COMPOSITION COMPRISING SARGASUSA AND CEMENT

Abstract

COMPOSITION COMPRISING SARGASSUM AND CEMENT The invention relates to a composition comprising at least cement and dried and ground brown algae of the Sargassaceae family, the amount of cement being at least 50% by weight relative to the total weight of said composition, it also relates to a construction material comprising the composition according to the invention, sand and gravel, a method for preparing the construction material and its use for manufacturing an article chosen from a concrete block, cast concrete, a slab, a prefabricated panel. Figure for the abstract: Fig. 1

Description

Title of the invention: COMPOSITION COMPRISING SARGASSUM AND CEMENT Field of invention

[0001] The invention relates to the field of construction materials and in particular the field of ecological materials also called eco-materials.

[0002] More particularly, the present invention relates to a cement concrete type material incorporating particular algae and having improved mechanical properties; this material is part of an approach to enhancing the value of invasive algae species. State of the art

[0003] The most widely used material in the world for building construction is concrete. In fact, it is estimated that 50% of the raw materials consumed worldwide are used for building construction. It should also be noted that global cement production has increased by 80% over the last ten years and could triple by 2050.

[0004] The construction sector is a major consumer of energy, particularly energy produced from fossil raw materials. In addition, this sector generates 25% of greenhouse gas emissions. For example, the production of cement, which is one of the constituents of concrete, generates approximately 5% of global emissions in CO2 equivalents. More specifically, 2 / 3 of the CO2 emissions linked to the manufacture of cement come from the chemical reaction of clinker manufacture.

[0005] It has also been noted that industrial activity linked to the construction of buildings generates large volumes of non-recyclable waste.

[0006] Based on these findings, the development of eco-materials designed at least in part from bio-sourced and renewable raw materials appears to be a way forward. Even more so, the development of eco-materials designed from raw materials considered to be waste

[0007] According to the decree of December 19, 2012, published in the Official Journal of December 23, 2012, which specifies the conditions for awarding the “biosourced building” label, the concept of biosourced material is defined as “a material derived from plant or animal biomass that can be used as a raw material in construction products” including: wood, flax, cellulose wadding, cereal straw and other plants, hemp, cotton, animal wool. “Construction materials or construction and decoration products containing a quantity of biosourced material” are considered biosourced construction products. Materials to earth base (rammed earth, bricks, coatings, cob, etc.) natural and geo-sourced, are also part of this category of materials.

[0008] The present invention is part of this development of bio-sourced eco-materials since it uses, as renewable natural materials, algae from the Sargassaceae family.

[0009] Sargassum or Sargassum spp. are brown algae considered as invasive species under the Marine Strategy Framework Directive (Marine Action Plan Channel - North Sea - Environmental Objectives and Associated Indicators - 2012). They accumulate along the coastline of certain regions and are not currently really used.

[0010] Sargassum demonstrates a great capacity for regeneration and adaptation as well as a very good capacity for reproduction, proliferation and colonization of new environments, often to the detriment of native species: in fact, they can grow 10 cm per day in spring. They are now considered to be expanding and very invasive in many countries with coasts bordering the Atlantic Sea, the Mediterranean Sea, the English Channel or the North Sea.

[0011] In France, the phenomenon is known mainly in Overseas France, and more particularly in the Antilles, where sargassum washes up in thousands of tons on the beaches and causes considerable economic losses, particularly in the tourism sector, the main sector of activity on these islands. This phenomenon is also visible in the West Cotentin, where the economic activity of fishing and in particular mussel farming is strongly impacted, in fact the accumulation of sargassum at the foot of mussel parks forms a barrier which limits the circulation of water and therefore the supply of food for the molluscs.

