WO2019043598A1 - Procédé de préparation de dalles/feuilles/blocs photocatalytiques et dalles/feuilles/blocs photocatalytiques associés - Google Patents

Procédé de préparation de dalles/feuilles/blocs photocatalytiques et dalles/feuilles/blocs photocatalytiques associés Download PDF

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WO2019043598A1
WO2019043598A1 PCT/IB2018/056594 IB2018056594W WO2019043598A1 WO 2019043598 A1 WO2019043598 A1 WO 2019043598A1 IB 2018056594 W IB2018056594 W IB 2018056594W WO 2019043598 A1 WO2019043598 A1 WO 2019043598A1
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Stefano Allevi
Gian Luca Guerrini
Enrico SCALCHI
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Italcementi S.P.A.
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Publication of WO2019043598A1 publication Critical patent/WO2019043598A1/fr

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    • 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
    • C04B28/28—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 organic polyacids, e.g. polycarboxylate cements, i.e. ionomeric systems
    • 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
    • C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
    • C04B20/10—Coating or impregnating
    • C04B20/1055—Coating or impregnating with inorganic materials
    • C04B20/1066—Oxides, Hydroxides
    • 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
    • C04B28/18—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 mixtures of the silica-lime 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
    • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • C04B40/0028—Aspects relating to the mixing step of the mortar preparation
    • C04B40/0039—Premixtures of ingredients
    • 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
    • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • C04B40/0028—Aspects relating to the mixing step of the mortar preparation
    • C04B40/0039—Premixtures of ingredients
    • C04B40/0042—Powdery mixtures
    • 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
    • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • C04B40/0067—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability making use of vibrations
    • 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
    • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • C04B40/0071—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability making use of a rise in pressure
    • 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
    • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • C04B40/0082—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability making use of a rise in temperature, e.g. caused by an exothermic reaction
    • 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
    • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • C04B40/02—Selection of the hardening environment
    • C04B40/0231—Carbon dioxide hardening
    • 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
    • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • C04B40/02—Selection of the hardening environment
    • C04B40/024—Steam hardening, e.g. in an autoclave
    • 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
    • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
    • C04B2111/00612—Uses not provided for elsewhere in C04B2111/00 as one or more layers of a layered structure
    • 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
    • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
    • C04B2111/0081—Uses not provided for elsewhere in C04B2111/00 as catalysts or catalyst carriers
    • C04B2111/00827—Photocatalysts
    • 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
    • Y02P40/18—Carbon capture and storage [CCS]

Definitions

  • the present invention relates to a process for the preparation of photocatalytic slabs/sheets/blocks and the slabs/sheets/blocks thus obtained, that can be preferably used as paving elements or building blocks.
  • the invention relates to paving elements (slabs and sheets) and building blocks and the preparation process from low-cost raw materials, among which water and carbon dioxide. These materials are suitable for numerous applications in the construction industry and in infrastructures.
  • Concrete blocks or slabs are produced by means of a casting, pressing, compacting process or a combination of vibrations and pressures. They are generally characterized by various geometries and are operatively positioned with mosaic laying solutions (due to their typical laying, they are also defined as self- blocking). Block floors can be applied in residential and urban areas, where they are subjected to light loads, and also for the construction of surfaces subjected to medium-heavy loads such as pavements, pedestrian areas, areas surrounding buildings, bicycle lanes, parking lots and roads with slow traffic.
  • Sheets are concrete end-products produced by means of a casting, pressing, compacting process or a combination of vibrations and pressures. They generally have a rectangular form and differ from blocks in their larger surface and smaller thickness.
  • Floors with sheets can be applied in residential and urban areas, where they are subjected to light or medium loads, such as pavements, pedestrian areas, areas surrounding buildings, bicycle lanes, parking lots and roads with slow traffic.
  • concrete tiles for outdoor use (terrazzo tiles) is used instead of the term sheets.
  • photocatalytic slabs/blocks have been the object of previous patent applications of the Applicant such as, for example WO98/05601, WOO 1/00541, EP786283 and EP1601626.
  • photocatalytic slabs/sheets/blocks are described, together with methods for the production of the relative cement-based compositions which face and solve the problem of a reduction/abatement in the pollutants present in the atmosphere, deriving from production processes (industrial and handicraft activities) and combustion processes (heating and vehicle traffic).
  • the main source of pollution is caused by vehicle traffic, responsible for the emission into the atmosphere of engine combustion products, powders released due to the wear of brakes, tyres, road surface and hydrocarbons that vaporize from the tanks.
  • the main pollutants are carbon monoxide, nitrogen oxides (NOx), sulfur oxides (SOx), volatile organic compounds (COV), suspended total particles (PTS) containing numerous pollutants such as lead, cadmium, polycyclic aromatic hydrocarbons, aldehydes, benzene.
  • European standard UNI 11241:2007 and the American standard ASTM C936-08 define the features that self-blocking concrete blocks must have.
  • the standard ASTM C 936-08, for example, provides the essential specifications that a concrete block must meet: an average compression strength of 8,000 psi (55MPa); an average water absorption not higher than 5%; resistance to at least 50 freezing/thawing cycles with an average loss of material not higher than 1%.
  • the blocks can also meet additional requirements, among which a reduced efflorescence (for example, a reduced release of reaction products due to concentration gradients); a good colour retention; abrasion resistance, etc.
  • the blocks are also produced with a bi- layer technology, by compacting or eliminating excess water from (dewatering) two different layers, fresh-on-fresh coupled, so as to have an upper layer (that which remains exposed to the surface) having a high quality and finish (and often coloured and/or with photocatalytic properties) and a lower layer made of a traditional cement-based material.
  • Slabs are also prefabricated in concrete, produced with analogous melting, pressing or compacting processes, which, in general, must meet the requirements of ASTM C90- 16a, i.e. the standard specifications for reinforced concrete masonry units.
  • the slabs in conformance with these standards are guaranteed to meet the specifications and be acceptable with respect to resistance, geometry, duration and fire resistance, and can generally be adopted for use in standard commercial building projects.
