EP2543788A1 - Modular construction elements - Google Patents

Abstract

The component has a rigid front wall (12) and a rigid rear wall (14) that are maintained at a distance from each other. A cavity (24) is allowed to extend between the two walls, and an insulating material of plant origin i.e. cereal straw, is housed inside the cavity. The rigid front wall and the rigid rear wall are made of composite materials made of a mixture of aggregates and plant-based binder compounds derived from living organisms. The binder compounds include organic acid, acetic acid, or hydraulic lime.

Description

The present invention relates to modular building elements incorporating materials of plant origin to achieve particular buildings for housing.

The use of plant-based materials in residential buildings has been known since the beginning of time. The mud, for example, a mixture of clay and vegetable fibers makes it possible to bond stones together to raise walls or to form the floor of a half-timbered construction.

Since a recent time, it has been imagined to build dwellings using residues of plant materials, whose destination was quite different but whose properties and conditioning are appropriate. It is for example straw of wheat or barley packaged in parallelepiped bales of about ten kilograms. These bales of straw are relatively compact but nevertheless trap a lot of air which is an asset for the thermal insulation. Thus, between vertical uprights, straw bales are mounted on each other to make panels. These panels are then covered with a coating to seal them. These straw bales are made of relatively long straw strands, pressed and tied into standard presses. Also, the straw bales have an adjustable length of about 90 cm, and a constant section; their width is about 50 cm and their thickness is 36 cm. Also, they are installed horizontally flanks against flanks between vertical uprights and offset by half a length to each layer. In this way, the thickness of the panel thus produced corresponds to the thickness of the straw bales plus the thickness of plaster.

Always using the same material, the straw, packaged in the same form, it was imagined to prefabricate the panels so as to come and assemble them to form buildings. We can refer in particular to the document W02009 / 106793 which describes a method of manufacturing such panels. According to this document, we first realize a frame inside which we install straw bales parallelepiped of so as to completely fill the inner space of the frame, and then pushes, in a plane substantially parallel to the middle plane of the frame, rods through the bales of straw to hold them in place and stiffen the assembly. Then we cover the two opposite faces of the panel to seal it in particular.

Thus, the thickness of the panels is conditioned by the thickness of the bales of straw. This standard thickness is due to existing presses to make these bales. Moreover, this thickness must be minimal to allow easy handling and to maintain their parallelepiped shape.

Also, a problem that arises and that aims to solve the present invention is to provide a modular building element whose thicknesses can be adjusted freely and whose thermal properties are improved.

For this purpose, the present invention provides a modular building element comprising two rigid walls held at a distance from one another and a cavity extending between said two walls, said modular building element comprising an insulating material of origin plant housed inside said cavity. According to the invention, said rigid walls are made of a composite material made of a mixture of plant aggregates and binder based on compounds derived from living organisms.

Thus, a feature of the invention lies in the implementation of rigid walls including plant aggregates and thus having mechanical and, in particular, thermal properties. Indeed, thanks to the plant aggregates, air is trapped in the rigid walls, which allows to lower their thermal conductivity, and thus to improve the thermal resistance of the building element. In addition, these rigid walls are made at an advantageous cost with binders and inexpensive aggregates.

These walls can be kept apart from each other at a predetermined distance. In addition, said insulating material of plant origin is advantageously a mixture of free particles. In this way, the cavity between the two walls can be filled with the mixture of free particles without thickness constraint. In this way, a sandwich construction element having two walls made of vegetable aggregates and a binder is obtained. to make them rigid, the binder being derived from living organisms, and the walls being kept at a distance from each other to receive in the cavity which separates them the insulating material of vegetable origin. Therefore, the thickness of the modular building elements can be adjusted by adjusting the thickness of the walls themselves and the distance between them.

According to a first variant embodiment of the invention, said insulating material of plant origin comprises a mixture of free particles. In this way, since the two walls are held in a fixed position at a distance from one another, the insulating material is poured loose between the two walls so as to extend entirely throughout the cavity.

Preferentially, said insulating material of vegetable origin comprises stalks and cereal leaves; more precisely straw. These rods and cereal leaves have the advantage of being obtained at a very advantageous cost, and moreover they allow to imprison large amounts of air. Thanks to this trapped air, the thermal insulation capabilities are particularly increased. It will also be observed that the imprisonment of an air space between two rigid walls makes it possible to better attenuate the transmission of acoustic waves.

