Technical Field

The present invention relates to products for construction, in particular prefabricated products of concrete.

Background Art

In the construction field, urbanization and paving of large areas, the use of prefabricated concrete elements such as solid pieces, slabs, blocks, curbs and the like is known and appreciated.

Such products are usually produced by molding the concrete in special molds using vibrating presses. They can be composed in their entirety of a single homogeneous concrete mixture. In this case, they are called “single-layer” products. Alternatively, they can be composed of two different concrete mixtures. In this case, they are called“double-layer” products.

The two concrete mixtures differ from each other in their so-called mix design. The mix design is obtained by dosing different aggregates with specific particle size curves and with the addition of a suitable cement binder, e.g. type II/ A-L 42.5 cement and/or lime.

Furthermore, various additives are often used which have plasticizing and water-repellent properties. The result is a mixture with a so-called“moist earth” consistency, i.e. with a low ratio of water and cement (about 0.2 - 0.4 in mass). This type of mixture allows maximizing the mechanical characteristics of the resulting concrete, typically maximizing strength.

In the following treatise, specifically considered will be solid pieces or blocks for the creation of self-locking floors; slabs for the creation of traditional or floating floors and/or for the creation of ventilated facades; blocks for the creation of exposed walls for curtain walls, load-bearing, fireproof and containment walls; curbs for the creation of perimeter borders for floors or roadways; and the like.

Such prefabricated products are expressly mentioned only by way of example and without any limitative intent. The expert in the field will not have any difficulty in applying the invention to other elements similar in terms of structure and/or intended use. It is the applicant’s opinion that these solutions, while widely appreciated, may be subject to further improvements.

For example, the behavior of concrete products in poor lighting conditions can be improved. In such conditions, in order to guarantee the correct visibility of the layout of lanes and paths, or of the encumbrance of walls and curbs, special lighting is required.

A lighting system however entails additional time and costs in the installation phase, and high costs for the supply of electricity for the entire operating life of the system.

In addition, the installation of lighting systems, even just for courtesy, in prefabricated structures and floors often requires tampering with the elements described above and/or ad hoc realization.

These operations are often carried out on site, during the installation of the prefabricated products.

However, precisely because of the high mechanical characteristics of the vibro- compressed concrete, these operations are difficult and often involve undesirable surface alterations compared to what was imagined during the project phase.

Description of the Invention

The object of the present invention is therefore to overcome the drawbacks highlighted above in relation to the background art.

In particular, one aim of the present invention is to make available prefabricated concrete products that help solve the problem of visibility in low light conditions, which increase the safety of the products and which limit energy consumption.

Brief Description of the Drawings

This object and these aims are achieved by means of a prefabricated product of vibro-compressed concrete according to claim 1.

To better understand the invention and appreciate its advantages, some exemplary yet non-limiting embodiments thereof are described below, referring to the attached drawings, in which:

- Figure 1 shows schematically an embodiment of a prefabricated concrete product according to the invention; and

- Figure 2 schematically shows another embodiment of a prefabricated concrete product according to the invention.

Embodiments of the Invention

The invention relates to a prefabricated product 10 of vibro-compressed concrete for construction works.

The product 10 according to the invention comprises an outer portion 12 made of a first concrete mixture and having an outer surface 14 intended, in use, to be exposed to sight.

In the product 10 according to the invention the first mixture comprises fragments 16 of glass comprising photoluminescent pigments.

More in detail, within the first concrete mixture fragments 16 of glass are dispersed, in quantities ranging from 0.1% to 10% by weight, preferably between 3% and 5% by weight of the total of the first mixture.

The fragments 16 of glass preferably have an average particle size of about 1-10 mm, preferably of about 3-6 mm.

The photo-luminescent pigments present in the glass, known in themselves, are able to absorb a portion of the light radiation to which they are exposed (typically ultraviolet radiation) and then, themselves, emit a slight light radiation when the external radiation fails.

Different types of pigments are known, capable of emitting light of different colors such as e.g. yellow, green, blue and orange.

