WO2023282734A1

WO2023282734A1 - Microcement for providing a polished finish to concrete floors and walls based on dry mixture compositions that include cellulose ethers, pregelatinised starch ether and redispersible acrylic polymer

Info

Publication number: WO2023282734A1
Application number: PCT/MX2022/050057
Authority: WO
Inventors: Daniel VAZQUEZ CARRERA
Original assignee: Vazquez Carrera Daniel
Priority date: 2021-07-06
Filing date: 2022-07-06
Publication date: 2023-01-12
Also published as: MX2021008187A

Abstract

The invention relates to dry mixture compositions that comprise non-ionic cellulose ether, polycarboxylate ether copolymer compound, CaSo4- 2H2O, pregelatinised starch ether, redispersible acrylic polymer and Arbocel W40 to obtain a microcement that can be used to provide a polished finishing to concrete floors and facade walls (visible concrete) and restore worn concrete floors, walkways, crossbars and pillars, on levelled surfaces, plaster, stucco, textures, and where a smooth polished finish must be provided, it can be used indoors and outdoors. One of the advantages of the composition is that, due to the large number of dispersants it provides, together with the reinforcement of the redispersible acrylic polymer which absorbs the different elastic, or contraction, stresses to which the microcement can be subjected, expansion joints are not required as occurs with other similar types of cladding.

Description

MICROCEMENT FOR GIVING A POLISHED FINISH TO CONCRETE ROADS AND WALLS BASED ON DRY MIX COMPOSITIONS INCLUDING CELLULOSE ETHER, PRE-GELATINIZED STARCH ETHER AND REDISPERSIBLE ACRYLIC POLYMER

5

FIELD OF THE INVENTION

The present invention falls within the branch of the construction industry in general, particularly to compositions for cementitious adhesives.

10

BACKGROUND OF THE INVENTION

AND! Polished concrete has always been one of the most logical choices in high-traffic industrial and commercial applications. However, in recent years it has also become a very attractive alternative for interiors and domestic uses.

The new techniques in polished concrete have allowed professionals to create increasingly elegant and higher quality finishes, which has increased its popularity, regardless of the client's profile and needs. 20 In addition to looking good, a polished concrete floor and wall offers exceptional durability for a low investment.

AND! polished concrete flooring is based on a well-proportioned concrete mix over a rustic floor. The ideal thickness of the application of the concrete mixture will depend on the estimates of the professional, who will consider all the pertinent conditions of the space to work.

The types of polymer-based cement to be used in the mortar will depend on the desired finish on the floor, including texture and color. The mixture, according to the size of the cloths for the application and the estimated traffic.

30 When looking for a colorful finish, it is customary to use white cement in the mix, which makes each tone stand out.

Currently, the polishing process involves resins and diamond discs, as well as specialized equipment such as a smoothing machine and a polisher. professional are necessary to achieve the desired results during polishing.

But polishing not only works to achieve the most suitable result according to the wishes of the user, but also to avoid problems in the long term. For example, special attention must be paid to the cracks and marks that appear during the procedure, in order to make them disappear in a timely manner.

Improper proportions during initial mixing can cause unwanted cracking and marking. Small holes in the finish and other minor irregularities can easily become serious problems in the long run.

Another example of common problems is that when there is an incorrect and uneven application of pigments, there can also be unwanted staining.

It is known that slurries of organic or inorganic substances in powder form, such as clays, ground silicate, carbon black, ground rock and hydraulic binders, are frequently combined with mixtures in the form of dispersants, this in order to improve their properties. Processing properties, ie, kneadable, spreadable, pulverized, pumpable, or fluidizable.

Said mixtures are capable of breaking the agglomerated solids, dispersing the particles formed and, in this way, improving fluidity. This effect is also used in particular, in a specific way in the production of construction material mixtures that comprise hydraulic binders, such as cement, lime, gypsum, calcium sulphate hemihydrate (basanite), or anhydrous calcium sulphate (anhydrite), or latent hydraulic binders such as fly ash, blast furnace slag or pozzolans.

