Method for producing a building structure, like an acoustic barrier

Abstract

The invention provides an additive manufacturing method for building a structure, in particular an infrastructural construction, more in particular a sound barrier, comprising: - providing an earth composition comprising 20-70 wt.% clay and silt, 70-30 wt.% sand, less than 10 wt.% gravel and less than 4 wt.% water, in particular less than 2.5 wt.% water, more in particular less than 1.5 wt.% water, more in particular less than 1 wt.% water; - mixing said earth composition with an air flow with a pressure of 2-10 bar, in particular 2-5 bar, at a mixing volume ratio of between 1:50 and 1:150 earth composition to air and resulting in a flow rate of between 50-400 m3 / hour; - pneumatically conveying said air-earth composition mixture to an additive manufacturing robot at its nozzle; - adding at or near the nozzle an additional amount of water to result in 5-10 wt.%, in particular 7-10 wt.% water in said earth composition, more in particular 7-9 wt.% water content, and - depositing, in particular spraying, said earth composition via said nozzle for building said structure.

Description

[0001] P100976PC00

[0002] Method for producing a building structure, like an acoustic barrier

[0003] Field of the invention

[0004] The invention relates to method for producing a building structure, in particular an acoustic barrier, and an acoustic barrier.

[0005] Related Applications

[0006] The present application claims the benefit of priority from Dutch Patent Application NL2038550, filed on September 1st, 2024, in the name of Jelle Feringa, The Netherlands.

[0007] The entire contents of the above-referenced applications and of all priority documents referenced in the Application Data Sheet filed herewith are hereby incorporated by reference for all purposes.

[0008] Background of the invention

[0009] Mankind builds structures almost as long as we know. Mankind tries to build these structures as efficient as possible.

[0010] The following references relate either to additive manufacturing of structures, or to processing of material for building structures.

[0011] Aejmelaeus-Lindstrbm, Johan Julius Petrus. 2021. “Rock Printing. Robotic Fabrication of Jammed Architectural Structures from Bulk Materials”. https: / / doi.org / 10.3929 / ethz-b-000497546.

[0012] Aejmelaeus-Lindstrbm, Petrus, Gergana Rusenova, Ammar Mirjan, Jesus Medina Ibanez, Fabio Gramazio, and Matthias Kohler. 2020. “Rock Print Pavilion: Robotically Fabricating Architecture from Rock and String”. Construction Robotics 4 (1-2): 97-113. https: / / doi.org / 10.1007 / s41693-020-00027-8.

[0013] Curto, A., L. Lanzoni, A.M. Tarantino, and M. Viviani. 2020. “Shot-Earth for Sustainable Constructions”. Construction and Building Materials 239 (April): 117775- 76. https: / / doi.Org / 10.1016 / j.conbuildmat.2019.l 17775.

[0014] Hack, Norman, Hendrik Lindemann, and Harald Kloft. 2019. ADAPTIVE MODULAR SPATIAL STRUCTURES FOR SHOTCRETE 3D PRINTING. Kloft, Harald, Hans-Werner Krauss, Norman Hack, Eric Herrmann, Stefan Neudecker, Patrick A. Varady, and Dirk Lowke. 2020. “Influence of Process Parameters on the Interlayer Bond Strength of Concrete Elements Additive Manufactured by Shotcrete 3D Printing (SC3DP)”. Cement and Concrete Research 134 (August): 106078-79. https: / / doi.Org / 10.1016 / j.cemconres.2020.106078.

[0015] Lindemann, H., R. Gerbers, S. Ibrahim, F. Dietrich, E. Herrmann, K. Drbder, A. Raatz, and H. Kloft. 2019. “Development of a Shotcrete 3DPrinting (SC3DP) Technology for Additive Manufacturing of Reinforced Freeform Concrete Structures”. In First RILEM International Conference on Concrete and Digital Fabrication - Digital Concrete 2018, edited by Timothy Wangler and Robert J. Flatt, 287-98. RILEM Bookseries. Cham: Springer International Publishing, https: / / doi.org / 10.1007 / 978-3- 319-99519-9_27.

[0016] Research, Gramazio Kohler. 2017. “Rock Print: A Manistone”. October 2017. https: / / vimeo.com / 238725946.

