Systems and methods for curing precast concrete products - Patents.com

Abstract

A method for curing a concrete product having a cavity is described, the method including placing the concrete product on a base, sealing an opening to the cavity with a cover plate, introducing carbon dioxide (CO2) gas into the cavity to effect carbonation of the concrete product, and unsealing the opening in response to the concrete product reaching a target specification. Also described is a system for curing precast concrete products.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Patent Application No. 62 / 945,936, filed December 10, 2019, the entire contents of which are incorporated herein by reference.

[0002] (Technical field) FIELD OF THE DISCLOSURE This application relates generally to precast concrete products, and more particularly to systems and methods for curing such precast concrete products. [Background technology]

[0003] Concrete products are ubiquitous in building structures in many parts of the world. Thus, improvements in systems and methods for curing precast concrete products are always desirable, and even small improvements in systems and methods for curing precast concrete products can provide widespread benefits to today's construction industry. Summary of the Invention

[0004] Precast concrete products such as pipes, manholes, culverts, etc. are conventionally placed in an enclosed chamber, space, room or vessel and cured with heat and steam, or carbon dioxide. Calcium-rich materials containing calcium silicate phases, such as hydraulic cements, slags, and non-hydraulic cements, react with carbon dioxide in the presence of water and are converted to strength-contributing phases containing calcium carbonate.

[0005] The present disclosure relates to a method for producing precast concrete products in which fresh concrete is hardened with carbon dioxide to obtain strength. The walls of the demolded and optionally pretreated concrete product act as a vessel to hold the pressure. In certain embodiments, no external pressurized vessel or hardening chamber is utilized to activate the concrete. Instead, the interior or exterior space of the hollow concrete product is used as a chamber and carbon dioxide penetrates the concrete wall in a unidirectional manner. No external airtight enclosure is required. The innovation relates to the production of precast concrete products, such as hollow precast concrete products, including but not limited to concrete pipes, culvert boxes, manholes, box girders, and hollow core slabs.

[0006] In one aspect, accordingly, there is provided a method of curing a concrete product having a cavity therein and an opening to the cavity, the method including positioning the concrete product on a base, sealing the opening with a cover plate, introducing carbon dioxide (CO2) into the cavity to effect carbonation of the concrete product, and unsealing the opening in response to the concrete product reaching a target strength (and / or other target specification(s)).

[0007] The methods described above and herein may further include, in whole or in part, and in any combination, one or more of the following additional features and / or steps.

[0008] In some embodiments, introducing CO2 into the cavity includes pressurizing the cavity to a first pressure for a first time, and then increasing the pressure in the cavity to a second pressure for a second time.

[0009] In some embodiments, the introduction of CO2 is through the cover plate and / or the concrete product.

[0010] In some embodiments, the opening is one of an open upper end and an open lower end of the concrete product, and positioning includes placing the other of the open upper end and the open lower end on the base so as to enclose the other of the open upper end and the open lower end.

[0011] In some embodiments, the method includes balancing the first and second pressures on the cover plate such that the cover plate continues to seal the opening while the first and second pressures are present.

[0012] In some embodiments, the method includes pouring and demolding the concrete product prior to positioning the concrete product, wherein the steps of positioning the concrete product and introducing CO2 are performed subsequent to and proximate in time to the demolding step.

[0013] In some embodiments, the steps of positioning the concrete product and introducing CO2 are performed immediately after the step of demolding.

[0014] In some embodiments, the method includes performing at least one of a setting, hydration, and pretreatment step on the concrete product prior to the step of introducing CO2.

[0015] In some embodiments, the method includes hydrating the concrete product after completing the step of introducing CO2.

[0016] In some embodiments, the method includes pressurizing the cavity to a predetermined pressure of CO2.

[0017] In some embodiments, the method includes varying the predetermined pressure of CO2.

[0018] In some embodiments, the predetermined pressure is equal to or greater than atmospheric pressure.

[0019] In some embodiments, sealing the opening is such as to allow at least some CO2 to escape from the cavity during carbonation of the concrete product.

[0020] In some embodiments, pouring is performed using one or a combination of zero slump concrete, wet concrete, and self-compacting concrete.

[0021] In some embodiments, the ready mixed concrete is produced using one or a combination of hydraulic cement, non-hydraulic cement, slag, pozzolanic material, fly ash, silica fume, and calcium hydroxide as a binder.

[0022] In some embodiments, the casting is performed as one of dry casting and wet casting.

[0023] In some embodiments, introducing CO2 is carried out by introducing a gas comprising CO2 at a concentration of 5% to 99.5% CO2 by weight.

[0024] In another aspect, there is provided a system for curing a precast concrete product having a cavity therein, the cavity having an open lower end and an open upper end, the system comprising: a base sized to receive the precast concrete product thereon and to cover the lower end of the cavity, a cover plate sized to be received on the precast concrete product and to cover the upper end of the cavity, a carbon dioxide (CO2) source, and a CO2 conduit configured to be fluidly connected to the CO2 source and to be fluidly connected to the cavity.

[0025] The systems described above and herein may further include one or more of the following additional features and / or steps, in whole or in part, and in any combination.

[0026] In some embodiments, the system includes a height control system connected between the base and the cover plate and operable to move the cover plate between a closed position and an open position, where the cover plate covers an upper end of the cavity.

[0027] In some embodiments, the system includes a frame connected between the base and a cover plate, the cover plate being hinged to the frame for movement between a closed position, in which the cover plate covers an upper end of the cavity, and an open position.

[0028] In some embodiments, the CO2 conduit is fluidly connected to the cavity through one or more of the cover plate, the wall of the precast concrete article, and the base, and the CO2 source is configured to pressurize the cavity to at least two different pressures that are above atmospheric pressure.

[0029] In some embodiments, a flow control valve is disposed in fluid communication with the CO2 source, the flow control valve configured to control the rate and / or pressure of CO2 gas provided into the cavity.

[0030] In another aspect, a method of curing a concrete product having a cavity therein is provided, the method including sealing the cavity, performing carbonation of the concrete product by introducing carbon dioxide (CO2) gas into the cavity, and unsealing the cavity in response to the concrete product achieving target specifications (such as strength and / or other target specification(s)).

[0031] The methods described above and herein may further include, in whole or in part, and in any combination, one or more of the following additional features and / or steps.

[0032] In some embodiments, the method includes placing at least one container in the cavity prior to sealing the cavity, the at least one container containing pressurized CO2 gas therein, and introducing the CO2 gas into the cavity includes releasing the CO2 gas from the at least one container into the cavity.

[0033] In some embodiments, introducing CO2 into the cavity includes pressurizing the cavity to a first pressure for a first time, and then increasing the pressure in the cavity to a second pressure for a second time.

[0034] In some embodiments, the at least one container comprises at least one of a tire tube and a tire.

[0035] In some embodiments, introducing CO2 into the cavity includes operating at least one valve fluidly connected to at least one of the tire tube and the tire.

[0036] In some embodiments, sealing the cavity is performed with a cover plate and further includes balancing the first and second pressures with the cover plate such that the cover plate continues to seal the opening while the first and second pressures are present.

[0037] In some embodiments, the method includes pouring and demolding the concrete product prior to sealing the cavity, and the step of introducing CO2 is carried out after and close in time to the step of demolding.

[0038] In some embodiments, the step of introducing CO2 is performed immediately after the step of demolding.

[0039] In some embodiments, the method includes performing at least one of a setting, hydration, and pretreatment step on the concrete product prior to the step of introducing CO2.

[0040] In some embodiments, the method includes hydrating the concrete product after completing the step of introducing CO2.

[0041] In some embodiments, the method includes pressurizing the cavity to a predetermined pressure of CO2.

[0042] In some embodiments, the method includes varying the predetermined pressure of CO2.

[0043] In some embodiments, the predetermined pressure is equal to or greater than atmospheric pressure.

[0044] In some embodiments, the method includes sizing at least one container to occupy between 10% and 98% of the volume of the cavity.

[0045] In some embodiments, at least one of a tire tube and a tire is used.

[0046] In some embodiments, the casting is performed as one of dry casting and wet casting.

[0047] In some embodiments, introducing CO2 is performed by introducing a gas comprising CO2 at a CO2 concentration of between 5% and 99.5% by weight.

