WO2016087006A1 - Procédé de fabrication d'une masse à mémoire de forme - Google Patents

Procédé de fabrication d'une masse à mémoire de forme Download PDF

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Publication number
WO2016087006A1
WO2016087006A1 PCT/EP2014/076771 EP2014076771W WO2016087006A1 WO 2016087006 A1 WO2016087006 A1 WO 2016087006A1 EP 2014076771 W EP2014076771 W EP 2014076771W WO 2016087006 A1 WO2016087006 A1 WO 2016087006A1
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WO
WIPO (PCT)
Prior art keywords
steel slag
mixture
shape retaining
slag material
retaining mass
Prior art date
Application number
PCT/EP2014/076771
Other languages
English (en)
Inventor
Philippe Descamps
Frédérique BOUILLOT
Original Assignee
Recoval Belgium
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Recoval Belgium filed Critical Recoval Belgium
Priority to PCT/EP2014/076771 priority Critical patent/WO2016087006A1/fr
Priority to BE2015/5322A priority patent/BE1024612B1/fr
Priority to PCT/EP2015/078641 priority patent/WO2016087635A1/fr
Priority to EP15804790.2A priority patent/EP3227248A1/fr
Publication of WO2016087006A1 publication Critical patent/WO2016087006A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/02—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 hydraulic cements other than calcium sulfates
    • C04B28/08—Slag cements
    • C04B28/082—Steelmaking slags; Converter slags
    • 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
    • C04B28/24—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 alkyl, ammonium or metal silicates; containing silica sols
    • C04B28/26—Silicates of the alkali metals
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/10—Compositions or ingredients thereof characterised by the absence or the very low content of a specific material
    • C04B2111/1075—Chromium-free or very low chromium-content materials
    • 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
    • C04B2111/60—Flooring materials
    • 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
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Definitions

  • the present invention relates to an environmentally friendly method of producing a shape retaining mass having a compressive strength of at least 2 MPa, in particular a basement material, including the use of steel slag particulate material.
  • Said shape retaining mass has a considerably reduced leaching behaviour of the heavy metals which are contained in the steel slag particulate material.
  • Steel slag materials are by-products which are generated during the production of steel.
  • Stainless steel slags derived from the production of stainless steel are a particular group of slags.
  • Stainless steel slags comprise mainly calcium oxide (CaO) and silicon dioxide (Si0 2 ).
  • CaO calcium oxide
  • Si0 2 silicon dioxide
  • the stainless steel slags contain considerable amounts of heavy metals, such as notably chromium and often also of nickel and/or of molybdenum, which are problematic in view of their leaching behaviour. According to some legislations, the dumping of these stainless steel slags as waste need to be carried out under controlled conditions.
  • the leaching problems of stainless steel slags can be solved by crushing the steel slags, removing the valuable stainless steel particles therefrom and by applying the different fractions of the remaining crushed slags in bounded applications.
  • the coarser fractions of the crushed stainless steel slag can be used in concrete or asphalt.
  • these fines are in general separated off from the coarser sand fraction (having a particle size larger than 0.5 mm) of the stainless steel slags by a wet separation technique.
  • these fines are aggregated into larger grains so as to form a coarser granular material.
  • said coarser granular materials are carbonated under a relatively low pressure by means of carbon dioxide so as to produce a carbonated granular material.
  • the carbonation converts calcium and/or magnesium hydroxides into calcium and magnesium carbonate phases with binding properties that heal the microcracks in the fine steel slag particles, significantly reducing their water demand, and bind them together within each grain, providing thereby a harder, coarser material.
  • the carbonated granular materials of WO 2009/090219 have the advantage that they can be manufactured in advance and stored so that they can be mixed with cement and water in a conventional manner.
  • granulation and carbonation equipment is needed and the granulation and carbonation process is also time consuming and thereby relatively expensive.
  • the carbonation process cannot be carried out on-site, in order to produce basement layers, so that binder compositions are still required to produce the final product (concrete).
  • gaseous C0 2 is used for the carbonation process which cannot be introduced in larger volumes such as basement layers, or is at least difficult to be introduced, so that notwithstanding the fact that a shaping and carbonation step has already been carried out, a binder is still needed to produce the final product.