[0012] The stranding of seaweed on the coasts of the West Indies or Normandy coasts leads to the formation of a layer which can sometimes reach more than 50 cm and whose decomposition of organic matter is likely to pose significant health problems. Several studies have shown that exposure to toxic fumes from decomposing and uncollected sargassum seaweed is dangerous for health, causing in particular toxic respiratory irritations (release of hydrogen sulfide H2S). It therefore appears crucial not to allow these seaweeds to decompose on the coast.

[0013] Furthermore, sargassum is known to easily accumulate heavy metals and several studies have shown that it can be contaminated by arsenic and pesticides such as chlordecone, which makes it difficult to recycle. However, burning it (as is the case in Mexico) poses enormous pollution problems and burying it (as is the case in Florida) creates problems of soil contamination by the chemical components that these algae can carry.

[0014] The use of algae in the manufacture of construction materials has already been proposed in the prior art.

[0015] The article “Electron Microscopy Characterization of Sargassum Spp. from the Mexican Caribbean for Application as a Bioconstruction Material » Microsc. Microanal. 27 (Suppl 1), 2021 by Luis Bernardo Lôpez-Sosa et al. doi: 10.1017 / S1431927621010874 aims at a mixture of cement and sargassum (95-5%) washed with distilled water and dried to increase thermal insulation. The algae used are not crushed.

[0016] Patent KR101347792 B1 describes a cement composition comprising algae and the production of high compressive strength concrete. The proportion of algae ranges from 10 to 40 parts per 100 parts of cement. This patent does not mention the use of sargassum.

[0017] Finally, the applicant's patent application FR 3 117 483 A1 relates to a construction material of the building brick type comprising dried algae, in particular brown algae from the Sargassaceae family mixed with clayey soil.

[0018] Faced with the problems presented by sargassum, the present invention proposes a solution which implements the collection and direct recovery of these algae without energy-intensive transformation or generation of waste. In addition, any contaminants are encapsulated and therefore do not risk being released into the environment. Summary of the invention

[0019] A first object of the invention relates to a composition comprising at least cement and dried and ground brown algae of the Sargassaceae family, the quantity of cement being at least 50% by weight relative to the total weight of said composition.

[0020] A second object of the invention relates to a construction material comprising a composition according to the invention, sand, preferably having a 0 / 5 grain size and gravel, preferably having a 5 / 20 grain size.

[0021] A third object of the invention relates to a method for preparing the construction material according to the invention comprising the following steps, in this order: • mixing the sand and gravel so as to obtain a homogeneous mixture; • add to the mixture obtained in the previous step, the brown algae of the family dried and crushed Sargassaceae then mix; • add the cement and mix; • add water; • possibly pour the mixture obtained in the previous step into a mold adapted; • let the mixture dry; • recover the dried material.

[0022] Advantageously, the construction material according to the present invention is a cement concrete. This concrete is stable over time and it has advantageous properties, particularly in terms of mechanical properties and thermal insulation. More particularly, the construction material according to the invention, when dried, has a high compressive strength.

[0023] A fourth object of the invention is the use of the construction material according to the invention or obtained according to the method according to the invention to manufacture an article chosen from a concrete block, cast concrete, a slab, a prefabricated panel.

[0024] Another advantage of the material according to the present invention is that it comprises a significant volume quantity of algal biomass resulting from photosynthesis, which makes it a real carbon sink.

[0025] Furthermore, the process of preparing the material, which consists of mixing the dried and crushed algae with cement and other natural components such as sand and gravel, is energy-efficient.

[0026] As a result, the material obtained allows an overall reduction in CO2 emissions and has a positive carbon balance.

[0027] The materials obtained are stable and do not lead to a release of toxic compounds into the environment.

[0028] Other aspects, properties and advantages of the present invention will appear on reading the description and examples which follow. Description of figures

[0029] [Fig.l] represents the speed of ultrasonic pulses (103 m / s) as a function of the percentage of sargassum in the formulation. Description of the invention

[0030] By “construction material”, within the meaning of the present invention, is meant any type of material used in the construction sector, preferably concrete, and more particularly a concrete block, cast concrete, a slab, a prefabricated panel. Algae

[0031] The composition according to the present invention comprises at least cement and brown algae of the Sargassaceae family.

