EP0510486B1 - Composite stone resp. composite plate - Google Patents

Description

The present invention relates to a composite stone or a composite panel as a covering for walkways and. Like. With the features of the preamble of claim 1.

It is known to stones or slabs with which walkways, passable pedestrian areas and. The like. To be proven to be made of concrete. This is primarily due to cost reasons. In order to give the surfaces of these concrete blocks or concrete slabs a pleasing appearance, they are in many cases subjected to a special treatment so that they are given a natural stone-like character.

Furthermore, it is known to use natural stones or slabs of natural stone for such purposes. Granite, a deep rock with a crystalline structure, is used particularly often for this purpose. Such a rock has a very dense structure, ie only a low absorbency, which makes the rock very resistant to weathering. Since stones or slabs of this type have to withstand relatively high loads, because a load from vehicles must also be expected in pedestrian areas only, the stones or Slabs are relatively thick, which means that relatively large amounts of natural stone have to be used, which is associated with relatively high costs.

A composite stone or a composite panel with the features of the preamble of claim 1 is known from EP-A-0 053 092 B1. In this known composite stone, a two-component adhesive is used as an adhesive between the natural stone portion and the concrete portion, which is applied in a very thin layer to the underside of the natural stone portion.

The invention has for its object to provide a composite stone or a composite panel of the type specified, which has a particularly good adhesive strength between the natural stone portion and the concrete portion.

According to the invention, this object is achieved by a composite stone or a composite panel with the characterizing features of patent claim 1.

The decisive factor for whether such a composite stone can replace a stone consisting of a single material is the adhesive strength between the natural stone portion and the concrete portion. The connection between the two materials must be designed in such a way that the connection does not break due to stress or thermal stress, which inevitably would result in destruction of the stone or the slab, since in such a case the lower part of the concrete is no longer together would absorb and transfer the corresponding loads of the natural stone, but instead only the upper natural stone would, which would lead to an immediate break due to its small thickness. To achieve particularly good adhesive strength, the invention provides two measures: firstly, mechanical interlocking (dowelling effect) is provided between the natural stone component and the adhesive mortar component, and secondly, adhesion is achieved by bonding between the two different types using the special adhesive mortar based on cement-synthetic resin Materials brought about. The mechanical interlocking or latching is achieved by recesses running at an oblique angle to the underside of the natural stone slab, into which the adhesive mortar penetrates, so that in the hardened state of the adhesive mortar it essentially fills the recesses. There are then undercuts between adhesive mortar and natural stone, which make it difficult to separate the two materials at the interface when applying opposing tensile forces. In addition, these inclined recesses increase the adhesive surface on the underside of the natural stone slab, which further improves the adhesive effect. It is essential that the recesses run obliquely to the underside of the natural stone slab, so that the undercuts mentioned result because, in contrast to recesses which are made at right angles to the underside, the interface between the materials acts at an angle and not parallel to the direction of the attacking tensile forces.

Systems are referred to as mortar whose aggregate grain has a maximum diameter of 4 mm. The mortar grain can therefore penetrate into the recesses provided and thereby produce the desired mechanical toothing effect. This would not have been possible to this extent if the concrete layer had been applied directly to the natural stone, ie without an intermediate layer of adhesive mortar. as usual concretes have aggregate sizes up to 32 mm. The existing relatively large aggregate grains would have prevented a corresponding toothing effect.

At the interface between natural stone and adhesive mortar, both a mechanical interlocking effect and an adhesive effect are achieved by curing the adhesive mortar. The adhesive mortar-concrete interface is less critical anyway, since both materials are applied fresh to fresh and bind or harden together. The adhesive mortar is applied to the underside of the natural stone portion so that it essentially fills the recesses. Although the concrete itself does not essentially penetrate into the depressions, the fact that the adhesive mortar and concrete form a solid bond anyway due to their similar composition and the joint setting and hardening, a condition is achieved as if the concrete directly with the natural stone portion would interlock over the recesses. As mentioned, however, such a toothing effect would not have been achievable without adhesive mortar, since with correspondingly large aggregate grains of the concrete, it cannot penetrate into the recesses (the width of which must not be too large in order not to impair the toothing effect). It is only possible to ensure the desired toothing effect with the adhesive mortar.

