LU101093B1 - CARRIER-LIKE CONSTRUCTION MATERIAL COMPRISING COATED LINEN ANAS - Google Patents

Abstract

The present invention relates to a method of manufacturing a carrier concrete based on flax shives, said method having a phase of coating the flax shives comprising the following steps: incorporation into a shredder of linen in a aqueous mixture comprising at least one inorganic binder; a brewing inerting treatment of the flax shives and the aqueous mixture comprising the at least one inorganic binder for penetration of said aqueous mixture into the pores and channels of said flax shives; and curing the flax shives by drying to seal said pores and solidification of the flax shives to obtain coated flax shives.

Description

CARRIER-LIKE CONSTRUCTION MATERIAL COMPRISING COATED LINEN ANAS

Description

Technical field and prior art

The present invention relates to the field of building, and more particularly to the manufacture of a building material of concrete type based on flax aggregates (or flax shives). The object of the present invention relates more specifically to a concrete based on flax shives, said linseed, which is carrier and contains linseed granules coated with a mineral binder milk such as for example lime and / or cement, and optionally a surfactant and / or a plasticizer.

Concrete carrier, here includes a concrete for use in the construction of a masonry element such as for example the construction of a load-bearing wall. Such linseed concrete is called carrier because it has a compressive strength of between 3 and 7 MPa.

For the purposes of the present invention, the term "flax granules" or "flax shives" is intended to mean, throughout the following description, the by-products derived from the linseed scutching lines. The shives generally have a length of less than 250 mm and a density of between 75 and 105 kg / m3. These shives are most often the co-products of the scutching lines after the step of defibration of flax. The use of these flax shives in the manufacture of a concrete finds many advantageous applications in the construction industry, and particularly the construction industry and in particular the construction of new buildings.

Concrete is a composite building material that is conventionally manufactured from mineral aggregates (gravel greater than 1 cm) agglomerated with a powdery mineral binder (for example a cement, lime or calcium sulphate). .

The mortar is also a composite building material made from granules (chippings smaller than 1 cm) agglomerated with a powdery mineral binder similar to that of a concrete. Generally, whether a concrete or a mortar, the mineral binder is hydrated, in other words put in contact with water during a mixing process called "mixing" allowing agglomeration aggregates.

We speak of concrete (or mortar) based on hydraulic binders.

Conventional concrete manufacturing techniques are widely known from the state of the art.

However, we know that the building sector strongly affects the environment through the consumption of natural resources and energy.

These consumptions are accompanied by emissions of waste and pollutants acting on the global climate, local and internal.

In this context, it is preferable that buildings are energy efficient and use materials with low environmental and health impacts.

Thermal regulation is thus gradually reinforced in order to limit the energy needs of buildings; To this end, many labels have been created to promote technological innovation around these energy reductions.

Thus, the requirements of the various thermal regulations and the development of several labels, lead to the implementation of envelopes increasingly airtight and very efficient in terms of thermal insulation.

At the same time, incentives are proposed for biobased materials to make a significant contribution to the composition of building materials.

One of the objectives set at the end of the Grenelle is to reach 10% of biobased materials in the building, excluding timber, by 2020.

Among these biosourced materials, concretes incorporating plant particles such as hemp, flax or miscanthus concretes meet these challenges.

The valorization of agricultural productions for non-food purposes has therefore taken a new dimension in recent decades: a new era is opening up for plants thanks to advances in research in the field of building materials.

Concretes incorporating chenevots from the hemp plant have been known since the 1990s.

The chènevotte, rich in lignins, is the inner part of the textile hemp stalk.

The publication in 2007 of professional rules for the execution of hemp concrete works shows the maturity and structuring of this sector.

The latter is organized to provide hemp quantities sufficient for industrial use (approximately 350000 m3 / year).

Today, the applications of hemp concrete in the building are mainly limited to filling often associated with a wooden frame or non-load bearing elements, due to rather weak mechanical strengths.

The main qualities of hemp concrete are therefore based on their low environmental impact as well as their hygrothermal behavior limiting the energy needs of the building while ensuring a good level of comfort felt.

