IE52589B1 - Process for the manufacture of a surface for sports centres,in particular tennis courts - Google Patents

Abstract

The covering layer of the coating comprises brick dust and finely divided mineral aggregates, particularly coarse siliceous sand, which are bound by a hydraulic mortar, such as a mortar used particularly for paving. For the preparation, the brick dust, the mineral aggregates and the solid components of said mortar are dry mixed and the dry mixture is applied to the prepared background, is levelled and pressed, for example by means of rollers. Then, it is sprayed with water to wet uniformly the pressed layer of the mixture. The mortar contains cement, sand and/or calcareous rock, methylcellulose and, as desired, vinyle chloride and vinyle propionate copolymer, polycondensate of melamine-formaldehyde, polyacrylic amide, trass and/or a fibrous material, preferably asbestos.

Description

This invention relates to a process for the manufacture of a surface for sports centres, particularly tennis courts, in which process brick dust, mineral material and tile cement, viz, hydraulic-setting thin-bed mortar according to DIN 18156 - Part 1 in its version of April 1977, Part 2 in its version of March 1978, is applied to a prepared foundation.

Published DE-A-31 11 128.9 of the 20th March, 1981, claims a surface for sports centres, particularly tennis courts, and the manufacture thereof. The top layer of that surface is formed of a setting mass substantially consisting of brick dust, mineral material and inorganic binder. The setting mass is a doughy, aqueous paste, which contains as binder a tile cement; viz. a hydraulic-setting thin-bed mortar according to DIN 18156. In accordance with process for manufacturing the surface a doughy paste composed of tile cement, brick dust and mineral material, preferably quartz sand, in water is applied to a prepared foundation with a substantially flat surface.

The invention according to the said·· DE-A20 31 11 128.9 originates with the inventor of the invention of the present Application. The said DE-A-31 ll 128.9 is referred to in the present Application, so far as necessary for explanation and understanding of the present invention.

According to the said prior proposal, the components of the - 3 surface are applied to the prepared foundation in the form of an aqueous paste, and set there. The prepared paste should have a porridge-like consistency with a relatively small water content, so that after setting has taken place, the surface is reliably permeable to water. The preparation of a usable paste involves some difficulties since on contact of the tile cement with moist brick dust caking can occur, and the high viscosity of the paste being formed requires large forces to achieve uniform mixing of all components.

When the prepared aqueous paste is being transported to the prepared foundation the danger exists that the previously leveled foundation surface will be disturbed by wheel impressions or the like. After setting, the layer formed from the aqueous paste exibits a smooth, dense surface, comparable to the surface of cement that has set. This surface must be mechanically roughened in a special operating step before it can be used as a tennis court or the like.

It is an object of the present invention to provide a process for the manufacture of a surface for sports centres, particular20 ly tennis courts, which surface possesses the advantages set out in the German DE-A-31 11 128.9, while avoiding the disadvantages associated with the preparation and application of an aqueous paste of the components of the surface. In particular, the invention seeks to facilitate the Application to the prepared foundation, to increase the water permeability of the finished surface and/or to eliminate the need for mechanically roughening the surface after it has set.

Accordingly, the invention provides a process for the man30 ufacture of a surface for playing areas of sports centres, particularly tennis courts, which process comprises: (a) applying a dry-mixed aggregate of brick dust, mineral material and tile cement onto a prepared foundation; (b) levelling and compacting the aggregate; and (c) spraying water upon the compacted aggregate so as to 5 moisten it uniformly, wherein the tile cement is a hydraulic-setting thin-bed mortar according to DIN 18156 - Part 1 in its version of April 1977, Part 2 in its version of March 1978.

Advantageous embodiments of the process according to the invention relates to the choice of tile cement and mineral material, the composition of the dry-mixed aggregate, the order of addition of the components in the preparation of the aggregate, the Application of the aggregate to the foundation surface and the preferably repeated spraying of the compacted aggregate with very fine droplets of water, as set out in the dependent claims.

Thus, according to the process of the invention, a surface for sports centres, particularly tennis courts,is obtained, which comprises a brick dust-containing cover layer upon a mainly conventional foundation, for example upon a foundation with the typical sequence of layers of a tennis court according to DIN 18035 page 5; in such a case the dry-mixed aggregate is applied to the dynamic layer of a foundation of the type described, in order to produce a surface for a tennis court.