It is also essential that the provided depressions and the mechanical toothing achieved thereby ensure a shrinkage compensation. In contrast, the adhesive mortar layer, which is considerably thicker than a pure two-component adhesive layer, shrinks to an increased extent, but this does not lead to detachment effects on the natural stone portion due to the interlocking achieved.

In the production of the composite stone, the concrete portion is poured onto the underside of the natural stone portion after it has been provided with the adhesive mortar mentioned above. The adhesive mortar contains both an inorganic binder (cement) and an organic binder (synthetic resin). After setting or hardening, both agents ensure a firm bond between the two different materials, whereby it should be emphasized that due to the high density and low absorbency of the natural stone material, the organic binder in the adhesive mortar is of essential importance in order to achieve a sufficient adhesive effect. It is only by adding the organic binder to the adhesive mortar in connection with the mechanical interlocking measures described above that it is possible to create a composite stone that is sufficiently resilient and can be used instead of the pure natural stone.

The depressions are expediently designed as grooves or as bores. In practice, the underside of the natural stone portion has as many depressions as possible in order to increase the toothing effect that can be achieved. However, since the installation of the depressions in the underside of the natural stone slab represents a considerable additional workload, limits are set here for practical reasons and for reasons of cost. It has proven to be advantageous in terms of the toothing effect and the amount of work involved to provide 2 to 3 depressions in every running 10 cm natural stone slab. Grooves are preferred because they are easier to manufacture than holes and provide larger undercut areas.

In the standard solution according to the invention, the depressions all run parallel to one another and only extend in one direction over the underside of the natural stone slab. In other words, the depressions are not arranged crosswise, ie in two intersecting directions. Although this arrangement would further improve the toothing effect, it would result in additional processing effort for the natural stone slab, which is not absolutely necessary to achieve sufficient adhesive strength.

An embodiment of the invention, which has a plurality of depressions, is characterized in that the depressions of one half of the stone or plate are arranged inclined in opposite directions to those of the other half of the stone or plate. Here, the depressions also run only in one direction over the underside of the natural stone slab, but the depressions of one half have an opposite tendency to the depressions of the other half. In the middle, a trapezoid arises between adjacent recesses on the underside of the natural stone slab, i.e. a dovetail-shaped undercut that ensures particularly good interlocking and supports the concrete's adhesion to natural stone. In addition, this embodiment is particularly well suited for cases in which high shear forces can occur from both sides, since half of the stone or the plate has depressions in the form of continuous or interrupted grooves or bores pointing in this direction at an acute angle.

The composite stone according to the invention or the composite plate according to the invention are produced in such a way that the corresponding plate-shaped natural stone portion is provided with the depressions on its underside. For example, the corresponding grooves are cut obliquely into the underside of the natural stone slab. The natural stone slab is then placed in a suitable shape, with the underside facing upwards. On the underside and in the milled recesses the adhesive mortar is then applied, whereupon the mold is poured with concrete. This can be a conventional concrete used for corresponding artificial stones or artificial slabs. After the concrete has solidified, the mold is opened and the finished stone is removed. This is then ready for use after appropriate post-processing, cleaning, etc.

The adhesive mortar used consists of the usual additives (sand), water and binders, cement being used in combination with an organic binder (synthetic resin). The binder matrix formed from inorganic and organic constituents ensures the required adhesive strength, in particular in the case in question here, in which a natural stone with low absorbency (low porosity) is to be bonded to concrete. Water-emulsifiable epoxy resins (ECC) are used as the preferred organic binder. The epoxy resins used in ECC technology are based on the cement mechanism, so they can practically always be processed if the cement allows it. A subsequent loss of adhesion due to effects on the bandage level, as is the case for example with certain thermoplastics, is ruled out.

Reactively crosslinked thermoplastics, for example acrylates or butadiene-styrene, are used as a further preferred organic binder. Reaction partners are the hardener systems from epoxy technology. Depending on the formulation, these materials enable the advantages of thermoplastics and thermosets to be bundled without having their disadvantages.

The proportion of synthetic resin in the adhesive mortar is preferably 20-30% of Cement weight of the adhesive mortar. The layer of adhesive mortar applied is expediently 3-5 mm thick.

