HARDENING ACCELERATOR COMPOSITION CONTAINING DISPERSANTS

Abstract

A process for the preparation of a hardening accelerator composition by reaction of a water-soluble calcium compound with a water-soluble silicate compound, said reaction being effected in the present of a water-soluble dispersant having at least one polyalkyleneglycol structural unit with a functional group at one end of the polyalkyleneglycol, being able to interact as an anchor group with the surface of cement particles, the hardening accelerator composition and its use.

Claims

1. A process for the preparation of a hardening accelerator composition comprising reacting a calcium compound with a silicon dioxide containing component under alkaline conditions, wherein the reaction is carried out in the presence of an aqueous solution of a water-soluble dispersant comprising at least one polyalkyleneglycol structural unit with a functional group at one end of the polyalkyleneglycol, said functional group capable of interacting as an anchor group with the surface of cement particles.

2. The process according to claim 1 wherein the calcium compound is a calcium salt.

3. The process according to claim 2 wherein the calcium salt is a water-soluble calcium salt.

4. The process according to claim 1, wherein the molar ratio of calcium from the calcium compound to silicon from the silicon dioxide containing component is from about 0.6 to about 2.

5. The process of claim 4, wherein the molar ratio of calcium from the calcium compound to silicon from the silicon dioxide containing component is from about 1.1 to about 1.8.

6. The process according to claim 1, wherein the functional group being able to interact as an anchor group with the surface of cement particles comprises carboxylate radicals, phosphate radicals, phosphonate radicals, silane radicals, the silane radicals being able to react with water to a silanol compound under alkaline conditions and/or at least 3 hydroxy radicals.

7. The process according to claim 6 wherein the at least 3 hydroxy radicals are derived from a sugar compound.

8. The process according to claim 1, wherein the functional group being able to interact as an anchor group with the surface of cement particles comprises at least 5 hydroxy radicals, at least 3 carboxylate radicals, at least 2 phosphonate radicals or at least 2 silane radicals, the silane radicals being able to react with water to a silanol compound under alkaline conditions.

9. The process according to claim 1, wherein the functional group being able to interact as an anchor group with the surface of cement particles contains two phosphonate radicals and is represented by the following general structure (I),
RO-(AO).sub.nCH.sub.2CH.sub.2N[CH.sub.2PO(OM).sub.2].sub.2(I) wherein A is the same or different and independently from each other an alkylene with two to 18 carbon atoms, optionally ethylene and/or propylene, further optionally ethylene, n is an integer from 5 to 500, and M is H, an alkali metal, earth alkali metal and/or an amine, and R is H or a saturated or unsaturated hydrocarbon residue.

10. The process according to claim 9, wherein n is an integer from 10 to 200.

11. The process of claim 10, wherein n is an integer from 10 to 100.

12. The process of claim 9, wherein R is a C1 to C15 alkyl radical.

13. The process according to 1, wherein the polyalkyleneglycol comprises at least 5 repeating units, and contains more than 80 mol-% of ethyleneglycol units, optionally more than 90 mol-% of ethyleneglycol units.

14. The process of claim 13, wherein the polyalkyleneglycol comprises from 10 repeating units to 500 repeating units.

15. The process of claim 14, wherein the polyalkyleneglycol comprises from 10 to 200 repeating units.

16. The process according to claim 1, wherein at the other end of the polyalkyleneglycol structural unit, no group is present, which would be substantially able to interact as an anchor group with the surface of cement particles.

17. The process according to claim 1, wherein the reaction is carried out completely or partially in the presence of an aqueous solution containing a viscosity enhancer polymer, comprising at least one of polysaccharide derivatives or (co)polymers with an average molecular weight M.sub.w higher than 500,000 g/mol, the (co)polymers containing structural units derived (optionally by free radical polymerization) from non-ionic (meth)acrylamide monomer derivatives and/or sulphonic acid monomer derivatives.

18. The process of claim 17, wherein the viscosity enhancer polymer comprises polysaccharide derivatives or (co)polymers with an average molecular weight M.sub.w higher than 1,000,000 g/mol.