  • EP 2 160 367 describes the use of stainless steel slags, specifically, as fillers in construction materials in particular asphalt or hydraulic mortar or concrete compositions, which are containing hydraulic or bituminous binding agents.
  • the filler is produced by finely milling a coarser fraction of crushed steel slags which preferably has a relatively high content of steel (e.g. obtained by a magnetic separation process).
  • the finely milled fractions obtained having for example a particle size of less than 63 ⁇ , have a smaller gamma dicalcium silicate content than the above described fines since it is produced starting from a coarser fraction of the crushed steel slags so that they absorb much less water.
  • these fillers are only used in small amounts in concrete and asphalt.
  • Step 1 mixing of a binder composition [composition (B), herein after] comprising at least one carbonating agent which is selected from a group consisting of potassium carbonate, potassium bicarbonate and a magnesium carbonate hydroxide hydrate compound of general formula (I): xMgC0 3 .yMg(OH)2.zH 2 0 wherein x is a number in the range of 3.5 - 4.5, y is a number in the range of 0.5 - 1 .5, and z is a number in the range of 3.5 - 5.5, with at least a particulate steel slag material, thereby forming a mixture [mixture M, herein after] and wherein said particulate steel slag material is containing calcium silicate phases and at least chromium and is present in said mixture M in an amount of at least 50 % by dry weight (dry wt. %), relative to the total dry weight of the mixture M, and
  • Step 2 hardening of the mixture M, as obtained in Step 1 ., in the presence of water; thereby producing the shape retaining mass.
  • Another aspect of the present invention is directed to a shape retaining mass prepared according to the method of the invention.
  • Another aspect of the present invention is directed to the use at least one carbonating agent which is selected from a group consisting of potassium carbonate, potassium bicarbonate and a magnesium carbonate hydroxide hydrate compound of general formula (I): xMgC03.yMg(OH) 2 .zH 2 0 wherein x is a number in the range of 3.5 - 4.5, y is a number in the range of 0.5 - 1 .5, and z is a number in the range of 3.5 - 5.5 for carbonation of a particulate steel slag material.
  • xMgC03.yMg(OH) 2 .zH 2 0 wherein x is a number in the range of 3.5 - 4.5, y is a number in the range of 0.5 - 1 .5, and z is a number in the range of 3.5 - 5.5 for carbonation of a particulate steel slag material.
  • the dry weight percent of the particulate steel slag material present in the mixture M of Step 1 is generally equal to or of at least 20 wt. %, preferably equal to or of at least 40 wt. %, more preferably equal to or of at least 60 wt. %, even more preferably equal to or of at least 75 wt. %, and most preferably equal to or of at least 80 wt. %, relative to the total dry weight of the mixture M of Step 1 .
  • the dry weight percent of the particulate steel slag material present in the mixture M of Step 1 will generally be equal to or of at most 99 wt. %, more preferably equal to or of at most 95 wt. %, even more preferably equal to or of at most 90 wt. %, most preferably equal to or of at most 88 wt. %, relative to the total dry weight of the mixture M of Step 1 .
  • Step 1 of the method of the present invention use is made of particulate steel slag materials containing calcium silicate phases and at least chromium.
  • the particulate steel slag material containing calcium silicate phases and at least chromium suitable to be used in the method of the invention may include notably the fine fractions of relatively slowly cooled steel and stainless steel slags, in particular special stainless steel slags produced during the production of chromium steel or nickel-chromium steel such as notably described in EP 2 160 367, EP 2 238 087 and WO 2009/090219, the whole content of those are herein incorporated by reference.
  • the term "particulate steel slag material” is defined herein as any steel slag material which consists of loose particles. These particles may be of different sizes so that at least 50 vol.% of the particulate steel slag material has a particle size smaller than 1 .0 mm, preferably smaller than 0.8 mm more preferably smaller than 0.5 mm. On the other hand, at least 50 vol.% of the particulate steel slag material has preferably a particle size larger than 1 ⁇ , more preferably larger than 5 ⁇ and most preferably larger than 10 ⁇ .