[0048] In another aspect, a method of curing a concrete product is provided, the method including: surrounding an exterior surface of the concrete product with a sleeve having a shape that at least partially conforms to the exterior surface of the concrete product, the sleeve being proximate to but spaced from the exterior surface to define a space between the exterior surface and the sleeve; sealing the space between the exterior surface and the sleeve; introducing carbon dioxide (CO) gas into the space between the exterior surface and the sleeve to effect carbonation of the concrete product, wherein at least a portion of the CO gas passes inwardly through the exterior surface of the product; and unsealing the space between the exterior surface and the sleeve in response to the concrete product achieving a target specification (such as strength and / or other target specification(s)).

[0049] The methods described above and herein may further include, in whole or in part, and in any combination, one or more of the following additional features and / or steps.

[0050] In some embodiments, the concrete product includes a cavity therein and an opening to the cavity, and enclosing the exterior surface of the concrete product excludes sealing the opening.

[0051] In some embodiments, enclosing the exterior surface of the concrete article leaves the opening open.

[0052] In some embodiments, the introduction of CO2 gas into the space is performed through a sleeve.

[0053] In some embodiments, sealing the space between the outer surface of the concrete product and the sleeve includes placing a cover plate over the concrete product, the cover plate operatively connected to the sleeve at least during the CO2 gas introducing step by one or more of being weighted to balance the pressure of the CO2, hinged to the sleeve, and guided relative to the sleeve.

[0054] In some embodiments, the cover plate includes an opening therein that at least partially aligns with the opening to the cavity of the concrete product when the cover plate is placed over the concrete product.

[0055] In another aspect, a system is provided for curing a precast concrete product having a cavity therein, the cavity having an open lower end and an open upper end, the system comprising: a base sized to receive the precast concrete product thereover, thereby covering the lower end of the cavity; a sleeve sized to contain the concrete product therein, the sleeve having a lower end disposed on the base and sealed against the base; a cover plate sized to be received over the precast concrete product, thereby covering the upper end of the cavity, the cover plate operably connected to the sleeve such that the cover plate seals a space between the sleeve and an exterior surface of the concrete product, thereby sealing the space; and a carbon dioxide (CO2) source configured to be fluidly connected to the space.

[0056] The systems described above and herein may further include one or more of the following additional features and / or steps, in whole or in part, and in any combination.

[0057] In some embodiments, the CO2 source fluidly connects to the space via at least one of the sleeve and the cover plate.

[0058] In some embodiments, the cover plate is hinged to the sleeve so that it is pivotable between an open position, in which the concrete product can enter and exit the sleeve, and a closed position, in which the cover plate seals the space between the concrete product and the sleeve.

[0059] In some embodiments, the CO2 source is configured to pressurize the cavity to at least two different pressures that are above atmospheric pressure. [Brief description of the drawings]

[0060] Reference is now made to the attached figures. [Figure 1] FIG. 1 is a schematic diagram of a system for curing a concrete product. [Diagram 2] 2A and 2B are schematic diagrams of a system for curing concrete articles and a sealing mechanism for one or more concrete articles, respectively, according to another embodiment. [Diagram 3] FIG. 3 is a schematic diagram of a system for curing a concrete product according to another embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view of a portion of the system of FIG. [Diagram 5] FIG. 5 is a schematic diagram of an alternative example non-limiting embodiment of a cover plate and a base of the system of FIG. [Figure 6] FIG. 6 is a schematic diagram of a system for curing a concrete product according to another embodiment. [Figure 7] FIG. 7 is a schematic diagram of a system for curing a concrete product according to another embodiment. [Figure 8] FIG. 8 is a schematic diagram of a system for curing a concrete product according to another embodiment. [Figure 9] FIG. 9 is a schematic diagram of a system for curing a concrete product according to another embodiment. [Figure 10] FIG. 10 is a schematic diagram of a system for curing a concrete product according to another embodiment. [Figure 11] FIG. 11 is a schematic diagram of a system for curing a concrete product according to another embodiment. [Figure 12]FIG. 12 is a schematic diagram of various sealing portions of a system according to some embodiments described herein. [Figure 13] FIG. 13 illustrates a method for curing a concrete article. [Figure 14] FIG. 14 illustrates an alternative method for curing a concrete article. [Figure 15] FIG. 15 illustrates an alternative method for curing a concrete article. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] (Detailed Description) Precast concrete products, such as pipes, manholes, culverts, are traditionally cured using heat and steam. Precast concrete products can also be cured with carbon dioxide placed in an enclosed chamber, space, room, or vessel. Calcium-rich materials containing calcium silicate phases, such as hydraulic cements, slags, and non-hydraulic cements, react with carbon dioxide in the presence of water and are converted to strength-contributing phases containing calcium carbonate.

[0062] The present disclosure relates to systems and methods for producing precast concrete products (P) in which fresh concrete is cured with carbon dioxide (CO2) to gain its strength. In some embodiments, the walls of the demolded, and in some embodiments pretreated, concrete product (P) act to contain and retain CO2 pressure, thereby helping to reduce curing time and costs. The present technology may improve at least some aspects of the production of hollow concrete products (P), such as precast concrete products including concrete pipes, culvert boxes, manholes, box girders and hollow core slabs.

[0063] With the above in mind, this specification will first describe non-limiting embodiments of a system for curing a precast concrete product (P), then describe non-limiting examples of various candidate materials and casting methods that may be associated with the system, and then describe non-limiting examples of various possible methods of curing concrete that may be performed, for example, using one or more of the illustrated embodiments of the system.

[0064] (System 100) Referring to FIG. 1, a system 100 for curing a precast concrete product (P) is shown. The system 100 includes a base 102, such as a floor, a lower seal 104 disposed on the base 102, and an upper seal 106 engaged with a cover plate 108. The seals 104, 106 may be rubber gaskets, sealers, epoxies, O-rings, or any other suitable seals. The seals 104, 106 may encompass a sleeve-like concrete product (P), for example as shown in FIG. 5 by numeral 306′. Such a sleeve-like concrete product (P) may cover up to about 20% of the height of the concrete product (P) in some embodiments. Although such a configuration may provide sealing advantages, other height percentages are also contemplated. In some embodiments, the lower seal 104 and / or the upper seal 106 may be omitted.

[0065] In this embodiment, the seals 104, 106 and cover plate 108 are annular to conform to and seal against the corresponding portion(s) of the concrete product (P), although other shapes and seals may be used, for example, where the concrete product (P) is of a different shape. In some embodiments, the cover plate 108 is dimensioned and / or its material is selected to provide a weight of the cover plate that balances the gas pressure that may be present in the concrete product (P), as described herein. As described and shown in more detail below, in its various embodiments and applications / systems, the cover plate 108 may be weighted (e.g., to hold the concrete product (P) sealed as described without the need for additional mechanical force applied to the cover plate 108) and / or may be hinged and / or guided on one or more rods / supports and / or may be automatically translatable (e.g., via a suitable conventional powered actuation mechanism). The base 102, seals 104, 106, and cover plate 108 are sized to cover a cavity (C) in at least one size of precast concrete product (P). In some embodiments, the seals 104, 106 and cover plate 108 are made large enough to enclose and cure any one of a number of different sizes of precast concrete products (P) and / or cavities (C), as described in more detail below.

[0066] The system 100 further includes a carbon dioxide (CO2) source 110 operable to supply CO2 into the cavity (C) in the precast concrete product (P) and a pressure gauge 112 mounted through the cover plate 108 to monitor gas pressure in the cavity (C). As shown, in some embodiments, one or more suitable CO2 conduits 110P, such as pipes or ducts, are capable of fluidly connecting to the carbon dioxide (CO2) source 110 and receiving CO2 therefrom. The CO2 conduits 110P pass through the cover plate 108 for the purpose of supplying CO2 into the cavity (C) in the precast concrete product (P) to harden the precast concrete product (P). In other embodiments, the concrete product (P) may have a different shape.

[0067] In some embodiments, the interface(s) between the CO2 conduit 110P and the cover plate 108 may be sealed to be at least substantially impermeable to gas. In some embodiments, some or all of the CO2 conduit(s) 110P may be made flexible to facilitate movement of the cover plate 108 over each given concrete product (P). In other embodiments, the CO2 conduit 110P may be rigid and / or removable from the cover plate 108, such as via a clip-on connector, to provide for movement of the cover plate 108 over each given concrete product (P).

