IE45252B1

IE45252B1 - Cementitious composition

Info

Publication number: IE45252B1
Application number: IE1411/77A
Authority: IE
Original assignee: Bretagne Metallurg
Priority date: 1976-07-13
Filing date: 1977-07-07
Publication date: 1982-07-14
Also published as: LU77729A1; DE2729528A1; OA05705A; FR2358368B1; PL116820B1; ES460941A1; BE856767A; DE2729528C2; SE426691B; FR2358368A1; JPS5817139B2; CH622758A5; IE45252L; PL199528A1; SE7708097L; GB1584055A; NL7707701A; IT1080206B; CA1084644A; DK316977A

Abstract

This mortar is made up of clay, cement, mixing water and an additional agent. The weight proportion of clay is at least equal to that of cement. The additional agent is chosen from urea-formaldehyde and melamine-formaldehyde resins and their derivatives. The weight percentage of the said agent, calculated as the weight of solids contents of this agent relative to the weight of solids contents of the clay-cement mixture, is between 1 and 20 %. Such a mortar can be employed for the manufacture of coherent products which have favourable mechanical characteristics, with absence of fissures.

Description

The invention concerns shapeable cementitious compositions or mortars based on clay and cement with a proportion by weight of clay at least equal to that of cement, their preparation and use, and the set products made from them.

Clay being, by weight or volume, much cheaper than cement, reduction of the cost of cements has long been sought by mixing the latter with clay, but the set products obtained have mediocre mechanical charac10 teristics and tend to crack.

To render clay-cement-water mixtures more homogeneous, it is known to add adjuvants tending to deflocculate or wet the mixture, breaking up agglomerates and allowing the gauging water to disperse better in the said mixture. But such a deflocculating effect, even if it facilitates the mixing, still leads to set products of mediocre durability and cohesion.

The present invention provides a shapeable cementitious composition comprising a cement, clay in a proportion by weight at least equal to that of the cement, gauging water, and hydrophilic amino-resin capable of increasing the thixotrophy of the mixture and a cross-linking during setting of the cementitious composition, the dry weight of such amino-resin present being from 1 to 20% of the total dry weight of the clay and cement. It also provides a method 45282 - 3 of making such a composition by mixing the said components in the said proportions. It further provides a set clay/cement product which contains by dry weight at least as much clay as cement and has dispersed therethrough cross-linked amino-resin, the dry weight of cross-linked amino-resin present being from 1 to 20% of the total dry weight of the clay and cement, the cement iii each case being calculated as the unset material.

Set products according to the invention can have good mechanical characteristics with nocracks. The cross-linking amino-resins used can possess adherent properties like those of gum arabic and may be those currently used for the gluing of plywoods or compressed woods. Preferred are the cross-linking resins of formaldehyde with urea or melamine and these may be used in pulverised form or, more generally, in the form of an aqueous solution containing a minimum of 5 wt.% of water. When the resin is used as a 50 wt. % aqueous solution which provides all the gauging water, and the weight ratio of cement to clay is 1:4, then as the total contribution of water to the mixture must usually correspond at the maximum to 25% by weight of the cement, the maximum weight of dry resin is of the order of 5% of the dry weight of the clay-cement mixture.

The clay constituent of the mixture can be pure clay or clayey soil more or less loaded with sand.

It is preferred to use basic clay (e.g. pH greater than 8) or clay rendered basic by the addition of sodium silicate and/or sodium aluminate.

I 45352 4 The cement constituent of the mixture is preferably rich in calcium aluminate.

The vzeight of dry clay is preferably between 2 and 4 times that of the cement.

She invention involves, apart from these principal features, certain other features vzhich are preferably used at the same time and which will be more explicitly mentioned hereafter.

The composition and process according to the invention can be used for making all the items currently made of cement, concrete and/or clay sUch as bricks, tiles, pottery, panels, slabs, plates whether corrugated or not, pipes and caissons, and in any suitable way, particularly by extrusion, drawing, moulding, injection, easting, application by trowel, , hot or even cold.

