Composition based on calcium oxide

Abstract

A composition, in particular a setting accelerator for mineral binders, containing or being made of: a) calcium oxide in the particle form; b) an inhibitor for the reaction of calcium oxide with water and c) optionally water.

Claims

1. A composition comprising: a) calcium oxide in particle form, b) an inhibitor for the reaction of calcium oxide with water and c) water; wherein the composition is present as a slurry or suspension and contains based on the total weight of the composition: 25-75% by weight of the calcium oxide; 0.5-10% by weight of the inhibitor, the inhibitor being a phosphoric acid ester of a polyhydric alcohol; and 25-75% by weight of the water.

2. The composition as claimed in claim 1, wherein the composition is present as either an aqueous suspension that is storage-stable for at least 5 minutes or an aqueous slurry that is storage-stable for at least 5 minutes.

3. The composition as claimed in claim 1, wherein the phosphoric acid ester is selected from among glyceryl phosphate, disodium glyceryl phosphate and/or a hydrate thereof.

4. The composition as claimed in claim 1, wherein the calcium oxide has a specific surface area of 1-50 m.sup.2/g of calcium oxide.

5. The composition as claimed in claim 1, wherein the composition is present as either an aqueous slurry that is storage-stable for at least 60 minutes or an aqueous suspension that is storage-stable for at least 60 minutes.

6. The composition as claimed in claim 1 further comprising at least one alkali metal carbonate.

7. The composition as claimed in claim 1, wherein the composition is present in the form of an at least two-component composition, with the calcium oxide, the inhibitor and the water being present in a first component while further constituents of the composition are present together in a second component or are present separately from one another as further individual components.

8. The composition as claimed in claim 1, further comprising a mineral binder composition.

9. The composition as claimed in claim 8, wherein the mineral binder composition contains at least one mineral binder and, in each case based on the binder content: a) calcium oxide in a proportion of from 0.001 to 10% by weight; b) a phosphoric acid ester of a polyhydric alcohol in an amount of from 0.001 to 5% by weight; c) optionally a carbohydrate in an amount of 0.001-1% by weight; and d) optionally an alkali metal carbonate in an amount of from 0.001 to 6% by weight.

10. A molding obtained by curing a composition as claimed in claim 8 after addition of water.

11. A process for producing a composition as claimed in claim 8 wherein a composition containing: calcium oxide in particle form, an inhibitor for the reaction of calcium oxide with water, the inhibitor being a phosphoric acid ester of a polyhydric alcohol, and water, is mixed with at least one constituent of a binder composition.

12. A method for accelerating the setting and/or curing of a mineral binder and/or a mineral binder composition, said method comprising adding a composition as claimed in claim 1 to the mineral binder and/or the mineral binder composition, and then setting and/or curing the mineral binder and/or the mineral binder composition.

13. The method as claimed in claim 12, wherein the mineral binder and/or the mineral binder composition is of a spray concrete composition.

14. The method as claimed in claim 12, wherein the composition is added to the mineral binder composition in an amount effective to increase the compressive strength of the mineral binder composition after 6 minutes from the time that the composition was added.

15. The method as claimed in claim 12, wherein the setting and/or the curing occurs at temperatures above 50 C. and/or at pressures of more than 1.5 bar.

16. A method comprising: adding a phosphoric acid ester of a polyhydric alcohol to a composition containing calcium oxide in particle form and water, the phosphoric acid ester being added in an amount effective to stabilize the composition and/or inhibit the reaction of calcium oxide with water; wherein the addition of the effective amount of phosphoric acid ester results in a composition that is present as slurry or suspension and contains based on the total weight of the composition: 25-75% by weight of the calcium oxide; 0.5-10% by weight of the phosphoric acid ester; and 25-75% by weight of the water.

17. The method as claimed in claim 16, wherein the addition of the effective amount of phosphoric acid ester to the composition maintains the stability of the slurry or the suspension over a period of time of at least 5 minutes, and/or the addition of the effective amount of phosphoric acid ester to the composition controls the inhibition of the reaction of the calcium oxide with the water such that over a period of time of at least 5 minutes the amount of the calcium oxide comprised in the composition does not decrease by more than 10% by weight.

