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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B1/00—Producing shaped prefabricated articles from the material
  • B28B1/54—Producing shaped prefabricated articles from the material specially adapted for producing articles from molten material, e.g. slag refractory ceramic materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B11/00—Apparatus or processes for treating or working the shaped or preshaped articles
  • B28B11/24—Apparatus or processes for treating or working the shaped or preshaped articles for curing, setting or hardening
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B11/00—Apparatus or processes for treating or working the shaped or preshaped articles
  • B28B11/24—Apparatus or processes for treating or working the shaped or preshaped articles for curing, setting or hardening
  • B28B11/245—Curing concrete articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28C—PREPARING CLAY; PRODUCING MIXTURES CONTAINING CLAY OR CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28C5/00—Apparatus or methods for producing mixtures of cement with other substances, e.g. slurries, mortars, porous or fibrous compositions
• • 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
  • C04B28/04—Portland cements
• • 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
• • 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
  • C04B40/0259—Hardening promoted by a rise in pressure
• • E—FIXED CONSTRUCTIONS
  • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
  • E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
  • E01C5/00—Pavings made of prefabricated single units
  • E01C5/06—Pavings made of prefabricated single units made of units with cement or like binders
• • E—FIXED CONSTRUCTIONS
  • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
  • E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
  • E01C5/00—Pavings made of prefabricated single units
  • E01C5/06—Pavings made of prefabricated single units made of units with cement or like binders
  • E01C5/065—Pavings made of prefabricated single units made of units with cement or like binders characterised by their structure or component materials, e.g. concrete layers of different structure, special additives
• • E—FIXED CONSTRUCTIONS
  • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
  • E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
  • E01C5/00—Pavings made of prefabricated single units
  • E01C5/20—Pavings made of prefabricated single units made of units of plastics, e.g. concrete with plastics, linoleum
• • 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
  • C04B2111/00017—Aspects relating to the protection of the environment
• • 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
  • C04B2111/20—Resistance against chemical, physical or biological attack
  • C04B2111/21—Efflorescence resistance
• • 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
  • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
  • C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
• • 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 subject-matter relates to landscaping products comprising steel slag, compositions and processes for preparing same.
• Steel slag has shown the potential to replace cement as an alternative binder if carbonation activation is performed.
• Steel slag is well known by its reaction with carbon dioxide.
• Replacing cement with the activated steel slag in the production of landscaping products will reduce the energy consumption, the natural resource consumption, and the total carbon emission.
• the reduction of carbon dioxide emission comes from two factors; a) the elimination of Portland cement usage in the product, b) the permanent storage of carbon dioxide in the landscaping product due to the carbonation activation process.
• Landscaping products include various types of products, such as cast stone, pavers, slabs, retaining block walls, caps, curbs, edges, steps and facade.
• a paver is a paving stone, tile, brick or brick-like piece of concrete commonly used as exterior flooring.
• Concrete pavers are commercially made by pouring a mixture of aggregate, Portland cement, admixtures and pigments (if required) into a mold with various shapes and allowing to set. Although each of those ingredients demonstrates its own unique microstructure property, all of them are similarly constructed of aggregate-skeleton, binding medium, and air voids.
• Interlocking concrete pavers and stone pavers are different types of paver. When putting the interlocking pavers together, no cementitious paste, chemical admixture or retaining method is usually used; instead the weight of the paver itself is used to assemble them together. Pavers can be used to cover roads, driveways, patios, walkways, and any outdoor platform.
• Retaining walls are precast concrete products that rely primarily on their mass for stability.
• the retaining walls can be easily stacked on top of each another.
• Retaining walls can be used in residential and commercial applications.
• the retaining walls are produced in different size, feature, texture and style.
• Cast stone is considered as one of the concrete masonry products that best imitates natural -cut stone and is mostly used in architectural applications.
• the application of cast stone products varies from architectural to structures and garden ornaments.
• Precast concrete curbs are installed along a street or roadway, forming an edge for a sidewalk. Precast concrete curbs are available in convenient lengths and are generally quick and easy to install.
• Precast concrete facade panels are used to provide a better finishing to exterior and interior walls. These panels are used to clad all or part of building facades or free-standing walls used for landscaping, soundproofing, and security walls.
