Patent Application
20090200703
The present invention relates to the production of molded blocks from a hydraulically setting compound, in which fibers, in particular optical fibers, are embedded.
Molded blocks of hydraulically setting compounds with integrated fibers have long been known. Hydraulically setting compounds, also referred to hereafter as a matrix, are understood as meaning concrete, fine-grained concrete, mortar, gypsum and similar materials, which generally contain a hydraulic binder, aggregates, additives, admixtures and water. Within the scope of the invention, reference is made to molded blocks, which are intended to include not only the classic blocks with a square or rectangular base area but also those with a triangular, trapezoidal or rhomboidal base area and all conceivable round forms, such as a circle, ellipse, etc.
The advancing development of optical fibers is increasingly lowering their costs. In addition, the demand for exclusive design effects is increasing. Under these boundary conditions, molded blocks of hydraulically setting or cast compounds in which optical fibers are embedded in such a way that light penetrates through the bricks have been proposed in DE 93 10 500 U and WO 03/097954.
However, the production process claimed in WO 03/097954 is complex and unsuitable for production on an industrial scale. It is important to achieve a constant supply and distribution of the matrix in the formwork. The maintenance of constant thicknesses for the individual layers of matrix or fiber is also problematic. DE 93 10 500 U says nothing about the question of production.
The object of the present invention was therefore to find a process by which fibers can be incorporated in molded blocks, in particular of concrete, with a fixed orientation.
This object is achieved by a process and a device for producing molded blocks from hydraulically setting compounds (matrix) and fibers embedded therein, in which a formwork comprising a frame with a vertically movable base is used. The base of the formwork is initially set to a defined height below the upper edge of the frame, filled with hydraulically setting compound, the fibers are placed on in the desired direction and incorporated into the compound, and then the base is lowered by a predetermined amount. The steps are repeated until the desired height of the molded block is achieved.
The molded block produced in this way can also be used to obtain smaller blocks by means of cutting it up transversely and longitudinally with respect to the direction of the fibers.
Cement is suitable in particular as the hydraulic binder for the matrix. Suitable cements are, for example, Portland cement, Portland slag cement, Portland fly-ash cement, Portland limestone cement, Portland composite cement and blast-furnace cement. Portland cement and Portland slag cement are preferred.
In a way known per se, the matrix may contain natural and/or artificial aggregates, admixtures and/or additives.
Admixtures are, for example, natural and artificial pozzolans, color pigments, polymer dispersions, stone dusts, etc.; typical amounts are, for example, 3 to 8% by weight for color pigments and up to 30% by weight for fly ash, stone dusts, etc.
Additives are, for example, air-entraining agents, liquefiers, plasticizers, accelerators, retarders, etc. If present, amounts of each of up to 5% by weight, in individual cases of up to 10% by weight, are used.
In principle, sand, gravel or stone chippings are used. To achieve a uniform and dense distribution of the light-conducting fibers, sand mixtures with a maximum size of aggregate of approximately 2 mm have proven successful. The mass ratio of cement and sand is generally between 1:1 and 1:3.
The fibers are, in particular, optical fibers, so that the molded blocks produced according to the invention are transmissive to light in the direction of the incorporated fibers. The process and the device are, however, also ideally suited to the embedding of other fibers, in particular where it is important that the arrangement and orientation of the fibers within the molded block can be set in a specific manner.
Accordingly, textile glass fibers, plastic fibers, carbon fibers, natural fibers, etc., come into consideration as fibers. Instead of individual fibers, it is also possible to incorporate mats, bonded fabrics, rovings or, with particular preference, woven fabrics, referred to hereafter as fabrics for short.
It goes without saying that the fibers and the hydraulically setting compound must be compatible with one another, as is the case for example with the known optical fibers of silicate glass and cement.
Furthermore, the proportion of the fibers in the matrix must be appropriately set to ensure the required strength and load-bearing capacity of the molded block. In the case of optical fibers, suitable proportions are, for example, 2 to 10% by volume, preferably 5 to 8% by volume, with which satisfactory light transmission is achieved.
The formwork is preferably to be adapted in width, length and depth to the desired dimensions of the molded blocks. For example, dimensions of 50 cm×200 cm are suitable. The depth, which determines the maximum height of the molded block, may be, for example, 50 cm. It is advantageous for the process and the device of the invention that the height can be freely varied within the range of the minimum height, determined by the height of a layer of hydraulic compound and fibers, and the depth of the formwork.
