Corrosion-Reducing Composition and Use Thereof

Abstract

The invention relates to a composition which comprises at least one liquefying agent for a hydraulic composition and at least one aminoalcohol, selected from the group consisting of 2-amino-2-methyl-1-propanol and N-aminopropyl-monomethyl ethanolamine. The invention also relates to the use of said composition for reducing corrosion, especially on steel formwork in precast components or on concrete steel of concrete constructions.

Description

TECHNICAL FIELD

The invention relates to the field of corrosion inhibitors on steel, in particular on steel shuttering in prefabricated elements or on reinforcing steel for concrete constructions. The invention relates especially to a composition comprising at least one plasticizer for a hydraulically setting composition and at least one amino alcohol selected from the group consisting of 2-amino-2-methyl-1-propanol and N-aminopropylmonomethylethanolamine.

PRIOR ART

Steel shuttering are molds for casting concrete into which fresh concrete for producing concrete components, also known as prefabricated elements, is introduced. After curing of the concrete, the steel shuttering is normally removed again. The corrosion of steel shuttering represents a great problem and can lead to a reduction in the quality of the concrete, in particular the surface quality of the concrete, and, for example, to undesirable traces of rust on visible concrete. To suppress rust, a concrete release agent, also known as forming oil, is generally applied to the steel shuttering before use. These forming oils have the disadvantage that they have only a limited ability to suppress corrosion and thus rust formation and also that they have to be applied individually to each piece of steel shuttering before each use, which is both uneconomical and environmentally polluting.

The use of steel as reinforcement in constructions is widespread. Steel-reinforced concrete is of particular importance. The steel is introduced into a hydraulically setting material and reinforces this. The steel is used particularly in elongated form, especially as rods or grids, and is also frequently referred to as reinforcement or armoring iron by those skilled in the art. The corrosion of steel present in hydraulically setting materials is of great economic importance. Corrosion of the steel inlays reduces their strength and thus the strength of the concrete. Furthermore, the corrosion products such as iron oxides or iron oxide hydrates have a greater volume than the uncorroded steel itself. This results in stresses in the concrete which can lead to cracks or splitting off of entire pieces.

Addition of corrosion inhibitors such as nitrites, amines, alkanolamines, their mixtures with inorganic or organic acids or phosphoric esters to the fresh concrete or treatment of surfaces of cured steel-reinforced concrete with a penetrating corrosion inhibitor is known. However, in order to be able to display their action, the corrosion inhibitors have to be used in large amounts, which can be a disadvantage from both an economic point of view and an ecological point of view.

The use of concrete plasticizers has been known for a long time. For example, it is known from EP 1 138 697 B1 or EP 1 061 089 B1 that (meth)acrylate polymers having ester and if appropriate amide side chains are suitable as concrete plasticizers. Here, this concrete plasticizer is added as additive to the cement or to the cement before milling and leads to a high degree of plasticization or reduction of the water requirement of the concrete or mortar produced therefrom.

DESCRIPTION OF THE INVENTION

It is therefore an object of the present invention to provide compositions for reducing corrosion, in particular on steel shuttering or on reinforcing steel, which overcome the disadvantages of the prior art. It has now surprisingly been found that a composition comprising at least one plasticizer for a hydraulically setting composition and at least one amino alcohol selected from the group consisting of 2-amino-2-methyl-1-propanol and N-aminopropylmonomethylethanolamine is highly suitable for preventing or reducing corrosion on steel shuttering or on reinforcing steel. In addition, such compositions have excellent processability and a high stability.

Ways of Performing the Invention

The present invention relates to a composition comprising or consisting of at least one plasticizer for a hydraulically setting composition and at least one amino alcohol selected from the group consisting of 2-amino-2-methyl-1-propanol and N-aminopropylmonomethylethanolamine. Particular preference is given to a composition comprising or consisting of at least one plasticizer and 2-amino-2-methyl-1-propanol. N-Aminopropylmonomethylethanolamine is also referred to as 2-[(3-aminopropyl)methylamino]ethanol (CAS No. 41999-70-6).

