The pursuit of alternative cementitious binder system has been necessary for extending the performance and lifespan of extreme-engineered structures. The deterioration of cement exposed to extreme conditions poses threat to the entire structures and their integrity. A number of alternatives for conventional Portland cement has thus far been proposed, yet their long-term durability performance, especially in extreme environments is an ongoing topic of studies. This dissertation explores the applicability of alkali-activated cement for extreme engineering by investigating the fundamental degradation mechanism and nanostructural changes in this material induced by exposure to extreme environments. To this end, alkali-activated fly ash, slag and blend of both fly ash and slag were exposed to extreme conditions involving high $CO_2$, high temperature or potential gradient which accelerates leaching upon contact with water. The structural evolution of binder gel in alkali-activated cement exposed to extreme environments was investigated using multi-analytical tools. The obtained results provide new insight into the durability performance of the binder system, which establishes fundamental knowledge of deterioration phenomena driven by extreme conditions. The thesis is concluded by summarizing the implication of the results and potential topics of future studies.