| Bitumous materials are vulnerable to aging in the process of construction and service time of pavement because of the influence of temperature, water, oxygen, ultraviolet(UV) light and other environmental factors, which will affect the service performance and service life of bitumen pavement seriously. Based on different causes of bitumen aging, aging is usually divided into thermal oxidation aging and photo oxidation aging. These two kinds of aging occur simultaneously during service life of bitumen pavement, thus it is of significant importance to seek suitable anti-aging modifiers for improving both thermal oxidation and photo oxidation aging resistance of bitumen simultaneously. Many published researches showed that layered silicates could improve thermal oxidation aging resistance of bitumen obviously, while they have little influence on photo oxidation aging resistance of bitumen. However, the effect of inorganic nanoparticles on aging resistance of bitumen is just the reverse. Accordingly, layered silicates and inorganic nanoparticles are compounded to develop a novel anti-aging modifier, it can be promising modifiers to improve both thermal oxidation aging and photo oxidation aging resistance of bitumen simultaneously.In this paper, different inorganic nanoparticle s with surface modification and organic vermiculite(OEVMT) were compounded, and the influence of different combinational compound modifiers on physical and rheological properties of SK-70 base bitumen before and after aging was investigated, then the opti mal combination was determined. After that the compound modifier was added in different kinds of base bitumens and styrene-butadiene-styrene copolymer(SBS) modified bitumen by the optimal combination. The physical and rheological properties of different kinds of compound modified bitumens before and after aging were studied. The chemical structures of different kinds of compound modified bitumens before and after aging were characterized by Fourier transform infrared(FTIR) spectroscopy, then the aging resistance mechanism of compound modified bitumen was also studied. The main results obtained are as follows:(1) Based on the influence of different compound modifiers on physical and rheological properties of SK-70 base bitumen after Thin Film Oven(TFOT), pressure aging vessel(PAV) and UV aging, it can be found that the compound modifier s containing nano-ZnO and OEVMT show the best improvement in aging resistance of bitumen, which is the optimal compound modifier combination.(2) After adding the compound modifier by the optimal combination, the high-temperature stability and rutting resistance of different types of base bitumens are enhanced, while the plastic deformation capacity is reduced by a certain extent. Compound modifier can improve the physical and rheological properties of these bitumens after TFOT, PAV, UV and natural light aging. Moreover, it also can improve the low-temperature rheological performance of heavy-traffic 90# bitumen after PAV aging, and has little influence on that of alpha 70# and heavy-traffic 110# bitumen after PAV aging.(3) The influences of different proportion compound modifiers on the performance of SBS modified bitumen before and after aging are not uniform. The proportion of 1%OEVMT+2%Nano-ZnO can remarkable improve the thermal oxidation and photo oxidation performance of SBS modified bitumen. Based on physical and rheological properties, it can be concluded that 1%OEVMT+2%Nano-ZnO is the optimum content. Meanwhile, it can be found that surface modified nano-ZnO and OEVMT compound has a good synergistic effect on improving the aging resistance of SBS modified bitumen.(4) Fourier transform infrared spectroscopy test result shows that the compound modifiers can remarkable prevent the carbonyl formation in three types of base bitumens and SBS modified bitumen in the process of TFOT, UV and PAV aging in comparison with the corresponding blank samples, which contributes to the good thermal oxidation and ultraviolet aging resistance of compound modified bitumens. |
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