Molecular dynamics simulations on TiO2 quantum dots modified asphalt: Impact of size and concentration of quantum dots

Abstract

With exceptional solar reflectivity and fluorescent characteristics, TiO2 quantum dots (QDs) modified asphalt has been proposed as an innovative cool pavement technology. However, interaction mechanism and thermodynamic properties of TiO2 QDs modified asphalt at microscale have not been well understood. In this study, electronic and optical properties of TiO2 QDs with varied sizes were investigated based on quantum mechanics (QM) calculations. Moreover, molecular dynamics (MD) simulations were implemented to evaluate mechanical moduli and intermolecular dynamics of TiO2 QDs modified asphalt with different quantum sizes and concentrations. The results from QM calculations unveil that as size of TiO2 QDs rises from 6 Å to 12 Å, energy gap and binding energy of TiO2 QDs decreases by 0.928 eV and 526.38 eV, respectively while density of state (DOS) and absorption coefficient of TiO2 QDs increases. Besides, the results from MD simulations reveal that quantum size imposes significant impact on mechanical moduli of modified asphalt while concentration of TiO2 QDs brings notable influence on interaction between quantum dots and asphalt. Specifically, as concentration of QDs rises from 10 % to 30 %, cohesive energy density (CED) and solubility parameter (SP) of modified asphalt is improved by up to 457 % and 136 %, respectively. With increasing quantum size, bulk modulus, shear modulus, and Young’s modulus of modified asphalt is enhanced by up to 372 %, 206 % and 24 %, respectively. The outcomes of this study provide insights into formula and application of advanced asphalt pavement with TiO2 QDs.