EP1324865B1 - Method for producing in a continuous installation a compacted rolled concrete composition reinforced with metal fibres, and continuous installation therefor - Google Patents

Abstract

The invention concerns a method for producing in a continuous installation a compacted rolled concrete composition reinforced with metal fibres, which consists in feeding a vibrating metering means with pre-sized metal fibre plates to be delivered on a conveyor in a proportion ranging between 25 and 60 kg of fibres per m<3> of dry fibre-free concrete constituents, and in supplying a hydraulic binder in a proportion ranging between 180 and 400 kg/m<3> of dry fibre-free concrete constituents, the proportion of mixing water being determined such that the mixer delivers continuously a composition having a water content between 90 and 150 litres of water per m<3> of dry fibre-free concrete constituents.

Description

The present invention relates to a method of manufacturing continuous plant of a compacted rolled concrete composition reinforced with metal fibers packaged in pre-glued wafers, as well as continuous power plant and a continuous fiber feeder for the implementation of this manufacturing process. The compacted rolled concrete composition fiber-reinforced material obtained by said process enables the production of continuous pavements or industrial areas without joints.

To achieve a durable pavement in poured concrete without joined, it is known a process, called process of continuous reinforced concrete (BAC), wherein steel bars, generally 16 mm in diameter, are connected to each other continuously along the entire length of the floor. Once the steel bars are laid, the concrete is applied, usually using a slipform machine. The reinforced concrete however, continues to be a cumbersome technique to implement and expensive.

After reinforcement with steel fibers, the traditional concretes, perverted or cast, make it possible to produce industrial pavements (often covered and thus less exposed to bad weather and temperature variations than pavements) of large size reaching up to 2000 m ² without joints, the properties of the fibers to space the joints. On the other hand, these concretes have so far not been used effectively for the manufacture of continuous pavements without joints, despite the interest shown by such an application. Indeed, relatively high dosages of cement and water generate in these concretes a hydraulic shrinkage to which is added the thermal shrinkage. The mechanical stresses are such that the fibers can not control them. As a result, the phenomena of shrinkage of the concrete cause a much greater cracking than paving, with an unacceptable degree of opening usually reaching several millimeters. Thus it is necessary to practice joints. in these pavements in order to locate the effects of the shrinkage and to reduce the crack openings, which makes the economic advantages of a continuous roadway lose and considerably slows down the development in pavements of the concretes of fibers that are perforated or cast.

The compacted rolled concrete compositions are different conventional concretes cast or perverted by the fact that, for similar mechanical properties or higher, they require a reduced dosage with hydraulic binder and reduced water content. In the two types of conventional concrete mentioned above, it is known to insert metal fibers. Reduction of binding dosage and water content however, gives compacted rolled concrete the advantage of lower hydraulic pressure, resulting in less cracking marked: provided that fibers with an anchorage are used sufficiently powerful in the concrete matrix and know how to integrate correctly these fibers at the time of concrete manufacture, so it is possible to realize a continuous pavement in compacted rolled concrete reinforced with metal fibers. The lower water content of concrete compacted roll also provides sufficient lift for implement the material with road equipment (paver for bituminous mixes) and then compact it with a compactor vibratory and pneumatic compactor, and finally to deliver it without delay under circulation. On the other hand, the consistency of cast concrete requires implemented with traditional techniques of formwork machine sliding or vibrating rule and does not allow a re-circulating after a sufficient setting time which is generally at least 7 days.

The metal fibers used in industrial paving are the more often drawn fibers generally having threads of 1 mm in diameter. The different existing fibers are different each other by the type of active anchorage in the concrete matrix.

To solve the problem of agglomeration of fibers in balls, some fiber manufacturers have turned to shapes geometric and fiber surface aspects that allow a direct use from the manufacturing plant, without treatment complementary. On the other hand, the laboratory tests and the experiment on projects show that these fibers are not the best performing market, at least as regards the mechanical properties and control of the cracking of the concrete + fiber composite material metal.

It is known from French Patent No. 2,225,392 a method of incorporating reinforcing metal fillers into concrete constituted by groups held together by a bond able to be attacked by a disintegrating component, this process introducing said groups into the clean mixture to give birth to the concrete, to mix then all for a good distribution macroscopic, to subsequently cause the disintegration of said binding and to prolong the mixing of the mixture for a good microscopic distribution. This is indeed an integration, in concrete, fibers that have been previously pre-glued into platelets. The mixing in two distinct phases, is carried out either in a mixer mounted on a vehicle called a mixer truck during its 15 minutes or more, or in a mixing pass in approximately 1 minute in the mixer of the power station.

It should therefore be noted that, prior to this invention, the manufacture of cast or extruded concrete reinforced with fibers Pre-glued platelets has always been done in central discontinuous or in a truck called mixer. The fibers are introduced manually or by a specific machine, either directly in the plant mixer, either in a truck called mixer. Use of a truck said mixer has the disadvantage of a mixing quality unsatisfactory and the risk of heterogeneity in the distribution of fibers. The manual introduction of fibers packaged in a bag, on a feeding belt or directly in the mixer, has disadvantages the risk of dosing error and yields that remain low. The use of specific machines makes it possible to increase the rates: these are simple systems that, at best, weigh the quantities of fibers needed to make each batch in the kneader the batch plant. Note that poured or extruded concrete fiber-reinforced products are generally used in areas such as industrial slabs, most often used manually, or in civil engineering works such as piles in foundations. The production rates necessary for feeding the worksite remain relatively low and are suitable for batch plant production.