Apart from brick dust, the surface must contain hard, preferably rounded particles of inert material, for example particles of quartz sand. A further and particularly inportant difference from conventional brick dust-containing cover layers - 5 is that in the process according to the invention a set layer is obtained, in which tile cement serves as a specialised additional binder. Surprisingly, it has been found that in carrying out the process according to the invention there is avoided the formation of a hard, pavement-like or concretelike cover layer, and instead, after the prescribed addition of water, a loosely bound mass is obtained from the drymixed and compacted aggregate after the setting reaction has taken place. It seems obvious that the clay minerals of the brick dust take part in the setting process caused by the tile cement.

In accordance with the process of the invention, on the one hand the solidity of the brick dust layer can be considerably increased, so that a greater resistance to wear is obtained; on the other hand the value of the sliding characteristic, determined for example as static or sliding friction of the court surface under a specific load, can be adjusted over a wide range by the selected choice of the proportion of the components of the surface layer. In spite of the increased strength, the sliding characteristic in particular of wellknown brick dust top layers can be maintained. In addition, the sliding characteristic can be adjusted to definite values for selected requirements. Finally, by selecting certain thichnesses, the degree of softness of the top layer can be influenced for a given composition.

The process according to the invention produces a top layer of unusually high resistance to wear, so that even after many hours of tennis playing practically no maintenance work and/or service are required. The top layer is frost proof, so that when combined with a winter-proof foundation no special renovation work is needed after the winter break.

The top layer made in accordance with the invention, is shown to be resistant to water, but it is water permeable to the required degree; i.e. after a fall of rain superfluous quantities of water are conducted rapidly, i.e. within a few minutes, through the porous top layer to the foundation, which conducts them away. Even during considerable, prolonged dry periods, the surface particles of the top layer do not become loose, so that no noticeable dust formation occurs.

Xn this way, the surface according to the invention permits playing, largely independent of weather, without additional measures, such as the conventional sweeping, rolling and/or watering. Since the formation of dust is quite considerably reduced, the surface made in accordance with the invention can also be provided as a floor layer in indoor tennis courts and the like.

Finally, the top layer in accordance with the invention can be very easily repaired,-by simply applying freshly prepared aggregate onto the worn locations, and carefully spraying it with water thereafter. The newly applied material sets and adheres to the existing surface material even in very thin layers, without the necessity of additional measures.

The following description gives details of the process according to the invention in relation to the preparation of a top layer for tennis courts. The important components for preparing such a top layer are brick dust, tile cement and quartz sand.

The brick dust used is the well known, commercially available product, which is widely used for the preparation of the top layer in known tennis courts. Preferably brick dust of grade 0/3 is used, i.e. a material the mean particle diameter of which is not substantially greater than 3 mm. - 7 Tile cement is also a known, commercially available product, which is designated hydraulic-setting thin-bed mortar by the trade (See DIN 18156, parts 1 and 2). Hydraulic hardening thin-bed mortars of this kind are powdery mixtures of hydraulic binders, mineral additives (not exceeding 0.5 mm particle size) and organic additives. Within the scope of the invention the tile cements used are preferably those which satisfy the requirements for thin-bed mortar of DIN 18156-M (compare DIN 18156, part 2). In the present case, as distinct from the usual working-up of tile cement, the dry tile cement powder is carefully mixed with further solid substances, and the mixture obtained is uniformly moistened with water.

The composition of such tile cements is known. For example, German Patent Specification 1 158 430 discloses the use of a mortar which, when dry, contains 24.8 to 89.9 % of Portland cement by weight,0.2 to 6.5 % methyl cellulose by weight having a viscosity between 10 and 7000 cP, measured in a 2% aqueous solution, and about 10 to 75% additives such as sand or ground limestone, and to which, in use, about 10 to 40% of water is admixed, so that the viscosity of the aqueous phase of the mixture amounts to at least 500 cP, for laying flagstones and tiles. The surface to be tiled is covered with a layer of mortar, and the tiles are pressed dry into the latter. U.S. Patent Specification 2 934 932 gives a range of exemplary tile cement compositions which are usable for the present purpose. From German Patent Specification 1 646 493 a bedding mortar is known which contains, apart from cement and graded sand, 0.1 to 1.5 % methyl cellulose by weight and 1.0 to 10 % by weight of an interpolymer of to 80 % by weight vinyl chloride and 80 to 20 % by weight vinyl propionate. In addition, this bedding mortar can also contain 5 to 25 % by weight of trass. Moreover, German 2589 Auslegeschrift 2 146 709 describes the use of a mortar mixture for laying flagstones and tiles in the thin-bed process, consisting of 25 to 85 % by weight of cement, 0.05 to 0.15 % by weight methyl cellulose of viscosity 1000 to 3000 cP measured in a 2% aqueous solution, 1.5 to 6 % by weight of sulfonic acid group-containing Melamine Formaldehyde condensation product having a viscosity of 40 to 500 cP, measured in a 20% aqueous solution, 0.02 to 0.1 % by weight of water soluble, non-ionic polyacrylamide, in each case based on the total weight of the dry mixture, the remainder being sand and/or ground limestone. This mortar mixture can additionally contain 0.5 to 5 % by weight of asbestos fibres.

