GB2451120A

GB2451120A - Block paving sand

Info

Publication number: GB2451120A
Application number: GB0714116A
Authority: GB
Inventors: John Thomas Liddy; Paul Andrew Darby
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-07-20
Filing date: 2007-07-20
Publication date: 2009-01-21
Anticipated expiration: 2027-07-20
Also published as: GB0714116D0; GB2451120B

Abstract

A block paving sand which comprises kiln dried sand mixed with a water-soluble polymer, a silicate in the form of powdered or crystalline water glass, and a metal hydroxide in powdered or granulated form. The block paving sand is filled into gaps between blocks and then water is applied thereto. Upon contact with the water, the polymer coats the sand and then sets hard, thereby stabilising the paving block.

Description

IMPROVED BLOCK PAVING SAND

BACKGROUND

The present invention relates to an improved sand for use in block paving applications, clay paviors, slabs and any other products in relation to the laying of paths, driveways, forecourts, patios and the like, or to any similar application where stability is required.

Embodiments of the invention may also find utility for filling gaps between sections of runways and in various other heavy duty civil engineering applications.

When laying block paving, for example as part of a road or driveway, it is known to fill the gaps between adjacent blocks with kiln dried sand so as to provide structural stability to the blocks. However, ordinary kiln dried sand has the disadvantage that it tends to disperse and disappear from between the blocks, especially during wet and windy weather or when the road or driveway is being swept, leaving gaps between the blocks. These gaps eventually result in structural instability, since the blocks then become free to move with respect to each other. Furthermore, the block paved road or driveway becomes unsightly, and weeds may grow in the gaps between the blocks.

Indeed, ordinary kiln dried sand allows weeds to grow between the blocks even when the gaps are filled with the sand.

It is known to provide a polymeric sealant to block paved roads or driveways after laying, which can help to ameliorate these problems, but the application of sealant is time consuming and expensive.

It is also known, for example from US 5,244,304, JP2285103 and JP 10265251, to provide a cementitious material including a polymer component for use in laying paving slabs and the like. These cementitious materials may be used as a base layer or as a jointing compound, but are disadvantageous in that once set, it is extremely difficult to clean up spillages and splashes which can cause staining of the paving slabs and the like. This is because cementitious materials tend to set permanently and cannot thereafter be removed without chipping or other physical force. These materials are also messy and unpleasant to apply, being in a paste-like cementitious form that is wholly unsuited as a jointing compound for block paving and the like.

Other jointing compounds known, for example, from DE 4421970, WO 00/50355 and WO 97/07303, use mixtures of liquid polybutadiene, a flow enhancer and dry particulate material such as sand, crushed glass or fine aggregate. These mixtures are advantageous in that they are relatively easy to handle and do not adhere to paving slabs or the like when spilled thereon. However, the mixtures are designed to set upon exposure to air or oxygen, which can make handling difficult and means that the mixtures require careful storage. Furthermore, flow enhancers generally contain environmentally-unfriendly organic solvents. It will be appreciated that polybutadiene is not a water-soluble polymer.

A coloured asphaltic paving material is known from JP 61254701. This material comprises a resin emulsion, quartz sand pigment, silica asphalt emulsion, a thickening agent and a defoaming agent. This material is used in a manner similar to ordinary asphalt, being spread in fluid form onto a surface (e.g. a tennis court) and allowed to set. It is wholly unsuitable for use as a jointing compound for block paving, being messy to apply and requiring heating.

A block paving sand that solves many of the problems outlined above is known from WO 03/037817 in the names of the present applicants. This block paving sand comprises kiln dried sand mixed with a water-soluble polymer. However, experiments undertaken by the present applicants have shown that there is still some room for improvement.

BRIEF SUMMARY OF THE DISCLOSURE

According to a first aspect of the present invention, there is provided a material for filling gaps between paving blocks or the like, the material comprising dried sand mixed with a water-soluble polymer, at least one silicate in the form of a powdered or crystalline water glass, and a metal hydroxide in powdered or granulated form.

According to a second aspect of the present invention, there is provided a method of stabilising paving blocks or the like comprising a plurality of blocks laid adjacent to each other with gaps therebetween, wherein the gaps are filled with a material comprising dried sand mixed with a water-soluble polymer, at least one silicate in the form of a powdered or crystalline water glass, and a metal hydroxide in powdered or crystalline form, and wherein water is subsequently applied to the material near upper surfaces of the blocks.

According to a third aspect of the present invention, there is provided a material for filling gaps between paving blocks or the like, the material comprising, by weight: 89% dried sand, 6.7% vinyl acetate/ethylene copolymer, 1.8% crystalline sodium silicate, 1.8% calcium hydroxide or aluminium hydroxide, and 0.7% herbicide.

Preferably, the material is a non-cementitious and/or non-asphaltic material. In particular, preferred embodiments of the present invention do not contain Portland cement.

