WO1993016965A1

WO1993016965A1 - Geopolymeric binder material

Info

Publication number: WO1993016965A1
Application number: PCT/GB1993/000373
Authority: WO
Inventors: Pierre Marc Fouche
Original assignee: Pretoria Portland Cement Company Limited; Gomersall, John, Edward
Priority date: 1992-02-27
Filing date: 1993-02-23
Publication date: 1993-09-02
Also published as: ZA931375B; AU3570793A

Abstract

A dry composition suitable for use as a binder upon being mixed with water, the composition comprising a mixture of an alkaline earth metal compound selected from the group consisting of the oxides and hydroxides of calcium and magnesium, a salt of a cation selected from the group consisting of ammonium, potassium and sodium which is capable of reacting with the alkaline earth metal compound to produce the hydroxide of the cation, a source of silica and a source of an alumina silicate.

Description

GEOPOLYMERIC BINDER MATERIAL

THIS invention relates to compositions of matter of the type known in the trade as binder and more particularly geopolymeric binders. The term "geopolymeric" is understood in the trade as referring to a material which is composed of or which includes a binder component which has the general chemical formula

(Si-0-Al-O-)_n, [also known as polysialates] , and

(Si-0-Al-0-Si-0-)_n, [also known as polysialate- silioxos] .

It is known to produce geopolymers of the type in question by reacting a sodium or potassium silicate solution with an aluminium bearing source material , such as an alumina rich clay, and incorporating a filler material , such as sand and/or stone aggregate into the mixture to produce a castable or mouldable material which may be used in the same manner as cement or concrete. Since the alkali metal silicate contains a large percentage water it is in these applications normally preferred to form the silicate on site by reacting sodium or potassium hydroxide with silica gel [SiO^]- The product of choice in this regard is sodium hydroxide which is not only very corrosive, but also hygroscopic and expensive. These considerations are at least in part responsible for the low penetration of geopolymers into the conventional porcelanic cement market which cement is based on hydrated calcium silicates. It is an object of the present invention to provide a dry composition of matter in a form ready to mix with water and filler material and suitable for use as a binder material, e.g. as a conventional cement substitute. It will however be appreciated that the composition may also find various other applications.

According to the present invention there is provided a dry composition suitable for use as a binder upon being mixed with water, the composition comprising a mixture of an alkaline earth metal compound selected from the group consisting of the oxides and hydroxides of calcium and magnesium, a salt of a cation selected from the group consisting of ammonium, potassium and sodium which is capable of reacting with the alkaline earth metal compound to produce the hydroxide of the cation, a source of silica and a source of an alumina silicate.

In one form of the invention the cation salt is selected from the group consisting of the carbonates and hydrocarbonates of ammonium, potassium and sodium, ammonium chloride and ammonium nitrate. In the preferred form of the invention the salt is sodium carbonate. Also in the preferred form of the invention the alkaline earth metal compound is calcium hydroxide.

The source material of silica and the alumina silicate may be a single composite material. Thus, that source material may be in the form of an alumino-silicaceous clay. Alternatively, the source may comprise powdered blast furnace slag.

In the preferred form of the invention the source material may at least in part be constituted by fly- ash. The composition may in addition also include other sources of silica such as, for example, fumed silica condensate.

In the mixture of the composition according to the invention the ingredients may be present in the follow¬ ing stoichiometric equivalent mole ratio:

Alkaline earth metal oxide/hydroxide 1 - 1,2

Cation salt 1

Fly-ash 1

SiC>2 [fumed silica condensate] 1 - 3

Thus, in one specific formulation according to the invention the ingredients may be present in the follow¬ ing mass ratio:

Sodium carbonate 10 - 35 parts Calcium hydroxide 10 - 50 parts Si0₂ 20 - 80 parts Fly-ash 50 - 120 parts [depending on the amount of reactive alumina silicate present therein]

A preferred composition of this formulation according to the invention comprises the following ingredients in the mass ratio as indicated:

Sodium carbonate 24 parts

Calcium hydroxide 38 parts

Fumed silica condensate 60 parts

Fly-ash 100 parts

The dry composition of the invention may be made into a binder material by mixing it with between 20 and 50 parts of water.

