Adjuvant combination of a milling assistant and a concrete admixture for accelerated hydration of cementitious binders

Abstract

An adjuvant combination composed of a milling assistant and a concrete admixture for a composition including cement, for accelerating cement hydration, wherein the milling assistant includes at least one amino alcohol and at least one cement hydration accelerator selected from chlorides, thiocyanates, nitrates, nitrites and hydroxides, and the concrete admixture includes a reaction product of at least one calcium compound with at least one silicon compound selected from a silicon dioxide compound, a silica compound and a silicate compound. Using the adjuvant combination produces a significant acceleration in the hardening of a composition including cement, after the addition of water. This is an advantage especially in the production of prefabricated concrete components, allowing quicker deshuttering.

Claims

1. An admixture combination of a grinding aid and a concrete admixture for a composition comprising cement for accelerating cement hydration, where the grinding aid comprises 2 to 40 wt % of at least one amino alcohol, 10 to 40 wt % of at least one cement hydration accelerator selected from chlorides and thiocyanates, and 0 to 25 wt % of at least one glycol, based on the weight of the grinding aid, the concrete admixture comprises a reaction product of at least one calcium compound with a silica sol, the reaction of the calcium compound with the silica sol takes place in the presence of a solvent, in order to form the reaction product, and the reaction product is not cement clinker or cement.

2. The admixture combination of claim 1, wherein the at least one amino alcohol is triethanolamine.

3. The admixture combination of claim 1, the grinding aid comprising a non-zero amount of the at least one glycol, the glycol being selected from diethylene glycol, propylene glycol, and dipropylene glycol.

4. The admixture combination of claim 1, the concrete admixture further comprising at least one comb polymer.

5. A combination of a grinding aid and a concrete admixture in a composition comprising cement as hardening accelerator for accelerating cement hydration on addition of water, where the grinding aid comprises 2 to 40 wt % of at least one amino alcohol, 10 to 40 wt % of at least one cement hydration accelerator selected from chlorides and thiocyanates, and 0 to 25 wt % of at least one glycol, based on the weight of the grinding aid, the grinding aid optionally further comprising one or more cement additives selected from polymer compounds and defoamers; the concrete admixture comprises a reaction product of at least one calcium compound with a silica sol; the reaction of the calcium compound with the silica sol takes place in the presence of a solvent, in order to form the reaction product; and the reaction product is not cement clinker or cement.

6. The combination in the composition of claim 5, wherein the at least one amino alcohol is triethanolamine.

7. The admixture combination of claim 1, wherein the grinding aid comprises 5 to 25 wt % of one or more alkali and/or alkaline earth chlorides, 5 to 25 wt % of one or more alkali and/or alkaline earth thiocyanates, and 2 to 30 wt % of the at least one amino alcohol, based on the weight of the grinding aid.

8. The admixture combination of claim 1, wherein the molar ratio of silicon to calcium in the reaction product is in the range of 0.005 to 0.4.

9. The admixture combination of claim 1, wherein the at least one calcium compound is selected from the group consisting of calcium chloride, calcium nitrate, calcium formate, calcium acetate, calcium bicarbonate, calcium bromide, calcium citrate, calcium chlorate, calcium hydroxide, calcium oxide, calcium hypochloride, calcium iodate, calcium iodide, calcium lactate, calcium nitrite, calcium phosphate, calcium propionate, calcium sulfate, calcium sulfate hemihydrate, calcium sulfate dihydrate, calcium sulfide, calcium tartrate, calcium gluconate, calcium sulfamate, calcium maleate, calcium fumarate, calcium adipate, and calcium aluminate.

10. The admixture combination of claim 9, wherein the at least one calcium compound is selected from the group consisting of calcium nitrate and calcium sulfamate.

11. The admixture combination of claim 1, wherein the average particle diameter of the silica sol is 1 to 150 nm.

12. The admixture combination of claim 1, wherein the solvent is water.

Description

EXAMPLES

(1) The invention is elucidated further by examples below, which, however, are not intended to restrict the invention in any way. Unless otherwise specified, all amounts are given by weight.

(2) Grinding Aid (MH)

(3) A grinding aid MH is obtained by mixing the components listed in the table below, in the proportions indicated.

(4) TABLE-US-00001 Parts by weight Water 63.2 Calcium chloride 15.1 Triethanolamine 10.4 Diethylene glycol 6.80 Acetic acid 4.00 Defoamer 0.30 Biocide* 0.20 *Acticide from Thor GmbH

(5) Concrete Admixture 1 (BZM1)

(6) 47.4 wt % of Ca(NO.sub.3).sub.24 H.sub.2O (from Yara GmbH & Co., Germany), 6.0 wt % of methyl-diethanolamine were dissolved in 11.9 wt % of water and introduced into a 2 liter beaker. Thereafter 34.7 wt % of Cembinder 110 (silica sol from AkzoNobel, Sweden: particle size 2.5 nm, pH 6, colloidally dissolved polysilicic acid molecules with 7.2% SiO.sub.2 content) were added over the course of an hour. The contents of the 2 liter beaker were stirred using a paddle stirrer (RW 20.n, Ika Labortechnik) having a paddle stirrer diameter of 5 cm at 500 to 2000 rpm during the addition of Cembinder 110 and also for a further 15 minutes. This was followed by 30 seconds of homogenization with a rotor-stator mixer (PT2100, Polytron, Kinematica, Switzerland). Mixing with the rotor-stator mixer was followed by a further 15 minutes of stirring with a paddle stirrer. The pH of Cembinder 110 was 6.0.