[0017] Rust, Romana, Achilleas Xydis, Christian Frick, Jurgen Strauss, Christoph Junk, Jelle Feringa, Fabio Gramazio, and Matthias Kohler. 2021. “Computational Design and Evaluation of Acoustic Diffusion Panels for the Immersive Design Lab - An Acoustic Design Case Study”, 10-11.

[0018] Schweiker, Marcel, Elisabeth Endres, Joschua Gosslar, Norman Hack, Hildebrand Linda, Creutz Mascha, Andrea Klinge, et al. 2021. “Ten Questions Concerning the Potential of Digital Production and New Technologies for Contemporary Earthen Constructions”. Building and Environment 206 (August): 108240-41. https: / / doi.Org / 10.1016 / j.buildenv.2021.108240.

[0019] Tarantino, Angelo Marcello, Franco Cotana, and Marco Viviani, eds. 2023. Shot-Earth for an Eco-friendly and Human-Comfortable Construction Industry. Springer Tracts in Civil Engineering. Cham: Springer Nature Switzerland. https: / / doj.Grg / 10. 1007 / 978-3 -031-23507-8.

[0020] Veenendaal, Diederik. 2022. “3d Printed Shot-Earth (3dpse)”.

[0021] The following patent publications provide background art for the current application: US2339892A, US2793080, W02023110000A1, WO2021099293 Al, US20230147930A1, WO2022268262A3, EP3852990A1, EP3957400A1,

[0022] WO1996011309A1, WO2022268263A1, US20230264384A1, AU7359987A,

[0023] US11207849. Additional literature on manufacturing of structures are:

[0024] Schroeder, Horst. 2016. “Sustainable Building with Earth”. Cham: Sprinter International Publishing.

[0025] ZHANG NAN ET AL: "Pumping-less 3D concrete printing using quick nozzle mixing", AUTOMATION IN CONSTRUCTION, ELSEVIER, AMSTERDAM, NL, part 166, 14 July 2024 (2024-07-14), ISSN: 0926-5805, DOI:

[0026] 10.1016 / J.AUTCON.2024.105609.

[0027] CURTH ALEXANDER ET AL: "3D printing earth: Local, circular material processing, fabrication methods, and Life Cycle Assessment", CONSTRUCTION & BUILDING MATERIALS, part 421, 8 March 2024 (2024-03-08), page 135714, ISSN: 0950-0618, DOI: 10.1016 / j .conbuildmat.2024.135714

[0028] FALESCHINI FLORA ET AL: "Sustainable mixes for 3D printing of earthbased constructions", CONSTRUCTION AND BUILDING MATERIALS, ELSEVIER, AMSTERDAM, NL, part 398, 19 July 2023 (2023-07-19), ISSN: 0950- 0618, DOI: 10. 1016 / J.CONBUILDMAT.2023 .132496

[0029] Anonymous: "3d printed earthen acoustic noise barrier van Terrestrial", Informatieblad, 22 May 2024 (2024-05-22), pp 1-1, https. / / w / prorajL l / siteassets / terres: trial, pdf (Author is the current inventor Jelle Feringa).

[0030] Summary of the invention

[0031] A disadvantage of prior art is that none of the references provided a method that allows economic manufacturing of structure that are durable, recyclable, and sustainable. Due to its artisanal approach to construction thus far, earthen structures are costly. Earthen construction’s current dependency on intense labour and artisanry hinders its accessibility. The German Association for Building with Earth (Dachverband Lehm) indicates a worktime of 8-12 hours for a cubic metre of rammed-earth wall, which results in a price point that stifles impact, both in terms of economy and sustainability. A method is presented that allows for an industrial approach towards earthen construction.

[0032] Hence, it is an aspect of the invention to provide an alternative to rammed earth construction, which preferably further at least partly obviates one or more of abovedescribed drawbacks. There is provide an additive manufacturing method for building a structure, in particular an infrastructural construction, more in particular a sound barrier, comprising:

[0033] - providing an earth composition comprising 20-70 wt.% clay and silt, 70-30 wt.% sand, less than 10 wt.% gravel and less than 4 wt.% water, in particular less than 2.5 wt.% water, more in particular less than 1.5 wt.% water, more in particular less than 1 wt.% water;

[0034] - mixing said earth composition with an air flow with a pressure of 2-10 bar, in particular 2-5 bar, at a mixing volume ratio of between 1 :50 and 1 : 150 earth composition to air and resulting in a flow rate of between 50-400 m3 / hour;

[0035] - pneumatically conveying said air-earth composition mixture to an additive manufacturing robot at its nozzle;

[0036] - adding at or near the nozzle an additional amount of water to result in 5-10 wt.%, in particular 7-10 wt.% water in said earth composition, more in particular 7-9 wt.% water content, and

[0037] - depositing, in particular spraying, said earth composition via said nozzle for building said structure.

