ES2443586T3 - Reinforcing steel bars for concrete provided with bituminous protection against oxidation, as well as a related treatment method - Google Patents

Abstract

Metal bar (B), of any type and diameter for applications in the construction of steel structures or for reinforcements, obtained by means of a treatment (P) that provides for the application of a bituminous antioxidant protection medium (Sb-Eb), Optimally compatible with any type of concrete, for construction structures with and without reinforced concrete that are not affected by corrosion and for this reason have durability over time, characterized by being obtained through a treatment (P) that provides the impregnation of the bar itself with a bituminous solution based on oxidized bitumen (Sb) and a bituminous emulsion (Eb), this being done by: - a first immersion (F1) of one or more metal bars at room temperature (B0) in a first tank (V1), which contains a bituminous solution based on oxidized bitumen (Sb) and quick-drying technical solvents, also called "cold solution (Sb)", said solution stored at a temperature (T1) between 6 ° C and 10 ° C, for an interval (Δt1) between one and two minutes, in order to obtain bars impregnated with bitumen (B1); - a first drying (F2) of the impregnated bars (B1) in the air; - a second immersion (F3) of said impregnated bars (B1) in a second tank (V2) containing a bituminous emulsion (Eb), also called "hot emulsion (Eb)", said emulsion being stored at a temperature (T2) between 350 ° C and 450 ° C, preferably approximately 400 ° C, for an interval (Δt2) between one and two minutes, in order to obtain 20 bars impregnated and treated with the bituminous emulsion (B2); and - a final stage (F4) of drying said bars (B2) impregnated and treated with the bitumen emulsion, allowing them to cool to room temperature (TA) during an interval (Δt3), variable depending on the ambient temperature (TA), between approximately ten minutes in winter and approximately twenty minutes in summer, in order to obtain metal bars (B) that are not affected by corrosion and therefore have durability over time.

Description

Reinforcing steel bars for concrete provided with bituminous protection against oxidation, as well as a related treatment method.

The present invention relates to steel bars provided with bituminous antioxidant protection means, as well as their corresponding industrial production process.

Steel is a material widely applied in the construction industry, preferred thanks to its particular properties and mechanical performance.

Its main application in construction are the works of steel structures and reinforcements, the latter option being preferred for more conventional techniques, in which they constitute the skeleton resistant to the bending and shear stresses of reinforced concrete.

The fundamental disadvantage that steel suffers constitutes the fact that although it is iron-carbon alloys and not simply iron (despite the current Italian jargon the operators of the sector call it "iron"), it is subject to a degradation process due to the corrosion of the iron in the alloy, an inevitable oxidation process for any kind of steel other than stainless steel (which in any case has a much higher cost than conventional steel), caused by a spontaneous phenomenon and irreversible triggered by the physical-chemical interaction with the environment in which it is stored.

The most common corrosive agents constitute oxygen and water, although it is usually said that the metal oxidizes, continuously discarding: the oxide, namely the layer of steel and therefore of oxidizing iron, penetrates along the time more and more deeply in the metal sections, until the total loss of the resistance properties of the constructive element, or even until its complete destruction.

Typically, corrosion in construction structures manifests itself with the separation of reinforced concrete surfaces that is visible over time, which can occur not only in large infrastructure, for example, in bridges, but also in the most unprotected parts of buildings.

Theoretically, such a corrosion phenomenon should not occur, since the concrete usually constitutes a reducing and non-oxidizing alkaline environment, and therefore protective of the metal bars themselves. Actually, the alkalinity of the environment surrounding the reinforcement elements decreases over time until they disappear completely due to the entry of aggressive substances, such as carbon dioxide, sulfur dioxide or chlorides.

This contradiction between theory and practice is due to the fact that the theory makes the conjecture that the cementitious matrix is impenetrable for the acidifying agents mentioned above, but the concrete manufactured in the work is not always perfectly analogous. to laboratory samples, and although the preset value of the relationship between water, cement and the volume of air included in the mixture is respected, the cementitious matrix in any case presents a certain given level of porosity that justifies said acid penetration , which causes the degradation of the rods and the concrete itself. The part of the iron that oxidizes, in fact, turning into oxide, has the characteristic that its volume expands, which causes the initial cracks in the concrete coating, especially in those cases (unfortunately, very frequent) in the which has an unsuitable thickness. Therefore, the triggered process of decomposition of the product is irreversible, until an intervention is carried out with cleaning, protection and restoration of the entire damaged part.

However, it is not necessary that the metallic object be macroscopically related to corrosion in order for its technological decomposition to occur. In fact, an additional disadvantage of the corrosion of steel is inherent in the reduction of its functional efficiency due to this fact, which can only occur for specific strength sections, in which there may even be the maximum mechanical stress at which The construction structure is submitted.

