WO2008135503A1

WO2008135503A1 - Method for continuously projecting low density concrete

Info

Publication number: WO2008135503A1
Application number: PCT/EP2008/055354
Authority: WO
Inventors: Laurent Goudet; Hugues Baquet
Original assignee: S.A. Lhoist Recherche Et Developpement; DEVELOPPEMENT CHANVRE Société à action simplifiée (RCS : 502 281 074)
Priority date: 2007-05-04
Filing date: 2008-04-30
Publication date: 2008-11-13

Abstract

The invention relates to a method for projecting a low-density concrete, that comprises the homogenisation of a light granulate with a binder in order to obtain a mixture at atmospheric pressure, transferring the mixture at atmospheric pressure to a pneumatic conveying path (13) at a predetermined pressure higher than the atmospheric pressure, said transfer being carried out in a sealed and continuous manner, pneumatically conveying the mixture at the predetermined pressure to a projection outlet (17), partially hydrating the mixture in a controlled manner in order to hydrate the binder and to obtain said low-density concrete, said hydration being carried out during said pneumatic conveyance, and projecting said low-density concrete on a surface or substrate.

Description

"LOW CONCRETE CONTINUOUS PROJECTION METHOD

DENSITY"

The present invention relates to a continuous projection process of "low density" concrete. The invention also relates to a device for continuously projecting such a concrete.

The invention is mainly applicable to the construction sector in particular for the thermal and acoustic insulation of surfaces or support, such as walls, screeds, slabs or roofs, for the renovation of walls or as a framework filling.

By "low density concrete" is meant a compound comprising at least one binder, especially an air binder, and at least one light granulate of polystyrene or vegetable type, in particular based on hemp, straw, flax, maize, wood or the like or a mixture thereof, as well as optionally a solid and / or liquid additive and / or adjuvant. The interest of this type of concrete resides in a very good thermal insulation but also an acoustic correction. In order to optimize the insulation coefficient, the proportion of lightweight granulate of insulating nature is then maximized compared to the other components of the low density concrete. Large thicknesses of these concretes will often be applied to ensure good insulation.

"Low density concrete" will be considered in the present invention as consisting mainly of a light aggregate as defined above, consolidated, or even coated with at least one binder and not the other way around. The low-density concrete thus obtained is therefore substantially compressible when it is used before curing, unlike most concretes for which the granulate (s) are embedded in a mass of binder (s) and which are little or no majority. compressible. Such a low density concrete will have a density of between 150 kg / m ³ and 950 kg / m ³ and preferably a density of between 200 kg / m ³ and 500 kg / m ³ .

Among the binders mentioned above, mention may be made of aerial binders, such as slaked lime, hydrated dolomite, or hydraulic binders, such as cements, natural hydraulic lime or hydraulic binders based on lime, or a mixture of those -this.

The aforementioned hydraulic binders can be combined or not with pozzolans. As binding agent, mention may also be made of "non-reactive" binders, such as certain clays, in association or otherwise with the abovementioned binders.

By "air binder" is meant binders whose uptake results from a carbonation, in particular by the CO ₂ of the atmosphere. The term "hydraulic binder" means binders whose uptake results from a pozzolanic reaction in the presence of water. Hydraulic binders based on lime, means any combination of a pozzolanic reagent fin (clay, ash, metakaolin ...) and lime.

By light granulate is meant any granulate (sometimes called aggregate) of the type of polystyrene beads or type of plant origin. Mention may in particular be made of chenevot, the non-fibrous part of the hemp stalk, after mechanical defibration or any other method of processing the plant, and / or other hemp components, such as fibers, fibrils, dust and powder of hemp. hemp, or wood or flax. The terms "slaked lime" or "hydrated lime" represent a compound consisting primarily of calcium hydroxide.

Low density concretes, in particular hemp concretes, are well known in the field of construction, in particular for their insulating property, as described, for example, in patent EP 1 406 849. Their implementation is essentially done by bunching. . This is to pour the concrete between 2 walls (banches). This process suffers from many disadvantages. First of all, this process is fundamentally discontinuous in its phase of preparation, mixing and implementation. This makes it slower than a continuous process, resulting in low productivity.

Moreover, if one of the two faces of the panels can be mounted directly on the entire height of the wall or the wall to be erected, the other is mounted in levels or layers. The formwork levels thus obtained are gradually filled one after the other. At the interface of two concrete beds, the successive layers do not bind and constitute zones of weakness. Removal cracks appear. This process by bunching thus has a reduced efficiency in terms of the insulation sought by this type of low density concrete because there are discontinuities in the implementation of aggregates between the different levels of filling. A shrinkage of the concrete, linked to an excess of water during the mixing, also occurs from one layer to another, due to a partial take of one layer before processing of the next. Finally, the composition of the concrete may vary from one level to another, resulting in a lack of homogeneity in the insulating wall.

