GB2300631A

GB2300631A - Lightweight product; concrete

Info

Publication number: GB2300631A
Application number: GB9609730A
Authority: GB
Inventors: David Michael Beaumont
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-05-10
Filing date: 1996-05-10
Publication date: 1996-11-13
Also published as: GB9509424D0; GB9609730D0

Abstract

Lightweight products particularly lightweight concrete products which are formed from a cement binding agent mixed with a lightweight aggregate include an aggregate which is formed at least in part from a substance capable of being changed from a solid form to a flowable form during curing to produce voids in the product. The substance may be ice or dry ice.

Description

"An ImProved Product" This invention relates to an improved product formed from a binding agent mixed with an aggregate and more particularly, but not exclusively to an improved lightweight concrete product.

It is well known to produce lightweight concrete building products such as, for example, blocks from a lightweight aggregate which is bound together by cement.

The conventional lightweight aggregates used in ash blocks are normally the ashes resulting from the combustion of solid fuels such as coal.

This type of lightweight aggregate has been readily available and comparatively inexpensive, but the reduction in the use of solid fuel for the production of electricity has resulted in shortages and an increase in the cost of bottom ash for making lightweight blocks.

Although other types of lightweight aggregate are known these are usually more expensive than ash and increase the cost of the finished product.

The object of this invention is to produce a relatively low cost lightweight concrete product. An example of such a product would be suitable for use as a building block.

According to one aspect of the invention, a product suitable for use as a lightweight building block comprises a mixture of a bonding agent and an aggregate which are mixed together, formed into the desired shape, and cured; wherein at least part of the aggregate is a substance which is of a solid form during mixing and forming of the product and reverts to a flowable form when the product is cured or is curing.

Preferably, the substance is ice which reverts to water when the product is cured or is curing.

Alternatively, the substance is dry ice which reverts to carbon dioxide gas when the product is cured or is curing.

Preferably, also, the substance is formed into granules or particles prior to introduction into the mix of bonding agent and aggregate.

The granules or particles are, preferably, of spherical or other solid geometrical shape.

Alternatively, the granules or particles may be of a hollow spherical or hollow geometrical shape.

Preferably, the bonding agent is cement which is mixed with water, aggregate and said substance.

According to another aspect of this invention, a method of forming a lightweight product comprises mixing measured quantities of cement, aggregate and water together, forming granules or particles from a substance which is capable of being changed from a solid to a flowable form, adding the granules or particles of the substance to the mix of cement, aggregate and water immediately prior to forming the product therefrom, carrying out additional mixing, forming the product and allowing the product to cure and the substance to change to a flowable form to leave voids in the cured or semi-cured product.

Preferably, the method comprises mixing measured quantities of cement, aggregate and water together, freezing water to form granules or particles of ice, adding the ice to the mix of cement, aggregate and water immediately prior to forming the product therefrom, carrying out additional mixing, forming the product and allowing the product to cure and the ice to melt to leave voids in the cured or semi-cured product.

Alternatively, the method may comprise mixing measured quantities of cement, aggregate and water together, forming granules or particles of dry ice, adding the ice to the mix of cement, aggregate and water immediately prior to forming the product therefrom, carrying out additional mixing, forming the product and allowing the product to cure and the dry ice to change to gaseous form to leave voids in the cured or semi-cured product.

In a preferred embodiment of the invention, a lightweight building block is formed by mixing together quantities of cement, aggregate and water in conventional manner. Typically the ratio of cement to aggregate by weight can vary from 1 to 5, to 1 to 25 according to the type of aggregate used and the strength of concrete required and a typical mixing time is in the region of 45 seconds.

Water is frozen and formed into granules or particles of ice which are used to replace, for example, 25% of the normal volume of the conventional aggregate which can be, for example, sand, crushed limestone, pumice or the like.

The granules or particles of ice can be solid spheres and a diameter of approximately 5 millimetres has been found to be particularly suitable. However, it is envisaged that other solid geometrical shapes or indeed hollow spheres or hollow geometrical shapes could be used.

Immediately prior to pouring the concrete to form the building blocks, the ice is added to the mix which is then mixed again for the minimum time necessary to thoroughly and evenly distribute the ice granules throughout the mix.

In a typical case the additional mixing time after addition of the ice granules is 15 seconds. The mix is then poured from the mixer to form the building blocks by, for example, a conventional moulding process and the cast blocks are then cured.

The size of the granules of ice used is dependent upon the method of and the speed of curing of the blocks so that the ice granules remain solid until at least initial curing and fixing of the product concrete matrix has taken place.

Once this initial curing has taken place, the ice granules melt leaving voids in the product and the major portion of the water content drains from the product during the curing and/or drying of the product. The formation of the voids in the product reduces the final weight of the block and reduces the amount of aggregate which has to be used. It will be appreciated that this reduction in the quantity of conventional aggregate used produces proportional reductions in the overall cost of some types of products.

In a modification substances other than water formed into ice granules can be used providing the substance is capable of being formed into a solid shape and is able to revert into a flowable form during the curing of the product so as to escape therefrom leaving voids in the matrix of the final product. One such additional substance may be dry ice which at normal ambient temperatures reverts to carbon dioxide gas.

Although the foregoing method is particularly suitable for the production of low cost lightweight building blocks, it will be appreciated that it can be used for forming other types of products without departing from the scope of the invention.

Claims

Claims:

1. A product suitable for use as a lightweight building block comprising a mixture of a bonding agent and an aggregate which are mixed together, formed into the desired shape, and cured; wherein at least part of the aggregate is a substance which is of a solid form during mixing and forming of the product and reverts to a flowable form when the product is cured or is curing.

2. A product according to claim 1, wherein the substance is ice which reverts to water when the product is cured.

3. A product accordingto claim 1, wherein the substance is dry ice which reverts to carbon dioxide gas when the product is cured or is curing.

4. A product according to any one of the preceding claims, wherein the substance is formed into granules or particles prior to introduction into the mix of bonding agent and aggregate.

5. A product according to claim 4, wherein the granules or particles are of spherical or other solid geometrical shape.

6. A product according to claim 4, wherein the granules or particles may be of a hollow spherical or hollow geometrical shape.

7. A product according to any one of the preceding claims, wherein the bonding agent is cement which is mixed with water, aggregate and said substance.

8. A method of forming a lightweight product comprising mixing measured quantities of cement, aggregate and water together, forming granules or particles from a substance which is capable of being changed from a solid to a flowable form, adding the granules or particles of the substance to the mix of cement, aggregate and water immediately prior to forming the product therefrom, carrying out additional mixing, forming the product and allowing the product to cure and the substance to change to a flowable form to leave voids in the cured or semi-cured product.

9. A method according to claim 8, comprising mixing measured quantities of cement, aggregate and water together, freezing water to form granules or particles of ice, adding the ice to the mix of cement, aggregate and water immediately prior to forming the product therefrom, carrying out additional mixing, forming the product and allowing the product to cure and the ice to melt to leave voids in the cured or semi-cured product.

10. A method according to claim 8, comprising mixing measured quantities of cement, aggregate and water together, forming granules or particles of dry ice, adding the ice to the mix of cement, aggregate and water immediately prior to forming the product therefrom, carrying out additional mixing, forming the product and allowing the product to cure and the dry ice to change to gaseous form to leave voids in the cured or semi-cured product.

11. A product constructed substantially as hereinbefore described.

12. A method substantially as hereinbefore described.