METHOD FOR THE PRODUCTION OF BUILDING ELEMENTS PARTICULARLY SUITED FOR USE AS BRICK FACINGS

Abstract: Method for the production of building elements preferably brick facings by granulation of a mixture of 40-60% by weight of cement, 60-40% by weight of aggregate, 0.5-2% by weight of thickening agent such as carboxymethylcellulose and preferably colouring agent or one or more additives and water in an amount of 8-17% by weight based on the dry matter of the mixture, hot pressing the granules under a pressure of 50-100 kg/cm<2> and at a temperature above 100<o>C to form single elements or a string, and cutting the string into single elements, and storing the elements in a humid atmosphere until a considerable setting of the cement has taken place. The method is considerably simpler and quicker than the known methods for the production of brick facings.

Description: METHOD FOR THE PRODUCTION OF BUILDING ELEMENTS PARTICULARLY SUITED FOR USE AS BRICK FACINGS. The invention relates to a method for the production of building elements particularly suited for use as brick facings. It is well known to use brick facings in the form of tiles and lime sand bricks. Tile elements are difficult to produce as the production includes i.e. shaping of the units and subsequent baking of these. In addition to this the shaped units may be considerably deformed during baking. Finally, the production of brick facings in the form of tile elements presents considerable drawbacks with respect to obtaining specific and reproducible colours as the colour development to a large extent is determined by the composition of the clay used in the production. Likewise, the production of lime-sand brick facings which requires the use of pressure vessels, is difficult and time consuming. The object of the invention is to provide a quick method for the production of building elements of a uniform shape and reproducible appearance, and particularly building elements for use as brick facings. This object is obtained by the method of the invention, said method being characterized in that a mixture of 40-60% by weight of cement, 60-40% by weight of aggregate, 0.5-2% by weight of thickening agent, and optionally a colouring agent or one or more additives and water in an amount of 8-17% by weight based on the dry matter of the mixture is granulated, that the granules are pressed under a pressure of 50-100 kg/cm 2 and at temperature over 100°C to form a single element or a string which is subsequently cut into single elements, and that the element or elements is stored in a humid atmosphere until a considerable setting of the cement has taken place. Previous attempts to accelerate the production of cement building elements by pressing in moulds have faced the problem that the pressed units only can be removed from the moulds with great difficulties. According to the invention it has surprisingly been found that by- using the pressure and temperature conditions mentioned above combined with a thickening agent a steam film is formed on the surface of the pressed unit, and that this steam film acts as a release agent which makes it possible to release the element from the mould. It has been found that the building elements made according to the method of the invention exhibits a sufficiently large stability with respect to shape and are sufficiently weather resisting to be used as brick facings on outer walls. By proper choice of colouring agent it has proved possible to obtain elements of strongly varying colours and including colours similar to those of conventional red and yellow bricks. The building elements may not only be produced in the form of planar units but also as angular elements for use on wall corners. The production of granules is preferably effected by mixing the solid components i.e. cement, aggregate preferably in the form of sand and a thickening agent such as carboxymethylcellulose, a separating agent such as zinc stearate, and optionally a solid colouring agent. The solid mixture thus obtained is then added to the apportioned amount of water in the vessel in a mixing apparatus, and it is mixed until a viscous mass is obtained. The viscous mass thus obtained is allowed to stand for preferably about 1/2 hr. or more. However, this period may be reduced considerably by using a moistening agent in the mixture of cement, aggregate and water. The granulation of the viscous mass is preferably effected by means of one or more horizontally placed metal nets with a mesh size ranging from 0.5 to 2 cm and by rotating impellers moving in parallel direction with the nets and in a short distance above their top surface. When using moulds for hot pressing of the granules the mould parts used preferably have a surface temperature of 120-160°C. Temperatures above approx. 160°C should normally be avoided as there is a tendency at such temperature for the material to burn to the mould parts. The pressure used is as mentioned 50-100 kg/cm 2 and preferably 75-95 kg/cm 2 . The pressure partly depends on the water content of the granules as a low water content requires a relatively high pressure. After placing the granules into the mould but before pressing an upper layer of a paste containing colouring agent, cement, and water may be added. In this manner special colour effects may be produced by this in the surface of the elements. After the hot pressing has taken place the product formed has a certain plasticity. On the one hand this plasticity is sufficiently great to allow a string to be cut into the desired pieces, and on the other hand sufficiently limited that the elements directly formed or those formed by cutting of the string have a sufficiently great strength to be handled. Thus, the elements formed may immediately be packed e.g. in plastic bags which present the advantage of securing the maintenance of a proper moisture content during the continuing setting of the cement. The elements packed in plastic bags are preferably kept at room temperature for about one week. After such storing they are sufficiently strong to be transported to the building site and used. Even though the elements formed by the method of the invention have a great mechanical strength it may, in some cases, be desirable to increase the strength by incorporating reinforcement fibres into the mixture of starting materials. Such fibres may be of inorganic and/or organic origin. The invention will now be further described with reference to the following: Example A mixture was produced containing: Rapid cement 50.0 kg Sand 50.0 kg Carboxymethylcellulose 0.7 kg Yellow iron oxide 2.5 kg 103.20 kg This mixture was added to the mixing tank of a conventional mixing apparatus containing 13.5 kg water and was stirred until a uniform, viscous mass was obtained. The product formed was allowed to stand for 1/2 hr. and was then granulated by being pressed through a metal net with a mesh size of 1 cm by means of rotating impellers moving in an path close to and parallel with the net. The granules were introduced into a mould of the dimensions 5.4 x 22.8 cm in an amount of 200 g. The material was subsequently pressed together to a thickness of 0.7 cm by means of heated mould parts with a surface temperature of 135°C and under a pressure of 85.5 kg/cm 2 . The pressure was maintained for a period of about 0.4 sec. The pressed unit formed was then released from the mould, and was immediately packed in a plastic bag. The packed pressed units were then stored for about 1 week at room temperature. Elements produced as described above were used as brick facings on a hard sheet of rock wool fibres forming the outside of an outer wall. This resulted in a wall which was difficult to distinguish from a normal wall of conventional yellow bricks in terms of appearance. After having been exposed to the influence of the weather for a period of 4 1/2 months the wall showed no signs of deterioration or change in the brick facings.

