Geopolymers are promising ecofriendly materials for temperature-resistant applications. For this purpose, the synthesis of thermally resistant, alkali-activated binders based on metakaolin with additives (silica sand, calcite and mullite) has been studied. In this work, the stabilities of the mechanical and thermal properties of geopolymer binders based on metakaolin with additives during scale transfer are investigated. The geopolymer is prepared by mixing metakaolin, silica sand, calcite and mullite with two different alkaline silicate solutions. The scale-up process does not affect the processing conditions. After the temperature tests at the laboratory and pilot scales (two ramps selected 200 and 400 • C/min) the same phases crystallized (leucite, wollastonite and kalsilite), and the microstructure (viscous flow formation) is the same, thus confirming the scalability of the formulation. These different results show that these formulations displaying a value of 50 MPa and λ = 1.45 W m − 1 K − 1 , are promising for fire protection and fire resistance applications.