On the other hand, the road works are highly mechanized and appeal to high-yield gear. Food from these sites in materials treated with hydraulic binders and road concretes (eg example for continuous reinforced concrete or rolled concrete compacted) necessitated the development of plants much higher hourly output than the plants traditional staple foods. A discontinuous power plant disadvantage a production cycle in which the different constituents are first conveyed into the mixer in the context of of a first operation, then the mixer enters into action in order to mix these constituents, finally the mixer is emptied into the truck used for transportation. That's why another type of plant has been put so that it can operate without requiring a shutdown of the mixer at each load cycle of materials. These plants are called "continuous" because the mixer is powered by permanence by a conveyor on which are deposited the quantities required aggregates and hydraulic binder; the mixer is never stopped during the production of the concrete that it delivers in a hopper buffer for filling transport trucks. For this reason, the production rates of continuous power stations are clearly higher than those of most batch plants. The Continuous power plants are therefore well suited to road works, especially as manufacturers have made sure that they can move them construction site to another, much more easily than power plants discontinuous. So we talk about "mobile" plants or even "Hypermobiles" (that is to say, in this case can be transported with only two tractor trucks).

French Patent No. 2,633,922 discloses a method of for the manufacture of a fiber reinforced compacted rolled concrete, according to which 7 to 15% of a plant is fed continuously into a mixer of a plant. cement or road binder, 4 to 7% by weight of water, 0.8 to 4% by weight of metal fibers, these being introduced by a special measuring device, the remainder of the composition being essentially composed of serious from 0 to 31.3 mm. However, this patent is absolutely silent on this doser special and how the fibers are fed by the feeder in the mixer.

French Patent No. 2,654,830 describes a device for continuous weighting of fibers in a building material of works of art. However, the problem with this device lies in the makes the fibers form balls or hedgehogs in the means fiber distribution to the means of transport of the material to be strengthen by the fibers. According to this patent, vibrating chutes distribution means are associated with separation means of fibers, such as toothed rotors, pressurized air injection nozzles or reciprocating rakes, in order to dislocate these hedgehogs from fibers. However, all these means of separation are not sufficiently described or illustrated in this patent to enable their implementation effective implementation by a practitioner.

U.S. Patent 4,022,439 A discloses the characteristics of the preamble of claim 1 or 8 respectively.

• partant de fibres métalliques préencollées en plaquettes, de doser ces fibres dans du béton roulé compacté fabriqué avec des cadences élevées compatibles avec une production en centrale continue pour des chantiers routiers très mécanisés,
• de faire en sorte que la colle liant les fibres en plaquettes soit dissoute de façon à libérer le maximum de fibres pour leur action individuelle de renforcement en flexion et de contrôle de la fissuration du béton roulé compacté mis en oeuvre sur chantier ; un autre but est de libérer dans le béton toutes les fibres préalablement conditionnées en plaquettes préencollées ;
• et d'obtenir avec ces fibres une précision de dosage comprise entre -5 % et +10 % de la valeur de dosage nominal requis, sur un prélèvement instantané effectué à n'importe quel moment de la production du béton de fibres, sachant que cet objectif est important pour garantir des performance correctes et homogènes du matériau composite béton + fibres mis en oeuvre sur chantier.

The correct introduction of metal fibers in a continuous plant is indeed subject to much greater difficulties than in a batch plant: it is necessary at the same time to avoid the problem of agglomeration of the fibers into balls, while integrating the quantity of fibers. required in concrete with acceptable accuracy. The purpose of the process according to the invention is to provide a satisfactory response to these difficulties, which until now have remained unresolved, in particular for the determination of pre-sized metal fiber plates. The method according to the invention proposes a continuous plant manufacture of a rolled compacted concrete reinforced with fibers which effectively avoids, or at least limits to a very low probability, the formation of balls of fibers at the manufacturing stage of the Compacted rolled concrete reinforced with fibers. Another object is to avoid or limit the formation of fiber balls in the other two stages of transport and implementation of compacted rolled reinforced fiber concrete. Finally, one more goal is to completely avoid the formation of these balls. The method according to the invention also aims:

• starting from pre-glued metal fibers in platelets, to dose these fibers in compacted rolled concrete manufactured with high speeds compatible with continuous plant production for highly mechanized roadworks,
• to ensure that the glue binding the fibers into platelets is dissolved so as to release the maximum of fibers for their individual flexural strengthening action and control of the cracking of compacted rolled concrete implemented on site; another purpose is to release into the concrete all the fibers previously packaged in pre-glued platelets;
• and to obtain with these fibers a dosing precision of between -5% and + 10% of the required nominal dosage value, on an instantaneous sampling carried out at any time during the production of the fiber concrete, knowing that this This objective is important to ensure the correct and homogeneous performance of the concrete + fiber composite material used on site.

a) l'alimentation en continu de plusieurs types de granulats délivrés sur un convoyeur,

b) l'alimentation en continu de fibres métalliques à partir d'un moyen de dosage vibrant sur ledit convoyeur,

c) l'alimentation en continu dans un malaxeur des granulats et des fibres délivrés par le convoyeur, d'un liant hydraulique et d'eau de gâchage pouvant contenir un ou plusieurs adjuvants du béton,

caractérisé par le fait que :

qu'il consiste à alimenter en continu, au cours de l'étape a) précitée, sur le convoyeur, un produit solvant, par exemple de l'eau, pour dissoudre la colle qui maintient les fibres en plaquettes, ledit produit solvant étant délivré sur le convoyeur au niveau ou au voisinage du point de chute des fibres délivrées par le moyen de dosage

l'étape b) précitée consiste à alimenter le moyen de dosage vibrant précité en plaquettes de fibres métalliques préencollées pour délivrer lesdites plaquettes de fibres et/ou lesdites fibres décollées sur le convoyeur au cours de l'étapë a) précitée, lesdites fibres étant alimentées dans une proportion comprise entre 25 et 60 kg de fibres par m³ de constituants secs du béton sans fibre, et

que l'étape c) consiste à alimenter le liant hydraulique dans une proportion comprise entre 180 et 400 kg/m³ de constituants secs du béton sans fibre, la proportion d'eau de gâchage étant déterminée de façon que le malaxeur délivre en continu une composition de béton roulé compacté de fibres qui présente une teneur en eau comprise entre 90 et 150 litres d'eau par m³ de constituants secs de béton sans fibre. Le fait de délivrer des fibres sous forme de plaquettes préencollées permet d'éliminer ou de réduire le nombre et la taille des boules de fibres dans la composition de béton. Ainsi, les plaquettes de fibres imbibées préalablement de produit solvant se décollent par l'action combinée de cisaillement énergique engendré par le malaxeur et d'ajout d'eau au niveau des bras du malaxeur.

