DE2013395B2 - PROCESS FOR PRODUCING A FREE-FLOWING EXPANDING CEMENT SLUSH - Google Patents

Description

The invention relates to a method for producing a free-flowing and expanding cement paste with a low ratio of water to cement, by grinding a Portland cement clinker with the help of a grinding aid and subsequent admixture of an alkali or alkaline earth lignosulfonate as a retarder and an alkali carbonate.

Common portland cement is made by adding a ground mixture of limestone and clay or Shale is burned to form clinkers, which are mainly composed of mixed calcium silicates, Calcium aluminates and calcium aluminoferrites exist. The clinker is ground together with a few percent gypsum to form a fine powder that when mixed with water makes a pulp.

Properly made cement paste sets within a few hours and then slowly hardens. When sand and crushed rock and / or gravel are mixed into the slurry, concrete is obtained. During the initial stages of hardening, while the concrete is in contact with water or with water vapor If there is saturated air, it expands a little. If the concrete then has an environment with If exposed to less moisture, it will shrink. The shrinkage occurs to a greater extent than that initial expansion, and the resulting overall shrinkage may cause stress cracking and other undesirable effects occur in the concrete.

It is known that when mixing a larger amount of water with a given amount of cement powder the shrinkage is increased and a weaker, more porous concrete is obtained. On the other hand, it will If the lowest possible initial ratio of water to cement powder is applied, the result is a concrete that with a view to reducing shrinkage and increasing the absolute strength of the concrete over-that Weight ratio of water to cement powder used in the conventional production of concrete is between 0.4 and 0.6. With lower ratios, a concrete that is too solid, cannot be worked achieved.

It was also already known. To use grinding aids, alkali or alkaline earth lignosulfonates and alkali carbonates as additives to cement.
So was used to prevent water loss

ίο one for cementing oil wells used cement paste an alkali or alkaline earth lignin sulfonate and an alkali metal salt is added (US Pat. No. 2,646,360 and US Pat. No. 2,684,720). This known method however, it is based on cement ground to the usual grain size and for the production of the cement paste a common water additive is used.

According to US-PS 22 25 146 glycol is used as a grinding aid for grinding Portland cement. In this process too, however, the cement is ground to the usual grain size.

With the help of the known methods, a conventional cement paste is obtained, which becomes a solidified product with usual shrinkage and moderate strength values.

The invention is based on the object of a method for producing a free-flowing To provide cement slurry with a lower ratio of water to cement than it has been applied so far. A cement paste is to be obtained, which leads to an improved concrete with lower shrinkage and higher strength than conventional concrete types.

In a method of the type specified at the outset, this object is achieved in that the Portland cement clinker with the addition of 0.0025 to 0.005 parts by weight of a polar and non-polar group containing surface-active agent as grinding aid, based on one part by weight of the finely ground Cement clinker, on a specific surface

between 6000 and 9000 cm ² / g according to Bla ine is ground and that the finely ground cement, based on one part by weight, also 0.0025 to 0.01 parts by weight of alkali or alkaline earth metal lignosulfonate and 0.2 parts by weight of water containing 0.0025 to 0.005 part by weight of an alkali carbonate, are mixed.

With the help of the method according to the invention, it is possible to produce a free-flowing cement paste with a as low as 0.2 as low as water to cement ratio.

In contrast to the specific surface of conventional Portland cement clinker of 4000 cmVg (determined according to the Blainee method, ASTM regulation C 204), the clinker ground according to the invention has a specific surface in the range from 6000 to 9000 cm ² / g . It could be assumed that clinker ground to such a fineness would hydrate quickly and set suddenly when mixed with water. An alkali or alkaline earth lignosulfonate, such as sodium, potassium, ammonium, calcium or magnesium lignosulfonate, is added to delay hydration and at the same time to keep the pulp processable despite the low water content. The added water contains an alkali carbonate such as sodium, potassium or ammonium carbonate (the term "alkali metal" used here is intended to include ammonium). With this combination of additives it is no more

required, the cement powder used according to the invention To add plaster of paris.

In order to achieve the required high degree of fineness of the powder, the cement clinker is a Grinding aids added. The grinding aid carries also helps to keep the cement free flowing and influences the workability and the setting properties of the cement paste as well as the strength properties of the concrete.