For the avoidance of doubt, the expression "paving blocks or the like" in the context of the present application may encompass block paved roads or driveways or the like, clay paviors, slabs and any other products in relation to the laying of paths, driveways, forecourts (including petrol/gasoline station forecourts), patios, airport runways, roads and other civil engineering applications.

Preferably, the material includes at least 3% by weight water-soluble polymer, and will generally include from 3% to 25% by weight water-soluble polymer. In a particularly preferred embodiment, the material includes from 4% to 10% by weight water-soluble polymer.

The dried sand may be kiln dried, or may be sand that has been allowed to dry naturally in the sun (for example in hot climates).

The water-soluble polymer is preferably dispersed throughout the dried sand as a fine powdered or granulated formulation.

The provision of a water-soluble polymer component in the material means that the application of water to the material once it has been filled into the gaps between adjacent blocks will tend to dissolve at least a part of the polymer component. The polymer solution will then tend to coat the sand particles, causing them to adhere to each other upon drying. Indeed, the water-soluble polymer is preferably chosen so as to cause the material to set solid after being wetted and subsequently dried. Water may be applied by way of a hosepipe or the like, or by way of natural rainfall. The water-soluble polymer component advantageously comprises grains or particles coated with a solubilising agent which, upon contact with water, enhances the solubility of the polymer component in the water. Because the solubilising agent will tend gradually to be washed away from exposed regions of the material subject to repeated rainfall or wetting, the set polymer component in these regions will tend to be relatively insoluble and thus will remain relatively stable, becoming more and more so over time. However, a degree of elastomeric flexibility is retained so as to allow for thermal expansion and mechanical deformation due to heavy vehicles passing over the block paving, and any cracks or defects in the material once laid will tend to be self-healing upon subsequent rainfall or wetting.

Generally, the polymer will only be dissolved in regions close to the tops of the gaps between adjacent blocks where water can penetrate, thereby causing the material to set solid only at and close to the tops of the gaps. This provides room for thermal expansion and contraction of the blocks below the surface of the block paving.

Furthermore, as the top surface of the material is eroded through natural causes, further rainfall or the like will tend to cause newly-exposed areas of the material to harden, thereby extending the life of the block paving.

It is preferred that the polymer is only partially soluble in water under conditions of normal rainfall or application of water through a hosepipe or the like, thereby helping to prevent the material from setting solid below the exposed surfaces.

For the avoidance of doubt, it is emphasised that the material of preferred embodiments of the present invention does not contain Portland cement, at least not in an amount substantial enough to cause the material to set in a cementitious manner, and non-asphaltic (i.e. does not contain asphalt or asphalt-like components). The material is preferably applied in a dry powdered or particulate form, and may thus easily be swept or otherwise applied into interstitial gaps in block paved surfaces or the like. Because the material does not set until water is applied and can safely be exposed to air or oxygen without setting, it is easy to store and handle. Furthermore, even once set, materials of embodiments of the present invention can be resolvated simply through the addition of water, allowing spillages and the like to be cleaned away with relative ease.

Particularly preferred polymers for use with embodiments of the present invention are the ELOTEX� FX2300 range of redispersible binders based on a copolymer of vinyl acetate and ethylene, with polyvinyl alcohol as a protective colloid and mineral anti-block agents, e.g. kaolin, as additives. The FX2320 member of the FX2300 product family has been found to be especially effective.

Alternative polymers suitable for use with the present invention include polyvinyl family polymers such as polyvinyl acetate and vinyl acetate/versatate copolymer (for example that sold under the trade names of RHOXIMAT� PAV 33 or RHOXIMAT� PAV 43), styrene maleic anhydride polymer, styrene butadiene copolymer (with an optional kaolin filler, for example as sold under the trade name of RHOXIMAT� PSB 150), hydroxymethyl cellulose, hydroxyethyl cellulose, poly(2-butenedioic) acid, poly(methoxyethene), acrylics, acrylic copolymers and mixtures thereof. It will be appreciated that other water-soluble polymers may be effective.

The polymer component is preferably mixed in with the other components as a powdered or granulated formulation.

The at least one silicate in the form of a powdered or crystalline water glass may be sodium silicate, potassium silicate, lithium silicate or other appropriate silicate. These silicates or water glasses have the particular property that the powdered or crystalline form is initially highly soluble in water, but then sets as a glassy solid which is much less soluble in water. Moreover, these silicates react and harden to a glassy solid particularly well in acid conditions, for example in slightly acid rain.

The at least one metal hydroxide is preferably calcium hydroxide, most preferably in the form of hydraulic lime, or aluminium hydroxide. It is to be understood that hydraulic lime is distinguished from Portland cement and other cements, and is not considered in the art as a cementitious material.

Hydraulicity is the ability of lime to set under water (i.e. without requiring exposure to air). Hydraulic lime is produced from limestone containing clay and other impurities which enables it to set without exposure to air. It is used for providing a faster initial set in more extreme conditions (including under water). It is understood by the present applicants that approximately 90% of hydraulic lime comprises calcium hydroxide.

