Investigation of anti-aging mechanism of multi-dimensional nanomaterials modified asphalt by FTIR, NMR and GPC

Abstract

Asphalt is susceptible to being aged when exposed to thermal, oxygen and photo environment during construction or service period. To solve this issue, researchers used different sorts of nanomaterials to bring improvements to anti-aging properties of asphalt. Multi-dimensional nanomaterials (MDN) are the substances composed of two or more kinds of nanomaterials with different dimensions. Previous studies have proved the anti-aging efficiency of MDN but its mechanism is still unclear. In this paper, base asphalt was firstly modified by 1% organic expanded vermiculite (OEVMT) and 3% inorganic particles (nano-zino oxide (ZnO), nano-silica (SiO2), nano-titania (TiO2)). Then thin film oven test (TFOT), pressure aging vessel (PAV) test and ultraviolet (UV) aging test were employed on all samples. Macroscopic properties changes were characterized by physical and rheological tests while microscopic chemical structure changes were observed by Fourier transform infrared spectrometer (FTIR), Nuclear transform infrared (NMR) and Gel permeation chromatography (GPC). Results showed that MDN decreases the increment in softening point, viscosity aging index and complex modulus aging index while increases the retained penetration and phase angle aging index. Meanwhile, the addition of MDN reduces length of straight chains of unaged materials shown by NMR results, which demonstrates that the internal friction decreases when asphalt molecules move. According to GPC results, the decreased amount of large molecules is attributed to the intercalated /exfoliated structure formed by OEVMT. FTIR test results illustrated that MDN is helpful to reduce the number of sulfoxide function groups because of the absorbing/ reflecting effects of inorganic nanoparticles on ultraviolet radiation.