Concrete curing system with controlled co2 concentration

Abstract

The curing system and method for manufacturing concrete products uses a curing chamber receiving formed intermediates composed of water, aggregate, and a gaseous binder. A source of an input gas is fluidly connected to a gas inlet of the curing chamber, the input gas including carbon dioxide having a source concentration of carbon dioxide. A flow rate of the input gas flowing through the valve and into the curing chamber is modulated, for carbonation curing of the formed intermediates. Concentration sensors are configured to generate signals indicative of a concentration of the carbon dioxide within the curing chamber. A controller determines that a concentration difference between the source concentration and the concentration of the carbon dioxide within the chamber is above a difference threshold, and causes a mitigation action to decrease the concentration difference.

Description

CONCRETE CURING SYSTEM WITH CONTROLLED CO2 CONCENTRATIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority on United States patent application no. 63 / 664,782 filed June 27, 2024, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

[0002] This disclosure relates generally to concrete products and, more particularly, to systems and methods used for manufacturing concrete products and to curing systems used to cure concrete products.BACKGROUND

[0003] In manufacturing traditional concrete products, a dry mixture, which may include a cement binder and an aggregate, is mixed with water. The resultant intermediate may undergo a conditioning step, in which some of the water it contains is evaporated. The conditioned intermediate product subsequently undergoes a separate curing step, in order to obtain the final concrete product. The extraction and production of cement binders, such as Ordinary Portland Cement, is energy intensive and has a negative environmental impact. Moreover, certain parameters may affect how the concrete products is manufactured.SUMMARY

[0004] In accordance with one aspect, there is provided a curing system for manufacturing concrete products, comprising: a curing chamber sized for receiving formed intermediates composed of water, aggregate, and a gaseous binder, the curing chamber having a gas inlet and a gas outlet; a source of an input gas fluidly connected to the gas inlet of the curing chamber, the input gas including carbon dioxide at a source concentration of carbon dioxide; a valve fluidly connected to the source of the input gas and upstream of the gas inlet, the valve having a plurality of positions to modulate a flow rate of the input gas flowing through the valve and into the curing chamber; concentration sensors in communication with the curing chamber and configured to generate signals indicative of a concentration of the carbon dioxide within the curing chamber at each of a respective position of the concentration sensors along a flow path within the curingchamber extending from the source of the input gas to the gas outlet; and a controller operatively connected to the valve and to the concentration sensors, the controller having a processing unit operatively connected to a computer-readable medium having stored thereon instructions executable by the processing unit to: cause the valve to inject a flow of the input gas into the curing chamber for curing the formed intermediates; based on one or more of the signals received from one or more of the concentration sensors, determine that a concentration difference between the source concentration and the concentration of the carbon dioxide within the chamber is above a difference threshold; and cause a mitigation action to decrease the concentration difference.

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

[0006] In certain aspects, the computer-readable medium has instructions executable by the processing unit to determine that the concentration difference is below the difference threshold by subtracting the concentration of the carbon dioxide within the chamber based on one of the signals received from one of the concentration sensors from the source concentration.

[0007] In certain aspects, the one of the concentration sensors is located at the gas outlet of the curing chamber.

[0008] In certain aspects, the concentration sensors includes a first sensor and a second sensor located at two different locations spaced apart along a length of the curing chamber extending from the gas inlet to the gas outlet, the computer-readable medium further having instructions executable by the processing unit to: determine that a concentration gradient within the curing chamber is below a gradient threshold by computing a difference between a first concentration based on a signal received from the first sensor and a second concentration based on a signal received from the second sensor.

[0009] In certain aspects, the first sensor is located upstream of the second sensor.

[0010] In certain aspects, one or more fans are provided in the curing chamber, the controller operatively connected to the one or more fans, the computer-readable medium further having instructions executable by the processing unit to: cause the mitigation actionby causing the one or more fans to rotate, thereby inducing mixing of the input gas in the curing chamber.

[0011] In certain aspects, an auxiliary conduit fluidly connects the source of the input gas to the curing chamber at a location between the gas inlet and the gas outlet, an auxiliary valve fluidly connected to the auxiliary conduit, the first sensor and the second sensor being both located within the curing chamber, the controller operatively connected to the auxiliary valve, the computer-readable medium further having instructions executable by the processing unit to: cause the mitigation action by opening the auxiliary valve to induce a local flow of the input gas directly into the curing chamber via the auxiliary conduit while bypassing the gas inlet of the curing chamber.

[0012] In certain aspects, temperature sensors are distributed along the flow path extending from the source of the input gas to the gas outlet of the curing chamber, the temperature sensors operable to generate signals indicative of a temperature inside the curing chamber, the temperature sensors operatively connected to the controller, the computer-readable medium has the instructions executable by the processing unit to: determine that a temperature gradient within the curing chamber is above a gradient threshold; cause a mitigation action to decrease the temperature gradient.

[0013] In certain aspects, a heater is fluidly connected to the auxiliary conduit, the heater operatively connected to the controller, the computer-readable medium has the instructions executable by the processing unit to: cause the mitigation action by powering the heater to increase a temperature of the input gas flowing into the curing chamber via the auxiliary line.

[0014] In certain aspects, an outlet valve is located downstream of the gas outlet of the curing chamber, the controller operatively connected to the outlet valve, the computer- readable medium further having instructions executable by the processing unit to: cause the mitigation action by opening both of the valve and the outlet valve to induce a flow of the input gas through the curing chamber until the concentration difference becomes below the difference threshold.

[0015] In certain aspects, the computer-readable medium further has instructions executable by the processing unit to: cause the opening of the valve such that an inlet flow of the input gas is injected at an inlet flow rate; and cause the opening of the outlet valvesuch that the outlet flow is outputted out of the curing chamber at an outlet flow rate, the inlet flow rate and the outlet flow rate are selected such that a gas hourly space velocity (GHSV) is within a range of 20 to 100 L / (kg hour), the GHSV corresponding to a ratio of a flow rate of a reactive gas contained in input gas to a mass of the gaseous binder of the formed intermediates contained in the curing chamber.

[0016] In certain aspects, a recirculation conduit fluidly connects the gas outlet of the curing chamber to the gas inlet of the curing chamber along a flow path parallel to the curing chamber, a recirculation valve fluidly connected to the recirculation conduit and operable to permit a recirculation flow from the gas outlet of the curing chamber back to the gas inlet of the curing chamber, and means operatively connected to the recirculation conduit for inducing the recirculation flow in the recirculation conduit.

[0017] In certain aspects, the concentration sensors include an outlet concentration sensor located at or downstream of the gas outlet of the curing chamber, the controller operatively connected to the outlet concentration sensor, the computer-readable medium having the instructions executable by the processing unit to: determine that the concentration difference between the source concentration and the concentration of the carbon dioxide at the gas outlet of the curing chamber based a signal received the outlet sensor is below a second difference threshold; and cause a flow of from the gas outlet of the curing chamber back to the gas inlet of the curing chamber via the recirculation conduit.

[0018] In certain aspects, a bypass conduit fluidly connects the source of the input gas to a location downstream of the curing chamber along a flow path parallel to the curing chamber, a bypass valve fluidly connected to the bypass conduit and operable to permit a bypass flow from the source of the input gas to the location while bypassing the curing chamber.

[0019] In certain aspects, the computer-readable medium has the instructions executable by the processing unit to: determine that the concentration difference between the source concentration and the concentration of the carbon dioxide at the gas outlet of the curing chamber based a signal received the outlet sensor is below a second difference threshold; and cause a bypass flow of the input gas into the bypass conduit for bypassing the curing chamber.

[0020] In certain aspects, the computer-readable medium further has instructions executable by the processing unit to: determine that the concentration of the carbon dioxide within the chamber is below a concentration threshold; and cause the mitigation action by opening the valve to inject a flow of the input gas in the curing chamber unit the concentration is at or above the concentration threshold.

[0021] In certain aspects, the binder includes one or more of steel slag, stainless steel slag, calcium, alumina, silica, and iron oxides.

[0022] There is further provided a method of manufacturing concrete products from formed intermediates composed of water, aggregate, and a gaseous binder, the method comprising: with the formed intermediates within a curing chamber for carbonation curing, injecting an input gas into the curing chamber via a gas inlet, the input gas including carbon dioxide at a source concentration of carbon dioxide; modulating a flow rate of the input gas flowing into the curing chamber via the gas inlet; determining a concentration of the carbon dioxide within the curing chamber at each of a number of positions within the curing chamber; determining a concentration difference between the source concentration and the concentration of the carbon dioxide at each of said number of positions within the chamber; and in response to determining that the concentration difference is above a difference threshold, causing a mitigation action to decrease the concentration difference.

