Research On Preparation And Performances Of Direct Coal Liquefaction Residue Modified Asphalt

Direct Coal Liquefaction Residue(DCLR)is the by-product of Coal to Liquid(CTL)technology.It can be developed as an asphalt modifier.According to the physical properties of DCLR,pre-treated methods were applied to DCLR,and the asphalt was modified by Tetrahydrofuran Soluble(THFS)which was extracted from DCLR.Firstly,the preparation process of THFS modified asphalt was studied and its properties were evaluated in this paper.Based on orthogonal test and grey relational degree analysis,the optimum preparation process of THFS modified asphalt was determined: the shear temperature was 150 oC,the shear time was 45 min,and the shear rate was 4000 r/min.It was also found that the high-temperature properties of THFS modified asphalt were improved while the low-temperature properties were declined.As a result,the THFS content was recommended as 6%.The microstructures of THFS modified asphalt were characterized by using compositions analysis,elements analysis,gel permeation chromatography and infrared spectroscopy.The test results showed that the molecular weight and colloid unstable coefficient Ic of THFS modified asphalt became larger with the THFS content increased.However,the element composition and new functional group of THFS modified asphalt was not changed which indicated the THFS asphalt modification was physical modification.Secondly,the rheological behaviors of THFS modified asphalts were studied in this paper.Through the temperature scanning and frequency scanning test,combining with the CAM model,the test results demonstrated that the high-temperature properties of THFS modified asphalt were improved but the low-temperature properties and resistance to fatigue were decreased with the THFS content increased.Accordingly,the application scopes of THFS modified asphalt were limited.When the THFS content was less than 6%,the modified asphalt could be applied to the middle and lower surface layer of asphalt pavement.Thirdly,multi-indexes were used to evaluate the temperature susceptibility of THFS modified asphalt,and the test results showed that the temperature susceptibility of asphalt was improved by adding THFS.Meanwhile,the anti-aging properties of THFS modified asphalt were also evaluated.It was found that the RPR(Residual Penetration Ratio)and RD(Residual Ductility)were decreased,the SPI(Softening Point Increment)and RVR(Residual Viscosity Ratio)were increased with the THFS content increased.Based on the aging kinetics method and the microstructure of THFS modified asphalt,the first-order kinetics equation of THFS modified asphalt was established.It was found that the aging rate k,the colloid unstable coefficient Ic and the ratio of carbonyl absorption peak area were increased,but the activation energy Ea was decreased with the THFS content increased.Thus,the anti-aging properties of THFS modified asphalt were deteriorated after adding THFS.Finally,dioctyl maleate(DOM)was used to improve the low-temperature properties of THFS modified asphalt in this paper.It was found that DOM could improve the low-temperature properties,resistance to fatigue,temperature susceptibility and anti-aging properties of THFS modified asphalt,but decline the high-temperature properties of THFS modified asphalt.The optimum THFS and DOM content was recommended as 6% THFS+1%DOM.Economic and environmental benefits analysis on the THFS modified asphalt indicated that the appilication of THFS composite modified asphalt could not only reduce the cost,but also reduce oil consumption,greenhouse gas emissions.