Raw construction materials whose composition includes submerged area sediments and fibers, and low-carbon process for preparing a finished product including sediments

Abstract

The construction material (M) comprises sediments (5) including clay, particles consisting of silt, and less fine particles consisting of grains of sand whose characteristic size does not exceed 2 mm, the material having a formulation making it possible to limit the grains of sand in the total dry matter of the material to less than 34% by weight. It consists of a raw mixture, obtained without cooking, which includes said sediments (5), water (W) and fibers (6) including filaments of natural and / or synthetic fibers, the fibers representing a mass fraction of between 2 and 30% of the material (M) which can be obtained at the end of a shaping step (64), for example with compression. A method for obtaining the material can make it possible to provide a finished low-carbon construction product that is robust, lightweight or semi-lightweight, thermally correcting or thermally insulating. Figure for abstract: Figure 4

Description

Title of the invention: Raw construction materials whose composition includes submerged zone sediments and fibers, and low-carbon process for preparing a finished product including sediments Technical field

[0001] The present disclosure relates, in particular in the field of the construction of buildings or low-energy buildings (BBC), to components or materials of which a fraction comes from dredged sediments. The invention relates more particularly to a raw construction material combining dredged sediments and fibers. A method for obtaining a finished product including the ready-to-use material is also provided, while avoiding energy-intensive cooking step(s). Technological background

[0002] Dredging sludge, which was traditionally abandoned or buried, poses environmental problems. It has been proposed to mix other materials with the constituents of the dredged sludge, in particular by adding hydraulically setting binders such as cement and / or lime. Thus, document WO 02 / 074391 describes a method for treating dredged material at high temperature, using a lime-based binder. After cooling, a chelating agent is added, which provides a decontamination and solidification effect on the substance, making it usable as a filler in a composite material.

[0003] Dredged sediments are not considered suitable for construction, except by resorting to complex transformation processes and / or requiring high-temperature treatment. A disadvantage of current uses is that the material obtained has a high carbon footprint. There is therefore a need for techniques for producing materials based on dredged materials that are less costly for the environment, while achieving mechanical strength compatible with the construction field. Summary

[0004] In order to overcome one or more of the problems mentioned above, the invention proposes a construction material, comprising sediments (sediments recovered from at least one submerged area, for example dredged sediments) of one or more particular types among marine sediments, river sediments, fluvial and / or lake sediments, recovered sediments of which a first fraction of particles comprises clay, a second fraction of particles less fine than in the first fraction consists of silt and a third fraction of particles, less fine than in the second fraction, consists of sand grains whose characteristic size does not exceed 2 mm, the material consisting of a raw mixture, i.e. obtained without cooking, which includes: said sediments (e.g. dredged sediments); water; and fibers (typically including natural fiber filaments, e.g. plant fiber, and / or synthetic fiber filaments). While the fibers represent a mass fraction of between 2 and 30% of the construction material, the total dry matter of the material includes a portion of sand grains which may be overall lighter than the other finer components of the sediments, for example with the third fraction representing no more than 34% by weight, preferably less than 29 or 25%, of this dry matter of the construction material.

[0005] This solid material composition allows for formulation flexibility, minimizing or eliminating the use of hydraulic binders, with easy and energy-saving shaping, and good stability for use in construction. Unlike cement concrete or concrete incorporating excavation waste (such as uncalcined clay cement), it is possible to obtain a material with a relatively low density. This material advantageously allows to take advantage of the properties of materials that are difficult to recover, generally considered as waste, by limiting the use of energy-intensive transformations (no cooking). The use of chemical transformation additives / adjuvants can be avoided or reserved only for the satisfaction of specific needs encountered: it is understood that it is permissible to rule out the use of chemical reactions by additives (forming or not a hydraulic binder) if a high-performance ecological construction is desired.

[0006] It is recalled here, as generally accepted in the field of construction materials, that sand brings together particles larger than approximately 63 microns, the smaller particles blocking the interstices between the grains of sand. The sand particles are therefore those retained by a sieve with a grain size of 63 pm (or 0.0025 in). In all that follows, the submerged zone sediments may include in particular marine sediments, river / fluvial or lake sediments, whether obtained by dredging, by filtration / filtering, or by any other process. The submerged (submarine) nature of these sediments is therefore to be interpreted without the slightest limitation and may include the optional case of zones periodically or alternately covered by a mass of water then not covered.

[0007] In designs for obtaining a finished material, ready for use as a thermal insulation element, the fraction of fibers exceeds 15% of the mass of the material (which constitutes a finished material, ready for use). In alternative embodiments, the material includes between 2 and 10% of fibers (mass proportion) relative to the mass of the material. The material may be structural, possibly having a density of more than 900 kg / m3 for example (without exceeding 1500 kg / m3).

[0008] With the above-mentioned compositions, whether the mass proportion of fibers is high or not, regardless of the thermal insulation coefficient obtained, it is possible to produce construction parts, for example blocks, which have good stability over time and which withstand a compressive force. A sedimentary brick or similar component can be obtained with insulating properties where appropriate, by limiting the density of the block to less than 1500 or 1600 kg / m3, for example less than 900 kg / m3.

[0009] The presence of sand grains makes it possible to improve the compactness of the material and to avoid excessive clay content. Limiting the fraction of sand grains, combined with the presence of fibers, is advantageous in order to make the mixture particularly easy to compress while minimizing problems of cracking and insufficient mechanical strength.

[0010] According to a particular feature, the components of the three respective fractions of the ground powder of the sediments are mechanically linked, with fibers interposed between the clay, the silt and the sand grains. Optionally, the material is obtained without additives having previously been heated or fired at more than 200°C (without lime or cement for example). The material can be obtained with a low-carbon process.

[0011] According to a design option, the material has a three-dimensional structure to form a building block. In this structure, a binder from the sediments (for example clay) is preferably distributed homogeneously, at least as regards a core part of the block. The block is for example obtained by a mechanical forming process with compression, without chemical alteration of the binder (or binder-forming part) of the sediments. It is understood that the material may result from a mixture without chemical conversion or chemical reaction / recombination by being devoid of chemical transformation additive, and / or at least result from a mixture without chemical setting (of the hydraulic setting type or similar).

[0012] The sediments may be selected from one or more layers of a sediment discharge (which has been discharged after a dredging or filtration operation). The sediments are therefore of marine, lake, port or fluvial origin (rivers, streams) for example.

[0013] In embodiment options, a chemical additive is used, for example to carry out a surface transformation of a block of the material, to produce a waterproof coating. meabilization (which may involve the creation of chemical bonds with all or part of the components present in the sediments - dredged sediments or others). When mineral fillers (such as sand or fine siliceous extracts, or even crushed materials or powders) are added in addition to the sediments, it may be expected that these mineral fillers represent less than 20 or 25% by weight of the dry matter of the material.

