GB2166427A

GB2166427A - Composition - silicate bound pumice, pulverised fuel ash, light expanded clay aggregates, cintered clay, furnace bottom ash, sand and or aerated concrete

Info

Publication number: GB2166427A
Application number: GB8428075A
Authority: GB
Inventors: Kenneth Mckenzie Brown
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-11-06
Filing date: 1984-11-06
Publication date: 1986-05-08
Also published as: GB8428075D0; GB2166427B

Abstract

A composite material, bonding light weight aggregates with the alkali metal silicates such as those of sodium and potassium and alkaline earth metal silicates such as those of magnesium and calcium, having a mean weight ratio of silica to alkali metal oxide or alkaline earth metal oxide of 4:1 to 1:1 with varying densities, either as soluble glass, powder, solution, and/or clay loaded solutions produces bonding of a variety of aggregates from fine to large aggregates, either separately or in a variety of combinations of both aggregate sizes and materials, wholly or partly substituting cement and/or lime as the bonding agent. The aggregates may be mixed dry in a mechanical mixer to which the desired quantities of silicate/s and water are added together with fluorosilicate if required. The material can be cast into moulds and may be vibrated or compressed, or alternatively extruded. The material can, when sufficiently set, be kiln, or autoclave cured.

Description

SPECIFICATION Composition - pumice, P.F.A., L.E.C.A., C.C., F.B.A., sand and A.C.

This invention relates to a composite material, bonding lightweight aggregates with the alkali metal silicates such as those of Sodium and Potassium and Alkaline earth metal silicates such as those of Magnesium and Calcium, having a mean weight ratio of Silica to Alkali Metal Oxide or Alkaline earth metal oxide of 4:1 to 1:1 with varying densities, either as soluble glass, powder, solution and clay loaded solutions.

The intention of this invention is that the silicates produce good bonding of a variety of known lightweight aggregates, from fines or powders to large aggregates of pumice, pulverised fuel ash, light expanded clay aggregates, cintered clay, furnace bottom ash, sand and aerated concrete, either separately, or in a variety of combinations of both aggregate sizes and materials, either wholly or partly substituting cement and/or lime as the bonding agent.

In accordance with the present invention a method of making the material comprises of mixing 6.0 kgs of 6-15mm aggregate pumice and 4.0 kgs of pumice powder, mixed dry in a mechanical mixer, to which 1.5 litres of 39.7% Sodium Silicate solution with a weight ratio SIO2/NA2O of 3:2:1 is added and mixed until the desired consistency is attained at which stage 100 grams of Sodium Fluorosilicate is added together with 100 grams of water. Some additional water may be required depending on the initial water content of the aggregates. The material can then be put into moulds, which may be vibrated or compressed. Alternatively the material can be extruded.

The methods of curing the material are diverse and will depend on the desired finished product characteristics. Bonding starts with air drying to ambient temperature, with the displacement of moisture, which is assisted by the Sodium Fluorosilicate in the mix. Bonding can at this stage be considered satisfactory for limited applications, however, a stronger bond results if additional or alternative curing methods are employed. Additional drying, removal of moisture by raising the temperature of the material to 100 C will improve the bond, as will the kiln firing time.When all moisture has been removed, normally at least one hour at 100"C, the temperature is then raised to at least 350"C, the Silica in the material then starts to flow more readily (approximately 350 C is considered to be the flux temperature for this material). A 10%-15% allowance on this temperature should be made (385 C-400 C) to be certain that flux point is reached, and to ensure that a good bond is achieved. Some additional firing at more elevated temperatures may be desirable for more specialised applications.

An alternative method of curing would be by steam autoclave on similar lines to the previously mentioned method, either in part or as a complete curing method.

An additional method of curing would be by Carbon Dioxide (CO2) gas curing, either in or out of moulds by way of probe gassing, hood gassing, through pattern gassing or vacuum gassing. Either method will result in a reaction which while not fully understood is thought to arise in part by the silica film surface reactions with the carbon dioxide to form a hydrated silica gel membrane and partly by loss of water from the underlying silicate in the gas stream from the silica coated aggregates.

These effects cause a rapid increase in the viscosity of the silicates, forming a substantially glass like bond. This CO2 method of curing is most advantageous for in mould curing, and can be considered a completed process, or alternatively some additional curing may be desirable dependant upon application, and/or production method.

Additives, plasticisers, aeration agents, pigments or/and dyes, can be used in the mixes as described, as desirable.

A variety of facing finishes are attainable from this mixed product either at the moulding stage or after curing. The material can be cut, drilled, shaped or dressed and lends itself well to numerous process or production face finishes. Having good compressive strengths for its density, with a good degree of thermal insulation and fire resistance. With low water retention, expansion and contraction, and dry shrinkage, making the material suitable for a variety of possible uses such as building blocks, bricks, roof, floor and wall tiles, paving, wall, roof and floor slabs, refractories, crucible linings, moulds, vessels, monuments, ornaments, ceramics, columns and beams.

1. A composite material containing pumice, pulverised fuel ash, light expanded clay aggregates, cintered clay, furnace bottom ash, sand or aerated concrete either separately or in a variety of combinations of materials, and at least one of the alkali metal silicates such as those of sodium and potassium.

2. A composite material containing pumice, pulverised fuel ash, light expanded clay aggregates, cintered clay, furnace bottom ash, sand or aerated concrete either separately or in a variety of combinations of materials, and at least one of alkaline earth metal silicates such as those of magnesium and calcium.

