Density functional theory (DFT) is a quantum mechanical modeling method used to investigate the electronic structure of many-body systems, primarily atoms and molecules. In the context of cement and concrete, DFT is employed to study the atomic and molecular interactions within the cementitious materials, providing insights into the chemical processes that govern the behavior of these materials under various conditions. This theoretical approach is crucial for predicting material properties and optimizing compositions, particularly under severe environmental conditions where chemical durability and mechanical integrity are challenged.