SYSTEM FOR CONTROLLING THE DENSITY AND ORIENTATION OF FERROMAGNETIC FIBERS IN A FLUID CEMENT MATRIX

Abstract

A system for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix. It comprises a pumping module and a 3D printing module. These modules include alignment coils combined with vibration coils that produce corresponding permanent and oscillating magnetic fields, facilitating greater fluidity of the mixture and the correct orientation of the fibers in alignment with the axis of the applied magnetic field. Specifically, the nozzle of the printing module incorporates a two-stage architecture, allowing for a first stage of combined treatment (alignment + vibration) followed by a second stage of alignment only. The mixture is fluidized, clogging is prevented, and the fibers are oriented so that the material flows optimally toward the nozzle outlet.

Description

Procedure and system for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix Object of the invention The present invention relates to a method for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix. The present invention also relates to a system for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix. The method and system of the present invention allow for modifying the rheology of the fluid cementitious matrix, thereby promoting the rotation of the ferromagnetic fibers. The procedure and system of the present invention is applicable both in direct pouring into molds, as well as in the case of digital printing where the flow is controlled by means of a printing nozzle, obtaining in either case as a result the presence of a certain volume fraction of fiber in the fluid cementitious matrix, where the fibers are oriented in a certain direction. The procedure and system that are the subject of the present invention allow the volume fraction of fiber added to fresh cementitious materials to be monitored from its earliest stages, which also allows the control of its density in the pouring or printing process. The procedure and system, which are the subject of this invention, are of particular application in the construction industry. Background of the invention and technical problem to be solved The industrial manufacturing of cement-based structural building elements primarily employs a matrix of cementitious composite materials, which in some cases also contains a certain volume fraction of fibers. The purpose of adding fiber to the cementitious matrix is ​​to improve some of its physical properties, specifically providing discrete material reinforcement that ultimately enhances some of its final mechanical properties. Therefore, it is of great industrial interest that the fibers can be conveniently oriented and displaced to areas of higher probability of cracking, according to the calculations that have been previously included in the construction project. The random inclusion of fibers within the cementitious matrix prevents and controls cracking once the material has solidified. Its effectiveness increases with the technical capacity to control two crucial fiber conditions: first, the specific relative orientation of the fiber with respect to certain directions determined by the load-bearing stress lines within the structural members; and second, the local fiber concentration, or density, determined by the magnitude of the load stresses. Controlling both conditions represents a significant technological challenge in construction today, and it allows for increased manufacturing efficiency (both technically and economically) by reducing the amount of fiber reinforcement required under the same structural requirements. The standard process of placing this cementitious material in a mold requires four preliminary steps: mixing, pumping, and finally pouring and vibration. All of these processes affect the final orientation and density of the fiber once it is in the mold. During the prefabrication stage of reinforced structural members, always within the initial time frame when the cementitious material is fluid, the fiber is added and the mixing process is carried out appropriately, always with the aim of initially achieving a homogeneous distribution of both fiber density and orientation. After the mixing process is complete, the fluid cementitious mass is transported by continuous pumping to the molds or formwork. This requires the fluid to pass through conduits with a specific flow rate to be poured into the molds that define the shape of the piece. Pre-pouring alignment can allow for an increased volume of fiber in the pour, leading to greater fiber effectiveness.These two processes are technically complex because the presence of fiber alters the flow regimes through the pipes, potentially causing blockages, which can lead to delays and subsequent economic losses. Furthermore, in certain quantities, fiber alters the rheology of the material, affecting its workability. Furthermore, the increasing incorporation of digital design and modeling advancements in the construction industry has been a constant since the beginning of this century. Among these technologies are integration processes such as the advancement of additive manufacturing combined with the automation provided by robotics. These technological advancements incorporate improvements in cementitious materials engineering due to the integration of specific research areas such as rheology. All of this has enabled the introduction