Systems and methods for controlling a curing phase of carbonated precast concrete products

Abstract

The disclosed method for manufacturing a concrete product includes performing, in a curing chamber, a carbonation curing process on a formed intermediate of the concrete product, monitoring one or more product properties of the formed intermediate during the carbonation curing process, and terminating the carbonation curing when a detected change in the one or more product properties of the formed intermediate, or in a rate of change of the one or more product properties of the formed intermediate, reaches or exceeds a predetermined threshold value.

Description

SYSTEMS AND METHODS FOR CONTROLLING A CURING PHASE OF CARBONATED PRECAST CONCRETE PRODUCTSCROSS-REFERENCE TO RELATED APPLICATIONS[1] This application claims priority on United States Patent Application No. 63 / 578,081 filed on August 22, 2023, the entire content of which is incorporated herein by reference.TECHNICAL FIELD[2] This disclosure relates generally to concrete products and, more particularly, to systems and methods for the manufacturing of carbonation cured precast concrete products.BACKGROUND[3] The manufacturing of the carbonated precast concrete products involves various phases, such as drying and curing phases. The carbonated precast products are removed from a curing chamber after a curing phase, which may last several hours. The physical properties of the cured precast products are then be evaluated, after the curing process, to ensure that the required performance of the cured precast products is met. The drying and curing phases has a direct influence on the material properties of the carbonated precast concrete products. Postproduction performance testing using conventional testing methods may be contemplated, for instance by sampling a production run out of the curing chamber before palletizing. However, such post-production performance testing may significantly impact the production turnover time and costs, especially for large scale production.SUMMARY[4] There is accordingly provided a method of manufacturing a concrete product, the method comprising: performing, in a curing chamber, a carbonation curing process on a formed intermediate of the concrete product; monitoring one or more product properties of the formed intermediate during the carbonation curing process; and terminating the carbonation curing when a detected change in the one or more product properties of the formed intermediate, or in a rate of change of the one or more product properties of the formed intermediate, reaches or exceeds a predetermined threshold value.[5] The method as defined above and described herein may further inclusion one or more of the following steps and / or features, in whole or in part, and in any combination.[6] In certain embodiments, the monitoring includes monitoring one or more of a mechanical property, a dimension, and a chemical property of the formed intermediate during the carbonation curing process.[7] In certain embodiments, the carbonation curing process is performed as part of a simultaneous conditioning and curing process.[8] In certain embodiments, the carbonation curing process includes drying the formed intermediate prior to initiating carbonation curing of the formed intermediate.[9] In certain embodiments, the monitoring includes receiving a data signal associated with a measurement of a dimensional change of the formed intermediate during the carbonation curing process.

[0010] In certain embodiments, the dimensional change is a volume variation and / or an axial dimension variation of the formed intermediate.

[0011] In certain embodiments, the monitoring includes monitoring one or more of: a compressive strength of the formed intermediate; a vibrational property of the formed intermediate; a change in a moisture content of the formed intermediate; a change of a surface color of the formed intermediate; and a change in a thermal conductivity of the formed intermediate.

[0012] In certain embodiments, the monitoring includes measuring a change in a chemical composition of the formed intermediate, the chemical composition including one or more of: a calcium oxide content; a magnesium oxide content; a free lime content; a di calcium silicate content; a tri calcium silicate content; a calcium hydroxide content; a merwinite content; a gehlenite content; a calcium carbonate content; and a carbon content.

[0013] In certain embodiments, the monitoring includes monitoring one or more of the following parameters of the formed intermediate during the carbonation curing process: a pH; relative humidity; ultrasonic pulse velocity; and electrical resistivity.

[0014] There is also provided a system for manufacturing a concrete product, the system comprising: a curing chamber receiving therein a formed intermediate of the concrete product, the curing chamber being configured to perform a carbonation curing process of the formed concrete intermediate within the curing chamber; a controller in communication with the curingchamber, the controller including a processing unit and a non-transitory computer-readable memory communicatively coupled to the processing unit and comprising computer-readable program instructions executable by the processing unit for: during the carbonation curing process, monitoring a change in one or more product properties of the formed intermediate and / or monitoring a change in a rate of change of the one or more product properties; and causing the carbonation curing process to terminate upon receiving a signal indicative of the change in the one or more product properties or the change in the rate of change of the one or more product properties corresponding to a predetermined threshold value.

[0015] The system as defined above and described herein may further inclusion one or more of the following features, in whole or in part, and in any combination.

[0016] In certain embodiments, the computer-readable program instructions are executable by the processing unit for, during the carbonation curing process, receiving a data signal associated with a measurement of a dimensional change of the formed intermediate during the carbonation curing process, the dimensional change being a volume variation and / or an axial dimension variation of the formed intermediate.

[0017] In certain embodiments, the computer-readable program instructions are executable by the processing unit for, during the carbonation curing process, monitoring one or more of: a compressive strength of the formed intermediate; a vibrational property of the formed intermediate; monitoring a change in a moisture content of the formed intermediate; a change of a surface color of the formed intermediate; and a change in a thermal conductivity of the formed intermediate.

[0018] In certain embodiments, the computer-readable program instructions are executable by the processing unit for, during the carbonation curing process, measuring a change in a chemical composition of the formed intermediate, the chemical composition including one or more of: a calcium oxide content; a magnesium oxide content; a free lime content; a di calcium silicate content; a tri calcium silicate content; a calcium hydroxide content; a merwinite content; a gehlenite content; a calcium carbonate content; and a carbon content.

[0019] In certain embodiments, the computer-readable program instructions are executable by the processing unit for, during the carbonation curing process, monitoring one or more of the following parameters of the formed intermediate during the carbonation curing process: a pH; relative humidity; ultrasonic pulse velocity; and electrical resistivity.

[0020] There is further provided a method of manufacturing a concrete product, the method comprising: providing a composition including a binder, an aggregate, and water, wherein the binder is a steel slag; mixing the binder, the aggregate, and the water to produce a concrete mixture; imparting a form to the concrete mixture to provide a formed intermediate having a first water-to-binder ratio; conducting carbonation curing of the formed intermediate; detecting a change in one or more product properties of the formed intermediate or detecting a change in a rate of change of the one or more product properties of the formed intermediate, the one ore more product properties including a mechanical property, a dimension, and / or a chemical property of the formed intermediate; and terminating the carbonation curing when the detected change reaches or exceeds a predetermined threshold value.

[0021] The method as defined above and described herein may further inclusion one or more of the following steps and / or features, in whole or in part, and in any combination.

[0022] In certain embodiments, conducting the carbonation curing includes conditioning the formed intermediate to obtain final water-to-binder ratio less than the first water-to-binder ratio, the conditioning of the formed intermediate performed priorto or concurrently with the carbonation curing, wherein when the conditioning is performed priorto the carbonation curing the conditioning and the carbonation curing are performed in series and when the condition is performed concurrently with the carbonation curing the formed intermediate is concurrently cured and conditioned.

[0023] In certain embodiments, the detected change includes a dimensional change, the dimensional change being a volume variation and / or an axial dimension variation of the formed intermediate.

[0024] In certain embodiments, the one or more product properties includes one or more of: a compressive strength of the formed intermediate; a vibrational property of the formed intermediate; a moisture content of the formed intermediate; a surface color of the formed intermediate; a thermal conductivity of the formed intermediate; pH; relative humidity; ultrasonic pulse velocity; and electrical resistivity.