Hemp concrete presents qualities that explain the development of its manufacture and its use more and more widespread as a masonry element, especially in the construction or renovation of non-load bearing walls of type (non exhaustive list) : - External Thermal Insulation (ITE) on masonry walls or concrete support; Exterior Thermal Insulation (ITE) on pole / beam system; External Thermal Insulation (ITE) on wood frame;

Insulation by filling a post / beam system;

Insulation by filling a wood frame system;

Thermal insulation from the inside (IT1) on masonry walls or concrete support; Thermal insulation by the interior (ITI) on wooden frame;

Mixed External Thermal Insulation (ITE) on post / beam system and Insulation by filling a post / beam system; - Mixed External Thermal Insulation (ITE) on wood frame system and Insulation by filling of a wood frame system.

The flax shives, an agricultural co-product of flax, whose production is close to 1500000 m3 / year, are also of interest in concrete, given the performance levels that can be obtained.

These materials from flax have been the subject of much research in recent years.

Today, we know how to make non-load bearing concrete from flax aggregates.

We are talking about flax concrete.

Linen concretes are composite building materials in which the mineral aggregates traditionally used for the manufacture of conventional concrete are at least partially replaced by flax aggregates (or flax shives).

However, the manufacture of a flax concrete is largely dependent on the realization of a concrete having a fast drying, a low chemical reactivity with the environment, small dimensional variations as a function of hygrothermal variations.

The manufacture of a carrier linen concrete is therefore complex.

It is known that the various plant particles, if used in their natural forms, do not exhibit good behavior with hydraulic binders, in particular with Portland cement.

Sometimes the presence of certain constituents of the plant aggregates completely prevents the hydration reaction of the cement. It is a complex phenomenon in which the various constituents of the cement are subjected to different degrees, to the action of the sugars, tannins, phenols and hemicelluloses contained in the vegetable raw material. Indeed, several studies have reported the inhibitory effect of these compounds on the setting of cement.

We can cite for example the work of: MAGNIONT 2010, ESPINOZA 2009, PEYRATOUT 2007, DUPRE 2005, CEREZO 2005 and GOVIN 2004, etc.

The manufacture of a flax concrete, whether it is a carrier or a non-carrier, is largely dependent on the production of so-called stabilized linseed concretes, that is to say having, in addition to a low chemical reactivity with the environment , small dimensional variations as a function of the hygrothermal variations to which they are subjected.

A number of recurring hypotheses have been identified in the literature (FISCHER 1974, HACHEMI 1989, DUPRE 2005, CEREZO 2005, SEDAN 2007, etc.) in an attempt to explain this phenomenon of delay in setting.

Indeed, the majority of studies carried out on this topic have revealed that cement setting delays are linked: on the one hand, to the exchanges that can occur at the matrix / lignocellulosic granulate interface and to the hydrolysis and solubilization of certain compounds such as sugars, hemicelluloses and pectins caused by the strongly alkaline medium developed by hydration of the cement; and - on the other hand, to the decrease in the concentration of Ca 2+ ions during the setting phase of the cement which are fixed by the plant fibers (GOVIN 2004, SEDAN 2007, MAGNIONT 2010).

Today, although there is no real certainty about the different interactions between lignocellulosic aggregates and hydraulic matrices, we know that the mechanical characteristics of building materials can be improved by better interface quality ( interphase) between the hydraulic matrix and the fibers (FISCHER 1974, PIMIENTA et al 1994, GOVIN 2004, CEREZO 2005, SEDAN 2007, LAIDOUDI 2012, etc.). The fiber-matrix adhesion can be improved by modifying the topology of the surface of the plant particle.

Thus, various treatments make it possible to modify the surface of these agro-sourced aggregates and consequently make it possible to create a strong bond at the fiber-matrix interface.

Good adhesion to the interface in turn contributes to improving the charge transfer between the fibers and the matrix and consequently to the increase in mechanical properties.

Various treatments applied, either to the plant material, or to the cement matrix, have indeed been proposed in the literature: several surface modification techniques of natural fibers have been the subject of numerous citations in the bibliography (LEDHEM 2000, KHAZMA 2001, GOVIN2004, PEHANICHA 2004, LAZKO 2011, NOZAHIC 2011, LAIDOUDI 2012 and 2013, etc.).

Four classes of treatment that are listed in the bibliography are most often distinguished: physical treatments, chemical treatments, heat treatments and mixed treatments.

The physical treatments act in two distinct ways: o either by the prior swelling of the vegetable granulate, o or by coating the fiber.

In a 2001 KHAZMA publication entitled "Influence of Sucrose Addition on the Performance of a Lignocellulostic Composite with a Cementious Matrix", a coating of the fiber is disclosed by adding sucrose in large amounts in order to improve the setting time and increase the mechanical properties thereof.

