Method for manufacturing carbonated precast concrete products with enhanced durability

Abstract

A method for manufacturing a carbonated precast concrete product with enhanced durability. A method of making a carbonated precast concrete product comprises: obtaining a mixture comprising at least one binder material, aggregate, and water; molding the mixture into a molded intermediate; demolding the molded intermediate to obtain a demolded intermediate, the demolded intermediate having a first water: binder ratio; humidifying the demolded intermediate to provide a humidified article having a second water: binder ratio that is less than the first water: binder ratio of the demolded intermediate; humidifying at least one surface of the humidified article with an aqueous medium, thereby causing the humidified article to gain weight and providing a humidified product, a first portion of the humidified product having a third water: binder ratio greater than a fourth water: binder ratio of a remainder of the humidified product; the humidified product is cured with carbon dioxide to obtain a carbonated precast concrete product.

Description

[0001] This application is a divisional application of the Chinese patent application with an application date of April 20, 2021, application number "202180038863.6", and invention name "Method for manufacturing carbonated precast concrete products with enhanced durability". The original application is the Chinese national phase application of international application PCT / CA2021 / 050533.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Patent Application No. 63 / 034,037, filed on June 3, 2020, which is incorporated herein by reference in its entirety. Technical Field

[0004] The present disclosure generally relates to precast concrete products such as, but not limited to, concrete pipes, traffic barriers, walls, boxes, culverts, tiles, pavers, hollow core slabs, patio slabs, steps, curbs, retaining walls, and concrete blocks. More particularly, the present disclosure relates to carbonated precast concrete products and methods of making the same. Background Art

[0005] Precast concrete has been widely adopted in the construction industry. Precast concrete is a building product that is cast into reusable molds or forms under controlled factory conditions. It cures in a controlled curing environment in the factory. After curing, it is then transported to the construction site.

[0006] Precast concrete has a wide range of structural and architectural applications. Some common examples include pavers, foundations, slabs, beams, floors, columns, walls, retaining walls, manholes, sewer pipes, blocks, modular boxes, bridge decks, etc.

[0007] Traditionally, Portland cement is used as a binder in the manufacture of precast concrete products. However, the manufacture of Portland cement is known to have undesirable environmental impacts. For every ton of Portland cement produced, approximately one ton of CO2 is released. The acquisition of Portland cement involves quarrying, the emission of atmospheric pollutants and requires the use of large kilns that require large amounts of energy.

[0008] Cement-based precast products rely on hydration of cement to achieve satisfactory strength. Heat and steam curing techniques have been widely adopted as standard curing methods to accelerate early strength development of conventional cement-based precast concrete products.

[0009] Curing precast concrete in a CO2-rich environment can provide a reduction in the environmental impact of precast concrete. This is known as carbonated precast concrete. Although such carbonated precast concrete has certain environmental advantages, there is still a need to improve other physical properties of carbonated precast concrete, such as its ability to better withstand freeze-thaw cycles and wear. Summary of the invention

[0010] In one aspect, a method for making a carbonated precast concrete product is provided, the method comprising: obtaining a mixture comprising at least one binder material, an aggregate, and water; molding the mixture into a molded intermediate; demolding the molded intermediate to obtain a demolded intermediate, the demolded intermediate having a first water:binder ratio; conditioning the demolded intermediate to provide a conditioned article, the conditioned article having a second water:binder ratio less than the first water:binder ratio of the demolded intermediate; moistening at least one surface of the conditioned article with an aqueous medium, thereby causing the conditioned article to gain weight and providing a moistened product, a first portion of the moistened product having a third water:binder ratio greater than a fourth water:binder ratio of the remainder of the moistened product; and curing the moistened product with carbon dioxide to obtain a carbonated precast concrete product.

[0011] In another aspect, a method for making a carbonated precast concrete product is provided, the method comprising: obtaining a base mixture comprising at least one binder material, an aggregate, and water, and an outer layer mixture comprising at least one second binder material, a second aggregate, and water; molding the base mixture and the outer layer mixture into a multi-layer molding intermediate having an outer layer and a base; demolding the multi-layer molding intermediate to obtain a demolded multi-layer intermediate having a first water:binder ratio for the base and a second water:binder ratio for the outer layer; conditioning the demolded multi-layer intermediate to provide a conditioned multi-layer article having a reduced amount of water relative to the amount of water in the demolded multi-layer intermediate having the first water:binder ratio and the second water:binder ratio; moistening at least one surface of the outer layer of the conditioned multi-layer article with an aqueous medium to cause the outer layer to gain weight, thereby providing a moistened multi-layer product wherein the outer layer has a third water:binder ratio greater than the second water:binder ratio; and curing the moistened multi-layer product with carbon dioxide to obtain a carbonated precast concrete product.

