In a method for manufacturing foam concrete elements, a mixture appropriate for casting is prepared, comprising substantially a granular material, particularly silicates, water, ciment and foam, the material being poured in a mold, and thereafter the blank is withdrawn from the mold when it has acquired a sufficient resistance and it is finally allowed to harden. In order to readily and rapidly manufacture constant density bricks, before filling the mold, a temperature riser and setting accelerator agent is added to the mixture, this agent heating the final mixture in the mold by an electric field at a high frequency and a homogenous temperature comprised between 40 and 80 C. The heating in the mold of the final mixture is effected so rapidly that the expansion of the mixture due to the heating is finished before the setting of the ciment. The element is withdrawn from the mold after a heating comprised between 20 to 120s.