WO2023008991A2

WO2023008991A2 - Dry-blend compositions comprising re-dispersible acrylic polymer, cellulose ethers, ethylene vinyl acetate copolymer and polyester fibre, for use in forming joints and giving a float finish to cement panels, polystyrene panels, fibreglass panels and ceramic coatings for water tanks

Info

Publication number: WO2023008991A2
Application number: PCT/MX2022/050067
Authority: WO
Inventors: Daniel VAZQUEZ CARRERA
Original assignee: Vazquez Carrera Daniel
Priority date: 2021-07-30
Filing date: 2022-07-27
Publication date: 2023-02-02
Also published as: WO2023008991A3; MX2021009300A

Abstract

The present invention relates to dry-blend compositions comprising redispersible acrylic polymer, non-ionic cellulose ether, vinyl or ethylene acetate copolymer, toxitropic starch solution, CaSO4-2H2O and 6 mm polyester fibre applied to form joints and give a float finish to cement panels, polystyrene panels, fibreglass panels and ceramic coatings for water tanks, wherein the present invention provides a low-cost, clean and innovative building construction system that overcomes all the drawbacks of the technologies because it does not only use conventional cement for construction.

Description

DRY MIX COMPOSITIONS COMPRISING REDISPERSIBLE ACRYLIC POLYMER, CELLULOSE ETHERS. COPOLYMER OF VINYL ACETATE ETHYLENE AND POLYESTER FIBER. USEFUL FOR JOINING AND GIVING A FLOAT FINISH TO CEMENT PANELS. POLYSTYRENE PANELS. FIBERGLASS PANELS AND CERAMIC COATINGS FOR POOLS.

FIELD OF THE INVENTION The present application relates to the construction industry branch and in particular generally refers to walls made with construction panels and particularly to wall systems made of cement, polystyrene, fiberglass panels with a float finish. and ceramics.

BACKGROUND OF THE INVENTION

In Mexico, hundreds of thousands of new buildings are built every year, however, the use of traditional construction methods has the disadvantage of long periods to complete a work, which translates into high costs, especially labor, In the same way, the high costs of materials used are also counted.

There are countless materials for economical construction through complex assembly systems, which can be based on low-quality concrete, polystyrene, wood, ceiling panels, mesh, drywall, etc. However, they lower the quality of the built work, since they do not have the acoustic, thermal, impact or abrasion resistance, and durability properties of concrete-based materials. All those materials that are placed on a black work surface are known as finishes, coatings or coatings. That is, they are the final materials that are placed on floors, walls, soffits, roofs, exterior works or in holes and openings of a construction. The finishes have the function or main objective of protecting all base materials or blackwork, as well as providing beauty, aesthetics and comfort, therefore, these materials must correspond to adequate functions with the intended use and in the areas where the work requires its placement.

Within these finishes is the conventional plaster leveling, which is the best system to achieve a uniform, monolithic, stain-free and smooth surface, with incomparable resistance to use. In contrast, sheathing systems use large gypsum boards to speed installation, and result in higher strength, harder, and more monolithic surfaces than are achieved with normal gypsum board.

Within these finishes there are also cement panels that the market offers to builders, architects and contractors, which is a resistant and waterproof base for tiles and stone coverings in bathrooms, for example. They can also be used as a fire resistant substrate, and are ideal for all kinds of ceramic, stone, clay or flattened paste finishes on walls and ceilings. The panels are easily applied on wooden or metal frames, for load-bearing or dividing walls, thus obtaining highly durable systems.

The cement panels, manufactured in a continuous process, are made up of a Portland cement core reinforced with a double polymerized fiberglass mesh, which covers both surfaces and their edges. This composition makes the panels fire resistant and dimensionally stable. In addition to being used in interior applications, the panels can be used in all types of construction such as fencing, exterior trim, mobile homes, exterior fireplaces, canopies, façade remodeling.

The dimensions and composition of these cement panels were specially designed for indoor use subjected to conditions of high environmental humidity or direct water, such as bathtubs, individual or serial showers, bathroom floors, kitchen and bathroom countertops, and steam rooms. . Aggregate Portland cement core is resistant to water penetration and does not deteriorate with moisture. Cement boards are manufactured in three widths to minimize cutting required and to facilitate handling and installation. Larger dimension panels are available for large scale projects such as commercial kitchens and serial showers.