• An aspect of the disclosure relates to a process for preparing landscaping products comprising: i) mixing a dry part ; and a liquid part; wherein said dry part is comprising an aggregate and a binder, wherein said binder is consisting of steel slag and optionally cement; and wherein said liquid part is comprising water and a chemical admixture;
• step ii) molding and compacting the mixture of step i) to a shaped product having an initial water to slag ratio
• step iii) optionally reducing the initial water to slag ratio of said shaped product of step ii) to provide a shaped product having a pre-carbonation water to slag ratio;
• step iv) curing the shaped product of step ii) or iii) with carbon dioxide to provide said landscaping products.
• a further aspect of the disclosure relates to a landscaping product comprising:
• a binder consisting of steel slag and optionally cement.
• a further aspect of the disclosure relates to a landscaping product prepared by the process described herein
• FIG. 1 is a schematic representation of an exemplary carbonation set-up
• FIG. 2 is an XRD of hybrid EAF and BOF (EBH) slag as received and after carbonation;
• FIG. 3 is TG and DTG for carbonated and as-received EAF and EAF -BOF hybrid slag compacts
• Landscaping products include: cast stone, pavers, slabs, retaining blocks walls, edges, curbs, caps, steps and facade.
• Various standards may apply with regard to expected performance of the products. The following standards are useful references to better understand the typical technical performances required for representative products.
• reference to a landscaping products comprising a binder consisting of steel slag (and optionally cement) is understood to mean that the binder in the final landscaping product is a carbon dioxide-cured binder, or in other words a carbon dioxide-cured landscaping products. Therefore, the expressions landscaping products/ dioxide-cured landscaping products as well as binder/ carbon dioxide-cured binder can be used interchangeably or substituted anywhere in the specification if required to improve clarity.
• Retaining wall ASTM C 1372: Standard Specification for Dry-Cast Segmental Retaining Wall Units
• Paving stones ASTM C936: Standard Specification for Solid Concrete Interlocking Paving Units
• Canadian Standard Association - CSA A231.2 Precast concrete paving slabs/precast concrete pavers. This Standard specifies requirements for concrete paving slabs manufactured from hydraulic cement concrete to be used in the construction of pavement and roof coverings. This Standard includes units with architectural finishes or tactile surfaces.
• Curb BNQ 2624-210: Prefabricated Concrete Curbs - Dimensional. Geometric and Physical Characteristics
• steel slag is used herein as the sole component of a binder or the main component of a binder together with a proportion of cement, if needed, to allow for the production of landscaping products wherein carbon dioxide is used as the curing agent. In other words, all or a majority of the cement is replaced by steel slag. Carbon dioxide is also applied to promote strength and activate the slag.
• the binder is consisting of steel slag.
• the binder is consisting essentially of steel slag.
• the binder is consisting of steel slag and cement, wherein the slag to cement ratio is up to 20, alternatively the ratio is up to 15 or up to 10.
• the slag to cement ratio is about 7 to about 9.
• the landscaping products of the present disclosure preferably have a water absorption of less than about 5% and a compressive strength of about 55 MPa, or preferably 60 MPa, or higher.
• the landscaping product is a paver and preferably has a water absorption of less than about 5% and a compressive strength of about 55 MPa, or preferably 60 MPa, or higher.
• the landscaping products preferably have a compressive strength of about 55 MPa, or preferably 60 MPa, or higher.
• the landscaping products have a water absorption of less than about 6% and a compressive strength of about 45 MPa.
• the landscaping product is an architectural cast stone or a paver and has a water absorption of less than about 6% and a compressive strength of about 45 MPa.
• the landscaping products have a water absorption of less than about 8.5% and a compressive strength of about 20 MPa.
• the landscaping product is a retaining wall and has a water absorption of less than about 8.5% and a compressive strength of about 20 MPa.
• EAF, BOF and some ladle steel slags can be used to produce paving stones as defined herein.
• Step slag herein refers to the slag by-product produced from steel-making manufacturers.
• Steel slag may include slag produced from Basic Oxygen Furnaces (BOF).
• Steel slag may also include slag produced from Electric Arc Furnaces (EAF).
• EAF Electric Arc Furnaces
• EBH slag are also contemplated as useful herein and refers to EAF-BOF Hybrid, which is a type of steel slag formed of a mixture of EAF and BOF produced slags.
• Steel slag as used herein may further include ladle slag.
• Ladle slag herein refers to a type of steel slag.
• Ladle slag is produced as a by-product from a ladle refining operation.
• molten steel produced in an EAF or BOF process undergoes an additional refining process based on the quality of the desired steel.
