Multiscale investigation on enhancing the adhesion properties of SFP materials through interfacial modification

Semi-flexible pavements (SFP) are composite structures that combine flexibility and rigidity, ensuring high loadbearing capacity and enhanced durability. However, their performance in practical application largely depends on the adhesion between asphalt and cement-based grout, which remains a challenge in practical applications. This paper proposes an interfacial immersion method using a silane coupling agent to enhance the adhesion properties of SFP. To enhance the adhesion property of SFP, an interfacial immersion method is proposed in this paper. A multiscale investigation on improving the adhesion property of SFP material using interfacial modification. Firstly, pull-off tests were conducted to assess the adhesion properties of SFP at the macroscale, considering grout materials of different strengths and aggregates with varying characteristics under interfacial modification. Secondly, contact angle tests were performed to analyze changes in the surface free energy of the asphalt interface in SFP at the mesoscale. Finally, atomic force microscopy (AFM) was utilized to evaluate the adhesion performance of the asphalt interface in SFP at the microscale after interfacial modification. Experimental results show that the proposed method significantly enhances the adhesion properties of SFP, with bond strength increasing by up to 165.6 % in SFP formed with alkaline aggregates. After immersion in a silane coupling agent solution, micro-protrusions form on the asphalt surface, increasing contact area and creating a modification layer that strengthens adhesion. Surface free energy rises by 39.79 %, improving wettability and molecular interactions. Additionally, dissipated energy increases, enhancing stress relaxation capacity and lowtemperature performance due to improved surface polarity, roughness, and viscoelasticity of the modified layer. The research results can provide an insight into interface engineering for SFP, offering a practical approach to improving pavement performance through targeted interface modification.