MULTIPURPOSE DEVICE FOR THE PRODUCTION OF CONCRETE AND LIMEED EARTH AND THE PROCESS IMPLEMENTED THEREON

Description

BE2024 / 5947 2 Concrete mixer trucks, such as a tow truck, position themselves under the mixer and collect the concrete from the mixer into the mixer through the mixer's filling opening. These mixer trucks, equipped with a rotating drum, keep the concrete moving during transport to prevent it from hardening before being delivered to the construction site. 5 The mixer has an opening at its bottom which allows the concrete thus produced to exit and be introduced into the mixer's opening. Depending on the case, the mixer truck can collect one or more batches of production from the mixer. Such concrete batching plants are well known from the prior art; see, for example, document FR2953423, which describes an installation comprising a series of industrial equipment designed for the handling, dosing, and transport of granular materials intended for concrete production. It consists of several separate storage hoppers, each dedicated to a type of granular material according to its particle size, and several conveyor belts. The installationIt also includes a main conveyor belt, which collects the metered materials from one or the other of the carrier belts. This conveyor belt transports the aggregates to the top of two separate mixing towers. Inside each mixing tower, the aggregates are mixed with a hydraulic binder, water, and, if necessary, admixtures. This homogeneous mixture forms a slurry of concrete ready to be unloaded and used on construction sites. Concrete plants are closely dependent on trucks and ongoing construction sites to produce concrete due to the specific characteristics of the material and the logistical constraints associated with its use. Indeed, unlike other manufactured products, concrete is a perishable material with a very limited shelf life after mixing. Once the components of concrete (cement, aggregates, and water) are mixed, a chemical reaction called hydration begins. This reaction causes the concrete to set, that is, to gradually harden, which startsquickly after mixing. If the concrete is not used within a relatively short timeframe (generally between 1 and 2 hours, depending on the formula and conditions), it begins to harden, becoming unusable for placement. 2024 / 5947 BE2024 / 5947 3 For this reason, concrete plants produce the material only on demand, according to the immediate needs of ongoing construction sites or, in the absence of immediate needs and to make the concrete plant profitable, produce precast concrete elements, which can be stored and are intended for later resale. Unfortunately, this production of concrete elements represents a low value-added activity with minimal, or even negative, profitability. The invention aims to overcome the drawbacks of the prior art by offering an effective alternative for maintaining the activity of concrete plants during temporary drops in concrete demand. To solve this problem, the invention provides a multi-purpose device 10 for the production of concrete and limed earth, as indicated at the beginning, comprising:-feed hoppers, each equipped with a top unloading opening and a bottom discharge opening, said feed hoppers comprising a first series of aggregate hoppers and a second series of soil hoppers, -a mixer, -a conveyor belt connecting said first series of aggregate hoppers and said second series of soil hoppers to the mixer, -a plurality of silos comprising a first series of cement storage silos and a second series of quicklime storage silos, each series of silos being connected to the mixer by at least one feeding device, -a water inlet device, -a mixer discharge device comprising a first a position allowing the evacuation of the concrete produced through a first opening of a first transverse section for supplying concrete transport vehicles and a second position allowing the evacuation of the limed earth produced through a second opening of a second transverse section for supplyingdump trucks, the second transverse section being greater than the first transverse section, said mixer discharge device being arranged to move from the first position to the second position, and from the second position to the first position, 2024 / 5947 BE2024 / 5947 4 - a first control system comprising a series of elements which controls at least said first series of aggregate hoppers, said at least one feeding device for said first series of cement storage silos, - a second control system comprising a series of elements which controls at least said second series of earth hoppers, said at least one feeding device for said second series of quicklime storage silos, - a third control system comprising a series of organs which control at least one element chosen from among said conveyor belt, said mixer, said water inlet device, and being synchronized with the first control system when it is active and with the second control systemWhen active, the mixer discharge device is in the first position when the first control system is active and the second control system is inactive, and in the second