GB1602845A

GB1602845A - Sprayable cementitious compositions

Info

Publication number: GB1602845A
Application number: GB12567/77A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-03-23
Filing date: 1978-03-23
Publication date: 1981-11-18

Description

(54) IMPROVEMENTS IN AND RELATING TO SPRAYABLE CEMENTITIOUS COMPOSITIONS (71) I, EDWIN FRANK COOPER, of Tunnel Research & Development Limited, 17 Croner Avenue, Whitley Bay Tyne and Wear; a British subject do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a cementitious composition and a method of building up a structure using such a compositive.

An object of the invention is to provide a single pack sprayable cementitious composition which can be built up into load bearing parts, e.g. a structural membrane as for instance in lining tunnels and mine galleries by spraying of successive layers. In order to effect this the composition must form a coherent gel in as short a time as possible after mixing with water, enabling further layers to be added onto previous layers of the cementitious material which are already self-supporting.

In accordance with this invention, a cementitious composition which is sprayable on addition of water comprises a major amount by weight of a pulverulent mixture of fly ash and cement, the balance of the composition comprising chopped fibers, an accelerator, a thixotropic agent and a plasticizer.

The proportion of the composition is preferably about one part by weight of cement to two parts by weight of fly ash, 0.5 to 2.5% of chopped fine fibre of 0.5 to 3 mm in length not more than 1 mm thick and 1 to 2.5% of silicate may be added if used, the percentages being by weight of the composition.

A cementitious composition of this kind on addition of water is thixotropic within two minutes and thus sufficiently coherent and self supporting to accept a further layer after that period. It is thus advantageous to admix water to the composition at the last possible moment to prevent clogging of feed lines and nozzles with the gelling material.

In order to overcome this, the invention proposes a method ofspraying a one-pack cement composition wherein the composition, in pulverulent form, is pumped dry from a reservoir or store to a nozzle, where it is admixed with water as it is discharged from the nozzle.

The invention preferably also includes the steps of building up a structure by thus adding water to a composition according to the invention in a plurality of layers. Such a structure may be located so as to become a load bearing structure, for example in lining tunnels.

The composition of the invention is particularly suited to dry, i.e. pneumatic pumping as both major constituents cement and fly ash are powder materials, in contrast to many proposed gritty cement and concrete mixes.

In a preferred embodiment of the invention, a cement composition comprises:- Parts by Ingredients weight cement powder 60 fly ash 130 chopped fibres 2 sodium silicate 3 plasticizer 4 thixotropic reagent 1 A suitable plasticiser is available as Agilplast CH74 and a thixotropic agent as RODOPOL 83. The silicate is preferably anhydrous rather than as water-glass.

Portland or sulphate resistant cement and fly ash may be present in weight ratios 1:2 and minor quantities (less than 10% of the cement by weight) of other ingredients for example, oven dried sand, pulverised light weight aggregate, chopped polypropylene fibres, Agilplast CH74 as plasticiser, polypropylene and/or polyvinyl chloride, sodium silicate as accelerator, and a water proofing agent may be used.

The fibres may be natural animal or vegetable fibres or synthetic filaments, and should be i to 1 inch in length and of up to I mm diameter.

The silicate and plasticizer reacts with the cement to accelerate gelling of the cementitious mix when water has been added thereto.

Spraying the mixture as illustrated in the accompanying drawing, which is a cross section of a tunnel or mine gallery showing spraying in progress. The mixture described above is pumped pneumatically by a pump 10 from a reservoir 11 to a nozzle 12 and the mix is mixed with water in the nozzle to form a spray 13 of droplets of cementitious slurry. The mixture can then be sprayed in passes of up to 2 inches thick with mesh reinforcement being laid before spraying, for lining of tunnels etc., and can be used up to + inch thickness for finishing domestic walls, the surface being skimmed manually before setting. The drawing shows a rock wall 14 lined with a first already gelled layer 15, and a second layer 16 actually being sprayed on.

The method and composition of the invention can be used for the construction, by adding the necessary layers, in turn, of tunnel linings, embankment shoring walls, linings of dams and reservoirs and other water retaining structure, the building of domestic and commercial premises, construction of firewalls in mines.

In a lightweight form, a skin of the composition can provide effective thermal insulation of pipes, e.g. pipes connecting radiators to a boiler, and conversion insulation of steelwork for whatever purpose, and its insulating properties lend themselves to use in building houses because also of its load bearing strength.

The mix becomes thixotropic within two minutes and achieves an initial set in 15 minutes, a final set is achieved in about one hour.

