EP0385131B1 - Process for the treatment of supports for reinforcements - Google Patents

Description

The invention relates to a method for the treatment of holding rods for holding steel reinforcements in the manufacture of gas concrete, in which the holding rods are first immersed in a liquid separating agent, the coating thus formed is then hardened, then the steel reinforcements are attached to the holding rods and put them together be coated with an anti-corrosion agent using the holding rods.

When manufacturing reinforced gas concrete components, it is necessary to provide the steel reinforcements (reinforcement mats and reinforcement bodies) with a corrosion protection coating before introducing them into the viscous gas concrete mass. In order to apply the anti-corrosion agent to the steel reinforcements, they are usually immersed in a bath filled with the anti-corrosion agent. So-called holding rods are used to hold the steel reinforcements during this immersion process, several of which are each fixed to a traverse or a frame. When the steel reinforcements are immersed in the corrosion protection agent, the holding rods are also coated with the corrosion protection agent. After the corrosion protection agent has dried, the reinforcements can be introduced into the casting mold. For this purpose, the trusses are placed on the upper edge of the mold. The holding rods now hold the steel reinforcements attached to them at the correct mutual distance and at a distance from the mold base and the side walls of the mold. The gas concrete mass is then poured into the mold. It floats to the desired height under the effect of aluminum powder. After the so-called green gas concrete block one for transportation and has reached sufficient strength for cutting, the holding rods are unlocked by the steel reinforcements and pulled up out of the gas concrete block by lifting the crossbars. Before they can be used again, it is usually necessary to clean these holding rods, on the one hand because they are also coated with the anti-corrosion agent and on the other hand because there may be gas concrete residues adhering to the anti-corrosion agent If the anti-corrosion coating and any gas concrete residues were not removed, then this would be the case the support rods are covered with another coating layer when immersed again in the anti-corrosion agent bath, as are the gas concrete particles adhering to the rod. In this way the coating on the holding rods would become thicker and thicker. This would have the consequence that the holding rods can no longer be inserted through holes in the crossbeams and can no longer be pulled out. Gas concrete particles, which adhere to the holding rods and are fixed by a renewed coating, would also form projections on the holding rods, which make it difficult to pull them out of the stiffened gas concrete block and, if pulled out, can also damage the same. For this reason, the holding rods have to be cleaned after they have been pulled out of the stiffened gas concrete block, which is very complex and for which larger amounts of solvent are required. Since these solvents are mostly flammable, considerable protective measures are also necessary. In addition, the use of solvents is not very environmentally friendly.

The desire for an environmentally friendly corrosion protection system has triggered the development of a water-based paint, i.e. a water-thinnable lacquer. These water-based paints provide an irreversible film, i.e. once they have dried, the corrosion protection coating can no longer be removed with water or solvents. Holding rods, which were immersed in a bath with water-based paint along with the steel reinforcement attached to them, can no longer be made free of paint after the water-based paint has dried using solvents.

In a known method of the type mentioned at the beginning (DE-OS 36 40 029), an aqueous release agent is applied to the holding rods before the corrosion protection agent is applied. This consists of 1.4 to 2.5% by mass of cellulose glycolic acid, 44 to 52.6% by mass of an inert inorganic powder such as slate flour, talc, chalk, kaolin, quartz powder and 46 to 53.5% by mass of water. These ingredients are stirred into a homogeneous mixture. The holding rods are immersed in the release agent consisting of these components. After immersion, a release agent coating with a layer thickness of 250 to 350 μm remains on the holding rods. Then the holding rods with the steel reinforcements attached to them are provided with a coating, in particular a powder coating. The aim of the separating layer is to ensure that it adheres better to the powder coating composition than to the holding rods, so that when the holding rods are pulled out, the coating of the holding rods formed by powder coating remains together with the separating layer in the gas concrete.

In addition to the fact that it is not known whether this release agent can fully perform its function even in the case of corrosion protection coatings consisting of a water-based paint, the known release agent has various disadvantages. This is because this is not a commercially available product, but must be manufactured separately from the above-mentioned components, for which weighing units, time and mixer are required. Drying the relatively thick coating layer requires a long time or special energy-consuming drying devices. The relatively thick coating of an average of 300 µm can also be stripped when the holding rods are pushed through the relatively narrow bores of the crossmember or the support frame and also when inserted into the spacers of the reinforcement cages. Where the release agent layer has been stripped off, there is direct contact between the anti-corrosion agent and the holding rod. The anti-corrosion agent will stick to these points when pulled out on the holding rod and at least a partial cleaning of the holding rods is required. The release agent also contains a high proportion of water. This leads to corrosion of the steel holding rods. The corroded (rusted) surface of the holding rods becomes rough, so that when the holding rods are pulled out of the gas concrete block, at least parts of the separating agent layer remain on the holding rods. The same applies to those parts of the separating agent layer which lie at the upper end of the holding rods and which were not coated with the anti-corrosion agent when immersed in the latter. In particular, gas concrete remains can get caught here. As a result, at least partial cleaning of the holding rods is necessary in order to remove these residues as well.