The chemical treatments mainly consist of replacing the hydrophilic hydroxyl groups by hydrophobic groups (esterification).

Thermal treatments are mainly carried out on solid wood or wood aggregates (roasting, hydrolysis, etc.).

Finally, the mixed treatments consist for example in the combination of heat and chemical treatments.

The choice of treatment should be made by seeking the best possible improvement of the characteristics of the aggregate in terms of compatibility with the cement matrix and decrease in hydrophilicity.

This treatment must require a minimum of steps, be able to be done with the least possible energy consumption and represent a minimum economic and environmental cost.

The Applicant submits that the various treatments proposed so far are complex and hamper the development of the flax industry in the building sector.

Object and summary of the present invention

The present invention aims to improve the situation described above.

The present invention is more particularly intended to remedy the various disadvantages mentioned above by proposing a new treatment of flax shives which makes it possible to obtain a carrier flax concrete having particularly advantageous properties, both in terms of its thermal insulation capabilities. and acoustic only its ability to transmit water vapor, that of its dimensional stability vis-à-vis the hygrothermic variations of its environment.

The present invention relates, in a first aspect, to a method of manufacturing a carrier concrete based on flax shives.

According to the invention, the method has a phase of coating the flax shives comprising the following steps: an incorporation in a shredder of flax shives in an aqueous mixture comprising at least one inorganic binder; a brewing inerting treatment, for example for about 3 to 10 minutes, flax shives and the aqueous mixture comprising the at least one inorganic binder for penetration of the aqueous mixture into the pores and channels of flax shives (eg impregnation of flax shives with the mixture), and o curing of flax shives by drying for pore filling and solidification of flax shives to obtain coated flax shives. Inerting by stirring the aqueous mixture in the pores and channels of flax shives typically allows to make the anas hydrophobic so that they are inert to chemical reactions especially when setting the concrete. Here, the water dissolves the sugars contained in the shives. Its sugars then migrate towards the cement matrix and prevent its hydration. Clogging the pores and channels of flax shives then prevents the subsequent recovery of moisture.

As a result, the concrete made from the coated flax shives thus obtained has excellent dimensional stability properties with respect to hygrothermal variations.

This proposed mineralization therefore decreases the hydrophilic nature of flax and its water absorption capacity.

Advantageously, the incorporation step comprises adding to the kneader at least one adjuvant product.

Preferably, the at least one adjuvant product comprises a surfactant and / or a plasticizer. The incorporation of a surfactant into a cementitious matrix makes it possible to have a better dispersion of the components so as to avoid an agglomeration effect and thus a heterogeneity of the material. The incorporation of a plasticizer in a cementitious matrix makes it possible to have a better workability of the fresh concrete. This then makes it possible to avoid the gaps when filling the molds for molding the blocks.

The plasticizer also makes it possible to use less water for the hydration of the cement.

The surfactant and / or the plasticizer used to obtain the coated flax shives can be any surfactant and / or plasticizer known in the concrete industry to maintain the mixture with a certain plasticity and its homogeneity.

It is thus possible to use, inter alia, surfactants based on ethoxylated fatty alcohols and / or a plasticizer based on poly-naphthalenes or poly-melamines.

Advantageously, the surfactant and / or the plasticizer is used in dilute aqueous solution or in powder at the rate of about 0.5 to 3.5% by weight of surfactant and / or plasticizer relative to the weight of binder (s). ) used at a rate of approximately 50 to 150 liters of water per 1 m3 of shives.

This may vary according to the degree of humidity of the latter.

The Applicant observes that going beyond 3.5% would make the setting of the concrete impossible or make the concrete much too fluid.

These two adjuvants can also be mixed together in a proportion of about 0.5 to 3% by weight relative to the weight of binder (s) used (s).

Advantageously, the coating phase comprises prior to the incorporation step an initial mixing of at least one inorganic binder with water to obtain the aqueous mixture comprising the at least one inorganic binder.

Preferably, this initial stirring step is carried out very rapidly for about 150 to 200 seconds.

Optionally, the inorganic binder comprises lime and / or cement capable of forming after drying a hard shell around said shives of flax.

It is understood here that the cement used to coat the flax shives can be any cement of known type, forming after drying a hard shell around said shives.