position when the first control system is inactive and the second control system is active. As can be seen, the multi-purpose concrete and limestone production device according to the present invention makes it possible to produce concrete and limestone in the same installation, thus allowing the production of limestone when there is no concrete to produce. The industrial production of limestone is a process aimed at improving the properties of clayey or silty soils for applications such as road construction or embankments. This treatment is based on the addition of quicklime to the soil to modify its mechanical and chemical characteristics. Indeed, waterlogged soils containing clay make construction sites complicated because the soils are then plastic and loose, and the construction equipment sinks into the mud. Liming the soils allows for this.Stabilizing, modifying, and drying soils facilitates subsequent civil engineering work. When natural clay soils are limed with quicklime, they are stabilized, their resistance qualities are improved, and plasticity is reduced. Indeed, quicklime (calcium oxide) is highly effective for drying any damp soil. After being mixed with clay soil, quicklime absorbs water via an exothermic reaction that consumes soil water through hydration of the quicklime, but also through evaporation. CaO + H₂O → Ca(OH)₂. This process occurs immediately upon the addition of lime. Next, the lime added to the soil modifies the distribution of charges on the surface of the clay soil particles through an ionic exchange between the sodium in the soil and the calcium. This process is triggered as quickly as possible after the addition of lime and reduces the soil's capacity to retain water. Finally, the soil is stabilized (a medium-term effect that occurs gradually). The silica and alumina contained in the soil react with the lime to form 10Aluminates and silicates (pozzolans) reduce soil compressibility. Furthermore, the addition of quicklime also improves soil health by increasing the pH level when the water in the soil slakes the quicklime, according to the aforementioned exothermic reaction. Soil liming can take place on-site by spreading and then burying, or in some cases off-site. In the latter case, the soil is transported to a facility where it is prepared for liming. Soil preparation generally consists of crushing and sieving to remove coarse elements and obtain a homogeneous particle size. Lime, often produced locally from limestone, is transported in the form of quicklime (calcium oxide) to the soil preparation facility. In the liming process, the soil and lime are mixed in specific proportions, calculated according to the properties of the original soil and the desired performance. This mixing is carried out in industrial equipment, such as mixers, to guarantee a distribution.homogeneous lime in the soil. Once mixed, as previously indicated, the chemical reaction between the lime and the water present in the soil begins immediately. This reaction, called flocculation, leads to a decrease in the soil's plasticity and an improvement in its cohesion. In some cases, an additional supply of water is necessary to optimize the reaction and avoid excessive dust. The limed soil is then transferred to temporary storage areas or transported directly to the site of use. Such limed soil production facilities are well known in the prior art; see, for example, document CN111593641A, which describes a facility for treating soil with lime to obtain a solidified soil for construction. In the device and process according to the present invention, it is intended to produce limed earth and concrete in a multi-purpose device. Although a concrete batching plant and a lime-spreading plant include equipment 10Similar industrial processes (mixers, hoppers, and silos) present challenges related to soil liming and concrete production. In general, it is crucial to avoid using lime in the concrete manufacturing process due to the negative chemical interactions it causes, compromising the mechanical properties and durability of the concrete.15 Furthermore, lime increases the porosity of concrete. This promotes the penetration of aggressive agents, such as water, chloride ions, or carbon dioxide, which can accelerate degradation phenomena, such as reinforcement corrosion or carbonation. Increased porosity also reduces the watertightness of concrete, compromising its use in applications where impermeability is essential.20 Finally, the presence of lime can cause incompatibilities with chemical admixtures commonly used in concrete production, such as plasticizers or set retarders. These incompatibilities can alter the rheological properties of the concrete, making its application on site more difficult and 25affecting the quality of the final product. Furthermore, in concrete production, the product obtained is a plastic, very moist, pasty / liquid product that is discharged from the mixer as a liquid paste which flows out to be transported in this state to the site of use by means of a vehicle, such as a concrete mixer truck. Also, the 30 concrete plants are equipped with pipes that