Shrinkage reducer for mineral binder composition and its use

Abstract

An additive, in particular a shrinkage reducing agent, for mineral binder compositions including at least one super absorbent polymer SAP and at least one defoamer D. Further, a mineral binder composition including the additive, processes and methods for the mixing thereof, and to hardened articles obtainable therefrom.

Claims

1. An admixture for mineral binder compositions, comprising at least one superabsorbent polymer SAP and at least one defoamer D, wherein the admixture does not comprise water, wherein the at least one defoamer D is selected from the group consisting of mineral oils, vegetable oils, or white oils which may comprise a wax and/or hydrophobic silica, silicones, which can be modified by alkoxylation or fluorination, alkyl esters of phosphoric or phosphonic acid, alkoxylated polyols, and alkoxylated fatty alcohols, and wherein the weight ratio of the at least one SAP to the at least one defoamer D is from 2:1-1:10.

2. The admixture according to claim 1, wherein the at least one superabsorbent polymer SAP is selected from the group consisting of polyacrylamide, polyacrylonitrile, polyvinyl alcohol, isobutylene maleic anhydride copolymers, polyvinylpyrrolidone, homo- and copolymers of monoethylenically unsaturated carboxylic acids, which can be partially or fully neutralized, and co- and terpolymers of the monoethylenically unsaturated carboxylic acids with vinylsulfonic acid, (meth)acrylamidoalkylsulfonic acid, allylsulfonic acid, vinyltoluenesulfonic acid, vinylphosphonic acid, (meth)acrylamide, N-alkylated (meth)acrylamide, N-methylol (meth)acrylamide, N-vinylamide, N-vinylformamide, N-vinylacetamide, vinylpyrrolidon, hydroxyalkyl (meth)acrylate, ethylacrylate, methylacrylate, (meth)acrylic acid esters of polyethyleneglycolmonoallylethers, vinylacetate and/or styrene.

3. The admixture according to claim 1, wherein at least one superabsorbent polymer SAP is a polyacrylic acid which can be partially or fully neutralized and which is crosslinked.

4. The admixture according to claim 1, wherein the admixture is combined with an aqueous solution or dispersion, and the at least one SAP and the at least one defoamer D combined comprise an amount of up to 85 wt.-%, based on the total weight of the admixture and the aqueous solution or dispersion.

5. A mineral binder composition comprising the admixture according to claim 1, wherein the mineral binder composition includes: a) 10-65 wt.-% of at least one mineral binder, b) 0.01-0.5 wt.-% of the at least one SAP, c) 0.05-2 wt.-% of the at least one defoamer D, d) 0-85 wt.-% of aggregates, e) 0-10 wt.-% of other additives selected from the group consisting of plasticizers, superplasticizers, accelerators, retarders, rheology modifiers, anti-settling agents, pigments, corrosion inhibitors, fibers, strength enhancers, waterproofing additives, alkali-aggregate reaction inhibitors, chromate reducers, and/or anti-microbial agents, and f) optionally water, each based on the total dry weight of the mineral binder composition.

6. A mineral binder composition according to claim 5, wherein the at least one mineral binder is a mixture of at least one CEM I or CEM II and at least one calcium sulfoaluminate cement.

7. A mineral binder composition according to claim 5, wherein the mineral binder comprises a) 0.1-8 wt.-%, each based on the dry weight of the mineral binder composition, of a CSA cement and b) 2-64.9 wt.-%, each based on the dry weight of the mineral binder composition, of a CEM I and/or a CEM II.

8. A mineral binder composition according to claim 5, wherein the mineral binder composition comprises a) 0.02-1.0 wt.-% of a polycarboxylate ether composed of (meth)acrylic acid and methyl polyalkylene glycol (meth)acrylates and having a molecular weight Mw of 8,000 to 200,000 g/mol and b) a maximum of 1 wt.-% of at least one thickener selected from the group consisting of starch, pectin, amylopectin, modified starch, cellulose, modified cellulose, casein, welan gum, xanthan gum, diutan gum, galactomannanes, alginates, tragacanth gum, dextran, polydextrose, and layered silicates, each based on the total weight of the mineral binder composition.

9. A method of producing a hardened article comprising the steps of 1) mixing a mineral binder composition according to claim 5 with water, 2) Optionally conveying the mixture obtained in 1) to the location of placing, 3) Placing the mixture obtained in 1) into any desired shape, 4) curing the mixture obtained in 1), wherein step 1) is done in a continuous process by means of a static and/or dynamic mixer.

10. A process comprising forming an article by additive manufacturing from a material that includes a water-containing mineral binder composition of claim 5.

11. A shaped article obtainable by curing a mineral binder composition according to claim 5.

12. The admixture according to claim 1, wherein the at least one defoamer D is selected from the group consisting of ethoxylated 2,4,7,9-tetramethyl-5-decyn-4,7-diol, a combination of fatty alcohol alkoxylate and polysiloxane, and a combination of a mineral oil and a silicone oil comprising hydrophobic silica.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows the surface of example 8 after 7d of hardening. The crack in the surface is clearly visible.

(2) FIG. 2 shows the surface of example 9 after 7d of hardening. No cracks in the surface are visible.