[0068] The carbon dioxide (CO2) source 110 may be any suitable carbon dioxide (CO2) source, such as a conventional carbon dioxide (CO2) source, and therefore will not be described in detail herein. In some embodiments, the carbon dioxide (CO2) source 110 is configured to control the rate and pressure of CO2 delivered into the cavity (C) in the precast concrete product (P). To this end, and as shown in FIG. 1, one or more of the carbon dioxide (CO2) source 110 and / or CO2 conduits 110P may include flow control valves 114 that are manually and / or actively controlled. The flow control valves 114, and their associated controls, may be conventional, and therefore will not be described in detail herein.

[0069] The cover plate 108 in this embodiment is made from a suitable metal and is dimensioned to have a sufficient weight to keep the cavity (C) in the precast concrete product (P) at least substantially sealed during the hardening process. It will be appreciated that depending on the pressure(s) at which the carbon dioxide (CO2) source 110 may be configured to pressurize the cavity (C) in the precast concrete product (P) with CO2, the cover plate 108 may be made to have a different weight. That is, the weight of the cover plate 108 may be selected to sufficiently compress the seals 104, 108 to keep the cavity (C) in the precast concrete product (P) at least substantially sealed during the hardening process. In other embodiments, depending on the shape of the cavity (C) and the shape of the precast concrete product (P) to be sealed and hardened, the seals 104, 108 and the cover plate 108 may have different shapes.

[0070] (System 200) 2A, there is shown a system 200 for curing a precast concrete product (P). System 200 is similar to system 100, and therefore corresponding parts of system 200 are marked with the same reference numerals as used with respect to system 100.

[0071] The difference between the system 100 and the system 200 is that the system 200 includes a cover plate 108 attached to a height control system 204. In this embodiment, the height control system 204 includes a vertically oriented support member 206, for example a steel bar. At its lower end 206A, the support member 206 is connected to the base 102 via a suitable connection, such as a sealed connection to prevent CO2 from escaping from the cavity (C) through the interface between the support member 206 and the base 102. At its upper end 206B, when the cover plate 108 reaches a suitable position, the support member 206 is connected to the center of the cover plate 108 via a translation assembly 208 that is received on the upper end 206B of the support member 206. In other embodiments, the cover plate 108 may remain connected to the translation assembly 208 while the concrete product (P) is being placed in place, for example when the concrete product is in close proximity to the support member 206 and in some embodiments is in a shape that can be positioned around the support member 206 by moving horizontally over the support member 206. In other embodiments, different configurations of the sealing mechanism may be used. For example, as shown in FIG. 2B, the sealing mechanism may have a support member such as a frame including one or more rods 206′ arranged at one or more distances from one another, the rods 206′ being selected to allow one or more concrete products (P) to be moved under the cover plate 108′ while the cover plate 108′ is movably / translatably connected to the one or more rods 206′. Once in position, the translation assembly 208′ may be operated, whether manually and / or automatically, to move the cover plate 108′ into position to seal the inside(s) of the concrete product (P). To this end, and as shown by the double-ended arrow in FIG. 2B, the translation assembly 208′ may be configured to be movable / translatable up and down. In one embodiment, once the cover plate 108′ seals the concrete product (P), it may be fixed in place via one or more suitable mechanisms (e.g., bolts / nuts), which may be automatic or manual.Thus, Figure 2B shows different embodiments of a sealing mechanism, which may be connected to a CO2 source, such as the CO2 source of Figure 2A, and thus may be part of the system 200. Any number of sealing mechanisms may be used to cure multiple concrete products (P) in parallel. Any number of CO2 sources may be used for each concrete product (P) and / or sealing mechanism.

[0072] The translation assembly 208 may be threaded into corresponding threads on the upper end 206B of the support member 206 and may be manually operable by its rotation relative to the support member 206 in one of two directions to translate the cover plate 108 up and down relative to the support member 206. It is contemplated that any other suitable configuration of translation assembly 208 may be used, such as, but not limited to, an actively actuated translation assembly 208 that may be controlled via one or more suitable actuators, such as, for example, electric motors that may be operably connected to a suitable controller, such as a computer. These details may be conventional and will not be described in detail herein. In other embodiments, the translation assembly 208 may be a different type of translation assembly, such as a hydraulic and / or electric translation assembly operable to provide the functionality of the system 200 as described herein.

[0073] (System 300) 3 and 4, there is shown a system 300 for curing a precast concrete product (P). System 300 is similar to system 100 and therefore corresponding parts of system 300 are marked with the same reference numerals as used in relation to system 100.

[0074] The difference between system 100 and system 300 is that system 300 includes one or more frame members 302 forming a frame supporting cover plate 306. One or more frame members 302 may be vertically disposed and may be optionally connected to base 102. In another example, the frame may be attached to or disposed on a floor. In some embodiments, a single frame member 302 may form frame 302F. Frame 302F in this embodiment is open to opposite lateral sides of precast concrete product (P) as shown in FIG. 4 and thus does not form a chamber above precast concrete product (P). In other embodiments, frame 302F may be different. Frame / support 302F may be of a larger size than concrete product (P) to contain concrete product (P). Frame / support 302F may be made of, by way of non-limiting example, steel, iron, stainless steel, FRP, plastic, or aluminum. Frame / support 302F need not be covered and / or may be made using one or more meshes.

[0075] Another difference between systems 100 and 300 is that in system 300, a cover plate 306 is hinged, e.g., via one or more hinges 304, to the top of frame 302F so as to be movable between a closed position 306C and an open position 306O (shown in dashed lines in FIG. 3). In this embodiment, but not necessarily in other embodiments, the cover plate 306 is pivotable about the one or more hinges 304 between the closed position 306C and the open position 306O.

[0076] In the closed position 306C, the cover plate 306 encloses the cavity (C) within the precast concrete product (P) and allows the CO2 curing process to occur as described herein below. In the open position 306O, the cover plate 306 does not sufficiently obstruct the top of the frame 302F to allow the precast concrete product (P) to be inserted into the frame 302F for curing and the precast concrete product (P) to be removed from the frame 302F after curing. It is contemplated that any other movable connection, such as a translational joint, may be used in place of or in addition to the hinge 304.

[0077] 3, in this embodiment, one of the frame members 302 is threaded at its top end and passes through a slot or opening in the cover plate 306 when the cover plate 306 is in the closed position 306C. A bolt and / or nut and / or other fastener can be attached to the top end of that frame member 302 to lock the cover plate 306 in the closed position 306C and / or tightened to increase compression of the top seal(s) 106 by the cover plate 306. It is contemplated that any suitable fastener may be used. In some embodiments, fasteners may be omitted.

[0078] 4, as shown in this embodiment, the top seal 106 is annular and thinner than the walls of the precast concrete product (P). In at least some embodiments and applications, this helps to improve the enclosure of the cavity (C) and placement of the precast concrete product (P) into the system 300. In some embodiments, the top seal 106 may have a different thickness and / or shape. Now referring to FIG. 5, in some embodiments, the cover plate 306 may have a different shape.

[0079] One alternative example of the cover plate 306 is shown in the center drawing of FIG. 5 and labeled as 306′. Still referring to FIG. 5, in some embodiments, the base 102 may be separate from the floor on which at least a portion of the system 300 may be placed and may have a different suitable shape. One alternative example of the base 102 is shown in the right drawing of FIG. 5 and labeled as 102′. In some embodiments, such as non-limiting alternative embodiment 102′, the bottom seal(s) 104 may be part of the base 102′ and / or may be omitted.

[0080] (System 400) 6, there is shown a system 400 for curing a precast concrete product (P). System 400 is similar to system 100 and therefore corresponding parts of system 300 are given the same reference numerals as used in relation to system 100.

[0081] The difference between system 100 and system 400 is that system 400 has a base 402 including a base portion 402B, which may be cast, for example, from concrete or otherwise be, for example, part of the floor (or may alternatively be separate from the floor), and a base plate 402P disposed on base portion 402B. In some embodiments, base plate 402P may be an integral part of base portion 402B and / or may be omitted. As shown, in this embodiment, bottom seal 104 is integral with base plate 402P, but in other embodiments it may not be.

[0082] As shown, the CO2 conduit 110P from the CO2 source 110 passes through the base portion 402B of the base 402 and is positioned to open beyond the outlet of the CO2 conduit 110P into a cavity (C) of the precast concrete product (P) when the precast concrete product (P) is placed in the system 400. In some embodiments, the system 400 may be configured to cure a precast concrete product (P) that may have one or more cavities (C). In some such embodiments, the system 400 may have one or more CO2 conduits 110P for each cavity (C) of the precast concrete product (P), such as three or more CO2 conduits 110P in total.

