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WO2025104200A1 - Aqueous geopolymer composition based on dredging sediments, geopolymer material obtained from the aqueous geopolymer composition, and uses thereof in particular in the field of eco concretes - Google Patents

Aqueous geopolymer composition based on dredging sediments, geopolymer material obtained from the aqueous geopolymer composition, and uses thereof in particular in the field of eco concretes Download PDF

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Publication number
WO2025104200A1
WO2025104200A1 PCT/EP2024/082412 EP2024082412W WO2025104200A1 WO 2025104200 A1 WO2025104200 A1 WO 2025104200A1 EP 2024082412 W EP2024082412 W EP 2024082412W WO 2025104200 A1 WO2025104200 A1 WO 2025104200A1
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Prior art keywords
aqueous
geopolymer
mass
sediments
composition
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PCT/EP2024/082412
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French (fr)
Inventor
Nadia SAIYOURI
Lisa MONTEIRO
Jacqueline SALIBA
Humberto YANEZ-GODOY
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Centre National de la Recherche Scientifique CNRS
Ecole National Superieure dArts et Metiers ENSAM
Universite de Bordeaux
Institut Polytechnique de Bordeaux
Original Assignee
Centre National de la Recherche Scientifique CNRS
Ecole National Superieure dArts et Metiers ENSAM
Universite de Bordeaux
Institut Polytechnique de Bordeaux
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Publication of WO2025104200A1 publication Critical patent/WO2025104200A1/en
Pending legal-status Critical Current
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/006—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing mineral polymers, e.g. geopolymers of the Davidovits type
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/04—Waste materials; Refuse
    • C04B18/0436—Dredged harbour or river sludge
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/00034—Physico-chemical characteristics of the mixtures
    • C04B2111/00206—Compositions defined by their elemental analysis
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/10—Compositions or ingredients thereof characterised by the absence or the very low content of a specific material