of new automated construction methods that utilize the characteristics of these materials.As a general rule, these new technologies or techniques, which primarily use cementitious materials as their construction material, are collectively identified as "DFC" (Digital Fabrication with Concrete), while digital printing is referred to as 3DPC (3D Printing Concrete). In this document, the general concept of "printing cementitious materials" will be used under these same terms. Oriented fibers in structural members offer mechanical advantages in various building elements, such as surface structural members like thin tunnel lining panels, linear structural elements like columns or beams, or for the manufacture of pipes submerged in water. Cementitious materials incorporating fibers are characterized by high compressive strength, remarkable tensile strength, and excellent durability. The fibers can retard or prevent the formation and propagation of cracks and fissures, and are a key factor influencing toughness, tensile strength, ductility, and energy absorption capacity. Many authors set 2% volume fraction as the fiber density limit; above this limit, problems such as blockages in pumping / extrusion, pouring through nozzles, etc. appear in construction processes. The fibers added to the cementitious material can be made of various materials, in some cases being ferromagnetic materials so that the fiber can interact with magnetic fields. To analyze the construction process in a cementitious material with added fibers, the approach can be made from the point of view of the cementitious material matrix or from the point of view of the reinforcing ferromagnetic fibers themselves. Taking the matrix of the fluid cementitious material as the center of the initial construction process, it can be said that it must possess a set of properties generally coded in a specific adjective for each stage within the construction sequence. Thus, for example, when pumping, the fluid matrix must be pumpable (this property is usually called "pumpability" or "deliverability"), and this presupposes optimal rheological conditions so that it can flow through the conduits. The same fluid must have "extrudability" characteristics to allow for a controlled and constant flow in the impression heads. Similarly, it must have properties of spontaneous filling of the molds during pouring with minimal vibration; this property is called "castability" or "placeability."Once the material is in place, some digital printing technologies require that the structure does not collapse; these rheological requirements are grouped under the adjective "buildability". The technological and scientific challenge has been to harmonize the different rheological properties and requirements of the same fluid cementitious material in different processes, sometimes with conflicting properties, in order to achieve a suitable final product. In other cases, a cementitious material is designed that can change and adapt to each process by modifying its rheology: that is, a material whose rheological characteristics can be "tuned" depending on the construction process it undergoes. Conversely, taking the ferromagnetic reinforcing fiber as the center of analysis, the cementitious matrix is ​​required to be as low in viscosity as possible in order to favor its rotation (orientation), or its displacement, caused by the irradiation of magnetic fields or other phenomena. Flowable cementitious materials, as a rule, possess non-Newtonian properties and their rheological properties fall within the category of "Bingham-type" fluids. This means they exhibit a dual viscosity depending on the deformation (shear rate): on the one hand, a static viscosity ("o") under small deformations, which causes the fibers to "perceive" the fluid as a solid in which movement / rotation is impossible; and on the other hand, a dynamic or plastic viscosity ("o") of smaller magnitude that responds linearly to the deformation of the fluid matrix. Generally, these two rheological parameters completely determine the fluid behavior of cementitious materials and similarly affect the fiber's ability to rotate within the matrix. Due to the chemical and physical variation that fresh cementitious materials undergo during construction processes, these two rheological parameters undergo changes in their values, which induces a non-linear behavior that is studied in a subfield of rheology called "thixotropy". The orientation of the fiber is affected by the rheology of the cementitious materials in each of the construction processes and is considered to be determined by: - induction of a certain orientation of the fibers within the cementitious matrix due to the construction processes themselves, such as mainly pumping, pouring and magnetic vibration of the ferromagnetic fibers themselves; and - Induction of a specific fiber orientation within the cementitious matrix due to forced processes (external induction) such as the application of continuous or alternating magnetic fields, which cause an orienting torque. Regarding the induction of a certain orientation of the fibers within the cementitious matrix due to the construction processes themselves, as already introduced, the induced orientation / displacement of the fiber within a cementitious material has various causes. The existence of these induced forces in the construction processes themselves allows