The alkali-activated fly ash/slag (AAFS) pastes exhibit complex compositions and heterogeneous spatial distributions of phases, necessitating a comprehensive tool capable of quantifying phase assemblage, characterizing ion diffusion, and unveiling microstructure evolution. However, existing techniques have limitations in providing interpretability and visual analyses. This study introduces a versatile analysis methodology for energy dispersive X-ray spectroscopy (EDS) images, encompassing data preprocessing, data interpretation, and four downstream applications: phase inference, phase quantification, ion diffusion characterization, and quantification of phase spatial distributions. Through the analysis of five representative elements, this study successfully identifies and quantifies three components in precursors (slag, quartz, mullite) and four reaction products (slag-products, quartz-products, mullite-products, mixture products) in the AAFS pastes. Moreover, by characterizing ion diffusion and quantifying spatial distributions, insights into the interactions among various precursors and reaction products are elucidated. The proposed EDS image analysis methodology is expected to yield valuable understandings of the reaction mechanisms and phase evolution involved in utilizing solid waste as cementitious materials.