Interaction Mechanism And Rheological Properties Investigation Of Waste Cooking Oil Pre-Desulfurized Crumb Tire Rubber Modified Asphalt

The performance improvement and industrialization promotion of Asphalt Rubber are restricted due to the storage stability problem.The compatibility of crumb tire rubber（CTR）and asphalt can be improved by desulfurization and degradation of CTR in high temperature asphalt via Terminal Blend technology.However,combustion and explosion prone to occur due to the volatilization of light component in asphalt after long-term high-temperature stirring,as well as asphalt aging.Based on the Terminal Blend technology,the ideas and research results of desulfurized CTR modified asphalt and bio-asphalt,and in view of the shortcomings of existing CTR modified asphalt technology,waste cooking oil（WCO）was proposed because of its advantages with high flash point,economy and environmental protection,to instead of asphalt for desulfurization and degradation of CTR in advance.And then re-crosslink reaction takes place after the addition of pre-desulfurized CTR product,styrene-butadiene-styrene block copolymer（SBS）and sulfur into virgin asphalt to prepare pre-desulfurized CTR modified asphalt with excellent performance and storage stability in this research.The stages of WCO pre-desulfurized CTR and re-crosslink of modified asphalt involve complex chemical reactions,which have an important impact on the rheological properties of modified asphalt.In order to understand,apply and promote the WCO pre-desulfurized CTR modified asphalt technology,the in-depth systematic researches on the interaction mechanism and rheological properties of modified asphalt in the process of pre-desulfurized CTR modified asphalt were conducted.In the stage of desulfurization and degradation of CTR in WCO,the reaction process was characterized from multi-angle by combined usage of multiple macro and micro analysis.The desulfurization and degradation of CTR were revealed by using particle size of CTR,microstructure,chemical component,molecule weight size and distribution,molecule structure and rheological properties.The desulfurization processing was selected preliminarily based on the degree of desulfurization and micro chemical analysis.In order to avoid the growth of soluble molecule chain caused by long-term treatment under high mass ratio of CTR and WCO,2 hours of the desulfurization time is recommended when the desulfurization temperature at the range of 240 to 280℃.The relationship between physicochemical state of the pre-desulfurized CTR and the rheological properties of the modified asphalt under different preparation processings were explored via rheological tests.It is found that both light component volatilization and continuing desulfurization of CTR exist at the asphalt modification of pre-desulfurized CTR with a lower desulfurization degree.The effects of pre-desulfurization degree of CTR on the rules of rheological properties of modified asphalts are quite different under different preparation temperatures.The concept of stable pre-desulfurized CTR was proposed in terms of this phenomenon.According to the two-way feedback of the CTR pre-desulfurization processing and mid-temperature performance of the modified asphalt,the stable pre-desulfurized CTR was obtained after 2 hours of desulfurization and concentration for 2 hours.The use of composite SBS and sulfur not only retains the softening and desensitizing effect of pre-desulfurized CTR,but also continues the toughening and elasticizing effect of SBS,and the pre-desulfurized CTR composite SBS modified asphalt with balanced,excellent high-and low-temperature rheological properties can be obtained at the usage of 4 wt.%SBS and 0.4 wt.%sulfur.The time-sweep test,rheological master curve and multi stress creep recovery test were used to investigate the wide-temperature rheological properties and rutting resistance at damage condition of the stable pre-desulfurized CTR and its composite modified asphalt.And the rheological properties under different aging stages were studied,the essence of aging performance attenuation was revealed from a microscopic perspective.It is found that the pre-desulfurized CTR plays an elastic toughening effect in the high temperature and low frequency region,and improves the viscosity ratio in the low temperature and high frequency region.In the damage condition,pre-desulfurized CTR supplements the elasticity of asphalt,but it does not perform enough under overload condition.SBS can improve the deformation resistance of pre-desulfurized CTR modified asphalt under slow speed load,and crack resistance under high speed load.The anti-deformation ability of pre-desulfurized CTR composite SBS modified asphalt under high temperature and overload condition is greatly enhanced with the existence of sulfur.Pre-desulfurized CTR can significantly improve the aging resistance of modified asphalt.The cross-linked structure formed in pre-desulfurized CTR composite SBS modified asphalt significantly reduces the oxidation degree of the binder system and inhibits the degradation of polymer molecules,the high-and low-temperature rheological properties after aging have been effectively improved.With the help of micro chemical analysis methods,the interaction mechanism of total process of pre-desulfurized CTR modified asphalt was revealed,and the effect rules of microscopic parameters on macroscopic rheological properties were explored.It is found that the aromatization of rubber molecule,the stabilization of sulfoxide group and the destruction of amide generally exist in the pre-desulfurized CTR modified asphalt.The increase in the aromaticity and the decrease in oil molecule improve the deformation resistance of the modified asphalt at high temperature,but the low temperature crack resistance is damaged.SBS can chemically combine with residual oil molecule and rubber molecule chain to improve high-temperature performance of the modified asphalt,but it cannot form a stable colloidal system with pre-desulfurized CTR and virgin asphalt.Sulfur can promote the re-crosslink reaction between SBS,pre-desulfurized CTR and virgin asphalt to form a uniform and stable colloid system,improve the relative molecular weight of macromolecular phase,and greatly improve the high temperature deformation resistance and deformation recovery ability of composite modified asphalt.The thermal storage stability of stable pre-desulfurized CTR and its composite modified asphalt was studied through rheological tests and fluorescence images,and it is confirmed that WCO pre-desulfurization technology can achieve stable dispersion of CTR.In the presence of sulfur,the pre-desulfurized CTR composite SBS modified asphalt can be stably stored at high temperature,and the composite modified asphalt can achieve storage stability when the virgin asphalt sources are different.The segregation indexes R_Sδand R_STC suitable for evaluating the storage stability of composite modified asphalt were proposed.When|R_Sδ|≤0.2 and R_STC≤0.15,the storage stability of composite modified asphalt is qualified.Finally,the road performance of pre-desulfurized CTR modified asphalt mixture was evaluated,and it is found that the preferred pre-desulfurized CTR composite SBS modified asphalt has excellent high-temperature rutting resistance,low-temperature crack resistance,water damage resistance and fatigue performance.It is demonstrated that the WCO pre-desulfurization technology and composite modified asphalt technology proposed through research in this study have important engineering guidance significance for obtaining high-performance CTR modified asphalt and its asphalt mixture.