Curing chamber for continuous curing of precast concrete products

Abstract

A system and method for curing a concrete product. A curing chamber is pressurized with a gas to a curing pressure for curing the concrete product. A molded intermediate of the concrete product is inserted into a depressurization chamber. The molded intermediate of the concrete product is transferred from the depressurization chamber into the curing chamber while the curing pressure within the curing chamber is maintained. The molded intermediate of the concrete product is cured in the curing chamber at the curing pressure. After the curing, the concrete product is removed from the curing chamber, via the depressurization chamber, while the curing pressure within the curing chamber is maintained.

Description

CURING CHAMBER FOR CONTINUOUS CURING OF PRECAST CONCRETE PRODUCTSTECHNICAL FIELD

[0001] This disclosure relates generally to concrete products and, more particularly, to systems and methods used for manufacturing precast concrete products in a substantially continuous and / or uninterrupted fashion.BACKGROUND

[0002] In manufacturing concrete products, a dry mixture, which may include a binder and aggregate, is mixed with water. The resultant intermediate typically undergoes a conditioning step in which some of the water it contains is evaporated, and a curing step, in order to obtain the final concrete product.

[0003] In the existing technology, the concrete products are cured in a batching process. Un-cured concrete products are placed inside the curing chamber, carbon dioxide or other necessary gasses are injected into the chamber, the conditions (e.g., temperature and pressure) within the curing chamber are brought to curing conditions, and, after curing has been completed, the gases are exhausted from the curing chamber and the concrete products are removed. This batch curing process, while suitable for its intended purposes, remains time-consuming and requires constant emptying and replenishing of gases within the chamber. Additionally, the curing chamber has to be continuously brought back up to curing conditions (the desired pressure and temperature suitable for curing) after each batch / cycle. In addition, filling and emptying may induce loss of gases to atmosphere, thus reducing efficiency of the curing process. Hence, improvements are sought.SUMMARY

[0004] According to one aspect, there is provided a system for curing a concrete product, comprising: a pressurized gas source providing gas; a curing chamber, the curing chamber including a gas inlet in communication with the pressurized gas source for providing the gas for curing the concrete product at a curing pressure, the curing chamber having a first access opening enclosed by an inner closure, the inner closure beingdisplaceable between an open position and a closed position, wherein the concrete product passes through the first access opening for entry into and exit from the curing chamber when the inner closure is in the open position, and the curing chamber being sealed closed when the inner closure is disposed in the closed position; a depressurization chamber in communication with the curing chamber via first access opening, the depressurization chamber having a second access opening enclosed by an outer closure, the outer closure being displaceable between an open position and a closed position, wherein the concrete product passes through the second access opening for entry into and exit from the depressurization chamber when the outer closure is in the open position, and the depressurization chamber being sealed closed when the outer closure is disposed in the closed position, the outer closure being independently operable from the inner closure, wherein the outer closure is configured to be disposed in the closed position when the inner closure is opened to provide communication between the depressurization chamber and the curing chamber while maintaining the curing pressure of the gas within the curing chamber, and the inner closure is configured to be disposed in the closed position when the outer closure is opened to provide access to the depressurization chamber while maintaining the curing chamber sealed to maintain the curing pressure of the gas within the curing chamber; and handling equipment for displacing the concrete product in and out of the curing chamber via the access opening between the depressurization chamber and the curing chamber.

[0005] The system as defined above and described herein may further include one or more of the following features, in whole or in part, and in any combination.

[0006] In an embodiment, the depressurization chamber includes an inlet depressurization chamber and an outlet depressurization chamber respectively communicating with the curing chamber via separate access openings.

[0007] In an embodiment, the access opening to the curing chamber includes a curing chamber inlet connected to the inlet depressurization chamber and a curing chamber outlet distinct from the curing chamber inlet and connected to the outlet depressurization chamber.

[0008] In an embodiment, the curing chamber inlet, the curing chamber outlet, the first access opening and the second access opening are configured to open and close sequentially.

[0009] In an embodiment, the handling equipment includes a receptacle displaceable along a track.

[0010] In an embodiment, the curing chamber is configured to be airtight during the curing of the concrete product.

[0011] In an embodiment, the maximum pressure is 14 psi.

[0012] According to another embodiment, there is provided a method for curing a concrete product, comprising: pressurizing a curing chamber with a gas to a curing pressure for curing the concrete product; inserting a molded intermediate of the concrete product into a depressurization chamber; transferring the molded intermediate of the concrete product from the depressurization chamber into the curing chamber while maintaining the curing pressure within the curing chamber; curing the molded intermediate of the concrete product in the curing chamber at or above the curing pressure; and removing, after the curing, the concrete product from the curing chamber, via the depressurization chamber, while maintaining the curing pressure within the curing chamber.

[0013] The method as defined above and described herein may further include one or more of the following features, in whole or in part, and in any combination.

[0014] In an embodiment, inserting the molded intermediate of the concrete product into the depressurization chamber further includes inserting the molded intermediate of the concrete product into an inlet depressurization chamber connected to a curing chamber inlet.

[0015] In an embodiment, removing the concrete product from the curing chamber via the depressurization chamber further includes transferring the concrete product, via a curing chamber outlet distinct from the curing chamber inlet, into an outlet depressurization chamber distinct from the inlet depressurization chamber.

[0016] In an embodiment, inserting the molded intermediate of the concrete product into the depressurization chamber includes opening an outer closure of an access opening to the depressurization chamber while an inner closure between the curing chamber and the depressurization chamber remains closed, and wherein transferring the molded intermediate from the depressurization chamber into the curing chamber includes closing the outer closure of the depressurization chamber and opening the inner closure between the depressurization chamber and the curing chamber.

[0017] In an embodiment, the method further comprises continuously injecting the gas into the curing chamber.

[0018] In an embodiment, the inserting the molded intermediate of the concrete product, the transferring the molded intermediate of the concrete product from the depressurization chamber into the curing chamber, and the removing the concrete product from the curing chamber each include using handling equipment to displace the concrete product in and out of the curing chamber.

[0019] In an embodiment, the handling equipment includes a receptacle displaceable along a track.

[0020] In an embodiment, the pressurizing the curing chamber with the gas includes pressurizing the curing chamber with the gas to a maximum pressure of 14 psi.

[0021] In a further aspect, there is provided a method for curing a concrete product, comprising: pressurizing a curing chamber with a gas to a curing pressure for curing the concrete product; inserting a molded intermediate of the concrete product into the curing chamber while maintaining the curing pressure of the gas within the curing chamber; curing the molded intermediate of the concrete product inside the curing chamberwith the gas at the curing pressure; and after the curing, removing the concrete product from the curing chamber while maintaining the curing pressure of the gas within the curing chamber.

[0022] The method as defined above and described herein may further include one or more of the following features, in whole or in part, and in any combination.

[0023] In an embodiment, the method further comprises inserting the molded intermediate of the concrete product into a depressurization chamber prior to inserting the molded intermediate of the concrete product into the curing chamber.

[0024] In an embodiment, inserting the molded intermediate of the concrete product into the depressurization chamber further includes inserting the molded intermediate of the concrete product into an inlet depressurization chamber connected to a curing chamber inlet.

[0025] In an embodiment, removing the concrete product from the curing chamber further includes transferring the concrete product, via a curing chamber outlet distinct from the curing chamber inlet, into an outlet depressurization chamber distinct from the inlet depressurization chamber

[0026] In an embodiment, the method further comprises continuously injecting the gas into the curing chamber.

[0027] Many further features and combinations thereof concerning the present improvements will appear to those skilled in the art following a reading of the instant disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Fig. 1 is a schematic view of a system used for curing and conditioning a concrete product;

[0029] Figs. 2A and 2B is schematic views of continuous curing chambers;

[0030] Fig. 3 is a flowchart illustrating steps of a method of curing a concrete product; and

[0031] Fig. 4 is a schematic representation of a controller in accordance with one embodiment.DETAILED DESCRIPTION

[0032] There remains growing interest worldwide to reduce the environmental footprint of precast concrete. Carbonation curing technology is among the most promising solutions. During carbonation curing, precast concrete hardens mainly through the so- called carbonation reaction which happens between carbon dioxide and the oxides, and / or hydroxide of calcium and / or magnesium, with the existence of water. Under appropriate raw material selection, mix design and process control, carbonated precast concrete may be as strong and durable as traditional precast concrete, and suitable for a variety of applications.

[0033] Manufacturing precast concrete with carbonation curing technology or mineralization may address concerns over climate change. Under appropriate processing condition, freshly cast concrete products may achieve rapid hardening when being exposed in CCh-rich environment. This CO2 sequestration may help to mitigate the CO2 emissions associated with the construction industry. Other advantages of carbonated precast concrete may include the improvement of productivity through rapid hardening, the reduction of production cost through the replacement of ordinary Portland cement with environmental-friendly and less expensive binders such as steel slag, and so on.