The at least one amino alcohol of the composition according to the invention is 2-amino-2-methyl-1-propanol or N-aminopropylmonomethylethanolamine or a mixture of 2-amino-2-methyl-1-propanol and N-aminopropylmonomethylethanolamine.

Possible plasticizers are ones which are suitable for plasticizing a hydraulically setting composition or reducing its water requirement. For the purposes of the invention, “plasticizers” includes superplasticizers which are frequently also referred to as fluidizers.

In a preferred embodiment, the plasticizer comprises or consists of polycarboxylate, preferably polycarboxylate ether (PCE). The polycarboxylate preferably comprises or consists of at least one polymer A of the formula (I).

Here, the symbols M each represent, independently of one another, H⁺, an alkali metal ion, alkaline earth metal ion, divalent or trivalent metal ion, ammonium ion or organic ammonium group. Here and in the following, the term “independently of one another” in each case means that a substituent can have different possible meanings in the same molecule. Thus, for example, carboxyl groups and sodium carboxylate groups can be simultaneously present in the polymer A of the formula (I), i.e. the radicals R₁ can in this case be H⁺ and Na⁺ independently of one another.

It will be clear to a person skilled in the art that firstly the group in question is a carboxylate to which the ion M is bound and secondly the charge of polyvalent ions M has to be balanced by counterions.

Furthermore, the substituents R are each, independently of one another, hydrogen or methyl. This means that the polymer A is a substituted poly(acrylate), poly(methacrylate) or poly((meth)acrylate).

Furthermore, the substituents R¹ and R² are each, independently of one another, C₁-C₂₀-alkyl, cycloalkyl, alkylaryl or -[AO]_n—R⁴. Here, A is a C₂-C₄-alkylene group and R⁴ is a C₁-C₂₀-alkyl, cyclohexyl or alkylaryl group, while n is from 2 to 250, in particular from 8 to 200, particularly preferably from 11 to 150.

Furthermore, the substituents R³ are each, independently of one another, —NH₂, —NR⁵R⁶, —OR⁷NR⁸R⁹. Here, R⁵ and R⁶ are each, independently of one another, H or a C₁-C₂₀-alkyl, cycloalkyl or alkylaryl or aryl group or a hydroxyalkyl group or an acetoxyethyl (CH₃—CO—O—CH₂—CH₂—) or hydroxyisopropyl (HO—CH(CH₃)—CH₂—) or acetoxyisopropyl group (CH₃—CO—O—CH(CH₃)—CH₂—) or R⁵ and R⁶ together form a ring of which the nitrogen of —NR⁵R⁶ is part so as to build up a morpholine or imidazoline ring. Furthermore, the substituents R⁸ and R⁹ are each, independently of one another, a C₁-C₂₀-alkyl, cycloalkyl, alkylaryl, aryl or hydroxyalkyl group and R⁷ is a linear or branched C₂-C₄-alkylene group, in particular isomers of C₂-C₄-alkylenes, preferably ethylene, propylene, isopropylene or —C(CH₃)₂—CH₂—.

Finally, the indices a, b, c and d indicate the molar ratios of these structural elements in the polymer A of the formula (I). These structural elements are present in a ratio of

a/b/c/d=(0.05−0.9)/(0.05−0.9)/(0−0.8)/(0−0.5),

in particular a/b/c/d=(0.1−0.9)/(0.1−0.9)/(0−0.5)/(0−0.1),

preferably a/b/c/d=(0.1−0.9)/(0.1−0.9)/(0−0.3)/(0−0.06),

while the sum a+b+c+d=1. The sum c+d is preferably greater than 0.

The proportion of the polymer A of the formula (I) is typically from 10 to 100% by weight, in particular from 25 to 50% by weight, based on the weight of the plasticizer.

The polymer A can be prepared by free-radical polymerization of the respective monomers

or by polymer-analogous reaction of a polycarboxylic acid of the formula (III)

In the polymer-analogous reaction, the polycarboxylic acid is esterified or amidated by means of the appropriate alcohols, amines. Details regarding polymer-analogous reactions are disclosed, for example, in EP 1 138 697 B1 on page 7 line 20 to page 8 line 50, and in the examples therein or in EP 1 061 089 B1 on page 4, line 54 to page 5 line 38 and in the examples therein. In a variant thereof, as is described in EP 1 348 729 A1 on page 3 to page 5 and in the examples thereof, the polymer A can be prepared in the solid state.