The corrosion process in dry environments is mainly due to chemical reactions with oxidizing gases. This phenomenon consists in the tendency to recover the oxidized form, naturally because in it the metals remain stable. The combination with the oxygen in the atmosphere is provided in order to form the corresponding oxide, or with other atmospheric agents in order to form carbonates, sulfates, hydroxides or sulphides. In humid environments, however, corrosion occurs thanks to electrochemical reactions. These reactions are linked to the passage of an electrical intensity through the solutions. If two different metals are submerged in water or simply introduced into the soil, which is always assumed to be at least wet, a potential difference between them is generated, and in the event that there is a union between them through a conductive element is traversed by an electric current, since the most reactive metal tends to oxidize in the same way that occurs in a battery element. If, for example, the steel in question is in contact with another less reactive metal, or characterized by a lack of homogeneity of its composition, it will be in danger of corrosion. The corrosion phenomenon described so far occurs, obviously, if the metal is "discovered", that is, without any protection. In order to prevent, in fact, the degradation of steel structures, it is necessary to coat cementitious products with suitable barriers that isolate the metal from corrosion agents in the external environment.

The protection of metal surfaces, in particular of the bars, as it is known technically today, is obtained thanks to the application of an antioxidant paint (rust resistant paint), with the application of fungible protective anodes and protective coatings of the steel bars themselves with non-ferrous metals.

The use of such type of coatings is always necessary since the most widely used metal material in the residential sector is low alloy steel, which is significantly affected by an attack due to rust, although the disadvantages in this case are linked to excessive cost of applying said protective coating.

In order to be able to extend the duration in time of the products of the steel structure, it is first necessary a correct prevention, already conceived in the design stage, since it is essential that it strictly depends on the environmental operating conditions of The structure itself. Additionally, during the interval in which the structure is in maintenance tasks, the frequency and quality of maintenance interventions are essential in terms of the useful life, although these tasks have the additional disadvantage of representing a cost. newspaper that has its importance.

Thus, maintenance is an important stage in the life of a metallic product or a product that comprises reinforced concrete and it is essential to manufacture it in a timely manner with certain modalities adapted to the requirements of the environment, and to the extent that the costs involved are viable.

An additional disadvantage, in fact, lies in the cost of the surface coating that can be applied, although still more labor is required for both the necessary operations of cleaning the rusty parts (sandblasting in the case of structures that cannot be demolished, scratched using a steel brush, if the parts to be removed have reduced dimensions) as for the subsequent painting cycle, from the first layer of rust-resistant primer, also referred to as "grip layer", which It should be applied with a brush, roller or by airless spray, in order to avoid further unwanted oxidation of the metal, to subsequent paint coatings with passivating pigments (necessary to obtain a thin passive layer on steel to block its oxidation and the reaction with the possible aggressive substances that can penetrate the layers of coating paint, forming indissoluble components that are not aggressive for material to be protected).

An additional disadvantage not less important compared to the previous ones is linked precisely to the cost of said paint with antioxidant pigment (with a base of epoxy polyamide having a high content of metallic zinc or with a base of chromates, metaborates, or phosphates, as zinc phosphate), not being able to neglect an adequate choice and that it is essential to orient it to a higher quality of products that have an optimal adhesion with the metal substrate and a good grip on the next layer of paint.

Even the case of the less expensive solution, in which it is preferred to save labor for the cleaning and preparation of the surfaces, and choose to carry out an approximate removal of the oxide from the metal bars, suffers from the inconvenience of requiring, for the protection of metal surfaces, from the use of expensive primer layers, for the conversion or stabilization of oxide, based on solutions of sulfuric acid or tannins with or without sulfuric acid, associated with which there is the additional cost of universal layers of primer, which in turn comprise phenolic resins modified with alkyl resins, compatible with any type of paint, always with the purpose of obtaining a barrier effect in relation to water vapor, oxygen, and aggressive and corrosive substances, since the Primer layer alone generally has no waterproof properties.

Likewise, it is essential to bear in mind that in the case of such expensive maintenance operations, it is necessary to add the cost of a previous dismantling and the collection and transport of the concrete coating to the tank, as well as its subsequent replacement.

An additional procedure for the protection of the metal surfaces of steel bars, or of metal bars in general, is described by applying coating paints with a base of bitumen, bituminous combinations, epoxy or epoxy polyurethane , of alkyl resins, of chlorinated rubber and finally of a combination of PVC and acrylic resins, although for all such solutions the disadvantage of the cost of labor is always evident and is comparable (being higher in most cases) to cost of the products themselves that must be applied.

