GB2152921A

GB2152921A - Cement-based adhesive compositions

Info

Publication number: GB2152921A
Application number: GB08401773A
Authority: GB
Inventors: Alan David Jones; Stephen John Dootson
Original assignee: British Industrial Sand Ltd
Current assignee: British Industrial Sand Ltd
Priority date: 1984-01-24
Filing date: 1984-01-24
Publication date: 1985-08-14
Also published as: GB8401773D0; GB2152921B

Abstract

A cement-based adhesive and pointing mortar composition in dry mix form, comprises a hydraulic cement (15-50 wt%), an aggregate, (50-80 wt%) polyvinyl acetate powder (1-5 wt%) and a high swelling clay in an amount of from 1 to 10% by weight of the composition. The composition is suitable for fixing tiles such as stone facings and brickslips to surfaces such as walls and floors and as a pointing mortar for pointing the tile joints.

Description

SPECIFICATION Improvements in cement based adhesive compositions This invention relates to a cement based adhesive composition which can be used as a fixative for fixing tiles such as stone facing tiles and brickslips to a variety of surfaces. In particular the invention relates to such a composition which can be used as a fixative as aforesaid and as a pointing mortar.

Bedding mortars comprising a mixture of sand, portland cement and water prepared on site can be used to fix tiles such as stone facings and brickslips. The mixture is applied to the back of the tile as a thick layer approximately 6 mm thick after thoroughly soaking the tile and the surface to which it is to be fixed. Polyvinyl acetate liquid emulsion may be added to the bedding mortar to improve the working characteristics of the mortar and increase the adhesion of the tiles to the surface. Proprietory tile adhesives known as hydraulically hardening mortars and consisting of a dry factory prepared mixture of portland cement, sand and an organic additive such as polyvinyl acetate powder and a cellulose derivative, for example, methyl cellulose, methyl hydroxyethyl cellulose or hydroxyethyl cellulose.The cellulose derivatives prevent dewatering of the mortar when in contact with dry tiles or surfaces, and control the hydration of the cement.

Once the tiles are in place, a pointing mortar is then separately prepared and applied across the tile joints.

The pointing mortar generally consist of a mixture of four parts sand to one part cement, although this ratio may be varied. The sand will usually contain a natural amount of a clay-like or silty material which gives the pointing mortar its plasticity or "fattiness" characteristic so as to provide for a satisfactory filling of the joints between the tiles.

The conventional and proprietary beding mortars and tile adhesives described above are unsuitable for use as pointing mortars as they lack this requisite plasticity or "fattiness" characteristic. Furthermore, the combination of polyvinyl acetate and the cellulose derivative in the proprietary adhesives would tend to cause staining of the face of the tiles after drying and hardening of the mortar and the stains would be very difficult to remove, if these adhesives were to be used for pointing.

According to one aspect of the present invention there is provided a cement-based adhesive and pointing mortar composition in dry mix form, comprising a hydraulic cement, an aggregate, polyvinyl acetate powder and a high swelling clay in an amount of from 1 to 10% by weight of the composition.

According to another aspect of the present invention there is provided a cement-based adhesive and pointing mortar, comprising the dry mix composition described above, mixed with a sufficient amount of water to produce a workable material.

The combined adhesive and pointing mortar of the invention can be used both for fixing tiles such as stone facings and brickslips to surfaces such as walls and floors and as a pointing mortar for pointing the tile joints.

Thus, it is not necessary for a separate pointing mortar to be applied to the tiles after bedding; the bedding and pointing may be carried out in one operation.

The polyvinyl acetate improves the adhesion of the tiles to the surface, while the high swelling clay prevents loss of water by absorbtion into the tiles or the surface. The high swelling clay also serves to increase the plasticity and fattiness of the adhesive by acting as a gelling agent. Thus, on fixing tiles to a surface using the adhesive, the adhesive is squeezed out between the tile joints as a gel which can then be smoothed with a trowel to provide pointed joints.

Suitable high swelling clays include high swelling sodium bentonites. A particularly preferred clay is Volclay sodium bentonite commercially available from the American Colloid Company which consists predominantly of montmorillonite. Other swelling sodium bentonites may be used, e.g. Fulbent types, although it has been found that with such clays the water content of the composition becomes more critical.

If non-swelling or low swelling clays are used, tile slip resistance is poor and the pot life of the adhesive is severely reduced.

The hydraulic cement component of the composition may be selected from any suitable conventional cement such as white or grey portland cement and aluminous cement, but is preferably portland cement.

This component is preferably present at 15 to 50% by weight of the composition.

The aggregate material again can be any suitable conventional material, such as sand or perlite, but is desirably sand of a preferred grain size range of 0.15 to 5.0 mm. The aggregate component is preferably present at 50 to 80% by weight of the composition.

The composition preferably comprises fom 1 to 5% by weight polyvinyl acetate.

Suitable polyvinyl acetates include redispersible spray dried vinyl acetate-ethylene copolymers and vinyl acetate-vinyl versanate copolymers, e.g. Vinapol V1080 and Vinapol 1070 commercially available from Vinyl Products Ltd.

To produce a workable material, the dry mix composition must generally be mixed with water at a ratio of one part water to 3.5 to 10 parts by weight of dry mix.

The invention will now be illustrated by the following Example.

Example % by weight white or grey portland cement 23 sand 69 polyvinyl acetate powder 3 sodium bentonite clay 5 The above dry mix composition can be mixed with water to form a combined tile adhesive and pointing mortar which can be used to fix stone facing tiles or brickslips to a surface and point the tiles in one operation.

Claims

1. A cement-based adhesive and pointing mortar composition in dry mix form, comprising a hydraulic cement, an aggretate, polyvinyl acetate powder and a high swelling clay in an amount of from 1 to 10% by weight of the composition.

2. A composition as claimed in Claim 1, in which the hydraulic cement comprises portland cement.

3. A compositon as claimed in Claim 1 or Claim 2, in which the hydraulic cement is present at 15 to 50% by weight of the composition.

4. A composition as claimed in any preceding claim, in which the aggregate comprises sand.

5. A composition as claimed in Claim 4, in which the sand has a grain size of 0.15 to 5.0 mm.

6. A composition as claimed in any preceding claim, in which the aggregate is present at 50 to 80% by weight of the composition.

7. A composition as claimed in any preceding claim, in which the polyvinyl acetate powder is present at from 1 to 5% by weight of the composition.

8. A composition as claimed in any preceding claim, in which the high swelling clay is a sodium bentonite clay.

9. A composition as claimed in Claim 8, in which the high swelling clay is Volclay sodium bentonite clay.

10. A cement-based adhesive and pointing mortar composition in dry mix form, substantially as herein described with reference to the Example.

11. A cement-based adhesive and pointing mortar, comprising the dry mix composition of any one of Claims 1 to 10, mixed with a sufficient amount of water to produce a workable material.

12. An adhesive and mortar as claimed in Claim 11, in which one part by weight of water is mixed with from 3.5 to 10 parts by weight of dry mix composition.