[0025] In certain embodiments, the detected change in the one or more product properties, includes a change of a chemical composition, the change in chemical composition being related to: a calcium oxide content of the formed intermediate; a magnesium oxide content; a free limecontent; a di calcium silicate content; a tricalcium silicate content; a calcium hydroxide content; a merwinite content; a gehlenite content; a calcium carbonate content; and / or a carbon content.

[0026] In certain embodiments, the carbonation curing has a carbonation curing rate and the conditioning has a conditioning rate, the carbonation curing rate positively correlated with the conditioning rate, and the conditioning rate being constant during substantially all of the concurrent conditioning and curing of the formed intermediate.

[0027] The present disclosure provides an improved approach to control the curing process based on one or more product properties of the precast concrete products, determined while they are enclosed in the curing chamber.

[0028] In accordance with one aspect, there is provided a method of manufacturing a concrete product, the method comprising: performing, in a curing chamber, a carbonation curing process on a formed intermediate of the concrete product; monitoring one or more product properties of the formed intermediate during the carbonation curing process; and terminating the carbonation curing when a detected change in the one or more product properties or in a rate of change of the one or more product properties of the formed intermediate reaches or exceeds a predetermined threshold value.

[0029] In accordance with another aspect, there is also provided a method for terminating a carbonation curing process of a formed concrete intermediate performed in a curing chamber, the method implemented via a controller including a processing unit, and a non-transitory computer- readable memory communicatively coupled to the processing unit and comprising computer- readable program instructions executable by the processing unit for: during the carbonation curing process, monitoring a change in one or more product properties of the formed intermediate and / or monitoring a change in a rate of change of the one or more product properties; and causing the carbonation curing process to terminate upon receiving a signal indicative of the change in the one or more product properties or the change in the rate of change of the one or more product properties corresponding to a predetermined threshold value.

[0030] The methods as defined above and described herein may also include one or more of the following features and / or steps, in whole or in part, and in any combination.

[0031] In certain aspects, the monitoring includes monitoring at least one of a mechanical property, a dimension, and a chemical property of the formed intermediate during the carbonation curing process.

[0032] In certain aspects, the carbonation curing process is performed as part of a simultaneous conditioning and curing process.

[0033] In certain aspects, the carbonation curing process includes drying the formed intermediate prior to initiating carbonation curing of the formed intermediate.

[0034] In certain aspects, the monitoring includes receiving a data signal associated with a measurement of a dimensional change of the formed intermediate during the carbonation curing process.

[0035] In certain aspects, the dimensional change is one of a volume variation and an axial dimension variation of the formed intermediate.

[0036] In certain aspects, the monitoring includes monitoring a compressive strength of the formed intermediate.

[0037] In certain aspects, the monitoring includes monitoring a vibrational property of the formed intermediate.

[0038] In certain aspects, the monitoring includes monitoring a change in a moisture content of the formed intermediate.

[0039] In certain aspects, the monitoring includes monitoring a change of a surface color of the formed intermediate.

[0040] In certain aspects, the monitoring includes monitoring a change in a thermal conductivity of the formed intermediate.

[0041] In certain aspects, the monitoring includes measuring a change in a chemical composition of the formed intermediate, the chemical composition including at least one of: a calcium oxide content; a magnesium oxide content; a free lime content; a di calcium silicate content; a tri calcium silicate content; a calcium hydroxide content; a merwinite content; a gehlenite content; a calcium carbonate content; and a carbon content.

[0042] In certain aspects, the monitoring includes monitoring at least one of the following parameters of the molded intermediate during the carbonation curing process: a pH; gas concentration or pressure; relative humidity; ultrasonic pulse velocity; and electrical resistivity.

[0043] There is further provided, in another aspect, a method of manufacturing a concrete product, comprising: providing a composition including a binder, an aggregate, and water; mixing the binder, the aggregate, and the water to produce a concrete mixture; imparting a form to the concrete mixture to provide a formed intermediate having a first water-to-binder ratio; conducting carbonation curing of the formed intermediate; and terminating the carbonation curing when a detected change in one or more product properties of the formed intermediate, or a detected change in a rate of change of the one or more product properties of the formed intermediate, reaches or exceeds a predetermined threshold value.

[0044] The method as defined above and described herein may also include one or more of the following features and / or steps, in whole or in part, and in any combination.

[0045] In certain aspects, conducting the carbonation curing includes conditioning the formed intermediate to obtain final water-to-binder ratio less than the first water-to-binder ratio, the conditioning of the formed intermediate performed prior to or concurrently with the carbonation curing, wherein when the conditioning is performed priorto the carbonation curing the conditioning and the carbonation curing are performed in series and when the condition is performed concurrently with the carbonation curing the formed intermediate is concurrently cured and conditioned.

[0046] In certain aspects, the detected change includes a change in at least one of: a mechanical property; a dimension; and a chemical property of the formed intermediate.

[0047] In certain aspects, the detected change includes a dimensional change.

[0048] In certain aspects, the dimensional change is at least one of a volume variation and an axial dimension variation of the formed intermediate.

[0049] In certain aspects, the one or more product properties includes a compressive strength of the formed intermediate.

[0050] In certain aspects, the one or more product properties includes a vibrational property of the formed intermediate.

[0051] In certain aspects, the one or more product properties includes a moisture content of the formed intermediate.

[0052] In certain aspects, the one or more product properties includes a surface color of the formed intermediate.

[0053] In certain aspects, the one or more product properties includes a thermal conductivity of the formed intermediate.

[0054] In certain aspects, the detected change in the one or more product properties, includes a change of a chemical composition, the change in chemical composition being related to at least one of a calcium oxide content of the formed intermediate; a magnesium oxide content; a free lime content; a di calcium silicate content; a tri calcium silicate content; a calcium hydroxide content; a merwinite content; a gehlenite content; a calcium carbonate content; and a carbon content.

[0055] In certain aspects, the one or more product properties monitored during the carbonation curing include: a pH; gas concentration or pressure; relative humidity; ultrasonic pulse velocity; and electrical resistivity.

[0056] In certain aspects, the carbonation curing has a carbonation curing rate and the conditioning as a conditioning rate, the carbonation rate positively correlated with the conditioning rate, and the conditioning rate being constant during substantially all of the concurrent condition and curing of the formed intermediate.

[0057] In certain aspects, the binder is steel slag.

[0058] In accordance with an alternate embodiment, there is also provided a method of manufacturing a concrete product, comprising: providing a composition including a binder, an aggregate, and water; mixing the binder, the aggregate, and the water to produce a concrete mixture; imparting a form to the concrete mixture to provide a formed intermediate having a first water-to-binder ratio; and concurrently conditioning and curing the formed intermediate by conditioning the formed intermediate while curing the formed intermediate, wherein the formed intermediate is concurrently cured and conditioned to obtain final water-to-binder ratio less than the first water-to-binder ratio.

[0059] In certain embodiments of this method, the curing has a carbonation curing rate and the conditioning has a conditioning rate, the carbonation rate positively correlated with the conditioning rate.

[0060] In certain embodiments of this method, the conditioning rate is constant during substantially all of the concurrent conditioning and curing of the formed intermediate.BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Fig. 1 is a schematic view of a system used for curing and conditioning a concrete product;

[0062] Figures 2 to 5 are flowcharts illustrating the steps of methods of manufacturing a concrete product, and of terminating a carbonation curing process, as defined herein; and

[0063] Fig. 6 is a schematic representation of a controller in accordance with one embodiment.DETAILED DESCRIPTION

[0064] 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 a 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.