  • Fig. 1 is a diagram representing the phase transitions during the cooling of dicalcium silicate
  • Fig. 2 is a flow chart representing a process for separating a fine stainless steel slag fraction from coarser fractions for use in the method of the present invention.
  • microcracks explain the disadvantageous water absorption properties that had been found hitherto in slag containing ⁇ -dicalcium silicate, as water is absorbed by capillarity into them.
  • the increase in volume in the transition from the ⁇ polymorphic state to the ⁇ polymorphic state not only causes microcracks but even grain fracture and separation.
  • the fine fraction of the slag will be disproportionately rich in comparatively soft ⁇ - dicalcium silicate. Due to the abovementioned microcracks and the associated capillarity, this fine fraction of the slag will have a water absorption capacity of over 20%. Moreover, it can retain this water for longer periods of time.
  • molten slag is extracted from the stainless steel furnace 1 and brought to cooling pits 3. After cooling, the solidified slag will be dug from these cooling pits 3 and fed through a hopper 4.
  • the hopper 4 comprises a grid for stopping all oversized slag pieces 6, in this particular case those bigger than 300 mm. As oversized pieces could damage the crushers used in the later process, these oversized pieces 6 are removed for later particular treatment, such as breaking with hammers and extraction of large metal fragments before being fed again through the hopper 4.
  • the slag particles smaller than 300 mm fall through the hopper 4 onto a first conveyor belt.
  • This first conveyor belt then transports them through a first metal handpicking cabin 8 to a first crusher 9 and a first sieve 10.
  • operators remove large metal pieces 1 1 from the slag particles on the conveyor belt.
  • the first sieve 10 After the slag particles are crushed in the first crusher 9, they go through the first sieve 10 which separates them into three fractions: particles bigger than 35 mm, particles between 14 and 35 mm and particles smaller than 14 mm.
  • the fraction of particles bigger than 35 mm is taken by a second conveyor belt through a second metal handpicking cabin 13 and a first metal separating magnetic belt 14, where more metal pieces 15 and 16 are removed.
  • the particles bigger than 35 mm are then put back into the first crusher 9.
  • the fraction of particles between 14 and 35 mm goes into a second crusher 17 and a second sieve 18, where after being crushed again it is separated into two fractions: a fraction of particles smaller than 14 mm and a fraction of particles bigger than 14 mm.
  • the fraction of particles bigger than 14 mm is taken by a third conveyor belt through a second metal separating magnetic belt 20, where more metal 21 is removed, and back into the second crusher 17.
  • a fine fraction 24 of particles smaller than 0.5 mm is particularly rich in ⁇ -dicalcium silicate, as discussed above.
  • said fine fraction 24 of particles smaller than 0.5 mm are especially used in the method according to the invention.
  • the larger particles can also be further finely milled so as to obtain a milled material having a particle size distribution which shows a D 0 value which is smaller than 100 ⁇ , preferably smaller than 70 ⁇ and more preferably smaller than 40 ⁇ . Milling said coarser fractions of the slag material to a smaller particle size enables to recover more valuable steel from the slag material, in particular stainless steel.
  • the steel slag material which is milled is a steel slag fraction which still contains a relatively high amount of stainless steel.
  • the particulate steel slag material as used in Step 1 . of the method according to the present invention may have a relatively high ⁇ - dicalcium silicate content, in particular at least 3 wt. %, preferably at least 5 wt. % and more preferably at least 7 wt. % of ⁇ -dicalcium silicate, and can thus be formed by the fines separated off from the crushed steel slag material.
  • the particulate steel slag material as used in Step 1 . of the method according to the present invention has generally a relatively high basicity.
  • the term "basicity” is intended to mean the ratio between the calcium content, expressed as wt.% CaO, as present in the particulate steel slag material and the silicon content, expressed as wt.% Si0 2 , as present in the particulate steel slag material.
  • the basicity is more particularly usually higher than 1 .2, in particular higher than 1 .4 and often higher than 1 .6.
  • dicalcium silicates are formed upon a slow cooling of the steel slag, which is also responsible for the (partial) disintegration of the steel slag, i.e. to a so- called dusting or falling of the steel slag.
