WO1988001609A1

WO1988001609A1 - Use of substituted alkyl phosphonates in concrete and mortar mixes, cement slurry and latex paints

Info

Publication number: WO1988001609A1
Application number: PCT/EP1987/000449
Authority: WO
Inventors: Eberhard Christ; Uwe Schubert
Original assignee: Eberhard Christ
Priority date: 1986-08-28
Filing date: 1987-08-15
Publication date: 1988-03-10
Also published as: AU7851887A; DE3629234C1

Abstract

Use of substituted alkyl phosphonates, known per se, in concrete and mortar mixes, cement slurries (cement paste) as well as in aqueous latex paints, in quantities of between 0.001 and 1.0 % by weight in relation to the cement, in concrete and mortar mixes and cement slurries, or between 0.1 and 0.32 % by weight in relation to the content of solid matter of the dispersion, in latex paints, in order to reduce the diffusion of carbon dioxide into the concrete parts and possibly to increase the compression strength of concrete parts.

Description

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Use of substituted alkyl phosphonates in concrete and mortar mixes, slurries and dispersion paints

The invention relates to the use of substituted alkyl phosphonates in concrete and mortar mixtures, slurries (cement paste) and emulsion paints to reduce the diffusion of carbon dioxide in concrete parts and to increase the compressive strength of concrete parts.

Corrosion-protecting properties of Portland cements have been known for decades. Although concrete is one of the few building materials that largely withstand the weather and general environmental influences without external protective coatings, concrete repair has recently been a pressing problem for the construction industry. Reinforced exposed concrete parts and reinforced concrete parts are particularly at risk. Due to environmental influences, acidic components act on the concrete. Parts or cement blocks that are not used too are attacked directly. As a result of this action, the attacked components lose their basic pH value, which is particularly suitable for protecting the reinforcements against corrosion.

Such damage and its causes have been reported in numerous specialist publications (H. Klopfer, Bau¬ tenschutz + Bausanierung, No. 3/1978, p. 86 ff and PH Oechsner et al, Bautenschutz + Bausanierung No. 3 1980, p. 104 ff ).

The hydration of the di- and tricalcium silicates, which deliver the lower-calc, fibrous calcium silicate hydrate, is primarily responsible for the strength development of a Portland cement. As a result, calcium hydroxide is released, which initially only plays a subordinate role for the strength of the concrete. In the longer term, the calcium hydroxide absorbs carbon dioxide from the outside to form calcium carbonate. This natural hardening process, which progresses from the outside inwards, takes decades or centuries with thick masonry or strong concrete parts, which results in the extraordinary strength of old buildings.

After the carbonation of the material surrounding them, the reinforcement steels laid in the concrete have lost all or part of their corrosion protection in the form of the alkaline environment initially present. The corrosion on the surface of the reinforcement steels, which initially appears as discoloration of the Exposing exposed concrete and the associated volume expansion of the corrosion products loosen the concrete ceiling, as a result of which all or part of the rusted reinforcing steel is exposed and the original surface profile of the component is disturbed.

DE-PS 23 48 081 describes the use of sparingly soluble barium silicate hydrates as an additive to concrete and mortar mixtures which contain gypsum, gypsum stone or anhydride in order to bind sulfate ions and to slow the carbonation.

To restore damaged surfaces, it is also known to use mortars with dispersions based on acrylate / styrene butadiene and cement mortars and concretes modified with epoxy resin for repairing corrosion damage. to replace both the binders and the normally used active pigment red lead with other suitable substances. With regard to the dispersion paints applied to exposed concrete parts, it should be noted that these are also halogen-free and must not impair the breathability of the concrete with regard to water permeability, but at the same time form a barrier for carbon dioxide. So far, only acrylic resin colors have met these requirements (see, for example, R. Engelfried, Farbe + Lack, No. 7/1983, p. 513 ff, which speaks of carbonization brakes in connection with concrete coatings.)

The object of the present invention is to provide additives for concrete and mortar mixtures, slurries and for emulsion paints, which not only reduce the diffusion of carbon dioxide in concrete parts and thus have a retarding influence on the carbonation in concrete parts, so that they are able to protect the underlying reinforcing steel from corrosion, but also, if possible, the mechanical properties improve the above-mentioned mixtures, in particular increase the compressive strength of the finished concrete parts.

The solution to this problem is the use of at least one substituted alkylphosphonate or a mixture of substituted alkylphosphonates in concrete and mortar mixtures and slurries in quantities of 0.001 to 1.0% by weight, based on the weight fraction of cement, and in emulsion paints in quantities from 0.1 to 0.32% by weight, based on the solids content of the dispersion.

Such substituted alkylphosphonates and their free acids are known, for example, as sequestering agents, such as l-hydroxyethane-l, l-diphosphonic acid (Rδmpp, Chemische lexicon, 8th edition, p. 1804), and as surfactants in detergents (see for example EP- A-26529).