The grinding aids most suitable for the purposes of the invention are generally surface-active substances which contain both polar and non-polar groups. The polar groups of the surfactants are attracted to the ions on the surface of the cement components, so _{that) 5,} the non-polar groups to the outside. In this way, the cement grains are practically made somewhat hydrophobic and in this way premature hydration is prevented and the cement, despite its fineness, is kept in a free-flowing state.

The preferred grinding aid for carrying out the process according to the invention is diethyl carbonate. Other suitable grinding aids are polyglycol derivatives and other nonionic surface-active substances, Sulfonates and other anionic surfactants, alkylammonium salts and other cationic ones surfactants and the like.

The experiments described below serve to illustrate the invention.

In these tests, type I and type 11 clinker was used, which had the following analytical values exhibited:

Type Type II C ₃ S 60.97 54.17 C ₂ S 19.45 26.13 C ₃ A 10.28 4.48 C ₄ AF 7.30 13.28 Na ₂ O 0.10 0.46 K ₂ O 0.45 0.20 Loss on ignition 0.11 0.10 Free calcium oxide 0.42 0.17 Insoluble residue 0.06 negate permeable

In cement technology, "C" means calcium oxide, "S" means silica, "Α" means aluminum oxide and "F" ferric oxide. The symbols "Na", "K" and "O" have the usual chemical meanings.

In the general test procedure, the clinker and any grinding aid used were ground in porcelain grinding vessels with hard ceramic balls. The type I clinker was ground with diethyl carbonate for two days to a Blaine surface (ASTM regulation C 204) of about 7500 cm ^{2 / g.} When using most of the other tested grinding aids, a longer time is required to reach this value of the specific surface area. However, diethyl carbonate is preferred mainly because of its beneficial effects on workability, retarding setting, compressive strength and dimensional changes of the cement paste obtained later.

The ground clinker was dry mixed with the specified amount of calcium lignosulfonate. Mixing in a paint paddle mixer for one minute was sufficient to achieve good mixing. The one with Lignosulfonate mixed ground clinker was introduced into a two-chamber mixer, the other one Chamber contained a solution of potassium carbonate in water. After sucking the air it was the partition between the two chambers removed and the cement powder and the solution several Minutes mixed together.

The cement paste obtained was pressed into cubic steel molds after hardening under for one day The 2.54 cm-long concrete cubes were removed from the molds and placed in a water vapor-saturated atmosphere. These cubes were periodically tested for compressive strength subject. Those obtained with type I cement clinker as defined above Results are shown below:

Grinding aid
middle

surface
(cm ² / g)

Lignosulfonate

K ₂ CO ₃

consistency

Compressive strength (kg / cm)

1 day

7 days

28 days

90 days

180 days

A. 7780 1.5 3.0 3-4 590.6 766.3 787.4 A. 7780 1.0 1.5 3-4 295.3 1328.8 1342.8 A. 7780 1.0 0.5 3-4 921.0 1054.6 1504.5 B. 6800 1.0 0.5 5 35.1 773.4 1870.2 C. 7800 1.0 0.5 5 815.6 1293.6 1581.9 D. 8400 1.0 0.5 5 984.3 1075.7 1567.9 D. 7030 1.0 0.5 5 1574.9 E. 8650 1.0 0.5 4th 260.1 1307.7 2088.1 E. 8150 1.0 0.5 140.6 1441.2 1694.4

2355.2

2432.6

2446.6

2559.2

Jy

Upper LiBiio- 5 Con 20th 13 395 7 repayments V 6th ISO Tai area sull'onal sistance 1117.9 f (enr / g) K ₂ CO., 878.8 2376, j 8450 1.0 5 Compressive strength (kg / cm ") 808.5 continuation 8170 1.0 5 1153.0 W repayment Miihl- 7420 1.0 0.5 5 I tug 843.7 28 repayments hills- 8200 1.0 0.5 4th 49.2 808.5 1870.2 2109.2 middle 8400 1.0 0.5 3-4 42.2 1272.5 1406, i F. 8400 1.0 0.5 1 31.6 1174.1 1567.9 F. 8740 1.0 0.5 3-4 21.1 1195.2 1828.0 G 8130 1.0 0.5 4-5 31.6 583.5 1441.2 II 8130 0.75 0.5 1 28.1 1406.1 1 7000 1.0 0.5 5 38.6 1589.0 J 0.35 28.1 1490.4 K 0.5 42.2 1434.2 L. 21.1 1560.8 L. L.