  • the particulate steel slag material as used in Step 1 . of the method according to the present invention has generally a calcium content of at least 30%, in particular at least 40% by dry weight CaO and a silicon content of at least 15%, in particular at least 20% by dry weight SiO 2 (the calcium and silicon contents are based on the molecular weight of CaO and SiO 2 respectively but it is generally understood that the calcium and silicon do not have to be present in their oxide form but are in particular in other amorphous or crystalline phases, in particular in silicates.
  • the particulate steel slag material as used in Step 1 . of the method according to the present invention comprises preferably more than 50% by dry weight, more preferably more than 60% by dry weight and most preferably more than 70% by dry weight of crystalline phases, the remaining phases being amorphous.
  • the particulate steel slag material as used in Step 1 . of the method according to the present invention has generally a pH of at least 8.5, in particular at least 10, and even more particular at least 1 1 .
  • the pH has been measured after immersion of the shape retaining mass in demineralised water during 24 hours in a liquid/volume ratio of 10.
  • the particulate steel slag material of the method according to the present invention usually contains substantial amounts of heavy metals such as chromium, in particular chromium VI in the form of Cr0 "2 and Cr 2 0 7 "2 and often also molybdenum in anionic form such as Mn0 "2 , which constitute a significant environmental and public health problem.
  • Molybdenum (Mo) and chromium (Cr) present in the particulate steel slag material can be very mobile and can hence be subjected to prompt leaching from the slag.
  • the slag cannot be disposed of in ordinary landfills; it should be treated as special waste, which makes disposal more costly.
  • the method according to the invention is especially effective in the immobilization of Cr and Mo, as present in the particulate steel slag material, in the final shape retaining mass, in particular road construction materials.
  • said particulate steel slag material may comprise in particular at least 1000 ppm, more particularly at least 3000 ppm and even more particularly at least 5000 ppm of chromium.
  • said particulate steel slag material may comprise in particular at least 100 ppm, in particular at least 1000 ppm, and more particularly at least 2500 ppm of molybdenum.
  • the particulate steel slag material of the present invention may also comprise nickel (Ni).
  • Ni nickel
  • said particulate steel slag material can comprise at least 300 ppm nickel, in particular at least 400 ppm nickel and more particularly at least 500 ppm nickel.
  • the dry weight percent of the composition (B) present in the mixture M of Step 1 is generally of at least 1 wt. %, preferably at least 5 wt. %, preferably at least 8 wt. %, more preferably at least 10 wt. %, and even more preferably at least 12 wt. %, relative to the total dry weight of the mixture M of Step 1 .
  • the dry weight percent of the composition (B) present in the mixture M of Step 1 is generally at most 45 wt. %, more preferably at most 35 wt. %, more preferably at most 30 wt. %, even more preferably at most 25 wt. %relative to the total dry weight of the mixture M of Step 1 .
  • composition (B) may comprise one or more than one carbonating agent.
  • the composition (B) mixed with the particulate steel slag material in Step 1 consists essentially of the carbonating agent, as detailed above.
  • the expression "consists essentially of” is intended to denote that any additional ingredient different from the carbonating agent, as detailed above, is present in an amount of at most 1 % by weight, based on the total weight of the carbonating agent in the composition (B).
  • the composition (B) mixed with the particulate steel slag material in Step 1 . of the method of the present invention comprises a carbonating agent in an amount advantageously of above 1 wt. % more preferably above 5 wt. %, more preferably above 10 wt. %, more preferably above 15 wt. %; more preferably above 20 wt. %, more preferably above 25 wt. %, , based on the total weight of the composition (B). It is further understood that the weight percent of the carbonating agent in the composition (B) will generally be at most 99 wt. %, preferably at most 95 wt. %, preferably at most 90 wt. %, more preferably at most 80 wt. %, more preferably at most 75 wt. %, , based on the total weight of the composition (B).
  • the mixture M of Step 1 comprised the carbonating agent in an amount of at least 1 dry wt. %, preferably at least 2 dry wt. %, more preferably at least 3 dry wt. %, relative to the total dry weight of the mixture M of Step 1 .
