PROCESS FOR THE PREPARATION OF A CALCIUM SILICATE HYDRATE SEED COMPOSITION USEFUL AS A HARDENING ACCELERATOR FOR CEMENTITIOUS COMPOSITIONS

Abstract

A process for the preparation of a calcium silicate hydrate seed composition useful as a hardening accelerator for cementitious compositions, comprises making a first jet and a second jet to collide in an interaction zone in the presence of an aqueous solution of at least one polymeric water-soluble dispersant. The first jet comprises an aqueous solution of a calcium compound, and the second jet comprises an aqueous solution of a silicate compound. Calcium silicate hydrate seeds precipitate and a primary calcium silicate hydrate seed composition is obtained. The primary calcium silicate hydrate seed composition is subjected to a shearing treatment, preferably a continuous shearing treatment. Unlike the traditional approaches for synthesizing CSH particles, the new process is readily scalable and the obtained calcium silicate hydrate seed composition is more stable against sedimentation, viscosity-increase or gelation.

Claims

1. A process for the preparation of a calcium silicate hydrate seed composition useful as a hardening accelerator for cementitious compositions, comprising (a) making a first jet and a second jet to collide in an interaction zone in the presence of an aqueous solution of at least one polymeric water-soluble dispersant, wherein the first jet comprises an aqueous solution of a calcium compound, and the second jet comprises an aqueous solution of a silicate compound, to precipitate calcium silicate hydrate seeds and to obtain a primary calcium silicate hydrate seed composition, and (b) subjecting the primary calcium silicate hydrate seed composition to a shearing treatment.

2. The process according to claim 1, wherein the primary calcium silicate hydrate seed composition is discharged from the interaction zone within less than 1 s.

3. The process according to claim 1, wherein a first pressurized liquid stream is released through a first nozzle to form the first jet, and a second pressurized liquid stream is released through a second nozzle to form the second jet.

4. The process according to claim 3 wherein the first pressurized liquid stream and/or the second pressurized liquid stream has a pressure in the range of from 10 to 200 bar.

5. The process according to claim 1, wherein the aqueous solution of the polymeric water-soluble dispersant is comprised in at least one of the first jet and the second jet.

6. The process according to claim 5, wherein the aqueous solution of the polymeric water-soluble dispersant is comprised in the first jet.

7. The process according to claim 1, wherein the shearing treatment of step (b) comprises releasing the primary calcium silicate hydrate seed composition through a third nozzle.

8. The process according to claim 1, wherein the pressure drop upon releasing the calcium silicate hydrate seed composition through the third nozzle is in the range of from 2 to 20 bar.

9. The process according to claim 1, wherein in step (a), the first jet and the second jet are made to collide in an interaction zone, and the shearing treatment in step (b) comprises recycling the primary calcium silicate hydrate seed composition to the interaction zone.

10. The process according to claim 1, wherein step (a) and/or step (b) are carried out at a temperature in the range of from 5 to 70 C.

11. The process according to claim 1, wherein the calcium compound is selected from calcium chloride, calcium nitrate, calcium formate, calcium acetate, calcium bicarbonate, calcium bromide, calcium carbonate, calcium citrate, calcium chlorate, calcium fluoride, calcium gluconate, calcium hydroxide, calcium oxide, calcium hypochloride, calcium iodate, calcium iodide, calcium lactate, calcium nitrite, calcium oxalate, calcium phosphate, calcium propionate, calcium stearate, calcium sulphate, calcium sulphate hemihydrate, calcium sulphate dihydrate, calcium sulphide, calcium tartrate, calcium aluminate and mixtures thereof.

12. The process according to claim 1, wherein the silicate compound is selected from sodium silicate, potassium silicate, aluminium silicate, sodium metasilicate, potassium metasilicate, and mixtures thereof.

13. The process according to claim 1, wherein the molar ratio of calcium to silicon is in the range of from 0.6 to 2.

14. The process according to claim 1, wherein the calcium silicate hydrate seed composition has a solids content of 5 to 90 wt.-%.

15. The process according to claim 1, wherein the polymeric water-soluble dispersant is selected from polymers having a carbon-containing backbone to which are attached pendant ionic anchoring groups and polyether side chains, non-ionic polymers having a carbon-containing backbone to which are attached pendant hydrolysable groups and polyether side chains, the hydrolysable groups upon hydrolysis releasing ionic anchoring groups, sulfonated melamine-formaldehyde condensates, lignosulfonates, sulfonated ketone-formaldehyde condensates, sulfonated naphthalene-formaldehyde condensates, phosphonate containing dispersants, phosphate containing dispersants, and mixtures thereof.