Description

WORKING EXAMPLES

(1) 1. Substances and Methods

(2) 1.1. Substances

(3) The following substances were used for the working examples:

(4) TABLE-US-00001 TABLE 1 Substances used Abbreviation Substance PCE Polycarboxylate ether plasticizer (e.g. Sika Viscocrete 20 HE, obtainable from Sika Schweiz AG); solids content: 40% by weight GPD Glyceryl phosphate disodium salt (obtainable from Sigma Aldrich Schweiz); 10% by weight in H.sub.2O NaCt Sodium carbonate; 10% by weight in H.sub.2O CaOx Calcium oxide (Nekafin 2 from Kalkfabrik Netstal AG, Switzerland, having a specific surface area (BET) of 1.9 m.sup.2/g) CarC Caramel Colour 1085 (sugar color of the type INS No. 150a, obtainable from Sugro AG, Switzerland); dry content: 60% by weight Fruct Fructose in powder form Gluc D (+) glucose monohydrate in powder form Suc Sucrose in powder form Glyc Glycerol (>90%) NaGlu Sodium gluconate in powder form

(5) Sodium carbonate is commercially available from various suppliers in pure form (purity >97%). This was in each case dissolved in the amount indicated in table 1 in water and used as aqueous solutions.

(6) 1.2. Production of Slurries

(7) 1.2.1 Slurry containing GPD

(8) A slurry consisting of 24 g of CaOx, 16 g of water and 12 g of GPD (=1.2 g of glyceryl phosphate disodium salt and 10.8 g of water) was produced by mixing. The slurry will hereinafter be referred to as slurry SL.

(9) The slurry SL produced in this way has been found to be storage-stable for at least 30 minutes.

(10) 1.2.2 Further Slurries

(11) Furthermore, slurries containing various other inhibitors were produced. All slurries contained 30 g of CaOx, 28 g of water and the inhibitors indicated in the table below in the specified amounts.

(12) TABLE-US-00002 TABLE 2 Designation Inhibitor Amount [g] Stability [min] SLK1 CarC 0.25 1 SLK2 0.5 2 SLK3 1.0 9 SLK4 Fruc 0.1 2.5 SLK5 0.25 10 SLK6 0.5 18 SLK7 Glu 0.13 1 SLK8 0.19 3 SLK9 0.25 15 SLK10 0.5 40 SLK11 Glyc 0.5 20 SLK12 Suc 0.25 3 SLK13 0.5 10 SLK14 3.0 66 SLK15 NaGlu 0.5 4

(13) The stabilities of the slurries SLK1-SLK15 produced in this way are shown in the table and can be set to values in the range from 1 to 66 minutes by means of the type and amount of the inhibitor.

(14) 1.3. Mortar Mixtures

(15) The mortar mixture M1 used has the dry compositions described in table 3.

(16) TABLE-US-00003 TABLE 3 Dry composition of mortar mixture Component M1 Portland cement of the type CEM I 52.5 R 750 g (Normo 5R; obtainable from Holcim Schweiz) Limestone filler* 141 g Sand 0-1 mm* 738 g Sand 1-4 mm* 1107 g Sand 4-8 mm* 1154 g *Residual moisture contents of the aggregates used in each case may be found in table 4.

(17) To make up the mortar mixtures, the sands, the limestone filler, the cement and optionally a slurry or CaOx were mixed dry at a temperature of 20 C. for 1 minute in a Hobart mixer. The mixing water (water/cement value or w/c=0.44), to which the polycarboxylate ether plasticizer (PCE; always 0.9% by weight based on cement) and optionally further substances (NaCt, GPD) had previously been added was introduced over a period of 30 seconds and the mixture was mixed for a further 2.5 minutes. The total wet mixing time was in each case 3 minutes.