According to the invention, it was found that when the substituted alkylphosphonates are used, in addition to the use of their surfactant properties which cause the cement-old mixtures to liquefy, in particular a delay or reduction in the carbon dioxide diffusion in concrete parts is caused (delay in carbonation). In addition, surprisingly, when the cement-containing mixtures are hardened, the compressive strength and bending tensile strength and the acid resistance of the hardened parts are increased if the substituted alkylphosphonates are used in concrete and mortar mixtures and slurries. With regard to the plasticizing effect of the substituted alkylphosphonates, it should be noted that plasticizers of the prior art normally have to be added in amounts of not less than 2% by weight, based on the proportion of cement.

DE-PS 27 55 551 describes the use of 2,2,2-tris (hydroxymethyl) ethylphosphonic acid to retard the setting or hardening of cement. The aqueous solution of the phosphonic acid is added in a concentration of 0.75% to the cement mixture without reference.

DE-AS 1 154 028 relates to a process for the liquefaction of inorganic sludges to which salts of acylation products of phosphorous acid are added.

WO 85/01043 includes the use of substituted phosphonates for retarding the setting of cement stillages, while EP-Al 0 166 798 describes a delaying additive for cement mixtures.

US Pat. No. 3,794,506 describes the use of unsubstituted alkylphosphonates exclusively for the consolidation of soil.

According to the invention, at least one is used in concrete and mortar mixtures and stillage to reduce the diffusion of carbon dioxide in concrete parts from 0.001 to 1.0% by weight, preferably 0.01 to 0.5% by weight, based on cement Substituted alkyl phosphonate or a mixture of substituted alkyl phosphonates used, in particular 0.015 to 0.035 wt .-%. The use of the substituted alkyl phosphonates as additional medium in aqueous emulsion paints, according to the invention, takes place in amounts of 0.1 to 0.32% by weight, based on the solids content of the dispersion.

To increase the compressive strength of concrete parts, the same amounts of the substituted alkylphosphonates used according to the invention are used, i. H. When using a total of 0.001 to 1.0% by weight, preferably 0.01 to 0.5% by weight, based on the cement of at least one substituted alkyl phosphonate or a mixture of substituted alkyl phosphonates, in addition to reducing the diffusion an increase in the compressive strength of the concrete parts of the carbon dioxide can also be observed.

If more than 5% by weight of the additives is used, the stability properties of both the cement-containing parts produced and the applied dispersion paints deteriorate.

Substituted alkylphosphonates which are suitable for use according to the invention have the general formula

R / -PO (ox) ₂ _7 _m where X is H, Na, K, Ca, Ba, Al or Zn and R is selected from the group of a) 1-hydroxyalkane radicals having 2 to 6 carbon atoms and with m = 2 to complete a 1-hydroxyalkane-l, 1-diphosphonate, b) primary, secondary or tertiary aminoalkanes with 1 to 6 carbon atoms and with m = 1 to complete an amino-polymethylene phosphonate and c) polyethylene diaminopolymethylene radicals of the general formula

H ₂ N / _ ~ (CH ₂ -CH ₂ ) -NH_7 _n - (CH _j ) _Q - where n = 1 to 5 and o = 1 to 6 to complete a polyethylene diamine polymethylene phosphonate.

Since the substituted alkyl phosphonates used according to the invention are used in extremely low concentrations, the acidity of the free acid plays only a minor role.

The sodium salt of diethylene-triamine-pentamethylene-phosphonic acid is preferably used in the context of the present invention.

The substituted alkylphosphonic acids or the salts of these acids used according to the invention are able to largely seal the concrete against carbon dioxide which penetrates from the outside, or to bind carbon dioxide, in order to counteract a change in pH value by carbonation . As a result, the reinforcement steels lying in the concrete are better protected against corrosion, since the carbonation process is significantly slowed down. An increase in the compressive strength of the concrete parts can also be observed.

The expression "concrete and mortar mixtures" in which the abovementioned substituted alkylphosphonates can be used in the amounts mentioned is to be understood in the broadest sense and includes in particular screed mortar, masonry mortar, stuffing mortar and others made of cement, sand, gravel, tress, Expanded clay, foam lava, pumice, foamed polystyrene, cork, polyurethane foam and other, organic or inorganic-chemical additives with the addition of water, hydraulically solidifying mixtures. These concrete and mortar mixtures can also contain a wide variety of concrete additives and mortar additives, such as can be found in the book "Additives, Paints, Auxiliaries for Concrete and Mortar" by Albrecht and Mannherz, Bauverlag GmbH, 1968, without claiming to be complete.