Preferably, the inorganic binder used comprises a cement of CEM I (or Portland cement) type and / or of CEM IL type

Such CEM I cement which contains at least 95% of clinker K and at most 5% of secondary constituents is particularly suitable for reinforced concrete or prestressed concrete (high strength and quick release).

CEM II type cement (or composite Portland cement) has less clinker K than CEM type cement - it contains at least 65% clinker (K) and at most 35% other secondary constituents.

The main constituent of clinker (the tricalcium silicate) is delayed hydration when the cement comes into contact with the sugars contained in the shives. The use of CEM II limits the number of clinker - sugar reactions, which makes it possible to avoid a delay in setting. The use of such a cement is thus suitable in particular for reinforced concrete in general (cast on site or prefabricated) as well as for work requiring a moderate rise in temperature or for work requiring high initial strengths.

Preferably, the cement is implemented at a rate of up to 75 kilograms per 1 m3 of flax shives.

In the same way, the lime used to coat the flax shives can be any lime of known type (hydraulic lime, pre-formulated lime, specific mixture of the two) forming after drying a hard shell around the shives.

Preferably, the lime used has a density of the order of 500 - 900 kg / m3.

Preferably, the lime is implemented at a rate of up to 75 kilograms per 1 m3 of shives.

The Applicant observes that beyond the given limit of 75kg of binder for 1m3 of anas, the compressive strength performance no longer guarantee the carrier character of the concrete. The compromise between carrier and insulator is mainly by the amount of anas added to the mixture. It is found that the more one puts of anas, the more one is insulating but less concrete is carrier.

It is understood that the inorganic binder can also comprise a mixture of lime and cement (with a substantially equal proportion or not) implemented at a rate of about 20 to 75 kilograms per 1 m3 of shives.

In a particular embodiment, the step of curing the flax shives is performed under predetermined storage conditions for a given period.

Preferably, the cure period is at least 7 days.

Preferably, the storage conditions comprise an ambient storage temperature substantially equal to 20 ° C. ± 5 ° C. and / or a relative humidity of the air, or hygrometric degree, substantially equal to 60% ± 10%.

Preferably, the flax shives are stored protected from the weather.

The flax shives used are advantageously flax shives but can also be shives oleaginous linseed.

It will be understood here that the coated granules obtained after cleaning can be stored for later use, but they can also be used immediately for the manufacture of linseed concrete as such.

In this case, following the coating phase of flax shives, the method comprises a phase of obtaining the concrete comprising: a mixture of flax shives aggregates coated with a mineral filler that may contain: sand (for example in a particle size of between 0-10 and / or 0-8), and / or gravel (for example in a particle size of between 4 - 6.3 and / or 2 -6 and / or 3-6 and / or 4 - 6), and / or pozzolan (for example with a particle size between 4-7 and / or 0-4 and / or 0-7); an addition of pre-wetting water; an addition of at least one binder and mixing water; and molding followed by drying.

In a preferred embodiment of the invention, the flax concrete is obtained by adding sand, gravel and / or pozzolan to 1 m 3 of coated flax shives to a total weight of between 625 and 3100 kilograms, then adding a pre-wetting water corresponding to up to 3/4 of the total water of the mixture during mixing, 250 to 1450 kilograms of binders (lime and / or cement) and 0.5 to 3.5% by weight. mass of plasticizing adjuvant with respect to the mass of binders.

The mixture is then mixed with the rest of the water and then molded and dried.

In this embodiment, the resulting linseed concrete has a density of between 800 and 1700 kg / m3, good thermal insulation qualities. It also has good qualities of acoustic insulation and transmission with water vapor.

According to a second aspect, the present invention relates to a carrier concrete based on flax shives that can be obtained by the manufacturing method such as that described above.

It should be noted here that the coating technique of the linseed granules according to the invention makes it possible to considerably reduce the water absorption of flax shives from approximately 300 -350% initially to 150 - 250%, to increase the resistances. mechanical values of 0.2 - 0.5 MPa at 4 - 6 MPa.

This technique also makes it possible to reduce the dimensional variations of the thus obtained flax concrete, which are of the order of 1.5 to 2.5 mm / m instead of 5 to 8 mm / m without coating treatment.

Linen concrete obtained here in the context of the invention thus has, compared to conventional concretes, qualities of lightness, thermal insulation and acoustic insulation, and permeability to water vapor which, together with the advantage to allow the valorization of co-products of flax, explain the development of its manufacture and its use as element of masonry, in particular the construction of bearing walls.

