Mechanical properties and durability of fiber reinforced geopolymer composites: A review on recent progress

Geopolymer concrete has similar mechanical properties to ordinary Portland cement (OPC) concrete, and even better properties in high temperature, high corrosion environment. However, geopolymer still has the disadvantages of large shrinkage and high brittleness, which greatly limit its application. Fiber reinforcement is widely used in various geopolymer systems to overcome the brittleness issue, but still retains the high strength. Over the past 10 years, great progress has been made in the research of fiber reinforced geopolymers in the aspect of toughening efficiency and durability improvement. Many studies have been conducted on fiber reinforced geopolymers, but there are still few systematic summaries on the addition of inorganic fibers and organic fibers to geopolymers. What is more there are many novel studies such as the application of geopolymers to 3D printing and the new concept of fiber factor have not been reviewed. In this paper, inorganic fibers, natural fibers and synthetic fibers in geopolymers are briefly reviewed, and their specific effects on geopolymers' compressive, flexural, tensile strength, fracture toughness, shear strength and durability such as shrinkage, chemical resistance, freeze–thaw resistance are reviewed. The current understanding of bonding mechanism and fiber‐geopolymer interface are also discussed, and related knowledge gaps and future work challenges are correspondingly pointed out. Over the past 10 years, a significant advance has been made in the research of fiber reinforced geopolymers in terms of toughening efficiency and durability improvement. This paper, as a mini review, focuses on three types of fibers, that is, inorganic fiber, natural fiber and synthetic fiber, in geopolymers, and their specific effects on compressive, flexural and tensile strengths, fractural toughness, shear strength and durability including shrinkage, chemical and freezing–thaw resistances.