[0038] There is further provided an additive manufacturing system for producing a structure, in particular an outdoor structure, in particular an infrastructural structure, in particular a sound barrier, said additive manufacturing device comprising a robot system having a nozzle for depositing an earth composition, an air pumping system for providing a flow of air, a water pumping system and a controller, operationally coupled with said robot system, said air pumping system, and said water pumping system, said controller running a computer software program for:

[0039] - controlling the water pumping system for providing a flow of water from said water pumping system for providing a set earth composition to water weight ratio to result in 5-10 wt.%, in particular 7-10 wt.% water in said earth composition, more in particular 7-9 wt.% water content, and

[0040] - controlling the air pumping system for providing a flow of pressured air from said air pumping system for providing a set pressure of 2-10 bar, in particular 2-5 bar, an earth composition to air mixing volume ratio of between 1 :50 and 1 : 150 and resulting in a flow rate of between 50-400 m3 / hour. With respect to earth compositions, earth usually comprises four elements: Clay, silt, sand and gravel. These components are defined by the particle size in a practical manner. Clay is the fraction that passes a sieve with sieve opening of 0.002 mm (2 micron). Silt is the fraction that passes a sieve with sieve opening of 0.063 mm (63 micron) but does not pass the sieve with sieve opening of 0.002 mm. Sand is the fraction that passes a sieve with sieve opening 2 mm but that does not pass the sieve with sieve opening 0.063 mm. Finally, gravel is the fraction that does not pass the sieve with sieve opening 2 mm.

[0041] Where traditional approaches yield a cubic meter of structure per 8-12 hours, the proposed method allows for the realization of 0.5 - 5 cubic meter and more per hour; which renders a significant increase in productivity. Moreover, where traditional means of manufacturing, such as the ramming of earth in a formwork with pneumatic hammers yields an anisotropic material, where the presented method yield a uniform, isotropic material, reducing engineering efforts associated with accounting for anisotropic properties, such as shear forces in a retention wall.

[0042] The earth composition is in fact pneumatically transported to the robot and the nozzle. At the nozzle, the earth composition is sprayed, allowing the building of substantially massive structures. It also allows procession of large quantities of earth composition. In particular, the flow of air is provided using a rotor pump or a similar pump. This in contrast to using a cavity pump or progressive cavity pump. A rotor pump effectively provides a stream of air at sufficient pressure and flow rate to pneumatically transport the earth composition and spray the earth composition at the nozzle. This allows compaction (discussed below) and allows transport of the earth composition over large distances as explained.

[0043] While since 2010 considerable progress has been realized in the realm of additive manufacturing in the construction industry and in 3D printed concrete in particular, so far there has been little advances made in the automation of earthen construction. This is notable, since existing artisanal approach to earthen construction render the sustainable approach to construction costly. So far additive manufacturing in construction have focussed on extrusion and or sprayed methods, or methods where the wet mixture is pumped to a nozzle. In the method presented, dry material (with its water content <= 5%) is conveyed pneumatically from the material hopper to the nozzle. Water is introduced at the nozzle: Water is added to the dry mix at the nozzle. A controller controls and monitors the water content, ensuring the correct consistency of the mix and providing a degree of quality control. Application: The now-moistened mix is sprayed at high velocity onto the surface where it adheres and compacts due to the force of the spray. A high green strength is developed due to the high flow of pressurised air, providing a considerable degree of mechanical compaction. Thus, the kinetic impact energy of the compressed air thus is the energy compacting the earth composition onto the structure that is being build. In contrast to 3D concrete printing methods, which rely on a hydration, which is accelerated by means of additives (such as calcium chloride, sodium silicate and aluminium sulphate, known as accelerators), to develop “green strength” as is the case in system that relies on a on a wet mixture.

[0044] In this respect, green strength refers to the early-stage strength that the concrete must achieve to avoid deformation or collapse during the printing process. The quick gain in green strength is crucial for several reasons:

[0045] • Layer Adhesion: The newly extruded layer must have enough strength to adhere to the previous layer without causing the structure to collapse or deform.