us to affirm that despite achieving homogeneity of fibers and orientations in the initial fiber and material mixing processes, subsequent processes give rise to preferred orientations in the fiber, resulting in anisotropic structural pieces. As mentioned, these forces that induce a specific preferred orientation of the fibers within the cementitious matrix can occur during the pouring process into the mold or formwork. In this case, the induced torque exerted on the fiber, resulting from the so-called "wall effect" caused by the internal geometry of the mold on fiber alignment, is particularly relevant. According to this "wall effect," the fibers tend to align parallel to the mold walls during pouring. Therefore, it is advisable to establish certain strategies in the pouring process if fiber orientation in structural elements is to be controlled. This wall effect has been indirectly observed in numerous experimental studies based on strength tests. When considering the influence of the "wall effect" on fiber orientation, it is necessary to take into account parameters considered relevant to the reinforcing fiber, such as: fiber material type, chemical interaction with the cementitious matrix, geometry (slenderness, anchorages, roughness, etc.), length, fiber content (volume fraction), and whether the fiber is monodisperse (a single type) or polydisperse (different types). In the theoretical predictive determination of fiber orientation indices caused by the wall effect, some studies consider it a basic rule that it is not possible to find a fiber perpendicular to a mold wall at a distance less than half the fiber length. Due to this wall effect, there is a preferred fiber orientation in the vicinity of any solid interface within the flow or molds. The preferred orientation due to the wall effect does not depend on the flow or the process inside the slab; it is induced as soon as the material is poured into the formwork and depends only on the fiber length and the geometry of the element being poured. Considering other induced fiber orientation pairs, the second most significant cause after the wall effect is that of construction processes involving mechanical vibration applied to molds via vibrating tables. When vibrations on the order of tens of Hz are applied, it has been observed that the mechanical vibration causes the fibers to align in a plane perpendicular to the direction of the vibration. This results in the fibers orienting themselves in parallel horizontal planes in the most common case. This induced alignment effect due to mechanical vibration is so significant that some authors conclude there is essentially no difference, in terms of fiber distribution and orientation, between cementitious materials poured and subjected to mechanical vibration and those that have been sprayed. Some experimental studies on the molding process reveal that mold geometry and the pouring strategy, combined with vibration, are relevant factors in achieving controlled fiber orientation. Furthermore, using a transparent metaphor fluid (hydrogels such as Carbopol) with aggregates of varying dimensions (polydisperse), the effectiveness of applying magnetic vibration before and after pouring into a rectangular mold has been observed in fiber orientation. It is worth noting that in the specific case of self-compacting concrete (SCC), the pumping or "flow of fresh concrete" through the pumping lines has also been identified as playing a significant role in the induced alignment of the fibers. This type of cementitious material has been modified rheologically due to the presence of chemical admixtures, which lower the static yield strength to improve its moldability in formwork. However, this has the disadvantage of causing detrimental fiber segregation dynamics. In the case of pumping, at each cross-section of the pipe, the pumping pressure induces a shear stress gradient in the cementitious material that is linearly distributed along the radius (as shown in Figure 1 accompanying this description), where the value of τ is zero at the pipe axis and is maximum near the inner wall of the pipe.As a result of the difference in shear stress, the relatively larger aggregates migrate to regions with lower shear rates (i.e., the center of the pipe), which is called shear-induced migration, forming granular material and leaving a more fluid, paste-rich layer in the vicinity of the pipe wall, which is known as the lubrication layer or slip layer. As an induced process that influences the orientation of the fibers within the cementitious matrix, it is also worth mentioning, as already mentioned, the "extrusion" through extrusion nozzles in emerging technologies for printing cementitious materials with reinforcing fibers. During extrusion, the fibers align themselves in the longitudinal direction to the extrusion axis. Recent studies have focused specifically on fiber alignment induced by extrusion. Some of these studies, conducted with fiberglass in a cementitious matrix, have shown that when the fiber volume proportion is small, say 1% of the fiberglass, most of the fiber can align in the extrusion direction. Other studies analyze the addition of steel fibers in extrusion processes. When the proportion of fibers in the total volume increases to 2% or 4%, the volume of fibers along the transverse direction increases significantly, although the percentage of fibers aligned along