Hardening accelerator composition for cementitious compositions

Abstract

The invention concerns a process for the for the preparation of a hardening accelerator composition by reaction of a water-soluble calcium compound with a water-soluble silicate compound, the reaction being carried out in the presence of an aqueous solution which contains a plasticizer suitable for hydraulic binders, characterized in that said reaction is being carried out in the presence of apatite and that the molar ratio of calcium to phosphor in the hardening accelerator is from 25/1 to 400/1.

Claims

1. Process for the preparation of a hardening accelerator composition, containing calcium silicate hydrate, by reaction of a water-soluble calcium compound, optionally calcium salt, with a water-soluble silicate compound, the reaction of the water-soluble calcium compound with the water-soluble silicate compound being carried out in the presence of an aqueous solution which contains a plasticizer for hydraulic binders, selected from the group of (A) comb polymers, (B) polycondensates containing (I) at least one structural unit consisting of an aromatic or heteroaromatic moiety bearing a polyether side chain and (II) at least one structural unit consisting of an aromatic or heteroaromatic moiety bearing at least one phosphoric acid ester group, (C) lignosulphonates and/or (D) -naphthalene sulphonate formaldehyde condensates (BNS), characterized in that the reaction of the water-soluble calcium compound with the water-soluble silicate compound is being carried out in the presence of apatite and that the molar ratio of calcium to phosphorus in the hardening accelerator is from 25/1 to 400/1.

2. The process according to claim 1, characterized in that the aqueous solution which contains the plasticizer or the plasticizers for hydraulic binders contains the apatite.

3. The process according to claim 1, characterized in that the apatite is hydroxylapatite or comprises hydroxylapatite.

4. The process according to claim 1, characterized in that the apatite is a halogenapatite or comprises a halogenapatite.

5. The process according to claim 1, characterized in that the hardening accelerator composition contains calcium-silicate-hydrate and apatite.

6. The process according to claim 1, characterized in that the molar ratio of silicon to phosphorus in the hardening accelerator composition is higher than 10/1, optionally from 50/1 to 400/1, further optionally from 80/1 to 300/1.

7. The process according to claim 1, characterized in that the apatite is produced in an in-situ reaction between phosphate ions and the water-soluble calcium salt, optionally during the reaction of the water-soluble calcium compound, optionally calcium salt, with the water-soluble silicate compound.

8. The process according to claim 7, characterized in that the apatite is produced during the reaction of the water-soluble calcium compound, optionally calcium salt, with the water-soluble silicate compound and characterized in that the apatite is produced in the initial reaction phase before 10 weight % of the water-soluble calcium compound, optionally calcium salt, and before 10 weight % of the water-soluble silicate compound have reacted.

9. The process according to claim 1, characterized in that the apatite is added to the aqueous solution which contains a plasticizer for hydraulic binders, selected from the group of (A) comb polymers, (B) polycondensates containing (I) at least one structural unit consisting of an aromatic or heteroaromatic moiety bearing a polyether side chain and (II) at least one structural unit consisting of an aromatic or heteroaromatic moiety bearing at least one phosphoric acid ester group, (C) lignosulphonates and/or (D) -naphthalene sulphonate formaldehyde condensates (BNS) before 10 weight % of the water-soluble calcium compound, optionally calcium salt, and before 10 weight % of the water-soluble silicate compound have reacted.

10. The process according to claim 1, characterized in that the plasticizer for hydraulic binders is selected from the group of (A) comb polymers and is present as a copolymer which contains, on the main chain, side chains having ether functions and acid functions.

11. The process according to claim 1 characterized in that the plasticizer for hydraulic binders is selected from the group of (A) comb polymers and is produced by free radical polymerization in the presence of acid monomer and polyether macromonomer, so that altogether at least 45 mol %, optionally at least 80 mol %, of all structural units of the copolymer are produced by incorporation of acid monomer and polyether macromonomer in the form of polymerized units.

