FR3108055A1 - Earth-based mortar - Google Patents

Abstract

The present invention relates to a method for spraying or injecting an earth-based mortar comprising the steps of: i) preparation of the mortar by mixing: ia) an earth with a particle size less than or equal to 15 mm in a volume proportion of 20 to 40%; ib) a binder comprising slag or metakaolin and, optionally lime, in a volume proportion of 25 to 50%; ic) aggregates with a particle size between 2 and 15 mm, and in a volume proportion of 0 to 20%; id) fibers in a volume proportion of between 10 and 30%; ie) of the crystallizer in a volume proportion of between 1 and 4%; and if) water in a volume proportion of between 5 and 10%; ii) pumping the mixture obtained in i); andiii) injecting the mixture into a mold or spraying the mixture onto a vertical or horizontal surface.

Description

Earth-based mortar

The present invention relates to a method of manufacturing an earth-based mortar which can be used both by injection and by spraying.

If we talk about earth, it immediately comes to mind that it is one of the oldest building materials. Indeed, building in raw earth made it possible to exploit the closest material, the one you have under your feet, available almost everywhere in the world.

Now, the mechanical characteristics of it were unsuitable for obtaining durable constructions. Also, the earth has been associated with other materials, often local and natural, as well as minerals, in order to obtain building materials.

One of these materials, known as rammed earth, uses raw earth compacted in a formwork or bedding. The earth is then thrown into the formwork in thin layers of 10 cm to 1m, then manually compacted in the formwork using a pestle.

This type of material makes it possible to obtain an earth-based wall that is sufficiently porous to allow ideal breathing of the premises it defines. Now, this material is very sensitive to erosion due to its porosity and therefore only offers a very limited hold over time.

If concrete has established itself for centuries as the benchmark construction material, new environmental regulations for new buildings will emerge this year in France (RE 2020) and which will lead to a rethinking of construction. This new regulation will require to further improve the environmental performance of a building by taking into account not only the insulation but the overall environmental impacts associated with this construction. Thus, we must take into account all the components of the building, its plot but also the site with the taking into account of the energy consumption of the site, the consumption and water discharges of the site, the disposal and treatment of earthworks waste.

This change therefore requires an in-depth review of construction processes to optimize energy expenditure.

The inventors have now developed a new process for manufacturing an earth-based mortar that not only allows the earth resulting from the construction site to be used but also does without cement. This process, which can be used for both vertical and horizontal surfaces and concrete blocks, considerably reduces the energy consumption of the associated construction and therefore the environmental impact of a site.

A first object of the invention therefore relates to a method of spraying or injecting an earth-based mortar comprising the steps of:

i) preparation of the mortar by mixing:

ia) soil with a particle size of 15 mm or less in a volume proportion of 20 to 40%;

ib) a binder comprising slag or metakaolin and, optionally lime, in a volume proportion of 25 to 50%;

ic) aggregates with a particle size between 2 and 15 mm, and in a volume proportion of 0 to 20%;

id) fibers in a volume proportion of between 10 and 30%;

ie) of the crystallizer in a volume proportion of between 1 and 4%; (5% of the weight of the binder to be added by volume) and

if) water in a volume proportion of between 5 and 10%.

ii) pumping the mixture obtained in i); and

iii) injection of the mixture into a mold or projection of the mixture on a vertical or horizontal surface.

The volume proportion of each component corresponds to the volume occupied by this component relative to the total volume of the mortar mixture.

The term “mortar” is understood to mean both a coating, which can be applied to a surface and having a resistance of at least 5 MPa, an assembly or filling mortar with a resistance of at least 10 MPa, and a mortar intended for the manufacture of a load-bearing wall with a strength of at least 15 MPa.

The process according to the invention can therefore allow the creation of a plaster as well as a wall.

Advantageously, the mortar prepared by the process according to the invention comprises cement in a proportion by volume less than or equal to 1%, preferably less than or equal to 0.5% and, particularly preferably, a proportion by volume of 0% of cement.

The environmental impact of the process according to the invention is therefore much less than that of existing processes which generally use at least 10% cement.

Soil is understood to mean the soil resulting from earthworks or excavation (quarry) operations, excluding topsoil.

