperature grade of bio-oil rejuvenated P20 decreases to PG-28,which shows good low-temperature flexibility.Bio-oil also has good restoration and recovery ability for the fatigue performance of aged asphalts,among which the fatigue life of bio-oil rejuvenated P20 is significantly higher than that of unaged asphalt.Since the fatty acids in bio-oil contain a large number of carbonyl groups,the FTIR carbonyl index cannot be used to evaluate the rejuvenation effect of bio-oil on aged asphalts.The abundant light components in bio-oil can effectively dissolve and dilute the aging products in asphalt,and restabilize the asphalts'colloid structure,thus restoring the properties of the aged asphalts effectively.