Study On The Properties Of The Warm Mix Asphalt On Plateau Regions

In comparison with the conventional hot mix asphalt technology,warm mix asphalt technologies,with the advantages of lower mixing temperature,lower emissions and less energy consumption,are more suitable for the plateau regions where there are shorter construction sessions and fragile eco-systems.The service life of the flexible pavement structures on the plateau regions is significantly reduced due to the strongly photo-oxidation of asphalt binder which is caused by the high ultraviolet radiation intension.Nevertheless,the previous studies mainly focused on the ultraviolet aging of hot mix asphalt binders(including modified hot mix asphalt binders),although the application of warm mix asphalt in these plateau regions might be more potential.Given this,it is necessary and meaningful to evaluate the ultraviolet aging of the warm mix asphalt binder.In this paper,the aging mechanisms,including the heat-oxidation and photooxidation,of the asphalt binder and the properties of the ultraviolet rays were comprehensively reviewed and summarized.The advantages and disadvantages of the previous research methodologies and the corresponding aging equipment for the ultraviolet aging of asphalt binder and asphalt mixture were analyzed.On the foundation of the literature review,a custom-designed aging chamber were developed and the specific asphalt sample preparation methods for in-door ultraviolet aging were proposed.The temperature sensitivities of the ultraviolet aging properties of the 60/70 and SBS modified PG 76 were characterized using the Fourier Transform Infra-Red spectroscopy(FTIR)and the dynamic shearing rheometer(DSR).The changes of the warm mix additives,i.e.,Sasobit and Evotherm 3G were identified.To evaluate the effects of the light fractions and warm mix additives on the ultraviolet aging of the asphalt binder,fresh 60/70,short-term aged(STA)60/70,STA Sasobit and Evotherm 3G warm mix asphalt binder were ultraviolet aged in laboratory and the corresponding changes of their rheological properties and chemical fractions were characterized using DSR and FTIR,respectively.An asphalt mortar preparation method was introduced and the rheological tests were performed for determining the changes of its properties before and after aging.Based on the experimental results,the following conclusions can be obtained:The photo-oxidation contribution rate,a part of the ultraviolet aging,increases because of temperature increasing;After ultraviolet aging the changes of the Sasobit are not significant while it of Evotherm 3G are significant;After ultraviolet aging,the changes of the fresh asphalt binder and Sasobit warm mix asphalt binder in chemical properties and rheological properties are significant;andThe rheological properties of the asphalt mortar cannot be significantly changed after ultraviolet aging.In addition,the limitations of the experimental methodologies and apparatus were analyzed in this paper.The further study area was discussed at the end of this paper.