[0012] In yet another aspect, a method for making a carbonated precast concrete product is provided, the method comprising: obtaining a demolded intermediate from a molding mixture comprising at least one binder material, aggregate, and water, the demolded intermediate having a first water:binder ratio; conditioning the demolded intermediate to provide a conditioned product, the conditioned product having a second water:binder ratio less than the first water:binder ratio of the demolded intermediate; moistening at least one surface of the conditioned product with an aqueous medium to cause the conditioned product to gain weight, thereby providing a moistened product, a first portion of the moistened product having a third water:binder ratio greater than a fourth water:binder ratio of a remainder of the moistened product; and curing the moistened product with carbon dioxide to obtain the carbonated precast concrete product.

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

[0014] In certain embodiments, moistening the at least one surface comprises applying the aqueous medium using an application method selected from: partially or fully immersing the at least one surface in an aqueous liquid; spraying the aqueous medium onto the at least one surface; or applying the aqueous medium to the at least one surface using a roller device.

[0015] In certain embodiments, moisturizing at least one surface of the conditioned article comprises moisturizing the at least one surface until the conditioned article achieves a weight gain of at least 10 g / m2.

[0016] In certain embodiments, applying the aqueous medium comprises applying water, a water-based solution, and / or a water-based slurry to at least one surface.

[0017] In certain embodiments, applying the aqueous medium comprises applying the aqueous medium at a temperature of 15°C to 25°C.

[0018] In certain embodiments, conditioning the demoulded intermediate comprises conditioning the demoulded intermediate until 20 wt % to 70 wt % of the initial moisture content of the demoulded intermediate is removed.

[0019] In certain embodiments, obtaining the mixture includes: obtaining a dry portion and a liquid portion, the dry portion having at least one aggregate material and at least one binder material, the liquid portion having water; and mixing the dry portion with the liquid portion to obtain the mixture.

[0020] In certain embodiments, the method comprises mixing an additive with the dry portion and the liquid portion.

[0021] In certain embodiments, the method includes mixing the microfibers with a dry portion.

[0022] In certain embodiments, obtaining a mixture includes obtaining a mixture having at least one binder material, the at least one binder material being non-gelling.

[0023] In certain embodiments, obtaining a mixture includes obtaining a mixture having at least one binder comprising steel slag and cement, wherein a weight ratio of steel slag to cement is from 1:20 to 20:1.

[0024] In certain embodiments, obtaining a mixture includes obtaining a mixture having aggregate in a weight ratio of the aggregate to the total weight of the mixture of 0.3 to 0.8.

[0025] In certain embodiments, obtaining a mixture comprises obtaining a mixture wherein a weight ratio of the additive to the total weight of the mixture is between 0.005 and 0.010.

[0026] In certain embodiments, obtaining a mixture includes obtaining a mixture comprising an admixture.

[0027] In certain embodiments, the admixture is a water-resistant admixture.

[0028] In certain embodiments, the admixture is a plasticizer, a superplasticizer (superplasticizer), or a polycarboxylate-based water reducer.

[0029] In certain embodiments, molding the mixture includes shaping the mixture into a shaped intermediate.

[0030] In certain embodiments, molding the mixture includes densifying the shaped intermediate to provide a molded intermediate.

[0031] After reading this disclosure, many additional features and combinations of the present improvements will be apparent to those skilled in the art. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flow chart illustrating a method for manufacturing a carbonated precast concrete product;

[0033] Figure 2 is a schematic diagram of a precast concrete product having two distinct layers throughout its thickness;

[0034] Figure 3 is shown for making Figure 2 A flow chart of a method for carbonated precast concrete products in a double layer as shown in;

[0035] Figure 4 is a schematic diagram of a precast concrete product having three layers throughout its thickness;

[0036] Figure 5 is a graph showing the average moisture content of precast concrete products at different stages of manufacture using the method of the present disclosure; and

[0037] Figure 6 is a graph showing the change in moisture content measured through its thickness of a precast concrete sample prepared with the mix design of Sample A after conditioning (solid line) and then after surface wetting (dashed line). DETAILED DESCRIPTION

[0038] The present method for preparing carbonated precast concrete products may require less cement, and in some cases may not require cement, and may allow the concrete to store CO2 within the product. The carbonated precast concrete products of the present disclosure may advantageously have improved resistance to physical erosion, such as resistance to freeze-thaw cycles and wear. Carbonation curing also provides the possibility of introducing industrial waste as a cement substitute. These wastes include, for example, slag. The method of the present disclosure may not only be able to reduce the CO2 footprint of concrete, but also allow precast concrete products to be manufactured in a more affordable manner due to the use of currently underutilized low-cost industrial wastes such as slag and bottom ash. Slag is a byproduct of steelmaking and is produced during the separation of molten steel from impurities in a steelmaking furnace. Slag appears as a molten liquid melt and is a solution containing silicates and oxides that solidifies after cooling. Bottom ash is a coarse, granular, incombustible byproduct of coal combustion collected from the bottom of the furnace.