[0083] Cover Plate Description: The cover plate may be weighted, hinged, or rod guided (top cover system similar to 100, 200 and 300).

[0084] (System 500) 7, there is shown a system 500 for curing a precast concrete product (P). System 500 is similar to system 100 and therefore corresponding parts of system 500 are marked with the same reference numerals as used in relation to system 100.

[0085] The difference between system 100 and system 500 is that system 500 has one or more CO2 conduits 110P that traverse the wall of the precast concrete product (P), as shown. In this embodiment, system 500 has two CO2 conduits 110P, but in other embodiments, system 500 may have one or more than two CO2 conduits 110P with corresponding CO2 conduit(s) 110P that traverse the wall(s) of the precast concrete product (P) to inject CO2 into its cavity (C) during the hardening process.

[0086] In some embodiments, the system 500 may include an injection assembly 502 for each of the one or more CO2 conduits 110P, which may help limit or prevent CO2 leakage outside of the cavity (C) during the curing process. Referring now to FIG. 7, three non-limiting examples of injection assemblies 502 are shown, labeled 502A, 502B, and 502C, respectively. The injection assembly 502A may include an epoxy or other suitable sealer 504 at the interface between the CO2 conduit 110P and an opening defined through the wall of the precast concrete product (P) that receives the CO2 conduit 110P therein. In some embodiments, the epoxy and / or other suitable sealer 504 may be injected at the interface, for example, although other installation methods may be used.

[0087] The injection assembly 502B may include a rubber plug 506 having a suitable one or more openings defined therein, which may be attached to the outer end of the CO2 conduit 110P as shown and / or inserted into the interface between the CO2 conduit 110P and an opening defined through the wall of the precast concrete product (P) receiving the CO2 conduit 110P therein. The rubber plug 506 is one example of a sealing member 506 that may be used. Other sealing member(s) are also contemplated.

[0088] For example, the injection assembly 502C may include an expansion plug 508 having a suitable opening or openings defined therein, which may be attached or inserted into the outer end of the CO2 conduit 110P as shown, and / or inserted into the interface between the CO2 conduit 110P and an opening defined through a wall of the precast concrete article (P) receiving the CO2 conduit 110P therein. The expansion plug 506 is another example of a sealing member 506 that may be used. Other sealing member(s) are also contemplated.

[0089] (System 600) Referring now to FIG. 8, a system 600 for curing a precast concrete product (P) is shown. The system 600 can use a base 102 and one or more seals 104 as described above. However, in this embodiment, the system 600 can have a cover plate 602 that is sized and / or made from a material(s) selected to provide a weight of the cover plate 602 that balances the CO2-containing gas pressure that may be present within the concrete product (P). In other embodiments of the system 600, the cover plate 602 can be hinged or guided on a rod(s), for example, similar to other embodiments described herein (e.g., similar to the top cover systems of 100, 200, and / or 300). The CO2-containing gas in this embodiment can be provided by one or more containers 604 that contain pressurized CO2-containing gas(es). In some embodiments, the container(s) 604 can be a vehicle tire and / or tire tube, as shown diagrammatically in FIG. 8. In some embodiments, the container(s) 604 may be used vehicle tires and / or tubes to reduce waste. The container(s) 604 may be retrofitted with one or more valve(s) 606, such as a conventional valve, which may be passive or powered, configured to release gas to provide pressurization of the concrete product (P) as described herein. In some embodiments, one or more containers may be interconnected via one or more conduits 608 to reduce the number of valves 606 to less than one per container 608. In some embodiments, and this may vary in other embodiments, the valve(s) 606 may be configured to provide a total flow rate of gas that is less than 30 standard cubic feet per minute. This may make it possible to have a single valve 606 for multiple containers 604. In some embodiments, the CO2-containing gas in the container(s) 604 may have a CO2 concentration between 5% and 99.5% by mass.

[0090] In some embodiments, the container(s) 604 may be sized to occupy 10% to 98% of the volume of the cavity (C) and may be positioned therein such that it does not come into contact with the interior wall(s) of the concrete product (P) that defines the cavity (C). In one aspect, this may lower the CO2 volume / content required to fill the cavity (C) and allow the cavity (C) to be filled with CO2 more quickly since the cavity (C) has less available free volume. Also, at the end of the carbonation process, less CO2 remains in the cavity (C). This allows for a faster carbonation process and less CO2 to be used for the carbonation process. The pressure built up between the concrete walls of the product (P) and the container(s) 604 allows the gas / CO2 to penetrate the concrete walls and the CO2 to react with the binder of the concrete walls in the presence of water, thereby allowing for carbonation / strengthening of the product (P). In some applications, and depending on the use, for example, the object(s) 604 may be refilled and reused for each new concrete product (P) that is carbonated using the system 600, or may be sized and / or pressurized to carbonate more than two concrete products (P) before requiring refilling.

[0091] (System 700) 9, yet another embodiment of a system 700 is shown. Similar to system 600, system 700 includes reducing the CO2-fillable volume of cavity (C) with one or more objects 702. As shown, in some embodiments, object(s) 702 may be a gas-containing balloon, i.e., an expandable bag, expandable plastic, or expandable rubber, that is placed in cavity (C) and can be inflated to occupy 10% to 98% of the volume of cavity (C), with similar goals and results as those described with respect to system 600 above.

[0092] The fill gas can be air, nitrogen, carbon dioxide, oxygen, or any other gas. The object 702 that holds the gas can be made of a flexible material such as plastic. The gas pressure inside the object 702 can be higher than the pressure of the CO2 introduced into the cavity (C). Furthermore, the object 702 can be made of steel, iron, aluminum, or FRP. The object 702 can be reused for each new product (P) that is carbonated using the system 700.

[0093] (System 800) 10, yet another embodiment of a system 800 is shown. Similar to system 700, system 800 includes reducing the CO2-fillable volume of a cavity (C) with one or more objects 802. As shown, in some embodiments, the object(s) 802 may be a hollow manifold, bladder, tube, or the like.

[0094] (System 900) 11, yet another embodiment of a system 900 is shown. The system 900 includes an external sleeve 902 that is positioned proximate to an exterior wall of a concrete product (P) and receives CO2 from one or more CO2 sources 110. The sleeve 902 is preferably made of steel, iron, aluminum, FRP, plastic, or any other suitable material. The sleeve 902 may be made of an impermeable material that prevents gas from escaping. Thus, when introduced into the sleeve 902, the CO2 is pressurized at the exterior surface of the wall of the product (P) and therefore penetrates the wall inwardly into the cavity (C), as shown by the arrows in FIG. 11. The sleeve 902 may correspond in shape to the shape of the product (P) and may be surrounded / sealed at one end (e.g., bottom) by the base 102 and seal(s) 104, and at the top end by a cover plate 904, which may be implemented similarly to any one of the above embodiments except that the cover plate 904 includes an opening 906 arranged to be in fluid communication with the cavity (C). The opening 906 may allow the CO2 to escape the cavity (C) after passing through the wall of the product (P). In some embodiments, the opening 906 may be used to depressurize the cavity (C) to create a larger pressure differential across the wall of the product (P), thereby increasing the penetration of the CO2 through the wall. In some cases, this may help speed up the carbonation process. Any suitable means may be used to depressurize the cavity (C), such as one or more conventional fans, pumps, vacuums, etc.

[0095] As an example, the system 900 may be used to carry out a carbonation process in which the product (P) is enclosed by a sleeve 902 after any pre-treatment of the product (P) as described herein. The gap between the product and the sleeve 902 may be greater than 1 mm from all sides / edges. Carbon dioxide gas is introduced into the gap between the product (P) and the sleeve 902. The concentration of the injected carbon dioxide may be greater than 5%. The penetration of the gas into the concrete wall is thereby carried out unidirectionally to the inside of the cavity (C). The gas may be injected at a constant or variable flow rate during the carbonation process. In the case of a variable injection flow rate, the flow rate may be initially lower than 30 standard cubic feet per minute and gradually increased over time. The initial low flow rate approach may help to reduce the porosity of the concrete product (P) without causing significant leakage. A higher carbon dioxide flow rate may be applied as calcium carbonate and other carbonation reaction products are produced and partially fill the pores in the concrete product (P). This method may aid in rapid early strength development and reduce significant leakage.