12. The process according to claim 11, characterized in that a structural unit is produced in the copolymer by incorporation of the acid monomer in the form of polymerized units, which structural unit is in accordance with one of the general formulae (Ia), (Ib), (Ic) and/or (Id) ##STR00013## where R.sup.1 is H or a branched or non-branched C.sub.1-C.sub.4 alkyl group, CH.sub.2COOH or CH.sub.2COXR.sup.3, X is NH(C.sub.nH.sub.2n) or O(C.sub.nH.sub.2n) with n being 1, 2, 3 or 4 or is a chemical bond, wherein the nitrogen atom, respectively the oxygen atom is bonded to the CO-group; R.sup.2 is OM, PO.sub.3M.sub.2 or OPO.sub.3M.sub.2; with the proviso that X is a chemical bond if R.sup.2 is OM; R.sup.3 is PO.sub.3M.sub.2 or OPO.sub.3M.sub.2; ##STR00014## where R.sup.3 is H or a branched or non-branched C.sub.1-C.sub.4 alkyl group; n is 0, 1, 2, 3 or 4; R.sup.4 is PO.sub.3M.sub.2 or OPO.sub.3M.sub.2; ##STR00015## where R.sup.5 is H or a branched or non-branched C.sub.1-C.sub.4 alkyl group; Z is O or NR.sup.7; R.sup.7 is H, (C.sub.nH.sub.2n)OH, (C.sub.nH.sub.2n)PO.sub.3M.sub.2, (C.sub.nH.sub.2n)OPO.sub.3M.sub.2, (C.sub.6H.sub.4)PO.sub.3M.sub.2 or (C.sub.6H.sub.4)OPO.sub.3M.sub.2, and n is 1, 2, 3 or 4; ##STR00016## where R.sup.6 is H or a branched or non-branched C.sub.1-C.sub.4 alkyl group; Q is NR.sup.7 or O; R.sup.7 is H, (C.sub.nH.sub.2n)OH, (C.sub.nH.sub.2n)PO.sub.3M.sub.2, (C.sub.nH.sub.2n)OPO.sub.3M.sub.2, (C.sub.6H.sub.4) PO.sub.3M.sub.2 or (C.sub.6H.sub.4)OPO.sub.3M.sub.2, n is 1, 2, 3 or 4; and wherein each M is independently from each other H or a cation equivalent.