In order to further improve the adhesive strength between the natural stone portion and the concrete portion, the contact surface which later forms the binding plane is preferably additionally activated according to the invention. For this purpose, silanes are used, which on the one hand combine with the natural stone, but on the other hand contain reactive groups which combine with the plastic, which is contained in the subsequent mortar. In this embodiment, prior to the application of the adhesive mortar to the underside of the natural stone slab, this underside is provided with a bilayer reactive silane as a primer.

According to a particularly preferred embodiment of the invention, the stone or slab in the concrete portion is provided with a laterally projecting and surrounding concrete base. The base is expediently arranged in the lower region of the stone or the plate and has the purpose of providing a corresponding joint specification. In this way, the laying of the composite block designed according to the invention or the corresponding composite panel is made considerably easier. In addition, this results in a reduced edge pressure of the granite portion, since the base prevents the granite portions from adjacent stones or slabs from coming into contact with one another during laying.

It has proven particularly expedient to arrange the depressions in the two outer thirds of the slab-shaped natural stone portion. Here again, the depressions in one third are preferably arranged in the opposite direction to the depressions in the other third. Three grooves in a third are particularly preferred. In this embodiment, the desired mechanical Interlocking effect achieved in the two outer thirds, ie the areas in which the greatest release voltages occur.

In order to allow the adhesive mortar to penetrate into the depressions, their width corresponds to at least 1.5 to 2 times the diameter of the largest grain of the additive of the adhesive mortar. The depressions (grooves) preferably have a maximum width of 1 cm. With a varying size of the composite stone or the composite panel, the number of the depressions is therefore increased or decreased with the width of the depressions remaining the same. For example, for a stone size of 200 mm 2x2 = 4 grooves, for a stone size of 300 mm 2x3 = 6 grooves, for a stone size of 400 mm 2x4 = 8 grooves and for a stone size of 500 mm 2x5 = 10 grooves.

The depths of the depressions correspond to a maximum of one third of the thickness of the slab-shaped natural stone, so as not to endanger its resilience.

In the case of particularly high load cases, the composite block designed according to the invention or the composite panel designed according to the invention has reinforcement arranged in the concrete portion. The reinforcement is expediently connected to the plate-shaped natural stone portion via at least one reinforcement holder, the reinforcement holder engaging in at least one recess. This arrangement achieves two things: firstly, the reinforcement is securely held on the natural stone part so that the concrete pouring process can run smoothly, and secondly the reinforcement holder serves as a tie rod that anchors the reinforcement in the natural stone part and thus further increases the natural stone part-concrete composite effect. The corresponding tie rod effect is achieved in that the reinforcement holder with two oppositely directed legs engages in two adjacent oppositely inclined depressions. The opposite inclination of the recesses counteracts removal of the reinforcement holder from the recesses.

A reinforcement holder is preferably provided in the respective outer third of the composite block or the composite panel. The reinforcement holder can be made of plastic, for example. A further improvement in the composite effect is achieved in that the reinforcement holders are connected to one another, for example by means of fleeces etc.

Figur 1

eine Seitenansicht eines Verbundsteines;

Figur 2

eine Unteransicht auf den Natursteinanteil des Verbundsteines der Figur 1;

Figur 3

eine zweite Ausführungsform eines Verbundsteines in der Seitenansicht;

Figur 4

eine dritte Ausführungsform eines Verbundsteines in der Seitenansicht; und

Figur 5

eine vierte Ausführungsform eines Verbundsteines im Teilschnitt.

The invention is explained in detail below using exemplary embodiments in conjunction with the drawing. The drawing is not to scale. Show it:

Figure 1

a side view of a composite stone;

Figure 2

a bottom view of the natural stone portion of the composite stone of Figure 1;

Figure 3

a second embodiment of a composite stone in side view;

Figure 4

a third embodiment of a composite stone in side view; and

Figure 5

a fourth embodiment of a composite stone in partial section.

The composite stone 1 shown in FIGS. 1 and 2 has an approximately square shape with an edge length of 30 cm and a height of 8 cm. The stone has an upper granite portion 2 and a lower concrete portion 3. The granite part has a height of 2 cm, while the concrete part has a height of 6 cm.

