UV aging resistance improvement of SBS modified asphalt binder by organic layered double hydroxide and naphthenic oil: Its preparation, properties and mechanism

Abstract

To enhance the UV aging resistance of SBS modified asphalt, LDHs and naphthenic oil were selected to modify it compositely. Firstly, organic treatment for LDHs was carried out through the combination of surface modification method and intercalation modification method to improve its compatibility with asphalt, and effectiveness of organic treatment was evaluated through the microscopic testing methods. Then, organic LDHs/SBS modified asphalt binders were developed by melt blending method, on this basis, appropriate naphthenic oil was added for composite modification. Subsequently, the conventional physical properties, storage stability and rheological properties tests were carried out to evaluate the comprehensive properties of the prepared modified asphalt containing LDHs and naphthenic oil. On this basis, TOPSIS method was conducted for multi-index optimization to determine the optimal dosages of LDHs and naphthenic oil. Finally, UV aging resistance of the developed modified asphalt was also evaluated, and reaction mechanism was explored with FTIR and FM. Test results show that stearic acid (SA) was successfully absorbed on the surface of LDHs, and -SO32- in ultraviolet light absorber (UVT) has successfully entered the interlayer galleries of LDHs, thus achieving the organic treatment for LDHs. Organic LDHs can significantly improve the high temperature properties and storage stability of SBS modified asphalt, and naphthenic oil can also improve the storage stability of SBS modified asphalt at the proper dosage. In addition, the two modifiers can both effectively improve the UV aging resistance of SBS modified asphalt. Based on the multi-index optimization results, it is recommended that the optimal dosages of LDHs and naphthenic oil are 2 % and 2.5 %, respectively, and at this conditions, comprehensive properties of the prepared modified asphalt can achieve the best. Microstructure characterization tests results reveal that LDHs and naphthenic oil are only simply dispersed in asphalt and do not cause the structural damage of SBS modified asphalt. Meanwhile, the special layered structure of LDHs can hinder the mobility of asphalt molecular chains, which enhances the interaction force between asphalt molecular chains and SBS modifier molecular chains, thus improving the road properties of SBS modified asphalt.