GB2079739A

GB2079739A - Additives for cement compositions

Info

Publication number: GB2079739A
Application number: GB8023006A
Authority: GB
Original assignee: Diamond Shamrock Europe Ltd
Current assignee: Diamond Shamrock Europe Ltd
Priority date: 1980-07-14
Filing date: 1980-07-14
Publication date: 1982-01-27

Abstract

Compositions suitable for increasing the fluidity of hydraulic cement compositions comprise a dispersant for hydraulic cement compositions such as a naphthalene sulphonate formaldehyde condensation product in combination with a phenol C2 to C4 alkoxylate, e.g. ethoxylate, acting as an adjuvant for the dispersant.

Description

SPECIFICATION Additives for cement compositions The present invention relates to compositions suitable for increasing the fluidity of hydraulic cement compositions.

It is well known that cement compositions such as a mixture of Portland cement, sand and aggregate, require a certain minimum water content in order to be of a workable consistency. Moreover, such compositions gradually lose their mobility soon after preparation due to the onset of setting and in order to restore the workable consistency, further water is sometimes added. This may be necessary for instance if the time between mixing and casting is too long. A high initial water content or the addition of water after mixing to provide a high water content at the time of casting is undesirable because it can lead to reductions in mechanical strength, particularly compressive strength.Materials are known which when added to cement compositions increase their fluidity so that less water is needed initially to obtain a workable consistency and these materials may also have the effect of lengthening the time for which the cement remains workable without further water being added. Such materials are referred to herein as "dispersants for hydraulic cement compositions".

The known dispersants are often referred to as "water-reducing agents" or "super plasticizers". Amongst the best known of such materials are water-soluble aryl or alkyl aryl sulphonates, the organic part of which may optionally have been condensed with formaldehyde. Other such materials are lignin sulphonates and melamine/formaldehyde sulphonates.

We have now found that the action of cement dispersants can be improved by using the dispersant in combination with a phenol C2 to C4 alkoxylate. The use of this adjuvant in combination with cement dispersants enables one to use either still lower amounts of water in cement compositions containing the conventional amount of the dispersant or else to use less dispersant without having to use more than the usual amount of water.

Accordingly, the invention provides a composition suitable for increasing the fluidity of a hydraulic cement composition and comprising a dispersant for hydraulic cement compositions in combination with a phenol C2 to C4 alkoxylate.

Th dispersant may be any dispersant which increases the fluidity of a hydraulic cement composition or enables the production of a hydraulic cement composition of satisfactory fluidity with less than the normal amount of water.

Preferably the dispersant is an anionic polyelectrolyte dispersant, more preferably a sulphonate dispersant. Most preferably the dispersant is a naphthalene sulphonic acid formaldehyde condensate salt.

Other conventional dispersants which may be used include melamine/formaldehyde sulphonates and lignin sulphonates.

Where a formaldehyde-naphthalene sulphonate condensate is employed, the condensate preferably has a molecular weight of from 500 to 10,000, more preferably 600 to 2,000. Low molecular weight condensates are somewhat easier to manufacture than high molecular weight condensates but have a less efficient dispersant action. The adjuvant of the present invention may be particularly valuable in rendering these less effective dispersants adequately effective.

The adjuvants of the present invention are phenol C2 to C4 alkoxylates. It is to be understood that chemically equivalent materials such as may be obtained by, for instance, substitution of the phenolic nucleus to a degree which does not substantially detract from the adjuvant action of these compounds are intended to fall within the term "phenol C2 to C4 alkoxylate" as used herein. An example of such substitution is the formation of methyl phenol alkoxylates. Other equivalent compounds are sulphated alkoxylated phenols which may be used in the present invention in the form of any of their water soluble salts, for example alkali metal salts such as sodium or potassium salts or ammonium or alkanolamine salts such as monoalkanolamine ortrialkanolamine salts.

The term ''C2 to C4 alkoxylates" means alkoxylates formed with ethyleneoxy, propyloxy or butoxy units. It is preferred that the alkoxy units of the phenol C2 to C4 alkoxylate should be ethyleneoxy units, optionally including a minor proportion of propyleneoxy and1or butyleneoxy units. Preferably, the phenol alkoxylate contains on average at least 1.5 moles of alkoxy units per mole. More preferably, the alkoxylate contains from 2 to 10 ethyleneoxy units per molecule, e.g. from 3 to 6 ethyleneoxy units per molecule. In practice, the material used will generally be a mixture of alkoxylates having an average composition within the desired range.

Sulphated alkoxylated phenols may be prepared from the corresponding ethers by any of the recognised techniques of sulphation, for instance by reaction with oleum, chlorosulphonic acid or sulphur trioxide.

Generally, it will only be necessary to use a very small amount of the adjuvant of the present invention in combination with a dispersant to produce a substantial improvement in the performance of the dispersant.

In compositions according to the invention, it is therefore preferred to provide from 0.1 to 25% by weight of the phenol alkoxylate based on the combined weight of the dispersant and phenol alkoxylate. More preferably however the composition contains from 0.5 to 10% or still more preferably from 0.5 to 5% of phenol alkoxylate based on the weight of the dispersant and phenol alkoxylate combined.