Cracking of concrete pavements and façade walls can be caused by a combination of factors, such as drying shrinkage, thermal shrinkage, restraint (external or internal), subgrade settlement, and the application of loads.

The cracks that appear before the hardening of the concrete are usually the product of the accommodation of the mass of concrete or contraction of the surface, caused by a rapid loss of water, when the concrete is still in its plastic state. These cracks are the product of plastic contraction. As the concrete continues to set, cracks can develop on embedded members, such as reinforcing steel.

Plastic shrinkage cracks are relatively short-lived, and may appear before finishing work is completed, on those days when one or more of the following factors exist: wind, low humidity levels, and high temperatures. Under these conditions surface moisture evaporates faster than it can be replaced by a rise of bleed water to the surface.

This results in the top of the slab hardening faster than the bottom of the slab, and therefore as it hardens it begins to shrink more than the bottom concrete, allowing plastic cracking to develop in the slab. surface. After hardening, the concrete begins to dry out and shrink as a result of the release of moisture.

During the last fifty years, the use and study of fibers in construction has led to the development and manufacture of specific types of fibers that respond to different needs. Today, there are, and are used within the composition of concrete, glass fibers (especially resistant to alkalis), polypropylene, polyvinyl, polyethylene, steel, carbon, among others. Plastic, polypropylene, polyethylene or nylon microfibers help to reduce segregation of the concrete mix and prevent the formation of cracks during the first hours of concrete placement, or while the mix remains in a plastic state. Additionally, they control the appearance of cracks during the useful life of the element and provide greater resistance to fatigue. Polypropylene, glass and nylon fibers are materials used as microfibers intended to prevent concrete cracks in the fresh state, or during early ages due to plastic shrinkage. They are designed to be compatible with the highly alkaline environment of the concrete matrix: however, in your particular case, the glass fibers must be resistant to alkalis. Dispersants based on polycarboxylate ethers (PCEs) can be individually adapted to the requirements of the industry of! concrete. This is done by modifying the chemical composition of the copolymers.

PCEs generally have a polymeric backbone of carbon atoms and side chains comprising polyether structures. Acid groups are located on the main polymer chain. It is possible to modify the length of the side chain and the molar ratios of the acid groups and the polyether side chains, in order to obtain concrete and concrete of a very high quality.

To restore worn pavements, sidewalks, crosswalks and concrete columns, products are required that allow a very high plasticizing effect, fast setting, early strength, and low viscosity in cement produced with fibers. A high plasticizing effect, combined with good strengths, are currently possible from the composition of the present invention.

The composition of the invention also solves some drawbacks regarding the application of various floor covering materials that exist in the state of the art. One of the main things to note is that, for a correct execution, the total time for the finished coating can range between 3 or 4 days, even reaching longer times for full use of the coating, especially in the case of a coated floor. The time that elapses to finish the coating will be marked by the drying times between coats, thus, for example, between the primer coat and the base coat, a drying time is not necessary, but it is necessary between the base layer and the layer of fine microcement, and also between the layer of the latter and the sealing layer

However, this objective can also be achieved with products that are located in the state of the art, as is the case of plasticizers that have relatively long polyether side chains (greater than 300 g/mol), as described by For example, in Patent WO/05075529 A2, which results in fresh concrete having a decidedly high viscosity. As a result of this, freshly prepared concrete, especially in the case of low water/cement contents, is difficult to place and difficult to clean. shape. Consequently, in precast component jobs, molds can only be reliably filled at high cost and complexity.

A concrete mix that provides relatively low viscosity on the part of the concrete is Chryso's OPTIMA® 100, for example. This dispersant, which is not based on polycarboxylate technology (phosphonated polyether, corresponding to Patent WO 2010/112775 A1), however, is restricted in its use, since it particularly frequently does not show adequate plasticization at carbon content. low water/cement Said product also has retarding properties and is generally not so suitable for concrete of precast components.

Patent EP 2 090 553 A1 discloses a continuous process for the production of a copolymer comprising an acid monomer and a polyether macromonomer.

