Geopolymers and Their Matrix Composites: A State-of-the-Art Review

Geopolymers consisting of polymeric Si–O–Al networks are long-range, covalently bonded inorganic materials. In recent years, geopolymers and their composites have attracted considerable attentions in the fields of construction, metallurgy, and hazardous elements immobilization due to their unique properties such as low-temperature preparation, facile and cost-effective processing, excellent heat and corrosion resistance, and environmentally friendly feature. Due to the relatively low-temperature curing feature of geopolymers, additives with specific properties and functions can be easily incorporated or doped into geopolymers as needed, therefore, endowing them with electric and thermal conductive, electromagnetic wave absorbing, and luminescent features. In other words, geopolymers could be easily tailored as designed. Moreover, geopolymers and their composites can be converted into ceramic materials with controllable mechanical and thermal properties after being treated or holding at high temperature for a given period of time. This makes it possible to render geopolymers and their composites as promising precursors for the preparation of high-temperature ceramics with potential applications in aerospace, heat-resistant components, and stealth materials. This chapter is dedicated to providing an overview of recent advances empowering the development of geopolymers and their composites in the context of geopolymerization mechanisms, microstructure evolution, synthesis, characteristics, and potential applications (e.g., 3D printing and hazardous elements immobilization). Finally, the current challenges and future opportunities of geopolymers and their matrix composites are also addressed.