GB676408A - Method of constructing concrete building elements - Google Patents

Abstract

676,408. Moulding concrete building elements. BUTTRESS & McCLELLAN, Inc. Nov. 20, 1950, No. 28319/50. Class 87(ii) A method of making a concrete building member comprises: coating the surface of a concrete base layer 31 with a composition containing water-insoluble substance in an evaporable liquid whereby, after evapora, tion, a film 33 is deposited which will prevent formation of a bond between the concrete of the layer 31 and concrete poured on the sealing film and set and cured thereon, placing forms on the coated and at least partially set base layer, and casting in the forms a concrete element, allowing the superposed concrete element 58 to set and cure to form the building member and then removing the building member from the base layer. The sealing layer 31, which is preferably sprayed on the base layer, is composed, e.g. of (alone or in combination), paraffin wax, resin, a synthetic resin which does not harden when exposed to air, or heavy petroleum residues, and is applied in solution in, e.g. a volatile petroleum solvent. These substances can also be applied in the form of a stabilized emulsion in water, using a suitable emusifying agent such as soap. Finely divided solids may be added, e.g. powdered talc, graphite or ground micaceous material. After the base layer has set sufficiently, the 'form, e.g. of timber, in which the building member is to be cast is constructed on it. The form may be suitable for various members, e.g. columns, beams, frames, &c. The Specification describes a form for a wall panel, comprising a timber frame 35 of the required thickness and an inner frame 37 for forming an aperture, e.g. a window, which is laid on the cast base 31 in the required position. As the wet concrete is poured into the form it is vibrated by suitable tamping means, e.g. a power driven flexible vibrator. To prevent concrete from flowing under the form and lifting it from position fittings 43 are first cast in the base 31 in which bolts 42 are secured which pull down cross braces 44. This anchoring may be removed after the concrete has taken an initial set. Alternatively, the form may be held down by weights 47. e.g. bags of sand. Moulding strips 40 can be incorporated to give a desired panel edge section. Reinforcement 50, 51, which may protrude as at 50a, may be set in the form and supported above the base 31 by wire chains 53. Cover reinforcement 55, 56, may also be incorporated, also plates 180 to provide for welding the concrete panel to steel structures. Attachment for lifting the panel when cast comprise sleeves 168 tack-welded to nuts 166 and bars 167 welded across the faces of the nuts on opposite sides of the sleeves. The sleeves 168 are plugged during pouring by bolts, which can also be used to adjust the level of the lifting units. These lifting units are disposed in the best position relative to the centre of gravity of the member, e.g. on one side of it, in a panel, so that the panel will hang vertically when lifted. The surface of the cast panel may be coated with sealing preparation and another form 60 constructed in which a second panel is cast, and after the second panel has partially set additional panels can be cast successively on top of it. Sealing preparations may be applied to the final upper surface to improve curing. The forms for subsequently cast panels may be anchored either to the concrete base 21, or to the form for the previous panels. The upper face of the concrete in a form may be finished to give any required panel surface and the under face may also be given a required surface by covering the concrete base with material of a suitable texture.