Supporting and insulating large-sized hempcrete block for the construction of buildings

Abstract

The invention relates to a hempcrete block (1) comprising an aggregate (G) formed from hemp hurd, water (E) and a quick-setting binder (L), characterized in that the ratio of binder (L) to aggregate (G) by weight is between 2.12 and 2.17, and in that the ratio of water (E) to binder (L) by weight is between 0.85 and 0.88.

Description

[0001] DESCRIPTION

[0002] Large-sized load-bearing and insulating hempcrete blocks for construction projects

[0003] The invention relates to the field of construction materials and is concerned, more particularly, with a large load-bearing and insulating block made of hempcrete intended for architecture for the design and construction of so-called "passive" buildings.

[0004] Currently, hempcrete blocks intended for construction are either small in size and intended mainly for wall insulation, from the outside or from the inside, or of equivalent size to a brick or a cinder block and intended to participate in the load-bearing structure of vertical walls but with restrictions of use to the field of individual houses, or buildings of modest size.

[0005] However, it turns out that existing prefabricated hempcrete elements have very low mechanical resistance to compression (less than or equal to 0.22 MPa), which severely restricts their use as structural elements for the construction of works.

[0006] Due to its excellent thermal conductivity, hemp straw (known as "shives") is already used as aggregate in hempcrete, whether for the industrial production of prefabricated elements or for direct application on construction sites using formwork or spraying. However, this application is only advantageous if the proportion of hemp shives is very high in the mix. The higher the proportion, the less mechanically resistant the hempcrete becomes, and it cannot then be used as a load-bearing element.

[0007] In the construction field, building structures using large, solid stone blocks has long been a well-established practice. Stone offers high mechanical strength and good thermal inertia, but its very low thermal conductivity (X) necessitates the use of additional insulation. Thus, generally speaking, in conventional construction, a material is either load-bearing or insulating, and therefore does not possess both properties simultaneously.

[0008] In this problematic context, the invention sought a technical solution enabling hemp concrete blocks to form walls that are both load-bearing and self-supporting over a great height, exhibiting a compressive strength of more or less 2.5 MPa, and are also highly thermally insulating while being able to be easily and quickly implemented on a construction site.

[0009] This goal is achieved, according to the invention, by means of a hempcrete block comprising an aggregate formed from hemp shives, water and a fast-setting binder, characterized in that the ratio between the masses of binder and aggregate is between 2.12 and 2.17, and in that the ratio between the masses of water and binder is between 0.85 and 0.88.

[0010] According to a preferred embodiment of the invention, the block has a length of 180 cm, a width between 40 cm and 70 cm and a height of 90 cm.

[0011] Preferably, the hemp concrete of the block of the invention contains a mass of aggregate between 115 Kg and 150 Kg, a mass of binder between 250 Kg and 320 Kg and a mass of water between 215 Kg and 280 Kg.

[0012] According to an advantageous feature of the block of the invention, the aggregate of the hemp concrete contains 90% to 100% hemp shives and 0 to 10% recycled hemp concrete.

[0013] According to another feature of the block of the invention, the binder (L) is chosen from the group consisting of a quick-setting cement, lime, clay cement or a mixture of at least two of them.

[0014] According to yet another characteristic, the hempcrete block of the invention exhibits a compressive strength between 1.60 MPa and 3.00 MPa, a thermal conductivity between 0.08 W / mK and 0.1 W / mK, and a thermal resistance between 4.0 m 2 K / W and 8.75 m 2 K / W. According to a specific embodiment of the invention, the block includes reservations for the installation of connecting elements with blocks of the same type.

[0015] Another object of the invention is a method for machining a base block as defined above, characterized in that it comprises cutting said block to make recesses for assembly with adjacent blocks.

[0016] Yet another object of the invention is the use of a hempcrete block as defined above for the design and construction of passive structures.

[0017] The invention thus proposes blocks made from hemp shives, a healthy and bio-based material, binder, and water, which are both load-bearing and insulating. Such blocks not only comply with the strictest current standards but also exhibit environmental characteristics that far exceed them.

[0018] Thanks to their intrinsic properties resulting from the combination between the specific proportions of the different ingredients in the mixture and their unusual geometry, the blocks of the invention make it possible to design and build high, self-supporting load-bearing walls that are thermally insulating for relatively small thicknesses or widths and are suitable for all types of climates.

[0019] The installation of these blocks is significantly faster per square meter of facade (three times faster) and per cubic meter of wall (six times faster) than using smaller, conventional blocks such as bricks or concrete blocks. This is because the blocks of the invention do not require the intervention of three successive trades (masonry, plastering, and painting), which also advantageously shortens the construction time.

[0020] The blocks of the invention also have an excellent carbon footprint (1 hectare of planted hemp captures between 8 and 15 tonnes of CO2 in just 4 months), do not release any volatile organic compounds and have a very long life cycle (more than 100 years).

[0021] The industrial production of these blocks consumes very little energy because it requires neither baking nor artificial drying in an oven, and their transport is easy and economical, being compatible with conventional road and rail transport. Other features and advantages of the invention will become apparent upon reading the description of the invention that follows, with reference to the figures shown below.

[0022] [Fig. 1] is a perspective view of a preferred embodiment of the hempcrete base block according to the invention. [Fig. 2] is an exploded perspective view of an assembly of two blocks of Figure 1 for the construction of a wall.

[0023] [Fig. 3] is a perspective view of a second embodiment of a hempcrete block according to the invention after machining.

[0024] [Fig. 4] is a perspective view of a third embodiment of a hempcrete block according to the invention after machining.

[0025] [Fig. 5] is a perspective view of a fourth embodiment of a hempcrete block according to the invention after machining.