13. The process according to claim 11, characterized in that a structural unit is produced in the copolymer by incorporation of the polyether macromonomer in the form of polymerized units, which structural unit is in accordance with one of the general formulae (IIa), (IIb), (IIc) and/or (IId) ##STR00017## where R.sup.10, R.sup.11 and R.sup.12 are in each case identical or different and, independently of one another, are represented by H or a branched or non-branched C.sub.1-C.sub.4 alkyl group; E is a non-branched or branched C.sub.1-C.sub.6 alkylene group, a cyclohexylene group, CH.sub.2C.sub.6H.sub.10, 1,2-phenylene, 1,3-phenylene or 1,4-phenylene; G is O, NH or CONH; or E and G form together a chemical bond; A is C.sub.xH.sub.2x with x being 2, 3, 4 or 5 or CH.sub.2CH(C.sub.6H.sub.5); n is 0, 1, 2, 3, 4 and/or 5; a is an integer from 2 to 350; R.sup.13 is H, a branched or non-branched C.sub.1-C.sub.4 alkyl group, CONH.sub.2 and/or COCH.sub.3; ##STR00018## where R.sup.16, R.sup.17 and R.sup.18 are in each case identical or different and, independently of one another, are represented by H or a branched or non-branched C.sub.1-C.sub.4 alkyl group; E is a branched or non-branched C.sub.1-C.sub.6 alkylene group, a cyclohexylene group, CH.sub.2C.sub.6H.sub.10, 1,2-phenylene, 1,3-phenylene or 1,4-phenylene or a chemical bond; A is C.sub.xH.sub.2x with x being 2, 3, 4 or 5 or CH.sub.2CH(C.sub.6H.sub.5); n is 0, 1, 2, 3, 4 and/or 5; L is C.sub.xH.sub.2x with x is 2, 3, 4 or 5 or CH.sub.2CH(C.sub.6H.sub.5); a is an integer from 2 to 350; d is an integer from 1 to 350; R.sup.19 is H or a branched or non-branched C.sub.1-C.sub.4 alkyl group; R.sup.29 is H or a non-branched C.sub.1-C.sub.4 alkyl group; ##STR00019## where R.sup.21, R.sup.22 and R.sup.23 are in each case identical or different and, independently of one another, are represented by H or a branched or non-branched C.sub.1-C.sub.4 alkyl group; W is O, NR.sup.25, N, V is 1 if W is O or NR.sup.25; V is 2 if W is N; A is C.sub.xH.sub.2x where x=2, 3, 4 or 5 or CH.sub.2CH(C.sub.6H.sub.5); a is an integer from 2 to 350; R.sup.24 is H or a branched or non-branched C.sub.1-C.sub.4 alkyl group, optionally a C.sub.1-C.sub.4 alkyl group; and R.sup.25 is H or a branched or non-branched C.sub.1-C.sub.4 alkyl group, optionally a C.sub.1-C.sub.4 alkyl group; ##STR00020## where R.sup.6 is H or a branched or non-branched C.sub.1-C.sub.4 alkyl group; Q is NR.sup.10, N or O; V is 1 if Q is O or NR.sup.10; V is 2 if Q is N; R.sup.10 is H or a branched or non-branched C.sub.1-C.sub.4 alkyl group; A is C.sub.xH.sub.2x where x=2, 3, 4 or 5 or CH.sub.2CH(C.sub.6H.sub.5); and a is an integer from 2 to 350; R.sup.24 is H or a branched or non-branched C.sub.1-C.sub.4 alkyl group, optionally a C.sub.1-C.sub.4 alkyl group; M is independently from each other H or a cation equivalent.

14. The process according to claim 1, characterized in that in the polycondensate (B) the structural units (I) and (II) are represented by the following general formulae ##STR00021## where A are identical or different and are represented by a substituted or unsubstituted aromatic or heteroaromatic compound having 5 to 10 C atoms where B are identical or different and are represented by N, NH or O where n is 2 if B is N and n is 1 if B is NH or O where R.sup.1 and R.sup.2, independently of one another, are identical or different and are represented by a branched or straight-chain C.sub.1- to C.sub.10-alkyl radical, C.sub.5- to C.sub.8-cycloalkyl radical, aryl radical, heteroaryl radical or H where a are identical or different and are represented by an integer from 1 to 300 where X are identical or different and are represented by a branched or straight-chain C.sub.1- to C.sub.10-alkyl radical, C.sub.5- to C.sub.8-cycloalkyl radical, aryl radical, heteroaryl radical or H ##STR00022## where D are identical or different and are represented by a substituted or unsubstituted heteroaromatic compound having 5 to 10 C atoms where E are identical or different and are represented by N, NH or O where m is 2 if E is N and m is 1 if E is NH or O where R.sup.3 and R.sup.4, independently of one another, are identical or different and are represented by a branched or straight-chain C.sub.1- to C.sub.10-alkyl radical, C.sub.5- to C.sub.8-cycloalkyl radical, aryl radical, heteroaryl radical or H where b are identical or different and are represented by an integer from 1 to 300 where M is independently of one another an alkaline metal ion, alkaline earth metal ion, ammonium ion, organic ammonium ion and/or H, a is 1 or in the case of alkaline earth metal ions is 1/2.

15. The process according to claim 14, characterized in that the molar ratio of the structural units (I):(II) is 1:10 to 10:1.