• Additional fluxes and alloys are added to a ladle to remove the impurities within the steel and to produce steel with the desired properties. This operation is known as ladle refining, because it is executed in the transfer ladle.
• additional steel slags are generated, which are ladle slags.
• steel slag as used herein excludes iron slag and blast furnace slag that are typically generated during iron production.
• the morphology of steel slag as used herein plays a role in reactivity with carbon dioxide.
• Steel slag can be reactive with carbon dioxide as it is crystalline.
• Steel slag containing high calcium silicates and low iron compounds would be ideal candidates to receive carbonation activation to make slag-based landscaping products.
• iron slag cannot be used as the binder (in the production of landscaping products with the CO 2 curing process) herein as it is quenched by water spray to make an amorphous material. This amorphous material (iron slag) is not reactive with CO 2 .
• the strength gain in steel slag is dependent on the content of calcium silicates in slag. Carbonation activation of calcium silicates of any polymorph could produce calcium-silicate hydrates intermingled with calcium carbonate crystals, thereby contributing to slag-bond strength.
• the steel slag used for making landscaping products has a free lime content less than about 10%, preferably less than about 7.2%, or more preferably less than about 4% by chemical composition.
• the steel slag used for making landscaping product has a cumulative calcium silicate content (ex: C 2 S +C3S phase concentration) of at least about 15%, or more preferably more than about 40%.
• the steel slag used for making the building product has a S1O 2 content of at least about 6%, or more preferably at least about 15%.
• Coarser steel slag cannot be completely activated by carbon dioxide.
• the value of fineness for steel slag should be more than about 150 m 2 /kg on a Blaine fineness assay or more preferably more than about 300 m 2 /kg.
• the finer slag results in a landscaping product having appropriate mechanical properties whereas the coarse steel slag can result in a landscaping product that does not satisfy the necessary requirements.
• Size distribution of the slag can be characterized as D50 of 200 microns and less, preferably 100 microns or less, or more preferably 20 microns or less.
• the following table exhibits that the finer steel slag results in a higher carbon uptake and compressive strength for some samples of slags:
• the % basis is the weight of CO 2 with respect to the weight of slag (e.g. uptake of 11.5% means that 1 kg of slag can sequestrate 115 grams of carbon dioxide).
• a slag suitable for use in the present disclosure preferably displays a CO 2 uptake of at least about 4%, preferably about 10% CO 2 , and/or compressive strength of at least about 55 MPa preferably about 60 MPa for slag paste when measured on a slab specimen as described herein.
• a specimen of 80x80x60 mm is compacted/ formed at a pressure of 12.5 MPa with a water-to-slag ratio of about 0.08 to about 0.15.
• the formed specimens are then dried with/without a fan at ambient conditions for 2 to 7 hours.
• the water content of the sample reduces by about 40%.
• the semi-dried specimen is then subjected to carbonation activation.
• the carbonation process is conducted using a CO 2 gas with a purity of 99.5%.
• the gas is first warmed up by a heater attached to the CO 2 cylinder in order to prevent blocking the gas such that it does not get into the chamber.
• the mass gain method estimates the mass difference before and after carbonation.
• the mass difference together with water evaporated from the exothermic carbonation reaction, represents the mass gain due to carbon dioxide uptake.
• the carbonation reaction is exothermic in nature, and as a result some of the mixing water in the samples evaporates and condenses on the inner walls of the chamber. This water can be collected using absorbent paper and should be added to the mass of the carbonated sample since the water present in the chamber is part of the water in the original slag mass.
• cements can be used to produce slag- based pavers: Portland cement (Type I - Type V); Portland-Limestone Cement; Rapid hardening cement; Quick setting cement; Low heat cement; Blast-furnace slag cement; Portland-Slag Cement; High alumina cement; White cement; Colored cement; Pozzolanic cement (Portland- Pozzonlan Cement); Air entraining cement; Hydrographic cement; and Ternary Blended Cement as used herein, the cements that are useful are those that contain calcium silicate phases, specifically C3S, that enable them to gain strength when reacted with water. The presence of calcium silicate phases secures the short term and long term strength development.
• Water reducer is added to the concrete mixture in order to increase the compressive strength, reduce water content, decrease the porosity, and reduce the water permeability.
• the water reducing admixture is classified as plastizer or superplastizer (that is a polycarboxylate- based water reducer). Any admixture that is capable of reducing the required water content by up to about 50% or increasing the compressive strength by up to about 60% can be used as water reducer in the current innovation.