[0065] 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 CC>2-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 ofordinary Portland cement with environmental-friendly and less expensive binders such as steel slag.The mechanical properties of CO2 cured concrete products need to be evaluated to ensure the quality of products is satisfactory. The concrete units can be taken out of the curing chamber for post-production testing to evaluate the properties of the CO2 cured concrete products, in postproduction. However, this may increase the production turnover time and increase the costs. For instance a sampling of a production run can be inspected and tested afterthe manufacturing steps have occurred. However, rejections of production run may happen if the properties are not satisfactory. Accordingly, various methods for identifying the end of the curing phase based on one or more measured product properties of the carbonated formed intermediate are disclosed herein. The term “product properties as used herein is defined as being properties of the concrete product itself (or the formed intermediate during the carbonation curing process), as opposed to environmental properties (e.g., of the gas, etc.). Such product properties of the concrete product may include a physical, mechanical, dimensional and / or chemical property of the formed intermediate during the carbonation curing process or of the concrete product at a termination of the carbonation curing process. In certain embodiments, for example, the product properties that are monitored may include one or more of the following parameters of the molded intermediate or the concrete product: dimensional change; compressive strength; vibrational property; moisture content; surface color; thermal conductivity; chemical composition; pH; relative humidity; ultrasonic pulse velocity; and electrical resistivity.

[0066] A method of manufacturing a concrete product as described herein may generally 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 curing the conditioned intermediate with a gas containing carbon dioxide to obtain the concrete product.

[0067] 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, walls including retaining walls, boxes including modular boxes, culverts, tiles, pavers, foundations, slabs including hollow-coreslabs, patio slabs, steps, curbs, concrete masonry units, beams, floors, columns, manholes, sewage pipes, railroad ties, and other precast concrete products.

[0068] 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.

[0069] 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 (172”). 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 or fine 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 sieves of 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 .

[0070] The aggregate utilized in production of CO2 cured concrete can be normal-weight or lightweight aggregates. The aggregate can be natural or manufactured or recycled aggregates; or the combination of above.

[0071] 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).

[0072] The binder(s) suitable for manufacturing the disclosed carbonated precast concrete should be reactive towards carbon dioxide.

[0073] 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.

[0074] The binder(s) 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.

[0075] The binder(s) suitable for manufacturing carbonated precast concrete may include any combination of conventional binders and / or emerging binders. Preferably, the binder 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.

[0076] 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.

[0077] 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.

[0078] 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 landfill 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. Inanother example, at least fifty percent of ground slag may be smaller than 100 microns, and at least ten percent of ground slag may be smaller than 50 microns, i.e., D(50) < 100 microns, and D(10) < 50 microns.

[0079] 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.

[0080] 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.

[0081] 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 depending on the manufacturing process or operational parameters of carbon curing systems.

[0082] 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.

[0083] In an application 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.

[0084] 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 binder type and / or the 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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 beachieved through the known ways, such as any or a combination of vibration, compaction and compression.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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 leaves numerous 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 longer time 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.

[0096] 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.

[0097] 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 pink color is observed in the tested crosssection area, while a 50% CO2 penetration is obtained if pink color occupies a half of the tested cross section area.

[0098] 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 simplerterms, 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.

[0099] 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.

[0100] Carbonation curing may be carried out in a sealed enclosure with CO2 introduced either as a steady gas or as a continuously circulated gas.

[0101] 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 30% to 90%.

[0102] For carbonated precast concrete made of binders with hydraulic activity such as OPC, hydration curing may optionally be implemented to help carbonated precast concrete achievingfull 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.

[0103] 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.

[0104] In at least some embodiments, the step of conditioning the formed intermediate may be performed simultaneously with the step of curing. In other words, the production method may include concurrent conditioning and curing the formed intermediate. As described hereinafter, the conditioning includes drying the formed intermediate. This simultaneous conditioning and curing will be hereinafter referred to as the “SDC” process. Typically, the water-to-binder ratio is constant during the curing process because the water that is not required for the concrete composition has been removed during the conditioning process which is performed before the curing process. In the SDC process, the curing of the formed intermediate occurs while, at the same time, excess water is being evaporated out of the formed intermediate. Any precast concrete products, including but not limited to concrete masonry units, paving stones, retaining walls, slabs, traffic barriers, pipes, culverts, etc., can be produced with the SDC process.

[0105] The SDC process may be initiated once the formed intermediate is inserted in an enclosure sealed from an environment outside the enclosure. Such enclosure may be a closed chamber or vessel, in which one or more formed intermediate may be inserted. These one ormore formed intermediate may be placed on racks, such as perforated racks or mesh racks allowing flow circulation along all surfaces of the formed intermediate. The CO2 curing process may be initiated immediately once the one or more formed intermediate are placed in the enclosure. As the SDC process occurs, a final water-to-binder ratio less than an initial water-to- binder ratio is obtained. In other words, while the formed intermediate is being cured, a water content of the formed intermediate decreases from an initial water-to-binder ratio to a final water- to-binder ratio. The CO2 curing process may be initiated while the formed intermediates have the initial water-to-binder ratio, i.e., water-to-binder ratio of the formed intermediate at the time the formed intermediate are placed in the enclosure, immediately once the enclosure is closed. In order to reduce the water-to-binder ratio of the formed intermediates from the initial water-to- binder ratio to a final water-to-binder ratio, i.e., the water-to-binder ratio once the CO2 curing process is terminated, the concurrent conditioning is performed. A pore saturation within the formed intermediate may thus be reduced during concurrent conditioning and carbonation curing.

[0106] Herein, the expression “concurrent” denotes that two processes occur at the same time, simultaneously. In other words, while the formed intermediate is being cured, some water is being removed out of it as part of the conditioning process. The evaporation of water / moisture from the formed intermediate during the SDC process may be obtained via forced convection within the enclosure. Forced convection may be obtain via a gas circulation device, such as a fan or blower that induced the forced convection within the enclosure. The forced convection within the enclosure may be used to control the conditioning. By increasing or decreasing the forced convection, a desired conditioning rate may be obtained and / or varied. In some embodiments, the gas velocity generated by the gas circulation device may vary from 0.1 m / s to 2 m / s. The gas velocity may be adjusted by controlling the intensity of the gas circulation device. As part of the SDC process, it may not be required to measure the gas velocity. In other words, it may not be necessary for the operator to monitor the gas velocity, as long as the intensity (e.g., rotational speed) of the gas circulation device may be controlled, including by turning it ON or OFF.

[0107] 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., no inducement 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.

[0108] 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 SDC process 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.

[0109] 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 / orthe temperature of the gas flowing within the enclosure.

[0110] The pressure inside the enclosure may also be a factor influencing the conditioning rate. In some embodiments, the SDC process may occur at a pressure higher than ambient pressure. The enclosure may be pressurized during least part of the SDC process. 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 SDC process could also be initiated without pressurizing the enclosure. The enclosure may be depressurized during the SDC process or at the end thereof (i.e., once the carbonation curing reaches its desired effect on the formed intermediates). The SDC process may be performed free of additional external sources of pressure.

[0111] The conditioning rate may also be a function of a relative humidity (RH) within the enclosure, during the SDC process. 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, activatedcharcoal, 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.

[0112] 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 place

[0113] Fresh air can be introduced into the enclosure from the environment outside of the enclosure. A port may be provided to inject airthrough 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.

[0114] Aspects of the carbonation curing will now be further described.

[0115] The demolded fresh concrete may be contacted with carbon dioxide, CO2 or a gas containing CO2 while its moisture content is reduced during the simultaneous 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.

[0116] 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 simultaneous conditioning and CO2 curing process may continue for up to 240 hours.

