A cementitious material is provided that includes a phosphate based component and an alkali earth component. The alkali earth ion component has as a majority source a calcium aluminate calcium ion source of dodeca-calcium hepta-aluminate, or tricalcium aluminate. Magnesium oxide that has been fused and crushed to a size of less than 200 microns, alone or in combination with the calcium aluminate calcium ion source is also provided as the alkali earth ion component. When the phosphate based component and alkali earth ion components are combined in appropriate proportions, a rigid structure is obtained. A cementitious material formulation is also provided having an aqueous acidic phosphate solution as a part B and an alkali earth ion source as a part A that includes calcium aluminate, magnesium oxide or a combination thereof. Other additives include strength enhancing insoluble phosphate additive, an impurity metal reaction suppressant, tackifiers, anti-foaming agents, and the like.