This process still presents constraints, related to the difficulty of pouring the concrete in approach of the ceilings or slopes of roofs, braces (wood in diagonal) and in general in the presence all obstacles such as electricity, water, heating ...

Bunching also promotes hydration of the light aggregate, incorporated in the binder. However, the added water for the preparation of low density concrete must be used to hydrate the binder or binders but it is detrimental that the water is too in contact with light aggregates, such as hemp, which can absorb up to about 400% of its weight of water. This results in excessive water consumption and a critical drying problem, the duration of which will be increased unnecessarily. All of the above considerations argue for another method of setting up low-density concretes, which would be basically continuous, with high productivity and allowing a more homogeneous application, with a single support wall, unlike benching. According to the invention, it is intended to use a method of spraying low density concretes.

Several techniques of projection (or gunning) of concretes are known among which are distinguished in particular wet or wet projection methods and dry projection methods. Wet or wet projection methods are particularly dedicated to high density concrete (that is to say a concrete having a density up to 5 times higher than a low density concrete), the majority of which is granulated. is often sand (sand concrete). Their use for spraying low-density concretes, in particular hemp-lime concretes, would require an excessive dosage of lime as well as an addition of sand because of the compressibility of hemp-lime concretes which would be avoided in the context of a wet projection. The thermal performance of coatings made in this way would then be reduced by compared to the use of hemp-lime concrete correctly dosed, without sand.

Moreover, a wet projection technique also promotes hydration of the light aggregate, incorporated into the binder, which is detrimental, as mentioned above. The drying time of wet cast concrete is long, because of the time required to evacuate the mixing water, which can disrupt the progress of the construction.

The methods of dry projection, provide that the raw materials are mixed in dry form and that the mixture is hydrated just before the release of the lance, as in US 4 138 162.

Such a method often uses a high pressure and a high speed of the product to implement. Also this method is it suitable for concretes generally not or little compressible, in which the aggregates are embedded in a mass of binder (s) majority. With this dry method, the rebound losses on the treated wall are greater than in the case of the wet process. In addition, in US 4,138,162, in order to prevent high compressed air pressures from returning the dry mixture to the feed, a blocking zone replacing mechanical seals has been provided. This blocking zone allows the formation of a dry matter plug whose only part in contact with the flow of compressed air is broken and driven. The material pad prevents compressed air leaking upstream of the device.

The dry spraying techniques are therefore not suitable for the continuous preparation and projection of low density concrete comprising at least one light granulate of polystyrene or vegetable type, in particular based on hemp, straw, corn, flax, wood or the like which are compressible materials. Indeed, these aggregates are very bulky (they have a very low density) and are difficult to dose and transfer from one stage to another of the projection process. The mainly fibrous, compressible and bulky nature of the light aggregates leads to frequent blockages, especially at the transfer stage, after the mixing of dry constituents at atmospheric pressure, to the pneumatic transport under high pressure. Obstructions at the level of the metering units and the transfer unit compromise a truly continuous operation because such blocking requires disassembly, cleaning, reassembly and a new supply of dry constituents.

In addition, the dosage but above all the aforementioned transfer step are irregular with the traditional techniques of preparation and dry concrete spraying. This is due to an irregular and time-varying filling of the equipment used in these stages, in particular the cellular locks, notably because of the fibrous, compressible and bulky nature of the light aggregate and the variability of the composition and the density of the mixing before transfer, as well as the irregular size of light aggregates. The filling of the cells which are positioned vertically is irregular because the concrete of the hemp type has a strong propensity to remain agglomerated and difficult to descend into the cell at the time of the passage thereof, which will lead downstream irregular flow mixing which then causes an irregular projection of the concrete after wetting.

To overcome this disadvantage, it is possible to use a higher amount of air to avoid clogging at the outlet of the wetting equipment. Another disadvantage that appears as a consequence of the proportion too high of air compared to the concrete of Low density transported is the speed of impact too high, which causes rebound and therefore lost materials or need to pick up.

Moreover, the behavior of the light aggregate / binder mixture differs structurally (swelling of the assembly as well as hooking and entanglement of the fibers of the aggregate) of the behavior of the light aggregate alone; this unstable behavior of the light granulate / binder mixture is a function of the type of granulate and binder, the proportion of granulate with respect to the binder and the conditions of implementation, in particular atmospheric conditions. This random behavior of the light aggregate / binder mixture results in a chaotic flow downstream of the mixing unit of the low density concrete components.

In addition, the low density and high compressibility of low density concrete comprising at least one light aggregate, makes it difficult to transport pneumatically (under pressure) to effect the projection. It is understood that traditional projection techniques, developed for conventional concrete not or slightly compressible are poorly suited to low density concrete. The aforementioned drawbacks are all the more acute as the content of light aggregate in the low density concrete is high and therefore the binder content is low to maximize its insulation coefficient.

