Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
  • C04B14/02—Granular materials, e.g. microballoons
  • C04B14/04—Silica-rich materials; Silicates
  • C04B14/06—Quartz; Sand
• • 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
  • C04B20/02—Treatment
  • C04B20/023—Chemical treatment

Definitions

• the subject of the present invention is the upgrading of concrete at the end of its life, and more particularly the use of a fraction obtained from a carbonated used concrete as a substitute sand for the preparation of concrete or mortar.
• Building materials are materials used in the construction and public works sectors. They cover a wide range of materials, which mainly includes wood, glass, steel, aluminium, textiles, plastics (particularly insulation) and materials resulting from the transformation of quarry products, which can be more or less elaborate, in particular concrete, mortars and various derivatives of clay such as bricks, tiles, tiling and various sanitary elements.
• cements essentially consists of calcining a mixture of carefully chosen and dosed raw materials, also referred to by the term “raw”. Firing this cru gives an intermediate product, clinker, which, ground with any mineral additions, will give cement.
• the type of cement manufactured depends on the nature and proportions of the raw materials as well as the firing process.
• Portland cements which represent the vast majority of cements produced in the world
• aluminous cements or calcium aluminate
• natural quick cements sulpho-aluminous cements
• cements sulfo-belitic and other intermediate varieties.
• the most common cements are Portland type cements.
• Portland cements are obtained from Portland clinker, obtained after clinkering at a temperature of around 1450°C of a raw material rich in calcium carbonate in a kiln.
• the production of one tonne of Portland cement is accompanied by the emission of very large quantities of CO2 (approximately 0.8 to 0.9 tonnes of CO2 per tonne of cement in the case of a CEM I).
• Decarbonation is a chemical reaction that takes place when limestone, the main raw material for the manufacture of Portland cement, is heated at high temperature. The limestone is then transformed into quicklime and CO2 according to the following chemical reaction:
• the described process involves using recycled concrete fines comprising supplying recycled concrete fines with dgo 1000 ⁇ m to stockpiles or a silo as a feedstock, rinsing the feedstock to provide carbonaceous material, removing of the carbonaceous material and the cleaned exhaust, and the deagglomeration of the carbonaceous material to form the additional cementitious material, as well as the use of stockpiles or a silo containing a feedstock of recycled concrete fines with dgo 1000 pm for the cleaning of CO2-containing exhaust gases and the simultaneous production of additional cementitious material.
• this process requires the carbonated product to be dried before it can be used.
• the subject of the present invention is the use of a fraction whose particle size d is greater than or equal to 150 ⁇ m, said fraction having a loss on ignition varying from 3% to 30% and comprising:
• the fractions defined previously, by carbonation of a fraction obtained from a construction material, in particular a concrete, at the end of its life, in which the finest particles have been removed can be used as sands for the preparation of mortars or concretes, which makes it possible to recycle used concrete and to preserve natural resources while maintaining resistance mechanical properties comparable to those of concrete or mortars prepared from conventional sands.
• the fraction obtained from used construction materials must first be carbonated, this makes it possible to significantly reduce the general carbon footprint associated with the production of new construction materials such as concrete or mortar.
• sand means any sand that can be used by a person skilled in the art for the preparation of construction material
• loss on ignition means the cumulative content of bound water, organic matter, CO2 of carbonates (calcareous loads and carbonated part of the material) and any oxidizable elements.
• the loss on ignition is determined by calcination in air at a temperature of (950 +/- 25°C) according to the method described in standard NF EN 196-2 (classification index P 15-472) - Methods of cement testing - Part 2: Chemical analysis of cements; And
• construction material means concrete or mortar.
• dw corresponds to the diameter below which there is 10% of the total mass of the particles of the sample considered. This can be determined by any method known to those skilled in the art, in particular by dry or wet laser granulometry.
• “dgo” corresponds to the diameter below which 90% of the total mass of the particles of the sample considered is found. This can be determined by any method known to those skilled in the art, in particular by dry or wet laser granulometry.
• the diameter of the particles can be determined by any method known to those skilled in the art, in particular by scanning electron microscopy, morphogranulometry or by laser granulometry.
• the proportions expressed in % correspond to mass percentages relative to the total weight of the entity (eg clinker or cement) considered.
• a subject of the present invention is therefore the use of a fraction having the characteristics, in particular grain size and mineralogical characteristics, described previously as sand for the production of concrete or mortar.
• the subject of the present invention is the use of a fraction as defined above as sand for the production of concrete or mortar, said fraction having the following characteristics, chosen alone or in combination: the particle size dw of the fraction is greater than or equal to 180 pm. More preferably, the particle size dw of the fraction is greater than or equal to 200 ⁇ m.