To this end, the subject of the invention is a process for the continuous production of a fiber-reinforced compacted rolled concrete composition, comprising the following steps:

a) the continuous supply of several types of aggregates delivered on a conveyor,

b) feeding continuously metal fibers from a vibrating metering means on said conveyor,

c) feeding continuously in a mixer aggregates and fibers delivered by the conveyor, a hydraulic binder and mixing water may contain one or more adjuvants of the concrete,

characterized by the fact that:

that it consists in continuously feeding, during the above-mentioned step a), on the conveyor, a solvent product, for example water, to dissolve the adhesive which keeps the fibers in platelets, said solvent product being delivered on the conveyor at or near the point of fall of the fibers delivered by the dosing means

said step b) comprises supplying said vibrating dosing means with pre-bonded metal fiber wafers to deliver said fiber wafers and / or said loose fibers to the conveyor during said step a), said fibers being fed in a proportion of between 25 and 60 kg of fibers per m ³ of dry constituents of fiber-free concrete, and

that step c) consists in feeding the hydraulic binder in a proportion of between 180 and 400 kg / m ³ of dry constituents of the concrete without fiber, the proportion of mixing water being determined so that the kneader delivers continuously a compacted rolled fiber concrete composition which has a water content of between 90 and 150 liters of water per m ³ of dry constituents of fiber-free concrete. Providing fibers in the form of pre-glued wafers eliminates or reduces the number and size of fiberballs in the concrete composition. Thus, the wafers of fibers impregnated with solvent product are peeled off by the combined action of energetic shear generated by the mixer and addition of water at the arms of the kneader.

Advantageously, the transport of compacted rolled concrete fiber reinforced is carried out by a dump truck, and not by truck-mixer, and the implementation of the concrete on the road is carried out by a finisher, to maintain the desired characteristics for the mixture constituents of fiber-reinforced concrete.

Preferably, the method consists in feeding continuously, during the above-mentioned step a), on the conveyor, a solvent product, by example of water, to dissolve the glue that keeps the fibers in platelets, said solvent product being delivered on the conveyor at the level of or in the vicinity of the point of fall of the fibers delivered by the means of dosage.

According to a first variant, the dosing means comprises successively at least one vibrating metering tank and a corridor vibrating or a weighing mat. For example, the method consists of feeding in solvent product said corridor so that the fibers bathe at least partially in the corridor whose bottom is filled with solvent and are delivered together with said solvent product on the conveyor from said corridor.

According to another variant, the method consists in delivering said solvent product by at least one nozzle located just downstream of the point of falling fibers on the conveyor.

Advantageously, the process consists in delivering the fibers on the conveyor, after feeding a first type of aggregates and before feeding the last type of aggregates, so that the fibers are integrated into the mass of different types of aggregates.

According to another characteristic of the invention, the method consists in calculating the proportion of mixing water delivered in step c) above mentioned in the mixer, depending on the water content specific to the each type of granulate fed in step a).

In a particular embodiment, the method consists of to feed in step a) a total proportion of aggregates between 83 and 93 % by weight of dry constituents of the concrete without fiber, and in step c) a cement or road binder in a proportion of between 7 and 17% by weight of dry constituents of fiber-free concrete, of which 0.3 to 1.8% by weight weight of the hydraulic binder consists of a retarding adjuvant concrete and / or plasticizer introduced into the mixing water to lubricate intergranular contacts and delay the setting of the concrete.

• une série de trémies disposées par intervalles au-dessus d'un convoyeur entraíné par moteur, chaque trémie étant apte à délivrer sur le convoyeur un type de granulat, chaque trémie étant associée à un moyen de mesure pondérale ou volumétrique de la quantité de granulat délivré par ladite trémie,
• un moyen de dosage vibrant apte à délivrer sur le convoyeur des fibres métalliques, ledit moyen de dosage étant associé à un moyen de mesure pondérale de la quantité de fibres délivrées,
• un ou plusieurs silos aptes à délivrer chacun un liant hydraulique, chaque silo étant associé à un moyen de mesure pondérale ou volumétrique de la quantité de liant délivré, un autre silo pouvant être utilisé pour doser un pulvérulent complémentaire comme des cendres volantes par exemple,
• un moyen d'alimentation en eau de gâchage associé à un moyen de réglage du débit d'eau de gâchage,
• un malaxeur comportant un réseau de buses d'injection dans la chambre de malaxage, ledit réseau étant alimenté en eau de gâchage par ledit moyen de réglage du débit, le liant hydraulique étant délivré à l'entrée du malaxeur à partir dudit silo et l'ensemble des fibres et des granulats étant délivré par le convoyeur dans le malaxeur, pour le malaxage de l'ensemble des constituants du béton compacté roulé renforcé de fibres,

caractérisé par le fait qu'il comporte un moyen d'alimentation de produit solvant pour délivrer sur le convoyeur, au niveau ou au voisinage de la sortie du moyen de dosage vibrant, un produit solvant destiné à dissoudre la colle des plaquette et à libérer ainsi les fibres métalliques pré-encollées délivrées par ledit moyen doseur. Avantageusement, ledit moyen d'alimentation en produit solvant est agencé de façon à délivrer le produit solvant en aval de la première trémie d'alimentation en granulats et en amont de la dernière trémie d'alimentation en granulats.The subject of the invention is also a continuous plant for carrying out the process defined above, comprising:

• a series of hoppers arranged at intervals above a conveyor driven by motor, each hopper being able to deliver on the conveyor a type of granulate, each hopper being associated with a means of weight or volumetric measurement of the quantity of granulate delivered by said hopper,
• a vibrating metering means capable of delivering metal fibers onto the conveyor, said metering means being associated with a means of weight measurement of the quantity of fibers delivered,
• one or more silos each capable of delivering a hydraulic binder, each silo being associated with a means of weight or volumetric measurement of the quantity of binder delivered, another silo that can be used to determine a complementary powder such as fly ash, for example,
• mixing water supply means associated with a means for controlling the mixing water flow,
• a kneader comprising a network of injection nozzles in the kneading chamber, said network being supplied with mixing water by said flow control means, the hydraulic binder being delivered to the kneader inlet from said silo and the all the fibers and aggregates being delivered by the conveyor into the kneader, for the kneading of all the constituents of the rolled reinforced compacted concrete of fibers,

characterized by the fact that it comprises a means for supplying a solvent product for delivering on the conveyor, at or near the exit of the vibrating dosing means, a solvent product intended to dissolve the glue of the wafers and thus to release pre-bonded metal fibers delivered by said metering means. Advantageously, said solvent feed means is arranged to deliver the solvent product downstream of the first aggregate feed hopper and upstream of the last feed hopper of aggregates.