Definitions

  • Aqueous geopolymer composition based on dredged sediments a geopolymer material obtained from said aqueous geopolymer composition, and their applications in particular in the field of ecological concretes
  • the present invention relates to an aqueous geopolymer composition based on dredged sediments, a geopolymer material obtained from said aqueous geopolymer composition, the use of said aqueous geopolymer composition as a binder for the manufacture of concrete, a filling grout, a concrete pavement, a compacted road layer, bricks, a retaining wall, a quayside breakwater, or pre-cast concrete, and a concrete comprising said geopolymer material.
  • the present invention falls within the framework of the recovery of non-immersible dredging sediments in ecological concretes for applications in public works.
  • Water is an agent of physical and chemical erosion of the rocks and soils it drains. Mineral and/or organic particles in suspension accumulate, thanks to the processes of flocculation or gravitation, in the bottom of river and sea ports and rivers; this is the natural process of sedimentation.
  • sea ports and waterways it is necessary to dredge the bottoms in order to maintain navigability (river traffic) and/or prevent flood risks.
  • the concept of dredging also includes the operations of digging new ports, in particular marinas, or access channels for boats with increasingly deep drafts, the extension of existing ports, and port maintenance work (pleasure, commercial, industrial, fishing), often estuary ports which have a natural tendency to silting up.
  • Dredged sediments are a mixture of sands, silts and clays. Traditionally, all or almost all marine sediments, regardless of their level of contamination, were "slammed" off the coast, in pits dedicated to their immersion.
  • a first strategy for storing sediments consists of depositing the sediments by pumping them into basins dug on the ground.
  • the characteristics of the sediments change under the influence of, in particular, contact with air, which causes oxidation of the environment, temperature differences, which influence microbial activity, and a decrease in water content, which causes dehydration of the environment.
  • the sediment is in fact capable of adsorbing and transforming contaminants and transferring them to the soil or water tables. Trace element contamination of soils is likely to disrupt biological activity and therefore lead to long-term harmful consequences for the overall functioning of the ecosystem.
  • the presence of inorganic or organic contaminants can also cause long-term effects, particularly for species at the end of the food chain due to the bio-accumulative and/or bio-amplifiable nature of these substances.
  • a second strategy for storing sediments consists of storing/burying them in waste storage facilities.
  • Onshore sediment recovery channels have been the subject of growing interest from port and waterway managers in France due to regulations that make it increasingly difficult to "sludge" sediments. dredged, the downward revision of management thresholds, the main consequence of which is to increase the volumes to be treated on land, and the financial aspect, since the recovery of sediments would allow managers to transform a material currently considered as waste into a material with a use value, a source of savings or even profits.
  • There are many ways to recover sediments on land However, their implementation on an industrial scale is not so simple and most often requires the pre-treatment and/or treatment of dredged sediments to sort them and reduce the pollutant levels to make them acceptable.
  • Pretreatment may include dewatering and separating the different layers to reduce volume, control contamination levels, and guide subsequent treatment.
  • Treatment generally allows.
  • the treatment may be a biological treatment (bioremediation, biowashing/bioleaching, spreading, composting), a physicochemical treatment (physicochemical extraction such as flotation or chemical washes), a thermal treatment (thermal desorption, pyrolysis, wet oxidation, molten salt baths), an immobilization treatment (platforms, in situ decantation, for drying), or a mixture thereof.
  • the recovery channels for dredged sediments include reclamation, beach replenishment, dune or bank reinforcement, backfilling (landscaped mounds, banks, earthworks or polder), construction materials in the construction sector (concrete, bricks, road materials and roads).
  • WO2016/198176 describes a supplementary cementitious material for use in association with a bearing cement as a hydraulic binder.
  • the supplementary cementitious material is obtained from dredged sediments comprising sorting the sediments for recovery of the fine part, contacting the fine part with portlandite (Ca(OH)2, CaO), dehydration and then heat treatment (calcination).
  • the invention relates firstly to an aqueous geopolymer composition, characterized in that it comprises dredging sediments, at least one alkali silicate and at least one metakaolin, and in that the aqueous geopolymer composition is free of alkaline base and the metakaolin represents at least 15% by mass relative to the total mass of the aqueous geopolymer composition.
  • the aqueous geopolymer composition of the invention makes it possible, on the one hand, to recover dredging sediments and, on the other hand, to produce a geopolymer material which has good characteristics in terms of mechanical properties so that it can be used in construction materials. Furthermore, the presence of at least 15% by mass of metakaolin and the absence of alkaline base introduced into the aqueous geopolymer composition contribute to obtaining good mechanical properties while reducing CO2 emissions (balance between the mass of CO2 emitted and the compressive strength in MPa).
  • the aqueous geopolymer composition of the invention thus makes it possible to provide a common response to the problems of sediment management and the need for public works to develop new materials using local and renewable resources to limit the impact Carbon footprint of concrete production and material transportation.
  • concrete is the most consumed material in the world after water and cement, one of its main constituents, and is responsible for 5 to 7% of global CO2 emissions. This alarming figure is not expected to decrease, as by 2030, global demand for cement is expected to increase by 216%.
  • the invention proposes the reuse of dredged sediment in new low-CO2 mortars while ensuring proximity to production and ease of supply to limit transportation.
  • the aqueous composition is capable of geopolymerizing (i.e. polycondensing) to form a geopolymer material.
  • dredged sediments are precursors of geopolymerization and participate in the geopolymerization reaction to form a geopolymer material.
  • the geopolymer composition is an aqueous composition. In other words, it comprises water.
  • the aqueous geopolymer composition comprises from 15 to 40% by mass approximately of water, particularly preferably from 17 to 30% by mass approximately of water, and more particularly preferably from 20 to 25% by mass approximately of water, relative to the total mass of the aqueous geopolymer composition.
  • the water content is thus sufficient to allow the geopolymerization reaction without creating too much porosity in the final geopolymer gel which could then lead to shrinkage or contraction.
  • the water preferably comes mainly, and even more preferably only, from recovered dredging sediments and alkali silicate which can be in the form of an aqueous solution.
  • the water content of the dredged sediments can be determined according to standard NF P94-047. It then makes it possible to determine the water content of the aqueous geopolymer composition.
  • sediments are materials resulting from the erosion of rocks by water, wind and other erosion agents, and which, depending on their origin, can be fluvial, glacial, lacustrine or marine.
  • the dredged sediments (used in the aqueous geopolymer composition) are untreated.
  • the dredged sediments used in the composition have not undergone any chemical or thermal treatment(s). They are therefore used as is without prior chemical or thermal treatment(s).
  • the dredged sediments used in the aqueous geopolymer composition are therefore in a natural state. They are, for example, different from calcined sediments, mine tailings and/or foundry sludge.
  • the first materials have undergone a high-temperature heat treatment which removes a large portion of organic matter; the second and third materials are loaded with metals.
  • dredged sediments come from the sea and are controlled in terms of pollution (e.g. metal thresholds defined by the ministerial decree of August 9, 2006 and the decree of December 23, 2009).
  • the dredged sediments used in the composition of the invention have in particular metal contents lower than these thresholds.
  • the aqueous geopolymer composition preferably comprises from 25 to 65% by mass approximately of dredged sediments, particularly preferably from 30 to 45% and particularly preferably from 30% to 40% by mass of dredged sediments, relative to the total mass of the aqueous geopolymer composition.
  • the dredged sediments have a particle size of at most about 100 ⁇ m, and particularly preferably at most about 60 ⁇ m.
  • the dredged sediments used in the composition preferentially correspond to a fine fraction of dredged sediments.
  • the dredged sediments used in the aqueous geopolymer composition are preferably muddy silty sediments.
  • the muddy silty sediments are characterized by a high content of SiO2 and/or AI2O3.
  • X-ray diffraction analyses preferentially show similar mineralogies consisting mainly of quartz (SiC), Albite (NaAlSisOs) and Muscovite (KAl2(AISi30io)(OH,F)2).
  • the dredged sediments comprise at least approximately 25% by mass of SiO2, and more particularly preferably at least approximately 40% by mass of SiO2, relative to the total mass of the dredged sediments.
  • the dredged sediments comprise at least approximately 8% by mass of AI2O3, and more particularly preferably at least approximately 10% by mass of AI2O3, relative to the total mass of the dredged sediments.
  • the dredged sediments comprise silicon and aluminum, so that the SiC/AkC mass ratio is greater than or equal to 2, particularly preferably ranging from 2.1 to 4.0, and more particularly preferably ranging from 2.8 to 3.1.
  • the dredging sediments used in the aqueous geopolymer composition may comprise from 65% to 80% by mass approximately of silt, and preferably from 68% to 75% by mass approximately of silt, relative to the total mass of the dredging sediments. This is also referred to as the silt fraction.
  • the dredging sediments used in the aqueous geopolymer composition may comprise at least approximately 2% by mass of clay, preferably at least approximately 3% by mass of clay, and even more preferably from approximately 4% to 10% by mass of clay, relative to the total mass of dredged sediments. Also referred to as the clay fraction.
  • the mechanical properties of the geopolymer material may vary and/or not be reproducible.
  • the aqueous geopolymer composition of the invention makes it possible to guarantee good reproducibility of mechanical performance and/or stable mechanical performance regardless of the clay content of the dredged sediments.
  • the dredging sediments preferably comprise at most approximately 30% by mass of sand, and particularly preferably from 10% to 25% by mass of sand, relative to the total mass of the dredging sediments. This is also referred to as the sandy fraction or sandy particles.
  • the sand grains are too large to be able to bind to the geopolymer matrix, creating areas of voids, microfissures and a heterogeneous geopolymer material.
  • the content of silt, clay, and sand in the dredged sediments can be determined using the laser granulometry method.
  • the dredged sediments may further comprise organic matter.
  • the mechanical properties of the geopolymer material may vary and/or not be reproducible.
  • the organic matter content of the dredged sediments may be determined by a thermal calcination test at 450°C according to standard XP P94-0947.
  • the aqueous geopolymer composition of the invention makes it possible to guarantee good reproducibility of mechanical performance and/or stable mechanical performance regardless of the organic matter content of the dredged sediments.
  • the dredged sediments comprise at least approximately 3000 mg of organic matter, more preferably approximately 4000 to 15000 mg of organic matter, and even more preferably approximately 6000 to 14000 mg of organic matter, per kg of sediment.
  • the sediments preferably have a specific surface area ranging from 0.200 m 2 /g to 0.700 m 2 /g, and particularly preferably from 0.450 m 2 /g to 0.700 m 2 /g. This specific surface area reflects the quantity of gas that can be adsorbed to completely cover the surface of the sediments.
  • the specific surface area is preferably measured by the B.E.T. method.
  • the alkali silicate may be a sodium or potassium silicate and preferably a sodium silicate.
  • the alkali silicate has a Si/alkali metal molar ratio ranging from 1 to 2, and particularly preferably from 1.2 to 1.7. This thus makes it possible to further improve the compressive strength of the geopolymer material formed.
  • the aqueous geopolymer composition preferably comprises from 5 to 20% by mass approximately of alkali silicate, and particularly preferably from 7 to 12% by mass approximately of alkali silicate, relative to the total mass of the aqueous geopolymer composition.
  • the aqueous geopolymer composition comprises at least 15% by mass of metakaolin, preferably from 20 to 40% by mass approximately of metakaolin, and particularly preferably from 30 to 38% by mass approximately of metakaolin, relative to the total mass of the aqueous geopolymer composition.
  • metalakaolin means a dehydroxylated aluminosilicate. It is preferably obtained by dehydration of a kaolin or a kaolinite. This dehydration is conventionally obtained by calcination.
  • the metakaolin is a kaolin calcined at a temperature ranging from approximately 750°C to approximately 850°C.
  • Metakaolin can be analyzed by differential thermal analysis (DTA) [absence or presence of a crystallization point or peak], nuclear magnetic resonance (NMR) [27 Al NMR spectrum], and/or X-ray diffraction (XRD).
  • DTA differential thermal analysis
  • NMR nuclear magnetic resonance
  • XRD X-ray diffraction
  • the aqueous geopolymer composition can be characterized by a water/solid mass ratio (dredging sediments, alkali silicate, metakaolin) ranging from approximately 0.30 to 0.45, and preferably ranging from approximately 0.30 to 0.35.
  • the alkali silicate, the metakaolin, and the dredged sediments are defined by a mass ratio of alkali silicate/(metakaolin + dredged sediments) ranging from approximately 0.08 to 0.30, and particularly preferably ranging from approximately 0.10 to 0.20.
  • the aqueous geopolymer composition may further comprise one or more additives, such as recycled aggregates (sand, gravel, gravel) or crushed concrete; alkaline reagents (glass powder, rice husk ash, silica fume), additional highly aluminosilicate cementitious materials such as fly ash or silica fume.
  • additives such as recycled aggregates (sand, gravel, gravel) or crushed concrete
  • alkaline reagents glass powder, rice husk ash, silica fume
  • additional highly aluminosilicate cementitious materials such as fly ash or silica fume.
  • the second subject of the invention is a geopolymer material, characterized in that it is obtained by polycondensation and/or hardening of an aqueous geopolymer composition in accordance with the first subject of the invention.
  • Geopolymers are essentially mineral chemical compounds or mixtures of compounds comprising silico-oxide (-Si-O-Si-O), silico-aluminate (-Si-O-AI-O), ferro-silico-aluminate (-Fe-O-Si-O-AI-O), or alumino-phosphate (-AI-OPO-) type units, created by a geopolymerization process (i.e. polycondensation).
  • the most common geopolymers are those based on aluminosilicates designated under the term “poly(sialate)”.
  • the geopolymer obtained from the aqueous geopolymer composition is an aluminosilicate geopolymer.
  • the aluminosilicate geopolymer preferably results from the polycondensation of oligo(sialate) type oligomers formed from a mixture of at least one aluminosilicate, an alkaline reagent (e.g. alkali metal silicate) and water.
  • an alkaline reagent e.g. alkali metal silicate
  • the geopolymer may have the following formula: M n [-(Si-O2)z-AI-O] n .wH2O in which M is an alkali metal ion, and n represents the degree of polycondensation, w is the number of chemically bonded water molecules, and z is the number of silicon atoms that constitute a single oligomeric aluminosilicate chain.
  • M is an alkali metal ion
  • n represents the degree of polycondensation
  • w is the number of chemically bonded water molecules
  • z is the number of silicon atoms that constitute a single oligomeric aluminosilicate chain.
  • the latter depends, in turn, on the molar ratio of SiC /AkOs contained in the geopolymer. The choice of this ratio varies depending on the desired setting time and strength.
  • a sialate i.e., Mn(-Si-O-AI-O-)n
  • a sialatesiloxo i.e., Mn (-Si-O-AI-O-Si-O-) n
  • a sialate disiloxo i.e., Mn (-Si-O-AI-O-Si-O-Si-O) n
  • the aluminosilicate geopolymer of the invention preferably has an Si/AI atomic ratio ranging from 2.5 to 3.5.
  • the aqueous geopolymer composition makes it possible to form a geopolymer material having little shrinkage, better dimensional stability, better compressive strength at more than 28 days, and preferably at 90 days, better durability and reduced setting time.
  • the geopolymer material of the invention preferably has a compressive strength beyond 28 days of at least approximately 6 MPa, particularly preferably of at least approximately 6.5 MPa, and particularly preferably of at least approximately 7 MPa.
  • the compressive strength can be determined according to standard NF EN 1015-11, in particular using a press electromechanical with a capacity of 100 kN at a constant loading speed of 0.6 mm/min.
  • the third subject of the invention is the use of an aqueous geopolymer composition in accordance with the first subject of the invention, as a binder for the manufacture of concrete, a filling grout, a concrete pavement, a compacted road layer, bricks, a retaining wall, a quayside breakwater, or a pre-cast concrete, or for the manufacture of concrete, a filling grout, a concrete pavement, a compacted road layer, bricks, a retaining wall, a quayside breakwater, or a pre-cast concrete (i.e. use of the aqueous geopolymer composition in accordance with the first subject of the invention as such).
  • composition can in particular be used directly to manufacture concrete without adding additives.
  • the aqueous geopolymer composition based on dredged sediments of the invention is used as a binder (geopolymer binder).
  • binder means a compound which serves to agglomerate solid particles in the form of powder or aggregates.
  • the dredged sediments are precursors of geopolymerization and react with the alkali silicate and the metakolin, to form a binder which will make it possible to bind the granular elements of the concrete and provide mechanical resistance.
  • the binder can be used in the fields of public works and construction. This allows a 45% reduction in CO2 emissions, with higher performance than that obtained with Portland cement.
  • the fourth subject of the invention is a concrete, characterized in that it comprises a geopolymer material in accordance with the second subject of the invention.
  • the concrete does not include natural aggregates (sand, gravel, gravel) other than those present in the dredged sediments.
  • the concrete may be made of a geopolymer material in accordance with the second subject of the invention.
  • Figure 1 shows the compressive strength of a geopolymer material in accordance with the invention and of materials not in accordance with the invention.
  • Figure 2 shows the porosity characteristics of a geopolymer material in accordance with the invention and of a material not in accordance with the invention.
  • Figure 3 shows scanning electron microscopy (SEM) images of a geopolymer material in accordance with the invention and of a material not in accordance with the invention.
  • Example 1 characterization of the dredging sediments used in the composition of the invention
  • the Garonne estuary is mainly composed of two distinct granulometric fractions: sediments with a strong sandy tendency upstream of the estuary and silty-muddy sediments downstream.
  • the silty-muddy sediments were recovered at Pauillac and left to evaporate in tanks perforated with a geotextile for 1 to 3 months. Drying was carried out by infiltration and evaporation of the water. All fractions of the sediment were recovered.
  • the recovered dredged sediments comprise 71% by mass of silt, 24.5% by mass of sand, and 4.5% by mass of clay, relative to the total mass of dredged sediments. They have a particle size according to the NF P94-056 and NF P94-057 standards ranging from 2 to 50 ⁇ m.
  • the dredged sediments were also subjected to environmental tests in accordance with the decree of 9 August 2006 and the GEODE guide which determines the reference levels in France. No trace of contamination by heavy metals, PAHs and PCBs was observed. Indeed, the levels of contaminants measured were low and below the NI and N2 thresholds.
  • the recovered dredged sediments comprise 41.38% by mass of SiO2, and 14.19% by mass of AI 2 O3. They have a SiO 2 /AI 2 O 3 mass ratio of 2.91.
  • the recovered dredged sediments comprise approximately 10500 mg of organic matter per kg of sediment.
  • the recovered dredged sediments have a water content of 145% by mass, relative to the total mass of sediments and water, then 30% by mass, relative to the total mass of sediments and water after drying in the tanks.
  • Example 2 preparation of a geopolymer material in accordance with the invention
  • 620g of dredging sediment in water as recovered and described in Example 1 (477g of dredging sediment in 143g of water) and 477g of metakaolin are introduced into a mixer sold by the company "CV Equipement", then mixed for 10 seconds.
  • 310g of an aqueous solution of alkali silicate 139.5g of alkali silicate in 170.5g of water
  • the mixer was then stopped to remove the resulting aqueous geopolymer composition adhering to the walls and bottom of the bowl and then the resulting composition is mixed at high speed 125 rpm for 60 seconds.
  • aqueous geopolymer composition is defined in Table 1 below:
  • a geopolymer material in accordance with the invention MG is obtained having a compressive strength of 7 MPa.
  • the compressive strength can be determined according to standard NF EN 1015-11, in particular using an electromechanical press with a capacity of 100 kN at a constant loading speed of 0.6 mm/min.
  • the compressive strength of the geopolymer material of the invention was compared with that of several comparative materials not in accordance with the invention in which the metakaolin was replaced by cement ("CEM I 52.5 N PM") (MOI), blast furnace slag (MO2), the metakaolin was removed and not replaced (MO3), or the amount of metakaolin used was less than 15% by mass and an alkali base was added (MO4).
  • CEM I 52.5 N PM cement
  • MO2 blast furnace slag
  • MO3 blast furnace slag
  • MO4 the amount of metakaolin used was less than 15% by mass and an alkali base was added
  • MOI is obtained from an aqueous composition comprising 60% by mass of dredging sediment, 7% by mass of cement, 27% by mass of water and 6% by mass of sodium silicate. MOI is not part of the invention.
  • M02 is obtained from an aqueous composition comprising 60% by mass of dredging sediments, 7% by mass of blast furnace slag, 27% by mass of water and 6% by mass of sodium silicate. M02 is not part of the invention.
  • M03 is obtained from an aqueous composition comprising 67% by mass of dredging sediment, 27% by mass of water and 6% by mass of sodium silicate. M03 is not part of the invention.
  • MO4 is obtained from an aqueous composition comprising 60% by mass of dredging sediments, 7% by mass of metakaolin, 27% by mass of water, and 6% by mass of sodium silicate. MO4 is not part of the invention.
  • Figure 1 shows the compressive strength of the different materials MG, MOI, MO2, MO3, and MO4. Only the material according to the invention MG is viable in terms of durability. In particular, the value of 7 Mpa is largely satisfactory for the development of applications in public works.
  • Figure 2 shows the porosity characteristics of the MG and M04 materials, measured using a device sold under the trade name “AutoPore V” by the company “MICROMERITICS”. Figure 2 shows a refinement of the porosity for M04 compared to MG. The abscissa axis represents the size diameters of the pores in pm.
  • FIG. 3 shows scanning electron microscopy (SEM) images of the MG and M04 materials taken with a device sold under the trade name “MEB-FEG Zeiss Ultra55” by the company “ZEISS Groupe”.
  • SEM scanning electron microscopy

