Study On Physical Modification And Performance Of Coal Tar Pitch

As the residue of coal tar after distillation,coal tar pitch adheres with aggregates excellently,and the road surface exhibits higher friction coefficient than petroleum asphalt.On the other hand,it is more sensitive to temperature,ductility is poor,security is low and aging resistance is especially bad,which limit its application in road construction.In this paper,coal tar pitch was modified with intercalated kaolinite and petroleum asphalt.The aging properties of modified coal tar pitch were studied in details and the aging mechanism was analyzed by IR.Raw kaolinite was first intercalated with dimethyl sulfoxide?DMSO?under ultrasonic field,and the structure and morphology of intercalated kaolinite were researched.The results show that the hydrogen bonds between aluminum hydroxyl and silicon oxygen bond are weakened because of DMSO intercalation,the interlayer space of kaolinite expands from 0.716nm to 1.124nm and the intercalation rate reaches 98.57%.After composited with coal tar pitch,the dispersed thin layers were stripped off from the original stacked pseudo-hexagonal plates,which means the kaolinite is delaminated.The aging properties of modified coal tar pitch were tested based on GB standards.The results reflect that when the dosage of kaolinite is 6wt%,the penetration ratio is 50.4%and the ductility at 15?reaches 26.7cm while the penetration ratio is only 35.3%and the ductility is 20.4cm for raw coal tar pitch,which indicate that oxidation was weakened in the aging process.This result was further confirmed by IR spectroscopy that compared with raw coal tar pitch,the increasing extent of carbonyl is reduced by 80.0%and the sulfoxide is reduced by 32.4%for modified coal tar pitch.The delaminated kaolinite might improve the anti-aging property in the way of obstructing air access and delaying air transmission.At the same time,intercalated kaolinite improves thermal stability of coal tar pitch,and the accumulative weight loss of modified coal tar pitch at 650?decreases from 85.41%to78.04%.To further improve the properties of coal tar pitch,it was modified with petroleum asphalt and aromatic oil.The penetration reaches the maximum value 63.7 10^-1mm when the heating time is 3h and ductility reaches the maximum value 115.3cm at heating temperature of 110?.With the increase of petroleum asphalt content,the softening point decreases gradually,but the penetration and ductility increase.After aging,the penetration ratio and ductility show a parabolic variation.When the asphalt content is 18wt%,the penetration ratio is 56.1%and the ductility is 29.4cm,both reaching the maximum value.Then composited with intercalated kaolinite,the integrative modified coal tar pitch can reach the technology of 70^#road asphalt.