In a particular embodiment, the dosing means vibrator comprises a first vibrating tank having on its wall cylindrical internal helical ramp on which the platelets of fibers are able to move by vibration from the bottom of the tank to its top, said helical ramp extending at its apex by a intermediate chute opening above the center of a second vibrating tank, said second tank also having on its wall internal cylindrical helical ramp on which the platelets of fibers are able to move from the bottom to the top of the second tank, the helical ramp of the second tank leading to a vibrating corridor that delivers the fibers above the conveyor, said solvent supply means comprising at least one nozzle located substantially above the upstream end of said vibrating corridor.

The advantage of providing two vibrating tanks in series is to eliminate irregularities in the supply and distribution of from the only first vibrating tank, the latter being fed with Discontinuous fiber feed by a forklift regularly filled with fiber boards from large bags called "big bags".

Advantageously, the first vibrating tank comprises a articulated arm interposed between the top of the helical ramp and the intermediate chute, said arm being adapted, in a closed position, to prevent the passage to the chute and return the fibers to the center and the bottom of the first tank, and in an open position variable, to allow the passage of a controlled amount of fiber to said intermediate chute.

According to another characteristic, said intermediate chute has parallel vibrating fingers located substantially in vertical planes, fixed at their upstream end and free at their end downstream, so that the agglomerations of platelets fibers and obtain a more even distribution in the diet fiber plates of the second tank, the longitudinal extension of the fingers being parallel to the direction of movement of said platelets of fibers.

In a particular embodiment, the second vibrating tank is equipped with a fiber level detector stored in said second tank, said detector being connected to a control motor of the articulated arm, in order to move said arm towards its closed position or vice versa to its open position, when the amount of fiber stored in the second tank is higher or conversely less than a predetermined threshold value.

According to another characteristic, the second tank is equipped with a frequency modulator to vary its vibration and thus its fiber flow rate, said modulator being controllable by the weighing the quantity of fibers delivered at the outlet of the second tank. Indeed, the second tank can be mounted on load cells, the flow of fibers being fixed by the centralized control of the doser in the cabin of control of the plant. The operator of the plant may enter the flow desired fiber on a digital controller, then the CPU will operate automatically to control the modulator of frequency. Fiber flow can also be verified by a logger graphic and printer edition.

Advantageously, the plant is equipped with a unit of centralized control connected to the various means of weight measurement or volumetric hoppers, silo and dosing medium, and than the means for regulating the flow rate of the water supply means of mixing, to calculate and control the flow of water to feed into the mixer according to the water content, the flow rate of each granulate and / or the flow rate of the solvent product.

According to yet another characteristic, each hopper and each silo opens on a treadmill driven by his own drive motor, whose speed can be controlled by the centralized control unit, according to the measured weight, for control the flow of each component of the concrete.

The invention will be better understood and other purposes, characteristics, details and benefits will become clearer at course of the detailed explanatory description which follows of a mode of presently preferred embodiment of the invention, with reference to the attached schematic drawing.

• la figure 1 est une vue schématique de l'ensemble de la centrale continue conforme à l'invention ;
• la figure 2 est une vue schématique agrandie et partielle d'une trémie associée à un tapis peseur ;
• la figure 3 est une vue en perspective d'une plaquette de fibres pouvant être utilisée dans le procédé de l'invention ;
• la figure 4 est une vue schématique et en élévation latérale du moyen de dosage vibrant utilisé dans la centrale de l'invention ;
• la figure 5 est une vue schématique de dessus de la figure 4 suivant la ligne V-V, en position ouverte du bras articulé ;
• la figure 6 est une vue partielle et analogue à la figure 5 montrant le bras articulé en position fermée ;
• la figure 7 est une vue schématique agrandie et partielle du malaxeur visible sur la figure 1 ;
• la figure 8 est une vue en coupe de la figure 7 suivant la ligne VIII-VIII ;
• la figure 9 représente une page écran visible sur le terminal de l'unité de commande centralisée de la figure 1.

On this drawing :

• Figure 1 is a schematic view of the entire continuous plant according to the invention;
• Figure 2 is an enlarged and partial schematic view of a hopper associated with a weighing belt;
• Figure 3 is a perspective view of a fiber wafer that can be used in the method of the invention;
• Figure 4 is a schematic side elevational view of the vibrating dosing means used in the plant of the invention;
• Figure 5 is a schematic top view of Figure 4 along the line VV, in the open position of the articulated arm;
• Figure 6 is a partial view and similar to Figure 5 showing the articulated arm in the closed position;
• Figure 7 is an enlarged and partial schematic view of the kneader visible in Figure 1;
• Figure 8 is a sectional view of Figure 7 along the line VIII-VIII;
• FIG. 9 represents a screen page visible on the terminal of the centralized control unit of FIG. 1.

In Figure 1, there is shown schematically the whole of an installation for a continuous plant of manufacture of Compacted rolled concrete reinforced with fibers.