On the underside 4, the granite portion 2 is provided with 6 grooves 5 which run parallel to one another and extend upwards from the underside. The grooves have a width of approximately 8 mm and an average depth of approximately 1 cm. They extend obliquely upwards, the three grooves on the left side of the stone being inclined in opposite directions to the three grooves on the right side of the stone, but with both types of grooves pointing towards the center of the stone. This results in undercuts. A dovetail shape is created between the two central grooves. An adhesive mortar layer (not shown) is provided between the concrete portion 3 and the granite portion 2, which completely fills the grooves, so that there is a good toothing effect between the two portions.

Figure 2 shows an illustration of the underside of the granite portion 2 of the stone. It can be seen that the grooves 5 run through from one side to the other side. To increase the toothing effect, grooves could also be arranged in a direction offset by 90 °; however, this would require additional work that is not absolutely necessary for reasons of adhesive strength.

Figure 3 shows a side view of another embodiment of a composite stone. This stone essentially corresponds to the stone of FIGS. 1 and 2, but has in its concrete part 3 a base 6 running all around in the lower area, which defines the joint dimension and one large edge pressure of the granite parts of neighboring stones prevented. The base has a width of 1 - 2 mm. The distance from the top of the stone to the top of the base is 3 cm.

An embodiment for producing a composite stone will now be described.

First, a granite slab with the dimensions shown above was sawn. The oblique grooves shown and described were then milled on the underside of the granite slab, the grooves on one side being milled in the opposite direction to the grooves on the other side. Then the grooved granite slab was placed in a suitable shape with the underside facing upwards. Then the underside of the plate was provided with a 3 - 5 mm thick layer of adhesive mortar that filled the recesses. The adhesive mortar consisted of a commercially available emulsifiable epoxy resin, cement, sand and water. The proportion of synthetic resin in the adhesive mortar was 20-30% of the cement weight of the adhesive mortar. Sand and water were added in the usual proportions.
After the adhesive mortar had been applied, the mold was filled with concrete in the not yet hardened state, a concrete which was customary for such artificial stones being used. After the concrete hardened, the mold was removed. The stone was then ready for use after possible post-treatments, such as deburring, cleaning.

Another advantage of the solution according to the invention is that the composite stone or the composite panel can be provided with a reinforcement, which is housed in the concrete portion. In this way, the load capacity of the stone or slab can be improved compared to a comparable natural stone or slab. The Reinforcement is usually provided in the corresponding tensile zone of the stone or slab.

The preferred height of the stone or slab is 8, 10 and 12 cm. The natural stone portion is always 2 cm high, while the concrete portion varies in height depending on the load requirements, i.e. has one of 6, 8 or 10 cm.

Figure 4 shows a further embodiment of a composite stone in a side view. This composite stone is also composed of a natural stone part 2 and a concrete part 3. Between the natural stone portion 2 and the concrete portion 3 there is an adhesive mortar layer 7 (ECC adhesive mortar), which is shown in FIG. 5 with an increased thickness. The adhesive mortar completely fills the corresponding depressions on the underside 4 of the natural stone portion 2 and also forms a continuous layer between the flat section of the underside 4 and the concrete portion 3. In this embodiment, three recesses 5 in the form of grooves are provided in the two outer thirds of the composite stone. These grooves are inclined upwards and outwards. As a result, a corresponding toothing effect is achieved as in the embodiments in FIGS. 1 to 3.

FIG. 5 shows a fourth embodiment of a composite stone in partial section. This composite stone is also composed of a plate-shaped natural stone part 2, an adhesive mortar layer 7 and a concrete part 3. The adhesive mortar layer fills recesses 5, 8, which are provided on the underside 4 of the natural stone portion, as in the embodiment of FIG. 4 in the two outer thirds. In this embodiment, the depressions extend a third, however, not in the same direction as each other, but in the outer area of the stone two depressions 8 are provided, which extend in opposite directions in the drawing upwards and to the left and right. Another depression in this outer third is inclined upwards and outwards.

