Extrudable paste, construction material and associated manufacturing method

Abstract

The invention relates to a paste intended to be extruded in order to form a cellular building material, the paste comprising: - a composition representing 75% to 85% of the total weight of the paste; and - water representing 15% to 25% of the total weight of the paste, wherein the composition comprises: a clay mixture representing 35% to 55% by weight of the composition, the clay mixture comprising more than 90% by weight of the clay mixture minerals chosen from the koalinite group of, sand representing 40% to 60% by weight of the composition, and a mineral binder representing 5 to 12% by weight of the composition, the mineral binder being other than clay.

Description

Extrudable paste, construction material and associated manufacturing process

[0001] The invention relates to the field of extrudable raw earth pastes, construction materials manufactured from these raw earth compositions and associated manufacturing processes, in particular for use in the field of construction and public works. Technological background

[0002] It is known to use earth-based compositions to manufacture, for example, building construction materials. These compositions are generally fired at very high temperatures (above 1000°C) in order to vitrify the clay so as to confer mechanical strength and impermeability to the resulting building material. Indeed, by vitrifying the clay mixture at temperatures between 900°C and 1400°C, it is possible to increase its density and reduce its porosity optimally.

[0003] However, currently known raw earth materials do not have sufficient mechanical resistance or water resistance to withstand bad weather in a sustainable manner without deteriorating.

[0004] However, the cooking step is energy-intensive and results in additional manufacturing costs.

[0005] The inventors further noted that the currently known raw earth construction materials are mainly manufactured by pressing because their compositions do not allow them to be obtained by extrusion, particularly for the manufacture of honeycomb and large-scale construction materials.

[0006] Indeed, these prior art materials form aggregates and a non-homogeneous paste in the extruder. Consequently, the extrusion of these raw earth materials is currently not satisfactory because it is not possible to determine in advance the shape and intrinsic composition of the product obtained via extrusion.

[0007] Therefore, the use of these pastes to form a solid construction material via an extruder is not industrializable because the product resulting from the extrusion is not predictable or repeatable and does not have satisfactory mechanical resistance and water resistance.

[0008] One idea behind the invention is therefore to solve the above-mentioned problems.

[0009] Another idea underlying the invention is to provide a raw earth paste which makes it possible to form by extrusion a raw earth construction material with excellent mechanical properties and good water resistance.

[0010] Another idea underlying the invention is to obtain a construction material, more particularly a honeycomb construction material with excellent mechanical properties and good water resistance.

[0011] Another idea underlying the invention is to provide a manufacturing process by extrusion of a raw earth material making it possible to obtain a solid and homogeneous construction material in its composition.

[0012] According to one embodiment, the invention provides a paste intended to be extruded in order to form a honeycomb construction material, the paste comprising:- a composition representing 75% to 85% of the total mass of the paste, and- water representing 15% to 25% of the total mass of the paste, wherein the composition comprises:a clay mixture representing 35% to 55% by mass of the composition, the clay mixture comprising more than 90% by mass of the clay mixture of minerals selected from the kaolinite group,sand representing 40% to 60% by mass of the composition, anda mineral binder representing 5 to 12% by mass of the composition, the mineral binder not being clay.

[0013] Thanks to these specific characteristics, it is possible to extrude the paste to form a honeycomb construction material in raw earth with excellent mechanical properties and good water resistance.

[0014] All of these characteristics act in synergy to obtain the aforementioned properties.

[0015] Indeed, the composition and specific range of the clay mixture combined with the specific range of the mineral binder allows to obtain a coherent and manipulable paste. This is related to the fact that the minerals of the kaolinite group are less sensitive to the basic effects of binders and to the negative impact on plasticity, which makes it possible to avoid the phenomenon of flocculation of the paste in a basic environment. In addition, the specific range of mineral binder makes it possible to obtain, after drying of the paste, a raw earth material with excellent water resistance allowing it to withstand repeated immersion in water without causing flaking or cracking of the construction material.

