AU733668B2 - Surface finish of cementitous nature and containing glass beads - Google Patents

Description

SURFACE FINISH OF CEMENTITIOUS

NATURE

AND CONTAINING GLASS BEADS FIELD OF INVENTION The present invention relates to surface finishes for pathways, walls; swimming pools and other structures and more particularly relates to a surface finish which is of a cementitious nature and which includes least one aggregate type comprising glass beads. More particularly, the invention relates to a mix forming and to a method of producing the finishes.

BACKGROUND OF THE INVENTION In the building industry there has been prolific use of aggregate surfaces for paving footpaths, surfacing of prefabricated building panels and slabs to provide attractive and functional facades and in and around swimming pools and the like. The known aggregate mixes have invariably utilized aggregate materials which include stones, pebbles and the like mixed in a matrix of cementitious material-selected from cement or resin.

The selection of pebbles and stones as the aggregate material usually dictates the appearance of the finish particularly with respect to its color and texture. When resins are used, the aggregate provides the final suface coloration as the cementitious resins '1 are generally clear. An alternative surface coating may be formed by using colored mortar with pebbles and stones.

Despite the use of a wide range of aggregates to produce a variety of surface finishes successfully preparing a cementitious surface matrix using as the .aggregate material glass beads either alone or with another aggregate materials 9 selected from precious or semi precious stones, sands, quartz, marble, granites and the like has been difficult to achieve.

It was previously thought to be unsatisfactory to attempt to use other than conventional aggregates in hard-wearing surface finishes as the bonding achieved was inferior compared with conventional aggregates. In the building industry it has been considered unwise to use materials such as glass beads as aggregates as the glass is generally considered to be insufficiently porous or tough enough to establish an effective bond. The bond is also compromised by alkalinity bleeding out from the glass beads.

A number of approaches have been followed in the use of glass beads and cement formulations to provide surfaces having good light reflectivity. U.S.

Patent No. 4,218,260 to Metzler discloses reflective concrete bodies in the form of slabs which can be used on road surfaces. The concrete slabs incorporate crystal balls of a uniform particle size within the range of about 0.2-0.6 millimeters. The glass balls in the reflective slabs are configured so that they are arranged in even horizontal rows through the vertical distribution of the slab.

After the slabs are formed and the concrete matrix allowed to harden for a suitable period of time, for example, 29-30 days, the surface is etched with a l .phosphoric acidsolution to expose at least 50% of the top layer of glass balls.

As an alternative to the use of glass beads of a uniform size, EP 518,854 discloses a cement formulation incorporating glass beads in which a particular particle size distribution of small and large beads is employed to ensure good oo": "reflectivity and compaction of the beads so that they are firmly incorporated into the cement matrix through the use of an adhesive agent. In EP 518,854, two particle size distributions are employed. The larger particle size component is in the range of o. 1.5 -7 millimeters; the smaller particle size component is within the range of 1.2-1.5 millimeters. The components are employed in relative concentrations in which the smaller size component is present in a greater amount than the larger size component, preferably in a proportion of the smaller component to the larger 2 fcomponent of about 2: 1.

Yet, another cement formulation employing glass spheres of relatively smaller particle sizes is disclosed in British Patent No. 1,397,737. Here, glass spheres approximately 0.25mm to 1.75mm in diameter, which are coated with a water-repellent material such as a silicone, are employed to form a reflectorized concrete screed laid down at a thickness of at least 1/2-inch and preferably from 1/4-inch to about 2 1/2, inches. The concrete screed can be formed from a blend of white portland cement, calcined flint particles, a titanium oxide pigment, and a binding agent which is designed to assist in preventing the reflective spheres from loosening under wear.

SUMMARY OF INVENTION The present invention comprises a surface finish for application to a vertical, horizontal, or sloping surface/s of a structure or object which provides a substrate for said surface finish, the surface finish comprising a matrix formed from a combination of at least a cementitious material, water, and glass beads.

The surface finish comprises a blended matrix of cementitious mortar, an o aggregate of glass beads used alone or in conjunction with other aggregates selected from precious stones, semiprecious stones, or raw stones, and liquid *i adhesive which comprise a combination of a siliconiser and polymeriserer for •enhancing the bond between the cementitious mortar and glass beads. The finish may be applied to the surface of a structure, such as a building facade as a paving surface, or to other suitable objects formed from a material capable of forming a bond with the finish.

The consistency and/or blend of the matrix may be varied according to the nature of the substrate surface to which the surface coating is applied. Thus, the mix can vary according to whether or not the surface is Horizontal, vertical, or sloped and according to the type of material which forms the substrate. For instance, application of the finish to a vertical surface requires the mix to bind to the surface, and this is achieved by ensuring that the mix assumes the right plastic consistency.

The present invention provides a method of preparing a surface finish in a sequence of operations which can be: a) mixing a cementitious mortar with water and a liquid or powdered adhesive; b) introducing glass beads into the mix alone or with another aggregate; c) blending the mix for a pro-selected duration until the mix reaches a predetermined consistency; d) applying the mix to a substrate surface of a structure or other object; e) allowing the mix to soft set; f) exposing a predetermined surface area of the beads by either washing or sponging the surface of the finish with water; or :i g) allowing the mix to hard set and washing with hydrochloric acid.

The cementitous material preferably is washed away such that 30-60% of the surface area of a substantial number of the glass beads on the surface of the ~matrix is exposed. Preferably, no more than 40% of the bead surface area is exposed at the surface of the matrix.

More specifically, in accordance with the present invention, there is provided a process for the application of a reflective surface finish to a substrate structure. In carrying out the process, there is provided a reflective cementitious composition comprising portland cement, glass beads, and a barrier-forming material selected from the group consisting of a polymerizer and a siliconizer and mixtures thereof.

