CH628008A5 - Low porosity, aggregate-containing cement composition and process for the production thereof - Google Patents

Description

The invention relates to a low-porous cement paste containing aggregates and a process for their production. The cement composition according to the invention consisting of a hydraulic cement with alkali bicarbonates and lignosulfonates results in cement slurries which have a longer setting time and less expansion, which can be attributed to the alkali aggregate reactions and other aids.

Cements are produced by calcining suitable raw materials, generally a mixture of calcareous and clay-containing materials, which produces sintered slag or cement clinker. Portland cements have the largest share of the quantities produced. Conventionally, the clinker is made with small amounts of gypsum, i.e. up to about 9%, mixed and usually ground in a kind of ball mill to a finely divided texture with a relatively large surface area, which then results in the finished cement.

The gypsum-containing, ground clinker is mixed with the required amount of water to a paste. Properly prepared cement paste sets within a few hours and then hardens slowly. Cement slurries are mixed either with fine aggregates or sand for the preparation of mortar or with coarser aggregates such as gravel, stones and the like for the preparation of concrete. The cement paste acts as a cementing substance. Its composition is decisive for the strength and other properties of the resulting mortar or concrete.

One of the main factors determining the properties of the hardened cement paste and consequently mortar and concrete is the ratio of water to cement in the fresh mix. The lower the water-cement ratio, the higher the strength, the lower the shrinkage and

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better resistance to frost and corrosion. A low water-cement ratio is therefore sought - in conventional practice it is usually between 0.4 and 0.6 - in order to obtain a concrete or mortar with minimal shrinkage and increased ultimate strength. However, one solution to this is not to be seen simply in reducing the water-cement ratio of conventional Portland cements.

So, unfortunately, the fact that reducing the water content improves the properties of the hardened concrete can only be exploited to a certain extent, since the lowering of the water content simultaneously leads to a deterioration in the workability of the concrete mixture. The demand for satisfactory workability of the fresh concrete mix is the reason for the fact that the water content of the concrete mix is in practice far above the amount of water that would be required for a complete hydration of the cement. While the amount of water required for complete hydration of the cement is around 22-23%, in conventional practice an amount of water becomes from there. 40% and usually between 45-80% used.

Even with the use of conventional water reducing agents (mainly lignosulfonates from sulfite waste liquor in the manufacture of pulp), only a reduction of the added water by about 10% is possible. The water remaining in a concrete mix made of ordinary cement is still far above the amount necessary for a complete hydration of the cement. Thus, if it were possible to reduce the water content without degrading workability or without other disadvantages, a significant gain in strength and an improvement in some other properties of the hardened concrete could be achieved.

Attempts have been made for a long time to produce a cement with a low porosity by reducing the water-cement ratio. For example, U.S. Patent No. 2,174,051 to Winkler shows that greater strength can be achieved with a lower water-cement ratio and that certain organic compounds such as tartaric acid, citric acid and the like can be added to influence the setting time .

According to Braun's U.S. Patent No. 2,374,581, ordinary water (cementitious) Portland cement can be added with small amounts of tartaric acid, tartaric salts, and bicarbonates to reduce the rate of setting at high temperatures when concreting oil wells at conventional water-cement ratios .

Lea U.S. Patent No. 2,646,360 suggests adding a gypsum-containing cement slurry, an alkali metal or an earth alkali metal lignin sulfonate, and an alkali metal salt of an inorganic acid (e.g. sodium carbonate) to reduce water loss and so on reduce the amount of water initially required.

On the other hand, U.S. Patent No. 3,118,779 to Leonard discloses that sodium carbonate acts as an accelerator when added to a Type III Portland cement (asphalt) without the presence of lignin.

According to Landry U.S. Patent No. 3,689,296, formaldehyde-modified calcium lignosulfonates are used in Portland cements to replace all or part of the usual amount of gypsum addition. The amount of water required for a mixture of a certain liquid level is reduced.

US Pat. No. 3,689,294 by Braunauer gives rise to previous efforts to produce low-porosity cements by grinding Portland cement without gypsum up to a specific surface area between 6000-9000 cm2 / g (Blaine) and by mixing with alkali or alkaline earth metal lignosulfonates, Alkaline carbonate and water.