In addition, for the hydration of concrete, the traditional techniques of dry projection, provide a wetting end pneumatic transport by simply adding water. This technique is likely to cause a non-uniform distribution of water during the placement of the concrete and especially to hydrate the light aggregate, which is highly detrimental, as mentioned above. Finally, traditional projection techniques favor an acceleration of the mass to be sprayed at the end of the projection unit, which causes compaction, in order to promote the resistance, the tightness, the reduction of shrinkage and to improve the adhesion of the concrete layer to the receiving wall. This acceleration is detrimental to low density concrete, which must be deposited on the wall without being compressed, in order to maximize its insulation coefficient. Such acceleration also produces a lot of material rebound on the wall so a lot of loss because these material rebounds are not often recovered.

In general, several layers are required for walls covered with high density concrete with traditional techniques, in order to obtain the desired thickness, unlike low density concrete with light aggregates, which is implemented to a thickness up to a few tens of centimeters, typically 20 to 30 cm, ideally at one time.

It is also useful for the support wall to be covered to be openwork, of the small mesh type, in order to create "breathable" walls made up of an interior wall made of hemp concrete, an air gap and an outer wall made of bricks or stones. Conventional projection techniques, because of the high pressure, do not make it possible to work in support on perforated walls of lattice type because the shotcrete passes through, which excludes the application in certain countries. The use of small mesh meshes also reduces the time of intervention on site.

Machines for flocking, for example cellulose, are also known; these are able to transport light aggregates, but not to obtain a mechanical strength of the projected coating. Low density concrete is a heterogeneous material that will intervene in the mechanics of the wall and not just insulate it. It is therefore necessary to obtain a mechanical resistance during the projection. Indeed, the density of a low density concrete is about 5 to 6 times higher than the density of flocking. It is therefore necessary to avoid the creep of said concrete, despite the aforementioned thickness of its implementation. The present invention aims to overcome at least in part the aforementioned drawbacks of the state of the art by providing a method of spraying a low density concrete comprising:

a homogenization of a light aggregate with a binder to obtain a dry mixture, at atmospheric pressure, a transfer of said dry mixture at atmospheric pressure to a pneumatic conveying path in which a predetermined pressure prevails, greater than said atmospheric pressure, said transfer being effected in a sealed and continuous manner,

a pneumatic transport of said dry mixture at said predetermined pressure towards a projection outlet,

wetting with a dispersion of water in a gas of said dry mixture during said pneumatic transport, and

- A projection of said concrete thus obtained on a surface or a support. The projection method according to the invention makes it possible to overcome the main disadvantages of the known method of the bunching, namely that the bunch is slow, basically discontinuous, requires two full support walls, has withdrawals and ruptures detrimental to isolation at the level of the layer transitions and favors harmful hydration of the light granulate as well as the inhomogeneity of the filling. Indeed, the method according to the invention requires a support surface of only one side, which support can even be perforated, of tight mesh type mesh; the light aggregate sticks to itself, and intertwines continuously the entire surface or the substrate to be covered, without any risk of shrinkage or rupture of the granulate layer.

In addition, the method according to the invention makes it possible to provide a technique which is ergonomic and which largely limits the manual mixing operations to be carried out by the user. In addition, the consumption of air and water is reduced and the method according to the invention allows dry and dust-free mixing of the binder and granulate.

According to the invention, the method has a sealed and continuous transfer step which makes it possible to bring the constituents of the low density concrete at atmospheric pressure to a pneumatic transport where the homogeneously mixed constituents are transported towards the outlet of projecting into a stream of air from a blower or the like. Dust production is limited. In addition, during pneumatic transport, the homogeneous mixture of constituents is wetted by a dispersion of water in a gas. As a result, the humidification step makes it possible to incorporate water to preferentially hydrate the binder without excessively wetting the granulate, which is in this case a material capable of strongly absorbing water. The drying time is considerably reduced and the plasticity of the mixture increased.

In summary, according to the invention, the discharge rate of low density concrete is even even for a concrete containing little binder and therefore compressible because the waterproof and continuous transfer also reduces the risk of blockage. In addition, the regularity of the outlet flow is also due to a controlled humidification which also avoids obstructions and undesirable agglomerations. Furthermore, the humidification according to the invention avoids the creep of the applied layer while promoting drying. These qualities increase the insulation coefficient of the coating produced by the process according to the invention, which coating is otherwise homogeneous and regular in its composition over the entire surface or support to be covered.

In order to ensure the continuous nature of the process according to the invention, despite the presence of light aggregates often majority of said low density concretes, the dosage of said aggregates is adapted to their light nature, especially fibrous.