In the Mexican market there is bread! DUROCK brand cement, manufactured according to ANSI standards for cement substrates (Cementitious Backer Units - CBU), according to ANSI A 118.9 for test methods and specifications for CBU, and ANSI A 118.9 for CBU indoor installation. The ASTM designation for DUROCK Cement Board is C1325, and for DUROCK Exterior Cement Board is C1186.

All DUROCK cement board products meet the ASTM E136 standard for non-combustibility, and are UL Listed 34L2.

However, when said cement boards are finished floated with cementitious material, or with stucco, there is the possibility of damage to the stucco by moisture, for example, this limits its use in humid climates. Also, stresses caused by shipping stucco finished panel transportable buildings preclude their use in the lucrative manufactured housing market.

Methods exist to produce a textured or stucco appearance on panels, referring to an exterior finish system applied directly to cement board, polystyrene board and fiberglass board, with a finishing texture coating.

Texture coating on such panels can be applied as a single coat or in multiple thin coats, and often uses a full-wrap, alkali-resistant fiberglass mat or gasket to reinforce the coating against heat. cracking.

However, textured coatings have not enjoyed a large share in the Mexican market, because thin coatings are relatively fragile and are incompatible with wall panel finishes, mainly those made of polystyrene.

With the emergence of expanded polystyrene, different systems have emerged that take advantage of its light weight, as well as its thermal benefits, its stability, and its easy transformation. This has caused its incorporation into construction to have been progressive and accelerated in recent times.

Expanded polystyrene is not a hygroscopic material, that is, it does not have the capacity to absorb water. Even submerging the material! during 28 days in its entirety in water, the absorption of the material oscillates between 1% and 3% of its volume. These levels of water absorption make it difficult to screed the polystyrene panels, but the problem can be considerably reduced with the new technologies applicable to the composition of the present invention.

With the composition of the present invention, the float finish to cement panels, polystyrene panels and fiberglass panels can be installed and finished in a much shorter time, instead of using traditional stucco, which allows construction times shorter.

Another current problem that exists in the installation of panel walls is the type of joints where the finish is visible. When it comes to a thin joint sealing tape which, although usually waterproof, however, such tapes do not absorb the stucco or mortar mix, resulting in poor adhesion between the stucco and the tape, which leading to deformation of the surface.

Another serious problem is cracking of the joints. Cracking not only disrupts the monolithic appearance of the finish, but also allows moisture to penetrate behind the stucco or mortar plaster and rot or corrode the structural structure of the panel. In addition, these cracks are entry points for insects or fungi that can damage the interior of the wall.

Consequently, direct-applied exterior finish systems to cement boards, polystyrene panels, and fiberglass panels are rarely used where there is a wide variation in daily temperature, especially when combined with a high rate of wet cycling. / dry, as is the case in northwestern Mexico. Direct-applied exterior finish systems to cement board, Styrofoam board and fiberglass board are also occasionally used in the rapidly growing manufactured housing market due to the added stress placed on the walls during installation. transport.

There is the problem of solving the problems of joint opening and cracking of the exterior finish of the panels, which could significantly expand the market for applications of stucco or mortar plasters to cement boards, polystyrene panels and fiberglass panels, that generally use fiber cement and other substrates. Builders could not only use fiber cement substrates and stucco in wetter climates, but from the composition of the present invention fiber cement substrates and the use of stucco could also be expanded into new markets, such as manufactured homes and modular buildings.

The effectiveness of the use of the composition of the present invention can be evaluated on test walls consisting of several assembled panels, as set forth below;

A paneled test wall is finished with a cladding! composition material, and is subjected to a rack test. The rack test applies an in-plane shear force to the test wall, resulting in relative movement of the panel, until the siding cracks. The maximum deflection distance at which the finish will crack is a measure of the performance of the float finish to panels.

Polymeric adhesives used in cement board joint tapes tend to soften and lose holding power at 48°C, a temperature often reached on exterior vertical walls of a building exposed to full summer sun, primarily in northwestern Mexico.

Another problem is that cement building boards can become saturated with water in humid environments if installed incorrectly, or if the finish coat fails. Many adhesives adhere poorly to wet substrates. Cement hydrates quickly when in contact with the environment, so try to protect it from moisture, or use it as quickly as possible. Cement has a degree of fineness such that the finer its grains, the faster high mechanical resistance is obtained, but there is a permanent danger of shrinkage occurring due to drying.

