EP1945594A1

EP1945594A1 - Method of improving the adhesion of cement-bound coatings to concrete surfaces

Info

Publication number: EP1945594A1
Application number: EP06806593A
Authority: EP
Inventors: Thomas Staffel; Siegbert Weber
Original assignee: BK Giulini GmbH
Current assignee: BK Giulini GmbH
Priority date: 2005-11-05
Filing date: 2006-10-28
Publication date: 2008-07-23
Also published as: US20080264293A1; DE102005052791A1; DE102005052791B4; JP2009514768A; JP2013136516A; JP5300483B2; JP5755270B2; WO2007051569A1

Abstract

The present invention relates to plastering mortars which exhibit enhanced adhesion to concrete surfaces and comprise monofluorophosphates, to adhesion primers comprising monofluorophosphates, and to a method of improving the adhesion of cement-bound plasters to concrete surfaces, which involves applying a monofluorophosphate to the concrete surface.

Description

Process for improving the adhesion of cementitious coatings to concrete surfaces

The present invention relates to rendering mortars having improved adhesion to concrete surfaces, primers and the use of monofluorophosphates to improve the adhesion of cementitious plasters to concrete surfaces.

Components with concrete surfaces are becoming increasingly popular for a variety of reasons. On the one hand, concrete structures are created, on the other hand, prefabricated components such as concrete walls, floor slabs, etc., find diverse applications. In both cases, it is usually necessary to refine the surfaces after the carcass has been completed. For this purpose, as a first step, a plaster is applied to the surfaces, which is then provided with paints, wallpaper, plain plaster or other wall coverings. For particularly flat concrete surfaces, it is possible to apply a plain plaster directly.

Plasters can basically be subdivided into cement-bound plasters and gypsum plasters. With gypsum plaster, there are major problems, especially on concrete surfaces, since gypsum and concrete react differently during drying or changing temperatures. In particular, when applying gypsum plaster on relatively fresh concrete must be expected to flake off the gypsum plaster, since concrete shrinks when drying, gypsum not. For this reason cement-based plaster is recommended especially for fresh concrete surfaces.

But also cement-bound plaster mortars do not always adhere satisfactorily to concrete surfaces, especially in precast concrete parts. It has therefore already been proposed to use plate dowels for better connection of the plaster with the concrete surface.

The use of primers is also widespread. Primer primers predominantly contain quartz sand in a plastic-based binder. These primers are applied to the concrete surface, creating a rough surface on which the plaster can adhere better.

However, plastic-based primers require a certain minimum processing temperature and a longer drying time to actually give a stable load-bearing surface.

There is therefore still a need for simple and safe solutions for the production of adhesion of plaster on concrete surfaces. The object of the present invention was accordingly to provide a plaster or a primer that give a secure adhesion to concrete surfaces.

Surprisingly, it has now been found that this object is achieved by the use of monofluorophosphates as an additive to plaster, concrete and / or adhesion primer.

In one embodiment, therefore, the present invention provides a plaster of mortar containing a monofluorophosphate. In another embodiment, an adhesion primer containing a monofluorophosphate is provided.

In the context of the present invention, rendering mortars are to be understood as meaning mixtures which comprise at least one hydraulically curing binder and an additive. Suitable hydraulically curing binders are cement, lime, mixtures thereof and gypsum. Particularly preferred are cement-bound plaster mortars in which cement, such as Portland cement, slag cement, trass cement, etc., which form hydraulic binder, and lime cement plasters.

The aggregate is usually sand. The sand typically has a predominant grain fraction between 0.25 and 4mm, depending on the type of plaster. For fine plaster, the maximum thickness is typically 0.5 to 1 mm, for brushes thicker, 8 to 10 mm. Other materials, such as plastic granules, expanded minerals, etc. may alternatively or additionally be included as an additive depending on the type of plaster. in light plaster or clear plaster.

In addition, the plaster may contain per se known additives and admixtures, such as e.g. Air entraining agents, solidification accelerators, setting retarders and dyes.

As a rule, the plaster mortar is a dry mix which must still be dressed with water.

The monofluorophosphates used according to the invention for improving the adhesion and their preparation are known per se. Monofluorophosphates and in particular sodium monofluorophosphate have hitherto been used, inter alia, as wood preservatives (US 4,824,484), as corrosion inhibitors (US 4,608,092, US 4,613,450 and US 5,071,579) and for reducing the flaking of concrete (DE 692 05 968). Their use as an accelerator for concrete is also known.