Preferably, the barrier forming material comprises a latex polymer. The portland cement is employed in an amount within the range of 113-213 of the total weight of the formulation. The glass beads have particle sizes within the range of millimeters and a weight average particle size within the range of 1.5-4.5 millimeters. The beads are employed in a particle-size distribution defining a major component within a relatively large incremental size range and a minor component within a smaller incremental size range. The weight of the beads within the large incremental size range is greater than the weight within the smaller incremental size range. Preferably, this weight ratio is in the range of 2-3 and more preferably within the range of about 2-2.6. The latex polymer is present in an amount within the range of at least 2 wt.% of the glass beads but less than 8 wt.% of the total amount of cement and glass beads in the formulation. The cement formulation is hydrated with water in an amount to provide a water/cement ratio within the range of about 1/3-2/3 to provide a cementitious paste which is then applied to the surface of the substrate structure. Normally, the water content is near the upper end of this range to provide a water content of 65 wt.% of the cement. The paste preferably is applied to a thickness within the range of about 1/4-1/2-inch and, after any trowelling or other surface treatment to provide a smooth surface, is allowed to set for a time to form an initial set. Thereafter, the surface is washed with an aqueous medium to remove a small amount of cementitious material from the surface layer of the beads to form partially-exposed areas of the beads.

00 1.00 In a preferred embodiment of the invention, two washing steps are carried out. The initial washing step is carried out with fresh water after the cernentitious plaster is formed and reaches an initial Gillmore setting time but prior to the time it reaches a final Gillmore set. After the cementitious material reaches a final set, a second washing step is then carried out with a hydrochloric acid solution having a pH of less than 2 and usually less than I.

In another aspect of the invention, there is provided a structure having a reflective surface finish. The structure comprises a substrate material having an interface surface. The substrate material can take the form of a concrete surface and, more specifically, a curved surface formed of (shotcrete) concrete such as used in swimming pools. A reflective material is disposed on the inteface surface of the substrate and comprises a plurality of glass beads and a cementitious material providing a matrix for the beads. At least a portion of theglass beads project out of the exposed surface of the matrix to provide an exposed surface area of the glass beads such that they are partially encapsulated within the matrix to provide an encapsulated surface area. At least a portion of the beads have a boundary layer of a barrier material interposed between the bead surfaces encapsulated within the matrix but are free of the boundary material on bead surfaces projecting outwardly from the matrix. The beads have an average particle size within the range of 1.5-4.5 millimeters land a particle size distribution defining a major component of the beads within a relatively large incremental size range and a minor component of the beads within a smaller "."incremental size range. The weight of the beads in the large incremental size range is greater than the weight of beads in the small incremental size range. Preferably, the weight ratio of beads within the large incremental size range to the small incremental size range is within the range of 2-3.

In yet another aspect of the invention, there is provided a dry cement formulation which is adapted to be hydrated and applied to a substrate surface to provide a reflective surface.

The composition comprises portland cement in an amount within the range of 1/3-2/3 of the total weight of the formulation. The formulation further comprises glass beads having particle sizes between upper and lower values within the range of 1'5 millimeters and a 6 weight average particle size within the range of 1.5-4.5 millimeters. The beads have a particle size distribuion defining major and minor components of the beads. The major component is within a relatively large incremental size range having an average value greater than the midpoint of the, aforementioned upper and lower values. The minor component of the beads is within a smaller incremental size range having an average value below this midpoint. The weight of the beads in the large size range is greater than the weight of the beads within the small incremental size range. The formulation further comprises a latex polymer present in an amount of at least 2 wt.% of the glass'beads but less than 8 wt.% of the total amount of the cement and glass beads in the formulation.

Preferably, the latex polymer is present in an amount within the range of 3-5 wt.% of the portland cement. According to one embodiment of the method aspect the adhesive comprises a siliconiser and polymerizer mixed together. In a further aspect of the invention, the aggregate bead/cement ratio is 5:8 or five part beads to 8 parts cement. Alternatively, the bead/cement ratio may be BRIEF DESCRIPTION OF THE DRAWINGS 1 Figure 1: shows a structural element including the surface finish according to one embodiment ofthe invention; Figure 2: shows the surface finish according to an alternative embodiment of the invention wherein differet size glass beads are used; and Figure 3: shows an alternative embodiment of the finish including other selected aggregates.

DETAILED DESCRIPTION OF THE INVENTION oo The present invention involves a cementitious composition comprising a mixture oo•* of glass beads in a poilland cement composition together with a barrier-forming material which functions once the cementitious composition is hydrated and allowed to set to protect the glass beads from the surrounding matrix 7 environment. While the glass beads employed in the present invention can be similar to those described previously, the present invention proceeds in a fashion directly contrary to the prior art in its distribution of glass beads along a particle size distribution which results in a relatively large bead component and a relatively small bead component which functions to provide a strong surface reflective material which is not only highly reflective but also provides good integrity.

Thus, rather than using a more or less uniform particle size of beads, as in the aforementioned patent to Metzler, or a particle size distribution in which relatively small beads are employed as a major component together with somewhat larger beads, in the present invention the larger size beads provide the major bead component.The surface finish of the present invention comprises a matrix of cement, water, an adhesive, and glass beads defining an aggregate material. The adhesive can be introduced into the mix with the water to facilitate bonding between the glass beads and the mortar. As described below, known adhesives may be used such as Xycrylic polymerizer mixed with a siliconiser to provide a mechanical locking, and thus binding between the beads and the mortar. In utilizing the surface finish of the present invention, many variations of aggregate mix can be achieved to provide different aesthetic, bonding, and structural effects.

