COMPOSITION BASED ON CALCIUM SILICATE HYDRATE

Abstract

The invention relates to a composition comprising 5-50 wt % of calcium silicate hydrate, 10-60 wt % of at least one water-soluble, acid group-containing polymer comprising polyether groups, and 5-40 wt % of at least one polyalkylene glycol ether. Further disclosed is a process for preparing this composition, and cementitious mixtures comprising the composition. A further aspect of the present invention is the use of the composition of the invention in cementitious mixtures for accelerating the development over time of the dispersing action of the acid group-containing polymer after addition of the mixing water and a subsequently accelerated curing of the mixture.

Claims

1. A composition comprising 5-50 wt % of calcium silicate hydrate, 10-60 wt % of at least one water-soluble, acid group-containing polymer comprising polyether groups, 5-40 wt % of at least one polyalkylene glycol ether of the formula (1)
R.sup.(C.sub.H.sub.2O).sub.H(1) where R.sup. is hydrogen or an aliphatic hydrocarbon radical having 1 to 20 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms, or an optionally substituted aryl radical having 6 to 14 C atoms, the aryl radical comprising no acid groups, and independently at each occurrence and in a manner identical or different for each (C.sub.H.sub.2O) unit is 2, 3, 4 or 5, and is 3 to 200.

2. The composition according to claim 1, wherein the polyether groups of the at least one water-soluble, acid group-containing polymer are polyether groups of the structural unit (I),
*U(C(O)).sub.kX-(AlkO).sub.nW(I) where * indicates the bonding site to the acid group-containing polymer, U is a chemical bond or an alkylene group having 1 to 8 C atoms, X is oxygen, sulfur or a group NR.sup.1, k is 0 or 1, n is an integer whose average value, based on the acid group-containing polymer, is in the range from 3 to 300, Alk is C.sub.2-C.sub.6 alkylene, and within group (Alk-O).sub.n Alk may be identical or different, W is a hydrogen, a C.sub.1-C.sub.6 alkyl, or an aryl radical or is the group YF, where Y is a linear or branched alkylene group having 2 to 8 C atoms and optionally may carry a phenyl ring, F is a 5- to 10-membered nitrogen heterocycle which is bonded via nitrogen and which as ring members, besides the nitrogen atom and beside carbon atoms, optionally may have 1, 2 or 3 additional heteroatoms selected from oxygen, nitrogen, and sulfur, it being possible for the nitrogen ring members to have a group R.sup.2, and for 1 or 2 carbon ring members to be present in the form of a carbonyl group, R.sup.1 is hydrogen, C.sub.1-C.sub.4 alkyl or benzyl, and R.sup.2 is hydrogen, C.sub.1-C.sub.4 alkyl or benzyl.

3. The composition according to claim 1, wherein the acid group of the water-soluble polymer is at least one from the series of carboxyl, phosphono, sulfino, sulfo, sulfamido, sulfoxy, sulfoalkyloxy, sulfinoalkyloxy, and phosphonooxy group.

4. The composition according to claim 1, wherein the water-soluble, acid group-containing polymer comprising polyether groups is a polycondensation product comprising (II) a structural unit containing an aromatic or heteroaromatic and a polyether group, (III) a phosphated structural unit containing an aromatic or heteroaromatic.

5. The composition according to claim 4, wherein the structural units (II) and (III) are represented by the following general formulae
A-U(C(O)).sub.kX-(AlkO).sub.nW(II) where A is identical or different and is represented by a substituted or unsubstituted, aromatic or heteroaromatic compound having 5 to 10 C atoms in the aromatic system, the other radicals possessing the definition stated for structural unit (I); ##STR00007## where D is identical or different and is represented by a substituted or unsubstituted, aromatic or heteroaromatic compound having 5 to 10 C atoms in the aromatic system where E is identical or different and is represented by N, NH or O where m=2 if E=N and m=1 if E=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 unbranched 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 is identical or different and is represented by an integer from 0 to 300.

6. The composition according to claim 4, wherein the polycondensation product comprises a further structural unit (IV) which is represented by the following formula ##STR00008## where Y independently at each occurrence is identical or different and is represented by (II), (III) or further constituents of the polycondensation product.

