EP0519385B1 - Method for the production of a reinforcement spacer and spacer - Google Patents

Abstract

A reinforcement spacer (80) has a body of polymer concrete, the polymer concrete consisting of a cured plastic material (108), into which aggregates are incorporated in the form of grains (110, 110''). The surface (112) is post-treated in such a manner that grains (110, 110') project from the surface (102) of the cured plastic material (108), permitting an intimate chemical and physical bond with the cement paste of a concrete composition into which the spacer is to be embedded. <IMAGE>

Description

The invention relates to a method for producing a spacer for reinforcement, with a body made of polymer concrete, in which a body is first formed from a hardenable plastic mass with additives in the form of mineral grains, then the plastic mass is cured, the grains being formed in this way Plastic matrix are integrated so that a body with a closed, smooth surface formed by hardened plastic material is formed.

The invention further relates to a spacer for reinforcement, with a body made of polymer concrete, the polymer concrete consisting of a hardened plastic material, in which additives in the form of mineral grains are integrated.

Such a method and such a spacer are known from DE-U-87 04 698.

When creating concrete components that are provided with reinforcement, it is necessary to arrange the reinforcement at a certain distance from the inside of a formwork into which the liquid concrete is then poured. The spacers not only ensure precise positioning of the reinforcement within the formwork and therefore in the finished concrete component, but also ensure that the reinforcement is at a certain minimum distance from the outside of the concrete component to be created, i.e. the reinforcement is covered with a certain layer of concrete. This "necessary coverage" must be at least 2 cm for buildings. The spacer is thus integrated into the hardened concrete mass of the component.

The interface transition area between the outside of the spacer and the hardened concrete mass surrounding it represents a region susceptible to corrosion. Since a spacer with its formwork-side edge lies directly against the formwork, but is otherwise enclosed by the hardened concrete mass, is a transition zone that can be recognized from the outside of the component between spacer and the hardened concrete mass lying against it, which is particularly exposed to environmental influences.

The interface transition area therefore represents a critical area since the two adjacent solid phases, ie spacers on the one hand and hardened concrete mass on the other hand, have different mechanical and chemical properties, for example different expansion coefficients. The fluctuating temperatures to which a component is exposed gradually create capillary or hair gaps between the surface of the spacer and the concrete surrounding it. There have been attempts to use spacers to produce from the same concrete material as the concrete material which is to subsequently enclose the spacer, it was nevertheless found that, due to the different processing methods, capillary gaps nevertheless arise between the interface transition regions. The spacer is prefabricated, i.e. it consists, for example, of an already hardened concrete material, so that, even in the event that the concrete mass to be poured in is constructed identically to the concrete mass from which the spacer was made, heterogeneous, i.e. different bodies, when the component is hardened available. In particular, it was found that prefabricated spacers made of concrete have a certain water absorption capacity, which leads to water being withdrawn from the hardening, poured-in concrete mass in the interface area, which leads to impairments of the hardening concrete material during hydrate formation, so that chemically differently formed after hardening Concrete phases lie opposite, which results in different mechanical and chemical properties in the interface area, which gradually lead to capillary or hair gap formation in the interface area.

Such spacers made of concrete are known from DE-A-1 484 140. In this document it is mentioned that larger boundary surfaces of the concrete body can be roughened in a manner known per se in order to achieve better adhesion in the concrete.

Post-treatment measures for concrete components are described in the document "Concrete Practice", Concrete and Cement Association, Slough 1975, pages 42-43, in order to carry out surface finishing operations, for example on exposed concrete components such as washed concrete, which bring about the desired surface structure. Such finishing operations can be mechanical abrasion, abrasion by sandblasting, chemical ablation.