According to Allemand et al U.S. Patent 3,782,984, adding 0.5-5% alkali metal acid carbonates to Portland cements accelerates the setting time.

In the French publication "Les Adjuvants du Ciment", published by Albert Joisel (Soisy, France 1973), published by the author, it is stated on page 102 that sodium carbonate acts as a retardant in ordinary Portland cement, and again on page 132,

that sodium bicarbonate can be added to gypsum-containing Portland cement in the usual way.

The prior art described above is not to be regarded as exclusive and does not include the entire technology for the production of low-porosity cement.

It is therefore an object of this invention to provide methods for preparing an improved, free-flowing, aggregate-containing cement composition with low porosity. The aim is also to make it possible to make high-strength concrete and mortar available with low-porosity Portland cement without gypsum, with improved workability, longer setting time and less expansion.

This object is achieved by the cement composition defined in claim 1 and by the method for producing the same defined in claim 3. According to one embodiment of the method, the alkali bicarbonate is mixed with the cement and the lignin is added to the mixed water, after which the two mixtures are combined. According to a further embodiment of the method, the lignin is mixed with the cement, the alkali bicarbonate is added to the water and then the cement-lignin mixture is added to the alkali bicarbonate water. In a further embodiment, lignin, bicarbonate and water are mixed together before being added to the ground cement.

Further details and advantages of the invention result from the following detailed description.

Cements that can be used in this invention are Portland cements. Portland cement is the most commonly used hydraulic cement. Cement clinker of the types described above are ground to 3.500 cm2 / g (Blaine) and finer, i.e. up to 9,000 cm2 / g.

As an aid to achieving the desired degree of fineness, grinding aids are usually used in the cement industry which support the effectiveness of the grinding process. Satisfactory grinding aids include water-soluble polyols such as ethylene glycol, polyethylene glycol and other water-soluble diols. In general, the grinding aids are added to the cement clinker in an amount of 0.005-1.0%, based on the weight of the cement. The ground cement can contain a lot of setting inhibitors. Additional examples of grinding aids can be found in U.S. Patents 3,615,785 and 3,689,294. Although it is typical to use grinding aids in the manufacture of cement, they are not part of the present invention.

The method of the present invention is therefore based on a gypsum-free Portland cement. According to the method of the present invention, low porous mortars and types of concrete can be produced from the cement slurries. The term "low porous" cement, as used here, means a loose or free-flowing and processable cement slurry with a water-cement ratio (W / Z) of below 0.40 down to 0.2, with processable Mortars and types of concrete with a W / Z ratio of preferably 0.35 down to 0.25.

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In one embodiment of the method, the gypsum-free hydraulic cement is 0.1-1.0%, preferably 0.3-0.8%, based on the weight of the dry, ground cement of an alkali or alkaline earth metal lignosulfonate or alkaline earth metal sulfated Lignins put together. The lignosulfonates are a by-product of the sulfite digestion of wood materials. The waste liquids from this digestion process contain large amounts of lignin and lignin products in combination with other materials. The sulfated lignins, on the other hand, are produced in the reaction of Li-gnins, which are obtained by alkaline digestion of acid hydrolysis or other known extraction processes with an inorganic sulfite, for example sodium sulfite. Any of the various water-soluble sulfonated lignins or lignosulfonates are useful in the present invention. However, it is preferable to use sulfonated lignins that are free of hydrocarbons. Sulphated lignins as obtained from the reaction of sulphites with alkali lignin do not contain any significant amounts of these hydrocarbons and can therefore be used as they are. The sulfonated lignins can be converted to water-soluble alkaline earth salts and used as such, as described in U.S. Patent No. 2,141,570.

In another embodiment of the method, the sulfated lignin can be combined with the ground cement or with the mixed water. When using these different working methods, no significant differences could be observed in the results.