In the concrete part 3 there is a reinforcement 10 made of conventional structural steel, which is composed of longitudinal bars and cross bars. This reinforcement is connected via a reinforcement holder 9 in the outer third of the stone to the natural stone portion 2, the reinforcement holder 9 also acting as a tie rod since it is anchored in the corresponding recesses 8, 8. The reinforcement holder 9 is made of plastic or iron and has two diverging legs 11 which engage resiliently in the two oppositely running depressions 8, 8. The diverging legs 11 are held in the natural stone portion 2 by the oppositely inclined depressions 8, 8. The two legs 11 open into a curved main part 12, the free legs of which end in two clamp elements 13, which resiliently enclose a corresponding bar of the reinforcement 10. It is understood that the embodiment of the reinforcement holder shown and described here is only exemplary; other suitable embodiments can also be used. It is only essential that the reinforcement holder is anchored in the natural stone portion and clamped onto the respective reinforcement bar. As shown in FIG. 5, this anchoring can be achieved with the aid of two diverging legs which engage in two diverging depressions.

Claims (17)

1. A composite stone or a composite plate as covering for sidewalks etc., comprising an upper plate-like portion (2) of a natural stone with low absorbency, especially granite, and a lower reinforcing concrete portion (3) which has been freshly applied to the lower side (4) of the plate-like natural stone portion (2), said lower side (4) having been provided with a bonding agent, and bonds to the lower side of the plate-like natural stone portion (2) after curing, characterized in that the plate-like natural stone portion (2) has on its lower side (4) facing the concrete a plurality of depressions (5) extending in an oblique-angled manner with regard to the lower side (4), and in that the bonding agent is an adhesive mortar on the base cement-synthetic resin which, by interlocking with the plate-like natural stone portion (2), has penetrated into the depressions (5) and substantially fills out the same.
2. The composite stone or composite plate according to claim 1, characterized in that the depressions (5) are formed as grooves.
3. The composite stone or composite plate according to claim 1, characterized in that the depressions are formed as bores.
4. The composite stone or composite plate according to one of the preceding claims, characterized in that the depressions (5) of the one half of the stone or plate of the natural stone portion (2) are inclined in an opposite manner with regard to those of the other half of the stone or plate of the natural stone portion (2).
5. The composite stone or composite plate according to one of the preceding claims, characterized in that the synthetic resin proportion takes up 20-30 % of the cement weight of the adhesive mortar.
6. The composite stone or composite plate according to one of the preceding claims, characterized in that the applied adhesive mortar layer has a thickness of 3-5 mm.
7. The composite stone or composite plate according to one of the preceding claims, characterized in that the adhesive mortar is a mortar on a cement-epoxy resin base.
8. The composite stone or composite plate according to one of the claims 1 to 6, characterized in that the adhesive mortar is a mortar on the base of cement and epoxidated acrylates.
9. The composite stone or composite plate according to one of the preceding claims, characterized in that the lower side (4) of the natural stone plate has been activated with silanes reactive on both sides.
10. The composite stone or composite plate according to one of the preceding claims, characterized in that the stone or the plate has a laterally projecting and enclosing concrete base (6) within the concrete portion (3).
11. The composite stone or composite plate according to one of the preceding claims, characterized in that the concrete portion (3) has an armouring (10).
12. The composite stone or composite plate according to one of the claims 2 to 11, characterized in that the depressions (5)are formed as dovetail-like grooves.
13. The composite stone or composite plate according to one of the preceding claims, characterized in that the depressions (5) are located in the two outer thirds of the plate-like natural stone portion (2).
14. The composite stone or composite plate according to one of the preceding claims, characterized in that the width of the depressions (5) corresponds to at least 1,5 to 2 times the diameter of the largest grain of the aggregate of the adhesive mortar.
15. The composite stone or composite plate according to one of the preceding claims, characterized in that the depth of the depressions (5) at maximum corresponds to one third of the thickness of the plate-like natural stone portion (2).
16. The composite stone or composite plate according to claim 11, characterized in that the armouring (10) is connected to the plate-like natural stone portion (2) by means of at least one armouring holder (9), said armouring holder engaging into at least one depression (8).
17. The composite stone or composite plate according to claim 16, characterized in that the armouring holder (9) engages into two adjacent oppositely inclined depressions (5) with two oppositely directed legs.

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