Thus, in the preferred composition comprising 24 parts of sodium carbonate as described above, the dry mix is preferably made up into a wet mix by the addition of 40 parts of water. Sand may be worked into the mix either before or after the addition of water. In. accordance with a specific aspect of the invention., however, it is preferred to make up the dry mix with water and thereafter to work the wet mix into up to 300 parts of sand.

According to a second aspect of the invention there is provided a two pack binder mixture comprising a first pack made up of the alkaline earth metal compound, the cation salt as defined above and the silica, and a second pack containing the source of alumina silicates.

An example of the invention will now be described without thereby limiting the scope of the invention.

E X A M P L E 1

A dry mix of powdered ingredients was made up as follows:

Parts by mass

Sodium carbonate [ aCθ3J - 24 Calcium hydroxide [Ca(0H)2J - 30

Silica [Fumed silica condensate] Siθ2 ~ 60

Fly-ash - 100

The fly-ash used in the mixture was Class F fly-ash obtained from Matla power station in the Eastern Transvaal, South A rica and would accordingly have had the following typical composition and ignition properties.

Constituent % by Mass

Si0₂ 40,04 - 50,6 A1203 26,30 - 38,93

Two test cubes were produced from the above mixture.

In the first instance the four components set out above were thoroughly mixed first on their own and then with 300 parts of sand. 40 Parts of water were then added to the mixture to obtain a wet mix. The wet mix was introduced into a vibrating cubic mould and allowed to set at room temperature. After curing the moulded cube at room temperature for 7 days it was found that the cube had a compressive strength of more than 15 mPa.

In the second instance the Na2CC>3, Ca(0H)2 and Si<_>2 was first mixed with 40 parts of water whereafter the fly-ash was added and thoroughly mixed. The resulting slurry was then added to the sand [300 parts] and again thoroughly mixed. A cube was produced as described above and was found after 7 days of curing to have a compressive strength of between 18 and 30 mPa.

Countless variations of the invention may be devised without departing from the spirit of the invention.

Claims

Clα.irY S

1. A dry composition suitable for use as a binder upon being mixed with water, the composition comprising a mixture of an alkaline earth metal compound selected from the group consisting of the oxides and hydroxides of calcium and magnesium, a salt of a cation selected from the group consist¬ ing of ammonium, potassium and sodium which is capable of reacting with the alkaline earth metal compound to produce the hydroxide of the cation, a source of silica and a source of an alumina silicate.

2. The composition of claim 1 wherein the cation salt is selected from the group consisting of the carbonates and hydrocarbonates of ammonium, potassium and sodium, ammonium chloride and ammonium nitrate.

3. The composition of claim 1 wherein the cation salt is sodium carbonate.

4. The composition of claim 1 wherein the alkaline earth metal compound is calcium hydroxide.

5- The composition of claim 1 wherein the source material of silica and the alumina silicate is a single composite material material in the form of an alumino-silicaceous clay or a powdered blast furnace slag.

6. The composition of claim 1 wherein the silica and alumina silicate source material is at least in part constituted by fly-ash.

7. The composition of claim 6 which in addition also includes fumed silica condensate.

8. The composition of claim 1 wherein the ingrediet are present in the following stoichiometr . equivalent mole ratio:

Alkaline earth metal oxide/hydroxide 1 - 1,2

Cation salt 1

Fly-ash 1

SiC>2 [fumed silica condensate] 1 - 3

9. The composition of claim 8 wherein the ingredients are present in the following mass ratio:

Sodium carbonate 10 - 35 parts

Calcium hydroxide 10 - 50 parts

Si0₂ 20 - 80 parts

Fly-ash 50 - 120 parts

10. The composition of claim 1 in the form of a two pack binder mixture comprising a first pack containing of the alkaline earth metal compound, the cation salt as defined above and the silica, and a second pack containing the source of alumina silicates.