Small-Angle X-Ray Scattering (SAXS) is an analytical technique used to study the microstructure and mesostructure of materials at nanometer to micrometer scales. In the context of cement and concrete, SAXS provides detailed insights into the pore structure, particle size distribution, and phase separation within cementitious materials, particularly under severe environmental conditions. SAXS works by measuring the scattering of X-rays as they pass through a sample, with the scattering pattern providing information about the size, shape, and distribution of pores and particles within the material. This technique is invaluable for understanding the hydration processes of cement, the formation of C-S-H (calcium silicate hydrate) phases, and the interaction of these phases with environmental agents such as salts and pollutants (Scrivener and Nonat 2011).