  • the carbonating agent comprises a magnesium carbonate hydroxide hydrate compound of general formula (I): xMgC0 3 .yMg(OH)2.zH 2 0 wherein x is a number in the range of 3.5 - 4.5, preferably x is 4, y is a number in the range of 0.5 - 1 .5, preferably y is 1 and z is a number in the range of 3.5 - 5.5, preferably z is 4 or 5.
  • x is a number in the range of 3.5 - 4.5, preferably x is 4, y is a number in the range of 0.5 - 1 .5, preferably y is 1 and z is a number in the range of 3.5 - 5.5, preferably z is 4 or 5.
  • Preferred magnesium carbonate hydroxide hydrate compounds are chosen among hydromagnesite (i.e. 4MgC0 3 .Mg(OH)2.4H 2 0) and dypingite (i.e. 4MgC0 3 .Mg(OH)2.5H 2 0).
  • the magnesium carbonate hydroxide hydrate compounds of general formula (I) are known in the art. They can be manufactured according to known methods in the art. Generally they can be made by exposure of magnesium compounds, e.g. MgO or Mg(OH) 2 (or mixtures thereof) to C0 2 under a variety of conditions.
  • EP 2 508 496 describes the use of these hydrated magnesium carbonate compounds of formula (I) in binders which are based on the formation of magnesium silicate hydrates (MSH) and used to formulate a concrete, mortar or plaster and other construction chemical products. These binders can be used to replace the known binders Portland cement, high alumina cement and the like. According to the teachings of EP 2 508 496, the amount of extra calcium compounds, e.g. Ca(OH) 2 and/or CaO, has to be limited, because these calcium ions are forming calcite in the presence of hydromagnesite (i.e. 4MgC0 3 .Mg(OH)2.4H 2 0), which results in a decrease of its efficacy.
  • hydromagnesite i.e. 4MgC0 3 .Mg(OH)2.4H 2 0
  • the hydrated magnesium carbonate compounds of formula (I) can act as very efficient carbonating agents and reduce leaching of heavy metals, in particular chromium and molybdenum in the final shape retaining mass.
  • WO 2009/156740 also describes the use of these hydrated magnesium carbonate compounds of formula (I) in admixture with magnesia as a binder composition used to make construction products.
  • the carbonating agent comprises potassium carbonate and/or potassium bicarbonate.
  • the carbonating agent in Step 1 can further comprise a carbonation enhancing compound selected from the group consisting of magnesium oxide (MgO), calcium oxide (CaO), calcium magnesium oxide (i.e calcined dolomite), and mixtures thereof , preferably MgO.
  • the molar ratio of said carbonation enhancing compound to the carbonating agent is advantageously of at least 1 ,0, preferably at least 1 .5, more preferably at least 3.0. It is further understood that the molar ratio of said carbonation enhancing compound to the carbonating agent will generally be at most 10, preferably at most 8 and more preferably at most 6.
  • the composition (B) mixed with the particulate steel slag material in Step 1 . of the method of the present invention further comprises a gel forming binder composition in an amount advantageously above 1 wt. %, preferably above 10 wt. %, more preferably above 20 wt. %, more preferably above 30 wt. %, based on the total weight of the composition (B). It is further understood that the weight percent of said gel forming binder composition in the composition (B) will generally be of at most 99 wt. %, preferably of at most 95 wt. %, more preferably at most 80 wt. %, more preferably at most 70 wt. %, based on the total weight of the composition (B).
  • the gel forming binder composition comprises a glass compound and said glass compound is containing more than 50 % by dry weight of SiO 2 .
  • the gel forming binder composition consists of the glass compound.
  • Non limitative examples of suitable glass compounds may include, but not limited to, industrial silicated glass, such as hollow glasses (from bottles, cups, etc.) or flat glass, different from natural silicate glasses (such as pozzolana, tuff , pumice) or any other industrial silicate glasses (especially such as blast furnace slag, silica fume, fly ash from thermal power plants), as notably described in EP 1250397 B1 , its whole content is herein incorporated by reference,
  • the glass compound comprises however glass powder, in particular soda-lime glass powder.