The blend proportions and constituents over and above the essential constituents are primarily determined by the particular application of the surface coating and, 9o*°•q more particularly,whether it would be used on a horizontal, vertical, or sloping :°-isubstrate surface. The nature and quality of the substrate material is also a determinant of the mix.

Referring to Figure 1, there is shown a surface finish 1 applied to the surface of a 9 structural element 2. Surface finish 1 comprises a matrix formed from at least a cementitious material 3 and water into which is mixed spherical glass beads 4 which may be of the same or different sizes. The glass beads provide a large surface area for binding with the cementitious material 3. However, in order to enhance the natural adhesion between the glass beads 4 and cement 3, an adhesive is added which can have the effect of chemically abrading or etching the smooth surface of the glass beads to provide proper adhesion. The adhesive can be either a powder or liquid and can comprise a mixture of a siliconiser and a polymerizer. The polymerizer retards the set so, if necessary to compensate for this, the siliconiser accelerates the set. The polymefizer fortifies the cement mix, increases hardness, durability, bonding capability, and chemical resistance to alkalinity bleed from the glass beads. The surface finish is prepared by mixing the cementitious material with the glass beads in a slurry which is formed by adding water and an adhesive. Most of the glass beads are distributed throughout the slurry to ensure consistent structural integrity of the surface finish matrix.

Ideally, the outer surface 5 of the surface finish matrix is formed by glass beads near the surface which sit proud of the cementitious material. Ideally, the surface area presenting to and forming the outside of the surface finish would be 30% to of the surface area of each bead but preferably closer to 60%. Thus, 9* and preferably no more than 40%, of the beads along the surface 5 would be visible 9above the surface upon completion of the finish. The proportion of the glass beads which are exposed is determined largely by the amount of washing of the surface prior to final setting of the surface finish. This has the effect of washing away the l ayer of mortar nearest the outside thereby exposing the glass beads close to the surface of the matrix. The glass beads interlock within the matrix providing 9 resistance against various forces applied to the surface finish such as tensile compressive, or bending forces enhancing the structural integrity of the finish. The interlocking also prevents the tendency of glass beads to spill off from the matrix thereby preserving the integrity of the surface finish. According to a preferred embodiment, the bead sizes throughout the matrix are varied. For instance, for a particular surface finish one may choose beads from different sizes whereby the smaller diameter beads would assume the spaces between the larger diameter beads in a given finish thereby creating the interlocking between the beads. According to one embodiment, the surface finish would have a ratio ofcementitious material to glass beads of 1: 1.

Alternatively, the ratio would be 5:4. The color of the cement mortar which is used determines the color transmitted by the glass beads. As the beads are clear, they are internally reflective. If white cement is used, the glass beads tend to reflect a white color; whereas, if a darker cement suchas grey is used, the bead reflection would be grey. Thus, the beads reflect the color of the cement that is used. In 9 another embodiment a mixture of colored beads may be used so that a mixed color effect is achieved. In an alternative embodiment, the matrix is prepared by selecting, in addition to the glass beads, aggregates selected from earth materials o°°9.

such as semi-precious gems, precious gems, sands, or quartz, marble, and pebble *10e O0 aggregates.

S..

S.The polymerizer used in the present inention may be of any suitable type which is compatible with the cement, preferably white portland cement as stated above and which functions to act as a seal or barrier between the glass beads and the cement during hydration to enable good mechanical locking of the beads in place after the formulation has finally set. Polymers which are compatible with portland cement and used in special purpose concrete applications are incorporated into products commonly referred to as polymer-modified concrete (PMC) or polymer-portland cement concrete (PPCC). Such polymers can take the form of latex-type polymers which are sometimes used in so-called latex-modified concrete (LMC). Typical of such polymers are styrene butadiene rubber-type polymers, polyvinyl acetate ethylene co-polyrnerp., and polyacrylate homopolymers, including polymers of acrylic acid, methylacrylic acid, niethyl methacrylate, and butylacrylate. A particularly preferred polymerizer for use in the present invention is an acrylic hemopolymer available from Rohm Haas Company under the designation "DRYCRYL DP-2903." This polymer is a freeflowing white powder which passes through a 200-mesh sieve and mixes intimately with the cement powder. Although it is typically added in an amount of about 10% of the hydraulic cement to increase the workability of the concrete paste, it is used in smaller amounts in the present invention. Other suitable polymers which can be used in accordance with the present invention include various polymer latexes which are used in latex-modified concrete, such as styrene acrylic copolymer latexes, acrylonitrile butadiene copolymers, and chlorinated polyvinyl acetate polymers and copolymers.

In the normal application of the product of the present invention, the cement-glass bead Smixture, either with or without the presence of a relatively fine aggregate as described later, is provided as a dry mixture which is hydrated for application. The polymerizer functions, upon addition of water to the mixture, to coat the glass beads and protect them from attack by cement components, such sodium or potassium-based alkalies which can lead to frosting of the glass beads thus retarding their reflectability in the final product and ultimately degrading the beads. The latex polymer provides a barrier material which is interposed between the surfaces of the bead and the encapsulating matrix material. This boundary layer will not harden so long as the adjacent cementitious mixture is hydrated. Thus, the boundary layer begins to harden after the cement

II

achieves an initial set and begins to harden. The matrix material is partially removed from the surface to expose the beads as described below. The washing step as described below removes the polymerizer along with the cementitious material to provide the bead surfaces which are free of the boundary material.