Alkali bicarbonate is used in an amount of 0.1-2.0%, preferably 0.7-1.5%, based on the dry cement weight. Sodium bicarbonate is preferred. It is unimportant how the bicarbonate is added, for example by the direct inclusion of bicarbonate or by adding sodium ash and carbon dioxide saturation. It has been found that when alkali bicarbonate is used, the setting time and the workability compared to the use of alkali carbonates increases unexpectedly with a water / cement ratio of below 0.4. It has also been found that when the alkali bicarbonate is added to the cement, an unexpected increase compared to the addition of alkali carbonate is achieved. Even more surprising was the fact that dissolving the alkali bicarbonate in the mixed water gives even better results in terms of controlling the setting time and improved flow than when using other mixing processes. The amount of water used is 20-40%, based on the dry cement weight or a water-cement ratio (W / Z) of 0.4-0.2. The way in which the bicarbonate is added to the water can be varied. For example, the bicarbonate can be added itself, or it can be added to soda ash and saturated with carbon dioxide.

In some cases it may also be desirable to add an additional component to the low porous system in order to achieve a substantial extension of the plastic period of the mortar and the concrete, while still having sufficient compressive strength after one day. These components, used in small quantities, for example 0.1-0.2%, are mainly derived from two classes of substances, namely surface-active agents and conventional water reducing agents / setting delays. Anionic surfactants can consist of the sodium salt of the sulfonated alkali diphenyl oxide, whereas nonionic surfactants can consist of polyethylene glycol and the like. Fabrics from the class of

Water reducing agents / setting retardants are hydrocarbons such as wood molasses, sucrose, dextrose and hydroxy acids such as sodium gluconate. Typical air discharging or extracting agents such as tri-butyl phosphate can advantageously also be used in low-porous systems.

Another important advantage of the present invention is that the addition of alkali bicarbonate significantly reduces the potential for the alkali aggregate reaction that occurs in the alkali (NaOH) formation in the cement. The potential expansion when using alkali carbonate and alkali bicarbonate in low porous systems was measured using a highly reactive additive (crushed tempered glass) according to the procedure given in ASTM C-22. The results showed a smaller expansion of a low porous mortar prepared with NaHC03 compared to a corresponding Na2C03 system. In addition, even small amounts (0.05-1.5%) of lithium salts reduce the expansion of both low-porous hard glass mortars containing alkali carbonates and bicarbonates.

With the various combinations of additives and mixing processes, the need to add gypsum is avoided, and a free-flowing, workable, low-porous cement mass is created with an extensive and controllable setting time. The outstanding results obtained by using the additives and the method according to the present invention were completely unexpected for the production of low-porosity cements in view of the prior art. As described above, each of the additives has previously been used in gypsum-containing Portland cements. However, none of the products produced according to the prior art even comes close to the performance achieved with the low-porous cements produced according to the present invention.

The application of the present invention is clear from the following examples.

example 1

This example is intended to show the extended setting time of the cement paste, which was produced with alkali bicarbonate instead of alkali carbonate. In this example, Type I Portland cement clinker ground to 5.075 cm2 / g (ASTM C-204) was used with the following analysis.

Clinker%

SI02 21.70 A1203 6.06 Fc203 2.51

CaO 67.5 MgO 0.99 Na20 0.06 K20 0.28 Burning loss 0.62 Insoluble 0.14

The changes in the physical properties (that of the setting time was the most striking) of cement slurries with alkali carbonates and alkali bicarbonates are shown in Table 1. The amount of the sulfonated lignin was kept constant at 0.45% by weight, based on the cement, and the water-cement ratio was 0.25. The amount of the alkali carbonate was set to give equivalent molar amounts of C03 =.

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Table I

Comparison of alkali carbonates and bicarbonates in relation to the properties of low porous cement slurries

Experiment no. Type of carbonate% flow * Setting time compressive strength

(Min.) Kp / cm2

1 day 7 days

1 Na2C03 1.16 4 * 13 728 81-2

2 Na2HC03 1.0 4 * 38 714 1326.50

3 K2C03 • 1.5 H20 1.97 4 12 763 945

4 KHCOj 1.19 4 * 19 672 1160.60

Comment:

* The flow units are chosen arbitrarily (see explanation below) and are used in all examples. The nature of the cement paste used in Table 1 is based on the following scale:

1. hardly plastic porridge, moves only with difficulty, even when using vibration;

2. plastic paste, but not free-flowing, flows easily under vibration;

3. free-flowing porridge, but thick, can be poured without vibration;

4. easy flowing porridge.