[0034] The current disclosure teaches a curing chamber that can cure, via CO2, the concrete products in an uninterrupted way. In contrast with existing CO2 curing chambers, the disclosed curing chamber can cure precast products continuously. The concrete products may be loaded and unloaded in a pressurized chamber without interrupting the curing process. The curing chamber may be continuously pressurized with CO2, thereby minimizing any CO2 losses.

[0035] The process of producing CO2 cured concrete products may include mixing a composition including a binder, an aggregate, optionally an admixture and water to produce a concrete mixture; imparting a form to the concrete mixture to provide a formed intermediate; optionally conditioning the formed intermediate to obtain a conditioned intermediate; and drying and curing the conditioned intermediate with a gas containing carbon dioxide to obtain the concrete product.

[0036] Carbonated precast concrete is a composite material that is essentially composed of a binding medium within which are embedded fragments of aggregate. This composite material is hardened in an enriched CO2 environment normally at its early age. Examples of carbonated precast concrete products include concrete pipes, traffic barriers, retaining walls, modular boxes, culverts, tiles, pavers, foundations, slabs, hollow-core slabs, patio slabs, steps, curbs, concrete masonry units, cinder blocks, masonry veneers, beams, floors, columns, manholes, sewage pipes, railroad ties, and other precast concrete products.

[0037] The aggregate used in carbonated precast concrete production is typically a binary blend of coarse aggregate and fine aggregate. Coarse aggregate generally refers to aggregate with particle size larger than 4.75 mm (No. 4 sieve). Fine aggregate refers to aggregate with particle size smaller than 4.75 mm. ASTM C33 specifies the quality requirements for coarse aggregate and fine aggregate. Similar specifications are also given by local government or regulatory authority, e.g., OPSS 1002, AASHTO M6 and AASHTO M80. The decision in selecting the right type and blend of aggregate is often influenced by the experience gained in manufacturing and evaluating conventional precast concrete, and also limited by supplying availability.

[0038] Among the required quality of aggregate, the maximum size and the grading of the particles are two important parameters. It is believed to affect the material cost, workability, surface quality and void content of precast concrete. Determined by the product type, application and minimum thickness (or depth) of precast concrete, the minimum clear spacing between reinforcing bars (if applicable), and the supplying availability, the maximum allowable size of coarse aggregate is often 37.5 mm (11 / 2”). The most frequently used maximum size of coarse aggregate is 19 mm (3 / 4”) or 9.5 mm (3 / 8”). For fine aggregate, it is allowed to contain a maximum of 5% (mass) particles coarser than 4.75 mm (No. 4 sieve) by ASTM C33. About the grading of aggregate, well-graded coarse orfine aggregate is generally preferred for precast concrete production, i.e., the aggregate is preferred to have relatively consistent or fair representation from every size of particle within the specified sieve sizes. For fine aggregate, an empirical factor called fineness modulus is also chosen to represent the weighted average size and distribution of the aggregate. It is obtained by summing the accumulated percentages retained on the sievesof the standard series: Nos. 4, 8, 16, 30, 50, and 100 (with openings 4.75, 2.36, 1.18, 0.6, 0.3 and 0.15 mm), and then dividing the sum by 100. The higher the fineness modulus, the coarser is the aggregate. According to the specification of ASTM C33, the fineness modulus of fine aggregate should be 2.3-3.1.

[0039] The aggregate utilized in production of CO2 cured concrete can be normalweight or lightweight aggregates. The aggregate can be natural or manufactured or recycled aggregates; or the combination of above.

[0040] After the aggregate suitable for manufacturing carbonated precast concrete is determined, attention is turned to other raw materials of the mixture. These raw materials include binders, water and additives (e.g., chemical admixtures and minerals).

[0041] The binder(s) suitable for manufacturing carbonated precast concrete may be any or a combination of cementitious and supplementary cementitious binders, which may be termed conventional “binders”. The conventional binders are the ones commonly accepted for normal (non-carbonated) precast concrete production. These binders may include: ordinary Portland cement (OPC), high alumina cement, white cement, calcium sulfoaluminate cement, magnesium cement, hydrated lime, supplementary cementitious materials including ground granulated blast furnace slag (GGBFS), fly ash, bottom ash, and natural and calcined pozzolanic materials, and OPC blended with limestone or supplementary cementitious materials.

[0042] The binders) suitable for manufacturing carbonated precast concrete may include emerging binders, which have weak or no hydraulic activity and also have not been recognized as supplementary cementitious materials. The main characteristics of the emerging binders are low cost and low carbon footprint, because they are either derived from waste sources or manufactured with less energy consumption and CO2 emission than conventional cementitious binders. These binders include: belite cement, wollastonite, steel slag, stainless steel slags, bottom ash from municipal solid waste incineration, and so on.

[0043] The binders) suitable for manufacturing carbonated precast concrete may include any combination of conventional binders and / or emerging binders. Preferably, thebinder that is suitable for manufacturing the disclosed carbonated precast concrete contains at least 10% by weight emerging binders. More preferably, the binder that is suitable for manufacturing the disclosed carbonated precast concrete contains at least 25% by weight emerging binders. More preferably, the binder that is suitable for manufacturing the disclosed carbonated precast concrete contains at least 50% by weight emerging binders. More preferably, the binder that is suitable for manufacturing the disclosed carbonated precast concrete contains at least 75% by weight emerging binders. More preferably, the binder that is suitable for manufacturing the disclosed carbonated precast concrete contains 100% by weight emerging binders.

[0044] As shown in the examples below, steel slag may be used herein as the sole component of the binder for carbonated precast concrete production. “Steel slag” herein refers to the slag by-product produced from making steel. Steel slag may include slag produced from Basic Oxygen Furnaces (BOF), also known as slag from the Linz-Donawitz (LD) process, or LD slag. Steel slag may also include slag produced from Electric Arc Furnaces (EAF). Steel slag as used herein may further include ladle slag, which is produced as a by-product from a ladle refining operation. Steel slag as used herein may further include stainless steel slag generated from stainless steel production, which is mainly generated from the argon oxygen decarburization (AOD) and / or ladle metallurgy (LM) process. In addition, steel slag can be a combination of above slags. For example, hybrid slags as used herein refers to EAF-BOF Hybrid, which is a type of steel slag formed of a mixture of EAF and BOF produced slags.

[0045] In one embodiment, the steel slag used herein has a cumulative calcium silicate content (ex: CS + C2S + C3S phase concentration) of at least about 15% by weight. In one embodiment, the steel slag used herein has a cumulative calcium silicate content (ex: CS + C2S + C3S phase concentration) of at least about 20% by weight. In one embodiment, the steel slag used herein has a cumulative calcium silicate content (ex: CS + C2S + C3S phase concentration) of at least about 30% by weight. In one embodiment, the steel slag used herein has a cumulative calcium silicate content (ex: CS + C2S + C3S phase concentration) of at least about 40% by weight. In one embodiment, the steel slag used herein has a SiC>2 content of at least about 6% or more preferably at least about 15% by weight.

[0046] The steel slag may include a mixture of coarse slag pieces and fine slag pieces. Coarse slag pieces may have a Blaine fineness less than about 50 m2 / kg and fine slag pieces may have a Blaine fineness greater than about 50 m2 / kg. The coarse slag pieces, the fine slag pieces, or both may be land-filled as an outcome from typical steel making process. Received steel slag originating from waste (such as land-fill and / or industrial waste) may optionally be refined. Refining the steel slag may include filtering the received steel slag to separate fine slag pieces from coarse slag pieces. Alternatively, or additionally, refining the received steel slag may also include pulverizing the steel slag to a fine powder. In some exemplary embodiments, the filtered fine pieces are pulverized while coarser pieces are not pulverized. For example, for EAF steel slag, the slag may be pulverized to a Blaine fineness of at least 50 m2 / kg, and preferably about 180 m2 / kg. For example, for hybrid slag steel slag (mix of EAF and BOF and ladle slag), the slag may be pulverized to a Blaine fineness of at least 100 m2 / kg and preferably about 240 m2 / kg. In other exemplary embodiments, the steel slag may be pulverized to a finer size. In another example, at least fifty percent of ground slag may be smaller than 100 microns, and at least ten percent of ground slag may be smallerthan 50 microns, i.e., D(50) < 100 microns, and D(10) < 50 microns.

[0047] It will be understood that “steel slag” as used herein excludes iron slag and blast furnace slag that are typically generated during iron production and that may be used in making cement, such as pozzolanic slag.

[0048] Any potable water may be suitable for the production of the disclosed carbonated precast concrete. The addition amount of water should be controlled to the minimum value for a desired workability of concrete mixture, for the considerations of reducing conditioning time and also achieving the desired concrete density with the available manufacturing tools.