The siliconizer which can be employed as a optional component in the present invention includes materials which will include silicon-containing materials which are miscible with or emulsifiable in water and which functions to etch the surface area of glass beads exposed to the cement to facilitate bonding within the matrix.

Suitable siliconizors include alkali metal ,silicates such as potassium.silicate or sodium silicate (water glass) or other water-soluble sodium silicates such as sodium sesquisilicate, sodium orthosilicate, anhydrous metasilicate sodium, and sodium metasilicate pentahydrate. An especially suitable siliconizer for use in the present invention is sodium silicate available from Xypex, Australia, under thedesignation QUICKSET. This product which is conventionally used as a set accelerant for portland cement functions similarly here, but the accelerating effect of the siliconizer is offset by the polymerizer which provides a counterbalancing set-retarding effect.

The size distribution of the glass beads is important in providing relatively large beads to provide a good reflective surface area in the matrix while providing smaller beads which are interspersed within the larger beads so that they can be effectively interspersed between the relatively large beads. As described in greater detail below, the beads can be characterized as falling within two particle size distributions with the larger particle size being the predominant component. Overall the average particle size of the beads preferably will be within the range of 1.5-4.5 millimeters and more preferably within the range of about 2-3 millimeters. Although a differential particle size distribution 12z is important in carrying out the present invention, the upper limit of the particle size distribution normally should be no more than three times the magnitude of the lower limit.

While a few beads may be outside of this range, preferab)y at least 90% of the glass beads will fall within the, designated particle size distribution. The major and minor components of the beads can he characterized in terms of average particle size values, the larger component having a average particle size greater than the midpoint of the upper and lower particle size distribution ranges and the minor component having an average particle size below this midpoint. The weight of the beads in the larger size range, as noted previously, is greater than the weight of the beads in the smaller incremental size range. Again considering the overall particle size distribution of the beads, preferably the upper value is from 2-3 times greater than the lower value and preferably no more than 2 1/2 times greater than the lower value.

The glass beads used in the present invention preferably have a size distribution within relatively narrow confines in which a major component of the beads is within a relatively large size range, termed the "large increment," and a minor component of the beads in a somewhat smaller size range, termed the "small increment." A particularly preferred particle size, distribution for the glass beads is one in which the major component of the glass beads is within a size range of about 2.5-3.5 millimeters in diameter and a minor component is within a small increment of 1.5-2.5 millimeters. The glass beads within the •large increment size range are the predominant component, and preferably the weight ratio of beads within the large increment size range to those within the minor increment size range will be within the is range of about 2-3 and more preferably within the range of about 2.0 to 2.6. Ar, described in greater detail below where the formulation is designed for use as a "neat" cement (without the addition of aggregate), the ratio of the large increment portion of the beads to the small increment portion will be near the upper end of the range. Where o o it is designed for use in which it is to be mixed with an aggregate, such as sand, to form a concrete mixture, it will normally be near the lower end of this range.

Is This relationship can be illustrated by two formulations, both of which are designed to be provided to the user in 50-lb. bags. The first formulation designed for use as a neat cement contains 25 lbs. of glass beads, 24 Ibs. of Type I white cement, and 1 lb. of the aforementioned polymerizer DRYCRYL DP-2903. The beads are present in two increments. The large increment has a bead size ranging from 2-5-3.3 mm and is present in an amount of 18 lbs. The smaller increment has a bead size within the range of 1.5-2.5 mm and is present in an amount of 7 Ibs. The weight ratio of the large increment to the small increment is about 2.6.

A second formulation, also supplied in 50-lb. units, contains 16.5 Ibs. of glass beads, 32,5 Ibs. of Type I white cement, and 1 lb. of the above-described polymerizer. Here the relative amounts of beads within the same increment, falling within the same upper and lower increments as described above, is 1 1 Ibs. of beads within the 2.5-3.3 mm increment and 5.5 Ibs. within the range of 1.5-2.5 mm, providing a major increment to minor increment ratio of 2. This formulation can be mixed with 17-20 Ibs. of aggregate of the same size of the beads, typically predominantly within the range of 1.5-3.3 mm, to provide a concrete mix for use in structural applications. Greater amounts of aggregate can be used, if desired. Another suitable bead-size distribution provides a small incremental size range of 1-1.5 mm in a large incremental size range of about 2.4-3.3 mm. Within the small increment bead distribution is about 70 wt.% at or near 1.5 mm, 20% at 1.2-1.3 mm and at 1 mm. The large increment has a distribution of about 65-70% at 3.3 nun, 20% at 2.7 mm, and about 1 0-15% at about 2.4 mm. The relative concentration of the S: bead/cement Formulation is about 50% beads and 50% Portland cement including the polymerizer. Other bead distributions which have been found to be useful in carrying out the invention are'as.follows: 10 wt.% at 1.4 mm, 20 wt.% at 1.7 mm, and 70 wt.% at mm; 10 wt.% at 2.36 mm, 20 wt.% at 2.0-2,8 mm, and 70 wt.% at 2.36-3.35 mm; 10 wt.% at 2.8 mm, 20 wt.% at 2.36-3.35 mm, and 70 wt.% at 2.85-4.0 mm; 10 wt.% at 2.36-3.35 mm. 20 wt.% at 2.85-4.0 mm, and 70 wt.% at 5.0 mm; and 10 wt.% at 2-2.8 mm, 20 wt.% at 14- 2.36-3.35 mm., and 70 wt.% at 2.85-4.0 mm. The beads in the aforementioned distributions can he formulated with an equal amount of white cement and polymerizer. By way of illustration of a formulation containing aggregate, the formulation can contain 25 wt.% beads at a particle size distribution ranging from 2.36 mm to 3.35 mm; 30 wt.% of aggregate having an average size of 3-4 mm; 5 wt.% having an average particle size of 2 mm; and 40 wt.% of white Portland cement containing the polymerizer.

