Currently, cement and concrete industries have been contributing to the CO CO22 emission worldwide. Because of that, the efforts to minimize CO CO22 have been the subject of many researches. This study focus on the use of GGBFS and fly ash in mortar specimens as a patial replacement of cement. Because of the limitation of the initial compressive strength, the newly efforts to enhance the strength through CO CO22 Curing was adapted. To accelerate the reaction with CO CO22, , MgO was replaced by percentage from 0 to 100%. Results showed that compressive strength values at 7 days with CO CO22 curing done on specimens was higher than that with no CO CO22 curing. Similar trend was observed at 14 days too. It is therefore appeared that CO CO22 curing has an obvious effect on compressive strength development of mortar specimens.