After shaping of the composition it is advisable to maintain it in a humid (preferably saturated) atmosphere for some hours (for example for 24 hours at 60°C in an atmosphere saturated with water) and then leave it to dry slowly.

The setting which results from this is accompanied by slow progressive cross-linkage of the resin, in spite of the alkalinity of the medium - a surprising phenomenon seeing that the said resins are considered to be capable of undergoing polymerisation only in the presence of aeid catalysts.

The products obtained after such a slow setting can exhibit good cohesion and other mechanical properties comparable to those of similar known products of asbestos30 cement vzhich comprise 30 vol. % more of cement and are consequently much heavier.

S 2 S 2 - 5 Dried coherent products according to the invention may exhibit mechanical resistance, to traction as much as to compression, of at least 30% greater than that of products made from clay-cement mortars of identical composition but in the absence of amino-resins.

Set products according to the invention can have smooth exterior surfaces of good appearance and keeping the colours of the initial constituents (red if pure clay predominates, ar.d white if the predominant constituent is kaolin, a clay rich in white mica).

The quantity of water absorbed in the clay is preferably reduced, before mixing the clay with the cement, by adding to the clay an adjuvant selected from flocculents and materials capable of rendering the clay water-repellent, the dry weight of the adjuvant added being 0.5 to 5 parts per thousand based on the dry weight of the clay.

For example an aqueous solution of such adjuvant may be premixed and pounced with the clay. Suitable such adjuvants are for example: - polyelectrolytes of the polyacrylamide type such as those distributed under the name MAGNAFLOC Trade Mark R 155 by the CAVIEM Company, - quaternary ammonium salts such as those distributed under the name NORAMIUM Trade Mark M2SH by the PlERREFITTE-AUBY Company, especially if the clay used is loaded with crystals of high specific surface and lamellars in particular, and - fatty amines such as those distributed under the name ETABIRAM Trade Mark 677 S by the PIERREFITTEAUBY Company. - 6 45353 Cellulose or one of its derivatives .is incorporated in the mixture, e.g. added to the clay before mixing with the cement, in a proportion between 3 and 30% by dry weight of the clay, preferably in the form of a very fine powder or of a solution in a solvent which is neutral relative to the cement. This can give low density products with good thermal and sound insulation properties suitable for use in the construction of dwellings.

Aluminium may be incorporated in the mixture, e.g. added to the clay and/or cement.

This metal creates a gaseous expansion, which reduces the density of the final product obtained. Moreover the aluminium salts formed by the reaction of the aluminium with the lime present in the cement protect the product against ageing and against chemical attack by the air and by carbonic acid.

The proportion by weight/cJluminium powder is advantageously between 0.1 and 2 parts per thousand based on the dry weight of the clay-cement mixture.

The composition may contain a vinyl, acrylic, or A.B.S. (acrylic-butadiene-styrene) polymer emulsion or solution, the dry polymer weight generally being between 5 and 25% of the dry weight of the cement-clay mixture.

This can render the set products water-proof and resistant to abrasion by giving their surfaces a glazed, smooth and dense finish.

To improve the mechanical resistance of the set products it is advantageous to reinforce the composition used by elements with a glass base, the elements being in the form of powder, silica gel or. preferably in the form of fibres, the glass is dissolved superficially by the alkaline material with which it and then regenerated on drying to form which is closely bound tc the crystals is closely mixed, a solid phase of clay and set cement.

Claims

1. CLAIMS : I.A shapeable cementitious composition comprising a cement, clay in a proportion by weight at least equal to that of the cement, gauging water, and hydrophilic 5 amino-resin capable of increasing the thixotrophy of the mixture and of cross-linking during setting of the cementitious composition, the dry weight of such amino-resin present being from 1 to 20% of the total dry weight of the clay and cement. 10

2. A composition according to claim 1 wherein the weight of clay present is between 2 and 4 times that of the cement.

3. A composition according to claim 1 or 2 wherein the clay comprises basic clay or clay rendered 15 basic by the addition of sodium silicate or sodium aluminate.