Where aggregate is used it is used as a replacement primarily for a portion of the beads within the large increment size range. The aggregate will normally have an average particle size distribution similar to that of the large increment beads and closer to the average particle size of the large increment beads to the small increment beads. The formulation of cement beads and aggregates is particularly useful for horizontal surfaces where good skid resistance is a desired property.

The average particle size of the glass beads employed in the present invention, i.e., the average size taking into account both the small beads and the large beads, is preferably within the range of 2-4 millimeters and more preferably within the range of 2-3 millimeters. The average particle size, as referred to here, is the weight average particle size of the beads based upon the distribution of beads in the mixture. Thus, for example, for the second formulation described above and **ppp.

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assuming an even distribution of beads across the major increment of 2.5-3.3 mm.

•po• and the minor increment across the range of 1.5-2.5 mm. the average particle size would be about 2.6 mm.

"By providing the preferred particle size distribution in accordance with the present invention, a substantial proportion of the small beads as well as the larger beads are set within the cement matrix at the surface of the applied formulation so that the p beads are mechanically locked in place by the encapsulating cement mortar. If substantial quantities of small beads, that is, those below the desired lower limit, are

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present in the formulation when the surface is washed to remove mortar from the beads, the removal of substantial amount of mortar from the large beads would leave a substantially smaller bead exposed above the matrix surface throughout most of its surface area, thus exposing the small bead to removal from the matrix surface.

Preferably, the overall size distribution of the beads is such that the ratio of the upper limit of the major portion to the lower limit of the minor portion is less than 3 and preferably less than 2.5. Thus, where the range of the smaller minor portion of the beads is within the range of 1.5 2.5 millimetres (discounting a few beads which may be inadvertently present below the lower 1.5 millimeter range), the upper limit of the large increment is less than 4.5 millimeters and preferably less than 3.7.

The beads used in the present invention involve a distribution of relatively large beads intermixed with relatively small beads in an arrangement which provides a large overall reflective surface in the matrix while retaining the beads locked in place within the matrix after the cement hardens. In an idealized situation, only two grades of beads are employed. The small beads would be about 113-213 the diameter of the large beads. This would enable at the conclusion of the washing step to permit exposure above the upper surface of the matrix material of both the large and small beads without washing out a substantial portion of the smaller beads. As a practical matter, uniformly graded beads which are of a single size within very close tolerances usually will not be available and the large beads and the small beads used in the present invention can be considered to fall within ranges as described below.

Preferably, the beads employed in the present invention have a size distribution such that a large proportion of the beads, preferably at least 80-90 wt.% or more lie within a range in which the lower limit in bead size is about 2-2-1/2 times the lower limit.

At about the mid point of this range, that is, from 40-60% through the range, a 16 medium point can be established above which the weight ratio of the beads, the large increment as described below, to the beads below the range is substantially greater than one.

The polymers used in the present invention can include those polymers which are conventionally used in polymer concrete mixtures. Typically, such polymers as used in conventional polymer-modified concrete or mortar are used to effect the final properties affecting concrete structure such as increases in flexural strength and increased resistance to degradation due to freezing and thawing cycles and to reduce the permeability of the concrete structures. Such polymers, as are used in polymermodified concrete can be used in carrying out the present invention, although, because of the different purpose to which the polymeric additives are put in the present invention, they are used in substantially lower concentrations than used in their conventional application. The amount of Polymer in the glass bead cement formulation can be characterized in terms of its concentration relative to the glass beads and its concentration relative to the Portland cement component. Normally, the latex polymer will be present in an amount of less than g wt.% and usually in an amount of less than 5 wt.% of the total amount of the cement and glass beads in the *UUU.. o formulation. Considering the bead content alone, the Polymer preferably will be used in an amount of at least 2 usually in an amount within the range of about 4-6 wt.% of the glass beads, depending upon the Presence of aggregte materials such as relatively fine aggregate as described below. In terms of the amount of Sopolymerizer relative to the portland cement component, usually it will be preferred to add the polymerizer in an amount of 3-5 wt.% of the cement component. For a better description of polymers which may be used in carrying out the present 17 invention, reference is made to the ACI Manual of Concrete Practice. 1997, The Aineri- Concrete Institute, Part5, Sections ACI 548.5 R-94, "Guide for Polymer Concrete Overlays," and ACI 548.3R-95, "State-of-the-Art Report on Polymcr- Modified Concrete," the entire disclosures of which are incorporated herein by reference. In considering these reference materials, it is to be noted that the high concentration, called for therein should not be used, but instead the relatively small concentrations as described above should be employed.

Preferably, beads mixed with other aggregates should be mixed with substantially the same size aggregate as the beads to achieve proper grading within and adequate strength of the matrix. For instance, if a 3mm bead size is chosen as the predominant bead, then if there is to be used an additional aggregate material, a 3mm size aggregate should be chosen. In an alternative embodiment, the proportion of the cementitious material may be greater than the proportion of glass beads by weight with the selection of proportions dictated by the particular application of the surface finish. To enhance adhesion between the glass beads and the cement an adhesive is introduced. In addition to the adhesive, other admixtures are used according to the properties of the surface finish required. The oo*.oo S°ratio of admixture to cement used can be in the region of 250 ml to 40 kg by o:00 0:4 weight of cement.