[0039] Examples of precast concrete products that can be produced using the methods described herein include, but are not limited to, 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 blocks, beams, floors, columns, manholes, sewer pipes, railroad ties, and other precast concrete products.

[0040] The manufacture of carbonated precast concrete products differs from the manufacture of conventional cement-based precast concrete primarily in the application of carbon dioxide during the carbonation curing process and a wider selection of suitable binder sources (e.g., cement). Carbonated precast concrete obtains its strength primarily through the reaction between carbon dioxide gas introduced with the aid of sufficient water in the mix and oxides and / or hydroxides of calcium and / or magnesium in the binder. Precast parts containing such minerals typically undergo rapid hardening when exposed to high or low concentrations of CO2.

[0041] Freeze-thaw durability and wear durability

[0042] In some cases, the lack of durability of certain existing concrete structures can result in severe and detrimental damage, rendering the product unsuitable for its intended application. The present disclosure relates to methods by which concrete products having improved durability, more specifically improved freeze-thaw durability and abrasion durability, can be made. In some cases, the disclosed methods can improve other mechanical / physical properties.

[0043] Freeze-thaw damage is caused by internal tensile stresses that build up due to repeated freezing and thawing cycles. The hydraulic pressure of water expansion and the dilatation forces of unfrozen water particles contribute to the damage caused by freeze-thaw cycles. The damage caused to precast concrete can be exacerbated when deicing salts are present during the freeze-thaw process.

[0044] Surface wear is the gradual loss of quality of the concrete surface due to repeated cycles of wear. Abrasion is one of the main surface wear mechanisms and refers to the wear and tear of other solid objects moving along the concrete surface. The source of wear depends on the application of precast concrete.

[0045] The durability of precast concrete products is measured by a series of standard tests. The tests and requirements vary depending on the product type and its application. As an example, an overview of standard tests for precast concrete pavers and retaining walls is given below. The present disclosure refers to multiple standards (e.g., ASTM standards). It should be understood that these standards correspond to the versions available on the filing date of this patent application.

[0046] There are several methods for evaluating the wear resistance of precast concrete. In addition to the sandblasting test method (ASTM C418) for evaluating the wear resistance of concrete paving materials specified by ASTM C936, the rotating-cutter method (ASTM C944) can also be used to measure the wear resistance of precast concrete products. In the rotating-cutter method, the test equipment consists of a drill press and a rotating cutter. The concrete sample is placed under the rotating cutter, and a constant vertical load of 98N is applied to the spindle that rotates the cutter. The sample is subjected to friction loss for two minutes at a speed of 200rpm, and the mass loss rate is calculated (ASTM, 2019a).

[0047] Precast concrete paving materials are tested for freeze-thaw durability in accordance with CSA A231.2 or ASTM C1645 as required by ASTM C936. During the test, the precast concrete specimens are completely immersed in a 3% sodium chloride solution. They are subjected to a 24-hour freeze and thaw cycle, with 16 hours of freezing and 8 hours of thawing. After 28 freeze-thaw test cycles, the mass loss of the precast concrete shall not exceed 225 g / m 2Total surface area, or the mass loss of precast concrete after 49 freeze-thaw test cycles should not exceed 500g / m 2 Total surface area (ASTM, 2019b, ASTM, 2018a, CSA, 2005).

[0048] Precast concrete retaining walls are tested for freeze-thaw durability according to ASTM C1262. During the test, the retaining wall specimens are placed face down in water at a depth of 13 ± 2 mm (ASTM, 2018b). After 100 freeze and thaw cycles, the weight loss of a group of five specimens should not exceed 1% of their initial weight, or after 150 cycles, the weight loss of four of the five specimens should not exceed 1.5% of their initial weight (ASTM, 2017). One freeze and thaw cycle is defined as a full freeze cycle followed by a full thaw cycle. The retaining wall specimens can also be partially immersed in a 3% sodium chloride solution. In this case, the requirement of less than 1% mass loss is usually reduced to 40 freeze-thaw test cycles.

[0049] Carbonated concrete may exhibit low freeze-thaw resistance, thus making it unsuitable for applications such as paving and retaining walls. In addition, carbonated precast concrete may not perform well under abrasive conditions, making it unsuitable for paving applications.

[0050] Using conventional methods, moisture starvation is often present on the surface of precast concrete prior to carbonation curing. It is believed that while this surface moisture starvation does not significantly affect the compressive strength of carbonated precast concrete, certain other properties of carbonated concrete products such as the flexural strength, surface hardness, and surface durability (including at least one of abrasion resistance and freeze-thaw resistance) of the product are compromised. Therefore, carbonated precast concrete products often do not meet certain durability requirements for applications in which they are intended to be used.

[0051] It has been found that the methods disclosed herein can improve at least certain durability properties of carbonated precast concrete products, as measured by freeze-thaw resistance and abrasion resistance. It has also been observed that the carbonated precast concrete products so made can maintain their strength over time and freeze-thaw cycles.

