Study On Low-temperature Performance Of Direct Coal Liquefaction Residue Modified Asphalt

Direct coal liquefaction residue is an inevitable by-product of direct coal liquefaction technology.The traditional way is to treat it directly as waste or burns with coal-coking products.After research it is found that DCLR can be developed into a asphalt modifier of road that can turned its into a benefit.Due to the differences of physical properties and composition between DCLR and petroleum asphalt,the low-temperature performance of DCLR modified asphalt is poor.In order to ensure the low-temperature performance of DCLR modified asphalt and can disperse uniformly and stably in asphalt phase for a long time.This paper will select five different types of compatibilizers to improve its low-temperature performance,and use different evaluation methods of low-temperature performance(Double-Edge-Notched Tension test,Extended Bending Beam Rheometer test,analysis viscoelastic parameters of Burgers model)to study its low-temperature performance.Firstly,five kinds of compatibilizers(aromatic oil,kerosene,benzaldehyde,silane coupling agent and xylene)were selected in this paper.Based on their material properties,the best preparation technology of DCLR modified asphalt containing compatibilizer was determined by the experimental design and mathematical analysis,and considering the influence of compatibilizer types,content and shear time on the comprehensive performances of DCLR modified asphalt.Secondly,based on the theory of fracture work,the low-temperature performance of DCLR modified asphalt with different compatibilizers was characterized by the Double-Edge-Notched Tension test.It was found that the addition of compatibilizers would affect the tensile flexibility of asphalt to a certain extent,and the appropriate compatibilizers could significantly reduce the possibility cracking inside the DCLR modified asphalt.At the same time,based on the technology of SEM and the microstructure analysis of six kinds of DCLR modified asphalt by image processing software shows that the addition of compatibilizer can affect the dispersion of DCLR in asphalt,and help DCLR to disperse evenly and stably in asphalt,it can avoid the aggregation of DCLR in asphalt to some extent.Thirdly,the effect of physical hardening on the low-temperature performance of DCLR modified asphalt was studied by the macro and micro combination of Extended Bending Beam Rheometer test and AFM.The results show that continuous low temperature is an important reason for the physical hardening of asphalt.The lower the ambient temperature is,the more significant the physical hardening is.The occurrence of low temperature physical hardening results in the reliability of the low temperature grade of asphalt to decrease.The temperature and the duration of the low temperature jointly determine the loss of the low temperature grade of asphalt.At the same time,the continuous low temperature will induce the wax crystallization,aggregation of asphaltenes,resins and so on will destroy the asphalt phase equilibrium system and form a beehive structure with increased body state,which is more likely to produce stress concentration.The addition of compatibilizer can reduce the loss of low temperature grade of DCLR modified asphalt to some extent,weaken the adverse effect of physical hardening on the low-temperature performance of asphalt,and avoids early or excessive cracking of asphalt in the actual pavement environment.Finally,based on the joint analysis of the viscoelastic parameters evaluation indexes of burgers model at low temperature,it can be found that the addition of compatibilizer can improve the stress relaxation ability of asphalt,release and dissipate the excessive accumulated energy in the asphalt rapidly,so as to reduce the storage of energya,improve the low-temperature performance of DCLR modified asphalt.Combining with the above macro and micro test methods and the verification analysis of the mathematical model,it can be determined that the effect of five compatibilizers on the low-temperature performance of DCLR modified asphalt is in the order of aromatics oil > silane coupling agent > benzaldehyde > kerosene>xylene.