allow the concrete to flow into the filling ports of the concrete mixer trucks, which are standardized and perfectly adapted to concrete. The flow of concrete into the trucks must be done cleanly in order to avoid splashing on the bodies and on the platform on which the truck is positioned to be loaded, and to prevent further concrete from being poured. Limed earth, on the other hand, is a solid product that has been treated to eliminate / reduce the free water pore that gives the earth its plastic character before liming. Limed earth exhibits fairly immediate cohesive characteristics that can disrupt its flow and clog the mixer outlet.Surprisingly, in the device and process according to the invention, the same installation is used to produce a solid product (limed earth), substantially dry and a pasty / liquid product, rich in water, without negatively impacting the mechanical and durability properties of the formed concrete. Indeed, in the device and process according to the invention, feed hoppers allow a carrier conveyor belt to be supplied with aggregates and sand or limed earth, depending on the material to be produced. The carrier conveyor belt is connected to the mixer to discharge its contents. 15 If the material to be produced is concrete, the means of feeding the cement storage silo is activated by the first control system, and cement is added to the mixer. The first control system also includes the control elements that control the opening of the lower discharge ports of the feed hoppers of the first series of aggregate hoppers. 20 If the material to be produced is limed earth, the means of feeding the quicklime storage silo is activated by the second control system.quicklime is introduced into the mixer. The second control system also includes the control elements which control the opening of the lower discharge ports of the feed hoppers of the second series of earth hoppers. Each of the first and second control systems is synchronized with the third control system of the mixer. In the multi-purpose device according to the present invention, the mixer comprises a discharge device which includes a first position for the discharge of concrete through a first opening in a first transverse section and a second position allowing the discharge of limed earth through a second opening in a second transverse section, with the second transverse section being larger than the first transverse section. The discharge device of the mixer is arranged to move from the first position to the second position, and from the second position to the first position, depending on the material being produced. Indeed,The mixer discharge device is in the first position when the first control system is active and the second control system is inactive, and in the second position when the first control system is inactive and the second control system is active. Thus, when the first control system is activated, concrete is produced. The aggregates are brought from the first series of hoppers to the conveyor belt. The conveyor belt brings these aggregates to the mixer. The means of feeding the first series of cement storage silos brings the cement to the mixer. The quantity of water supplied to the mixer is adjusted according to demand. The mixer discharge device is in the first position, which allows the discharge of concrete through an opening in a first transverse section for feeding a concrete mixer truck. The second control system is inactive. When the second control system is active, limed earth is produced. The earth is brought from said second series of hoppers to the conveyor belt.conveyor. The conveyor belt brings this earth to the mixer. The feeding means of the second series of lime storage silos brings lime to the mixer. If necessary, a determined quantity of water can be added to the mixer. The mixer discharge device is positioned in a second location which allows the limed earth to be discharged through an opening in a second cross-section for feeding dump trucks. This second cross-section is larger than the first cross-section to avoid clogging the mixer discharge device and to allow a fluid flow of the limed earth. Indeed, a mixer that discharges limed earth requires a larger discharge opening than one designed for concrete due to the differences in physical properties between these materials. Limed earth is generally less fluid and more cohesive than concrete. The combination of fine earth particles and 30% lime increases adhesion between the grains, which reduces the material's capacity toto flow freely. Unlike concrete, which is designed to have a homogeneous consistency and a certain fluidity thanks to water, limed earth can exhibit an irregular texture with agglomerated pieces or compacted areas. In addition, the water content of limed earth is often lower than that of concrete, which accentuates this tendency to clog. These characteristics imply that a larger discharge orifice is necessary to avoid blockages and allow efficient material evacuation.5 The use of the mixer, the conveyor belt, the water device as well as the mixer discharge device of the concrete plant to