[0052] The present disclosure relates to a method for manufacturing carbonated precast concrete products. The main components used to manufacture carbonated precast concrete include binder, aggregate and water. Other additives may be included depending on the type of raw materials and the specifications for carbonated precast concrete.

[0053] Adhesives

[0054] The cementing and / or non-cementing binder in the carbonated precast concrete includes any one of the following carbonatable materials and combinations thereof: ordinary portland cement, other types of cement, non-hydraulic cement, hydraulic cement, ground granulated blast-furnace slag powder (ground granulated blast-furnace slag, GGBFS), steel slag, fly ash, bottom ash, stainless steel slag and other materials rich in CaO and / or MgO and / or calcium silicate content. Any suitable combination of two or more adhesives can be used. In some cases, a single adhesive can be used. In some embodiments, the adhesive is a cementing binder, and may include ordinary portland cement, other types of cement, non-hydraulic cement, hydraulic cement and combinations thereof. In some embodiments, the adhesive is a non-cementing binder, and may include steel slag, fly ash, bottom ash, stainless steel slag and other materials rich in CaO and / or MgO, calcium silicate content, and combinations thereof. In a particular example, the binder is a non-cementitious binder and comprises less than 5 wt%, less than 4 wt%, less than 3 wt%, less than 2 wt%, or less than 1 wt% cement.

[0055] For example, steel slag can be used herein as the sole component of the binder or as the main component of the binder together with a certain proportion of cement (if desired) to allow the production of carbonated precast concrete products, in which carbon dioxide is used as a curing agent. In other words, all or most of the cement is replaced by steel slag. Carbon dioxide is also used to increase strength, cure and activate the slag.

[0056] In one embodiment, the binder consists of steel slag.In some cases, the binder comprises steel slag and another suitable component.

[0057] In one embodiment, the binder consists essentially of steel slag. In an example, the term "consisting essentially of" as used herein can mean at least 90 weight %, at least 91 weight %, at least 92 weight %, at least 93 weight %, at least 94 weight %, at least 95 weight %, at least 96 weight %, at least 97 weight %, or at least 98 weight %. In some cases, the binder can include a majority (e.g., greater than 50 weight %) of steel slag.

[0058] In one embodiment, the binder comprises steel slag and cement, and the weight ratio of steel slag to cement is about 1:20, about 1:15, about 1:10, 1:5, about 1:20 to about 20:1, about 1:10 to about 10:1, or about 1:5 to about 5: 1. Alternatively, in some embodiments, the weight ratio of steel slag to cement is about 20:1, or about 15:1, or about 10:1, or about 5:1.

[0059] In another embodiment, in particular in a multi-layer product as defined herein, the binder in the top / outer layer consists of or consists essentially of steel slag, or comprises steel slag and cement in a weight ratio of about 1:20 to about 20:1, or the weight ratio of steel slag to cement is about 20:1, or about 15:1, or about 10:1, or about 5:1.

[0060] In one embodiment, the weight ratio of the binder (e.g., any or all of slag, cement, and other carbonatable materials) to the total weight of the composition comprising aggregate+binder+water+additives is in the range of about 0.20 to about 0.60, preferably about 0.25 to about 0.50, or more preferably about 0.30 to about 0.50.

[0061] cement

[0062] In the present disclosure, the following non-limiting list of cements may be used to produce carbonated precast concrete: Portland cement (Type I to Type V); Portland limestone cement; rapid hardening cement; rapid setting cement; low heat cement; blast furnace slag cement; Portland slag cement; high alumina cement; white cement; colored cement; pozzolanic cement (Portland-pozzolana cement); air-entrained cement; hydrographic cement; non-hydraulic cement and ternary blended cement.

[0063] As used herein, useful cements are cements that contain a calcium silicate phase, particularly C3S, which enables the cement to gain strength when reacting with water. The presence of the calcium silicate phase ensures short-term and long-term strength improvements.

[0064] Steel slag and stainless steel slag

[0065] "Steel slag" herein refers to the slag byproduct produced by steelmaking. Steel slag may include slag produced by a basic oxygen furnace (Basic Oxygen Furnace, BOF), also known as slag from a top-blown oxygen furnace steelmaking (Linz-Donawitz, LD) method, LD slag. Steel slag may also include slag produced by an electric arc furnace (Electric Arc Furnace, EAF). Steel slag as used herein may also include ladle slag. Steel slag may be a combination of the above slags. It should be understood that "steel slag" as used herein does not include iron slag and blast furnace slag, such as pozzolanic slag, which are typically produced during iron production and can be used to make cement.

[0066] As used herein, "ladle slag" refers to a type of steel slag. Ladle slag is produced as a by-product from ladle refining operations. In various steelmaking processes, molten steel produced in EAF or BOF process undergoes additional refining process based on the desired quality of steel.