This land may therefore present a very great diversity of nature depending on the site from which it comes. We can thus find soils incorporating gypsum, silt, limestone, silica, clay or even a mixture thereof.

Prior to the use of soil, care will be taken to determine the presence or absence of traces of metallic elements (Pb, As, etc.) so as to prevent any contamination.

Advantageously, the earth used in the process according to the invention will have a particle size less than or equal to 10 mm, preferably less than or equal to 6 mm.

Obtaining soil with a desired particle size from such a variety of sources will generally require, in addition to determining the particle size of the soil, a sieving operation.

According to a preferred embodiment, the method according to the invention will therefore preferably comprise a step of sieving the soil prior to step i).

The very great adaptability of the process according to the invention to the different types of existing soil allows it to use the same soil from the site on which the process is implemented.

According to another preferred embodiment, the method according to the invention will preferably comprise a step prior to step i) of extracting the earth and, optionally, of sieving it.

The term “slag” is understood to mean the slag formed during the melting or production of the metal by the liquid process. It is a mixture composed mainly of silicates, aluminates and lime with various metal oxides except iron oxides.

The slag will preferably be used in a volume proportion of between 10 and 30%.

By metakaolin is meant the product of a calcination of kaolin and / or kaolin clay.

Preferably, the binder comprises slag and, optionally, lime.

Lime will preferably be used in a volume proportion of between 0 and 25%.

By lime is meant artificial lime which essentially comprises calcium and magnesium oxide and / or calcium and magnesium hydroxide.

Advantageously, the lime is chosen from the group comprising hydraulic lime and air lime.

Preferably, hydraulic lime will be used, which preferably does not include cement.

Preferably, an NHL 3.5 or NHL 5 hydraulic lime will be used.

Preferably, the use of NHL 3.5 Z or NHL 5 Z hydraulic lime will be avoided, as long as it contains cement.

By aggregates, we mean both natural aggregates (eg gravel or sand) and recycled aggregates (eg concrete or crushed mortar).

Now it is possible to mix the different types of aggregates, natural and recycled, in varying proportions.

As regards the particle size, a particle size of between 4 and 10 mm and, particularly preferably, a particle size of between 4 and 6 mm will be preferred.

As with soil, it is possible to use aggregates from all or part of the site on which the process is implemented.

In the event that the land used incorporates aggregates. Then the proportion of aggregates added on top of the soil is adapted so that the total volume proportion of aggregates is between 0 and 20%.

According to yet another preferred embodiment, the method according to the invention will preferably comprise a step prior to step i) of extracting aggregates and, optionally, of sieving them.

By crystallizer, sometimes also called mineralizing, is meant compounds capable of forming, by a reaction qualified as mineralization, crystalline and insoluble complexes with the soluble compounds of the mortar (free lime).

By way of example of such compounds, mention may be made, for example, of silicate salts, carbonate salts (eg natron), alginate salts.

Such crystallizers are known for use in waterproofing concrete, in particular under the names PENETRON, XYPEX, mineralizing B HYDRO-MINERAL, etc.

Preferably, the crystallizer comprises silicate ions capable of forming silicate complexes with calcium hydroxide, in particular calcium, magnesium, sodium or even potassium silicate.

Preferably, calcium and / or magnesium silicate will be used.

The term “fibers” is understood to mean both synthetic fibers (eg polypropylene fibers, glass fibers, carbon fibers, etc.) and natural fibers (eg hemp).

Advantageously, the fibers used are solid fibers, that is to say they have a structure devoid of cavities.

Typically, the fibers used have a length between 5 and 100 mm, preferably between 5 and 70 mm and, particularly preferably between 10 and 50 mm.

According to a preferred embodiment, natural fibers or plant fibers will be used. To obtain such plant fibers, it is possible to use fiber plants, a large part of which are well known.

For bast fibers, corresponding to the fiber of the bark, one can cite for example hemp, jute, kenaf, barrel liana, flax, nettle, papyrus, esparto, fibers linden, bamboo fibers, Provence cane fibers, seagrass, miscanthus fibers, bagasse, etc.

For leaf fibers, we can cite Manila hemp (from abaca), piña (from pineapple), agave leaf fiber (eg sisal).