[0014] In some examples, the material forms a component or building block with a density less than or equal to 550 or 650 kg / m3, with in this case fibers which possibly represent between 10% and 30% (optionally less than 25% and possibly more than 15%) of the mass of the building material. This makes it possible to propose a very lightweight design, for example adapted for needs to minimize the weight of a wall or wall zone in which several components or blocks are assembled, for example vertically.

[0015] The fibers may include one or more of the following types of fibers, including synthetic fibers and natural fibers. All or part of the natural fibers correspond, for example, to fibers of agricultural or industrial origin, such as: - raw or processed materials based on plant fibres such as lignin or cellulose, such as cellulose or cardboard wadding, paper or cardboard derivatives (in raw, shredded, chewed, crushed, or other form), sawdust and its derivatives, etc.; - hemp in the form of raw or processed fibers, hemp shiv, tow, dust, or as a mixture of hemp components; - cork aggregates in raw or processed forms; - flax in the form of raw or processed fibers, shives, tow, dust, or in a mixture; - chopped or unchopped cereal or polygonaceae straw, or any other part of the plant (husks, roots, mixtures, etc.) in raw or processed form; - various plants or parts of natural or cultivated plants, in raw or processed form, such as hay, cotton, corn, miscanthus, rapeseed, reed, sunflower, wood chips of various species, bamboo, ferns, algae, etc.

[0016] Furthermore, it may be provided, in the same formulation (typically including water), a mixture of several binders, several fibers, several fillers, several adjuvants. The fibers may be derived, at least in part, from dried straw (based on cellulosic plants / parts of plants). In embodiments, whatever the nature of the fibers chosen, it is possible to provide a proportion of fibers greater than or equal to 10% by weight of the material, for example greater than or equal to 15%.

[0017] According to a feature, the material is porous and compacted, preferably being obtained by a mechanical process that includes compression. Thus, the material can constitute a structural element, usable in a wall of a building, in an external partition. Where appropriate, the compaction effect is obtained by static compression, for example by using at least one hydraulic jack. The compaction effect can also be obtained by a dynamic process, a vibrating process, or any other type of process. The compaction effect can also be obtained by a combination of several successive or simultaneous compaction operations, for example static compaction and vibration.

[0018] Surprisingly, the material including the fibers (which provide a certain elasticity), resulting from the compression which is for example exerted vertically by a displacement of one or two plates, is stable and a vertical rebound effect with an increase in height directly after the compression is not observed. It appears that the composition using sediments with a low sand content is suitable for stabilizing the molded and compressed body, in particular for absorbing a certain amount of water sustainably and stably.

[0019] According to a feature, the construction material is shaped to form or form part of a rigid construction block having two opposite faces and a side face corresponding to a slice defining a thickness of the block. The material results for example from a mixture without chemical bonding by being devoid of chemical transformation additive. Alternatively, an adjuvant can be used by providing a new chemical bond.

[0020] Whether the material is formed in the form of a building block or in the form of a flowable composition, this material is optionally free of mineral filler, in particular aluminum-based additive, and / or free of hydraulic binder (in particular without lime, cement).

[0021] In embodiments, the density of the material is less than or equal to 1500 kg / m3, preferably less than or equal to 1100 kg / m3, for example less than or equal to 800 or 900 kg / m3. The material may be shaped into a block, for example of the brick type. The fibers may be fibers which may have, dry or substantially dry, a density of between 30 and 230 kg / m3, in uncompressed bulk packaging.

[0022] In options, the building block may include a core portion that typically represents at least 70% by weight of the block, having a homogeneous sediment composition, without hydraulic binder and / or having one less additive, which differs from the intended surface composition of the block (for example with a formulation that does not exclude a surface addition of cement, waterproofing by chemical bonding, etc. on a surface area).

[0023] According to a feature, the sum of the fractions (first fraction, second fraction and third fraction) represents 50% or more than 50% of the total dry mass, preferably more than 65 or 70% of the total dry mass of the building material. Thus, it is possible to massively convert an undesirable substance extracted from a discharge / resting area of submerged area sediments (marine, river or similar sediments) to form the majority of the dry mass of the material. This material can be structural, for example as a result of compression forming six faces (with three pairs in opposite parallel manner, for example) of a block suitable for use in a building. Other uses are of course possible, for example in a partitioning assembly or a decorative construction.

[0024] In embodiments, one or more of the following features may be provided with regard to the composition of the construction material: - the fibers represent more than 2%, for example more than 10% or 20%, of the weight of the material, knowing that the density of the material can be for example between 200 kg / m3 and 1500 kg / m3 (possibly remaining less than or equal to 700 kg / m3). - the first fraction, the second fraction and the third fraction cumulatively form at least 70% or 75% of the total dry matter of the material. -the material is structural, preferably with fibers representing less than 15% of the material's weight. - the density of the material (volume mass) is greater than or equal to 700 kg / m3, possibly between 900 kg / m3 and 1500 kg / m3. - the density of the material is between 700 kg / m3 and 800 or 900 kg / m3, so the material can be considered semi-lightweight.

[0025] Sediments, particularly when it comes to dredged sediments, are sediments, such as marine or river sediments, which have for example been taken from a (typically impermeable) lagoon basin, allowing a sufficient period to elapse to typically allow stratification in the basin / reservoir, after the dredged sediments have been discharged. Regardless of the area from which the sediments are taken, the dredged sediments may have undergone: - exposure to the open air, for example in lagoons, typically so that certain physicochemical parameters adjust with the drying of the sediments (this includes in particular the salinity level (chlorides), for example to be compatible with the standards in force for agricultural spreading).

[0026] Over a period of time which may be greater than 6 months, possibly greater than 1 year, the different fractions of the sediments separate into several distinct layers, the finest fraction most often migrating to depth. In exemplary embodiments, it is in this fraction that the dredged sediments are collected by presenting / including the first fraction, the second fraction and the third fraction. This can ensure that the silty part and the part with clay constitute a very significant, typically majority (for example greater than 55 or 60% by weight) part in the dredged sediments entering into the composition / formulation of the construction material. Of course, it is also permitted to integrate submerged sediments / from an underwater location that do not require lagooning, such as sediments from filtration, flocculation, or dehydration by press processes.

[0027] According to another aspect, there is provided a prefabrication element comprising the construction material as presented above, for example as a structural core material, a filler material, or a homogeneous material for shaping the prefabrication element. A panel or brick format can be obtained. The main binder (compared to any other source used in the manufacture of the element) consists of clay from the first fraction (belonging to the sediments).

[0028] The prefabrication element can be obtained directly by compression molding (without a subsequent chemical or mechanical treatment step), for example by drying after demolding. The prefabrication technique is carried out using a composition of the construction material which is particularly light, for example less than 900 kg / m3, and more generally less than 1500 kg / m3, while avoiding cooking. The compression can be carried out with a compression force less than or equal to 2, 5 or 10 MPa.