16. The process according to claim 15, wherein the dispersant is selected from polycarboxylate ethers; phosphorylated polycondensates obtained by a condensation reaction of an aromatic compound having a phosphate moiety, an alkoxylated hydroxyaryl compound having a polyoxyalkylene chain and formaldehyde; and mixtures thereof.

17. The process according to claim 1, wherein an alkanolamine selected from the group of triisopropanolamine and methyl diethanolamine is present i) in the first jet or in the second jet of the process step a) or ii) is added before or after the shearing treatment of process step b) to the primary calcium silicate hydrate seed composition obtained in step a).

18. The process according to claim 1, wherein the shearing treatment is a continuous shearing treatment.

19. The process according to claim 4, wherein the first pressurized liquid stream and/or the second pressurized liquid stream has a pressure in the range of 10 to 100 bar.

20. The process according to claim 8, wherein the pressure drop upon releasing the calcium silicate hydrate seed composition through the third nozzle is in the range of from 2 to 10 bar.

Description

EXAMPLES

Methods

[0221] Weight-average molecular weight values have been determined by gel permeation chromatography (GPC). As a stationary phase, a sequence of 3 columns PSS MCX, 5 m, 1000 , ID 8.0 mm300 mm (available from PSS), conditioned at 40 C., has been used. As a mobile phase, an eluent of 80 vol.-% of an aqueous solution of Na.sub.2HPO.sub.4 (0.07 mol/L) and 20 vol.-% of acetonitrile has been used. The injection volume was 100 L at a flow rate of 1.0 mL/min. The molecular weight calibration was performed with polystyrene sulfonate standards for RI detector (standards available from PSS Polymer Standards Service).

Materials

[0222] As polymeric water-soluble dispersants, the following polymers were used:

[0223] Glenium ACE30 is a commercially available polycarboxylate ether (obtainable from BASF Italia S.p.A.) based on the monomers maleic acid, acrylic acid, vinyloxybutyl-polyethyleneglycol 5800 (Mw=40.000 g/mol, solids content 45 wt.-%).

Preparation of Phosphorylated Polycondensate

[0224] A reactor, equipped with heating and stirrer is charged with 175 g of a polyethyleneglycol monophenylether (Mn 3500), 36.8 g of a polyethyleneglycol monophenylether phosphate with 4 to 5 ethylene glycol units in average, and 6.3 g of paraformaldehyde. The reaction mixture is heated to 100 C. and the polycondensation is started by the addition of 14 g of methane sulfonic acid. The reaction mixture is stirred for 360 min. The polycondensate is then diluted with water and neutralized to obtain a solution with 43.4 wt.-% solid content and a molecular weight of 27680 g/mol.

[0225] Precursor solution 1 and precursor solution 2 were prepared by homogenizing the components as shown below:

[0226] Precursor solution 1 was prepared as follows: To 93.5 g of a mixed polymer solution (Glenium ACE30 and the phosphorylated polycondensate prepared as described above, weight ratio 2.86:1, based on solids content of polymer solutions), 258.4 g of 51 wt.-% aqueous Ca(NO.sub.3).sub.2 was added under stirring. The resulting mixture was diluted with 215.6 g of water obtaining 567.5 g of precursor solution 1.

[0227] Precursor solution 2 was prepared as follows: To 462.2 g of water at 40 C., 105.3 g of solid sodium metasilicate pentahydrate was added under stirring. The resulting mixture was stirred for 1 h until complete dissolution of the solids obtaining 567.5 g of precursor solution 1.

Example According to the Invention

[0228] A series of two microjet reactors connected in series, manufactured by nanoSaar GmbH was used. Said device has two nozzles each of which has an associated high pressure pump and feed line for injecting a liquid medium into the reactor.

[0229] The Ca(NO.sub.3).sub.2-containing precursor solution 1 and the sodium metasilicate pentahydrate-containing precursor solution 2 were pressurized and transported to the first microjet reactor and ejected through nozzles with a diameter of 800 m/800 m symmetrical nozzle size. No gas flow through the reactor was adopted. The primary calcium silicate hydrate seed composition was withdrawn from the first microjet reactor and the stream was divided into two partial streams which were introduced into a second microjet reactor having two nozzles with a diameter of 1400 m/1400 m symmetrical nozzle size. The calcium silicate hydrate seed composition was withdrawn from the second microjet reactor and collected.

[0230] Flow-rates, pressures and amounts of the first pressurized liquid stream and the second pressurized liquid stream are shown in table 1 below. By this procedure, CSH seed compositions 1 to 18 were prepared. Their specifications are shown in table 2.