The main components of the grinding aids used are listed below:

A - alkali lignin

B - polyglycol derivative with 20 monomer units and one mole of nonylphenol in the polyglycol chain

C - polyglycol derivative with 13 monomer units and one mole of nonylphenol in the polyglycol chain

D - polyglycol derivative with 6 monomer units and one mole of trimethylnonylphenol in the Polyglycol chain

D - diethyl carbonate

F - polyglycol derivative with 10 monomer units and resin acid in the polyglycol chain

G - Sodium Dodecylbenzenesulfonate

H - Polyethylene glycol monostearate with 65 monomer units in the polyethylene chain

I - alkyl sulfonate and sulfocarboxylate

J - alkyl sulfosuccinate and alkyl sulfonate, amine salts and isopropyl alcohol

K - alkyl sulfosuccinate and alkyl sulfonate, amine salts

L - alkyl sulfosuccinate and alkyl phenol polyglycol

The consistency of the cement paste is given in the table according to the following rating:

0 - Sets in the mixing tank.

1 - Not very plastic, must be crushed into the form

will.

2 - Difficult to move, even when the

Shape.

3 - Easy flowing when the shape is vibrated.

4 - Free flowing when the mixing chamber is shaken.

5 - Free flowing.

6 - Very thin.

From the experiments summarized in the table it can be seen that the choice of a special Mahi auxiliaries the consistency of the cement paste finally produced from the ground clinker influenced. The grinding aid does not regulate the consistency itself, but works in conjunction with the present calcium lignosulfonate and potassium carbonate. If, for example, when using the grinding aid L the proportion of lignosulfonate and potassium carbonate is reduced to 0.50% and 0.25%, respectively get a pulp that sets in the mixing chamber.

By increasing the level of calcium lignosulfonate and potassium carbonate above the preferred amounts the consistency of the cement paste obtained is generally not improved. As in the case of the grinding aid A, excess additive can affect the breaking strength of the concrete.

It should be emphasized that a poor consistency of the cement paste does not necessarily translate into a low one Strength of the concrete leads. Various masses with a consistency of 1 have a strength value after 28 days, which is only slightly lower than that of corresponding samples with a consistency of 5. the However, samples with the highest strength values after 28 days had the best consistency of the pulp from 4 and 5.

Those with clinker of type II according to the definition given above using 0.5% of the The mentioned grinding aid and 0.5% potassium carbonate are summarized below:

Grinding aid
middle

surface
(ctnVg)

Lignosulfonate

consistency

Compressive strength (kg / cm ² )

1 day

7 days 28 days

90 days

180 days

A. 6400 0.5 4-5 878.8 1441.2 1771.7 1996.7 2516.9 D. 6860 0.5 5 98.4 1870.2 2137.3 E. 7900 1.0 6th 21.1 850.7 1117.9 2144.3 2369.3 E. 7900 0.5 5 492.1 2116.2 2376.3 2474.7 F. 6630 1.0 6th 10.5 10.5 1884.2 2439.6 F. 6630 0.3 5 731.2 2074.0 1975.6 2010.8

As before, the proportion of grinding aid used was 0.5 percent by weight, based on the cement. The Type II cement hydrates more slowly than the Type I cement and therefore less retarding action is required. An aqueous paste was obtained with 1.0% calcium lignosulphate and 0.5% potassium carbonate, and the compressive strength of the concrete obtained was considerably lower than normal. By adjusting the content of lignosulfonate to 0.5%, a slurry, in general, ₀ with the ideal consistency 5 achieved even a small amount of 0.3% lignosulfonate together with the grinding aids D led to a paste with this consistency.