7. The composition according to claim 1, wherein the water-soluble, acid group-containing polymer comprising polyether groups is at least one copolymer which is obtained by polymerization of a mixture of monomers comprising (V) at least one ethylenically unsaturated monomer which comprises at least one radical from the series of carboxylic acid, carboxylic salt, carboxylic ester, carboxylic amide, carboxylic anhydride, and carboxylic imide and (VI) at least one ethylenically unsaturated monomer having a polyether group.

8. The composition according to claim 7, wherein the ethylenically unsaturated monomer (V) is represented by at least one of the following general formulae from the group of (Va), (Vb), and (Vc) ##STR00009## where R.sup.7 and R.sup.8 independently of one another are hydrogen or an aliphatic hydrocarbon radical having 1 to 20 C atoms B is H, COOM.sub.a, COO(C.sub.qH.sub.2qO).sub.rR.sup.9, or CONH(C.sub.qH.sub.2qO).sub.rR.sup.9 M is hydrogen, a mono-, di- or trivalent metal cation, ammonium ion, or an organic amine radical a is 1/3, 1/2 or 1 R.sup.9 is hydrogen, an aliphatic hydrocarbon radical having 1 to 20 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms, or an optionally substituted aryl radical having 6 to 14 C atoms q independently at each occurrence and in a manner identical or different for each (C.sub.qH.sub.2qO) unit is 2, 3 or 4 and r is 0 to 200 Z is O, NR.sup.16 R.sup.16 independently at each occurrence is identical or different and is represented by a branched or unbranched C.sub.1 to C.sub.10 alkyl radical, C.sub.5 to C.sub.8 cycloalkyl radical, aryl radical, heteroaryl radical or H, ##STR00010## where R.sup.10 and R.sup.11 independently of one another are hydrogen or an aliphatic hydrocarbon radical having 1 to 20 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms, or an optionally substituted aryl radical having 6 to 14 C atoms R.sup.12 is identical or different and is represented by (C.sub.nH.sub.2n)SO.sub.3H with n=0, 1, 2, 3 or 4, (C.sub.nH.sub.2n)OH with n=0, 1, 2, 3 or 4; (C.sub.nH.sub.2n)PO.sub.3H.sub.2 with n=0, 1, 2, 3 or 4, (C.sub.nH.sub.2n)OPO.sub.3H.sub.2 with n=0, 1, 2, 3 or 4, (C.sub.6H.sub.4)SO.sub.3H, (C.sub.6H.sub.4)PO.sub.3H.sub.2, (C.sub.6H.sub.4)OPO.sub.3H.sub.2, or (C.sub.nH.sub.2n)NR.sup.14.sub.b with n=0, 1, 2, 3 or 4 and b=2 or 3 R.sup.13 is H, COOM.sub.a, COO(C.sub.qH.sub.2qO).sub.rR.sup.9, or CONH(C.sub.qH.sub.2qO).sub.rR.sup.9, where M.sub.a, R.sup.9, q, and r possess definitions stated above R.sup.14 is hydrogen, an aliphatic hydrocarbon radical having 1 to 10 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms, or an optionally substituted aryl radical having 6 to 14 C atoms Q is identical or different and is represented by NH, NR.sup.15 or O; where R.sup.15 is an aliphatic hydrocarbon radical having 1 to 10 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms, or an optionally substituted aryl radical having 6 to 14 C atoms.

9. The composition according to claim 1, which is present as a powder.

10. The composition according to claim 1, wherein the molar ratio of calcium to silicon in the calcium silicate hydrate is 0.6 to 2.0.

11. The composition according to claim 1, wherein, in formula (1) of the polyalkylene glycol ether, R.sup. is an aliphatic hydrocarbon radical having 1 to 4 C atoms, independently at each occurrence and in a manner identical or different for each (C.sub.H.sub.2O) unit is 2 or 3, and is 8 to 100.

12. A process for preparing a composition according to claim 1, which comprises reacting a water-soluble calcium compound with a water-soluble silicate compound, the reaction of the water-soluble calcium compound with the water-soluble silicate compound taking place in the presence of water which at least partly comprises the at least one acid group-containing polymer.

13. The process according to claim 12, wherein the molar ratio of calcium to silicon is 0.6 to 2.0.

14. A mixture comprising a cementitious binder and 0.01 to 10 wt % of a composition according to claim 1, based on the overall mass of the mixture.

