Preparation Of Diffusible Rejuvenator And Its Influence On Performances Of Recycled Bitumen And Recycled Asphalt Mixture

The recycling of reclaimed asphalt pavement (RAP), which can protect the environment and conserve nonrenewable resources, is a recycling technology for asphalt pavement in conformity with the principle of sustainable development. The road performance of RAP deteriorates due to the ageing of bitumen wrapping around the surface of reclaimed aggregates, thus the diffusing of rejuvenator into the aged bitumen, which can restore the properties of aged bitumen by reconstituting the chemical component and colloidal structure, is crucial to the road performance enhancement of recycled asphalt pavement. However, the diffusibility of rejuvenator is commonly not considered highly, making the diffusibility of rejuvenator too poor to improve performance of recycled asphalt mixture effectively, therefore the the popularization and application of recycled asphalt mixture in high-grade highways is restricted. Therefore it is necessary to develop a rejuvenator with good diffusibility for the popularization and application of recycling of RAP.Based on the theories of dissolving-diffusion and chemical component reconstituenting, catalytic cracking slurry and chemical oil with epoxide group were selected as chemical component reductant and penetrant respectively for the preparation of diffusible rejuvenator. Influence of penetrant on the diffusibility of rejuvenator was investigated; asphaltenes dissolving experiment and infrared spectrum were employed to explore the mechanism of penetrant on the diffusibility enhancement of rejuvenator. Effects of rejuvenator on the properties of recycled bitumen and recycled asphalt mixture were studied. The main conclusions are as following:(1) Based on influence of rejuvenator diffusing on the penetration and chemical components of aged bitumen, a new method, which employs the changing of penetration and chemical components of aged bitumen after rejuvenator diffusing into aged bitumen to characterize the diffusibility of rejuvenator, was developed.(2) Diffusible rejuvenator composed of chemical oil with epoxide group and catalytic cracking slurry was prepared, its diffusibility was evaluated by the method mentioned above, the result indicates that the rejuvenator with penetrant exhibits better diffusibility than the rejuvenator without penetrant.(3) Asphaltenes dissolving experiment and infrared spectrum results reveal that the asphaltenes can be dissolved in the penetrant with epoxide group and the attraction force between asphaltenes can be reduced by the chemical reaction between epoxide group and asphaltenes, which can facilitate the dispersion of accumulated asphaltenes of aged bitumen and destory the network model dimensional structure caused by asphaltenes accumulating, therefore the physical obstacle of the structure on the rejuvenator diffusing into aged bitumen declined and the diffusibility of rejuvenator into aged bitumen was enhanced.(4) Investigations on influence of diffusible rejuvenator and common rejuvenator on the physical properties of aged bitumen indicate that the diffusible rejuvenator can restore the physical properties of aged bitumen with different aging degree more effectively; it can restore the physical properties of aged bitumen with different aging degree to the condition that is of the virgin bitumen. which can be explained as that the commom rejuvenator can only restores the colloidal structure of aged bitumen by changing the contents of aromatic and asphaltenes, the effect is finite; however, for diffusible rejuvenator, it can restore the colloidal structure of aged bitumen by both changing the contents of aromatic and asphaltenes and dissolving asphaltenes at the same time, therefore the effect of the diffusible rejuvenator on the colloidal structure restoration of aged bitumen is more effective than commom rejuvenator.(5) Result of Bending-Beam Rheometer testing indicates that the creep stiffness of the aged bitumen declined to294MPa and the creep rate increased to0.317after adding15%diffusible rejuvenator, however, after adding the same content of commom rejuvenator, the creep stiffness of the aged bitumen declined to327MPa and the creep rate increased to0.273, which indicates that the diffusible rejuvenator is more effective on the improvement of cracking resistance under low temperature than commom rejuvenator, which can be also explained as that the influence of diffusible rejuvenator on the colloidal structure restoration of aged bitumen is more effective than commom rejuvenator.(6) The colloidal stability index of the aged bitumen increased from2.76to3.85, penetration index declined from3.36to1.14after adding15%diffusible rejuvenator, indicating that the colloidal structure of aged bitumen transformed from Gel to Sol-Gel; however, after adding the same content of commom rejuvenator, the colloidal stability index increased from2.76to3.25, penetration index declined from3.36to2.23, the colloidal structure of aged bitumen was still Gel structure, which can prove that the diffusible rejuvenator on the colloidal structure restoration is more effective than commom rejuvenator.(7) The investigation of Atomic Force Microscope (AFM) indicates that after adding diffusible rejuvenator into aged bitumen, the size of bee structure caused by asphaltenes accumulating in aged bitumen declined, the distribution of the bee structure got even, the microstructure of aged bitumen became smooth, which was close to the microstructure of virgin bitumen; however, when adding the same content of commom rejuvenator, the microstructure of aged bitumen changed slightly, which can further prove that the diffusible rejuvenator on the colloidal structure restoration is more effective than commom rejuvenator.(8) Road performance testing of recycled asphalt mixture indicate that the fatigue life under0.2stress ratio and of the failure strain of the recycled asphalt mixture containing15%diffusible rejuvenator were10005and2473respectively; whereas for the recycled asphalt mixture containing the same content of commom rejuvenator, the fatigue life at0.2stress ratio and the failure strain were7473and2077respectively, indicating that the diffusible rejuvenator can improve the road performance testing of recycled asphalt mixture more significantly than common rejuvenator, which can be explained as that the diffusible rejuvenator can diffuse into the aged bitumen wrapping around the surface of reclaimed aggregates more deeply and restore the colloidal structure of aged bitumen more effectively, so as to improve the properties of aged bitumen better more significantly.