[0023] The method as defined above and described herein further includes, in certain embodiments, one or more of the following features, in whole or in part, and in any combination.

[0024] In certain embodiments, the method includes determining a concentration gradient of carbon dioxide within the curing chamber, and determining that the concentration gradient is below a gradient threshold.

[0025] In certain embodiments, an inlet valve is fluidly connected to the gas inlet and an outlet valve is fluidly connected to a gas outlet of the curing chamber, and causing the mitigation action includes: opening both the inlet valve and the outlet valve to induce a flow of the input gas through the curing chamber between the gas inlet and the gas outlet, until the concentration difference drops below the difference threshold.DESCRIPTION OF THE DRAWINGS

[0026] Reference is now made to the accompanying figures in which:

[0027] Fig. 1 is a schematic representation of a curing system in accordance with one embodiment;

[0028] Fig. 2 is a flowchart illustrating steps of a method of manufacturing concrete products with the curing system of Fig. 1;

[0029] Figs. 3A and 3B are exemplary graphs illustrating possible temperature variations in the curing chamber during a curing process with the curing system of Fig. 1 ;

[0030] Fig. 4 is a graph illustrating variations of temperature inside the curing chamber and variations of weights of the concrete products during a curing process with the curing system of Fig. 1;

[0031] Fig. 5 is an exemplary graph illustrating a possible pressure variation in the curing chamber during a curing process with the curing system of Fig. 1;

[0032] Fig. 6 is a schematic representation of a controller to be used with the curing system of Fig. 1 ; and

[0033] Fig. 7 is a flowchart illustrating steps of a method of manufacturing concrete products as described herein.DETAILED DESCRIPTION

[0034] Various representative embodiments of the described technology will be described more fully hereinafter with reference to the accompanying drawings, in which representative embodiments are shown. The present technology concept may, however, be embodied in many different forms and should not be construed as limited to the representative embodiments set forth herein. Rather, these representative embodiments are provided so that the disclosure will be thorough and complete, and will fully convey the scope of the present technology to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. Like numerals refer to like elements throughout.

[0035] It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another. Thus, a first element discussed below could be termed a second element without departing from the teachings of the present technology. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0036] The terminology used herein is only intended to describe particular representative embodiments and is not intended to be limiting of the present technology. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.Introduction

[0037] There remains growing interest worldwide to reduce the environmental footprint of precast concrete. Carbonation curing technology is among the most promising solutions. During carbonation curing, precast concrete hardens mainly through the so- called carbonation reaction which happens between carbon dioxide and the oxides, and / or hydroxide of calcium and / or magnesium, with the existence of water. Under appropriate raw material selection, mix design and process control, carbonated precast concrete may be as strong and durable as traditional precast concrete, and suitable for a variety of applications.

[0038] Manufacturing precast concrete with carbonation curing technology may address concerns over climate change. Under appropriate processing condition, freshly cast concrete products may achieve rapid hardening when being exposed in CCh-rich environment. Depending on its composition, one tonne of precast concrete has the potential of permanently fixing up to 200 kg CO2 in less than 24 hours of early-age carbonation. This 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 thereplacement of ordinary Portland cement with environmental-friendly and less expensive binders such as steel slag, and so on.

[0039] Mineral carbonation is based on the reaction of CO2 with metal oxide bearing materials to form insoluble carbonates, with calcium and magnesium being the most attractive metals. Mineral carbonation occurs when a high concentration CO2 is brought into contact with metal oxide bearing materials with the purpose of fixing the CO2 as carbonates.

[0040] Due to initiatives regarding carbon emissions, mineral carbonation of CO2 into cement-based materials has gained attention in recent years. The cement industry is a primary producer of carbon dioxide (CO2), which is recognized as a major greenhouse gas. Thus, disadvantageously, large amounts of CO2 are produced by the chemical reactions occurring in the manufacture of cement. Industrial metal oxide bearing residues, such as steel slag, can be carbonated and may be used as a much-reduced CO2-emitting alternative. Concretes processed as such display improved physical performance and better overall resistance to freeze-thaw cycles, sulfate salts, and acids. In addition to binder activation, carbonation’s valorizing potential can also be exploited to recycle suitable industrial wastes into raw building materials. The perpetual fixation of carbon dioxide in building products conduces a more sustainable stance for the concrete industry as it fulfills mandates for lower carbon footprint.

[0041] In the context of the present disclosure, the expressions “cement” and “binder” have different meanings. A binder is a material that, when mixed with water will cause hardening of the mixture to obtain a concrete product. A cement is a specific type of binder. For instance, binders include Ordinary Portland Cement, steel slag, stainless steel slag, and so on. Cements include Ordinary Portland Cement, other kinds of cement. Slags are binders, but they are not considered cements. Binders may include hydraulic binders, such as cement, and gaseous binders, such as wollastonite (C-S), slags (e.g., steel slags). A binder is referred to as “hydraulic” when it reacts with water to cause curing and thus hardening of the concrete product. As defined herein, a binder will be referred to as “gaseous”, i.e., a gaseous binder, when an ingredient other than water is primarily responsible for the hardening of the concrete product. In other words, reaction of the binder material with an ingredient other than water is the dominant mechanism responsible for curing of the concrete product. In the case of steel slag, while it may have some limitedhydraulic properties it is primarily activated by the reaction between the steel slag and carbon dioxide gas such as to reach to ensure curing of the product to a level than provides satisfactory performance. Thus, steel slag is considered a gaseous binder, as defined herein, since it is a gas, carbon dioxide, that is the major contributor to the curing of a concrete product made using steel slag as the binder. A concrete product made with steel slag as the binder and using only water for curing may harden, at least partially, but will likely have a very low compressive strength rendering it practically unusable. A concrete product using steel slag as the binder needs carbon dioxide to cure and achieve suitable properties (e.g., compressive strength).

[0042] Hence, the binder used in this disclosure is a gaseous binder. In this context, the expression “gaseous binder” implies that although a binder may have some hydraulic properties, that is, it may partially harden with water, a gas, such as carbon dioxide allows, is the primary driver of the curing process and thus responsible for allowing the concrete product to achieve its full structural potential during curing. In other words, a binder that is gaseous is a binder that reacts with a gas, such as carbon dioxide, to cure and to achieve suitable compressive strength, even though some hardening may be achieved with water alone. Examples of gaseous binders include steel slag, stainless steel slag, calcium, alumina, silica, and iron oxides, to name a few.

[0043] U.S. Pat. No. 10,112,871 and U.S. Pat. No. 11 ,358,902, the entire contends of which are incorporated herein by reference in their entirety, describe a method of producing a wet-cast slag-based concrete product particularly where the wet-cast slagbased concrete product is partially or completely set inside a mold, pre-conditioned outside of the mold and then subjected to mineral carbonation with exposure to CO2 in a carbonation enclosure.

[0044] There remains growing interest worldwide to reduce the environmental footprint of precast concrete. Conversion of carbon dioxide into solid calcium carbonate, via carbonation, is among the most promising solutions. During carbonation, 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.

[0045] Manufacturing precast concrete with carbonation 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 CO2- rich environment. This CO2 conversion may help to mitigate the CO2 emissions associated with the construction industry. Other advantages of carbonated precast concrete may include the improvement of productivity through rapid hardening, the reduction of production cost through the replacement of ordinary Portland cement with environmental-friendly and less expensive binders such as steel slag.

[0046] In accordance with a first aspect of the present technology, there is provided a system and method for the conversion of carbon dioxide (CO2) into a solid calcium carbonate for use in CO2 containing concrete products, the system comprising at least one carbonation enclosure; at least one gas handling system; at least one control system; at least one source of carbon dioxide; at least one metal-oxide bearing material; at least one computer-implemented machine learning method for optimizing the conversion of carbon dioxide into a solid calcium carbonate.Curing System

[0047] Referring now to FIG. 1 , an exemplary system for conditioning and curing a concrete product is shown at 10. The system 10 may be referred to as a scrubbing system since it may be used to at least partially clean flue gas out of carbon dioxide as will be discussed below. The system 10 includes a source of an input gas 11 that contains carbon dioxide 11 at a source concentration of carbon dioxide. In some embodiments, more than one source of input gas may be used. The source of the input gas 11 may be a reservoir or tank, pneumatically connected to an enclosure 12 via a line 13. The source of the input gas 11 may be a device generating flue gas, such as a thermal engine (e.g., gas turbine engine, reciprocating engine, etc.). In other words, the source of the input gas 11 may be a source of flue gas being at a CO2 concentration of at least about 10%, but typically around 15% to 50%. For a remainder of the present disclosure, the gas contained in the source 11 will be referred to as “input gas” since it may contain other constituents than only CO2.