0 The proportions of the mixed constituents which make up the matrix are oo° e o ".00 determined according to the particular application and appearance required for the oo 00004: surface finish. Thus, examples of blends would be 50% glass beads to selected aggregate such as pebbles, 75% glass head to 25% gem stones, 70% glass .0: bead to 30% gem stones. Bead or aggregate ratio selection depends on the surface finish required. Thus, the ratio is essentially determined by choice for a particular proportion of bead required to be seen prominently on the surface of the mix.

When the surface finish is used in structures in contact with water, a water proofing additive, is desirable. The water proofing agent should be of the cementitious crystalline type that chemically controls and permanently fixes non-soluble crystalline growth throughout the capillary voids of the cement.. The admixture should be used to permanently waterproof structures either above or below ground where water ingress is a predicted problem. The adhesive may also act as a waterproofing agent. T'he weight of the admixture per cubic meter of surface finish is determined according to the level of water pressure to which the structure is likely to be subjected. Furthermore, where the waterproofing mixture is used, the amount of water required for the slurry will reduce by 5 to 20 litres per cubic metre depending on the dosage rate and mix design. The water proofing mixture can also act as a set retardant. Thus. when a water proofing admixture is used precautions must be used to adjust the mixture to accommodate the effects that the water proofing admixture has on the matrix. The waterproofing admixture, which may also be Xycrilic polymerizer, also has the advantage of increasing adhesive strength and bonding, although in doing this it slightly retards the setting time but as indicated, this is compensated for by the use of a siliconizer which has an accelerating effect on setting of the cement.

Figure 2 shows an alternative embodiment of the invention this time showing the surface finish containing beads of varying sizes. Thus, beads 6 fall in the upper end .ooo•i of the size range, beads 1 in the middle and beads 8 in the lower end. These beads may be spherical and regular or irregular.

Figure 3 shows the finish formed with beads of different sizes as in figure 2 19 however, in this embodiment the finish also includes a non glass aggregate 9 blended with aggregates 6, 7 and 8. According to the method aspect, the invention may be realized by applying various methodological steps according to the selected method and application to which the surface finish will be put. The cement formulation is hydrated with water in a suitable amount, normally about 65 wt.% of the portland cement. After hydration, it is applied to the surface of the substrate structure in a layer which may range from a thickness of about to a maximum of about V2-inch and usually at a thickness of V4-318-inch. After application of the surface material, it is allowed to reach an initial set and then washed in order to remove, surface matrix material and partially expose a surface layer of the beads. This preferably is followed by a second washing step. Typically the formulation may be applied to the substrate structure on one day, spray washed about one to three hours after application, allowed to set overnight, and then washed on the subsequent day to provide for an exposure period after application within the range of about one-one and one half days. The timing of the initial washing step is important in that it should take place after the cement matrix material has set *sufficiently to prevent the beads from being washed from the matrix but before the polymerizer fortifying the boundary layer is hardened to the point where it cannot be ii: removed from the exposed surface area.

As will be recognized by those skilled in the art, the setting time of the cement will depend upon a number of factors including the cement constituents, the amount of *°°water in the paste slurry, and the ambient temperature and humidity conditions under which the cement slurry is applied to the substrate surface. The setting C characteristics of a cement slurry can be characterized in terms of Gillmore setting times determined in accordance with ASTM C266.

Zo The washing'step should be delayed at least for a period until the cementitious composition containing the glass beads reaches an initial Gillmore setting time, typically about one to three hours under temperate weather conditions of 25'C. The washing step should be delayed for a time after the initial Gilimore set is reached but should normally take 1-3 hours after initial Gillmore set and before final Gillmore set to ensure that the latex polymerizer, which hardens in the absence of water, can be washed off of the exposed surface beads.

It will also be recognized that the ambient conditions, principally temperature, will have a significant effect on the time required to reach an initial Gillmore setting time as well as the subsequent delay period before carrying out the washing step. For example, at a temperature of about 15'C the washing step should be carried out about 2-4 hours afler reaching initial set. At a substantially higher temperature of about where hardening occurs substantially more rapidly, the washing step normally should be carried out about 1-2 hours after initial Gillmore setting time.

S. The washing step can be carried out within an aqueous medium such as fresh water or with a muriatic acid solution diluted to provide a weak acid having a pH of about Preferably, two washing steps are involved, the first with fresh water after the initial Gillmore setting time but before the final Gillmore setting time and the second 0with acid solution after the final Gillmore setting time, In either case, the initial O O washing step should be applied through a relatively low pressure nozzle, eg., with j the nozzle displaced about, one to two feet from the surface being washed. Where *•ee two washing steps are employed, the acid solution used in the second step can be more acidic than would be the case where acid is used in the initial washing step. A

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suitable washing solution used for the second step can he formed from a mixture of one part water with one part muriatic acid at 20 degrees baume.

In the most rudimentary form, a mix may be achieved by manual hand mixing, such as in a bucket or wheelbarrow or by manual mixing on a flat surface. This is suitable for small applications, but for larger applications a mechanical mixing device should be used. Preferably, a paddle mixer is used such that the paddles are set off the barrel bin with hard plastic blades attached to the end of the paddle to scrape and clean the bowl. This prevents crushing of the glass and grinding of the beads by the paddles against the barrel resulting in crushing and degradation of the beadsl Where a finish is to be applied to a vertical surface, certain additional preparatory steps are required. First the surface of the substrate is laid with a patch coat which seals the substrate material from unwanted bleed out. The patch coat comprises a slurry including a siliconiser, polymeriser, cement and water but no S aggregate. This mix must be mixed to the required paste consistency to ensure

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binding to the substrate. Following this, the full mix is applied comprising cement, o S S: •water, adhesive and selected glass beads and if required, other aggregates.

il: According to one embodiment of the method aspect, the mixture may also include the addition of aggregates selected from precious or semi-precious gems, sands crushed quartz, marble or pebbles. These aggregates may be introduced during the early mixing phase when a slurry is formed or alternatively, a selected aggregate may be broadcast on the oooo•S surface finish just after laying and either before or after washing of the surface to expose the glass beads. The recommended method is however, to niix the aggregate selected with S o* the matrix so the design consistency of the finish is assured.