[0029] According to one aspect, there is also provided a method of preparing a finished construction product, the method comprising the steps essentially consisting of: - gather three fractions of particles from sediments from submerged area(s) (requiring dredging or not), knowing that a first of the fractions comprises clay, a second of the fractions comprises particles less fine than in the first fraction and consisting of silt, and a third fraction of particles less fine than in the second fraction consisting of grains of sand whose characteristic size does not exceed 2 mm; - determining a quantity of fibers corresponding to a flow rate or a weight of fibers to be mixed with the three fractions, this quantity being predetermined so as not to exceed a representative mass of the solid particles of the sediments in the finished product, whereby a dose of fibers can be obtained; - mixing together the dose of fibers and the three fractions during a mixing step to obtain a compactable material, using water and optionally at least one adjuvant; and - obtaining the finished product by shaping the compactable material, by example by carrying out compaction and reducing the water content; the process allowing, by a selection of the sediments possibly conditioned on or confirmed by an analysis step and / or a dosage to estimate a representative value of the share by weight of the third fraction in the sediments, to limit to less than 34%, for example less than 29% or more particularly less than 25% (by weight), the overall mass fraction / content of sand grains in the finished product.

[0030] The method may include, before mixing, the analysis and / or dosage step to estimate the representative value of the weight share of the third fraction in the sediments of the submerged / underwater zone. It is understood that the third fraction is in the minority and for example lower than both the first fraction and the second fraction. The content of sand grains may be lower than a threshold, for example 20% or 25% by weight in the dry matter of the sediments on the one hand, and limited at the end of the method to less than 34% in the total dry matter of the final material constituting the finished product.

[0031] In certain variants, a dosage or analysis may be simply confirmatory, and carried out in parallel or after mixing, knowing that the origin of the sediments and / or the type of selection in these sediments may already leave no doubt as to the low sand content or at least a content lower than the aforementioned threshold (for example with regard to previous analyses of this source / basin / place of origin of sampling of dredged sediments or other sediments from an underwater zone).

[0032] The method can make it possible to obtain robust products, by avoiding compositions subject to cracking or problems of resistance over time, while making it possible to achieve mechanical and thermal performances (for insulation for example) which are high, in particular with the use of fibers present and distributed in a homogeneous manner, at more than 2% by weight in the construction material constituting the block or finished construction product. The amount of fibers can represent a mass fraction between 2 and 30% of the material.

[0033] In some options, the fibers are placed in a container and slip, including sediment fractions and water, is sprayed onto the fibers. In this case, the slip can be obtained, for example, without separation of solid components in the collected sediments (e.g., dredged sediments).

[0034] The fractions typically come from the same dredged sediments (these sediments may optionally correspond to the same sediment sample or the same geographical origin of the sample). In some projects, all components are natural or naturally sourced materials (100% natural or naturally sourced materials). The process may require energy-efficient shaping, with a low carbon footprint, typically without any cooking. The finished construction product has good compromise between its lightness and its mechanical strength.

[0035] According to a particular feature, the shaping of the finished product is carried out without adding chemical bonds of a nature different from that already present in the product, or at least carried out without a cooking step. The process may include a step of decomposing aggregates containing the three fractions. This step is, for example, carried out before mixing with the fibers, by: - grinding the aggregates, - and / or solubilization of the aggregates with the addition of water using a stirring device.

[0036] The shaping can make it possible to manufacture cladding plates (for example cast between two sheets, such as thin plates / partitioning plates and / or plates having a thickness varying between 10 and 38 mm, semi-lightweight or lightened panels (for example with a thickness between 38 and 160 mm, possibly of the order of 10 cm), large format bricks whose length can be for example between three and five times greater than its thickness, compact format bricks (for example 200*100*100 mm), blocks with a thickness greater than or equal to 180 mm (which can correspond to a height for blocks which can form exterior wall bricks).

[0037] The block may be a brick or similar component of a load-bearing wall. In the case of an exterior wall brick or similar component, it is understood that the construction material may make the block / brick self-insulating (thus reducing the thickness of the additional element added for insulation). It is interesting to be able to obtain such a type of structural block, including sediments from a submerged area (from an environment or seabed), without cooking.

[0038] When a building block is shaped, for example to have a substantially constant thickness between two plates of which at least one is mobile, the building block is compressed so as to reduce an initial volume of the compactable material, which may optionally have undergone drying subsequent to mixing. More broadly, starting from an initial volume of the compactable material received in a mold cavity or similar receptacle, the compression of the compactable material may correspond to a compression rate representing a volume reduction of between 10 and 50% (for example between 10 and 40%), in order to obtain the constituent block of the finished construction product.

[0039] In exemplary methods, the fibers (including natural fiber filaments for example), represent a mass fraction of between 2 and 30% of the material, optionally between 5 and 40%, which may include the range between 10 or 12% and 35%. Synthetic fibers may form or be part of the fibers, in options.

[0040] The process can be obtained without an endothermic reaction or without an exothermic reaction. It is permissible to refrain from limiting oneself to a mechanical process, therefore of the type without chemistry / without chemical additive. A natural part can be used upstream of the mixing, for example by planning to dry the dredged sediments or other sediments taken from an underwater area in a natural manner for a period exceeding 6 months or 1 year. If necessary, it is then sufficient to collect the sediments, for example by selecting them from a lower settling layer.

[0041] The sediments, in particular when it comes to dredged sediments, can be selected so that the sand (with a particle size greater than 63 microns) represents less than 34% of the dry matter, for example less than 25% of the dry matter. Optionally, the selection is carried out to collect dredged sediments with a substantially homogeneous distribution of the sand (third fraction) in the dredged sediments, for example without variation exceeding 20 or 30% between two mass contents of sand measured in samples taken from the same layer of dredged sediments collected for the manufacturing process of the construction material (the measurements being carried out for example after mixing the sample taken).

[0042] Prior to compression, the water content may be greater than or equal to 20% or 30% by mass in the compactable material. This level may vary with the fiber content. A fiber level greater than 5% of the mass of the construction material may facilitate conditions for rapid compression, which may include repeated impacts on at least one of the surfaces formed by the material received in the mold, for shaping.

[0043] By this method, it is possible to create robust blocks with a high content of dredged sediment, which typically constitute more than 30% of the solid part of the finished material / product or more than 30% of the mass of the finished material / product.

[0044] The material which incorporates the dredged sediments, with a composition formulated in the manner set out above, can be used as a construction component or binder (for the production of the construction block or component). Examples of construction components / blocks are covering elements, in particular floor coverings, such as tiles, slabs, paving stones or borders, wall coverings, such as interior or exterior facade elements, facing tiles, cladding elements, or roof coverings of the tile type. Other examples concern the production of extruded or molded construction modules, such as bricks, or the production of various extruded blocks.

[0045] The construction material can be used (integrated into) for the production of composite elements, such as construction panels of the prefabricated panel type, prefabricated blocks, prefabricated wall elements, or any other prefabricated building element.

[0046] The construction material can be used for the production of insulation modules, such as partition panels, or lightweight insulating construction modules (with a density of less than 1500 kg / m3, preferably less than 900 or 1000 kg / m3, more preferably less than 700 kg / m3).