According to the invention, monofluorophosphates, preferably alkali metal and alkaline earth monofluorophosphates and in particular sodium, potassium, magnesium are suitable. and / or calcium monofluorophosphate. Very particular preference is given to sodium and / or potassium monofluorophosphate.

According to a preferred embodiment, the monofluorophosphate in an amount of 0.05 to 5 wt .-%, preferably 0.05 to 1 wt .-% and in particular 0.1 to 0.5 wt .-% based on the binder of the plaster added to this.

A particular advantage of this embodiment is that no pre-treatment or other additional steps on the site are required, the dosage can be done accurately and precisely already in the production of the plaster in the factory.

In a further preferred embodiment, a, preferably aqueous solution with a proportion of 1 to 30 wt .-%, preferably 5 to 30 wt .-% and in particular 10 to 25 wt .-% monofluorophosphate used as a primer. The upper limit results here from the solubility of the monofluorophosphate, wherein the primer should be a stable solution, which should show no precipitation of monofluorophosphate even when cooled to, for example, 5 ⁰ C. Of course, an application of more monofluorophosphate than necessary is also to be avoided from a cost point of view. The lower limit results from the amount to be applied in each case. Depending on the method of application, this can be determined by the person skilled in the art in such a way that preferably the desired amount of monofluorophosphate can be applied once or twice.

The application of the adhesion primer according to the invention should take place in amounts of 1 to 100 g / m ² , preferably 10 to 80 g / m ² and in particular 20 to 50 g / m ² . The adhesion primer according to the invention can be applied in a manner known per se, for example by brushing, rolling, spraying or dipping.

The job can be done in one or more steps, which should preferably be between two applications a drying in two or more applications.

The advantage over conventional primers is that after drying can be started directly with the cleaning. A waiting time, as required for curing the plastic-based binder of the known primers, is eliminated. Another advantage of this embodiment is that the use of the monofluorophosphate is targeted only at the point where it is needed, namely at the interface between concrete and plaster.

Furthermore, the adhesion primer according to the invention can be provided with further ingredients, such as fungicides, dyes, etc., so that additional effects can be achieved by the order.

If further ingredients are included, they are available in the usual amounts for the particular ingredient.

The following examples are intended to further illustrate the invention without, however, limiting it to the specific embodiments. Unless otherwise indicated, all% data are by weight.

example 1

Commercially available masonry mortar was water-treated according to instructions, and then plates of dimensions 25 cm x 24 cm and a thickness of about 2.5 cm were cast to produce a concrete surface. The plates were with a provided with commercially available base plaster and then visually assessed before and after weathering for 2 ^Λ A months outdoors. The base plaster was also prepared according to instructions with water and then applied a quantity of about 950 g evenly by trowel on the plates.

For the plates 1 and 2, about 1, 5 g of sodium or potassium monofluorophosphate was mixed with 1600 g of base plaster and 300 g of water, which corresponds to about 0.3% monofluorophosphate based on the binder.

For plates 3 and 4, about 1.5 g of sodium or potassium monofluorophosphate was dissolved in 28.5 g of water, and the solution was spread on the plate with a brush. After 1 h, the plate was dry and it was started with the plaster application.

Plate 5 was prepared as a comparison without monofluorophosphate.

In another series of tests, steel reinforcement was incorporated into the plates so that part of the steel protruded from the surface to investigate the influence of exposed steel reinforcements. Again, 5 plates were prepared, plates 6 and 7 analogous to plates 1 and 2, plates 8 and 9 analogous to plates 3 and 4, and plate 10 analogous to plate 5.

The results are summarized in Table 1.

Already in this simple experiment shows that sodium and potassium monofluorophosphate cause both as an admixture to the plaster as well as in a pretreatment of the concrete surface a significant improvement in adhesion. Cracking is avoided, the adhesion significantly increased. This applies regardless of whether reinforcing steel protrudes from the concrete surface or not. Example 2

From a standardized concrete sample plates were prepared with the dimensions 35 cm x 25 cm x 5 cm, taken from the molds after one day and then stored for one week in water and three weeks in standard climate.

A lime cement adhesive fine plaster CS III according to DIN EN 998-1 (KHF ™, Schwenk Putztechnik GmbH & Co. KG, DE) is optionally mixed with sodium monofluorophosphate, prepared according to instructions and with a thickness of 0.7 cm with a trowel on the , if necessary, applied with an aqueous solution of sodium monofluorophosphate coated test plates.

The composite is assessed visually by scanning electron micrographs (SEM) of the boundary layers.