• the particle size dw of the fraction is greater than or equal to 250 ⁇ m; the dgo particle size of the fraction is less than or equal to 4000 pm. More preferably, the dgo particle size of the fraction is less than or equal to 3000 ⁇ m. Quite preferably, the dgo particle size of the fraction is less than 2000 ⁇ m; the fraction has a loss on ignition varying from 4% to 25%, more preferably from 6% to 20%; the fraction contains 30% to 70% SiC>2. More preferably, the fraction contains from 40% to 60% SiO 2 ; the fraction contains 10% to 30% CaO. More preferably, the fraction contains from 10% to 20% CaO; the fraction contains 2% to 10% Al 2 O 3 .
• the fraction contains from 4% to 8% of Al 2 O 3 ; the fraction contains 1% to 3% Fe 2 O 3 . More preferably, the fraction contains from 1% to 2.5% of Fe 2 O 3 ; the fraction additionally contains from 0.1% to 3%, preferably from 0.5% to 2% of MgO; the fraction also contains from 0.05% to 2%, preferably from 0.1% to 1% of TiO 2 ; the fraction also contains from 0.1% to 3%, preferably from 0.5% to 2.5% of K 2 O; the fraction also contains from 0.05% to 2%, preferably from 0.1% to 1%, of Na 2 O; the fraction also contains from 0.01% to 1%, preferably from 0.05% to 0.5% of P 2 Os; the fraction also contains from 0.005% to 0.2%, preferably from 0.01% to 0.1% of Mn 2 O 3 ; and/or the fraction additionally contains from 0.05% to 3%, preferably from 0.1% to 1.5%, of SO 3 .
• the fraction described above is therefore obtained by carbonation of a fraction obtained from a construction material, in particular a concrete, at the end of its life.
• the present The subject of the invention is also a method for preparing a fraction as described previously, said method comprising the following steps: iron removal and crushing of the construction material; screening of the crushed product in order to obtain a fraction with the desired dgo; drying of the fraction thus obtained; separation using a dynamic separator to obtain the fraction with the desired d; and carbonating the fraction obtained by with a gas containing CO2, such as a cement gas.
• the removal of iron and the crushing of the construction material can be carried out according to any method known to those skilled in the art, in particular by shearing the scrap metal from the concrete then by magnetic removal by "omeric” and finally crushing of the construction material by a crusher with percussion, for example, which favors the reduction of the size of the aggregates.
• Sifting is a mechanical operation carried out using devices commonly called sieves which makes it possible to select the grains.
• the sieve only lets through its mesh elements smaller than a certain size. They are equipped with perforated grids with openings of a size determined according to the size of the grains sought. There are inclined vibrating screens and horizontal vibrating screens.
• the screening can be carried out according to any method known to those skilled in the art.
• the fraction obtained after screening is a 0/4 mm fraction, preferably 0/2 mm.
• the fines fractions are obtained by using a dynamic separator which separates the particles it receives according to their size, shape and density.
• the product feeding the separator falls on the rotating distribution hub.
• the centrifugal force throws the particles: the coarser ones are thrown towards the periphery, their speed decreases and, under the action of gravity, fall into the refusal cone from where they are evacuated to then be carbonated.
• the finer particles are drawn by the rising air towards the separation zone where variable pitch selection vanes impart an additional centrifugal force to them which removes the remaining coarse particles.
• the speed of rotation, the ventilation and the angle of the blades of the turbine makes it possible to adjust the desired particle size. If the ventilation of the separator is provided by hot air, it also has the ability to dry the materials.
• the fraction described above can therefore be used as sand for preparing a concrete or a mortar without this affecting the properties, in particular mechanical properties, of said concrete or mortar.
• the rate of substitution of the natural sand used to prepare the concrete or the mortar by the fraction described above can be up to 70%, more preferably up to 50%, very preferably up to 30% .
• a sieve with a square mesh of variable size was used to proceed with the elimination of the finest particles except for the F-0 fraction which corresponds to raw "concrete sand", i.e. without removal of finest particles.
• fractions retained by the sieve i.e. refusal
• a bottled gas mixture containing 25% CO2 for 6 hours with stirring in a heated mixer (temperature set at 55°C).
• Table 1 Mineralogical composition and particle size of fractions F-0 to F-3.
• Example 2 Concretes/mortars
• concrete 3 is prepared with the same elements as concrete 1 but substituting
• the compressive strength of concretes 1 to 3 was measured according to standard NF EN 12390-3 on test specimens measuring 11x22cm after 7 and 28 days of wet curing (20°C).
• concretes 3 and 4 have a carbon balance reduced by 8.5% and 10.8% respectively.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Civil Engineering (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)
• Silicates, Zeolites, And Molecular Sieves (AREA)
• Glass Compositions (AREA)

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• 2021
  • 2021-08-02 FR FR2108400A patent/FR3125814A1/fr active Pending
• 2022
  • 2022-08-01 US US18/293,511 patent/US20250122121A1/en active Pending
  • 2022-08-01 WO PCT/FR2022/051533 patent/WO2023012423A1/fr not_active Ceased
  • 2022-08-01 EP EP22758564.3A patent/EP4380905A1/de active Pending

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