ACCELERATOR FOR HYDRAULIC BINDING AGENTS WITH LONG PROCESSING TIME AND VERY EARLY STRENGTH

Abstract

The present invention relates to an accelerator for hydraulic binding agents, comprising at least one phosphoric acid ester of a multivalent alcohol and at least one calcium compound. The accelerator according to the invention is capable of producing a very fast-curing mortar or concrete composition which has a high early strength and, nevertheless, very favourable processing properties and thus allows early dismantling or early loading and does not cause any losses in the final strength.

Claims

1. An accelerator for hydraulic binders, comprising at least one phosphoric acid ester of a polyhydric alcohol and at least one calcium compound.

2. The accelerator as claimed in claim 1, characterized in that the calcium compound is an inorganic or organic calcium salt or a mixture of inorganic and/or organic calcium salts, preferably calcium oxide and/or calcium hydroxide.

3. The accelerator as claimed in claim 1, characterized in that the calcium compound prior to use is a solid having a specific surface area, measured by the BET method, of between 1 and 50 m.sup.2/g, preferably between 1.5 and 30 m.sup.2/g, more preferably between 1.9 and 10 m.sup.2/g.

4. The accelerator as claimed in claim 2, characterized in that the amount of the phosphoric acid ester relative to the total surface area of the calcium compound is 0.001 to 0.05 g of phosphoric acid ester per m.sup.2 of calcium compound, preferably 0.005 to 0.04 g of phosphoric acid ester per m.sup.2 of calcium compound, more preferably 0.008 to 0.02 g of phosphoric acid ester per m.sup.2 of calcium compound.

5. The accelerator as claimed in claim 1, characterized in that free acid groups of the phosphoric acid ester are deprotonated or wholly or partly neutralized to form salt, the salt being an alkali metal salt or a salt of polyvalent cations, preferably a sodium, calcium or aluminum salt.

6. The accelerator as claimed in claim 1, characterized in that the phosphoric acid ester is a partial ester of a polyhydric alcohol, preferably a monoester of a di- or trihydric alcohol, more preferably of glycerol.

7. The accelerator as claimed in claim 1, characterized in that the phosphoric acid ester is glycerol phosphate or disodium glycerol phosphate or a hydrate thereof.

8. An admixture for hydraulically setting systems, comprising at least one accelerator as claimed in claim 1 and at least one superplasticizer.

9. The admixture as claimed in claim 8, characterized in that the superplasticizer comprises or consists of lignosulfonates, sulfonated naphthalene-formaldehyde condensates, sulfonated melamine-formaldehyde condensates, sulfonated vinyl copolymers, polycarboxylate ethers or mixtures thereof.

10. A mixture comprising hydraulic binder, comprising at least one hydraulically setting binder and at least one accelerator as claimed in claim 1.

11. The mixture comprising hydraulic binder as claimed in claim 10, comprising the phosphoric acid ester in an amount of 0.001 to 2 wt %, preferably 0.01 to 1 wt %, more preferably 0.02 to 0.6 wt %, based on the amount of the binder, and comprising the calcium compound in an amount of 0.001 to 10 wt %, preferably 0.1 to 5 wt %, more preferably 0.5 to 3 wt % of calcium, based on the weight of the binder.

12. The mixture comprising hydraulic binder as claimed in claim 10, characterized in that the total BET surface area of the calcium compound per kilogram of hydraulic binder is 50 to 70 m.sup.2 per kg of binder, preferably 55 to 65 m.sup.2 per kg of binder, more preferably 57 to 63 m.sup.2 per kg of binder.

13. A method for producing a mixture comprising hydraulic binder, characterized in that a phosphoric acid ester and a calcium compound are added together and/or separately from one another to a hydraulic binder.

14. The use of a phosphoric acid ester in combination with a calcium compound, especially in the form of an accelerator as claimed in claim 1, for accelerating the setting and/or hardening of hydraulic binders and also mortar or concrete produced therefrom.

15. A method for accelerating the setting and/or hardening of hydraulic binders and also mortar or concrete produced therefrom, characterized in that a setting and hardening accelerator as claimed in claim 1 is added to a mixture which comprises hydraulic binders.

16. The method as claimed in claim 15, characterized in that the phosphoric acid ester is added in an amount of 0.001 to 2 wt %, preferably 0.01 to 1 wt %, more preferably 0.02 to 0.6 wt %, based on the amount of the hydraulic binder, and the calcium compound is added in an amount of 0.001 to 10 wt %, preferably 0.1 to 5 wt %, more preferably 0.5 to 3 wt % of calcium, based on the weight of the hydraulic binder.