15. A method comprising utilizing the composition according to claim 1 in a pulverulent mixture comprising a cementitious binder, for accelerating the development over time of the dispersing action of the acid group-containing polymer following addition of the mixing water and a subsequently accelerated curing of the mixture.

Description

EXAMPLES

[0113] Gel Permeation Chromatography

[0114] Sample preparation for the determination of molar weight was carried out by dissolving polymer solution in the GPC eluent, giving a polymer concentration in the GPC eluent of 0.5 wt %. This solution was then filtered through a syringe filter with polyethersulfone membrane and pore size of 0.45 m. The injection volume of this filtrate was 50-100 l.

[0115] The average molecular weights were determined on a Waters GPC instrument with model name Alliance 2690 with a UV detector (Waters 2487) and an RI detector (Waters 2410). [0116] Columns: Shodex SB-G Guard Column for SB-800 HQ series [0117] Shodex OHpak SB 804HQ and 802.5HQ [0118] (PHM gel, 8300 mm, pH 4.0 to 7.5) [0119] Eluent: 0.05 M aqueous ammonium formate/methanol mixture=80:20 (parts by volume) [0120] Flow rate: 0.5 ml/min [0121] Temperature: 50 C. [0122] Injection: 50 to 100 l [0123] Detection: RI and UV

[0124] The molecular weights of the polymers were determined using two different calibrations. First they were determined relative to polyethylene glycol standards from PSS Polymer Standards Service GmbH. The molecular weight distribution curves of the polyethylene glycol standards were determined by light scattering. The masses of the polyethylene glycol standards were 682 000, 164 000, 114 000, 57 100, 40 000, 26 100, 22 100, 12 300, 6240, 3120, 2010, 970, 430, 194, 106 g/mol.

[0125] Chemistry of Polycarboxylate Ethers Used

[0126] The polymers used have the following composition:

TABLE-US-00001 TABLE 1 Mol of acrylic Mol of Mw Polymer acid macromonomer Macromonomer (g/mol) A 10 1 VOBPEPG-3000 21 000 B 5 1 VOBPEPG-3000 27 000

[0127] The abbreviation VOBPEPG-3000 stands for vinyloxybutyl-polyethylene/propylene glycol of blockwise construction. Block A contains only polyethylene glycol, block B a random mixture of ethylene glycol and propylene glycol. The molar mass is 3000 g/mol. The structure conforms to formula with n23, k13, l28.

##STR00006##

[0128] The MPEG500 and MPEG1000 used in all of the examples are Pluriol A 500 E and Pluriol A 1020 E, respectively (commercial products from BASF SE).

[0129] Preparation of Polycarboxylate Ether B

[0130] A 1000 ml four-neck flask with thermometer, pH meter, and reflux condenser was charged with 385 g of water and 360 g (0.12 mol) of VOBPEPG-3000.

[0131] This mixture is cooled to 15 C. Then 0.5 g of 2% strength FeSO.sub.4*18H.sub.2O solution and 42.4 g (0.59 mol) of 99% acrylic acid are added. This is followed by addition of 1.8 g of mercaptoethanol and 5 g of Briggolit FF6. At this point a pH of around 4.6 becomes established. After a mixing time of 2 minutes, 2.5 g of 50% strength H.sub.2O.sub.2 solution are added. Polymerization begins after a short time and a steady temperature rise is seen. After about 2 minutes, the reaction attains the temperature maximum of about 42 C. and a pH of 4.2. After a further 5 minutes, the batch is adjusted to a pH of 5.5 with 30 g of 20% strength NaOH solution. This gives a clear aqueous polymer solution pale yellowish in color and having a solids content of 50 wt %.

[0132] Polycarboxylate ether A is prepared analogously, with the solids content likewise being 50 wt %.

[0133] Using the solution of polymer A for preparing additive V1, and the solution of polymer B for preparing additive V2, each of the solutions is dried using a Niro Mobil Minor spray dryer. Atomization took place with a two-fluid nozzle with a stream of nitrogen. Entry temperature 230 C., exit temperature 100 C.

