Research On Short-term Aging Of Asphalt Based On Film Method

Aging will cause the asphalt to become hard and brittle,lose bonding performance and reduce the service life of pavement.Short-term aging is the shortest and most rapid stage of the aging process.It represents aging of storage,transportation,mixing,paving and other construction processes after the asphalt is processed.Simulation of asphalt aging is a procedure in asphalt characterization for predicting actual aging under controlled laboratory conditions.Thin film oven(TFO)test and rolling thin film oven(RTFO)test were usually used to simulate asphalt short-term aging.However,the aging time of TFO is long and the aging is limited to the surface.RTFO could not be applied to modified asphalt with high viscosity,and glass bottles are difficult to clean.Whether the above two methods can equivalently simulate the actual short-term aging remains to be verified.In view of this,a short-term aging method with convenient experiment,easy cleaning and strong applicability was proposed in this study.47 sets of aging tests were carried out under different asphalt film thicknesses,aging temperatures and aging times.The aging degree of asphalt was studied by Dynamic Shear Rheometer(complex shear modulus,phase angle,critical temperature)and Fourier Transform Infrared Spectroscopy(sulfoxide index).The short-term aging equation considering different aging conditions is established,and the field short-term aged asphalt is extracted from asphalt mixture at a construction site.The relationship between laboratory and field short-term aging is built to guide practical engineering.Firstly,the proposed short-term aging method is preliminarily tested and validated.In this study,Dynamic Shear Rheometer(DSR)and Fourier Transform Infrared Spectroscopy(FTIR)were used to analyze the aging asphalt,so as to determine the aging mould and specific test steps.The results show that FTIR has a large error in quantitative analysis,so DSR is used to quantitatively characterize the aging degree of asphalt in this study.Then,the aging tests of asphalt with different film thickness,aging temperature and aging time were carried out according to the experimental steps of short-term aging method.It was found that the aging rate of asphalt could be expressed by an improved Arrhenius equation.The equation shows that the aging rate is closely related to aging temperature and film thickness.Three short-term aging equations are established.Because complex shear modulus and phase angle are based on a fixed test temperature,and critical temperature is a global parameter,which can effectively avoid the diversity of results caused by material temperature sensitivity.The critical temperature parameter is recommended for the development of short-term aging equation in this paper.The applicability of other source of base asphalt,SBS modified asphalt and crumb rubber modified asphalt to the critical temperature aging equation was studied.It was found that the equation has good applicability,and further showed that the aging rate of asphalt was not affected by asphalt sources and modifiers,but related to aging temperature and film thickness.Finally,filed short-term aged asphalt was extracted from asphalt mixture at a construction site using a method without losing asphalt performance.It was found that RTFO could not simulate short-term aging in the field.150?-900?m-179 min is recommended as a short-term aging simulation method for base asphalt.And 170?-900?m-127 min is recommended as a short-term aging simulation method for SBS modified asphalt with Warm Mix Asphalt(WMA)additives.