[0046] • Shape Retention: As each layer is deposited, it must maintain its shape under the weight of subsequent layers. Without sufficient green strength, the layers could spread or slump, leading to defects in the printed structure.

[0047] • Load-bearing Capacity: As the structure grows taller, the lower layers need to have developed enough strength to support the increasing weight.

[0048] Accelerators enhance the hydration process, ensuring that the concrete gains the required green strength quickly, allowing for continuous and stable layer deposition. The balance between setting time, workability, and early strength is critical in 3D printing, and additives such as the aforementioned accelerators are key in achieving this balance.

[0049] The current method and system allow stopping and starting the deposition or building reducing the formation of a “cold joint”. In particular, it can even be possible to produce without formation of a “cold joint’.

[0050] In 3D concrete printing (3DCP), cold joints are formed when there is an interruption in the printing process that causes a delay between the deposition of successive layers of concrete. These joints occur because the previously printed layer has started to set before the next layer is deposited, leading to a potential weak interface between the layers.

[0051] Formation of Cold Joints in 3DCP

[0052] 1. Layer-by-Layer Deposition:

[0053] 3DCP involves the continuous extrusion of concrete in layers to build up a structure. Ideally, each new layer is deposited on top of the previous layer while it is still fresh enough to bond effectively.

[0054] 2. Interruption or Delay:

[0055] If there is a significant delay between the deposition of layers — due to factors such as equipment malfunction, a pause in the printing process, or logistical issues — the earlier layer may begin to set and harden. The extent of this setting depends on the time elapsed and the properties of the concrete mix.

[0056] 3. Weak Interface:

[0057] When the next layer is eventually deposited onto a layer that has already begun to set, the bond between the two layers may not be as strong as it would have been if the layers had been deposited continuously. This results in a cold joint — a plane of weakness where the strength and durability of the concrete structure might be compromised.

[0058] Challenges and Implications of Cold Joints

[0059] • Structural Integrity: Cold joints can compromise the structural integrity of the printed object, as the bond between layers may not develop full strength. This can lead to potential failure under load or environmental stress.

[0060] • Durability: The presence of cold joints can make the structure more susceptible to issues such as water penetration, freeze-thaw damage, and other environmental factors, reducing the overall durability of the concrete structure.

[0061] • Aesthetics: Cold joints can also affect the aesthetic quality of the printed structure, as they may be visible as lines or discontinuities on the surface. Mitigating Cold Joints in 3DCP

[0062] To reduce the formation of cold joints in 3DCP, several strategies can be employed:

[0063] 1. Optimizing Print Speed: Ensuring that the printing process is continuous and uninterrupted helps prevent the formation of cold joints by minimizing the time between layer deposition.

[0064] 2. Using Set Retarders: Chemical additives known as retarders can be used to slow down the setting time of the concrete, allowing for more time between layers without risking the formation of cold joints.

[0065] 3. Interlayer Bonding Agents: In some cases, bonding agents or additional surface treatments may be applied to the previously printed layer before depositing the next layer, enhancing the bond between them.

[0066] 4. Controlling Environmental Conditions: Managing the temperature, humidity, and other environmental factors can help control the rate at which the concrete sets, reducing the likelihood of cold joints.

[0067] In a method described as “shot-earth 3D printing,” the process is designed in such a way that cold joints are minimized or even eliminated. This is achieved through continuous deposition, rapid layer bonding, and the specific properties of the material. In shot-earth 3D printing, material is applied at high velocity through a nozzle, allowing for continuous and seamless layer deposition.

[0068] A high-velocity spraying helps to create a mechanical interlock between layers. The kinetic energy of the material as it impacts the surface helps to consolidate the new layer with the previous one, enhancing the bond and further reducing the formation of cold joints. The process also involves the natural compaction of the material due to the impact, which improves the density and bonding of the material, reducing the potential for cold joints.

[0069] Materials are designed to retain moisture, which is crucial for the drying process. This retained moisture allows for better bonding between layers, and reduce crack formation. In most known 3D earth printing, a contour is printed, not a solid structure as drying otherwise becomes a problem.