[0016] The specific range of sand forms an overall skeleton for the dough in order to increase on the one hand the rigidity of the dough while allowing coherent extrusion and on the other hand the permeability in order to allow the evacuation of water.

[0017] The inventors have observed by carrying out various confidential tests that pastes comprising the same components in different ranges form a paste comprising non-homogeneous aggregates making the paste non-extrudable to form honeycomb construction materials in raw earth. In addition, the paste obtained degrades easily and does not have sufficient water resistance to obtain construction materials, in particular honeycomb construction materials. The same findings have been observed for pastes comprising clay minerals which do not include minerals chosen from the kaolinite group.

[0018] The term mineral binder within the meaning of the present invention encompasses hydraulic binders and aerial binders. Thus, the mineral binder representing 5% to 12% by mass of the composition is chosen from hydraulic binders and aerial binders or a combination of at least one hydraulic binder with at least one aerial binder, excluding clay.

[0019] The term hydraulic binder within the meaning of the present invention is a mineral binder having hydraulic properties, that is to say which hardens by chemical reaction with water.

[0020] The term air binder within the meaning of the present invention is defined as a mineral binder which can set upon contact with carbon dioxide (CO2) present in the air, i.e. it hardens by reaction with the CO2 present in the air, forming, for example, calcite.

[0021] The kaolinite group includes the following minerals: kaolinite, dickite, endellite, halloysite, nacrite and odinite.

[0022] The sand of the aforementioned composition has a granulometry compatible with extrusion.

[0023] According to embodiments, such a paste may comprise one or more of the following characteristics.

[0024] According to one embodiment, the clay mixture is composed of more than 50% by mass of said clay mixture of the kaolinite mineral. According to an advantageous embodiment, the clay mixture is composed of more than 60%, preferably more than 70%, more preferably more than 80%, even more preferably more than 90% or more than 99% by mass of said clay mixture of the kaolinite mineral. According to one embodiment, the clay mixture is composed of a percentage chosen from 65%, 75%, 85%, 95% by mass of said clay mixture of the kaolinite mineral.

[0025] Thanks to these characteristics and in particular the presence of the mineral kaolinite, it is found that the paste obtained is easily homogenized and has excellent properties, in particular a plasticity allowing extrusion in order to form a honeycomb construction material. This is due to the fact that the mineral kaolinite is not very sensitive to the basic effects of binders which usually have a negative impact on the plasticity of the paste via phenomena of flocculation of the paste in a basic environment.

[0026] According to one embodiment, the minerals of the kaolinite group are of the secondary kaolinite type, that is to say that they have a smaller size than the minerals of the kaolinite group of the primary kaolinite type.

[0027] According to one embodiment, the Kaolinite group minerals have a cumulative oversize at 40 µm of less than 10% of the total mass of the Kaolinite group minerals. In other words, the total mass of the Kaolinite group minerals with a size greater than 40 micrometers is less than 10% of the total mass of the Kaolinite group minerals. In other words, at least 90% by mass of the Kaolinite group minerals have a size less than 40 µm, and only a small fraction, i.e., less than 10% by mass, has a size greater than 40 µm. The method used to calculate the cumulative oversize is wet sieving.

[0028] According to one embodiment, the average diameter of the minerals of the Kaolinite group is between 10 and 20 µm, and for example equal to approximately 15 µm.

[0029] Thus, the fine grain size of the kaolinite group minerals allows for increased exchanges with the other components of the paste. The result is a paste that can be properly extruded in a homogeneous manner, i.e., without forming aggregates. As a result, this allows for the production of a honeycomb construction material after drying, which is homogeneous in its composition and has excellent mechanical properties.

[0030] According to one embodiment, the minerals of the Kaolinite group have a specific surface area of ​​between 20 and 80 m² / g, and preferably between 70 and 80 m² / g.

[0031] According to one embodiment, the minerals of the Kaolinite group have a water vapor absorption capacity: 4.5 to 7% by mass.