[0134] Preparation Protocol for Nanoscale CSH Solution

[0135] Preparation of Carrier Component T

[0136] Raw materials used:

[0137] Calcium hydroxide (Merck KGaA, purity 97%) [0138] Calcium acetate monohydrate (Sigma Aldrich Co. LLC, >99.0%) [0139] Defoamer (Melflux DF 93 from BASF Construction Solutions GmbH, solids content=60.0 wt %) [0140] Na waterglass (BASF SE, Natriumwasserglas 37/40 PE, solids content 36.1 wt %, modulus n(SiO.sub.2)/n(Na.sub.2O)=3.4) [0141] Polymer A as 36.1 wt % strength aqueous solution

[0142] Description of Synthesis:

[0143] Calcium Source CL:

[0144] The calcium source CL has the following composition:

TABLE-US-00002 Substance Fraction wt % Calcium hydroxide suspension (30 wt %) 32.7 Calcium acetate monohydrate 10.1 Water 57.2

[0145] The calcium source is prepared by the following steps: [0146] (i) introducing the water [0147] (ii) adding an aqueous 30 wt % calcium hydroxide suspension [0148] (iii) adding calcium acetate monohydrate.

[0149] The suspension is stirred permanently at 40 rpm (revolutions per minute) using a mechanical agitator with paddle stirrer, in order to prevent sedimentation of the calcium hydroxide.

[0150] Silicate Source SL:

[0151] The silicate source SL has the following composition:

TABLE-US-00003 Substance Fraction wt % Na waterglass (36.1 wt % form) 49.8 Water 50.2

[0152] The silicate source SL is prepared by introducing water and adding Na waterglass with stirring at 40 rpm.

[0153] Stabilizer Solution STL:

[0154] The stabilizer solution STL had the following composition:

TABLE-US-00004 Substance Fraction wt % Polymer A (36.1 wt % strength aqueous solution) 38.7 Melflux DF 93 (defoamer) 2.3 Water 61.0

[0155] The stabilizer solution STL is prepared by the following steps: [0156] (i) introducing the water [0157] (ii) adding polymer A [0158] (iii) adding Melflux DF 93

[0159] The solution is stirred permanently at 40 rpm and the temperature is adjusted to 22 C.

[0160] To produce the carrier component T, the stabilizer solution STL is introduced into a reactor and stirred at 40 rpm. Connected to this reactor is a 20 ml 3-channel mixing cell. The mixing cell is equipped with an Ika Ultra Turrax which drives a rotor-stator dispersing tool (Ika, S 25 KV-25F) at 10 000 rpm. The stabilizer solution STL is pumped in circulation through the mixing cell using an Ismatec MCP process peristaltic pump, with a pumping rate of 108.83 g/min at a rotary speed of 50 rpm. During a synthesis time of 150 minutes, the calcium source CL and the silicate source SL are introduced in parallel into the mixing cell by means of peristaltic pumps, at a constant mass ratio of CL/SL=1.36, and are mixed with the stabilizer solution STL. The calcium source CL is pumped into the mixing cell at a constant pumping rate of 2.33 g/min, and the silicate source SL at a constant pumping rate of 1.71 g/min. In total, 1.53 parts by weight of the stabilizer solution STL are mixed with 1.36 parts by weight of the calcium source and 1.0 part by weight of the silicate source. Following complete metering of the calcium source CV and the silicate source SL, the reaction mixture is stirred for a further 15 minutes at 40 rpm. The resultant solids content of the carrier component T is 16.5 wt %.

[0161] General Preparation Protocol for Comparative Product V4 and Inventive Products V5 to V9

[0162] The quantities of MPEG 500 and polymer A or polymer B as indicated in table 2 are mixed with stirring into 1 kg of 16.5% carrier component T (nanoscale CSH suspension).

[0163] This mixture was dried using a Niro Mobil Minor spray dryer. Atomization took place with a two-fluid nozzle and a stream of nitrogen. Entry temperature 230 C., exit temperature 100 C. The result is a fine, nonsticking, white powder. The powder has a residual moisture content of 1.7 wt %.

[0164] Preparation Protocol for Comparative Example V3

[0165] For comparative example V3, polycarboxylate ether solution in methylpolyethylene glycol (MPEG500) is prepared in a method based on example 4 of EP 2574636 A1 (see page 10, lines 20-27), with pure MPEG500 being used rather than an MPEG500/glycerol carbonate mixture. It is obtained in the form of an anhydrous liquid. The mixing of the polycarboxylate ether solution with the binder system takes place in analogy to use example 1 on page 10 of EP 2574636 A1. 1000 g of binder system, consisting of 500 g of cement (CEM I 52.5 R, Milke type from HeidelbergCement) and 500 g of fine silica sand (type H33 from Quarzwerke Frechen), are stirred at 500 revolutions per minute in a beaker with an axial stirrer. Added to this mixture are 3.0 g of polycarboxylate ether solution in methylpolyethylene glycol (additive V3A) (corresponding to 0.30 wt % of pure polycarboxylate ether, based on the cement content).