[0096] The rate of carbon dioxide pressure build-up may depend on the gas injection rate, the volume of the space between the sleeve 902 and the product, the concrete mix proportions, the concrete permeability, the porosity, the type of concrete, and the product shape. The carbonation reaction may be exothermic. Additional and external heat / temperature may not be required for the carbonation curing process. The activation process may be carried out at ambient temperature and humidity. The built-up pressure between the concrete wall and the external sleeve 902 may cause the gas to penetrate the concrete wall and, in the presence of water, the carbon dioxide to react with the binder. In this configuration, the reaction begins at the outer surface of the product (P). In some embodiments, the gas injection and carbonation curing process may continue for at least 5 minutes.

[0097] Some of the gas in the space between the product (P) and the sleeve 902 can pass through the concrete walls and exit the inner layer of the product (P). If some carbon dioxide remains inside the space at the end of the carbonation curing process, the carbon dioxide may be released before the product (P) is released from the system 900. In another configuration, the sleeve 902 may be sized to be placed in the cavity (C) to encompass the inner concrete walls of the product (P), thus preventing the CO 2 The gas may permeate from the inner layer to the outer layer of the product (P). EXAMPLES

[0098] (About the materials) The concrete products (P) referred to in the description of the various embodiments of systems 100 to 900 above may be made from prior art concrete using any known conventional method in the prior art. In some embodiments, the concrete may include Portland cement or other hydraulic cement as the primary cementitious material. The ready mixed concrete may be, for example, zero slump concrete, wet concrete, or self-compacting concrete (SCC). The concrete products may be either dry cast or wet cast.

[0099] In some embodiments, concrete may be produced using a slag-based binder. The primary binder in the production of slag-based concrete may be slag from steel and stainless steel plants. Other by-product materials such as zinc, iron, copper, sludge, etc. may also be utilized as binders. Various steel slags may be collected from steel plants practicing various steel making methods. The types of slags that may be incorporated as the primary binder in the production of slag-based concrete include stainless steel slag, reduced steel slag, oxidized steel slag, converter steel slag, electric arc furnace slag (EAF slag), basic oxygen furnace slag (BOF slag), ladle slag, quenched steel slag, and annealed steel slag.

[0100] The calcium oxide content of the slag may be greater than 10%, greater than 15%, and in some embodiments greater than 20%. The silica oxide content may be greater than 6%, greater than 8%, and in some embodiments greater than 12%. The total iron oxide content of the slag may be less than 40%, and in some embodiments less than 30%. The steel slag may have a cumulative calcium silicate content of at least 20% and a free lime concentration of less than 10%. All the above values ​​are based on the mass / weight of the slag. In some embodiments, the bulk density of the slag is between 1.0 and 2.0 g / cm 3 and its apparent density may be in the range of 2.0 to 6.0 g / cm 3 may vary up to

[0101] The slag may be ground to smaller sizes in some embodiments before being incorporated into the mix to produce concrete. Grinding of the slag may be performed in any mechanical machine such as ball mill, rod mill, autogenous mill, SAG mill, pebble mill, high pressure grinding roll, VSI or tower mill. The grinding process may be performed either wet or dry. If wet grinding of the slag is selected, the ground slag may be selected to be either fully dried or semi-dried at the end of grinding. Sieving the slag is an alternative option to obtain slag with smaller particle size. Slag passing mesh #10 (2000 microns), mesh #50 (297 microns), mesh #200 (74 microns), mesh #400 (37 microns) may be used as binder. Sieves may be utilized to screen the slag after grinding or before grinding. Thus, any or a combination of grinding and screening methods may be performed to obtain slag with the appropriate particle size.

[0102] In some embodiments, the slag is at least 150 m 2 / kg, and at least 200m 2The slag may be ground and / or screened to a Blaine fineness of 100 / kg. In some embodiments, for use in slag-based concrete, 50% of the slag may be smaller than 200 microns (D50=200), smaller than 150 microns (D50=150), smaller than 100 microns (D50=100), smaller than 50 microns (D50=50), smaller than 25 microns (D50=25), and in some embodiments, smaller than 10 microns (D50=10). In some embodiments, the free lime content of the slag may be reduced using any standard known method in the prior art before the free lime of the slag is incorporated into the mix. In other embodiments, the slag may first be aged to reduce its calcium hydroxide content and then incorporated into the mix. The slag content may be 5% or more by weight of the concrete, and in some embodiments, 20% or more by weight of the concrete.

[0103] Various types of aggregates, including natural or artificial normal weight and lightweight aggregates, may be incorporated into concrete as fillers in the production of slag-based concrete. Examples of candidate lightweight aggregates include natural lightweight aggregates (e.g., pumice), expanded clay aggregates, expanded shale aggregates, recycled plastic aggregates, and expanded iron slag aggregates. Other usable aggregates include crushed stone, manufactured sand, gravel, sand, recycled aggregates, granite, limestone, quartz, chalk dust, marble dust, quartz sand, and artificial aggregates. These aggregates can be incorporated into the mix as fine and / or coarse aggregates. The aggregate content can be as much as 90% of the concrete weight.

[0104] In some embodiments, mineral and chemical admixtures may be introduced into the mixture. Mineral admixtures may include fillers, supplementary cementitious materials, and pozzolanic materials. Candidate mineral admixtures include fly ash, calcined shale, silica fume, zeolite, GGBF, limestone powder, hydraulic cement, and non-hydraulic cement, or a combination thereof. On the other hand, chemical admixtures may be mixed to satisfy specific properties. Candidate chemical admixtures include, but are not limited to, accelerators, retarders, viscosity modifiers, air entrainers, foaming agents, ASR inhibitors, non-segregation agents, corrosion inhibitors, shrinkage reducers, crack reducers, plasticizers, superplasticizers, water reducers, water repellents, efflorescence control agents, and workability retention agents. Fibers may be added to the slag-based concrete in some embodiments. One or a combination of cellulose fibers, glass fibers, micro synthetic fibers, natural fibers, PP fibers, PVA fibers, and steel fibers may be incorporated into the mixture.

[0105] The slag-based concrete product may be either dry cast concrete or wet cast concrete. The fresh slag-based concrete may be made as zero slump concrete, wet concrete, or self-compacting concrete (SCC). For example, in some embodiments, the self-compacting concrete (SCC) may have a water to slag weight ratio greater than 0.2. In some embodiments, the wet cast concrete may have a water to slag weight ratio greater than 0.1. In some embodiments, the dry cast concrete may have a water to slag weight ratio less than 0.5.

[0106] (Mixing and Manufacturing) The concrete product (P) mentioned in the description of the various embodiments of the systems 100 to 900 above may be manufactured using prior art mixing methods. In some embodiments, the concrete product (P) may be manufactured by homogeneously mixing all batch components, which may include: binder, aggregate, chemical admixtures, mineral admixtures, fibers, and water. For example, in one approach, the dry components are mixed for at least one minute, and water and other liquid components are added after mixing. In another approach, water may be added gradually during mixing of the dry components. If no water-reducing admixtures are mixed, the water content of wet cast concrete and self-compacting concrete may be higher than that of dry cast or zero-slump concrete. Any existing methods, techniques, and equipment used in the prior art to manufacture the concrete product (P) may be implemented in the manufacture of zero-slump concrete, wet concrete, and self-compacting / setting conventional concrete and slag-based concrete.

[0107] (Reinforcement) As shown in FIG. 2A for example, the concrete product (P) mentioned in the description of the various embodiments of the systems 100 to 900 above may have a wall thickness of, for example, about 1 mm to 350 mm (although any other wall thickness may be used as well) and may be optionally reinforced with reinforcement (PR) such as carbon steel, stainless steel, and / or FRP reinforcing bars. In one embodiment, a mold is prepared before pouring the concrete product (P), and in some embodiments, the reinforcement is placed inside the mold before pouring. In some embodiments, the diameter of the bars (PR) may vary from 1 mm to 100 mm, and the yield strength is, for example, between 100 MPa and 2100 MPa. In some embodiments, the reinforcement (PR) of the precast concrete product (P) may be designed according to codes and standards that may be applicable in the jurisdiction in which the precast concrete product (P) may be designed. These specific measurements and characteristics are non-limiting examples only.

