HK1092128B - Screed comprising recycled glass waste - Google Patents

Description

The present invention relates to a flowing screed, for example an anhydrite or alpha-hemihydrate calcium sulphate based flowing floor screed, a cementitious flowing floor screed or a blended cementitious flowing floor screed comprising recycled waste glass sand for the construction of floating, unbonded and bonded screeds. In addition the invention relates to a method for the production of screeds and a method of the remediation of recycled glass waste via the production of any of the above flowing screed types in either bagged format or through delivery to site in bulk.

Within the context of this specification the word "comprises" is taken to mean "includes, among other things". It is not intended to be construed as "consists of only".

A flowing screed is one which can be pumped or poured and comprises a mixture of cement/s, aggregate/ sand and water, calcium sulphate aggregate/ sand and water applied to a eg concrete slab, insulation board or over underfloor heating etc to give a smooth surface finish. Known screeds of this type are ISOCRETE GYVLON TM supplied by Isocrete, LAFARGE GYVLON and AGILIA SCREED supplied by Lafarge, RMC READY-SCREED SUPAFLO supplied by RMC and TARMAC TRUFLOW supplied by Tarmac.

An ever increasing volume of glass waste is resulting in considerable pressure on available land fill space. In view of this, considerable pressure is being exerted tc clean up environmental problems associated with the disposal of glass and one process that has been developed to reduce this pressure is a process involving the recycling of waste glass. In this recycling process the waste glass is generally subjected to crushing, washing, grading and sieving to provide a glass sand.

The process however suffers from the disadvantage that the residue glass sand must then be disposed of. At present this is achieved by incorporation into tarmac/ashphalt and roadfill sub-base materials. Clearly, other methods of disposal are desirable.

Cementitious compositions comprising calcium sulphate and glass as a pozzolan are known from US 2003/0041783 . Such cementitious compositions require the presence of kaolin as an essential element and are typically used as mortors or concretes.

Calcium sulphate compositions are also known from US2002/0121326 . Such compositions are characterised by their improved adhesion to plastic and metal surfaces due to the presence of (a) one or more water-redispersable polymer powders based on vinyl esters, vinyl aromatic olefino, 1,3-dienes or vinyl halide monomers and (b) one or more alkali metal and for alkaline earth metal salts of short chain fatty acids.

Cementitious compositions comprising gypsum, optical glass production waste in the form of a sand and also an aggregate and optical glass production waste in the form of a pozzolanic glass are known, in RU 2130910 . These compositions are characterised by a high density.

Therefore, a need exists for a process for the remediation of recycled glass waste to produce a product which is environmentally stable. In addition there is a need for a new product comprising recycled glass waste which is environmentally stable.

The present invention addresses or reduces at least one of the problems set out above.

It has now been found that screed production is one possible method of remediation and encapsulation of the waste glass material within an inorganic matrix resulting in an non-contaminating stable product. Advantageously, the process eliminates the need for landfill disposal of the waste glass and reduces the need for mined or quarried natural materials to be used.

A first aspect of the invention provides the use of a composition comprising (i) 15% to 75% by weight of an aggregate of recycled glass waste or a recycled glass waste sand residue; and (ii) 15% to 65% of a calcium sulphate binder selected from at least one of an alpha hemihydrate plaster, a beta hemihydrate plaster, an anhydrate or a combination of two or more thereof; and 10% to 20% by weight of water based on the weight of the composition as a flowable screed.

Preferably an embodiment of the screed according to the invention is a flowing screed which preferably comprises recycled glass waste in the form of an aggregate A flowing screed comprises water in an amount that enables the screed to flow.

An embodiment of a screed according to the invention comprises a recycled glass waste or recycled glass waste sand residue. This provides the advantage that the glass being of a lower specific gravity than conventional sand floats more easily in the flowing floor screed suspension than conventional sands and or aggregates.

Preferably an embodiment of a screed according to the invention additionally comprises a powder binder or slurry preferably comprising at least one of Calcium Sulphate, Portland Cement, High Alumina Cement, Calcium Sulpho-Aluminate

Cement, Silica Fume, Limestone Powder, Pulverised Fuel Ash blast furnace slag or a combination of two or more thereof. More preferably the powder binder comprises Calcium Sulphate. Most preferably the powder binder comprises Calcium Sulphate combined with at least one of water, portland cement, High Alumina Cement, Calcium Sulpho-Aluminate Cement, Silica Fume, Limestone Powder, Pulverised Fuel Ash, blast furnace slag or a combination of two or more thereof. Preferably the Calcium Sulphate is combined with 10% to 90% by weight of at least one of water, portland cement, High Alumina Cement, Calcium Sulpho-Aluminate Cement, Silica Fume, Limestone Powder, Pulverised Fuel Ash, blast furnace slag or a combination of two or more thereof.

The screed comprises 15 to 65%, by weight of the powder binder or slurry.

The calcium sulphate is selected from at least one of alpha hemihydrate, beta hemihydrate, anhydrite or a combination of two or more thereof.

Preferably an embodiment of the screed comprises a cement selected from at least one or more of alpha hemihydrate, beta hemihydrate, anhydrite combined with one or more of Portland Cement, High Alumina Cement, Calcium Sulpho-Aluminate Cement or a combination of two or more thereof.

Preferably, an embodiment of a screed according to the present invention comprises a mixture of alpha hemihydrate, beta hemihydrate, anhydride, High Alumina Cement and Portland Cement.

Preferably, an alternative embodiment of a screed according to the present invention comprises a mixture of Calcium Sulpho-Aluminate Cement and Portland Cement in addition to one or more of alpha hemihydrate, beta hemihydrate and/or anhydrite.