[0048] The enclosure 12 defines an inner space or chamber 12A, also referred to as a curing chamber, that is sized to accept a plurality of concrete products C to be cured. Inthe 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.

[0049] The dimensions of the curing chamber 12A are carefully designed based on the quantities of the intended reactive / non-reactive material and / or mixture with aggregates, the characteristics of the input gas, as well as the reaction kinetics between the absorbent material and the input gas.

[0050] The curing system 10 includes a delivery system and entry ports equipped with valves, seamlessly linked to the curing chamber 12A. This configuration may facilitate the replenishment of the input gas either through continuous or under closed loop conditions, enabling both batch and continuous operations as will be discussed below. The curing chamber 12A has a gas inlet 12B and a gas outlet 12B.

[0051] More specifically, the system 10 includes an inlet valve 14 that fluidly connects the source 11 to the gas inlet 12A of the curing chamber 12A. The inlet valve 14 may thus have a closed configuration in which the inlet valve 14 fluidly disconnects the source 11 from the curing chamber 12A and one or more open configurations in which the inlet valve 14 fluidly connects the source 11 to the curing chamber 12A through the inlet valve 14. Each of the one or more open configurations may be associated with a respective flow circulating area. Hence, a mass flow rate of the input gas through the inlet valve 14 may be controlled by varying the flow circulating area. The inlet valve 14 may thus be an actuated valve. The inlet valve 14 thus has a plurality of positions to modulate a flow rate of the input gas flowing there through.

[0052] The system 10 includes a bypass conduit 15 that fluidly connects a section of the line 13 upstream of the curing chamber 12A to a section of the line 13 located downstream of the curing chamber 12A while bypassing the curing chamber 12A. The bypass conduit 15 therefore defines a bypass flow path via which the input gas maybypass the curing chamber 12A. A bypass valve 16 is fluidly connected to the bypass conduit 15 and has open and closed configurations to selectively permit the input gas to bypass the curing chamber 12A. The bypass valve 16 may have a variable flow circulating area to control a flow rate of the input gas therethrough. In some embodiments, the bypass valve 16 is in its open configuration when the inlet valve 14 is in its closed configuration.

[0053] The system 10 further includes an outlet valve 17 fluidly connected to the gas outlet 12C of the curing chamber 12A. The outlet valve 17 is used to allow a by-product gas to leave the curing chamber 12A. More specifically, as the concrete products C absorb the CO2 contained in the input gas, a concentration in CO2 in the input gas decreases over time. Also, emanation from the concrete products C may cause a constitution of the input gas to vary. Hence, the gas that exits the curing chamber 12A may be referred to as the “by-product gas”. At some point, the concentration is not sufficient to allow further curing of the concrete products C. Thus, the outlet valve 17 opens to allow the at least partially depleted input gas, which is referred to below as the by-product gas, to exit the curing chamber 12A. The outlet valve 17 thus has a closed configuration to prevent the input gas from exiting the curing chamber 12A and an open configuration to allow the input gas from leaving the curing chamber 12A. Also, the outlet valve 17 may act as a pressure regulating valve permitting some of the input gas to exit the curing chamber 12A when a pressure inside the curing chamber 12A exceeds a given pressure threshold. The outlet valve 17 may thus have a plurality of open positions to vary a flow rate of a flow exiting the curing chamber 12A.

[0054] In some embodiments, the system 10 includes a recirculation conduit 18 extending from a first location on the line 13 downstream of the curing chamber 12A and upstream of the outlet valve 17 to a second location on the line 13 downstream of the inlet valve 14 and upstream of the curing chamber 12A. The recirculation conduit 18 bypasses the curing chamber 12A and is used to recirculate at least a portion of the by-product gas when said portion still has a concentration of CO2 being above a given threshold. A recirculation valve 19 is fluidly connected to the recirculation conduit 18 and has open and closed configurations for selectively allowing a flow of the by-product gas through the recirculation conduit 18. A flow circulating area of the recirculation valve 19 may be adjusted to vary a flow rate of the by-product gas through the recirculation conduit 18. Apump 19A or any other suitable means may be used to induce a flow of the by-product gas through the recirculation conduit 18.

[0055] As the input gas travels along the curing chamber 12A along direction D1 , its concentration in CO2 may decrease such that the concrete products C located closer to the outlet valve 17 may be exposed to a gas having a lower concentration of CO2 compared to the concrete products C located closer to the inlet valve 14. To at least partially remedy this drawback, the curing chamber 12A may include auxiliary inlet ports 12B longitudinally distributed along the direction D1. An auxiliary line 20 may stem from the line 13 upstream of the inlet valve 14 and fluidly connects the source of the input gas 11 to the auxiliary inlet ports 12B. As illustrated, a plurality of sub-conduits 21 may stem from the auxiliary line 20 and each may be fluidly connected to a respective one of the auxiliary inlet ports 12B. An auxiliary valve 22 is fluidly connected to the auxiliary line 20 and used to selectively connect or disconnect the source 11 to the auxiliary inlet ports 12B. The auxiliary valve 22 may have a variable flow circulating area to vary a flow rate of the input gas flowing therethrough and flowing into the auxiliary inlet ports 12B.

[0056] In some embodiments, it may be desired to ensure a uniform temperature of the input gas injected in the curing chamber 12A to minimize temperature gradient across the curing chamber 12A. To do so, heaters 23 may be provided along the auxiliary line 20 to heat the input gas before it reaches the auxiliary inlet ports 12B of the curing chamber 12A. The heaters 23 may alternatively be located inside the curing chamber 12A. Alternatively, the heaters 23 may heat walls of the enclosure 12. Uniform temperature and higher temperature may lead to improved absorption of CO2 by the concrete products C.

[0057] In some embodiments, the enclosure 12 may be used to cure the concrete products C 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 is 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).

[0058] In some embodiments, blowers 24 may be located in the curing chamber 12A and operable to circulate the gas contained in the curing chamber 12A. This may help inuniformizing properties of the gas contained in the curing chamber 12A. These properties may include, for instance, CO2 concentration, temperature, relative humidity, and so on.

[0059] In some embodiments, the concrete products C may be supported by a balance operable to generate a signal indicative of weights of the concrete products C. The weight variation from a start of the curing process may be indicative of whether or not the curing of the concrete products C is completed.

[0060] A desiccant material may be located inside the curing chamber 12A to absorb humidity released from the concrete products C during a conditioning and / or curing phase. 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 be used. For instance, a de-humidifier, an air conditioning, and any other suitable means may be used.

[0061] The system 10 includes a controller 30 operatively connected to the inlet valve 14, the bypass valve 16, the outlet valve 17, the recirculating valve 19, the auxiliary valve 22, the heaters 23, and the blowers 24. The controller 30 is further connected to a plurality of sensors, such as concentration sensors 31 distributed longitudinally along the direction D1 to measure the variation of the concentration of CO2 along the curing chamber 12A and to other sensors 32, such as pressure sensors, humidity sensors, flow rate sensors, gas velocity sensors, and temperature sensors, which may be longitudinally distributed along the curing chamber 12A. The concentration sensors 31 may be, for instance, infrared sensors or near-infrared (NIR) sensors. The concentration in CO2 may bedetermined via gas chromatography, mass spectrometry, or similar non-destructive methods. The temperature sensors may be thermocouples or infrared sensors.

[0062] To assess the percentage of CO2 converted during curing, the mass gain method may be used. This method, expressed in the following equation, estimates the mass difference before and after carbonation. The mass difference, together with water evaporated from the exothermic carbonation reaction, represents the mass gain due to carbon dioxide uptake or conversion. The carbonation reaction is exothermic in nature, and as a result some of the water used in the mixture evaporates and condenses on the inner walls of the enclosure 12 and is collected in a water collection tank. The mass of the wastewater is added to the mass of the cured concrete products since it was part of the original mixture.Methods

[0064] Referring now to Fig. 2, a method for curing the concrete products C is shown at 200. The method 200 includes causing the inlet valve 14 to inject a flow of the input gas into the curing chamber 12A for curing the formed intermediates a 202; determining that a concentration difference between the source concentration of the input gas from the source 11 and the concentration of the carbon dioxide within the chamber 12A based on one or more of the signals received from one or more of the concentration sensors 31 is above a difference threshold at 204; and causing a mitigation action to decrease the concentration difference at 206.

