Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/20—Silicates
  • C01B33/26—Aluminium-containing silicates, i.e. silico-aluminates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/16—Clays or other mineral silicates
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/20—Silicates
• • 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
  • C04B28/008—Mineral polymers other than those of the Davidovits type, e.g. from a reaction mixture containing waterglass
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/63—Pore volume
  • B01J35/633—Pore volume less than 0.5 ml/g
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/63—Pore volume
  • B01J35/635—0.5-1.0 ml/g
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/64—Pore diameter
  • B01J35/647—2-50 nm
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/66—Pore distribution
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P40/00—Technologies relating to the processing of minerals
  • Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding

Definitions

• the present invention relates to the field of geopolymers and, more particularly, to the field of geopolymers with controlled porosity.
• the present invention aims at providing a method of preparation in which the main formulation parameters make it possible simultaneously to control the total porosity of the geopolymer as well as its porous modes, ie micro-, macro- and mesoporous thus opening the way to an engineering of the porosity of these materials.
• the present invention also relates to the geopolymers obtainable by said process, their various uses and this particularly in the field of catalysis and filtration.
• the initial reactive material contains essentially silica and aluminum from an aluminosilicate source
• the material obtained is amorphous aluminosilicate inorganic polymer [13], [14] termed "geopolymer" [15].
• the geopolymer is prepared by activating the alumino-silicate source from the high pH solution. This preparation consists of kneading together the various components and then keeping the material obtained under defined conditions of temperature, pressure and relative humidity until the final geopolymer is obtained.
• a simplified reaction mechanism is, however, generally accepted [37]: it consists mainly of a dissolution / polycondensation mechanism whose different steps take place simultaneously. Initially, the solid grains of the alumino-silicate source are suspended in the aqueous phase. At high pH, the dissolution of the source aluminosilicates is rapid and leads to the appearance of chemical species (aluminates, silicates, aluminosilicates, etc.) in the activation solution, which phase may also contain silicate species. This process is water consuming.
• the supersaturation of the solution causes the appearance of a gel linked to the polycondensation of the oligomers in the aqueous phase.
• the size of the oligomers formed depends on the size of the compensating cation [38].
• geopolymers develop a high porosity, which makes them particularly advantageous in applications as insulation.
• Geopolymers are also used as binders [16-20] in the formulation of building materials [21, 22], concretes or mortars [23, 24] and fireproof materials [25-27].
• binders [16-20] in the formulation of building materials [21, 22], concretes or mortars [23, 24] and fireproof materials [25-27].
• Several production methods are known [28, 29], allowing their implementation on site or in the context of prefabrications [30, 31].
• geopolymers can be used as a matrix for coating or inerting toxic waste [32-34].
• the porous nature of the geopolymers can make it a particularly interesting support for various applications such as catalysis or filtration.
• the present invention makes it possible to provide a solution to the need presented above and consists of a process making it possible to obtain geopolymers as monolithic materials whose porosity can be controlled as soon as they are formulated.
• the results obtained by the inventors have made it possible to develop a method by which the porosity of the material is as well controlled in the macroporous zone as in the mesoporous zone, said control being applied as much to the total porosity of the material as to 'to the pore distribution of it.
• the term "geopolymer” is intended to mean an amorphous aluminosilicate inorganic polymer. Said polymer is obtained from a reactive material containing essentially silica and aluminum, activated by a strongly alkaline solution, the solid / solution mass ratio in the formulation being low, in particular less than 0.6 and, advantageously, less than 0.5.
• the structure of a geopolymer is composed of an Si-O-Al lattice formed of silicate (SiO 4 ) and aluminate (AlO 4 ) tetrahedra bound at their vertices by oxygen atom sharing. Within this network, there is (are) one (or more) charge compensating cation (s) also called compensation cation (s). These cations symbolized later by the letter M make it possible to compensate for the negative charge of the complex A1O 4 ⁇ .
• the geopolymer prepared according to the process of the present invention can be microporous, macroporous or mesoporous. Advantageously, it is a macroporous or mesoporous geopolymer.
• microporous a material whose pore diameter (dp) is less than 2 nm
• mesoporous a material such as 2 ⁇ dp ⁇ 50 nm
• macroporous a material whose pore diameter is greater than 50 nm.
• the present invention exposes the possibility of defining by the formulation the porosity of the geopolymer and this, more particularly in the macro and mesoporous domains.
• the method which is the subject of the present invention is remarkable because an identical porosity of the final material can come from several different initial formulations.