Chemical additives are the magic ingredients that give modern tile adhesives their unique properties. AND! content of these additives is generally below 1%. Only redispersible polymers are additive in higher concentrations. Chemical additives can only be added in powder form to the dry mix composition. If several additives are used, it is necessary for them to be compatible with each other and, above all, for there to be a synergy between them. Cellulose is a biopolymer composed exclusively of b-glucose 1 molecules (from hundreds to several thousand units), since it is a homopolysaccharide. Cellulose is the most abundant organic biomolecule since it forms the majority of the terrestrial biomass. The arrangement of cellulose and other polysaccharides in a plant cell wall. Cellulose is formed by the union of b-D-glucose molecules through β1,4-0-glucosidic bonds. When completely hydrolyzed, glucose is obtained.

Cellulose has a linear or fibrous structure, in which multiple hydrogen bonds are established between the hydroxyl groups of different juxtaposed glucose chains, making them impenetrable to water, which makes it insoluble in water, and originating compact fibers that constitute the cell wall of plant cells. Cellulose is a structural polysaccharide in plants, since it is part of the supporting tissues. The wall of a young plant cell contains about 40% cellulose; wood 50%, while the purest example of cellulose is cotton, with a percentage greater than 90%.

The phenomenon of adhesion of panels with mortar, takes place by virtue of being in front of a system formed by two materials that are intended to be joined and which are called adherents, and a second material that establishes the union and which is called joint or adhesive union. Adherence can be defined as the ability to transfer a force from! adherent through the adhesive bond. In fact, the adhesion will be all the greater the greater the mechanical energy that the adhesive bond can absorb.

When talking about mechanical adhesion in a ceramic coating, it refers to a type of adhesion based on the cohesion of the adhesive achieved in the hydration process of a mortar.

It is characterized by the mechanical coupling between adhesive and adherent, texture or surface micro-roughness of the adherent, porosity and capularity of the adherent, and kinetics of penetration of the adhesive into pores and capillaries. The wetting or wetting capacity of the adhesive

The cohesion of the system in cement agglomerates is achieved after a maturation process that materializes with the formation of hydrated calcium silicate among other compounds.

The name chemical adhesion comes from the fact that in most cases organic chemistry is involved in achieving adhesion. The incorporation of polymeric resins in mortars for placing ceramic tiles considerably improves their fresh and final properties.

With the pre-mixed composition of the present invention, panel system contractors can offer white, smooth or textured, ready-to-decorate surfaces on concrete ceilings and columns located above street level. The easy application and excellent adhesion make the material of the invention an ideal compound! for filling small holes and cracks, as well as for second and subsequent coat applications with drywall and/or cement board methods and tools.

Various documents related to the present invention can be found in the state of the art:

For example, US Patent 5,732,520 describes a method of forming a single layer synthetic stucco finished exterior wall.

In accordance with that invention, fiber cement panels are installed in a building frame with the adjacent edges of the panels forming narrow gaps. Polyurethane caulk is applied to the gaps and applied low-profile, cloth-backed joint tape over adjacent panel edges to cover gaps and caulk. A high build, flexible resinous latex emulsion is then applied directly to the panels and adhesive tape to form a synthetic stucco finish.

U.S. Patent 5,732,520 differs from the composition of the present invention in that cracking can be prevented first by applying additional coats of the present joint composition, prior to applying the final coat of the joint finishing composition. the panel surface.

In addition, the US 5,732,520 method is expensive as compared to the composition of the invention, as it is time consuming and requires skilled workers. Furthermore, this technique often does not produce satisfactory results.

Likewise, the document ES2050932 refers to an invention that consists of a coupling between two panels of interlaminar structure, where each one comprises: an insulating layer that is covered on one of its sides with a first metal plate and on its other side with a second metal plate, each of the panels having a prismatic connecting edge for coupling by means of the connecting elements of another similar panel to said connecting edge.

United States of America patent No. 8,488,762, granted on December 3, 2002, to Caijun Shi, describes and protects a cellular concrete in which Portland cement is substituted with fiberglass base powder in the mix to obtain said concrete. The addition of fiberglass base powder increases the stability of the cellular cement mix, it is made from calcium-containing materials including Portland cement, granulated slag, lime, silicon materials include fine sand and base silicon.