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Abstract

The present invention relates to an aqueous geopolymer composition based on dredging sediments, to a geopolymer material obtained from the aqueous geopolymer composition, to the use of the aqueous geopolymer composition as a binder for producing a concrete, a filling grout, a concrete pavement, a compacted road layer, bricks, a retaining wall, a dock breakwater, or a precast concrete, and to a concrete comprising the geopolymer material.

Description

Composition aqueuse géopolymère à base de sédiments de dragage, un matériau géopolymère obtenu à partir de ladite composition aqueuse géopolymère, et leurs applications en particulier dans le domaine des bétons écologiques Aqueous geopolymer composition based on dredged sediments, a geopolymer material obtained from said aqueous geopolymer composition, and their applications in particular in the field of ecological concretes

[0001] La présente invention est relative à une composition aqueuse géopolymère à base de sédiments de dragage, un matériau géopolymère obtenu à partir de ladite composition aqueuse géopolymère, l'utilisation de ladite composition aqueuse géopolymère, comme liant pour la fabrication d'un béton, d'un coulis de comblement, d'une chaussée de béton, d'une couche routière compactée, de briques, d'un mur de soutènement, d'une digue de quai, ou d'un béton pré-fabriqué, et un béton comprenant ledit matériau géopolymère. [0001] The present invention relates to an aqueous geopolymer composition based on dredged sediments, a geopolymer material obtained from said aqueous geopolymer composition, the use of said aqueous geopolymer composition as a binder for the manufacture of concrete, a filling grout, a concrete pavement, a compacted road layer, bricks, a retaining wall, a quayside breakwater, or pre-cast concrete, and a concrete comprising said geopolymer material.

[0002] La présente invention s'inscrit dans le cadre de la valorisation des sédiments de dragage non immergeables dans des bétons écologiques pour des applications en travaux publics. [0002] The present invention falls within the framework of the recovery of non-immersible dredging sediments in ecological concretes for applications in public works.

[0003] L'eau est un agent d'érosion physique et chimique des roches et des sols qu'elle draine. Les particules minérales et/ou organiques en suspension s'accumulent, grâce aux processus de floculation ou de gravitation, dans le fond des cours d'eau et ports fluviaux et maritimes ; c'est le processus naturel de sédimentation. Dans les ports maritimes et les cours d'eau, il est nécessaire de draguer les fonds afin de maintenir la navigabilité (circulation fluviale) et/ou prévenir les risques d'inondation. La notion de dragage englobe également les opérations de creusement de nouveaux ports, en particulier de ports de plaisance, ou de chenaux d'accès pour des bateaux ayant des tirants d'eau de plus en plus élevés, l'extension des ports existants, et les travaux d'entretien des ports (plaisance, commerce, industriel, pêche), souvent des ports d'estuaire qui ont une tendance naturelle à l'envasement. Les matériaux dragués sont divers, allant du bloc de pierre au limon (plus ou moins compacté) en passant par des sables de diverses granulométries, sans oublier les déchets jetés à la mer. Leur degré de pollution est également variable, selon la nature du polluant et sa quantité, si le dragage est effectué pour l'ouverture d'un nouveau site en milieu naturel ou pour l'entretien ou l'agrandissement dans un port existant à activités polluantes, plus ou moins anciennes. [0004] Les sédiments de dragage sont un mélange de sables, de limons et d'argiles. Traditionnellement l'intégralité ou la quasi-intégralité des sédiments marins, quel que soit leur niveau de contamination, étaient « clapés » au large des côtes, dans des fosses dédiées à leur immersion. Or, afin de préserver l'environnement, et plus particulièrement les milieux aquatiques, plusieurs arrêtés du 14 juin 2000, du 9 août 2006, et du 23 décembre 2009 ont interdit l'immersion des sédiments trop fortement contaminés, par exemple en éléments métalliques, hydrocarbures aromatiques polycycliques (HAP), tributyl étain (TBT), et/ou polychlorobiphényles (PCB) ; avec des seuils prédéfinis NI, N2 et SI ; et impose alors une gestion à terre. En France, 50 millions de m3 de sédiments sont dragués tous les ans, avec 90% de ce volume immergé dans le cadre de la réglementation des milieux marins et estuariens. Les 10% restants, une fois sortis des eaux, sont gérés à terre. [0003] Water is an agent of physical and chemical erosion of the rocks and soils it drains. Mineral and/or organic particles in suspension accumulate, thanks to the processes of flocculation or gravitation, in the bottom of river and sea ports and rivers; this is the natural process of sedimentation. In sea ports and waterways, it is necessary to dredge the bottoms in order to maintain navigability (river traffic) and/or prevent flood risks. The concept of dredging also includes the operations of digging new ports, in particular marinas, or access channels for boats with increasingly deep drafts, the extension of existing ports, and port maintenance work (pleasure, commercial, industrial, fishing), often estuary ports which have a natural tendency to silting up. The dredged materials are diverse, ranging from stone blocks to silt (more or less compacted) through sands of various grain sizes, not forgetting waste thrown into the sea. Their degree of pollution is also variable, depending on the nature of the pollutant and its quantity, whether the dredging is carried out for the opening of a new site in a natural environment or for maintenance or expansion in an existing port with polluting activities, more or less old. [0004] Dredged sediments are a mixture of sands, silts and clays. Traditionally, all or almost all marine sediments, regardless of their level of contamination, were "slammed" off the coast, in pits dedicated to their immersion. However, in order to preserve the environment, and more particularly aquatic environments, several decrees of June 14, 2000, August 9, 2006, and December 23, 2009 prohibited the immersion of sediments that were too heavily contaminated, for example with metallic elements, polycyclic aromatic hydrocarbons (PAHs), tributyltin (TBT), and/or polychlorinated biphenyls (PCBs); with predefined thresholds NI, N2 and SI; and then impose onshore management. In France, 50 million cubic meters of sediment are dredged every year, with 90% of this volume being disposed of in accordance with regulations governing marine and estuarine environments. The remaining 10%, once removed from the waters, is managed on land.

[0005] Une première stratégie de stockage des sédiments consiste à déposer les sédiments par pompage dans des bassins creusés à terre. Or, les caractéristiques des sédiments évoluent sous l'influence notamment de la mise en contact avec l'air qui entraîne une oxydation du milieu, des différences de température qui influencent l'activité microbienne et d'une diminution de la teneur en eau qui entraîne une déshydratation du milieu. Le sédiment est en effet capable d'adsorber et de transformer les contaminants et de les transférer vers le sol ou les nappes phréatiques. La contamination en éléments trace des sols est susceptible de perturber l'activité biologique et donc d'entrainer à long terme des conséquences néfastes sur le fonctionnement global de l'écosystème. La présence de contaminants inorganiques ou organiques (TBT, PCB, HAP) peut également provoquer des effets à long terme, notamment pour les espèces en bout de chaine alimentaire en raison du caractère bio-cumulable et/ou bio- amplifiable de ces substances. [0005] A first strategy for storing sediments consists of depositing the sediments by pumping them into basins dug on the ground. However, the characteristics of the sediments change under the influence of, in particular, contact with air, which causes oxidation of the environment, temperature differences, which influence microbial activity, and a decrease in water content, which causes dehydration of the environment. The sediment is in fact capable of adsorbing and transforming contaminants and transferring them to the soil or water tables. Trace element contamination of soils is likely to disrupt biological activity and therefore lead to long-term harmful consequences for the overall functioning of the ecosystem. The presence of inorganic or organic contaminants (TBT, PCB, PAH) can also cause long-term effects, particularly for species at the end of the food chain due to the bio-accumulative and/or bio-amplifiable nature of these substances.

[0006] Une deuxième stratégie de stockage des sédiments consiste à les stocker/enfouir dans des installations de stockage des déchets. Des filières de valorisation à terre des sédiments ont fait l'objet d'un intérêt grandissant de la part des gestionnaires des ports et des voies navigables de France de par la réglementation qui rend de plus en plus difficile « le clapage » des sédiments dragués, la révision à la baisse des seuils de gestion dont la principale conséquence est d'augmenter les volumes devant être traités à terre, et l'aspect financier, puisque la valorisation des sédiments permettrait aux gestionnaires de transformer un matériau aujourd'hui considéré comme un déchet, en un matériau ayant une valeur d'usage, source d'économies voire de profits. Les filières de valorisation à terre des sédiments sont multiples. Toutefois, leur mise en œuvre à une échelle industrielle n'est pas si simple et requiert le plus souvent le prétraitement et/ou le traitement des sédiments dragués pour les trier et diminuer les teneurs en polluants pour les rendre acceptables. [0006] A second strategy for storing sediments consists of storing/burying them in waste storage facilities. Onshore sediment recovery channels have been the subject of growing interest from port and waterway managers in France due to regulations that make it increasingly difficult to "sludge" sediments. dredged, the downward revision of management thresholds, the main consequence of which is to increase the volumes to be treated on land, and the financial aspect, since the recovery of sediments would allow managers to transform a material currently considered as waste into a material with a use value, a source of savings or even profits. There are many ways to recover sediments on land. However, their implementation on an industrial scale is not so simple and most often requires the pre-treatment and/or treatment of dredged sediments to sort them and reduce the pollutant levels to make them acceptable.