The formwork should consist of a material, or at least be provided inside with a material, from which the matrix becomes adequately detached to ensure damage-free demolding. The formwork materials that are used for precast concrete units are accordingly suitable. The use of release agents, as are likewise known from the production of precast units, is possible.
The adjustment of the base may be performed in a way no per se by means of a spindle drive, a hydraulic mechanism or the like. It is advantageous for the demolding, and for cleaning that may be necessary, if the side walls of the formwork are foldable.
Preferably used for introducing the matrix is a device such as that already known as a mortar carriage. Mortar carriages are used for the laying of large-format masonry units (bricks, aerated concrete, sand-lime blocks) by the thin-bed fixing technique (thin layer of mortar of a thickness of about 5 mm). This involves applying the masonry mortar to the upper side of each course of blocks with the aid of a mortar carriage. The mortar carriage is a rectangular metal box which is open at the top and bottom and the width of which coincides with the width of the blocks being used. It is filled from above with mortar and subsequently pulled over the upper edge of a course of blocks in the longitudinal direction of the wall. A thin layer of mortar is applied to the upper side of the blocks via the open underside of the box and a defined gap.
Alternatively, the matrix may also be applied by means of a spraying device.
In a particularly preferred embodiment, the fibers or fabrics are kept on one or more rollers and, from there, are laid onto the compound and appropriately cut to the required length. This may preferably involve using a suitable device to stretch the fibers over the molding length and fix them, which advantageously avoids displacement of the fibers within the compound. Suitable for this, for example, is a clamping device, with which the fibers or fabrics are fixed on both sides of the formwork.
Alternatively, in particular in the case of stiff fibers, fibers that are already cut to length may be placed into the formwork.
The incorporation of the fibers or fabrics, and possibly simultaneous deaeration of the compound, is expediently performed by surface or external vibrators. A smoothing device with an integrated vibrating device can likewise be used.
In a preferred embodiment, the mortar carriage or the spraying device may be made to pass over the formwork and/or the formwork is moved under the mortar carriage or the spraying device. Particularly high rates of production can be realized if the formwork and the mortar carriage or at the spring device are made to move.
In a particularly preferred embodiment, the fibers or fabrics are introduced by the mortar carriage and so are brought into the formwork together with the hydraulically setting compound. This expediently involves deaeration of the compound by means of an internal or external vibrator on the mortar carriage.
With the process and the device according to the invention, patterns can also be created in the molded block. For this purpose, the fibers may be entirely or partially omitted in one or more layers.
The invention is to be explained in more detail on the basis of the accompanying figures, without however being restricted to the configurations described. Unless otherwise indicated, all values given in % refer to the weight.
In the figures:
a-f show diagrams of a device according to the invention with a clamping device for fixing the fibers or fabrics in various stages of the process.
In
According to the invention, at the beginning of production the base 3 of the formwork 1 is below the upper edge of the formwork with a defined difference in height s. This difference in height s corresponds to the height of a layer of hydraulically setting compound 5 and fibers 6. The mortar carriage 4 travels over the formwork 1 along the upper edge of the latter and thereby fills it with an amount of matrix 5 that can be exactly set. Subsequently, the fibers 6 required for one layer are placed onto the fresh surface of the matrix 5, either as individual fibers or as fabrics, incorporated with the smoothing device and cut to length.
For the next step, the base 3 of the formwork 1 is lowered by the height s of a layer comprising matrix 5 and fibers 6 and the filling operation is repeated in the same way. During the filling operation, the formwork 1 may be vibrated from the outside to deaerate the matrix 5, or compaction is performed by means of the smoothing device.
In
In
In
Subsequently, as represented in
After the severing, the clamping device 8, 9 is released, the base 3 of the formwork 1 is lowered and it is filled again with matrix 5. Then the operation is repeated, see
The invention has been explained on the basis of the example of a rectangular block; other forms with triangular, trapezoidal, polygonal, round or curved base areas can also be analogously obtained by corresponding choice of the form of formwork. The walls may be made perpendicular or else inclined with respect to the base area. In addition, it is possible by mechanical finishing, for example sawing, to adapt the outer contour more specifically to desired forms.
Although the process has proven to be particularly successful in the case of light-transmitting blocks, it can also be advantageously used in the case of other fibers for which exact alignment is desirable.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 007 920.5 | Feb 2006 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP07/01302 | 2/15/2007 | WO | 00 | 11/14/2008 |