It has been found that a particularly preferred embodiment of the polymer is that in which c+d>0, in particular d>0. As radical R³, —NH—CH₂—CH₂—OH, in particular, has been found to be particularly advantageous. Such polymers A have a chemically bound ethanolamine which can be split off. The ethanolamine is an extremely efficient corrosion inhibitor. Due to the chemical attachment of the corrosion inhibitor, the odor is greatly reduced compared to the case where it is merely mixed in. Furthermore, it has been found that such polymers A also display significantly greater plasticizing properties.

In a further preferred embodiment, the plasticizer of the present composition according to the invention comprises or consists of at least one polysaccharide, vinylic copolymer or at least one sulfonate, preferably on the basis of a lignosulfonate, naphthalenesulfonate or melaminesulfonate. The vinylic copolymer is preferably based on a polyvinyl alcohol or polyvinyl ether. The plasticizer preferably comprises, consists of or is based on Na, Ca or Mg lignosulfonate, Na, Ca or Mg naphthalenesulfonate, Na or Ca melaminesulfonate or a sulfonated melamine- or naphthalene-formaldehyde condensate. Particular preference is given to Na lignosulfonate or Na naphthalenesulfonate.

In a further embodiment, the composition of the invention can contain further additives, preferably a solvent, in particular water. The composition of the invention is preferably a dispersion, in particular an aqueous dispersion, or a solution, in particular an aqueous solution.

Suitable solvents are water and organic solvents. The choice is made according to technical but preferably also ecological considerations, for example toxicity, water hazard classes or biodegradability.

Particularly useful organic solvents are alcohols, preferably methanol, ethanol, propanol, isopropanol, butanol, higher alcohols such as ethylene glycol, glycerol, polyether polyols such as polyethylene glycols and ether alcohols such as butyl glycol, methoxypropanol and alkylpolyethylene glycols, and also aldehydes, esters, ethers, amides or ketones, in particular acetone, methyl ethyl ketone, hydrocarbons, in particular methyl esters, ethyl esters, isopropyl esters, heptane, cyclohexane, xylene, toluene, white spirit and mixtures thereof. Preference is given to ethyl acetate, ethanol, isopropanol or heptane, and mixtures thereof.

Very particular preference is given to water as solvent. Preference is also given to mixtures of water with alcohols having a proportion of water of more than 50% by weight, preferably more than 65% by weight, in particular more than 80% by weight.

Particular preference is given to a composition comprising Na lignosulfonate or Na naphthalenesulfonate, 2-amino-2-methyl-1-propanol and water.

Examples of further additives are additives as are customary in concrete technology, in particular surface-active substances, stabilizers against heat and light, mold release agents, chromate reducers, dyes, antifoams, accelerators, retardants, further corrosion inhibitors, air-introducing or deaerating substances, pore formers, pumping aids, viscosity regulators, hydrophobicizing agents or thixotropes, shrinkage reducers.

The proportion of the amino alcohol is from 0.1 to 20% by weight, preferably from 0.5 to 10% by weight, particularly preferably from 1 to 5% by weight, based on the total weight of the composition.

The proportion of the at least one plasticizer is from 10 to 99.9% by weight, preferably from 50 to 95% by weight, more preferably from 80 to 90% by weight, based on the total weight of the composition.

The proportion of water or solvent is from 0 to 70% by weight, preferably from 5 to 50% by weight, more preferably from 10 to 40% by weight, based on the total weight of the composition.