  • the Applicant has now surprisingly found a process for the preparation of photocatalytic slabs/sheets/blocks by means of carbonation, which overcomes the drawbacks of the processes of the state of the art, maintaining a high photocatalytic activity in the end-product and which is also a particularly interesting process from an economic point of view, as it allows a preparation starting from low-cost raw materials, in large quantities and with a minimum environmental impact.
  • This result was completely unexpected as the carbonation reaction tends to depress the reactivity of the photocatalyst based on Ti0 2 on which the photocatalytic activity of the block/sheet/slab depends, under certain environmental conditions (quantity of C0 2 and water/humidity available).
  • the object of the present invention therefore surprisingly relates to a process for the preparation of photocatalytic blocks/sheets/slabs which comprises the following steps:
  • composition wherein the composition in solid powder form comprises: at least one binder selected from ground calcium silicate or its precursors and/or relative mixtures, having an average particle size ranging from about 1 ⁇ to about 100 ⁇ , preferably from 5 ⁇ to 50 ⁇ ;
  • Ti02 titanium oxide having an average particle size ranging from about 10 nm to about 200 nm and with a specific surface area ranging from about 10 m2/g to about 300 m2/g;
  • liquid composition comprises, at least:
  • step b) discharging the mixture in suspension obtained from step a) into a
  • step d) curing the compacted mixture in suspension obtained in step c), at a
  • the photocatalyst based on titanium dioxide can be in the form of photocatalytically active anatase or rutile, and can be possibly supported on another inorganic material (for example, calcium carbonate, pozzolan charge, silica, or pigment - mineral oxide).
  • another inorganic material for example, calcium carbonate, pozzolan charge, silica, or pigment - mineral oxide.
  • the process according to the present invention can also provide vibration in the mould during steps b) and c) for discharging and compacting the mixture in suspension in the mould.
  • Step d) for curing the mixture is preferably carried out at a temperature ranging from 60°C to 110°C, for a time ranging from 15 hours to 70 hours, in an atmosphere saturated with vapour, containing water and C0 2 and having a pressure within the range varying from atmospheric pressure to 2 bar above atmospheric pressure.
  • Step d) for curing the mixture is more preferably carried out at a temperature ranging from 80°C to 100°C, for a time ranging from 20 hours to 60 hours, in an atmosphere saturated with vapour containing water and C0 2 and having a pressure within the range varying from atmospheric pressure to 2 bar above atmospheric pressure.
  • Step d) for curing the mixture is even more preferably carried out at a temperature equal to or lower than about 60°C for a time ranging from 15 hours to 50 hours, in an atmosphere saturated with vapour containing water and C0 2 and at atmospheric pressure.
  • the mould used in step b) of the process according to the present invention has the geometry of a block, sheet or slab and, by compacting the suspension in the mould in step c), a solid preform in the form of a block, sheet or slab is obtained, which is then subjected to the curing step d) of the process according to the present invention.
  • the process can also comprise, before step d), a step for drying the preform.
  • composition in powder form used in step a) of the preparation process according to the present invention comprises:
  • At least one binder selected from ground calcium silicate or its precursors and/or relative mixtures, having an average particle size ranging from about 1 ⁇ to about 100 ⁇ , preferably from 5 ⁇ to 50 ⁇ ;
  • Ti0 2 titanium oxide having an average particle size ranging from about 10 nm to about 200 nm and with a specific surface area ranging from about 10 m 2 /g to about 300 m 2 /g.
  • the photocatalyst based on titanium dioxide can be in the form of photocatalytically active anatase or rutile, and can be possibly supported on another inorganic material (for example, calcium carbonate, pozzolan charge, silica, or pigment - mineral oxide).
  • another inorganic material for example, calcium carbonate, pozzolan charge, silica, or pigment - mineral oxide.
  • the hydraulic binder can also be obtained by chemical transformation from any suitable precursor material, for example from a precursor of calcium silicate different from woUastonite.
  • a binder can also be produced from reactive precursor materials (for example from precursor particles) through a transformation process.
  • the precursor particles can have any size and form which depend on the characteristics of the final application.
  • the transformation process generates the corresponding binding elements having dimensions and forms similar to those of the precursor particles.
  • a binding element comprises a nucleus (represented by the black internal portion), a first layer (represented by the white central portion) and a second layer or encapsulating layer (represented by the outer portion).
  • the first layer can comprise only one layer or various sub-layers and can completely or partially cover the nucleus.
  • the first layer can exist in a crystalline phase, an amorphous phase or a mixture thereof and can be in a continuous phase or in the form of discrete particles.
  • the second layer can comprise only one layer or various sublayers and can completely or partially cover the first layer.
  • the second layer can comprise a plurality of particles or it can be a continuous phase, with minimum discrete particles.
  • a binder can have any size and any morphology, regular or irregular, solid or hollow, depending on the desired application.
  • Exemplary morphologies comprise: cubes, cuboids, prisms, disks, pyramids, polyhedrons or polyvalent particles, cylinders, spheres, cones, rings, tubes, crescents, needles, fibers, filaments, flakes, spheres, substrates, beads, grapes, granules, oblongs, bars, ripples, etc.
  • calcium silicate refers to minerals existing in nature or synthetic materials that are compounds containing one or more calcium- silicon groups, such as CaSi0 3 (also known as wollastonite or pseudo- wollastonite", sometimes formulated as CaO.Si0 2 ), Ca 3 Si 2 0 7 (also known as “Rankinite”, sometimes formulated as 3Ca0.2Si0 2 ), Ca 2 Si0 4 (also known as "Belite”, P-Ca 2 Si0 4 or “Larnite", a-Ca 2 Si0 4 , a'-Ca 2 Si0 4 or y-Ca 2 Si0 4 sometimes formulated as 2CaO.Si0 2 ), Ca 3 Si0 5 (also known as "Alite” sometimes formulated as 3CaO.Si0 2 ).