[0032] According to a particular variant, the brown algae used are algae of the genus Sargassum and preferably they are chosen from Sargassum fluitans and Sargassum muticum.

[0033] Sargassum fluitans is a drifting macroalgae and Sargassum muticum is a macroalga attached to a substrate.

[0034] The algae used according to the present invention are harvested from the coasts where they wash up, or directly from the surface of the sea, by any means known to those skilled in the art. The algae thus harvested contain between 70% and 90% water.

[0035] The algae used according to the present invention are dried, that is to say the water present in the algae is eliminated.

[0036] According to a first implementation of the invention, the drying of the algae is carried out in the open air, without external intervention, that is to say without the implementation of an energy-consuming process. The drying time according to this process is between 1 and 15 days. According to a preferred variant, the algae are dried on racks exposed to the sun or on sand heated in the sun.

[0037] According to a second implementation of the invention, the drying of the algae is carried out by heating the harvested algae, for example in an oven, a dryer or a smokehouse. The drying time according to this method is between 0.5 and 8 days.

[0038] Dried seaweed is defined as no longer containing water, or only traces of water. Dried seaweed has lost at least 80% of its initial mass, generally about 90% of its initial mass.

[0039] Advantageously, the brown algae are not rinsed. This variant makes it possible not to increase the production cost, and furthermore, avoiding a rinsing step makes it possible to reduce the carbon footprint of the material preparation process.

[0040] According to another implementation of the invention, the algae are rinsed with fresh water after their collection, so as to partially or completely eliminate the deposited sea salt.

[0041] These algae have a high level of alginates which are polysaccharides organized into fibers. Alginates are the salts of alginic acid, coupled with calcium (AlgCa) or magnesium (AlgMg) ions.

[0042] Alginic acid, CAS number 9005-32-7, is a heteropolymer formed by the chaining of two monosaccharides derived from GD-mannose, [3-D-mannuronic acid and aL-guluronic acid, some monomers being acetylated. The bond is made via [3-1-4. The proportion and distribution of these two monomers is different from one alginate to another, which explains the differences in physical and chemical properties observed depending on the origin of each alginate.

[0043] Depending on the species, alginates represent 18 to 40% of the dry matter of algae.

[0044] Alginates extracted from algae are used in various industrial sectors, such as the food, pharmaceutical and cosmetic industries, as gelling agents, thickeners, stabilizers or emulsifiers.

[0045] Seaweeds of the Sargassaceae family also contain the following components:

[0046] - fucoidans which are sulfated polysaccharides present in the cell walls lular; these are polymers of fucose and sulfate esters;

[0047] - laminarans or laminarins, carbohydrate storage polysaccharides;

[0048] - cellulose;

[0049] - many photosynthetic pigments such as chlorophyll a and c, b- carotene and xanthophylls;

[0050] - phenolic compounds such as bromophenols, fucols, phlorethols, and others.

[0051] The brown algae used are crushed and possibly sieved.

[0052] Advantageously, the brown algae are ground into particles with a dimension of less than 1.25.10 2 m (12.5 mm), preferably between 1.104 m and 1.25.102 m.

[0053] According to a first variant, the brown algae are in the form of particles with a dimension between 1.10 4 m and 4.103 m.

[0054] According to a second variant, the brown algae are in powder form, preferably of a size ranging from 1.10 4 m (100 pm) to 1.10 3 m.

[0055] The introduction of a quantity of brown algae into the material according to the present invention makes it possible not only to improve the structural qualities of the material but also to constitute a carbon sink. Cement

[0056] The composition according to the invention also comprises cement.