[0047] In a flowable state with a water content that may exceed a mass fraction threshold greater than the water content in the finished product, a compactable material for obtaining the construction material is usable in an additive manufacturing process or manufacturing process using at least one movable deposition head or device depositing the material (typically along a path), such as by means of a 3D printer, of construction elements, buildings or houses, or decorative objects.

[0048] In options, the construction material can be used in a method of constructing a two-component system with either on the one hand the constituents in solid form, and on the other hand the constituents in liquid form (in a state with water content suitable for flowability), or the constituents in the form of two pastes, for the production of mastic, glue or sealing mortar. Brief description of the drawings

[0049] Other characteristics, details and advantages of the invention will appear on reading the detailed description below, and on analyzing the appended drawings given as non-limiting examples and in which: - [Fig.l] is a flowchart of steps for obtaining a compactable material based on dredged sediments, capable of undergoing shaping in embodiments of the invention; - [Fig.2] is a sectional view schematically illustrating the distribution, here in three main fractions, of solid components entering into the composition of a construction material in an example in accordance with the invention; - [Fig.3] shows, in a top view, an example of a mold with multiple cavities. - [Fig.4] is a flowchart illustrating some steps that can be used to obtain a construction material, according to an example of a process in accordance with the invention; - [Fig.5A] illustrates, in section, a shaping step with compression starting from a compactable material mainly based on dredged sediments, in a first production option; - [Fig.5B] illustrates, in section, a shaping step with compression on two opposite sides, starting from a compactable material mainly based on dredged sediments, in a second production option. - Figures 6A, 6B, 6C, and 6D illustrate modules or blocks made of a material in accordance with the invention. - [Fig.7] is a diagram illustrating the evolution of compressive strength with increasing proportion of sand, for tests with and without the presence of fibers. - [Fig.8] is a diagram illustrating the favorable impact of the fibers and the attenuation effect of this impact with the increasing proportion of sand. Description of embodiments

[0050] The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily to the scale of practical applications. In the different figures, identical references indicate identical or similar elements.

[0051] With reference to [Fig. 1], an example of steps for obtaining a compactable material MC is illustrated, which can define in advance the solid matter composition of the construction material M. As described below, sediments 5 from a submerged area, corresponding for example at least in part to dredged sediments, are included in the composition of the construction material, these sediments being for example marine or fluvial sediments. More broadly, the expression dredged sediments is to be considered in its usual broad sense, that is to say sediments of marine, lake, port or fluvial origin (rivers, streams) having been recovered by dredging, by filtration, or by any other means. Dredged sediments

[0052] Dredged sediments may be sediments physically treated by drying, crushing, grinding and screening. Such sediments 5 are an example of submerged area sediments.

[0053] The raw sediments 4 may have been discharged for a certain period of time in an area subject to precipitation (rain), allowing leaching. A storage step 41 may be carried out, controlled over a certain time, for example to allow the cleaning of a layer or part of dredged sediments, constituting the sediments 5, which will be able to be taken from the whole stored at this step 4L. In the method, as for example in the case illustrated in [Fig.l], a collection step 43 of the dredged sediments may be preceded by an analysis step 42, an analysis of the composition and / or the granulometry of the components, in order to ensure, for example, that the quality of the sediments is compliant / adapted to the mechanical transformation steps planned to obtain the material M.The analysis step can be carried out as a control, which makes it possible to obtain dredged sediments without deviating, for example, from a composition range in which clay and / or silt are present in sufficient mass proportion, possibly for . that one of clay and silt represents more than half of the dry mass in the sample taken from the storage area.

[0054] Whether dredging is carried out or not, the sediments 5 may undergo filtration or sieving. One or more sieves may be used during the analysis step, starting from a sample representative of the composition of the sediments 5. The analysis may, in addition to the granulometry and parameters representative of the mineral composition, relate to water content, organic matter content or other types of analysis.

[0055] A dehydration step 44 may optionally be carried out, in order to lower the water content below a mass content threshold. This may then facilitate a grinding step 45. More generally, the method may involve a grinding step 45 which ensures the disintegration of heterogeneous solid parts that are too large (aggregates), which results in a powdery whole (which may still contain water in a minor proportion) forming the sediments 5.

[0056] Whatever the method of obtaining such a powdery mixture, the sediments 5 have in their composition clay 5a corresponding to a first fraction, particles consisting of silt 5b and forming a second fraction, and less fine particles consisting of grains of sand 5c, forming a third fraction, the characteristic particle size of which does not exceed 2 mm (a 9 mesh (2.0 mm) sieve can for example discriminate any larger grains or aggregates). The formulation of the material is carried out so as not to include solid particle sizes larger than in the third fraction and to limit the mass share of sand to less than 34% or possibly less than 29% (and for example less than 25%) by weight, in the total dry matter of the material M. Introduction of fibers - examples of fibers

[0057] With reference to [Fig. 1], the compactable material MC can be obtained before a shaping step 64. The compactable material MC is obtained without cooking and the finished material obtained according to the method consists of a raw mixture, i.e. obtained without cooking. The composition of this material includes the sediments 5 from the submerged zone, a residual part of water W and fibers 6, which include filaments of natural and / or synthetic fiber. In this composition, the fibers 6 represent a mass fraction of between 2 and 30% of the material M which can be obtained at the end of the shaping step 64. To ensure a sufficient fiber content, a dosage can be carried out.

[0058] The fibers 6 can come from the same base material or correspond to a mixture of different fibers. The fibers 6 include filaments of natural and / or synthetic fiber. All or part of the fibers can undergo a treatment to separate impurities, for example to separate dust when it comes to fibers Plant-based. Straw, hemp, shavings / sawdust that can release cellulose fibers through defibering, flax, and horsehair are examples of fibers that can be used in the blend. Among plant fibers, coconut fibers, palm fibers, or similar fibers can be used. Glass fibers, cellophane, and textile fibers are also suitable.

[0059] It is understood that the density of the fibers taken before mixing can vary. The table below illustrates the fact that the density of the fibers 6 is typically less than 215 kg / m3, being below 130 kg / m3 in non-limiting examples.

[0060] [Tables 1] Fibre Brief description Measured density (kg / m3) cellulose wadding Insulation, possibly made from recycled newspapers (with antifungal and fire retardant additive) 37 Sawdust Local resource in the presence of forest (hardwoods such as oak and chestnut for example) 212 chopped straw Chopped cereal straw may be preferred 100 chopped flax Lengths greater than those in the case of straw can be obtained 87 fine hemp strand Very finely chopped hemp strand 156 Fine hemp shiv Granules of finely chopped hemp shiv. 115

[0061] The fibers can help to stabilize the mixture, before and after compaction, in particular by compensating for the phenomena of shrinkage of the clay during drying, which prevents cracking during drying. They also contribute to improving the tensile strength and the thermal insulation properties of the material M, while making it lighter (by reducing the density of the material M).