Likewise, universal coatings for steel are known in the art that do not require the application of a primer layer and which are particularly suitable for painting on old coatings, although in the case of such universal coatings the disadvantages are linked both to the cost of labor, as with the cost of the product to be applied.

One of the most widespread protection procedures today is hot-dip immersion galvanization, since it represents a type of coating that provides a fairly effective and durable solution over time by protecting the steel twice (both physically and electrochemically) , although today it seems less and less economically advantageous as an application solution. In fact, hot-dip immersion galvanization, in fact, constitutes an industrial process that guarantees the physical protection of the steel coated by the zinc surface layer that isolates it materially from the environment, while electrochemical protection is activated by the greater electronegativity of zinc in comparison with steel. In fact, a Zn-Fe element is formed, so that zinc is sacrificed to protect iron, especially in accidentally damaged areas (likewise, this is called "cathodic protection").

However, the disadvantage of the above protection procedure is inherent in its poor reliability since it is always necessary to properly test the operation of the galvanized itself, since an insufficient zinc coating on the metal surfaces can compromise the duration of the coating itself, which It is a function of the thickness of the applied zinc and the type of environment in which the product is located, factors that determine the speed of corrosion of the coating.

The corrosion of the zinc layer, in fact, generally takes place especially in the first period of life of the concrete product, when the degree of alkalinity inside it is still very high, since zinc, unlike iron, it is oxidized in this type of environment, although in any case the use of galvanized bars provides a non-negligible increase in the durability of the reinforced concrete itself, since zinc, when subjected to corrosion, performs its protection function in relation to with the steel located below. Since zinc corrosion products, in fact, do not expand as in the case of rust, they do not cause mechanical damage to the surrounding concrete. Zinc corrosion is an indication in any case that there is a cathodic protection of steel, although as a result the steel progressively loses its coating. Once the protection period ends due to the disappearance of the zinc protection layer, the steel begins to corrode as in the case of conventional reinforcements, although the increase in the useful life of the cementitious structures themselves is evident.

An additional disadvantage of such a hot-dip immersion galvanization process is shown in the fact that it cannot be applied to metal reinforcements of construction products that are already installed, and that only require maintenance, in this case being able to resort to a maximum of cold galvanized, although this last treatment is even less effective and durable than the previous one.

Therefore, since corrosion of the reinforcements inside clusters can also occur in the case of a well-prepared cementitious mixture, although it passes more slowly over time, sometimes the radical decision is taken to replace the conventional reinforcement by another type of less reactive material, such as stainless steel, titanium or even composite fibers, although the disadvantage of such solutions is obviously linked to a much higher cost.

An additional known technical solution is the coating of conventional steel bars with corrosion resistant materials, such as epoxy resins. The application of such materials, however, suffers from certain disadvantages with respect to the storage of the bars before their use and their handling when they are deposited, and also with respect to a non-perfect adhesion of the surfaces coated with the concrete. .

In document DD 101 198 A1 a metal bar is described that has all the features of the preamble of claim 1, and a process for the treatment of metal bars that has all the features of the preamble of claim 2.

Consequently, the main objective according to the present invention is to provide, on an industrial level, steel bars provided with a valid means of antioxidant protection, through a production process that is simple to implement and with a minimum productive cost.

A further objective according to the present invention, no less important than the previous one, is to obtain steel bars that can be stored without oxidation, even if they are left outdoors for prolonged intervals, without any problems associated with their handling and with the necessary operations of bending and cutting, and that can be used at any time without it being necessary to perform an unwanted treatment of brushing the oxidative surface layer that normally forms in the usual steel bars when, after manufacturing by wire drawing wire, are stored, even for short intervals.

A further objective according to the present invention is to provide steel bars that guarantee the resistance over the centuries of the construction elements constructed with composite products of reinforced concrete, and thus prevent the unwanted phenomenon of hidden or obvious oxidation of steel. with the corresponding impoverishment of the resistance characteristics of both the steel bars and the reinforced concrete that covers them.

The aforementioned objectives are achieved by means of metal bars of any type and diameter intended for construction applications for structural steel works or for reinforcements, according to claim 1, and providing a process for the treatment of metal bars according to claim 2.

The present invention and the corresponding production process are completely new, since there are no steel bars of a similar shape and characteristics, and they are inventive in nature since they completely solve the problem that until now remained unresolved regarding the corrosion of steel, especially if it is present as reinforcement in buildings that comprise reinforced concrete.