[0032] According to one embodiment, the minerals of the Kaolinite group comprise the following chemical composition, according to the dry chemical analysis method, expressed as a % of the total mass of the minerals of the Kaolinite group: Al2O3: 22.5; SiO2: 53.5; TiO2: 0.9; Fe2O3: 6.9; K2O: 3.6; CaO: 0.7; MgO: 0.

[0033] According to one embodiment, the mineral binder represents 7 to 11% by mass of the composition.

[0034] According to one embodiment, the mineral binder is chosen from: a hydraulic binder, an aerial binder or a mixture of these.

[0035] According to one embodiment, the mineral binder comprises one or more hydraulic binders.

[0036] According to one embodiment, the mineral binder comprises one or more aerial binders.

[0037] According to one embodiment, the mineral binder comprises one or more hydraulic binders and one or more aerial binders.

[0038] According to one embodiment, the hydraulic binder is a Portland cement. According to one embodiment, the Portland cement is chosen from: “CEM 1 52.5 T”, “CEM 3 C 32.5 N-LH SR”.

[0039] According to one embodiment, the mineral binder comprises natural hydraulic lime comprising between 8% and 14% silica, also called NHL3.5.

[0040] According to one embodiment, the aerial binder is aerial lime.

[0041] According to a preferred embodiment, the mineral binder is chosen from: air lime, hydraulic lime, Portland cement or a mixture thereof.

[0042] According to one embodiment, the water represents 19% to 20% of the total mass of the paste, the clay mixture represents 39% to 41% by mass of the composition, and the mineral binder represents 9% to 11% by mass of the composition, the mineral binder preferably being NHL3.5 hydraulic lime.

[0043] According to one embodiment, the water represents 17.2% to 18.3% of the total mass of the paste, the clay mixture represents 39% to 41% by mass of the composition, the mineral binder represents 6 to 8% by mass of the composition, the mineral binder preferably being CEM 1 52.5 T.

[0044] According to one embodiment, the clay mixture comprises halloysite. Halloysite has the advantage of being relatively insensitive to the basic effects of binders, basic effects which usually have a negative impact on the plasticity of the paste via flocculation phenomena of the paste in a basic medium.

[0045] According to one embodiment, the clay mixture comprises less than 10% of minerals chosen from quartz and muscovite.

[0046] According to one embodiment, the clay mixture comprises less than 10%, preferably less than 5% and even more preferably less than 3% by mass of the clay mixture of minerals from the smectite group.

[0047] According to one embodiment, the clay mixture does not contain minerals from the smectite group.

[0048] According to one embodiment, the sand has a grain size greater than 0 mm and less than 5 mm, preferably less than 4.5 mm.

[0049] According to one embodiment, the sand has dimensions in which the distance separating the two most distant ends of a grain of sand are less than 10 mm, preferably less than 5 mm.

[0050] According to one embodiment, the invention also provides a raw earth honeycomb construction material comprising:- a composition representing at least 90% of the total mass of the raw earth material, and- water representing less than 10% of the total mass of the paste,in which the composition comprises: a clay mixture representing 35% to 55% by mass of the composition,the clay mixture comprising more than 90% by mass of said clay mixture of minerals chosen from the kaolinite group,sand representing 40% to 60% by mass of the composition, anda mineral binder representing 5 to 12% by mass of the composition.

[0051] According to one embodiment, the sand has a grain size of less than 5 mm.

[0052] According to one embodiment, the honeycomb construction material has dimensions greater than: - 250 mm in height; - 400 mm in length; and - 150 mm in width.

[0053] According to one embodiment, the construction material is not cooked, that is to say that it has not undergone a cooking step and in particular that it has not been subjected to a temperature greater than 100°C.

[0054] According to one embodiment, the building material comprises a plurality of cells which extend in a thickness direction of the building material.

[0055] According to one embodiment, the aforementioned construction material is obtained by extrusion via the aforementioned paste.

[0056] Thanks to these characteristics, a raw earth construction material is obtained which has excellent water resistance without the need for a subsequent cooking step.