[0065] The method 200 may include determine that the concentration difference is below the difference threshold by subtracting the concentration of the carbon dioxide within the chamber 12A based on one of the signals received from one of the concentration sensors 31 from the source concentration. The one of the concentration sensors 31 may be located at the outlet of the curing chamber 12A. The concentration of the gas injected into the curing chamber 12A from the source 11 is known. The concentration difference may be computed with a subtraction. Alternatively, one of the concentration sensors 31 may be located upstream of the curing chamber 12A and operable to generate a signal indicative of the concentration of the input gas. These two values may be subtracted to obtain the concentration difference.

[0066] In some embodiments, the concentration sensors 31 includes a first sensor and a second sensor located at two different locations spaced apart along a length of the curing chamber 12A extending from the inlet to the outlet along the direction D1. The method 200 may further include determining that a concentration gradient within the curing chamber 12A is below a gradient threshold by computing a difference between a first concentration based on a signal received from the first sensor and a second concentration based on a signal received from the second sensor. The first sensor is located upstream of the second sensor. The expression “concentration gradient” implies a variation of concentration along the length of the curing chamber 12A. The greater the concentration difference between two locations in the curing chamber 12A, the greater is the gradient.

[0067] Some of the mitigation actions that may be used to are described below. The mitigation actions are used to either reduce the concentration gradient within the chamber 12A or ensure that there is enough CO2 inside the chamber 12A for proper carbonation curing of the concrete products C.

[0068] In some embodiments, the method 200 includes causing the mitigation action by causing the one or more fan or blower 24 to rotate to induce mixing of the input gas in the curing chamber 12A. The movements of the gas inside the chamber 12A caused by the one or more blower 24 may help in uniformizing the temperature, concentration, relative humidity and so on within the chamber 12A.

[0069] In some cases, it may be possible to locally inject the input gas where it is determined, from the concentration sensors 31 , that the concentration is below than a desired value. In this case, the mitigation action may include opening the auxiliary valve 22 to induce a local flow of the input gas directly into the curing chamber 12A via the auxiliary line 20 while bypassing the inlet of the curing chamber and the inlet valve 14. Any of the sub-conduits 21 may be used. In some cases, valves may be individually located on each of the sub-conduits 21 to select where along the curing chamber 12A more CO2 is needed.

[0070] In some cases, the sensors include temperature sensors 32 distributed along the flow path extending from the source of the input gas 31 to the outlet of the curing chamber 12A. The temperature sensors operable to generate signals indicative of a temperature inside the curing chamber 12A. The method 200 may include determine that a temperature gradient within the curing chamber is above a gradient threshold; and cause a mitigation action to decrease the temperature gradient.

[0071] The mitigation action may include powering the blower(s) 24. In some cases, the mitigation action may include powering the heater(s) 23 to increase a temperature of the input gas flowing into the curing chamber 12A via the auxiliary line 20.

[0072] In some embodiments, the causing of the mitigation action may include opening both of the inlet valve 14 and the outlet valve 17 to induce a flow of the input gas through the curing chamber 12A until the concentration difference becomes below the difference threshold. This may include causing the opening of the inlet valve 14 such that an inlet flow of the input gas is injected at an inlet flow rate; and causing the opening of the outlet valve 17 such that the outlet flow is outputted out of the curing chamber 12A at an outlet flow rate. The inlet flow rate and the outlet flow rate are selected such that a gas hourly space velocity (GHSV) is within a range of 20 to 100 L / (kg hour) the GHSV corresponding to a ratio of the inlet flow rate of reactive gas in the input gas (e.g., CO2 in the flue gas) to a mass of the binder of the formed intermediates contained in the curing chamber 12A. The reactive gas is the component of the input gas that reacts with the binder. For instance, flue gas includes CO2, which reacts with the binder, and other constituents that do not react with the binder. In some embodiments, the concentration sensors 31 include an outlet concentration sensor located at or downstream of the outlet of the curing chamber 12A. The method 200 may include determining that the concentration difference between the source concentration and the concentration of the carbon dioxide at the outlet of the curing chamber 12A based a signal received the outlet sensor is below a second difference threshold; and cause a flow of from the outlet of the curing chamber back to the inlet of the curing chamber 12A via the recirculation conduit 18. This situation may be used if the concrete product 16 did not absorb enough CO2 for the CO2 concentration to substantially decrease. Hence, the gas exiting the curing chamber 12A may have enough CO2 left in it to be re-used as the input gas. The gas exiting the curing chamber 12A may thus be reinjected at the inlet of the curing chamber 12A via the recirculation conduit 18.

[0073] In some embodiments, the method 200 includes determining that the concentration difference between the source concentration and the concentration of the carbon dioxide at the outlet of the curing chamber 12A based a signal received the outlet sensor is below a second difference threshold; and causing a bypass flow of the input gas into the bypass conduit 15 for bypassing the curing chamber 12A. The bypass conduit 15 may be used to allow the input gas to bypass the curing chamber 12A when not needed,for instance, if a concentration of the CO2 in the curing chamber 12A is satisfactory. The input gas may then be used in another curing chamber 12A.

[0074] In some embodiments, the method includes determining that the concentration of the carbon dioxide within the chamber is below a concentration threshold; and causing the mitigation action by opening the inlet valve 14 to inject a flow of the input gas in the curing chamber 12A unit the concentration is at or above the concentration threshold.

[0075] Referring now to Fig. 7, a method 700 of manufacturing concrete products, beginning with formed intermediates composed of water, aggregate, and a gaseous binder, is depicted.

[0076] The method 700 includes, at step 702, with the formed intermediates within the curing chamber 12A, injecting an input gas into the curing chamber via a gas inlet, the input gas including carbon dioxide at a source concentration of carbon dioxide. At step 704, the method 700 includes modulating a flow rate of the input gas flowing into the curing chamber via the gas inlet. At step 706, a concentration of the carbon dioxide is determined within the curing chamber at each of a number of positions within the curing chamber. The method 700 then includes, at step 708, determining a concentration difference between the source concentration and the concentration of the carbon dioxide at each of said number of positions within the chamber. Accordingly, at step 710 and in response to determining that the concentration difference is above a difference threshold, a mitigation action is caused to decrease the concentration difference.

[0077] The method 700 may be implemented in conjunction with the curing system 10 as described herein. Additionally, the method 700 may further include any of the method steps described elsewhere herein (including, for example, method 200) and / or implement any features of the present curing system 10.

[0078] In a particular embodiment, the method 700 further includes determining a concentration gradient of carbon dioxide within the curing chamber, and determining that the concentration gradient is below a gradient threshold.

[0079] In another particular embodiment, the method 700 further includes providing an inlet valve fluidly connected to the gas inlet and an outlet valve fluidly connected to a gas outlet of the curing chamber, and causing the mitigation action by: opening both the inlet valve and the outlet valve to induce a flow of the input gas through the curing chamberbetween the gas inlet and the gas outlet, until the concentration difference drops below the difference threshold.Continuous flow curing vs. Cycling purging curing

[0080] The methods 200 and 700 are applicable to both processes: continuous flow curing and cycling purging curing. In continuous flow curing method, both of the inlet and outlet valves 14, 17 are left open and there is a constant flow of the input gas entering the curing chamber 12A and a constant flow of the by-product gas exiting the curing chamber 12A. In some cases, the concrete products C may consume more or less of the carbon dioxide, which may lead to a concentration gradient in the curing chamber. The mitigation actions described above may be used to reduce the concentration gradient. In the cycling purging curing method, the inlet valve 14 is open to fill the curing chamber 12A with the input gas. The outlet valve 17 may be open momentarily to purge the curing chamber 12A from air it contains. At some point, the outlet valve 17 is closed and the curing chamber 12A is fluidly isolated from an environment outside therefrom for a given period of time. The concentration sensors may provide indication about how the concentration in CO2 varies through the process. If a gradient greater than a set threshold is present, the mitigation actions described above may be used. The concentration sensors 31 may further provide an indication of how the concentration decreases during the curing of the concrete products C. At some point, the concentration may fall below a threshold below which little to no carbonation curing occurs. The outlet valve 17 may then be open to purge the curing chamber 12A of the by-product gas and new input gas may be admitted by opening the inlet valve 14.

[0081] Hence, the curing system 10 may be used to remove at least a portion of carbon dioxide contained in flue gas. The curing system 10 may be used to “clean” flue gas before freeing this gas into the environment.