This plant comprises a first hopper 1 represented in Figure 2, intended, for example, to contain and distribute gravel, a first load cell 2, whose frame is hinged substantially at point 3 on the lower end of the hopper 1. The weighing frame 2 carries an endless treadmill 4, driven by a drive motor 7 which rotates the rollers 5, via a chain 6, the drive shaft being attached to one end of the frame of the load cell 2 relative to the hinge 3. The other end of the load cell 2 is connected to a strain gauge 8, suspended from the frame B of the plant, which frame also supports the first hopper 1. The chippings contained in the first hopper 1 fall, as indicated by the arrow F1, on the carpet weigher 4, which is rotated in the anti-clockwise direction, according to the arrow F2, so that the chippings fall to the left end of the weighing belt, as indicated by the arrow F3, on the conveyor belt 9. The strain gauge is connected by an electrical cable to a centralized control unit U, as shown in Figure 1. Of course, the first conveyor belt 9 is also motorized and its engine, as well as the engine 7 mentioned above, can be controlled by the unit U.

A second hopper 11 is located near the first hopper 1 and also has at its lower end a scale 12, whose chassis is inverted compared to that of the first load cell 2. Indeed, its engine 17 is located at the left end of the chassis, so that the strain gauge 18 is fixed at its right end, the carpet weighing the second scale 12 being driven clockwise in Figure 1 so that the granulate contained in the second hopper 11 falls towards the right on the conveyor belt 9 and covers the first granulate previously filed. Of course, the conveyor belt 9 is counterclockwise in Figure 1. The strain gauge 18 is also suspended from frame B and is connected by line 20 to the unit U.

The first conveyor belt 9 comes pouring all the first two aggregates on a second conveyor belt 19 motorized, as shown in Figure 1. Above this second carpet 19 are located two other hoppers 21 and 31, the third hopper 21 being intended to deliver a third granulate constituting concrete, while the fourth hopper 31 may not be operational in the example described below of embodiment of the invention. Good heard, the number of hoppers can vary and one could predict, by example, six hoppers containing different types of aggregates for different types of concrete. Like other hoppers, each hopper 21 and 31 is associated with a load cell 22, 32, each load being associated with its own electric motor 27, 37 and its own strain gauge 28, 38. Each strain gauge and each motor can be connected by lines 30 and 40 to the unit U.

As shown in FIGS. 1 and 4, the control unit comprises also a dosing means D provided with a vibratory corridor 41, whose outlet end opens on a chute 42 located above the second conveyor belt 19, upstream of the third hopper 21.

The dosing means D has an elevator 43, which has at its lower end wheels 43a guided in vertical grooves 44 and at its upper end casters 43b guided in vertical grooves 45, the upper portion of these grooves 45 being bent horizontally to allow the tilting of the lift truck 43 in the up position, as visible on the Figures 1 and 4. The lift truck 43 is intended to be filled by loads in big bags (whose weight is for example 1,100 kg) pre-sized fiber boards P, for example of the type of platelets visible in Figure 3. These plates are, for example, dumped into the tank of the elevator 43 in the low position from large bags filled with pads, as indicated by the arrow F4 on the figure 4.

In the high position of the lift truck 43, it discharges its content as indicated by the arrow F5 in a first tank cylindrical 46, which is provided at its upper end with a deflector 47 to prevent the P fiber wafers from falling out of tank.

The first tank 46 is mounted on a base 48, which rests on an intermediate frame 50a with a set of springs 49 intercalated and dampers not shown, said intermediate frame 50a resting on a base frame 50b equipped at each corner with a load cell 51. The base 48 is equipped with two vibrating motors 52 arranged from and other of the base 48, to vibrate the first tank 46 in adding the combined effect of springs and dampers. Both motors rotate at the same speed so as to generate vibrations sufficient in the cylindrical tank 46 to raise the platelets of fibers by vibration along a helical ramp 53 disposed on the cylindrical inner wall of the first tank 46.

As best seen in FIGS. 5 and 6, the platelets of fibers rise from the bottom to the top of the tank turning in the counter-clockwise, as indicated by the arrow F6, and an articulated arm 54 is provided at the top of the tank 46 to allow the passage of fiber boards either to an intermediate chute 55, as indicated by the arrow F7 (see Figure 5), or towards an inclined plate 56 towards the center of the tank 46 to allow the return of platelets to the bottom of it, as indicated by the arrow F8 (see Figure 6). As indicated by line 57, the articulation of arm 56 is motorized and its engine can be controlled by the unit U, via the sensor 70.

The trough 55 is provided with a plurality of fingers 58, parallel to each other, oriented substantially in the direction of F7 displacement of the fiber plates, so as to better distribute the platelets. The chute 55 opens above the center of a second cylindrical tank 59, smaller, which also comprises a base 60 on which are mounted on both sides two electric motors vibrators 61 and a set of springs and dampers 49 on the chassis intermediate 50a supra. The second small tank 59 comprises also a helical ramp 63 on its inner wall, to make move fibers and / or fiber boards from bottom to top by turning counter-clockwise as shown by the arrows F9 in FIG. 5. The helical ramp 63 opens at its top on a second trough 64, which extends radially outwardly of the vessel 59 and opens above the corridor 41 which is equipped with vibrating motors (not shown) Vibrating fingers may also be provided on the output of the chute 64. This vibrating corridor 41 is mounted via springs 65 on an upright 66 at its upstream end and suspended at its downstream end via springs 67 to the frame B. At the upstream end of the vibrating corridor 41 at least one nozzle 68 for injecting water can be provided from the network, a valve 69 for adjusting this flow, for example via the unit U. A. For example, the vibrating corridor 41 can be filled with about a half centimeter of water to start taking off the fiber pads. The direction of travel of the fibers in the corridor 41 is indicated by the arrows F10. The fibers as well as the water or the solvent product fall from the corridor 41 on the second conveyor belt 19 above. In a variant preferred embodiment shown in Figures 3 and 4, the nozzle 68 is disposed above of the last trough 64, to increase the duration moistening the fibers before they fall on the conveyor.

As can be seen in FIG. 4, the entire means of dosage D rests on the ground S or on a mobile trailer, as the frame B.