The results in Table I show an increase in setting time and excellent compressive strength after 7 days for 25 bicarbonate systems in contrast to carbonate systems.

Example 2

This example shows the extended setting time of cement slurries in which the use of alkali bicarbonate 30 was preferred to that of alkali carbonate. In addition, the special mixing sequences according to the invention are shown in comparison with other mixing schemes in which the same substances are used. In this example, Portland cement clinker type I was also ground to 5.075 cm 2 / g (ASTM C-204) as in example 1.

Table II shows the changes in physical properties (the most striking of the setting time) 40 of cement slurries with alkali carbonates and alkali bicarbonates using two blending schemes. The mix scheme designation from Table II means that all components within a bracket are first mixed together and then with the next component or components. In test series 4 and 8, in which an embodiment according to the method of the invention is shown, the cement (Z) is mixed with a sulfated alkali lignin (LS) and the alkali bicarbonate (AK) is mixed with water (W) and then mixing the two mixtures. Alkali carbonates were used in the experiments with odd numbers and alkali bicarbonates were used in the remaining experiments in other mixing procedures. The amount of the sulfonated lignin was kept constant at 0.45% by weight, based on the cement, and the water-cement ratio was 0.25. The amount of alkali carbonate was set to give equivalent molar amounts of CO 3 = in all examples.

Table II

Comparison of alkali carbonates and bicarbonates and the effect of the mix sequence on the properties of low porous cement slurries

attempt

Mixed sequence

Carbonate type

%

flow

Tie

Compressive strength

No.

time kp / cm2 1 day

7 days

1

(Z + LS + AC) + W

Na2C03

1.26

4 *

13

728

812

2nd

(Z + LS + AC) + W

NaHCOj

1.0

4 *

38

714

1326.50

3rd

(Z + LS) + (AC + W)

Na2C03

1.26

4 *

23

707

941.50

4th

(Z + LS) + (AC + W)

NaHC03

1.0

4 *

143

686

1169

5

(Z + LS + AC) + W

K2C03 • 1.5 H20

1.97

4th

12th

763

945

6

(Z + LS + AC) + W

khco3

1.19

4 *

19th

672

1160.60

7

(Z + LS) + (AC + W)

K2C03 • 1.5 H20

1.97

4 *

20th

756

1001

8th

(Z + LS) + (AC + W)

khco3

1.19

4 *

141

798

1340.50

Comment:

* The flow units are chosen arbitrarily (see explanation below) and are used in all examples. The nature of the cement paste used in Table II is based on the following scale:

1. hardly plastic porridge, moves only with difficulty, even when using vibration;

2. plastic paste, but not free-flowing, flows easily under vibration;

3. free-flowing porridge, but thick, can be poured without vibration;

4. easy flowing porridge.

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The results of experiments 4 and 8 from Table II clearly show the unexpected increase in the setting time for bicarbonate systems compared to carbonate systems and clear additional advantages when dissolving the bicarbonate in water without significantly changing the other properties (flow and pressure resistance).

Example 3

This example shows that the sulfated lignin can either be mixed dry or dissolved in the mixed water. Here part of the clinker from example 1 was placed on one

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Grind the surface of 4.525 cm2 / gm (Blaine). The mixing scheme designation from Table III means that first all components within a bracket are mixed and then the next component or components are mixed. In experiment No. 1 in Table III, for example, the cement (Z), the sulfonated alkali lignin (LS) and the alkali carbonate (AC), which here consisted of sodium bicarbonate, are first mixed together. The water (W) was then mixed in. The amount of sulfated lignin was kept constant at 0.35% by weight of the cement. The water-cement ratio was 0.25.

Table III

Effects of the mixing sequence on the properties of low porous cement slurries

Mixed sequence

Carbonate type

%

flow

Setting time (min.)

