**3. Properties of Geopolymers**

Geopolymers are known for their exceptional fire resistance up to 1400 ◦C, as well as their resistance to heat and acid [30]. These materials have high early compressive strength, excellent fracture toughness, long-term durability, low apparent porosity or nanoporosity, and freeze-thaw resistance. Geopolymer composites and concrete present similar mechanical properties to OPC-based materials, or better [31]. Its Mohs hardness ranges from four to seven [30].

One of the important properties of geopolymer binders is that they can be use to immobilization toxic waste [32]. Geopolymer materials have been observed to exhibit zeolitic and feldspathoid-like behavior, which allows them to immobilize hazardous elemental wastes within their matrix. This property makes them an effective binder for converting semi-solid waste into solid adhesive materials. [32]. Moreover, geopolymers have excellent workability because of the particle shape of raw materials, which allows their fluent production [16]. Previous studies have indicated that the addition of certain materials can enhance the workability of geopolymers. For example, the inclusion of silicon powder, calcium carbonate, or specific amounts of superplasticizer have been shown to improve their workability [16].

Furthermore, a high slag content in geopolymer mixtures can accelerate the initial and final setting time. A decrease in the molar concentration of NaOH can extend the setting time of FA-based geopolymer. [16].

Geopolymers can be strengthened using various types of material, such as carbon, glass, minerals, or steel, which can be used to produce advanced composite materials with improved mechanical properties, such as flexure, tension, shear, and flexural fatigue, particularly at high temperatures. This is due to the excellent adhesive properties of geopolymer binders, making them an attractive option for reinforcement [16].