The compositions of the invention may be incorporated into hydraulic cement compositions at any stage during their production. The composition of the invention may be present in any of the dry ingredients used to make up a fluid cement composition or may be added with the mixing water. The compositions of the invention may be added to reduce the fluidity of a cement composition which has already been produced by mixing the requisite ingredients.

Accordingly, the invention also provides a hydraulic cement composition comprising hydraulic cement forming ingredients, a dispersant for the hydraulic cement and a phenol C2 to C4 alkoxylate.

Preferably, the cement composition contains from 0.1 to 3% by weight of the dispersant based on the dry weight of cement in the composition and preferably the relative proportions of the phenol alkoxylate and dispersant are as stated above.

The cement may be any type of hydraulic cement although those containing Portland cement are expected to be of greatest commercial significance. The cement composition may contain aggregate of varying kinds and particle size as is conventional in concrete and mortar production.

The adjuvant compositions of the invention may be used in the production therefore of reinforced concrete, road making concrete or prefabricated concrete and may be particularly effective in the preparation of mortars for injection moulding.

The invention includes a method of forming a settable cement mixture which method comprises forming a workable mixture of cement ingredients, water, a cement dispersant and a phenol C2 to C4 alkoxylate. The invention also provides a hydraulic cement composition for use in conjunction with one or more cement dispersants (by the addition of these dispersants) and comprising hydraulic cement forming ingredients together with a phenol C2 to C4 alkoxylate.

The invention also embraces cement structures formed by setting hydraulic cement of the invention.

The following examples are given by way of illustration.

Examples In the following Examples, the following materials are referred to by the following codes.

Dispersant A Condensation product of naphthalene sulphonic acid and formaldehyde - molecular weight of approximately 1700.

Dispersant B Condensation product of naphthalene sulphonic acid and formaldehyde - molecular weight of approximately 700.

Adjuvant A Condensate of phenol and ethylene oxide with an average of 4 moles ethylene oxide per mole phenol.

Adjuvant B Condensation product of nonyl phenol and ethylene oxide with an average of 9.5 moles ethylene oxide per mole of phenol.

Adjuvant C Sulphated condensate of phenol with an average of 4 moles/mole of ethylene oxide per mole of phenol.

Cement compositions were prepared according to the following two basic formulations: Formulation A Formulation B Mixed aggregate (1/4"to 3/4" diameter) 28 Kgs 28 Kgs Sand 14 Kgs 14 Kgs Portland Cement 7.72 Kgs 7.72 Kgs Water 3.84 Kgs 3.04 Kgs Dispersant See Table See Table Adjuvant Water/Cement Ratio 0.497 0.393 The figures for water given above include the water content of all the other ingredients.

These ingredients were mixed as follows in accordance with British Standard 50 75: Part 1: 1974 Clauses B4.2.1. & B4.2.2 The aggregate and sand were placed in the pan of a pan type mixer and approximately half of the mixing water was added. The material was then mixed for two minutes. After standing for three minutes, the mixer was restarted and the cement was gradually added during the next 30 seconds. The remainder of the mixing water was then added during the following 30 seconds and the concrete was then mixed for a further three minutes. Where dispersant and adjuvantwere included, these were added with the second batch of mixing water.

After mixing, the mixture was allowed to rest and samples were taken at intervals for testing to see how the characteristics of the mixture altered on standing. The mixture was in each case tested for "slump" and "flow" in a method based on DIN 10481972 Section 1 Clause 312. The test was performed on a flow table comprising a board measuring 70 by 70 centimetres covered by a flat steel plate 2 millimetres thick. The middle of the plate was marked as was a 20 centimetre diameter circle therearound. The table top was hinged to allow a vertical movement of the far edge of four centimetres between a pair of stops. The hinged section of the table weighed 16 kilograms.In performing a test, a sample of concrete taken at a noted time from the mixture prepared above was filled into a slump cone 20 centimetres high having an internal diameter of 13 centimetres at the top and 20 centimetres at the bottom. Prior to filling, the inner surfaces of the table and cone were wetted. Concrete was placed in two equal layers into the cone at the centre of the table and likely tapped with ten strokes of a wooden bar. After filling, excess concrete was struck off and the residue removed from the plate. Half a minute after striking off the concrete, the cone was lifted slowly vertically upwards and laid to one side. The table was then lifted fifteen times in approximately 15 seconds up to the upper stop and released and allowed to fall of its own accord.A note was taken of the initial drop in height of the cone of concrete immediately on removal of the supporting cone mould and of the average diameter of the heap after the repeated jarring of the table top. This test was carried out using samples of concrete taken from the mixture at various times from 5 minutes to 120 minutes after its mixing was completed.

The results of the tests are shown in the accompanying table in which runs 1 23 and 4 are provided for the purposes of comparison.