Compressive strength kp / cm2

1 day 7 days

(Z + LS + AC) + W

NaHC03

0.80

4 *

32

644

1207.50

(Z + AC) + (LS + W)

NaHCG3

0.80

4 *

36

749

1284.50

(Z + LS) + (AC + W)

NaHC03

0.80

4 *

98

756

1197

Z + (LS + AC + W)

NaHC03

0.80

4 *

96

735

1344

The data resulting from Table III clearly show that the sulfated lignin can either be added to the mixed water or mixed dry with the cement without significantly changing the properties of the slurry.

Example 4

This example further demonstrates the superiority of low porosity cement slurries prepared with NaHC03 instead of Na2C03. Ground cement with different surface contents of the type I clinker from different origins was used. Table IV shows the comparatively longer setting times and higher compressive strengths after 7 days for the NaHC03 cement systems with 35 low porosity. The water-cement ratio was 0.25 in each experiment. The amount of alkali carbonate was determined to give approximately equivalent molar amounts of C03 = for each cement clinker for each surface area.

Table IV

Effects of different cement clinkers and total area on the properties of low-porosity cements

clinker

surfaces

Carbonate type

%

flow

Setting time

Compressive strength

Area

(Min.)

kp / cm2

cm2 / gm

1 day

7 days

B1

6,500

NaHC03

1.20

4th

31

707

1078

B1

6,500

Na2C03

1.60

4th

18th

819

847

A2

5,650

NaHC03

0.60

4th

49

527

1368.50

A2

5,650

Na2C03

0.76

2nd

20th

714

983.50

C3

4,800

NaHC03

1.00

4 *

63

826

1253

C3

4,800

Na2C03

1.26

4 *

32

875

924

Remarks:

1 0.80% sulfated lignin

2 0.45% sulfated lignin

3 0.50% sulfated lignin

Example 5

This example shows that cement with different surface contents and a different origin than in

Example 1 can be used. The cement clinkers «B» and «C» are clinkers of Portland cement type I of various origins. W / C = 0.25 in all cases.

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Table V

Effects of different clinkers and surface contents on properties of low porous cement slurries

clinker

surfaces

Mixing scheme

flow

Setting time

Compressive strength

Area

(Min.)

kp / cm2

cm2 / gm

1 day

7 days

B1

6.225

(Z + LS + AQ + W

4 *

29

931

1039.50

B1

6.225

(Z + LS) + (AC + W)

4 «

58

924

1113

B1

6.225

Z + (LS + AC + W)

4 *

56

973

1155

B2

4,825

(Z + LS + AC) + W

4 *

45

784

1137.50

B2

4,825

(Z + LS) + (AC + W)

4 *

78

749

1207.50

C2

4,800

(Z + LS + AC) + W

4 *

73

721

896

C2

4,800

(Z + LS) + (AC + W)

4 *

135

735

1011.50

C2

4,800

Z + (LS + AC + W)

4 *

127

707

854

C2

3,900

(Z + LS + AQ + W

4 *

58

658

1011.50

C2

3,900

(Z + LS) + (AC + W)

4 *

180

623

913.50

C2

3,900

Z + (LS + AC + W)

4 *

170

581

829.50

Remarks:

1 0.55% sulfated lignin and 1.0% NaHC03

2 0.50% sulfated lignin and 1.0% NaHC03

Table V shows that no significant differences were observed when using 25 clinkers from different origins or when grinding clinkers to different specific surface contents.

Example 6 30

The use of alkali bicarbonates, which is preferable to the use of alkali carbonates, improves the flowability even in cases where wall currents occur. The addition of the alkali bicarbonate to the water also improves the fluidity. The examples in Table VI illustrate this, with 0.45% sulfated or sulfonated lignin and equivalent molar amounts of C03 = with the ground clinker «A» and 0.50% sulfated alkali lignin and equivalent molar amounts of C03 = with the ground Clinker «B» were used.