[0067] As used herein, "EBH slag" refers to an EAF-BOF hybrid, which is a type of steel slag formed from a mixture of EAF-produced slag and BOF-produced slag.

[0068] Stainless steel slag may include slag produced by stainless steel production. Stainless steel slag is mainly produced by argon oxygen decarburization (AOD) and / or ladle metallurgy (LM) methods.

[0069] Chemical composition of steel slag:

[0070] In one embodiment, the steel slag used herein has a cumulative calcium silicate content (eg, CS+C2S+C3S phase concentration) of at least about 15 wt%.

[0071] In one embodiment, the steel slag used herein has a cumulative calcium silicate content (eg, CS+C2S+C3S phase concentration) of at least about 20 wt%.

[0072] In one embodiment, the steel slag used herein has a cumulative calcium silicate content (eg, CS+C2S+C3S phase concentration) of at least about 30 wt%.

[0073] In one embodiment, the steel slag used herein has a cumulative calcium silicate content (eg, CS+C2S+C3S phase concentration) of at least about 40 wt%.

[0074] In one embodiment, the steel slag used herein has a SiO2 content of at least about 6 wt. % or more preferably at least about 15 wt. %.

[0075] Chemical composition of stainless steel slag:

[0076] In one embodiment, the stainless steel slag used herein has a SiO2 content of at least about 15 wt. % or more preferably at least about 20 wt. %.

[0077] In one embodiment, the stainless steel slag used herein has a calcium oxide content of at least about 30 wt. %, or more preferably at least about 35 wt. %.

[0078] Physical properties of steel slag:

[0079] The steel slag may include a mixture of coarse slag pieces and fine slag pieces. The coarse slag pieces may have a particle size of less than about 50 m 2 / kg Blaine fineness, and the fine slag can have a fineness greater than about 50m 2 / kg Blaine fineness. As a result from a typical steelmaking process, coarse slag pieces, fine slag pieces, or both may be landfilled. Received steel slag originating from waste (e.g., landfill and / or industrial waste) may optionally be refined.

[0080] Refining the slag may include filtering the received slag to separate fine slag pieces from coarse slag pieces.

[0081] Alternatively or additionally, refining the received slag may also include crushing the slag into a fine powder. In some exemplary embodiments, the filtered fine pieces are crushed without crushing the coarser pieces. For example, for EAF slag, the slag may be crushed into at least 50 m 2 / kg and preferably about 180m 2 For example, for EBH slag (a mixture of EAF and BOF and ladle slag), the slag can be crushed to at least 100 m 2 / kg and preferably about 240m 2 / kg Blaine fineness. In other exemplary embodiments, the slag can be crushed into a finer size. In another example, at least 50% of the ground slag is less than 100 microns, D(50) < 100 microns.

[0082] Aggregates

[0083] Aggregates can be normal weight and lightweight natural source materials or artificial materials. According to the size of the aggregate, it can be divided into coarse aggregate and fine aggregate. The type, proportion and size of coarse aggregate and fine aggregate vary with their availability, cost and gradation, and also with the workability required for the concrete mixture and the desired surface texture and characteristics of the carbonated precast concrete. In some embodiments, the fine aggregate has less than 5% of particles with a diameter greater than 3 / 8". In some embodiments, the coarse aggregate has a diameter greater than 1 / 4". In another embodiment, the coarse aggregate has a diameter greater than 1 / 2". In some embodiments, the term "normal weight" as used herein refers to naturally occurring or crushed gravel or sand from limestone, granite, etc. with a specific gravity of about 2.7. In some embodiments, the term "lightweight aggregate" as used herein refers to natural or artificial particles with a specific gravity ranging from about 0.3 to about 1.9. In this article, the expression "about" means a change of plus or minus 10% of the value.

[0084] In one embodiment, the weight ratio of aggregate to the total weight of the composition comprising aggregate+binder+water+additives ranges from about 0.3 to about 0.8, preferably from about 0.4 to about 0.7, or more preferably from about 0.40 to about 0.65.

[0085] additive

[0086] Additives used herein include, but are not limited to, air entraining admixtures, water reducing admixtures, shrinkage reducing admixtures, corrosion inhibiting admixtures, quick-setting or slow-setting admixtures, viscosity modifiers, pigments, waterproofing admixtures, and other natural or chemical additives. Additional ingredients / additives include fibers (e.g., Euclid's PSI Multi-Mix 80), which can be added when formulating carbonated precast concrete depending on its final application. Additives can also be mineral admixtures.

[0087] Water reducing admixtures are added to concrete mixtures to increase compressive strength, reduce water content, reduce porosity, and reduce water permeability. Water reducing admixtures are classified as plasticizers or superplasticizers (i.e., polycarboxylate / salt-based water reducers). Any water reducing admixture that can reduce the required water content by up to about 50% or increase the compressive strength by up to about 60% can be used as a water reducing admixture in the current innovation. The admixtures used in this innovation should meet the requirements of ASTM C494 (Standard Specification for Chemical Admixtures for Concrete, ASTM International, West Conshohocken, PA, 2019).