16. The process according to any of claim 14, characterized in that the polycondensate contains a further structural unit (III) which is represented by the following formula ##STR00023## where Y, independently of one another, are identical or different and are represented by (I), (II), or further constituents of the polycondensate where R.sup.5 are identical or different and are represented by H, CH.sub.3, COOH or a substituted or unsubstituted aromatic or heteroaromatic compound having 5 to 10 C atoms where R.sup.6 are identical or different and are represented by H, CH.sub.3, COOH or a substituted or unsubstituted aromatic or heteroaromatic compound having 5 to 10 C atoms.

17. The process according to claim 16, characterized in that R.sup.5 and R.sup.6 in structural unit (III), independently of one another, are identical or different and are represented by H, COOH and/or methyl.

18. The process according to claim 16, characterized in that the molar ratio of the structural units [(I)+(II)]:(III) is 1:0.8 to 3 in the polycondensate.

19. The process according to claim 1, characterized in that the hardening accelerator composition contains i) 0.01 to 75, optionally 0.01 to 51, further optionally 0.01 to 15% by weight of calcium, ii) 0.01 to 75, optionally 0.01 to 55, further optionally 0.01 to 10% by weight of silicate calculated as SiO.sub.4, iii) 0.001 to 60, optionally 0.1 to 30, further optionally 0.1 to 10% by weight of plasticizer for hydraulic binders selected from (A), (B), (C) and/or (D), iv) 24 to 99, optionally 50 to 99, further optionally 70 to 99% by weight of water and v) 10.sup.5 to 2.5%, optionally 10.sup.5 to 1.63%, further optionally 10.sup.5 to 0.5% by weight of phosphorus.

20. The process according to claim 1, characterized in that the hardening accelerator composition contains no (Portland) cement or that less than 20 weight % of (Portland) cement with respect to the total weight of the hardening accelerator composition is contained.

21. The process according to claim 1, followed by a process step in which the hardening accelerator composition is dried, optionally by a spray drying process.

Description

EXAMPLES

1. Plasticizers According to this Invention

(1) In the examples a comb polymer (A) was used, which was usually abbreviated as G.ACE 30. This abbreviation refers to the comb-type polymer Glenium ACE30, a commercialized polycarboxylate ether (obtainable from BASF Italia S.p.A.) based on the monomers maleic acid, acrylic acid, vinyloxybutyl-polyethyleneglycol-5800 (M.sub.w=40.000 g/mol (measured by G.P.C); the solid content of the sample is 44 weight %).

(2) Preparation of Phosphated Polycondensates (General Procedure)

(3) Also polycondensates (B) were used. The polycondensates (B) were produced according to the following general procedure:

(4) A reactor, equipped with heating and stirrer is charged with a compound according to structural unit (I), for example polyethylenglycol monophenylether (in the following called PhPEG), a compound according to structural unit (II), for example polyethylenglycol monophenylether phosphate or phenoxyethanol phosphate (in the following called phosphate) and a keton compound (IIIa), for example formaldehyde (paraformaladehyde can be used as well as aqueous formaldehyde or trioxane). The reaction mixture is heated to temperatures typically between 90 C. and 120 C. and the polycondensation is started by the addition of the acid catalyst (typically sulfuric acid or methansulfonic acid). Typically the reaction mixture is stirred for 1 to 6 hours until the desired molecular weight range has been achieved. The polycondensate is than diluted with water and neutralized to obtain a solution with 25-80 weight % solid content. Details of the process and the respective monomers according to the general procedure are summarized in table 1. In the table Phosphate type A means phenoxyethanol phosphate, B is polyethylenglycol monophenylether phosphate with 4 to 5 ethylene glycol units in average and C means polyethylenglycol monophenylether phosphate with 3 to 4 ethylene glycol units in average. The formaldehyde source F is a 30.5% aqueous solution of formaldehyde, P is paraformaldehyde. The Acid type S is sulphuric acid.