[0057] For the purposes of this text, the term "cement" means a hydraulic binder, i.e. a compound which hardens under the action of water. Cement is generally composed of clinker and other components such as silica fumes, pozzolan, blast furnace slag. Clinker is a product resulting from the firing at very high temperature of a mixture of approximately 80% limestone and 20% aluminosilicates.

[0058] Cements are generally classified under the name “CEM” followed by a Roman numeral from I to V depending on their clinker and other component content.

[0059] Preferably, the cement used in the present invention is of category CEM II. CEM II cements, also called composite Portand cements, contain at least 65% clinker.

[0060] Preferably, the composition according to the present invention consists of dried and ground brown algae of the Sargassaceae family and at least 50% cement.

[0061] Preferably, the composition comprises from 2 to 14%, preferably from 5 to 12% and more preferably from 6 to 11% by weight of dried brown algae relative to the total weight of the mixture of cement and dried brown algae. Building material

[0062] The present invention also relates to a construction material, preferably a cement concrete comprising the composition according to the invention.

[0063] Preferably the construction material according to the present invention comprises: a composition according to the present invention; sand, preferably with a grain size of 0 / 5; gravel, preferably with a grain size of 5 / 20.

[0064] The grain size of sands and gravels is defined by the diameters d / D given in mm, d being the diameter of the smallest grain and D the diameter of the largest grain.

[0065] Advantageously, the sand used in the materials according to the invention is formed of grains of size less than 5 103 μm, preferably ranging from 20 106 μm to 2 103 μm.

[0066] Advantageously, the gravels used in the materials according to the invention are formed from particles of size ranging from 5 103 m to 20 103 m.

[0067] Preferably, the construction material according to the present invention comprises: from 10 to 20%, preferably from 12 to 18% and more preferably from 14 to 16% by weight of a composition according to the present invention; from 25 to 40%, preferably from 28 to 35% and preferably from 31 to 33% of sand, preferably having a grain size of 0 / 5; from 45 to 60%, preferably from 50 to 56% and preferably from 53 to 55% of gravel, preferably having a grain size of 5 / 20.

[0068] Advantageously, the construction material according to the present invention comprises from 0.5 to 3.0%, preferably from 0.6 to 2.5% by weight of brown algae of the Sargassaceae family relative to the total weight of the construction material.

[0069] The construction materials, preferably cement concretes, according to the invention are prepared according to a process comprising the following steps, in this order: -mix the sand and gravel to obtain a homogeneous mixture; -add to the mixture obtained in the previous step, the dried and crushed brown algae of the Sargassaceae family then mix;

[0070] -add the cement and mix;

[0071] - add water, preferably mixing water; - possibly pour the mixture obtained in the previous step into a mold;

[0072] -dry or let dry;

[0073] - recover the dried material.

[0074] At each stage, the mixing is carried out in such a way as to obtain a homogeneous product. Of course, the preparation of a homogeneous material, in particular a homogeneous concrete, falls within the skills of a person skilled in the art. In addition, it is also within the skills of a person skilled in the art to calculate the quantity of water to be added in depending on the desired consistency of the final material, particularly for the final concrete.

[0075] The material obtained is then left to dry.

[0076] Advantageously, the composition according to the present invention is used for the preparation of a cement concrete, in particular a concrete block or a cast concrete, slabs, prefabricated panels.

[0077] The compositions according to the present invention are advantageously used in the manufacture of construction materials, in particular in the manufacture of cement concretes.

[0078] The cement concretes according to the invention have a high compressive strength. The compressive strength is measured by sonic auscultation according to standard NF EN 12504-4 of July 2021, a high-strength concrete corresponds to a value V such as 3700m / s <V<4200 m / s.

[0079] Ultrasonic pulse velocity testing is a non-destructive test used to determine the quality of concrete on site. This test essentially involves evaluating the speed of the electronic pulse passing through the concrete from a transmitting transducer to a receiving transducer.