[0108] (Pouring and placement) The ready mixed concrete can be poured into a suitable conventional mold using any method known in the prior art. The ready mixed concrete can be zero slump concrete (dry concrete), wet concrete or self-compacting concrete. Steel, iron, aluminum, plastic or FRP molds are preferably lubricated prior to pouring to facilitate demolding. Wet cast concrete may, in some embodiments and applications, have the interior of the mold vibrated by an internal or external vibrator for up to 120 seconds. Dry cast concrete may be formed by a combination of pressing / compression and vibration. Self-compacting concrete may not require internal or external vibration. The cast concrete may be dry cast concrete or wet cast concrete. For example, steel, FRP or other types of concrete reinforcement may be placed in the mold prior to pouring to reinforce the concrete.

[0109] (Pretreatment) Prior to a given carbonation activation treatment, the concrete product (P) may be subjected to a pretreatment. Pretreatment is optional and depends on the type of concrete (conventional or slag-based), the type of concrete product (dry cast or wet cast) and the mix proportions. Under certain conditions, pretreatment is not necessary. The pretreatment step reduces the moisture content of the concrete to a ratio of water to second binder by weight before the CO2 hardening. In some embodiments, the pretreatment step may be performed either before or after demolding.

[0110] In some pretreatments of the demolded concrete product (P) (de-mold), and depending on the method and / or materials used to produce a given concrete product (P), after demolding, the concrete product (P) may begin to lose its moisture content, resulting in excess voids within the concrete. The evaporation rate of demolded concrete depends on the temperature, relative humidity, initial moisture content, surface area of ​​the product, and air flow if the mold is exposed to wind. In addition to natural evaporation, in preferred embodiments, one or a combination of the following evaporation and / or heating devices may be used to accelerate the evaporation rate: heating elements, drum heaters, floor heating mats, fans, heaters, blowers or fan heaters.

[0111] Heating appliances (e.g. elements / wires or underfloor heating mats or drum heaters) may be installed to cover the exterior or interior surface of the demolded concrete product (P). The elements may heat the demolded concrete walls and accelerate the evaporation process to reduce the moisture content of the concrete. Fans, heaters, fan heaters and blowers may be placed inside the hollow demolded concrete product (P) (to reduce the moisture content from the inside) or in front of the exterior surface (to reduce the moisture content from the outside).

[0112] These pretreatment steps may continue until the initial water to binder ratio by weight is reduced by up to 95%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, or 1%. Any of the above pretreatment methods for concrete may result in an increase in porosity, defined by volume, in the demolded concrete of 90%, 60%, 50%, 40%, 30%, 20%, 10%, 5%, or 0.1% of the concrete volume. Note that the water to binder ratio of the pretreated concrete may be less than the water to binder ratio of the first binder by weight.

[0113] The pretreatment of the concrete inside the mould may take place before a given concrete product (P) is demolded. In this case, the concrete product (P) may be pretreated and / or set inside the mould before being demolded. For example, in the case of wet cast concrete and self-compacting concrete, if pretreatment is required, it may be preferred that the concrete is pretreated and / or set inside the mould.

[0114] The mold may be kept at room temperature and humidity to allow the free water to evaporate gradually. This may allow partial or complete hydration and hardening of the binder. The rate of hydration and hardening may depend on the type of binder, its chemical composition and the mix proportions of the concrete. Fans, heaters, fan heaters, blowers, heating elements / wires, floor heating mats or drum heaters may be utilized to facilitate pre-conditioning and hardening of the concrete while it remains inside the mold. In another embodiment, the concrete product (P) may remain inside the mold to harden completely or partially without performing any of the pre-conditioning methods described above. In another embodiment, some of the pre-conditioning steps may be performed inside the mold and the remaining parts may be performed outside the mold.

[0115] (Demolding) The concrete product (P) may be demolded immediately after casting or may be allowed to set / pre-treat / hydrate in the mold, for example for up to 7 days, before demolding. In another example, the concrete may be demolded immediately after casting and subjected to carbonation hardening. Demolding may be performed, in certain embodiments, when the compressive strength of the concrete is 0.01 MPa or greater. These specific measurements and properties are non-limiting examples only.

[0116] (Curing / carbonation method) With the systems 100 to 900 described herein in mind, a method for hardening a concrete product (P) will now be described. A non-limiting example of a method of the present technology, method 1000, is shown in FIG.

[0117] In one particular embodiment of the method for curing a precast concrete product (P), the demolded concrete product is sealed from the bottom and top, or sides, such as by using the base(s) 102, cover plate(s) 108, seal(s) 104, 106, and / or the above-mentioned injection assembly(s) 502. As mentioned above, in some embodiments, the sealing may be done by rubber gaskets 106, sealers 504, epoxies 504, O-rings 106, or any other known sealing method in the prior art. This may limit or at least substantially prevent CO2 from escaping from the cavity (C) of the concrete product (P). In another example, the bottom sealer / seal 104 may be placed in the mold prior to casting the concrete product (P), and the concrete product (P) may be cured according to one or more methods described herein while at least partially in the mold. In an example where only the weight of the cover plate 108 is used to seal the top of the concrete product (P), the cover plate 108 can apply pressure to the top seal(s) 106 to ensure minimal CO2 leakage from the top end of the concrete product (P).

[0118] The weight of the cover plate(s) 108 can be selected so as not to crack or damage the concrete product (P). The weight and thickness of the cover plate(s) 108 may be selected to be greater than the force applied to keep the cover plate(s) 108 in place. In some embodiments, the thickness of the cover plate(s) 108 may be greater than 1 mm. In some embodiments, the cover plate(s) 108 may be made of steel, iron, stainless steel, FRP, plastic, or aluminum. Depending on which of the above systems 100 to 900 is used, the cover plate(s) 108 may or may not be connected in any way to the base 102 and thus may simply rest on the concrete product (P) and cover the cavity (C). As mentioned above, in some such embodiments, the cover plate(s) 108 includes at least one opening that is connected to one or more CO2 sources 110 via one or more CO2 conduits 110P. In some embodiments, the diameter of each such opening may be between about 1 mm and 500 mm. These specific measurements and characteristics are non-limiting examples only.

[0119] CO2 may be introduced in pure form or as part of a suitable gas, such as an inert gas, through opening(s) in cover plate(s) 108 and / or through CO2 conduit(s) 110P. One non-limiting example is that a gas containing CO2 that may be introduced into cavity (C) to harden the optionally pretreated concrete product (P) may be introduced at ambient temperature, for example, at a concentration of 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 99.5% CO2 by weight.

[0120] CO 2 may be injected to fill the internal cavity (C) of the concrete product (P). In some such embodiments, CO 2may be injected to fill the cavity (C) to atmospheric pressure or one or more pressures above atmospheric pressure. In some embodiments, the internal pressure may be monitored with a pressure gauge 112 mounted on the cover plate(s) 108. As noted above, in some embodiments, the internal pressure may be monitored and controlled using pressure sensor(s) 112 mounted on the cover plate(s) 108 via a controller and flow control valve(s) 114.

[0121] In some embodiments, the concrete product (P) may be carbonated under CO2 gas for a period of time between, for example, 5 minutes and 15 minutes, depending on, for example, the concentration of CO2. In some embodiments, the CO2 curing process may continue for up to 72 hours. These specific measurements and properties are non-limiting examples only.

[0122] In some embodiments of the concrete product (P), no external energy or heat may be required during the carbonation hardening process. The CO2 activation step may be an exothermic reaction that increases the temperature of the concrete product (P).

[0123] In some embodiments, the carbonation hardening process may be carried out at atmospheric pressure, or under constant carbon dioxide pressure, above atmospheric pressure, or under various gas pressures during the activation process. In some embodiments, the carbonation hardening process may be carried out either at variable carbon dioxide pressure. For example, in some embodiments, the initial pressure of CO2 in the cavity (C) may be from 0 to 10 psig for, for example, 5 to 15 minutes, depending on the particular composition of the concrete product (P).

[0124] The pressure of the CO2 in the cavity (C) may then be gradually increased over time to one or more higher pressures. Such an initial low pressure approach may help reduce the porosity of the concrete without causing significant leakage. In some cases, higher carbon dioxide pressures may be applied as calcium carbonate and other carbonation reaction products are produced and partially fill the pores in the concrete. Such an approach may help in rapid early strength development of the concrete product (P) and may help reduce leakage.

[0125] In some embodiments, at each pressure increment, the carbonation cure may continue for at least 5 minutes. This spacing approach helps prevent carbon dioxide from escaping through the outer layer of the product and may also help protect the integrity of the concrete product (P) at an early stage. In some embodiments, the pressure of the CO2 / gas in the cavity (C) may be reduced at the end of the carbonation activation step to minimize the amount of carbon dioxide remaining in the cavity (C) before the cavity (C) is unsealed. In some embodiments, the remaining gas may be vented to the atmosphere at the end of the curing step or recycled. In some embodiments, the recycling step(s) may be performed without reducing the gas pressure. This recycled gas may be used for the next batch production.