As mentioned above, the outer surface 14 of the outer portion 12 of the product 10 is intended, during the correct use of the product 10, to be exposed to the users’ sight. For example, if the product 10 is intended for flooring, the outer surface 14 is the walk-on surface.

According to several embodiments, the product 10 according to the invention further comprises an inner portion 22 made of a second concrete mixture different from the first mixture.

Some possible differences between the two mixtures are describer later on in more detail. If the outer portion 12 comprises an outer surface 14 intended, in use, to be exposed to sight, the inner portion 22 comprises an inner surface 24 intended, in use, to be placed against a support structure.

For example, in the case of solid pieces, slabs and other products 10 intended for flooring, the inner surface 24 is that which is placed on the substrate during installation and which therefore remains covered during the entire operating life of the product 10.

Similarly, in slabs intended for the construction of ventilated facades, the inner surface 24 is that which is placed against the wall to be covered and/or to the support structure, while the outer surface 14 is the opposite one.

In the case of building blocks, potentially all walls can be exposed during the operating life of the product 10, which is why all walls can be considered as outer surfaces 14.

In this case, if the product 10 comprises an inner portion 22 made of a second mixture, the latter represents a sort of core which can be almost completely covered by the outer portion 12.

As mentioned above, the two concrete mixtures differ from each other.

For example, they may differ only in terms of the fragments 16 of glass, present in the first mixture and absent in the second mixture. Alternatively, the two mixtures may also differ as regards one or more of the other components of the concrete.

As is well known, concrete comprises aggregates, a cement binder, e.g. cement type II/A-L 42,5 or lime, and one or more additives.

The two mixtures may differ from each other also for one or more of these elements.

For example, the second mixture, which originates the inner surface 24 and is therefore not exposed to sight during the operating life of the product 10, may comprise aggregates of a higher particle size and lower quality, which give it a less refined appearance compared to the first mixture.

The first mixture may also comprise a photo-catalytic cement, known in itself. When exposed to sunlight or ultraviolet radiation, this cement is able to accelerate the natural oxidation processes of pollutants and their degradation into non-toxic and non -harmful substances.

Since the outer surface 14 of the first mixture is exposed to sight, it may also be exposed to ultraviolet radiation (whether solar and/or artificial), which supports the operation of the photo-catalytic cement very well.

Among the well-known effects of photo-catalytic cement, the most appreciated are a significant reduction in pollutants and the maintenance of the original color of the concrete itself.

A photo-catalytic cement adapted to be used in the product 10 according to the invention is e.g. Tx Active® cement marketed by Italcementi S.p.A.

The first mixture can also comprise quartz aggregates.

These aggregates, characterized by high hardness, are particularly appreciated in floors designed to withstand very high traffic and/or vehicular traffic.

The hardness of the quartz in fact strongly limits floor wear, even in the case of intense use.

In this regard, it should be noted that the fragments 16 of photo-luminescent glass are also characterized by high hardness, which makes them equally suitable for this type of use.

Other photo-luminescent materials, such as e.g. resins and polymers, are known, but are not adapted to be used in products according to the invention because they cannot adequately withstand wear.

As mentioned above, concrete mixtures also comprise aggregates that make up a large part of the mixture itself in volume.

Usually, in ordinary concrete, these aggregates are made of sand and/or gravel and represent about 70-80% by weight of the entire mixture.

The use of other aggregates can however have some specific advantages.

For instance, in the product 10 according to the invention, the first mixture and/or the second mixture may comprise expanded clay and/or pumice and/or expanded glass.

These aggregates have the advantage of combining adequate mechanical characteristics with an extremely low apparent density.

The use of expanded clay and/or pumice and/or expanded glass therefore makes it possible to obtain a lighter concrete mixture. As an example, consider that ordinary concrete has a density of about 2200 kg/m3, while concrete comprising expanded clay and/or pumice and/or expanded glass can reach a density of between 1000 and 1600 kg/m3.

In addition, the density of expanded clay, pumice and expanded glass is very low because of their honeycomb structure which allows the inclusion of many small air bubbles.