For fibers originating from seeds or fruit, mention may be made of coir, rice husks or straw or even cotton.

Finally, the mortar can integrate other additives such as plasticizers, water-retaining agents, water-repellent agents, biocides, fungicides, dispersants, air entrainer (hunter), setting accelerators, retarders setting, thinners, antifreeze agents or expansion agents.

Naturally, each of these adjuvants can be added to the mortar alone or in combination with one or more other adjuvants.

Stage i) of mixing can be carried out according to techniques well known to those skilled in the art.

Advantageously, the mixing is carried out using a mixer, in particular a mobile mixer with horizontal or vertical axes allowing the mixing to be carried out on the site itself where the wall must be carried out.

If the earth-based mortar can be used immediately at the end of step i), it is also possible, by then omitting to add the water, to bag the mixture at the end of step i) for its transport and / or storage before being finalized prior to its use in step ii) of the process according to the invention.

Pumping step ii) can be carried out according to techniques well known to those skilled in the art.

This pumping step is carried out using a pumping means such as a piston pump or a worm pump.

Advantageously, the mixture is heated to a temperature greater than or equal to 40 ° C, preferably greater than or equal to 45 ° C during this pumping step so as to allow rapid setting of the mortar, especially in the case of spraying. on a vertical surface.

Such a temperature may possibly be obtained by the sole friction of the mixture obtained at the end of step i) with the surfaces of the device allowing pumping (eg friction of the mixture with the surface of the endless screw).

According to a particular embodiment of the method according to the invention, it is intended for injection into a mold for a building element.

Indeed, the specific characteristics of the mortar obtained allow its industrial use in the manufacture of construction elements such as borders, concrete blocks, paving stones, etc.

By mold of at least one construction element is meant a mold chosen from the group comprising molds for concrete blocks, hollow or solid, for curbs, paving stones and slabs.

In this case, the method according to the invention may further comprise the step of:

iv) compressing the mixture injected into a mold for at least one construction element.

This compression step is performed by devices well known to those skilled in the art.

If necessary, this step can be followed or preceded by a step of stirring the mixture in the mold to limit the presence of bubbles. This stirring step can be carried out by means of vibrating devices positioned in the mold or associated with it. Examples include vibratory tables or vibrating probes (needles).

This step can be followed by a step v) of drying and demoulding.

According to another particular embodiment of the method according to the invention, it is intended for projection on a horizontal or vertical surface, preferably on a vertical surface.

Indeed, and surprisingly, the characteristics of the earth-based mortar according to the invention, and in particular its rapid setting, allow it to be projected onto a vertical surface in layers of about ten centimeters and without observing any subsidence. It is also possible to carry out successive applications of the mortar according to the invention by applying a recovery time of between 30 minutes to 6 hours between two successive layers, preferably between 1 and 3 hours.

Now and preferably, the surface on which the earth-based mortar is projected comprises a reinforcing element, which can for example take the form of a frame, which frame can be metallic, plastic (polyethylene, polypropylene, etc.) vegetable (bamboo, cane from Provence, etc.).

As for the projection as such, it is carried out by means of devices well known to those skilled in the art. Typically, such a projection is carried out by means of a projection lance placed at the outlet of the pumping means.

Such a projection lance takes the form of a flexible pipe of suitable section at the end of which a projection nozzle is positioned. Typically, such a projection lance further incorporates an air inlet slightly upstream of the nozzle, which air inlet contributes to the projection of the earth-based mortar than to the driving of said earth-based mortar in view of its projection on a vertical or horizontal surface.

A second object of the invention relates to the earth-based mortar as obtained at the end of step i) of the process described above.

Such a mortar according to includes:

a) soil with a particle size of 15 mm or less in a volume proportion of 20 to 40%;

b) a binder comprising slag or metakaolin and, optionally lime, in a volume proportion of 25 to 50%;

c) aggregates with a particle size between 2 and 15 mm, and in a volume proportion of 0 to 20%;

d) fibers in a volume proportion of between 10 and 20%;

e) of the crystallizer in a volume proportion of between 1 and 4%; (5% of the weight of the binder to be added by volume) and

f) optionally water in a volume proportion of between 5 and 10%.