In a further embodiment, the present invention provides a hydraulically setting composition which comprises or consists of the composition of the invention and also at least one hydraulically setting binder. The hydraulically setting binder is preferably a mineral binder such as cement, gypsum plaster, fly ash, fumed silica, slag, slag sand, limestone filler or quicklime. Preferred hydraulic binders encompass at least one cement, in particular at least one cement in accordance with European standard EN 197 or calcium sulfate in the form of anhydrite, hemihydrate or dihydrate; or calcium hydroxide. Preference is given to portland cements, sulfoaluminate cements and high-alumina cements, in particular portland cement. Mixtures of cements can lead to particularly good properties. For fast curing, use is made of, in particular, fast-setting cement-containing binders which preferably contain at least one high-alumina cement or another aluminate source, for example, aluminate-supplying clinker and, if appropriate, calcium sulfate in the form of an anhydrite, hemihydrate or dihydrate; and/or calcium hydroxide. Cement, in particular portland cement, is preferred as constituent of the hydraulic binder. Particular preference is given to a low-chromate cement.

The composition of the invention is preferably added to the hydraulically setting binder so that the proportion of composition of the invention is from 0.1 to 5% by weight, preferably from 0.2 to 2% by weight, particularly preferably from 0.4 to 1.5% by weight, based on the weight of the hydraulically setting binder.

The composition of the invention is produced by mixing the amino alcohol 2-amino-2-methyl-1-propanol or N-aminopropylmonomethylethanolamine with at least one plasticizer, with it being immaterial whether the amino alcohol is added to the plasticizer or vice versa. An aqueous composition or solution is produced by adding water or an organic solvent during production of the plasticizer, in particular in the preparation of the polymer A of the formula (I), or by subsequent mixing of the plasticizer, the amino alcohol or the plasticizer and the amino alcohol with water or an organic solvent. Preference is given to mixing the plasticizer with water or an organic solvent, preferably water, and subsequently adding the amino alcohol. The composition of the invention can be present as a clear or opaque solution or as a dispersion, i.e. as emulsion or suspension.

In the production of the hydraulically setting composition, the composition of the invention is preferably added simultaneously with the make-up water to the hydraulically setting composition, preferably the dry concrete mix, or mixed last into the hydraulically setting composition after addition of the make-up water.

In a further embodiment, the present invention provides for the use of the composition of the invention for reducing or preventing corrosion of steel, in particular corrosion on steel shuttering of prefabricated elements or on reinforcing steel of concrete constructions. The composition of the invention is particularly useful for reducing or preventing corrosion on steel shuttering used for the production of prefabricated elements.

In a further embodiment, the present invention provides for the use of 2-amino-2-methyl-1-propanol and/or N-aminopropylmonomethylethanolamine for reducing or preventing corrosion on steel shuttering of prefabricated elements or on reinforcing steel of concrete constructions.

In a further embodiment, the present invention provides a method of reducing corrosion on steel shuttering of prefabricated elements or on steel reinforcement of steel-reinforced concrete constructions, in which the composition of the invention is added to the fresh concrete and the fresh concrete is brought into contact with the steel.

The present invention further provides a concrete construction which has been protected against corrosion of steel shuttering or against corrosion of steel reinforcement and which comprises at least one composition according to the invention. The concrete construction is advantageously a building work or a component of an above-ground or underground construction, in particular a building or tunnel, a road or a bridge, in particular a building work which is produced from prefabricated elements.

The present invention therefore further provides a prefabricated element comprising the composition of the invention. The prefabricated element is, for example, a pipe, a wall, ceiling or floor slab, a tubbing element, prop, bridge bearer, bridge segment, binder, a flight of stairs or a platform.

The present composition according to the invention has the advantage that it simultaneously acts as plasticizer for a hydraulically setting composition and as corrosion inhibitor for steel. As a result, the corrosion protection is improved further above the corrosion-inhibiting action of the amino alcohol because the use of the plasticizer reduces the amount of make-up water required in the production of concrete and thus decreases the water/cement value (w/c value). The lower the water/cement value, the less susceptible is/are the steel shutting or steel inlays which come into contact with the concrete to corrosion.

According to this embodiment, no subsequent addition of a plasticizer or corrosion inhibitor is therefore necessary and a process step is therefore saved in the use of the cement. Such a cement is therefore a ready-to-use product which can be produced in large quantities.

A further advantage of the composition of the invention is that the corrosion inhibitor can be introduced directly into the hydraulically setting composition and the corrosion inhibitor does not have to be applied to the steel shuttering or steel inlays before the steel shuttering or steel inlays is/are used. This results in improved corrosion protection and a saving of time.

