**1. Introduction**

Geopolymers are aluminosilicate materials of the Alkali-activated materials family. The geopolymerization reaction is not yet fully understood; many studies have shown that the activation of an aluminosilicate source by a highly basic alkaline solution results in the formation of amorphous materials, showing similar compressive strength to that of a traditional binder made with Ordinary Portland Cement (OPC) [1]. OPC has many disadvantages, such as excessive consumption of energy from non-renewable sources, intolerable volumes of CO2 emissions, and questionable durability, among others. Given these facts, current environmental requirements aim to reduce the CO2 impact of the construction industry, which is generally caused by the production of cement, one of the materials responsible for greenhouse gas emissions. Therefore, finding an alternative binder with the same strength but containing no cement is a major challenge that we are facing today. To avoid the effects of OPC on the environment, some studies have shown that geopolymers can indeed be used as binders in construction materials instead of OPC.

Fire is a frequent event that causes great damage to buildings. The degradation of physical and mechanical properties due to high temperature exposure is regarded as the primary cause of structural damage caused by fire [2]. Protecting these structures from fire is of extreme importance; therefore, the refractory materials for construction are particularly important.

This paper is focused on the (ambient and high) temperature resistance test, which is an engineering technique intended to evaluate the stability of a material under severe or unusual operating conditions. It was performed on geopolymer mortars manufactured in the building materials research laboratory of Cracow, University of Technology. The main goal of this test was to observe the behavior of those mortars in terms of their mechanical and physical properties after their exposure to ambient and high temperature.

Poland has extensive hard coal and brown coal resources. Therefore, the power industry is mostly based on these two original energy carriers. The power plants producing heat and electric energy create combustion byproducts. These products include carbon dioxide, but mainly slags and fly ash [3].