(5) TABLE-US-00002 TABLE 1 Polymer composition of phosphated polycondensate PhPEG CH.sub.2O Acid Reaction Reaction Solid Mol. Weight Mn [g/mol] Phosphate source type Temp. Time Content M.sub.w Example [g] type [g] [g] [g] [ C.] [min] [%] [g/mol] B1 5000 B PF S 110 300 47.2 34200 800 140 58 32

2. Preparation of Accelerator Compositions

(6) The table 2 shows the details for the synthesis of CSH suspensions according to this invention. This table has to be read according to the following rules. The chemicals labeled P1, P2, P3 and P4 (column B, C, D, E) are added into the reactor always at the point of time t=0 (the start of the reaction) or when it is specified at the time specified. The chemicals labeled S1, S2, S3 and S4 (column F, G, H, I) are fed during the course of the synthesis with a constant feeding rate. In columns J, K, L, M the start of the feedings of products S1, S2, S3, S4 respectively are given as well as the durations of the feedings of S1, S2, S3, S4. All quantities are given in order to obtain 1000 g of hardening accelerator at the end of the synthesis. In column N are given the temperatures at which S1 (T1) and S2 (T2) are maintained, in column O are given the temperatures at which S3 (T3) and S4 (T4) are maintained, and in column P the temperature of the reactor during the synthesis. All syntheses are further stirred 30 minutes after the addition of reactants.

(7) In the examples Acc. 23 to Acc. 27 calcium chloride, respectively calcium bromide, were added at the point of time t=0 to the reaction mixture. It is supposed that due to the presence of halogenide ions at least partially halogenapatite is produced.

(8) The samples Acc. 1 (C), Acc. 13 (C) and Acc. 15 (C) are comparison examples, as the samples Acc. 1 (C) and Acc. 13 (C) are produced without apatite, whereas for the Acc. 15 (C) the addition of the apatite is at the end of the production process.

(9) Calcium phosphate was also tested as a source of calcium ions. Due to its very low solubility in water the hardening accelerator suspensions could only be obtained in a rather diluted form. Due to the high amount of phosphate (molar ratio of calcium to phosphate is 3/2) the hardening accelerator effect was inferior to the hardening accelerators according to this invention with much lower phosphate contents.