  • the glass powder comprises preferably comminuted glass cullet particles.
  • Glass cullet is a waste product comprising industrial silicate glass and flat and hollow (container) glass that cannot be introduced in a furnace to be valorised.
  • the glass powder used in the method according to the present invention comprises preferably more than 60% more preferably more than 65% by dry weight of Si0 2 .
  • the glass compound is silica fume.
  • Silica fume is an amorphous polymorph of silicon dioxide. It is an ultrafine powder containing more than 85% by dry weight of Si0 2 . As it contains no or nearly no CaO, only silica-gel is formed in the absence of CaO.
  • the glass compound is fly ash, such as Class C and Class F fly ash.
  • silica-gel material which provides a high mechanical strength to a finished product. Due to the alkaline nature of the particulate steel slag material of the present invention, as detailed above, the production of said silica-gel material may also occur upon mixing with said particulate steel slag material thereby forming a finished product having a high mechanical strength. However, such a finished product suffers dramatically from leaching of heavy metals, in particular chromium and molybdenum.
  • the Inventors have now found that the combined use of the binding ability of a cheaper gel forming binder composition with the carbonating agent, in particular a magnesium carbonate hydroxide hydrate compound of general formula (I) provides a less costly method for producing a final shape retaining mass still having a suitable mechanical strength and having a strongly reduced leaching of the heavy metals, in particular chromium and molybdenum.
  • the gel forming binder composition is completed by adding to the glass compound at least one basic reagent suitable to activate the glass compound before being mixed with the particulate steel slag material in Step 1 . of the method of the present invention and/or after being mixed with the particulate steel slag material in Step 1 . of the method of the present invention.
  • This is especially advantageous when particulate steel slag material has a reduced pH, for example by having been weathered for some time, i.e. by natural carbonation.
  • the dry weight ratio of the glass compound to the basic reagent is greater than 3, preferably greater than 4, more preferably greater than 5.
  • Non limitative examples of suitable basic reagent may include, but not limited to, sodium and/or potassium hydroxide and/or calcium hydroxide, lime, cement, in particular blast furnace cement.
  • the composition (B) mixed with the particulate steel slag material in Step 1 consists essentially of the carbonating agent, as detailed above, and the gel forming binder composition, as detailed above.
  • the expression "consists essentially of” are intended to denote that any additional ingredient different from the carbonating agent, as detailed above, and the glass binder, as detailed above, is present in an amount of at most 1 % by weight, based on the total weight of the carbonating agent in the composition (B).
  • the presence of the gel forming binder composition enables to reach suitable mechanical strength and the carbonating agent enables to control the leachability, over time, of the heavy metals contained in the shape retaining mass.
  • the combination of the gel forming binder composition with the carbonating agent allows to reduce the amount of the carbonating agent in the mixture without affecting the final properties of the shape retaining mass in terms of compressive strength and leachability.
  • a reducing agent in particular a chromium reducing agent capable of transforming hexavalent chromium into a trivalent chromic form by donating one or more electrons, may be added.
  • the Applicant has found that the addition of reducing agents in Step 1 . of the method of the invention further improves the retention of chromium in the final shape retaining mass, i.e. the finished product.
  • Said reducing agent may be added to the composition (B), as detailed above, prior to mixing with the particulate steel slag materials or may be added to the particulate steel slag materials, as detailed above, prior to mixing with the composition (B) or may be added to the mixture M formed in Step 1 . prior to hardening of said mixture M.
  • Non limitative examples of suitable reducing agents may notably include ferrous sulphate (FeS0 4 ), in particular ferrous sulfate heptahydrate (FeS0 4 .7H 2 0), stannous chloride (SnCI 2 ), stannous sulphate (SnS0 4 ), stannous oxide (SnO), stannous hydroxide (Sn(OH) 2 ), stannous manganese sulphate , iron sulphide (FeS), and/or ferrous chloride (FeCI 2 ), in particular ferrous chloride tetrahydrate (FeCI 2 .4H 2 0) and combinations thereof.
  • Preferred reducing agents are FeS0 4 .7H 2 0, SnS0 4 , SnCI 2 , SnO, Sn(OH) 2 and combinations thereof.