• To formulate a geopolymer is to choose [5, 10, 36]:
• a high pH activation solution characterized in particular by its amount of water and the amount of soluble silicates it may possibly contain.
• the pore properties of the material are influenced by the specific choices of the species selected for the preparation. Thus, a judicious determination of all the parameters of formulation and implementation allows a priori to control several properties related to the porosity of the geopolymer.
• controlled porosity is used to control the total porosity, the class of the porosity and / or the pore distribution.
• the present invention is therefore characterized by a reasoned choice of certain parameters from the formulation of the geopolymer to be prepared after having first defined the poral characteristics of said geopolymer.
• the present invention therefore relates to a process for preparing a controlled porosity geopolymer comprising a step of dissolution / polycondensation of an aluminosilicate source in an activating solution that may optionally contain silicate components, said process comprising the following successive steps consisting of a. define at least one characteristic of the porosity of the geopolymer to be prepared; b. determining a value or an element for at least one parameter selected from the total amount of water, the total amount of silica, the compensation cation, and the particle size distribution of the possible silicate components, to obtain the characteristic defined in step (a); vs. select said value or said element predetermined in step (b).
• Step (a) of the method according to the present invention consists in defining at least one characteristic selected from the group consisting of the total porosity, the porosity class and the pore distribution such as the pore size distribution in a given class. .
• at least two of these characteristics and, more particularly, the three characteristics are defined in step (a).
• Step (b) of the method according to the present invention can be implemented in different ways.
• this step consists of testing different values (or different elements) for at least one parameter among the previously listed parameters and determining the value (or the element) making it possible to obtain at least one characteristic defined in step (a). ).
• step (b) of the method according to the invention may consist of identifying the value (or the element) making it possible to obtain at least one characteristic defined in step (a) on the basis of previously obtained data. and in particular accessible to the skilled person in scientific publications or patent applications. It may be necessary to repeat the step
• the present invention relates to a process for the preparation of a geopolymer with controlled porosity comprising a step of dissolution / polycondensation of an aluminosilicate source in an activation solution that may optionally contain silicate components, said process comprising a step to select: a pre-determined value for the total quantity of water and / or for the size distribution of the possible silicate components in order to obtain a geopolymer whose porosity accessible to water is between about 15% and 1%; 65%.
• the porosity accessible to water of the geopolymer is of the order of 15%, of the order of 20%, of the order of 25%, of the order of 30%, of the order of 35%.
• % of the order of 40%, of the order of 45%, of the order of 50%, of the order of 55%, of the order of 60% or of the order of 65%; a pre-determined value for the total amount of silica in order to obtain a geopolymer having a monomodal microporosity, mesoporosity or macroporosity and / or
• the work of the inventors has made it possible to show that the total porosity of the geopolymers can be controlled by modifying the formulation parameters of these materials, in particular the water content.
• the amount of water influences the total porosity of the geopolymer presumably by conditioning: the space initially separating the source aluminosilicate solid particles,
• the quantity of water can in particular be fixed via the molar ratio H 2 O / M 2 O with H 2 O corresponding to the sum of the quantity expressed in moles of water present in the activation solution and the quantity expressed in moles of water optionally bound to the alumino-silicate source and M 2 O corresponding to the molar amount of compensation cation oxide in the activation solution.
• H 2 O / M 2 O molar ratio makes it possible to increase the total porosity of the geopolymer thus obtained.
• the inventors have shown that an H 2 O / M 2 O molar ratio greater than 10, advantageously greater than 11 makes it possible to obtain a geopolymer whose porosity accessible to water is greater than 50%.
• the pre-determined value for the particle size distribution of the possible silicate components is advantageously chosen from a pre-determined value of the median diameter of the particle size distribution of the possible silicate components or a predetermined value of the extent of the particle size distribution of the particles. possible silicate components.
• the lower the median diameter of the silicates components used the more the polymer obtained has a porosity accessible to low water.
• the smaller the extent of the particle size distribution of the silicate components the lower the pore distribution of the geopolymer obtained is centered, and therefore the lower the total geopolymer porosity.
• the class of porosity (macropores, mesopores or micropores) can to be chosen as soon as it is implemented by selecting a total concentration of suitable silica.
• the porous mode depends on the porosity proper to the gel. This amounts to modifying the polycondensation behavior, for example by doping the amount of silicate monomers by adding reagents into the activation solution.
• the unreacted silica also seems to lead to a steric hindrance of the residual aqueous poral space, thus to a decrease in the porous mode of the material.