According to a second variant embodiment of the invention, said stems and cereal leaves consist essentially of long strands. In addition, they are entangled so as to form a relatively homogeneous carpet. It will be observed that such a carpet can be obtained directly from straw packaged in round bales using a type of press: "round-baller". These round boots are then unwound to form said carpet. This homogeneous carpet can then be advantageously held in a vice between the two rigid walls without the need to form a sealed box.

As will be explained in more detail in the following description, the binder is advantageously based on protein compounds, for example casein or hemoglobin. Hemoglobin for example is also obtained at an advantageous cost from slaughterhouses where the animals' blood is collected. When the protein compounds are used in dehydrated form, water is obviously added to form a homogeneous binder in the form of a paste.

Preferentially, an organic acid is added to the protein-based binder, for example acetic acid, which makes it possible to coagulate these proteins, which finally become encrusted. The plant aggregates are then entangled in the bulk proteins, and drying all hardens.

In addition, said binder preferably comprises hydraulic lime, in particular when casein is used, and which has the advantage of hardening in the presence of water, and hence of improving the rigidity of the walls after they have been dried.

Advantageously, said plant aggregates comprise stems and short strand cereal leaves. In this way the mechanical strength of the walls is then greatly improved in compression. Moreover, the building elements according to the invention work essentially in compression to support their own weight. They are in this self-supporting, and require no additional reinforcing element.

According to a particularly advantageous embodiment, said two rigid walls have edges, and said edges are interconnected by peripheral walls to close said cavity. In this way, and especially when the insulating material of vegetable origin is in the form of short strands, it is easy to pour it inside the cavity without loss.

In addition, the construction element according to the invention further comprises spacers to keep said two walls at a distance from each other. This also makes it possible to stiffen the construction element.

The building elements of the aforementioned type are obviously made in series so as to standardize production and thus reduce costs. Of course, buildings for housing or for any other use are mounted by means of a plurality of building elements of the aforementioned type.

• la Figure 1 est une vue en élévation de face d'un élément modulaire selon un premier mode de mise en ouvre de l'invention;
• la Figure 2 est une vue de côté de l'élément modulaire représenté sur la figure 1 ;
• la Figure 3 est une vue schématique en coupe droite horizontale de l'élément modulaire représenté sur la figure 1 ; et,
• la Figure 4 est une vue schématique en perspective d'un élément modulaire selon un second mode de mise en oeuvre.

Other features and advantages of the invention will become apparent on reading the following description of particular embodiments of the invention, given by way of indication but not limitation, with reference to the accompanying drawings in which:

• the Figure 1 is a front elevational view of a modular element according to a first embodiment of the invention;
• the Figure 2 is a side view of the modular element shown on the figure 1 ;
• the Figure 3 is a schematic view in horizontal cross-section of the modular element represented on the figure 1 ; and,
• the Figure 4 is a schematic perspective view of a modular element according to a second mode of implementation.

The Figures 1 and 2 illustrate a modular building element 10 according to a first embodiment of the invention, the first having its front wall 12, the second, its front walls 12 and rear 14. In addition, on the figure 2 , are also shown peripheral walls, an upper wall 16 opposite a lower wall 18 and a first lateral 20. On the figure 3 the second side wall 22 opposite the first one 20 there is the front wall 12 opposite the rear wall 14.

The two walls, front 12 and rear 14 are kept at a distance from each other and they define between the two, a cavity 24 closed by the walls, lower 18, upper 16, and lateral 20, 22 so as to form a waterproof case.

As will be explained below, the cavity 24 is filled with insulating materials of plant origin, while the front walls 12, rear 14 and side walls 20, 22 are made of a composite material made of a mixture of aggregates. plant and binder based compounds from living organisms and preferably protein compounds.

As regards the plant aggregates, they allow both to trap air, which is advantageous for thermal insulation. Cereal straw is a beneficial vegetable granulate because it is a by-product of cereal crops and is therefore available at an advantageous cost in the form of long or short strands. The same applies to the products of defibration of flax or hemp, beet pulp collected in sweets, miscanthus or any other lignocellulosic product. The residues of logging or wood are also advantageously used as aggregates.

In order to produce the composite material, the plant aggregates of the aforementioned type are firstly milled inside a knife mill, for example. This grinding makes it possible to give them a particle size having a size whose distribution is comprised, for example, between 2 mm and 10 mm.