The contents of these printed works are also to be regarded as part of the present Application, insofar as they concern the composition of tile cement i.e. hydraulic-setting thinbed mortar in the sense of DIN 18156, part 1 and part 2.

According to these printed works such tile cements consist essentially of about 24.8 to 89.8 % by weight of cement, about 10 to 75 % by weight of additives such as sand and/or ground limestone and about 0.2 to 6.5 % by weight of methyl cellulose, and can additionally contain other chosen components, namely up to 10 % by weight of an interpolymer of vinyl chloride and vinyl propionate, up to 6 % by weight of melamine formaldehyde condensation product, up to 0.1 % by weight of polyacrylamide, up to 25 % by weight of trass and/or up to 5 % by weight of fibrous material, preferably asbestos. As examples, the following cements may be mentioned: Portland cement, Portland slag cement, lime slag cement, iron ore cement, Puzzolan cement and the like. The following compositions have proved particularly suitable for the present purpose: - 9 52588 Tile cement I with 48% by weight Portland cement PZ 55 F 45% by weight washed, firerdried Quartz sand 0.1 - 0.6 mm 5 4.2% by weight dispersible powdered polymeride on the basis of Vinyl chloride/vinyl propionate 2.5% by weight Methyl cellulose (degree of substitution 30% methoxyl; viscosity 10 000 mPas for 10 a 20% aqueous solution according to Brookfield at 20°C and 20 rpm). 0.3% by weight Tile cement II with Calcium oxalate. 47% by weight blast-furnace cement HOZ 35 L 15 48% by weight washed, fire-dried quartz sand 0.2 to 0.6 mm 2.5% by weight Methyl hydroxyethyl cellulose (degree of substitution 25 % methoxyl, 10 % Ethylene glycol ether; viscosity; 20 20 000 ntPas for a 2% aqueous solution according to Brookfield at 20°C and 20 rpm) 2.0 % by weight cellulose fibres, diameter: approximately 30 urn, length approximately 300 um 0.5 % by weight Calcium chloride. 89 - 10 The quartz sand used is that commonly used in the building industry with the quality grade coarse; such quartz sand has an average particle size of up to 0.7 mm. The designation quartz sand is to include, apart from finely ground silicon dioxide, other fine-grain, inert mineral substances also, as well as mixtures of silicon dioxide with such mineral substances.

Sofar as desired, further additives can be provided along with the given essential components, such as dyes, fungicidal, bactericidal or herbicidal agents and other known additives.

The hardness and cohesion of the top layer obtained by the process of the invention, as well as the sliding behaviour at the surface of this top layer, can be adjusted over a wide range by the appropriate choice of the proportions of the named components. The desired sliding behaviour cannot be achieved without a minimum proportion of quartz sand, especially in wet conditions. With the prescribed proportions of brick dust and quartz sand, an increase in the proportion of tile cement leads to an increase in hardness and an incease in the coefficients of static friction and sliding friction. These coefficients of friction can be used as a criterion for the sliding behaviour. To determine these coefficients of friction, a test object (10cm lcng, 5an wide, 0.5cm thick) of smooth shoe-sole rubber is advanced over the surface to be tested under a load of 150 N with a speed which begins at 0 and finally reaches 3 cm/sec. The necessary tensile forces are measured with a dynamometer, and the coefficient of friction is obtained by means of the formula: coefficient of friction = tensile force/load The coefficient of static friction relates to the force necessary to bring the test object into motion; the coefficient - 11 of sliding friction corresponds to the necessary force at a speed of 3 cm/sec. Under these conditions coefficients of friction, static and sliding, were determined for known brick dust surfaces in the range of about 2.7 to 3.0. Coefficients of friction in this range can be achieved also in top layers made according to the invention, by appropriate choice of the proportions of the various components. With the prescribed proportions of brick dust and tile cement, raising the proportion of quartz sand leads to a lowering of these coefficients of friction, resulting in a promotion of sliding on the top layer surface.