[0062] The fibers 6 represent a mass fraction of between 2 and 30% of the material M, with a preference for a proportion greater than 10%, in particular for the fa building blocks such as bricks, especially when no hydraulic binder is part of the composition of the material M. Preparation process(es)

[0063] Material M has a composition that limits or eliminates chemical additives. More generally, this material M makes it possible to produce prefabricated parts or blocks, which are industrializable components with a low energy cost, in the absence of cooking. When the material is prepared without the addition of a hydraulic binder, the material is more easily recyclable if the structure or construction that uses it must be destroyed: possibility of reversibility to recover the starting materials.

[0064] With reference to [Fig. 4], a given mass of sediment 5 (dredging sediment in certain preferred examples) and a predetermined quantity of fibers 6 can be introduced into a tank 8, for example dry. The fibers 6 may have undergone a step of defibering a raw material 6' when they are natural fibers. More broadly, the fibers 6 can be natural and / or synthetic, being introduced in bulk into the tank 8 or similar suitable container. They are for example dry at the start, at the time of dosing. The weight in fibers is chosen to represent a mass fraction which may be less than 40 or 50%, for example between 2 or 4% and 30% of the final material M.

[0065] In a method according to a first embodiment, the solid starting ingredients can be mixed when they are in the form of loose particles (substantially dry mixing). The sediments 5 recovered from the submerged zone(s), the fibers 6 which constitute all or part of these ingredients can be weighed during a first preliminary step 61 to allow a dosage of the respective quantities. Optionally, the water W can also be dosed. In such a method, provision is made for the addition of water W, for example by spraying a homogeneous solution containing the water W and possibly adjuvants 7, for example natural adjuvants. The spraying can be carried out before or during a mixing step 62 making it possible to obtain a moistened material M' which has the desired consistency and composition. In variants, all or part of the adjuvants 7 may be introduced in an addition step 62' carried out after formation of a mixture combining the sediments 5 and the fibers 6, or more broadly after a mixing step 62 (which may be a mixing step to homogenize the sediments 5 in a malleable composition).

[0066] Among the examples of adjuvants 7, mention may in particular be made of water-retaining components or agents, plasticizers or superplasticizers, in particular natural or of natural origin. More broadly, one or more adjuvants (including those mentioned above) may be used, including the following natural or naturally derived adjuvants: - lipid extracts, such as hard oils, black soap, linseed oil, or others oil-producing or non-oil-producing plants; - glues of plant or animal origin such as starch-based glues, glues based on flour, cellulose, methylcellulose, gums or plant saps, glues made from skin, bones or cartilage, etc.; - protein extracts such as casein or its derivatives; - tannins or tannin extracts; - fermented or non-fermented plant extracts such as fermented fibers, animal excrement, algae extracts, roots, etc. - wetting agents or surfactants, such as soap; - salts of metals or metalloids such as salts of iron, aluminum, boron, ammonium, etc. but also metal oxides. - chemical components of natural or synthetic origin, in particular acidic or basic agents, oxidation, reduction, polymerization, chelation, etc.

[0067] Whether or not one or more adjuvants are added, the process may consist of using all dry ingredients. In this case, sediments that have undergone drying must be chosen. Fibers may be added later. At least the sediments may be ground. Typically, the solid mixture (without fibers or with the fibers, preferably dried) may be ground to obtain a powder. The optimum moisture content for grinding the clay resource consisting of the dredged sediments may be determined beforehand. A moisture content of 15% or less (possibly 20% or less) may allow efficient grinding, using a crusher such as a jaw crusher, a wheel crusher, a hammer crusher, a knife crusher, or any other suitable type of crusher. This powder is then mixed dry in given proportions with fibers 6, for example natural fibers. Any natural additives are diluted with mixing water, dosed very precisely. This solution is added by spraying into the dry mixture of fibers 6 and sediment powder 5, set in motion under the action of a suitable mixer or agitator A, to obtain a compressible whole (compactable material MC). The agitator A may correspond to a double whisk mixer). Any other suitable device / agitator A may be suitable, whether it is a manually operated agitator, or a mechanical and / or automated agitator.

[0068] Using the stirrer A, stirring can be carried out for a suitable duration. The mixing step 62 (here with mechanical stirring) is for example carried out for at least 10 to 15 minutes, in order to form a mixture M' whose particles are moistened. These moistened particles can be free of dust.

[0069] In a method according to a second embodiment, a homogeneous slip is previously manufactured by mixing the sediments 5 in the form powder or aggregates, water and any additives. Then, the process provides for spraying this slip onto the fibers 6 which are dry or relatively dry fibers, during a mixing step - which can involve the tank 8 with the agitator A. This mixing step also leads to obtaining a compactable material, with the desired consistency.

[0070] There may be different possibilities for obtaining the slip: - by carrying out the crushing step 45, and incorporating the dredged sediments 5 into water or an aqueous mixture. This is permitted in particular when the sedimentary part has been dried or recovered in a dry state. Any suitable machine / equipment can then be used to carry out the mixing, if necessary manually. The equipment can be mechanized and / or automated (mixers, concrete mixers, etc.). - using a pile of dredged sediment in a wet state, first solubilizing the sediment 5 in mixing water, for example using a blade mixer. Concrete mixers, a planetary mixer arrangement, or any other suitable equipment may be suitable.

[0071] In embodiments, the type of mixture is semi-dry, allowing static, dynamic compression, vibro-compaction or any other suitable type of compaction. When the shaping method is based on static compression. It may also be possible to compress or mold materials from more plastic or viscous mixtures.

[0072] In some embodiments, the material exhibits significant ductility. A compressed block, for example by reducing the volume of compactable material MC by more than 20%, can be subjected to strong compression without rupture. In practice, tests show that the block collapses. Some materials obtained can, for example, be compressed to more than 50% of their initial height without rupture or apparent disorder. No rupture is observed before or during this collapse. This property is of interest for applications at the seismic level. Example(s) of compression

[0073] Static compression may be suitable for reducing the volume by moving from the compactable material MC to the material M which may constitute a finished construction material. When the thickness of the material M is significant, for example exceeding 4 or 5 cm, the mixture may optionally be deposited in successive layers of 4 to 5 cm (this depending on the filling height and possibly the composition retained / water content). The weight of each of these layers can be determined precisely in advance, by dividing the fresh mass of the compactable material MC by the number of layers made. To know the total fresh mass of the material, test compressions preliminary steps are carried out, in order to adjust the mass of material according to the desired final height.

[0074] The following steps can be performed: a) pouring of the compactable material MC into the mold 10 b) distribution of the compactable material MC homogeneously in the mold 10 ; c) tamping the material vertically, at the corners and edges; d) general dynamic compaction of this material: for example, a few impulses are given by means of a contact member or any other suitable tool on a cover or plate element applied in the mold on the compactable material MC; in doing so, the compaction can be distributed or adjusted to maintain a correct level (horizontality) on the surface of the material subjected to contact for compaction; e) if a subsequent layer is added, optional creation of a grip for the next layer, by staking the surface of the compacted layer using a suitable tool.