EXAMPLES

The invention is illustrated below with the aid of examples.

1.1 Raw Materials Used

TABLE 1
Raw materials used; the percentages are % by weight
based on the total weight of the raw material
Commercial name	Supplier	Type	Abbreviation
Liquiment ® N	Liquiment	Na	Liquiment
	Linz GmbH	naphthalenesulfonate
		(40%), water (60%)
Borresperse NA 244	Borregaard,	Na lignosulfonate	Borresperse
	Germany	(45%), water (55%)
Borrement CA 124	Borregaard,	Ca lignosulfonate	Borrement
	Germany	(50%), water (50%)
AMP-90 ®	The Dow	2-Amino-2-methyl-	AMP-90
	Chemical	1-propanol (90%),
	Company	water (10%)
XTA - 758	Huntsman	N-aminopropylmono-	XTA
		methylethanolamine or
		2-[(3-aminopropyl)-
		methylamino]ethanol
		(CAS No. 41999-70-6)
2-(Dimethylamino)-	Fluka,	2-(Dimethylamino)-	DMA
ethanol	Switzerland	ethanol
Triethanolamine	Fluka,	Triethanolamine	TEA
	Switzerland

1.2 Polymer A Used

TABLE 2
Abbreviations used.
Abbreviation	Meaning	Mw*
PEG 1000	Polyethylene glycol without	1000 g/mol
	terminal OH groups
PEG3000	Polyethylene glycol without	3000 g/mol
	terminal OH groups
EO/PO(50/50)2000	Block copolymer of ethylene	2000 g/mol
	oxide and propylene oxide in
	a ratio of 50:50 without
	terminal OH groups
*Mw = average molecular weight

The polymer A-1 indicated in table 3 was prepared from poly(meth)acrylic acid by polymer-analogous reaction with the corresponding alcohols and amines in a known manner. The polymer A-1 is present in partially neutralized (NaOH) form. (M=H⁺, Na⁺).

The polymer A is used as an aqueous solution in these examples. The polymer content is 40% by weight. This aqueous solution is referred to as A-1L. The concentrations of A-1 indicated in the following tables are in each case based on the content of aqueous solution A-1L.

TABLE 3
Polymer A-1 corresponds to the formula (I) with M = H+, Na+.
R =	H
R1 =	-PEG1000-OCH3:-PEG3000-OCH3	57.2:42.8 molar ratio
R2 =	EO/PO(50/50)2000-OCH3
R3 =
a/b/c/d =	0.640/0.358/0.002/0.000
Mw	72 000

2. Corrosion Behavior of Plasticizer and Amino Alcohol on Steel Plates 5% by weight of cement (CEM I 42.5 R) was mixed with 95% by weight of water and this mixture was filtered. This results in “serum”. A mixture of serum and amino alcohol or plasticizer or of serum, amino alcohol and plasticizer was then produced and 3 drops of this mixture were in each case applied to a steel plate (20×20 cm, ST 35). The amounts of amino alcohol or plasticizer added to the serum are shown in table 4. The % figures are in each case the % by weight of aqueous solutions of the amino alcohol or of the plasticizer, based on the total mixture of serum and the aqueous solutions of amino alcohol or of the plasticizer.

TABLE 4
Corrosion behavior of amino alcohol or
plasticizers in serum on steel plates
			Severity of
No.	Substance	Addition (%)	corrosion
1	Serum only	—	severe
2	A-1L	0.35	severe
3	A-1L	1	severe
4	A-1L	2	medium
5	Borresperse	0.35	medium
6	Borrement	0.35	severe
7	Liquiment	0.35	severe
8	AMP-90	0.3	none
9	2-(Dimethylamino)ethanol	0.3	low
10	Triethanolamine	0.3	medium
11	XTA	0.3	low-medium
12	A-1L/Borrement	0.25/0.1	severe
13	A-1L/AMP-90	2/0.1	low
14	A-1L/AMP-90	1/0.3	low
15	A-1L/AMP-90	1/0.1	low
16	A-1L/AMP-90	0.35/0.1	low
17	A-1L/AMP-90	0.35/0.01	medium
18	A-1L/Borrement/AMP-90	0.25/0.1/0.1	low
19	A-1L/Borrement/AMP-90	0.33/0.01/0.01	severe
20	A-1L/XTA	0.35/0.1	low