the extrusion direction is even higher. Some studies suggest that pump extrusion methods have great potential for improving the fracture properties of fiber-reinforced concrete (FRC), with significant implications for the construction industry. It can be established that, when extrusion nozzles are used for the specific case of pouring using 3D printing nozzles, two factors are key in determining the efficiency of the process: the cementitious materials and the geometric characteristics of the fiber. Currently, research is underway to develop digital casting and mold-making strategies. This technological area, known as "smart dynamic casting," comprises a set of additive technologies applied to mold making and casting strategies. This approach focuses on the automated design of molds. Using metallic fibers, certain multi-layer casting strategies on linear elements have been shown to improve strength (by approximately 57%) in flexural tests. As already mentioned, in addition to the construction processes themselves that induce a certain preferred orientation of the fibers within the cementitious matrix, there is also the possibility of inducing a certain orientation of the fibers within the cementitious matrix due to forced processes (external induction). Among the possibilities that have been investigated in the induced alignment of fibers by means of external agents, it is found that magnetic orientation methods can be assistants that allow to favor said induced alignment. However, the extrusion of fiber-containing materials and its possible effects on fiber orientation has been scarcely investigated in the case of cementitious materials. Regarding the possible effects of magnetic fields during casting processes, there are very few case studies in the literature; the closest to this area of ​​study focuses on the interaction that the cast fiber may have with the magnetic fields of the continuous reinforcing bars that are already present in the mold. The articles on this aspect are known: "Orientation of steel fibers in concrete attracted by magnetized rebar and its effects on bond behavior" (Xuhui Zhang, Fengbo He, Ji Chen, Caiqian Yang, and Fu Xu. Cement and Concrete Composites, 138:104977, 2023. ISSN 0958-9465) and "Towards innovative and sustainable buildings: A comprehensive review of 3D printing in construction" (Habibelrahman Hassan, Edwin Rodriguez-Ubinas, Adil Al Tamimi, Esra Trepci, Abraham Mansouri, and Khalfan Almehairbi. Automation in Construction, 163:105417, 2024. ISSN 0926-5805) . Thus, the desirability of achieving a process that allows modifying the rheology of the cementitious mass from the initial flow or transport of the fiber mixed in the compound has been identified, that is, before pouring the mixture into its final position. This would allow, on the one hand, an improvement in the tectonic performance of certain existing structural members in prefabricated elements in the construction industry, and on the other hand, an improvement in the economic performance or yields that come with the rational and efficient use of cementitious compounds reinforced with ferromagnetic fibers. Description of the invention In order to solve the aforementioned problems, the present invention relates to a method and a system for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix. The procedure for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix, according to the present invention, comprises: or apply an oscillating magnetic field to the cementitious matrix to induce a vibration in the ferromagnetic fibers; and or apply a constant magnetic field on the cementitious matrix to induce an orientation of the ferromagnetic fibers in alignment with the axis of the applied magnetic field. Applying an oscillating magnetic field to the cementitious matrix allows modification of the rheological behavior of the mixture, pumpability, and subsequent fiber alignment. Through the described procedure, it is possible to optimize the different construction processes carried out on the cementitious compound (i.e., on the cementitious matrix that contains the ferromagnetic fibers), making said cementitious compound pumpable, extrudable, moldable (in the case of pouring construction procedures) or printable (in the case of 3D printing construction procedures of construction elements). All of the above allows for improvements to the rheological requirements of fluid cementitious materials. By applying an oscillating magnetic field to the cementitious matrix, the ferromagnetic fibers are allowed to vibrate following the oscillation frequency of the magnetic field; this phenomenon causes shear within the cementitious matrix (or cementitious medium) which causes a reduction in the static yield stress "o" and the dynamic stress "" (Bingham model). Therefore, the fiber is used as a magnetorheological system in its fresh state, and as a reinforcement in its hardened state. Preferably, the application of the oscillating magnetic field is carried out with an oscillation of the magnetic field at a frequency on the order of tens of hertz (Hz). The coils responsible for this operation are the vibrating coils whose design requirements do not need a homogeneous field. Also, preferably, the oscillating magnetic field is applied over an area whose maximum dimension is on the order of magnitude of the size of the ferromagnetic fibers. This type of vibration, with a level in the