Review on the Adhesion of Geopolymer Coatings

[Image: see text] Geopolymers are considered to be green materials with excellent fire resistance performance and potential substitutes for ordinary Portland cement (OPC). This review article focuses on the adhesion of geopolymer coatings subjected to elevated temperature. Their high adhesion strength is the basis for geopolymers being used as coating materials to work with the substrate. The adhesion strength is related to many factors, such as chemical composition of the raw materials, the formulation of the geopolymer, substrate type, surface roughness of the substrate, etc. The Si/Al ratio has different effects on compressive strength and bonding strength. The water content affects the polymerization process—the adhesion strength decreases with increasing water content. Careful tailoring of the mix ratio design is essential to make the geopolymer coating have excellent adhesive performance. These mix design factors include Si/Al ratio, Al/Na ratio, water content, precursor type, alkali cation type, curing conditions, etc.