[0049] Additives that are suitable for manufacturing carbonated precast concrete include any or a combination of the following: air entraining admixture, water reducing admixture, water repellent admixture, accelerating admixture, retarding admixture, rheology modifier, efflorescence control admixture, foaming agent, alkali silica reaction inhibitor, shrinkage reducer, corrosion inhibiting admixture, pigment, mineral admixture,reinforcing fiber, polymer, and so on. The dosages of the additives used to manufacture the carbonated precast concrete may vary, for instance depending on the manufacturing process or operational parameters of carbon curing systems. In one example, the dosage ofthe water reducer admixture may be 1 % of weight of the binder. Other percentages may be contemplated.

[0050] In some embodiments, the composition may include one or more chemical admixture and / or one or more mineral. The chemical admixture may include an accelerator, a retarder, a viscosity modifying agent, an air entertainer, a foaming agent, an alkali silica reaction inhibitor, an anti-wash-out, a corrosion inhibitor, a shrinkage reducer, a concrete crack reducer, a plasticizer, a super plasticizer, a sealer, a paint, a coating, a water reducer, a water repellant, an efflorescence controller, a polymer powder, a polymer latex, and a workability retainer. In at least some embodiments, the composition may be mixed with one or more of cellulose fibers, glass fibers, micro synthetic fibers, natural fibers, polypropylene fibers, polyvinyl alcohol fibers, and steel fibers.

[0051] In some embodiments, the production of a concrete mixture includes mixing water, the aggregate (such as described above), and the binder (such as described above) including steel slag.

[0052] In at least some embodiments, the mixing of the binder, the aggregate, and the water to produce the concrete mixture may provide a wet mixture having a mixture water- to-binder ratio. The mixing of the binder, the aggregate, and the water to produce the concrete mixture may include a dry (or dryer) mixture having a different mixture water-to- binder ratio. The binder content in the mixture may vary from 8% to 50%, depending on the bindertype and / orthe contemplated application of carbonated precast concrete. There are many suitable ways to perform the mixing of the concrete mixture, for example with a pan mixer.

[0053] The moisture content of the concrete mixture may be reduced from high moisture content to the optimum moisture content, and may even go below the optimum moisture content required for the carbonation reaction. In some embodiments, the mixing of the binder, the aggregate, and the water includes mixing the binder, the aggregate, and the water to obtain a water-to-binder ratio of from 0.10 to 0.5.

[0054] The presence of carbon dioxide inside the chamber / enclosed environment / vessel during the concurrent conditioning and curing process (described hereinafter) may result in a calcium carbonate precipitation that may improve strength development in concrete products.

[0055] After a homogeneous mixture with a desired workability is obtained following the step of mixing the binder, aggregate, and water, the mixture may be emptied from the mixer and then transported to the molding place.

[0056] A molded intermediate may be obtained by imparting a form to the concrete mixture before any curing phases. Imparting a form to the concrete mixture may require an amount of the mixture to be cast into a mold with pre-set dimensions and shape, followed with being leveled. The freshly prepared concrete mixture may be transferred into the mold by any appropriate means. In some embodiments, the production method includes inserting a reinforcing material inside the mold before the casting / forming of the concrete mixture. The reinforcing material may be defined by or include bars or rods that are made at least partially, or entirely, of one or more of carbon steel, stainless steel, and fiber reinforced polymer. The reinforcing material could have other shapes, such as pellets, beads, etc.

[0057] The forming may be obtained by casting the concrete mixture in a mold to provide the formed intermediate. The concrete mixture may be formed and consolidated under compaction and / or vibration to provide the formed intermediate. Consolidation is performed to condense precast concrete mixture in the mold to the required thickness or height. Consolidation may be achieved through the known ways, such as any or a combination of vibration, compaction and compression.

[0058] If using a wet mix, it may be consolidated within the mold by internal or external vibrators. In some cases, the consolidation step lasts no more than 120 seconds. Dry cast concrete may be compacted / pressed / pressurized / formed into the mold by compaction and or vibration. The imparting of the form may include casting the concrete mixture in a shape of a precast, a concrete pipe, a box culvert, a draining product, a paving slab, a floor slab, a traffic barrier, a wall manhole, a retaining wall, a paver, a tile, or a shingle.

[0059] The mold may be made of steel, iron, aluminum, and plastic, FRP or another material. The mold may be pre-lubricated prior to casting in order to facilitate the demolding process.

[0060] Once the molded intermediate is shaped, it can be demolded. In some cases, the formed intermediate may require to be maintained in the mold for a period of generally less than 24 hours. This may define a conditioning of the formed intermediate, or referred to as a pre-curing or pre-conditioning step of the formed intermediate. This process may help the formed intermediate to obtain sufficient green strength before being demolded. Such pre-curing step may happen when, for example, a wet concrete mixture is used for forming the formed intermediate. Such pre-curing, if required, may be conducted at room temperature. It can also be accelerated at elevated temperature.

[0061] The pre-conditioning of the formed intermediate may be performed until a water-to-binder ratio, which may correspond to an initial or first water-to-binder ratio after imparting the form to the formed intermediate, reaches a second water-to-binder ratio lower than the first water-to-binder ratio. After such a pre-conditioning step of the formed intermediate, the conditioned, formed, intermediate may be demolded to provide a demolded conditioned intermediate. This demolded conditioned intermediate may then go through a carbon curing step.

[0062] In some embodiments, a carbon curing of the formed intermediate may be performed on the formed intermediate while the formed intermediate is still in the mold. Alternatively, the carbon curing may be performed on the demolded intermediate. More than one carbon curing step may be contemplated, such as one performed while the formed intermediate is still in the mold, and a subsequent carbon curing step on the demolded intermediate in a partially cured state. In at least some embodiments, the production method may include demolding the formed intermediate before any carbon curing.

[0063] A conditioning step may be performed so as to reduce the moisture within the consolidated precast concrete or formed intermediate (whether pre-conditioned or not). During this step, water may evaporate from the consolidated precast concrete or formed intermediate so as to reduce the moisture content thereof. The released moisture leavesnumerous pores inside the consolidated precast concrete or formed intermediate, which may allow to achieve a desired CO2 uptake and a uniform carbonation throughout the whole consolidated precast concrete or formed intermediate. In an embodiment, the conditioning step may start when the consolidated precast concrete remains in the mold. It may alternatively occur after it has been demolded. This conditioning step is optional. It may be conducted at room conditions with a temperature of 15-28 °C and a relative humidity of 20-60%. In some embodiments, the conditioning step may be assisted with a forced air circulation, such as by a blower. Other known ways of reducing the moisture, e.g. heat, can be alternatively used during the conditioning step. Alternatively, no forced air circulation may be used during the conditioning step, if energy saving is preferred and / or a longertime for conditioning is acceptable. In some embodiments, the conditioning of the formed intermediate includes conditioning the formed intermediate at a temperature ranging from 15 degrees C to 28 degrees C and with a relative humidity ranging from 30% to 60%. In some embodiments, the conditioning of the formed intermediate includes conditioning the formed intermediate until from 20% to 80% by weight of the water is evaporated. In some embodiments, the conditioning of the formed intermediate includes exposing the formed intermediate to a forced air flow.

[0064] The duration of the conditioning step may be influenced by multiple factors. For example, a desired moisture content or desired moisture loss from the consolidated precast concrete before carbon curing occurs. This may be affected by dimensions of the consolidated precast concrete, its geometry, its volume, and / or initial water-to-binder ratio of he consolidated precast concrete, as some possibilities. For example, in some cases, for a precast concrete with a thickness of 30 mm or greater, an initial water loss of 20-80% (by mass) may be required for a conditioned precast concrete to achieve satisfactory CO2 uptake and strength as well as 100% CO2 penetration, if carbonation curing is required to be completed in hours instead of days.

[0065] The degree of CO2 penetration may be visually determined by spraying phenolphthalein indicator onto the whole cross section of carbonated precast concrete (i.e., after carbon curing), via destructive testing (e.g., compressive strength). The percentage of the area without pink color against the whole cross area is estimated as degree of CO2 penetration. For example, a 100% CO2 penetration is obtained if no pinkcolor is observed in the tested cross section area, while a 50% CO2 penetration is obtained if pink color occupies a half of the tested cross section area.

[0066] After the conditioning step, the conditioned precast concrete goes through the carbon curing step. A carbon curing is performed to obtain the concrete product. In some embodiments, the carbonation reaction between calcium-rich materials and carbon dioxide occurs once calcium leached from the material and CO2 are dissolved in water. In a concrete sample, the carbonation reaction generally happens at a specified pore saturation. Once the pores are filled with water and the saturation rate is at or near 100%, there is little to no carbonation reaction. This observation is also valid when there is no water in the pore, or where the pore saturation is zero percent. The optimum pore saturation, or in simpler terms, the moisture content of the mix, results in the highest carbonation reaction rate. Diverging from the optimum moisture content may lead to a lower carbonation reaction and lower concrete performance.