local environment of each ferromagnetic fiber, has the advantage of not producing segregation. Optionally, an oscillating magnetic field could also be applied to induce vibration in the overall environment of the component or structural element. This vibration occurs due to resonance and the coincidence of a fiber volume distributed throughout the mass, but its effect on segregation at this level is unknown. Preferably, the application of the constant magnetic field occurs prior to pouring the cementitious matrix onto a mold or prior to extruding the cementitious matrix through an extrusion nozzle. By applying this constant magnetic field, homogeneous magnetic fields induce a mechanical torque on the ferromagnetic fibers, causing them to align with respect to the magnetic axis of the coil (Hemholtz, Maxwell, etc. type coil). This induced torque on the fiber is responsible for the controlled alignment of the fiber, and the coil used is called the guide wire. Since the fibers are made of a ferromagnetic material, they may have a magnetization history (hysteresis) and may have been previously magnetized. Controlled alignment of the fibers, prior to pouring, can allow for an increase in the volume fraction of fiber in the pour. By pre-vibrating the ferromagnetic fibers, the subsequent fiber alignment operation is more efficient, causing a greater number of fibers to rotate due to the magnetic torque induced by the coils. As already mentioned, the present invention also relates to a system for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix. The system for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix, the subject of the present invention, comprises: or a pumping module configured to be located in correspondence with an outlet of a cementitious compound feed hopper, wherein the pumping module comprises first vibration coils and first alignment coils, wherein: The first vibration coils are configured to produce at least one oscillating magnetic field pulse configured to induce a vibration in the ferromagnetic fibers; and The first alignment coils are configured to produce at least one pulse of constant magnetic field configured to induce an orientation of the ferromagnetic fibers in alignment with the axis of the applied magnetic field; and or a printing module configured to be arranged in correspondence with a print head or nozzle, wherein the printing module comprises second vibration coils and second alignment coils, wherein: The second vibration coils are configured to produce at least one oscillating magnetic field pulse configured to induce a vibration in the ferromagnetic fibers; and The second alignment coils are configured to produce at least one pulse of constant magnetic field configured to induce an orientation of the ferromagnetic fibers in alignment with the axis of the applied magnetic field. According to one possible aspect of the invention, the system for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix also comprises an extrusion module configured to be arranged between the outlet of a pumping conduit and an inlet of the print head or nozzle, wherein the extrusion module comprises third vibration coils and third alignment coils, wherein: or the third vibration coils are configured to produce at least one oscillating magnetic field pulse configured to induce a vibration in the ferromagnetic fibers, and; or the third alignment coils are configured to produce at least one pulse of constant magnetic field configured to induce an orientation of the ferromagnetic fibers in alignment with the axis of the applied magnetic field. According to another possible aspect of the invention, the printing module is configured to be arranged along a first section and a second section of the print head or nozzle, where the printing module comprises: or a configuration of second vibration coils overlapping second alignment coils, wherein said overlapping configuration is configured to be arranged along the first section of the print head or nozzle, and; or a configuration consisting simply of second alignment coils configured to be arranged along the second section of the print head or nozzle. Preferably, the first vibration coils of the pumping module are configured to be arranged along a first section of the hopper outlet and the first alignment coils of the pumping module are configured to be arranged along a second section of the hopper outlet. Also preferably, the third vibration coils of the extrusion module are configured to be arranged along a first section of the pumping duct outlet and the third alignment coils of the extrusion module are configured to be arranged along a second section of the pumping duct outlet. Brief description of the figures A series of figures, non-limiting examples, are briefly described here to help to better understand the invention: Figure 1 shows a schematic view of a longitudinal section of a conduit through which a "non-Newtonian" fluid circulates with a velocity profile characteristic of the circulation of this type of fluid in conduits. Figure 2 shows a schematic view of a cross-section of the duct in Figure 1 through which the "non-Newtonian" fluid circulates with a velocity profile characteristic of the circulation of this type of fluid in ducts. Figure 3 shows a schematic view of the pumping module, according to a possible embodiment of the system for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix, the