基于老化的石墨烯/橡胶粉复合改性沥青蠕变特性及微观结构分析

Creep characteristics and microstructure analysis of graphene/rubber powder composite modified asphalt based on aging

为了分析石墨烯掺量以及老化对石墨烯/橡胶粉复合改性沥青蠕变-恢复性能、蠕变参数以及蠕变中瞬时弹性变形、延迟弹性变形以及不可恢复黏性变形等各组成部分相对比例的影响,以不同石墨烯掺量的橡胶沥青为研究对象,采用60℃蠕变-恢复试验,分析其旋转薄膜烘箱(RTFOT)老化和压力(PAV)老化蠕变-恢复性能。首先,基于Burgers模型拟合沥青蠕变变形,为了减少Burgers模型拟合误差,利用蠕变柔量与时间的关系,预估Burgers模型的瞬时弹性模量,进而拟合模型剩余参数;其次,计算各类变形占总体蠕变变形比例,分析石墨烯掺量对不同老化阶段橡胶沥青蠕变变形的影响规律;最后,采用扫描电镜(SEM)观测不同老化程度的橡胶沥青、石墨烯/橡胶粉复合改性沥青微观结构。研究结果表明:RTFOT老化后橡胶沥青的蠕变值显著大于原样沥青,而经历PAV老化后,其蠕变值减小;石墨烯的掺加使得老化对橡胶沥青蠕变值的影响减小;RTFOT和PAV老化后,橡胶沥青及复合改性沥青的瞬时弹性变形所占比例、总体变形比例均有一定程度的减小;RTFOT老化后其延迟弹性变形所占比例显著减小,而黏性变形所占比例增加;PAV老化后其延迟弹性变形所占比例有一定程度的上升;SEM显示,原样橡胶沥青呈现明显的非均质性,老化后橡胶粉颗粒减少,橡胶颗粒呈现溶胀状态;原样石墨烯/橡胶粉复合改性沥青与橡胶沥青微观结构相似,老化后复合改性沥青中出现较大面积的团聚物。

To analyze the influence of graphene content and aging on creep-recovery performance,creep parameters and the relative proportion of elastic deformation,delayed elastic deformation,and irrecoverable viscous deformation.Crumb rubber asphalt with different graphene contents were prepared and subjected to a rolling thin-film oven test(RTFOT)and pressure aging vessel(PAV)aging.Repeated creep-recovery tests of 60°C were applied to the specimen.First,based on the Burgers model,the creep parameters of each asphalt sample were determined.To reduce the fitting error of the Burgers model,the estimation of the instantaneous elastic modulus of the Burgers model was dependent on the relationship between the creep compliance and time.Then,proportions of different deformations for asphalt at different aging stages were calculated and the influence of graphene content on the deformation proportions was analyzed.Finally,scanning electron microscopy(SEM)was performed to observe the microstructure of the rubber asphalt and graphene/rubber asphalt at different degrees of aging.The results show that the RTFOT rubber asphalt presents the greatest creep followed by the PAV asphalt and original rubber asphalt,the effect of aging on rubber asphalt creep is reduced by increasing graphene content,and RTFOT leads to a significant decrease of the delayed elastic deformation proportion.However,its proportion increases to a certain extent after PAV.In addition,the SEM shows that the original rubber asphalt exhibits obvious heterogeneity and the identifiable rubber particles decrease and present a swelling state after aging.The microstructure of the original graphene/rubber asphalt is similar to that of rubber asphalt.However,a large area of agglomerates appears in the graphene/rubber asphalt after aging.4 tabs,13 figs,21 refs.