[0067] Carbon dioxide gas, which may have a purity ranging from 5% to 99.9% may be used for carbonated precast concrete production. The pressure of carbon dioxide gas may be adjusted to from 0 MPa to 0.827 MPa (0-120 psi) during the carbonation curing process which may last from 5 minutes up to 240 hours at around 20-80 degrees C temperature and 20-90% relative humidity.

[0068] Carbonation curing may be carried out in a sealed enclosure with CO2 introduced either as a steady gas or as a continuously-circulated gas.

[0069] As described above, in some cases, a carbon curing step may be performed on the conditioned intermediate, either formed and still in the mold or demolded. In some embodiments, the mineralization process (i.e., the carbonation process) of the conditioned intermediate includes exposing the formed intermediate to the gas containing carbon dioxide at a pressure ranging from 0 psi to 120 psi. In some embodiments, the curing of the conditioned intermediate includes curing the conditioned intermediate for from 5 minutes to 240 hours. In some embodiments, the curing of the conditioned intermediate includes curing the conditioned intermediate at a temperature ranging from 20 degrees C to 80 degrees C. In some embodiments, the curing of the conditioned intermediate includes curing the conditioned intermediate at a relative humidity ranging from 10% to90%. In other embodiments, the conditioned intermediate is cured at a relative humidity of from 30% to 90%.

[0070] For carbonated precast concrete made of binders with hydraulic activity such as OPC, hydration curing may optionally be implemented to help carbonated precast concrete achieving full strength. During the hydration curing, carbonated precast concrete products are stored in humid environment for 1 day or longer following the general procedure known in the industry.

[0071] The carbonated precast concrete may be moisturized. This moisturizing step may include, for example, submerging the carbonated precast concrete in water; spraying the carbonated precast concrete with water; and / or misting the carbonated precast concrete with water. In some embodiments, the carbonated precast concrete is moisturized by being soaked in tap water or water saturated with hydrated lime for a period of at most 24 hours, or by being sprinkled, sprayed and / or misted with tap water. In certain embodiments, this moisturizing is performed for period of time from 0.5 to 48 hours. The preferred moisture content increase for the moisturized carbonated precast concrete is 0.5% by weight or higher, for example at least 0.55 %, at least 0.6 %, at least 0.65 %, at least 0.7 %, or at least 0.75 %. There can be a delay of up to 24 hours between the proposed moisturizing step and the followed post-hardening treatment. Such a moisturizing step can be advantageous for carbonated precast concrete made of a binder with hydraulic activity. Optionally, water used for soaking / spraying can contain minerals / chemicals like efflorescence reducer admixture or water repellent. Alternatively, carbonated precast concrete can be surrounded by water vapour during a post-hardening treatment. Yet, in some embodiments, the steps of moisturizing and carbon curing may overlap or may occur concurrently.

[0072] The conditioning rate may be a function of a flow circulation rate within the enclosure. Flow circulation rate can vary during the concurrent conditioning and curing. For example, in some cases, the gas circulation device may be non-operational (e.g., noinducement of flow). This implies that the carbon dioxide injected inside the enclosure may remain stationary. This may be done by varying a rotational speed of the blower.

[0073] The conditioning rate may also be a function of a temperature of the flow. For example, in some cases, the gas within the enclosure may be heated, while it is in the enclosure and / or before it being injected inside the enclosure. The drying and curing processes may therefore include circulating heated gas about the formed intermediate in the enclosure. The gas within the enclosure may also be at room temperature or not heated by any external means. In other words, in at least some embodiments, the conditioning may be performed free of additional external sources of heat. Varying the temperature of the gas within the enclosure may be obtained via a heater. The heater may include one or more heating elements within the enclosure. In some alternatives, the body of the enclosure may be heated externally. For example, the body of the enclosure may be heated by external heating blanket. Other heating means may be contemplated, such as for example, heating wires, a heat exchanger, or solar power. A combination of one or two of the above conditioning methods can be implemented.

[0074] A temperature increase within the enclosure may increase the conditioning rate. A temperature decrease may decrease the conditioning rate. By varying the temperature within the enclosure, the conditioning rate may be controlled. The conditioning rate may thus be a function of, at least, the flow circulation rate and / or the temperature of the gas flowing within the enclosure.

[0075] The pressure inside the enclosure may also be a factor influencing the conditioning rate. In some embodiments, the drying and curing processes may occur at a pressure higher than ambient pressure. The enclosure may be pressurized during least part of the drying and curing processes. Pressurization of the enclosure may occur once the one or more formed intermediates are placed inside the enclosure. Pressurization may be performed immediately once the formed intermediates are placed and the enclose is sealed. The drying and curing processes could also be initiated without pressurizing the enclosure. The enclosure may be depressurized during the drying and curing processes or at the end thereof (i.e., once the carbonation curing reaches its desired effect on theformed intermediates). The drying and curing processes may be performed free of additional external sources of pressure.

[0076] The conditioning rate may also be a function of a relative humidity (RH) within the enclosure, during the drying and curing processes. An accelerated carbonation curing occurs while the relative humidity of the chamber of the enclosure is kept low. The fresh concrete products are dried or semi-dried with the help of reduced RH. Low RH can be obtained by the presence of absorbent materials and / or elevated temperature combined with air flow (e.g., with the blower) inside the enclosure for better efficiency. In embodiments where absorbent or desiccant materials, when present, may be silica gel, clay, calcium oxide, calcium chloride, molecular sieve, activated charcoal, any other industrial absorbents or a combination of any of these. The presence of the absorbent in an enclosed environment with gas circulation generated by the fan or blower) or other means) may gradually reduce the moisture content of the fresh concrete, whether the gas is heated or not. The RH inside the chamber may also be lowered using any mechanical equipment including dehumidifiers that use heating and ventilation or condensation methods for extracting water from the air.

[0077] The amount of absorbent materials required may depend on the type of material used, the total water content in the concrete products, the type of concrete products and the required or target specifications sought. The absorbent materials may be used for several cycles. The absorbent materials may be replaced by new materials after they lose their capacity for capturing moisture from the air. The absorbent materials can be placed in any position inside the chamber, or can be distributed uniformly inside the chamber.

[0078] In another embodiment, the concurrent conditioning and curing step may be executed by introducing and circulating high-temperature air, which may be compressed air. If the hot and dry air is introduced into the chamber, the utilization of absorbent materials will be optional.

[0079] In another example, the air inside the chamber may be heated by elements, heaters and other known means. If the air inside the chamber is heated up, the utilization of absorbent materials may be optional. In another embodiment, the body of the chambermay heated by external heating blanket and other known means in prior art. If the body of the chamber is heated up while the CO2 curing process is underway, the utilization of absorbent materials will be optional. A combination of one ortwo of the above conditioning methods can be implemented.

[0080] Fresh air can be introduced into the enclosure from the environment outside of the enclosure. A port may be provided to inject air through one of the walls of the enclosure. In another embodiment, fresh air may be supplied from a sub-compartment or another source (e.g., reservoir, tank, sub-chamber) that is part of the chamber or system.

[0081] Aspects of the carbonation curing will now be further described.

[0082] The demolded fresh concrete may be contacted with carbon dioxide, CO2 or a gas containing CO2 while its moisture content is reduced during the water extraction and CO2 curing process. The carbon dioxide gas introduced to cure the concrete is at 5%, preferably 10%, preferably 20%, preferably 30%, preferably 40%, preferably 50%, preferably 60%, preferably 70%, preferably 80%, preferably 90%, or preferably 99.5% purity. The gauge pressure of the gas will gradually increase to a range of 0.1 psi and optionally to 100 psi.

[0083] Carbon dioxide at a concentration being at least 5% by volume is injected in the enclosure. Other concentrations are contemplated, such as between 5% to 99% by volume. In embodiments where the enclosure is pressurized, the concrete products may be kept under conditioning and CO2 pressure for a given time limit, which may be at least 10 minutes, though the conditioning and CO2 curing process may continue for up to 240 hours.

[0084] In some embodiments, the drying rate can be varied in the presence of carbon dioxide during the concurrent conditioning and curing. Drying variation may be provided by different means such as airflow having a varying speed, temperature variation, or relative humidity variation (by one or more of a desiccant material and mechanical means).

[0085] Referring now to Fig. 1 , an exemplary system for curing a concrete product is shown at 10. The system 10 includes a source of carbon dioxide 11 , which may be areservoir or tank, pneumatically connected to an enclosure 12 via a line 13. In the embodiment shown, the system 10 includes a heater 14 for heating the carbon dioxide as it flows from the source of carbon dioxide 11 to the enclosure 12. In the present configuration, the system 10 includes a valve 15 that may be selectively opened or closed to allow or restrict the flow of carbon dioxide toward the enclosure 12.

