GB851222A - Method and means for producing moulded articles of concrete and the like materials - Google Patents

Abstract

851,222. Moulding concrete. INDUSTRIAL DEVELOPMENT CO., ESTABLISHMENT. July 5, 1957 [July 10, 1956], No. 21431/57. Class 87(2). The concrete, which is held under mechanical compression throughout the moulding operation, is subjected to fluid diffusion until excess water is expelled and is then treated with steam under pressure, being heated to 120-180‹, the action of the steam being maintained until the concrete has become hard. In the mould shown in Fig. 2 for the production of concrete piping, a cylindrical shell 10 has a hollow core 13 which carries a series of outwardly extending rings 16. These rings support #-shaped channel member 17 to which are secured metal sheets 18 joining one another when the mould is inoperative along lines 19. An expansible filtering or diffusing layer 20 may surround these metal sheets. Inside the shell 10 is fitted a grid 21 over the inner surface of which are fitted a number of spaced carrier sheets 22 carrying in turn on their inner surfaces a series of longitudinal strips 23. The strips form an airpermeable and expansible system of staves opening along narrow slots at the joining lines 24. Between the cylindrical systems 18 and 23 is formed the moulding chamber A for the concrete. Compressed air admitted to the core 13 at a pressure of 3-10 kg/sq. cm. acts on the channel members 17 so as to produce a mechanical pressure on the moulded mass and to open the slots at the joints 19. Compressed air is then guided through ports to the inside of the channel members 17 and thence through the slots 19 to the concrete in which it diffuses driving the excess water outwardly into the permeable area on the inside wall of shell 10. During the second or digesting stage, steam is applied under a constant or pulsating pressure of 3-10 kg/sq. cm. in the same way as the compressed air and on condensing is removed by the compressed air since the latter is held at the same pressure as the steam during the time required for the exhausting of the condensate. After, or simultaneously with, the steam treatment, reacting fluids such as vaporised sulphur, silicon tetrafluoride, and solutions of silicone elastomers and resins may be diffused through the concrete to modify its final properties.