[0088] Waterproofing admixtures are designed to provide bulk water resistance to concrete by affecting the capillary action of water in and out of concrete. Waterproofing admixtures can act as static pore pluggers, creating a more difficult path for water migration, or they can act as reactive chemicals, creating an "in situ" hydrophobic material that not only plugs the pores but also chemically repels water from the concrete surface.

[0089] In certain embodiments of the present disclosure, an additive according to what is described herein is present in a conditioned demoulded product (ie, a conditioned article) or a portion thereof, intended to undergo a surface wetting step as described herein, and is an air entraining admixture.

[0090] In one embodiment, the weight ratio of the air entraining admixture as an additive to the total weight of the composition comprising aggregate+binder+water+additives is in the range of about 0.0001 to about 0.001, or about 0.0002 to about 0.0008, or about 0.0004 to about 0.0006.

[0091] In certain embodiments, the water repellent admixture is present only in the conditioned demoulding product (ie, conditioned article) or a portion thereof, such as a multi-layer product, and is not intended / needed to undergo a surface wetting step as described herein.

[0092] In certain embodiments, the waterproofing admixture is present in the composition comprising the binder, aggregate and water in a weight ratio (relative to the total weight of the composition) of at least about 0.005, or at least about 0.006, preferably at least about 0.007, or at least about 0.008, or at least about 0.009, or at least about 0.010.

[0093] In certain embodiments, the waterproofing admixture is present in the composition comprising the binder, aggregate, and water in a weight ratio of at least about 0.005 and as much as about 0.009 to 0.010 relative to the total weight of the composition.

[0094] Water:Binder Ratio

[0095] The water:binder ratio depends on the manufacturing process (wet cast or dry cast), the content of binder and aggregate, and the use and dosage of water reducers in the mix design. Typically, the water:binder ratio varies from about 0.10 to about 0.50 (weight basis ratio).

[0096] In one embodiment, the water:binder ratio is in the range of about 0.10 to about 0.25.

[0097] In one embodiment, the water:binder ratio can be at least about 0.10, or at least about 0.11, or at least about 0.12, or at least about 0.13, or at least about 0.14, or at least about 0.15, or at least about 0.20, or at least about 0.25.

[0098] In one embodiment, the weight ratio of water to the total weight of the composition comprising aggregate+binder+water+additives ranges from about 0.01 to about 0.10, preferably from about 0.05 to about 0.10 or more preferably from about 0.06 to about 0.08.

[0099] Reference Figure 1, a method 100 for manufacturing a carbonated precast concrete product according to the present disclosure is provided. As will be described in more detail below, the method 100 includes a step 102 of mixing raw materials, the raw materials comprising a binder, an aggregate, water and some optional additives. The method 100 includes molding a mixture of at least one binder, an aggregate and water into a molding intermediate. In the embodiment shown, molding the mixture into a molding intermediate includes: a step 104 for molding the mixture to obtain a molded intermediate; and a step 106 of densifying the molded intermediate to obtain a densified intermediate, which can correspond to the molding intermediate. An optional step 108 of initially curing the molded intermediate can be performed. A step 110 of demolding the molded intermediate to obtain a demolded intermediate is performed. The demolded intermediate has a first water:binder ratio. A step 112 of conditioning the demolded intermediate to provide a conditioned article having a second water:binder ratio. The second water:binder ratio of the conditioned article is less than the first water:binder ratio of the demolded intermediate. A step 114 of moistening the surface of the conditioned article to obtain a moistened product is included. The moistening step 114 causes the conditioned article to gain weight. The first portion of the moistened product has a third water:binder ratio that is greater than a fourth water:binder ratio of the remainder of the moistened product. In some embodiments, the first portion having the third water:binder ratio may correspond to an outer layer or outer surface of the moistened product, and the remainder of the moistened product having the fourth water:binder ratio may correspond to a core of the moistened product that is at least partially surrounded or covered by the outer layer or outer surface. An optional step 116 of air drying the moistened product may also be included, followed by a step 118 of curing the moistened product with carbon dioxide. The optional step 119 of Figure 1 Each of steps 102 to 118 is described in more detail below.

[0100] Mixing of components

[0101] The mixing step 102 is performed with at least one binder material, aggregate, water and optional additives such as admixtures. In one embodiment, prior to the mixing step 102, the method comprises the steps of a) providing a dry portion and a liquid portion, the dry portion comprising at least one aggregate material and at least one binder material, and the liquid portion comprising water and optional additives; and combining the dry portion and the liquid portion.

[0102] In some embodiments, additives and additional ingredients may be optionally introduced into the mixture and, if desired, vary depending on the intended use of the concrete product.