To prepare a top layer suitable especially for a tennis court surface, 100 parts by volume of brick dust can be mixed with 10 to 90 parts by volume of quartz sand and 20 to 60 parts by volume of tile cement. (Working with parts by volume has proved itself well in practice, since in this way the effects of the widely fluctuating moisture content of the brick dust, which in practice is difficult to estimate, are eliminated to a great extent). Preferably for the preparation of a drymixed aggregate, 100 parts by volume of brick dust are mixed with 20 to 60 parts by volume of quartz sand and 35 to 55 parts by volume of tile cement. The tile cement used in this case has the composition given above as tile cement I or tile cement II", and this did not lead to any differences in the proporties of the top layer worth mentioning.

Thanks to the great solidity of the top layer prepared in accordance with the invention, the surface can be created on the prepared foundation in a relatively thin layer. The minimum layer thickness is determined by the intended length of life of the surface. In this connection the minimum layer thickness of the finished set surface should be 10 mm, or at the very least 5 mm. A maximum value for the thickness - 12 of the layer arises from the observation that as the thickness is increased the top layer becomes increasingly soft; for this reason the thickness of the layer should not exceed 35 mm, and certainly not more than 30 mm. With greater layer thicknesses the possibility of cracking and a reduction in the water permeability must be expected.

Layer thicknesses between 15 and 25 mm have proved themselves well, and a layer thickness of about 20 nun is particularly preferred. In the process according to the invention the previously dry-mixed aggregate is applied in the dry condition to the prepared foundation, smoothed flat and compacted. Compaction reduces the thickness of the layer, so that the loose dry aggregate must be applied to a greater layer thickness in order to yield a surface with the above specified layer thicknesses after compaction and setting.

In general, the thickness of the layer of loose, unbound aggregate diminishes by about 15 to 20 % by reason of compaction and setting, so that the dry, loose aggregate must be applied to the prepared foundation in a correspondingly thicker layer in order to obtain the above mentioned layer thicknesses in the finished surface.

For many applications a satisfactory surface layer is obtained if the surface according to the process of the invention is generated upon a level, solid, dry and water-pervious found25 ation. Such a foundation can by constituted by the natural, available ground, or it may be specially prepared. The typical layer sequence for tennis courts, comprising a filter layer, a bearing layer and a dynamic layer according to Drw 18035, page 5 may be considered especially appropriate as a foundation, and the top layer prepared according to the invention will then serve as the final surface. With reference to DIN 18035, page 5, the contents thereof are referred to in the present Application, so far as necessary for the further description of foundation, filter layer, bearing layer and dynamic layer including the materials, 5358» - 13 particle sizes and requirements of those layers. Furthermore, the process of the invention permits the surface to be made upon a water-permeable, bituminous or cement-bound base, for example on a base in the form of a known hard court. If a given asphalt or concrete layer is to serve as a base, and its water permeability is insufficient, a number of holes may be bored through this layer into the water-absorbing subsoil.

The dry-mixed aggregate prepared from the named components 10 is applied in the dry state to the substantially level surface of the prepared foundation or subsoil. The mixing of the components can take place in conventional apparatus, for example in rotating drums internally equipped with agitating members. For example, the devices commonly used for the preparation of concrete have been found satisfactory, e.g. the known vehicles for simultaneously mixing and transporting ready-mixed concrete. Preferably, the brick dust and the quartz sand are put into the mixing drum or the like first, these two components roughly mixed with each other, by allowing the drum to rotate several times. Thereafter, the powdery, dry tile cement is added, and uniformly dispersed among the other ingredients. In adding the tile cement it is useful to avoid any localized excess of tile cement. So far as possible, the tile cement should be introduced to the prepared mixture of quartz sand and dust while the mixing drum is rotating. After the addition of the tile cement, mixing should be continued for at least 5 minutes, in order to obtain a reliably uniform distribution.

The resulting dry-mixed aggregate is applied to the surface of the foundation in the prescribed layer thickness, then levelled and finally compacted in the dry condition.

Compaction can be carried out with various appliances.

A manually pulled roller has proved suitable, as commonly used for the compaction of tennis courts. Compaction should 52588 - 14 not be taken too far, since afterwards when watering the moisture only penetrates to an unsatisfactory extent into the compacted material. Preferably, the rolling is finished when the layer thickness of the loosely applied and levelled aggregate has been reduced by about 15-20%.

Afterwards, the compacted aggregate layer, still dry, is sprayed with water. In carrying out the spraying, there should be achieved a uniform absorption of moisture through the entire thickness of the layer of the compacted material.