(10) TABLE-US-00003 TABLE 2 Details of preparation of accelerators and hardening acceleration A B H Q A P1 C D E F G S3 I J K L M N O P Solid R Sample G. ACE30 P2 P3 P4 S1 S2 G. ACE30 S4 S1 S2 *) S3 *) S4 *) T 1/T 2 T 3/T 4 T Content A Acc. 1 (C) 105.5 g 259.1 g 214.3 g 110.6 g Metso + 0 0 20 C. 20 C. 23.18% 1.29 (H.sub.2O) CN51 310.8 g water 100 100 20 C. Acc. 2 105.5 g 0.47 g 259 g 214.2 g 110.3 g Metso + 0 0 20 C. 20 C. 22.65% 2.38 Na.sub.2HPO.sub.4 (H.sub.2O) CN51 310.7 g water 100 100 20 C. Acc. 3 105.5 g 0.236 g 0.236 g 259 g 214.2 g 110.3 g Metso + 0 0 20 C. 20 C. 22.38% 2.09 Na.sub.2HPO.sub.4 Na.sub.2HPO.sub.4 at (H.sub.2O) CN51 310.7 g water 100 100 20 C. t = t.sub.0 + 30 min Acc. 4 105.5 g 0.47 g 259 g 214.3 g 110.6 g Metso + 0 0 20 C. 20 C. 22.63% 1.44 Na.sub.2HPO.sub.4 at (H.sub.2O) CN51 310.8 g water 100 100 20 C. t = t.sub.0 + 30 min Acc. 5 103.6 g 29.2 g of 236.2 g 209.9 g 110.3 g Metso + 0 0 20 C. 20 C. 22.77% 2.11 HAP1 (H.sub.2O) CN51 310.7 g water 100 100 20 C. Acc. 6 103.5 g 58.4 g of 207.3 g 209.9 g 110.3 g Metso + 0 0 20 C. 20 C. 22.77% 2.27 HAP1 (H.sub.2O) CN51 310.7 g water 100 100 20 C. Acc. 7 103.6 g 29.2 g of 236.2 g 209.9 g 110.3 g Metso + 0 0 20 C. 20 C. 22.89% 2.11 HAP2 (H.sub.2O) CN51 310.7 g water 100 100 20 C. Acc. 8 103.5 g 58.4 g of 207.3 g 209.9 g 110.3 g Metso + 0 0 20 C. 20 C. 22.83% 2.27 HAP2 (H.sub.2O) CN51 310.7 g water 100 100 20 C. Acc. 9 103.6 g 29.2 g of 236.2 g 209.9 g 110.3 g Metso + 0 0 20 C. 20 C. 22.84% 2.08 HAP3 (H.sub.2O) CN51 310.7 g water 100 100 20 C. Acc. 10 103.5 g 58.4 g of 207.3 g 209.9 g 110.3 g Metso + 0 0 20 C. 20 C. 22.80% 2.28 HAP3 (H.sub.2O) CN51 310.7 g water 100 100 20 C. Acc. 11 103.5 g 42.86 g of 222.9 g 209.8 g 110.3 g Metso + 0 0 20 C. 20 C. 22.78% 1.63 HAP1b (H.sub.2O) CN51 310.7 g water 100 100 20 C. Acc. 12 103.5 g 58.4 g of 207.3 g 209.9 g 110.3 g Metso + 0 0 20 C. 20 C. 22.72% 1.53 HAP3b (H.sub.2O) CN51 310.7 g water 100 100 20 C. Acc. 13 (C) 40.7 g 464 g 215.5 g 111 g Metso + 53 g 0 0 0 20 C. 20 C. 20 C. 1.32 (H.sub.2O) CN51 115.8 g water 50 50 50 50 Acc. 14 40.5 g 102.4 g of 363.2 g 214.8 g 110.6 g Metso + 52.9 g.sup. 0 0 0 20 C. 20 C. 20 C. 22.68% 1.84 HAP1c (H.sub.2O) CN51 115.5 g water 50 50 50 50 Acc. 15 (C) 40.5 g 102.4 g of 363.2 g 214.8 g 110.6 g Metso + 52.9 g.sup. 0 0 0 20 C. 20 C. 20 C. 22.70% 1.31 HAP1c at (H.sub.2O) CN51 115.5 g water 50 50 50 50 t = t.sub.0 + 50 min Acc. 16 39.9 g 0.61 g of 461 g 215.1 g 110.8 g Metso + 52 g 0.54 g of 5 5 5 0 20 C. 20 C. 20 C. 22.74% 2.14 Ca(OH).sub.2 (H.sub.2O) CN51 115.7 g water H.sub.3PO.sub.4 (85%) + 50 50 50 5 50 4.38 g of water Acc. 17 40.6 g 0.54 g of 463.8 g 215.4 g 110.9 g Metso + 53 g 0 0 0 20 C. 20 C. 20 C. 22.81% 1.98 H.sub.3PO.sub.4 (85%) (H.sub.2O) CN51 115.8 g water 50 50 50 50 Acc. 18 40.6 g 0.81 g of 463.6 g 215.3 g 110.9 g Metso + 53 g 0 0 0 20 C. 20 C. 20 C. 22.67% 2.05 H.sub.3PO.sub.4 (85%) (H.sub.2O) CN51 115.8 g water 50 50 50 50 Acc. 19 40.6 g 0.34 g of 463.9 g 215.4 g 110.9 g Metso + 53 g 0 0 0 20 C. 20 C. 20 C. 22.74% 1.91 Na.sub.2HPO.sub.4 (H.sub.2O) CN51 115.8 g water 50 50 50 50 Acc. 20 40.6 g 0.67 g of 463.8 g 215.3 g 110.9 g Metso + 53 g 0 0 0 20 C. 20 C. 20 C. 22.62% 1.9 Na.sub.2HPO.sub.4 (H.sub.2O) CN51 115.8 g water 50 50 50 50 Acc. 21 40.6 g 1.01 g of 463.6 g 215.2 g 110.8 g Metso + 53 g 0 0 0 20 C. 20 C. 20 C. 22.66% 1.9 Na.sub.2HPO.sub.4 (H.sub.2O) CN51 115.7 g water 50 50 50 50 Acc. 22 40.6 g 1.16 g of 0.187 g of 458.6 g 215.1 g 110.8 g Metso + 53 g 0.54 g of 5 5 5 0 20 C. 20 C. 20 C. 22.73% 2.3 CaCl.sub.2, 2 H2O NaOH 1M (H.sub.2O) CN51 115.7 g water H.sub.3PO.sub.4 (85%) + 50 50 50 5 50 4.38 g of water Acc. 23 40.6 g 2.31 g of 0.374 g of 453.2 g 214.8 g of 110.6 g Metso + 53 g 1.08 g of 10 10 10 0 20 C. 20 C. 20 C. 22.68% 2.08 CaCl.sub.2, 2 H2O NaOH 1M (H.sub.2O) CN51 115.5 g water H.sub.3PO.sub.4 (85%) + 50 50 50 10 50 8.74 g of water Acc. 24 40.6 g 0.94 g of 0.187 g of 458.9 g 215.1 g of 110.8 g Metso + 53 g 0.54 g of 5 5 5 0 20 C. 20 C. 20 C. 22.56% 1.92 CaBr.sub.2 NaOH 1M (H.sub.2O) CN51 115.7 g water H.sub.3PO.sub.4 (85%) + 50 50 50 5 50 4.38 g of water Acc. 25 40.6 g 1.88 g of 0.374 g of 453.7 g 214.8 g of 110.6 g Metso + 53 g 1.08 g of 10 10 10 0 20 C. 20 C. 20 C. 22.56% 1.85 CaBr.sub.2 NaOH 1M (H.sub.2O) CN51 115.5 g water H.sub.3PO.sub.4 (85%) + 50 50 50 10 50 8.74 g of water Acc. 26 40.6 g 0.471 g of 0.094 g of 461.5 g 215.3 g of 110.9 g Metso + 53 g 0.27 g of 5 5 5 0 20 C. 20 C. 20 C. 22.52% 2.05 CaBr.sub.2 NaOH 1M (H.sub.2O) CN51 115.7 g water H.sub.3PO.sub.4 (85%) + 50 50 50 5 50 2.19 g of water *) Start Time Duration [min]

