​This study focused on the development of an innovative calcium carbonate (CC)-raw bentonite (RB) mortar for high temperature purposes. The main strategy proposed in this work relies on the synergistic thermal and chemical activation of CC/RB-based mortar to produce a hardened material with optimal engineering properties. Instead of calcining RB before alkali-activation, thermochemical activation was applied to the CC/RB-based mortar to produce a thermally stable hardened material. This process resulted in the formation of stable minerals, such as wollastonite and gehlenite, alongside the formation of solidified melt at high temperatures, leading to the densification of the microstructure and the creation of a hardened material with higher performance and stability compared to cured samples. The hardened mortar with the highest compressive strength value (∼57 MPa) was obtained by adjusting the CC/RB weight ratio at 50 wt%/50 wt%, Na2O concentration of 7.5 wt%, sand/waste glass (WG) aggregate weight ratio of 25 wt%,/75 wt%, and exposure temperature of 1000 °C. Surprisingly, the proposed strategy produced a hardened material with a considerable compressive strength of ∼23 MPa without adding Na2O. Accordingly, the proposed approach can resolve the economic and environmental shortcomings of using a chemical alkali-activator.​