Description

EXAMPLES

Preparation of the Hardening Accelerator Compositions

[0118] It is possible to prepare the hardening accelerator compositions according to the processes described in WO2010/026155, replacing the polycarboxylate ethers by the subject dispersants. Here Optima100, which is a commercial dispersant for cementitious compositions obtainable from the company Chryso, was used. Optima100 is a 29.9 weight % solution of a polyethylene glycol structure with a diphosphonate anchor group.

[0119] Solutions 1, 2 and 3 were prepared according to the weight percentages given in Table 1.

TABLE-US-00002 TABLE 1 preparation of hardening accelerators 1, 2 and 3 Total solid Mixing Procedure Stirring content ID Solution 1 Solution 2 Solution 3 with feeding rates Temp. rate (rpm) (weight %) Acc1 51.95 g of 20.83 g of 25.5 g of 1 in 3 at 2 in 3 at 20 C. 400 4.88% CN51 Metso + Optima 41.56 ml/h 38.12 ml/h 21.74 g 100 + 880 g water water Acc2 51.74 g of 20.75 g of 38.11 g of 1 in 3 at 2 in 3 at 20 C. 400 5.25% CN51 Metso + Optima 41.40 ml/h 38 ml/h 21.66 g 100 + 867.7 g water water Acc3 51.46 g of 20.67 g of 50.6 g of 1 in 3 at 2 in 3 at 20 C. 400 5.63% CN51 Metso + Optima 41.25 ml/h 37.8 ml/h 21.58 g 100 + 856 g water water

[0120] CN 51 is a 51 weight % calcium nitrate solution, Metso is sodium metasilicate pentahydrate powder from PQ corporation. Optima100 was used as a 29.9 weight solution of the dispersant.

[0121] Solutions 1, 2 and 3 are prepared before starting the reaction by dissolving the water-soluble salts and mixing Optima100 in water at room temperature until the complete dissolution. The reaction is started by feeding the respective solutions according to the mixing procedure indications in table 1 at the given addition rates under mechanical stirring. The stirring rate(s) and the temperature are controlled during the whole synthesis. After the addition of the reactants, the suspension is further mixed for 30 minutes and afterwards collected and stored. The solid content of the suspension is measured by drying 3 g+/0.1 g of the suspension in a crucible in porcelain 24 hours in an oven at 60 C. The solid content is given in the table 1.

Calorimetric Measurements

[0122] The influence of the hardening accelerators was tested on the cement Bernburg 42.5 R by the measurement of the heat released in heat flow calorimetrical measurements. The accelerator suspension was mixed with the batching water and the resulting suspension mixed with 25 g of the cement. The water to cement (w/c) ratio was set to 0.5.

[0123] The dosage of the accelerators to be tested is expressed as weight percentage of solid content with respect to the cement weight. The dosage in weight % of solid content was 1.0 weight % for Acc1, 1.10 weight % for Acc 2 and 1.14 weight % for Acc 3. For each trial, the dosage in actives is about 0.35 weight % with respect to the cement. Actives means here the solid content of the samples minus the portion of the dispersant Optima100, in other words the inorganic part of the solids content.

[0124] FIG. 1: calorimetric Measurements

[0125] The addition of the subject hardening accelerator as described herein accelerates the acceleration period, which is defined in H. F. W. Taylor (1997): Cement Chemistry, 2.sup.nd edition, p. 212ff. The comparison example without accelerator shows the lower heat development of samples without accelerator. The subject accelerators Acc1, Acc2 and Acc 3 are superior to the comparison example. Samples of hardening accelerators prepared in the absence of the dispersant Optima100 resulted in basically no accelerating effect in calorimetric measurements and also in measurements of early strength as respective comparative results in WO2010/026155 show.

[0126] It will be understood that the embodiments described herein are merely exemplary, and that one skilled in the art may make variations and modifications without departing from the spirit and scope of the claims. Further, all embodiments disclosed are not necessarily in the alternative, as various embodiments may be combined to provide the desired result.