Improvement Mechanism of Adhesion Performance of Anti-stripping Agents and Coupling Agents on Asphalt-Aggregate Interface Based on Molecular Dynamics

This study examined the mechanisms for improving the adhesion performance of the asphalt-aggregate interface with two anti-stripping agents and two coupling agents.The investigation of contact behavior between various asphalt-aggregate surfaces was conducted using molecular dynamics(MD)simulations.The interaction energy and the relative concentration distribution were employed as the parameters to analyze the enhancement mechanisms of anti-stripping agents and coupling agents on the asphalt-aggregate interface.Results indicated that the adhesion at the asphalt-aggregate interface could be strengthened by both anti-stripping agents and coupling agents.Anti-stripping agents primarily improve adhesion through the reinforcement of electrostatic attraction,while coupling agents primarily upgrade adhesion by strengthening the van der Waals.Hence,the molecular dynamics modeling and calculation techniques presented in this study can be utilized to elucidate the development mechanism of the asphalt-aggregate interface through the use of anti-stripping agents and coupling agents.

Mechanical characteristics of tensile strength ratio method compared to other parameters used for moisture susceptibility evaluation of asphalt mixtures

In this study,mechanical characteristics of tensile strength ratio(TSR)were evaluated by comparing it to other methods in evaluating moisture sensitivity of asphalt mixtures.Twenty types of asphalt mixtures with and without anti-stripping additives were prepared and tested in the laboratory.Uniaxial compressive strength(UCS)and indirect tensile(IDT)testing were conducted to determine the mixture’s tensile strength ratio and cohesion ratio(CR).Determining TSR alone was found to be insufficient when evaluating moisture resistance.There is a need to consider both TSR and wet IDT strength to properly evaluate moisture behavior of asphalt mixtures.Moreover,it was found that the cohesion and the IDT strength have a good relation in which the minimum condition of the slope,must be met.However,it was observed thatβvalues change depending on material type and temperature.Hence,there is a need to evaluate theseβvalues for varying material and testing temperature.In addition,it was found that the TSR and CR results are highly correlated with an average difference of 1.5%.Furthermore,other tests such as Marshall stability and dynamic immersion were also conducted.It was found that Marshall stability ratio(MSR)and Marshall stability to flow ratio(MSFR)values are less sensitive to moisture effect when measuring moisture resistance compared to TSR values.Finally,the 48 h testing result of the dynamic immersion test showed better correlation with TSR values.