Synthesis Of Zinc Oxide/Expanded Vermiculite Composite And Its Influence On Properties Of Asphalt Materials

Asphalt is highly susceptible to aging when exposed to environmental impacts like heat,oxygen,and ultraviolet light.It has been reported that the expanded vermiculite(EVMT)and nano zinc oxide(ZnO)can significantly improve the thermoand oxygen-oxidative aging resistance of asphalt owing to their shielding functions of heat,oxygen,and ultraviolet light,respectively.However,at present,the two materials are mainly added to asphalt after direct mixing,which leads the two modifiers not to function uniformly in the asphalt.Besides,the agglomeration of ZnO particles weakens the modification effect of ZnO on asphalt.Considering a sufficient loading area for the ZnO particles can be offered by the high specific surface area of EVMT,the zinc oxide/expanded vermiculite composite(ZnO/EVMT)can be formed by loading ZnO particles on the surface of EVMT,which can better improve the anti-aging properties of asphalt and achieve uniform dispersion of the ZnO particles.The research work will significantly improve the reliability of inorganic nanomaterials in retarding the asphalt aging,and provide new ideas for the development of asphalt anti-aging agents.The ZnO/EVMT was synthesized by the modified hydrolytic precipitation method,and the crystal structure,surface morphology,functional groups,and UV absorbance properties of ZnO/EVMT were characterized.Further,the influence of different amounts of ZnO/EVMT on both high and low-temperature properties of the asphalt before and after aging were investigated.the aging degree of different asphalt was evaluated and the aging resistance mechanism of ZnO/EVMT modified asphalt was explored.Besides,an appropriate amount of the modifier was proposed.Finally,asphalt mixtures containing 0% and 5% ZnO/EVMT were prepared,and the effect of ZnO/EVMT on the road performance before and after short-term and long-term aging was evaluated.The road performance sensitivity of different asphalt mixtures to aging was compared,and the aging degree of asphalt in the modified and unmodified mixture after the UV aging was compared.(1)Calcining treatment has little effect on the EVMT,EVMT can serve as good support for ZnO particles.ZnO particles can achieve a dense and uniform distribution on the surface of EVMT.Meanwhile,the loading process does not damage the layer structure of EVMT and the organic treatment successfully expands the layer spacing of EVMT.Moreover,compared with EVMT,the absorbance of UV light in the wavelength range of 200nm～380nm by ZnO/EVMT can be greatly enhanced after the loading process.(2)ZnO/EVMT slightly enhances the high-temperature properties of the unaged asphalt and has little effect on the high-temperature properties of the short-term thermo-oxidative aged asphalt.ZnO/EVMT reduces the low-temperature properties of the unaged asphalt,but when the dosage of ZnO/EVMT reaches 4%,the low-temperature crack resistance of the asphalt after long-term thermo-oxidative aging can be improved.Regardless of aging methods,all amounts of ZnO/EVMT can retard the aging of asphalt.Asphalt with 6% and 4% ZnO/EVMT exhibit the most significant thermo-and photo-oxidative aging resistance,respectively,and 5%ZnO/EVMT is proposed as a reference.ZnO/EVMT can effectively inhibit the transformation of the light components to heavy components.(3)ZnO/EVMT has no significant effect on the high-temperature performance of the asphalt mixture.For both unaged and long-term aged asphalt mixture,ZnO/EVMT is able to improve the low-temperature crack resistance,water stability,and fatigue crack resistance.ZnO/EVMT can both reduce the susceptibility of the pavement performance to short-term and long-term aging,and can inhibit the aging of the asphalt in the mixture during the UV aging process.