[0057] In addition, it is possible to obtain large-sized raw earth building materials.

[0058] According to one embodiment, the raw earth construction material has an apparent density of between 1.75 and 1.85 g / cm 3 .

[0059] According to one embodiment, the raw earth construction material has a compressive modulus of rupture of between 3500 and 6000 kPa (35 to 60 bars).

[0060] According to one embodiment, the raw earth construction material has a flexural modulus of rupture of between 2 and 3 N / mm². The method used is the 3-point bending test according to ISO 178.

[0061] According to one embodiment, the raw earth construction material has a dry thermal conductivity of between 0.47 and 0.52 W m -1 K -1 .

[0062] According to one embodiment, the raw earth building material has water resistance, the building material being considered to have water resistance when, after carrying out 20 cycles, the building material does not exhibit flaking or cracking or very slight flaking which has no negative impact on the water resistance or on the physical properties of the building material.

[0063] Each cycle is defined by a step of immersing the construction material for 4 hours in water, then a drying step at 70°C for 20 hours.

[0064] According to one embodiment, the invention also provides a method for manufacturing a honeycomb construction material, the method comprising the following steps:- providing a paste as mentioned above,- inserting the paste into the extruder,- extruding the paste via an extruder in order to form a honeycomb material,- drying the paste in order to obtain a honeycomb construction material as mentioned above.

[0065] According to one embodiment, the extrusion step is carried out by applying an extrusion pressure of between 800 kPa and 1100 kPa.

[0066] Thanks to these characteristics, the dough is extruded evenly.

[0067] According to one embodiment, a step of cutting the dough is provided at the extruder outlet in order to form the honeycomb material.

[0068] According to one embodiment, the extruder is a single-screw extruder. According to one embodiment, the extruder is designed to operate under partial or full vacuum conditions, i.e., under vacuum.

[0069] According to one embodiment, the time elapsing between the step of inserting the dough into the extruder and the cutting step is less than 45 minutes, preferably less than 30 minutes, even more preferably less than 20 minutes.

[0070] Thanks to these characteristics, it is possible to extrude the dough before the dough stiffens and therefore becomes non-deformable.

[0071] According to one embodiment, the drying time of the paste is between 4 and 9 days at a temperature between 40 and 55°C, preferably between 45 and 50°C, in an atmosphere having a relative humidity between 50% and 90%, preferably between 60% and 80%. For example, the paste is dried for 21 days at 50°C at a relative humidity level between 60 and 80%.

[0072] According to one embodiment, the method does not include a cooking step at a temperature above 100°C.

[0073] According to one embodiment, the manufacturing method consists of carrying out the following steps: - providing a paste as mentioned above, then - inserting the paste into an extruder, then - extruding the paste via the extruder, then - cutting the extruded paste, then - letting the paste dry at a temperature between 20 and 100°C in order to obtain a honeycombed raw earth construction material, - mechanically treating the paste in order to finalize the desired shape. Brief description of the figures

[0074] The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes, with reference to the accompanying drawings.

[0075] The figure represents a sectional view of a building material according to one embodiment.

[0076] Illustrates the method of manufacturing a construction material according to one embodiment.

[0077] Several methods of producing the paste and the process for manufacturing the honeycomb construction material will be described below, highlighting the aforementioned beneficial properties.

[0078] The first step 10 of the manufacturing process of the honeycomb construction material is to provide a paste as mentioned above.

[0079] Table 1 below shows the characteristics of a paste according to a first embodiment and a second embodiment.

[0080] Table 1: PasteFirst embodimentSecond embodimentComposition (% of the total mass of the paste)80.582.2Clay mixture (% by mass of the composition)4040Sand (% by mass of the composition)5053Mineral binder (% by mass of the composition)Lime NHL 3.510CEM 1 52.5 T7Water content of the paste (% of the total mass of the paste)19.517.8

[0081] In the first and second embodiments, the clay mixture comprises more than 90% by mass of the clay mixture of minerals selected from the kaolinite group. The sand has a grain size of between 0 mm and 5 mm. The sand is derived from altered granites composed mainly of quartz, feldspars and mica.

