The Mechanism Of Interfacial Enhancement Of Graphene Modified Asphalt

Asphalt,an important binding material in civil engineering field,has been mainly employed to construct pavement and waterproof coating.In recent years,graphene,as a two-dimensional carbon material,can significantly improve the mechanical properties,fatigue properties and anti-aging properties of modified asphalt.Therefore,this thesis focus on the interface strengthening mechanism of modified asphalt by graphene with various intrinsic structures via macro-rheology,micro-analysis and molecular dynamics simulation methods.The main research contents and results are as follows:(1)The enhancement mechanism of mechanical properties of base asphalt by the size effect of graphene was investigated by using nano-sized graphene(NG)and micro-sized graphene(MG).The results show that compared with0.02wt% NG modified asphalt binder,the irrecoverable creep compliance(Jnr)value of MG modified asphalt is reduced by 24.0%.This is due to the strongπ-π interaction between large-sized graphene and asphalt through their aromatic ring structure,inducing the asphaltic polar components around graphene to produce strong O-H…S hydrogen bond,which can improve the density of asphalt colloidal structure and enhance the mechanical properties of asphalt binder.(2)The base asphalt was modified by micro-sized exfoliated graphene(EG)with no vacancy defect and vacancy-defected graphene(VDG)to reveal the vacancy defects effect of graphene on the mechanical properties and anti-aging properties of modified asphalt via multi-scale methods.The results demonstrate that compared with 0.02wt%EG modified asphalt,Jnr value of0.02wt%VDG modified asphalt is reduced by 31.5%,which is attributed to the electrostatic adsorption is formed between the vacancy defects of graphene and the paraffin chain segments of asphalt,increases the concentration of asphaltene in colloid,forms a dense and ordered asphaltene accumulation structure,promotes the transformation of asphalt from sol structure to gel structure,and thus improves the mechanical properties and anti-aging properties of asphalt.(3)The SBS asphalt was modified by graphene with fewer vacancy defects(FG)and abundant vacancy defects(AG)respectively,aiming at clarify the enhancement of the vacancy defects degree of graphene on SBS modified asphalt.The results show that compared to 0.05wt%FG-SBS modified asphalt,the fatigue life of 0.05wt%AG-SBS modified asphalt is increased by 43.9%.This is because graphene with a high vacancy defect degree can enhance the swelling of butadiene segment of SBS by electrostatic adsorption with light components of asphalt,the continuous phase of butadiene segment of SBS is further looser,improving the compatibility of SBS modified asphalt,enhancing their high temperature rutting resistance and low temperature cracking resistance.(4)The enhancement essence of mechanical properties at high and low temperatures of CR modified asphalt by 3DPG under different contents were revealed.The results display that compared to CR modified asphalt,the Jnr value of 0.1wt%3DPG/CR modified asphalt is decreased by 41.3%,which is attributed to the enhancement of the compatibility between CR and asphalt matrix.In addition,curves inwards of 3DPG at low temperature can promotes the movement of aromatic components while resisting external forces,inhibiting the low temperature cracking properties of CR modified asphalt.While 3DPG is curved outward at high temperature,which can resist the internal stress of expansion and further hinder the diffusion of asphalt molecules.(5)The enhancement mechanism of mechanical properties at high and low temperature in SBS/CR modified asphalt was explored by adding different content of 3DPG.The results demonstrate that compared with SBS/CR modified asphalt,the modulus of SBS/CR modified asphalt by 2%3DPG at353 K is increased by 46.2%.This is because in 2% dosage,3DPG has the strongest electrostatic adsorption with CR molecules,leading to the optimal ductility of SBS molecule.SBS acts as a "bond" to further bridge various dispersed CR molecules,effectively enhancing the cohesion and viscosity,improving the mechanical properties.The results of this thesis deepen the understanding of the strengthening mechanism of graphene-modified asphalt,and provide a theoretical basis for the design of modified asphalt.