Under the intermediate chute 55 is provided a support for a level detector, for example an ultrasonic sensor 70, for detect the level of the fibers in the second tank 59 and control automatically the displacement of the articulated arm 54, depending on whether the level in the second tank is greater than a predetermined threshold value. The fact of having two tanks in series makes it possible to avoid irregularities supply and distribution of the fibers at the outlet of the dosing means, these irregularities being inevitable in the case of the use of a single tank.

The position of the articulated arm 54 with respect to the chute intermediate 55 is electronically controlled according to the information given by the sensor 70, so as to vary the flow of fibers which passing from the first tank 46 to the second tank 59.

Of course, one could envisage other systems of dosing of fiber pads to the conveyor belts of the plant.

• un diamètre compris entre 0,38 et 1,05 mm,
• une longueur totale comprise entre 19 et 80 mm,
• une longueur des parties d'extrémité comprise entre 1,5 et 4 mm,
• un décalage transverse entre la partie centrale et chaque partie d'extrémité d'au moins 0,75 mm,
• un angle de recourbement, défini entre chaque portion intercalaire et la partie centrale, au minimum égal à 20°, et
• un angle obtus inférieur ou égal à 160° entre chaque portion intercalaire et la partie centrale,
• un angle obtus entre chaque portion intercalaire et partie d'extrémité, et,
• une résistance à la traction minimale de 900 N/mm².

By way of example, it is possible to choose platelets P whose metal fibers consist of substantially cylindrical wires comprising a substantially rectilinear longitudinal central part extending on each side by means of an intermediate portion of a portion of curved end whose shape is of the type that prohibits the attachment of two neighboring fibers, said son having

• a diameter of between 0.38 and 1.05 mm,
• a total length of between 19 and 80 mm,
• a length of the end portions of between 1.5 and 4 mm,
• a transverse offset between the central portion and each end portion of at least 0.75 mm,
• a bending angle, defined between each intermediate portion and the central portion, at least equal to 20 °, and
• an obtuse angle less than or equal to 160 ° between each intermediate portion and the central portion,
• an obtuse angle between each intermediate portion and end portion, and
• a minimum tensile strength of 900 N / mm ² .

Advantageously, the yarns constituting the fibers have a diameter between 0.65 and 0.85 mm and a length ratio total / diameter between 65 and 85. In particular, the fibers have a total length / diameter ratio of the order of 80. According to one feature, each curved end portion is formed of a rectilinear portion connected to the central part by said inclined part comprising at least two elbows.

Advantageously, the fibers used in the present invention are fibers of 0.75 mm in diameter, with a total length of 60 mm and with a tensile strength of at least 1100 N / mm ² , marketed for example under the brand "Dramix 80/60". This fiber is also of interest, at equal weight proportion in the concrete, a number of fibers twice that of the number of fibers of 1 mm diameter traditionally used. Due to a work hardening pushed further to wire drawing, the thinner wire also has a higher elastic limit which makes it more efficient than a wire of 1 mm in diameter.

The plate P comprises a plurality of fibers f1, f2 ... fn, where n is any integer, for example equal to 20.

In the example described here, the metal fibers are therefore spilled on the first two layers of aggregates and before the deposit of the third layer of aggregates.

The second conveyor belt 19 comes pouring all fiber aggregates on a third conveyor belt 79, which opens in a mixer 80.

The plant comprises one, or two, or more silos 81, which each contain a hydraulic binder, for example a cement standardized CPJ (Portland cement) or CLK (slag cement), or a road binder, for example the product sold under the trademark "LIGEX" by the company CALCIA. The lower outlet of each silo 81 opens on a pipe containing an endless screw 82 for transporting the binder up to a hopper 83. This hopper 83 can receive binders from several silos. The lower output of the hopper 83 opens onto another worm 84, which delivers the hydraulic binder on a weighing belt 85 inside a housing 78, one end of which is connected to a strain gauge 86 to weigh the amount of hydraulic binder.

Of course, the level sensor 70, the load cells 51 and the other motors of the dosing means D are connected by different lines 71 to 73 to the centralized control unit U. The strain gauge 86 is also connected by a line 74 to the unit U.

The weighing belt 85 delivers the hydraulic binder to the inlet of a double conveyor containing two endless screw conveyors 87 for introducing said hydraulic binder into the kneader 80, substantially in the vicinity of the entry of the mixture of fibers and aggregates delivered by the third conveyor belt 79.

The mixer is also fed with mixing water via the water network, as indicated by valve 88, and adjuvants plasticizers contained in a tank 89. A mixing valve 90 allows admixture from tank 89 to be mixed with water from the network 88. This mixture of water and adjuvant is distributed to the interior of the mixer 80 via a network of pipes 91 pierced holes to inject the mixture into the mixer over two 92. As shown in Figure 8, the pipes 91 preferably comprises a simultaneous arrival of mixture on both sides of the mixer, the network comprising a U-shaped parallel branch over trees 92. Each tree 92 has diametrical blades 93 provided at their ends with pallets 94 inclined to form a discontinuous helical ramp. The blades of each shaft are shifted so as to allow the mixing of all the constituents of compacted rolled concrete reinforced with fibers, when the two trees are rotated in opposite directions, as visible by the arrows F11 in FIG.

By way of example, the adjuvant makes it possible to delay concrete for several days, with a proportion of 0.8% of the weight of the hydraulic binder. Such a plasticizer may be a plasticizer marketed under the trademark "CIMAXTARD" by the company Axim.

At the outlet of the mixer 80, the mixture of concrete and fibers arrives on a fourth conveyor belt 99, which carries the composition to a hopper 100 whose bottom is closed by a helmet consisting of two oscillating arms 101 which are able to deviate for unloading the contents of the hopper 100 into a truck 102.

The opening of the oscillating arms 101 is controlled by the responsible for the plant for filling trucks.

The unit U is connected to a terminal comprising a screen 110 and a keyboard 111 for entering set values of the different component flow rates and speeds of different treadmills.

FIG. 9 shows a page of the screen 110, in running of an exemplary embodiment of the method of the invention.