Claims: C l a i m s 1. A method for the production of building elements particularly suited for use as brick facings c h a r a c t e r i z e d in that a mixture of 40-60% by weight of cement, 60-40% by weight of aggregate, 0.5-2% by weight of thickening agent and optionally a colouring agent or one or more additive, and water in an amount of 8-17% by weight of water based on dry matter of the mixture is granulated, that the granules are pressed under a pressure of 50-100 kg/cm 2 and at a temperature over 100°C to form a single element or a string which is then cut into single elements, and that the single element or elements is stored in a humid atmosphere until a considerable setting of the cement has taken place. 2. A method according to claim 1 c h a r a c t e r i z e d in using sand as an aggregate. 3. A method according to claim l or 2 c h a r a c t e r i z e d in using carboxymethylcellulose as a thickening agent. 4. A method according to claim 1,2, or 3 c h a r a c t e r i z e d in that the granules are hot pressed in a mould, the mould parts of which have a surface temperature of 120-160°C. 5. A method according to any of the proceeding claims c h a r a c t e r i z e d in using a pressing pressure of 75-95 kg/cm 2 . 6. A method according to any of the proceeding claims c h a r a c t e r i z e d in storing the pressed element or elements in plastic bags.

Inventors: WEIDEMANN JOERN ULRIK, WEIDEMANN, JOERN ULRIK
Applicants: WEIDEMANN & SONNER L P
Application year: 1986
Main classification: B28B3
IPC codes: C04B28, C04B40