For this reason, these materials have, compared to ordinary concrete, much better characteristics in terms of thermal and acoustic insulation and are therefore particularly suitable for the construction of external walls.

In accordance with other embodiments, the first mixture and/or the second mixture comprise mineralized hemp.

Mineralized hemp is obtained by treating the woody part of useful hemp or fiber hemp plants (cannabis sativa).

This woody part, called hemp core, is treated with lime until it is completely mineralized.

The lime used in this process is mostly hydrated lime, i.e. calcium hydroxide or Ca(OH)2 and a small amount of quicklime, i.e. calcium oxide or CaO.

The fibrous material obtained in this way can replace or join the other aggregates in the concrete mixture, introducing some specific advantages.

Hemp (as well as pumice, expanded clay and expanded glass) is also rather light and has excellent insulating properties.

Moreover, hemp is a renewable resource and has the particularity of having a negative balance in terms of CO ₂ . In fact, like all plants, hemp plants absorb CO ₂ from the atmosphere and use it to build their own structure.

Once mineralized with lime, the structure of the hemp core stabilizes and retains its carbon for an indefinite time.

The use of mineralized hemp is therefore one of the few industrial processes which allows removing a quantity of CO2 from the atmosphere.

The use of hemp in building products has been studied by the applicant and is the basis of the products it markets under the name Blocco ambiente - Tecnocanapa. According to the type of use it is provided for, the outer surface 14 of the outer portion 12 of the product 10 according to the invention may comprise one or more of the surface finishes out of those suitable for this kind of product.

Such surface finishes may, for example, be those already used for the treatment of natural or artificial stones intended for similar uses.

Some finishes, such as polishing and smoothening, guarantee a smooth and uniform surface with low roughness, adapted to be used in civil environments where, for example, pedestrians, pushchairs, hand trolleys, bicycles or the like have to transit.

Other finishes, on the other hand, such as hammering, shot-peening, chiseling and bush-hammering, guarantee a very rough, coarse and harsh surface, adapted to be used in industrial environments where, for example, motorized trucks, motor vehicles or the like have to transit, or for walls requiring a rustic finish. There are also finishes such as brushing and sandblasting which ensure a surface with intermediate roughness.

As is widely known in the industry, the same surface of the same product 10 may comprise areas with different finishes, e.g., in order to create aesthetic effects.

Furthermore, different finishes allow creating tactile bands on the flooring for blind and visually impaired users.

By way of example, figure 1 shows a solid piece 10 according to the invention, comprising a single portion made of a first mixture of concrete and having an outer surface 14 intended, during use, to be exposed to sight.

The first mixture comprises fragments 16 of glass comprising photo- luminescent pigments.

This embodiment, which has the well-known single-layer structure, is simple to create and has the advantage of exposing the photo-luminescent fragments 16 on all the side faces of the solid piece 10.

One drawback of this embodiment is that it requires a large amount of photo- luminescent fragments 16, many of which remain inside the mixture and are not at all exposed to sight.

Still by way of example, Figure 2 shows a solid piece 10 according to the invention, comprising an outer portion 12 and an inner portion 22. The outer portion 12 is made with a first concrete mixture and has an outer surface 14 intended, in use, to be exposed to sight.

The first mixture comprises fragments 16 of glass comprising photo- luminescent pigments.

The inner portion 22, on the other hand, is made with a second concrete mixture and has an inner surface 24 intended, in use, to be placed next to a support structure.

As can be seen, the thickness sl of the outer portion 12 represents a minimum part of the overall thickness st.

This embodiment, which incorporates the known double-layer structure, is more complex to be made and has the drawback of exposing the photo-luminescent fragments 16 on only one face of the solid piece.

On the other hand, a notable advantage of this embodiment is that it requires a relatively small amount of photo-luminescent fragments 16.

As an example, it should be considered that, according to some embodiments of solid pieces or slabs with a double-layer structure, for each square meter of flooring, a quantity of photo-luminescent fragments 16 comprised between lOOg and lOOOOg, preferably comprised between 200g and 2000g, even more preferably comprised between 600g and 800g, is sufficient.