Description

EXAMPLES

[0041] All percentage figures refer, unless otherwise indicated, to weight percent (wt %) based on the weight of the overall composition.

1. Liquid Admixtures

1.1. Production of the Admixtures

Admixture Z1

[0042] 5.0 g of a glycerol 2-monophosphate (glycerol phosphate disodium salt pentahydrate, available for example from Sigma Aldrich Schweiz) were dissolved in 160.0 g of a liquid polycarboxylate ether superplasticizer (Sika Viscocrete 20 HE, available from Sika Schweiz AG). Between 1 and 1.6 wt % of this solution, based on the cement, were added together with the tempering water to the mortar mixture.

Admixture Z2

[0043] As a reference without accelerator of the invention, the polycarboxylate ether superplasticizer (Sika Viscocrete 20 HE, available from Sika Schweiz AG) used for Z1 was used as the admixture. Between 1 and 1.6 wt % of this admixture, based on the cement, were added together with the tempering water to the mortar mixture.

Admixture Z3

[0044] As a further reference without accelerator of the invention, another polycarboxylate ether superplasticizer (Glenium ACE30, available from BASF Admixtures Deutschland GmbH) was used as the admixture. Between 1 and 1.6 wt % of this admixture, based on the cement, were added together with the tempering water to the mortar mixture.

1.2. Production of the Example Mortar Mixtures with Liquid Admixtures

[0045] Cement used for mortar mixtures MM1 and MM2 was a quick-setting Portland cement CEM I 52.5R.

[0046] The sands (maximum grain size 8 mm), the cement, and, in the case of MM2, also 3 wt % (based on the weight of the cement used) of calcium oxide (Nekafin 2 from Kalkfabrik Netstal AG, Switzerland, having a specific surface area (BET) of 1.9 m.sup.2/g) used were dry-mixed in a Hobart mixer for 1 minute. The tempering water, with the respective admixture dissolved therein, was added over the course of 30 seconds, followed by further mixing for 2.5 minutes more. The total wet mixing time was 3 minutes. The proportionally adjusted water/cement ratio (w/c ratio) of the mortar was 0.4 in all the mixtures.

1.3. Mortar Tests with Liquid Admixtures

[0047] To illustrate the activity of the accelerator or admixture of the invention, admixtures Z1, Z2, and Z3 were added to mortar mixtures MM1 and MM2 (see tables 1 and 2). Example B1 with admixture Z1 represents an inventive example, whereas examples V2 to V6 represent comparative examples. For determining the activity of the accelerator or admixture of the invention, determinations were made of the extent of spread (EOS) (table 1) and of the compressive strength (table 2).

TABLE-US-00001 TABLE 1 Extent of spread (EOS) in mm after 0, 20, 40, and 60 minutes (min). EOS EOS EOS EOS Admixture Mortar after after after after No. (wt %) mixture 0 min 20 min 40 min 60 min B1 Z1 (1.38 MM2 (with 215 205 151 111 wt % 3 wt % based on of CaO based cement) on cement) V2 Z2 (1.09 MM2 (with 211 197 136 111 wt % 3 wt % based on CaO based cement) on cement) V3 Z3 (1.10 MM2 (with 197 187 153 131 wt % 3 wt % based on CaO based cement) on cement) V4 Z1 (1.60 MM1 250 247 251 213 wt % based on cement) V5 Z2 (1.60 MM1 263 245 237 231 wt % based on cement) V6 Z3 (1.60 MM1 257 235 213 210 wt % based on cement)

[0048] The extent of spread (EOS) of the mortar was determined according to EN 1015-3.

[0049] The values set out in table 1 show that the workability of the mortar to which the accelerator of the invention has been added is largely retained, in comparison to unaccelerated or differently accelerated compositions. For the rapid production of prefabricated components, and also for road or runway construction, the EOS values after 20 min in particular are important. An EOS value of more than 200 mm after 20 min is evidence of very good workability during the time usually required for quick-setting concrete applications. For use in road or bridge building or for the production of prefabricated concrete elements which must be deshuttered, transported, stacked or prestressed after just a few hours, or for runway renovations, however, high early strength values (for example, compressive strengths after 4 or 6 hours) are still much more important than the extent of spread.