[0070] The current method and system provide a structure with reduces shrinkage. In fact, it even allows building a structure that in time does show minimal to no shrinkage. Shrinkage is limited to 0.5%. In fact, when adding fibrous material, shrinkage can be reduced further. Other approaches use water in the mixture that adds up to 20% in weight, where here, in contrast, material is deposited close to the plastic limit, with a total water content that ranges from 7-9% in weight. Hence with little or no yield stress containing buildability by a limited build height, in 3dcp that limitation has been overcome by means of additives, in 2k systems accelerant is added at the nozzle dramatically increasing yield stress. Since earthen construction as described here utilises little or no binder, that approach of accelerant does not applicable here, hence the high green strenght being a key and unique property. Due to the low yield stress in in extrusion based systems, a course of 20-50cm can be printed before the structure collapses under a buckling load. Due to the high green strength of the compacted structure no such limitations are imposed to the shot-earth approach described

[0071] The current method and system allow printing the earth composition at least 100 meters from the earth composition source. Thus, the earth composition can be pneumatically transported at least 100 meters. In fact, it allows 3D printing up to 1000 meters away from a source of earth composition. The flow of air that is used was found to allow transportation of the earth composition of as much as 1500 meters. The large range of application lower construction costs and provides considerable flexibility in terms of the logistics involved in handling the materials that are sprayed. In an embodiment, the pneumatic transport takes place using a conduit having an internal cross section of 60 mm. In such a conduit, a pressure of 8 bar and a flow rate of 10-12 m3 / h is attained.

[0072] Other examples working parameters: pressure Nm3 / minimal: 6,7bar o 38mm printed volume 1.5m3 / hr earth composition, distance: 240m pressure Nm3 / minimal: 5.5 bar o 38mm printed volume 2.4m3 / hr earth composition, distance: 100m pressure Nm3 / minimal: 3bar o 38mm printed volume 2.4m3 / hr earth composition, distance: 60m pressure Nm3 / minimal: 9-l lbar o 60mm printed volume 9m3 / hr earth composition, distance: 800m pressure Nm3 / minimal: 2.8 bar 0 32mm printed volume 2m3 / hr earth composition, distance: 40m

[0073] Both the reduction or even lack of formation of a “cold joint” and the reduced shrinkage, and the increased production range is a result of the approach developed, which is to use as little water as possible and to blow dry earthen material to the nozzle, rather than pumping a wet mixture to the nozzle.

[0074] It was found that for production of a sound or acoustic barrier which has to comply with many technical requirements provides a good, affordable end sustainable product. The produces sound barrier complies with requirements like for instance including static and dynamic wind loads, the loads of (high-speed) trains passing by, live (snow and ice, maintenance loads) and dead loads (self-weight and attached components), seismic loads, impact loads, thermal loads, foundation loads, vibration loads, human induced loads (vandalism) construction loads (temporal loads during installation).

[0075] Detailed description of the invention

[0076] Below some particular embodiment are described. These embodiments can be combined.

[0077] In an embodiment of the method, said earth composition comprising clay, silt, sand and gravel (aggregate) is used in ratio’s between a coarse mixture of 30% in weight of both clay and silt, and 70% in sand and gravel, where the mirrored ratio of 70% in weight of clay and silt and 30% in sand and gravel provide the productive mixture range.

[0078] In an embodiment of the method, it further comprises providing said nozzle at a distance of 1-50 cm from a deposition position, whereby providing sufficient pneumatic compaction

[0079] In an embodiment of the method the structure comprises a structure core and a structure surface exposed to the elements, wherein when said deposition position is at said structure core a natural fiber composition is mixed with said earth composition at a mixing volume ratio of between 1 : 1 and 1 : 10 of said earth composition to said natural fiber composition, and reducing said natural fiber amount to below 1 :0.1 mixing volume ratio when said deposition position is less than 5 cm from said structure surface. In an embodiment of the method the mixing volume ratio and the flow rate are set for deposition at least 10 kg of earth composition per hour. In a particular embodiment, the deposition of earth is at an upper limit of 8-10 cubic meter of earth per hour. In a more particular embodiment, depositing (in fact, spraying) 0.5-5 m3of said earth composition per hour is achieved.