From the document DE-U-87 04 698 mentioned at the outset it is known to produce the body of a spacer element from polymer concrete. Polymer concrete is understood to mean a material made of concrete in which, in order to improve the properties of use, the hydraulic binder has been completely or partially replaced by materials based on synthetic resins. Polymer concrete is thus a mixture of a synthetic resin such as epoxy resin, polyurethane resin or polyester resin, which is mixed with fillers in the form of grains, in particular with mineral fillers, such as quartz sand, quartz powder, dolomite or other stone powder. Appropriate catalysts and accelerators are added to the synthetic resin, so that if this mass is in casting molds is poured in, correspondingly shaped spacers are formed after the material has hardened. Depending on the type of use, holding elements, usually in the form of curved wire elements, can be integrated into the hardening plastic mass, by means of which the spacers can be clipped or pushed onto reinforcing bars of the reinforcements. If the spacer serves as an end cap for a reinforcement bar, ie it ensures the correct distance between one end of a reinforcement bar and a corresponding outer wall, the spacer usually has a blind hole into which the reinforcement bar can be inserted. In this case, no further holding elements are necessary.

The mixing ratios between aggregates and synthetic resin are chosen so that the resulting body of the spacer has a very high compressive strength and breaking strength, and also has such a coefficient of thermal expansion that comes as close as possible to that of concrete. So that the tensile impact materials are evenly distributed in the body, such a consistency of the plastic resin composition is chosen that the granular additives do not sink during the hardening due to gravity, but float in the hardening synthetic resin composition. The resulting spacers then have a closed, smooth surface made of hardened plastic material.

It has now been found in long-term trials that over time a capillary gap gradually forms between the closed outer surface of the spacer made of hardened plastic material and the hardened concrete mass surrounding it, through which moisture can penetrate from the outside.

It has been found, for example, that in concrete walls which are provided with such spacers made of polymer concrete, after a period corresponding to 15 years, moisture from the outside can penetrate up to 20 mm into the border area between the outside of the spacer and concrete. Since the necessary coverage corresponds approximately to this dimension, it is possible after this time period at the latest that moisture comes into direct contact with the reinforcing bar, i.e. that corrosion can occur. However, since buildings are normally built for a much longer period of time, impairments have to be accepted from this point in time at the latest.

It is therefore an object of the present invention to overcome these disadvantages and to improve a method of the type mentioned and a spacer of the type mentioned in such a way that the penetration of moisture between the surface of the body of the spacer and the concrete surrounding it for a long time Time period, is prevented.

According to the invention the object is achieved in a method in that so much plastic material is subsequently removed from the surface of the cured body that countless grains protrude from the cured plastic material, thereby creating countless connection points for concrete.

According to the invention, the object is achieved with a spacer in that the previously closed surface of the body is subsequently treated by removing plastic material in such a way that countless grains of the aggregates protrude from the surface of the hardened plastic material, which represent countless connection points for concrete.

By exposing the grains contained in the plastic material, which mostly consist of quartz-containing sand, a chemical bond with the cement glue is the poured in Concrete mass possible. This means that these exposed grains protruding from the plastic matrix are chemically integrated into the calcium silicate and calcium aluminate matrix of the poured hardening concrete during hardening and thereby form intimate connection points between the body of the spacer on the one hand and the calcium silicate / calcium aluminate matrix of the hardening concrete mass on the other hand . At the same time, an intimate mechanical interlocking is formed between the body of the spacer made of polymer concrete and the hardening concrete mass. This particularly intimate chemical / physical bond in the transition area between the outside of the spacer body and the hardening concrete mass surrounding it ensures a permanent tight connection in this interface area, in which no moisture can penetrate for decades. Due to this intimate chemical / physical connection between the surface of the spacer and the hardened concrete mass surrounding it, external mechanical stresses can be absorbed much better and can be better distributed due to the large surface area in the interface area between the spacer and the surrounding concrete. As a result, stresses which arise due to different temperature coefficients in thermal expansions can be better dissipated without a capillary or hair gap forming between these materials in the border area. Even if microscopic gaps should form, whereby these can only arise in the transition area between hardened cement paste and directly adjacent areas on hardened plastic matrix, the entire interface transition area, due to the numerous direct chemical connection points via the protruding grains, provides such a way of moisture penetrating from the outside high flow resistance that even a capillary action is not sufficient, that moisture can penetrate to a large extent. The intimate chemical / physical Composite can be understood as a kind of "labyrinth seal" that prevents the ingress of moisture.