[0007] Le prétraitement peut comprendre la déshydratation et la séparation des différentes couches pour réduire le volume, contrôler les niveaux de contamination, et orienter le traitement postérieur. Le traitement permet généralement. Le traitement peut être un traitement biologique (bioremédiation, biolavage/biolixiviation, épandage, compostage), un traitement physico-chimique (extraction physico-chimique telle que flottation ou lavages chimiques), un traitement thermique (désorption thermique, pyrolyse, oxydation humide, bains de sels fondus), un traitement d'immobilisation (plateformes, décantation in situ, pour séchage), ou un de leurs mélanges. Les filières de valorisation des sédiments de dragage incluent le régalage, le rechargement des plages, le renforcement dunaire ou de berges, le remblaiement (buttes paysagères, berges, terre-plein ou polder), les matériaux de constructions dans le domaine du BTP (bétons, briques, matériaux routiers et voieries). [0007] Pretreatment may include dewatering and separating the different layers to reduce volume, control contamination levels, and guide subsequent treatment. Treatment generally allows. The treatment may be a biological treatment (bioremediation, biowashing/bioleaching, spreading, composting), a physicochemical treatment (physicochemical extraction such as flotation or chemical washes), a thermal treatment (thermal desorption, pyrolysis, wet oxidation, molten salt baths), an immobilization treatment (platforms, in situ decantation, for drying), or a mixture thereof. The recovery channels for dredged sediments include reclamation, beach replenishment, dune or bank reinforcement, backfilling (landscaped mounds, banks, earthworks or polder), construction materials in the construction sector (concrete, bricks, road materials and roads).

[0008] À titre d'exemple, la demande internationale WO2016/198176 décrit un matériau cimentaire supplémentaire pour une utilisation en association avec un ciment portlant comme liant hydraulique. Le matériau cimentaire supplémentaire est obtenu à partir de sédiments de dragage comprenant le tri des sédiments pour la récupération de la partie fine, la mise en contact de la partie fine avec de la portlandite (Ca(OH)2, CaO), la déshydratation puis le traitement thermique (calcination). [0008] For example, international application WO2016/198176 describes a supplementary cementitious material for use in association with a bearing cement as a hydraulic binder. The supplementary cementitious material is obtained from dredged sediments comprising sorting the sediments for recovery of the fine part, contacting the fine part with portlandite (Ca(OH)2, CaO), dehydration and then heat treatment (calcination).

[0009] Cependant, les coûts de traitement sont élevés, notamment en raison des volumes considérables à traiter et de la complexité de certains des processus. Par ailleurs, un arrêté de 2016 prévoit qu'en 2025 de nouveaux seuils viendront s'appliquer (Loi Leroy), impliquant de nouveaux volumes de sédiments à gérer à terre. Enfin, les opérations de valorisation industrialisâmes restent relativement rares et avec une montée en échelle difficile. [0009] However, processing costs are high, particularly due to the considerable volumes to be processed and the complexity of some of the process. Furthermore, a 2016 decree provides that in 2025 new thresholds will come into force (Leroy Law), implying new volumes of sediment to be managed on land. Finally, industrialized recovery operations remain relatively rare and difficult to scale up.

[0010] Par conséquent, il existe un besoin de trouver une voie de valorisation des sédiments de dragage qui puisse permettre de répondre à la problématique sociale, technique et environnementale que représente leur gestion. Il existe en particulier un besoin en nouvelles voies de valorisation des sédiments de dragage qui soient faciles à mettre en œuvre, industrialisâmes, qui puissent s'affranchir de procédés de traitement et/ou prétraitement et qui conduisent à un ou plusieurs matériaux ayant de bonnes performances mécaniques pour être utilisés dans les matériaux de construction. [0010] Consequently, there is a need to find a way of recovering dredged sediments that can address the social, technical and environmental issues that their management represents. In particular, there is a need for new ways of recovering dredged sediments that are easy to implement, industrializable, that can be freed from treatment and/or pretreatment processes and that lead to one or more materials with good mechanical performance for use in construction materials.

[0011] L'invention a pour premier objet une composition aqueuse géopolymère, caractérisée en ce qu'elle comprend des sédiments de dragage, au moins un silicate alcalin et au moins un métakaolin, et en ce que la composition aqueuse géopolymère est exempte de base alcaline et le métakaolin représente au moins 15% en masse par rapport à la masse totale de la composition aqueuse géopolymère. [0011] The invention relates firstly to an aqueous geopolymer composition, characterized in that it comprises dredging sediments, at least one alkali silicate and at least one metakaolin, and in that the aqueous geopolymer composition is free of alkaline base and the metakaolin represents at least 15% by mass relative to the total mass of the aqueous geopolymer composition.

[0012] La composition aqueuse géopolymère de l'invention permet d'une part de valoriser les sédiments de dragage et d'autre part de conduire à un matériau géopolymère qui présente de bonnes caractéristiques en termes de propriétés mécaniques pour pouvoir être utilisé dans des matériaux de construction. Par ailleurs, la présence d'au moins 15% en masse de métakaolin et l'absence de base alcaline introduite dans la composition aqueuse géopolymère, participent à l'obtention de bonnes propriétés mécaniques tout en réduisant les émissions de CO2 (balance entre la masse de CO2 émise et la résistance à la compression en MPa). [0012] The aqueous geopolymer composition of the invention makes it possible, on the one hand, to recover dredging sediments and, on the other hand, to produce a geopolymer material which has good characteristics in terms of mechanical properties so that it can be used in construction materials. Furthermore, the presence of at least 15% by mass of metakaolin and the absence of alkaline base introduced into the aqueous geopolymer composition contribute to obtaining good mechanical properties while reducing CO2 emissions (balance between the mass of CO2 emitted and the compressive strength in MPa).

[0013] La composition aqueuse géopolymère de l'invention permet d'apporter ainsi une réponse commune aux problématiques de gestion des sédiments et de nécessité pour les travaux publics de développer de nouveaux matériaux en utilisant des ressources de proximité et renouvelables pour limiter l'impact carbone de production du béton et des transports de matériaux. En effet, le béton est le matériau le plus consommé au monde après l'eau et le ciment, un de ses constituants principaux, et est responsable de 5 à 7% des émissions de CO2 mondiales. Ce chiffre alarmant ne devrait pas diminuer, car d'ici 2030, la demande mondiale de ciment devrait augmenter de 216%. L'invention propose la réutilisation des sédiments de dragage dans de nouveaux mortiers à faible teneur en CO2 tout en assurant une proximité de production et une facilité d'approvisionnement pour limiter le transport. [0013] The aqueous geopolymer composition of the invention thus makes it possible to provide a common response to the problems of sediment management and the need for public works to develop new materials using local and renewable resources to limit the impact Carbon footprint of concrete production and material transportation. Indeed, concrete is the most consumed material in the world after water and cement, one of its main constituents, and is responsible for 5 to 7% of global CO2 emissions. This alarming figure is not expected to decrease, as by 2030, global demand for cement is expected to increase by 216%. The invention proposes the reuse of dredged sediment in new low-CO2 mortars while ensuring proximity to production and ease of supply to limit transportation.

[0014] La composition aqueuse est apte à géopolymériser (i.e. polycondense) pour former un matériau géopolymère. [0014] The aqueous composition is capable of geopolymerizing (i.e. polycondensing) to form a geopolymer material.

[0015] En particulier, les sédiments de dragage sont des précurseurs de la géopolymérisation et participent à la réaction de géopolymérisation pour former un matériau géopolymère. [0015] In particular, dredged sediments are precursors of geopolymerization and participate in the geopolymerization reaction to form a geopolymer material.

[0016] Dans la présente invention, la composition géopolymère est une composition aqueuse. En d'autres termes, elle comprend de l'eau. [0016] In the present invention, the geopolymer composition is an aqueous composition. In other words, it comprises water.

[0017] De préférence, la composition aqueuse géopolymère comprend de 15 à 40% en masse environ d'eau, de façon particulièrement préférée de 17 à 30% en masse environ d'eau, et de façon plus particulièrement préférée de 20 à 25% en masse environ d'eau, par rapport à la masse totale de la composition aqueuse géopolymère. [0017] Preferably, the aqueous geopolymer composition comprises from 15 to 40% by mass approximately of water, particularly preferably from 17 to 30% by mass approximately of water, and more particularly preferably from 20 to 25% by mass approximately of water, relative to the total mass of the aqueous geopolymer composition.

[0018] La teneur en eau est ainsi suffisante pour permettre la réaction de géopolymérisation sans pour autant créer trop de porosité dans le gel géopolymère final qui pourrait alors conduire à un retrait ou rétrécissement. [0018] The water content is thus sufficient to allow the geopolymerization reaction without creating too much porosity in the final geopolymer gel which could then lead to shrinkage or contraction.

[0019] L'eau provient préférentiellement majoritairement, et encore plus préférentiellement uniquement des sédiments de dragage récupérés et du silicate alcalin qui peut être sous la forme d'une solution aqueuse. [0019] The water preferably comes mainly, and even more preferably only, from recovered dredging sediments and alkali silicate which can be in the form of an aqueous solution.

[0020] La teneur en eau des sédiments de dragage peut être déterminée selon la norme NF P94-047. Elle permet ensuite de déterminer la teneur en eau de la composition aqueuse géopolymère. [0021] Dans l'invention, les sédiments sont des matériaux issus de l'érosion des roches par les eaux, le vent et les autres agents d'érosion, et qui, selon leur origine, peuvent être fluviatil, glaciaire, lacustre ou marin. [0020] The water content of the dredged sediments can be determined according to standard NF P94-047. It then makes it possible to determine the water content of the aqueous geopolymer composition. [0021] In the invention, sediments are materials resulting from the erosion of rocks by water, wind and other erosion agents, and which, depending on their origin, can be fluvial, glacial, lacustrine or marine.

[0022] La sédimentation ou attérissement est le dépôt de matériaux alluvionnaires (galets, graviers, sables, limons, fines...) érodés en amont et déposés par le cours d'eau dans certaines zones en aval (notamment lors des phases de crues) ou accumulés en bord de mer par les courants marins. [0022] Sedimentation or landfall is the deposit of alluvial materials (pebbles, gravel, sand, silt, fines, etc.) eroded upstream and deposited by the watercourse in certain areas downstream (particularly during flood phases) or accumulated at the seaside by marine currents.