  • the compounds based on calcium silicate can contain amorphous calcium- silicon (non-crystalline) phases or pseudo-amorphous in addition to the described crystalline phases. These compounds can also comprise one or more ions and metal oxides and oxides (aluminium, magnesium, iron or manganese oxides, for example) and mixtures thereof, or they can comprise a quantity of magnesium silicate, present in nature or in synthetic forms, in a quantity ranging from simple traces (1%) to about 50% or more by weight.
  • the production process according to the present invention can therefore make use of a composition in powder form comprising, as binder, magnesium silicate, in addition to calcium silicate.
  • magnesium silicate refers to minerals existing in nature or synthetic materials which are compounds containing one or more magnesium- silicon groups, such as, for example, Mg 2 Si0 4 (also known as “Forsterite”) and Mg3Si 4 0io(OH)2 (also known as “Talc”). These compounds can comprise one or more ions and metal oxides and oxides (for example, aluminium, magnesium, iron or manganese oxides) or mixtures thereof, or they can comprise a quantity of magnesium silicate, present in nature or in synthetic forms, in an amount ranging from simple traces (1%) to about 50% or more by weight.
  • the binder in the solid composition in powder form is preferably CaSi0 3 (also known as wollastonite or pseudo-wollastonite", sometimes formulated as CaO.Si0 2 ), having an average particle size ranging from about 1 ⁇ to about 100 ⁇ , more preferably from 5 ⁇ to 50 ⁇ .
  • the ground wollastonite has an average particle size ranging from about 5 ⁇ to 50 ⁇ , a density ranging from about 0.6 g/ml to about 0.8 g/ml (free) and from about 1.0 g/ml up to about 1.2 g/ml (after compacting - tapped density), a surface area ranging from about 1.5 m 2 /g to about 2.0 m 2 /g.
  • precursor of calcium silicate refers to any material which, through adequate transformations, forms the desired binder.
  • the precursor particles can comprise, for example, oxides and non-oxides of silicon, titanium, aluminum, phosphorus, vanadium, tungsten, molybdenum, gallium, manganese, zirconium, germanium, copper, niobium, cobalt, tantalum and/or alkaline elements (beryllium, magnesium, calcium, strontium, barium and radium).
  • precursors comprise oxides such as silicates, titanates, aluminates, phosphates, vanadates, tungstates, molybdates, gallates, manganates, zirconates, germinates, cuprates, stannates, hafnates, chromates, niobates, cobaltates, plumbates, ferrites, indates, arsenates, tantalates and combinations thereof.
  • the precursors comprise silicates such as orthosilicates, sorosilicates, eye lo silicates, inosilicates, phyllo silicates, tectosilicates and/or hydrated calcium silicate.
  • waste materials can be used as precursor particles for some applications.
  • the waste materials can comprise, for example, minerals, industrial waste materials or industrial chemical materials.
  • Waste materials that can be used as precursors are, for example, mineral silicate, iron mineral, periclase, gypsum, iron (II) hydroxide, flying ash, background ash, slag, glass, battery residues, recycled cement, paper ash or concentrated inverse osmosis brine salts.
  • Further precursors can comprise various types of rocks containing minerals such as cal-silicate rock, Hebron gneiss, stratified gneiss, argillite, quartzite, intermediate precambric sediments, dark-colored quartz, calcareous quartz with secondary limestone beds, biotites from metasedimentary shale, gneiss biotite, schist mica, quartzite, Washington gneiss, Devonian gneiss, amphibolites, calcite and dolomite marble.
  • minerals such as cal-silicate rock, Hebron gneiss, stratified gneiss, argillite, quartzite, intermediate precambric sediments, dark-colored quartz, calcareous quartz with secondary limestone beds, biotites from metasedimentary shale, gneiss biotite, schist mica, quartzite, Washington gneiss, Devonian gneiss, amphibolites, calcite and dolomite marble.
  • the precursor can also comprise igneous rocks such as andesite, anortosite, basinite, boninite, carbonatite and charnockite, sedimentary materials such as, for example, argillite, arkosite, breccie, chert, flint, cataclassite, chalk, clay, Lighine, limestone, mudstone, sandstone, shale and silton, metamorphic materials such as, for example, amphibolites, epidiorites, gneiss, granulite, marble, pelite, phyllite, quartzite, schist, skarn, carbonate and soapstone, and other varieties of rocks such as adamellite, apinite, afanite, borolite, epidosite, felines, Corpines, ganister, ijolite, jiadeitite, jasperide, kenyte, vogesite, larvikite, litchfieldite, luxul
  • the binder comprises a nucleus, a first layer and a second layer or encapsulating layer: depending on the starting material, the first and second layer can contain various types of substances.
  • the first layer using various precursors, the same can be made of silica, alumina or titania.
  • the second layer can be modified by selecting the precursor.
  • the second layer can comprise various types of carbonates, such as pure carbonates, carbonates with multiple cations, carbonates with water or with an OH group, carbonates stratified with water or with an OH group, carbonates containing anions, carbonates containing silicates and carbonates containing minerals.
  • a first layer rich in silica is obtained, and a second layer, or encapsulating layer, in CaC0 3 , starting from fosterite (Mg 2 Si0 4 ), a first layer rich in silica is obtained, and a second layer, or encapsulating layer, in MgC0 3 .
  • the second layer can be modified by introducing further anions and/or cations to modify the physico/chemical properties such as fire resistance or acid resistance.
  • the second layer can be modified by
  • the second layer can consequently comprise phosphates, for example, sulfates, fluorides or combinations of the same.
  • Binding matrix refers to a matrix comprising a plurality of binders and which forms a three-dimensional network.
  • the binding matrix can be porous or non- porous.
  • the porosity degree depends on a series of variables which can be used for controlling the porosity, such as temperature, pressure, design of the reactor, reaction time, precursor material and the quantity of liquid and gas introduced during the curing process. According to the desired final application, the porosity of the matrix can range from about 1% by volume to about 99% by volume.
  • the binding matrix can incorporate one or more fillers mixed with the binding elements based on calcium silicate and/or relative precursors in step a) of the process according to the present invention.
  • the concentration of the binders in the binding matrix is variable.