• the particle size distribution of the silica used has an impact on the modalities of space and therefore on the porosity of the material.
• amount of silica is meant the sum of the silica supplied by the aluminosilicate source and the silica possibly present in the activation solution.
• the SiO 2 / M 2 O molar ratio makes it possible to assess the total amount of silica, SiO 2 corresponding to the molar amount of silicon oxide supplied by the alumino-silicate source and the silica possibly present in the activation solution.
• those skilled in the art can obtain and / or calculate these values, without inventive effort, by using standard chemical analyzes, such as weighing or X-ray fluorescence, of all the reagents used.
• a SiO 2 ZM 2 O molar ratio greater than 1 and especially greater than 1.1 makes it possible to obtain a geopolymer exhibiting a monomodal mesoporosity whereas a molar ratio SiO 2 / M 2 O less than 1, in particular less than 0.9, in particular less than 0.8 and, more particularly, less than 0.7 makes it possible to obtain a geopolymer having a monomodal macroporosity.
• the pore distribution and in particular the pore size in a pore range can also be predetermined by an appropriate formulation.
• a geopolymer having a monomodal porosity and, more particularly, a monomodal macroporosity or mesoporosity whose distribution of pore volumes is more or less extensive can be synthesized by choosing one or more suitable compensation cation (s). With the water and silica content fixed in the material, the size and arrangement of the oligomers formed depends on the size of the compensating cations used. The porosity distribution thus controlled seems to be an intrinsic porosity to the initial oligomeric structures.
• the compensation cation is especially chosen from alkali metals, alkaline earth metals and mixtures thereof.
• Mating means mixtures of two or more alkali metals, mixtures of two or more alkaline earth metals and mixtures of one or more alkali metals with one or more alkaline earth metals.
• the alkali metals lithium (Li), sodium (Na), potassium (K), rubidium (Rb) and cesium (Cs) are more particularly preferred.
• the alkaline earth metals magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Ba) are more particularly preferred.
• the amount of compensation cation (s) that can be used in the context of the process of the present invention is between 0.1 and 10, especially between 0.5 and 5, in particular between 0.8 and 2, especially with respect to the molar amount of Al 2 O 3.
• the amount of cation (s) compensation is chosen so that the molar ratio M 2 (VAl 2 O 3 is equal to 1.
• the selection step consists of selecting a compensation cation from potassium, sodium and cesium to obtain an extent of the pore distribution of the geopolymer containing as potassium compensation cation, less than the extent of the pore distribution of the geopolymer containing sodium compensation cation, itself less than the extent of the pore distribution of the geopolymer containing as cesium compensation cation.
• the person skilled in the art will be able to determine, as a function of the compensation cation or of the mixture of compensation cations used, the influence on the porosity distribution without doing proof of a particular inventive effort.
• any alumino-silicate source known to those skilled in the art can be implemented in the context of the process of the invention.
• this Alumino-silicate source is a solid source containing amorphous aluminosilicates.
• amorphous aluminosilicates are chosen in particular from the minerals of natural aluminosilicates such as illite, stilbite, kaolinite, pyrophyllite, andalusite, bentonite, kyanite, milanite, grovenite, amesite, cordierite, feldspar, allophane, etc .; calcined natural aluminosilicate minerals such as metakaolin; synthetic glasses based on pure aluminosilicates; aluminous cement; pumice; calcined by-products or industrial mining residues such as fly ash and blast furnace slags respectively obtained from the burning of coal and during the processing of cast iron ore in a blast furnace; and mixtures thereof.
• natural aluminosilicates such as illite, stilbite, kaolinite, pyrophyllite, andalusite, bentonite, kyanite, milanite, grovenite, amesite, cordierite
• the alumino-silicate source used in the context of the present invention is in a solid form and, advantageously, in the form of a powder or a mixture of particles. These particles have in particular a median diameter (d50) of between 0.1 and 40 ⁇ m, in particular between 0.5 and 20 ⁇ m and, in particular, between 1 and 10 ⁇ m.
• d50 median diameter
• metakaolin is used as alumino-silicate source, it is in the form of particles whose median diameter (d50) determined by laser particle size is about 6 microns.
• particles whose average diameter (d50) is 6 microns means that half of the particles have a diameter of less than 6 microns.