However, for the exposed applications, there are currently no acceptable solutions that combine redispersible acrylic polymer, nonionic cellulose ether, polycarboxylate ether copolymer compound, CaSO ₄ - 2H ₂ O and toxitropic starch solution to manufacture compositions for jointing and floating finishing of cement panels, polystyrene panels and fiberglass panels.

OBJECT OF THE INVENTION

One object of the present invention is to propose dry mix compositions, useful for joining and floating finishing cement panels, with polystyrene panels and fiberglass panels.

Another object of the present invention is to provide an inexpensive, clean and innovative material for building construction systems, which overcomes all the disadvantages of the technologies because it does not use only conventional cement for construction.

Another object is to provide finishes to protect all base or black-work materials, as well as to provide beauty, aesthetics and comfort to these materials.

Another object is to propose a composition that is easy to apply and has excellent adherence to Venetian blinds or ceramic coatings for swimming pools. DESCRIPTION OF THE INVENTION

The present invention relates to dry mix compositions comprising nonionic cellulose ether, composed of polycarboxylate ether copolymer, CaSO ₄ - 2H ₂ O, pregelatinized starch ether, redispersible acrylic polymer, and polyester fiber with utility for joint and float finish cement boards, with polystyrene panels, fiberglass panels, and any concrete or cement substrate that you want to give a fine float finish. In accordance with the present invention, the dry mix compositions for use in the manufacture of cementitious mortars for joining and floating finishing panels, comprise the following percentage by weight of total solids:

• Redispersible acrylic polymer - 53.18 to 76.58%;

• Nonionic cellulose ether - 6.07 to 6.69%;

• Ethylene vinyl or acetate copolymer — 5.05 to 5.57%;

• Toxitropic starch solution - 3.03 to 3.50%; · CaSO ₄ -2H ₂ O - 20.25 to 22.33 %;

• 6mm polyester fiber - 0.5 to 2.5%.

In accordance with the present invention, the preferred dry mix compositions for use in the manufacture of cementitious mortars for joining and floating finishing panels, comprise the following percentage by weight of total solids:

• Redispersible acrylic polymer - 63%;

• Nonionic cellulose ether - 6%; · Ethylene vinyl or acetate copolymer — 5%;

• Toxitropic starch solution - 3%;

• CaSO ₄ -2H ₂ O - 21%;

• 6 mm polyester fiber - 1%.

In the composition of the invention, the jointing material is used to fill the joints, that is, the necessary space left between the panels or ceramic pieces, and which are essential for a correct placement of the material, since they allow to compensate the small dimensional differences that the pieces present, as well as compensate for the expansion and contraction movements that panel or ceramic-based coatings may present.

In one embodiment, adjacent panels are placed with no gap between them. In another embodiment, adjacent panels are placed with a gap between them.

In a preferred embodiment, an elastomeric finish with the composition of the present invention is applied to the paneled wall system.

In one embodiment, the elastomeric finish comprises an elastomeric primer and an elastomeric texture coat. In another preferred embodiment, the elastomeric finish is a texture coating.

In the composition of the invention, redispersible polymeric powders are used that are made by means of atomizations of organic materials. These powders are responsible for producing the high adhesion resistance in vitrified and low-absorption materials, based on the application of thin layers of mortar. The name "redispersible powder" derives from the behavior or "dispersion" of the particles when they come into contact with water. During hardening, elastic polymeric bridges are created between the weak mineral components of the mortar, achieving substantial improvements in adhesion to the most varied supports, and even to those that otherwise could not be reversed. The polymer modification additionally confers flexibility to the adhesive and improves thixotropy, flowability and water retention.

Hydrogels are used in the composition of the invention, which are polymers that have the ability to swell in water in the presence of water or aqueous solvents. The polymeric structure is capable of retaining solvents, forming a swollen gel phase with cross-linked systems, which does not dissolve.

Starch granules are relatively insoluble in water, due to the close packing of the molecules near their surface. Mixing and heating of the starch with water results in the absorption of about 25 to 30% water by weight. When the temperature approaches at 60-70 °C, the starch granules swell, acquiring a large amount of water, 3 to 10 times their own weight, although they remain separated from each other. As the temperature continues to rise, the water uptake increases, up to 20 times the weight of the starch, until eventually the granule bursts and empties its contents into the surrounding liquid and the mixture becomes highly viscous.