[0117] Referring now to Fig. 1 , which depicts an exemplary system for conditioning and curing a concrete product is shown at 10. The system 10 includes a source of carbon dioxide 1 1 , which may be a reservoir or tank, pneumatically connected to an enclosure 12 via a line 13. In theembodiment 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 open or closed to allow or restrict the flow of carbon dioxide toward the enclosure 12.

[0118] The enclosure 12 defines an inner space or chamber 12A that is sized to accept the plurality of concrete products 16 to be cured. 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 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.

[0119] 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. The enclosure 12 may be a deployable structure (e.g. bag).

[0120] 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.

[0121] 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 600 such as the one shown and described below with reference to Fig. 6. 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.

[0122] 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 and the heating of the air may be used. A desiccant material 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 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 the enclosure 12 during the simultaneous curing and conditioning may beused. For instance, a de-humidifier, an air conditioning, and any other suitable means may be used.

[0123] 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 as shown in Fig. 5.

[0124] Referring to Fig. 5, a method of manufacturing a concrete product that includes concurrently conditioning and curing the formed intermediate by conditioning the formed intermediate while curing the formed intermediate, wherein the formed intermediate is concurrently cured and conditioned.

[0125] In the embodiment wherein concurrent conditioning and curing does occur, the carbonation curing rate is positively correlated with the concurrent conditioning rate. There is accordingly a positive correlation between the carbonation curing rate and the concurrent conditioning rate. In the SDC process, one cannot occur without the other. If the conditioning rate increases, the carbonation rate will also increase. The positive correlation between conditioning rate and carbonation curing rate may not be a linear correlation. The effect of a variation of the conditioning rate on the carbonation curing rate may not be immediate. However, the higher the conditioning rate, the higher the carbonation curing rate is, up to a limit. Indeed, the positive correlation has an asymptotical behavior. In at least some embodiments, the conditioning rate is constant during substantially all of the SDC process (> 90% of the SDC process time). Consequently, the carbonation curing may be substantially constant. The conditioning and / or curing rate may vary in other embodiments. The SDC process can be paused and resumed. For example, there may be a stabilization phase between subsequent SDC phases. During the stabilization phase, the partially carbon cured formed intermediate may be in latency. Chemical reaction between the material of the partially cured formed intermediate and the gas in its surrounding environment may continue during this phase; however, no external work may be done during the stabilization phase to cause such curing, i.e., the stabilization phase may include passive curing, without external work to actively cure. During this stabilizing phase, the moisture gradient in the concrete medium changes while overall moisture content remains the same. In other words, the moisture gradient (lower moisture on the surface and higher in the core) in thebeginning of stabilization may be higher. By the end of this stabilization period, this gradient is reduced. However, the stabilization period occurs in the presence of CO2. This means that during this stabilization period, the drying has substantially stopped, but the carbonation reaction and moisture balancing are still ongoing.Method of identifying the end of the CO2 curing phase

[0126] The following sections will generally refer to the methods schematically depicted in Figs. 2-4.

[0127] The curing time, CO2 pressure, and other operational parameters are dictated by the concrete mixture, RH and temperature of ambient environment within the enclosure. In existing processes, an operator may monitor all these conditions and decide on how long the curing process needs to last in order to obtain an end product with satisfying properties. However, it may be desirable to make the operation independent of these parameters, at least in part. As such, once the parameters are set for a selected production run, the carbon curing process, whether part of the SDC process described above or not, may last until a measured property of the carbonated formed intermediate reaches a target property. According to the present disclosure, the actual performances of the concrete products involving carbonation curing are used as the basis for ending the curing process rather than relying on the operational parameters. Methods of identifying the end of the CO2 curing period are disclosed herein.

[0128] Generally, the CO2 curing period should end once the products have achieved the desired performance level. The performance of the products depends on the degree and depth of carbonation reaction throughout the concrete material which is not known until the end of curing period, for example when the product is removed from the curing chamber and its performance is tested using conventional testing methods. While trial and error methods have been used in the past, the optimum duration of the curing period could not be found integrally as part of the curing process. Also, the optimum curing duration may be affected by a number of factors, such as the ambient conditions within the enclosure, as described above, but also by moisture content, material types, and product size from one production batch to the other. If the carbonation curing period is not ended on time, valuable production time may be wasted. In parallel, if the carbonation curing period is ended prematurely, the quality of the products may be reliable. The product requirements may not meet the standard requirement and / or the quality of products may not satisfy the customer’s needs. It may become even more challenging to identify the actual optimumcuring duration for carbonated precast concrete products of greater thicknesses and / or sizes. Indeed, the carbonation may not be uniform across the whole carbonated precast concrete. As such, relying on the ambient conditions within the enclosure to evaluate the state of cure of the carbonated precast concrete product may be unreliable or provide inconstant product properties from one production batch to the other. Optimizing process time for any new products is unique as it depends on the mix design, its dimensions, and performance requirements. Causing the end of the curing process based on one or more product properties of the carbonated formed intermediate, measured while the products are within the curing chamber, may significantly reduce the required time to develop and optimize the production of any new products.

[0129] Methods for detecting the reaching of the desired performance level as part of the manufacturing process is therefore valuable. The proposed process may ensure that the quality of concrete products is met before the curing process, also referred to herein below as curing phase, is stopped and before the carbonated formed intermediate are removed from the chamber, and based on one or more product properties of the carbonated formed intermediate. Control of the curing time based on the monitoring of conditions such as temperature, pressure or RH may thus not be required to achieve the desired performances of the end products. Using these methods will ensure that the carbonation curing period is not extended unnecessarily, while maintaining production results in high quality products that have the desired performance level.

[0130] Referring generally to Figs. 2-4, the end of the curing phase is determined based on a change in a property of the formed intermediate that is monitored during curing, for example a physical property such as a dimensional variation of the formed intermediate. Since dimensional variations may be substantially smaller than the overall dimensions of the formed intermediate being cured, these dimensional variations may also be referred to as a strain. The volume of reactants and products may not be exactly equal in the carbonation reaction. Therefore, volume / length variations may be an indication of this chemical reaction. During the curing process, as carbonation reaction progresses, the volume / length variation may be monitored, and its value or rate can be relied upon to dictate the end of curing. This predetermined value may be referred to herein as a threshold value of the property or product properties of the formed intermediate itself. During the curing process, the formed intermediate may shrink. This may be caused by the carbonation reaction and / or the drying of the formed intermediate, during the SDC process. A desired final dimension of the monitored dimensions may be set based on empirical or statistical models, or experimentations, which may allow to identify the final dimension associated with the desired mechanical property(ies) of the carbonated precast concrete product.Once the dimension of the carbonated formed intermediate reaches the desired final dimension, the CO2 curing process may be stopped. The dimensional change may be an axial dimension change or a radial dimension change, a volume change or surface area change, depending on the formed intermediate. For example, a longitudinal dimension, a widthwise dimension or a heightwise dimension of the formed intermediate may be measured at a first time during or prior to curing process. For example, in an embodiment, a first measurement of at least one of the longitudinal dimension, the widthwise dimension or the heightwise dimension of the formed intermediate may be taken before it is placed inside the enclosure for condition and carbon curing, or once it is inside the enclosure before any conditioning and carbon curing is performed. Such measurement may be the reference measurement of the formed intermediate. The one or more dimensions that were subject to an initial or reference measurement may be monitored during the curing and / or the SDC process. The dimensional variation may be measured using the reference measurement, and one or more subsequent measurements.

[0131] The reference measurement(s) and continued (or intermittent) measuring during the curing and / or SDC process may be made using various suitable measurement devices.