[0080] In an embodiment of the additive manufacturing system the computer software program further receives information on the building design of the structure, and controls a weight ratio of a mineral binder to the earth composition to further stabilizes the material in terms of a distance to a surface of the structure. If added, such a binder is usually only added at the outer core of the structure to further stabilize the structure. In a stabilised rammed earth construction, the amount of binder is usually between 5% and 10 wt.%, while unstabilised rammed earth does not use binder. The amount can be gradually increased when depositing the outer layer. At the final outer layers, the binder can be added up to 10 And 1 wt.% of the earth composition. Usually, the amount of binder is less than 5 wt.%. starting from the last outer 10% of the structure, the amount of binder added can substantially linearly increase to a maximum of 10 wt.%. If desired in specific constructs or structures, binder may be added to the earth composition to provide additional strength, for instance when large vibrations are expected. As a further advantage, no accelerator is required as the used amounts of biner are low, providing a limited amount of reactive mass.

[0081] In an embodiment of the additive manufacturing device the computer software program further receives information on the building design of the structure, and controls a ratio of a hydrophobic agent to the earth composition in terms of a distance to a surface of the structure.

[0082] In an embodiment of the additive manufacturing system the computer software program further controls the water pumping system for starting and stopping the flow of water.

[0083] In an embodiment of the additive manufacturing system the computer software program further controls the air umping system for starting and stopping the flow of pressured air.

[0084] It was further found in “progressive insight” or “new insight” that it is possible to formulate an alternative earth composition based upon locally available components of the soil of earth. In particular, an earth composition can be used comprising 40-50 wt.% gravel, 40-50 wt.% sand. These components sand and gravel may provide 80-95 wt.% of the earth composition. In addition, 5-15 wt.% clay and silt are provided. The water content of the earth composition and further processing parameters are: less than 4 wt.% water, in particular less than 2.5 wt.% water, more in particular less than 1.5 wt.% water, more in particular less than 1 wt.% water. Mixing said earth composition with an air flow with a pressure of 2-10 bar, in particular 2-5 bar, at a mixing volume ratio of between 1 :50 and 1 : 150 earth composition to air and resulting in a flow rate of between 50-400 m3 / hour. This earth composition with air is pneumatically conveyed to an additive manufacturing robot at its nozzle. In this earth composition, adding at or near the nozzle an additional amount of water to result in 5-10 wt.%, in particular 7-10 wt.% water. More in particular, there is 7-9 wt.% water content. The gravel in such an earth composition is from a sieve fraction smaller than 12 mm. In particular it is from a sieve fraction larger than 2 mm.

[0085] The terms “upstream” and “downstream” relate to an arrangement of items or features relative to the propagation of the earth composition to the structure and finally onto the structure.

[0086] The term “substantially” herein, such as in “substantially consists”, will be understood by the person skilled in the art. The term “substantially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term “substantially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” includes also embodiments wherein the term “comprises” means “consists of’.

[0087] The term "functionally" will be understood by, and be clear to, a person skilled in the art. The term “substantially” as well as “functionally” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective functionally may also be removed. When used, for instance in “functionally parallel”, a skilled person will understand that the adjective “functionally” includes the term substantially as explained above. Functionally in particular is to be understood to include a configuration of features that allows these features to function as if the adjective “functionally” was not present. The term “functionally” is intended to cover variations in the feature to which it refers, and which variations are such that in the functional use of the feature, possibly in combination with other features it relates to in the invention, that combination of features is able to operate or function. For instance, if an antenna is functionally coupled or functionally connected to a communication device, received electromagnetic signals that are receives by the antenna can be used by the communication device. The word “functionally” as for instance used in “functionally parallel” is used to cover exactly parallel, but also the embodiments that are covered by the word “substantially” explained above. For instance, “functionally parallel” relates to embodiments that in operation function as if the parts are for instance parallel. This covers embodiments for which it is clear to a skilled person that it operates within its intended field of use as if it were parallel.

[0088] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0089] The devices or apparatus herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation.

[0090] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements. In the device or apparatus claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The invention further applies to an apparatus or device comprising one or more of the characterising features described in the description and / or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterising features described in the description and / or shown in the attached drawings.

[0091] The various aspects discussed in this patent can be combined in order to provide additional advantages. Furthermore, some of the features can form the basis for one or more divisional applications.

[0092] Brief description of the drawings

[0093] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

[0094] Figure 1 schematically depicts an embodiment of an additive manufacturing device;

[0095] Figure 2 shows data regarding an earth composition, and

[0096] Figure 3A-5B experimental results when varying the amount of water of the sprayed flow.

[0097] The drawings are not necessarily on scale

[0098] Description of preferred embodiments

[0099] Figure 1 schematically depicts a shot-earth 3D printing system. The system comprises an air compressor 1.