TABLE-US-00003 TABLE 1 Reaction condition for the preparation of calcium silicate hydrate seed compositions. flow rate pressure weight flow rate pressure weight pressure Ca-stream .sup.[1] Ca-stream .sup.[1] Ca-stream .sup.[1] Si-stream .sup.[2] Si-stream .sup.[2] Si-stream .sup.[2] shearing time # [L/min] [bar] [kg] [L/min] [bar] [kg] [bar] [min] 1 1.60 25 15.3 1.63 24 14.3 about 7.5 3.5 to 5 2 1.65 26 14.3 1.69 25 13.4 8 6.8 3 1.65 24 to 35 13.3 1.69 25 to 37 12.5 8 6.5 4 1.75 29 to 30 112.5 1.79 29 to 30 105.8 about 6.0 4 to 5 5 1.75 29 to 30 112.5 1.79 29 to 30 105.8 about 6.0 4 to 5 6 1.75 29 to 30 112.5 1.79 29 to 30 105.8 about 3.0 4 to 5 7 1.75 29 to 30 112.5 1.79 29 to 30 105.8 about 6.0 4 to 5 8 1.75 35 to 37 112.5 1.79 35 to 37 105.8 5 3.0 9 1.75 35 to 37 112.5 1.79 35 to 37 105.8 4 7.5 10 1.75 37 to 33 112.5 1.79 37 to 33 105.8 4 6.0 11 1.75 40 to 50 112.5 1.79 40 to 50 105.8 4 5.5 12 1.75 49 to 53 112.5 1.79 50 to 55 105.8 4 2.5 13 1.80 29 to 30 13.4 1.84 29 to 30 12.6 about 6.0 4.5 to 5 14 1.80 29 to 30 13.3 1.84 29 to 30 12.5 about 6.0 4.5 to 5 15 1.80 29 to 30 11.1 1.84 29 to 30 10.5 5 5.0 16 1.80 29 to 30 10.1 1.84 29 to 30 9.5 5 4.5 17 1.80 33 to 37 11.1 1.84 33 to 37 10.5 5 5.0 18 1.80 36 to 39 6.3 1.84 36 to 39 5.9 5 3.0 .sup.[1] First pressurized liquid stream of precursor solution 1 .sup.[2] Second pressurized liquid stream of precursor solution 2

TABLE-US-00004 TABLE 2 Specifications of the prepared calcium silicate hydrate seed compositions of table 1. viscosity after viscosity viscosity solids content preparation after 1 d after 7 d sedimentation # pH consistency [wt.-%] [mPa .Math. s] [mPa .Math. s] [mPa .Math. s] after 7 d 1 10.7 milky, 21.9 n.d. .sup.[1] 294 232 no homogeneous 2 10.8 milky, 22.1 n.d. .sup.[1] 240 213 no homogeneous 3 10.8 milky, 21.9 n.d. .sup.[1] 180 175 no homogeneous 4 10.8 milky, 21.9 n.d. .sup.[1] 364 341 no homogeneous 5 10.8 milky, 21.9 n.d. .sup.[1] 364 341 no homogeneous 6 10.8 milky, 21.9 n.d. .sup.[1] 364 341 no homogeneous 7 10.8 milky, 21.9 n.d. .sup.[1] 364 634 no homogeneous 8 10.8 milky, 22.0 n.d. .sup.[1] 614 604 no homogeneous 9 10.8 milky, 22.0 n.d. .sup.[1] 614 604 no homogeneous 10 10.8 milky, 22.0 n.d. .sup.[1] 614 604 no homogeneous 11 10.8 milky, 22.2 n.d. .sup.[1] 678 851 no homogeneous 12 10.8 milky, 22.2 n.d. .sup.[1] 709 975 no homogeneous 13 10.8 milky, 20.1 839 693 572 no homogeneous 14 10.8 milky, 20.1 839 693 572 no homogeneous 15 10.8 milky, 20.1 839 693 572 no homogeneous 16 10.8 milky, 20.1 839 693 572 no homogeneous 17 10.8 milky, 20.5 1667 1390 1166 no homogeneous 18 10.8 milky, 20.5 1667 1390 1166 no homogeneous .sup.[1] n.d. = not determined

[0231] The results of table 2 show that all calcium silicate hydrate seed compositions 1 to 18 are homogeneous and have a milky consistency. No sedimentation occurs with the inventive compositions after storage for 7 days.

Testing ProcedureEarly Strength Development of Concrete

[0232] The concrete mixes (table 3) were each filled into concrete steel cubes (15/15/15 cm), and after 6 h, 9 h, 16 h and 24 h at a temperature of 20 C. and relative humidity of 65%, a hardened concrete cube was obtained. The hardened concrete cube was demolded, and the compressive strength was measured according to DIN EN 12390-3.