[0086] The enclosure 12 defines an inner space or chamber 12A that is sized to accept the plurality of concrete products 16 to be cured. Certain features of the chamber 12A will be shown in Fig. 2 and discussed in further detail below. In the embodiment shown, the enclosure 12 includes top, bottom and side walls interconnected to one another in an airtight manner. In the context of the present disclosure, “airtight” implies that there is little to no leakage of gas through the enclosure 12 at a pressure differential at which the enclosure 12 is subjected to. The pressure differential corresponds to a difference between the pressure inside the enclosure 12 and an ambient pressure outside the enclosure 12. The enclosure 12 may be structurally designed to withstand a pressure differential created by a greater pressure of the carbon dioxide inside the enclosure 12 than an atmospheric pressure outside the enclosure 12. A blower 17 may be located in the chamber 12A of the enclosure 12 and is operable to generate an airflow F that may accelerate the conditioning and / or curing process.

[0087] In some embodiments, the enclosure 12 may be used to cure the concrete products 16 using a low-pressure curing. In the context of the present disclosure, the expression “low-pressure” implies pressures that exceed the ambient pressure by at most 10% of the ambient pressure. More detail about low-pressure curing are presented in United States patent application number 17 / 581 ,320 filed January 21 , 2022, the entire content of which is incorporated herein by reference.

[0088] In some embodiments, a curing pressure (i.e., the gas pressure at which the chamber 12A is to be maintained for the curing process) may be between 0.05 and 14 PSI. In these embodiments, therefore, the minimum pressure for curing is 0.05 PSI and the maximum pressure for curing is 14 PSI. Various other curing parameters may be maintained at predetermined curing levels throughout the curing procedure, such as a temperature within the chamber 12A and a relative humidity within the chamber 12A.Therefore, any one or more (or all) of these parameters within the curing chamber are maintained at or about their target curing levels, even when products are introduced into or removed from the curing chamber. As such, the curing process may be said to be substantially continuous, whereby these parameters are maintained substantially constant - even during loading and unloading of the products into and from the curing chamber.

[0089] The system 10 may further include one or more sensors 18, which may include one or more of a temperature sensor and a humidity sensor. The temperature sensor and humidity sensor 18 are operatively connected to the chamber 12A and are operable generate one or more signals indicative of a temperature and a humidity level inside the enclosure 12. A scale or balance 19 may support the enclosure 12 and is used to measure a weight variation of the concrete products 16 during the conditioning and curing phase. The balance 19 may send a signal indicative of a weight of the enclosure 12 containing the concrete products 16. More specifically, water content of the concrete products 16 is expected to evaporate during the conditioning and curing phase. The balance 19 may measures this weight variation and may be used to determine whether the conditioning and curing process is completed.

[0090] In the embodiment shown, the system 10 includes a controller 20 that may be operatively connected to the temperature and humidity sensor 18, to the balance 19, to the heater 14, to the blower 17, and to the valve 15. The controller 20 may therefore independently control the injection of carbon dioxide through the valve 15 and the actuation of the blower 17. In the embodiment shown, the controller 20 includes a computing device 400 such as the one shown and described below with reference to Fig. 4. The controller 20 may act as a data logger to save temperatures, weights, pressures, etc. data points during the conditioning and curing process. The controller 20 is operable to receive data from the temperature and humidity sensor 18 and from the balance 19; and to control operating parameters of the heater 14, the valve 15, and the blower 17. These operating parameters may include, for instance, a temperature of the heater 14, whether the valve 15 should be opened, closed, or at an intermediate position to control a flow of carbon dioxide through the valve 15, a rotational speed of the blower 17, and so on. The controller 20 may include different conditions depending on product type produced. In some embodiments, the controller 20 may be programmed to resume acuring process to assure product quality, for instance if the process is interrupted by a power outage. In some embodiments, the controller 20 may be configured to monitor process information and data points to assure repeatability of the operating conditions, as well as modulate, as a function of the of actual moisture content in the protects and / or to the different temperature and relative humidity conditions resulting from the effects of seasonality.

[0091] In the present embodiment, and as will be explained further below, the conditioning phase occurs while concrete products 16 are located inside the enclosure 12. During the conditioning phase, it is expected that water would be released from the concrete product 16. Since the enclosure 12 is closed to an environment outside the enclosure 12, it is desirable to absorb the extracted humidity from the concrete product. In the present case, a desiccant material 21 is located inside the enclosure 12 and is used to absorb excess humidity. In an alternate embodiment, the air within the enclosure may be heated to reduce its relative humidity and increase its moisture retaining capability. A combination of the desiccant material 21 and the heating of the air may be used. The desiccant material 21 may be a hygroscopic material that is used to induce or sustain a state of dryness in its vicinity. These desiccant materials may absorb water. The desiccant material 21 may, in one particular example, include silica gel. Desiccant materials may be in forms other than solid, and may work through other principles, such as chemical bonding of water molecules. Desiccant materials may include, in any combinations, activated charcoal, calcium sulfate, calcium chloride, zeolites, and so on. The desiccants materials may be adsorbent materials as opposed to absorbent material. An absorbent material would contain the water by allowing the water to penetrate through it. An absorbent material may be porous and the water may be absorbed by penetrating porosities of the absorbent material. An adsorbent material will stick to water molecules. In other words, the water will be detained by the adsorbent material by being adhered to a surface of the adsorbent material. The adsorbent material may attract moistures and hold it like a magnet on its surface. It will be understood that any means able to extract humidity from theenclosure 12 during the curing and conditioning steps may be used. For instance, a dehumidifier, an air conditioning, and any other suitable means may be used.

[0092] It is to be understood that in certain embodiments, the present method for terminating a carbonation curing process need not include or be limited to a process whereby conditioning and curing occur concurrently. For example, the present method for terminating a carbonation curing process may include an initial step of conditioning followed in time by the curing. However, in certain embodiments, the present method for terminating a carbonation curing process may include concurrently conditioning and curing the formed intermediate.

[0093] Referring now to Figs. 2A and 2B, the curing chamber 12A is shown, with previously-described elements of the curing chamber 12A and surrounding enclosure 12 omitted for clarity. As discussed above, the curing chamber 12A, also referred to as a pressure vessel or enclosed room, is under pressure (i.e., constantly filled with carbon dioxide, for instance via line 13), and it is used to cure the precast concrete products. In the shown embodiment, the curing chamber 12A is configured to minimize the quantity of carbon dioxide lost during the carbonation process, as well as the production downtime that occurs during a traditional batch curing process. The disclosed curing chamber 12A may thus be referred to as a continuous curing chamber 12A, as it is configured to perform a substantially continuous curing process of subsequent concrete products, i.e., without needing to cool, empty and refill the chamber 12A with carbon dioxide between processes.

[0094] The chamber 12A includes one or more openings 22. In the embodiment of Fig. 2A, the curing chamber 12A includes a first opening 22A (also referred to as a chamber inlet 22A) and a second opening 22B (also referred to as a chamber outlet 22B). In other cases, such as the embodiment of Fig. 2B, the chamber 12A may include a single opening 22C that functions as both an inlet and an outlet to the chamber 12A. The opening(s) 22 may include an air lock system, and the concrete products 16 are displaced in and out of the chamber 12A via the opening(s) 22. In the embodiment of Fig. 2A, the concrete products 16 may be displaced into the chamber 12A via the chamber inlet 22A and out of the chamber 12B via the chamber outlet 22B. In the embodiment of Fig. 2B, the concrete products 16 are displaced into and out of the chamber by the same opening22, namely opening 22C. These openings 22 (i.e., openings 22A, 22B, 22C, etc.) may also be referred to herein as “entryways” or more generally “access openings”.

[0095] As shown in Figs. 2A and 2B, one or more depressurization chambers 30 (also referred to as decompression chambers) are provided outside the curing chamber 12A. The depressurization chambers are located adjacent the curing chamber, and configured such that the depressurization chamber is in communication with the interior of the curing chamber via the access opening 22A, 22B, 22C of the curing chamber. In the embodiment of Fig. 2A, a first depressurization chamber 30A and a second depressurization chamber 30B are provided, and respectively disposed at the chamber inlet 22A and chamber outlet 22B. Other numbers of depressurization chambers 30 may be contemplated, for instance to correspond with the number of openings 22. In the embodiment of Fig. 2B, for example, a single depressurization chamber 30 is provided and located at the access opening 22C of the curing chamber 12A. Each depressurization chamber 30, also referred to as a decompression chamber or entry lock chamber, includes a entryway or “access opening” 32 (illustratively entryways 32A, 32B for chambers 30A, 30B respectively), which are closed by a closure that is displaceable between respective open and closed (sealed) position. The depressurization chamber therefore includes its own access opening (i.e., an outer opening) through which a concrete product passes for entry into and exit from the depressurization chamber 30, and this access opening is capable of being sealed by an outer closure. The outer closure of the depressurization chamber, which either provides access to the depressurization chamber or seals it, is independently operable from the inner closure which seals the adjoining curing chamber 12A. These two closures are configured to be operated independently, whereby one can be opened while the other remains closed, and vice versa. Thus, the inner closure between the depressurization chamber and the curing chamber can be opened, while the outer closure remains closed, to provide communication between the depressurization chamber and the curing chamber. Alternately, when the inner closure is closed, the outer closure can be opened such as to provide access to the depressurization chamber while keeping the curing chamber sealed to maintain the gas in the curing chamber. This provides an “air lock” type system.

