A study was carried out to determine the effects of high curing temperature and long-term storage on the reaction products and microporosity in metakaolin (MK)-blended cement pastes cured at 60°C after 53 months of hydration and to evaluate the stability of the hydrated phases formed during the pozzolanic reaction. The results showed that C-S-H, stratlingite and hydrogarnet were the main hydrated phases formed under these working conditions. On the other hand, the pore structure of the MK-blended pastes was refined. This demonstrates that there was no evidence of any conversion reaction from the hexagonal metastable phase to a stable cubic phase after 53 months of curing