produce limed earth makes it possible to maintain the activity of concrete plants during periods of low demand punctual concrete demand. Preferably, in the multi-purpose concrete and lime-based earth production device according to the present invention, said device includes at least one feeding device for the first series of silos and a powder transport device, more particularlyan endless screw, arranged to transport material from the first series of cement storage silos to the mixer. Preferably, in the multi-purpose device for the production of concrete and limed earth according to the present invention, said at least one feeding device for the second series of quicklime storage silos is a powder transport device, more particularly an endless screw, arranged to transport quicklime from the second series of quicklime storage silos to the mixer. Advantageously, according to the present invention, the mixer 20 comprises an outlet of a predetermined cross-section and in which said mixer discharge device comprises a wall, said wall being arranged to slide in a direction of movement in a slide equipping the mixer to pass from said first position to said second position and from said second position to said first position, the wall comprising said first outlet 25 and said second outlet whose geometric centers are aligned with a straight lineparallel to said direction of movement, said first position being a position in which the first orifice of the wall faces said outlet orifice of the mixer and said second position being a position in which the second orifice of the wall faces said outlet orifice of the mixer, and in which the wall has a smaller dimension and in which said outlet orifice has a larger dimension, said smaller dimension of the wall being greater than said larger dimension of the outlet orifice. More particularly, according to the present invention, the cross-section of the outlet orifice of the mixer is a substantially circular cross-section. In an advantageous embodiment according to the present invention, the cross-sections of the first and second orifices are substantially circular cross-sections. More particularly, according to the present invention, said first series of cement storage silos comprises at least 2 silos, preferably at least 3 cement storage silos.10Preferably, in the multi-purpose concrete and limestone production device according to the invention, said second series of quicklime storage silos comprises at most 3 silos, preferably at most 2 silos, preferably 1 quicklime storage silo. Advantageously, the mixer volume is at least 2 m³, preferably at least 3 m³. Preferably, the multi-purpose concrete and limestone production device according to the invention further comprises a holding hopper at the mixer inlet, controlled by said third control system. Advantageously, the holding hopper volume is at least 2 m³, preferably at least 3 m³. Preferably, the feed hoppers are chosen from among helmet hoppers and drive hoppers. Advantageously, the aggregates comprise sands, gravels, and crushed stone of predetermined particle sizes. Preferably, the said first series of aggregate hoppers comprises between sand hoppers, between gravel hoppers, and between crushed stone hoppers, where n is an integer between 1 and 3. 2024 / 5947BE2024 / 5947 11 Advantageously, the said second series of earth hoppers comprises between 1 and 3 hoppers arranged to contain similar or different types of earth. Preferably, the mixer discharge device comprises a movable partition, including said first orifice, arranged such that said first orifice is in fluid connection with said second orifice in said first position and such that said first orifice is not in fluid connection with said second orifice in said second position. In the first position of the mixer discharge device, the movable part is arranged so that said first orifice is in fluid communication with said second orifice. The discharge of the mixer contents thus passes, for example, through said second orifice, then through the first orifice to feed a concrete transport vehicle. In the second position of the mixer discharge device, the movable part is arranged so that said first orifice is not inFluid communication with the second orifice. The contents of the mixer are thus discharged through the second orifice to feed a dump truck. The moving parts travel, for example, in a straight line along a rail, by rotation around a vertical axis, or pivot around a horizontal axis. Other embodiments of the multipurpose device for producing concrete and limed earth according to the invention are indicated in the attached claims. The present invention also relates to a concrete and limestone production installation comprising: a) a multi-purpose concrete and limestone production device according to the present invention, the mixer of which is arranged on a structure which is arranged with the first series of silos and the second series of silos on a floor surface on which concrete transport vehicles or dump trucks are capable of circulating to position themselves under the mixer; b) a series of earth storage bays and a series of aggregate storage bays arranged on the floor surface. 