The particular behavior of the mixture granulat light / binder reported above contributes to a good homogenization of said dry mixture but requires a step of restabilization or reorganization. This restabilization of the dry aggregate granulate / binder mixture, associated or immediately downstream of the homogenization stage makes it possible to regularly feed the transfer step into said mixture without risk of blockage or chaotic behavior at this transfer step . The step of transferring homogenized constituents at atmospheric pressure to pneumatic transport under high pressure is critical in order to avoid frequent blockages. The transfer step must therefore both satisfy sealing and regularity constraints as well as preventing any blockage. According to the invention, advantageously, the transfer step is provided by sealed equipment, with wear and anti-lock recovery system and a regular filling system. In addition, the step of dosing the light aggregate is also carried out by equipment preventing the blockage. According to a particular embodiment of the invention, the humidification by dispersion of water in a gas is obtained by nebulization or spraying, ensuring, by a control and distribution of the spray, to preferentially humidify the binder (s) and as little as possible the light granulate (s), whose wetting is detrimental as indicated above. Advantageously, the step of homogenization of the raw materials is a moderate stirring, or even a coating of the granulate (s) by the binder (s). This homogenization step may take place in the device according to the invention or outside thereof, beforehand, for example, by introducing a ready-to-use mixture into said device.

Preferably, the process according to the invention comprises, at the end of said homogenization or just downstream thereof, a restabilization or reorganization of the light granulate / binder mixture. Advantageously, the method according to the invention comprises, prior to said homogenization, storage, dosing and transport of said light granulate and said binder.

Advantageously, the step of spraying the low density concrete is directional, ensuring the convergence of the concrete during its application.

In a preferred embodiment, the method according to the invention further comprises a recycling of said low density concrete sprayed onto said surface or said support and having been rebounded on the latter, said recycling comprising a storage, an assay, a feed said low density concrete sprayed and kneading thereof with said dry mixture. According to the invention, the low-density concrete is sprayed pneumatically, so it is projected onto a surface or a support with a predetermined flow rate and speed which must be sufficient to prevent clogging and ensure an exit of the appropriate material, while permitting an application of a layer of relatively large thickness without or reduced creep. For this purpose, it is difficult to completely avoid this rebound phenomenon, but to minimize losses it is advantageous to recycle the bounced material. This is what the invention provides. Advantageously according to the invention, the recycled low density concrete is further stored, metered and then introduced and kneaded with said mixture of light aggregate and binder. Since the low density concrete is recycled after homogenization, it is incorporated by post-mixing into the fresh mixture and is thus diluted in fresh material.

According to the invention, the binder is chosen from an aerial binder, a hydraulic binder or a mixture thereof. Preferably, the binder comprises an air binder, such as slaked lime. It can also be envisaged that the binder is a cement, a whitewash, a natural hydraulic lime or a hydraulic binder based on lime or a mixture thereof. The aforementioned hydraulic binders can be combined or not with pozzolans. As a binder, "non-reactive" binders, such as certain clays, may also be considered in combination or otherwise with the abovementioned binders.

According to the invention, the light granulate is preferably of plant origin, in particular based on hemp, more preferably on hemp hemp, or on the basis of straw, maize, wood or flax or the like. In an advantageous embodiment, the sealed and continuous transfer is a rotational transfer about an axis of rotation of the dry mixture from said homogenization step which occurs along a longitudinal axis which is substantially perpendicular to the axis of rotation above and in a different horizontal plane. The invention also relates to a device for spraying a low density concrete to at least partially overcome the disadvantages of known projection devices, in that the device is a continuous device that does not lock and allows avoid double bunching and / or creep. To solve this problem, there is provided according to the invention a device comprising:

a homogenization means connected to a feed in a light granulate and to a binder feed, to form a homogenized dry mixture at atmospheric pressure,

a pneumatic conveying route of said homogenized mixture in which a predetermined pressure prevails, greater than said atmospheric pressure, and which has a projection output of said low-density concrete, a sealed and continuous transfer unit, arranged to connect said means of homogenizing at atmospheric pressure to said pneumatic transport path where said predetermined pressure prevails, and,

a humidifying means comprising means for dispersing water in a gas, disposed in said pneumatic transport path, before said projection outlet.

As mentioned above, said sealed and continuous transfer unit prevents jamming, which allows a regularity of mixed flow within the pneumatic transport path.

In addition, the sealing of the transfer unit is of considerable importance given the pressure differences upstream and downstream of said transfer unit. The constituents (light aggregate and binder) will therefore be homogeneously transported and may pass through said humidifying means disposed in said transport path, which will allow regular humidification. In addition, this incorporation of water is controlled and partially humidifies the mixture in order to hydrate the binder optimally by moistening the granulate as little as possible. Therefore, the sealed and continuous transfer unit makes it possible to impose a regular flow rate of the dry mixture in said pneumatic conveying path and, in conjunction with the partial humidification by a dispersion of water in a gas, maintains this flow rate regularity. output of the low density concrete thus formed; the device according to the invention therefore allows to project a considerable thickness of concrete on a surface or a support and thus avoid the bunching and / or creep.

