Research on the adhesion mechanism and compatibility of acrylate composite polyurethane binder - aggregate based on surface free energy theory

The raw materials selection and design of waterproof polymer concrete for steel bridge deck paving lack clarity regarding the adhesion mechanism and optimal compatibility between acrylate composite polyurethane binder (APUB) and various aggregates. This study systematically investigates these issues based on surface free energy (SFE) theory. Initially, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) techniques are utilized to characterize chemical structure of APUB. Subsequently, obtaining the SFE parameters of APUB and aggregates through contact angle tests, and establishing the evaluation indices compatibility ratios ERs (ER1 and ER2) for the most compatible APUB-aggregate pairs. Finally, the correlation between ERs and the water stability of the APUB-aggregate pair is verified through shear tests conducted on sandwich specimens immersed in water. The findings reveal that APUB exhibits both acidic and non-polar surface properties. The SFE values of all aggregates surpasses that of APUB, indicating APUB's ability to wet the surfaces of all aggregates. Under dry conditions, non-polar basalt and limestone aggregates exhibit strong adhesion to APUB. This is primarily due to the combined effects of acid-base chemical reactions and the principle of compatibility, with the former predominating. Under wet conditions, APUB on non-polar basalt and limestone surfaces exhibits reduced susceptibility to displacement and detachment by water. The closer the polarity component of polar aggregates is to that of water, the easier water can displace APUB from the polar aggregate surfaces. Correlation analysis between the maximum shear force of the immersed specimens and the ER2 indicates that the APUB-basalt pair has the best compatibility. The cohesive work of APUB is crucial in establishing compatibility indicators for evaluating APUBaggregate pairs. This study provides a theoretical basis for the raw material selection and design of polymer concrete for steel bridge deck paving.