Then, these plant aggregates are mixed with a binder in mass proportions included, for example, between one for one and one for two. Examples of suitable binders are given below. The mixture is then kneaded to be homogenized. Under certain circumstances, the mixture is heated, for example at temperatures between 70 ° and 90 ° C, so as to promote chemical reactions where appropriate. In addition, heating reduces the viscosity of the mixture and therefore accelerates homogenization. This heating is for example carried out by means of microwaves.

The homogeneous mixture is then poured into wall-shaped molds which it is desired to obtain, and the molds are held at 50 ° C. for 24 hours, under which demolding takes place. The molds, for example consist of flat bottom rectangular tray 250 cm long and 120 cm wide and they are closed by means of a plate of the same size which is embedded in the rectangular tray. The demolded parts are then stored in a ventilated enclosure at a temperature for example between 30 ° and 70 ° C.

With regard to the binder based on compounds from living organisms, some examples will be given below.

A first example of a binder is made from milk protein substances and more particularly from casein. Also, casein is mixed with hydraulic lime in varying proportions. The proportion of hydraulic lime is preferably less than 50% of the mixture by weight. Preferably, the ratio by weight casein / hydraulic lime is close to 80/20. Acetic acid in the form of alcohol vinegar is then added to this first mixture in proportions close to twice the dry matter of said first mixture.

A second example of a binder is made from dehydrated hemoglobin to which water and acetic acid are added. We will observe that hemoglobin from animal blood can be obtained at a very advantageous cost from slaughterhouses.

We will now give examples of mixing leading to the production of composite materials for forming the rigid walls of the modular building element according to the invention.

Example 1

The first binder mentioned above, based on casein, is mixed with ground wheat straw whose calibrated strands measure about 2 mm. This calibration is obtained by sieving the straw after grinding. The mass proportion of binder relative to the straw is three to two. The mixture is homogenized and heated by means of microwaves. It is then poured into a mold according to the aforementioned procedure.

The composite then obtained has an apparent density of 430 kg / m ³ , while its elastic modulus of elasticity, determined by sonic auscultation is 1.25 GPa. The compressive and flexural strengths of the composite are 5.08 and 3.8 MPa, respectively. As for the thermal conductivity, it is 0.12 W / m / K. This gives a rigid composite having a high mechanical strength coupled with a low thermal conductivity.

Example 2

The same first binder is mixed with milled and sieved wheat straw whose average length of strands is here 10 mm. The proportions of the mixture by weight are identical. The composite material then obtained has a bulk density of 388 kg / m ³ and a dynamic modulus of elasticity of 0.7 GPa. The mechanical strengths at compression and bending are respectively 2.78 MPa and 2.5 MPa. With regard to thermal and thermodynamic characteristics, the thermal conductivity is 0.10 W / m / K.

Example 3

The same first binder is here mixed with wheat straw having strands of different lengths and more precisely the two lengths of the straw used in the previous examples. Thus, wheat straw has, by weight, 50% straw with short strands of 2 mm and 50% straw with strands 10 mm long. The binder and the straw are mixed in proportions similar to the previous examples of three for two. The apparent density of the composite thus obtained is then 415 kg / m ³ and the modulus of elasticity of 1.1 GPa. The mechanical compressive and tensile strengths are respectively 3.7 MPa and 3.1 MPa. The thermal conductivity is 0.11 W / m / K.

Example 4

Compared to the previous examples, the wheat straw is here replaced by flax tows crushed and calibrated by sieving to 2 mm. The proportions of binder and tow are similar to the previous examples. The apparent density is 602 kg / m ³ and the compressive strength and tensile strength are close to 6.15 MPa. The coefficient of thermal conductivity is 0.19 W / m / K.

Example 5

In this example, the straw is replaced by crushed flax shives calibrated by sieving to 2 mm. They are mixed in proportions similar to the previous examples to the same first binder. After pouring into the mold, the mixture is pressed by means of a hydraulic press with a pressure close to 1 bar. A bulk density material of 590 kg / m ^{3 is} then obtained. The mechanical flexural and compressive strengths are respectively 10.5 MPa and 7.5 MPa, while in tensile strength is 3 MPa. The flexural, tensile and compressive moduli are respectively 1480 MPa, 1725 MPa and 128 MPa. In addition, the deformations at break are 0.18% in tension and 15% in compression, while the coefficient of fish is close to 0.4. In view of these detailed mechanical characteristics, it can be seen that the composite material thus obtained is more rigid than for the preceding examples, in particular by applying a pressure during molding. With regard to the thermodynamic properties, the thermal conductivity of the composite obtained is 0.15 W / m / K.