There are a large variety of applications to which the surface finish may be put. Once the matrix is mixed to the required consistency, it may be applied by hand according to rendering techniques either to horizontal, vertical and indeed surfaces of almost any shape.

One application of the finish is in surfacing of swimming pools, in which case 22 waterproofing additives can be included in the matrix.

As an alternative to the use of mortar it is possible to utilise vinyl based resins which may either be rolled onto a surface by hand, (called hand laminating) or alternatively sprayed with a suitable gun under air pressure. According to this application the gun sprays the beads, a catalyst and resin at'once, leaving the beads to set in the clear finish formed on the surface.

As an alternative to the above described method aspect, it is possible to form tiles once the matrix has mixed and set. Thus, rather than immediately applying the surface finish after the required consistency is achieved upon mixing, the mixture can be placed in a mold and allowed to set thereby forming a tile which can later be used as a surfacing material over a structural or non-structural substrate such as prefabricated or precast panels for use in the building industry including high rise.

Where the surface finish is applied by use of a gun, the surface to which the finish is to be applied can have an adhesive membrane applied to its surface to provide o* support for the glass beads and resin mixture when sprayed on under air pressure.

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The beads used in the various applications of the present invention are made of •OV "glass. The main ingredient is silica, sand, ash and limestone. These are generally •weighed during manufacture and mixed with minor ingredients such as metal oxides.

The most commonly used beads are made from recycled glass and arc spherical or •irregularly shaped.

Tinting of the glass beads may be achieved by mixing coloration or by incorporating fine particles of metal such as gold or magnesium in the beads. Gold or magnesium will provide a red bead. Cobalt will provide a blue bead.

Although the preferred shape for the glass beads is spherical it will be appreciated that other shapes may be used in the surface according to requirements. Such bead 23 shapes would include for example, elliptical, oval pear, rectangular, triangular, cylindrical, prismic, hexagonal, octagonal and other prismic shapes.

The methodology of the present invention is particularly adaptable to pre-cast fabrication whereby pre-cast structural members such as concrete panels which arc cart in situ in factories may have applied to them the surface finish according to the present invention and its various embodiments. Thus, the surface finish can be applied to building panels which may either be structural or cosmetic, moulded off site and prepared with the surface finish prior to delivery. Apart from structural panels, panels may also be manufactured including the surface finish when used for pavings, slabs, stepping stones, brick and tile pavers, floors, wall decorations.

According to one method of prefabrication, the surface finish is applied while the concrete which forms the prefabricated panel is still wet. The bead finish is then applied to the still wet panel enabling the panel and the surface finish to combine in the one setting process. This allows the surface finish to be integral with the setting

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••go and enhances the overall structural integrity of the substrate.

Another application of the present invention is in the manufacture of bead sheeting which involves applying the surface finish according to the invention and its embodiments to netting, paper, synthetic, metal wooden or other surface. Once the ooo.

surface finish sets, the sheeting which forms the substrate surface finish may

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••then be attached to a structure using an adhesive according to the surface to which the sheeting is to be adhered. The bead sheeting or bead netting is applied to an existing structure using polymerised siliconised adhesive. Synthetically based or cementitious based adhesive is used depending on the material or surface to which the sheet is to be adhered. Thus, the surface finish according to the, invention and its various embodiments has numerous applications in building and industry.

2+ Among the applications are the use of the surface finish for reflective purposes and this is particularly useful in safety applications such as in mines, on roads and roadside structures, airports for runway markings, on entrances to tunnels, platform edging and for outlining structures for night attention. Thus, the substrates to which the surface finish of the present invention may.be applied are limited only to those having finish compatible surfaces and include a variety of materials surfaces and objects. Depending upon the substrate material selected, a suitable adhesive is chosen or alternatively the substrate surface is prepared in order to receive and support the glass bead surface finish. The film may also be used in maritime applications for instance, in illuminating dangerous rock outcrops, channel markings, pole markings, ferry wharfs and entrances where reflective materials are, required. Yachts, boats, ships, etc. which require permanent reflective safe marking may also have the Finish applied. Other maritime applications include marker boys, oo color coding of moorings, night illumination of ferry's, private wharfs, pontoons and obstructions in maritime waterways. Other maritime applications include safety markings for wetsuits and surf boards. The glass beading may also be used in furniture applications including table tops, lounges and other items of furniture.

Other building applications include use of the surface finish for driveways, paths, courtyards, interior and exterior floors, garden edging on retaining walls, stepping stones, and other applications where safety is required.

It will be recognized by persons skilled in the art that numerous variations and modifications may be made to the invention as broadly described herein without departing from the overall spirit and scope of the invention.