  • the concentration of binders in volume can be high, and in this situation some binding elements are in contact with each other. This occurs if the filler is incorporated in the binding matrix, but the type of filler and/or the quantity of filler is such that the volumetric dilution level of the binding element is relatively low. Or the concentration of binders by volume can be relatively low and in this situation, the binding elements are more prevalent inside the binding matrix so that few binding elements are in contact with each other, or even none.
  • the term "at least one filling material or filler” refers to filling materials or fillers with a fine particle size.
  • the filler is preferably a material based on Si0 2 , such as quartz, to impart the necessary hardness to the final product.
  • the filler can also comprise calcium carbonate (CaC0 3 ) or other materials based on carbonate.
  • the filler consists of a plurality of particles that can have an average particle size within the range of about 5 ⁇ to about 1 mm, preferably from 10 ⁇ to 100 ⁇ , even more preferably from 20 ⁇ to 90 ⁇ .
  • the preferred filler consists of one or more materials based on S1O 2 or based on silicate such as quartz (Si0 2 ), mica (aluminium silicate) and feldspar (material based on aluminium silicate) (for example ground quartz, ground mica, ground feldspar).
  • silicate such as quartz (Si0 2 ), mica (aluminium silicate) and feldspar (material based on aluminium silicate) (for example ground quartz, ground mica, ground feldspar).
  • the filler can comprise natural, synthetic and recycled materials, such as glass, recycled glass, coal scraps, material rich in calcium carbonate and material rich in magnesium carbonate.
  • the filler can therefore comprise one or more materials which are incorporated in the binding matrix.
  • a filler can be inert or active.
  • An inert material is not subject to any chemical reaction during the curing phase and does not act as a nucleation site, even if it can interact physically or mechanically with the binding matrix.
  • the inert filler can be selected from polymers, metals, inorganic particles, aggregating materials and the like. Specific examples are basalt, stone, recycled PVC, rubber, metal particles, alumina particles, zirconium particles, carbon particles, carpet particles, KevlarTM particles and combinations thereof.
  • An active filler chemically reacts with the binding matrix during the curing phase, it is subject to chemical reactions and/or acts as nucleation site.
  • Magnesium hydroxide for example, can be used as filler and can chemically react with a component based on calcium which dissolves from the binding matrix to form calcium and magnesium carbonate.
  • the binding matrix can form from 1% by volume to 99% by volume of the construction material, preferably the volume fraction of the binding matrix ranges from 8% to 90% by volume, more preferably from 8% to 30% by volume.
  • the binding elements can be positioned inside the binding matrix, in relation to each other, according to various orientations.
  • a photocatalyst based on titanium oxide (Ti0 2 ) refers to titanium oxide or one of its precursors, preferably titanium oxide at least partially in the form of anatase.
  • titanium oxide at least partially in the form of anatase means that the particles of photocatalyst in the composition in powder form are particles of titanium oxide (Ti0 2 ) having an anatase structure at least for 5%, preferably 25%, more preferably at least 50%, even more preferably 70%, as weigh percentages with respect to the total weight of the titanium oxide (Ti0 2 ).
  • a quantity of over 85% of the particles of titanium oxide (Ti0 2 ) are particles of titanium oxide with an anatase structure.
  • precursor of titanium oxide means that the preferred photocatalyst is not limited to "Ti0 2 at least partially in the form of anatase” but is also extended to any product which, when mixed in the solid composition of step a) of the process according to the present invention, can form Ti0 2 , mainly in the form of anatase, in the subsequent reaction steps of the process.
  • titanium paste for example, can be considered as being a valid precursor for the photocatalyst based on titanium oxide in the process according to the present invention.
  • Matrixes of Ti0 2 doped with suitable atoms such as Fe(III), Mg(II), Mo(V), Ru(III), Os(III), Re(V), V(IV), Rh(III), N, C and W (tungsten) are intended as being included in the definition "precursor of titanium oxide".
  • these atoms can substitute, at the atomic level, the Ti(IV) present in the Ti0 2 matrix for at least 0.5% by mass, with respect to the total titanium oxide
  • the (binder)/(filler) weight ratio ranges from about (15 to 50) to about (50 to 85).
  • the composition in solid powder form used in the process according to the present invention comprises from 0.1 to 15% by weight of photocatalyst based on titanium oxide, with respect to the total weight of the powder composition.
  • the composition in solid powder form preferably comprises about 25% by weight of ground calcium silicate, about 65% by weight of the filler based on silicon dioxide and about 10% by weight of titanium oxide, said percentages being defined with respect to the total weight of the powder composition.
  • the solid powder composition can also comprise a pigment selected from an inorganic metal oxide (for example black iron oxide, cobalt oxide and chromium oxide) or a glass material having a colour selected from black, white, red, yellow and brown, light blue or green and mixtures thereof.
  • an inorganic metal oxide for example black iron oxide, cobalt oxide and chromium oxide
  • a glass material having a colour selected from black, white, red, yellow and brown, light blue or green and mixtures thereof for example black iron oxide, cobalt oxide and chromium oxide
  • the pigment can be present in quantities ranging from about 0.1% to about 5%, preferably from 0.2% to 3%, even more preferably from 0.5% to 2% by weight with respect to the total weight of the powder composition.
  • the powder composition comprises a binder such as ground “wollastonite” or “pseudo-wollastonite", a filler selected from the group consisting of glass, quartz and/or sand and a photocatalyst based on titanium oxide which is anatase titanium oxide for over 85% of the particles.
  • a binder such as ground “wollastonite” or "pseudo-wollastonite”
  • a filler selected from the group consisting of glass, quartz and/or sand and a photocatalyst based on titanium oxide which is anatase titanium oxide for over 85% of the particles.
  • the liquid composition used in step a) of the preparation process according to the present invention comprises water and a dispersant.
  • the dispersant can be a polymeric salt in a concentration ranging from about 0.1% to about 2% by weight with respect to the total weight of the liquid composition.
  • the polymeric salt can be a salt of an acrylic homopolymer, for example.
  • suspension denotes a wet mixture.
  • the suspension is a wet mixture consisting of about 95% by weight of the composition in powder form and about 5% by weight of the liquid composition.