(7) In this way, an aqueous dispersion of a reaction product of the calcium compound and of the silica sol was prepared. The Si:Ca molar ratio in the initial components was 0.31. Each of the wt % figures is based on the total weight of the accelerator.

(8) Concrete Admixture 2 (BZM2)

(9) 70.8 wt % of Ca(NO.sub.3).sub.2 (50 wt % in H.sub.2O, Yara GmbH & Co., Germany), 9.8 wt % of sodium thiosulfate, 6.4 wt % of methyldiethanolamine were dissolved in 4.8 wt % of water and introduced into a 2 liter beaker. Thereafter 4.9 wt % of silica sol (Cembinder 2509, particle size 5 nm, pH 10.5, colloidally dissolved polysilicic acid molecules with 15.4 wt % SiO.sub.2 content) were added over the course of 15 minutes and the pH was adjusted to a level of 3.8 using 3.3 wt % of formic acid. The fraction of water was approximately 44 wt % and the silicon:calcium ratio was 0.058. Each of the weight figures is based on the total weight of the accelerator. The contents of the 2 liter beaker were stirred using a paddle stirrer (RW 20.n, Ika Labortechnik) having a paddle stirrer diameter of 5 cm at 500 to 1000 revolutions per minute during the addition of the silica sol and also for a further 5 minutes.

(10) The pH during the reaction was consistently in the range of 3.8-3.9.

(11) BZM2 is a very finely divided calcium silicate hydrate-comprising suspension.

(12) Mortar Mixture

(13) The activity of the admixture combination was tested on a standard mortar according to EN 196-1 with the following composition:

(14) TABLE-US-00002 Portland cement (CEM I 42.5N) 450 g Standard sand 0-4 mm 1350 g Water 225 g

(15) The cement used was a mixture consisting of equal parts by weight of the three Swiss cement grades CEM I 42.5N Holcim (Siggenthal), CEM I 42.5N Vigier, and CEM I 42.5N Jura Cement (Wildegg), which had a Blaine fineness of approximately 3400 cm.sup.2/g.

(16) Testing

(17) Compressive strengths were ascertained for the aforementioned mortar mixture 8 h, 12 h, 24 h, and 48 h after addition of the tempering water. The test for determining the compressive strength (in MPa) took place by means of prisms (4040160 mm) according to EN 196-1.

(18) Working

(19) The mixing procedure was carried out in analogy to the EN 196 standard. The procedure was repeated a number of times, with addition of no additive or with addition of the grinding aid (MH) only, the concrete admixture (BZM1 or BZM2) only, or the admixture combination of MH and BZM1 or BZM2. The grinding aid, when used, was ground with the cement before the mixing of the components of the mortar mixture, and the cement thus modified was used for the mortar mixture. If the concrete admixture was used, it was dissolved or dispersed in the tempering water and added with the tempering water into the mortar mixture.

(20) The amounts of grinding aid and/or of concrete admixture used are listed in tables below and expressed in wt % based on the cement weight.

(21) Two variants were tested. In variant A, the water/cement (w/c) figure was 0.5 (in analogy to EN 196). In variant B, there was a departure from the standard composition of the mortar, and the water/cement (w/c) figure was 0.4. Additionally, in variant B, the mortars were admixed additionally with 1 wt % (based on the cement weight) of a plasticizer (Sika ViscoCrete 1020X, available from Sika Deutschland GmbH), in order to improve the workability of the mortar mixtures.

(22) Assembled in the tables below are the results (all percentages are wt % based on the cement weight):

(23) Variant A

(24) TABLE-US-00003 1 2 3 4 5 6 MH 0.3% 0.3% 0.3% BZM1 4.0% 4.0% BZM2 4.0% 4.0% Compressive [MPa] [MPa] [MPa] [MPa] [MPa] [MPa] strength 8 h 1.4 3.1 3.8 3.2 5.2 6.2 12 h 4.9 9.5 11.2 9.5 9.4 14.5 24 h 19.7 19.2 25.0 23.4 21.4 27.0 48 h 30.5 33.7 35.3 32.7 33.9 36.9

(25) Variant B

(26) TABLE-US-00004 1 2 3 4 5 6 MH 0.3% 0.3% 0.3% BZM1 4.0% 4.0% BZM2 4.0% 4.0% Compressive [MPa] [MPa] [MPa] [MPa] [MPa] [MPa] strength 8 h 0.5 2.5 6.1 1.8 5.7 9.5 12 h 3.5 13.1 20.4 12.4 14.2 24.7 24 h 31.3 37.4 40.5 38.0 39.7 42.2 48 h 53.1 59.2 53.8 53.3 57.4 55.0

(27) When the admixture combination is used there is a significant improvement in the compressive strength, especially after 8 h, in comparison to the same components when used individually. This is a synergistic effect, which cannot be explained by additive effects of the individual components.