The starch paste then changes from being a solution to being a gel and the individual granules of starch can no longer be distinguished.

The viscosity of the gel depends on several factors. Cooling of the gel increases its viscosity. Gel formation occurs when water is trapped between widely dispersed starch chains.

The present invention is further illustrated by the following examples. EXAMPLE 1

An envelope with the composition of the invention, with a content of 470 grams to prepare a 19-liter bucket of material for jointing and floating finishing of cement panels, polystyrene panels, fiberglass panels, and any concrete substrate or cement that you want to give a fine floated finish.

Is required:

1.- 470 grams of the composition of the present invention, which includes the following materials:

• Redispersible acrylic polymer - 300 g · Nonionic cellulose ether - 30 g

• Vinyl or ethylene acetate copolymer — 25 g

• Toxitropic starch solution - 15 g

• CaSO ₄ -2H ₂ O - 100 g

• polyester fiber - 5 g Total - 475 g

2.- A clean bucket with a volume of 19 liters

3.- Eight liters of gray or white cement 4.- A 19 liter bucket of sieved sand (for finishes it is recommended to sieve the sand very fine for optimal results)

5.- An electric beater with blades

6.- Drinking water.

It is recommended to sift or serve the sand with a fine mesh to prevent the natural gravel of the sand from making grooves when tracing or regulating the flattening. It is also recommended to use clean sand, it can be washed from a river, or medium granulometry marble.

It is recommended to test the adherence and control of the mixture before starting a flattening, in order to determine its correct functionality.

To obtain the best results, it is recommended to apply the compound of the invention with the consistency indicated in the package instructions, in order to reduce product waste to a minimum. If a more thinned material is desired for roller application, the compound can be thinned by adding clean water and mixing to the desired consistency using a low speed hand or mechanical mixer. If the applicator inadvertently goes too thin, just add additional compound to thicken it and mix again.

Each wall or panel should be covered in a continuous application, always following the joints of different mixes before each mix sets. For a single coat semi-smooth texture, apply flattening in random strokes, leaving coat marks as desired. About 20 minutes after initial application, lightly trowel, keeping it nearly flat, over surface with short passes in various directions. Give another pass with the trowel at the beginning of the initial setting (approximately 45 minutes).

For thick two-coat textures, apply the first coat covering the entire surface. After the surface has slightly firmed up, apply a second coat in short passes, as described above. Additional trowel application of a second coat should be as described for single coat finish. After finish has set and dried (approximately 24 hours) apply decorative finish sealer.

During the application on cement panels, maintain the temperature in a range of 25 to 36 C, established by the instructions on the packaging of the composition of the invention, and provide heating or ventilation when necessary. Prepare the panel surface by removing any significant bulges or cracks.

Fresh concrete must cure for 60 days or more. Remove any form of oils, greases or efflorescence. All surfaces must be dry, clean and sound. Seal any exposed metal with a good rust preventative primer. Fill cracks and holes, and smooth any bulges or voids to the same level as adjacent surfaces, with curing joint composition material of the invention.

Apply as many coats as necessary to produce a fill with no cracks or edge joints that could show through the decoration. Then incorporate a paste finish coat of the composition of the invention over these sites, after the composition of the controlled setting joint compound has hardened, although not necessarily dried.

Mix the compound lightly and make a test application. Add small amounts of water if necessary. Take special care that the surface is smooth and free of irregularities in the areas that are exposed to lighting at very oblique angles. Compound of the invention can be applied over joints and cracks left in the concrete by using a wedge, knife or trowel. Filling or smoothing out small holes, protrusions, bumps, etc., with the compound of the invention. Let dry. With two installers, apply a first coat of inventive compound over the entire surface of the ceiling, beam or column with a finishing trowel, wide roller or wedge. Keep moving in one direction, making sure each application overlaps the previous one. Continue pairing with a rubber pump or long-handled drywall knife to smooth the fresh application, leaving minimal overhangs and blemishes. Apply to texture second coat, simply add water or sand. Use a very liquid mixture for a fine texture, and a thicker one for rougher effects. A very rough or uneven concrete surface may require three or more coats, all applied the same way.

