AU656440B2

AU656440B2 - Cementitious compositions

Info

Publication number: AU656440B2
Application number: AU29627/92A
Authority: AU
Inventors: John W. Brook; David F. Factor; Frederick D. Kinney; Celeste L. Mccallen; Andrea M. Young
Original assignee: Sandoz AG
Current assignee: Sandoz AG
Priority date: 1991-11-27
Filing date: 1992-11-25
Publication date: 1995-02-02
Anticipated expiration: 2012-11-25
Also published as: JP3317529B2; ITRM920845A0; FR2684096A1; ITRM920845A1; CH684476A5; AU2962792A; FR2684096B1; DE4239062A1; JPH05229864A; IT1263029B

Description

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I- 1 656440

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): Sandoz Ltd.

ADDRESS FOR SERVICE: 4

S.

4*c 45155 DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TITLE: Cementitious compositions The following statement is a full description of this invention, including the best method of performing it known to me/us:la Case 154-0214 CEMENTITIOUS COMPOSITIONS This invention relates to cementitious compositions and more particularly to cementitious compositions containing fly ash and admixtures for use therein.

Fly ash is defined in Standard Specification C 618 of the American Society for Testing and Materials (ASTM) as "finely divided residue that results from the combustion of ground or powdered coal". ASTM C 618 (the contents of which are incorporated herein by reference) defines two distinct types of fly ash, Class F and Class C, the former (obtained from the combustion of anthracite or bituminous coal) being more common than the latter (obtained from the combustion of subbituminous coal or lignite). One characterizing feature of Class C fly ash is its higher lime content, stated by ASTM C 618 to be often "higher than 9* 15 The use of fly ash in cementitious compositions confers useful properties such as enhanced final strength and durability and reduced permeability, and it has been widely used in, for example, concrete. However, it also confers low early strength o (disadvantageous in many applications) and it retards the set time.

It has now been found, surprisingly, that the combination of a cementitious material, a selected fly ash and a particular type of admixture can give a cementitious composition which enjoys virtually all of the advantages of having fly ash incorporated therein, but without most, and sometimes all of the disadvantages. There is therefore provided, according to the present invention, a cementitious composition comprising a cementitious material; a fly ash which has a calcium oxide content of from 15-45% by weight; a hydroxycarboxylic acid; and a water-soluble source of alkali metal ions.

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2 Case 154-0214 By "cementitious material" is meant a material which comprises a hydraulic cement, that is, a calcium alumino-silicate which when mixed with water will set to form a hard product.

The most common type of such material is Portland cement, and for the purposes of this invention this is the preferred cementitious material. However, high alumina cement may also be used.

The cementitious material may contain other materials which are not in themselves cementitious but which can make a contribution to the setting of final product. Examples of these are the various natural and artificial pozzolans.

So The fly ash which is used in the compositions of this invention should not only be a Class I C'fly ash, but it should also have a calcium oxide content of from 15-45%, preferably from 25-30%, by weight. Compositions containing fly ashes with calcium oxide contents Slower than 15% do not give the excellent results of those containing fly ash with at least 15% calcium oxide.

The third component is a hydroxycarboxylic acid. Among the acids which can be used 15 are citric, malic, malonic, glycolic and glyoxylic acids.

The fourth component is a water-soluble source of alkali metal ions, preferably sodium or potassium. The alkali ions are preferably present such that the molar ratio of ions to hydroxycarboxylic acid of from 0.5:1 to 1.5:1, preferably 0.6:1-1:1. The source may be any water-soluble compound of an alkali metal which gives rise in water to a basic solution, with carbonates, bicarbonates and hydroxides being particularly useful.

In an alternative and preferred embodiment of the invention, an alkali metal salt of a hydroxycarboxylic acid is used, this being considered for the purposes of the invention to be a combination of components and Especially useful materials are tripotassium and trisodium citrates.

z z, r i e l 3 Case 154-0214 The proportions of these four ingredients expressed as weight percentages of the total of cementitious material fly ash salt are from 70-80% fly ash, from 20-27% cementitious material and from 0.5-4% salt when this is used as a combination of components and or, when the hydrocarboxylic acid and the alkali metal ion source are separate compounds, sufficient of these compounds to give theoretically this percentage of salt (the word "salt" is hereinafter used to encompass both possibilites).

The respective preferred percentages are 71-73% ash, 25-26% cementitious material and 2.5-3.5% salt.