  • a building material obtained through the process according to the present invention in the form of a block/sheet/slab can be porous or non-porous.
  • the porosity degree depends on a series of variables which can be used for controlling the porosity, such as the temperature, pressure, design of the reactor, reaction time, the precursor material and quantity of liquid and gas introduced during the curing process and the filler.
  • the porosity can range from 1% by volume to 99% by volume, preferably from 1% by volume to 70% by volume, more preferably from 1% to 10% by volume for applications requiring a high density and duration, and from 50% by volume to 70% by volume for applications requiring a low thermal conductivity.
  • the building material comprises one or more binding elements and a plurality of filler particles and photocatalyst, wherein the binding elements and plurality of filler particles together, form one or more binding matrix and the binding elements, the filler particles and the photocatalyst are substantially uniformly dispersed in these matrices and are bound together, allowing the composite building material to have an appearance similar to various types of natural stone.
  • the building material also comprises a pigment.
  • the pigment can be uniformly dispersed or substantially irregularly dispersed in the binding matrixes, according to the desired composite material.
  • a further object of the present invention relates to a block/sheet/slab in building material having a compression strength ranging from about 50 MPa to about 300 MPa and a flexural strength ranging from about 5 MPa to about 40 MPa and a water absorption lower than about 10%.
  • Another objective of the present invention relates to an article produced with a plurality of block/sheet/slab elements.
  • the process according to the present invention is particularly advantageous as it allows building blocks/sheets/slabs to be obtained based on the composite building material previously described, starting from low-cost raw materials, sequestering carbon dioxide in the curing process, wherein C0 2 is a reagent and water is the reaction medium, thus proving to be of particular interest from an environmental point of view and surprisingly obtaining a block/sheet/slab characterized by a relevant photocatalytic activity.
  • the curing step i.e. step d) of the process according to the present invention, proceeds by exposing the binder precursor to a reactive liquid.
  • the reagent present in the reactive liquid composition specifically diffused C0 2 and correlated species in solution, reacts with the chemical elements present in the binder precursor, causing the formation of the first and second layer of the binder.
  • This process is also known as HLPS (HLPS (Hydrothermal Liquid Phase Sintering) in the presence of gas.
  • the reagent of the liquid composition preferably reacts with at least a first chemical element (for example, Ca 2+ ) and the reaction causes the formation of the first and second layer of the binder, the first layer comprising a derivative of the precursor particle which generally does not comprise said first chemical element, whereas the second layer comprises a combination (for example, CaC0 3 ) of the reagent and said first chemical element.
  • the nucleus comprises the same or substantially the same chemical composition as the precursor particle (for example, CaSi0 3 ).
  • the peripheral portions of the nucleus can have a chemical composition slightly different with respect to the precursor particle due to a selective leaching process of particular chemical elements by the nucleus.
  • the nucleus and the second layer share said first chemical element (Ca 2+ , for example) of the precursor particle, whereas the nucleus and the first layer share at least a second chemical element of the precursor particle (for example, Si 4+ ).
  • Said first chemical element shared by the nucleus and the second layer can be an alkaline-hearth metal (beryllium, magnesium, calcium, strontium, barium, radium).
  • Said second chemical element shared by the nucleus and by the first layer can be silicon, titanium, aluminium, phosphorus vanadium, tungsten, molybdenum, gallium, manganese, zirconium, germanium, copper, niobium, cobalt, lead, iron, indium, arsenic and/or tantalum.
  • the carbonation reaction which, by nature, tends to poison the titanium oxide Ti0 2 , i.e. more specifically, tends to depress the reactivity of the photocatalyst based on Ti0 2 , on which the photocatalytic activity of the block/sheet/slab depends, does not have these effects under the specific reaction conditions of the process according to the present invention and with the specific solid composition, comprising a photocatalyst based on titanium oxide with the specific particle- size and specific- surface characteristics according to the present invention.
  • the photocatalytic activity of the block/sheet/slab obtained with the process according to the present invention increases, surprisingly increasing with the passing of time.
  • a solid powder composition comprising:
  • a binder consisting of ground woUastonite with a particle size ranging from 5 ⁇ to 50 ⁇ , a density ranging from 0.6 g/ml to 0.8 g/ml (free density) and from 1.0 g/ml to 1.2 g/ml (density after compacting - tapped density) a
  • - a filler consisting of ground Si0 2 with a particle size ranging from 40 ⁇ to 90 ⁇ , a density ranging from 0.7 g/ml to 0.9 g/ml (free density) and from 1.3 g/ml to 1.6 g/ml (density after compacting - tapped density);
  • Ti0 2 titanium oxide
  • the photocatalyst can be in the form of photocatalytically active anatase or rutile, and can possibly be supported on another inorganic material (for example, calcium carbonate, pozzolan charge, silicon, or pigment - mineral oxide).
  • another inorganic material for example, calcium carbonate, pozzolan charge, silicon, or pigment - mineral oxide.
  • the particles of calcium silicate mainly consisting of woUastonite, CaSi0 3 , react with the carbon dioxide dissolved in water. It is believed that the calcium cations are leached by the woUastonite and that they transform the peripheral portion of the nucleus of the woUastonite into woUastonite lacking in calcium. As the calcium cations continue to exit from the peripheral portion of the nucleus, the structure of the peripheral portion can become instable and break, thus transforming the peripheral portion of the nucleus of wollastonite lacking in calcium into a first layer mainly rich in silica. In the meantime, a second layer, mainly consisting of calcium carbonate, precipitates from the water.
  • a second layer mainly consisting of calcium carbonate
  • the first and second layer of the binding element can be formed from the precursor particle according to the following exothermic reaction (1):
  • the C0 2 is introduced as gas phase which dissolves in an infiltration fluid, water.
  • the dissolution of C0 2 forms acid carbonic species which cause a reduction in the pH of the solution.
  • the slightly acid solution dissolves the calcium species from CaSi0 3 .
  • the calcium cations released and the dissociated carbon species lead to the precipitation of insoluble carbonates. It is believed that the layers rich in silica remain on the mineral particles as depletion layers.