The homogenization means may also be present in the device according to the invention or, in a similar alternative, be separated from the projection device, for example, be part of a separate homogenization installation whose output is connected to the device according to the invention. the invention. Preferably, said binder feed comprises a storage means, a metering means and a transport means which are, for example, an extended feed hopper of a tubular in which said binder can flow, and between the two find an Archimedean screw or a valve to quantify the amount of binder introduced.

Advantageously, said supply of light granules comprises a scraper dispenser, which may advantageously comprise an equalizer and antilocking device, said supply being connected to a feed hopper which makes it possible, thanks to the presence of scrapers, to transport the light and fibrous granulate without obstruction. , nor blocking the transport, in particular between the strip and the chassis of the scraper dispenser. Preferably, said light-weight scraper dispenser comprises an upward portion in which there is an equalizer which also avoids blockages and a descending portion. This allows a transport of a reproducible amount in a space between the squeegees and thus promotes the regular flow. In addition, light aggregates which are too large in size and continuous operation of the device according to the invention are rejected thereof.

Advantageously, said sealed and continuous transfer unit comprises a rotary rotary valve. Preferably said sealed and continuous transfer unit comprises a recovery means and / or a wear indicator and more preferably, said sealed and continuous transfer unit comprises an anti-lock system, in particular a squeegee and a release opening.

In this way, the flow rate of the mixture of light aggregate and binder is as regular as possible to promote the continuous operation of the device according to the invention. The sealed rotary cellular sluice according to the invention, furthermore comprising the wear indicator and / or a recovery means as well as an anti-lock means consisting in particular of a scraper, makes it possible to fulfill the triple condition, which is particularly important for a continuity, sealing operation to maintain the pressure difference, regularity of dosage and prevention of any obstruction.

Advantageously, said dry mixture transfer unit is a rotary transfer unit about an axis of rotation substantially perpendicular to a longitudinal axis of said homogenizing means being in a different horizontal plane. In this way, the particular arrangement of the transfer unit and the homogenization means confers on the projection device according to the invention, a small space architecture. Other features, details and advantages of the invention will become apparent from the description given below, without limitation and with reference to the accompanying drawings.

Figure 1 is a schematic view of the device according to the invention. Figure 2 is a sectional view of said light aggregate feed of the device according to the invention.

Figure 3 is a sectional view of said sealed and continuous transfer unit of the device according to the invention. Figure 4 is a sectional view of a portion of the pneumatic transport path in which is disposed the humidification means according to the invention.

FIG. 5 illustrates the projection lance of the projection device according to the invention. Figure 6 is a sectional view of a homogenization means according to the invention.

Figure 7 is a sectional view of a homogenization means, coupled to a restabilization means of the mixture, according to the invention. In the figures, identical or similar elements bear the same references.

As can be seen in Figure 1, the device according to the invention comprises a binder feed 1, especially selected from an aerial binder or a hydraulic binder or a mixture thereof, and preferably contains slaked lime. As mentioned above, the feed may comprise a feed hopper 2 and a pipe 3 in which the binder contained in the hopper can flow. In addition, between the hopper 2 and the tubing 3, one can find an Archimedean screw 4 for dosing the amount of binder. The device also comprises a light aggregate feed 5, which is further illustrated in FIG. 2. The feed also comprises a feed hopper 6 and a scraper feeder 7 which dose and transports the light granulate into the tubing 8 which ends in a homogenization means 9 at atmospheric pressure, comprising for example an endless screw for advancing the mixture to said transfer unit 10.

The transfer unit 10 is explained in more detail in FIG. 3 but comprises, for example, as can be seen, a rotary cellular sluice 11 provided with seals 12 which makes it possible to bring the mixture to atmospheric pressure coming from the homogenization unit 9 to the pneumatic transport path 13 at a transport speed of 30 to 50 meters / minute. Indeed, as can be seen, the transport path 13 is powered by a fan 29. Of course, the blower 29, for example air, may be replaced by any other similar equipment to impose a flow of air or other gas for driving a powdery material in a conduit. In the transport path 13, the dry mixture is driven by the air stream created by said blower 29 or alternatively by a blower performing a similar function. In said transport path, the mixture will be partially moistened by the humidifying means 14 which comprises inter alia a tubular nebulization ring and a plurality of nebulizing nozzles 16. In addition, the tubular nebulization ring comprises a plug 15 allowing to access it if necessary. The moistening means is explained in more detail in FIG. 4. Once the mixture has been partially moistened, that is to say that the binder is moistened and the light granulate is as little as possible, the low density concrete is formed and can exit through the projection lance outlet 17 shown in more detail in Figure 5. The transport path 13 may consist of one or more parts, flexible or not, to connect together.

As can be seen in FIG. 2, the light granulate feed 5 comprises a scraper dispenser 7 which allows the dosing of the light aggregate, and this, in order to ensure the continuous operation of the device according to the invention, in spite of the presence of light aggregates often majority of said low density concrete. Indeed, the dosing means of said light aggregates, especially fibrous, must avoid any blockage or obstruction. The light aggregate feed hopper 5 advantageously takes into account the flow characteristics of the latter by its geometrical configuration and / or by other means such as, for example, the scraper dispenser 7.

