A cementitious print head and a cementitious printing methodology may include a feed barrel, a print head nozzle, a CO2 supply, a steam supply, a selective valve assembly in communication with the CO2 supply and the steam supply, a plurality of dual use extrusion head injectors, and a print head controller. The print head controller is operatively coupled to the selective valve assembly and is programmed to execute a CO2 and steam injection protocol where steam may be selected for injection by the extrusion head injectors into a cementitious composition as it is extruded from the print head nozzle to enhance a hydration reaction and formation of hydroxide in the cementitious composition before CO2 may be selected for injection by the extrusion head injectors into the cementitious composition as it is extruded from the print head nozzle to enhance a carbonation reaction in the cementitious composition.