[0126] The applied pressure of the gas in the cavity (C) may vary from atmospheric pressure to, for example, 100 psig, depending on the wall thickness, porosity, maturity of the concrete, concrete mix proportions, shape, and concrete components of the concrete product (P), and / or the sealing method used to seal the cavity (C). In some embodiments, the cavity (C) may not be completely airtight. Some of the injected gas may escape from the edge of the product or may penetrate completely through the wall thickness and eventually escape from the outer layer of the concrete product (P).

[0127] In some embodiments, once the target strength of the concrete product (P) (and / or other target specification(s), e.g., as set forth in “The cured concrete product (P) should satisfy the minimum standard requirement described in ASTM / ACI / CSA / NBC, as may be applicable for one or more intended uses”) is achieved, the supply of CO2 gas to the cavity (C) may be shut off, such as via the flow control valve(s) 114 described above, the remaining gas in the cavity (C) may be recycled or simply vented to the atmosphere, the cavity (C) may be opened, such as by moving the cover plate(s) 108 to the open position 306O as described above, the CO2 conduit(s) 110P may be removed from the wall of the concrete product (P) (if inserted therein as described above), and the hardened concrete product (P) may then be removed from any used system 100, 200, 300, 400, 500.

[0128] In some embodiments where the system is used with hinged and / or fixed cover plates 108, the hinged and / or fixed may help reduce the effort required to operate the system and / or help reduce the weight of the cover plates 108 required, respectively. In embodiments where an automated jacking / moving / lifting system is not used to move the cover plate(s) 108 between the closed and open positions (306C, 306O), as described above with respect to the system 200, the cover plate(s) 108 may be lifted or otherwise moved between the closed and open positions (306C, 306O) by a crane, forklift, or other suitable equipment. The same or similar suitable equipment may be used to remove the hardened concrete product (P) from the system 100, 200, 300, 400, 500.

[0129] After the hardened concrete product (P) is removed, the system 100, 200, 300, 400, 500 may then be ready to accept a new precast concrete product (P) into the system for curing using one or more of the methods described above. In methods where one or more CO2 conduit(s) 110P are inserted through the wall(s) of the precast concrete product (P), after the precast concrete product (P) has cured / carbonated and the CO2 conduit(s) 110P have been removed from the wall, the opening(s) remaining in the concrete product (P) after curing can be filled with a suitable material, such as by filling with cement paste, grout, concrete, mortar, polymer or epoxy.

[0130] 14, yet another method 1100 for curing a concrete product (P) having a cavity (C) therein is shown. The method 1100 may include disposing at least one container (e.g., 604) containing pressurized carbon dioxide (CO2) gas within the cavity (C), sealing the cavity (C), introducing CO2 from the at least one container into the cavity (C) to effect carbonation of the concrete product, and unsealing the cavity (C) in response to the concrete product reaching a target strength (and / or other target specification(s)).

[0131] In some embodiments of the method 1100, the step of introducing the CO2 into the cavity (C) may include pressurizing the cavity (C) to a first pressure for a first time and then increasing the pressure in the cavity (C) to a second pressure for a second time. In some embodiments of the method 1100, the at least one container may include at least one of a tire tube and a tire. In some embodiments of the method 1100, introducing the CO2 into the cavity (C) may include operating at least one valve fluidly connected to at least one of the tire tube and the tire. In some embodiments of the method 1100, sealing the cavity may be performed with a cover plate, such as a suitable one of the cover plates described above, and may further include balancing the first and second pressures with the cover plate such that the cover plate continues to seal the opening while the first and second pressures are present. In some embodiments of the method 1100, the method 1100 may include pouring and demolding the concrete product before sealing the cavity, and the step of introducing CO2 may be performed after the step of demolding and close in time to the step of demolding. In some embodiments of the method 1100, the step of introducing CO2 may be performed immediately after the step of demolding.

[0132] In some embodiments of the method 1100, the method 1100 may also include performing at least one of a setting, hydration, and pretreatment step on the concrete product prior to the step of introducing the CO2. In some embodiments of the method 1100, the method 1100 may also include hydrating the concrete product after completion of the step of introducing the CO2. In some embodiments of the method 1100, the method 1100 may also include pressurizing the cavity to a predetermined pressure of CO2. In some embodiments of the method 1100, the method 1100 may also include varying the predetermined pressure of CO2. In some embodiments of the method 1100, the predetermined pressure may be equal to or greater than atmospheric pressure. In some embodiments of the method 1100, the method 1100 may also include sizing the at least one container to occupy between 10% and 98% of the volume of the cavity. In some embodiments of the method 1100, at least one of the tire tube and the tire may be pre-used (i.e., a previously used product, thereby allowing for a reduced footprint of the method 1100 on the environment). In some embodiments of the method 1100, casting of the product (P) may be performed as one of dry casting and wet casting. In some embodiments of the method 1100, introducing CO2 may be performed by introducing a gas containing CO2 at a concentration of 5% to 99.5% CO2 by weight.

[0133] 11, a method 1200 of curing a concrete product (P) is also provided, the method including the steps of: surrounding an outer surface of the concrete product (P) with a sleeve 902 having a shape that at least partially conforms to the outer surface (OS) of the concrete product (P), the sleeve 902 being positioned proximate to the outer surface (OS), also as shown in FIG. 11, to define a space 908 between the outer surface (OS) and the sleeve 902; sealing the space 908 between the outer surface (OS) and the sleeve 902; and introducing CO2 into the space 908 between the outer surface (OS) and the sleeve 902 to perform carbonation of the concrete product (P). As shown, in some embodiments, the step of introducing CO2 may include at least a portion of the CO2 passing through the outer surface (OS) of the product in an inward direction (i.e., from the sleeve 902 into the concrete product (P)). In some embodiments of method 1200, the method may also include unsealing the space 908 between the outer surface (OS) and the sleeve 902 in response to the concrete product (P) achieving the target strength (and / or other target specification(s)) and, for example, removing the sleeve 902 from the concrete product (P) or removing the concrete product (P) from the sleeve 902, depending on the particular embodiment of the system 900 used to perform method 1200.

[0134] As seen in FIG. 11, in some such embodiments, the concrete product (P) includes a cavity (C) therein and an opening to the cavity (C), except that surrounding the outer surface (OS) of the concrete product (P) seals the opening (O) to the cavity (C). As seen further in FIG. 11, in some such embodiments, surrounding the outer surface (OS) of the concrete product (P) may leave the opening (O) open, for example, to facilitate the passage of CO2 through the wall of the concrete product (P). In some such embodiments, the introduction of CO2 to the space may be performed through the sleeve 902. As seen further in FIG. 11, in some such embodiments, sealing the space 908 between the outer surface (OS) and the sleeve 902 includes placing a cover plate 904 over the concrete product (P), the cover plate 904 being operably connected to the sleeve 902, for example by being pivotally connected thereto, or as another example, as described in any of the above embodiments, at least during the step of introducing CO2. As seen in FIG. 11 , in some such embodiments, the cover plate 904 may include an opening 904′ therein, which may be at least partially aligned with an opening (O) to a cavity (C) in the concrete product (P) when the cover plate 904 is placed over the concrete product (P).

[0135] The systems and methods described herein may be used to produce a concrete product (P) that may at least satisfy the minimum standard requirement(s) set forth in ASTM / ACI / CSA / NBC. The systems and methods described herein may be used to produce a concrete product (P) that may be made using one or a combination of hydraulic cement, non-hydraulic cement, slag, pozzolanic material, fly ash, silica fume, and calcium hydroxide as a binder. The above description is intended to be exemplary only, and those skilled in the art will recognize that modifications may be made to the described embodiments without departing from the scope of the present technology. For example, a given system for curing a precast concrete product (P) may have at least a partial combination of features from one or more of the above-described embodiments. Still other modifications that fall within the scope of the present technology will be apparent to those skilled in the art in light of consideration of this disclosure.