This scraper feeder 7 is connected to a feed hopper light aggregate advantageously secured to the frame of the metering device, and comprises an upward portion 7a and a downward portion 7b. Preferably an equalizer 18 of the light aggregate is located on the upward portion 7a. of the doser band. The equalizer 18 is typically of flexible material and comprises a plurality of flexible elements 18 'interconnected, preferably by an end which further allows, in the illustrated case to fix the equalizer to the raclette feeder. The flexible elements 18 'of the equalizer 18 are arranged to be movable relative to each other independently so as not to exert pressure on the light aggregate and also to prevent blockage of the fibers of the aggregate. In particular, the equalizer is of the brush or brush type whose vibrations due to the flexible character contribute to avoid the aggregation of the light aggregate.

In a particular embodiment of this scraper feeder, the ascension of the scrapers 19 and therefore the aggregate is done at the top of the strip, as shown by the orientation of the scrapers 19 and the advancement arrows in FIG. 2. As can be seen in FIG. 3, the transfer unit of the homogenized constituent elements coming from the homogenization means 9 at atmospheric pressure, towards the pneumatic transport path 13, under high pressure is preferably carried out by means of FIG. a specific rotary alveolar lock 11, to avoid frequent blockages. No equipment available commercialents does not fulfill the triple condition of tightness, regularity, dosage and prevention of any obstruction. Such a rotary alveolar transfer lock 11 according to the invention (see FIG. 3) preferably comprises a large number of cells 20 in order to allow a regular transfer of the homogenized material. The rotary lock 11 typically comprises at least 4 cells 20, advantageously at least 6 cells, preferably at least 8 or 10 and more preferably 12 or 18 cells 20.

Preferably, the axis of rotation of the rotary lock is substantially perpendicular to a longitudinal axis of the homogenizing means, such as, for example, the axis of a worm which could be there to improve the compact aspect of the device according to the invention.

Advantageously, the speed of rotation of the rotor around the axis of rotation 26 of the cellular lock 11 is high, typically at least 10 revolutions / minute, preferably at least 15 and even at least 20 revolutions / minute. , so as to ensure the most regular supply possible of the homogenized material coming from the homogenizing means 9 to the pneumatic transport path 13. The transfer unit of the device according to the invention further comprises a sealing system, preferably with recovery and wear indicator; in the case of the rotary alveolar lock 11 mentioned above, this system consists of two continuous lateral seals 21, preferably in the form of discs, mounted on a support plate 22, itself on pressure springs 23. Typically, Sealing ensured by the continuous side seals 21 is completed by a continuous peripheral seal 12 per cell wall 20. Furthermore, the transfer unit according to the invention comprises an anti-lock system, typically made in the form of a squeegee 24 and a clearance opening 25, in the case of the rotary cellular lock 11 of Figure 3. Advantageously, the rotary honeycomb lock will be oversized to prevent the cells are completely filled with dry mixture. This over-sizing makes it possible to add a contribution of regularity to the device according to the invention and contributes to avoiding blockages of the device.

According to a preferred embodiment of the invention illustrated in FIG. 4, the humidification means 14 of the device is a nebulizer, preferably moistening the binder (s) and, to the least extent, the light aggregate (s), whose mooring is detrimental as mentioned above.

Advantageously, the nebulizer 14 comprises a nebulizing ring, which comprises a plurality of nebulization nozzles 16, typically 3 to 6, oriented in the direction of flow of the homogenized material and arranged upstream of the nozzle of the lance 17 at a distance of distance of 0.2 to 6 m. By way of example, in some embodiments, the aforesaid distance will be 3 to 5 m, while in other embodiments, this distance will be 0.2 to 1 m, depending on the composition of the mixture. .

The nebulizing nozzles 16 are a priori supplied with water dispersed in a high-pressure gas by an equipressure annular water distribution channel 28, offering an adjustable flow rate, typically between 0.4 and 4 liters / minute / nebulization nozzle. And a pressure of 10 to 20 bar, conditions necessary to obtain the fineness of water drops dispersed in said gas in order to effect the preferential wetting of the binder. This adjustable flow rate makes it possible to control the humidification and serves as a means of controlling the humidification.

In particular, each spray nozzle 16 of the nebulizing ring is oriented at an angle α (alpha) of between 15 ° and 35 °, preferably between 20 ° and 30 °, relative to the axis of the lance. as shown in Figure 4. According to another particular embodiment of the invention, each spraying nozzle 16 of the nebulization ring produces a solid cone with an opening angle β (beta) of between 10 ° and 45 °, preferably between 15 °. and 30 °. As can be seen in FIG. 5, the projection output of the low-density concrete of the device according to the invention is a lance, the upstream end of which is situated at the level of the humidification means 14 and the downstream end is ends with a spout 17, consisting of a tube of a few tens of centimeters, typically 35cm in length. Preferably, the lance is substantially rigid and includes the humidifying means. This lance may be a separate part to be fixed to the pneumatic transport path 13 or an integral part thereof with or without a change of material depending on whether the pneumatic transport path 13 is rigid or not. In particular, the spout 17 comprises one or more, in particular three grooves or projections 27, which will induce a rotary movement respectively reentrant or protruding spirals, typically on a rotation angle of between 90 and 270 degrees and a length between 150 and 450 mm and print a concentration of the jet during application.