(11) CN51 is a calcium nitrate aqueous suspension (51 weight % solid content) commercialized by Euroliquids. Metso is a sodium metasilicate powder (Na.sub.2SiO.sub.3, 5 H.sub.2O) commercialized by PQ corporation.

(12) In the samples Acc. 5 to Acc. 12 and Acc. 14 different suspensions of hydroxylapatite (labeled HAP-Nr., column C (P2)) were premanufactured and then used in the syntheses of the accelerators. The premanufactured hydroxylapatite was then added to the reaction mixture at the time t=0 (please compare with table 2). The hardening acceleration A in table 2 is the result of calorimetric experiments and will be explained in the text later on.

(13) Details of the premanufactured hydroxylapatite syntheses can be found in table 3. All quantities are given in order to obtain 1000 g of accelerator at the end (table 3). The temperature of all reactants and the reactor itself is controlled at 20 C. P1, P2 and P3 are added in advance into the reactor. The stirring time after the addition of phosphoric acid (S1) is 30 min. In the column S of table 3 is specified the time elapsed between the end of the synthesis of the premanufactured hydroxylapatite and the use in the synthesis of CSH. It is preferable that the hydroxylapatites are freshly synthesized as it can be concluded with the comparison of samples Acc. 6 and Acc. 11 as well as samples Acc. 9 and Acc. 12. This effect is attributed to the Ostwald ripening of the hydroxylapatite crystals over time.