The characteristics and proportions of each component of the mortar are as described above.

Advantageously, the mortar according to the invention is packaged in a bag and does not include water.

A third subject of the invention relates to a mixture intended for the preparation of a mortar according to the invention, which mixture comprises:

a) between 90 and 98% by weight of a binder (relative to the total weight of the mixture) comprising slag or metakaolin and, optionally, lime,

b) between 2 and 10% by weight, preferably between 3 and 8%, by weight of crystallizer (relative to the total weight of the mixture), preferably between 4 and 6%.

Preferably, this mixture comprises neither earth, nor aggregates, nor vegetable fibers which are intended to be added on the site to produce the earth-based mortar.

Advantageously, the binder comprises slag and, optionally, lime.

Typically, the mixture will include between 30 and 90% slag.

The mixture will further comprise between 0 and 50% lime.

Advantageously, the mixture according to the invention is packaged in a bag and does not include water.

A fourth object of the invention relates to a construction element capable of being obtained using such a mortar.

Such a product can take the form of any construction element, whether concrete block, solid or hollow, borders, paving stones and slabs.

A fifth object of the invention relates to the use of a mortar as described above for the production of construction elements.

By construction elements, we mean partitions, blocks, concrete blocks, hollow or solid, borders, paving stones, slabs, etc.

By realization, one understands the realization by injection or projection.

Other characteristics, details and advantages of the invention will emerge more clearly from the detailed description given below by way of indication.

Pr oced of pr earth mortar separation

The site soil has been sieved beforehand with a 10 mm mesh.

The sieved site soil is then incorporated into the mixer tank of a TURBOSOL T20X spraying machine. 4/6 gravel, hemp fibers (10 mm) are then incorporated and the mixture is quickly mixed for a few minutes (generally about 2 minutes). The water is then incorporated into the mixture and rapid mixing allows the mixture to homogenize. Finally, the binder is incorporated into the mixture and a longer mixing step is carried out (typically between 3 and 5 minutes) so as to obtain a smooth consistency of the mortar.

The mixture is then ready to be projected (or injected in the case of preparation of construction elements)

Examples of f ormulations

Different earth mortar formulations were prepared and made it possible to arrive at the formula according to the invention. The soils tested included gypsum, quarry waste (limestone), silts and clays.

Some tested formulas are described in Tables 1 to 4.

MATTER VOLUME (liters) DENSITY KG WEIGHT (kg) % VOLUME % MASSIC LIME 25 0.791 19.78 22% 16.84% DAIRY 25 1.165 29.13 22% 24.80% EARTH 25 1,545 38.63 22% 32.89% GRAVEL 4/6
RECYCLE 12.5 1.26 15.75 11% 13.41% NATURAL FIBER 12.5 0.156 1.95 11% 1.66% CRYSTALIZER 2 1,114 2.23 2% 1.90%

MATTER VOLUME (liters) DENSITY KG WEIGHT (kg) % VOLUME % MASSIC LIME 14 0.791 11.07 13% 9.31% DAIRY 28 1.165 32.62 25% 27.41% EARTH 28 1,545 43.26 25% 36.35% GRAVEL 4/6
RECYCLE 14 1.26 17.64 13% 14.82% NATURAL FIBER 14 0.156 2.18 13% 1.84% CRYSTALIZER 2 1,114 2.23 2% 1.87%

MATTER VOLUME (liters) DENSITY KG WEIGHT (kg) % VOLUME % MASSIC LIME 10 0.791 7.91 9% 6.75% DAIRY 30 1.165 34.95 27% 29.83% EARTH 30 1,545 46.35 27% 39.56% GRAVEL 4/6
RECYCLE 10 1.26 12.60 9% 10.75% NATURAL FIBER 20 0.156 3.12 18% 2.66% CRYSTALIZER 2 1,114 2.23 2% 1.90%

MATTER VOLUME (liters) DENSITY KG WEIGHT (kg) % VOLUME % MASSIC LIME 5 0.791 3.96 5% 3.37% DAIRY 15 1.165 17.48 14% 14.88% EARTH 40 1,545 61.80 37% 52.61% GRAVEL 4/6
RECYCLE 15 1.26 18.90 14% 16.09% NATURAL FIBER 20 0.156 3.12 19% 2.66% CRYSTALIZER 2 1,114 2.23 2% 1.90%

Earth mortar projection step

The projection of the earth mortar is then carried out on a previously prepared support.