[0082] The disclosed methods may enable dynamic adjustment of chamber properties (e.g., temperature, pressure, CO2 concentration, etc.) over time. This may allow for optimization of CO2 absorption, dissolution, and reaction with reactive or nonreactive absorbent materials.

[0083] Referring now to Figs. 3A-3B, examples of temperature cycling are shown. In some embodiments, the temperature of the input gas transitions from low initial values (e.g., 20-30°C) to enhance CO2 dissolution, to higher temperatures (e.g., 50°C) to promotefurther reaction and crystallization of the primary reaction product, carbonates (i.e., (Ca / Mg)CC>3). Temperature variations can be implemented in multiple steps as shown in the graphs of Figs. 3A-3B.

[0084] In some embodiments, it may be desired to increase the pressure in the curing chamber 12A above ambient pressure. To do so, the outlet valve 17 may be used to allow an outlet mass flow rate being less than an inlet mass flow rate thereby maintaining a given pressure in the chamber. The gauge pressure may be set to from 0 to 6 PSIG and is controlled by controlling a difference between inlet and outlet flow rates.Data

[0085] In some embodiments, the controller 30 is equipped with data pertaining to the parameters required to establish optimal conditions for curing specific product types, considering their composition and the ratio of reactive to nonreactive components, such as slag (binder), chemical / mineral admixtures, and granular materials in consolidated, liquid, or slurry forms. These optimal conditions may be determined through experimental methods or derived from theoretical correlations.

[0086] Detailed experimental data can be obtained from thermogravimetric measurement of precast specimens during curing. As illustrated in Fig. 4, the thermogravimetric results of the evaluation of temperature and mass gain for the pre- casted - control samples, with net dimensions assembling typical thicker products conditions is shown. It shows the complete profile of mass gain and temperature of the specimen, solid precast temperature 1-3, and the temperature of the bulk phase, for 24 h curing at predetermined concentration, pressure, and fluid dynamic conditions.

[0087] The closed-up shows the profile for the initial stage of carbonation, 1.5-2 h. The solid temperature increased the first hour reaching around 70 C, as well as an increase in the mass gain was achieved, with a higher rate measured at the initial 1 to 2 hour curing. After the first hour, the temperature started to decrease while the mass change continuously increased until it reaches a stable value around 20 hour curing.

[0088] The initial increase in mass and temperature primarily arises from the conversion of CO2 to metal carbonates (MCO3) within the reactive absorbent in solid or liquid phase. Since the reaction is exothermic, the temperature rises until the reaction rate can no longer sustain it, due to the formation of passive layer of carbonation products.These products include carbonates of metal cations, bicarbonates of metal cations, calcium aluminate carbonates, or hydrotalcite. By-products, which may manifest in solid, gas, or vapor phases, consist of calcium silicate hydrate (C-S-H), calcium aluminum silicate hydrate (C-A-S-H), calcium / magnesium hydroxide, and other secondary carbonate / hydrate products, along with water. Moreover, the controller can utilize machine learning to assist in selecting or improving current scrubbing chamber conditions. This is achieved by comparing actual process condition values with stored optimal data, thereby maximizing the yield of desired reactive products.

[0089] During batch operation, for the cycling purging curing method, there is an intermittent or nonexistent flow of the bulk phase entering and leaving the scrubbing system simultaneously. A flow stream containing measurable concentrations of gases, primarily carbon dioxide (CO2), enters an enclosure. The concentration of the input gas entering the enclosure is measured under standard temperature and pressure (STP) conditions, ranging from 5 to 100 vol%. and an intended gauge pressure from 0.1 to 6 Psig. Once the pressure and concentration are reached, or during ramping up, the gas can remain static with zero or close to zero velocity (m / s) or be under recirculation. The variation of the pressure in the chamber is shown in Fig. 5. The fluid dynamic conditions may be adjusted to enhance product transport from / to the input gas with the binder.

[0090] The reaction between the input gas and the concrete products C results in the formation of desired reactive products and by-products. Reactive products encompass carbonates of metal cations, bicarbonates of metal cations, calcium aluminate carbonates, or hydrotalcite, while by-products may manifest in solid and gas / vapor phases, such as calcium silicate hydrate (C-S-H), calcium aluminum silicate hydrate (C-A-S-H), calcium / magnesium hydroxide, and other secondary carbonate / hydrate products alongside water. This product formation hinders the dissolution of CO2 and further product formation. The present process disclosure addresses cyclic process conditions to enhance carbonation by influencing the inhibiting behavior of the passive product layers.

[0091] In the cyclic purging method, once the targeted conditions are attained (e.g., concentration and pressure), the content of the chamber is purged. This action results in a drop in system pressure to lower levels, typically ranging from 0-1 Psig as depicted in Fig. 5. This purging process can be repeated multiple times during the curing process andoptimized based on thermogravimetric experiments. The duration of purging and the level of pressure can range from 0-5 minutes and 0-6 Psig respectively.

[0092] As the input gas reacts with the concrete products, it leads to the formation of desired reactive products and by-products. Reactive products may include carbonates of metal cations, bicarbonates of metal cations, calcium aluminate carbonates, or hydrotalcite, while by-products can exist in solid and gas / vapor phases, such as calcium silicate hydrate (C-S-H), calcium aluminum silicate hydrate (C-A-S-H), calcium / magnesium hydroxide, and other secondary carbonate / hydrate products along with water. Such product formation inhibits the dissolution of CO2 and further formation of products. The current process disclosure covers cyclic process conditions, to enhance carbonation, by influencing the inhibitor behavior of the products.

[0093] In cyclic purging method, once the closed system, scrubbing chamber, has achieved targeted conditions such as concentration and pressure, then the bulk phase content is exhausted from the chamber. This will cause the pressure of the system drop to lower levels, 0-1 Psig. The duration of the purging and the level of pressure can be 0- 5mins and 0-6Psig. This process can be repeated several times during the curing process and can be optimized following thermogravimetric experiments.

[0094] The following text describes the different constituents of the concrete products C and steps that may be performed before placing the products in the curing chamber 12A for curing.Aggregate

[0095] 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-core slabs, patio slabs, steps, curbs, concrete masonry units, beams, floors, columns, manholes, sewage pipes, railroad ties, and other precast concrete products.

[0096] The aggregate used in carbonated precast concrete production is typically a binary blend of coarse aggregate and fine aggregate. Coarse aggregate generally refersto 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.

[0097] 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 (V / 2”). The most frequently used maximum size of coarse aggregate is 19 mm (3 / 4”) or 9.5 mm (3 / 8”). For fine aggregate, it is allowed to contain a maximum of 5% (mass) particles coarser than 4.75 mm (No. 4 sieve) by ASTM C33. About the grading of aggregate, well-graded coarse 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.

[0098] Although generally accounting for 50-75% of the volume in carbonated precast concrete, aggregate is often considered as an inert filler. The possible impact of aggregate on the manufacture and performance of carbonated precast concrete has been long overlooked.

[0099] In one embodiment of the current disclosure, the disclosed carbonated precast concrete is made of aggregate with no more than 10% accumulated mass retained on No. 8 sieve (2.36 mm opening) and larger-size sieves. In another embodiment of currentdisclosure, the disclosed carbonated precast concrete is made of aggregate with 100% passing No. 8 sieve (2.36 mm opening). In another embodiment of current disclosure, the disclosed carbonated precast concrete is made of aggregate with 100% passing No. 16 sieve (1.18 mm opening). In another embodiment of current disclosure, the disclosed carbonated precast concrete is made of aggregate with 100% passing No. 30 sieve (0.6 mm opening). In another embodiment of current disclosure, the disclosed carbonated precast concrete is made of aggregate with 100% passing No. 50 sieve (0.3 mm opening). In another embodiment of current disclosure, the disclosed carbonated precast concrete is made of aggregate with 100% passing No. 100 sieve (0.15 mm opening). In another embodiment of current disclosure, the disclosed carbonated precast concrete is made of aggregate with 100% passing No. 200 sieve (0.075 mm opening). In a further embodiment of the present disclosure, the disclosed carbonated precast concrete is made of sieved fine aggregate with 100% passing No. 8 (2.36 mm) and removed with particle 100% passing No. 100 sieve (0.15 mm opening).

[0100] In the context of the present disclosure, the expression “no more than Y% accumulated mass retained on No. X sieve” implies that, for a given mass of aggregate (e.g., 1 kg) no more than Y% of that mass will be retained on the No. X sieve. For instance, saying “no more than 10% accumulated mass retained on No. 8 sieve (2.36 mm opening)” means that for one kilogram of aggregate, no more than 100 grams of that aggregate will be retained on the No. 8 sieve; the remaining 900 grams of the aggregate will pass through openings of the No. 8 sieve.

