Geopolymers belong to a new class of materials with features similar to ceramics.Compared to ceramics, the production process of geopolymers is however more energy efficient since it requires consolidation at moderate temperatures (20-100℃).In the cement industry geopolymers, or more in general alkali activated materials, are particularly attractive as a potential sustainable alternative to ordinary Portland cement (OPC).Although alkaline solutions are required for the activation process, waste with suitable chemical composition can be exploited as starting materials.Waste materials such as slag or carbon fly ash can be properly activated at room temperature due to their chemical composition and amorphous structure.