[0132] Examples of the measurement device includes a lidar or other imaging device, such as a camera, or the like. Dimensions of the formed intermediate may be measured by image processing. In one example the dimensional change or strain of the formed intermediate being cured can be measured by a digital image correlation (DIC) technique. The DIC technique is a contactless method in contrast with the strain gauge method, which is described below. With the installation of at least one camera inside the curing chamber, the deformation and dimensional change of the formed intermediate may be monitored by implementing the DIC technique. Other image processing technique could be contemplated. In operation, the camera may be pointed at at least one of the formed intermediate within the curing chamber. In an application, the detection of dimensional change may be achieved on at least 10% of the formed intermediates present within the curing chamber during the curing process. Once the detected dimensional change of the formed intermediates reaches a predetermined value, the CO2 curing process may be stopped. The CO2 curing process may be stopped manually, such as by an operator of the curing chamber, or via a controller. For example, the measurement data or a signal indicative of thedimensional change may be conveyed to a controller, which may include a data logger. Upon processing the conveyed signal, the controller may cause the curing process to stop.

[0133] In at least some embodiments, the monitored dimension(s) is measured by one or more sensors. In an embodiment, the sensor is a strain gauge. One or more strain gages may be installed on at least one of the formed intermediates placed in the enclosure. The stain gauge may be installed onto a surface of the formed intermediate with adhesives, using known gauge installation techniques. The surface of the formed intermediate may require a surface preparation to allow a suitable adherence to the surface. Different types of strain gauge including but not limited to linear strain gages, shear strain gauges, column strain gages may be selected. In a particular case, once the monitored dimension (e.g., longitudinal dimension) has changed by 0.001 % during the curing process, the curing process is stopped. In another particular case, once the monitored dimension (e.g., longitudinal dimension) of the carbonated formed intermediate has changed by 0.01 % during the curing process, the curing process is stopped. These are provided only as some possibilities.

[0134] In another embodiment, the one or more sensors may be linear variable differential transformer (LVDT) transducers. At least one LVDT may be placed on one of the formed intermediates in the curing chamber (either before or after the formed intermediates are placed in the curing chamber). More than one formed intermediates may have such an LVDT placed thereon. The LVDT may monitor the movement or displacement of a surface of a selected formed intermediate relative to a reference point during the curing process. The LVDT sensors conveys a data signal indicative of a movement or displacement to the controller. An operator may stop the curing process manually or in another example the CO2 curing process may be caused to stop by the controller, once the dimension variation associated with the movement or displacement measured by the LVDT reaches a desired value.

[0135] Intrinsic product properties of the carbonated formed intermediate may be monitored. In an embodiment, an ultrasonic pulse velocity (UPV) equipment is installed on at least one of the formed intermediates that is subject to curing to determine its void structure, density, and cracks patterns. The compressive strength may also be derived from one or more measurements with the UPV equipment. A plurality of measurements at various locations on the formed intermediate being cured may be performed. Tomographic images of the void structure, density, and crack patterns may be obtained with the measurements data that are collected using the UPV equipment. The data generated from the UPV equipment may be used to dictate the end of theCO2 curing process. For example, if the concrete’s void percentage reported by UPV equipment is smaller than a desired value, the CO2 curing process may be stopped. In some applications, the desired void content of the carbonated formed intermediate may be 30% or preferably 20% or preferably 10% or even more preferably less than 5%. As another example, if the average pulse velocity reported by UPV is higher than a desired value, the CO2 curing process may be stopped. In some applications, the desired pulse velocity of the carbonated formed intermediate may be 2 km / sec or preferably 4 km / sec or preferably 4.5 km / sec or even more preferably higher than 5km / sec. In other cases, the CO2 curing may be stopped if the rate of change in the average pulse velocity by UPV reaches a threshold value. In certain embodiments, this threshold value of the average pulse velocity is about 0.05 km / sec / hr, whereby the CO2 curing can stop when the rate of change in the average pulse velocity reaches less than 0.05 km / sec / hr.

[0136] In operation, the surfaces of the formed intermediate being cured are contacted by the transmitter and receiver of the UPV equipment. The surfaces of the concrete units may be optionally prepared before the UPV equipment is placed on the concrete’s surface to ensure a smoother pulse transmission from the UPV equipment to concrete. Such surface preparation may be performed using known techniques in the art. For example, the surface can be smoothened by grinding or polishing. Additionally, a conductive medium such as UPV conductive gel can be provided on the surface and used for better contact between the surface of the concrete and the UPV probe.

[0137] The CO2 curing process may be stopped by an operator, as described above with respect to other embodiments, or caused to be stopped by the controller.

[0138] Vibration-based methods may be practised and the state of cure may be derived from vibrational properties of the carbonated formed intermediate. During the carbonation reaction, a matrix of calcium carbonate crystals is formed. Such matrix provides strength to the concrete. This means that the stiffness of the carbonated formed intermediate may is increase gradually over the course of the curing process. Vibration properties of any material is directly related to its stiffness. Therefore, measurements of vibrational properties of concrete may indicate its stiffness and consequently the level of carbonation, which may be used to dictate the end of the curing process.

[0139] In at least some embodiments, a modulus of elasticity or other mechanical properties of at least one ofthe carbonated formed intermediate may be computed by its stiffness and naturalfrequency(ies). Modulus of elasticity of concrete is a direct indication of strength development. Once the calculated modulus of elasticity exceeds a desired value, the curing process may be stopped. Its natural frequency(ies) may be obtained through vibration-based methods such as resonance frequency, ambient vibration, or induced vibration methods. Vibrational properties of the concrete unit can be measured using different types of sensors such as accelerometers, strain gauges, and LVDT sensors. For example, one or more accelerometer sensors may be installed on surfaces of at least one of the carbonated formed intermediates placed inside the curing chamber. Vibration may be induced on the carbonated formed intermediate using an actuator. The accelerometer sensors may convey a signal indicative of a measured acceleration to the controller. The modulus of elasticity of the carbonated formed intermediate may then be computed based on the measured acceleration and the set induced vibration energy injected into the carbonated formed intermediate. In a particular application, once the modulus of elasticity exceeds 30 GPa, the curing process may be stopped. Such threshold value may be different in other applications, such as lower that 30 GPa or higher, such as 40 GPa.

[0140] Alternatively, image processing of a real-time video of the carbonated formed intermediate may allow to identify its vibrational properties. For example, image analysis can be used to conduct vibration analysis in order to identify vibrational properties (i.e. vibration frequency, amplitude, and mode) from recorded or live videos. These properties can be used to estimate mechanical properties of concrete such as its stiffness and modulus of elasticity. The mechanical properties can be then used to estimate the performance of concrete. In certain embodiments, therefore, a camera is installed inside the curing chamber and is in communication with an image analysis system including for example a controller and suitable digital storage medium. Vibration may be induced to the carbonated formed intermediate. The camera captures images or an image stream and through image processing vibrational properties of the carbonated formed intermediate may be evaluated. The dynamic behavior of the carbonated formed intermediate is an intrinsic property of the material. A computed dynamic behavior of the carbonated formed intermediate, such as by processing the images or image stream may be obtained. Then, a comparison with set ordesired dynamic properties, e.g., within a predetermined range of dynamic properties for what is being considered as a target property / behavior and which may be associated with a target performance of the end product, may allow the determination of the state of cure.