To the essential ingredients as hereinabove described may be added other art-recognized ingredients. The most common other ingredient is aggregate, usually sand. Most useful compositions contain sand, usually to the extent of between 50 and 80% by weight of the i composition. Known admixtures (as defined in ASTM C 125), for example, lignosulphonates, napththalene sulphonate formaldehyde condensates and glucoheptonates may be used in art-recognized quantities. It is a surprising feature of this invention that 1,S many of these admixtures, which are known to be retarders in conventional cementitious compositions, do not exert any retarding influence on the compositions of the present invention.

Further components may be non-hydraulic glassy silicates, silica fume, rice hull ash, precipitated silica and the like. Fibers suitable for use in the construction industry may also be added to the cementitious composition of the invention. Further useful components are latices and similar polymeric modifying agents.

In an especially useful and preferred embodiment of the invention, the composition also comprises a source of borate ions. It has been surprisingly found that this gives a considerable degree of control over the set of these compositions. Any source of borate ion is useful, borax being a convenient one. Borate ion is preferably added at the rate of 0.5-3.0% by weight of the total weight of plus any admixtures present aggregate.

l t f -v i 4 Case 154-0214 The compositions of this invention are useful in many aspects of the building trade. They can be used, for example, as concretes, mortars and grouts. They set rapidly to give hard, impermeable masses and exhibit both high early and high final strengths. They also have excellent freeze-thaw durability.

The invention is further described with reference to the following examples in which all parts are expressed by weight.

Example 1 A high performance mortar is made by mixing the following materials: Portland cement 10.4 parts 00 0 0~ Class C fly ash (25% CaO) 28.0 parts o o tripotassium citrate 1.6 parts 00 S. fine sand 60.0 parts Water is added to the extent of 8.3% by weight of the total composition.

Test results are as follows: flow (5 drops) (ASTM C 230): Set Time (ASTM C 266) initial: 3.5 min.

final: 5.0 min Compressive strength (ASTM C 109) cube, air cured) 2 hr.: 33.5mPa 24 hr.: 65.0mPa 7 day: 85.0mPa Si Case 154-0214 Example 2 A high performance mortar is made by mixing the following materials: Portland Cement 8.6 parts Class C fly ash (25%CaO) 24.8 parts tripotassium citrate 1.0 parts borax 1.0 parts sodium sulphate 1.5 parts fine sand 63.0 parts Water is added to the extent of 8.3% by weight of the total composition and the text results 'are as follows (measured as described in Example 1) S% flow: Set time; initial: 28 min final: 30 min Compressive strength, 2hr: 18.6mPa 24 hr: 51.0mPa 7 day: 71.0mPa Q Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

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Claims

1. A cementitious composition comprising a cementitious material; a fly ash which has a calcium oxide content of from 15-45% by weight; a hydroxycarboxylic acid; and a water-soluble source of alkali metal ions.

2. A cementitious composition according to claim 1, wherein the fly ash has a calcium oxide content of from 25-30% by weight.

3. A cementitious composition according to claim 1 or claim 2, wherein the molar o* ratio of alkali metal ions to hydrocarboxylic acid is from 0.5:1-1.5:1, preferably 0.6:1-1:1.

4. A cementitious composition according to any one of claims 1-3, wherein the source of alkali metal ions is selected from alkali metal carbonates and hydroxides.

5. A cementitious composition according to any one of claims 1-3, wherein the hydroxycarboxylic acid and the source of alkali metal ions are provided by the alkali metal salt of the hydrocarboxylic acid.

6. A cementitious composition according to claim 1, wherein the weight percentages of the component per the total of cementitious material fly ash hydroxycarboxylic acid alkali metal ion source (hydroxycarboxylic acid alkali metal ion source being calculated as equivalent quantity of metal hydroxycarboxylate salt) are from 70-80% fly ash, from 20-27% cementitious material and from 0.5-4% salt.

7. A cementitious composition according to claim 6, wherein the weight percentages cn t\ r. I I I I 7 Case 154-0214 are 71-73% fly ash, 25-26% cementitious material and 2.5-3.5% salt.

8. A cementitious composition according to any one of claims 1-7, wherein the composition comprises from 60-80% by weight of sand.

9. A cementitious composition according to any one of claims 1-8, wherein the composition comprises borate ion to the extent of from 0.5-3.0% by weight of (a) any admixtures present aggregate. A cementitious composition substantially as described with reference to any one of the examples. Dated this 31st day of October 1994 I SANDOZ LTD. by its patent attorneys Davies, Collison, Cave St rrri I C Ct t A' z bi 1 -I c i AB _III1~L1_11- Case 154-0214 rSTRACT A cementitious composition comprising o 9 9. .t V r a cementitious material; a fly ash which has a calcium oxide content of from 15-45% by weight; a hydroxycarboxylic acid; and a water-soluble source of alkali metal ions. The compositions are useful as concretes, grouts and mortars. C,'