In this paper, results of a numerical study on pore continuity, permeability and durability of cementitious slurries for carbon sequestration projects are presented. The hydration model Hymostruc is used to simulate and visualize 3D virtual microstructures which are used to demonstrate the contribution of capillary pores to the continuity of the capillary pore system embedded in an evolving cementitious microstructure. Once capillary pores are blocked due to ongoing hydration, transport of CO2 species through the microstructure is avoided which may protect the slurry from leakage. Evaluating the pore continuity of the capillary pore system during hydration of the microstructure is therefore indispensable for a robust cementitious sealing material and is the main objective for slurry design. Simulations are conducted on slurries exposed to ambient temperatures of 20 °C, 40 °C, and 60 °C, and a durability outlook regarding the CO2 ingress is given as well. Aggregates and associated interfacial transition zones (ITZs) are introduced in the slurry system that may cause alternative porous path ways through the system. Pore continuity analysis shows the relevance of numerical simulations for assessing the capillary pore structure inside an evolving microstructure in relation to its sealing and durability performance.