The invention has for its object to provide a method for the treatment of holding rods for the holding of steel reinforcements in the manufacture of gas concrete of the type mentioned, which enables the use of commercially available, inexpensive products as a release agent, in which a complete detachment of a water-resistant corrosion protection layer is guaranteed , no residues of gas concrete adhere to the holding rods, which means that the holding rods do not have to be cleaned after each work step.

This is achieved according to the invention in that the holding rods are immersed in a hot bath of molten paraffin which is solid at room temperature and has a softening temperature of about 50 to 70 ° C. when using a water-based paint.

The paraffin used to carry out the method according to the invention is a commercially available and also relatively inexpensive product. If suitable process conditions are adhered to, it can also be applied in a very thin layer thickness as a release agent coating to the holding rods by immersion, a layer thickness of approximately 20 to 50 μ being completely sufficient. Each holding bar consumes only about 1 g. In addition to the low production costs of the release agent, the extremely low consumption also has an advantageous effect. Furthermore, the small layer thickness has the advantage that the release agent layer has the diameter of the holding rod practically not enlarged. As a result, the risk that the release agent layer is stripped when the holding rods are inserted into the bores of the cross members or support frame and into the spacers of the reinforcement cages is extremely low. The thin paraffin layer also adheres very well to the holding rods and even where it has been stripped off, there is still a residual film which prevents the corrosion protection coating from sticking to the holding rod when it is pulled out of the gas concrete block. It has been found that the anti-corrosion coating is removed from the holding rod without any residues and without problems when the holding rods are pulled out of the gas concrete block and remains as an empty shell in the gas concrete block. The excellent separating effect of the paraffin is due to the fact that the green gas concrete block heats up strongly during the ripening process. The temperature of the gas concrete mass rises to approx. 80 to 90 ° depending on the binder content. This temperature causes the paraffin to melt. As a result, it detaches from the surface of the holding rod and forms a lubricant film between the holding rod and the corrosion protection coating when the holding rod is pulled out of the gas concrete block. The melting paraffin also prevents gas concrete from sticking to the upper areas of the holding rod, where there is no longer any corrosion protection coating. The support rods can therefore be pulled out of the gas concrete block completely bare and free of any residues, be they corrosion protection agents or gas concrete residues. Cleaning after every work process is not necessary. In addition, a thin paraffin film remains on the holding rod even after it has been pulled out protects the bearing against corrosion before applying a new paraffin coating. The holding rods do not need to be dried after the paraffin layer has been applied, rather it is sufficient if they are cooled to room temperature. The paraffin layer solidifies. The solidified paraffin layer behaves neutrally and in no way influences the water-based paint when the steel reinforcements and the holding rods are immersed in the anti-corrosion agent bath.

The holding rods are expediently left in the paraffin bath until they have approximately reached their temperature. It was found that a very thin release agent layer of approximately 0.8 to 1 g can be achieved with this procedure. This thin release agent layer has the advantage of a low consumption of paraffin and, in addition, the thinner this layer, the lower the risk of unwanted stripping of the paraffin layer. When using a paraffin with a softening temperature of 52 to 54 ° C and a paraffin bath temperature of 80 ° C, optimal results were achieved with a diving time of about 5 minutes. The amounts consumed per stick were around 0.8 to 1 g.

To reduce the immersion time, the rods can be warmed up before being placed in the paraffin bath. However, additional facilities would be required for this.

In order to avoid these additional devices, the method can expediently also be carried out in such a way that the holding rods are heated by the gas concrete block that heats up during the ripening, that the holding rods are pulled out of the gas concrete block at the end of the ripening and still in warm condition can be immersed in the paraffin bath. This immersion of the support rods immediately after they are pulled out of the gas concrete block is possible because the support rods can be pulled bare and residue-free from the gas concrete block and do not have to be cleaned first.

It is also advantageous if the holding rods are allowed to cool to about room temperature after being immersed in the paraffin bath and before the water lacquer is applied. In this way it is achieved that the paraffin layer solidifies on the holding rods and under no circumstances can any components of the paraffin get into the anti-corrosion agent bath. Since the anti-corrosion agent bath is at room temperature, it may also be sufficient if the holding rods are brought to room temperature only when immersed in the anti-corrosion agent bath, since the paraffin layer also solidifies when immersed.