TABLE Example Super- Formu- Initial Slump in mm. Flow in mm Number Plasticizer lation Addition 5min 30min 60min 120min Smin 30min 60min 120min (% Dry Wt on Cement) 1 0.5% Dispersant A 100 100 100 50 460 460 460 400 A 2 0.5% Dispersant B 30 30 30 20 240 240 235 195 A 3 0.5% Dispersant A 40 40 40 10 180 180 180 180 A 0.005% Butyl Dioxitol 4 0.5% Dispersant A 160 160 150 30 490 490 440 300 A 0.005% Adjuvant B 5 0.5% Dispersant A 60 50 40 20 215 200 195 150 6 0.5% Dispersant A 180 180 180 140 > 500 > 500 > 500 > 500 A 0.005% Adjuvant A 7 0.5% Dispersant A 180 180 150 100 > 500 > 500 445 423 A 0.025% Adjuvant A 8 0.5% Dispersant A 0.005% AdjuvantA B 130 120 110 110 430 415 405 385 9 0.5% Dispersant B 110 110 90 40 385 385 325 275 A 0.025% Adjuvant A 10 0.5% Dispersant A 120 110 90 - 440 420 400 B 0.005% Adjuvant A 11 0.5% Dispersant A 160 160 100 60 480 480 420 370 A 0.005% Adjuvant C The term "naphthalene sulphonic acid" as used in this specification embraces both ct and ss naphthalene sulphonic acids.

Although the dispersant compositions of the invention have been described with reference to their use in forming fluidised cement compositions, they may also be used to increase the fluidity of compositions containing other hydraulic binders such as lime, gypsum and burned magnesite or mixtures of two or more of these.

Claims

1. A composition suitable for increasing the fluidity of a hydraulic cement composition and comprising a dispersant for hydraulic cement compositions in combination with a phenol C2 to C4 alkoxylate.

2. A composition as claimed in claim 1 wherein the dispersant is an anionic polyelectrolyte dispersant.

3. A composition as claimed in claim 2 wherein the dispersant is a sulphonate dispersant.

4. A composition as claimed in claim 3 wherein the dispersant is a salt of an aromatic sulphonic acid or a salt of a condensation product of an aromatic sulphonic acid and formaldehyde.

5. A composition as claimed in claim 4 wherein the dispersant is a salt of a naphthalene sulphonic acid formaldehyde condensate.

6. A composition as claimed in claim 5 wherein the said condensate has a molecular weight of from 500 to 10,000.

7. A composition as claimed in claim 6 wherein the said condensate has a molecular weight of from 600 to 2000.

8. A composition as claimed in any one of the preceding claims wherein the alkoxy units of the phenol C2 to C4 alkoxylate are ethyleneoxy units and optionally a minor proportion of propyleneoxy and/or butyleneoxy units.

9. A composition as claimed in claim 8 wherein the phenol alkoxylate contains from 2 to 10 ethyleneoxy units per molecule.

10. A composition as claimed in claim 9 wherein the phenol alkoxylate contains from 3 to 6 ethyleneoxy units per molecule.

11. A composition as claimed in any one of the preceding claims comprising from 0.1 to 25% by weight of the phenol alkoxylate based on the combined weight of dispersant and phenol alkoxylate.

12. A composition as claimed in claim 11 containing from 0.5 to 10% by weight of the phenol alkoxylate based on the combined weight of dispersant and phenol alkoxylate.

13. A composition as claimed in claim 12 containing from 0.5 to 5% by weight of the phenol alkoxylate based on the combined weight of dispersant and phenol alkoxylate.

14. A composition as claimed in claim 1 substantially as hereinbefore described in any one of the Examples.

15. A hydraulic cement composition comprising hydraulic cement forming ingredients, a dispersant for the hydraulic cement and a phenol C2 to C4 alkoxylate.

16. A cement composition as claimed in claim 15 wherein the dispersant and/or the phenol alkoxylate are as they are defined in any one of claims 2 to 10.

17. A cement composition as claimed in claim 15 or claim 16 comprising 0.1 to 3% of the dispersant by weight of the total dry weight of the cement in the composition.

18. A cement composition as claimed in claim 17 comprising 0.2 to 1% of the dispersant by weight of the total dry weight of the cement in the composition.

19. A cement composition as claimed in any one of claims 15 to 18 wherein the relative proportion of dispersant and phenol alkoxylate are as defined in one of claims 11 to 13.

20. A cement composition as claimed in claim 15 substantially as hereinbefore described in any one of the Examples.

21. A hydraulic cement composition for use in conjunction with one or more cement dispersants and comprising hydraulic cement forming ingredients together with a phenol C2 to C4 alkoxylate.

22. A method of forming a settable cement mixture which method comprises forming a workable mixture of cement ingredients, water, a cement dispersant and a phenol C2 to C4 alkoxylate.

23. A method as claimed in claim 22 wherein the dispersant, the phenol alkoxylate and/or the amount thereof are as defined in any one of claims 2 to 10 or 17 to 19.

24. A method as claimed in claim 22 substantially as hereinbefore described in any one of the Examples.

25. A cement structure formed by setting a hydraulic cement composition as claimed in any one of claims 15to 20.