Research Progress of Self-cleaning Technology of Cement-based Superhydrophobic Materials

Superhydrophobic materials, as a new family of intelligent bionic materials, have been widely used in aerospace, construction, electricity generation and other fields, due to their excellent self-cleaning, anti-ice-condensation and anti-corrosion properties; however, their use in the highway transportation field is still in the exploratory stage of research. The self-cleaning properties of cement-based superhydrophobic materials originate from the ‘lotus effect’ found in nature. The micro-nano structure and low surface energy of a superhydrophobic surface reduce adhesion between pollutants and the coating. These two effects endow the surface of a cement-based material with excellent self-cleaning properties, thereby providing a new paradigm for the active antifouling of such materials. The theory surrounding the self-cleaning behavior of cement-based superhydrophobic materials is presently immature, as is the corresponding technology. Cement-based superhydrophobic materials are mainly prepared through the cooperation of surface micro-nano composite structures and low surface energy chemicals, which facilitate their self-cleaning functions. Techniques for preparing cement-based superhydrophobic materials mainly include hydrophobically modifying surfaces and integrating hydrophobic modifications. Hydrophobic materials like silanes/ siloxanes and stearic acid are frequently used, because they are environmentally friendly and inexpensive. Treatment methods that endow the surfaces of cement-based materials with superhydrophobicity mainly include coating, templating, and layer-by-layer self-assembly. Superhydrophobically modifying a surface has little effect on the mechanical strength of the cement-based material, while integral superhydrophobic modification delays cement hydration reactions and reduces the mechanical strength of the cement-based material through the inclusion of the hydrophobic material. Cement-based superhydrophobic surface coatings are more widely used, because of simple construction, cost effectiveness, and low energy consumption. While methods for evaluating the self-cleaning performance of cement-based superhydrophobic materials have not been unified, the simulated pollutant collection method is widely used. Preparation techniques, evaluation methods and material durability require further study from the perspective of practical engineering applications, as multiple factors affect the engineering structures of cement-based superhydrophobic materials. In this paper, we summarize progress in self-cleaning-technology research for cement-based superhydrophobic materials. The self-cleaning mechanisms of superhydrophobic surfaces, preparation technologies, performance analyses and methods for evaluating the self-cleaning performance of these materials are introduced. Problems associated with this self-cleaning technology are discussed, and prospects are proposed, with the aim of providing a reference for the preparation of durable and environmentally friendly new cement-based superhydrophobic materials. © 2023 Cailiao Daobaoshe/ Materials Review. All rights reserved.