  • the dry weight percent of the reducing agent in the mixture M is generally at least 0.01 wt. %, preferably at least 0.03 wt. %, more preferably at least 0.25 wt. %, even more preferably at least 0.50 wt. %, most preferably at least 1 .00 wt. %, based on the total dry weight of the particulate steel slag material.
  • the dry weight percent of the reducing agent in the mixture M will generally be at most 8.0 wt. %, more preferably at most 6.0 wt. %, most preferably at most 5.0 wt. %, based on the total dry weight of the particulate steel slag material.
  • Step 1 of the method according to the present invention, other ingredients, may be added to improve further the final properties of the shape retaining mass according to its desired end use.
  • Said other ingredients may be added to the composition (B), as detailed above, prior to mixing with the particulate steel slag material or may be added to the particulate steel slag material, as detailed above, prior to mixing with the composition (B) or may be added to the mixture M formed in Step 1 . prior to hardening of said mixture M in Step 2.
  • Suitable other ingredients may notably include, but not limited to (i) fine and/or coarse aggregates having a particle size larger than the particle size of the particulate steel slag material such as notably sand, natural gravel, crushed stone and the like; (ii) inert filler.
  • the dry weight percent of the other ingredients in the mixture M is generally equal to or at least 0.01 wt. %, preferably equal to or at least 0.03 wt. %, more preferably equal to or at least 0.25 wt. %, even more preferably equal to or at least 0.50 wt. %, most preferably equal to or at least 1 .00 wt. %, based on the total dry weight of the mixture M.
  • the dry weight percent of the other ingredients in the mixture M will generally be equal to or at most 79 wt. %, preferably equal to or at most 50 wt. %, more preferably equal to or at most 30.0 wt. %, most preferably equal to or at most 10 wt. %, based on the total dry weight of the mixture M.
  • Step 1 of the method according to the present invention, the particulate steel slag material, as detailed above, the carbonating agent, as detailed above, optionally the gel forming binder composition, as detailed above, optionally the reducing agent, as detailed above, and optionally the other ingredients are mixed as to obtain an homogeneous mixture M according to known practice in the art.
  • Step 2 it is preferred to compact the mixture (M) by means of a compactor, in particular by means of a roller-compactor (i.e. a so-called road roller).
  • a roller-compactor i.e. a so-called road roller.
  • the mixture (M) is first spread in a layer and this layer is then compacted before it has hardened.
  • Step 2 of the method of the present invention the hardening of the mixture M, as obtained in Step 1 ., occurs in the presence of water and the amount of water relative to total dry weight of the mixture M is advantageously equal to or at least 5 wt. %, preferably equal to or at least 10 wt. %, more preferably equal to or at least 15 wt. %.
  • additional water may be added to the particulate steel slag materials, as detailed above, or may be added to the composition (B), as detailed above, prior to mixing with the particulate steel slag materials or may be added to the mixture M.
  • the particulate steel slag material as used in the method according the invention is having a too high water content then the particulate steel slag material can be dried according to methods known in the art.
  • Another aspect of the present invention is directed to a shape retaining mass prepared according to the method of the invention, as described in detail above.
  • the shape retaining mass according to the invention advantageously has a compressive strength higher than 2 MPa, with a compressive strength of higher than 3 MPa being preferred and a compressive strength of higher than 4 MPa being particularly preferred wherein a compressive strength is measured in accordance with the ASTM standard test method D 698-12. More advantageously, it has a compressive strength falling in the range between 2 MPa and 50 MPa.
  • the shape retaining mass according to the invention advantageously has a Cr and/or Ni leaching of less than 0.5 mg/L, preferably less than 0.30 mg/L, more preferably less than 0.20 mg/L, even more preferably less than 0.10 mg/L, the leaching test of the shape retaining mass being measured according to DIN 38414-S4/EN 12457-4.
  • the shape retaining mass according to the invention advantageously has a Mo leaching of less than 1 .0 mg/L, preferably less than 0.50 mg/L, more preferably less than 0.20 mg/L, even more preferably less than 0.10 mg/L, the leaching test of the shape retaining mass being measured according to DIN 38414-S4/EN 12457-4.