Detailed description of different examples of implementations of the invention

The following examples are provided by way of a simple illustration of the invention, with respect to which they have no limiting character.

Example 1: Manufacture of Concrete Containing a Binder Granule Coated with Binder (Lime Milk and Cement) and Surfactant A) Manufacture of Coated Granulate

In a kneader of the known type, 50 kilograms of lime, 25 kilograms of cement were poured on which 70 liters of water were poured, supplemented with 3 kilograms of surfactant.

We stir for 180 seconds and then add 1 m3 of shives.

Stir for another 5 minutes then add water depending on the moisture of the flax shives until a perfectly homogeneous mixture.

It is allowed to dry for at least 7 days under specific conditions and the resulting coated granulate is stored for further use. B) Concrete manufacturing

1 m3 of coated granulate obtained in the preceding step is introduced into a kneader, to which is added a mixture of mineral filler: sand of particle size 0-8, gravel with a grain size of 4 - 6.3 and pozzolan of particle size 4 - 7, to a total weight of 450 to 700 kilograms.

A first quantity of pre-wetting water is then poured while maintaining the mixing until a homogeneous mixture is obtained.

250 to 1450 kilograms of lime and cement are added, with 0.5 to 3.5% by weight of plasticizer binder added to the binder (s). The mixture is then mixed with water and then molded and dried.

A linen concrete is obtained whose density is between 800 and 1700 kg / m3.

Example 2: Manufacture of Concrete Containing a Binder Granule Coated with Binder (Lime Milk and Cement) and Surfactant and Plasticizer A) Manufacture of Coated Granulate

In a kneader of the known type, 50 kilograms of lime, 25 kilograms of cement were poured onto which 70 liters of water were added with 1.5 kilograms of surfactant and 1.5 kilograms of plasticizer.

We stir for 180 seconds and then add 1 m3 of shives.

Stir for another 5 minutes then add water depending on the moisture of the flax shives, until a non pasty mixture.

It is allowed to dry for at least 7 days under specific conditions and the resulting coated granulate is stored for further use. B) Concrete manufacturing

1 m3 of coated granulate obtained in the preceding step is introduced into a kneader, to which is added a mixture of mineral filler: sand of particle size 0-8, gravel with a grain size of 4 - 6.3 and pozzolan of 4-7 mm. up to a total weight of 450 to 700 kilograms.

A first quantity of pre-wetting water is then poured while maintaining the mixing until a homogeneous mixture is obtained. 250 to 1450 kilograms of lime and cement are added, with 0.5 to 3.5% by weight of plasticizer binder added to the binder (s).

The mixture is then mixed with water and then molded and dried.

A linen concrete is obtained whose density is between 800 and 1700 kg / m3.

Example 3: Manufacture of concrete containing a binder granulate coated with binder (milk of lime and cement) A) Manufacture of coated granulate

In a kneader of the known type, 50 kilograms of lime, 25 kilograms of cement are poured on which 70 liters of water are poured.

We stir for 180 seconds and then add 1 m3 of shives.

Stir for another 5 minutes and then add water according to the moisture of the flax shives, until a perfectly homogeneous mixture.

It is allowed to dry for at least 7 days under specific conditions and the resulting coated granulate is stored for further use. B) Concrete manufacturing

1 m3 of coated granulate obtained in the preceding step, to which is added a mixture of mineral filler: sand of particle size 0-8, gravel of particle size 4 - 6.3 and pozzolane of particle size 4 are introduced into a kneader. 7, to a total weight of 450 to 700 kilograms.

A first quantity of prewetting water is then poured while maintaining the mixing until a perfectly homogeneous mixture is obtained. 250 to 1450 kilograms of lime and cement are added. The mixture is then mixed with water and then molded and dried.

A linen concrete is obtained whose density is between 800 and 1700 kg / m3.

Thus, the present invention relates to a linen concrete which is characterized in that it contains linseed granules coated with a milk of lime and / or cement optionally supplemented with a surfactant and / or plasticizer.

The coated linseed granulate used in the manufacture of prefabricated carrier concrete according to the invention is obtained by the following succession of operations carried out in a kneader: a) brewing of the binder (s) (milk lime and / or cement) with water added with an adjuvant product (surfactant and / or plasticizer); (b) Addition of flax shives and brewing; c) cures of flax shives coated for at least 7 days under specific conditions. The impregnation of the flax shives by the mixture of binder (s) and possibly adjuvants leads to the filling of the pores of flax shives, the mixture penetrating the pores and channels of the flax before solidifying, as this could be demonstrated by microscopic observations.

