This study focuses on the numerical modeling of the reaction and microstructure development of a one-part granite-based geopolymer, which is often used for carbon capture and storage (CCS) applications. This work extends the capabilities of GeoMicro3D to model one-part geopolymers containing different precursors and activators (solid and in solution). The model considers the particle size distribution of different solids and the real shape of particles to prepare the initial simulation domain. Further, the dissolution rates of different solids estimated from the experiments were used to model the dissolution of different elements in the pore solution. Subsequently, the model utilizes classical nucleation probability modeling coupled with thermodynamic modeling to estimate the precipitation of products in the microstructure. Experiments were performed to study the pore solution, reaction degree, and amount of products in the microstructure, which were further compared with the simulation results to check the rationality of the model.