The above objectives and their derived advantages, as well as the characteristics of the present invention and the corresponding production process according to the present invention, will become more clearly apparent from the following detailed description of some preferred solutions, which is provided by way of example not limiting, referring to the attached drawings.

Figure 1 shows a schematic global view of a set of three stages F1-F2-F3, in which the dotted arrows indicate the sequence of said stages that form the industrial process P for the production of the B bars equipped with an antioxidant protection means according to the present invention, until transported in articulated T trucks.

Figure 2 shows a schematic top plan view of only the impregnation stage F1, shown in Figure 1, in which a plurality of steel bars B0 can be seen at the entrance of the impregnation tank V1, which are subjected to an impregnation process and then said bars are impregnated with a bituminous solution B1 and taken to the exit; the arrows parallel to the bars B0-B1 indicate the orientation of the movement of the bars B0-B1 themselves, while the small arrows oriented downwards and upwards respectively indicate the thermal range ΔT1 and the impregnation interval Δt1.

A schematic top plan view of only the emulsion treatment stage F2, shown in Figure 1, is shown in Figure 3, in which a plurality of steel bars B1 can be seen at the entrance of the emulsion tank V2, which they are subjected to an emulsion treatment process and then said bars are impregnated and treated with a B2 bitumen emulsion and taken to the exit; the arrows parallel to the bars B1-B2 indicate the orientation of the movement of the bars B1-B2 themselves, while the small arrows oriented downwards and upwards respectively indicate the thermal range ΔT2 and the emulsion range Δt2.

A conventional steel bar is illustrated in Figure 4, in particular a rod that assembles the concrete B0.

A bar B1 impregnated with the cold bituminous solution Sb is illustrated in Figure 5.

A bar B2 treated with the hot bituminous emulsion Eb is illustrated in Figure 6.

And finally, in figure 7 a bar B is illustrated, already dried, in rectilinear configuration and bent 90 °, prepared for use.

From the attached figures, it follows that the metal bars B, of any type and diameter for applications in the construction of steel structures or for reinforcements, according to the present invention are characterized fundamentally because they have been subjected to an industrial production process P which foresees the treatment with an Sb-Eb bituminous antioxidant protection medium, optimally compatible with any type of concrete, for construction structures with and without reinforced concrete that are not affected by corrosion and for this reason present durability over time.

According to the present invention, the industrial production process P is obtained by applying a series of stages, as shown in Figures 1, 2 and 3, respectively the impregnation stages F1, emulsion treatment F2, and drying F3, leading to perform these steps sequentially:

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A first stage F1 (figures 1 and 2) of immersion of a plurality of metal bars B0 of any kind and diameter for use in the market construction sector (figure 4) in a first tank V1 containing a bituminous solution Sb , also referred to as cold solution Sb, said solution being stored at a temperature T1 between 6 ° C and 10 ° C, for an interval Δt1 between one and two minutes in order to obtain bars impregnated with bitumen B1 (Figure 5);

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An intermediate stage F2 for drying the impregnated bars B1 in the air.

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A second step F3 (Figures 1 and 3) of immersing said impregnated bars B1 (Figure 5) in a second tank V2 containing a bituminous emulsion Eb, also called hot emulsion Eb, said emulsion being stored in a thermal range ΔT2 of about 400 ° C, during an interval Δt2, understood between one and two minutes in order to obtain bars impregnated and treated with the bitumen emulsion B2 (Figure 6);

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And a final stage F4 of drying said bars B2 impregnated and treated with the bitumen emulsion (Figure 6), allowing them to cool to room temperature TA for an interval Δt3, variable depending on the external temperature, between approximately ten minutes in winter and approximately twenty minutes in summer, in order to obtain metal bars B (figure 7) that are not affected by corrosion and for this reason have durability over time.

The metal bars B are preferably obtained using metal bars B0 of any class and diameter for applications in the market construction sector, of a type comprising low alloy steel, since the steel bars used to provide a reinforcement are made usually in carbon steel and usually have a circular cross section (hence the common denomination of "rod"). The outer surface of said commercially available B0 bars is characterized by a particular groove called

"Knurled", whose function is to improve the adhesion of the concrete structure with the bars themselves. The

bars that are obtained in this way are called bars with "improved adhesion" or bars "with ribs" and are usually known as "knurled rods".

Until a few decades ago, the standards envisaged the use of bars with few irregularities, and the worsening inside the concrete was avoided by forming hook-shaped curves at the ends of the bars that constituted adequate internal grips.