In FIG. 9, D1 denotes chippings having a diameter between 5 and 12 mm, with a flow rate of 75.4 T / H (ton per hour), having a natural water content of approximately 1.70%, gravel being intended to constitute 44% of the dry constituents of fiber-free concrete, D2 means crushed sand, the diameter of which is between 0 and 4 mm, with a flow rate of 48.3 T / H and a water content of 4.30%, for constitute 27.30% of the weight of the dry constituents of fiber-free concrete, D3 wet rolled sand having a diameter of between 0 and 4 mm, with a flow rate of 28.9 T / H and a water content of 8.40%, to constitute 15.80% of the weight of the dry constituents of fiber-free concrete, D4 to D6 may designate other types of aggregates or aggregates, but are not not used in this example, P1 refers to the hydraulic binder that is supplied with a flow rate of 21.7 T / H to constitute 12.9% by weight of dry constituents of concrete without fiber, P2 can be another powder (eg fly ash) added to P1, X1 being a first adjuvant which constitutes 0.35% of the dry weight of the hydraulic binder P1, which corresponds to a flow rate of about 80 kg or 80 liters per hour, X2 or X3 may designate other adjuvants and E designating the water of mixing which has a proportion of 5.20% of the weight of the constituents dry concrete with a flow rate of 3.3 T / H.

Of course, since the aggregates D1 to D3 are not dry but contain water, the flow of water to be supplied will not be equal to 5.5 % of total machine speed.

The actual water flow to be supplied will be calculated below. In this indeed, we start from the total machine flow, namely the wet concrete flow rate without fiber provided by the machine, which corresponds to 177.6 T / H, namely the sum of the flows of the components D1 to D3, P1 and E.

To obtain the dry flow delivered by the plant, excluding fiber, it divide the wet flow by 1 + 5.2% = 1.052, which gives a total dry flow rate of 168.8 T / H.

The theoretical flow rate of water is then equal to this total dry flow rate 168.8 T / H x 5.2% = 8.78 T / H.

The quantity of water coming from the granulate D1 is equal to 0.44 x 168.8 x 0.017 = 1.26 T / H water. Similarly, the quantity of water supplied by the aggregate D2 is equal to 0.273 x 168.8 x 0.043 = 1.98 T / H water. For D3, the amount of water added is 0.158 x 168.8 x 0.084 = 2.24 T / H, ie in total, for all aggregates D 1 at D3 a flow of water equal to 5.48 T / H which must be deducted from the flow of water The theoretical value of 8.78 T / H, ie 3.3 T / H of water actually to be supplied in the mixer.

The plant is used with a flow rate of 177.6 T / H corresponds to only 60% of its rated capacity of the order of 400 T / H here limited to 300 T / H by the capacity of the binder doser hydraulic used.

The aggregates used may comprise from 70 to 100% of crushed materials, having sharp angles and a shape close to the square, and a particle size of between 0 and 14 mm so as to avoid the phenomena of segregation, that is to say separation of large elements. The concrete composition also preferably comprises a plasticizer which facilitates compaction by intergranular lubrication and allows to obtain a density close to 2400 kg / m ³ of wet concrete without fibers with favorable consequences, such as higher strength and the possibility of reducing the dosage by hydraulic binder

The optimum water content is determined by the Proctor test Modified and varies between 4 and 6% of the dry constituents of concrete.

Advantageously, the composition comprises a content of hydraulic binder of 250 to 300 kg per cubic meter of dry concrete without fiber, a water content of 4 to 6% of the weight of the dry constituents of the fiber-free concrete, about 100 to 150 liters of water per cubic meter of concrete, a dosage of metal fibers between 30 and 40 kg per cubic meter of dry concrete without fiber. For example, the composition includes 280 kg of hydraulic binder and 110 liters of water per cubic meter of dry concrete without fiber.

Advantageously, the composition further comprises a retardant plasticizer content between 0.3 and 1.8% of the weight of the hydraulic binder.

Moreover, the instantaneous precision of fiber dosing obtained with the plant according to the invention is between - 5% and + 10%, which can not be achieved with a mixer truck. Rates in the continuous plant of the type of the invention are between 200 and 1,000 tonnes / hour of concrete, while staple power plants can usually only reach half of these cadences.

Although the invention has been described in connection with a particular example of realization, it is obvious that it is not in no way limited and that it includes all the technical equivalents of means described and their combinations if they fall within framework of the invention.

Claims (15)

1. Process for the manufacture in a continuous mixing plant of a metal-fibre-reinforced roller-compacted concrete composition, comprising the following steps:

   a) continuous feeding of several types of aggregate (D1, D2, D3, D4) delivered onto a conveyor (9, 19, 79);

   b) continuous feeding of metal fibres (f1, f2 ... fn) from a vibrating metering means (D) onto the said conveyor; and

   c) continuous feeding into a mixer (80) of the aggregates and fibres delivered by the conveyor, of a hydraulic binder (P1) and of mixing water (E) possibly containing one or more concrete admixtures;

   characterized in:

   that it consists in continuously feeding, during the aforementioned step a), onto the conveyor (9, 19, 79), a solvent, for example water, for dissolving the adhesive bonding the fibres together in packs, the said solvent being delivered onto the conveyor at or near the drop point for the fibres (P, f1, f2 ... fn) delivered by the metering means (D).