Preferably an embodiment of a screed according to the present invention comprises a limestone powder filler.

Preferably an alternative embodiment of a screed according to the present invention comprises a pulverised fuel ash powder filler.

Preferably an alternative embodiment of a screed according to the present invention comprises a silica fume powder filler.

Preferably, an embodiment of a screed according to the invention comprises a retarder to retard the cement hydration or calcium sulphate set time thereby extending the pot-life of the flowing screed. Preferably the retarder comprises at least one of citric acid, tartaric acid, boric acid, sodium gluconate, Rochelle salt, tri-sodium citrate, sodium tri-polyphosphate, a chelating agent or a combination of two or more thereof.

Preferably, an embodiment of a screed according to the present invention comprises an accelerator to promote hydration of the cement or calcium sulphate materials or for promoting powder binder crystalline formation. Preferably the accelerator comprises at least one of lithium carbonate, sodium carbonate, an alkali earth salt, aluminium sulphate, potassium sulphate, a phosphate salt or a combination of two or more thereof. This provides the advantage that the cements and/or calcium sulphates will hydrate or set rapidly once retardation has ceased.

Preferably, an embodiment of a screed according to the present invention comprises a plasticiser. Preferably the plasticiser comprises at least one of a melamine, lignosulphonate, casein or a combination of two or more thereof which enhance the flow characteristics of the flowing floor screed without having to add excess water. Thus, reduced amounts of water can be used and/or excess water can be avoided.

Preferably, an embodiment of a screed according to the present invention comprises a liquid and/or powdered organic polymers. Preferably the liquid and/or powdered polymers comprise at least one of organic polymers, co-polymers, ter-polymers or a combination of two or more thereof which improve surface abrasion, bond strength to substrates and aggregate and or sand suspension.

In order to assist with understanding the number of components and their amounts in an embodiment of a screed according to the invention, Table 1 below shows the preferred components in tabular form wherein the components in the columns to the left are made up of the components in the column to the right. The % ranges show amount by weight.

Where several components are specified as present in an amount of 0% - 100% by weight, this indicates that that component could be optionally absent or present in an amount of up to 100% by weight. Clearly, a skilled person would appreciate that at least one of the optional components must be present.

In a second aspect the invention provides a method according to claim 14.

Preferably, an embodiment of the method includes the steps of keeping the powder binder or slurry components separate from the glass sand until the screed is required and then mixing the components on site directly before applying the flowing screed to a floor substrate or of first combining the components and mixing them either on site or off site in a bulk ready-mix truck or ready-mix pump truck before applying the flowing screed to a floor substrate surface.

The recycled glass waste used in the present invention is processed by remediation of recycled glass waste which comprises the steps of crushing, washing, sieving and grading of waste glass to produce a sand residue as a component in the production of a flowing screed.

Claims (15)

1. Use of a composition comprising (i) 15 to 75% by weight of an aggregate of recycled glass waste or a recycled glass waste sand residue ; and (ii) 15 to 65% of a calcium sulphate binder selected form at least one of alpha hemihydrate plaster, beta hemihydrate plaster, anhydrite or a combination of two or more thereof ; and 10% to 20% by weight of water based on the weight of the screed as a flowable floor screed.
2. Use according to claim 1, wherein the binder comprises 20% to 100% by weight of a cement.
3. Use according to claim 1 or claim 2, wherein the binder comprises 0 to 80% by weight of a filler.
4. Use according to any one of claims 1 to 3, wherein the binder comprises 0 to 10% by weight of an organic polymer.
5. Use according to any one of the preceding claims, wherein the binder comprises 0 to 5% by weight of a retarder.
6. Use according to any one of the preceding claims, wherein the binder comprises 0 to 5% by weight of an accelerator.
7. Use according to any one of the preceding claims, wherein the binder comprises 0 to 5 % by weight fo a water reducing agent.
8. Use according to any one of claims 2 to 7, wherein the cement comprises, in addition to at least one of the alpha hemihydrate, the beta hemihydrate or the anhydrate, one or more of portland cement, high alumina cement and calcium sulphoaluminate cement.
9. Use according to any one of claims 3 to 8, wherein the filler is selected from one or more of limestone powder, pulverised fuel ash, blast furnace slag, silica fume and hydrated lime.
10. Use according to any one of claims 4 to 9, wherein the organic polymer is a powder or liquid selected from one or more of SBR, Acrylic, vinyl acetate, ethylene, cellulose ethers and gums.
11. Use according to any one of claims 5 to 10 wherein the retarder is selected from one or more of citric acid, boric acid, sodium gluconate, rochelle salt, sodium tri poly-phosphate, tri-sodium citrate, tartaric acid, chelating agent and hydroxy carboxylic acids.
12. Use according to any one of claims 6 to 11, wherein the accelerator is selected from one or more of lithium salts, sodium salts, potassium salts, aluminium salts, phosphate salts and sugars.
13. Use according to any one of claims 7 to 12, wherein the water reducing agent is selected from one or more of melamine, melamine formaldehyde, lingo-sulphonates, caseins, napthalene formaldehyde, sulphonate melamine polycondensate .
14. A method of screeding a floor comprising the steps of mixing the components of the compositions of any one of claim 1 to 13 in the desired amounts before applying to the floor.
15. A method according to claim 14, wherein the components are kept separate until the screed is required and then mixing the components on site directly before applying the flowing screed to a floor substrate or of first combining the components and mixing them either on site or off site in a bulk ready-mix truck before applying the flowing screed to a floor substrate or surface.