2024 / 5947 BE2024 / 5947 12(c) said feed hoppers being arranged such that a peak of the discharge opening of said feed hoppers is at the level of said floor surface; (d) said carrier conveyor belt having a discharge point below the level of the floor surface and a discharge point above the mixer. In a preferred embodiment of the present invention, said holding hopper is positioned above the mixer and in which said discharge point of the carrier conveyor belt is located above said holding hopper. Other embodiments of the concrete and lime production plant according to the invention are indicated in the attached claims. The present invention relates finally to a process for producing concrete and limed earth in a multi-purpose device according to the invention, comprising the steps of: a. concrete production comprising i) feeding a conveyor belt with one or more aggregates from a first series of aggregate hoppers ii) feeding a mixer by pouring said one or moreaggregates of the conveyor belt iii) a cement supply from a first series of cement storage silos iv) a water supply to said mixer by a water inlet device said supplies i) to iv) being controlled by control elements of a first control system v) an activation of said mixer to form concrete by activation of a third control system vi) a discharge of concrete from said mixer through a mixer discharge device arranged in the first position, b. production of limed soils comprising 2024 / 5947 BE2024 / 5947 13 vii) a supply of soils to a conveyor belt from a second series of soil hoppers, viii) a supply of the mixer by discharge of soils from the conveyor belt, ix) a quicklime supply from a second series of quicklime storage silos x) a possible water supply to said mixer by said water inlet device said supplies vii) to x) being controlled by control devices of a second control system 10xi) an activation of said mixer to form limed earth by activation of a third control system xii) a discharge of the limed earth from said mixer through said mixer discharge device disposed in the second position, said third control system being synchronized with the first control system when it is active and with the second control system when it is active, said mixer discharge device being in the first position when the first control system is active and the second control system is inactive and in the second position when the first control system is inactive and the second control system is active. More particularly, in the process according to the present invention, the quantity of concrete produced during an activation of the mixer and / or the quantity of limed earth during an activation of the mixer is less than 3m³, more particularly less than 2m³. Advantageously, in the process according to the present invention, the cement 25 and the aggregates feed a waiting hopper before feeding the mixer,controlled by said third control system. In an embodiment of the process according to the invention, earth and quicklime feed a waiting hopper before feeding the mixer, controlled by said third control system. 30 2024 / 5947 BE2024 / 5947 14 In a preferred embodiment of the process according to the present invention, the quantity of aggregates and cement in the waiting hopper or the quantity of earth and quicklime in the waiting hopper is less than 3m³, more particularly less than 2m³. Advantageously, the feed hoppers are chosen from among helmet hoppers and drive hoppers, wherein the first and second control systems comprise control elements that activate the helmets of the helmet hoppers or the conveyor belts of the drive hoppers. In a particular embodiment of the present invention, the aggregates comprise sands, gravel, and crushed stone of predetermined particle sizes. Other embodiments of the concrete production process and ofLimed earth according to the invention is indicated in the attached claims. Other features, details, and advantages of the invention will become apparent from the following description, which is not exhaustive and refers to the drawings and examples. In the drawings, Figure 1 shows a schematic view of a multi-purpose device for producing limed concrete and earth according to the invention. Figure 2 shows a schematic view of a drainage device according to the invention. It should be noted that these figures are schematic and not to scale. In the figures, identical or analogous elements are identified by the same reference numerals. As illustrated in Figure 1, the device includes feed hoppers, comprising a plurality of feed hoppers. Each feed hopper of the plurality of feed hoppers is dedicated to specific materials such as gravel, sand, and soil. Each hopper has a large discharge opening located at ground level, thus facilitating access for unloading.Materials are moved using an excavator or loader on the ground surface and pushed into hoppers whose loading openings are at ground level. The hoppers are thus positioned 30 2024 / 5947 BE2024 / 5947 15 below ground level. This design allows mobile machinery such as loaders or excavators to directly unload their contents into the