According to another aspect, the invention relates to a method for producing a prefabricated concrete product 10.

The method according to the invention comprises the phases of:

providing the components: at least one aggregate, a cement binder, water, and fragments 16 of glass comprising photo-luminescent pigments;

dosing the aggregate in a percentage comprised between 65% and 75% by weight;

dosing the cement binder in a percentage comprised between 18% and 30% by weight;

dosing the fragments 16 of glass comprising photo-luminescent pigments in a percentage comprised between 0.1% and 10% by weight;

dosing water in a percentage comprised between 4% and 8% by weight; mixing the dosed components so as to obtain a first mixture; amalgamating the first mixture so as to make it uniform;

placing the first mixture in a mold;

applying a combined action of vibration and compression to the first mixture in the mold;

removing the product 10 from the mold; and

waiting for the curing of the first mixture.

According to some embodiments of the method, the phases of removing the product 10 from the mold and waiting for the curing of the first mixture, if necessary, can be carried out in reverse order, i.e. letting the mixture cure in the mold and then removing it once it has cured.

The method according to the invention may also comprise other phases, to be carried out independently of those described above.

For example, the method may comprise the phases of:

dosing the aggregate in a percentage comprised between 80% and 90% by weight;

dosing the cement binder in a percentage comprised between 10% and 20% by weight;

dosing water in a percentage comprised between 2% and 5% by weight; mixing the dosed components so as to obtain a second mixture;

amalgamating the second mixture so as to make it uniform;

placing the second mixture in a mold;

applying a combined action of vibration and compression to the second mixture in the mold;

waiting for the curing of the second mixture.

In accordance with an embodiment of the method, the first and the second mixture can be placed in the same mold.

In this case, the second mixture is placed in the mold, the combined action of vibro-compression is applied for the first time, the first mixture is placed on top of the second mixture, and the combined action of vibro-compression is then applied for the second time.

The two mixtures are then left to cure together. With the embodiments of the method described above, a product 10 is obtained comprising an outer portion 12 made with the first mixture and an inner portion 22 made with the second mixture.

In accordance with some embodiments, the method also comprises the phase of also preparing a photo-catalytic cement and/or quartz aggregates in the first mixture.

In accordance with some embodiments, the method also comprises one or more of the following phases:

preparing expanded clay in the first mixture and/or in the second mixture; and/or

preparing pumice in the first mixture and/or in the second mixture; and/or preparing expanded glass in the first mixture and/or in the second mixture; and/or

preparing mineralized hemp in the first mixture and/or in the second mixture.

The at least one aggregate prepared with the method according to the invention may comprise one or more out of pumice, expanded clay, expanded glass, mineralized hemp.

In accordance with some embodiments, the method further comprises, after the phase of removing the product 10 from the mold, the phases of treating an outer surface 14 made with the first mixture by one or more of the following treatments: polishing, smoothening, brushing, sandblasting, hammering, shot- peening, chiseling, bush-hammering.

As the skilled person can well understand, the invention allows overcoming the drawbacks highlighted above with reference to the background art.

In particular, the present invention provides a product 10 on the outer surface 14 of which are provided photo-luminescent fragments 16.

These fragments 16 are able to store light energy while they are exposed to external light radiation (typically solar radiation) and then release their own light radiation when the external one fails.

Such behavior ensures that, according to the invention, the products are clearly visible in the dark and that, therefore, in many of the applications for which they are intended, no lighting system is necessary.

The invention therefore helps to solve the problem of visibility in poor lighting conditions, increases the safety of the products and limits the consumption of energy.

It is clear that the specific characteristics are described in relation to different embodiments of the invention with the intent of exemplifying and not limiting. Obviously an expert in the field can make further changes and variations to the present invention, in order to satisfy contingent and specific needs.

For example, the technical characteristics described in relation to an embodiment of the invention may be extrapolated from it and applied to other embodiments of the invention.

These changes and variations are also included in the scope of protection of the invention, as defined by the following claims.