[0141] In certain embodiments, the moisture content of the carbonated formed intermediate may be an indicator of the state of cure. A moisture content of the formed intermediate iscontinually decreasing during the curing process. A CO2 penetration and dissolution through the material may correlate with the moisture content of the carbonated formed intermediate. Measuring the moisture content of the material may provide an indication of the state of the carbonation reaction. The moisture content of carbonated formed intermediate may be measured and compared against a predetermined value. Such predetermined value may be obtained through empirical or statistical models, for example. Once the moisture content of the carbonated formed intermediate reaches the predetermined value, the curing phase may be stopped. The CO2 curing process may be stopped by an operator, as described above with respect to other embodiments, or caused to be stopped by the controller once the moisture content reaches the predetermined value. In an application, once the moisture content of the carbonated formed intermediate reaches 5%, the curing process may be stopped. In another application, the curing process may be stopped once the moisture content of concrete reaches 2%. In yet another application, the curing process may be stopped when the moisture content is lower than 2%, most preferably equal to or lower than 0.5%. In other cases, the carbon curing may be stopped if the rate of change of the moisture content reaches a threshold value. In one possible embodiment, this threshold value is 0.05% / hr, whereby the CO2 curing can stop when the rate of change of moisture content is less than 0.05% / hr. Other techniques and parameters may also be used, as described herein, for determining when the CO2 curing phase can be stopped.

[0142] Other values relating the moisture loss may be computed and used to cause the end of curing phase. For example, in an embodiment, an amount of moisture loss may be measured based on a mass loss of the carbonated formed intermediate. In one example, once the amount of water escaped from the carbonated formed intermediate during the curing phase exceeds 0.1 % of the carbonated formed intermediate weight, the curing process may be terminated. In some variants, the rate of water escaped could also be relied upon. A lower rate of water escaping during the CO2 curing phase may suggest a lower rate of mineralization. Once the rate of water loss during the CO2 curing phase reaches a reference value, the curing phase can be caused to be stopped. In one example once the rate of water escaped from the carbonated formedintermediate during the curing phase is less than 1 kg / sec, the curing process may be terminated. This is only given as an example.

[0143] The moisture content of the carbonated formed intermediate inside the curing chamber may be measured by an infrared sensing equipment. Other measurement means may be contemplated, such as by a microwave sensing equipment.

[0144] Change in the moisture content of concrete and also carbonation reaction may affect the color on a surface of the concrete product. As the carbonation reaction progresses during curing, the moisture content may vary. This may be reflected in a surface color of the concrete product. A change in the surface color may be informative. Monitoring the surface color of the carbonated formed intermediate may be used to determine the end of curing and thus cause the active process to stop. The color change may indicate whether the mineralization process (i.e., the carbonation process) has completed or not and whether the curing process may be ended. In an embodiment, at least one camera is installed inside the enclosure where curing is performed. In at least some embodiments, up to one camera per carbonated formed intermediate in the enclosure may be present in the enclosure so as to monitor the color change of each one of the carbonated formed intermediates individually. The images or image streams may be conveyed to a controller and, through image processing for example, the color of one or more surfaces of the carbonated formed intermediate may be determined. Once the color of the one or more surfaces reaches a reference color, which may be derived from data stored into the controller, the controller may cause the curing process to stop. In some variants, an operator may stop the process manually.

[0145] In one embodiment, the image processing converts the images or image streams from the cameras to a 256 RGB (Red, Green, Blue) color value. The color of the one or more surfaces that are monitored may be provided in a value ranging from 0 to 255 for red, green and blue. The RGB color data associated with the detected color may be processed. As part of the image processing, the processed RGB color data may be compared to reference RGB data, which may be stored in the controller. Once the processed RGB data correlates with the reference RGB data and / or reaches a set threshold, the controller may cause the curing process to stop. In one example, the RGB value of the formed intermediate prior to curing is 0, 0, 50 and it changes to 0, 0, 150 as a result of curing. As such, in this example, the controller may cause the curing process to stop once the RGB value of 0, 0, 150 is reached. In another example, where the color variation is monitored and the RGB values processed as the SDC process is initiated, the initial RGB valueis 100, 100, 100 and the SDC process may be caused to stop once the RGB value reaches to 210, 210, 210. In another example, where such method is applied in a non-simultaneous drying and curing process, the RGB values of concrete products before drying may be 0, 0 0. The drying process may then change the RGB value of one ore more surfaces of the formed intermediate being dried to 200, 200, 200. The CO2 curing process may then be initiated. Once the RGB values of the formed intermediate during the CO2 curing process reaches 255, 255, 255 the CO2 curing process is terminated. The CO2 curing phase can be terminated manually by an operator once the color of one or more of the surfaces have reached the desired color, e.g., in association with the RGB values, as discussed. In another example, the CO2 curing phase can be stopped automatically by the controller.

[0146] In accordance with another method, a performance level of the carbonated precast concrete products may be associated with measures of its compressive strength. Compressive strength may be measured using destructive or non-destructive methods or correlated to hardness or toughness values. Using these methods, the end of curing phase may be directly and definitely decided. The strength development of the formed intermediate during the CO2 curing phase may be an indicator of the end of curing phase. Once the compressive strength value of the carbonated formed intermediate reaches a reference value during the curing phase, the CO2 curing phase may be caused to be ended. The mechanical properties of carbonated formed intermediate in the enclosure may be evaluated by non destructive or destructive methods. In one example, the compressive strength may be estimated by a rebound hammer test, i.e. Schmidt Hammer test method. Such a compressive strength test can be conducted automatically, for example using a stand or robotic arm or other suitable actuator operable, in certain embodiments, within human intervention based on pre-programmed instructions. In one example, once the compressive strength of carbonated formed intermediate reaches 10 MPa ± 5 MPa, the CO2 curing process may be caused to be stopped. In another example, it may be stopped when the value reaches 20 MPa ± 5 MPa. Yet, in another example, it may be stopped when the value reaches 50 MPa ± 5 MPa. Other threshold may be contemplated in other applications. In another example, the tensile strength and / or the flexural strength of the concrete products can be measured for the purposes of determining when the CO2 curing process should be stopped. For example, in one embodiment at least one block or concrete product is removed from the curing chamber for testing purposes - without interrupting the curing process for the rest of the blocks. Tensile strength and / or flexural strength tests can then be conducted on this one sample block. In this embodiment, once the tensile strength of concrete products reaches 2 MPa,the CO2 curing process is stopped. In another example, once the flexural strength of concrete products reaches to 1 MPa, the CO2 curing process is stopped.

[0147] In a variant, a rate of change between values in the mechanical properties of a serial testing of the carbonated formed intermediate may trigger the end of curing instead of the values themselves. In one example, the CO2 curing is halted if the rate of change of the measured compressive strength reaches a threshold value, such as, in a particular case, 0.1 MPa per hour. Stated otherwise, if the rate of change of the measured compressive strength is less than 0.1 MPa per hour, the curing process may be stopped. The compressive strength is measured directly in this method, and is used to end the curing. Once the target compressive strength has been reached, the curing process can be terminated.

[0148] Accordingly, the method includes monitoring one or more product properties, as described herein, during the carbonation curing process and determining when there has been a change in the one or more product properties - or a change in a rate of change of the one or more product properties - that reaches or exceeds a predetermined threshold value as disclosed herein. When this threshold value of the change in the property - or of the change in the rate of change of the property - the carbonation curing process is terminated. For example only, the termination of the carbonation curing process can be stopped if the compressive strength reaches 20 MPa or if the rate of change of the compressive strength is less than 0.1 MPa per hour.

[0149] Other product properties of the carbonated formed intermediate may be measured and used to trigger the end of curing, such as toughness or hardness. In one embodiment, the toughness of carbonated formed intermediate during the CO2 curing phase may dictate the end of the CO2 curing phase. Once the toughness or hardness of one or more of the surfaces of the carbonated formed intermediate during the CO2 curing phase reaches a reference value, the CO2 curing phase may be caused to be stopped. In one example, a Mohs hardness value may be used to evaluate the surface hardness. In one example, the CO2 curing process may be terminated once the Mohs value is 4. In another example, the CO2 curing process is terminated once the Mohs value is 8. Other reference value could be set depending on the application.