(14) TABLE-US-00004 TABLE 3 Details of preparation of premanufactured apatites S J Delay between S1 synthesis and Q Start Time use in Solid A B C D F Duration Accelerator Content Sample P1 P2 P3 S1 [min] Synthesis [%] HAP1 21.7 g of 905.1 g of 7.3 g of 65.9 g of 0/10 min 0 2.85% G. ACE 30 water Ca(OH).sub.2 1M H.sub.3PO.sub.4 HAP2 22.4 g of 904.4 g of 7.2 g of 65.9 g of 0/10 min 0 2.82% B1 water Ca(OH).sub.2 1M H.sub.3PO.sub.4 HAP3 926 g of 7.4 g of 66.6 g of 0/10 min 0 1.49% water water 1M H.sub.3PO.sub.4 HAP1b 21.7 g of 905.1 g of 7.3 g of 65.9 g of 0/10 min 24 hours 2.84% G. ACE 30 water Ca(OH).sub.2 1M H.sub.3PO.sub.4 HAP3b 926 g of 7.4 g of 66.6 g of 0/10 min 24 hours 1.50% water water 1M H.sub.3PO.sub.4 HAP1c 21.7 g of 905.1 g of 7.3 g of 65.9 g of 0/10 min 0 2.83% G. ACE 30 water Ca(OH).sub.2 1M H.sub.3PO.sub.4
Calorimetry Tests

(15) In order to test the efficiency of the calcium silicate hydrate suspensions as accelerator, calorimetry tests were performed. It is known that the hydration heat released during the hydration of cement is directly connected to the mechanical properties of the cement paste (H. F: W. Taylor, The cement chemistry, 2nd Edition, 1997. The mechanical properties of mortars or concretes come from the cement matrix (H. F: W. Taylor, The cement chemistry, 2nd Edition, 1997). By monitoring the heat released during the hydration of cement, direct information about the mechanical strength development in mortars or in concretes made with this cement can be obtained. All tests were carried out at the constant W/C ratio of 0.5. Accordingly 50 g of cement and 25 g distilled water (containing if the case the accelerator in dispersed form (batching water)) were mixed with a stirrer during two minutes. Then 3 g of the cement paste were added and sealed in a plastic ampoule and inserted in the calorimeter (TAM-AIR, TA Instruments). The temperature is controlled at 20 C. The accelerator suspensions were first dispersed in the batching water, in the case of the blank comparison (without accelerator), only distilled water and cement was used. In this study, the dosage of accelerators, expressed with respect to the active content, is constant and equal to 0.35 weight % of active weight by cement weight. The active content is the quantity of calcium-silicate-hydrate in accelerator compositions and is calculated with the following method. We consider that the active content is the total solid weight (given by the measured solid content) minus the organic part, minus the sodium ions, minus the nitrate ions and minus the phosphate ions. The organic part, the sodium, the phosphate and nitrate ions are simply deducted from syntheses. In the following an example for the explanation of the calorimetric method is given.

(16) FIG. 1: Heat Flow Evolution of a Cement Paste

(17) The heat flow released during the hydration is measured by calorimetry and is proportional to the hydration rate of cement. The hydration acceleration can be therefore described by the first derivate of the heat flow with time. The performances of the hardening accelerator suspensions are estimated with the ratio:

(18) $A=\frac{\mathrm{Acc}{.}_{\mathrm{with}\mathrm{CSH}}}{\mathrm{ACC}{.}_{\mathrm{ref}}}$

(19) The acceleration values A, which are characteristic for the acceleration effect provided by the hardening accelerator compositions are listed in table 2 (last column). An acceleration of 1 does not give any improvement compared to the reference (blank without accelerator additive), an acceleration of 2 doubles the hydration rate in the first hours compared to the reference. For all calorimetric curves accelerated with the calcium silicate hydrate based accelerators a shift on the time scale to the left was observed. This means that the hydration starts earlier than for the reference. Also it means that the value A (hydration acceleration) can be considered as the relevant acceleration parameter.

(20) From the values of A it becomes clear that compared to the references the acceleration values are considerably higher, which means also a better dosage efficiency. The values correspond in general with concrete experiments.