DE2013395A1 - Free flowing cement paste - Google Patents

Description

Act: 46 ^ 983_

Applicant: Research Corporation, New York, 4o5 Lexington Avenue,

USA -..-- '■

gripping cement paste

The invention relates to a method of manufacture of cement paste and the paste-like cement masses produced in this way.

Conventional Portland cement is made by a ground mixture of limestone and clay or shale is burned with the formation of clinkers, which predominantly consist of mixed calcium silicates, gallium aluminates and calcium aluminum ferrite. Together with a few percent of gypsum, the clinker becomes a fine one Grind powder, which when mixed with water a Porridge gives *

Properly made cement paste sets within a few hours and then slowly hardens. When sand and crushed rock and / or gravel mixed into the slurry you get concrete. During the initial stages of hardening, while the concrete is in contact

stands with water or with air saturated with water vapor, it expands somewhat. When the concrete then is exposed to an environment with less "addiction", it shrinks. The shrinkage occurs in larger ip Than the 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 is the least possible If the initial ratio of water to cement powder is applied, the result is a concrete that is reduced in terms of Shrinkage and increase in the absolute strength of the concrete is superior.

The 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 strong and not workable is achieved. With help of the method according to the invention, however, it is possible to use a free-flowing cement paste with a ratio Water to cement production of only 0.2.

The main aim of the invention is therefore a free-flowing, pasty cement mass with a lower ratio of water to cement than has previously been used became.

The invention aims to produce a cement paste which leads to an improved concrete with lower shrinkage and higher strength than conventional types of concrete.
The stated goals and advantages can be achieved through the

009840 / U7 3

- 3 -

BA & ORIGINAL

Process according to the invention can be achieved.

The invention accordingly provides a method for producing free-flying, expanding cement paste, which is characterized in that cement clinker is converted into particles with a specific surface area grinds between 6000 and 9000 cm / g, a »part by weight of the ground cement clinker with at least 0.0025, preferably 0.005 to 0.010 parts by weight of an alkali ore Erdalkalignosulfonats mixed and then about 0.2 Parts by weight of water are added that contain at least 0.0025 »*

preferably 0.005 parts by weight of an alkali carbonate.

For better grinding, the cement clinker are at least 0.0025f preferably 0.005 parts by weight of a grinding aid added.

The invention also relates to an essentially consisting of finely ground cement, more free-flowing Cement paste containing about 0.2 parts by weight of water, at least 0.0025, for one part by weight of the finely ground cement, preferably 0.0050 parts by weight of a grinding aid, at least 0.0025, preferably 0.005 to 0.010 parts by weight of alkali or alkaline earth lignosulfonate and at least Contains 0.0025, preferably 0.005 parts by weight of an alkali carbonate.

In contrast to the specific surface of conventional Portland cement powder of 4000 cm / g (determined according to the method of Blaine, ASTM regulation C 204), the ground clinker according to the invention has a specific Surface in the range of 6000 to 9000 cm / g. It It could be assumed that clinker ground to such fineness would hydrate rapidly and upon mixing

009-84Q / -U73

sets suddenly with water. To delay hydration and at the same time to keep the pulp processable despite the low water content, an alkali or alkali metal lignosulfonate such as sodium, potassium, ammonium, calcium or magnesium lignosulfonate is added. The added water contains an alkali carbonate such as Hatrium-, potassium or ammonium carbonate (the term "alkali metal used herein is ¹¹ intended ammonium include). This combination of additives, it is no longer necessary, the W comparable accordance with the invention to add applied cement powder gypsum.

To achieve the required high degree of purity of the powder achieve, a grinding aid is added to the cement clinker. The grinding aid also contributes to the Keeping cement free-flowing and affects the workability and the setting properties of the cement paste as well as the strength properties of the concrete.

The most suitable for the purposes of the invention Grinding aids are generally surface-active substances that contain both polar and non-polar groups. The polar groups of the surfactants are created by the ions on the surface of the cement constituents attracted so that the non-polar groups face outwards. This is how the cement grains come in handy slightly hydrophobic and in this way prevents premature hydration and the cement despite its fineness preserved in free flowing condition.

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 non-ionic surfactants, sulfonates

009840 / U73

and other anionic surfactants ;; Substances, _r alkyl ammonium salts and other cationic surface active agents and the like.

The experiments described below serve to illustrate the invention.