[0023] Selon un mode de réalisation particulièrement préféré, les sédiments de dragage (utilisés dans la composition aqueuse géopolymère) sont non traités. En d'autres termes, les sédiments de dragage mis en œuvre dans la composition n'ont pas subi de traitement(s) chimique(s) et thermique(s). Ils sont par conséquent utilisés tels quels sans traitement(s) chimique(s) et thermique(s) préalable(s). Dans ce mode de réalisation, les sédiments de dragage utilisés dans la composition aqueuse géopolymère sont par conséquent dans un état naturel. Ils sont par exemple différents de sédiments calcinés, de résidus miniers et/ou de boues de fonderie. Les premiers matériaux ont subi un traitement thermique à température élevée qui ôtent une grande partie de matières organiques ; les deuxièmes et troisièmes matériaux sont chargés en métaux. A contrario, les sédiments de dragage viennent de la mer et sont contrôlés en termes de pollution (e.g. seuils en métaux définis par l'arrêté ministériel du 9 août 2006 et l'arrêté du 23 décembre 2009). Les sédiments de dragage utilisés dans la composition de l'invention ont en particulier des teneurs en métaux inférieurs à ces seuils. [0023] According to a particularly preferred embodiment, the dredged sediments (used in the aqueous geopolymer composition) are untreated. In other words, the dredged sediments used in the composition have not undergone any chemical or thermal treatment(s). They are therefore used as is without prior chemical or thermal treatment(s). In this embodiment, the dredged sediments used in the aqueous geopolymer composition are therefore in a natural state. They are, for example, different from calcined sediments, mine tailings and/or foundry sludge. The first materials have undergone a high-temperature heat treatment which removes a large portion of organic matter; the second and third materials are loaded with metals. On the contrary, dredged sediments come from the sea and are controlled in terms of pollution (e.g. metal thresholds defined by the ministerial decree of August 9, 2006 and the decree of December 23, 2009). The dredged sediments used in the composition of the invention have in particular metal contents lower than these thresholds.

[0024] La composition aqueuse géopolymère comprend de préférence de 25 à 65% en masse environ de sédiments de dragage, de façon particulièrement préférée de 30 à 45% et de façon particulièrement préférée de 30% à 40% en masse de sédiments de dragage, par rapport à la masse totale de la composition aqueuse géopolymère. [0024] The aqueous geopolymer composition preferably comprises from 25 to 65% by mass approximately of dredged sediments, particularly preferably from 30 to 45% and particularly preferably from 30% to 40% by mass of dredged sediments, relative to the total mass of the aqueous geopolymer composition.

[0025] De préférence, les sédiments de dragage ont une granulométrie d'au plus 100 pm environ, et de façon particulièrement préférée d'au plus 60 pm environ. En d'autres termes, les sédiments de dragage utilisés dans la composition correspondent préférentiellement à une fraction fine de sédiments de dragage. [0025] Preferably, the dredged sediments have a particle size of at most about 100 μm, and particularly preferably at most about 60 μm. In other words, the dredged sediments used in the composition preferentially correspond to a fine fraction of dredged sediments.

[0026] Les sédiments de dragage utilisés dans la composition aqueuse géopolymère sont de préférence des sédiments limoneux vaseux. [0026] The dredged sediments used in the aqueous geopolymer composition are preferably muddy silty sediments.

[0027] Les sédiments limoneux vaseux sont caractérisés par une teneur élevée en SiO2 et/ou AI2O3. Les analyses par diffraction aux rayons X montrent préférentiellement des minéralogies proches constituées majoritairement de quartz (SiC ), d'Albite (NaAlSisOs) et de Muscovite (KAl2(AISi30io)(OH,F)2). [0027] The muddy silty sediments are characterized by a high content of SiO2 and/or AI2O3. X-ray diffraction analyses preferentially show similar mineralogies consisting mainly of quartz (SiC), Albite (NaAlSisOs) and Muscovite (KAl2(AISi30io)(OH,F)2).

[0028] De façon particulièrement préférée, les sédiments de dragage comprennent au moins 25% en masse environ de SiÛ2, et de façon plus particulièrement préférée au moins 40% en masse environ de SiÛ2, par rapport à la masse totale des sédiments de dragage. [0028] Particularly preferably, the dredged sediments comprise at least approximately 25% by mass of SiO2, and more particularly preferably at least approximately 40% by mass of SiO2, relative to the total mass of the dredged sediments.

[0029] De façon particulièrement préférée, les sédiments de dragage comprennent au moins 8% en masse environ de AI2O3, et de façon plus particulièrement préférée au moins 10% en masse environ de AI2O3, par rapport à la masse totale des sédiments de dragage. [0029] Particularly preferably, the dredged sediments comprise at least approximately 8% by mass of AI2O3, and more particularly preferably at least approximately 10% by mass of AI2O3, relative to the total mass of the dredged sediments.

[0030] Selon une forme de réalisation préférée de l'invention, les sédiments de dragage comprennent du silicium et de l'aluminium, de sorte que le rapport massique SiC /AkC est supérieur ou égal à 2, de façon particulièrement préférée va de 2,1 à 4,0, et de façon plus particulièrement préférée va de 2,8 à 3,1. [0030] According to a preferred embodiment of the invention, the dredged sediments comprise silicon and aluminum, so that the SiC/AkC mass ratio is greater than or equal to 2, particularly preferably ranging from 2.1 to 4.0, and more particularly preferably ranging from 2.8 to 3.1.

[0031] Les sédiments de dragage utilisés dans la composition aqueuse géopolymère peuvent comprendre de 65% à 80% en masse environ de limon, et préférentiellement de 68% à 75% en masse environ de limon, par rapport à la masse totale des sédiments de dragage. On parle également de fraction limoneuse. [0031] The dredging sediments used in the aqueous geopolymer composition may comprise from 65% to 80% by mass approximately of silt, and preferably from 68% to 75% by mass approximately of silt, relative to the total mass of the dredging sediments. This is also referred to as the silt fraction.

[0032] Les sédiments de dragage utilisés dans la composition aqueuse géopolymère peuvent comprendre au moins 2% en masse environ de d'argile, préférentiellement au moins 3% en masse environ de d'argile, et encore plus préférentiellement de 4% à 10% en masse environ d'argile, par rapport à la masse totale des sédiments de dragage. On parle également de fraction argileuse. [0032] The dredging sediments used in the aqueous geopolymer composition may comprise at least approximately 2% by mass of clay, preferably at least approximately 3% by mass of clay, and even more preferably from approximately 4% to 10% by mass of clay, relative to the total mass of dredged sediments. Also referred to as the clay fraction.

[0033] Selon la teneur en argile des sédiments de dragage, les propriétés mécaniques du matériau géopolymère peuvent varier et/ou ne pas être reproductibles. [0033] Depending on the clay content of the dredged sediments, the mechanical properties of the geopolymer material may vary and/or not be reproducible.

[0034] La composition aqueuse géopolymère de l'invention permet de garantir une bonne reproductibilité des performances mécaniques et/ou des performances mécaniques stables quelle que soit la teneur en argile des sédiments de dragage. [0034] The aqueous geopolymer composition of the invention makes it possible to guarantee good reproducibility of mechanical performance and/or stable mechanical performance regardless of the clay content of the dredged sediments.

[0035] Dans la composition aqueuse géopolymère, les sédiments de dragage comprennent de préférence au plus 30% en masse environ de sable, et de façon particulièrement préférée de 10% à 25% en masse environ de sable, par rapport à la masse totale des sédiments de dragage. On parle également de fraction sableuse ou particules sableuses. [0035] In the aqueous geopolymer composition, the dredging sediments preferably comprise at most approximately 30% by mass of sand, and particularly preferably from 10% to 25% by mass of sand, relative to the total mass of the dredging sediments. This is also referred to as the sandy fraction or sandy particles.

[0036] Au-delà de 30% en masse de sable, les grains de sable sont trop importants pour pouvoir se lier à la matrice géopolymère, créant des zones de vides, de microfissures et un matériau géopolymère hétérogène. [0036] Beyond 30% by mass of sand, the sand grains are too large to be able to bind to the geopolymer matrix, creating areas of voids, microfissures and a heterogeneous geopolymer material.

[0037] Dans l'invention, la teneur des sédiments de dragage en limon, argile, et sable peut être déterminé avec la méthode de granulométrie laser. [0037] In the invention, the content of silt, clay, and sand in the dredged sediments can be determined using the laser granulometry method.

[0038] Les sédiments de dragage peuvent comprendre en outre des matières organiques. Selon la teneur en matières organiques des sédiments de dragage, les propriétés mécaniques du matériau géopolymère peuvent varier et/ou ne pas être reproductibles. La teneur en matières organiques des sédiments de dragage peut être déterminée par un essai thermique de calcination à 450°C selon la norme XP P94-0947. [0038] The dredged sediments may further comprise organic matter. Depending on the organic matter content of the dredged sediments, the mechanical properties of the geopolymer material may vary and/or not be reproducible. The organic matter content of the dredged sediments may be determined by a thermal calcination test at 450°C according to standard XP P94-0947.

[0039] La composition aqueuse géopolymère de l'invention permet de garantir une bonne reproductibilité des performances mécaniques et/ou des performances mécaniques stables quelle que soit la teneur en matières organiques des sédiments de dragage. [0040] Préférentiellement, les sédiments de dragage comprennent au moins 3000 mg environ de matières organiques, plus préférentiellement de 4000 à 15000 mg environ de matières organiques, et encore plus préférentiellement de 6000 à 14000 mg environ de matières organiques, par kg des sédiments. [0039] The aqueous geopolymer composition of the invention makes it possible to guarantee good reproducibility of mechanical performance and/or stable mechanical performance regardless of the organic matter content of the dredged sediments. [0040] Preferably, the dredged sediments comprise at least approximately 3000 mg of organic matter, more preferably approximately 4000 to 15000 mg of organic matter, and even more preferably approximately 6000 to 14000 mg of organic matter, per kg of sediment.

[0041] Les sédiments ont de préférence une surface spécifique allant de 0,200 m2/g à 0,700 m2/g, et de façon particulièrement préférée de 0,450 m2/g à 0,700 m2/g. Cette surface spécifique traduit la quantité de gaz pouvant être adsorbée pour couvrir complètement la surface des sédiments. [0041] The sediments preferably have a specific surface area ranging from 0.200 m 2 /g to 0.700 m 2 /g, and particularly preferably from 0.450 m 2 /g to 0.700 m 2 /g. This specific surface area reflects the quantity of gas that can be adsorbed to completely cover the surface of the sediments.

[0042] Dans l'invention, la surface spécifique est préférentiellement mesurée par la méthode B.E.T. [0042] In the invention, the specific surface area is preferably measured by the B.E.T. method.

[0043] Le silicate alcalin peut être un silicate de sodium ou de potassium et préférentiellement un silicate de sodium. [0043] The alkali silicate may be a sodium or potassium silicate and preferably a sodium silicate.

[0044] Selon une forme de réalisation préférée de l'invention, le silicate alcalin présente un rapport molaire Si/métal alcalin allant de 1 à 2, et de façon particulièrement préférée de 1,2 à 1,7. Cela permet ainsi d'améliorer encore la résistance à la compression du matériau géopolymère formé. [0044] According to a preferred embodiment of the invention, the alkali silicate has a Si/alkali metal molar ratio ranging from 1 to 2, and particularly preferably from 1.2 to 1.7. This thus makes it possible to further improve the compressive strength of the geopolymer material formed.

[0045] La composition aqueuse géopolymère comprend de préférence de 5 à 20% en masse environ de silicate alcalin, et de façon particulièrement préférée de 7 à 12% en masse environ de silicate alcalin, par rapport à la masse totale de la composition aqueuse géopolymère. [0045] The aqueous geopolymer composition preferably comprises from 5 to 20% by mass approximately of alkali silicate, and particularly preferably from 7 to 12% by mass approximately of alkali silicate, relative to the total mass of the aqueous geopolymer composition.