   that the aforementioned step b) consists in feeding the aforementioned vibrating metering means with packs (P) of prebonded metal fibres in order to deliver the said packs of fibres and/or the said fibres when separated onto the conveyor during the aforementioned step a), the said fibres being fed in a proportion of between 25 and 60 kg of fibres per m³ of dry constituents of the concrete without fibre; and

   that step c) consists in feeding the hydraulic binder in a proportion of between 180 and 400 kg/m³ of dry constituents of the concrete without fibre, the proportion of mixing water being determined so that the mixer continuously delivers a fibre-reinforced roller-compacted concrete composition having a water content of between 90 and 150 litres of water per m³ of dry constituents of the concrete without fibre.
2. Process according to Claim 1, characterized in that the metering means (D) comprises, in succession, at least one vibrating metering tank (46, 59) and a vibrating duct (41) or a weigh belt.
3. Process according to Claim 2, characterized in that it consists in feeding the said duct with solvent so that the fibres (P, f1, f2 ... fn) at least partially soak in the duct whose bottom is filled with the solvent and are delivered in conjunction with the said solvent onto the conveyor (9, 19, 79) from the said duct.
4. Process according to Claim 1, characterized in that it consists in delivering the said solvent via at least one nozzle placed just downstream of the point where the fibres (P, f1, f2 ... fn) drop onto the conveyor (9, 19, 79).
5. Process according to one of Claims 1 to 4, characterized in that it consists in delivering the fibres (P, f1, f2 ... fn) onto the conveyor (9, 19, 79), after the feed of the first type of aggregate (D1) and before the feed of the last type of aggregate (D2, D3 or D4), so that the fibres are incorporated into the mass of the various types of aggregate.
6. Process according to one of Claims 1 to 5, characterized in that it consists in calculating the proportion of mixing water (E) delivered into the mixer (80) in the aforementioned step c) according to the water content specific to each type of aggregate (D1-D3) fed at step a).
7. Process according to one of Claims 1 to 6, characterized in that it consists in feeding, at step a), a total proportion of aggregates of between 83 and 93% by weight of the dry constituents of the concrete without fibre and, at step c), a cement (P1) or road binder in a proportion of between 7 and 17% by weight of dry constituents of the concrete without fibre, of which 0.3 to 1.8% by weight of the hydraulic binder consists of a concrete set retarder and/or plasticizer admixture (X1) introduced into the mixing water in order to lubricate the intergranular contacts and retard the setting of the concrete.
8. Continuous mixing plant for implementing the process according to one of Claims 1 to 7, comprising:

   a series of hoppers (1, 11, 21, 31) placed at intervals above a motor-driven conveyor (9, 19, 79), each hopper being capable of delivering one type of aggregate (D1, D2, D3, D4) onto the conveyor and each hopper being associated with a means (2, 12, 22, 32) for measuring the volume or the weight of the amount of aggregate delivered by the said hopper;

   a vibrating metering means (D) capable of delivering metal fibres (f1, f2 ... fn) onto the conveyor, the said metering means being associated with a means (51) for measuring the weight of the amount of fibres delivered;

   one or more silos (81) each capable of delivering a hydraulic binder (P1), each silo being associated with a means (86) for measuring the weight or the volume of the amount of binder delivered, it being possible for another silo to be used to meter a complementary powder, such as fly ash for example;

   a mixing water feed means (88) associated with a means (90) for adjusting the flow of mixing water; and

   a mixer (80) that includes a rail (91) of injection nozzles in the mixing chamber, the said rail being fed with the mixing water via the said flow adjustment means (90), the hydraulic binder being delivered into the inlet of the mixer from the said silo, and all of the fibres and the aggregates being delivered by the conveyor into the mixer, in order to mix all of the constituents of the fibre-reinforced roller-compacted concrete;

   characterized in that the said mixing plant includes a solvent feed means (69) for delivering, onto the conveyor (9, 19, 79), at or near the outlet of the vibrating metering means (D), a solvent for dissolving the adhesive on the packs (P) and thus freeing the prebonded metal fibres of the packs (P) delivered by the said metering means.
9. Mixing plant according to Claim 8, characterized in that the said solvent feed means (69) is placed so as to deliver the solvent downstream of the first aggregate feed hopper (1) and upstream of the last aggregate feed hopper (21).
10. Mixing plant according to Claim 8, characterized in that the vibrating metering means (D) includes a first vibrating tank (46) having, on its internal cylindrical wall, a helical ramp (53) along which the fibre packs (P) can move by vibration from the bottom to the top of the tank, the said helical ramp being extended at its top by an intermediate chute (55) running out above the centre of a second vibrating tank (59), the said second tank also having, on its cylindrical internal wall, a helical ramp (63) along which the fibre packs can move from the bottom to the top of the second tank, the helical ramp of the second tank running out onto a vibrating duct (41), which delivers the fibres, above the conveyor (9, 19, 79), the said solvent feed means including at least one nozzle (68) placed substantially above the upstream end of the said vibrating duct.
11. Mixing plant according to Claim 10, characterized in that the intermediate chute (55) has parallel vibrating fingers (58) lying approximately in vertical planes, these fingers being fixed at their upstream end and free at their downstream end, so as to be able to separate the agglomerations of fibre packs and obtain a more uniform distribution in the feeding of the second tank with fibre packs (P), the longitudinal extension of the fingers being parallel to the direction of travel (F7) of the said fibre packs.
12. Mixing plant according to Claim 10 or 11, characterized in that the first vibrating tank (46) has an articulated arm (54) inserted between the top of the helical ramp (53) and the intermediate chute (55), the said arm being capable, in a closed position, of preventing the fibres from passing into the chute and of sending them back towards the centre and the bottom of the first tank and, in a variable open position, of letting a controlled amount of fibres pass into the said intermediate chute.
13. Mixing plant according to Claim 12, characterized in that the second vibrating tank (59) is equipped with a detector (70) for detecting the level of fibres stored in the said second tank, the said detector being connected to a motor for driving the articulated arm (54) so as to move the said arm towards its closed position, or conversely towards its open position, when the amount of fibres stored in the second tank is greater than, or conversely less than, a predetermined threshold value.
14. Mixing plant according to Claim 13, characterized in that the last tank (59) is equipped with a frequency modulator in order to vary its vibration and thus its output of fibres, it being possible for the said modulator to be controlled by the weighing of the amount of fibres delivered to the outlet of the second tank.
15. Mixing plant according to one of Claims 8 to 14, characterized in that it is equipped with a central control unit (U) linked to the various volumetric or gravimetric measuring means of the hoppers (1, 11, 21, 31), of the silo (81) and of the metering means (D) and to the flow adjustment means (90) of the mixing water feed means in order to calculate and control the flow of water (E) to be fed into the mixer (80) according to the water content, the flow of each aggregate (D1 to D3) and/or the flow of the solvent.

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