In the various examples above, the linseed concretes obtained have shown good performances as regards their dimensional stability, excellent qualities of sound insulation, thermal insulation, lightness, ability to transmit water vapor as well as good industrial machining ability, especially sawing and cutting.

The low density of flax concrete facilitates its implementation by the technical operators.

In addition, thanks to its interesting thermal properties, the implementation of this type of concrete can reduce or in some cases to do without additional thermal insulation. This additional function compared to other products in the same areas of application can generate savings of building materials throughout the project.

It should be observed that this detailed description relates to a particular embodiment of the present invention, but in no case this description is of any nature limiting to the subject of the invention; on the contrary, its purpose is to remove any imprecision or misinterpretation of the claims that follow.

It should also be observed that the reference signs in parentheses in the following claims are in no way limiting in nature; these signs are only intended to improve the intelligibility and understanding of the claims that follow as well as the scope of the protection sought.

Claims (19)

1. A method of manufacturing a carrier concrete based on flax shives, said method having a phase of coating the flax shives comprising the following steps: an incorporation in a shredder of linen shives in an aqueous mixture comprising at least one inorganic binder; an inerting treatment by mixing the flax shives and the aqueous mixture comprising the at least one inorganic binder for penetration of said aqueous mixture into the pores and channels of said flax shives; o a curing of flax shives by drying for a closure of said pores and solidification of flax shives to obtain coated flax shives. The method of claim 1 wherein the step of incorporating comprises adding to the kneader at least one adjuvant product. 3. The method of claim 2, wherein said at least one adjuvant product comprises a surfactant and / or a plasticizer. 4. The process according to claim 3, wherein said at least one adjuvant product comprises a surfactant based on ethoxylated fatty alcohols. 5. The method of claim 3 or 4, wherein said at least one adjuvant product comprises a plasticizer based on poly-naphthalenes or poly-melamines. 6. Process according to any one of claims 3 to 5, wherein the surfactant and / or the plasticizer is used in dilute aqueous solution or in powder at a rate of about 0.5 to 3.5% by weight of surfactant and / or plasticizer relative to the weight of binders used and at a rate of 50 to 150 liters of water per 1 m3 of shives. 7. Method according to any one of the preceding claims, wherein the coating phase comprises prior to the incorporation step an initial mixing of at least one inorganic binder with water to obtain said aqueous mixture comprising said at least one mineral binder. 8. The method of claim 7, wherein the initial mixing of at least one inorganic binder with water is carried out for 150 to 200 seconds. 9. Method according to any one of the preceding claims, wherein the stirring of flax shives and the aqueous mixture comprising the at least one inorganic binder is carried out for 3 to 10 minutes. 10. Method according to any one of the preceding claims, wherein the inorganic binder comprises lime and / or cement capable of forming after drying a hard shell around said shives. 11. The method of claim 10, wherein the inorganic binder comprises a cement type CEM I and / or type CEM II. 12. A method according to any one of the preceding claims, wherein the inorganic binder is implemented up to75 kilograms per 1 m3 of shives. 13. The method of claim 11 wherein the inorganic binder comprises a mixture of lime and cement implemented at a rate of 20 to 75 kilograms per 1 m3 of shives. 14. Method according to any one of the preceding claims, wherein the step of curing said shives is performed under predetermined storage conditions for a given period. 15. The method of claim 14, wherein the cure period is at least 7 days. 16. The method of claim 14 or 15, wherein the storage conditions comprise an ambient storage temperature equal to 20 ° C ± 5 ° C and / or a relative humidity of the air, or hygrometric degree, equal to 60%. ± 10%. 17. Method according to any one of the preceding claims, wherein the flax shives used are flax shives or oleaginous. 18. Process according to any one of the preceding claims, in which, following the coating phase of flax shives, the process comprises a phase for obtaining the load-bearing concrete comprising: a mixture of granules of flax shives coated with a mineral filler which may contain: sand, and / or gravel, and / or pozzolan; an addition of pre-wetting water; an addition of at least one binder and mixing water; and molding followed by drying. 19. A carrier concrete based on flax shives obtainable by a manufacturing method according to any one of claims 1 to 18.