There are three classifications of hydraulic limes, as follows: i) Feebly hydraulic lime (NHL2) -less than 12% clay content making it slower to set (about 20 days in water) ii) Moderately hydraulic lime (NHL3.5) -12%-i 8% clay content resulting in a slightly faster set (15-20 days in water) iii) Eminently hydraulic lime (NHL5) -up to 25% clay content providing a fast set (hours/days).

Preferred embodiments of the present invention use moderately hydraulic lime, but feebly or eminently hydraulic lime may be used in some embodiments.

In addition, the material of the present invention may include herbicide and/or fungicide (for example ACTICIDE� EP powder) and/or one or more colorants or dyes.

DETAILED DESCRIPTION

A particularly preferred formulation for the material of the present invention is made up in the following relative proportions: 100kg kiln dried sand; 7.5kg powdered vinyl acetate/ethylene copolymer with mineral anti-block agents and polyvinyl alcohol protective colloid; 2kg sodium silicate; 2kg hydraulic lime; 0.8kg herbicide/fungicide.

This material is intended to be sold and applied in dry granulated or powdered form.

It is to be noted that the present invention is suitable not just for block paving applications, but for any application where blocks or slabs or the like are laid and require interstitial stabilisation.

The preferred features of the invention are applicable to all aspects of the invention and may be used in any possible combination.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", mean "including but not limited to", and are not intended to (and do not) exclude other components, integers, moieties, additives or steps.

Claims

CLAIMS: 1. A material for filling gaps between paving blocks or the like, the material comprising dried sand mixed with a water-soluble polymer, at least one silicate in the form of a powdered or crystalline water glass, and a metal hydroxide in powdered or granulated form.
2. A material as claimed in claim 1, wherein the metal hydroxide is selected from the group consisting of: calcium hydroxide, aluminium hydroxide and mixtures thereof.
3. A material as claimed in claim 1, wherein the metal hydroxide is hydraulic lime.
4. A material as claimed in claim 3, wherein the hydraulic lime has a clay content of 12 to 18% by weight.
5. A material as claimed in claim 3, wherein the hydraulic lime has a clay content of 18 to 25% by weight.
6. A material as claimed in claim 3, wherein the hydraulic lime has a clay content of no more than 12% by weight.
7. A material as claimed in any preceding claim, comprising from 3% to 25% by weight water-soluble polymer.
8. A material as claimed in any preceding claim, comprising from 4% to 10% by weight water-soluble polymer.
9. A material as claimed in any preceding claim, wherein the water-soluble polymer is a polyvinyl family polymer.
10. A material as claimed in any preceding claim, wherein the water-soluble polymer is a vinyl acetate/ethylene copolymer.
11. A material as claimed in any preceding claim, wherein the water-soluble polymer is a vinyl acetate/versatate copolymer.
12. A material as claimed in any one of claims 1 to 9, wherein the water-soluble polymer is polyvinyl acetate.
13. A material as claimed in any one of claims 1 to 8, wherein the water-soluble polymer is selected from a group comprising: styrene maleic anhydride polymer, hydroxymethyl cellulose, hyd roxyethyl cellulose, poly(2-butenedioic) acid, poly(methoxyethene); styrene butadiene copolymer, acrylics, acrylic copolymers and mixtures thereof.
14. A material as claimed in any preceding claim, further comprising a herbicide and/or fungicide.
15. A material as claimed in any preceding claim, wherein the silicate is selected from a group comprising: sodium silicate, potassium silicate, lithium silicate and mixtures thereof.
16. A material as claimed in any preceding claim, further comprising a colorant or dye.
17. A material as claimed in any preceding claim, wherein the dried sand comprises kiln dried sand.
18. A material as claimed in any preceding claim, containing substantially no Portland cement.
19. A material as claimed in claim 1, the material comprising, by weight: 89% dried sand, 6.7% vinyl acetate/ethylene copolymer, 1.8% crystalline sodium silicate, 1.8% calcium hydroxide or aluminium hydroxide, and 0.7% herbicide or fungicide.
20. A material as claimed in any preceding claim, wherein the material is in dry, particulate, free-flowing form.
21. A material for filling gaps between paving blocks or the like substantially as hereinbefore described.
22. A method of stabilising paving blocks or the like comprising a plurality of blocks laid adjacent to each other with gaps therebetween, wherein the gaps are filled with a material as claimed in any preceding claim, and wherein water is subsequently applied to the material near upper surfaces of the blocks.
23. A method of stabilising paving blocks or the like comprising a plurality of blocks laid adjacent to each other with gaps therebetween, substantially as hereinbefore described.
24. Use of a material as claimed in any one of claims 1 to 21 for filling gaps between paving blocks or the like, characterised in that the material is applied to the gaps in dry granulated or particulate form.
25. Use according to claim 24, wherein water is applied to the material after the gaps have been filled.
26. Use of a material as claimed in any one of claims 1 to 21 in the manufacture of a formulation for filling gaps between paving blocks or the like.