Research On Preparation And Temperature Adaptability Characteristics Of TiO₂ Quantum Dots Modified Asphalt

The solar light response behavior of asphalt materials plays a key role in asphalt pavement temperature.However,asphalt is a kind of black material,which has the remarkable characteristics of high solar absorption rate and low fluorescence intensity,which leads to the temperature of asphalt pavement reaching 70～80℃in summer.Pavement temperatures rising not only exacerbate pavement diseases（i.e.rutting,waves,crowding,and oil spills）,but also exacerbate the urban heat island effect.In this paper,aiming at the high solar light absorption rate and fluorescence intensity of asphalt,Ti O₂ quantum dots modified asphalt with high solar light reflectivity and fluorescence intensity is designed and prepared.The optical properties and road performance of Ti O₂ quantum dots and Ti O₂ quantum dots-modified asphalt were studied by combining first-principles and molecular dynamics simulations as well as macro and micro experiments,and the temperature regulation behavior of Ti O₂ quantum dots-modified asphalt was determined.This research provides theoretical basis and technical support for the development and application of temperature-regulated asphalt pavement,and alleviates the high temperature disease of asphalt pavement.Firstly,based on the first principles of density functional theory,the optical properties of Ti O₂ quantum dots were studied.During the simulation process,four models of Ti O₂ quantum dots with different particle sizes of 6（?）,8（?）,10（?）,and 12（?）were established in Materials Studio 2019,and model verification and geometric optimization were performed.Based on the CASTEP module,the absorption spectrum and reflectance spectrum of Ti O₂ quantum dots were calculated,and the influence of particle size on the spectral characteristics was investigated.In addition,the optical properties（absorption spectrum,reflectance spectrum and fluorescence spectrum）of Ti O₂ quantum dots with three different particle sizes of 5 nm,10 nm and 20 nm were characterized.The research shows that the absorption intensity of Ti O₂ quantum dots increases with the increase of particle size,the solar reflectance decreases with the increase of particle size,and the fluorescence intensity increases with the increase of particle size.Secondly,the physical and mechanical properties of Ti O₂ quantum dots modified asphalt were studied by molecular dynamics simulation.During the simulation process,a molecular model of neat asphalt was established and the model was verified.The molecular structure model of modified asphalt with different particle sizes of Ti O₂quantum dots（6（?）,8（?）,10（?）,12（?））and different contents（5%,10%and 15%）was established.The density,cohesive energy density,solubility parameter,Young’s modulus,elastic modulus and shear modulus of Ti O₂quantum dots modified asphalt were calculated,and the influence of particle size and content of Ti O₂ quantum dots was investigated.The research shows:The density,cohesive energy density,solubility parameter and modulus of the modified asphalt all increased with the increase of the content of Ti O₂quantum dots.With the increase of the particle size of Ti O₂quantum dots,the density,cohesive energy density,solubility parameter and modulus of modified asphalt all decrease.Then,through infrared spectrum test,Brookfield viscosity test,DSR test,BBR test and other tests,the optical properties,chemical properties and road performance of Ti O₂ quantum dots modified asphalt were studied,and the influence of Ti O₂ quantum dots content and particle size was investigated.The research shows that the viscosity of modified asphalt increases as the content of Ti O₂ quantum dots increases and the particle size decreases;The anti-rutting factor of Ti O₂ quantum dots modified asphalt increases with the increase of content and the decrease of particle size.It can be seen that the addition of Ti O₂ quantum dots improves the anti-rutting ability of asphalt and improves its high temperature performance;In the range of5%～20%content,the anti-fatigue factor of Ti O₂ quantum dot-modified asphalt almost exceeds5000k Pa at 22℃,and the fatigue failure temperature is 22℃,it shows that the addition of Ti O₂quantum dots has little effect on the fatigue resistance of modified asphalt;The creep stiffness S of the modified asphalt increases with the increase of the content of Ti O₂ quantum dots,and the m value decreases with the increase of the content of quantum dots,the m/S value was used to evaluate the low temperature performance of modified asphalt,the experimental data show that the low temperature crack resistance of modified bitumen is worse as the particle size of Ti O₂ quantum dots increases and the content increases;FTIR analysis found that the functional groups of the asphalt did not change significantly before and after the addition of Ti O₂ quantum dots,indicating that the asphalt modification mechanism was physical modification.In addition,the solar reflectance and fluorescence spectra of Ti O₂ quantum dots modified asphalt were characterized.The test found that compared with the base asphalt,with the addition of Ti O₂quantum dots,the solar reflectance of the modified asphalt increased from 3%to 15%,and the fluorescence intensity increased by 10.9 times.Lastly,the temperature regulation behavior of Ti O₂ quantum dots modified asphalt was explored through indoor simulated illumination experiments.Compared with traditional asphalt,the surface temperature of Ti O₂ quantum dots modified asphalt coating decreased by 5.3°C;Compared with traditional asphalt mixture,the surface temperature of Ti O₂ quantum dots modified asphalt mixture decreased by 6.2°C.Thus,the effective temperature regulation behavior of Ti O₂ quantum dots modified asphalt was determined.