[0096] The above-mentioned air lock system may thus coordinate the opening and closing of the various doors or closures (i.e., chamber opening(s) 22 and entryway(s) 32)so that the chamber 12A, when pressurized with carbon dioxide, is never exposed to the outside atmosphere. As such, inserting and removing the concrete products 16 to and from the chamber 12A do not cause the pressure of carbon dioxide to drop inside the chamber 12A. Stated differently, the pressure of carbon dioxide inside the chamber 12A may remain substantially constant throughout the loading, curing, and unloading processes of the concrete products 16.

[0097] The fresh concrete products 16 are first entered into a depressurization chamber 30 (illustratively the first depressurization chamber 30A) before they are moved inside the chamber 12A. The cured concrete products 16 are also entered into a depressurization chamber 30 (illustratively the second depressurization chamber 30B) before as they are removed from the chamber 12A. In another embodiment, the chamber 12A includes a single opening 22 and is coupled to a single depressurization chamber 30 that is responsible for moving concrete products both in and out of the chamber 12A. Other numbers of openings 22 and depressurization chambers may be contemplated. As discussed above, the depressurization chamber(s) 30A may allow the chamber 12A to be maintained at a pressurized state throughout subsequent curing processes, as a minimum or negligible quantity of carbon dioxide escapes from the chamber 12A during the loading and unloading of concrete products 16 from the chamber. In some embodiments, the depressurization chamber(s) 30 may be pneumatically connected to the chamber 12A so that pressurized gas in the depressurization chamber(s) may be flowed back to the chamber 12A, thereby assisting in maintaining the concentration of pressurized gas in the chamber 12A.

[0098] In the shown embodiment, handling equipment 40 is provided for displacing or transporting the concrete products 16 in and out of the depressurization chambers) 30 and chamber 12A. For instance, the handling equipment can be a finger cart, a rack handling system, an automatic guided vehicle, an unattended fork lift, or another means for transporting the concrete products 16. One or more receptacles may be provided for such transporting, and such receptables may be configured for quickly displacing in and out of the various chamber(s) 30 and chamber 12A to minimize pressure losses. In some cases, the receptacles may be configured to travel along a predetermined path, for instance a track or rail 50 passing through the chamber(s) 30 and chamber 12A. In othercases, such track or rail 50 may be omitted, and the receptacles can displace freely within the chamber 12A. In some embodiments, a same receptacle may be used to transport the concrete products 16 both in and out of the chamber 12A, for instance in a conveyer-like manner. In other embodiments, two or more receptacles may be provided, each being responsible for a single direction in or out of the chamber 12A.

[0099] In the shown case, a first receptacle 40A is provided for transporting concrete products 16 to be cured through the first entryway 32A and into the first depressurization chamber 30A. At this stage, the first entryway 32A is open and the chamber inlet 22A is closed. Then, the first entryway 32A is closed and the chamber inlet 22A is opened to avoid carbon dioxide leaking outside closed system. This may be referred to as an entry locking procedure The first receptacle 40A then transports the concrete products 16 to be cured into the chamber 12A for the curing process to begin. The first receptable 40A may then exit the chamber 12A in a similar entry locking procedure. Once the curing procedure is complete, a second receptacle 40B may enter the chamber 12A via the chamber outlet 22B, collect the cured concrete product 16, and exit the chamber 12A and second depressurization chamber 30B via entry locking procedures. Other entry and exit means may be contemplated. For instance, a same receptacle may be used to transport concrete products 16 to be cured into the chamber 12A, and then the same receptacle may recover cured concrete products and exit the chamber 12A.

[0100] As discussed above, the one or more depressurization chambers 30 may ensure that little to no carbon dioxide is lost when the concrete products 16 are placed in or removed from the chamber 12A. As such, the concrete products 16 can be carbonated under a consistent carbon dioxide concentration.

[0101] In various embodiments, the chamber 12A chamber is configured to cure the concrete products 16 under constant, controlled, and / or adjustable temperature, relative humidity, air flow, gas pressure and gas concentration. The concrete products 16 may be conditioned and cured under the same conditions. In an embodiment, the concrete products 16 are cured at ambient temperature. In another embodiment, the concrete products 16 are cured at an elevated temperature, e.g. 40 degrees Celsius. In an embodiment, the concrete products 16 are cured at a maximum pressure of about 14 psi.In another embodiment, the concrete products 16 are cured at a pressure of 10 psi or less. In an embodiment, the precast concrete units are subjected to a relative humidity of 80%. In another embodiment, the precast concrete units are subjected to a relative humidity of 50%. In another embodiment, the precast concrete units are subjected to a relative humidity of 30%. In another embodiment, the precast concrete units are subjected to the relative humidity of 10%. In an embodiment, the concrete products 16 are cured at a CO2 concentration of 99.5%. In another embodiment, the concrete products are cured at a CO2 concentration of 80%. In another embodiment, the concrete products are cured at a CO2 concentration of 60%. In another embodiment, the concrete products are cured at a CO2 concentration of 30%. In another embodiment, the concrete products are cured at a CO2 concentration of 10%.

[0102] In addition to the chamber’s 12A CO2 pressure, the filling and emptying of the curing chamber 12A may not affect the other operational parameters of the chamber 12A such as the temperature, and CO2 concentration. Efficiency may increase, as little to no CO2 escapes from the chamber 12A between production cycles. The chamber 12A is always under pressure: the cured products are removed from the chamber 12A and the fresh concrete products are introduced into the chamber 12A without interrupting the curing process. Unlike a conventional CO2 curing process, the gas containing CO2 does not need to be released to the atmosphere at the end of each curing process.

[0103] As discussed above, CO2 may constantly introduced into the chamber 12A to maintain the pressure therewithin. In another embodiment, the CO2 may be consumed by the concrete products 16, with no CO2 is injected into the system. In such an embodiment, the pressure of gas inside the chamber may be gradually reduced.

[0104] In an embodiment, the chamber 12A is configured to reduce the RH of the gas inside the chamber 12A until it reaches a desired value while the chamber 12A is under pressure. The chamber 12A may maintain the RH and temperature at desired levels while the CO2 gas is injected into the chamber 12A to maintain the pressure. The chamber 12A may be airtight during the above-mentioned drying and curing processes. In another embodiment, the RH of the gas may steadily decrease during the drying and curingprocesses. In such an embodiment, the drying and curing processes begins at a predetermined maximum RH value and ends at a predetermined minimum RH value.

[0105] As discussed above, compressed air may be introduced in a concurrent conditioning and curing step. Various means for removing moisture and reducing the humidity from the compressed air can be used. For instance, in a refrigerant dehumidifying / cooling separation step, the warm compressed air may be cooled, which allows water to condense. The water may then separated from the air once the water is condensed. Additionally or alternatively, Over-compression: In this technique the air is compressed to a higher pressure than the intended working pressure. The air is allowed to expand to the working pressure after separation. Additionally or alternatively, in a membrane drying step, the process of selective permeation of the gas components in the air is utilized to separate out the water vapor. Hollow polymer fibers with an inner coating collect the water vapor in the air; the water is collected between the fibers while the dry air passes through the fibers. Additionally or alternatively, in an absorption drying step, which is a chemical process, water vapor is bound to an absorption material such as sodium chloride or sulfuric acid. The absorbent materials can be recycled and recused or an another example it can be a single use material. Additionally or alternatively, in an adsorption drying step, moist air flows over a hygroscopic material or “desiccant” and is dried in this process. For instance, silica gel, molecular sieves and activated alumina may be used as the hygroscopic or desiccant material. The desiccant material is saturated with adsorbed water over time and needs to be regenerated regularly to maintain its drying capacity and efficiency.

[0106] In various embodiments, the removal of water and moisture from the chamber 12A during the curing process may be done at ambient temperature, or it can be done at an elevated temperature. The temperature inside the chamber 12A may be increased by any known techniques and equipment, for instance heaters and hot air blowers. Various air temperatures inside the chamber 12A during the process may be contemplated for instance 150 Celsius degrees, or 100 degrees or 50 degrees or 30 degrees.

[0107] In various embodiments, dehumidifying equipment may be located inside or outside of the chamber 12A. For instance, if the dehumidifying equipment may bedisposed outside of the chamber 12A, it can be located on top of the chamber 12A or next to the chamber 12A on the ground. In another embodiment, the dehumidifying equipment may provide dry air and remove moisture from multiple chambers 12A at the same time.

[0108] In various embodiments, the desiccant material 21 , for instance a silica gel or sodium chloride, can be placed inside the chamber 12A. Alternatively, the desiccant material 21 can be placed outside of the main body of the chamber 12A. In some embodiments, the desiccant material 21 can be in a stationery position inside the chamber 12A, for instance placed on trays in a fixed condition.