It has been found in tests that under conditions which correspond to a service life of a concrete of 15 years (cyclical temperature changes, day / night, summer / winter, cyclical mechanical loads), the penetration depth of moisture is limited to a few millimeters. This penetration is based on a certain porosity of the hardened concrete material and is also favored by the hardening and aging processes of the concrete and plastic material. However, no further penetration was observed.

The task is thus completely solved.

In a further embodiment of the invention, a method removes the surface of the spacer in such a way that craters are formed between the protruding grains by broken grains.

This measure has the advantage that the cement paste of the concrete mass can penetrate into this crater when the spacer is embedded, thereby creating a particularly intimate bond.

In a further embodiment of the invention, the removal of the plastic material from the surface is carried out by a mechanical process.

This measure has the advantage that a particularly simple and inexpensive implementation of the method is possible. The quantities of material removed by the mechanical process, that is, hardened plastic material and broken-out grains can then be used again as additives in the production of other bodies by spacers, that is to say can be "recycled".

In a further embodiment of the invention, the removal is accomplished by sandblasting the outside of the body of the spacers.

This measure has the advantage that the removal can be accomplished by structurally simple and economical means.

In a further embodiment of the invention, the removal of plastic material from the surface of the bodies of the spacers is accomplished by chemically detaching hardened plastic material, in particular by etching the outside.

This measure has the advantage that this process can be carried out very easily, for example by immersing or spraying the body with such a solvent that dissolves the hardened plastic material.

In a further embodiment of the invention, the etching is carried out in such a way that an amount of plastic material is detached such that some grains break out.

This measure has the advantage that, as mentioned above in connection with the mechanical treatment, the craters of the broken-out or failed grains result in additional locations which enable a particularly intimate bond with the concrete mass.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the specified combination but also in other combinations or on their own without departing from the scope of the present invention.

Some exemplary embodiments according to the invention are described and explained in more detail with reference to the accompanying drawings.

Fig. 1

eine perspektivische Ansicht eines ersten Ausführungsbeispiels eines erfindungsgemäßen Abstandhalters;

Fig. 2

eine teilweise geschnittene Seitenansicht eines weiteren Ausführungsbeispiels eines erfindungsgemäßen Abstandhalters;

Fig. 3a

einen Schnitt durch eine Betonwand, in der eine Bewehrung integriert ist, die mit weiteren erfindungsgemäßen Ausführungsbeispielen an Abstandhaltern versehen ist;

Fig. 3b

eine vergrößerte ausschnittsweise Darstellung des in Fig. 3a mit gestrichelter Linie umgrenzten Bereiches;

Fig. 3c

eine weiter vergrößerte ausschnittsweise Ansicht des in Fig. 3b mit einem Kreis gekennzeichneten Bereiches;

Fig. 4

eine noch weiter, extrem vergrößerte ausschnittsweise Schnittdarstellung eines erfindungsgemäßen Abstandhalters in einem Verfahrensstadium seiner Herstellung vor der Behandlung der Oberfläche, und

Fig. 5

eine der Fig. 4 entsprechende Darstellung nach der Behandlung der Oberfläche.

Show it:

Fig. 1

a perspective view of a first embodiment of a spacer according to the invention;

Fig. 2

a partially sectioned side view of another embodiment of a spacer according to the invention;

Fig. 3a

a section through a concrete wall in which a reinforcement is integrated, which is provided with further embodiments of the invention on spacers;

Fig. 3b

an enlarged fragmentary representation of the area delimited in FIG. 3a with a broken line;

Fig. 3c

a further enlarged partial view of the area marked with a circle in FIG. 3b;

Fig. 4

an even further, extremely enlarged sectional view of a spacer according to the invention in a process stage of its manufacture before the treatment of the surface, and

Fig. 5

a representation corresponding to FIG. 4 after the treatment of the surface.