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Claims (20)

1. 2. The combination of claim 1 wherein the weight ratio of beads within the large o# incremental size range to beads within the small incremental size range is within the range of 2-3.
2. 3. The combination of claim 1 wherein the weight ratio of beads within the large incremental size range to the small incremental size range is within the range of about 2-2.6.
3. 4. The combination of claim 1 wherein said beads have an average particle size within the range of 2-3 millimeters. The combination of claim 1 wherein the major component of said beads is in a size range within 2.5-3.5 millimeters and the minor component of said beads is in a size range within 1.5-2,5 millimeters
4. 6. The combination of claim 5 wherein the beads of said major component of said beads has a maximum size which is no more than two times the size of the average size of beads within said minor component.
5. 7. The combination of claim 1 wherein the major component of said beads is in a size range within 2.5-4..0 millimeters and the minor component of said beads is in a size range of within 1.0-2.5 millimeters.
6. 8. The combination of claim 4 wherein the beads within said major component of said beads have a maximum size which is no more than three times the size of the average size of beads within said minor component.
7. 9. The combination of claim 1 wherein no more, than about 40% of the surface area of 9the beads at the surface of said matrix is exposed.
8. 10. The combination of claim 1 wherein said glass beads glass beads having a particle size distribution ranging from a lower value to an upper value having a magnitude no more than three times the magnitude of said lower value, said particle size distribution defining a major component of said beads within a relatively large incremental size range having an average value greater than the midpoint of said upper and lower values and a minor component of said beads within a smaller incremental size range having an average size below said midpoint wherein the weight of beads in the large incremental size range is greater than the weight of beads within the smaller incremental size range. 1 1. The combination of claim 10 wherein said upper value is from 2 to 3 times greater 27 than said lower value.
9. 12. The combination of claim 10 wherein said upper value is no more than 2 1/2 times greater than said lower value.
10. 13. In a dry cement formulation adapted to be hydrated and applied to a substrate surface to provide a reflective surface, the composition comprising: portand cement in an amount within the range of 1/3-2/3 of the total weight of said formulation; glass beads having particle sizes between lower and upper values within the range of 1-5 millimeters and a weight average particle size within the range of 1.5-4,5 millimeters, said beads having a particle size distribution defusing a major component of said beads within a relatively large incremental size range having a an average value greater than the midpoint of said upper and lower values and a minor component of said beads within a smaller incremental size range having an average value below said midpoint wherein the weight of beads in the large incremental size range is greater than the weight of beads within the small incremental size range; and a latex polymer present in an amount within the range of at least 2 wt.% of the glass beads in said formulation but less than 8 wt.% of the total amount of I cement and glass beads in said formulation.
11. 14. The formulation of claim 13 wherein said polymer is present in an amount within the range of 3-5 wt.% of said portland cement. °15. The combination of claim 13 wherein the major component of said beads is in a ooo° size range within 2.5-4.,O millimeters and the minor component of said beads is in a size range of within 1.0-2.5 millimeters.
12. 16. The combination of claim 15 wherein the major component of said beads is in a size range within 2.5-3.5 willimeters and the minor component of said beads is in a size range within 1.5-2.5 millimeters.
13. 17. The combination of claim 16 wherein the weight ratio of beads within the large incremental size range to beads within the small incremental size range is within the range of 2-3.
14. 18. The combination of claim 17 wherein the weight ratio of beads within the large incremental size range to the small incremental size range is within the range of about 2-2.6.
15. 19. The combination of claim 18 whmin said beads have an average particle size within the range of 2-3 millimeters. In a dry cement formulation adapted to be hydrated and applied to a substrate surface to provide a reflective surface, the composition comprising: portland cement in an amount within the range of 1/3-2/3 of the total weight of said formulation; glass beads having a particle size distribution ranging from a lower value to an upper value having a magnitude no more than three times the •ooo magnitude of said lower value, said particle size distribution defining a moor component of said beads within a relatively large incremental size range having an average value greater than the midpoint of said upper and lower values and a :minor component of said beads within a smaller incremental size range having an average size below said midpoint wherein the weight of beads in the large oo oo incremental size range is greater than the weight of beads within the S-smaller incremental size range. a barrier-forming material selected from the group consisting of a polymerizer and a siliconizer and mix- thereof present in an amount within the range of at least 2 wt.% of the glass beads in said formulation but less than 8 wt.% of the total amount of cement and glass beads in saidd formulation, saidd 29 barrier-forming material being effective upon hydration of said formulation for forming a boundary layer interposed between the surface of said beads and surrounding cementitious material.
16. 21. The formulation of claim 20 wherein said upper value is from two to three times greater than said lower value.
17. 22. The formulation of claim 21 wherein said upper value is no more than two and one-half times the said lower value.
18. 23. In the application of a reflective surface finish to a substrate structure, the method comprising: providing a reflective cementitious composition comprising: portland cement in an amount within the range of 1/3-2/3 of the total weight of said formulation; (ii) glass beads having particle sizes within the range of 1 millimeters and a weight average particle size within the range of 1.5-4.5 millimeters, said beads having a particle size distribution defining a major component of said beads within a relatively large incremental size range and a minor component of said beads within a smaller incremental size range wherein the weight of beads in the large incremental size range is greater than the weight of beads within the small °incremental size range; and ~(iii) a latex polymer present in an amount within the range of at least 2 wt.% of the glass beads in said formulation but less than 8 wt.% of the total amount of cement and glass beads in said formulation hydrating said formulation with water in an amount within the range of wt.% of said portland cement to provide a cementitious paste; and applying said paste to the surface of said substrate structure: and allowing said paste to form an initial set and thereafter washing the surface of said mortar with an aqueous medium to remove said cenientitious material from a surface layer of said beads to form partially-exposed areas of said beads in said surface layer to provide a reflective surface
19. 24. The method of claim 23 wherein the surface of said mortar is washed with said aqueous medium prior to the said cement forming a final set. The method of claim 24 further comprising carrying out a second washing step with an acidic solution subsequent to the formation of final set of said cementitious material.
20. 26. The method of claim 25 further comprising the step of brushing the surface of said material during the application of said acid medium. Dated this 26th day of October 1999. Beadcrete Pty Ltd By its Patent Attorneys •WALSH ASSOCIATES *e* o•