[0109] In another embodiment, the one or more desiccant materials 21 can be moving inside the chamber 12A. In such embodiments, the desiccant materials 21 can move in a horizontal direction, a vertical direction, or combinations thereof inside the chamber 12A. The desiccant materials 21 can undergo rotational movements whereby the desiccant materials 21 rotatably move inside the chamber 12A and collect moisture from various parts inside the chamber 12A. In another embodiment, the desiccant materials 21 can be placed on a conveyer belt inside the chamber 12A and be gradually moved between different positions inside the chamber. In an another embodiment, the desiccant materials 21 can be rotated in a wheel like apparatus. In this embodiment, the desiccant materials 21 are placed inside the wheel and the wheel rotates, with the diameter of the wheel varying based on the dimensions of the chamber 12A, as an example. The desiccant materials 21 may thus absorb moisture while they are rotating inside the chamber 12A.

[0110] In an embodiment, the desiccant materials 21 can be replaced and renewed during the drying and curing processes. In this embodiment, the curing process is halted, the old desiccant materials 21 are removed, and new desiccant materials 21 are placed inside the chamber 12A. In another embodiment, new desiccant materials 21 can be introduced into the system without halting the curing process. The addition of the new desiccant materials 21 can be done in a bulk through an inlet designed on the walls of the chamber 12A. Alternatively, such addition can be done in a gradual and continuous manner.

[0111] In various embodiments, a localized air system may be used. The flow rate of the localized air system may be higher than the flow rate of the air circulating inside thechamber 12A. In an embodiment, the localized airflow is two times higher than the air flow circulating inside the chamber 12A.

[0112] In various embodiments, pore saturation may be reduced during the concurrent conditioning and carbonation curing process. The fresh concrete products may be semidried with the help of reduced relative humidity. Low relative humidity (RH) inside the chamber 12A can be obtained by the presence of absorbent materials and / or elevated temperature combined with air flow (e.g., with the blower) inside the chamber 12A for improved efficiency. In some embodiments, the air flow speed generated by the blower or other suitable means may be at least 0.1 m / s. As discussed above, the absorbent or desiccant materials 21 may be silica gel, clay, calcium oxide, calcium chloride, molecular sieve, activated charcoal, any other industrial absorbents or a combination of the above. The presence of these materials in an enclosed environment with air flow generated by the fan or blower or by other means may gradually reduce the moisture content of the fresh / green concrete. The circulated air can be cold or hot. The RH inside the chamber 12A may also be lowered using any mechanical equipment including dehumidifiers that use heating and ventilation or condensation methods for extracting water from the air. The air circulation rate can vary during the concurrent conditioning and curing process.

[0113] In various embodiments, the quantity of absorbent materials required may depend on, for instance, the type of material used, the total water content in the concrete products, the type of concrete products and the required or target specifications sought. The fresh air can be introduced into the chamber 12A from outside the chamber 12A, or in another embodiment from inside the closed chamber 12A. The conditioning and CO2 curing processes may further continue to reduce the moisture content of concrete products 16 even after the carbonation reaction stops. The absorbent materials may be used for several cycles. The absorbent materials may be replaced by new materials after they lose their capacity for capturing moisture from the air. The absorbent materials can be placed in any position inside the chamber 12A, or can be distributed uniformly inside the chamber 12A.

[0114] In another embodiment, the air inside the chamber 12A may be heated by elements, heaters and other known means. In another embodiment, the body of thechamber 12A may heated by an external heating blanket. Other known heating means may be contemplated. Combinations of the above conditioning methods, i.e., dehumidifying equipment and desiccant materials 21 , may be contemplated.

[0115] In some embodiments, the drying rate can be varied in the presence of carbon dioxide during the concurrent conditioning and curing process. Drying variation may be provided by different means, for instance airflow having a varying speed, temperature variation, or relative humidity variation (i.e., by one or more of desiccant materials and mechanical means). In some embodiments, the step of concurrent conditioning and curing may be achieved without additional external source of heat.

[0116] In some embodiments, a racking system is provided structurally support the chamber 12A. The racking system may be made of steel, aluminium or any other known materials. Using the racking system to support the chamber 12A may allow the chamber to be designed with a lower wall thickness and roof elements, thereby reducing material consumption for manufacturing of the chamber 12A. This may result in a faster and cheaper production of the chamber 12A. The racking system may at least partially withstand the load created by the positive pressure building up inside the chamber 12A. In one embodiment, a plurality of boards forming the racking system are connected to the body of the chamber 12A so all boards contribute to withstanding the internal loads. In another embodiment, some of the boards participate in reducing the loads applied to the chamber’s 12A walls, while other boards are not connected to the chamber 12A. In this embodiment, the connected boards are disconnected before they are removed from the chamber 12A at the end of the curing phase. The connection between the boards of racking system to the chamber 12A can be done manually or automatically.

[0117] In various embodiment, to prevent the curing system from working continuously, or becoming interrupted by a failure of one of its components, a redundancy in one or more elements and components may be implemented. For instance, a breakdown of a component in the chamber 12A may result in an uneven distribution in the production of CO2-cured concrete. Therefore, in the design of the chamber 12A, more than one component may be provided for redundancy so that the failure of one component would not halt the process. The failed component would then be repaired during theregular maintenance period. Values, sensors and the door’s elements are among those components that require back up. Such redundancy may ensure that the production of precast concrete products continues without any undesired interruption. In addition, this redundancy may allow the conditions to remain the same in different locations of the chamber 12A.

[0118] In various embodiments, the walls of the chamber 12A may be designed and manufactured in a curved shape, for instance to reduce the required wall thickness. Some or all of the walls may assume this curved shape. In an embodiment, only the back and front walls of the chamber 12A take are curved walls, while the other walls are straight walls. In another embodiment, the back, front and top walls are curved walls, while the other walls are straight walls. The inclusion of one or more curved walls may improve the cost efficiency of the chamber 12A.

[0119] As discussed above, the handling equipment 40 (e.g., the receptacles 40A, 40B) can move freely within the chamber 12A, or may move along a track or rail 50. The handling equipment 40 may move the precast products inside the chamber 12A while the chamber 12A is under pressure and the curing of the concrete products 16 is underway. The movement of the handling equipment 40 does not hinder the operation chamber 12A or the curing of the concrete. The handling equipment 40 can remove cured products from the chamber 12A while the remaining products are cured with carbon dioxide. The handling equipment 40 can be moved along various axes. The movement of the handling equipment 40 is not affected by the pressure, and the movement of the handling equipment 40 does not affect the CO2 curing of concrete products 16. The curing process happens either when the handling equipment 40 is inside the chamber 12A or when it is out of the chamber 12A.

[0120] Referring now to Fig. 3, an exemplary method 100 for curing a concrete product 16 is shown.

[0121] At step 102, a curing chamber 12A is pressurized with gas, for instance carbon dioxide, to a curing pressure for curing the concrete product 16.

[0122] At step 104, a molded intermediate of the concrete product 16 is inserted into a depressurization chamber 30.

[0123] At step 106, the molded intermediate of the concrete product 16 is transferred from the depressurization chamber into the curing chamber 12A while maintaining the curing pressure within the curing chamber 12A.

[0124] At step 108, the molded intermediate of the concrete product 16 in the curing chamber 12A is cured at the curing pressure.

[0125] At step 110, after the curing, the concrete product 16 is removed from the curing chamber 12A, via the depressurization room 30, while maintaining the curing pressure within the curing chamber 12A.

[0126] Referring now to Fig. 4, the controller 20 operable to control at least some of the above-described methods may include a computing device 400, which may comprise a processing unit 402 and a memory 404 which has stored therein computer-executable instructions 406. The processing unit 402 may comprise, for example, any type of general- purpose microprocessor or microcontroller, a digital signal processing (DSP) processor, a central processing unit (CPU), an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, other suitably programmed or programmable logic circuits, or any combination thereof.

[0127] The memory 404 may comprise any suitable known or other machine-readable storage medium. The memory 404 may comprise non-transitory computer readable storage medium, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. The memory 404 may include a suitable combination of any type of computer memory that is located either internally or externally to device, for example random-access memory (RAM), read-only memory (ROM), compact disc readonly memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like. Memory 404 maycomprise any storage means (e.g., devices) suitable for retrievably storing machine- readable instructions 406 executable by processing unit 402.