Attempts have also been made to find additives that overcome the above problems, and that act as multifunctional additives, for example, as both a flocculant and a setting accelerator, in order to reduce the use of different additives in the preparation. of cementitious compositions, are shown in the following patents that involve chitosan:

The document BRPI0600628 describes a cementitious composition suitable for the construction of oil wells comprising chitosan in a proportion of 1-5%. The addition of chitosan to the portland cement matrix gives it greater mechanical resistance and reduces the probability of cracks in severe temperature conditions.

Application WO 86/00291 describes cementitious compositions comprising a flocculating agent selected from a list of polymers including chitosan. However, the preferred embodiment contemplates the use of carboxymethylcellulose.

Document JP52022026 describes a cementitious composition comprising portland cement and chitosan. The product molded with the composition described in this document has a resistance to bending higher than that achieved for the molded product in the absence of chitosan.

JP2QG1316162 discloses a method for increasing the strength of a calcium silicate wall and roof board comprising adding an acidic solution of chitin and chitosan to the base material during curing in an autoclave.

However, for the above applications, there are currently no acceptable solutions that combine nonionic cellulose ether, polycarboxylate ether copolymer compound, CaSO4-2H20, pregelatinized starch ether, and redispersible acrylic polymer.

Another disadvantage of using commercial and state-of-the-art materials is the expiration time of some of the components of these coatings. Depending on the manufacturers, there are products that present problems, especially those related to the sealing layer, which have an expiration date of 3 months from their manufacture (worst case), even if the product has not been opened. Therefore, if there is a variation in the volume of work in a company that applies this type of product, the quantity of this product in stock must be foreseen.

There are commercial products for which builders advise against their application on slippery surfaces, or with a slight slope that may favor slipping. Thus, these companies advise against its application in access ramps, wet areas, and shower or bathtub areas, unless some measure is taken to prevent slipping, which is not the case with the composition of the present invention.

OBJECT OF THE INVENTION

It is an object of the present invention is to use dispersants for the manufacture of microcements. Another object of the invention is to propose a microcement useful for giving a polished finish to concrete surfaces.

Another object of the invention is to propose a microcement useful for restoring worn pavements, sidewalks, crosswalks, and concrete columns. DESCRIPTION OF THE INVENTION

The present invention refers to dry mix compositions comprising nonionic cellulose ether, composed of polycarboxylate ether copolymer, CaSC>4-2H2O, pregelatinized starch ether, redispersible acrylic polymer and Arbocel W40, to obtain a microcement useful for giving a polished finish to concrete pavements, facade walls (exposed concrete type), restoring worn pavements, sidewalks, crosswalks, and concrete columns, on flattened surfaces, plaster, stucco, textures, and where a smooth polished finish is required. it can be used indoors and outdoors.

In accordance with the present invention, the dry mix compositions for use in the manufacture of microcement comprise the following percentage by weight of total solids: Nonionic cellulose ether - 32.69 to 44.46

%;

• Polycarboxylate ether copolymer compound - 2.97 to 3.16%;

• CaS0 ₄ - 2H ₂ 0 - 11.71 to 12.91

%; · Pregelatinized starch ether - 7.46 to 7.92

%;

• Redispersible acrylic polymer - 32.05 to 46.152

%;

• Arbocel W40 - 2 to 6%.

In accordance with the present invention, the preferred dry mix compositions for use in the manufacture of microcement comprise the following percentage by weight of total solids: Nonionic cellulose ether - 36.54%

• Polycarboxylate Ether Copolymer Compound - 2.92%

• CaS0 ₄ - 2H ₂ 0 - 11.69 % • Pregelatinized starch ether - 7.31%

• Redispersible acrylic polymer - 36.54%

• Arbocel W40 - 5%

One of the main advantages of the composition of the present invention is the quality of the microcement, in terms of its use in façade design, an advantage offered by this type of coating according to the proposed composition, since it is a continuous coating and also with decorative quality.

Another of the advantages of the composition is that due to the large amount of dispersants that it provides, together with the reinforcement of the redispersible acrylic polymer, which absorbs the different elastic or contraction stresses to which the microcement may be subjected, it does not it needs expansion joints, as if it occurs in other similar types of coatings. Advantageously, the microcement of the present invention increases the workability of fresh concrete, allowing it to be more workable, allows less water to be used in the mix to achieve better fluidity, improves the water/cement ratio and therefore the resistance of the concrete. and decreases the dose of cement in the concrete mix.