This composition and method can be used for lining tunnels and shoring-up partially collapsed workings, since a 4 inch thick concrete wall can be produced in a very short time.

WHAT I CLAIM IS: 1. A cementitious composition which is sprayable on addition of water comprising a major amount by weight of a pulverulent mixture of cement and fly ash, the balance of the composition comprising chopped fibres, an accelerator, a thixotropic agent and a plasticiser.

2. A composition according to claim 1 wherein said accelerator is anhydrous sodium silicate.

3. A composition according to any preceding claim comprising one part by weight of cement to two parts by weight of fly ash, 0.5 to 2.5% by weight of chopped fine fibers, 0.5 to 3.00 mm in length, and not more than 1 mm thick, and 1 to 2.5% by weight of sodium silicate.

4. A composition according to either claim 1 or 2, having the following compositions: Parts by Ingredient weight Cement powder 60 Fly ash 130 Chopped fibres 2 Sodium silicate 3 Plasticiser 4 Thixotropic reagent 5. A composition according to claim 1 comprising a mixture of Portland or Sulphate cement, pulverised fly ash, oven dried sand, pulverised light weight aggregate, chopped polypropylene fibers, one or more plasticizers, a thixotropic agent, one or more organic polymeric materials, an accelerator, and a water proofing agent.

6. A method of building up a structure by pumping a dry composition according to any of claims 1 to 5 to a spray orifice, adding water to the composition at the orifice and spraying the resultant mixture in a plurality of successive layers.

7. A tunnel lining when built up by the method of claim 6.

8. A method according to claim 6 of building up a structure when in the form of a tunnel lining substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

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Claims

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should be i to 1 inch in length and of up to I mm diameter.

The silicate and plasticizer reacts with the cement to accelerate gelling of the cementitious mix when water has been added thereto.

Spraying the mixture as illustrated in the accompanying drawing, which is a cross section of a tunnel or mine gallery showing spraying in progress. The mixture described above is pumped pneumatically by a pump

10 from a reservoir 11 to a nozzle 12 and the mix is mixed with water in the nozzle to form a spray 13 of droplets of cementitious slurry. The mixture can then be sprayed in passes of up to 2 inches thick with mesh reinforcement being laid before spraying, for lining of tunnels etc., and can be used up to + inch thickness for finishing domestic walls, the surface being skimmed manually before setting. The drawing shows a rock wall 14 lined with a first already gelled layer 15, and a second layer 16 actually being sprayed on.

The method and composition of the invention can be used for the construction, by adding the necessary layers, in turn, of tunnel linings, embankment shoring walls, linings of dams and reservoirs and other water retaining structure, the building of domestic and commercial premises, construction of firewalls in mines.

In a lightweight form, a skin of the composition can provide effective thermal insulation of pipes, e.g. pipes connecting radiators to a boiler, and conversion insulation of steelwork for whatever purpose, and its insulating properties lend themselves to use in building houses because also of its load bearing strength.

The mix becomes thixotropic within two minutes and achieves an initial set in 15 minutes, a final set is achieved in about one hour.

This composition and method can be used for lining tunnels and shoring-up partially collapsed workings, since a 4 inch thick concrete wall can be produced in a very short time.

WHAT I CLAIM IS: 1. A cementitious composition which is sprayable on addition of water comprising a major amount by weight of a pulverulent mixture of cement and fly ash, the balance of the composition comprising chopped fibres, an accelerator, a thixotropic agent and a plasticiser.
2. A composition according to claim 1 wherein said accelerator is anhydrous sodium silicate.
3. A composition according to any preceding claim comprising one part by weight of cement to two parts by weight of fly ash, 0.5 to 2.5% by weight of chopped fine fibers, 0.5 to 3.00 mm in length, and not more than 1 mm thick, and 1 to 2.5% by weight of sodium silicate.
4. A composition according to either claim 1 or 2, having the following compositions: Parts by Ingredient weight Cement powder 60 Fly ash 130 Chopped fibres 2 Sodium silicate 3 Plasticiser 4 Thixotropic reagent
5. A composition according to claim 1 comprising a mixture of Portland or Sulphate cement, pulverised fly ash, oven dried sand, pulverised light weight aggregate, chopped polypropylene fibers, one or more plasticizers, a thixotropic agent, one or more organic polymeric materials, an accelerator, and a water proofing agent.
6. A method of building up a structure by pumping a dry composition according to any of claims 1 to 5 to a spray orifice, adding water to the composition at the orifice and spraying the resultant mixture in a plurality of successive layers.
7. A tunnel lining when built up by the method of claim 6.
8. A method according to claim 6 of building up a structure when in the form of a tunnel lining substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.