[0101] Additionally, the disclosed carbonated precast concrete is made of fine aggregate with varying density. In one embodiment, the disclosed carbonated precast concrete is made of normal-weight aggregate, with dry rodded density in the range of 1100-1850 kg / m3. In another embodiment, the disclosed carbonated precast concrete is made of lightweight aggregate, with dry rodded density less than about 1100 kg / m3. In a further embodiment, the disclosed carbonated precast concrete is made of heavyweight aggregate, with dry rodded density greater than 2100 kg / m3, respectively.

[0102] The “dry rodded density” used herein refers to a mass per unit volume of dry aggregate, which includes the volume of the particles and the voids between the particles, compacted by rodding. Rodding compaction is a process by which a compaction force isapplied to the aggregate to increase particle to particle contact and decrease the volume of the voids between those particles.

[0103] In addition, the disclosed carbonated precast concrete is made of fine aggregate from different sources. In one embodiment, the disclosed carbonated precast is made of natural origin, such as sand. In another embodiment, the disclosed carbonated precast is made of manufactured aggregate from natural origin, such as crushed stone fine, expanded perlite, expanded shale, and so on. In a further embodiment, the disclosed carbonated precast is made of manufactured aggregate from recycled sources, such as crushed glass, crushed air-cooled granulated blast furnace slag, crushed construction and demolition waste (recycled concrete, brick, and stone rubble), and so on. Furthermore, in one embodiment, the disclosed carbonated precast concrete is made of a combination of the above-mentioned aggregates in terms of their particle size, and / or source, and / or density. In some embodiments, some slag may be used as a binder whereas some other slag may be used as an aggregate. A difference between slag as a binder and slag as an aggregate pertains mainly the particle size; slag as aggregate is usually much coarser than the slag as binder. In some cases, slag as a binder may differ from slag as an aggregate by their chemical compositions and reactivity to carbon dioxide or water; to make a slag as a binder, it has to be ground sufficiently fine and it has to have the compounds to react with carbon dioxide or water to harden. In one embodiment, particles of slag as used as a binder are finer than 0.8 mm whereas particles of slag as used as an aggregate have a fineness of greater than 0.8 mm (i.e. they are coarser than 0.8 mm). Therefore, if the aggregate includes particles of slag, these particles of slag are coarser than 0.8 mm.

[0104] Additionally, the disclosed fine aggregate can be of natural, or manufactured, or recycled origin. Furthermore, the described fine aggregate may be normal weight, or lightweight, or heavy weight according to its density. The described fine aggregate can also be a combination of a plurality of the above-mentioned aggregates in terms of their particle size, and / or source, and / or density. Thus, the aggregate may have many portions by mass, each of these portions may include particles having a respective density, fineness, and origin. The disclosed carbonated precast concrete may have the advantage of requiring at least 50% less conditioning time than regular carbonated precast concrete.In addition, the disclosed carbonated precast concrete may have greater CO2 uptake, strength, and durability than regular carbonated precast concrete.

[0105] Herein, the expression “finer than X mm”, where “X” is a numerical value, means that a particle of the aggregate has passed or is capable of passing through a sieve with a nominal aperture size of “X” mm, by following the sieve analysis method instructed by ASTM C136 (Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates). For instance, if a particle of the aggregate is finer than about 2.36 mm, it implies that this particle has passed (or is capable of passing) though a sieve with a nominal aperture size of 2.36 mm by following the ASTM C136 method. Similarly, the expression “coarser than Y mm”, where “Y” is a numerical value, means that a particle of the aggregate has retained on sieve with nominal aperture size larger than and equal to “Y” mm by following the ASTM C136 method.Binder, Water, and Additives

[0106] After the aggregate suitable for manufacturing the disclosed 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).

[0107] The binder(s) suitable for manufacturing the disclosed carbonated precast concrete should be reactive towards carbon dioxide. Put differently, the binder used is referred to as a gaseous binder since it primarily cures in presence of carbon dioxide. This is different than ordinary Portland cement (OPC) that is a hydraulic binder, which hardens in the presence of water. The contends of the present disclosure focuses on curing concrete products using a gaseous binder.

[0108] The binder(s) suitable for manufacturing the disclosed carbonated precast concrete may be any or a combination of cementitious and supplementary cementitious binders, which are termed conventional “binders” in this disclosure. The conventional binders are the ones currently 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.

[0109] The binder(s) suitable for manufacturing the disclosed 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, bottom ash from municipal solid waste incineration, and so on.

[0110] The binder(s) suitable for manufacturing the disclosed 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.

[0111] As shown in the examples below, steel slag may be used herein as the sole component of a 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, “EBH slag” 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.

[0112] In other words, “slag” herein refers to the slag by-product produced from making steel and / or stainless steel. Steel slag may include slag produced from Basic Oxygen Furnaces (BOF). Steel slag may also include slag produced from Electric Arc Furnaces (EAF). Steel slag as used herein may further include ladle slag. 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. Stainless steel slags are a by product of stainless steel production.

[0113] “Ladle slag” herein refers to a type of steel slag. Ladle slag is produced as a by-product from a ladle refining operation. In various steel making processes, molten steel produced in an EAF or BOF process undergoes an additional refining processes based on the quality of the desired steel. Additional fluxes and alloys are added to a ladle to remove the impurities within the steel and to produce steel with the desired properties. The reaction takes place in the presence of a slag in which the most significant oxides are SiO2, AI2O3, CaO, and MgO. This operation is known as ladle refining, because it is executed in the transfer ladle. During this process, additional steel slags are generated, which are ladle slags. It has been observed that the chemical compositions of ladle slag which are linked to the grade of the steel produced are highly variable and different from the chemical compositions of BOF and EAF steel slags. It has been observed that ladle slag shows higher aluminum oxide content and lower iron oxide content as compared to BOF and EAF steel slags. Generally, ladle slags exhibit a calcium oxide to silica oxide ratio of about 2.

[0114] “EBH slag” herein refers to EAF-BOF-Ladle Hybrid, which is a type of steel slag formed of a mixture of EAF and BOF and ladle produced slags.

[0115] In one embodiment, the steel slag used herein has a cumulative calcium silicate content (ex: OS + 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: OS + 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: OS + 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 slagused herein has a SiC>2 content of at least about 6% or more preferably at least about 15% by weight.

[0116] 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 EBH steel slag (mix of EAF and BOF and ladle slag), the slag may be pulverized to a Blaine fineness of at least 100 m2 / kg and preferably about 240 m2 / kg. In other exemplary embodiments, the steel slag may be pulverized to a finer size. In another example, at least fifty percent of ground slag may be smaller than 100 microns, and at least ten percent of ground slag may be smaller than 50 microns, i.e., D(50) < 100 microns, and D(10) < 50 microns.

[0117] 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.

[0118] Any potable water is 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.

[0119] Additives that are suitable for manufacturing the disclosed 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 silicareaction inhibitor, shrinkage reducer, corrosion inhibiting admixture, pigment, mineral admixture, reinforcing fiber, polymer, and so on. The dosages of the additives used to manufacture the disclosed carbonated precast concrete follow the general rules which are known for people with ordinary skill in the art.

[0120] In some embodiments, the providing of the composition includes providing the composition including 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. The mixing of the composition at 202 may include mixing the composition with one or more of cellulose fibers, glass fibers, micro synthetic fibers, natural fibers, polypropylene fibers, polyvinyl alcohol fibers, and steel fibers.

[0121] In some embodiments, the method 200 includes mixing the water, the aggregate, and the binder including steel slag. In some embodiments, the method 200 includes mixing the water, the aggregate, and the binder having a binder content being from 8% to 50% by weight of the concrete mixture. The binder may be devoid of cement. The binder may consist of steel slag.

[0122] In the context of the present disclosure, the expressions “binder” and “cement” have different meaning. A cement, such as Ordinary Portland Cement, is a kind of binder. A cement may be considered a binder, but not all binders are cements.