In the composition of the invention, the polycarboxylates are, for example, copolymers of maleic acid and/or acylic acid with polyether macromonomers (for example, alkoxylated vinyl ethers or alkylpolyalkylene glycols (meth)acrylate esters).

Dispersants based on polycarboxylate ethers can be individually adapted to the requirements of the present composition. This is done by including the other components. The composition of the present invention allows the reduction of the dose of cellulose ether that can be from 32.69 to 44.46%, percentage by weight of total solids, this without compromising the performance of the product and the application. Polycarboxylate is a type of superplasticizer in the form of a free-flowing powder, as a universal product, designed for fluid mortar applications with universal and special cementitious binders.

In the composition of the invention, the polycarboxylate must be mixed dry with the other dry ingredients in a minimum dose of 2.97 to 3.16% by total weight of cementitious components.

In such a composition, the ether polycarboxylate copolymer compound anchors its backbone to the surface of the cementitious binder particle while the unique comb structure as side chain stretches in water.

The combination of electrostatic force and steric stretching effect imparts low water demand and high flowability to mortars.

Polycarboxylate ethers generally have a polymeric backbone of carbon atoms and side chains comprising polyether structures. Acid groups are located on the main polymer chain. It is possible to modify the length of the side chain and the molar ratios of the acid groups and the polyether side chains in order to obtain concrete of very high quality.

The specific synthesis of these macromolecules, especially the side chains, is what makes the microcements of the invention much more specific, since depending on the specific application sought, they are capable of enormously varying the workability of concrete and concrete. , or they can significantly delay or speed up setting, improve initial and/or final strength, etc.

With this type of additives, water reductions of up to 40% can be achieved. All these characteristics offer new applications and make them optimal additives for making self-compacting concrete and concrete, concrete and concrete for precast, high-performance concrete and concrete, to restore worn pavements, and broken or cracked sidewalks.

In the composition of the invention, the redispersible polymer powders are included in a percentage by weight of 32.05 to 46.152%, where these powders Redispersibles are commonly made by atomizing 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 adherence to the most varied supports and even to those that otherwise could not be reversed. The polymer modification additionally confers flexibility to the system and improves thixotropy, flowability and water retention.

The present invention is further illustrated by the following examples:

EXAMPLE

PREPARATION MODE

Put 10 liters of gray or white cement in a 19-liter bucket, a 130-gram envelope with the composition of the invention, mix in the bucket for up to 2 minutes dry.

Put 2.5 liters of drinking water in another bucket, gradually add our cement mixture and the composition of the invention, beat with an electric mixer until a fine homogeneous paste is obtained.

If you need to work with a portion of the mixture, only add the water that you calculate to work, since the mixture once wet hardens from 80 to 120 minutes in a tray, the rest must be kept in a dry and cool place.

The substrate where the micro cement will be applied is moistened, it is applied by layers or hands, until the desired finish is obtained. If you want to shine it, it is necessary to accentuate the trowel or spatula on the finish as soon as it is in the process of setting very firmly until obtaining that effect (mirror type). To obtain optimal product performance, the support must be healthy, with open porosity, clean, without surface laitance, without a large amount of moisture, without oil, grease, previous layers, loose particles or other contaminants. Dust, loose or poorly adhered parts must be removed from the surface to be treated before applying the product. Temperature optimum for the use of this product ranges between 10 °C and 36 °C. Before starting to apply the next layer, it is recommended to let the primer dry for at least an hour, depending on environmental conditions such as temperature and/or humidity.

To finish concrete block walls, the surface must be porous to provide proper absorption or it must be sanded and scored to provide an adequate mechanical bond. Lightly spray walls with water to produce uniform absorption. Fill and level all voids, depressions and joints with material of the composition of the invention, dry; then place the subsequent layer.