  • the C0 2 preferably reacts with the calcium cations of the precursor nucleus of wollastonite, transforming the peripheral portion of the precursor nucleus into a first layer rich in silica and a second layer rich in calcium carbonate. Furthermore, the first and second layer present on the nucleus act as a barrier preventing further reactions between wollastonite and carbon dioxide.
  • a solid porous body i.e. the solid porous preform, comprising a plurality of precursor particles of the binding element
  • a liquid which partially saturates the pores of the solid porous body, which means that the pore volume is partially filled with water.
  • Gas-assisted HLPS processes therefore preferably use the space of partially infiltrated pores to allow a rapid gaseous diffusion whereby the gas rapidly infiltrates the solid porous preform, saturating with C0 2 , the thin liquid interfacing films of solvents in the pores.
  • Species based on C0 2 have a low solubility in pure water and it is therefore necessary to continuously provide a considerable amount of C0 2 which is distributed in the whole solid porous preform to allow a significant conversion of the carbonate.
  • the use of gas-phase diffusion allows a significant increase (about 100 times) in the diffusion with respect to the diffusion of soluble C0 2 in an equivalent time in liquid phase. This partially infiltrated state allows the reaction to proceed with a high carbonation degree in a certain period of time.
  • the gas containing the reagent is thus introduced into the partially saturated pores of the solid porous preform and the reagent is dissolved by the solvent.
  • the dissolved reagent then reacts with the first chemical element in the precursor particle to transform the peripheral portion of the precursor particle into the first layer and then into the second layer, as previously described.
  • the resulting binding element comprises the nucleus, the first layer and the second layer and is generally larger than the precursor particle, partially or completely filling the surrounding porous regions of the solid porous body and possibly binding particle of fillers or adjacent particles of photocatalyst in the solid porous preform.
  • a block/sheet/slab is therefore obtained substantially having the same size and form as the solid porous preform, but a higher density.
  • the liquid water in the pores increases the reaction rate as it is essential for the ionization of both the carbonic acid and the calcium species.
  • the quantity of water however, must be kept low (partial saturation condition) so that the gaseous C0 2 can be diffused in the porous matrix before being dissolved in the aqueous phase present in the pores.
  • porous preform which has an active role in the dissolution, also acts as model for the expansive growth of reactive crystals.
  • the binder and the binding matrix are formed with minimum distortions and residual stress, allowing the production of blocks/sheets/slabs also having large dimensions and/or complex forms.
  • the water in the curing step d) of the process according to the present invention, is fed with dissolved CO 2 and step d) is carried out at about 90°C and about 1.4 bar above atmospheric pressure for about 48 hours.
  • the water is already present (for example, as residual water from the previous mixing step) and water vapour is fed (for example to maintain the water level and/or prevent evaporation of the water) with CO 2 and the curing process d) is carried out at 60°C and at atmospheric pressure for about 19 hours.
  • the water is fed in the form of vapour with CO 2 and the curing process d) is carried out at 90°C and about 1.4 bar above atmospheric pressure) for about 19 hours.
  • a solid porous body or solid porous preform comprising a plurality of precursor particles of the binding element is introduced into an autoclave and heated.
  • the water necessary as solvent is introduced into the pores of the solid porous body by vaporization of the water in the autoclave.
  • a cooling plate positioned above the solid porous body, condenses the evaporated water which drips onto the porous body and into the pore of the solid porous body, partially saturating the pores of the solid porous body.
  • the above method for introducing water is one of the numerous possible different ways of introducing water.
  • the water can be heated and sprayed, for example.
  • the C0 2 reagent is pumped into the chamber of the autoclave and the carbon dioxide is diffused in the partially saturated pores of the porous body. Once it is inside the pores, the carbon dioxide dissolves in the water thus allowing the reaction between the precursor particles and carbon dioxide in order to transform the peripheral portions of the precursor particles into the first and second layer, and thus reaching the formation of the binding element and matrixes, as previously described for the gas-assisted HLPS method.
  • the infiltration means used for transporting the reagent into at least one portion of the porous preform comprises a solvent (for example water) and a reactive species (for example C0 2 ).
  • the solvent can be aqueous or non-aqueous and can comprise one or more components.
  • the solvent can be water and ethanol, ethanol and toluene or mixtures of various ionic liquids, such as ionic liquids based on cations such as alkyl- substituted imidazolium, and pyridine, with halide or tri-halogenaluminated anions.
  • the solvent must not be chemically reactive with the porous preform, even if the solvent can react chemically with the reactive species.
  • the solvent can be removed by means of a variety of separation methods known to skilled persons in the field.
  • the solvent is a liquid at the temperature at which the dissolved reactive species reacts with the porous matrix.
  • This temperature varies according to the specific solvent and reactive species selected. Low temperatures are preferable to higher temperatures, for saving energy and simplifying the process equipment, thus reducing the production costs.
  • the reactive species dissolve in the solvent as neutral species, anionic or cationic.
  • C0 2 can be at least one reactive species, as it is a gas at room temperature which can dissolve in water as neutral C0 2 , but it can generate reactive species such as H 3 H 3 0 + , HC03 " , H 2 C0 3 and C0 3 2 0 + , HC03 " , H 2 C0 3 and C0 3 2" .
  • the infiltration medium is in liquid state in the pores (for example in the interstitial spaces) of the porous preform.
  • the capillary forces can allow the spontaneous diffusion of the infiltration medium in the porous preform.
  • This type of wetting occurs when the infiltration medium has a very low contact angle ( ⁇ 90°C, for example).
  • the medium can partially fill (partially saturate) or completely fill (saturate) the pores.
  • the infiltration can also be effected so that some pores are filled whereas others are empty and/or partially filled. It is also possible that a porous preform infiltrated with gradients in the filling or saturation of the pores, be subsequently transformed into a porous preform uniformly infiltrated through the capillary flow.
  • the wetting does not occur spontaneously if the contact angle of the infiltration medium is high (>90°, for example). In this case, the fluids will not infiltrate into the porous preform unless an external pressure is applied. This approach is useful when the recovery of the infiltration medium is desired, by releasing the pressure (for example a reaction can be started or stopped by the pressure).