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

Type I. Type II O ₅ S 60.97 54.17 C ₂ S 19-45 26.13 G ₅ A 10.28 4.48 C ₄ AB 7.30 13.28 Ha ₂ O 0.10 0.46 K ₂ U 0.45 0.20 heat loss 0.11 0.10 fi-eiej * Ca ^ iumo ^ yd 0.42 0.17 unrecoverable Büekstancl 0.06 negate permeable

the TftchnoJlQgie of cement "C" means calcium

, "S ^ kitftlic acid, ί'Λ" aluminum oxide and "f ^M ferric oxide;. D ^ e Syjotbjojte ^w Iia ^| i, ¹¹ K" and * 0 ⁿ have the usual

In de ^ ¹ a ^ g ^ e ^ nejk Ve ^ s ^ chsduTChjftthrung, the clinker and the grinding aid, if used, were placed in porcelain grinding vessels with hard ceramic balls; gfmjikl, ejDi> The »K ^ l ^ nk ^ r VQW Type I was tested to a surface AaQh Blaine CASTM ^ Vctrschrif% C 204) of about during two layers of diet hyloarbonate ver-4er metBi; en andtrtn

^INSPECTE0

Grinding aid takes a long time to reach this specific surface area. However, diethyl carbonate is mainly used because of its beneficial effect on processability, retarding the setting, the compressive strength and the dimensional changes of the cement paste obtained later preferred·

The ground clinker was dry mixed with the specified amount of calcium lignosulfonate. To mix well One minute of mixing in a paint shaker was sufficient. The one with Lignosulfonate mixed ground clinker was introduced into a two-compartment mixer, the other chamber of which contained a solution of potassium carbonate in water. Hach was sucking out the air the partition between the two chambers removed and the cement powder and the solution together for several minutes mixed.

The resulting cement slurry was put into cubic steel molds pressed in. After curing under water for one day, the 2.54 cm concrete cubes were removed from the molds and stored in an atmosphere saturated with water vapor. These cubes were periodically subjected to the compressive strength test. Those with type I cement clinker The results obtained are shown below:

- 7 -00984Q / 1473

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0098Α0 / ΤΑ73

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0098A0 / U73

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

S - polyglycol derivative with 6 monomer units and one mole of trimethylnonylphenol in the polyglycol chain '

D - diethyl carbonate

F - polyglycol derivative with TO 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 sulfosuceinate and alkyl sulfonate, amine salts

L - alkyl sulfosuccinate and alkyl phenol polyglycol

The consistency of the cement paste is shown in the table below Rating given:

0 - Sets in the mixing tank.

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

will.

2 - Difficult to move, even if the shape vibrates.

3 - Easy flowing when the shape is vibrated.

4 - Free flowing when the mixing chamber is shaken

will.

5 - Free flowing.

6 - Very thin.

009840/1473

From the experiments summarized in the table it can be seen that the choice of a special grinding aid influences the consistency of the cement paste finally produced from the ground clinker. The grinding aid does not regulate the consistency itself, but works in conjunction with the calcium lignosulfonate and potassium carbonate present. If, for example, when using the grinding aid L, the proportion of lignosulfonate and potassium carbonate is reduced to 0.50 i » or 0.25 i · , a paste is obtained which sets in the mixing chamber. Increasing the proportion of calcium lignosulfonate and potassium carbonate above the preferred amounts generally does not improve the consistency of the cement paste obtained. As illustrated in the case of grinding aid A, excess additive can impair 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 materials with a consistency of 1 have a strength value after 28 days that 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 pulp consistency of 4 and 5.

The results obtained with clinker of type II using 0.5 # of said grinding aid and 0.5 » potassium carbonate are summarized below:

- 11 - 009840/1473

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009840/1473

Like Torher, the proportion of grinding aids 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 allows less retardation to be required. An aqueous slurry was achieved with 1.0 1 » calcium lignosulfate and 0.5 # potassium carbonate and the compressive strength of the concrete obtained was significantly lower than the normal value. By adjusting the content of lignosulfonate to 0.5 % , a slurry with the ideal consistency 5 is generally achieved. Even a small amount of 0.3 ^ lignosulfonate together with the grinding aid S resulted in a slurry of this consistency.

In the case of the hardened cement, from the cement slurry 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 · The fluctuations in the strength values after 7 days were much lower and were in the Range from 773 x 4 to 1307.7 kg / cm. The relative fluctuations in strength values after 28 days were even less; these values were in the range of 1406.1

to 2088.1 kg / cm. These differences steadily diminished and were when tested after 90 days or less 180 days, when essentially the final strength was achieved, no longer noticeable.

