A cementitious composition comprising a crystalline phase and an amorphous phase, and an activator selected from the group of materials comprising inorganic bases. In some cases the crystalline phase is gehlenite. In some cases the crystalline phase is anorthite. In some cases the amorphous phase is amorphous calcium aluminum silicate. In some cases the activator is elected from OPC (1-70 wt %), free lime (1-20 wt %), calcium hydroxide (1-20 wt %), and alkali hydroxides (NaOH, KOH 1 to 10 wt %), individually or in combination. A low lime cementitious material is cured by reaction with a curing reagent that includes a reagent chemical that is synthesized from CO2. Examples of such a reagent are oxalic acid and tartaric acid.