EXAMPLE 2

SYSTEM FOR INTERIOR DECORATIVE FINISHES The system for interior decorative finishes is a finishing system based on the composition of the invention that adds colors and textures to interior drywall or base coat flattened surfaces in a single application. The surface of the finishes can be semi-smooth or have any imaginable texture. The composition material is applied by trowel, similar to troweling for siding. The system is more economical to use and apply than any other specialized color finishing material.

For application on drywall, apply paste of the composition of the invention for fine coatings. If using drywall, reinforce all joints and inside corners with tape. Embed the tape and fill the ridges with veneer composition material and allow to set, but do not dry. As soon as the edges and joints are properly prepared (rough and coated), apply a thick, thin coat of the thin coating composition material over the entire area; reapply with mix from the same batch to full thickness. Fill in all gaps and imperfections. Leave the surface rough and open, cross-scratching it with a fine wire brush, sponge or fine broom as soon as the surface is slightly firm. Set basecoat to allow proper absorption of topcoat.

EXAMPLE 3 THIN COATINGS ON CEMENT PANEL A two-layer thin coating system to a cement panel, said coating for greater resistance to impacts and abrasion, which consists of a mixture of the composition of the invention for thin coatings and paste finishes applied on the cement panel. This construction system is particularly useful for commercial and institutional applications, such as schools and high-traffic commercial premises.

According to the method of the invention, the metal frames are separated and the cement panel is installed with the long edges, either parallel or perpendicular to the frames, leaving the rough side of the cement panels apparent.

Before treating the joints of the panels, the adhesive of the composition of the invention is applied in a continuous film in the areas of the joints, following the application instructions established on the packaging of the sachet containing the composition.

Next, according to one embodiment of the method of the invention, the joints must be treated with joint tape. Joint surfaces should be treated with a separate coat of the inventive joint compound in order to fully hide the paper tape. Once the joint dries completely, the entire surface of the wall is applied with adhesive of the composition of the invention.

The Mexican Standard NMX-C-234-ONNCCE-2015 establishes the specifications and test methods for flat uncompressed NT fiber cement boards (commonly called NT flat boards, cement planks, cement boards, NT fiber cement boards, cellulose or fiber cement boards NT) and establishes the conditions of acceptance for its use in one or more applications.

This Mexican standard applies to NT fiber cement flat sheets and their accessories made of the same material that are manufactured or marketed in national territory.

Products covered by this International Standard may be used for other purposes, provided they comply with the appropriate national or international codes or standards. Assembly of simple tensile tests

One of the most important phenomena in the mortar of the invention is the loss of mechanical properties over time. To know the loss of properties of the mortar over time, it is necessary to know the properties of the young material. The influence of the composition used on the behavior of the material must be evaluated mainly in the long term.

The mechanical properties of the mortar of the invention were found through mechanical tests. Two types of tests are generally used to characterize the behavior of the mortar: simple traction tests and bending tests at 4 points following the NMX-C-234-ONNCCE-2015 standard. The absence of regulations that regulate the terms and characteristics that the tensile tests of mortar must have is justified by the great difficulty that they entail. The big problem with these tests is that it is not possible to predict where the fracture of the material will occur. In most cases, the breakage occurs in the jaws that hold the specimen. The use of bone type geometries does not ensure the location of the fracture in the narrow part of the specimen. In addition, obtaining specimens with this shape is not easy due to the difficulty involved in cutting the mortar plates. Therefore, the use of bone-type specimens was discarded and rectangular specimens were used in both tensile and 4-point bending tests. The young material that was tested was stored in a climatic chamber for 28 days to complete the process of gaining resistance that cementitious materials have. The conditions under which it was stored were: temperature 20 C and an environmental humidity of 98 %.

The specimens were kept in this environment from their transport from the factory until just before the test was carried out. The tensile tests were carried out in the following universal testing machines: Instron 8501, Instron 8803 and Suzpecar. Hydraulic clamps cause the mortar to break in clamps, which is why mechanical clamps were chosen. The jaws that were chosen were smooth in profile with a slight roughness. that improves the contact between them and the test tubes. The ends of the specimens were clamped with these jaws. A ball joint was placed next to one of the clamps to allow it to rotate during the test and thus avoid introducing flexions in the specimens.