[0080] The principle of the ultrasonic pulse velocity test is that the speed of sound in a solid material is a function of the square root of the ratio of its elastic modulus E to its density P. The density and elastic properties of the material are related to its quality and strength, respectively.

[0081] The speed of the electronic pulses varies from 3 km / h to 5 km / h, on average. The frequency of the generated electronic pulse varies from 15 kHz to 175 kHz.

[0082] The apparatus used for ultrasonic pulse velocity testing consists of a transmitter and a receiver which are held against two faces of concrete. The electronic pulse of ultrasonic frequency is generated by the apparatus which is transmitted through the concrete using the transmitter. The emitted pulses are received by the receiver, which is located on the other face of the concrete.

[0083] When the electronic pulses are received, they are also recorded by the device.

[0084] The travel time of electronic pulses is measured as they travel from the transmitter to the receiver. The length of the path traveled by the pulses is divided by the travel time of the pulses which gives the average speed of propagation of the waves. The pulse speed is correlated with the strength of the concrete. The higher the pulse speed, the higher the strength of the concrete. Arrangement of transducers.

[0085] The measurement of the electronic pulse velocity through the concrete was carried out by direct transmission (in transparency): the direct transmission method is the most reliable method for measuring pulse velocity through concrete since the maximum pulse energy is transmitted perpendicular to the transmitter face. In addition, the pulse travel path can be measured clearly and accurately because it can be easily defined.

[0086] The following examples illustrate the invention without limiting its scope. Example

[0087] The following cement concretes were prepared according to the process described below from the following components: -CEM II cement, -sand of grain size (0 / 5), -gravel of grain size (6 / 10), -dried sargassum powder of size 4.104m (400 pm) -mixing water. Sargassum powder

[0088] Sargassum powder is obtained according to the following process.

[0089] 10 kg of sargassum were harvested on the coast and then dried in the sun. for 10 days. They were weighed before and after drying, it was determined that they had lost 90% of their initial mass.

[0090] The algae were then ground using a Mandine blender and sieved to obtain a powder of 4.104m. Material preparation process

[0091] In a first step, 1108.8 g of sand and 1885.0 g of gravel were mixed in a container for 30 seconds to obtain a homogeneous mixture.

[0092] Then, different contents of sargassum powder obtained above were added to the sand and gravel mixture and dispersed. The amount of sargassum added in each of the compositions A, B and C is specified in Table 1.

[0093] Then CEM II cement was added to the mixture of sargassum, sand and gravel and dispersed. The amount of cement added is specified in Table 1.

[0094] Finally, mixing water was added gradually while mixing with an electric mixer. The amount of water added is specified in Table 1.

[0095] Table 1 lists the quantities of the various constituents of cement concrete, as well as, in the penultimate column, the percentage of algae (sargassum) in the composition composed of cement + algae, and in the last column, the percentage of algae (sargassum) in the concrete composed of cement, algae, sand and gravel.

[0096] [Tables 1] CEMII cement (g) Sand (g) Sargassum (g) Gravel (g) Water (g) % algae in comp. ci-mentalgue s % algae in concrete Control 485.1 1108.8 0.0 1885.0 235.6 0% 0% A 485.1 1108.8 24.2 1885.0 286.0 4.8% 0.63% B 485.1 1108.8 48.5 1885.0 336.4 9.0% 1.25% C 485.1 1108.8 72.7 1885.0 386.8 13.0% 1.85%

[0097] Each concrete composition was then poured into a mold with dimensions of 102 m (cm) 11 X 22X6.

[0098] Then the concrete blocks were left to dry.

[0099] Measurement of the compressive strength of cement concretes

[0100] Table 2 shows the ultrasonic pulse velocities (UVV) in km / s for the control and the 3 compositions A, B and C (column 3), the percentage increase in the UVV of compositions A, B and C compared to the value at T0 (column 4) and the estimated compressive strengths of compositions A, B and C (column 5)

[0101] The measurements were carried out on concrete blocks with dimensions of 102 m (cm) 11 X 22X6.