  • the mass flow is interrupted when the pores are saturated.
  • the reactive species reacts with the precursor of the binding element to form one or more reaction products.
  • at least one reactive species becomes exhausted within the pore space and it must therefore be re-fed during the reaction.
  • the reactive species must be transported from the infiltration medium outside the porous preform through the pores. In a quiescent fluid, diffusion is the process through which the transport takes place. Consequently, for some HLPS methods, in which the reactions inside the pores are rapid with respect to all the other mass transport processes, the reaction is limited by considerable increases in the thickness of the porous preform. In this case, only the outer portion of the preform reacts completely with the reactive species, whereas the inner regions of the porous preform can remain only partially reacted or non-reacted.
  • the entrapped heat can increase the reaction rate inside the matrix with the result that the binding matrix will contain in its interior more product phase (i.e. the reaction product between the reactive species and a portion of the porous matrix) with respect to its exterior.
  • the diffusion can continue to provide pores with the reactive species and no gradient will be observed in the degree of reaction (or concentration of the reaction product).
  • concentration of the reaction product there is little difference in the chemical composition and/or phase moving from the inside to the outside of the composite material of the block/slab.
  • a uniform micro structured structure is generally preferred with respect to the composition in the body of the block/slab of interest, and it is also preferable to carry out HLPS reactions in a relatively short time, for example when large slabs are necessary (thick monolithic blocks) for applications such as roads or bridges. Both of the above objectives require balancing the reaction rate and the mass transport for HLPS processes.
  • the choice of the precursors, solvents and reagents are fundamental, as also the method for introducing the infiltration medium which is at least partially in relation to the thickness of the sample in its thinnest direction, the times considered acceptable for the process and the thermodynamic and kinetic constraints relating to the temperature, pressure and composition.
  • the porous preform can be directly infiltrated or it can be evacuated before any infiltration sequence.
  • Gases, liquids or solids or phase mixtures such as solids and liquids, gases and liquids, gases and solids, can be used as precursors (solvents and reagents).
  • a reagent such as C0 2 , for example, is a gas in the pure state (or with a purity not lower than 99%) but it is converted into a species in solution by dissolution in water. This can take place by gas diffusion in the porous matrix and subsequent condensation when it encounters a pore.
  • This type of precursor system is important when micro structures with carbonate phases are desired. The order of addition of the precursors (solvents and reagents) can influence the reaction yield and the micro structure of the material.
  • the solvent and the reactive species can be pre-mixed to form the infiltration medium and then introduced into the matrix in a single step.
  • the use of various infiltration sequences may be preferable.
  • the precursor of the solvent could be introduced first, for example, followed by the infiltration of the reactive species, or vice versa.
  • Numerous additives can be added to improve the HLPS process and the resulting products.
  • the additives can be solid, liquid or gaseous, in their pure state, but soluble in solvent phase or co-processed (for example, pre-mixed) with the porous matrix before the insertion of the infiltration medium.
  • Examples comprise nucleation catalysts, nucleation inhibition agents, solvent conditioners (for example, softeners), wetting agents, non-wetting agents, additives for cement or concrete, additives for building materials, additives for crystal morphology control, crystal growth catalysts, additives for slowing down crystal growth, pH buffers, ionic force regulators, dispersants, binders, rheological control agents, reaction-rate catalysts, electrostatic, steric, electro steric, polyelectrolyte dispersants, capping agents, coupling agents, acid or base pH modifiers, gas, liquid or solid generating additives (for example, when heated, pressurized, depressurized, reacted with another species, or exposed to any transformation variable) and biological or synthetic components.
  • solvent conditioners for example, softeners
  • wetting agents for example, wetting agents, non-wetting agents, additives for cement or concrete, additives for building materials, additives for crystal morphology control, crystal growth catalysts, additives for slowing down crystal growth, pH buffers
  • the solid composition used in the process according to the present invention comprising the photocatalytic element, can also be used in the processes/products described in US2016/0031757, US9216926, US2016/0096773, US 2016/00272544, US8313802, US8709960, US8114367, US8721784, US9095815, US9266147, US9221027, US2015/0225295, US2017/0336852, US2013/0122267, US 15/097,963, US2016/0272545, US2015/0266778, US2014/0342124, US2014/0127450, US2014/0127458, US2014/0314990, US2014/0272216, US2015/0056437, US9393715, US2014/0361471, US2014/0363665, WO2015/051243, US2016/0168720, US 14/715,497, in the provisional patent applications 62/247,590, 62/304, 107, 62/238,912,
  • Table 1 hereunder indicates the raw materials and relative proportions used in the production process of the block of Example 1 Table 1
  • the synthetic wollastonite (SC-C2) is commercialized by Donghai Golden Resources Industries, Donghai, China;
  • the sand is silico-calcareous river sand 0.1-3 mm commercialized by S ATAF; the aggregate, 3-6 mm, is commercialized by SATAF
  • the photocatalyst PC 105 is commercialized by Crystal, has a surface area of about 80 m /g and a particle size of about 12 nm.
  • superfluidifying agent Glenium 7500 (mixture based on polycarboxylates commercialized by BASF).
  • the solid components charged into the mixer were mixed for about 3 minutes, creating a dry solid composition.
  • the liquid composition (6.9 kg of water and 0.14 kg of Glenium 7500) was weighed and charged into the mixer containing the dry solid solution and the whole mixture was mixed for about 2 minutes until a uniform paste had been formed.
  • the paste thus obtained was charged into a hopper and sent to the experimental forming machine for moulding the block and then discharged from the feeding hopper of the machine into the cavity of the mould. During this step, the mould was subjected to vibration in order to fill the cavity effectively and uniformly.
  • the compression head of the press then subjected the wet mixture to compression for about 2 seconds or until the wet mixture had reached a height of 8 cm, producing a porous preform.
  • the preform or porous body was then introduced into a seasoning/curing autoclave having a diameter of about 210 cm and about 366 cm long, horizontal.