[0100] Via a conduit 2 the compressed air is provided to a hopper 12. The hopper 12 is filled with the earth composition described and below with respect to figure 2 from a container 10. In an embodiment, the earth composition is stored and provided in a silo, and from the silo provided into the hopper 12. This allowed continuous processing in stead of (semi) batch processing, or at least avoids logistical problems of providing a sufficient amount of earth composition. A static mixer can be added for providing a continuous processing end homogeneous earth composition. From the static mixer, the (mixed) earth composition is provided to the hopper 12. In the silo or in the hopper 12 a small amount of water, small enough to remain below the percentages referred to above of in the claims, in order to prevent or at least reduce possible dust problems. The mixed air and earth composition is provided to a robot arm 5 provided with a spray nozzle 7. The robot arm 5 can be provided on a displacement system (not depicted), for instance a wheeled vehicle. In this way, the controller 6 can control the manufacturing of the structure 8.

[0101] Via a water pump 13, water under pressure is provided at or near the nozzle 7. This amount of water is limited. In particular water is added to result in an amount of less than 10 wt.% of the total flow. The controller 6 controls the water pump 13 to control an amount of water added at the nozzle 7. The water under pressure is provided via a water conduit 4. From the nozzle 7, the mixed air and earth composition is sprayed. Usually, a substantially solid structure 8 may be built. The pneumatic spraying provides compaction with a compaction factor of between 1.2 and 1.5. In particular a compaction of the earth composition of 1.3-1.4 can be attained. Specifically, a compaction factor of substantially 1.35 can be attained. This provides a mechanical strength directly after praying. This provides a “green strength”. In contrast to “yield stress” which is relevant to extrusion printing, the currently claimed method provides a superior green strength. Due to this, large structures 8 can be built swiftly without having to wait for drying and / or settling.

[0102] A controller 6 controls the various flows of earth composition, water and air. The controller further controls position and orientation the robot arm 5 and if present the displacement device. In this way, the controller 6 controls the position and amount of earth composition that is deposited at any place, in order to provide 3D printing of the structure 8.

[0103] In figure 2, the x-axis (“sieve opening”) presents the diameter of the sieve, where the y-axis presents the percentage (weight percentage) of the material that passes the sieve (“weight passing the sieve”) radius in millimetre.

[0104] Examples

[0105] Using the earth composition characterised in figure 2, tests were done with varying amounts of water being added at or near the nozzle 7 via water pump 13.

[0106] The earth composition had 3 Wt.% of water.

[0107] The earth composition was pneumatically conveyed using 1 : 120 earth composition to water flow rate. The air pressure was 5 bar. This resulted in a flow rate of 300 m3 / h. Near the nozzle water was added at 5 Bar. In experiments, the added water was varied from 8 wt.%, to 5 wt.% and 3 wt.%. the result in pictures is demonstrated in figures 3A en 3B, 4 and 5A and 5B.

[0108] Result

[0109] When using 8 wt.% of water, the green strength is reduced and str structure that is being build collapses during spraying.

[0110] When using 5 wt.% of water, the method provided a good quality structure, see fig. 4. The method allows variations and details in the structure.

[0111] When using 3 wt.% of water, the earth composition clogged the conduit / hose transporting the air and earth composition. An agglomerate is shown in the mask of figure 5B.

[0112] It was found that providing an earth composition with a preselected particle size distribution, and using an amount of water and mixing with a predefined flow of air can provide a building method using mainly earth for providing a structure.

[0113] It will also be clear that the above description and drawings are included to illustrate some embodiments of the invention, and not to limit the scope of protection. Starting from this disclosure, many more embodiments will be evident to a skilled person. These embodiments are within the scope of protection and the essence of this invention and are obvious combinations of prior art techniques and the disclosure of this patent.