[0103] Forming and densification

[0104] The molding step 104 includes adding a sufficient amount of a mixed material comprising a binder, a suitable aggregate, water and optional additives to a mold by any known means to mold the components into a desired shape. Although "mold" or "molding" is used herein, the expression contemplates any hollow mold or matrix for providing a shape such as a frame / mold, which is then optionally flattened. In other words, the mixture can be molded in such a way as to define an inner cavity.

[0105] The densification step 106 includes, for example, using vibration or compaction or compression or a combination of forces to densify the shaped intermediate to a desired thickness, shape and density. The desired thickness, shape and density may be selected according to the desired application as known in the art.

[0106] The forming step 104 and the densifying step 106 may be collectively referred to herein as molding the product. In other words, the forming step 104 and the densifying step 106 may be considered as two sub-steps of the step of molding the mixture.

[0107] In one embodiment, before the shaping step 104, the method includes a further step of mixing at least one binder material, aggregate, water and optional additives to provide a base mixture, wherein the mixing can be performed before the mixing step 102, simultaneously with the mixing step 102, or after the mixing step 102. In one embodiment, the method includes a step of shaping the base mixture to provide a shaped intermediate, wherein the shaping step can be performed before the step 104, simultaneously with the step 104, or after the step 104. In another embodiment, one or more of the steps 102 and 104 can be repeated to mix the base mixture and shape the base. In other embodiments, each of the mixtures of at least one binder material, aggregate, water and optional additives can contain the same or different ratios of these components. However, at least one of these mixtures, especially the mixture undergoing the surface wetting step 114, contains a binder other than cement, such as a slag binder, or preferably steel slag. In the above embodiments, each of the molded product (i.e., the molded intermediate), the demoulded product (i.e., the demoulded intermediate), the conditioned demoulded product (i.e., the conditioned article), the moisturized precured molded product (i.e., the moisturized product), and the carbonated precast concrete product will be multi-layered (e.g., a two-layer or more layer product).

[0108] Initial curing (optional)

[0109] In some cases, particularly when precast concrete is manufactured by wet casting, a step 108 of initially curing the molded intermediate is optionally performed to give the molded intermediate a satisfactory initial strength before it is removed from the mold at 110. Precast concrete relies on hydration / setting or other physical / chemical / activation of the binder to achieve the desired strength gain during this initial curing stage, which lasts, for example, from 2 hours to several days.

[0110] Moisture conditioning (reducing the amount of water in demoulding precast concrete)

[0111] Although carbonation curing can be carried out immediately after the precast concrete is demoulded, the densified concrete is usually humidified for a certain period of time before the introduction of carbon dioxide gas. The humidification step 112 starts after the step 114 of demoulding the molded intermediate and before the step 118 of curing the demoulded intermediate with CO2. The humidification step 112 involves the controlled removal of excess water. Its main purpose is to promote rapid and uniform carbonation reaction in concrete by removing excess water. Excess water may limit the reaction by preventing CO2 from diffusing into the reactants, and insufficient water content may cause lack of water, thereby stopping the reaction. Therefore, for optimal carbonation, the optimal water content can be achieved before carbonation.

[0112] After the demoulding step 110, the demoulded intermediate (optionally after initial curing) product is subjected to a conditioning step 112. The conditioning step 112 can be carried out at room temperature, a temperature of 15°C to 25°C and a humidity of 30% to 60% and with or without the help of forced air circulation. The duration of the conditioning can vary from 10 minutes to 24 hours or longer. This step 112 of the conditioning step can help reduce the moisture content of the precast concrete by evaporating water. The released moisture leaves many pores inside the compacted precast concrete, which may be crucial for achieving uniform carbonation and desired CO2 absorption throughout the precast concrete product. Relatively large CO2 absorption and uniform carbonation distribution may be very important for the physical-mechanical properties of the carbonated precast concrete product. In one embodiment, at the end of the conditioning step 112, 20% to 70% by weight of the initial moisture in the mixture is removed from the precast concrete, preferably 30% to 60% by weight, and particularly 40% to 50% by weight. Other known methods of reducing moisture, such as heating, may alternatively be used during the conditioning step.

[0113] Expose the surface of the product to aqueous media

[0114] The method 100 of the present disclosure includes a step 114 of humidifying the surface of the conditioned product. The humidification step 114 includes exposing at least one surface of the conditioned product to an aqueous medium to cause weight gain. After the molded product is conditioned 112, the water content of the precast concrete or in other words the ratio of water to binder is reduced. Sufficient water content in the matrix can allow uniform carbon dioxide penetration and satisfactory CO2 absorption and satisfactory performance of the carbonated precast concrete. However, there are disadvantages associated with humidification as described in the prior art, that is, the outer (exposed) surface of the molded product loses moisture much faster than the interior of the precast concrete. This is believed to result in a lower moisture content on the outer surface when the moisture content inside is at an ideal level. The shortage of moisture on the outer surface makes the subsequent carbonation curing process on the outer surface incomplete, because curing requires a sufficient amount of water to promote the reaction between carbon dioxide and the calcium silicate phase or the oxides or hydroxides of calcium and magnesium.