1 shows a first exemplary embodiment of a spacer 10 according to the invention.

The spacer 10 has a body 12, from which a holding element 14 protrudes.

The holding element 14 consists of a bent wire made of spring steel.

The body 12 is constructed from polymer concrete 16.

The polymer concrete 16 consists of a hardened plastic material 18, in which grains 20 are contained in the form of quartz powder.

The plastic material 18 was formed by curing a synthetic resin (epoxy or polyester), as is commercially available, for example, under the name "ALPOLIT UP 303". Furthermore, the filler in the form of a quartz flour with a grain size distribution in the range from 20 »m to 1 mm is contained in the double proportion by weight (in other exemplary embodiments up to 5 times the proportion by weight) like the synthetic resin. The grains can be rounded and / or have broken surfaces. In addition, hardener and accelerator are included. The starting materials, as is well known in the art, mixed together, and poured into a mold that corresponds to the negative shape of the body 12. The holding element 14 is inserted into the hardening mass.

After hardening, a body 12 with a smooth, closed surface is first produced, which is then treated by removing hardened plastic material 18 as described in more detail below in connection with FIGS. 4 and 5, whereby grains are exposed.

The resulting body 12, as shown in FIG. 1, has a surface from which grains 20 protrude.

A rear side 22 of the body 12 is provided with a groove 24, which is used to place a reinforcement 28 on a reinforcement bar 26. The holding element 14 is shaped such that a reinforcing rod 26 inserted into the groove 24 is held by the holding element 14. The cold element 14 rests on a transverse reinforcing bar 30, so that a spacer 10 clipped onto the reinforcing bar 26 cannot slide downward (in the illustration of FIG. 1) along the reinforcing bar 30.

The spacer 10 bears against a formwork-side edge 32 on an inside of a formwork, not shown here, and ensures the appropriate distance between the inside of the formwork and the reinforcement 28. In the embodiment shown in FIG. 1, the formwork-side edge 30 is replaced by two Projections 34, 34 'are formed.

FIG. 2 shows a further spacer 40 according to the invention, whose body 42 also consists of polymer concrete 46, which has the same composition as described above in connection with FIG. 1.

This means that grains 50 are also integrated in a hardened plastic material 48 here.

The body 42 has a cylindrical section 52 which merges at a lower end (in the illustration in FIG. 2) into a conical support foot 54.

A cone tip 56 of the conical support foot 54 represents the formwork-side contact point of the spacer 40.

In the cylindrical section 52 there is a blind hole 58, open at the top on the side opposite the conical support leg 54, into which a plastic sleeve 60 open at the top is inserted.

The plastic sleeve 60 or the blind hole 58 serve to receive one end of a reinforcing bar 62.

The spacer 40 thus ensures the appropriate distance or the appropriate overlap between a lower end of a reinforcing bar 62, for example in a wall of a concrete pipe.

The spacer 40 is also produced by first pouring the body 42 into a suitable shape and then treating the outside thereof by means of a sandblasting process in such a way that grains 50 are exposed.

3a shows a practical application of spacers, namely a concrete wall 66, in which a reinforcement 68 is received, which is enclosed by concrete 67. 3a shows a vertical reinforcement bar 70 as well as several horizontal reinforcement bars 72, 72 ',... Of the reinforcement 68 in the sectional view of FIG. 3a.

At the lower end of the reinforcing bar 70, a spacer 80 can be seen, the body 82 of which is constructed essentially like the spacer 40 described in connection with FIG. 2, the lower end of which, however, is designed as a hemisphere 84.