[0050] Table 2 shows compressive strength values (in N/mm.sup.2) of the inventively accelerated mortar composition B1, and also of comparative example compositions V2 to V6 after 4 hours and 6 hours, measured using a needle penetrometer (Mecmesin BFG500 on prisms (4040160 mm) according to standard EN 196-1.

TABLE-US-00002 TABLE 2 Compressive strength in N/mm.sup.2 after 4 and 6 hours (h). No. Admixture (wt %) Mortar mixture After 4 h After 6 h B1 Z1 (1.38 wt %) MM2 (3 wt % CaO) 9.8 30.6 V2 Z2 (1.09 wt %) MM2 (3 wt % CaO) 3.4 15.4 V3 Z3 (1.10 wt %) MM2 (3 wt % CaO) 3.5 16.9 V4 Z1 (1.60 wt %) MM1 3.2 16.8 V5 Z2 (1.60 wt %) MM1 1.9 6.4 V6 Z3 (1.60 wt %) MM1 2.3 9.9

[0051] Table 2 shows clearly the effect of the inventive accelerator in example Bl. When the inventive accelerator is used, in comparison with conventional accelerators (V2, V3 or V4), virtually a doubling after 6 h, and after 4 h almost a tripling, of the strength values are found. The difference relative to the unaccelerated compositions (V5 and V6), as expected, is even greater. It is further apparent that the effect of the inventive accelerator, comprising a phosphoric acid ester of a polyhydric alcohol and a calcium compound, does not merely represent a linear combination of the effects of the individual components which already have accelerating activity, namely phosphoric acid ester (V4) or a calcium compound (V2 and V3). After 4 h, in particular, the compressive strength of the inventively accelerated composition (B1) is significantly higher than that of the individually accelerated compositions, even in spite of the fact that the concentration of phosphoric acid ester in B1 is lower than in V4. A significant, surprising synergistic effect is therefore observable.

2. Individually Added Admixtures

2.1. Substances Used

[0052] A conventional Portland cement CEM 152.5R was used in all of example mortar mixtures MM3, MM4, MMS, MM11, MM12, MM13, and MM14. For the mixtures MM6 to MM9, a cement/flyash mixture CEM IV/B (50 wt % Portland cement CEM I 42.5R+50 wt % silica-rich flyash) was used. The aggregate employed in all of the example mortar mixtures MM3-MM5 was a conventionally sand (maximum grain size 8 mm). In the case of mixtures MM6 to MM14, a finer sand is used, with maximum grain size 2 mm. The superplasticizer used in all of examples MM3-MM14 was a polycarboxylate ether (PCE)-based product (Sika Viscocrete 20 HE, available from Sika Schweiz AG). Mortar mixtures MM3, MM4, MM7, MM8, MM9, MM11, MM12,

[0053] MM13, and MM14 additionally contain calcium oxide (CaO), available under the trade name Nekafin 2 from Kalkfabrik Netstal AG, Switzerland). Mortar mixtures MM3, MM8, MM9, MM11, MM12, MM13, and MM14 additionally contained glycerol 2-monophosphate (glycerol phosphate disodium salt (GPD) pentahydrate, available for example from Sigma Aldrich Schweiz). The proportions of the GPD, CaO, and PCE additives in weight percent, based on the weight of the hydraulic binder used in the respective mixture MM3-MM9, are listed in table 3.

TABLE-US-00003 TABLE 3 Example mortar mixtures containing GPD (glycerol 2-monophosphate disodiunn salt pentahydrate), CaO (calcium oxide) and PCE (polycarboxylate ether superplasticizer). The percentages denote weight percent based on the weight of the hydraulic binder used. No. Mortar mixture GPD (%) CaO (%) PCE (%) B7 MM3 (inventive) 0.15 3 0.9 V8 MM4 (reference) 3 0.6 V9 MM5 (reference) 0.5 V10 MM6 (reference) 0.6 V11 MM7 (reference) 3 0.6 B12 MM8 (inventive) 0.04 3 0.6 B13 MM9 (inventive) 0.075 3 0.6 B14 MM11 (inventive) 0.05 3 0.5 B15 MM12 (inventive) 0.1 3 0.5 B16 MM13 (inventive) 0.15 3 0.5 B17 MM14 (inventive) 0.2 3 0.5

2.2. Production of the Example Mortar Mixtures

[0054] Hydraulic binder, sand, and (in the case of MM3, MM4, MM7, MM8, MM9, MM11, MM12, MM13, and MM14) calcium oxide, and also (in the case of MM3, MM8, MM9, MM11, MM12, MM13, and MM14) GPD, were dry-mixed in a Hobart mixer for 30 seconds. Over the course of 30 seconds, the tempering water and the superplasticizer were added, and mixing was continued for 3.5 minutes more. The total wet mixing time was 4 minutes. The proportionally adjusted water/cement ratio (w/c ratio) of the mortar was 0.45 in all of mixtures MM3 to MM9, and the w/c ratio was 0.5 in mixtures MM11 to MM14.

