This research developed an alkali-activated geopolymer (GP) cement using powdered granite waste (GW), blast furnace slag (BFS), and Zirconium aluminum Layered double hydroxide (Zr–Al–CO3 LDH). The alkali-activation reactions were promoted using NaOH and Na2SiO3 (1:1) as an alkaline activator. The durability of various GP mixes was tested by examining their mechanical properties against firing up to 800 °C and exposure to high doses of gamma rays. Results indicated that incorporating up to 30% granite powder into the GP mixture resulted in faster setting times: initial setting time decreased by 20%, and final setting time decreased by 33%. This improvement is attributed to the acceleration of alkali-activation reactions and the increased stiffness of the paste, which is due to the surplus soluble silicon ions released from the granite powder. Replacing BFS with 10% GW led to an improvement in strength by approximately 4–6%. However, increasing the replacement ratio resulted in a decline in mechanical properties. Enhancing the 80% BFS and 20% granite waste (GW) mixture with 0.5–1% of Zr–Al–CO3 LDH significantly increased compression resistance by 37% and 25% at all stages of the alkali activation process. This enhancement in compression resistance is attributed to the nano-filling effect of Zr–Al–CO3 LDH and its ability to improve the bonding between the BFS and granite particles. Furthermore, BFS (blast furnace slag) reinforced with LDH (layered double hydroxide) showed no loss of strength during durability tests against gamma-ray irradiation at doses up to 1000 kGy. Additionally, it demonstrated thermal stability when fired at temperatures up to 800 °C, in contrast to the GP mix made solely from BFS. This behavior is mainly due to the combined action of granite particles, which serve as energy storage and thermal insulating materials, with the nano-filling and/or absorptivity properties of Zr–Al–CO3 LDH within the GP matrix which reinforces the geopolymer structure to endure the detrimental impacts of these demanding environments.