The large differences initially achieved in the effects of the grinding aid on the rate of strength development diminish also over time and the differences in final strength are small. The through the

009840/1473

Grinding aids on the surface of the cement grains formed hydrophobic PiIm seems to be the initial one To hinder access of water to the particles and thus to retard hydration to an extent that of depends on the particular Hahlhilfiftel used. Of the hydrated cement has a higher specific volume than the non-hydrated powder and expands dissolves with the hydrophobic film bursting. This way there is a more direct access to the water and accelerates the hydration reaction. The rate of this reaction will later decrease when the hydration is complete Nearest value · For example, when the grinding aid A is used, the duration of the delay period is a few hours and it will be within 24 hours A relatively high strength of the pulp is achieved · When using grinding aid G, the delay period lasts quite a long time and the firmness of the porridge remains very low on the first day, increases but quickly 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 Lignosulfonet is required to prevent premature To prevent the cement paste from setting »With most grinding aids in type I cement 1.0 percent by weight of the lignosulfonate is required. With most of the grinding aids in the slower hydrating Type II cement there is a Share of 0.5 percent by weight of the lignosulfonate suitable and even smaller amounts can lead to good results. For example, cement was used

009840 / U73

II obtained of the type using the grinding aid D and 0.3 Ί "lignosulfonate exactly the same early Feetigkeitserhöhung within 24 hours, such as with cement Type I using the same Mahlhilfsnittele and 1.0 i" lignosulfonate.

Cement slurry that was produced in the water to cement ratio of 0.2 that is possible according to the invention shows not only a much greater strength, but also far less shrinkage than conventional cement slurry. The slurry produced according to the invention expands during the first day of hydration far more than ordinary cement slurry. The initial volume increase is 3 to 4 liters, compared to around 1 volume percent expansion in conventional cement paste. The result is an expanding cement paste, the expansion of which compensates for the shrinkage.

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

Which is stronger than normal initial stretch

009840/1473

at least sub tell for the very high compressive strength. A cement paste with a water to cement ratio of 0.2 would be without the susätsliohe extension a smaller final one Reach the degree of hydration. By the greater expansion, however, fats are raised for suaätsliche hydration. The increased proportion of the hydrated cementitious material in the slurry increases the strength of the slurry. Hence the firmness of the porridge about three times as high as the strength of conventional cement paste

Claims (7)

- 16 claims Free-flowing cement paste, characterized in that that it is per part by weight of the finely ground cement about 0.2 part by weight of water, at least 0.0025 part by weight of a grinding aid, 0.0025 part by weight of an alkali or alkaline earth lignosulfonate and 0.0025 parts by weight of an alkali carbonate contains. 2. cement slurry according to claim 1, characterized in that it is finely ground cement and about 0.2 parts by weight Water, 0.005 parts by weight of diethyl carbonate, 0.005 to 0.010 parts by weight of calcium lignosulfonate and 0.0025 to 0.0050 parts by weight of potassium carbonate per part by weight of the cement contains. 3. Cement according to claim 1 or 2, characterized in that it is in powder form and at least 0.0025 parts by weight of a grinding aid and an alkali or alkaline earth lignosu ^ fo- * contains nats. 4. A process for the production of free-flowing cement paste which expands on setting according to claims 1-3, characterized in that cement clinker is ^{ground into particles with a specific surface area between 6000 and 9000 cm 2} and the ground cement clinker with at least 0.0025 parts by weight of alkali or alkaline earth lignosulfonate and then mixed with about 0.2 parts by weight of water containing at least 0.0025 parts by weight of alkali metal carbonate per 1 part by weight of the ground cement. 009840 / U73 5 «Method according to claim 4-, characterized in that that the grinding of the cement clinker in the presence of at least O.OÖ25 -Gewi ent steep one Grinding aid performs. . 6. The method according to claim 5, characterized in that that a surface-active as a grinding aid Fabric with polar and non-polar groups used. 7. The method of claim 5 or 6, characterized in that as a grinding aid nat _{Diäthylcarbo-%} · used. 8. The method according to claim 4 to 7, characterized in that that as lignosulfonate calcium lignosulfonate and potassium carbonate is used as the carbonate. 0098 40 / U73