[0026] [Fig. 6] is a perspective view of a fifth embodiment of a hempcrete block according to the invention during a machining operation. For clarity, identical or similar features are identified by identical reference numerals in the description and throughout the figures.

[0027] Naturally, the embodiments of the block of the invention schematically illustrated in the figures above and described below are given only as non-limiting examples. It is explicitly provided for in the scope of the invention that different embodiments can be proposed and combined to create others.

[0028] The invention relates to the field of design and construction of structural works and is concerned, in particular, with a large hemp concrete block suitable and intended for the construction of so-called "passive" buildings.

[0029] In general, hempcrete is a material comprising an aggregate made of hemp straw (called shives), water, and a fast-setting binder. The basic hempcrete blocks that are the subject of the invention can be processed after manufacturing and adapted according to their intended use using various machining methods. The machined profiles of these blocks are shown in Figures 3 to 6. The blocks of the invention are particularly self-supporting and thermally insulating, which opens up interesting applications for them in the field of modern building construction requiring compliance with very strict environmental standards.

[0030] To achieve this objective, the invention provides that the ratio in hemp concrete between the masses of binder (L) and aggregate (G) is between 2.12 and 2.17, and that the ratio between the masses of water (E) and binder (L) is between 0.85 and 0.88.

[0031] According to the invention and as illustrated by Figure 1, the basic hempcrete blocks 1 are generally parallelepiped in cross-section and of large dimensions (before machining). They initially have a length of 180 cm, a width between 40 cm and 70 cm and a height of 90 cm.

[0032] The hemp concrete used to make these blocks contains an aggregate mass of between 115 kg and 150 kg, a binder mass of between 250 kg and 320 kg and a water mass of between 215 kg and 280 kg.

[0033] Preferably, the G aggregate of hempcrete contains 90% to 100% hemp shives and 0 to 10% recycled hempcrete.

[0034] The binder (L) is chosen from a group consisting of rapid-setting cement, lime, clay cement, or a mixture of at least two of these ingredients. The characteristics of the hemp shives, whether calibrated or not, fibrous or not, have only a minor influence on the final properties of the hempcrete. On the other hand, the nature and formulation of the binder (Vicat-type rapid-setting cement (registered trademark) or other, and / or lime, and / or MCC1 Materrup clay cement (registered trademark)) are important parameters, as the rapid setting time is fundamental to the industrial process and the production rate of the blocks.

[0035] A basic hempcrete block of the invention, having a length of 180 cm, a height of 90 cm and a width between 40 cm and 70 cm, exhibits a compressive strength between 1.60 MPa and 3.00 MPa, a thermal conductivity between 0.08 W / mK and 0.1 W / mK and a thermal resistance between 4.0 m 2 K / W and 8.75 m 2 K / W.

[0036] Preferably and as illustrated by figures 1 and 2, block 1 of the invention includes reservations 10 intended to receive connecting elements 2, preferably concrete and metal reinforcements A (figure 2), ensuring the connection with blocks 1 of the same type for compliance with DTU, standards and construction rules in force.

[0037] The blocks can preferably be machined directly at the factory or, if necessary, after delivery to the construction site, to create, preferably by cutting, the recesses 10 and the cutouts 11, 1a, 11b that allow them to be adapted to adjacent blocks for assembly according to the planned architectural design, as illustrated in Figures 3 to 6. Figure 6 illustrates the separation of a basic block 1 into two parts la, lb by cutting. Table 1 below shows the variations in compressive strength Rc as a function of the quantities (by mass) of the various concrete ingredients (aggregate G based on hemp shives, binder L, and water E), the L / G and E / L ratios, as well as the initial (MVi) and 90-day dry (MVs) density MV of the block.

[0038] [Table 1]

[0039] Table 2 below shows the variations of the thermal resistance coefficient Rt as a function of the thermal conductivity X and the width e (or thickness) of the block.

[0040] [Table 2]

[0041]

Claims

DEMANDS 1. Block (1) of hemp concrete comprising an aggregate (G) formed of hemp shives, water (E) and a fast-setting binder (L), characterized in that; - the ratio between the masses of binder (L) and aggregate (G) is between 2.12 and 2.17, - the ratio between the mass of water (E) and binder (L) is between 0.85 and 0.88, - its initial density (MVi) is between 580 kg / m3 and 750 kg / m3, - its compressive strength (Rc) is between 1.60 MPa and 3.00 MPa and, - its thermal resistance (Rt) is between 4.0 m 2 K / W and 8.75 m 2 K / W.

2. Block according to claim 1, characterized in that it has a length of 180 cm, a width between 40 cm and 70 cm and a height of 90 cm.

3. Block according to any one of the preceding claims, characterized in that the hemp concrete contains a mass of aggregate (G) between 115 Kg and 150 Kg, a mass of binder (L) between 250 Kg and 320 Kg and a mass of water (E) between 215 Kg and 280 Kg.

4. Block according to any one of the preceding claims, characterized in that the aggregate (G) of the hempcrete contains 90% to 100% hemp shives and 0 to 10% recycled hempcrete.

5. Block according to any one of the preceding claims, characterized in that the binder (L) is chosen from the group consisting of a quick-setting cement, lime, clay cement or a mixture of at least two of them.

6. Block according to any one of the preceding claims, characterized in that its thermal conductivity (X) is between 0.08 W / mK and 0.1 W / mK, 7. Block according to any one of the preceding claims, characterized in that it includes reservations (10) intended for the installation of connecting elements (2) with blocks of the same type.

8. A method for machining a basic block (1) made of hempcrete according to any one of the preceding claims, characterized in that it comprises cutting said block to make recesses (11, 1a, 11b) intended for assembly with adjacent blocks.

9. Use of a hempcrete block (1) according to any one of claims 1 to 7 for the design and construction of passive structures.

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