  • a preferred use of a shape retaining mass of the invention is as a construction material, in particular a road construction material such as basement or subbasement depending on the compressive strength obtained.
  • the shape retaining mass of the invention comprises calcite (CaC0 3 ).
  • calcite might be the result of the reaction of the amorphous phases of particulate steel slag material with the carbonating agent of the present invention.
  • multiple crystalline phases are also produced, including in particular the neo-formed phases magnesiochromite and magnesium chromium carbonate hydrates.
  • the presence of these crystalline phases might enable to fix some heavy metals, particularly chromium, more preferably chromium and/or nickel, in the structure thereof. In that way, the leachability of the shape retaining mass can be sufficiently controlled over time since heavy metals are fixed in the crystalline structures.
  • a shape retaining mass was produced by mixing the particulate steel slag material (i.e. stainless steel slag fines (0 - 0.5 mm)) with a carbonating agent, optionally a reducing agent, optionally a gel forming binder composition, optionally other ingredients and water.
  • a carbonating agent i.e. stainless steel slag fines (0 - 0.5 mm)
  • a reducing agent optionally a gel forming binder composition
  • other ingredients and water optionally other ingredients and water.
  • Tables 1 to 3 Specimens were made from this mixture by compacting it in a mould having an internal diameter of 54.8 mm and a height of 50 mm. with a pressure of 10 MPa.
  • the Proctor values of the different mixtures were determined, i.e. the water content at which in a Proctor test the highest dry density is obtained. Moisture contents which were close to this Proctor value were used in all the experimental test, as summarized in Tables 1 - 3.
  • Akermanite-Gehlenite Ca 2 (AI 25 Mg. 7 5)((AI 25 Si. 7 5)0 7 ) 5 /

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Processing Of Solid Wastes (AREA)

Abstract

L'invention porte sur un procédé de production d'une masse à mémoire de forme dotée d'une résistance à la compression d'au moins 2 MPa telle que mesurée conformément à la méthode d'essai normalisée ASTM D 698-12, le procédé comprenant l'étape 1 : mélange d'une composition de liant [la composition (B) ci-après] comprenant au moins un agent de carbonatation choisi dans le groupe constitué de carbonate de potassium, bicarbonate de potassium et composés hydratés d'hydroxyde de carbonate de magnésium de formule générale (I) xMgCO3.yMg(OH)2.zH2O, dans laquelle x est un nombre dans la plage de 3,5 à 4,5, y est un nombre dans la plage de 0,5 à 1,5 et z est un nombre dans la plage de 3,5 à 5,5, avec au moins une matière de scorie d'acier particulaire, de façon à obtenir un mélange [le mélange M ci-après], ladite matière de scorie d'acier particulaire contenant des phases de silicate de calcium et au moins du chrome et étant présente dans ledit mélange M dans une quantité d'au moins 50 % en poids sec par rapport au poids sec total du mélange M; et l'étape 2 : durcissement du mélange M tel qu'obtenu à l'étape 1, en présence d'eau, ce qui permet de produire la masse à mémoire de forme.
PCT/EP2014/076771 2014-12-05 2014-12-05 Procédé de fabrication d'une masse à mémoire de forme WO2016087006A1 (fr)

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PCT/EP2014/076771 WO2016087006A1 (fr) 2014-12-05 2014-12-05 Procédé de fabrication d'une masse à mémoire de forme
BE2015/5322A BE1024612B1 (fr) 2014-12-05 2015-05-22 Procédé de production d'une masse conservant une forme
PCT/EP2015/078641 WO2016087635A1 (fr) 2014-12-05 2015-12-04 Procédé de fabrication d'une masse à mémoire de forme
EP15804790.2A EP3227248A1 (fr) 2014-12-05 2015-12-04 Procédé de fabrication d'une masse à mémoire de forme

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CN111847943A (zh) * 2020-07-17 2020-10-30 攀钢集团研究院有限公司 一种矿渣微粉及其制备方法

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CN111847943A (zh) * 2020-07-17 2020-10-30 攀钢集团研究院有限公司 一种矿渣微粉及其制备方法

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