[0046] La composition aqueuse géopolymère comprend au moins 15% en masse de métakaolin, de préférence de 20 à 40% en masse environ de métakaolin, et de façon particulièrement préférée de 30 à 38% en masse environ de métakaolin, par rapport à la masse totale de la composition aqueuse géopolymère. [0046] The aqueous geopolymer composition comprises at least 15% by mass of metakaolin, preferably from 20 to 40% by mass approximately of metakaolin, and particularly preferably from 30 to 38% by mass approximately of metakaolin, relative to the total mass of the aqueous geopolymer composition.

[0047] Au-dessous de 15% en masse, les propriétés mécaniques telles que la résistance à la compression ne sont pas suffisantes. Au-dessus de 40% en masse, les performances écologiques (e.g. émissions de CO2) ne sont pas intéressantes par rapport à l'utilisation d'un ciment. [0048] Dans l'invention, l'expression « métakaolin » signifie un aluminosilicate déhydroxylé. Il est de préférence obtenu par déshydratation d'un kaolin ou d'une kaolinite. Cette déshydratation est classiquement obtenue par calcination. [0047] Below 15% by mass, mechanical properties such as compressive strength are not sufficient. Above 40% by mass, ecological performances (eg CO2 emissions) are not interesting compared to the use of a cement. [0048] In the invention, the expression "metakaolin" means a dehydroxylated aluminosilicate. It is preferably obtained by dehydration of a kaolin or a kaolinite. This dehydration is conventionally obtained by calcination.

[0049] Selon une forme de réalisation de l'invention, le métakaolin est un kaolin calciné à une température allant de 750°C environ à 850°C environ. [0049] According to one embodiment of the invention, the metakaolin is a kaolin calcined at a temperature ranging from approximately 750°C to approximately 850°C.

[0050] Le métakaolin peut être analysé par analyse thermique différentielle (ATD) [absence ou présence d'un point ou pic de cristallisation], résonance magnétique nucléaire (RMN) [spectre RMN27 Al], et/ou diffraction aux rayons X (DRX). [0050] Metakaolin can be analyzed by differential thermal analysis (DTA) [absence or presence of a crystallization point or peak], nuclear magnetic resonance (NMR) [27 Al NMR spectrum], and/or X-ray diffraction (XRD).

[0051] La composition aqueuse géopolymère peut être caractérisée par un rapport massique eau/solide (sédiments de dragage, silicate alcalin, métakaolin) allant de 0,30 à 0,45 environ, et de préférence allant de 0,30 à 0,35 environ. [0051] The aqueous geopolymer composition can be characterized by a water/solid mass ratio (dredging sediments, alkali silicate, metakaolin) ranging from approximately 0.30 to 0.45, and preferably ranging from approximately 0.30 to 0.35.

[0052] Selon une forme de réalisation préférée de l'invention, le silicate alcalin, le métakaolin, et les sédiments de dragage sont définis par un rapport massique silicate alcalin/(métakaolin + sédiments de dragage) allant de 0,08 à 0,30 environ, et de façon particulièrement préférée allant de 0,10 à 0,20 environ. [0052] According to a preferred embodiment of the invention, the alkali silicate, the metakaolin, and the dredged sediments are defined by a mass ratio of alkali silicate/(metakaolin + dredged sediments) ranging from approximately 0.08 to 0.30, and particularly preferably ranging from approximately 0.10 to 0.20.

[0053] La composition aqueuse géopolymère peut comprendre en outre un ou plusieurs additifs, tels que des granulats recyclés (sables, gravillons, graviers) ou de bétons concassés ; des réactifs alcalins (poudre de verre, cendres de balle de riz, fumée de silice), des matériaux supplémentaires cimentaires fortement aluminosilicatés comme les cendres volantes ou la fumée de silice. [0053] The aqueous geopolymer composition may further comprise one or more additives, such as recycled aggregates (sand, gravel, gravel) or crushed concrete; alkaline reagents (glass powder, rice husk ash, silica fume), additional highly aluminosilicate cementitious materials such as fly ash or silica fume.

[0054] L'invention a pour deuxième objet un matériau géopolymère, caractérisé en ce qu'il est obtenu par polycondensation et/ou durcissement d'une composition aqueuse géopolymère conforme au premier objet de l'invention. [0054] The second subject of the invention is a geopolymer material, characterized in that it is obtained by polycondensation and/or hardening of an aqueous geopolymer composition in accordance with the first subject of the invention.

[0055] Les géopolymères sont des composés chimiques essentiellement minéraux ou des mélanges de composés comprenant des motifs de type silico- oxyde (-Si-O-Si-O), silico-aluminate (-Si-O-AI-O), ferro-silico-aluminate (-Fe- O-Si-O-AI-O), ou alumino-phosphate (-AI-O-P-O-), créés par un processus de géopolymérisation (i.e. polycondensation). Les géopolymères les plus courants sont ceux basés sur les aluminosilicates désignés sous le terme « poly(sialate) ». [0055] Geopolymers are essentially mineral chemical compounds or mixtures of compounds comprising silico-oxide (-Si-O-Si-O), silico-aluminate (-Si-O-AI-O), ferro-silico-aluminate (-Fe-O-Si-O-AI-O), or alumino-phosphate (-AI-OPO-) type units, created by a geopolymerization process (i.e. polycondensation). The most common geopolymers are those based on aluminosilicates designated under the term “poly(sialate)”.

[0056] Dans la présente invention, le géopolymère obtenu à partir de la composition aqueuse géopolymère est un géopolymère aluminosilicate. [0056] In the present invention, the geopolymer obtained from the aqueous geopolymer composition is an aluminosilicate geopolymer.

[0057] Le géopolymère aluminosilicate résulte de préférence de la polycondensation d'oligomères de type oligo(sialate) formés à partir d'un mélange d'au moins un aluminosilicate, d'un réactif alcalin (e.g. silicate de métal alcaline) et d'eau. [0057] The aluminosilicate geopolymer preferably results from the polycondensation of oligo(sialate) type oligomers formed from a mixture of at least one aluminosilicate, an alkaline reagent (e.g. alkali metal silicate) and water.

[0058] Dans la présente invention, le géopolymère peut répondre à la formule suivante : Mn[-(Si-O2)z-AI-O]n.wH2O dans laquelle M est un ion de métal alcalin, et n représente le degré de polycondensation, w est le nombre de molécules d'eau liées chimiquement, et z est le nombre d'atomes de silicium qui constituent une seule chaîne aluminosilicate oligomère. Ce dernier dépend, à son tour, du rapport molaire de SiC /AkOs contenu dans le géopolymère. Le choix de ce rapport varie en fonction du temps de prise et de la force recherchés. Comme cette valeur augmente progressivement de 1 à 3, un sialate, c'est-à- dire Mn(-Si-O-AI-O-)n, un sialatesiloxo, c'est-à-dire Mn(Si-O-AI-O-Si-O-)n, ou un sialate disiloxo, c'est-à-dire Mn(-Si-O-AI-O-Si-O-Si-O)n, sera formé, respectivement. [0058] In the present invention, the geopolymer may have the following formula: M n [-(Si-O2)z-AI-O] n .wH2O in which M is an alkali metal ion, and n represents the degree of polycondensation, w is the number of chemically bonded water molecules, and z is the number of silicon atoms that constitute a single oligomeric aluminosilicate chain. The latter depends, in turn, on the molar ratio of SiC /AkOs contained in the geopolymer. The choice of this ratio varies depending on the desired setting time and strength. As this value gradually increases from 1 to 3, a sialate, i.e., Mn(-Si-O-AI-O-)n, a sialatesiloxo, i.e., Mn (-Si-O-AI-O-Si-O-) n , or a sialate disiloxo, i.e., Mn (-Si-O-AI-O-Si-O-Si-O) n , will be formed, respectively.

[0059] Le géopolymère aluminosilicate de l'invention a préférentiellement un rapport atomique Si/AI allant de 2,5 à 3,5. [0059] The aluminosilicate geopolymer of the invention preferably has an Si/AI atomic ratio ranging from 2.5 to 3.5.

[0060] La composition aqueuse géopolymère permet de former un matériau géopolymère ayant peu de retrait, une meilleure stabilité dimensionnelle, une meilleure résistance à la compression à plus de 28 jours, et de préférence à 90 jours, une meilleure durabilité et un temps de prise réduit. [0060] The aqueous geopolymer composition makes it possible to form a geopolymer material having little shrinkage, better dimensional stability, better compressive strength at more than 28 days, and preferably at 90 days, better durability and reduced setting time.

[0061] Le matériau géopolymère de l'invention a préférentiellement une résistance à la compression au-delà de 28 jours d'au moins 6 MPa environ, de façon particulièrement préférée d'au moins 6,5 MPa environ, et de façon particulièrement préférée d'au moins 7 MPa environ. [0061] The geopolymer material of the invention preferably has a compressive strength beyond 28 days of at least approximately 6 MPa, particularly preferably of at least approximately 6.5 MPa, and particularly preferably of at least approximately 7 MPa.

[0062] Dans l'invention, la résistance à la compression peut être déterminée selon la norme NF EN 1015-11, en particulier à l'aide d'une presse électromécanique d'une capacité de 100 kN à une vitesse de chargement constante de 0,6 mm/min. [0062] In the invention, the compressive strength can be determined according to standard NF EN 1015-11, in particular using a press electromechanical with a capacity of 100 kN at a constant loading speed of 0.6 mm/min.

[0063] L'invention a pour troisième objet l'utilisation d'une composition aqueuse géopolymère conforme au premier objet de l'invention, comme liant pour la fabrication d'un béton, d'un coulis de comblement, d'une chaussée de béton, d'une couche routière compactée, de briques, d'un mur de soutènement, d'une digue de quai, ou d'un béton pré-fabriqué, ou pour la fabrication d'un béton, d'un coulis de comblement, d'une chaussée de béton, d'une couche routière compactée, de briques, d'un mur de soutènement, d'une digue de quai, ou d'un béton pré-fabriqué (i.e. utilisation de la composition aqueuse géopolymère conforme au premier objet de l'invention en tant que telle). [0063] The third subject of the invention is the use of an aqueous geopolymer composition in accordance with the first subject of the invention, as a binder for the manufacture of concrete, a filling grout, a concrete pavement, a compacted road layer, bricks, a retaining wall, a quayside breakwater, or a pre-cast concrete, or for the manufacture of concrete, a filling grout, a concrete pavement, a compacted road layer, bricks, a retaining wall, a quayside breakwater, or a pre-cast concrete (i.e. use of the aqueous geopolymer composition in accordance with the first subject of the invention as such).

[0064] La composition peut en particulier être utilisée directement pour fabriquer du béton sans ajout d'additifs. [0064] The composition can in particular be used directly to manufacture concrete without adding additives.

[0065] La composition aqueuse géopolymère à base de sédiments de dragage de l'invention est utilisée comme liant (liant géopolymère). [0065] The aqueous geopolymer composition based on dredged sediments of the invention is used as a binder (geopolymer binder).