According to another particular embodiment of the invention, the spout is flat or oblong profile, preferably constant section along its length.

A particular embodiment of the homogenizing unit 9 and post-mixing is also shown in FIG. 6. As can be seen, it is composed of an outer body 30 and blades of particular and differentiated profiles 31 according to FIG. action (homogenization, coating, post-mixing or restabilization) mounted on a shaft 32. The orientation of the blades and the speed of rotation of the shaft are calculated to give the final mixture a regular output flow. In a preferred embodiment of the device according to the invention, the dosers of raw materials, of recycled product and the homogenization unit 9 are arranged as in FIG.

The granulate is dosed first (part A) immediately followed by the binder (part B). A homogenization zone and / or coating (part C) allows the binder to coat the particles of the aggregate, without there remaining loose binder not adhering to the aggregates.

The dosing of the recycled material (part D) is then carried out and a post-mixing zone (part E) makes it possible to incorporate the latter in a perfectly distributed manner, without forming a zone that is preferentially rich in recycled material. The mixture can then be restored or reorganized at F, in particular, for example, using a band device integral with the homogenizer, as shown diagrammatically in FIG. 7. The homogenized mixture leaves at G. According to a method particular embodiment of the invention, the restabilization device is as in Figure 7 mainly consisting of a wiper strip 34, located in the axis or not, secured or not to the homogenizer of Figure 6 and provided with A rigid and monolithic equalizer 33. It is understood that the present invention is in no way limited to the embodiments described above and that many modifications can be made without departing from the scope of the appended claims.

For example, the unit for homogenizing the raw materials is an equipment ensuring a moderate stirring, or even a coating of the granulate (s) by the binder (s).

In addition, it is envisaged according to the invention that the composition of the mixture being projected is modified by a suitable automation and the corresponding control interfaces. According to a preferred embodiment of the invention, the device further comprises a specific metering device for the recycling of rebound discharges of low density concrete. This recycling avoids the loss of this rebound material. Preferably, this metering device operates in a similar manner to the transfer lock of FIG. 3 but without a sealing device, which is useless here. On the contrary, the clearance between the rotor and the stator, commonly of the order of 1 to 2 mm in the case of a commercial lock, will typically be 5 to 7 mm, or even 10 mm, to prevent the recycled material do not stick to the lock. In addition, the recycled material requires to be introduced after mixing the raw materials (binder (s) and granulate (s)) and to be incorporated in a mixer extending the homogenization unit 9.

Advantageously, the device provides for the addition of liquid adjuvant by addition to nebulization water or concomitantly with it, or solid adjuvant in the binder (s) assay.

In order to increase the autonomy and the continuous nature of the device, it can be designed to be fed by raw materials in bulk, for example contained in silos. According to a particularly preferred embodiment of the invention, the device or guniteuse according to the invention has dimensions overall allowing a transport of said device on a removable platform vehiculable, on which the constituent elements are all arranged and ready to be used, while having a nominal capacity up to about 4 m ³ / h of low density concrete. The installation is mobile, autonomous and operational in less than an hour after arrival on site. By moveable removable platform, it is meant that the device is transportable as such (base frame) for example, by lifting with 4 slings hung at the four corners, transportable on a trailer frame (type chassis boat) allowing the gunning module to be removed from the trailer frame and lowered to the lowest point on site, while adjusting the horizontality, or even, without any limitation, being transportable on a container frame (not shown). In another variant, the gunning device is directly towable.

Claims

A method of projecting a concrete comprising:

homogenization of a light granulate with a binder to obtain a dry mixture, at atmospheric pressure, transfer of said dry mixture at atmospheric pressure to a pneumatic transport path (13) in which a predetermined pressure prevails, greater than said pressure atmospheric, said transfer being carried out in a sealed and continuous manner,

pneumatic transport of said dry mixture at said predetermined pressure to a projection outlet (17),

a humidification with a dispersion of water in a gas of said dry mixture during said pneumatic transport, and

- A projection of said concrete thus obtained on a surface or a support.

2. The projection method according to claim 1, wherein said humidification is obtained by nebulization or water spraying.

3. A process according to claim 1 or claim 2, comprising, prior to said homogenization, storage, dosing and transport of said light granulate and said binder.

4. Method according to any one of the preceding claims further comprising a recycling of said low density concrete sprayed on said surface or on said support and having been rebounded on the latter, said recycling comprising a storage, a dosage, a supply of said projected low density concrete and kneading thereof with said dry mix.