Claims

1. 1. A method of hardening a concrete article having a cavity therein, the wall of the concrete article having an opening to the cavity acting as a vessel for holding pressure, comprising: Positioning the concrete product on a base; sealing the opening with a cover plate; introducing carbon dioxide (CO2) gas into the cavity to effect carbonation of the concrete product; and unsealing the opening as the concrete product reaches target specifications; The method includes:

2. 2. The method of claim 1, wherein introducing the CO2 gas into the cavity comprises pressurizing the cavity to a first pressure for a first time period and then increasing the pressure in the cavity to a second pressure for a second time period.

3. 3. The method of claim 1 or 2, further comprising introducing CO2 gas through the cover plate and / or the concrete product.

4. 4. The method of claim 1, wherein the opening is one of an open upper end and an open lower end of the concrete product, and positioning further comprises disposing the other of the open upper end and the open lower end on the base so as to enclose the other of the open upper end and the open lower end.

5. The method of claim 2 , further comprising balancing the first and second pressures on the cover plate such that the cover plate continues to seal the opening while the first and second pressures are present.

6. 6. The method of claim 1, further comprising pouring and demolding the concrete product prior to positioning the concrete product, and wherein the steps of positioning the concrete product and introducing CO2 gas are performed after and closely in time to the demolding step.

7. 6. The method according to claim 1, wherein the steps of positioning the concrete product and introducing CO2 are carried out immediately after the step of demolding.

8. 8. The method of claim 1, further comprising subjecting the concrete product to at least one of the steps of setting, hydrating, and pre-treating prior to the step of introducing CO2.

9. 9. The method of claim 1, further comprising hydrating the concrete product after completing the step of introducing the CO2 gas.

10. 10. The method of any one of claims 1 to 9, further comprising pressurizing the cavity to a predetermined pressure of CO2 gas.

11. 11. The method of claim 10, further comprising varying the predetermined pressure of the CO2 gas.

12. 12. The method of any one of claims 1 to 11, further comprising sealing the opening to allow at least a portion of the CO2 gas to escape from the cavity during carbonation of the concrete product.

13. 7. The method of claim 6, wherein the casting is carried out using one or a combination of zero slump concrete, wet concrete, self-compacting concrete, Portland cement, and slag.

14. The method of claim 6, wherein the casting is performed as one of dry casting and wet casting.

15. 15. The method according to claim 1, wherein the introduction of CO2 gas is carried out by introducing a gas containing CO2 at a CO2 concentration of 5 mass % or more and 99.5 mass % or less.

16. 1. A system for curing a precast concrete product in which a wall of the precast concrete product having a cavity therein functions as a container for holding a pressure, the cavity having an open lower end and an open upper end, the system comprising: A base large enough to receive the precast concrete product thereon and cover the lower end of the cavity; A cover plate sized to be received on the precast concrete product and to cover the upper end of the cavity; a source of carbon dioxide (CO2) gas, and a CO2 conduit fluidly connected to the CO2 source and configured to fluidly connect to the cavity; A system comprising:

17. 17. The system of claim 16, further comprising a height control system connected between the base and the cover plate and operable to move the cover plate between a closed position, in which the cover plate covers a top end of the cavity, and an open position.

18. 18. The system of claim 16 or 17, further comprising a frame connected between the base and the cover plate, the cover plate being hinged to the frame for movement between a closed position in which the cover plate covers a top end of the cavity and an open position.

19. 19. A system according to any one of claims 16 to 18, comprising: A CO2 conduit fluidly connects to the cavity through one or more of the cover plate, the wall of the precast concrete article, and the base; and The system, wherein the source of CO2 gas is configured to pressurize the cavity to at least two different pressures above atmospheric pressure.

20. 20. The system of claim 16, wherein a flow control valve is disposed in fluid communication with the CO2 source, the flow control valve configured to control the rate and / or pressure of CO2 gas supplied into the cavity.

21. 1. A method of hardening a concrete product having a cavity therein, the walls of the concrete product acting as a vessel for holding a pressure, comprising the steps of: sealing the cavity; Carrying out carbonation of the concrete product by introducing carbon dioxide (CO2) gas into the sealed cavity; and unsealing the cavity in response to the concrete product reaching a target specification; The method includes:

22. 22. The method of claim 21, further comprising disposing at least one container in the cavity prior to sealing the cavity, the at least one container containing pressurized CO2 gas therein, and wherein introducing the CO2 gas into the cavity comprises releasing the CO2 gas from the at least one container into the cavity.

23. 23. The method of claim 21 or 22, wherein introducing the CO2 gas into the cavity comprises pressurizing the cavity to a first pressure for a first time period, and then increasing the pressure in the cavity to a second pressure for a second time period.

24. A method as described in claim 22 or 23, comprising disposing at least one container in the cavity prior to sealing the cavity, wherein the at least one container disposed in the cavity comprises at least one of a tire tube and a tire, and introducing CO2 gas into the cavity comprises operating at least one valve fluidly connected to at least one of the tire tube and the tire.

25. 25. The method of any one of claims 21 to 24, wherein sealing the cavity further comprises using a cover plate, the cover plate being one or more of: weighted to counterbalance the pressure of the CO2 gas; hinged to a member located proximate to the concrete article; and guided relative to the member.

26. 26. The method of any one of claims 21 to 25, further comprising pouring and demolding the concrete product prior to sealing the cavity, and wherein the step of introducing CO2 gas is carried out after and closely in time to the step of demolding.

27. 27. The method of claim 26, wherein the step of introducing CO2 gas is performed immediately after the step of demolding.

28. 28. The method of any one of claims 21 to 27, further comprising performing at least one of the steps of setting, hydrating, and pre-treating on the concrete product prior to introducing the CO2 gas.

29. 29. The method of any one of claims 21 to 28, further comprising hydrating the concrete product after completing the step of introducing the CO2 gas.

30. 30. The method of any one of claims 21 to 29, further comprising sizing at least one container to occupy between 10% and 98% of the volume of the cavity.

31. A method for hardening a concrete article, the wall of the concrete article acting as a vessel for holding pressure, comprising the steps of: enclosing the exterior surface of the concrete product with a sleeve having a shape that at least partially conforms to the exterior surface of the concrete product, such that the sleeve is disposed proximate to but spaced from the exterior surface to define a space between the exterior surface and the sleeve; sealing a space between the outer surface and the sleeve; introducing carbon dioxide (CO2) gas into the space between the outer surface and the sleeve to effect carbonation of the concrete product, wherein at least a portion of the CO2 gas passes inwardly past the outer surface of the product; and unsealing the space between the exterior surface and the sleeve in response to the concrete product achieving a target specification; The method includes:

32. 32. The method of claim 31, wherein the concrete article includes a cavity therein and an opening to the cavity, and enclosing the exterior surface of the concrete article excludes sealing the opening.

33. 33. The method of claim 32, wherein enclosing the exterior surface of the concrete article leaves the opening open.

34. 34. The method of any one of claims 31 to 33, wherein introducing CO2 gas into the space is performed through a sleeve.

35. 35. The method of any one of claims 31 to 34, wherein sealing the space between the outer surface of the concrete product and the sleeve includes placing a cover plate over the concrete product, the cover plate being operatively connected to the sleeve at least during the step of introducing CO2 gas by one or more of: being weighted to balance the pressure of the CO2, being hinged to the sleeve, and being guided relative to the sleeve.

36. 36. The method of claim 35, wherein the cover plate includes an opening therein that at least partially aligns with the opening to the cavity of the concrete product when the cover plate is placed over the concrete product.

37. 1. A system for curing a precast concrete product in which a wall of the precast concrete product having a cavity therein functions as a container for holding a pressure, the cavity having an open lower end and an open upper end, the system comprising: A base sized to receive the precast concrete product thereon and to cover the lower end of the cavity; a sleeve sized to contain the concrete article therein, the sleeve being disposed over the base and having a lower end sealed against the base; a cover plate sized to be received over the precast concrete product and cover an upper end of the cavity, the cover plate being operatively connected to the sleeve to seal a space between the sleeve and an exterior surface of the concrete product, thereby sealing the space; and a source of carbon dioxide (CO2) gas in fluid communication with the space; A system comprising:

38. 40. The system of claim 37, wherein the CO2 gas source is fluidly connected to the space through at least one of the sleeve and the cover plate.

39. 39. A system as claimed in claim 37 or 38, wherein the cover plate is pivotally hinged to the sleeve between an open position in which the concrete article can be displaced into and out of the sleeve, and a closed position in which the cover plate seals the space between the concrete article and the sleeve.

40. 40. The system of any one of claims 37 to 39, wherein the CO2 gas source is configured to pressurize the cavity to at least two different pressures above atmospheric pressure.

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