TABLE-US-00005 TABLE 2 Preparation of comparative product V4 and of inventive products V5 to V9 Amount of polymer Residual Amount of Type of solution in g Fraction of moisture Carrier carrier polyethylene (50 wt % polymer in content % Prod- compo- component glycol MPEG500 Type of strength the product after spray uct nent solution in g component in g polymer solution) in wt % drying V4 T 1000 0 A 110 47.7 1.9 V5 T 1000 MPEG500 55 A 110 38.1 1.7 V6 T 1000 MPEG500 35.4 A 70.8 36.2 2.2 V7 T 1000 MPEG500 27.5 A 165 48.1 2.3 V8 T 1000 MPEG1000 55 A 110 38.1 1.5 V9 T 1000 MPEG500 55 B 110 38.1 2.1

[0166] The residual moisture content in table 2 was determined by drying the sample to constant weight at 90 C.

[0167] Fraction of polymer in the product in wt % indicates the total amount of polymer in the product, originating from the preparation of the carrier component and in each case from the preparation of the products V4 to V9.

[0168] The particle size of the powder V5 was determined by laser granulometry on a Mastersizer 2000 (Malvern Instruments Ltd, Great Britain) using the fully automated measurement program implemented in the instrument (selected settings: shaking rate 40% and air pressure 1.5 bar), giving a measurement of 11 m (D50 value).

[0169] Performance Tests

[0170] Mixing and Testing Technique

[0171] For the testing of the adsorption and fluidization rate of the various plasticizers, an intensive mixture from Eirich, model EL 1 Laboratory, was selected, having an eccentrically arranged mixing tool and inclined mixing vessel. The background to the selection of the mixture was that it enables reliable and reproducible production of the cement mortars with the possibilities of variable adaptation of the speed of the mixing tool and detection of the electrical drive power during the mixing operation. In the mixer, the mixing vessel is actively driven, thereby transporting the mixture material to the mixing tool. As a result of the eccentric position of the mixing tool, in combination with the inclined mixing vessel, there is extensive change of position of the mixture material both vertically and horizontally. The inclination of the mixing vessel also acts to counter the separation of heavy particles into the outer regions, since gravity acts to return the entire mixing material into the mixing flow continuously. A computer control in conjunction with a frequency converter allows the speed of the mixing tool to be regulated steplessly in a range from 1 to 30 m/s. During the mixing operation, moreover, it is possible to capture and record the electrical drive power P at the mixing tool. In all of the experiments, the speed of the mixing tool was set at 4 m/s on the codirectional-flow principle. The speed of the mixing vessel was 1 m/s. All of the experiments were carried out with a constant dry-mix mortar weight of 1 kg.

[0172] In order to allow a quantitative comparison of the acceleration of the development, over time, of the dispersing activity on the part of the acid group-containing polymer, calculations were made of the stabilization time t.sub.s from the recorded power curve of the mixing tool. The numerical value of the stabilization time t.sub.s here is a direct measure of the development over time of the dispersing effect by the acid group-containing polymer. The smaller this value, the more rapid the development over time of the dispersing effect of the acid group-containing polymer.

[0173] The stabilization time (t.sub.s) is defined as the time at which the power curve of the mixing tool approaches the asymptote after the maximum drive power has been reached. Optimum material properties are present as soon as the power curve no longer drops significantly.

[0174] By calculation of the stabilization time, accordingly, it is possible to determine the mixing time required. For the calculation of stabilization time, the power P was standardized to the maximum power P.sub.max (see FIG. 1). Thereafter the power curve recorded was approximated with a mathematic function. This was done between the start of mixing to and until attainment of maximum power at time t.sub.max, by linear approximation. Shown by way of example in FIG. 2 is the standardized mixing power P/P.sub.max and its curve slope during the mixing operation, from which it is possible to calculate the stabilization time t.sub.s. The subsequent range was approximated with a decreasing exponential function (equation 1).