3. Corrosion Behavior of Mortar Mixtures on Steel Plates

A standard mortar mixture (1350 g of standard sand (in accordance with the standard EN 480), 450 g of cement (CEM I 42.5 R), 225 g of water, w/c value=0.5%) was admixed with a mixture of plasticizers and amino alcohol and applied in a 1 cm thick layer to a “white band” filter paper resting on a steel plate. After 24 hours, the severity of corrosion on the steel plates was assessed visually (table 5). The % figures for the addition are in each case the % by weight of the amino alcohol or of the plasticizer based on the total weight of cement.

TABLE 5
Corrosion behavior of mortar mixtures containing
amino alcohol or plasticizer on steel plates
			Severity of
No.	Substance	Addition (%)	corrosion
21	Mortar mixture only	—	severe
22	A-1L	1	severe
23	A-1L/AMP-90/Borresperse	0.96/0.02/0.02	low
24	A-1L/AMP-90/Borresperse	0.94/0.03/0.03	low

4. Slump, Compressive Strength and Air Pore Content of Concrete Mixtures

A concrete mixture of the compressive strength class C35/45, the slump class F5 and having a maximum particle size of 16 mm (GK16) and a water/cement value (w/c value) of 0.45 was produced in accordance with EN 934 from 360 kg/m³ of CEM I 52.5 R.

The concrete mixture was admixed with plasticizer or with a plasticizer/amino alcohol mixture and the slump was determined in accordance with EN 12350, the air pore content was determined in accordance with EN 12350 and the compressive strength of the cured prisms was determined in accordance with EN 12390.

The following plasticizers and amino alcohols were tested (table 6):

TABLE 6
Plasticizers and amino alcohols and mixtures thereof.
	No.	Substance	Addition (%)
	C1	A-1L/AMP-90/Borresperse	90/5/5
	C2	A-1L/AMP-90/Borresperse	80/10/10
	C3	A-1L/AMP-90/Borresperse	94/3/3
	C4	A-1L/AMP-90	90/10
	Ref 1	A-1L	100
	The addition is reported in % by weight based on the total weight of the plasticizer/amino alcohol mixture.

TABLE 7
Comparison of the processability or consistency of concrete mixtures
containing various plasticizer/amino alcohol mixtures.
Item	C1	C2	C3	C4	Ref 1
Addition in % by weight based on	0.5	0.56	0.53	0.52	0.48
cement
Slump [cm] after 10 min	62	56	57	59	59
Slump [cm] after 30 min	43	39	41	36	41
Slump [cm] after 45 min	35	33	34	33	34
Compressive strength [N/mm2]	39	32	34	39	38
after 16 h
Compressive strength [N/mm2]	49	43	46	50	41
after 24 h
Air pore content [%]	2.4	2.6	1.8	2	1.5

The results in table 7 show that the processability and consistency of concrete mixtures containing plasticizer and amino alcohol remains as good as that of a concrete mixture containing only plasticizer.

Of course, the invention is not restricted to the examples shown and described. It goes without saying that the abovementioned features of the invention can be used not only in the combination indicated in each case but also in other modifications, combinations and alterations or alone without going outside the scope of the invention.

Claims

1. A composition comprising at least one plasticizer for a hydraulically setting composition

and

at least one amino alcohol selected from the group consisting of 2 amino-2-methyl-1-propanol and N-aminopropylmonomethylethanolamine.

2. The composition as claimed in claim 1, wherein the plasticizer comprises or consists of at least one polycarboxylate, preferably at least one polycarboxylate ether.