• the admixtures used in this innovation should meet the requirements of ASTM C494 (Standard Specification for Chemical Admixtures for Concrete).
• Water repellent admixtures are designed to provide integral water repellency to concrete by affecting the capillary action of water into or out of the concrete. Water repellent admixtures can perform as static pore pluggers, creating a more difficult pathway for water migration, or can perform as reactive chemicals, forming situ" hydrophobic materials that not only plug pores, but also chemically repel water from cement surfaces.
• the typical range of water reducer admixture used in concrete varies from 0.2% to 3.5% of cementitious materials weight.
• water reducer (Viscocrete) was used at 2.2% of steel slag weight.
• Water repellent admixture is typically used as 0.1-3.0% of the cementitious materials weight.
• water repellent in the current invention (W-10, AE-3) was added to the materials at 2.2% of steel slag weight in the current invention. Aggregates
• the landscaping products are composed of aggregates embedded in a hard matrix of material.
• Aggregates can be either natural or artificial.
• Examples of aggregates include normal weight aggregate, natural lightweight aggregate, expanded clay aggregate, expanded shale aggregate, expanded slag aggregate, expanded steel slag aggregate, expanded iron slag aggregate, gravel aggregates, limestone aggregate and secondary aggregate.
• the aggregate is granite or limestone aggregate.
• the ratio of the mass of aggregate (A) to the total mass of the aggregate + cement + slag (A + C + S) ranges from 0.2 to 0.8, preferably from 0.45 to 0.6 or from 0.47 to 0.58.
• the dry part comprising the aggregate and binder (consisting of steel slag and cement) be mixed separately from the liquid part comprising water and a chemical admixture.
• the dry materials can be mixed until uniformity is achieved.
• the chemical admixture including water reducer or water repellant, is added to water. Liquid and dry materials are mixed also until a suitable dispersion is achieved.
• the mixture may have an initial water to slag ratio as high as about 0.20.
• the fresh mixture is then poured in the molds shaped in various forms and sizes.
• the precast making machine presses the fresh materials by compacting them at high pressure.
• the step of compacting can be effected by any conventional means such as compaction/ vibration or static compression, allowing to achieve the required density.
• the compaction/vibration can be as high as 12 MPa.
• the shaped product after molding and compaction preferably has a density of about 2000 to about 2800 kg/m 3 .
• the mix proportion with an initially high water content is desired in order to obtain a smooth surface.
• extra water in the fresh product prevents carbon dioxide to penetrate.
• a lower pre-carbonation water to slag ratio (such as about 0.08-0.13) can be obtained from the molded mixture having a higher water to slag ratio.
• directly curing the mixture prepared with an initial low water to slag ratio allows one to obtain a product with a rough surface.
• the suitable pre-carbonation water to slag ratio the mixture with a higher water to slag ratio is initially formed (e.g. up to about 0.20).
• the two expressions can be used interchangeably.
• the compacted and molded shaped product may, for example, be exposed to air for up to 7 hours.
• An industrial fan may also accelerate the air-drying process.
• the creation of several paths for the CO 2 penetration is the reason of pre-carbonation curing.
• a suitable amount of the water initially mixed with other ingredients should be removed during the air-drying process. For instance, when the initial water to slag ratio of 0.16 is used for the formation of the products, the air-drying process may be continued until the water to slag ratio drops to 0.08.
• the empty voids allow carbon dioxide to pass through the product while the remaining water secures the carbonation reaction.
• the pre-carbonation water to slag ratio is less than about 0.20; or alternatively a suitable water to slag ratio is from about 0.08 to about 0.13, 0.14 or 0.15.
• the products having a suitable water to slag ratio should be cured in presence of a CO 2 environment.
• the purity of carbon dioxide can be as high as of 99%.
• the purity of carbon dioxide can alternatively be lower such as 80%, 70%, or lower.
• flue gas with a CO 2 concentration of 12% can be used in production of slag -based products.
• the curing period can vary from 0.2 hours to 24 hours.
• the pressure of carbon dioxide can be adjusted from 0.01 to 0.50 MPa. Higher pressure (e.g. up to 1 MPa) may be used in appropriate industrial settings. Higher pressure is beneficial to accelerate the carbonation reaction and ultimately results in improved technical properties.
• FIG 1 therein illustrated is a schematic representation of an exemplary carbonation set-up.
• the products to undergo carbonation curing are placed within a curing chamber.
• a source of CO2 gas is warmed to ambient temperature by a heater and injected into the chamber.