(3) The following working examples illustrate the invention. The examples are not intended to limit the scope of the invention in any way.

EXAMPLES

Examples 1-7

(4) 1500 g of Ordinary Portland Cement (CEM I, 52.5N), 2250 g of quartz sand (particle size 0.06-0.3 mm), and 1100 g of calcium carbonate (average particle size 40 m) were mixed in a Hobart mixer for 1 minute at 23 C. and 50% relative humidity to make dry mix 1.

(5) 1500 g of Ordinary Portland Cement (CEM I, 52.5N), 100 g of calcium sulfoaluminate cement (Denka CSA #20), 2250 g of quartz sand (particle size 0.06-0.3 mm), and 1100 g of calcium carbonate (average particle size 40 m) were mixed in a Hobart mixer for 1 minute at 23 C. and 50% relative humidity to make dry mix 2.

(6) 20 g of a polycarboxylate ether (40% in water, polyacrylate backbone with Mn=7000 g/mol, methyl-terminated PEG side chain with Mn=2500 g/mol, carboxylate/ester ratio=3) were then added to the respective dry mix as given in table 1 below together with the additives from table 1 below and with 800 g of water and mixing was continued for 2 minutes. Total mixing time was appr. 3 minutes.

(7) TABLE-US-00001 TABLE 1 Example 1 2 3 6 7 (Ref) (Ref) (Ref) 4 5 (Ref) (Ref) Dry mix 1 2 2 2 2 2 2 dry mix 4850 4950 4950 4950 4950 4950 4950 weight [g] Defoamer 25* 25* 25** 25** D [g] SAP [g] 10 10 10 NPG [g] 25 Thickener [g] 5*** 5*** NPG: neopentylglycol (Sigma Aldrich, 99% purity) SAP: Starvis S5514F *mixture of mineral oil and silicone oil with hydrophobic silica **ethoxylated 2,4,7,9-tetramethyl-5-decyn-4,7-diol ***methylhydroxyethylcellulose

(8) Examples 4 and 5, of the above table 1 are according to the present invention. Examples 1-3, and 6-7 are comparative examples not according to the present invention.

(9) The following table 2 gives an overview of the results.

(10) Linear shrinkage was measured according to EN 12617-4 on prisms of 4040160 mm within 8 h and 16 h of mixing with water.

(11) TABLE-US-00002 TABLE 2 Example 1 2 3 4 5 6 7 Linear shrinkage 936 607 790 230 850 1880 950 @8 h [m/m] Linear shrinkage 948 612 638 +100 700 1581 1020 @16 h [m/m] n.m.: not measured

(12) As can be seen from the above results, the inventive example 4 shows a reduced linear shrinkage as compared to the comparative examples 1-3. Also inventive example 5 shows a lower shrinkage in comparison to comparative examples 1 and 6.

(13) Comparative example 7 shows that the use of neopentylglycol, an example of an alkylene glycol, cannot reduce the shrinkage.

Examples 8-9

(14) 450 g of white Portland Cement (CEM I, 52.5N), 30 g of calcium sulfoaluminate cement (Denka CSA #20), 195 g of fine quartz sand (particle size 0.075-0.3 mm), 435 g of quartz sand (particle size 0.06-0.8 mm), 364 g of calciumcarbonate (average particle size 50 m), and 2.25 g of a powdered polycarboxylate ether (polyacrylate backbone with Mn=5000 g/mol, Me-terminated PEG side chain with Mn=2700 g/mol, carboxylate/ester ratio=5.6) were mixed in a Hobart mixer for 1 minute at 23 C. and 50% relative humidity to make a dry mix. The additives from table 3 below were added to the dry mix together with 240 g of water and mixing was continued for 2 minutes. Total mixing time was appr. 3 minutes.

(15) TABLE-US-00003 TABLE 3 Example 8 (Ref) 9 Defoamer D [g] 7.5* 7.5* SAP [g] 1 Thickener [g] 3** 0.04** 0.15*** 0.15*** SAP: Starvis S5514F *ethoxylated 2,4,7,9-tetramethyl-5-decyn-4,7-diol **methylhydroxyethylcellulose ***Kelco-crete DGF

(16) As can be seen from the FIGS. 1 and 2, example 8, which is not according to the present invention, does show cracking. Whereas example 9, which is according to the present invention, does not show cracking.

Examples 10-11

(17) Examples 10 and 11 were prepared in the same way as example 4. However, the amounts of SAP and defoamer D were adjusted as can be seen from the following table 4. Example 10 is a reference which is not according to the present invention while example 11 is according to the present invention. Linear shrinkage testing of examples 10 and 11 was done as described above and results are included in table 4. These results show that inventive example 11 shows low linear shrinkage while comparative example 10, where the weight ratio of SAP to defoamer D is outside the preferred range, shows a high linear shrinkage.

(18) TABLE-US-00004 TABLE 4 Example 10 (Ref) 11 Dry mix 2 2 dry mix weight [g] 4950 4950 Defoamer D [g] 10* 75* SAP [g] 40 10 Linear shrinkage @16 h [m/m] 1654 736 *mixture of mineral oil and silicone oil with hydrophobic silica