[0075] During these successive steps a) to e), the mold 10 can remain stable / maintained static. Once the mold 10 is filled with all of its layers of mixture, a cover or movable part 1 of the mold 10 is placed on the surface of the mixture. This movable part 1 fits perfectly with a complementary part of the mold 10 where the compactable material MC is received. The surface of the mixture is perfectly level at the time of placement of the movable part 1. The static compression can be carried out by means of a hydraulic cylinder which exerts pressure on the cover / movable part 1 ([Fig.5A]), for example in a continuous, progressive and regular manner, in order to constrain the material in the mold 10. The cylinder can be centered so as to exert its pressure exactly in the center of the cover / movable part.Alternatively, another type of actuator / drive member, or several cylinders (for example, a large surface plate to form the moving part 1) can be used.

[0076] In a configuration favorable to obtain a perfectly homogeneous material M, the compression apparatus is equipped with two jacks, in high and low position, or any other device allowing a double high and low compression. [Fig.5B] schematically illustrates an example of configuration with compression distributed on two opposite sides, with the use of two mobile parts 1, 2 capable of forming contact surfaces parallel to each other.

[0077] Whatever the mold and compression apparatus used, the shaping step can implement a compression which continues / is carried out until the water in the mixture constituting the compactable material MC begins to emerge, for example through a flow interface arranged at the level of a bottom of the mold 10. The flow may reflect the compacted state, a sign that all the material has been compacted within the mold 10. A measurement step can be carried out and / or a preliminary adjustment is made so that the compression force is optimally configured for the shaping step 64 resulting in obtaining the material M, without deformation after demolding.

[0078] When a suitable compression force has been predetermined, suitable for the type of compactable material MC (depending on the composition of the mixture), typically, this parameter can be reproduced for all copies of the same formulation. At least one preliminary test to determine the value of the fresh mass of mixture / compactable material to be shaped, for a given mold 10 (or a given cavity CIO) can also be used to determine the optimal compression force.

[0079] In an optional step, a production specification adjustment can be carried out (in a parameterization step 63) in order to parameterize the machine or apparatus provided with at least one mold cavity to manufacture blocks without firing, for example to form bricks, joists, similar construction components or panels. Each compression part can optionally be part of a covering part common to several CIO cavities of a mold 10, 10'. As in the non-limiting case of [Fig. 3], a mold 10 thus makes it possible to form several blocks, for example building bricks or similar modules, by having CIO cavities, possibly distributed in different rows (at least two rows) and possibly including a partitioning wall or structure 12 for internally partitioning the mold 10.

[0080] The shaping step 64 is carried out in a closed mold, typically having previously adjusted compression parameters, for example as mentioned above. Alternatively, the mixture M' obtained in the stirring step can simply be poured into one or more molding cavities associated with a compression part. The compression part(s) may not be controlled by a control unit and / or do not require a human-machine interface. In the latter case, the mechanical pressing of the mixture to obtain the compacted material M may correspond to simple static compression. In this case, the homogeneity of the mixture can be achieved before starting to shape it.

[0081] In options, the mixture forming the compactable material can be placed in a mold 10 in successive layers by an automated deposition member. For a block having a thickness of more than 15 cm, this sequential deposition allows spreading and compaction of the mixture / compactable material MC. Deposition by an automated member can increase the rate, if necessary by associating this member with a weighing system: The fresh mass value of the material to be taken in total for a mold cavity 10 can simply be divided by the number of layers made.

[0082] To obtain rigid blocks suitable for construction, the method may provide for the introduction of the treated raw materials, forming the compactable material MC, into the cavity(ies) CIO, which may be part, if appropriate, of a machine for manufacturing bricks, modules or blocks without firing for pressing. The pressing time of the block without firing may be adjusted (for example between 20 and 30 seconds), and the pressure may be adjusted, so as to obtain a building block 9, 109, 209, 309. The pressure may be high, in particular for obtaining bricks 9, while remaining, for example, less than 5 or 10 MPa.

[0083] The shaping may include a static or dynamic compression step. In the case of static compression, compaction is ensured by the relatively slow bringing together of two surfaces between which the compactable material MC is located, which is retained laterally. [Fig.5A] illustrates the case of a mold 10 with a single moving part 1, for example in the form of an upper plate carrying out the compression towards the bottom, in a single direction of compression, here along an axis X which may typically be vertical.

[0084] In the case of dynamic compression, compaction is obtained by pounding the mixture to be compacted / material MC in a mold and / or vibro-compaction may be provided. In either of these compression modes, provision may also be made to be able to move a movable bottom 2, for example in the form of a lower plate parallel to the plate forming the movable part 1, as for example shown in the non-limiting case of [Fig.5B]. Parts 1 and 2 move towards each other. Drying

[0085] Once the material has been demolded, it can be left to dry on a suitable device. Drying of materials can be done in several different ways: - Passive air drying, - Optimized passive drying in greenhouses, - Active drying in a dryer.

[0086] In all these cases, the material M is obtained without cooking, or even a temperature increase approaching 80 or 100°C. The process is thus energy-efficient. A forced ventilation step, carried out mechanically or optimized by natural convection, can be carried out during drying. In the case of active drying, the temperature, ambient humidity and the ventilation level can be precisely controlled, according to a determined drying program. Conventionally, an air temperature between 25 and 50°C coupled with sufficient ventilation allows efficient drying.

[0087] Drying can be carried out with the materials M, in the form of blocks, suspended or arranged so as to allow air flow along several surfaces of the material, for example by using grids, pallets, lattices.

[0088] In certain options, before or after drying, a mechanical finish can be carried out, for example in order to obtain a ready-to-use product. This mechanical finishing step can also be integrated into the shaping step 64, which uses a rigid mold for forming a compacted product. The movable cover part 1 can slide along an internal face of the mold. The geometry and dimensions of the internal face can vary depending on the application. This internal face can be formed in a side wall which extends longitudinally around a central axis X from a bottom portion of the mold 10.

[0089] The building block made of material M may have a thermal conductivity of less than 0.5, for example, for information purposes, between 0.10 and 0.30 W m-1 K-1. It may be obtained following a compression step, with a reduction not exceeding 50% in volume. Additionally or alternatively, the following relationship can be satisfied: 0.001 < k*L < 0.07 where k is the mass ratio (mass share) of sand in the total dry matter of material M, and L represents a thermal conductivity of material M in the building block.