[0066] Dans l'invention, le terme « liant » signifie un composé qui sert à agglomérer des particules solides sous forme de poudre ou de granulats. [0066] In the invention, the term "binder" means a compound which serves to agglomerate solid particles in the form of powder or aggregates.

[0067] Dans la composition aqueuse géopolymère de l'invention, les sédiments de dragage sont des précurseurs de la géopolymérisation et réagissent avec le silicate alcalin et le métakolin, pour former un liant qui va permettre de lier les éléments granulaires du béton et apporter de la résistance mécanique. [0067] In the aqueous geopolymer composition of the invention, the dredged sediments are precursors of geopolymerization and react with the alkali silicate and the metakolin, to form a binder which will make it possible to bind the granular elements of the concrete and provide mechanical resistance.

[0068] Le liant peut être utilisé dans les domaines des travaux publics et de la construction. Cela permet ainsi de réduire de 45% les émissions de CO2, avec des performances plus élevées que celles obtenues avec le ciment de Portland. [0068] The binder can be used in the fields of public works and construction. This allows a 45% reduction in CO2 emissions, with higher performance than that obtained with Portland cement.

[0069] L'invention a pour quatrième objet un béton, caractérisé en ce qu'il comprend un matériau géopolymère conforme au deuxième objet de l'invention. [0069] The fourth subject of the invention is a concrete, characterized in that it comprises a geopolymer material in accordance with the second subject of the invention.

[0070] Dans un mode de réalisation, le béton ne comprend pas de granulats naturels (sable, gravillons, graviers) en dehors de ceux présents dans les sédiments de dragage. [0071] Le béton peut être constitué d'un matériau géopolymère conforme au deuxième objet de l'invention. [0070] In one embodiment, the concrete does not include natural aggregates (sand, gravel, gravel) other than those present in the dredged sediments. [0071] The concrete may be made of a geopolymer material in accordance with the second subject of the invention.

[0072] Réutiliser les sédiments de dragage en tant que matière première pour la conception d'un béton directement sur le site de dragage permettrait aux entreprises de simplifier la gestion à terre, de réduire les coûts, l'impact environnemental et d'inscrire leur modèle de consommation dans une économie circulaire. [0072] Reusing dredged sediments as a raw material for the design of concrete directly on the dredging site would allow companies to simplify onshore management, reduce costs, environmental impact and place their consumption model in a circular economy.

[0073] La présente invention est illustrée par les exemples de réalisation suivants, auxquels elle n'est cependant pas limitée. [0073] The present invention is illustrated by the following exemplary embodiments, to which it is however not limited.

[0074] Brève description des dessins [0074] Brief description of the drawings

[0075] L'invention est illustrée par les figures et les exemples qui suivent. [0075] The invention is illustrated by the following figures and examples.

[0076] La figure 1 montre la résistance à la compression d'un matériau géopolymère conforme à l'invention et de matériaux non conformes à l'invention. [0076] Figure 1 shows the compressive strength of a geopolymer material in accordance with the invention and of materials not in accordance with the invention.

[0077] La figure 2 montre les caractéristiques de porosité d'un matériau géopolymère conforme à l'invention et d'un matériau non conforme à l'invention. [0077] Figure 2 shows the porosity characteristics of a geopolymer material in accordance with the invention and of a material not in accordance with the invention.

[0078] La figure 3 montre des images par microscopie électronique à balayage (MEB) d'un matériau géopolymère conforme à l'invention et d'un matériau non conforme à l'invention. [0078] Figure 3 shows scanning electron microscopy (SEM) images of a geopolymer material in accordance with the invention and of a material not in accordance with the invention.

[0079] Exemples [0079] Examples

[0080] Les matières premières utilisées dans les exemples sont listées ci-après [0080] The raw materials used in the examples are listed below.

- sédiments de dragage à l'état naturel de la Garonne, qui proviennent plus spécifiquement du port de Bordeaux, - dredged sediments in their natural state from the Garonne, which come more specifically from the port of Bordeaux,

- silicate de sodium, « Xatico Benelux France », « Géosil B47T », rapport molaire SiOz/NazO = 1,7, densité = 1,57 g/cm3, 43,80 % en masse de NazO, 37,70 % en masse de SiÛ2 et 10,20 % en masse d'AkCh, - sodium silicate, “Xatico Benelux France”, “Géosil B47T”, SiOz/NazO molar ratio = 1.7, density = 1.57 g/cm 3 , 43.80% by mass of NazO, 37.70% by mass of SiO2 and 10.20% by mass of AkCh,

- métakaolin, « Argeco », obtenu par calcination flash d'argile kaolinitique, - ciment « CEM I 52,5 N PM », « Calcia » (64% en masse de CaO, 19,9% en masse de SiO2 et 3,9% en masse de AI2O3), - metakaolin, “Argeco”, obtained by flash calcination of kaolinitic clay, - “CEM I 52.5 N PM” cement, “Calcia” (64% by mass of CaO, 19.9% by mass of SiO2 and 3.9% by mass of AI2O3),

- laitier de haut fourneau, « Ecocem » (43,8% en masse de CaO, 37,7% en masse de SiO2 et 10,2% en masse de AI2O3). - blast furnace slag, “Ecocem” (43.8% by mass of CaO, 37.7% by mass of SiO2 and 10.2% by mass of AI2O3).

[0081] Sauf indications contraires, tous les matériaux ont été utilisés tels que reçus des fabricants, sans purification. [0081] Unless otherwise indicated, all materials were used as received from the manufacturers, without purification.

[0082] Exemple 1 : caractérisation des sédiments de dragage utilisés dans la composition de l'invention [0082] Example 1: characterization of the dredging sediments used in the composition of the invention

[0083] Dans cet exemple 1, des sédiments de dragage de la Garonne ont été sélectionnés. L'estuaire de la Garonne est composé majoritairement de deux fractions granulométriques distinctes : des sédiments à forte tendance sableuse en amont de l'estuaire et des sédiments limoneux-vaseux en aval. Les sédiments limoneux-vaseux ont été récupérés à Pauillac et laissés évaporer dans des bacs percés avec un géotextile pendant 1 à 3 mois. Le séchage s'est réalisé par infiltration et évaporation de l'eau. Toutes les fractions du sédiment ont été récupérés. [0083] In this example 1, dredged sediments from the Garonne were selected. The Garonne estuary is mainly composed of two distinct granulometric fractions: sediments with a strong sandy tendency upstream of the estuary and silty-muddy sediments downstream. The silty-muddy sediments were recovered at Pauillac and left to evaporate in tanks perforated with a geotextile for 1 to 3 months. Drying was carried out by infiltration and evaporation of the water. All fractions of the sediment were recovered.

[0084] Les sédiments de dragage récupérés comprennent 71% en masse de limon, 24,5% en masse de sable, et 4,5% en masse d'argile, par rapport à la masse totale de sédiments de dragage. Ils ont une granulométrie selon les normes NF P94-056 et NF P94-057 allant de 2 à 50 pm. L'analyse de la valeur au bleu de méthylène, réalisée conformément à la norme NF P94-068, et aux limites d'Atterberg NF P94-051, a confirmé la nature limono-argileuse des sédiments de dragage avec une faible plasticité. [0084] The recovered dredged sediments comprise 71% by mass of silt, 24.5% by mass of sand, and 4.5% by mass of clay, relative to the total mass of dredged sediments. They have a particle size according to the NF P94-056 and NF P94-057 standards ranging from 2 to 50 μm. The analysis of the methylene blue value, carried out in accordance with the NF P94-068 standard, and the Atterberg limits NF P94-051, confirmed the silty-clayey nature of the dredged sediments with low plasticity.

[0085] Les sédiments de dragage ont également été soumis à des tests environnementaux conformément à l'arrêté du 9 août 2006 et au guide GEODE qui détermine les niveaux de référence en France. Aucune trace de contamination par les métaux lourds, les HAP et les PCB n'a été observée. En effet, les niveaux de contaminants mesurés étaient faibles et inférieurs aux seuils NI et N2. [0086] Les sédiments de dragage récupérés comprennent 41,38% en masse de SiO2, et 14,19% en masse d'AI2O3. Ils présentent un rapport massique SiO2/AI2O3 de 2,91. [0085] The dredged sediments were also subjected to environmental tests in accordance with the decree of 9 August 2006 and the GEODE guide which determines the reference levels in France. No trace of contamination by heavy metals, PAHs and PCBs was observed. Indeed, the levels of contaminants measured were low and below the NI and N2 thresholds. [0086] The recovered dredged sediments comprise 41.38% by mass of SiO2, and 14.19% by mass of AI 2 O3. They have a SiO 2 /AI 2 O 3 mass ratio of 2.91.

[0087] Les sédiments de dragage récupérés comprennent 10500 mg environ de matières organiques, par kg des sédiments. [0087] The recovered dredged sediments comprise approximately 10500 mg of organic matter per kg of sediment.

[0088] Les sédiments de dragage récupérés ont une teneur en eau de 145% en masse, par rapport à la masse totale des sédiments et de l'eau, puis de 30% en masse, par rapport à la masse totale des sédiments et de l'eau après séchage dans les bacs. [0088] The recovered dredged sediments have a water content of 145% by mass, relative to the total mass of sediments and water, then 30% by mass, relative to the total mass of sediments and water after drying in the tanks.

[0089] Exemple 2 : préparation d'un matériau géopolymère conforme à l'invention [0089] Example 2: preparation of a geopolymer material in accordance with the invention

[0090] 620g de sédiments de dragage dans de l'eau tels que récupérés et décrits dans l'exemple 1 (477 g de sédiments de dragage dans 143 g d'eau) et 477g de métakaolin sont introduits dans un malaxeur vendu par la société « CV Equipement », puis mélangés pendant 10 secondes. Une fois, le mélange résultant homogénéisé, 310 g d'une solution aqueuse de silicate alcalin (139,5 g de silicate alcalin dans 170,5 g d'eau) est ajouté puis la composition résultante est mélangée à petite vitesse 62 tr/min pendant 90 secondes. Le malaxeur a été ensuite arrêté pour enlever la composition aqueuse géopolymère résultante adhérant aux parois et au fond du bol et puis la composition résultante est mélangée à grande vitesse 125 tr/min pendant 60 secondes. [0090] 620g of dredging sediment in water as recovered and described in Example 1 (477g of dredging sediment in 143g of water) and 477g of metakaolin are introduced into a mixer sold by the company "CV Equipement", then mixed for 10 seconds. Once the resulting mixture is homogenized, 310g of an aqueous solution of alkali silicate (139.5g of alkali silicate in 170.5g of water) is added and then the resulting composition is mixed at low speed 62 rpm for 90 seconds. The mixer was then stopped to remove the resulting aqueous geopolymer composition adhering to the walls and bottom of the bowl and then the resulting composition is mixed at high speed 125 rpm for 60 seconds.