[0150] In accordance with another method, the thermal conductivity of the concrete product is monitored, for the purposes of determining the appropriate time to terminate the concurrent conditioning and curing. Thermal conductivity of concrete depends on factors including its chemical composition and porosity. During curing, the chemical composition and porosity of theformed intermediate may vary as a result of the carbonation reaction. This variation slows down as the reaction nears completion. Therefore, by monitoring the thermal conductivity of the formed intermediate, the end of curing may be determined. In one example, once the measured thermal conductivity of concrete products reaches 1 .5 W / m.K during the curing phase, the curing process may be terminated. In another example, such value is 3.5 W / m.K. Other reference values may be contemplated depending on the application. Thermal conductivity can be measured both automatically and manually. Automatic measurement can be done by placing sensors and plates on certain units inside the chamber or by using robotic arms that would place the measuring devices on certain products when required. Manual measurement can be done by taking certain concrete units out of the curing chamber at the desired time and measuring them outside the chamber. This can be done by exhausting the chamber and resuming the curing after the measurement is performed or without interfering with the curing of the other concrete units in chamber.

[0151] In a variant, a rate of change between values in the thermal conductivity of a serial testing of the carbonated formed intermediate may trigger the end of curing instead of the values themselves. As an example, the thermal conductivity of the concrete units can be measured every 60 minutes and if the rate of change in thermal conductivity is determined to be less than 0.05 W / m.K per hour, curing can stop.

[0152] Other product properties of the carbonated formed intermediate during curing may be monitored. The monitored product properties may serve to determine whether the curing phase should be ended or pursued to reach the desired performance level of the end product. Here are some examples: the pH or change in pH of the carbonated formed intermediate during the CO2 curing phase, or the change of bulk or surface electrical resistivity of the carbonated formed intermediate. For example, once the electrical resistivity of the carbonated formed intermediate is 100 Q.m or less, the CO2 curing process may be caused to be ended. In one example, once the pH value of the surface reaches 8, curing can stop. In another example, once the pH value of the surface reaches 7.5, curing can stop. The pH value of the core can also be monitored. In one example, if this value reaches 8, curing can stop. In another example, once the pH value of the core of the concrete unit reaches 7.5, curing can stop.

[0153] In accordance with another method, a change in the chemical composition of the carbonated formed intermediate during curing is monitored, for the purposes of determining the appropriate time to terminate the concurrent conditioning and curing. Carbonation reaction thatoccurs during the curing phase results in the decomposition and composition of several chemicals. This may therefore affect the chemical composition of the material. As such, causing the termination of the curing phase by monitoring the chemical composition of the material may be contemplated. The chemical composition of the carbonated formed intermediate can be determined by any known means, including a real time XRF, XRD and elemental analyzer. Once the quantity of any chemical composition or chemical component reaches a reference value during the curing phase, the CO2 curing phase may be caused to be ended. In one example, once a calcium oxide content of the carbonated formed intermediate is reduced by at least 1 %, the CO2 curing process may be terminated. In another example, once a magnesium oxide content of the carbonated formed intermediate is reduced by at least 1 %, the CO2 curing process may be terminated. In another example, once a free lime content of the carbonated formed intermediate is reduced by at least 1 %, the CO2 curing process may be terminated. In another example, once a di calcium silicate content of the carbonated formed intermediate is reduced by at least 1 %, the CO2 curing process may be terminated. In another example, once a tri calcium silicate content of the carbonated formed intermediate is reduced by at least 1 %, the CO2 curing process may be terminated. In another example, once a calcium hydroxide content of the carbonated formed intermediate is reduced by at least 1 %, the CO2 curing may be terminated. In another example, once a merwinite content of the carbonated formed intermediate is reduced by at least 1 %, the CO2 curing process may be terminated. In another example, once a gehlenite content of the carbonated formed intermediate is reduced by at least 1 %, the CO2 curing process may be terminated. In another example, once a calcium carbonate content of the carbonated formed intermediate is increased by at least 1 %, the CO2 curing process may be terminated. In another example, once a carbon content of the carbonated formed intermediate is increased by at least 1 %, the CO2 curing process may be terminated. The minimum 1 % change in one or more of these parameters ensures that at least some carbonation has happened. In certain embodiments, and for the minerals mentioned herein, the actual change in one or more of these parameters may be higher than 1 %. In one embodiment, for example, if the calcium hydroxide content is reduced by 30%, curing can stop.

[0154] In some variants, the rate of change of the above chemical composition may be computed and used to trigger the termination of the curing process. In one example, once the rate of change in a CaO content reaches to 0.1 percent per hour, the curing process is ended. The chemical composition of the minerals is measured, which is an indication of the carbonationreaction. Independent of chamber performance, as long as the change in the mineral composition is observed, it can be concluded that curing is ongoing.

[0155] In one embodiment, the CO2 and / or N2 and / or 02 concentration during the carbonation phase is an indicator of the end of curing phase. Once the concentration of CO2 / N2 / O2 during the CO2 curing phase reaches to the desired value, the curing phase can be stopped. In one example once the 02 concentration during the curing phase is less than 20%, the curing process can be terminated. The measurement of thermal conductivity of the concrete product, which it is being cured, is explained above. Measurement of CO2, N2 and / or 02 concentrations can be performed using industrial sensors and measuring systems suitable forthis purpose.

[0156] The methods as described above may, in certain instances, be summarized as will now be described, with reference to Figs. 2-4.

[0157] As shown in Fig. 2, a method 200 for terminating a carbonation curing process of a formed concrete intermediate performed in a curing chamber is implemented via a controller including a processing unit, and a non-transitory computer-readable memory communicatively coupled to the processing unit and comprising computer-readable program instructions executable by the processing unit for: at step 202, monitoring a change in one or more product properties of the formed intermediate during the carbonation curing process; and, at step 204, causing the carbonation curing process to terminate upon receiving a signal indicative of the change in the one or more product properties corresponding to a set value of the one or more product properties.

[0158] As shown in Fig. 3, a method 300 of manufacturing a concrete product includes, at step 302, performing, in a curing chamber, a carbonation curing process on a formed intermediate of the concrete product. At step 304, the method includes monitoring one or more product properties of the formed intermediate during the carbonation curing process. At step 306, the method then includes terminating the carbonation curing when a detected change in the one or more product properties corresponds of the formed intermediate reaches or exceeds a predetermined threshold value.

[0159] As shown in Fig. 4, a method 400 of manufacturing a concrete product includes at step 402, providing a composition including a binder, an aggregate, and water; and at step 404, mixing the binder, the aggregate, and the water to produce a concrete mixture. The method thenincludes, at step 406, imparting a form to the concrete mixture to provide a formed intermediate having a first water-to-binder ratio, and, at step 408, concurrently conditioning and curing the formed intermediate by conditioning the formed intermediate while curing the formed intermediate, wherein the formed intermediate is concurrently cured and conditioned to obtain final water-to-binder ratio less than the first water-to-binder ratio. The concurrent conditioning and curing is terminated, at step 410, based on a monitored change in one or more product properties of the formed intermediate during the concurrent conditioning and curing.