[0090] By way of non-limiting example, a material M based on sediments 5 (for example, comprising more than 50%, typically more than 60% in the mass composition of the material) having a sand mass ratio of 0.04 and a thermal conductivity of 0.28 W m-1 K 1 has a coefficient k*L approximately equal to 0.011 (expressed in W m-1 K -1). The significant proportion of sediments from the underwater / immersed zone in the material can advantageously make it possible to obtain thermal insulation performance while satisfying robustness requirements for use in construction. This coefficient thus reflects a good compromise achieved by a material in accordance with the invention, at least for the case where a thermal insulation application is sought. Experimental tests

[0091] The two tables which follow show experimental results obtained after drying compositions, respectively obtained with and without fibers, by varying a mass ratio of sand in relation to the total sediments (which implies that an increase in the proportion of sand reflects a lower proportion of clay and silt). The sediments are dredged sediments, here recovered from the Rance and stored for 2 years. The same nature (with the same origin) of sediments is thus used for the purposes of these experimental examples. The case without added sand corresponds to a composition using these sediments which are quite poor in sand, with the majority of the sand grains having a submillimeter size and a stable rate (of the order of 7%) with a majority content of fine sands (for example less than 0.2 or 0.3 mm). The same type of sand is used to vary the proportion of sand upwards, with relatively fine sand of submillimeter size. In the first series as in the second series of tests, the same apparatus makes it possible to carry out a test of mechanical resistance to compression, for a dried composition resulting from a mixture and a controlled addition of water (addition of 450 g) to obtain a moldable texture.

[0092] Test specimens were then produced with the different compositions, by a dynamic compaction method in successive layers (typically 4 layers) with leveling, each in a mold of predefined dimensions. After demolding, each test specimen is identified by a pellet and dried by a predefined process, at a temperature of approximately 45°C. Drying is stopped when the mass variation no longer exceeds 1% between two weighings spaced by the same period.

[0093] The compressive strength test was carried out using a press with two plates, following the test protocol described by the NF XP13-901 test standard, at a speed of 2.5 mm / min. The Young's Modulus was calculated by software from the slope of the Stress / Strain curve in the elastic phase of the test. In the tests without fibers (carried out at an outside temperature of 10°C), the mass after drying of the specimens varies from 1.65 to 2.05 kg, taking into account the progressive addition of sand for tests 2 to 6. Table 2 (test table - without addition of fibers) shown below illustrates the values measured for the different specimens.

[0094] [Tables2] Test 1 2 3 4 5 6 Sand / sediment ratio (%) 0 5 10 15 20 25 Maximum compressive strength Rcmax (MPa) 2.73 3.64 2.95 2.53 2.65 2.69 Slump ratio at break (%) 2.1 2.4 2.3 2.3 2.2 2 Young's modulus (MPa) 311 407 267 241 259 231

[0095] In the absence of fibers, these results show a first trend according to which the compressive strength is not improved when the percentage of sand becomes too high (no improvement for the cases with 15, 20 or 25% of sand added). A significant effect of the sand appears, which to summarize: - is beneficial on compressive strength, when the overall rate of sand in the dry mass remains in the order of 7-17%, if we take into account the sand already present in the sediments used for these tests; - makes the structure more unstable when the added sand and the sand already present exceed 22-30% (with degradation of Young's modulus without any gain in compressive strength).

[0096] In the tests with the presence of fibers (carried out at an outside temperature of 10°C), a completely similar protocol is carried out, by mixing the fibers with the other solid components, before adding water. As for Table 2, the density of the test pieces is between 1280 and 1500 kg / m3. The difference in the series of tests is the addition of a test for the proportion of 2% added sand. The fibers are plant fibers not exceeding a length of 4 mm. The apparatus for the measurements remains the same as for Table 2. The values obtained for the different test pieces are reported in Table 3 (test table - with fibers).

[0097] [Tables3] Test 1 2 3 4 5 6 Sand / sediment ratio (%) 0 2 5 10 15 20 25 Max. compressive strength Rcmax (MPa) 4.05 3.37 3.59 3.72 3.15 2.94 2.78 Slump ratio at break (%) 3.8 3.7 3.1 3.9 4.2 4.6 4 Young's modulus (MPa) 215 172 225 177 156 136 157

[0098] A very significant contribution to mechanical resistance is observed linked to the addition of fibers in the mixture and without added sand (+ 50% comparing test 1 in table 2 and test 1 in table 3). This contribution decreases as the proportion of sand in the mixture increases. [Fig.7] illustrates the contribution of fibers and the impact of sand. As an indication, the density for the series of tests in table 3 using the same mold sizes and capacities is lowered with an average difference of 200 kg / m3, due to the presence of fibers.

[0099] At 5% sand, there is one exception: the addition of fibers (here at a rate of 5% - test 2) does not seem to have any impact on the mechanical performance of the material. We can just assume that at this specific percentage of added sand, a stiffness effect (with also a higher density than in tests 1 and 3) brought by the latter takes over, which would be consistent with the Young's modulus reported in Table 2 for test 2. For this case of sand dosage (without fibers), the sand would dictate the mechanical behavior of the material.

[0100] More broadly, it is found that the relatively low presence of sand can be beneficial but that a high proportion of the mass fraction in sand tends to reduce the mechanical resistance of the material M which also includes fibers. A composition making it possible to obtain a value greater than 3 Mpa for the maximum Compressive strength, in this type of test, can thus give full satisfaction in the field of construction. The fibers have a reinforcing effect which tends to disappear for an unbalanced composition because of the sand.

[0101] Of course, the precise values reflected by these tests may vary somewhat by changing the nature of the sediments, the given sand, and the nature of the fibers. However, there is a tendency to achieve a good compromise between lightness, certain thermal insulation properties, and mechanical strength, by advantageously limiting the sand fraction to less than 33-34% by weight in the total dry matter of the material M, and preferably by maintaining the mass fraction of sand below 34% of the total dry matter. A mass fraction of sand below 10 or 15% of dry matter may be even more preferred, in certain embodiments.

[0102] It is permissible to obtain building blocks having any of the compositions indicated above, with a proportion of fibers which may be greater than or equal to 2% by mass to allow varied uses. Blocks are however designed while avoiding the use of an unbalanced formulation which would present an excess of sand: a composition too rich in sand is likely to clearly counterbalance positive / advantageous effects provided by the fibers (see Figures 7 and 8). Example of material use - Formats

[0103] With reference to [Fig.6A], it is possible to obtain a parallelepiped block constituting a brick, therefore in the form of a solid block. By a simple adaptation of the mold, it is possible to produce both small format bricks and large format bricks, for example 40*20*10 cm. The use of a mold 10 makes it possible to obtain a block with two opposite flat faces and having a slice whose thickness is continuous. The density of such a block can vary, with a density for example less than 1500 kg / m3 and typically greater than or equal to 200 or 300 kg / m3.

[0104] Material M can therefore be used as a thermal insulator, in particular when it has a density of less than 800 kg / m3. More broadly, material M can be an insulator, a thermal corrector. In options where the density is high, it can help to form a thermal inertia mass or thermal sensor.

[0105] Rigid building blocks can be obtained by shaping, for example of the type using a mold or compression plate(s) system. As visible in [Fig.6A], the shaping can make it possible to obtain bricks 9 of compact format (for example 200*100*100 mm). Structural blocks 109 of thickness greater than or equal to 180 mm can also be produced, this thickness being a height in the laid state of the brick. One of these structural blocks 109, illustrated in [Fig.6B], is a Monomur type interlocking block. A central passage 110, or any other type of recess or reservation can be provided in this type of block.