A data acquisition system connected to a computer was used to record the behavior of the mortar of the invention during the tests. The data acquisition system has 4 channels. The data obtained were: the position of the actuator, the load, and the deformations. The precision of the measurements obtained were similar despite the fact that the tests were performed on different machines. Strains were taken using two Instron longitudinal extensometers, model 2620-602, with a 12.5mm base of measurement and a range of motion of ±2.5mm. These were placed one in front of the other in the central part of the test tubes. Two extensometers were placed, one on each side of the specimen, to record twists in the specimen, if any, during the test. The twists that occurred during the tests appeared due to the differences in the behavior of the material at its different points. In addition, the transfer of efforts between the jaws and the specimens generated some areas, close to the jaws themselves, in which the stresses are not uniform. The extensometers were placed inside the central third of the specimen to prevent the non-uniform local deformations that appear in the area near the jaws from distorting the measurements.

All trials were performed with displacement control. The displacement speed was set at 1 mm/minute. When assembling the extensometers, special care was taken to place them partially compressed to increase their opening range. The opening limit of the extensometers used was 2.5 mm; if this limit was reached during the test, the machine stopped so as not to damage the extensometer. The load supported by the material was found through the measurements provided by an Instron load cell that has a static load limit of 25 kN. The calibration of the extensometers in the tests that were carried out in the Instron machines was carried out automatically by the machines themselves. When the Suzpecar testing machine was used, both the load cell and the extensometers were manually calibrated.

The precision of the measurements obtained with the extensometers was ± 3 microns within the displacement range between -1500 microns and +2500 microns. Therefore, the measurements were within the range where the accuracy was remarkably good even with slightly pre-compressed extensometers.

Outside this interval, the measurements had worse precision, with absolute errors of up to 8 microns. We always worked within the interval where the precision was better to avoid obtaining data with a large absolute error.

The precompression of the extensometers was carried out manually and was set at approximately 900 microns. The specimens were cut in a rectangular shape and with dimensions of 300x50 mm to carry out the tensile tests. The approximate average thickness of the samples is 10 mm.

In general, the properties of the mortars improve when they have more closed pastes, that is, with less porosity. In the end, in the mortar, an attempt is made to reduce the porosity using the least amount of water possible. Some of these chemical products have been added to the mortar of the invention to see their influence on the mechanical properties of the material. In the case of the proposed composition, it is not only a matter of improving the properties of the compound to increase its field of application, but also an attempt is made to avoid the detrimental effects that the passage of time has on its mechanical properties.

While only a few features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. Therefore, it is to be understood that the appended claims are intended to cover all modifications and changes that fall within the true spirit of the invention.

Claims

CLAIMS Having sufficiently described my invention, I consider as a novelty and therefore claim as my exclusive property, what is contained in the following clauses:

1.- Dry mix composition useful in the manufacture of cementitious mortars to join and give a float finish to ceramic panels and/or coatings for swimming pools, characterized in that they include redispersible acrylic polymer, nonionic ethylene cellulose ethers, vinyl or acetate copolymer ethylene, toxitropic starch solution, calcium sulfate dihydrate, and 6mm polyester fiber.

2.- The dry mix composition for use in the manufacture of cementitious mortars to join and give a float finish to ceramic panels and/or coatings for swimming pools according to claim 1, characterized in that it includes the following percentage by weight of total solids :

• Redispersible acrylic polymer - 53.18 to 76.58%; · Nonionic cellulose ether - 6.07 to 6.69%;

• Ethylene vinyl or acetate copolymer — 5.05 to 5.57%;

• Toxitropic starch solution - 3.03 to 3.50%;

• CaSO ₄ -2H ₂ O - 20.25 to 22.33%;

• 6mm polyester fiber - 0.5 to 2.5%.

3.- The dry mix composition for use in the manufacture of cementitious mortars to join and give a floating finish to ceramic panels and/or coatings for swimming pools according to the previous claims, characterized in that it includes the following preferred percentage by weight of solids totals:

• Redispersible acrylic polymer - 63%;

• Nonionic cellulose ether - 6%; • Ethylene acetate or vinyl copolymer — 5%;

• Toxitropic starch solution - 3%;

• CaSO ₄ -2H ₂ O - 21%;

• 6 mm polyester fiber - 1%.