[0128] The methods and systems for operating the system 10 described herein may be implemented in a high level procedural or object oriented programming or scripting language, or a combination thereof, to communicate with or assist in the operation of a computer system, for example the computing device 400. Alternatively, the methods and systems for operating the system 10 may be implemented in assembly or machine language. The language may be a compiled or interpreted language. Program code for implementing the methods and systems for operating the system 10 may be stored on a storage media or a device, for example a ROM, a magnetic disk, an optical disc, a flash drive, or any other suitable storage media or device. The program code may be readable by a general or special-purpose programmable computer for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein. Embodiments of the methods and systems for operating the system 10 may also be considered to be implemented by way of a non-transitory computer-readable storage medium having a computer program stored thereon. The computer program may comprise computer-readable instructions which cause a computer, or more specifically the processing unit 402 of the computing device 400, to operate in a specific and predefined manner to perform the functions described herein, for example those described in the method 200.

[0129] Computer-executable instructions may be in many forms, including program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. Typically the functionality of the program modules may be combined or distributed as desired in various embodiments.

[0130] The embodiments described herein are implemented by physical computer hardware, including computing devices, servers, receivers, transmitters, processors, memory, displays, and networks. The embodiments described herein provide useful physical machines and particularly configured computer hardware arrangements. Theembodiments described herein are directed to electronic machines and methods implemented by electronic machines adapted for processing and transforming electromagnetic signals which represent various types of information. The embodiments described herein pervasively and integrally relate to machines, and their uses; and the embodiments described herein have no meaning or practical applicability outside their use with computer hardware, machines, and various hardware components. Substituting the physical hardware particularly configured to implement various acts for non-physical hardware, using mental steps for example, may substantially affect the way the embodiments work. Such computer hardware limitations are clearly essential elements of the embodiments described herein, and they cannot be omitted or substituted for mental means without having a material effect on the operation and structure of the embodiments described herein. The computer hardware is essential to implement the various embodiments described herein and is not merely used to perform steps expeditiously and in an efficient manner.

[0131] The technical solution of embodiments may be in the form of a software product. The software product may be stored in a non-volatile or non-transitory storage medium, which can be a compact disk read-only memory (CD-ROM), a USB flash disk, or a removable hard disk. The software product includes a number of instructions that enable a computer device (personal computer, server, or network device) to execute the methods provided by the embodiments.

[0132] In the context of the present disclosure, the expression “about” provided in the context of any specific value or range of values implies variations of plus or minus 10% of the value provided. Additionally, the examples provided herein are understood to be exemplary, and not limitative. Accordingly, those skilled in the art will readily appreciate that alternatives to these examples may exist, and that variations may be possible without departing from the scope of the teachings of the present disclosure in its entirety.

[0133] The term “connected” or "coupled to" may include both direct coupling (in which two elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements).

[0134] It is further noted that various method or process steps for embodiments of the present disclosure are described herein. The description may present the method and / or process steps as a particular sequence. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the description should not be construed as a limitation.

[0135] Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0136] While various aspects of the present disclosure have been disclosed, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the present disclosure. For example, the present disclosure as described herein includes several aspects and embodiments that include particular features. Although these particular features may be described individually, it is within the scope of the present disclosure that some or all of these features may be combined with any one of the aspects and remain within the scope of the present disclosure. References to “various embodiments,” “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. The use of the indefinite article “a” as used herein with reference to a particular element is intended to encompass “one or more” such elements, and similarly the use of the definite article “the” in reference to a particular element is not intended to exclude the possibility that multiple of such elements may be present.

[0137] The embodiments described in this document provide non-limiting examples of possible implementations of the present technology. Upon review of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made to the embodiments described herein without departing from the scope of the present technology. Yet further modifications could be implemented by a person of ordinary skill in the art in view of the present disclosure, which modifications would be within the scope of the present technology.

Claims

CLAIMS:1 . A system for curing a concrete product, comprising: a pressurized gas source providing gas; a curing chamber, the curing chamber including a gas inlet in communication with the pressurized gas source for providing the gas for curing the concrete product at a curing pressure, the curing chamber having a first access opening enclosed by an inner closure, the inner closure being displaceable between an open position and a closed position, wherein the concrete product passes through the first access opening for entry into and exit from the curing chamber when the inner closure is in the open position, and the curing chamber being sealed closed when the inner closure is disposed in the closed position; a depressurization chamber in communication with the curing chamber via first access opening, the depressurization chamber having a second access opening enclosed by an outer closure, the outer closure being displaceable between an open position and a closed position, wherein the concrete product passes through the second access opening for entry into and exit from the depressurization chamber when the outer closure is in the open position, and the depressurization chamber being sealed closed when the outer closure is disposed in the closed position, the outer closure being independently operable from the inner closure, wherein the outer closure is configured to be disposed in the closed position when the inner closure is opened to provide communication between the depressurization chamber and the curing chamber while maintaining the curing pressure of the gas within the curing chamber, and the inner closure is configured to be disposed in the closed position when the outer closure is opened to provide access to the depressurization chamber while maintaining the curing chamber sealed to maintain the curing pressure of the gas within the curing chamber; andhandling equipment for displacing the concrete product in and out of the curing chamber via the access opening between the depressurization chamber and the curing chamber.

2. The system as defined in claim 1 , wherein the depressurization chamber includes an inlet depressurization chamber and an outlet depressurization chamber respectively communicating with the curing chamber via separate access openings.

3. The system as defined in claim 2, wherein the access opening to the curing chamber includes a curing chamber inlet connected to the inlet depressurization chamber and a curing chamber outlet distinct from the curing chamber inlet and connected to the outlet depressurization chamber.

4. The system as defined in claim 3, wherein the curing chamber inlet, the curing chamber outlet, the first access opening and the second access opening are configured to open and close sequentially.

5. The system as defined in any one of claims 1 to 4, wherein the handling equipment includes a receptacle displaceable along a track.

6. The system as defined in any one of claims 1 to 5, wherein the curing chamber is configured to be airtight during the curing of the concrete product.

7. The system as defined in any one of claims 1 to 6, wherein a maximum pressure is 14 psi.

8. A method for curing a concrete product, comprising: pressurizing a curing chamber with a gas to a curing pressure for curing the concrete product; inserting a molded intermediate of the concrete product into a depressurization chamber;transferring the molded intermediate of the concrete product from the depressurization chamber into the curing chamber while maintaining the curing pressure within the curing chamber; curing the molded intermediate of the concrete product in the curing chamber at the curing pressure; and removing, after the curing, the concrete product from the curing chamber, via the depressurization chamber, while maintaining the curing pressure within the curing chamber.

9. The method as defined in claim 8, wherein inserting the molded intermediate of the concrete product into the depressurization chamber further includes inserting the molded intermediate of the concrete product into an inlet depressurization chamber connected to a curing chamber inlet.

10. The method as defined in claim 9, wherein removing the concrete product from the curing chamber via the depressurization chamber further includes transferring the concrete product, via a curing chamber outlet distinct from the curing chamber inlet, into an outlet depressurization chamber distinct from the inlet depressurization chamber.11 . The method as defined in claim 10, wherein inserting the molded intermediate of the concrete product into the depressurization chamber includes opening an outer closure of an access opening to the depressurization chamber while an inner closure between the curing chamber and the depressurization chamber remains closed, and wherein transferring the molded intermediate from the depressurization chamber into the curing chamber includes closing the outer closure of the depressurization chamber and opening the inner closure between the depressurization chamber and the curing chamber.

12. The method as defined in any one of claims 8 to 1 1 , further comprising continuously injecting the gas into the curing chamber.

13. The method as defined in any one of claims 8 to 12, wherein the inserting the molded intermediate of the concrete product, the transferring the molded intermediate of the concrete product from the depressurization chamber into the curing chamber, and the removing the concrete product from the curing chamber each include using handling equipment to displace the concrete product in and out of the curing chamber.

14. The method as defined in claim 13, wherein the handling equipment includes a receptacle displaceable along a track.

15. The method as defined in any one of claims 8 to 14, wherein the pressurizing the curing chamber with the gas includes pressurizing the curing chamber with the gas to a maximum pressure of 14 psi.

16. A method for curing a concrete product, comprising: pressurizing a curing chamber with a gas to a curing pressure for curing the concrete product; inserting a molded intermediate of the concrete product into the curing chamber while maintaining the curing pressure of the gas within the curing chamber; curing the molded intermediate of the concrete product inside the curing chamber with the gas at or above the curing pressure; and after the curing, removing the concrete product from the curing chamber while maintaining the curing pressure of the gas within the curing chamber.

17. The method as defined in claim 16, further comprising inserting the molded intermediate of the concrete product into a depressurization chamber prior to inserting the molded intermediate of the concrete product into the curing chamber.

18. The method as defined in claim 17, wherein inserting the molded intermediate of the concrete product into the depressurization chamber further includes inserting the molded intermediate of the concrete product into an inlet depressurization chamber connected to a curing chamber inlet.

19. The method as defined in claim 18, wherein removing the concrete product from the curing chamber further includes transferring the concrete product, via a curing chamber outlet distinct from the curing chamber inlet, into an outlet depressurization chamber distinct from the inlet depressurization chamber.

20. The method as defined in any one of claims 16 to 19, further comprising continuously injecting the gas into the curing chamber.

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