[0082] The paste according to the first or second embodiment thus obtained by mixing the elements indicated above has ideal mechanical and chemical properties for being extruded on the one hand and for solidifying after extrusion without a subsequent cooking step on the other hand in order to form a honeycomb construction material in raw earth having excellent water resistance.

[0083] Indeed, at the initial time T0, the paste has a weak consistency allowing extrusion. Then, notably through the effect of the mineral binder, the consistency of the paste increases over time until a solid paste is obtained which will become, after drying, the honeycomb construction material in raw earth.

[0084] The extrusion step must therefore be carried out quickly after the dough has formed in order to allow extrusion before the dough solidifies and therefore becomes non-extrudable.

[0085] According to the first embodiment, the dough becomes rigid 120 minutes after T0. Thus, extrusion must be carried out between T0 and before 120 minutes after T0.

[0086] Similarly, according to the second embodiment, the dough becomes rigid 30 minutes after T0. Thus, extrusion must be carried out between T0 and before 30 minutes after T0.

[0087] The second step 11 of the process is a step of inserting the paste thus obtained into the inlet of the extruder 20 followed by the third step 12 of extrusion.

[0088] Table 2 below shows the parameters applied to the dough during the third extrusion step 12 as well as the evolution of the dough consistency.

[0089] Table 2: First embodimentSecond embodimentExtrusion pressure (kPa)1000850Dough consistency at T0 (DaN)4.94.2Dough consistency evolution (DaN)0.75 DaN / 30 minutes4.5 DaN / 30 minutes6.5 DaN after 2 hours6.5 DaN after 30 minutes

[0090] Extrusion is carried out using a 20-screw vacuum extruder at a temperature between 25 and 30°C.

[0091] The paste is shaped and cut at the extruder outlet so that it takes the shape of the honeycomb construction material to be formed, for example having the shape of the construction material 1 in raw earth as illustrated with the.

[0092] Then the material enters the drying stage for 28 days at a temperature of approximately 50°C in order to form the honeycomb building material.

[0093] The characteristics of the honeycomb construction material thus obtained are presented in Table 3 below.

[0094] Table 3: First embodimentSecond embodimentPhysical properties of the honeycomb construction material obtained via the paste, after 28 days of drying at 50°CDrying shrinkage 21 days (expressed in %)1.31.1Open porosity (in %)2723.2Apparent density (g / cm 3 )1,751,85Modulus of rupture in bending (N / mm 2 )2.12.8Compressive modulus of rupture (EN 742-01 standard)Compression tests were carried out along the extrusion axis.Actual surface area (kPa)39004100Apparent surface area (kPa)18001900Moisture uptake (90°C to 18°C ​​– Relative humidity 85%) / dry mass2%1.5%

[0095] Experimental tests were carried out to assess the water resistance of the resulting raw earth honeycomb construction material.

[0096] The results are presented in Table 4 below.

[0097] Table 4: Water resistance – aging cycle of the construction materialA cycle is defined in these tests by a step of immersion of the construction material for 4 hours in water then, a step of drying at 70°C for 20 hours11 cycles carried outNothing to report. No flaking or cracking observed on the construction materialNothing to report. No flaking or cracking observed on the construction material17 cycles carried outNo cracking observed. Very slight flaking at the edges manifested by a millimeter loss of material which has no significant consequence on the water resistance of the construction material.No cracking observed. Very slight flaking at the edges manifested by a millimeter loss of material which has no significant consequence on the water resistance of the construction material.20 cycles carried outNothing to report apart from the slight flaking indicated in the previous line which has no negative consequences on the water resistance or the physical properties of the construction material.

[0098] Thus, the aforementioned pastes have the particular advantage of obtaining a honeycomb construction material in raw earth with excellent water resistance. Thus these construction materials can be used in the construction of buildings such as houses or apartment blocks.