Table VI

Improvement of the flow behavior of low porous cement slurries with alkali bicarbonates and the preferred mix sequences

Clinker surface mix sequence carbonate type flow setting compressive strength

area cm2 / gm

time (min.)

kp / cm2 1 day

7 days

A

5,025

(Z + LS + AC) + W

Na2C03

1-2

9

616

920.50

A

5,025

(Z + LS + AQ + W

NaHCOs

4th

35

679

1260

A

5,025

(Z + LS) + (AC + W)

Na2C03

2nd

20th

714

983.50

A

5,025

(Z + LS) + (AC + W)

NaHC03

4 *

49

525

1368.50

B

5,325

Z + (LS + AC + W)

Na2C03

3rd

13

798

945

B

5,325

Z + (LS + AC + W)

NaHC03

4 *

59

875

934.50

These results show that cement slurries with a 50% flow properties than those made with sodium carbonate - made from gypsum-free, ground clinker - were superior in their cement slurries.

Example 7

When using bicarbonates one would also see better properties, however, if sul-

An increase in the setting time was observed when alkali lignins derived from sulfite 55 were used.

isolated lignosulfonates were used. Overall, Table VII

Comparison of alkali bicarbonate and alkali carbonate when using a lignosulfonate derived from sulfite sludge

Type of carbonate Flow setting- compressive strength time kp / cm2

(Min) 1 day 7 days

Na2CO, 1.51 2 32 714 1067.50

NaHCO, 1.20 2 72 35 528.50

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Example 8

From this example it becomes clear how a low porous ground hard glass mortar, which was prepared with NaHCO-, expands significantly less in comparison with a corresponding low porous mortar with Na2C03. Samples C-1 and C-2 in Table VIII show the reduction in expansion after 14 and 18 days when NaHCG3 was replaced with NaHCG3 (with the equivalent molar amount of C03 =) in a low porous tempered glass mortar according to the procedure from ASTM C-227. Samples C-3 and C-4 show a significantly reduced expansion for both the NaHC03 and the Na2C03 systems with low porosity when a lithium salt (Li2C03) was contained in the ground hard glass mortar. These examples show the reduced expansion of a low porosity tempered glass mortar when an alkali carbonate has been replaced by an alkali bicarbonate, and also a reduction in the expansion of both Na2C03 and NaHC03 mortar with low porosity when the mixture is mixed Lithium carbonate had been added.

Table VIII

Expansion of low-porosity tempered glass mortar bars made with various alkali carbonates

Alkaline carbonate sample% expansion,%

14 days 28 days

C-1 NaHCOa 1.00

C-2 Na2C03 1.26

C-3 NaHC03 1.00

Li2C03 0.22

C-4 Na2C03 1.26

Li2C03 0.22

Remarks:

Glass: cement = 1.80 0.50% sulfated lignin W / C = 0.275

0.24

0.32

0.50

0.56

0.03

0.04

0.01

0.08

water-cement ratios with an acceptable water-cement ratio. 2.25 parts of fine sand per part of cement 35 were used in the preparation of the mortar.

Mortar results

Cement W / C compressive strength kp / cm2

I day 7 days

NP1

.40

294

560

NP1

.32

420

651

NP1

.27

420

616

Type III common

.60

161

497

Comment:

1 0.50% sulfated lignin 1.0% NaHC03

The results show that good strength is achieved with the low-porous additives.

Example 9

This example serves to illustrate the strength properties of low-porosity mortars (NP), which according to the method of this invention are compared to conventional water

Claims (11)