In the present invention, the cement for masonry is the finely pulverized material that may contain one or more of the following materials: Portland clinker: Any type of cement specified in the Mexican Standard NMX-C-414-ONNCCE, limestone, clay, pozzolan, granulated furnace slag, fly ash and gypsum. At the discretion of the producer, other materials can be incorporated, in addition, as a grinding aid or to impart certain properties to the mortar, in such a proportion that they are not harmful to the subsequent behavior of the product, in accordance with what is specified in NMX-C-133. SCFI. Cement for masonry (mortar), when mixed with sand and water, produces mortars with special characteristics that are used for gluing partitions, plastering, plastering, flattening, decorative work, etc.

In the invention, the mortar is the material made up of a finely pulverized hydraulic cementing agent, which, when added to it with water and sand, has the property of setting both in air and in water and forming a hardened mass that acquires mechanical resistance over time. of time to a maximum point. For the purposes of this Mexican Standard, masonry cement (mortar) is classified into a single type, with a single quality grade.

The physical specifications to characterize the quality of the cement for masonry (mortar) are established according to the determination of the unit and condition of health (expansion in autoclave), initial setting time, final setting time, compressive strength at seven and 28 days, air content and water retention. Properties and Tests Applicable to the microcement of the invention The main role of the microcement of the invention is linked to two main aspects: the control of the propagation of a crack in a material in a state of service, reducing the opening of the cracks, and the transformation brittle to ductile behavior of a material.

The most important aspect of mechanical performance for microcement-reinforced concrete is tensile behavior. However, it is difficult to carry out uniaxial tensile strength tests, especially if one wants to know the response of the material after the maximum load. The properties in the fresh state are influenced by the geometry of the microcement fibers and their dosage.

The manageability of the microcement depends on the volume dosage of the cellulose ether fibers, mainly, the geometry, the surface state and the bond between them, the dimensions of the aggregates and their relative quantity.

The present invention provides a fine microcement with a non-slip finish. This allows the applicator great flexibility in his work to adapt to the wishes and needs of his clients. This non-slip, safety-oriented, redispersible acrylic polymer-based finish allows a person to move safely in all of the wet and slippery areas described above.

The slump test with the Abrams cone in concrete reinforced with microcement presents certain difficulties, since the concrete matrix in most cases is cohesive and does not flow freely. For its part, to determine the impact resistance of concrete at ICONTEC, two types of tests were carried out: Impacted Plate Method and Drop-weight test (ACI-544.2R-89).

It should be said that the appropriate test to measure fluidity in this type of concrete is by means of the inverted cone, in which an internal vibration is used.

Toughness is the property that simultaneously takes into account the ability of a material both to resist a load and to deform. It is a measure of energy absorption expressed in units of force. by distance (N x mm). This property is determined in bending tests on beams or plates where the load and deflection are recorded.

Impact resistance is the breaking energy under an impulsive load. It is normally obtained from a test that includes a tablet, simply supported on its perimeter, into the center of which a sphere is dropped several times from a standard height.

Design parameters to repair slabs with concrete reinforced with microcement of the invention.

For the repair of concrete slabs reinforced with microcement of the present invention, it is necessary to take into account various parameters such as: the resistance of the soil that is below the slab, the magnitude and type of loads that act on the slab and the characteristics of the concrete, where the quality of the fiber of the microcement that is being placed on the slab is intrinsic.

It does not need very heavy machinery for its implementation, perhaps the heaviest machine used is an electric mixer for mixing mortars. Therefore, it will not take up much space in the workplace, nor does the company need extensive logistics to be able to apply this product.

The fine colored microcement of the composition of the invention is used for continuous coatings in which it is desired to obtain any type of decoration, both on the floor and on the walls. In addition, it also allows covering old ceramic tile or platelet coverings, as long as they are well protected against humidity.

Depending on the desired aesthetic finish and the conditions of the support to carry out the decorative coating, at least two or three layers of fine color must be applied. It is applied over the base coat, which must be moistened (spraying is recommended) for a better reception of this new layer.

The maximum thickness of this composition is around 0.1 mm, this layer of fine colored material will provide a thickness of 1 mm to the total coating.

