Method and apparatus for insulating building blocks and the blocks produced thereby

An apparatus for forming a molded insulating layer from expandable thermoplastic polymer particles on interior surfaces of an internal cavity of a concrete masonry block;

• said apparatus including:
• a male plug member dimensioned to be inserted within the internal cavity of the block with peripheral walls of said plug member spaced from interior surfaces of the cavity to form a peripheral compartment, said plug member including passages extending through external walls thereof through which steam, under pressure, can be directed into said peripheral compartment;
• a platen joined to the male plug member and adapted to close one end of the cavity when the male plug member is inserted within the cavity in position for carrying out the molding operation, said platen including a passageway communicating with the peripheral compartment through which the polymer particles can be injected into said peripheral compartment, said upper platen further including a second passageway communicating with the passages extending through the external walls of said plug member;
• and
• pressure-applying means for engaging opposed longitudinally extending sidewalls of the block and for applying an external, inwardly directed force thereto of a sufficient magnitude for counteracting the outwardly directed force created by the injection of steam, under pressure, into the peripheral compartment of the block cavity to thereby prevent said masonry block from cracking.