Effect of Silane Coupling Agent on Improving Adhesive Property between Acidic Aggregate and Hydraulic Asphalt

Silane coupling agents (SCAs) are a type of antistripping agent for improving the adhesive property between acidic aggregate and hydraulic asphalt. To evaluate the modified effect, find the optimal dosage of SCA, and study the modified mechanism at different dosages, the surface free energy (SFE) component, energy parameters, and the energy ratio were used to analyze the energy required in the asphalt-aggregate-water three-phase transformation. Additionally, the functional group index of organosilane and hydroxyl were used to evaluate the SCA binding effect at the asphalt–aggregate interface using Fourier transform infrared (FTIR) spectra. The results showed that with the increase of SCA, the SFE and FTIR parameters almost increased initially, reached the maximum at the 1.0% by weight, and then decreased. This indicates that the SCA can serve as a molecular bridge to improve the adhesive property between acid aggregate and hydraulic asphalt with the optimal dosage of 1.0% by weight. Insufficient SCA could not modify the adhesive property effectively, and excess SCA led to the hydrogen-bond association and SCA depolymerization, resulting in an adverse effect.