object of the present invention. Figure 4 shows a schematic view of the printing module (or pouring module), according to a possible embodiment of the system for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix, the object of the present invention. Figure 5 shows a schematic view of the extrusion module, according to a possible embodiment of the system for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix, the object of the present invention. Detailed description The present invention relates, as already mentioned, to a method and / or system for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix. As already mentioned, Figure 1 shows (see left side of the longitudinal section of the conduit (1) or pipe) a conventional velocity profile of a non-Newtonian fluid flowing inside a conduit (1). Figure 1 shows the different zones of the velocity profile that are taken into account in the present invention. Figure 1 (see left side of Figure 1) shows a velocity profile with a central "blunt" profile typical of a "Binham fluid" through a pipe. The central area of ​​Figure 1 shows the shear stress experienced by the fluid as it circulates through the conduit (1) or pipe. The right side of Figure 1 shows the shear rate of the pumped fluid (concrete) in different flow zones. Figure 2 shows a cross-section of the conduit (1) or pipe, where the different flow zones have been highlighted with different levels of gray. The following describes different aspects of the system for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix, according to a possible embodiment of the present invention. The system for controlling the density and orientation of ferromagnetic fibers, the subject of the present invention, comprises a pumping module (100), a printing module (200) (or pouring module), and, optionally, an extrusion module (300). The pumping module (100) is preferably located between an outlet (or feed) hopper (400) of the cementitious compound (cementitious matrix with the ferromagnetic fibers already added) and the inlet to a booster pump (not shown). The conduits (1) through which the cementitious compound circulates may be flexible (e.g., made of rubber) and may comprise a reinforcing steel lining. Figure 3 schematically shows the pumping module (100). As can be seen, the pumping module (100) is configured to be located in accordance with the cementitious compound feed hopper (400). The pumping module (100) comprises first vibration coils (101) and first alignment coils (102). As can be seen in Figure 3, the first coils (101, 102) are attached laterally to the hopper (400), achieving a vibration of the assembly without alignment, prior to and up to the opening of the gate or movement of the screw or pumping. It is important to note that, because magnetic fields are radiated onto the flow of cementitious compound, and these fields must be parallel to the flow, the material characteristics of the support ring (not shown) for the first coils (101, 102) must be non-ferromagnetic to avoid altering the magnetic field lines within the flow. This requirement is only met if the support ring holding the first coil assembly (101, 102) of the pumping module (100) is typically made of polymer-based composite materials, ceramic materials, or metals such as copper or certain stainless steels. The support ring must be manufactured in such a way that it does not alter the pumping flow and allows for the interconnection between the hopper outlet (400) and the pump suction inlet. The purpose of this pumping module (100) is to align the ferromagnetic fibers in the direction of the flow of the cementitious compound along the conduit (1), with the aim of reducing the number of blockages in situations where large fiber fractions are included. Figure 4 schematically represents the printing module (200) (or pouring module). The printing module (200) is configured to be positioned in correspondence with a print nozzle (or printhead) (or pouring nozzle). As can be seen, the printing module (200) comprises a second vibration coil (201) and a second alignment coil (202). As can be seen in Figure 4, the printing module (200) can be configured so that in a first section of the printing nozzle (or pouring nozzle), the second vibration coils (201) are overlapped with the second alignment coils (202), so that in said first section of the printing nozzle (or pouring nozzle), a joint effect of vibrating and aligning the ferromagnetic fibers in the cementitious matrix is ​​produced. Alternatively (not shown in Figure 4), in the first section of the printing nozzle (or pouring nozzle), only the second vibration coils (201) may be arranged. This is preferable if the ferromagnetic fibers are already aligned in the flow direction and the only aim is to modify the viscosity of the mixture and / or maintain minimum rheological conditions during periods of stoppage or reduced flow rate to prevent clogging or changes in the sample's rheology. Additionally, as shown in Figure 4, in a second section of the printing nozzle (or pouring nozzle), the second alignment coils (202) are arranged to produce the alignment of the ferromagnetic fibers (after vibration in the first section of the nozzle) in the exit direction of the cementitious compound from the printing nozzle (or pouring nozzle). Figure 5 schematically represents the extrusion module (300). The extrusion module (300) is