The performance of this product, and always in general terms, will be around 1.7-2 kg/m ² /mm of thickness. This performance can be modified depending on the conditions of the support, such as porosity, surface roughness, permeability, etc. The support of the previous layer, the leveling layer, must be prepared mechanically by means of sanding equipment or similar to eliminate the surface laitance and acquire an open-pored surface, whenever it is considered appropriate. The drying time of this material is around 3 days, depending on the weather conditions and the support.

According to the inventors, the microcement of the invention is used for all types of coatings, however, they also provide different materials for other compositions of their inventions, depending on the type of support to be coated, for example, they offer compositions if it is a question of coating a gypsum panel, or polystyrene, yes, on the same base layer a fine microcement, but if it is about covering a floor, a microcement with different characteristics or microconcrete, as some companies call it, is used.

This is a great advantage of the present invention, as it is able to create synergy with other of his inventions, an approach that suggests that a builder, the greater the variety of products he has, his work will be easier, since each work has a different typology and can be have a product that best suits the needs of the work; On the other hand, if a builder only has a standard product for microcement, it will be a more general product and will not be adapted to the real needs that are expected to be obtained from microcement.

The microcement of the present invention must be applied according to the following method;

The application of the microcement of the invention can be referred to as a trade of specialist bricklayers who are aware of the requirements to correctly apply the product. Respecting the work methods corresponding to each type of support will allow the applications to be completed successfully and give users all the guarantees offered by the microcement of the present invention.

According to the application method, the preparation of the support is as important as the application or protection of the microcement of the present invention. Before starting, it is essential to know the material that is You want to cover in order to plan the work correctly and choose the composition of the appropriate invention. Before beginning, the following questions should be considered:

Plan the work to give the microcement application adequate time and space between other activities. The application of microcement will always be left as the last trade to intervene except for the last coat of paint, the placement of trims, carpentry and toilets.

Depending on the application method, the support to be coated must be known in order to gather the appropriate material, it is necessary to control and monitor that the support is in optimal conditions to cover it.

Consolidate the surfaces to be coated with quick-setting, low-shrinkage mortars. In the case of applying the microcement of the invention on a cement-sand mortar with cracks, the support can be primed with concentrated liquid.

Protection of the microcement of the invention against humidity originating in the support. The microcement should not be applied on wet surfaces, it is necessary to remove them before starting the application or to interpose a physical barrier.

Depending on the application method, the surfaces that are not going to be coated must be adequately protected to avoid stains (microcement adheres very strongly and is difficult to clean once it is dry).

Plug the drain outlets and remove the stopcocks of the different water installations, as well as the accessories of the electrical installation.

The preparation of the support is as important as the application. If the support does not meet the necessary conditions, the microcement of the invention cannot be applied with guarantees. For proper preparation, the following issues must be considered:

Support cleaning. The support must be clean, free of dust and grease.

According to the application method, the state of the application base must be consistent. Supports with dusty mortar or loose tiles are not suitable. Depending on its state, it will have to be withdrawn or consolidated. I know recommends consolidating and regularizing the support with fast-setting, low-shrinkage mortars, which may be another of the inventions.

If the support is a common cement-based mortar, it must have gone through a sufficient setting process to prevent the appearance of cracks in the microcement. To prepare the support, it is recommended to use quality fast-setting cement mortars. It should be taken into account that the weather, ambient temperature and relative humidity affect the drying process of the mortar and accelerate or delay the setting process.

According to the application method, the planimetry of the application support is essential. It must correspond to the appearance that you want to obtain with the coating.

The microcement of the invention is applied in layers of no more than 1mm, and the sum of these will not exceed three millimeters, so it will not be possible to resolve planimetry issues with this product. Microcement, which can be applied to floors, walls and even ceilings, is not a self-leveling mortar. The final planimetry will depend on the support and the work of the applicator.

Protect the work area properly and the surfaces that are not going to be coated to avoid stains (microcement adheres very strongly and is difficult to clean when dry).

