A kit and a method for making a porous cement which self sets to hydroxyapatite and has an interconnected porosity is produced by mixing a calcium source and a phosphate source with a carbonate source and mixing this powdered component with a liquid component having an acid component. The liquid component comprises water or an aqueous solution containing an acid. The acid and the carbonate react to form carbon dioxide thereby producing an interconnected porosity in the normally solid self-hardening bone cement. The method requires only a relatively low weight percent of the acid and base to be mixed with the liquid and powder cement components.