• the skilled person at the time of formulation will, without inventive effort, calculate the amount of alumino-silicate source to be used depending on the composition of the alumino-silicate source used and the desired purpose ie desired properties for the geopolymer. Indeed, depending on the desired properties, a person skilled in the art will be able to choose the most suitable values to achieve this goal and thus will be able to set the molar ratios H 2 O / M 2 O and / or SiO 2 / M 2 O.
• activation solution is intended to mean a strongly alkaline aqueous solution which may optionally contain silicate components.
• strongly alkaline means a solution whose pH is greater than 9, especially greater than 10, in particular greater than 11 and more particularly greater than 12.
• the activation solution comprises the compensation cation or the mixture of compensation cations in the form of an ionic solution or a salt.
• the activation solution is chosen in particular from an aqueous solution of sodium silicate (Na 2 SiO), potassium silicate (K 2 SiO 2), sodium hydroxide (NaOH), potassium hydroxide ( KOH), calcium hydroxide (Ca (OH) 2 ), cesium hydroxide (CsOH) and their sulphates, phosphates and nitrates derivatives, etc ....
• sodium silicate Na 2 SiO
• potassium silicate K 2 SiO 2
• sodium hydroxide NaOH
• potassium hydroxide KOH
• calcium hydroxide Ca (OH) 2
• cesium hydroxide (CsOH) cesium hydroxide
• the silicates components present in the activation solution may be not only the silicates provided by the silicates of the compensation cations present in the activation solution but also other silicates added to the activation solution. These are especially selected from silica, colloidal silica and vitreous silica. It is therefore clear that the silicate components present in the activation solution are either only the silicate (s) provided in the form of silicate (s) of the compensation cations, or only the silicate (s) added (s). ) and selected from silica, colloidal silica and vitreous silica, a mixture of these two sources of silicates.
• the activating solution is prepared by mixing the various elements previously described which compose it. The mixture can be produced with more or less intense stirring depending on the nature of said elements.
• the solid / solution mass ratio is, in the context of the present invention, low, especially less than 0.6 and advantageously less than 0.5. This mass ratio corresponds to the mass of solids (ie alumino-silicate source + compensating cations + silicate components) on the mass of solution (ie activation solution).
• the process for preparing a controlled porosity geopolymer that is the subject of the present invention and, more particularly, the dissolution / polycondensation stages consists, first of all, in mixing the aluminosilicate source with the activation solution while stirring. more or less intense depending on the nature of the alumino-silicate source and the elements contained in the activation solution and then to preserve the material obtained under defined conditions of temperature, pressure and relative humidity until the final geopolymer.
• reaction time is also a function of the compensation cation (s) used.
• the reaction time may be between 5 minutes and 48 hours, in particular between 1 and 42 hours, advantageously between 5 and 36 hours and, in particular, between 10 hours and 24 hours.
• the reaction is carried out under tight conditions and under a pressure corresponding to atmospheric pressure.
• the present invention also relates to a geopolymer capable of being prepared by the method of the invention and having a monomodal mesoporosity with 50% of the pores having an accessibility diameter determined by mercury porosity extending over less than 5 nm (pore distribution strongly refined), between 5 and 10 nm (wider pore distribution) or over 10 nm (spreading pore distribution).
• the present invention also relates to a geopolymer capable of being prepared by the method of the invention and having a monomodal macroporosity with 50% of the pores having an accessibility diameter determined by mercury porosity extending over less than 10 nm (pore distribution strongly refined), between 10 and 50 nm (wider pore distribution) or over 50 nm (spread pore distribution).
• the present invention also relates to a catalytic support and / or species separation chemical composition comprising a geopolymer as defined above and the use of said geopolymer. All known uses of those skilled in the art implementing a geopolymer and in particular the uses described in the prior art cited above are contemplated within the scope of the present invention.
• the present invention relates, more particularly, to the use of a geopolymer as defined previously in catalysis or in filtration.
• Figure 1 shows the pore distribution as a function of mercury porosimetric accessibility diameter for geopolymers of controlled porous modes.
• Figure 2 shows the distribution of pore volumes as a function of mercury porosimetric accessibility diameter for geopolymers of different pore selectivity.
• Figure 3 shows the influence of silica and, more particularly, its particle size distribution on the mercury porosimetric accessibility diameter distribution for geopolymers of controlled porous modes.
• the aluminosilicate source used is metakaolin because this alumino-silicate source makes it possible to obtain more "pure" geopolymers whose properties are globally more homogeneous [39, 40].
• the metakaolin used is Pieri Premix MK (Grace Construction Products), whose composition determined by X-ray fluorescence is reported in Table 1.