It is advantageous to carry out this with the finest possible drops of water, and to avoid any substantial local excess of water. If too much water is applied to the surface of the compacted layer, the setting reaction takes place relatively quickly in the regions of the top layer close to the surface thereof, which impedes the progress of the moisture into deeper layers. In this way homogeneity of the surface through its entire thickness can be impaired. Good results were obtained, for example, by spraying the compacted surface with the finest possible spray, until the water remained briefly on the surface (before being absorbed). This spraying was repeated after a few minutes, again until the water remained on the surface for a short time, and the procedure was repeated once again.

In a practical test under these conditions, with a compacted layer 25ram thick, approximately 4 to 6 litres of water were applied per square meter.

After the compacted aggregate has been moistened as uniformly as possible, this layer sets through the entire layer thickness within about 12 hours. The court becomes playable after about 2 to 3 days in dry weather. After the layer sets, the surface if necessary can be dressed with very fine brick dust, in order to accelerate the appearance of the typical sliding behaviour of conventional brick dust courts.

I 82589 - 15 The surface prepared by the process of the invention can be used in a very great variety of sports places. This surface is specially suitable and intended for tennis courts. Since, when it is used as a tennis court, there is neither any excessive evolution of dust, nor does it need to be watered as is commonly necessary in conventional brick dust courts, this surface can also be provided in indoor sports areas. Further applications relate to inter alia hard courts for other ball games, long-jump tracks and tracks for running and sprinting.

Claims (15)

1. A process for the manufacture of a surface for playing areas of sports centres, especially tennis courts, which comprises (a) applying a dry-mixed aggregate of brick dust, mineral 5 material and tile cement onto a prepared foundation; (bi levelling and compacting the aggregate; and (c) spraying water upon the compacted aggregate so as to moisten it uniformly, wherein the tile csnent is a hydraulic-setting thin-bed mortar according 10 to DIN 18156 - Part 1 in its version of April 1977, Part 2 in its version of March 1978.

2. A process as claimed in claim 1, wherein the tile cement ccmprises about 24.8 to 89.8% canent by weight, about 10 - 75% by weight of additives such as sand and/or ground limestone, aid about 0.2 15 6.5% by weight methyl cellulose.

3. A process as claimed in claim 2, wherein the tile cement additionally comprises at least one further component selected from an interpolymer of vinyl chloride and vinyl propionate in a proportion not exceeding 10% by weight, a melamine formal20 dehyde condensation product in a proportion not exceeding 6% by weight, polyacrylamide in a proportion not exceeding 0.1% by weight, trass in a proportion not exceeding 25% by weight, and fibrous material in a proportion not exceeding 5% by weight.

4. A process as claimed in claim 3, wherein the fibrous material 25 is asbestos.

5. A process as claimed in ary one of claims 1 to 4, wherein the mineral material is finely divided quartz sand having a mean particle size from 0,01 to 0.7 mm.

6. A process as claimed in any one of claims 1 to 5, wherein 30 the aggregate is prepared from 100 parts by volume of brick dust, 10 to 90 parts by volume of mineral material, and - 17 about 20 to 60 parts by volume of tile cement, dry-mixed together.

7. A process as claimed in claim 6, wherein the mineral material is quartz sand. 5

8. A process as claimed in claim 6 or 7, wherein the aggregate is prepared by dry-mixing 100 parts by volume of brick dust with 20 - 60 parts by volume mineral material, and 35-55 parts by volume of tile cement.

9. A process as claimed in any one of claims 1 to 8, wherein 10 brick dust and mineral material are dry-mixed in a rotating mixing drum or the like, and then the dry powdery tile cement is added and uniformly distributed in the previous mixture by further mixing.

10. A process as claimed in any one of claims 1 to 9, wherein 15 the dry aggregate is applied to the surface of the foundation in a layer thickness of about l5-50mm.

11. A process as claimed in any one of claims 1 to 10, wherein the dry layer of aggregate is compacted by rolling.

12. A process claimed in any one of claims 1 to 11, wherein 20 the compacted layer of aggregate is sprayed with fine water droplets until liquid water remains visible on the surface of the aggregate layer.

13. A process as claimed in claim 12, wherein the spraying with fine water droplets is repeated several times. - 18

14. A surface for playing areas of sports centres, particularly tennis courts, whenever manufactured by a process claimed in any one of claims 1 to 13 or 15.

15. A process according to claim 1, substantially 5 as hereinbefore described.