[00001]$\begin{array}{cc}\frac{P}{P_{\max }}=P_0+P_1.Math.e^{-\frac{t-t_{\max }}{t_1}}+P_2.Math.e^{-\frac{t-t_{\max }}{t_2}}& \left(\mathrm{Equation}.Math..Math.1\right)\end{array}$

[0175] In this equation, P.sub.0, P.sub.1 and P.sub.2 are adapted power parameters, t.sub.1 and t.sub.2 are adapted time parameters. The stabilization time t.sub.s is defined as the time required for the curve slope to reach a criterion of (t.sub.s)=4.Math.10.sup.4 s.sup.1 (in this regard, see: Chopin, D.; de Larrad, F.; Cazacliu, B.: Why do HPC and SCC require a longer mixing time? Cement and Concrete Research 34, 2004, pp. 2237-2243 and Mazanec, O.; Schiel, P.: Mixing Time Optimisation for UHPC. Ultra High Performance Concrete (UHPC). In: Second International Symposium on Ultra High Performance Concrete, Mar. 5-7, 2008, pp. 401-408, ISBN: 978-3-89958-376-2).

[0176] On attainment of the stabilization time t.sub.s, all of the mortars investigated have optimum fresh mortar properties, which is a sign of complete dispersion of the starting materials.

[0177] Mixing and Testing Procedure

[0178] All experiments were carried out in an air-conditioned room at a temperature of 202 C./65% relative humidity. The dry starting materials were stored in a conditioned room at a temperature of 202 C. in the absence of air. The temperature of the mixing water was adjusted such that the temperature of the mixture material at the end of the mixing operation was 202 C. Prior to the addition of water, the dry starting materials (cement, silica sand, and pulverulent plasticizer) were homogenized for 30 seconds at a tool speed of 4 m/s. Thereafter the whole of the mixing water was added via a funnel over the course of 10 seconds to the dry-mix mortar mixture, and mixed with the other starting materials for 120 seconds. The stabilization times reported are always based on the wet mixing time, including addition of water.

[0179] Mixture of Composition

[0180] The cement mortar of examples I to X was composed of 500 g of cement (CEM I 52.5 R, Milke type from HeidelbergCement) and 500 g of fine silica sand (type H33 from Quarzwerke Frechen). The water content was 150 g (w/c=0.30).

[0181] Measurement of the Retardation Effect for Plasticizer by Heat Flow Calorimetry

[0182] The quality of cement hydration was characterized by isothermal heat flow calorimetry (TAM Air Thermostat, Thermometric with 12 channels). The temperature in the heat flow calorimeter at the start of hydration was 20 C. Cement, sand, and water (w/c of 0.30) were mixed with the respective additive in a test tube for one minute. The test tube was subsequently inserted into the sample chamber of the heat flow calorimeter, and data recording was commenced. The hydration data were recorded over a period of at least 24 hours. For evaluation, the cumulative heat flow was calculated, in J/g cement. Table 4 sets out the cumulative heat flow after 12 h. The higher the heat flow, the smaller the retardant effect of the plasticizer.

TABLE-US-00006 TABLE 3 Cumulative Additive in wt % Polymer in wt % Stabilization heat flow after Example Additive bwoc bwoc time t.sub.s [s] 12 h [J/g] Notes I 0 0 73.9 earth-moist heap, no fluidaztion II V1 0.30 0.30 96 III V2 0.30 0.30 51 52.4 IV V4 0.63 0.30 73 V3 V3A 0.60 0.30 35 48.7 VI V5 0.79 0.30 22 75.8 VII V6 0.83 0.30 25 72.5 VIII V7 0.62 0.30 33 71.1 IX V8 0.79 0.30 31 73.4 X V9 0.79 0.30 34 76.1 % bwoc: Amount of initial mass, based on the amount of cement The amount of additive was selected in examples II to X such that in each case the same amount of polymer was used, based on the amount of cement.

[0183] In table 3 it is apparent that only inventive examples VI to X permit an acceleration of the development over time of the dispersing activity of the acid group-containing polymer, in the present instance a polycarboxylate ether, following addition of the mixing water, as evident from the low values for t.sub.s, and, at the same time, a subsequently accelerated curing of the mixture, measured by way of the cumulative heat flow after 12 hours.