In addition to the substituted alkylphosphonates mentioned, other known additives such as epoxy resins or dispersions based on ABS can be added to the cement-containing mixtures. In this way, the adhesiveness of the compositions to surfaces to be repaired can be improved.

As cement constituents of the cement-containing mixtures, in particular the concrete and mortar mixtures, the following should preferably be mentioned: Portland cements, iron Portland cements, blast furnace cements, tress cements and puzzolements, to which known additives such as raw meal and / or fly ash are of course known can be added.

Because the substituted alkyl phosphonates used according to the invention liquefy at the same time, the cement-containing mixtures can be processed with a lower water content. The setting and solidification behavior is not adversely affected by the additives used according to the invention. Influences on the spatial stability of the finished concrete parts could not be observed. Test specimens were produced starting from a standard mortar with Portland cement 35F according to DIN 1164 with a water-cement value of 0.5 and tested as follows:

According to R. Engelfried (DEFAZET 9, 1977, p. 353 ff and Farbe + Lack 7, 1983, p. 513 ff), the diffusion of carbon dioxide into the test specimens was determined over the course of 11 days. The thickness of the test specimens was 10 mm or 3 mm.

When using a pure CO ₂ atmosphere, a conversion factor of 1: 9 was obtained for the CO ^ diffusion resistance numbers mentioned below for conversion to air mixtures.

Comparative example

The above basic composition according to DIN 1164 resulted in a C0_ diffusion resistance number of μ = 45 (corresponding to μ_ = 405 for an air mixture).

B ^'EXAMPLE 1

According to the comparative example, with the addition of 0.028% by weight of the sodium salt of diethylene tria-pentamethylene-phosphonic acid, based on the cement content, a similar test specimen was produced and the CO ₂ diffusion resistance number was μ = 92 (μ- = 830) certainly.

Example 2

With the addition of 0.028% by weight of the sodium salt of amino-trimethylenephosphonic acid, based on the cement portion, test specimens were produced as above, with a CO ^ diffusion resistance number of 98 (μ _Q = 880).

Example 3

With the addition of 0.25% by weight of the disodium salt of l-hydroxyethane-l, l-diphosphonic acid, based on the cement fraction, test specimens were produced as above, giving a CO ~ diffusion resistance number of 61 (μ- = 550) .

The CO_ diffusion resistance numbers illustrate the excellent effect of the additives used according to the invention. Multiplying by the layer thickness gives the diffusion-equivalent air layer thickness, which offers sufficient protection against carbon dioxide at values above 50 m. A layer of concrete only 0.06 m thick (according to the example) is already able to exceed the required diffusion-equivalent air layer thickness of more than 50 m. Pretreatment of the exposed reinforcement steel with corrosion-inhibiting agents, such as red lead, is therefore no longer necessary according to the invention.

It was also found that in a test specimen in whose production 0.5% by weight of a substituted alkyl sulfonate had been added according to the invention, the flexural tensile strength from 8.15 N / mm ² to 11.5 N / mm ² and the Compressive strength increased from 53 N / mm ² to 63 N / mm ² .

Claims

Patent claims

1. Use of at least one substituted alkyl phosphate or a mixture of substituted alkyl phosphonates in concrete and mortar mixtures and slurries for reducing the diffusion of carbon dioxide in concrete parts in amounts of 0.001 to 1.0% by weight, based on cement, and in emulsion paints in amounts of 0.1 to 0.32% by weight, based on the solids of the dispersion.

2. Use of at least one substituted alkyl phosphate or a mixture of substituted alkyl phosphonates in concrete and mortar mixtures and slurries according to claim 1 to increase the compressive strength of concrete parts.

3. Use according to claim 1 or 2 with the proviso that the substituted alkyl phosphonates in amounts of 0.01 to 0.5 wt .-%, preferably from 0.015 to 0.035 wt .-%, based on cement, are used.

4. Use according to claim 1 to 3 with the proviso that the substituted alkyl phosphonates of the general formula

/ where X is H, Na, K, Ca, Ba, Al or Zn and

R is selected from the group consisting of a) 1-hydroxyalkane radicals with 2 to 6 carbon atoms and with m = 2 to complete a 1-hydroxyalkane-1,1-diphosphonate, b) primary, secondary or tertiary aminoalkanes with 1 to 6 carbon atoms and with m = 1 to complete an amino-polymethylene phosphonase and

c) Polyethylenediamine polymethylene residues of the general formula

H ₂ N- (CH ₂ -CH ₂ ) -NH_7 _n - (CH ₂ ) _Q - where n = 1 to 5 and o = 1 to 6 to complete a polyethylene diamine polymethylene phosphonate.

5. Use according to claim 1 to 4 with the proviso that the sodium salt of diethylenetriamine-pentamethylene-phosphoric acid is used as a substituted alkyl phosphonate.