In the tests carried out, wooden frames were produced, which frames had a bottom in OSB plywood panel screwed to the wooden structure and a welded mesh type metal grid positioned in the middle of the frame to allow the incorporation of traditional elements. used in building trades (electrical wiring, water supply, etc.).

The projection of the various earth mortars described above was then carried out in two successive layers of 7 to 8 cm. The recovery time between the two coats was 30 minutes.

We can consider that this time is short because in reality the panels produced on a conventional site are of larger dimensions. This will systematically give a higher recovery time (approximately 1 to 2 hours).

In the end, the filling panels produced in the workshop represented a final thickness of 15cm. After spraying, the mortar held perfectly and a finish was carried out (rule, float or trowel depending on the panels.

Properties of earth mortar

Earth mortar samples were produced to test its properties.

The tests carried out are as follows:

Test on hardened concrete according to standard NF P18-459

Thermal conductivity test by the Metric flux method according to standard NF EN 12667

Hygrometric performance test by determining the properties of hygroscopic sorption. (Sorption and desorption curve) according to standard NF EN ISO 12571.

Air permeability and water tightness test.

Compression tests according to standard NF EN 12390-3 (by comparison with control elements).

Determination of dimensional variations due to humidity of aggregate concrete masonry elements according to standard NF EN 772-14. For each configuration.

Freeze / Thaw accelerated aging tests according to standard NF EN 771-1 + A1 / CN

Claims (10)

A method of spraying or injecting an earth-based mortar comprising the steps of:
i) preparation of the mortar by mixing:
ia) soil with a particle size less than or equal to 15 mm in a volume proportion of 20 to 40%;
ib) a binder comprising slag or metakaolin and, optionally lime, in a volume proportion of 25 to 50%;
ic) aggregates with a particle size between 2 and 15 mm, and in a volume proportion of 0 to 20%;
id) fibers in a volume proportion of between 10 and 30%;
ie) of the crystallizer in a volume proportion of between 1 and 4%; and
if) water in a volume proportion of between 5 and 10%;
ii) pumping the mixture obtained in i); and
iii) injection of the mixture into a mold or projection of the mixture on a vertical or horizontal surface. The method according to claim 1, characterized in that the mortar prepared by the method according to the invention comprises cement in a volume proportion less than or equal to 1%, preferably less than or equal to 0.5%. The method according to any one of claims 1 or 2, characterized in that the soil is obtained from earthworks or excavation operations, excluding topsoil. The method according to any one of claims 1 to 3, characterized in that the binder comprises slag and, optionally, lime. The method according to any one of claims 1 to 4, characterized in that the crystallizer comprises silicate ions capable of forming silicate complexes with calcium hydroxide, in particular calcium, magnesium or sodium silicate. or potassium. The method according to any one of claims 1 to 5, characterized in that the fibers are synthetic fibers and / or natural fibers. A mortar, characterized in that it comprises:
(a) soil with a particle size less than or equal to 15 mm in a volume proportion of 20 to 40%;
b) a binder comprising slag or metakaolin and, optionally lime, in a volume proportion of 25 to 50%;
c) aggregates with a particle size between 2 and 15 mm, and in a volume proportion of 0 to 20%;
d) fibers in a volume proportion of between 10 and 20%;
f) crystallizer in a volume proportion of between 1 and 4%; and
g) optionally water in a volume proportion of between 5 and 10%. A mixture for the preparation of a mortar according to claim 7, which mixture comprises:
a) between 90 and 98% by weight of a binder (relative to the total weight of the mixture) comprising slag or metakaolin and, optionally, lime,
b) between 2 and 10% by weight, preferably between 3 and 8%, by weight of crystallizer (relative to the total weight of the mixture), preferably between 4 and 6%. A building element obtained with a mortar according to claim 7. Use of a mortar according to claim 7 for the production of building elements.