The present invention can be applied in construction, preferably in the field of typical reinforcement of structural elements, such as beams and columns, which are characterized by two series of reinforcing bars:

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Longitudinal bars, arranged parallel to the axis of the element, both in the area subjected to a tensile stress, and in the area subjected to a compression stress, with the main function of cooperating with the concrete absorbing the bending forces or the stresses of compression-bending (in the area subjected to tensile stress, in view of the poor resistance to tensile stress presented by concrete, the B bars have the function of fully absorbing said tensile stress, while the subjected B bars they have the main function of compressing the structure to provide greater ductility, and in the same way, in the case of beams, the bars B, in the area subjected to a compression effort, are also used as clamp support bars);

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And transverse bars (called "clamps"), smaller in diameter than that of the longitudinal bars, arranged transversely with respect to the axis of the structure and having a triple function, namely, allow the maintenance of the position of the longitudinal bars before and during the pouring of concrete, they absorb the shear stresses to which the element is subjected, and reduce the length of free bending of the longitudinal bars B subjected to compression, avoiding deformation.

The choice of B0 rods comprising low alloy common steel is justified by the fact that they have a minimum cost in the construction market (current carbon steel and prestressing steel belong to said group), but the Process P according to the present invention can also be applied for reinforcing parts with reduced corrosion sensitivity, such as galvanized steel or stainless steel.

Regarding stainless steel reinforcing parts, it should be noted that due to its high cost to date, its application has been recommended and limited only for the construction of structures in very aggressive environmental conditions, especially related to the presence of seawater or Antifreeze salts, or in other cases where, due to the importance of the structure, a very long lifespan is required (for example, greater than 100 years). However, by applying the present process, it is possible to obtain an incomparable durability of the cementitious product, also with low-alloy steel bars B0.

B0 low alloy steel bars for reinforced concrete are manufactured in plants also in the form of bars

or rollers, mesh or reticles, for direct use in the work or as basic elements for subsequent transformations. Consequently, the process P referred to in the present invention can also be applied to such commercial products existing in the market, in order to provide excellent corrosion resistance.

Sb-Eb bituminous antioxidant protection means are obtained from bituminous substances, namely mixtures of naturally occurring hydrocarbons or obtained by distillation in crude oil processing, or mixtures of both types of hydrocarbons.

It is recalled, simply by way of descriptive example, that the bitumen can be natural or distilled.

Natural bitumen, which is found in oil fields in dark to black bodies, usually permeates porous rocks, comes from a low temperature natural distillation that occurs over millennia in the oil coating and comes into contact With atmospheric oxygen. In fact, the first material used by man for waterproofing was precisely cast asphalt, which included a mixture of aggregates and bitumen. This mixture also exists in the natural state in Abruzzo and Sicily (Ragusa) and subjected to a compression process with specially provided technological means, was reduced to a "mass", which is called "asphaltic mass", which today is no longer use.

Distilled bitumen comes from artificial distillation of crude oil, at an elevated temperature and for a few hours. Distilled bitumen is used today in all waterproofing works for road paving, etc.

Said bitumen, in productive plants, is poured into tankers at a temperature of approximately 100 ° C, transported to concrete mixing facilities, and poured into large tanks, in which it is kept at the same temperature, ready for use For roads, said bitumen is prepared with aggregate to form bituminous conglomerates, while for waterproofing tasks, bitumen is poured into specially arranged drums and cooled. Subsequently, the drums are transported to their place of use, where they are heated to an approximate temperature of 300 ° C and then distributed in terraces, bridges under construction, etc., in order to form a bituminous layer. Today, however, the conventional bituminous layer has been replaced by a prefabricated membrane, which is more convenient for transport and installation and has found a wide range of applications.

The classification of the different types of bitumen takes into account the physical-chemical characteristics (softening temperature, penetration, viscosity, ductility, combustibility, solubility in various solvents, etc.).

Natural bitumen is frequently mixed with the remaining artificial bitumen from the distillation of crude with tar; For this reason, it is no longer possible to make a clear distinction between these types of compounds.

The distinction of the different types of natural bitumen is made according to its origin, but also according to its application. The characteristics of natural bitumen are: solid or semi-solid consistency; hardness; color; and variable volatility. The natural bitumen burned with a sooty flame, softened with heat, and that acquires adhesion properties, is impermeable to water, insulating, resistant to atmospheric agents, and possesses a good degree of consistency.

Given the previous characteristics of natural and artificial bitumen, the industrial process of production P referred to in this document has been conceived, applying the idea of commercially available B0 steel bars with a bituminous antioxidant protection medium Sb-Eb , which can be applied by immersing the steel bars themselves in solutions and bituminous emulsions.