[0091] La composition aqueuse géopolymère est définie dans le tableau 1 ci- dessous : [0091] The aqueous geopolymer composition is defined in Table 1 below:

[0092] [Tableau 1]

Figure imgf000016_0001
[0092] [Table 1]
Figure imgf000016_0001

[0093] Après durcissement pendant 28 jours, on obtient un matériau géopolymère conforme à l'invention MG ayant une résistance à la compression de 7 MPa. [0094] Dans l'invention, la résistance à la compression peut être déterminée selon la norme NF EN 1015-11, en particulier à l'aide d'une presse électromécanique d'une capacité de 100 kN à une vitesse de chargement constante de 0,6 mm/min. [0093] After curing for 28 days, a geopolymer material in accordance with the invention MG is obtained having a compressive strength of 7 MPa. [0094] In the invention, the compressive strength can be determined according to standard NF EN 1015-11, in particular using an electromechanical press with a capacity of 100 kN at a constant loading speed of 0.6 mm/min.

[0095] La résistance à la compression du matériau géopolymère de l'invention a été comparée à celle de plusieurs matériaux comparatifs non conformes à l'invention dans lequel le métakaolin a été remplacé par du ciment (« CEM I 52,5 N PM ») (MOI), du laitier de haut fourneau (M02), le métakaolin a été supprimé et non remplacé (M03), ou la quantité de métakaolin utilisée est inférieure à 15% en masse et une base alcaline a été ajoutée (MO4). [0095] The compressive strength of the geopolymer material of the invention was compared with that of several comparative materials not in accordance with the invention in which the metakaolin was replaced by cement ("CEM I 52.5 N PM") (MOI), blast furnace slag (MO2), the metakaolin was removed and not replaced (MO3), or the amount of metakaolin used was less than 15% by mass and an alkali base was added (MO4).

[0096] MOI est obtenu à partir d'une composition aqueuse comprenant 60% en masse de sédiments de dragage, 7% en masse de ciment, 27% en masse d'eau et 6% en masse de silicate de sodium. MOI ne fait pas partie de l'invention. [0096] MOI is obtained from an aqueous composition comprising 60% by mass of dredging sediment, 7% by mass of cement, 27% by mass of water and 6% by mass of sodium silicate. MOI is not part of the invention.

[0097] M02 est obtenu à partir d'une composition aqueuse comprenant 60% en masse de sédiments de dragage, 7% en masse de laitier de haut fourneau, 27% en masse d'eau et 6% en masse de silicate de sodium. M02 ne fait pas partie de l'invention. [0097] M02 is obtained from an aqueous composition comprising 60% by mass of dredging sediments, 7% by mass of blast furnace slag, 27% by mass of water and 6% by mass of sodium silicate. M02 is not part of the invention.

[0098] M03 est obtenu à partir d'une composition aqueuse comprenant 67% en masse de sédiments de dragage, 27% en masse d'eau et 6% en masse de silicate de sodium. M03 ne fait pas partie de l'invention. [0098] M03 is obtained from an aqueous composition comprising 67% by mass of dredging sediment, 27% by mass of water and 6% by mass of sodium silicate. M03 is not part of the invention.

[0099] MO4 est obtenu à partir d'une composition aqueuse comprenant 60% en masse de sédiments de dragage, 7% en masse de métakaolin, 27% en masse d'eau, et 6% en masse de silicate de sodium. MO4 ne fait pas partie de l'invention. [0099] MO4 is obtained from an aqueous composition comprising 60% by mass of dredging sediments, 7% by mass of metakaolin, 27% by mass of water, and 6% by mass of sodium silicate. MO4 is not part of the invention.

[0100] La figure 1 montre la résistance à la compression des différents matériaux MG, MOI, M02, M03, et MO4. Seul le matériau conforme à l'invention MG est viable en termes de durabilité. En particulier, la valeur de 7 Mpa est largement satisfaisante pour le développement d'applications en travaux publics. [0101] La figure 2 montre les caractéristiques de porosité des matériaux MG et M04, mesurées à l'aide d'un appareil vendu sous la dénomination commerciale « AutoPore V » par la société « MICROMERITICS ». La figure 2 montre un affinement de la porosité pour M04 comparé à MG. L'axe des abscisses représente les diamètres de taille des porosités en pm. [0100] Figure 1 shows the compressive strength of the different materials MG, MOI, MO2, MO3, and MO4. Only the material according to the invention MG is viable in terms of durability. In particular, the value of 7 Mpa is largely satisfactory for the development of applications in public works. [0101] Figure 2 shows the porosity characteristics of the MG and M04 materials, measured using a device sold under the trade name “AutoPore V” by the company “MICROMERITICS”. Figure 2 shows a refinement of the porosity for M04 compared to MG. The abscissa axis represents the size diameters of the pores in pm.

[0102] La figure 3 montre des images par microscopie électronique à balayage (MEB) des matériaux MG et M04 effectuées avec un appareil vendu sous la dénomination commerciale « MEB-FEG Zeiss Ultra55 » par la société « ZEISS Groupe ». [0103] D'après la figure 3, le matériau géopolymère MG a une structure plus ordonnée et plus lisse témoignant d'une géopolymérisation plus complète. [0102] Figure 3 shows scanning electron microscopy (SEM) images of the MG and M04 materials taken with a device sold under the trade name “MEB-FEG Zeiss Ultra55” by the company “ZEISS Groupe”. [0103] According to Figure 3, the MG geopolymer material has a more ordered and smoother structure, indicating more complete geopolymerization.

Claims

Revendications Claims 1. Composition aqueuse géopolymère, caractérisée en ce qu'elle comprend des sédiments de dragage, au moins un silicate alcalin et au moins un métakaolin, en ce que la composition aqueuse géopolymère est exempte de base alcaline et le métakaolin représente au moins 15% en masse par rapport à la masse totale de la composition aqueuse géopolymère, et en ce que les sédiments de dragage sont non traités. 1. Aqueous geopolymer composition, characterized in that it comprises dredging sediments, at least one alkali silicate and at least one metakaolin, in that the aqueous geopolymer composition is free of alkaline base and the metakaolin represents at least 15% by mass relative to the total mass of the aqueous geopolymer composition, and in that the dredging sediments are untreated. 2. Composition selon la revendication 1, caractérisée en ce qu'elle comprend de 25 à 65% en masse de sédiments de dragage par rapport à la masse totale de la composition aqueuse géopolymère. 2. Composition according to claim 1, characterized in that it comprises from 25 to 65% by mass of dredging sediments relative to the total mass of the aqueous geopolymer composition. 3. Composition selon la revendication 1 ou 2, caractérisée en ce que le silicate alcalin présente un rapport molaire Si/métal alcalin allant de 1 à 2.3. Composition according to claim 1 or 2, characterized in that the alkali silicate has a Si/alkali metal molar ratio ranging from 1 to 2. 4. Composition selon l'une quelconque des revendications précédentes, caractérisée en ce que les sédiments de dragage comprennent au moins 3000 mg de matières organiques, par kg des sédiments. 4. Composition according to any one of the preceding claims, characterized in that the dredging sediments comprise at least 3000 mg of organic matter, per kg of sediments. 5. Composition selon l'une quelconque des revendications précédentes, caractérisée en ce que les sédiments de dragage comprennent au plus 30% en masse de sable, par rapport à la masse totale des sédiments de dragage. 5. Composition according to any one of the preceding claims, characterized in that the dredging sediments comprise at most 30% by mass of sand, relative to the total mass of the dredging sediments. 6. Composition selon l'une quelconque des revendications précédentes, caractérisée en ce que les sédiments de dragage comprennent du silicium et de l'aluminium, de sorte que le rapport massique SiC /AkOs est supérieur ou égal à 2, et de préférence va de 2,1 à 4,0. 6. Composition according to any one of the preceding claims, characterized in that the dredging sediments comprise silicon and aluminum, so that the SiC /AkOs mass ratio is greater than or equal to 2, and preferably ranges from 2.1 to 4.0. 7. Composition selon l'une quelconque des revendications précédentes, caractérisée en ce que le silicate alcalin, le métakaolin, et les sédiments de dragage sont définis par un rapport massique silicate alcalin/(métakaolin + sédiments de dragage) allant de 0,08 à 0,30. 7. Composition according to any one of the preceding claims, characterized in that the alkali silicate, the metakaolin, and the dredging sediments are defined by a mass ratio of alkali silicate/(metakaolin + dredging sediments) ranging from 0.08 to 0.30. 8. Composition selon l'une quelconque des revendications précédentes, caractérisée en ce qu'elle comprend de 20 à 40% en masse de métakaolin, par rapport à la masse totale de la composition aqueuse géopolymère. 8. Composition according to any one of the preceding claims, characterized in that it comprises from 20 to 40% by mass of metakaolin, relative to the total mass of the aqueous geopolymer composition. 9. Composition selon l'une quelconque des revendications précédentes, caractérisée en ce qu'elle comprend de 15 à 40% en masse d'eau, par rapport à la masse totale de la composition aqueuse géopolymère. 9. Composition according to any one of the preceding claims, characterized in that it comprises from 15 to 40% by mass of water, relative to the total mass of the aqueous geopolymer composition. 10. Composition selon l'une quelconque des revendications précédentes, caractérisée en ce qu'elle comprend de 5 à 20% en masse de silicate alcalin, par rapport à la masse totale de la composition aqueuse géopolymère. 10. Composition according to any one of the preceding claims, characterized in that it comprises from 5 to 20% by mass of alkali silicate, relative to the total mass of the aqueous geopolymer composition. 11. Matériau géopolymère, caractérisé en ce qu'il est obtenu par polycondensation et/ou durcissement d'une composition aqueuse géopolymère telle que définie à l'une quelconque des revendications précédentes. 11. Geopolymer material, characterized in that it is obtained by polycondensation and/or hardening of an aqueous geopolymer composition as defined in any one of the preceding claims. 12. Utilisation d'une composition aqueuse géopolymère telle que définie à l'une quelconque des revendications 1 à 10, comme liant pour la fabrication d'un béton, d'un coulis de comblement, d'une chaussée de béton, d'une couche routière compactée, de briques, d'un mur de soutènement, d'une digue de quai, ou d'un béton pré-fabriqué, ou pour la fabrication d'un béton, d'un coulis de comblement, d'une chaussée de béton, d'une couche routière compactée, de briques, d'un mur de soutènement, d'une digue de quai, ou d'un béton préfabriqué. 12. Use of an aqueous geopolymer composition as defined in any one of claims 1 to 10, as a binder for the manufacture of concrete, a backfill grout, a concrete pavement, a compacted road layer, bricks, a retaining wall, a quayside breakwater, or a pre-cast concrete, or for the manufacture of concrete, a backfill grout, a concrete pavement, a compacted road layer, bricks, a retaining wall, a quayside breakwater, or a pre-cast concrete. 13. Béton, caractérisé en ce qu'il comprend un matériau géopolymère tel que défini dans la revendication 11. 13. Concrete, characterized in that it comprises a geopolymer material as defined in claim 11.
PCT/EP2024/082412 2023-11-14 2024-11-14 Aqueous geopolymer composition based on dredging sediments, geopolymer material obtained from the aqueous geopolymer composition, and uses thereof in particular in the field of eco concretes Pending WO2025104200A1 (en)

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