• the pressure of CO 2 released in chamber is regulated by a regulator.
• a balance and data logger may be further provided.
• the density of final products is measured as about 2000 to about 2800 kg/m 3 .
• a process for preparing a landscaping product comprising:
• step ii) molding and compacting the mixture of step i) to a shaped product having an initial water to slag ratio
• step iii) optionally reducing the initial water to slag ratio of said shaped product of step ii) to provide a shaped product having a pre-carbonation water to slag ratio;
• step iv) curing the shaped product of step ii) or iii) with carbon dioxide to provide said landscaping product.
• a process for preparing a landscaping product comprising:
• step ii) molding and compacting the mixture of step i) to a shaped product having an initial water to slag ratio
• step iii) optionally reducing the initial water to slag ratio of said shaped product of step ii) to provide a shaped product having a pre-carbonation water to slag ratio; and iv) curing the shaped product of step ii) or iii) with carbon dioxide to provide said landscaping product.
• a process for preparing a landscaping product comprising:
• said dry part is comprising an aggregate (preferably granite or limestone aggregate) and a binder, wherein said binder is consisting of steel slag and optionally cement, wherein the slag (such as BOF, EAF, Ladle slag or EAF-BOF hybrid slag) has a free lime content less than about 10% and a cumulative calcium silicate content (ex: C 2 S +C 3 S phase concentration) of at least about 15%, a fineness of about 150 m 2 /kg or higher on a Blaine fineness, and wherein the cement is a Portland cement having calcium silicate phase, specifically C 3 S; and
• the slag such as BOF, EAF, Ladle slag or EAF-BOF hybrid slag
• liquid part is comprising water and a chemical admixture meeting the requirements of ASTM C494;
• the slag to cement (S/C) ratio is up to 20, alternatively the ratio is up to 15 or up to 10 or preferably about 7 to about 9, and
• the ratio of the mass of aggregate (A) to the total mass of the aggregate + cement + slag (A + C + S) is ranging from 0.2 to 0.8, preferably from 0.45 to 0.6;
• step ii) molding and compacting the mixture of step i) to a shaped product having an initial water to slag ratio (W/S), such as a W/S of up to about 0.20;
• W/S initial water to slag ratio
• step iii) when the water to slag ratio is higher than about 0.08-0.15 or 0.08-0.14 or 0.08-0.13, optionally reducing the initial water to slag ratio of said shaped product of step ii) to provide a shaped product having a pre-carbonation water to slag ratio of about 0.08-0.15 or 0.08-0.14 or 0.08-0.13;
• step iv) curing the shaped product of step ii) or iii) with carbon dioxide to provide said landscaping product.
• a process for preparing a landscaping product comprising:
• said dry part is comprising an aggregate (preferably granite or limestone aggregate) and a binder, wherein said binder is consisting of steel slag and cement, wherein the slag (such as BOF, EAF, Ladle slag or EAF-BOF hybrid slag) has a free lime content less than about 10% and a cumulative calcium silicate content (ex: C 2 S +C 3 S phase concentration) of at least about 15%, a fineness of about 150 m 2 /kg or higher on a Blaine fineness, and wherein the cement is a Portland cement having calcium silicate phase, specifically C 3 S; and
• the slag such as BOF, EAF, Ladle slag or EAF-BOF hybrid slag
• liquid part is comprising water and a chemical admixture meeting the requirements of ASTM C494;
• the slag to cement (S/C) ratio is up to 20, alternatively the ratio is up to 15 or up to 10 or preferably about 7 to about 9, and
• the ratio of the mass of aggregate (A) to the total mass of the aggregate + cement + slag (A + C + S) is ranging from 0.2 to 0.8, preferably from 0.45 to 0.6;
• step ii) molding and compacting the mixture of step i) to a shaped product having an initial water to slag ratio (W/S), such as a W/S of up to about 0.20;
• W/S initial water to slag ratio
• step iv) curing the shaped product of step ii) or iii) with carbon dioxide to provide said landscaping product.
• a landscaping product comprising:
• a binder consisting of steel slag and cement.