[0102] The measurements were carried out in accordance with the above description with a 58-E4800 sonic auscultation device from Controls with a generated electronic pulse frequency of 50 kHz.

[0103] The direct transmission method was used, the transmitter and the receiver being placed on two opposite faces of the concrete block and therefore separated by the length of the block, i.e. 0.21 m.

[0104] [Tables2] Sample % algae in the cement + sargassum composition Ultrasonic pulse velocity VIU (103 m / s) % increase in VIU compared to T0 Estimated compressive strength (MPa) Control T0 0% 3.58 22.15 A 4.8% 3.82 +7% 23.54 B 9.0% 4.06 +13% 25.00 C 13.0% 3.65 +2% 22.33

[0105] [Fig.l] represents the speed of ultrasonic pulses (103 m / s), data from column 3 as a function of the percentage of sargassum in the cement + sargassum composition of column 2.

[0106] The results of the sonic auscultation compressive strength tests show that the introduction of sargassum into cement concrete significantly increases its compressive strength, in particular the presence of 9% sargassum (1.25% in the concrete) improves the compressive strength by 13% compared to conventional concrete without sargassum (line 4).

[0107] According to the INIES database, the carbon footprint corresponding to the production of one m3 of concrete is 242 kg CO2 eq and it has been calculated that the production of 1 m3 of Sargassum concrete according to the invention produces 241 kg CO2 eq, i.e. a reduction of 1% in its carbon footprint.

Claims

Claims

1. Composition comprising at least cement and dried and ground brown algae of the Sargassaceae family, the amount of cement being at least 50% by weight relative to the total weight of said composition.

2. Composition according to claim 1 in which the brown algae are of the genus Sargassum and preferably chosen from Sargassum fluitans and Sargassum muticum.

3. Composition according to claim 1 or 2 in which the brown algae are ground into particles of size less than 1.25.102

4. m. Composition according to any one of the preceding claims in which the brown algae are in powder form, preferably of size ranging from 1.10 4 m to 1.10 3 m.

5. A composition according to any preceding claim wherein the brown algae are not rinsed.

6. Composition according to any one of the preceding claims comprising from 2 to 14%, preferably from 5 to 12% and more preferably from 6 to 11% by weight of dried brown algae relative to the total weight of the mixture of cement and dried brown algae.

7. Composition according to any one of the preceding claims in which the cement is of CEM II category.

8. Construction material comprising: • a composition according to any one of claims 1 to 7; • sand, preferably having a grain size of 0 / 5 and • gravel, preferably having a grain size of 5 / 20.

9. Construction material according to the preceding claim comprising: from 10 to 20%, preferably from 12 to 18% and more preferably from 14 to 16% by weight of a composition according to any one of claims 1 to 8; from 25 to 40%, preferably from 28 to 35% and more preferably from 31 to 33% of sand, preferably having a particle size of 0 / 5; from 45 to 60%, preferably from 50 to 56% and more preferably from 53 to 55% of gravel, preferably having a particle size of 5 / 20.

10. Building material according to claim 8 or 9 comprising from 0.5 to 3.0%, preferably from 0.6 to 2.5% of brown algae of the Sargassaceae family relative to the total weight of the building material.

11. A method of preparing the construction material according to any one of claims 8 to 10 comprising the following steps, in this order: • mixing the sand and gravel so as to obtain a homogeneous mixture; • adding to the mixture obtained in the previous step, the dried and crushed brown algae of the Sargassaceae family and then mixing; • adding the cement and mixing; • adding water; • optionally pouring the mixture obtained in the previous step into a mold; • allowing the mixture to dry; • recovering the dried material.

12. Use of the construction material according to any one of claims 8 to 10 or obtained according to the method of claim 11 for manufacturing an article chosen from a concrete block, cast concrete, a slab, a prefabricated panel.

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