Abstract: In a method of casting different types of concrete products without the need of using a curing chamber or an autoclave the concrete subsequent to mixing, is casted and externally and/or internally subjected to a vacuum treatment to have it de-watered and compacted. Then carbon-dioxide gas is supplied to the mass while maintaining a sub- or under-pressure in a manner such that the gas--as a result of the sub-pressure--diffuses into the capillaries formed in the concrete mass, to quickly harden the mass. In one embodiment (cf. FIG. 2)--in which the mass (1) is de-watered and compacted by means of a mat or plate (2) placed thereupon and exposed to a sub-pressure via a pipe or a line (5)--the carbon-dioxide gas is supplied (through line 6) via said mat or plate (2) while using the under-pressure prevailing in the mass. In another embodiment (cf. FIG.