[0123] In the embodiment shown, the method 200 includes mixing of the composition including the binder includes mixing the composition being free of another binder. In other words, only the binder that meets the MM ratio of at least 0.5 may be used in the composition. Alternatively, one or more second binder may be used. Preferably, a ratio of a mass of the binder to a sum of the mass of the binder plus a mass of the one or more second binder being at least 80%. Put differently, the binder that meets the MM ratio of at least 0.5 constitute at least 80% by weight of the total weight of binder used.Mixture and Forming

[0124] In the embodiment shown, the method may include a step of mixing the binder, the aggregate, and the water to produce the concrete mixture may include producing 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 producing a dry mixture having a different mixture water-to-binder ratio. Generally, the content binder in the mixture varies from 8% to 50%, in accordance with the binder type and also the application of carbonated precast concrete. The water-to-binder ratio may be about 0.15- 0.50. There are many suitable ways to perform the mixing of the concrete mixture, for example with a pan mixer.

[0125] Herein, a form is imparted to the concrete mixture. This may include casting the concrete mixture in a mould to provide a moulded intermediate. The method of the present embodiment includes a step of demoulding the moulded intermediate to provide a demolded intermediate. In some embodiments, the carbon curing of the formed intermediate may include curing the formed intermediate while the formed intermediate is still in the mould. Alternatively, the carbon curing may include curing the demolded intermediate.

[0126] The imparting of the form to the concrete mixture may include forming and consolidating the concrete mixture under compaction and vibration to provide the formed intermediate. In some embodiments, the imparting of the form may include transferring the freshly prepared concrete mixture by any appropriate means and casting in a prepared mould. The mould may be made of steel, iron, aluminum, plastic, FRP or another material. The mould may be pre-lubricated prior to casting in order to facilitate the demoulding process. If using a wet mix, it may be consolidated within the mould 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 mould 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.

[0127] In some embodiments, the method may include demoulding the formed intermediate before the carbon curing. The method may include conditioning the formed intermediate until a water-to-binder ratio, which corresponds to a first water-to-binder ratioafter the imparting of the form, reaches a second water-to-binder ratio lower than the first water-to-binder ratio. After the conditioning step, the conditioned intermediate may be demolded to provide a demolded conditioned intermediate. This demolded conditioned intermediate may then go through the carbon curing step.

[0128] In some embodiments, the method may include inserting a reinforcing material inside the mould before the casting of the concrete mixture. The inserting of the reinforcing material may include inserting bars made of the reinforcing material, the reinforcing material including one or more of carbon steel, stainless steel, and fiber reinforced polymer.

[0129] In some embodiments, the water-to-binder ratio before the conditioning may be about 0.2 with normal aggregates and from 0.07 to 0.1 with finer aggregates as described herein. The water-to-binder ratio may be about 0.15 before the conditioning. Thus, the finer aggregates may result in having to extract less moisture from the intermediate. This may, in turn, reduce a time of the condition step. Other water-to-binder ratios are contemplated depending on the binders and aggregates being used.

[0130] 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. The step of imparting a form to the concrete mixture may require an amount of the mixture to be cast into a mould with preset dimensions and shape, followed with being leveled. Consolidation is then conducted to condense precast concrete mixture in the mold to the required thickness or height. Consolidation may be achieved through the known ways, such as any or a combination of vibration, compaction and compression.

[0131] After molding is completed, the consolidated precast concrete may be taken out of the mould or demolded immediately if it is rigid enough. Otherwise, the consolidated precast concrete may be required to be maintained in the mold for a period generally less than 24 hours. This may be referred to as a pre-curing step. This process may help the consolidated precast concrete to obtain sufficient green strength before being demolded. It happens when a wet concrete mixture is used for precast concrete forming. Pre-curing, if required, may be conducted at room temperature. It can also be accelerated at elevated temperature.

[0132] 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 0.15 to 0.5.Conditioning

[0133] Although the conditioning step may start when the consolidated precast concrete remains in the mould, it may alternatively occur after the formed intermediate has been demolded. 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 may be assisted with a forced air circulation by the fan 24. 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 a longer time for conditioning is acceptable. This conditioning step may help to reduce the moisture content of precast concrete through water evaporation. The released moisture leaves numerous pores inside the consolidated precast concrete, which may allow to achieve a desired CO2 uptake and a uniform carbonation throughout the whole precast concrete product.

[0134] The duration of the conditioning step may be determined by the desired extent of initial water or moisture loss from the consolidated precast concrete, which is affected by the dimension and initial water-to-binder ratio of precast concrete, and other variables. As a general rule of thumb, 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 the 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.

[0135] The degree of CO2 penetration may be visually determined by spraying phenolphthalein indicator onto the whole cross section of carbonated precast concrete after it is broken by strength testing. 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 cross section area, while a 50% CO2 penetration is obtained if pink color occupies a half of the tested cross section area.

[0136] Due to the use of finer aggregate disclosed herein, the conditioning time required for manufacturing the disclosed carbonated precast concrete may be significantly decreased. As shown in the examples described below, carbonated precast concrete made of finer aggregate disclosed herein may need a conditioning time only 0.25 hour, instead of a conditioning time of 1 hour required for precast concrete with regular-size aggregate. For predetermined binder content and water-to-binder ratio, precast concrete with coarser aggregate would have a thicker layer of paste to cover each aggregate particle and also possibly more paste agglomerating among the pores between aggregate particles. By reducing the particle size of fine aggregates, the increased surface area of aggregate particles would need more paste to cover. This may help to reduce the thickness of paste coverage for each aggregate particle, and also reduce the tendency of paste agglomeration in the pores. As a result of this paste thinning effect, CO2 gas may penetrate to the reaction site more easily, and also the formed calcite may precipitate more easily as well during the carbonation curing process. Therefore, a shorter conditioning time may be possible for manufacturing carbonated precast concrete made of finer aggregates disclosed herein.

[0137] In some embodiments, the conditioning of the formed intermediate includes conditioning the formed intermediate at a temperature ranging from 15°C to 28 °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.

[0138] The conditioning time is a function of the size or volume of the concrete product. Longer conditioning time is needed for a thicker or larger concrete product. The conditioning time for a determined concrete product may be reduced by at least 50% with the suggested aggregate. Another factor influencing the conditioning time is the velocity of the air flow when forced drying is used, the relative humidity of the environment in which the intermediate is being conditioned, the temperature of this environment, and the microstructures (capillaries and pores) of the intermediate.Hydration

[0139] For carbonated precast concrete made of binders with hydraulic activity such as OPC, hydration curing may optionally be implemented to help carbonated precastconcrete achieving full strength. During the hydration curing, carbonated precast concrete products are stored in humid environment for 1 day or longer following the general procedure known in the industry.Moisturizing

[0140] The carbonated precast concrete may be moisturized. This moisturizing step may include, for example, submerging the cured intermediate in water; spraying the cured intermediate with water; and / or misting the cured intermediate with water. In certain embodiments, therefore, the cured intermediate is moisturized by being soaked in tap water or water saturated with hydrated lime for a period not longer than 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. 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 the post-hardening treatment.

[0141] In some embodiments, the concrete product may be wet or moisturized. In some embodiments, the carbonated precast concrete is soaked in tap water or water saturated with hydrated lime for a period not longer than 24 hours, or by being sprinkled with tap water. 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 optional wetting / moisturizing step and the followed post-hardening treatment. The described wetting or 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 the post-hardening treatment. Therefore, in some embodiments the steps of moisturizing and curing may overlap or may occur concurrently.

[0142] In some embodiments, during the water absorption testing, carbonated precast concrete is immersed in water for 24 hours and then oven-dried for not less than 24 hours at 100-115 °C.Computing device

[0143] With reference to Fig. 6, an example of a computing device 600 is illustrated. For simplicity only one computing device 600 is shown but the system may include more computing devices 600 operable to exchange data. The computing devices 600 may be the same or different types of devices. The controller 30 may be implemented with one or more computing devices 500.

[0144] The computing device 600 comprises a processing unit 602 and a memory 604 which has stored therein computer-executable instructions 606. The processing unit 602 may comprise any suitable devices configured to implement the method described herein such that instructions 606, when executed by the computing device 600 or other programmable apparatus, may cause the functions / acts / steps performed as part of the method as described herein to be executed. 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.

[0145] 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 readonly memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like. Memory 604 may comprise any storage means (e.g., devices) suitable for retrievably storing machine- readable instructions 606 executable by processing unit 602.

[0146] The methods and systems 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 described herein 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 described herein may be stored on a storage media or a device, for example a ROM, a magnetic disk, an optical disc, a flash drive, or any other suitable storage media or device. The program code may be readable by a general or special-purpose programmable computer for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein. Embodiments of the methods and systems described herein 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.

[0147] 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.

[0148] 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 use with computer hardware, machines, and various hardware components. Substituting thephysical 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.

[0149] 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).