  • the seasoning/curing chamber was filled with C0 2 gas for 12 minutes.
  • the temperature of the autoclave was then set at 60°C, whereas hot water at a temperature of 70°C was circulated on the bottom of the chamber in order to keep the chamber saturated with water vapour.
  • the atmosphere inside the seasoning/curing chamber was moved by means of a fan. When the atmosphere inside the seasoning/curing chamber had reached 60°C and a pressure of about 1.5 bar, the concentrations of gas by volume were about 84% C0 2 and 16% water vapour.
  • porous preform was then subjected to curing/seasoning under these conditions for about 20 hours.
  • the cured porous body was removed from the seasoning/curing chamber and positioned in an industrial oven at 90°C to remove any residual water (drying).
  • the compression strength of the block thus obtained was measured according to ASTM C 936 using a Controls test machine in load control. Five blocks were subjected to the compression strength test. The average compression strength proved to be equal to 65.3 MPa with a standard deviation of 5 MPa.
  • the synthetic wollastonite (SC-C2) is commercialized by Donghai Golden Resources Industries, Donghai, China;
  • the sand is silico-calcareous river sand 0.1-3 mm, commercialized by SATAF; the aggregate, 3-6 mm, is commercialized by SATAF
  • the photocatalyst PC 105 is commercialized by Crystal, has a surface area of about 80 m /g and a particle size of about 12 nm.
  • the blocks of Examples 1-3 were then tested to verify the photocatalytic activity.
  • the photocatalytic activity of cementitious materials containing titanium dioxide in the form of anatase was experimentally found during abatement tests of nitrogen oxides NOx according to the standard UNI 11247.
  • the samples used were obtained from the blocks produced, so as to have a size of 8 cm x 8 cm with a thickness of about 1 cm.
  • the photocatalytic characterization was carried out by positioning each sample inside a reaction chamber (with a volume of 3 litres) irradiated by a UV lamp having a spectrum of irradiance within the UV band ( ⁇ ⁇ 400 nm) mainly consisting of the spectrum line at 365 nm of mercury (the integrated irradiance at ⁇ ⁇ 350 nm must be 10% lower than the integrated irradiance between 350 nm e 400 nm).
  • the lighting system must allow an average irradiance (within the UV-A band) equal to 20+1 W/m on the surface of the sample, during the test run.
  • the concentration of NOx in the gas passing through the reactor is measured in the dark during the first step of the test (CB) and irradiating the sample with UV light during the second step (CL).
  • IIR average irradiance measured and possibly corrected (W m " ).
  • SA area of the sample measured (64+6 cm ).
  • the photocatalytic block obtained in Example 1 was pre-conditioned at a temperature of 20°C and with a R.U. of 90% for 7 days up to a constant weight (+ 10%). After this period the sample was positioned in an environment at 20°C and a R.U. of 60% until the photocatalytic characterization.
  • Table 4 indicates the Ac values obtained.
  • Example 1 A few blocks prepared according to the formulation of Example 1 were re-tested following the procedure indicated in Example 4, after being subjected to aging for a further 60 days, leaving them to mature in the laboratory environment (20°C, R.U. 60%).

Abstract

L'invention concerne un procédé de préparation de dalles/feuilles/blocs photocatalytiques comprenant les étapes suivantes, consistant à : a) mélanger une composition sous forme de poudre solide avec une composition liquide, la composition sous forme de poudre solide comprenant : - au moins un liant choisi parmi le silicate de calcium broyé ou ses précurseurs et/ou les mélanges relatifs, présentant une grosseur de particule moyenne de 1 à 100 µm ; - au moins une charge ; - un photocatalyseur à base d'oxyde de titane (Ti02) présentant une grosseur de particule moyenne de 10 à 200 nm et une surface spécifique d'environ 10 à 300 m2/g ; et la composition liquide comprenant, au moins : - de l'eau, - un dispersant ; b) transvaser le mélange en suspension obtenu à l'étape a) dans un moule ; c) compacter le mélange en suspension dans le moule et d) durcir le mélange compacté en suspension obtenu à l'étape c), à une température de 20 à 150°C, pendant une durée de 1 à 80 heures, dans une atmosphère d'eau et de CO2 à une pression allant de la pression atmosphérique à une pression de 4 bars au-dessus de la pression atmosphérique et présentant une concentration en CO2 dans l'eau allant de 10 à 90 %. Une telle dalle/feuille/bloc en matériau de construction présente une résistance à la compression de 50 à 300 MPa et une résistance à la flexion de 5 à 40 MPa et une absorption d'eau inférieure à 10 %. Un tel produit peut être utilisé comme élément de pavage ou comme bloc de construction et présente des propriétés dépolluantes, en mesure de transformer les agents atmosphériques présents dans l'air (par exemple, des oxydes d'azote - NOx) en produits ne nuisant plus à la santé humaine (par exemple, des nitrates).
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WO2021092986A1 (fr) * 2019-11-15 2021-05-20 广东特耐石新材料科技有限公司 Plaque de pierre artificielle autonettoyante à usage extérieur et son procédé de préparation
WO2021076585A3 (fr) * 2019-10-16 2021-05-20 Saudi Arabian Oil Company Produits de ciment à durcissement
IT202100016091A1 (it) 2021-06-21 2022-12-21 Nanomnia Srl Metodo di microgranulazione di particelle di polvere di cariche minerali per uso edile

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WO2021092986A1 (fr) * 2019-11-15 2021-05-20 广东特耐石新材料科技有限公司 Plaque de pierre artificielle autonettoyante à usage extérieur et son procédé de préparation
WO2021092985A1 (fr) * 2019-11-15 2021-05-20 广东盖特奇新材料科技有限公司 Dalle de pierre artificielle autonettoyante pour usage extérieur et son procédé de fabrication
IT202100016091A1 (it) 2021-06-21 2022-12-21 Nanomnia Srl Metodo di microgranulazione di particelle di polvere di cariche minerali per uso edile
EP4108644A1 (fr) 2021-06-21 2022-12-28 Nanomnia Srl Procédé de microgranulation de particules de poudre de charges minérales pour la construction

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