628 008 1. Low-porous, aggregate-containing cement mass, characterized in that it a) Portland cement with a cement grinding fineness according to Blaine of at least 3,500 cm2 / g, which contains essentially no calcium sulfate, b) alkali bicarbonate in an amount of 0.1 to 2.0 wt .-%, based on the dry, ground cement, and c) alkali or alkaline earth metal lignosulfonate or sulfonated lignin in an amount of 0.1 to 1.0 wt. -%, based on the dry, ground cement. wherein the aggregate containing cement has a water-cement weight ratio between 0.4 and 0.2. 2. Cement composition according to claim 1, characterized in that it is used as alkali bicarbonate sodium bicarbonate in an amount of 0.7 to 1.5% by weight and as lignosulfonate alkali metal gnosulfonate in an amount of 0.3 to 0.8% by weight. % contains. 2nd PATENT CLAIMS 3. A process for the preparation of the cement composition defined in claim 1, characterized in that (a) Portland cement of a Blaine cement grinding fineness of at least 3,500 cm 2 / g, which contains essentially no calcium sulfate, (b) alkali metal bicarbonate in an amount of 0.1 to 2.0% by weight 9c, (c) alkali or alkaline earth metal lignosulfonate or sulfonated lignin in an amount of 0.1 to 1.0% by weight and (d) water in an amount of 20 to 40% by weight , where all percentages are based on the dry weight of the ground cement, mixed in any order. 4. The method according to claim 3, characterized in that a) Portland cement of a cement grinding fineness according to Blaine of at least 3,500 cm2 / g, which contains essentially no calcium sulfate, with 0.1 to 1.0 wt .-% alkali metal or alkaline earth metal lignosulfonate or sulfonated Lignin and 0.1 to 2.0% by weight alkali bicarbonate are mixed and b) 20 to 40% by weight water is added to the mixed substances from process step a), where all percentages are based on the dry weight of the ground cement. 5. The method according to claim 4, characterized in that the amount of lignosulfonate is 0.3 to 0.8 wt .-% and / or the amount of alkali bicarbonate is 0.7 to 1.5 wt .-%, preferably as alkali bicarbonate Sodium bicarbonate and preferably used as lignosulfonate alkali metal lignosulfonate. 6. The method according to claim 3, characterized in that a) Portland cement of a cement grinding fineness according to Blaine of at least 3,500 cm 2 / g, which contains essentially no calcium sulfate, is mixed with 0.1 to 2.0% by weight of an alkali bicarbonate, b) 20 to 40% by weight of water are mixed with 0.1 to 1.0% by weight of alkali or alkaline earth metal lignosulphonate or sulphonated lignin and c) the mixed substances from process steps a) and b) are then combined, where all percentages are based on the dry weight of the ground cement. 7. The method according to claim 6, characterized in that the amount of lignosulfonate is 0.3 to 0.8 wt .-% and / or the amount of alkali bicarbonate is 0.7 to 1.5 wt .-%, preferably as alkali bicarbonate Sodium bicarbonate and preferably used as lignosulfonate alkali metal lignosulfonate. 8. The method according to claim 3, characterized in that a) Portland cement, a cement grinding fineness according to Blaine of at least 3,500 cnr / g, which contains essentially no calcium sulfate, with 0.1 to 1.0 wt .-% alkali or Alkaline earth metal lignosulfonate or sulfonated lignin is mixed, b) 20 to 40% by weight of water are mixed with 0.1 to 2.0% by weight of an alkali metal bicarbonate and c) the mixtures from process steps a) and b) are then combined, where all percentages are based on the dry weight of the ground cement. 9. The method according to claim 8, characterized in that the amount of lignosulfonate is 0.3 to 0.8 wt .-% and / or the amount of alkali bicarbonate is 0.7 to 1.5 wt .-%, preferably as alkali bicarbonate Sodium bicarbonate and preferably used as lignosulfonate alkali metal lignosulfonate. 10. The method according to claim 3, characterized in that a) 0.1 to 1.0 wt .-% alkali or alkaline earth metal lignosulfonate or sulfonated lignin and 0.1 to 2.0 wt .-% alkali bicarbonate with 20 to 40 wt. % Water are mixed and b) the mixture from process step a) is mixed with Portland cement with a Blaine cement grinding fineness of at least 3,500 cm 2 / g, which contains essentially no calcium sulfate, where all percentages are based on the dry weight of the ground cement. 11. The method according to claim 10, characterized in that the amount of lignosulfonate is 0.3 to 0.8 wt .-% and / or the amount of alkali bicarbonate is 0.7 to 1.5 wt .-%, preferably as alkali bicarbonate Sodium bicarbonate and preferably used as lignosulfonate alkali metal lignosulfonate.