5. Method according to any one of the preceding claims wherein said binder is selected from an aerial binder, a hydraulic binder, combined or not with pozzolans, a non-reactive binder or a mixture thereof.

6. Method according to any one of the preceding claims, comprising a step of restabilization or reorganization before the transfer step.

A method according to any one of the preceding claims, wherein said transfer is a rotational transfer about an axis of rotation of the dry mixture from said homogenization step, said homogenization occurring along a longitudinal axis which is substantially perpendicular to the aforementioned axis of rotation and in a different horizontal plane.

8. Device for projecting a concrete comprising:

a homogenization means (9) connected to a feed (5) in a light granulate and to a feed (1) by binder, to form a homogenized dry mixture at atmospheric pressure,

a pneumatic conveying path (13) of said homogenized mixture in which a predetermined pressure prevails, greater than said atmospheric pressure and which has a projection outlet (17) of said low density concrete,

a sealed and continuous transfer unit (10) arranged to connect said homogenizing means (9) to atmospheric pressure with said pneumatic conveying path (13) where said predetermined pressure prevails; and

- A humidifying means (14) comprising means for dispersing water in a gas, disposed in said pneumatic transport path (13), before said projection outlet (17).

9. Device according to claim 8 wherein said supply (1) binder comprises storage means (2), a dosing means and a transport means (4).

Apparatus according to claim 8 or claim 9, wherein said light granulate feed (5) comprises a scraper dispenser (7) of light aggregate connected to a feed hopper (6).

11. Device according to claim 10, wherein said lightweight granule metering device (7) comprises an equalizer and anti-lock device.

12. Device according to claim 10 or 11 wherein said scraper feeder (7) comprises an upward portion (7a) on which is an equalizer (18), and a downward portion (7b), said equalizer preferably being made of material flexible and comprising a plurality of flexible elements (18 ') interconnected, preferably one end, and arranged to be movable relative to each other.

13. Device according to any one of claims 8 to 12, further comprising a restabilization device, mainly consisting of a scraper strip (34), optionally located in the axis (32) of the homogenizer (9). ) and possibly integral homogenization device (9) and provided with a rigid and monolithic equalizer (33).

14. Device according to any one of claims 8 to 13, wherein said watertight and continuous transfer unit (10) comprises a rotary alveolar lock (11).

15. Device according to any one of claims 8 to 14, wherein said waterproof and continuous transfer unit (10) comprises an anti-lock system, in particular a squeegee (24) and a release opening (25).

16. Device according to any one of claims 8 to 15, wherein said projection outlet (17) is a lance whose upstream end is connected to said transport path (13), at the level of the humidifying means ( 14) and whose downstream end comprises a projection nozzle (17) which preferably comprises a plurality of grooves (27) or projections (27) each spiral, reentrant or outgoing.

17. Device according to one of claims 8 to 16, wherein said humidifying means (14) is a fogger, in particular a nebulizing ring connected to a plurality of nebulizing nozzles (16).

The device of claim 17, wherein the nebulizing nozzles (16) of said plurality of nebulizing nozzles (16) are oriented in the direction of flow.

The device of claim 17 or claim 18, wherein the nebulizing nozzles (16) of said plurality of nebulizing nozzles (16) are disposed at a distance of 0.2 to 6m.

20. Device according to one of claims 17 to 19, wherein said nebulizing ring comprises an equipressure annular water distribution channel (28) having an adjustable flow rate preferably in the range from 0.4 to 4 liters / minute / nebulizing nozzle (16) and a pressure of 10 to 20 bar.

21. Device according to one of claims 17 to 20, wherein said nebulizing nozzles (16) oriented in the direction of flow are inclined at an angle α relative to a longitudinal axis of said pneumatic transport path ( 13), said angle α preferably being in the range of 15 ° to 35 ° and preferably 20 ° to 30 °.

22. Device according to one of claims 17 to 21, wherein said nebulizing nozzles (16) form a solid cone having an opening angle β, said angle β being preferably in a range from 10 ° to 45 ° ° and preferably from 15 ° to 30 °.

23. Device according to any one of claims 8 to 22, comprising a dosing means arranged to recycle low density concrete having bounced, said metering means being connected to a kneader disposed downstream of said homogenizing means.

24. Device according to any one of claims 14 to 23, wherein the rotary alveolar lock (11) comprises at least 4 cells (20), preferably at least 6 cells (20), more preferably at least 8 or 10 cells (20) and most preferably 12 or 18 cells (20), and wherein the rotary rotary valve (11) has a rotation speed of at least 10 rpm, preferably at least 15 and more preferably at least 20 rpm.

25. Device according to any one of claims 8 to 24, wherein said dry mixture transfer unit is a rotary transfer unit about an axis of rotation substantially perpendicular to a longitudinal axis of said homogenizing means being in a different horizontal plane.