3. The composition as claimed in claim 2, wherein the polycarboxylate comprises or consists of at least one polymer A of the formula (I)

where

the symbols M each represent, independently of one another, H+, an alkali metal ion, alkaline earth metal ion, divalent or trivalent metal ion, ammonium ion or organic ammonium group,

each R is, independently of the others, hydrogen or methyl, R1 and R2 are each, independently of one another, C1-C20-alkyl, cycloalkyl, alkylaryl or -[AO]n—R4, where A=C2-C4-alkylene, R4=C1-C20-alkyl, cyclohexyl or alkylaryl and n=2-250, R3 is —NH2, —NR5R6, —OR7NR8R9, where R5 and R6 are each, independently of one another, H or a C1-C20-alkyl, cycloalkyl or alkylaryl or aryl group; or, a hydroxyalkyl group, or an acetoxyethyl (CH3—CO—O—CH2—CH2—) or hydroxyisopropyl (HO—CH(CH3)—CH2—) or acetoxyisopropyl group (CH3—CO—O—CH(CH3)—CH2—), or R5 and R6 together form a ring of which the nitrogen of —NR5R6 is part so as to build up a morpholine or imidazoline ring, where R7 is a C2-C4-alkylene group, and R8 and R9 are each, independently of one another, a C1-C20-alkyl, cycloalkyl, alkylaryl, aryl or hydroxyalkyl group, and a, b, c and d are molar ratios and a/b/c/d−=(0.05−0.9)/(0.05−0.95)/(0−0.8)/(0−0.5),

and a+b+c+d=1.

4. The composition as claimed in claim 3, wherein n=8-200, particularly preferably n=11-150.

5. The composition as claimed in claim 3, wherein

a/b/c/d=(0.1−0.9)/(0.1−0.9)/(0−0.5)/(0−0.1), preferably

a/b/c/d=(0.1−0.9)/(0.1−0.9)/(0−0.3)/(0−0.06).

6. The composition as claimed in claim 5, wherein c+d>0.

7. The composition as claimed in claim 1, wherein the plasticizer comprises or consists of at least one polysaccharide, vinylic copolymer or sulfonate, in particular a lignosulfonate, naphthalenesulfonate or melaminesulfonate.

8. The composition as claimed in claim 1, wherein the composition is a dispersion, in particular an aqueous dispersion.

9. The composition as claimed in claim 1, wherein the composition is a solution, in particular an aqueous solution.

10. The composition as claimed in claim 1, wherein the composition additionally contains further additives, preferably a solvent or water.

11. The composition as claimed in claim 1, wherein the proportion of the amino alcohol is from 0.1 to 20% by weight, preferably from 0.5 to 10% by weight, particularly preferably from 1 to 5% by weight, based on the total weight of the composition.

12. The composition as claimed in claim 1, wherein the proportion of the at least one plasticizer is from 10 to 99.9% by weight, preferably from 50 to 95% by weight, more preferably from 80 to 90% by weight, based on the total weight of the composition.

13. A hydraulically setting composition comprising a composition as claimed in claim 1 and at least one hydraulically setting binder.

14. A method of reducing corrosion of steel, comprising:

utilizing a composition as claimed in claim 1.

15. The method as claimed in claim 14, wherein corrosion on steel shuttering of prefabricated elements is reduced.

16. The method as claimed in claim 14, wherein corrosion on reinforcing steel of concrete constructions is reduced.

17. A method of reducing corrosion on steel shuttering of prefabricated elements, comprising:

utilizing 2-amino-2-methyl-1-propanol and/or N-aminopropylmonomethylethanolamine.

18. A method of reducing corrosion on reinforcing steel of concrete constructions, comprising:

utilizing 2-amino-2-methyl-1-propanol and/or N-aminopropylmonomethylethanolamine.

19. A process for producing a composition as claimed in claim 1, which comprises the step

a) mixing of the amino alcohol 2-amino-2-methyl-1-propanol or N-aminopropylmonomethylethanolamine and at least one plasticizer.

20. A method of reducing corrosion on steel shuttering of prefabricated elements or on steel reinforcement of steel-reinforced concrete constructions, wherein a composition as claimed in claim 1 is added to the fresh concrete and the fresh concrete is brought into contact with the steel.

21. A concrete construction comprising a composition as claimed in claim 1.

22. A concrete construction as claimed in claim 21, wherein the concrete construction is a building work or a component of an above-ground or underground construction, in particular a building, a road, a bridge or a tunnel.

23. A prefabricated element comprising a composition as claimed claim 1.