3. A composite material containing pumice, pulverised fuel ash, light expanded clay aggregates, cintered clay, furnace bottom ash, sand or aerated concrete either separately or in a variety of combinations of materials, and at least one of the alkali metal silicates such as those of sodium and potassium and at least one of the alkaline earth metal silicates such as those of magnesium and calcium.

4. As claimed in claims 1-3 whereby the silicate in the composition has a weight ratio of silica to alkali metal oxide or alkaline earth metal oxide of 4:1 to 1:1.

5. As claimed in claims 1-4 whereby the silica

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Composition - pumice, P.F.A., L.E.C.A., C.C., F.B.A., sand and A.C. This invention relates to a composite material, bonding lightweight aggregates with the alkali metal silicates such as those of Sodium and Potassium and Alkaline earth metal silicates such as those of Magnesium and Calcium, having a mean weight ratio of Silica to Alkali Metal Oxide or Alkaline earth metal oxide of 4:1 to 1:1 with varying densities, either as soluble glass, powder, solution and clay loaded solutions. The intention of this invention is that the silicates produce good bonding of a variety of known lightweight aggregates, from fines or powders to large aggregates of pumice, pulverised fuel ash, light expanded clay aggregates, cintered clay, furnace bottom ash, sand and aerated concrete, either separately, or in a variety of combinations of both aggregate sizes and materials, either wholly or partly substituting cement and/or lime as the bonding agent. In accordance with the present invention a method of making the material comprises of mixing 6.0 kgs of 6-15mm aggregate pumice and 4.0 kgs of pumice powder, mixed dry in a mechanical mixer, to which 1.5 litres of 39.7% Sodium Silicate solution with a weight ratio SIO2/NA2O of 3:2:1 is added and mixed until the desired consistency is attained at which stage 100 grams of Sodium Fluorosilicate is added together with 100 grams of water. Some additional water may be required depending on the initial water content of the aggregates. The material can then be put into moulds, which may be vibrated or compressed. Alternatively the material can be extruded. The methods of curing the material are diverse and will depend on the desired finished product characteristics. Bonding starts with air drying to ambient temperature, with the displacement of moisture, which is assisted by the Sodium Fluorosilicate in the mix. Bonding can at this stage be considered satisfactory for limited applications, however, a stronger bond results if additional or alternative curing methods are employed. Additional drying, removal of moisture by raising the temperature of the material to 100 C will improve the bond, as will the kiln firing time.When all moisture has been removed, normally at least one hour at 100"C, the temperature is then raised to at least 350"C, the Silica in the material then starts to flow more readily (approximately 350 C is considered to be the flux temperature for this material). A 10%-15% allowance on this temperature should be made (385 C-400 C) to be certain that flux point is reached, and to ensure that a good bond is achieved. Some additional firing at more elevated temperatures may be desirable for more specialised applications. An alternative method of curing would be by steam autoclave on similar lines to the previously mentioned method, either in part or as a complete curing method. An additional method of curing would be by Carbon Dioxide (CO2) gas curing, either in or out of moulds by way of probe gassing, hood gassing, through pattern gassing or vacuum gassing. Either method will result in a reaction which while not fully understood is thought to arise in part by the silica film surface reactions with the carbon dioxide to form a hydrated silica gel membrane and partly by loss of water from the underlying silicate in the gas stream from the silica coated aggregates. These effects cause a rapid increase in the viscosity of the silicates, forming a substantially glass like bond. This CO2 method of curing is most advantageous for in mould curing, and can be considered a completed process, or alternatively some additional curing may be desirable dependant upon application, and/or production method. Additives, plasticisers, aeration agents, pigments or/and dyes, can be used in the mixes as described, as desirable. A variety of facing finishes are attainable from this mixed product either at the moulding stage or after curing. The material can be cut, drilled, shaped or dressed and lends itself well to numerous process or production face finishes. Having good compressive strengths for its density, with a good degree of thermal insulation and fire resistance. With low water retention, expansion and contraction, and dry shrinkage, making the material suitable for a variety of possible uses such as building blocks, bricks, roof, floor and wall tiles, paving, wall, roof and floor slabs, refractories, crucible linings, moulds, vessels, monuments, ornaments, ceramics, columns and beams. CLAIMS

5. As claimed in claims 1-4 whereby the silica may be in the form of either soluble glass, powder, solutions, and clay loaded solutions.

6. As claimed in any preceeding claim wherein the compositions may contain fluorosilicate.

7. A composition as claimed in any preceeding claim whereby the material is set by air drying at ambient temperature.

8. A composition as claimed in any preceeding claim whereby the material is set by the introduction of carbon dioxide (CO2) gas to the silicates.

9. A composite material as claimed in any preceeding claim whereby curing is by raising the temperature to 100"C either by kiln or autoclave heat treatment.

10. A composite material as claimed in any preceeding claim whereby the temperature of the material is raised to at least 350"C-4000C either by kiln or autoclave heat treatment.

11. A composite material as claimed in any preceeding claim whereby the temperature of the material is raised to between 400 C-1000 C either by kiln or autoclave heat treatment.

12. A composite material as claimed in any preceeding claim whereby the temperature of the material is raised to between 1000 C-2000 C either by kiln or autoclave heat treatment.

13. A composite material substantially as described herein, according to any of claims 1-12.