[0114] Reference numbers

[0115] 1 air compressor

[0116] 2 hose with compressed air connecting compressor 1) to 12) shotcrete machine

[0117] 3 hose with that joins compressed air from compressor 1) with earthen mixture from shotcrete machine 12)

[0118] 4 water hose connecting water pump 13) to shotcrete machine 12)

[0119] 5 robot arm

[0120] 6 (robot) controller

[0121] 7 nozzle mounted on robot 5)

[0122] 8 structure being printed with the shot-earth additive manufacturing method described

[0123] 9 Signal cable from controller (6) to shotcrete machine (12) such that allows the robot 5) to control the shotcrete machine 12)

[0124] 10 earth composition container holding an earthen mixture

[0125] 11 dry earthen mixture and water join at the nozzle 7)

[0126] 12 shotcrete or gunite machine

[0127] 13 water pump

Claims

Claims1. An additive manufacturing method for building a structure, in particular an infrastructural construction, more in particular a sound barrier, comprising:- providing an earth composition comprising 20-70 wt.% clay and silt, 70-30 wt.% sand, less than 10 wt.% gravel and less than 4 wt.% water, in particular less than 2.5 wt.% water, more in particular less than 1.5 wt.% water, more in particular less than 1 wt.% water;- mixing said earth composition with an air flow with a pressure of 2-10 bar, in particular 2-5 bar, at a mixing volume ratio of between 1 :50 and 1 : 150 earth composition to air and resulting in a flow rate of between 50-400 m3 / hour;- pneumatically conveying said air-earth composition mixture to an additive manufacturing robot at its nozzle;- adding at or near the nozzle an additional amount of water to result in 5-10 wt.%, in particular 7-10 wt.% water in said earth composition, more in particular 7-9 wt.% water content, and- depositing, in particular spraying, said earth composition via said nozzle for building said structure.

2. The method according to claim 1, wherein said earth composition comprising clay, silt, sand and gravel (aggregate) is used in ratio’s between a coarse mixture of 30% in weight of both clay and silt, and 70% in sand and gravel, where the mirrored ratio of 70% in weight of clay and silt and 30% in sand and gravel provide the productive mixture range.

3. The method according to any one of the preceding claims, further comprising providing said nozzle at a distance of 1-50 cm from a deposition position, whereby providing sufficient pneumatic compaction4. The method according to claim 1, wherein said structure comprises a structure core and a structure surface exposed to the elements, wherein when said deposition position is at said structure core a natural fiber composition is mixed with said earth composition at a mixing volume ratio of between 1 : 1 and 1 : 10 of said earthcomposition to said natural fiber composition, and reducing said natural fiber amount to below 1:0.1 mixing volume ratio when said deposition position is less than 5 cm from said structure surface.

5. The method according to any one of the preceding claims, wherein said mixing volume ratio and said flow rate is set for deposition at least 10 kg of earth composition per hour, in particular at an upper limit of 8-10 cubic meter of earth per hour, more in particular depositing 0.5-5 m3of said earth composition per hour.

6. An additive manufacturing system for producing a structure, in particular an outdoor structure, in particular an infrastructural structure, in particular a sound barrier, said additive manufacturing device comprising a robot system having a nozzle for depositing an earth composition, an air pumping system for providing a flow of air, a water pumping system and a controller, operationally coupled with said robot system, said air pumping system, and said water pumping system, said controller running a computer software program for:- controlling the water pumping system for providing a flow of water from said water pumping system for providing a set earth composition to water weight ratio to result in 5-10 wt.%, in particular 7-10 wt.% water in said earth composition, more in particular 7-9 wt.% water content, and- controlling the air pumping system for providing a flow of pressured air from said air pumping system for providing a set pressure of 2-10 bar, in particular 2-5 bar, an earth composition to air mixing volume ratio of between 1 :50 and 1 : 150 and resulting in a flow rate of between 50-400 m3 / hour.

7. The additive manufacturing system of claim 6, wherein said computer software program further receives information on the building design of the structure, and controls a weight ratio of a mineral binder to the earth composition to further stabilizes the material in terms of a distance to a surface of the structure.

8. The additive manufacturing system of claim 6 or 7, wherein said computer software program further receives information on the building design of the structure, and controls a ratio of a hydrophobic agent to the earth composition interms of a distance to a surface of the structure.

9. The additive manufacturing system of claims 6 - 8, wherein said computer software program further controls the water pumping system for starting and stopping the flow of water.

10. The additive manufacturing system of claims 6-9, wherein said computer software program further controls the air pumping system for starting and stopping the flow of pressured air.

11. The additive manufacturing system of claims 6-10, wherein said air pump is a rotor-type pump.

12. A computer program product which, when executed on a data processing device, preforms the computer software program steps of claims 6-10.

13. Use of the method of any one of the preceding claims 1-5 for producing a sound barrier.

14. A sound barrier resulting from the method of any one of the preceding claims 1-5.-o-o-o-o-o-

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