Research Progress on the Adhesion Mechanisms between Organic Adhesives and Cement-Based Materials

Concrete infrastructure in China has entered a large-scale phase of maintenance and repair, with organic adhesives being essential materials for enhancing structural durability. Enhancing the long-term effectiveness of adhesion between these adhesives and cementitious materials is crucial for extending the service life of concrete structures. This study reviews the primary types of organic adhesives used for infrastructure repair work, including epoxy resins, polyurethanes, and silicone adhesives, and discusses the performance advantages of their various applications. The adhesion mechanisms are determined in terms of mechanical interlocking, intermolecular interactions, and thermodynamic interactions, identifying the main sources and driving forces behind adhesion. The degradation mechanisms of interfacial adhesion under moisture, salt solutions, adhesive aging, and cyclic load coupling are analyzed. Finally, the study summarizes various techniques for enhancing interface adhesion, providing insights and innovative approaches for the design of organic adhesives and adhesion durability. The main conclusions are as follows: The adhesion mechanism of organic adhesives to cement-based materials is primarily considered from three perspectives: mechanical interlocking, intermolecular interactions, and thermodynamic interactions. Compared to the roughness of the interface, the penetration of organic adhesives into the cement-based material promotes mechanical interlocking more effectively. In the absence of interface modification, hydrogen bonds formed between the adhesive and the substrate dominate the intermolecular interactions. Moreover, hydrophobic interactions between the adhesive and the substrate play a significant role in driving the interface adhesion process. Moisture is the predominant factor responsible for debonding at the interface between organic adhesives and cement-based materials. Moisture molecules replace the hydrogen bonds formed during the adhesion process, while aggressive ions accelerate the degradation of adhesion. Furthermore, moisture and aging effects gradually degrade the mechanical properties of the organic adhesives, weakening the interfacial adhesion strength. Environmental temperature and vibration loads also contribute to the deterioration of adhesion performance. Techniques such as interface roughening, jet treatment, and coating with silane coupling agents can significantly enhance the adhesion strength between organic adhesives and cement-based materials. These methods primarily alter the surface roughness, surface tension, and surface-active groups of the substrate. Additionally, reducing the viscosity of the organic adhesive over time, increasing the content of polar groups in the adhesive molecular structure, and improving the wetting of both the adhesive and substrate phases can further strengthen the interface adhesion. Summary and Prospects Both domestic and international scholars have conducted extensive research on the adhesive performance between organic adhesives and cement-based materials from a multi-scale perspective. Significant progress has been made in understanding adhesion mechanisms and enhancement techniques. However, research on the driving forces of adhesion at the micro-nano scale remains relatively underdeveloped, especially when compared to the adhesion mechanisms observed with metal materials. Furthermore, there are still several pressing issues regarding the environmental adaptability of adhesives and cement-based materials, which demand higher standards for their long-term reliability in practical applications. Although researchers have gained a deeper understanding of the mechanism of mechanical interlocking and clarified the corresponding intermolecular interactions, there is still a need to further analyze the individual contributions of mechanical interlocking and intermolecular interactions to overall adhesion. From a thermodynamically driven molecular adhesion mechanism perspective, optimizing the molecular structure of adhesives remains an area worth exploring. Existing studies typically link macroscopic adhesion strength directly with intermolecular interactions at the nano-scale, such as hydrogen bonds, while overlooking the important role of the mesoscopic mechanical properties of the adhesive interface. Therefore, it is essential to develop a method for characterizing the mesoscopic mechanical properties of the adhesive interface, taking into account the phase composition characteristics of cement-based materials. Furthermore, a more thorough understanding of the quantitative relationship between these properties, macroscopic adhesion strength, and nano-scale chemical composition is needed. The degradation mechanisms of interfacial adhesion of organic adhesives under coupled working conditions remain unclear. How factors such as vibration loads, temperature, and moisture coupling accelerate debonding of organic adhesives from cement-based materials requires further investigation. In addition, the time-dependent damage behavior of interface adhesion under service conditions should be explored in greater detail. This research is crucial for identifying key parameters that can enhance the durability of concrete structures, thereby providing technical support for ensuring the long service life of infrastructure. © 2025 Chinese Ceramic Society. All rights reserved.