[0099] The building material can come in different forms. An example of such a material is shown with the.

[0100] The building material according to one embodiment illustrated in is a brick 1 which has the general shape of a cube. Brick 1 has a height of 80 mm, a width of 80 mm and a height of 80 mm. Brick 1 has two cells 2 which extend and pass through brick 1. The two cells 2 are spaced from each other by a partition 3 which has a thickness of 8 mm. The tests in Table 3 were carried out on the aforementioned brick 1.

[0101] However, it is obvious that the material obtained using the aforementioned extrudable paste can have other shapes and dimensions, for example a general shape of a rectangular parallelepiped having a plurality of cells spaced from each other by partitions. The thickness of the partitions is between 5 and 10 mm.

[0102] The building material can be used in particular for wall construction.

[0103] Although the invention has been described in connection with several particular embodiments, it is obvious that it is in no way limited thereto and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the claims.

[0104] The use of the verb "comprise", "comprise" or "include" and its conjugated forms does not exclude the presence of other elements or other steps than those set out in a claim.

[0105] In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims

Raw earth paste intended to be extruded in order to form a honeycomb construction material, the paste comprising:- a composition representing 75% to 85% of the total mass of the paste, and- water representing 15% to 25% of the total mass of the paste,in which the composition comprises:a clay mixture representing 35% to 55% by mass of the composition, the clay mixture comprising more than 90% by mass of the clay mixture of minerals selected from the kaolinite group,sand representing 40% to 60% by mass of the composition, anda mineral binder representing 5 to 12% by mass of the composition, the mineral binder not being clay. The paste of claim 1, wherein the clay mixture is composed of more than 50% by mass of said clay mixture of the mineral kaolinite. Paste according to one of claims 1 to 2, in which the minerals of the Kaolinite group have a cumulative rejection at 40 µm of less than 10% of the total mass of the minerals of the Kaolinite group. Paste according to one of claims 1 to 3, in which the mineral binder represents 7 to 11% by mass of the composition. Paste according to one of claims 1 to 4, in which the mineral binder is chosen from: a hydraulic binder, an aerial binder or a mixture thereof. Paste according to claim 5, in which the mineral binder is chosen from: air lime, hydraulic lime, Portland cement or a mixture thereof. Paste according to claim 1 to 6, in which the water represents 19% to 20% of the total mass of the paste, the clay mixture represents 39% to 41% by mass of the composition, and the mineral binder is a mineral binder representing 9% to 11% by mass of the composition, the mineral binder preferably being hydraulic lime NHL3.

5. Paste according to claim 1 to 6, in which the water represents 17.2% to 18.3% of the total mass of the paste, the clay mixture represents 39% to 41% by mass of the composition, the mineral binder represents 6 to 8% by mass of the composition, the mineral binder preferably being CEM 1 52.5 T. A honeycomb construction material made of raw earth obtained by extrusion via the paste according to one of claims 1 to 8, the construction material comprising:- a composition representing at least 90% of the total mass of the raw earth material, and- water representing less than 10% of the total mass of the paste,in which the composition comprises: a clay mixture representing 35% to 55% by mass of the composition,the clay mixture comprising more than 90% by mass of said clay mixture of minerals chosen from the kaolinite group,sand representing 40% to 60% by mass of the composition, anda mineral binder representing 5 to 12% by mass of the composition. Building material according to claim 9, having dimensions greater than:- 250 mm in height;- 400 mm in length; and- 150 mm in width. Building material according to claim 9 or 10, the building material being subjected during its manufacture to temperatures below 100°C. A method of manufacturing a honeycomb construction material, the method comprising the following steps:- providing a paste according to one of claims 1 to 8,- inserting the paste into the extruder,- extruding the paste via an extruder to form a honeycomb material,- drying the paste to obtain a honeycomb construction material according to one of claims 9 to 11. The manufacturing method of claim 12, wherein the extrusion step is carried out by applying an extrusion pressure of between 800 kPa and 1100 kPa.

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