In the case of the hardened cement made from the cement paste obtained from cement of type I and cement of type II, the compressive strength values obtained after one day showed strong fluctuations in the range from 21 to 984.3 kg / cm ² . The fluctuations in the strength values after 7 days were much smaller and were in the range from 773.4 to 1307.7 kg / cm ² . The relative fluctuations in the strength values after 28 days were even smaller; these values ranged from 1406.1 to 2088.1 kg / cm ² . These differences steadily diminished and were no longer noticeable when tested after 90 days or 180 days when essentially the final strength was achieved.

The large initial differences in the effects of the grinding aid on the rate of strength development also diminish over time, and the differences in final strength are small. The hydrophobic film formed by the grinding aid on the surface of the cement grains appears to make the initial access of water to the particles more difficult and thus retard hydration to an extent which depends on the particular grinding aid used. The hydrated cement has a higher specific volume than the non-hydrated powder and expands, breaking the hydrophobic film. In this way a more direct access of the water is made possible and the hydration reaction is accelerated. The rate of this reaction will later slow down as hydration approaches full value. For example, if the Mahlhilfsmittcl Λ is used, the duration of the Vcrzögcrungspcriodc is a few hours, and it is achieved within 24 hours, a relatively high strength of the slurry at Vorwon dung of Mahlhilfsmittcl G the Vorzögerungs period takes quite a tango and the strength dos slurry remains on very goring on the first day, but increases rapidly on the next day.

The actual retardant is of course the combination of grinding aid, lignosulfonate and Carbonate In any case, at least 0.25 percent by weight of lignosulfonate is required to prevent premature To prevent the cement paste from setting. For most of the grinding aids in Type I cement, this is 1.0 Weight percent of the lignosulfonate required. With most grinding aids in the slower hydrating one Type II cement is suitable and at a level of 0.5 percent by weight of the lignosulfonate even smaller amounts can lead to good results. For example, with cement of the type II when using grinding aid D and 0.3% lignosulfonate, exactly the same early strength increase within 24 hours as with cement of type I obtained with the aid of the same grinding aid and 1.0% lignosulfonate.

Cement paste produced in the water to cement ratio of 0.2 possible according to the invention shows not only much greater strength, but also far less shrinkage than conventional ones Cement paste. The pulp made according to the invention expands during the first day of the Hydration far stronger than ordinary cement paste. So the initial volume increase is 3 to 4%, compared to about 1 volume percent expansion for conventional cement paste. As a result, will an expanding cement paste is achieved, the expansion of which compensates for the shrinkage.

The cement paste made with a water to cement ratio of 0.2 shows a third to a half the shrinkage of conventional cement paste with a water to cement ratio of 0.4 was produced. In the case of masses with a certain composition, the shrinkage is less than one third. Compared with conventional paste, which has a water to cement ratio of 0.6 the shrinkage is between a third and a quarter, with some masses with With a certain composition, the shrinkage is even less than a quarter.

The greater than normal initial expansion is at least partly responsible for the very high compressive strength. A cement slurry with a water to cement ratio of 0.2 would achieve a lower final degree of hydration without the additional expansion. However, the greater expansion creates space for additional hydration. The increased proportion of the hydrated cement material in the slurry increases the strength of the slurry . Therefore the firmness of the porridge otwu is three «mul as high as the firmness of conventional Zemont porridge.

70S 032/102

Claims (2)

Patent claims: 1. A process for the production of a free-flowing, expanding cement slurry with a low W / C ratio by grinding a Portland cement clinker with the aid of a Mahlhilfsmittcl and then adding an alkali or alkaline earth lignosulfonate as a retarding agent and an alkali carbonate, characterized in that the Portland cement clinker with the addition of 0 , 0025 to 0.005 parts by weight of a surface-active agent containing polar and non-polar groups as a grinding aid, based on one part by weight of the finely ground cement clinker, to a specific surface area between 6000 and 9000 cm ² / g according to BIa ine and that the finely ground cement , based on one part by weight, furthermore 0.0025-0.01 part by weight of alkali metal or alkaline earth metal lignosulfonate and 0.2 part by weight of water containing 0.0025-0.005 part by weight of an alkali metal carbonate, are added. 2. The method according to claim 1, characterized in that calcium cium lignosulfonate is used as the alkaline earth lignosulfonate and potassium carbonate is used as the alkali carbonate.