The following should be noted:

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The term "solution" means the dissolution of a substance, either solid or liquid, in an additional liquid, in which the excess substance is called "solvent" and the defective substance is called "dissolved substance"; while

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The term "emulsion" means a suspension in the form of droplets (in discontinuous phase) of a liquid in an additional liquid (in continuous phase) not mixable with the first (for example, the oil-in-water emulsion). The stability of an emulsion depends on numerous factors, such as: the size of the particles, the difference in density of both phases (discontinuous phase and continuous phase), temperature conditions, stirring during storage, the mode of preparation, etc. ., but above all the nature and quantity of stabilizers or emulsifiers.

In view of the above, it has been found that bitumen can be prepared in different ways, depending on the starting point (temperature range) of its degree of softening. The first type is obtained at 30 ° C / 50 ° C, the second at 50 ° C / 70 ° C, and the third at 70 ° C / 100 ° C. The second type with softening between 50 ° C and 70 ° C, precisely due to said degree of softening, is more suitable for obtaining a greater fluidity compared to the other two types and consequently, in this temperature range, it is obtained the so-called oxidized bitumen

or blown

Oxidized bitumen constitutes a product that is obtained by causing oxygen or air to act under conditions of high temperatures, in order to produce an increase in the penetration rate as long as a plastic mass is obtained. Oxidation occurs from the chemical point of view by dehydrogenating the product and causing higher molecular weight components. Said oxidized bitumen is compressed and reduced to form masses called "oxidized bitumen masses" in order to obtain oxidized bitumen prepared for softening and to obtain the hot bituminous emulsion Eb.

The industrial process P for the manufacture of the metal bars B referred to in the present invention, as already mentioned above, preferably uses low alloy steel bars B0 which are currently used in buildings made of reinforced concrete and prepared for its use in cementitious conglomerates in the natural state (see Figure 4) and a pair of V1-V2 tanks, the first V1 being used as an impregnation tank and the second V2 being used as an emulsion tank.

In order to obtain a better adhesion of the emulsion, the B0 steel rods (or rods) prepared for use are mechanically immersed in a metal tank of adequate dimensions for the processing environment and with the required quantity, comprising an appropriate solution , called "cold bituminous solution" Sb, which according to the present invention has an oxidized bitumen base and quick-drying technical solvents of known type, also called Sb bituminous impregnation solution.

The temperature T1 of said bituminous solution Sb. Is preferably between 6 ° C and 10 ° C, and the interval Δt1 is between one and two minutes.

During the period in which tasks are stopped or during vacations, it is necessary to take care to cover the impregnation tank V1 with a thin metal plate in order to prevent evaporation of the bituminous solution Sb.

The steel bars B0, which are at room temperature, for the bituminous impregnation stage F1 are submerged in the tank V1 (stage F1), which preferably constitutes a metal tank whose dimensions are approximately 20 meters in length and 10 meters in width , and which contains the cold bituminous solution Sb.

Then, the steel bars B0 are immersed in said cold bituminous solution Sb, remaining within a few minutes, preferably one or at most two minutes.

After said immersion, they are removed from said tank and allowed to air dry for the necessary time (step F2).

Once they have dried, the steel bars impregnated with the cold bituminous solution B1 are immersed in the emulsion tank V2 (step F3), which also preferably constitutes a metal tank whose dimensions are approximately 20 meters in length and 10 meters wide, and containing the hot bituminous emulsion Eb, in which the bars will remain for an additional two minutes.

The second metallic tank V2 contains the hot bituminous emulsion at a controlled temperature T2 between 350 ° C and 450 ° C, preferably approximately 400 ° C, in which the bars B1, as already mentioned, remain an approximate interval Δt2 between one and two minutes.

The bituminous emulsion Eb at said temperature is very fluid and acquires a binder function.

The bars B2, impregnated and treated in this way with the bitumen emulsion, are removed and allowed to dry for the necessary time (step F4), allowing them to cool to room temperature TA for an interval Δt3 which varies depending on the external temperature, being between approximately ten minutes in winter to approximately twenty minutes in summer, in order to obtain metal bars B that are not affected by corrosion and therefore have durability over time.

The bars B, thus impregnated, treated with the bituminous and dry emulsion, are ready to be loaded onto trucks and for transport after the construction site. For correct loading and transport of said bars B, it is envisaged to separate them with a polyethylene sheet in order to avoid that due to an increase in temperature the bituminous emulsion layer can be heated, and in order to prevent the bars themselves from sticking together. ”, That is to say that they adhere to each other.