The spacer 80 also consists of polymer concrete 86 and has a corresponding blind hole 88 for receiving the reinforcing bar 70.

A further spacer 90 can be seen in FIG. 3a, which is similar in function and design to the spacer 10 described in FIG. 1.

The spacer 90 has on its rear side 92 two projecting holding elements 94 and 95.

The formwork-side edge 98 opposite the rear side 92 is designed as a run-on slope 100. The spacer 90 is clipped onto the reinforcing bar 70 via the holding element 94 and clipped onto the reinforcing bar 72 ′ via the holding element 96.

In FIG. 3b, an area delimited in FIG. 3a at the lower end with a broken line is shown on an enlarged scale. In Fig. 3b a circular area is left out, which is shown in Fig. 3c on an even larger scale.

In Fig. 3b, on the left half, that is to the left of the dash-dotted vertical line, the body of the spacer 80 'is shown as it is produced in a mold by the aforementioned method, i.e. with a closed, smooth surface 102. The quartz grains 110 cannot be seen from the outside, even those which are immediately below the surface 102. The spacer 80 'with a smooth surface 102 integrated into the concrete wall 66 contains the risk that a capillary gap 106 will form over time between its entire smooth surface 102 and the concrete 67 surrounding it, over which moisture, such as this, from the outside is represented by an arrow 107, can penetrate between surface 102 and correspondingly opposite concrete surface. Liquid can penetrate through the gradually widening capillary gap 106 to the upper end of the spacer 80 'and then come into contact with the reinforcing bar 70 (see FIG. 3a) and cause corrosion there.

In Fig. 3b the spacer 80 is shown on the right side, i.e. with a treated surface 112 according to the invention, in which grains 110 protrude from the hardened plastic material 108.

As can be seen in particular from FIG. 3 c, a particularly intimate bond with the concrete 67 is formed. Even in the event that a capillary gap is formed between the surface 112 of the spacer 80 and the concrete 67 in the transition region should, as can be seen impressively from FIG. 3c, represent a labyrinth 114 which, as indicated by an arrow 115, opposes a significant flow resistance, as indicated by an arrow 115.

4 shows a section of the spacer 80 'on an even larger scale, the smooth surface 102 of which can be seen.

Quartz grains 110, 110 ', 110' 'are embedded in the hardened plastic material 108, but do not penetrate to the outside. The consistency of the synthetic resin is selected in the manufacture of the spacer 80 'so that the grains float in it, or at most sink under the influence of gravity, so that a smooth, closed surface 102 made of hardened plastic material 108 has therefore formed on the outside of the spacer 80' is.

According to the invention, the smooth surface 102 is then subjected to a treatment; in the exemplary embodiment shown, it is subjected to a mechanical treatment, namely a sandblasting treatment.

This produces the rough surface 112 shown in FIG. 5.

The rough surface 112 is formed on the one hand by the fact that plastic material 108 has been removed by the sandblast. This is due to the brittleness of the plastic material 108 in the form of small fragments. The resulting surface of the spacer 80 is correspondingly uneven or rough and enables an intimate connection with the cement paste of the concrete mass in which the spacer 80 is to be embedded. As can be seen from Fig. 5, the sandblasting treatment Ensure that so much of the plastic material 108 is removed that partial regions of the grains 110, 110 'protrude above the surface 112. There are thus “bare” areas of the bodies 110, 110 ′ which are no longer covered by plastic material 108.

From Fig. 5 it can also be seen that during the sandblasting treatment over the grain 110 'so much plastic material 108 was removed that the grain 110 has broken out completely. This creates a breakout roughness in the form of a crater 118 and contributes to the further roughness of the surface 112.

The grain 110 ″ protruding from the plastic material 108 is a broken grain, the protruding portion of which widens like a trumpet. When the spacer 80 is concreted in, the cement paste of the liquid concrete mass can penetrate into the undercut areas, as is indicated by an arrow 119. After hardening, this creates an intimate interlocking between the spacer and the hardened concrete mass.