[0150] 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.

[0151] It is noted that various connections are set forth between elements in the preceding description and in the drawings. It is noted that these connections are general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. A coupling between two or more entities may refer to a direct connection or an indirect connection. An indirect connection may incorporate one or more intervening entities. The term “connected” or "coupled to" may therefore 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).

[0152] It is further noted that various method or process steps for embodiments of the present disclosure are described in the preceding description and drawings. 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 particularsequence 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.

[0153] Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0154] 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.

[0155] 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 skillin the art in view of the present disclosure, which modifications would be within the scope of the present technology.

Claims

CLAIMS1. A curing system for manufacturing concrete products, comprising: a curing chamber sized for receiving formed intermediates composed of water, aggregate, and a gaseous binder, the curing chamber having a gas inlet and a gas outlet; a source of an input gas fluidly connected to the gas inlet of the curing chamber, the input gas including carbon dioxide at a source concentration of carbon dioxide; a valve fluidly connected to the source of the input gas and upstream of the gas inlet, the valve having a plurality of positions to modulate a flow rate of the input gas flowing through the valve and into the curing chamber; concentration sensors in communication with the curing chamber and configured to generate signals indicative of a concentration of the carbon dioxide within the curing chamber at each of a respective position of the concentration sensors along a flow path within the curing chamber extending from the source of the input gas to the gas outlet; and a controller operatively connected to the valve and to the concentration sensors, the controller having a processing unit operatively connected to a computer-readable medium having stored thereon instructions executable by the processing unit to: cause the valve to inject a flow of the input gas into the curing chamber for curing the formed intermediates; based on one or more of the signals received from one or more of the concentration sensors, determine that a concentration difference between the source concentration and the concentration of the carbon dioxide within the chamber is above a difference threshold; and cause a mitigation action to decrease the concentration difference.

2. The curing system of claim 1 , wherein the computer-readable medium has instructions executable by the processing unit to determine that the concentration difference is below the difference threshold by subtracting the concentration of the carbon dioxide within the chamber based on one of the signals received from one of the concentration sensors from the source concentration.

3. The curing system of claim 2, wherein the one of the concentration sensors is located at the gas outlet of the curing chamber.

4. The curing system of any one of claims 1 to 3, wherein the concentration sensors includes a first sensor and a second sensor located at two different locations spaced apart along a length of the curing chamber extending from the gas inlet to the gas outlet, the computer-readable medium further having instructions executable by the processing unit to: determine that a concentration gradient within the curing chamber is below a gradient threshold by computing a difference between a first concentration based on a signal received from the first sensor and a second concentration based on a signal received from the second sensor.

5. The curing system of claim 4, wherein the first sensor is located upstream of the second sensor.

6. The curing system of claim 4 or 5, further comprising one or more fans in the curing chamber, the controller operatively connected to the one or more fans, the computer- readable medium further having instructions executable by the processing unit to: cause the mitigation action by causing the one or more fans to rotate, thereby inducing mixing of the input gas in the curing chamber.

7. The curing system of any one of claims 4 to 6, further comprising an auxiliary conduit fluidly connecting the source of the input gas to the curing chamber at a location between the gas inlet and the gas outlet, an auxiliary valve fluidly connected to the auxiliary conduit, the first sensor and the second sensor being both located within the curing chamber, the controller operatively connected to the auxiliary valve, the computer- readable medium further having instructions executable by the processing unit to: cause the mitigation action by opening the auxiliary valve to induce a local flow of the input gas directly into the curing chamber via the auxiliary conduit while bypassing the gas inlet of the curing chamber.

8. The curing system of claim 7, comprising temperature sensors distributed along the flow path extending from the source of the input gas to the gas outlet of the curing chamber, the temperature sensors operable to generate signals indicative of a temperature insidethe curing chamber, the temperature sensors operatively connected to the controller, the computer-readable medium has the instructions executable by the processing unit to: determine that a temperature gradient within the curing chamber is above a temperature gradient threshold; and cause a second mitigation action to decrease the temperature gradient.

9. The curing system of claim 8, comprising a heater fluidly connected to the auxiliary conduit, the heater operatively connected to the controller, the computer-readable medium has the instructions executable by the processing unit to: cause the second mitigation action by powering the heater to increase a temperature of the input gas flowing into the curing chamber via the auxiliary conduit.

10. The curing system of any one of claims 1 to 9, comprising an outlet valve located downstream of the gas outlet of the curing chamber, the controller operatively connected to the outlet valve, the computer-readable medium further having instructions executable by the processing unit to: cause the mitigation action by opening both of the valve and the outlet valve to induce a flow of the input gas through the curing chamber until the concentration difference becomes below the difference threshold.

11. The curing system of claim 10, wherein the computer-readable medium further has instructions executable by the processing unit to: cause the opening of the valve such that an inlet flow of the input gas is injected at an inlet flow rate; and cause the opening of the outlet valve such that an outlet flow is outputted out of the curing chamber via the outlet valve at an outlet flow rate, the inlet flow rate and the outlet flow rate are selected such that a gas hourly space velocity (GHSV) is within a range of 20 to 100 L / (kg hour), the GHSV corresponding to a ratio of a flow rate of a reactive gas contained in input gas to a mass of the gaseous binder of the formed intermediates contained in the curing chamber.

12. The curing system of claim 10 or 11 , comprising a recirculation conduit fluidly connecting the gas outlet of the curing chamber to the gas inlet of the curing chamber along a flow path parallel to the curing chamber, a recirculation valve fluidly connected to therecirculation conduit and operable to permit a recirculation flow from the gas outlet of the curing chamber back to the gas inlet of the curing chamber, and means operatively connected to the recirculation conduit for inducing the recirculation flow in the recirculation conduit.

13. The curing system of claim 12, wherein the concentration sensors include an outlet concentration sensor located at or downstream of the gas outlet of the curing chamber, the controller operatively connected to the outlet concentration sensor, the computer- readable medium having the instructions executable by the processing unit to: determine that the concentration difference between the source concentration and the concentration of the carbon dioxide at the gas outlet of the curing chamber based a signal received the outlet concentration sensor is below a second difference threshold; and cause a flow of from the gas outlet of the curing chamber back to the gas inlet of the curing chamber via the recirculation conduit.

14. The curing system of claim 13, comprising a bypass conduit fluidly connecting the source of the input gas to a location downstream of the curing chamber along a flow path parallel to the curing chamber, a bypass valve fluidly connected to the bypass conduit and operable to permit a bypass flow from the source of the input gas to the location while bypassing the curing chamber.

15. The curing system of claim 14, wherein the computer-readable medium has the instructions executable by the processing unit to: determine that the concentration difference between the source concentration and the concentration of the carbon dioxide at the gas outlet of the curing chamber based the signal received the outlet concentration sensor is below a second difference threshold; and cause a bypass flow of the input gas into the bypass conduit for bypassing the curing chamber.

16. The curing system of any one of claims 1 to 15, wherein the computer-readable medium further has instructions executable by the processing unit to:determine that the concentration of the carbon dioxide within the curing chamber is below a concentration threshold; and cause the mitigation action by opening the valve to inject a flow of the input gas into the curing chamber until the concentration is at or above the concentration threshold.

17. The curing system of any one of claims 1 to 16, wherein the gaseous binder includes one or more of steel slag, stainless steel slag, calcium, alumina, silica, and iron oxides.

18. A method of manufacturing concrete products from formed intermediates composed of water, aggregate, and a gaseous binder, the method comprising: with the formed intermediates within a curing chamber for carbonation curing, injecting an input gas into the curing chamber via a gas inlet, the input gas including carbon dioxide at a source concentration of carbon dioxide; modulating a flow rate of the input gas flowing into the curing chamber via the gas inlet; determining a concentration of the carbon dioxide within the curing chamber at each of a number of positions within the curing chamber; determining a concentration difference between the source concentration and the concentration of the carbon dioxide at each of said number of positions within the chamber; and in response to determining that the concentration difference is above a difference threshold, causing a mitigation action to decrease the concentration difference.

19. The method of claim 18, further comprising determining a concentration gradient of carbon dioxide within the curing chamber, and determining that the concentration gradient is below a gradient threshold.

20. The method of claim 18 or 19, wherein an inlet valve is fluidly connected to the gas inlet and an outlet valve is fluidly connected to a gas outlet of the curing chamber, and wherein causing the mitigation action includes: opening both the inlet valve and the outlet valve to induce a flow of the input gas through the curing chamber between the gas inlet and the gas outlet, until the concentration difference is below the difference threshold.

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