• the specific surface area of this material, measured by the Brunauer-Emmet-Teller method, is equal to 19, 9 m 2 / g and the median diameter of the particles (d50), determined by laser granulometry, is equal to 5.9 ⁇ m.
• Table 1 Chemical composition of the meta-kao used.
• alkali metal hydroxide solutions employed were prepared by dissolving in ultrapure water granules of NaOH, KOH ( Prolabo, Rectapur, 98%) and CsOH (Alfa Aesar, 99.9%).
• the silica optionally added to the system is an amorphous silica (BDH) whose average diameter is equal to 128.81 ⁇ m.
• activation solutions containing alkali silicates were prepared.
• the alkali hydroxide solutions were obtained by dissolving the appropriate products in ultrapure water.
• the amorphous silica possibly added to the system is then introduced into these solutions and mixed for 30 minutes.
• the composition of these activation solutions is thus fully described by: the natures of the alkalis used in the formulation and their optional molar ratio, the molar ratio H 2 O / M 2 O, denoted by e, the molar ratio SiO 2 / M 2 O noted s.
• the geopolymer is prepared by mixing metakaolin and the activation solution in a standard laboratory mixer (European Standard EN 196-1) for 1 minute at slow speed and 2 minutes at fast speed. The material is then placed in teflon molds of dimensions 4 * 4 * 16 cm, vibrated for a few seconds, then placed in sealed conditions at 20 0 C and at atmospheric pressure for 24 hours. After this period, the geopolymer is demolded and placed in a sealed bag and stored at ambient pressure and temperature until use.
• a standard laboratory mixer European Standard EN 196-1
• the porosity of the geopolymers was characterized by: - porosimetry accessible to water according to the recommendations of the French Association for Construction (PSAC) and the French Association of Research and Testing on Materials and Constructions (AFREM), this method of measuring porosity is one of the most representative of the total porosity of building materials [43], the porosimetry with mercury intrusion. These measurements were carried out on a Micromeritics Autopore IV 9510 apparatus, whose investigative pressures ranged from 0.2 to 61000 psi.
• Table 2 summarizes measurements of water porosity carried out on geopolymers of different composition. A small variation in the water content strongly impacts the total measured porosity.
• Table 2 Composition of geopolymers and porosity accessible to associated water.
• the objective here is to formulate two materials having controlled and distinct porous modes: the first material must have a monomodal macroporosity centered on 100 nm, the second geopolymer a monomodal mesoporosity centered on 10 nm.
• the objective here is to formulate three materials presenting monomodal mesoporosities whose distribution of pore volumes is more or less extensive.
• the geopolymers were manufactured according to the following formulations:
• 50% of the pores have an access diameter of between 4.1 and 8.8 nm; the sodium geopolymer, the porosity is always monomodal, selective, but more spread distribution because pore range of greater size: 50% of the pores have an access diameter of between 9.9 and 16.5 nm.
• the objective here is to study the influence of the silicates components that may contain the activation solution and, more particularly, the influence of the nature of the silica introduced into the activation solution.
• Tixosil 38 (Precipitated silica from
• Table 3 compares the values of the total porosities of the geopolymers synthesized with Tixosil silicas 331 and 38 to the porosity of a geopolymer synthesized by a BDH precipitated silica.
• the median diameter and the extent of the particle size distribution have a significant influence on the porosity accessible to water: the lower the median diameter, the lower the total porosity.
• Table 4 summarizes the formulations of the geopolymers studied.
• the silica Tixosil 38 makes it possible to obtain geopolymers whose pore dispersion is centered around values smaller than the Tixosil 331.
• the silica Tixosil 38 has a grain size slightly smaller than the Tixosil 331, but especially much less dispersed. It should be emphasized that the porosity obtained is always mesoporous (silica content), refined (potassium compensating cation): the grain size of the silica therefore essentially influences the water-accessible porosity of the material and the characteristic dimensions of the diameter on which the porous mode is centered.
• a judicious formulation of the geopolymers makes it possible to control the macroporosity and / or the mesoporosity of these materials and opens the way to an engineering of the porosity of these materials, amorphous aluminosilicate inorganic polymers.
• Geopolymer stone for construction and decoration included rock residues and a poly (sialate), poly (sialate-siloxo) and / or poly (sialate-disoloxo) geopolymer binder., FR2831905, Editor. 2003. 25. Yan, S., Geopolymer Dry Powder Regenerated Polystyrene Heat Preservation and Heat Insulating Mortar., CN1762884, Editor. 2006.

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