The roughness of the surface 112 is thus composed of rough surface areas of the plastic material 108 and of projecting "bare" areas of grains 110, 110 ″. The roughness of the surface area of the plastic material 108 is composed of break-out points of removed plastic material and craters 118, in which broken-out grains 110 'were contained. A chemical connection to the hardening cement paste of the concrete mass is possible through the above bare areas of the grains, ie these grains made of quartz are chemically integrated into the silicate matrix. Thus, innumerable chemical connection points with the hardened cement paste, starting from the surface of the spacer 80, are created, which ensure that these connection points there are no longer any interface transition areas between two heterogeneous bodies in the actual sense, so that the risk of formation of capillary or hair gaps in these areas is completely eliminated.

Due to the intimate interlocking of the areas of the plastic material surface between the grains formed by the break-out points and craters 118, an intimate, mechanical bond is also provided in this area, so that overall, a spacer according to the invention is embedded in the concrete, which in the long term represents an intimate bond , which prevents the ingress of moisture.

The transition from smooth surface 102, as shown in FIG. 4, to roughened surface 112, as shown in FIG. 5, was previously described in connection with a sandblasting process.

It is also possible to achieve this roughening in mills with coarse-grained grinding material, or it is also possible to achieve this by chemical means. For the latter, the surface 102 is sprayed with a solvent that the hardened plastic material 108 dissolves. It is loosened until a few grains 110, 110 '' are also exposed. It is then not excluded that a wafer-thin film remains on the surface of the protruding grains, but this extremely small layer is removed mechanically when it is brought together with the hardening concrete mass.

Claims (8)

1. Method for the production of a spacer (10, 40, 80, 90) for reinforcements (28, 68), with a body (12, 52, 82) composed of polymer concrete (16, 46, 86), in which a body is first formed from a hardenable plastics mass containing aggregates in the form of mineral particles (20, 50, 110) and the plastics mass is then hardened, the particles (20, 50, 110) being integrated into the resulting plastics matrix so as to produce a body with a closed, smooth surface (102) formed by hardened plastics material (18, 48, 108), characterized in that such a quantity of plastics material (18, 48, 108) is subsequently removed from the surface (102) of the hardened body that innumerable particles (20, 50, 110) project from the hardened plastics material (18, 48, 108), creating innumerable bonding points for concrete.
2. Method according to Claim 1, characterized in that the plastics material (18, 48, 108) is removed in such a way that between the projecting particles (20, 50, 110) craters (118) are produced by broken-away particles (110').
3. Method according to either of Claims 1 or 2, characterized in that the removal is effected by a mechanical process.
4. Method according to Claim 3, characterized in that the removal is effected by sandblasting of the smooth surface (102).
5. Method according to either of Claims 1 or 2, characterized in that the removal is effected by a chemical separation of hardened plastics material (18, 48, 108), in particular by etching of the plastics material (18, 48, 108).
6. Spacer for reinforcements (28, 68), with a body (12, 42, 82) composed of polymer concrete (16, 46, 86), the polymer concrete (18, 46, 86) consisting of a hardened plastics material (18, 48, 108) into which are integrated aggregates in the form of mineral particles (20, 50, 110, 110', 110'') characterized in that the previously closed surface (112) of the body (12, 42, 82) is after-treated by removal of plastics material (18, 48, 108) in such a way that innumerable particles (20, 50, 110, 110'') of the aggregate project from the surface (112) of the hardened plastics material (18, 48, 108), constituting innumerable bonding points for concrete.
7. Spacer according to Claim 6, characterized in that between the projecting particles (20, 50, 110, 110'') there are points in the plastics material (108) which are craters (118) of broken-away particles (110').
8. Spacer according to either of Claims 6 or 7, characterized in that the mineral particles (20, 50, 110, 110', 110'') are broken quartz particles.

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