Whatever the composite material, rigid walls are obtained, whose dimensions can be with a suitable choice of mold, 1.20 m by 2.50 m for a thickness of 7.5 cm. Given the mechanical properties composite material, these walls are rigid and they can be adjusted facing each other to provide a cavity between the two.

The choice of this or that composite is conditioned by the height and width of the rigid walls necessary for the realization of the modular building element. Indeed, the larger the desired wall, and the higher the mechanical strength of the composite material must be high to withstand especially the bending. In contrast, thermal conductivity is an inverse function of thermal resistance. Also, to achieve building elements forming good thermal insulators, it is necessary to favor composite materials having the lowest coefficient of thermal conductivity possible.

Using the modular building element presented on the Figures 1 to 3 the front 12 and rear 14 walls have the aforesaid dimensions of 1.20 m by 2.50 m and a thickness of 7.5 cm each and are kept spaced from each other by a distance D of 25 mm. cm through the side walls 20, 22, lower 18 and upper 16. The walls 12, 14, 16, 18, 20, 22 are held together by gluing and / or by metal fasteners.

The cavity 24 and then filled here with milled wheat straw whose strands have a length of substantially between 1 mm and 10 mm, and which is introduced in bulk. The thermal conductivity of the milled straw is here 0.06 W / m / K, and the modular construction element shown in FIGS. Figures 1 to 3 at a thermal resistance of 5.6 K / W.

According to another embodiment of the invention, the insulating material of plant origin intended to be housed inside the cavity is relatively homogeneous and bonded so that it can be maintained between the two rigid walls without the need for a side wall. restraint.

To do this, we use long-stranded straws entangled with each other and forming carpet.

On the Figure 4 , where the references of elements similar to those of the previous figures are identical and assigned a sign "'" there is illustrated a building element 10' having a front wall 12 'and a rear wall 14'. These walls are obviously obtained in accordance with one of the examples above. Between the two walls 12 ', 14' extends a carpet 30 made of straw with entangled long strands. Unlike the previous embodiment, the construction element 10 'has no side walls and the straw mat 30 is flush with the edges of the walls 12', 14 '. In this way, the building elements of 10 'can be adjusted edge to edge while the straw mats are against each other and provide continuity between the walls. Furthermore, a longitudinal groove not shown here is formed in the edges of the building elements to be able to insert a seal which then protrudes from said edges. Also, when the construction elements are fitted edge to edge, the seals respectively bear against the opposite edge, which makes the seal tight.

These carpets are obtained directly from straw packaged in round boots. These round boots are made in the open field, after threshing cereals, using a press of the type: "round-baller" with which one picks the straw extended in Andean on the ground. These round boots are then recovered and stored for transport to the place of production of the building elements. They are then unwound to form the carpets. The carpets are homogeneous because during pressing, the collection means and needles can entangle the strands of straw.

Also, the carpet is held in a vice between the two rigid walls by means of screwed connections for example.

Claims (11)

Modular building element (10; 10 ') comprising two rigid walls (12, 14; 12', 14 ') held at a distance from one another and a cavity (24) extending between said two walls, said modular building element (10; 10 ') comprising an insulating material of plant origin housed inside said cavity;
characterized in that said rigid walls (12, 14; 12 ', 14') are made of a composite material made of a mixture of plant aggregates and binder based on compounds derived from living organisms. Construction element according to claim 1, characterized in that said insulating material of plant origin comprises a mixture of free particles. Construction element according to claim 1 or 2, characterized in that said insulating material of vegetable origin comprises stalks and cereal leaves. Construction element according to claim 3, characterized in that said rods and cereal leaves consist essentially of long strands. Construction element according to any one of claims 1 to 4, characterized in that said compounds derived from living organisms comprise protein compounds. Construction element according to any one of claims 1 to 5, characterized in that said binder comprises an organic acid. Construction element according to claim 6, characterized in that said binder comprises acetic acid. Construction element according to any one of claims 1 to 7, characterized in that said binder comprises hydraulic lime. Construction element according to any one of claims 1 to 8, characterized in that said plant aggregates comprise stems and short strand cereal leaves. Construction element according to one of Claims 1 to 9, characterized in that the said two rigid walls (12, 14) have borders, and in that said borders are interconnected by peripheral walls (20, 22) for closing said cavity. Construction element according to any one of claims 1 to 10, characterized in that it further comprises spacers for keeping said two walls at a distance from each other.

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