[0160] As shown in Fig. 4, a method 500 of manufacturing a concrete produce includes, at step 502, providing a composition including a binder, an aggregate, and water, and, at step 504, mixing the binder, the aggregate, and the water to produce a concrete mixture. The method then includes, at step 506, imparting a form to the concrete mixture to provide a formed intermediate having a first water-to-binder ratio. The formed intermediate is then currently conditioned and cured, at step 508, by conditioning the formed intermediate while curing the formed intermediate, wherein the formed intermediate is concurrently cured and conditioned to obtain final water-to- binder ratio less than the first water-to-binder ratio.

[0161] Referring now to Fig. 6, the controller 20 operable to control at least some of the abovedescribed methods may include a computing device 600, which may comprise a processing unit 602 and a memory 604 which has stored therein computer-executable instructions 606. The processing unit 602 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.

[0162] The memory 604 may comprise any suitable known or other machine-readable storage medium. The memory 604 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 604 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 read-only memory (CDROM), electro-optical memory, magnetooptical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like. Memory 604may comprise any storage means (e.g., devices) suitable for retrievably storing machine-readable instructions 606 executable by processing unit 602.

[0163] 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 600. 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 computerwhen 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 602 of the computing device 600, to operate in a specific and predefined manner to perform the functions described herein, for example those described in the method 200.

[0164] 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.

[0165] 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. The embodiments 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 usewith 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.

[0166] 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.

[0167] 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.

[0168] 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).

[0169] 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.

[0170] 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 methodstep 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.

[0171] 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.

[0172] 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 method of manufacturing a concrete product, the method comprising: performing, in a curing chamber, a carbonation curing process on a formed intermediate of the concrete product; monitoring one or more product properties of the formed intermediate during the carbonation curing process; and terminating the carbonation curing when a detected change in the one or more product properties of the formed intermediate, or in a rate of change of the one or more product properties of the formed intermediate, reaches or exceeds a predetermined threshold value.

2. The method of claim 1 , wherein the monitoring includes monitoring one or more of a mechanical property, a dimension, and a chemical property of the formed intermediate during the carbonation curing process.

3. The method of claim 1 or 2, wherein the carbonation curing process is performed as part of a simultaneous conditioning and curing process.

4. The method of claim 1 or 2, wherein the carbonation curing process includes drying the formed intermediate prior to initiating carbonation curing of the formed intermediate.

5. The method of any one of claims 1 to 4, wherein the monitoring includes receiving a data signal associated with a measurement of a dimensional change of the formed intermediate during the carbonation curing process.

6. The method of claim 5, wherein the dimensional change is a volume variation and / or an axial dimension variation of the formed intermediate.

7. The method of any one of claims 1 to 6, wherein the monitoring includes monitoring one or more of: a compressive strength of the formed intermediate; a vibrational property of the formed intermediate; a change in a moisture content of the formed intermediate; a change of a surface color of the formed intermediate; and a change in a thermal conductivity of the formed intermediate.

8. The method of any one of claims 1 to 7, wherein the monitoring includes measuring a change in a chemical composition of the formed intermediate, the chemical composition including one or more of: a calcium oxide content; a magnesium oxide content; a free lime content; a dicalcium silicate content; a tri calcium silicate content; a calcium hydroxide content; a merwinite content; a gehlenite content; a calcium carbonate content; and a carbon content.

9. The method of any one of claims 1 to 8, wherein the monitoring includes monitoring one or more of the following parameters of the formed intermediate during the carbonation curing process: a pH; relative humidity; ultrasonic pulse velocity; and electrical resistivity.

10. A system for manufacturing a concrete product, the system comprising: a curing chamber receiving therein a formed intermediate of the concrete product, the curing chamber being configured to perform a carbonation curing process of the formed concrete intermediate within the curing chamber; a controller in communication with the curing chamber, the controller including a processing unit and a non-transitory computer-readable memory communicatively coupled to the processing unit and comprising computer-readable program instructions executable by the processing unit for: during the carbonation curing process, monitoring a change in one or more product properties of the formed intermediate and / or monitoring a change in a rate of change of the one or more product properties; and causing the carbonation curing process to terminate upon receiving a signal indicative of the change in the one or more product properties or the change in the rate of change of the one or more product properties corresponding to a predetermined threshold value.1 1. The system of claim 10, wherein the computer-readable program instructions are executable by the processing unit for, during the carbonation curing process, receiving a data signal associated with a measurement of a dimensional change of the formed intermediate during the carbonation curing process, the dimensional change being a volume variation and / or an axial dimension variation of the formed intermediate.

12. The system of claim 10 or 11 , wherein the computer-readable program instructions are executable by the processing unit for, during the carbonation curing process, monitoring one or more of: a compressive strength of the formed intermediate; a vibrational property of the formed intermediate; monitoring a change in a moisture content of the formed intermediate; a change ofa surface color of the formed intermediate; and a change in a thermal conductivity of the formed intermediate.

13. The system of any one of claims 10 to 12, wherein the computer-readable program instructions are executable by the processing unit for, during the carbonation curing process, measuring a change in a chemical composition of the formed intermediate, the chemical composition including one or more of: a calcium oxide content; a magnesium oxide content; a free lime content; a di calcium silicate content; a tri calcium silicate content; a calcium hydroxide content; a merwinite content; a gehlenite content; a calcium carbonate content; and a carbon content.

14. The system of any one of claims 10 to 13, wherein the computer-readable program instructions are executable by the processing unit for, during the carbonation curing process, monitoring one or more of the following parameters of the formed intermediate during the carbonation curing process: a pH; relative humidity; ultrasonic pulse velocity; and electrical resistivity.

15. A method of manufacturing a concrete product, the method comprising: providing a composition including a binder, an aggregate, and water, wherein the binder is a steel slag; mixing the binder, the aggregate, and the water to produce a concrete mixture; imparting a form to the concrete mixture to provide a formed intermediate having a first water-to-binder ratio; conducting carbonation curing of the formed intermediate; detecting a change in one or more product properties of the formed intermediate or detecting a change in a rate of change of the one or more product properties of the formed intermediate, the one ore more product properties including a mechanical property, a dimension, and / or a chemical property of the formed intermediate; and terminating the carbonation curing when the detected change reaches or exceeds a predetermined threshold value.

16. The method of claim 15, wherein conducting the carbonation curing includes conditioning the formed intermediate to obtain final water-to-binder ratio less than the first water-to-binder ratio, the conditioning of the formed intermediate performed priorto or concurrently with the carbonationcuring, wherein when the conditioning is performed priorto the carbonation curing the conditioning and the carbonation curing are performed in series and when the condition is performed concurrently with the carbonation curing the formed intermediate is concurrently cured and conditioned.

17. The method of claim 15 to 16, wherein the detected change includes a dimensional change, the dimensional change being a volume variation and / or an axial dimension variation of the formed intermediate.

18. The method of any one of claims 15 to 17, wherein the one or more product properties includes one or more of: a compressive strength of the formed intermediate; a vibrational property of the formed intermediate; a moisture content of the formed intermediate; a surface color of the formed intermediate; a thermal conductivity of the formed intermediate; pH; relative humidity; ultrasonic pulse velocity; and electrical resistivity.

19. The method of any one of claims 15 to 18, wherein the detected change in the one or more product properties, includes a change of a chemical composition, the change in chemical composition being related to: a calcium oxide content of the formed intermediate; a magnesium oxide content; a free lime content; a di calcium silicate content; a tricalcium silicate content; a calcium hydroxide content; a merwinite content; a gehlenite content; a calcium carbonate content; and / or a carbon content.

20. The method of claim 16, wherein the carbonation curing has a carbonation curing rate and the conditioning has a conditioning rate, the carbonation curing rate positively correlated with the conditioning rate, and the conditioning rate being constant during substantially all of the concurrent conditioning and curing of the formed intermediate.

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