When examining different paraffins with different softening temperatures and different purities, paraffins with a softening temperature of approximately 52 to 65 ° C., preferably with a softening temperature of approximately 52 to 54 ° C., have proven to be particularly suitable. For paraffin with the latter softening temperature, the lowest paraffin consumption was around 0.8 to 1 g per holding rod. With regard to consumption, there was no difference between paraffin of greater purity, namely AGN paraffin 1035 from Alfred Graf, Nuremberg, and raw paraffin 10107 from Deutsche Texaco AG, chemical division paraffins and waxes, Hamburg. However, the cost of raw paraffin is only about 1/3 of the AGN paraffin 1035, since raw paraffins contain 2 to 3% oil.

Both types of paraffin with softening temperatures of 52 to 54 ° C gave an excellent release effect. The holding bars were bare along their entire length, where they had come into contact with anti-corrosion agents or gas concrete. Paraffins with higher softening temperatures, for example 62 to 64 °, also result in a relatively low consumption of 1 g / holding rod. Here, however, the separating effect in the area of the driving cap of the gas concrete block, i.e. where the paraffin layer was not additionally coated with corrosion protection agent, is less than that of gas concrete. Caking of green gas concrete was occasionally observed. At even higher softening temperatures, an increased consumption of paraffin was also found. Paraffins with softening temperatures of 52 to 54 ° are particularly recommended, since the paraffin is liquid over its entire length when the rods are pulled out, thus achieving the best separation effect. In order to prevent green gas concrete from sticking to the holding rod, it is important that the holding rods are provided with a paraffin separating layer over their entire length, which can somehow come into contact with anti-corrosion agent or gas concrete. In the anti-corrosion bath, the holding rods with the steel reinforcement should only be immersed as far as necessary, as this leads to the best result of the separating effect. This also ensures that the anti-corrosion sleeve remains in the gas concrete when the holding rods are pulled out.

When using paraffin with softening temperatures of 52 to 65 °, the paraffin bath is expediently heated to a temperature of about 80 ° C and by suitable Measures such as heating and insulation are also kept at this temperature when the support rods are immersed.

Appropriately, the procedure is such that, depending on the softening temperature of the paraffin, the bath temperature and the immersion time, taking into account any preheating of the holding rods, are set so that the thickness of the paraffin coating applied to the holding rods is approximately 10 to 50 μm, preferably approximately 20 to 25 μm, The last-mentioned layer thickness range corresponds to an amount of approximately 0.8 to 1 g of paraffin per holding rod.

The present property right is also intended to use paraffin, which is solid at room temperature and has a softening temperature of about 50 to 70 ° C, preferably 52 to 54 ° C, as a release agent for holding rods for the steel reinforcements in gas concrete production, the holding rods and the steel reinforcements are provided with an anti-corrosion coating made of water-based paint after the release agent has been applied.

Claims (10)

1. Method for the treatment of support rods for holding steel reinforcement in the production of aerated concrete, in which the support rods are first immersed in a liquid separating medium, then the coating formed thereby is hardened, then the steel reinforcement is hung on the support rods and coated together with the support rods with a corrosion protection medium, characterized in that the support rods, on use of a water-lacquer, are dipped in a hot bath of molten paraffin, which is solid at room temperature and has a softening temperature of about 50 to 70°C.
2. Method according to claim 1, characterized in that the support rods are left in the paraffin bath until they have attained approximately the temperature thereof.
3. Method according to claim 1 or 2, characterized in that the support rods are heated before introduction to the paraffin bath.
4. Method according to claim 3, characterized in that the heating of the support rods is effected by the aerated concrete block heating in the curing, in that the support rods are pulled out of the aerated concrete block at the end of the curing and are dipped while still warm into the paraffin bath.
5. Method according to at least one of claims 1 - 4, characterized in that the support rods are allowed to cool to about room temperature after the immersion in the paraffin bath and before the application of the water-lacquer.
6. Method according to claim 1, characterized in that paraffin with a softening temperature of about 52 to 65°C is employed.
7. Method according to claim 1 or 6, characterized in that paraffin with a softening temperature of about 52 to 54°C is employed.
8. Method according to claim 6 or 7, characterized in that the paraffin bath is heated to a temperature of about 80°C and is kept at this temperature also when dipping the support rods.
9. Method according to at least one of claims 1 - 8, characterized in that the thickness of the paraffin coating applied to the support rods amounts to approximately 10 to 50 µm, preferably about 20 to 25 µm, regardless of the softening temperature of the paraffin, the bath temperature and the dipping time, having regard to possible pre-heating of the support rods.
10. Use of paraffin, which is solid at room temperature and has a softening temperature of about 50 to 70°C, preferably 52 to 54°C, as separating medium for support rods for the steel reinforcements in the production of aerated concrete, wherein the support rods and the steel reinforcements are provided with a corrosion protection coating of water-lacquer after the application of the separating medium.