appropriate hopper or efficiently push aggregates and soil towards the loading opening. To further simplify the unloading process, the level of the upper openings of the hoppers can be adjusted to be slightly below ground level, thus avoiding losses of time and energy. The illustrated hoppers fall into two distinct types depending on the materials processed: so-called "helmet" hoppers for coarse granular materials and soil, and so-called "drive" hoppers for fine materials such as sand. In the case of helmet hoppers, the discharge opening is fitted with a very robust flap, 10capable of opening to release materials or closing hermetically to hold them in place. The valve's movement between the open and closed positions is controlled by actuators of the first or second control system, ensuring smooth and secure operation. For driven hoppers, unloading is ensured by an extraction conveyor, a reliable and widely used device for this type of fine material. The extraction conveyor is actuated by actuators of the second control system, allowing precise and continuous regulation of the material flow to the subsequent processing stages. During concrete production, sand and coarser aggregates 20 are poured from hoppers and conveyed to the lower end (loading point) of the conveyor belt 2, which is also located below ground level. This conveyor belt transfers the materials to a holding hopper 6. This hopper allows for the temporary storage of a determined quantity of material before transferring it to the mixer 7 for the final mix. 25An auger 5 ensures the transfer of the material from a cement silo 3 belonging to the first series of storage silos. This auger delivers the cement in a continuous and controlled manner to the mixer 7. In the mixer, the sand, the coarser aggregates and the cement are combined with water from a water supply device (not shown in the figure), allowing optimal hydration 30 of the mixture. 2024 / 5947 BE2024 / 5947 16 Once the concrete is homogeneous and ready, it is discharged from the mixer using a discharge device 8 in a first position which pours it through an opening of the first transverse section 9 directly into a mixer truck. This discharge device ensures a rapid and efficient transfer of the fresh concrete, while minimizing the risk of loss or segregation of the mixture. 5 A first automated control system (not shown in the diagram) includes control elements for aggregate hoppers 1, an endless discharge 5 feeding the cement from the cement silo in use, and the water inlet device. The conveyor belt 2, the waiting hopper 6, the mixer 7, and theThe mixer discharge device 8 is controlled by the third control system 10, which is synchronized with the first control system. These centralized control systems guarantee precise and efficient coordination of the different production stages, thus optimizing the performance of the concrete plant and ensuring continuous and reliable production. During the production of limed earth, one or more earths are 15 discharged from the hoppers and conveyed to the lower end of the carrier conveyor belt 2. This carrier conveyor belt transfers the materials to the holding hopper 6. The latter allows for the temporary storage of a determined quantity of material before transferring it to the mixer 7 for the final mix. An endless screw conveyor 5 ensures the transfer of quicklime from a quicklime silo 20 4 belonging to the second series of storage silos. This endless screw conveyor delivers the quicklime in a continuous and controlled manner to the mixer 7. In the mixer, the earth and quicklime are combined, possibly with water from aWater inlet device (not shown in the figure), allowing optimal formation of the mixture. 25 Once the limed earth is homogeneous and ready, it is discharged from the mixer using a discharge device 8 in a second position which empties it through an opening of a second transverse section 10 directly into a dump truck. This opening of a second transverse section 10 has a cross-section greater than the cross-section of the opening of the first transverse section 30 9 to prevent blockages and allow efficient discharge of the limed earth. This discharge device ensures a rapid and efficient transfer of the limed earth, while minimizing the risk of loss. A second automated control system (not shown in the diagram) includes control devices for the hoppers 1 to the ground, the endless conveyor 5 supplying the lime from the quicklime silo 4 in use, and possibly the water inlet device 5. The third control system is also synchronized with the second control system. These centralized control systemsguarantee precise and efficient coordination of the different production stages, thus optimizing the performance of the concrete plant and ensuring continuous and reliable production.10 As illustrated in Figure 2, an auger5 ensures the controlled delivery of quicklime from a quicklime silo4, belonging to the second series of storage silos. This auger delivers the quicklime continuously and precisely to the mixer7. Furthermore, the soil is transported to the mixer by a conveyor belt, although this is not shown in Figure 2.