configured to be located between the outlet of the pumping conduits (1) and the inlet to an extrusion mouth (not shown). The extrusion module (300) may be present in the printing processes in the stages prior to pouring. Regardless of the existence of a previous stage in which there has been a pumping module (100) that guarantees an aligned fiber output, the cementitious compound input by means of an extrusion module (300) may not be necessary, since in some cases it may not be necessary to align the fibers before the cementitious compound arrives at the print head or pouring head. The extrusion module (300) comprises a third vibration coil (301) and a third alignment coil (302). The magnetic alignment system described by modules (100, 200, 300) is independent of the geometry of the part being manufactured, allowing pouring to occur from any position on the part, whether externally or even internally. This same principle applies to printing, enabling fiber orientation according to the flow and allowing the print head to move along the part. Thus, the invention allows for a wide variety of pouring / printing strategies. In some processes, such as the discharge from a hopper (400), the optimal fiber alignment must be provided by the discharge cone, which can have a geometry like that shown in Figures 4 and 5. This geometry is linked to the preferred reduction angle "r". This angle can be controlled by a radial coil, allowing the preferred fiber orientation to be tuned by pulse sequences in such a way as to achieve the objective of introducing larger volume fractions of fiber into the cementitious mixtures. Each module (100, 200, 300) is designed to be associated with one of the construction processes (pumping, extrusion, and printing and / or pouring). The modules (100, 200, 300) have a functional and independent design, allowing them to be interchanged and / or removed from the overall process. Each of these modules (100, 200, 300) has three possible operating modes or settings: - AF Mode: In this mode, fiber alignment is activated by applying homogeneous magnetic fields in pulse sequences with periods on the order of seconds. In this mode, the module (100, 200, 300) causes the fibers running through the ducts (1) to align parallel to the flow direction. The pulse dynamics in this mode are executed at a rate that is proportional to the flow rate in the ducts (1): the higher the flow rate and fiber density, the higher the pulse frequency, in order to align as many fibers as possible. - VF mode: magnetic vibration by means of sinusoidal magnetic oscillations on the order of several tens of hertz. Under this setting, the vibration solenoids or coils (101, 201, 301) are activated with oscillating currents of approximately 50 to 60 Hz, which induces vibration in the fibers, causing a reduction in the blunt velocity profile (or reduction of "plug flow"), as shown in Figure 1, in the ducts (1) due to the appearance of shear forced by the vibrating fibers. - AV mode: in which both operations are performed in combination. The alignment coils (102, 202, 302) that generate homogeneous magnetic fields produce sequences of magnetic pulses, while the solenoids or vibration coils (101, 201, 301) cause vibrations. The functional outline of each module (100, 200, 300) consists of two synchronized stages before (pre) and after (post) the specific process, for example, before and after pumping, before and after extrusion, etc. The first stage is responsible for aligning the fibers at the upstream inlet, and the second stage ensures proper alignment after the process. To achieve this effect, the two stages are considered to have the following functionality: - Pre-stage: located in the pumping ducts (1), before extrusion. This stage is implemented using magnetic pulses or repeated signals at a given frequency (on the order of one-tenth of a hertz), and / or by magnetic vibration (with sinusoidal frequencies of tens of hertz: mechanical waves). The coil(s) are positioned so that their magnetic axis is parallel to the flow at all times. The fibers undergo a parallel alignment to the walls of the ducts (1) due to the pumping flow, but due to the non-Newtonian characteristics of the cementitious materials, this tendency will be less pronounced along the axis of the duct (1), precisely at the point where the coil performs its function.The advantage of this magnetic procedure in the pre-stage allows for two beneficial effects: the first is to facilitate the flow because the vibration makes the velocity profile "less blunt" (reduces the "plug-zone") and a second effect is to avoid fiber jamming because a larger fraction of the fiber is aligned in the direction parallel to the flow. - Post-stage: located at the extrusion outlet, forming part of the head or nozzle. Because a fraction of the fiber may be aligned by the induced torques of the process, it may be necessary to monitor the alignment process to control its quality. This post-stage therefore has two possible functions: the first is to measure the average alignment of the fibers with respect to the flow axis, and the second is to trigger the next stage if the alignment does not meet a cutoff value. The control of fiber density in the cementitious matrix can be improved, to some extent, by controlling the flow rate in the extrusion process, using an appropriate dosing system that controls the amount of fibers per unit of time.