At least one pair of lifting, immersion and translation means Ms of the bars B0-B1-B2-B, as shown in Figure 1, are provided with mechanisms designed to:

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immerse the steel bars B0 in the tank V1 so that they are impregnated with the cold bituminous solution Sb (step F1);

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remove said impregnated bars B1 from the tank V1, allowing them to air dry (step F2) and then move them to a tank V2 and then immerse them in the hot bituminous emulsion Eb (step F3);

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extract the bars impregnated and treated with the bitumen emulsion B2 of the last tank V2, leaving them in the air to dry (step F4), and thus obtain the bars B referred to in the present invention, which can then be prepared for loading in trucks to transport them to the construction site or for storage.

The B bars obtained with this process have the additional advantage that they can subsequently be bent or bent, depending on the requirements, since the hot bituminous emulsion at a temperature of approximately 400 ° C covers the steel bars with a predetermined thickness, perfectly compatible with this type of operations and for use with cementitious conglomerate to build reinforced concrete structures.

In case you want to obtain a greater thickness of the bituminous emulsion, it is necessary to reduce the temperature range ΔT2 of the hot emulsion, from a value of about 400 ° C to a value around 300 ° C, or alternatively, submerge the steel bars B2 a second time in the same bituminous emulsion tank V2 in order to obtain a second layer of bituminous emulsion that is deposited on the first, providing said greater thickness.

However, it is not recommended to make additional dives in the emulsion tank, as this could compromise the necessary cohesion between the cementitious conglomerate and the B bars, necessary to acquire an optimal strength of the reinforced concrete structure that you want to obtain.

It is envisaged that by means of the designed solution, virtually immune steel bars will be achieved over time, since while the cementitious conglomerate tends over the centuries in any case to disintegrate and partially reduce to dust, the steel bars , impregnated first with the cold bituminous solution and then with the hot bituminous emulsion, they will remain intact.

Consequently, the fundamental advantage of the present invention is to have conceived a productive industrial process that gives steel bars (or in general, metal bars) the characteristic of inalterability over time, allowing to obtain a binding power and adhesion Notable between the bars and the cementitious conglomerate in reinforced concrete structures, high resistance to atmospheric agents and unlimited durability over time.

An additional advantage, not less important than the previous one, is due to the fact that the steel bars treated in this way retain in any case the resistance properties (tensile strength, compressive strength, etc.) in the same degree as untreated ones, and therefore the need to demolish buildings, hotels or skyscrapers is avoided due to the advanced state of iron corrosion that is part of the elements made of steel, since the steel bars treated in this way resist much more time than those already known, even becoming indestructible over time.

As is evident from the above description and the attached figures, the additional advantages of the bars to which the present invention refers are precisely the result of the simplicity of its industrial production due to the construction characteristics of said bars (and typical of the rest of additional steel elements that constitute constructive reinforcements, which could also undergo the same impregnation process with the bituminous solution and emulsion), which leads to the additional advantage of minimizing production costs and by therefore of the installation and regulation costs (bending and cutting of the bars) in the work.

It should be noted that the present invention can be applied to steel bars for construction, both in steelworks, in which they are manufactured, and in warehouses (warehouses, workshops, etc.).

In the case of steel mills, it is necessary that the bars that leave the oven first cool to room temperature before immersing them in the cold bituminous solution Sb, while in the case of storing the bars in tanks, before submerging them In the cold bituminous solution Sb, it is necessary to subject them to a preliminary treatment in order to remove the oxide that usually forms on the outer surface. For example, a deoxidant treatment or other known treatment could be carried out in order to remove rust or other substances (grease, oil, etc.) that may hinder the good adhesion of the protective layer that permeates the bars.

Likewise, the present invention has the undoubted advantage that it allows an optimization of the protection of the bars against corrosion, also allowing the total automation in line of the production of the rods or other commercial products existing in the market, also in the form of bars or rollers, mesh or reticles, for direct use in the work or as basic elements for subsequent transformations; For this reason, the process according to the present invention can also be applied to said commercial products.

It is evident that numerous modifications, adaptations, integrations, variations and replacement of functionally equivalent elements can be made in the embodiments described herein, described purely by way of illustration and not limitation, without thereby departing from the defined protection sphere by subsequent claims.