4. A composition according to any of claims 1 fo 3 containing cellulose cr a derivative thereof in an amount of between 3 and 30% of the dry weight of 20 the clay.

5. A composition according to any of claims 1 to 4 Containing aluminium powder.

6. A composition according to any of claims 1 to 5 containing an emulsion of polymer - selected from 25 vinyl, acrylic and A.B.S. polymers.

7. A composition according to any of claims 1 to 6 containing such amino-resin selected from ureaformaldehyde and melamine-formaldehyde resins. 3. A method of preparing a shapeable Cementitious 30 composition which comprises mixing cement, clay in a proportion by weight at least equal fo that of the cement, gauging water, and hydrophilic amino-resin 45282 capable of increasing the thixotrophy of the mixture and of cross-linking during setting of the cementitious composition, the dry weight of such amino-resins present being from 1 to 20% of the total dry weight of the clay and cement.

8. 9. A method according to claim 8 which includes the step of reducing the quantity of water absorbed in the clay, before mixing the clay with the cement, by adding to the clay an adjuvant selected from floeeulents and materials capable of rendering the clay waterrepellent, the dry weight of adjuvant added being 0.5 to 5 parts per thousand based on the dry weight of the clay.

9. 10. A method according to claim 9 wherein said adjuvant comprises flocculent polyelectrolyte selected from polyacrylamides and quaternary ammonium salts.

10. 11. A method according to claim 9 wherein said adjuvant comprises a water-repellent fatty amine.

11. 12. A method according to any of claims 8 to 11 which includes h-e step of incorporating cellulose or a derivative thereof in the mixture to a dry weight of between 3 and 30% of the dry weight of the clay.

12. 13. A method according to claim 12 wherein a thereof cellulose or/derivative/is added in the form of fine powder .

13. 14. A method according to claim 12 or 13 wherein a ttlSFSOf cellulose or/ derivative/is added in solution in a solvent neutral to the cement.

14. 15. A method according to any of claims 8 to 14 which includes the step of incorporating in the mixture aluminium powder in a proportion by dry weight of 0.1 to 2 parts per thousand based on the dry weight of the clay and cement. 4S3 sa - 10

15. 16. A method according to any of claims 8 to 14 in which aluminium powder is incorporated in the mixture

16. 17. A method according to any of claims 8 to 16 which includes the step of incorporating in the mixture silica gel or glass in the form of fibres or powder.

17. 18. A method according to any of claims 8 to 17 which includes the step of incorporating in the mixture an emulsion of polymer selected from vinyl, acrylic and A.B.S. polymers, the dry weight of polymer added being between 5 and 25% of the total dry weight of the clay and cement.

18. 19. A method according to any of claims 8 to 18 whioh uses such amino-resin selected from urea-formaldehyde and melamine-formaldehyde resins.

19. 20. A composition obtained by a method according to any of claims 8 to 19.

20. 21. A process of making a set product which comprises shaping a· composition according to any of claims 1 to 7 and 20 and drying the shaped composition so that it sets and the amino-resin cross-links.

21. 22. A process according to claim 21 wherein the shaped composition is first maintained in a humid atmosphere and thereafter slowly dried.

22. 23. A process as claimed in claim 22 wherein said humid atmosphere is saturated with water vapour.

23. 24. The set product of a composition according to any of claims 1 to 7 and 20.

24. 25. A set clay/cement product which contains by dry weight at least as much clay as cement and has dispersed therethrough eross-linked amino-resin, the dry weight of cross-linked amino-resin present being from 1 to 20% of the total dry weight of the clay and - 11 cement, the cement in each case being calculated as the unset material.

25. 26. A set product according to claim 25 vzherein the resin is selected from urea-formaldehyde and 5 melamine-formaldehyde resins. A set product obtained by a process according :laims 20 to 23. ,. according to any of claims 24 to 27 A set product of a olay/ceraent composition,/ the product having cured resin dispersed therein and 10 being substantially as hereinbefore described.

26. 29. A process according to claim 21 substantially as hereinbefore described.