For the SEM images, the sample plates were sawn into approximately 10 mm thick strips using a rock saw. These were dried at 40 ^° C. to equilibrium moisture content and divided by means of a rock press so that the bond between concrete and plaster became visible at the fracture surface. The samples were then glued with "Carbon Cement" to bell on sample holder and made the surface electrically conductive by sputtering with gold. For this purpose, a Sputtercoater type SCD 005 was used by BAL-TEC, the working distance was 50 mm, the vacuum 5x10 ^'2 mbar in argon atmosphere, sputtering current 60 mA, time 60 s.

The results are shown in FIGS. 1 to 4. There are three magnification levels each.

Figure 1 shows the bond between a plaster with 0.1% sodium monofluorophosphate (based on the binder) and the concrete surface. One recognises, that the monofluorophosphate forms a porous lime sintering layer between the concrete and the plaster, which has a positive influence on the adhesion.

FIG. 2 shows the composite between an unmodified plaster and a concrete surface treated once with sodium monofluorophosphate, application rate 18.5 g / m ² . The hydration of the plaster in the composite zone is improved, the lime sintering layer on the concrete surface is thin and porous.

FIG. 3 shows the bond between an unmodified plaster and a concrete surface treated twice with sodium monofluorophosphate, total application amount 34.5 g / m ² . Compared to Figure 2, the hydration of the plaster is further improved, a further compression is achieved. The meshing of plaster and concrete has already gone so far that a point had to be found for the SEM image where the transition is still visible.

In FIG. 4, for comparison, the bond between an unmodified plaster and an untreated concrete surface is shown. It can be seen that there is a sharp border, the cement paste of the concrete is very dense, as well as the hardly recognizable calcine sintering layer.

As a result, it can be seen that both the admixture of monofluorophosphate to the plaster as well as the use as primer leads to the formation of a porous lime sintering layer, which significantly improves the adhesion of the plaster on the concrete surface.

Example 3

Analogously to Example 2, sample plates were prepared and coated with plaster. The liability was recorded by means of adhesion tests. For this purpose, the test plates were stored for 14 or 28 days in plastic film. Analogously to Example 2, 0.1% sodium monofluorophosphate was incorporated into the plaster or 18.5 or 34.5 g / m ² sodium monofluorophosphate was applied to the surface by treating it once or twice.

To determine the adhesive tensile strengths round test specimens were sawn from the plates after 14 and 28 days. An adhesive tensile tester Easy M (Freundl, DE) was used to measure the adhesive tensile strength.

The results, which represent mean values of two pororbodies, are summarized in Table 2.

Although the fluctuation range of the measured values was relatively high, it can be seen that a significant improvement in adhesion results both from an addition to the plaster and from a treatment of the concrete surface.

Claims

claims

1. plaster comprising a hydraulic binder and an aggregate, characterized in that at least one monofluorophosphate is included.

2. plaster according to claim 1, characterized in that one or more Alkalimonofluorphosphat (s), preferably sodium and / or potassium monofluorophosphate, is (are) included.

3. plaster according to claim 1 or 2, characterized in that based on the binder of the plaster mortar 0.05 to 5 wt .-%, preferably 0.05 to 1 wt .-% and in particular 0, 1 to 0.5 wt. -% monofluorophosphate are included.

4. adhesion primer for concrete surfaces containing at least one monofluorophosphate in aqueous solution.

5. adhesion primer according to claim 4, characterized in that monofluorophosphate in a proportion of 1 to 30 wt .-%, preferably 5 to 30 wt .-% and in particular 10 to 25 wt .-% is included.

6. Adhesion primer according to claim 4 or 5, characterized in that one or more Alkalimonofluorphosphat (s), preferably sodium and / or potassium monofluorophosphate, is (are) included.

7. Primer according to one of claims 4 to 6, characterized in that one or more further ingredients, such as fungicides, dyes, etc. is or are included.

8. A method for improving the adhesion of plaster on concrete surfaces, characterized in that at least one monofluorophosphate is applied to the concrete surface.

9. The method according to claim 8, characterized in that 1 to 100 g / m ² , preferably 10 to 80 g / m ² and in particular 20 to 50 g / m ² monofluorophosphate are applied to the concrete surface.

10. The method according to claim 9, characterized in that on the concrete surface one or more Alkalimonofluorphosphat (s), preferably sodium and / or potassium monofluorophosphate, is (are) applied.

11. walls or ceilings made of concrete, characterized in that they are plastered with a plaster according to one of claims 1 to 3.

12. walls or ceilings made of concrete, characterized in that they are plastered and before the plastering a primer according to one of claims 4 to 7 has been applied.

13. walls or ceilings made of concrete with at least one applied plaster layer, characterized in that the adhesion between plaster and concrete surface is improved by a method according to one of claims 8 to 10.