GB2101604A - Hardenable composition - Google Patents

Abstract

The invention provides a hardenable composition comprising from 30% to 75% by volume of aggregate particles, and from 70% to 25% by volume of an epoxy mortar, the composition containing from 5% to 9% by weight of epoxy resin binder and forming, after curing for seven days a product having a compression strength of at least 70 MPa.

Description

SPECIFICATION Hardenable composition Epoxy mortars are fluid or pasty materials consisting of mixtures of epoxy resin glues with particulate materials, such as sand and are well known. For example there is commercially available under the Trade Mark Belzona Molecular Quartz, an epoxy mortar consisting of one part by weight of epoxy resin (base and hardener) and eight parts by weight of particulate material having, the appearance of fine sand. But such materials are, due to the high cost of epoxy glues, too expensive for use as general flooring or structural materials.

British Patent Specification No. 921965 describes articles comprising granite chips and/or powder with epoxy resin binder in a proportion of binder to granite of 1 0-36% by weight. British Patent Specification No. 1140383 describes resin ceramic articles comprising one part by weight of epoxy resin to six to ten parts by weight of ceramic filler.

It has now been found that mixtures of epoxy mortars with controlled amounts of aggregate particles, the mixture containing less epoxy resin than those of the British Patent Specifications noted above, can give rise to hardenable compositions which set to products having high strength, often 50% or more greater than the strength of the epoxy mortar.

The invention provides a hardenable composition comprising from 30% to 75% by volume of aggregate particles, and from 70% to 25% by volume of an epoxy mortar, the composition containing from 5 to 9% by weight of epoxy resin binder and forming, after curing for seven days a product having a compression strength of at least 70 MPa.

In order that the hardened product shall have a high compression strength, it is of course necessary that the aggregate particles should have high strength. Apart from this, and the need for firm bonding to epoxy resins, the nature of the aggregate particles is not critical. Granite aggregate is preferred. But other stone aggregate or glass beads may be used instead.

The aggregate particles preferably have sizes in the range from 0.1 mm (150 British Standard Mesh) to20 mm. The aggregate may be of uniform size, but is preferably a mixture of particles of different sizes, as such mixtures pack better. Fines (material below 300 British Standard Mesh) should preferably be kept below 5% by weight and are ideally absent. The aggregate particles may be of regular or irregular shape.

The epoxy mortar comprises a mixture of an epoxy resin, generally in an amount of 10% to 30% by weight, with particulate material, generally in an amount of 70% to 90% by weight. Resins which are self-curing at ambient temperature, are generally mixtures of a linear epoxy polymer and an acidic or basic cross-linking agent; these have a short pot life and are mixed immediately prior to use. The particulate material preferably has a particle size range of from 0.05 mm to 2 mm (300 to 10 British Standard Mesh). Its nature is not yery critical, and silica sand or ground quartz are suitable, but it should preferably be more finely divided than the aggregate.

The compression strength of the cured product is strongly dependent on the proportion of aggregate to mortar in the composition, compositions with 40% to 50% by volume of aggregate and 60% to 50% by volume of epoxy mortar giving compression strength of 90-100 MPa or even more.

Preferably sufficient epoxy mortar should be used to substantially fill the interstices between the aggregate particles, since a product with air voids is inherently weaker than one without. If the strength of the aggregate is greater than the strength of the cured epoxy mortar (as is generally the case), then a large excess of epoxy mortar (over that necessary to fill the interstices between the aggregate particles) will tend to reduce the overall strength of the cured product. So the amount of epoxy mortar is preferably from 80% to 120% of that necessary to fill the interstices between the aggregate particles.

The compositions are prepared by mixing the ingredients together. While it is possible to mix the aggregate with the particulate material for the mortar and then add the epoxy resin, better results are obtained by forming the mortar by mixing together the epoxy resin and the particulate material, and then mixing the pre-formed mortar with the aggregate. Depending on the amount of epoxy mortar present, the compositions behave like concrete mixes of low to medium workability. Some compositions may be sufficiently workable to be compacted by vibrating the mould or shuttering only and could be used as in standard concrete construction technology. Other compositions may need to be compacted directly by vibrating hammer.

The following Examples illustrate the invention.

MATERIALS 1. Aggregate a) Castle-an-dinas granite aggregate in ; graded mixture of particle sizes fron; 0.1 5mm to20mm.

b) Castle-an-dinas granite aggregate in a single particle size between 5mm and 1 Omm.

2. Mortar 1 part by weight of epoxy resin with 8 parts by weight of fine sand.

METHOD The aggregate and the mortar were mixed together in the required proportions and formed into a 1 00mm cube. The cube was demoulded, compacted with a vibrating hammer, allowed to cure for 3 or 7 days, and tested for compression strength.

The following results were obtained. Proportions are in % by volume.

Aggregate Density Compression Strength Example a) b) Mortar (9 /elm3) (MPa) 1 80 20 2.19 49.4 2 70 30 2.24 74.9 3 60 40 2.33 94.4 4 50 50 2.26 94.5 5 52 48 2.32 108.0 6 100 2.00 36.7 The compositions of Examples2, 3, 4 and 5 in accordance with this invention give products which are stronger than the epoxy mortars used in their preparation, and are also much cheaper by virtue of containing approximately 50% of low cost aggregate.

Claims (11)

1. A hardenable composition comprising from 30% to 75% by volume of aggregate particles, and from 70% to25% by volume of an epoxy mortar, the composition containing from 5 to 9% by weight of epoxy resin binder and forming, after curing for 7 days, a product having a compression strength of at least 70 MPa.

2. A hardenable composition as claimed in claim 1, wherein the aggregate particles are of granite.

3. A hardenable composition as claimed in claim 1 or claim 2, wherein the aggregate particles have sizes in the range from 0.1 mm to20mm.

4. A hardenable composition as claimed in claim 3, wherein the aggregate is a mixture of particles of different sizes.

5. A hardenable composition as claimed in any one of claims 1 to 4, wherein the epoxy mortar comprises a mixture of an epoxy resin in an amount of 10 to 30% by weight with particulate material in an amount of 70 to 90% by weight.

6. A hardenable composition as claimed in claim 5, wherein the particulate material has a particle size range of from 0.05mm to2mm.

7. A hardenable composition as claimed in claim 6, wherein the particulate material of the epoxy mortar is more finely divided than the aggregate.

8. A hardenable composition as claimed in any one of claims 1 to 7, comprising from 40 to 50% by volume of the aggregate particles and from 60 to 50% by volume of the epoxy mortar.

9. A hardenable composition as claimed in any one of claims 1 to 8, wherein the amount of epoxy mortar is from 80 to 120% of that necessary to fill the interstices between the aggregate particles.

10. A hardenable composition as claimed in any one of claims 1 to 9, formed by first mixing together the epoxy resin with the particulate material to form the epoxy mortar, and then mixing the pre-formed epoxy mortar with the aggregate.

11. The product obtained by permitting a hardenable composition as claimed in any one of claims 1 to 10 to harden.