2.3. Mortar Tests

[0055] For determining the activity of the accelerator or admixture of the invention, determinations were made of the extent of spread (EOS) and of the compressive strength (tables 4 and 5). The extent of spread (EOS) of the mortar was determined according to EN 1015-3. The compressive strength was measured using a needle penetrometer (Mecmesin BFG500 on prisms (4040160 mm) according to standard EN 196-1.

TABLE-US-00004 TABLE 4 Extent of spread (EOS) in mm after 0 and 30 minutes (min) and compressive strengths in N/mm.sup.2 after 4, 6, 8 and 24 hours (h) for example mixtures MM3-MM5. Extent of Compressive spread (mm) strength (N/mm.sup.2) after 0 after 30 after after after after No. Mortar mixture min min 4 h 6 h 8 h 24 h B7 MM3 (inventive) 480 480 1.6 3.6 11.0 49.5 V8 MM4 (reference) 500 600 1.0 1.9 6.0 46.6 V9 MM5 (reference) 480 520 0.6 1.1 3.6 41.2

[0056] The inventive accelerator mixed in in the form of individual components also exhibits, in example B7, a much quicker development of compressive strength than the noninventive, comparative examples V8 and V9.

[0057] Table 5 shows that the strength values of the inventively accelerated mortar mixtures MM8 (example B12) and MM9 (example B13) after 48 hours are at least as high as those of the noninventive mixtures MM6 (example V10) and M7 (example V11).

TABLE-US-00005 TABLE 5 Compressive strengths in N/mm.sup.2 after 20, 24 and 48 hours (h) for example mixtures MM6-MM9. Compressive strength (N/mm.sup.2) No. Mortar mixture after 20 h after 24 h after 48 h V10 MM6 (reference) 1.1 3.1 17.2 V11 MM7 (reference) 3.0 6.4 16.9 B12 MM8 (inventive) 4.9 8.8 17.6 B13 MM9 (inventive) 9.5 11.4 20.4

[0058] Produced additionally was a further mortar mixture MM10, which differs from MM9 only in that, instead of 3 wt % of CaO having a specific surface area of 1.9 m.sup.2/g, just 1 wt % of CaO having a specific surface area of 6 m.sup.2/g was used. The values for extent of spread and compressive strength of MM10 were substantially identical to MM9. This shows the effect of the specific surface area of the calcium compound on the activity of the inventive accelerator.

[0059] Also measured were the compressive strengths of mortar mixtures MM11 to MM14 after 4 h, 6 h, and 8 h. The results are set out in table 6.

TABLE-US-00006 TABLE 6 Compressive strengths in N/mm.sup.2 after 4, 6 and 8 hours (h) for example mixtures MM11-MM14. Compressive strength (N/mm.sup.2) No. Mortar mixture after 4 h after 6 h after 8 h B14 MM11 (inventive) 0.8 3.0 7.6 B15 MM12 (inventive) 0.9 3.9 9.1 B16 MM13 (inventive) 2.1 7.5 13.6 B17 MM14 (inventive) 1.9 6.8 12.9

[0060] The inventive examples B14 to B17 show clearly that there is an optimum range for the synergy effect of the inventive accelerator. As the proportion of GPD goes up, with a constant proportion of CaO, there is an increase in the compressive strength of the mortar mixture. After an optimum value, however, in this case 0.15 wt % of GPD (MM13), the compressive strength falls again, surprisingly (MM14).

[0061] These examples show the outstanding effect of the accelerator of the invention, which in particular after very short times allows much higher early strengths than conventional accelerators, without bringing with it substantial disadvantages in workability, ultimate strength or other properties.

[0062] As a result of the use of the inventive accelerator in mortar or concrete compositions, it is possible to implement even higher cycle times, earlier load-bearing capacity or more rapid repair works than with conventionally accelerated compositions comprising hydraulic binders.

[0063] The working examples described above serve merely to demonstrate the effects and do not confine the invention to the applications shown. The inventive accelerator and an admixture comprising the inventive accelerator, in solid or liquid form, can be used in any compositions which comprise hydraulically setting binders.