[0106] Large format bricks, the length of which may be, for example, between three and five times greater than its thickness, can be produced using the compactable material MC. Self-supporting lightweight bricks which can be used for partitioning, lining or filling can be obtained, possibly by limiting the density of material M to less than 900 kg / m3.

[0107] More broadly, insulating or thermally correcting load-bearing or semi-load-bearing blocks, which make it possible to produce load-bearing or semi-load-bearing walls, or which can be used for filling and cladding post-and-beam frames (wood, concrete, steel, etc.) can be formed by essentially integrating the construction material, for example by being obtained directly by the shaping step with only the material MC. A simple apparatus, for example similar or identical to the molds 10, 10' of FIGS. 5A and 5B can allow compression to result in the construction material M.

[0108] Floor joists 309 or interjoist components can also be made with the construction material, as shown for example in [Fig.6D]. Modular blocks are thus made to compose, for example, floor joists, which can make it possible to make these parallel channels C3 in an assembled structure of the joist components made of the material M.

[0109] The shaping can use a mold having specific relief(s) or recess(es) or even partitions. The shaping can be used to manufacture formwork blocks, planks, as well as various accessory elements for a construction system based on masonry elements, glued, butted or nested.

[0110] The shaping can, directly or combined with an assembly step, make it possible to provide plates, panels usable for lining (possibly for lost formwork in the case of wall lining) or cladding, partitioning, or even to obtain false ceiling modules. By way of non-limiting example, the material forms all or part of panels which can be used in interior design, partitioning or wall lining, in the manner of a plasterboard. [Fig.6C] illustrates such a panel 209. The thickness e2 of the panel 209 can be greater than 10 or 20 mm, for example having a thickness of between 10 mm and 38 mm. In the production of thicker blocks or components, semi-lightweight panels can be obtained, for example with a thickness of between 38 and 160 mm.

[0111] A facing wall or partition, possibly structured to rest on a similar base or ground clearance, may be composed entirely or essentially of blocks of the building material M, such as bricks. These blocks may constitute an external structure (outside a building or forming the external wall of a building). A roofing element or assembly may cover such a structure to limit the risk of direct runoff onto the material M obtained without cooking, based on sediments 5. In decorative designs, such as an openwork claustra-type wall for example, it is understood that the blocks can be arranged in a staggered pattern or stacked in a suitable manner to form a vertical wall, possibly with openings. elongated. If necessary, a coating may be provided, optionally made from material M or material also having a composition based on submerged zone sediments (dredging sediments for example).

[0112] In certain uses, the material forms a structural bulk or even a coating or grout-type material. It can be produced in the form of grout, possibly mixable in situ (on the operating site) with a suitable binder or component to make it self-compacting. In certain uses, dredged sediments can thus be used for backfilling, taking advantage of their re-excavable nature (which facilitates maintenance).

[0113] In addition to certain advantages already mentioned, the use of marine, fluvial (or lake) dredged sediments corresponds to a natural resource that is easily available without impact on the environment: this makes it possible to recover at least in part dredging sludge or similar sediments currently considered as waste, while also limiting the need for new land to store this raw material. In addition, sediments of this type can simply undergo drying, without the need for a calcination step or similar treatment at a temperature exceeding 100°C. These sediments 5 make it possible to avoid digging or taking samples of natural resources with an irreversible impact on the landscape and the environment. The material M can be obtained without adding sand or a granulometric corrector.

[0114] The invention is in no way limited to the embodiments described and illustrated, which have been given only as examples. Thus, although blocks forming bricks or panels of generally parallelepiped shape have been presented, other shapes are permitted. For example, modules of cylindrical, hollow, or curved wall shape can be made with the construction material to form rigid construction blocks.

Claims

Claims

1. Construction material (M), comprising sediments (5) from a submerged area, for example of one or more kinds among marine sediments, river sediments, fluvial or lacustrine sediments, sediments (5) of which a first fraction of particles comprises clay (5a), a second fraction of particles less fine than in the first fraction consists of silt (5b) and a third fraction of particles less fine than in the second fraction consists of sand grains (5c) whose characteristic size does not exceed 2 mm, characterized in that the material (M) consists of a raw mixture, that is to say obtained without cooking, which includes: - said sediments (5); - water (W);and - fibers (6) including filaments of natural and / or synthetic fiber, the fibers (6) representing a mass fraction of between 2 and 30% of the material (M), and in that said third fraction represents less than 34% by weight of the total dry matter of the material (M).;

2. A building material according to claim 1, wherein the material (M) is porous and compacted, preferably being obtained by a mechanical process which includes compression.

3. A building material, shaped to form or form part of a rigid building block having two opposite faces and a side face corresponding to a slice defining a thickness of the block.

4. A building material according to any preceding claim, wherein the density of the material is less than or equal to 1500 kg / m3.

5. A building material according to any preceding claim, wherein the first fraction, the second fraction and the third fraction cumulatively form at least 50% of the total dry matter of the material (M).

6. A building material according to any preceding claim, wherein the fibers represent more than 2% or 20% of the weight of the material (M), knowing that the density of the material (M) is between 200 kg / m3 and 1500 kg / m3.

7. A building material according to any preceding claim, wherein the first fraction, the second fraction and the third fraction cumulatively form at least 70% of the total dry matter of the material (M), and in which the material is structural, preferably with: - fibers that represent less than 15% of the weight of the material (M), and - the density of the material that is between 900 kg / m3 and 1500 kg / m3.

8. A method of preparing a finished construction product (9; 109; 209; 309), comprising the steps essentially consisting of: - gathering three fractions of particles from sediments (5) from submerged zone(s), a first of the fractions comprising clay (5a), a second of the fractions comprising particles less fine than in the first fraction and consisting of silt (5b), and a third fraction of particles less fine than in the second fraction consisting of grains of sand (5c) whose characteristic size does not exceed 2 mm; - determining a quantity of fibers (6) corresponding to a flow rate or a weight of fibers to be mixed with the three fractions, said quantity being predetermined so as not to exceed a representative mass of the solid particles of the sediments (5) in the finished product, whereby a dose of fibers (6) can be obtained; - mixing together the dose of fibers (6) and the three fractions during a mixing step to obtain a compactable material (CM), using water and optionally at least one adjuvant; and - obtaining the finished product by shaping the compactable material, preferably by carrying out compaction and reducing the water content; the process allowing, by a selection of sediments possibly conditioned by or confirmed by an analysis step and / or a dosage to estimate a representative value of the share by weight of the third fraction in the sediments (5), to limit to less than 34% by weight the fraction or content of sand grains in the finished product.

9. Method according to claim 8, in which the shaping of the finished product (9; 109; 209; 309) is carried out without a cooking step, and in which a step of decomposition of aggregates containing the three fractions is carried out, before mixing with fibers (6), by: - grinding the aggregates, - and / or solubilization of the aggregates with the addition of water using a stirring device.

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