Testing ProcedureMonitoring Hydration Evolution for Cement Pastes (Calorimetry)

[0233] The hydration evolution of the cement pastes was measured using isothermal heat flow calorimetry. TAM Air from TA Instruments was used for measuring the development of the heat of hydration over time of samples containing either only the calcium silicate hydrate seed composition or a combination of the calcium silicate hydrate seed composition and triisopropanolamine (TIPA). The cement Milke CEM I 52.5 R was used for the calorimetry test. The water to cement ratio was 0.5 and the dosage of the accelerator suspensions was 4% by weight of cement. The weight ratio of the mix of the calcium silicate hydrate seed composition and triisopropanolamine (TIPA) was 90:10. The TIPA solution active content was 95%.

[0234] The accelerating performance of the calcium silicate hydrate seed composition or the combination of the calcium silicate hydrate seed composition with triisopropanolamine (TIPA) becomes evident by comparing the resulting heat of hydration curves with the heat of hydration curve of a cement reference sample (blank). The calorimetric heat of hydration of cement pastes at 20 C. is shown in FIG. 1 and reveal that for the samples containing the calcium silicate hydrate seed composition or a mix of the calcium silicate hydrate seed composition and TIPA the timespan required until the onset of the main hydration peak is much shorter compared to the reference sample. The steep increase in heat flow shown after the dormant phase is indicative for the good accelerating performance of the calcium silicate hydrate seed compositions. Moreover the synergetic effect between CSH-seeds and TIPA can be seen by the strong increase in the heat evolution, which is characterized by the rather sharp additional peak at 10 hours (FIG. 1).

[0235] The concrete samples using two different cements, namely Milke CEM I 52.5 R and Bernburg CEM I 42.5 R, were prepared as follows and the details of the concrete compositions are summarized in table 3: [0236] cement, sand and all aggregates were dry mixed for 15 seconds [0237] 80% of the mixing water was added and mixed for 2 minutes [0238] The calcium silicate hydrate seed composition and a superplasticizer (for obtaining the desired workability) were added to the remaining water. The resulting solution was added to the concrete mix and mixed for further 2 minutes.

TABLE-US-00005 TABLE 3 Concrete compositions Content [kg/m.sup.3] Content [kg/m.sup.3] CEM | 52.5 R 380 Milke CEM | 52.5 R 380 Bernburg Quartz sand 0.1-0.3 mm 135 135 Quartz sand 0.3-1.0 mm 78 78 Natural sand 0-4 mm 696 696 Gravel 2-5 mm 238 238 Gravel 5-8 mm 207 207 Gravel 8-11 mm 218 218 Gravel 11-16 mm 297 297 Superplasticizer 45 wt. %.sup.[1] 0.27% bwoc 0.27% bwoc CSH-suspension 22 wt. % 4% bwoc 4% bwoc Water 160 160 .sup.[1]Superplasticizer = Glenium ACE30

TABLE-US-00006 TABLE 4 a Strength development in Milke cement CSH-seeds sus. Milke CEM | 52.5 R Dosage % CS.sup.[1]6 h CS.sup.[1]9 h CS.sup.[1]16 h CS.sup.[1]24 h # [bwoc] [MPa] [MPa] [MPa] [MPa] 0* n.a..sup.[2] n.a..sup.[2] 38.00 47.40 4.sup.[3] 4 17.45 35.45 50.00 55.45 8.sup.[3] 4 18.5 36.50 51.55 54.75 .sup.[1]compressive strength at 20 C. .sup.[2]not determined .sup.[3]samples' codes of CSH-samples selected from Table 1 (see entry 4 and 8) *comparative example

TABLE-US-00007 TABLE 4 b Strength development in Bernburg cement CSH-seeds sus. Bernburg CEM | 52.5 R Dosage % CS.sup.[1]6 h CS.sup.[1]9 h CS.sup.[1]16 h CS.sup.[1]24 h # [bwoc] [MPa] [MPa] [MPa] [MPa] 1* n.a..sup.[2] n.a..sup.[2] 11.79 24.00 4.sup.[3] 4 2.45 7.67 22.00 29.50 8.sup.[3] 4 2.49 8.1 22.40 29.60 .sup.[1]compressive strength at 20 C. .sup.[2]not determined .sup.[3]samples' codes of CSH-samples selected from Table 1 *comparative example

[0239] It is evident from the results of table 3 and 4 that the addition of calcium silicate hydrate seed compositions (two samples were selected from table 2; entry 4 and 8) improves significantly the early strength development (at 6, 9 and 16 h) and also the compressive strength development up to 24 hours. The compressive strength values of the concrete specimens including the calcium silicate hydrate seed compositions (with or without TIPA) surpass those from the reference samples. The compressive strength values obtained with Bernburg CEM I 42.5 R cement are in general lower compared to the values obtained with Milke CEM I 52.5 R cement. This difference is due to the impact of the different cement types and their fineness.