The type of trowel used in the application will determine the appearance of the microcement coatings. If a flexible rubber trowel is used, the water will be more discreet. If the steel trowel is used, the microcement will “burn” and the mark of the tool will be more evident. The waters will be more evident with dark colors. Coordination of the work teams In works of a certain size, the coordination of the applicators will be taken into account to achieve a job without cuts. In the case of any distribution, it will begin with the room furthest from the exit door of the home or premises.

According to the application method, in each room it will begin in the corner opposite the door. The wider the room, the more applicators will be needed on that front. To avoid cuts you can keep for a time a microcement cord of the fresh invention, until that front is resumed again. It should be taken into account that whoever carries out the application work in a corridor (narrow area), will go faster than the one who is in charge of a larger surface.

If you know how to work microcement as described in the previous sections, you can obtain very elegant and natural finishes.

Depending on the application method, if you want the microcement coating to have a natural appearance, without noticing the trowel marks, you should apply the first coat as if it were the last. The microcement must be applied without leaving burrs or reliefs that reveal the passage of the trowel. If the next coat is applied over this type of application, the microcement will "burn" with the trowel, highlighting the irregularities of the previous coat. This effect will be more evident with the steel trowel.

The microcement of the invention must be regularized after each coat to avoid the effect described in the previous section. A smooth roughing will be carried out with a low-revolution rotary-orbital sander or by means of a sanding glove. The abrasion resistance of the microcement of the invention is quite high. For this reason, silicon carbide sandpaper must be used. As soon as the microcement goes down in tone, the operation will begin. This change in tone will indicate that the microcement is walkable and hard enough to proceed with sanding. The tone change will occur between 2 and 4 hours after application depending on the temperature, ambient humidity and ventilation of the room. The microcement of the present invention hardens quickly and is quite resistant to abrasion for being a continuous coating. Therefore, it is recommended to proceed with sanding when the tone change occurs to speed up the task.

When the sanding work is carried out, it must be ensured that the last coat of microcement is sanded smoothly. With one hand the sander or the sanding glove will be passed and with the other one will be checking by touch if the sanding is correct. If you work properly, you will avoid three types of characteristic stains: circles, contour lines and black marks. The sander will have to be of the rotary-orbital type to avoid leaving circles. will be procured keep it moving constantly. If the sanding were excessive, you would end up seeing the microcement of the previous coat and leaving some characteristic "contour lines" that would indicate that it has gone to the lower layer. As soon as the sandpaper wears out, it will have to be changed. If the change is not made, the sandpaper goes from sanding to polishing, leaving black marks on the microcement.

Subsequent touch-ups will leave obvious and unsightly marks. The best thing to do when the finish is not as desired is to reapply an additional coat. Overgoing an area with the trowel will leave dark marks. This can happen, for example, when material accumulates on the floor at the end of the application process, forcing us to pick up the excess microcement and work it more with the trowel.

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

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

1 Composition to make a microcement useful for giving a polished finish to concrete pavements, facade walls, restoring worn pavements, sidewalks, crosswalks, and concrete columns, characterized in that it includes non-ionic cellulose ether, composed of polycarboxylate ether copolymer, CaSC>4-2H2O, pregelatinized starch ether, redispersible acrylic polymer, and Arbocel W40.

2.- The microcement composition for use in the manufacture of adhesives according to claim 1, characterized in that it includes the following percentage by weight of total solids:

• Nonionic Cellulose Ether - 32.69 to 44.46%

• Polycarboxylate ether copolymer compound — 2.97 to 3.16%

• CaS0 ₄ - 2H ₂ 0 - 11.71 to 12.91%

• Pregelatinized starch ether - 7.46 to 7.92%

• Redispersible acrylic polymer - 32.05 to 46.152%

• Arbocel W40 - 2 to 6%

3.- The microcement composition for use in the manufacture of adhesives according to the previous claims, characterized in that it preferably includes the following percentage by weight of total solids: • Non-ionic cellulose ether - 38.46%

• Polycarboxylate Ether Copolymer Compound - 3.07%

• CaS0 ₄ - 2H ₂ 0 - 12.30%

• Pregelatinized starch ether - 7.69% · Redispersible acrylic polymer - 38.46%

• Arbocel W40 - 5%