Claims

1. A method for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix, characterized in that it comprises: applying an oscillating magnetic field to the cementitious matrix to induce vibration in the ferromagnetic fibers; and applying a constant magnetic field to the cementitious matrix to induce an orientation of the ferromagnetic fibers in alignment with the axis of the applied magnetic field.

2. A method for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix according to claim 1, characterized in that the application of the oscillating magnetic field is carried out with an oscillation of the magnetic field at a frequency on the order of tens of hertz.

3. A method for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix according to claim 1 or 2.characterized in that the application of the oscillating magnetic field occurs over an area whose maximum dimension is on the order of magnitude of the size of the ferromagnetic fibers.

4. Method for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix according to any of the preceding claims, characterized in that the application of the constant magnetic field occurs prior to pouring the cementitious matrix onto a mold or extruding the cementitious matrix through an extrusion nozzle.

5. System for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix characterized in that it comprises: a pumping module (100) configured to be located in correspondence with an outlet of a hopper (400) for supplying the cementitious compound, wherein the pumping module (100) comprises first vibration coils (101) and first alignment coils (102),where: the first vibration coils (101) are configured to produce at least one oscillating magnetic field pulse configured to induce vibration in the ferromagnetic fibers, and; the first alignment coils (102) are configured to produce at least one constant magnetic field pulse configured to induce an orientation of the ferromagnetic fibers in alignment with the axis of the applied magnetic field, and; or a printing module (200) configured to be arranged in correspondence with a print head or nozzle, where the printing module (200) comprises second vibration coils (201) and second alignment coils (202), where: the second vibration coils (201) are configured to produce at least one oscillating magnetic field pulse configured to induce vibration in the ferromagnetic fibers,and; the second alignment coils (202) are configured to produce at least one pulse of constant magnetic field configured to induce an orientation of the ferromagnetic fibers in alignment with the axis of the applied magnetic field.

6. System for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix according to claim 5, characterized in that it comprises an extrusion module (300) configured to be disposed between the outlet of a pumping conduit (1) and an inlet of the print head or nozzle, wherein the extrusion module (300) comprises third vibration coils (301) and third alignment coils (302), wherein: the third vibration coils (301) are configured to produce at least one pulse of oscillating magnetic field configured to induce a vibration in the ferromagnetic fibers,and; or the third alignment coils (302) are configured to produce at least one pulse of constant magnetic field configured to induce an orientation of the ferromagnetic fibers in alignment with the axis of the applied magnetic field.

7. System for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix according to claim 5 or 6, characterized in that the printing module (200) is configured to be arranged along a first and a second section of the print head or nozzle, wherein the printing module (200) comprises: or a configuration of second vibration coils (201) overlapping second alignment coils (202), wherein said overlapping configuration is configured to be arranged along the first section of the print head or nozzle,and; or a configuration consisting simply of second alignment coils (202) configured to be arranged along the second section of the print head or nozzle.

8. A system for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix according to any of claims 5 to 7, characterized in that the first vibration coils (101) of the pumping module (100) are configured to be arranged along a first section of the hopper outlet (400) and the first alignment coils (102) of the pumping module (100) are configured to be arranged along a second section of the hopper outlet (400).

9. A system for controlling the density and orientation of ferromagnetic fibers in a fluid cementitious matrix according to any of claims 5 to 8,characterized in that the third vibration coils (301) of the extrusion module (300) are configured to be arranged along a first section of the outlet of the pumping conduit (1) and the third alignment coils (302) of the extrusion module (300) are configured to be arranged along a second section of the outlet of the pumping conduit (1).

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