• a landscaping product (such as a paver) comprising:
• an aggregate preferably granite or limestone aggregate
• a binder consisting of steel slag and optionally cement
• the slag such as BOF, EAF, ladle slag or EAF-BOF hybrid slag
• the slag has a free lime content less than about 10% and a cumulative calcium silicate content (ex: C 2 S +C 3 S phase concentration) of at least about 15%, a fineness of about 150 m 2 /kg or higher on a Blaine fineness and wherein the cement is a Portland cement
• the landscaping products have a water absorption of less than about 8.5% (or less than about 6% or preferably less than about 5%) and a compressive strength of about 20 MPa (or about 55 MPa or preferably 60 MPa or higher)
• the slag to cement (S/C) ratio of up to 20 alternatively the ratio is up to 15 or up to 10 or preferably from about 7 to about 9.
• the ratio of the mass of aggregate (A) to the total mass of the aggregate + cement + slag (A + C + S) is ranging from 0.2 to 0.8, preferably from 0.45 to 0.6.
• a landscaping product (such as a paver) comprising:
• an aggregate preferably granite or limestone aggregate
• a binder consisting of steel slag and cement wherein the slag (such as BOF, EAF, ladle slag or EAF-BOF hybrid slag) has a free lime content less than about 10% and a cumulative calcium silicate content (ex: C 2 S +C 3 S phase concentration) of at least about 15%, a fineness of about 150 m 2 /kg or higher on a Blaine fineness and wherein the cement is a Portland cement; the landscaping products have a water absorption of less than about 8.5% (or less than about 6% or preferably less than about 5%) and a compressive strength of about 20 MPa (or about 55 MPa or preferably 60 MPa or higher)
• the slag to cement (S/C) ratio of up to 20 alternatively the ratio is up to 15 or up to 10 or preferably from about 7 to about 9.
• the ratio of the mass of aggregate (A) to the total mass of the aggregate + cement + slag (A + C + S) is ranging from 0.2 to 0.8, preferably from 0.45 to 0.6.
• the Portland cement used to produce paving stone of the following examples has the following chemical composition (%) CaO S1O2 A1 2 0 3 Fe 2 0 3 Na 2 0 K 2 0
• PSD particle size distribution
• ASTM C204 Standard Test Methods for Fineness of Hydraulic Cement by Air-Permeability Apparatus
• ASTM CI 10 Standard Test Methods for Physical Testing of Quicklime, Hydrated Lime, and Limestone
• ASTM CI 15 Standard Test Method for Fineness of Portland Cement by the Turbidimeter
• ASTM C311 Standard Test Methods for Sampling and Testing Fly Ash or Natural Pozzolans for Use in Portland-Cement Concrete
• ASTM D197 Standard Test Method for Sampling and Fineness Test of Pulverized Coal
• ASTM E2651 Standard Guide for Powder Particle Size Analysis
• XRD patterns of carbonated EBH slag panels are shown in Fig. 2.
• the basic mineral components that appear in the diffractograms are calcium silicates, calcium magnesium silicate (merwanite), gehlenite and iron compounds.
• the presence of calcium carbonate and the reduction of calcium silicate phases (C 2 S and C 3 S) were indicative of the carbonation reaction. Prolonged carbonation of 24 hours produced more calcium carbonate.
• thermogravimetry (TG) and differential thermogravimetric (DTG) curves for the as- received and carbonated EAF-BOF hybrid slag are presented in Fig. 3.
• the water loss in hydration product and CaCC>3 content of slag panels increased with an increase in the carbonation time from 2 h to 24 h.
• An increase in the water loss content indicates the formation of more hydration products.
• the chemical admixture was added to water. Liquid and dry materials were mixed until they were uniformly dispersed (typically about 5 minutes for the batch sizes used herein). The mixture was then poured in the mold. A 80x80x80 mm mold and 50x50x50 mm mold were used to produce a paver; however, molds with any size and shape can be used. A MTS machine was used as the precast making machine to form the pavers by compacting the mixture at pressure of about 12 MPa. The pressure compacted the mixture in order to produce a product with the density of 2600 kg/m 3 .
• a Pre -carbonation curing step is optionally performed using an industrial fan for the duration of time specified in the tables below.
• the carbonation curing step is conducted in the presence of 99%-pure CO 2 gas environment for a period of 24 hours under a pressure of 60 psi.
• Viscocrete water reducer
• the mix PV63
• the compressive strength and water absorption are improved compared to PVl 1 (no cement nor admixture) and also PV25 (no admixture).

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Mechanical Engineering (AREA)
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• Manufacturing & Machinery (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)
• Road Paving Structures (AREA)
• Press-Shaping Or Shaping Using Conveyers (AREA)
• Cultivation Of Plants (AREA)
• Soil Conditioners And Soil-Stabilizing Materials (AREA)

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