(18) 1.3. Test Methods

(19) To determine the effectiveness of the slurries as curing accelerators, the compressive strengths of various mortar mixtures were determined 6 hours after mixing the mortar mixtures with water. The test to determine the compressive strength (in N/mm.sup.2) was carried out on prisms (4040160 mm) in accordance with the standards EN 12390-1 to 12390-4.

(20) Immediately after the mortar mixtures had been mixed with water, the respective flow value (FV) was also measured. The flow value (FV) of the mortar mixtures was measured in accordance with EN 1015-3.

(21) The moisture content of the aggregates (sands, limestone filler) was determined gravimetrically as described above.

(22) 2. Mortar Tests

(23) To demonstrate the effects of the curing accelerators of the invention, various mortar tests were carried out.

(24) The experiments A1, B1 and C1 are comparative experiments in which no curing-accelerating additives apart from the plasticizer (PCE) were added. In the experiments A2, B2 and C2, the slurry SL was in each case mixed dry with the sand, the limestone filler and the cement as described in chapter 1.3 before addition of the mixing water. The slurry SL was in each case produced about 10 minutes before addition. In the experiments A3, B3 and C3, CaOx was mixed dry with the sand, the limestone filler and the cement before addition of the mixing water and GPD was added together with the mixing water.

(25) The experiments A1-A3 were carried out using completely dry aggregates (0% by weight of moisture), while moist aggregates were used in each of the experiments B1-B3 and C1-C3.

(26) TABLE-US-00004 TABLE 4 Result of mortar tests Moisture Compressive content of strength aggre- FV.sup.+ after 6 h No. gates.sup.1 NaCt.sup.2 CaOx.sup.3 GPD.sup.2 SL.sup.# [mm] [MPa] A1 0 230 0.9 A2 0.06 6.5 204 8.3 A3 0.06 3.00 1.50 195 7.9 B1 2 232 0.8 B2 0.06 6.5 202 7.4 B3 0.06 3.00 1.50 235 0.9 C1 6 232 0.8 C2 0.06 6.5 178 5.9 C3 0.06 3.00 1.50 235 0.9 .sup.1% by weight based on the total weight of the aggregates (sand and gravel, including residual moisture) .sup.2Addition together with mixing water; % by weight based on cement content .sup.3Addition to aggregates before addition of the mixing water; % by weight based on cement content .sup.#Addition to dry mixture; % by weight based on cement content .sup.+Flow value immediately after mixing with water

(27) Comparison of the experiments A2 and A3 shows that the slurry SL produced beforehand has at least as good an effect as curing accelerator with dry aggregates as does the separate addition of the individual components. The processability is also maintained at a high level as without accelerator (experiment A1).

(28) Experiment B2 shows that the accelerating effect of the slurry can be maintained even in the case of moist aggregates. In contrast, the prior addition of CaOx without inhibiting GPD (this is added only after a time delay together with the mixing water) to moist aggregates leads to a large decrease in the accelerating effect (experiment B3). This occurs even though the total amounts of CaOx and GPD used in the experiments B2 and B3 are essentially the same. However, owing to the absence of inhibitor in experiment B3, the CaOx is exposed to the moisture of the aggregates without protection. Comparison of the experiments C2 and C3 reveals an analogous picture.

(29) The above-described embodiments should, however, be interpreted merely as illustrative examples which can be modified in any desired way within the scope of the invention.

(30) Thus, for example, NaCt can be omitted as additional component in the examples. This results in lower compressive strengths. However, there is no qualitative change in terms of the actions and effects described.

(31) Furthermore, a different inhibitor, e.g. a different phosphoric acid ester and/or a carbohydrate such as glucose, fructose and/or sucrose, can be used instead of or in addition to GPD.

(32) It is likewise possible, for example, to replace the cement at least partly by a latent-hydraulic and/or pozzolanic binder. Larger aggregates can also be used in addition to or instead of the aggregates described (sands, limestone filler) in order to obtain, for example, a concrete composition. The above-described actions and effects are not changed thereby.