LEGEND

(B0) metal bars for applications in the existing construction sector in the market (B1) bars impregnated with bituminous solution (B2) bars treated with bituminous emulsion

(B)

 metal bars to which the present invention relates

(P)

industrial production process (Sb, Eb) bituminous type antioxidant protection means (Sb) bituminous solution or cold solution (Eb) bituminous emulsion or hot emulsion (F1) impregnation stage

(F2) stage of emulsion treatment (F3) drying stage (V1) impregnation tank (V2) emulsion tank

5 (T1) thermal range of the impregnation (Δt1) impregnation time (T2) emulsion thermal range (Δt2) emulsion treatment time (TA) room temperature

10 (Δt3) drying time (MS) means for lifting, dipping and transferring the bars (T) to articulated trucks to transport them

Claims (8)

1. Metal bar (B), of any type and diameter for applications in the construction of steel structures or for reinforcements, obtained by means of a treatment (P) that provides for the application of a bituminous type antioxidant protection medium (Sb-Eb ), optimally compatible with any type of concrete, for construction structures with and without reinforced concrete that are not affected by corrosion and for this reason have durability over time, characterized by being obtained through a treatment (P) which provides for the impregnation of the bar itself with a bituminous solution based on oxidized bitumen (Sb) and a bituminous emulsion (Eb), which is done by:

-

a first immersion (F1) of one or more metal bars at room temperature (B0) in a first tank (V1), which contains a bituminous solution based on oxidized bitumen (Sb) and quick-drying technical solvents, also called "solution in cold (Sb) ”, said solution being stored at a temperature (T1) between 6 ° C and 10 ° C, for an interval (Δt1) between one and two minutes, in order to obtain bars impregnated with bitumen (B1);

-

a first drying (F2) of the impregnated bars (B1) in the air;

-

a second immersion (F3) of said impregnated bars (B1) in a second tank (V2) containing a bituminous emulsion (Eb), also called "hot emulsion (Eb)", said emulsion being stored at a temperature (T2) comprised between 350 ° C and 450 ° C, preferably approximately 400 ° C, for an interval (Δt2) between one and two minutes, in order to obtain bars impregnated and treated with the bituminous emulsion (B2); Y

-

a final stage (F4) of drying said bars (B2) impregnated and treated with the bitumen emulsion, allowing them to cool to room temperature (TA) during an interval (Δt3), variable depending on the ambient temperature (TA), between approximately ten minutes in winter and approximately twenty minutes in summer, in order to obtain metal bars (B) that are not affected by corrosion and for this reason have durability over time.

2. Process for the treatment of metal bars (B) of any type and diameter for applications in the construction of steel structures or for reinforcements, characterized by providing for the impregnation of said bars with a bituminous solution based on oxidized bitumen (Sb) and a bituminous emulsion (Eb), this being done by:

-

a first immersion (F1) of one or more metal bars at room temperature (B0) in a first tank (V1), which contains a bituminous solution based on oxidized bitumen (Sb) and technical solvents of

fast drying, also called "cold solution (Sb)", said solution being stored at a temperature (T1) between 6 ° C and 10 ° C, for an interval (Δt1) between one and two minutes, in order to obtain bars impregnated with bitumen (B1);

-

a first drying (F2) of the impregnated bars (B1) in the air;

-

a second immersion (F3) of said impregnated bars (B1) in a second tank (V2) containing a bituminous emulsion (Eb), also called "hot emulsion (Eb)", said emulsion being stored at a temperature (T2) comprised between 350 ° C and 450 ° C, preferably approximately 400 ° C, for an interval (Δt2) between one and two minutes, in order to obtain bars impregnated and treated with the bituminous emulsion (B2); Y

-

a final stage (F4) of drying said bars (B2) impregnated and treated with the bitumen emulsion, allowing them to cool to room temperature (TA) during an interval (Δt3), variable depending on the ambient temperature (TA), between approximately ten minutes in winter and approximately twenty minutes in summer, in order to obtain metal bars (B) that are not affected by corrosion and for this reason have durability over time.

3.

Metal bar (B) according to claim 1, characterized in that said cold bituminous solution (Sb) is constituted by natural and artificial bitumen that can be found in the market today.

Four.

Metal bar (B) according to claim 1, characterized in that said hot bituminous emulsion (Eb) is constituted by natural and artificial bitumen that can be found on the market today,

5.

Metal bar (B) according to claim 1, characterized in that said cold bituminous solution (Sb) and said hot bituminous emulsion (Eb) can be replaced over time by solutions and emulsions constituted by other substances available in nature, but equivalents, as antioxidant protection means, designed to protect the bars or other metal structural elements against corrosion.

6.

Metal bar (B) according to claim 1, characterized in that it is preferably obtained using metal bars made of a low alloy steel (B0) of any kind and diameter for applications in the existing construction in the market.

7.

Process (P) according to claim 2, characterized in that lifting, immersion and translation means of the bars (Ms) designed to fully automate the production process (P) are provided.

8.

Process (P) according to claim 2, characterized by being able to automate industrially and because it is applicable not only to said low alloy bars (B0), but also to other types of metal structural elements existing in the market and other than the bars, such as rollers, mesh or reticles.