[0115] When operating the process defined herein, it is desirable to raise the surface moisture content of the outer surface to a sufficient level prior to carbonation curing. This ensures that a satisfactory degree of carbonation reaction can be achieved throughout the entire volume of the precast concrete product.

[0116] In step 114 of moistening the surface of the conditioned article by exposing the surface of the conditioned article to an aqueous medium, the surface moisture content can be increased by applying an aqueous medium (i.e., an aqueous material or an aqueous phase) to at least one surface of the conditioned article. The aqueous medium can be water alone, a water-based solution, or a water-based slurry. When the aqueous material is applied to the surface moistening process, there is no particular requirement for its temperature, although a temperature close to room temperature (i.e., about 15°C to about 25°C) is preferred. The aqueous medium used in this article to cause the surface weight gain of the conditioned article includes any aqueous form (suspension / solution or other phase / material) that contains a sufficient amount of CaO / Ca(OH)2 / MgO, is capable of transporting moisture to the surface, and is suitable for concrete manufacturing. Aqueous chemical solutions such as sodium silicate (water glass) with a concentration of 1% to 25% can also be used for surface moistening. Slurries of hydrated cement, steel slag, GGBFS, stainless steel slag, lime, non-hydrated cement, fly ash, or any material containing sufficient amounts of CaO / Ca(OH)2 / MgO having a solids content of 1% to 80% can also be used for surface wetting. When a slurry is used, its solids content can be from 1% to 25% on a mass basis, although a solids content of 5% to 10% is preferred. The slurry can be prepared by adding a CaO and / or MgO-rich material to a proportional amount of water, such as tap water, in a container equipped with an agitator at room temperature (15°C to 25°C). During the slurry preparation and surface wetting process, the agitator should be kept running to maintain a consistent solids content. The pH of the prepared aqueous medium should be from 6.5 to 13.5.

[0117] The aqueous medium can be applied using a variety of application methods, including but not limited to partially or completely immersing the surface in the aqueous liquid, or spraying the aqueous medium on the surface, or applying the aqueous medium to the surface using a roller or similar device. If immersion is selected, the precast concrete can be immersed in the aqueous liquid for a duration of 1 second to 5 hours, preferably 3 seconds to 5 seconds.

[0118] Regardless of the type of application method selected, after the surface moistening treatment is completed, the moistened product can achieve a surface moisture content of at least 10 g / m 2 Weight gain, preferably at least 50 g / m 2 , preferably 50g / m 2 Up to 350g / m 2 or 75g / m 2 Up to 325g / m 2 (Based on total wetted surface area of ​​precast concrete).

[0119] CO2 curing and optional air drying

[0120] After the surface moistening step 114, the moistened product can be cured (carbonated). Curing step 118 can be carried out immediately after the moistening step 114. During the curing step 118, this is done with carbon dioxide. In some embodiments, considering the waiting time required in the carbonated precast concrete manufacturing process, such as conveying the precast concrete moistened through the surface and loading it into the carbonation curing chamber, before the curing step 118, the step 116 of air-drying the moistened product after the moistening step 114 can be optionally carried out. This stage can last up to 1 hour, preferably 5 minutes to 20 minutes. During this period, the precast concrete moistened through the surface should not be exposed to an environment of overheating, overdrying or excessive wind. If more than 1 hour of air-drying time is required, the surface moistening activity should be delayed. Otherwise, the precast concrete moistened through the surface should be covered with plastic sheets or similar materials to prevent further loss of moisture before carbonation curing. In some embodiments, the air temperature is in the range of 15 degrees Celsius to 40 degrees Celsius, preferably about 22 degrees Celsius. The relative humidity may be in the range of 30% to 90%, preferably about 50%.The air flow velocity may be in the range of 0.1 m / sec to 100 m / sec, preferably about 2 m / sec.

[0121] In some embodiments, the precast concrete with surface humidification is placed in a pressure chamber and carbonation curing is performed in the pressure chamber. Carbon dioxide gas with a purity of 5% to 99.9% is introduced into the sealed pressure chamber. The concrete is cured with gas at atmospheric pressure or above atmospheric pressure. In the case of above atmospheric pressure, the pressure of the carbon dioxide gas in the chamber is adjusted to 0.07MPa to 0.689MPa (0.1psi to 100psi) during the carbonation curing process lasting at least 5 minutes, preferably 2 hours to 24 hours.

[0122] Layered Carbonation Product Structure

[0123] As discussed herein, the method 100 of the present disclosure can provide positive effects on certain mechanical properties and durability properties of carbonated precast concrete products, specifically wear resistance and freeze-thaw resistance. Therefore, such a method 100 can have the ability to provide products with combined beneficial properties. For example, a layered carbonated product structure can be prepared. The present disclosure contemplates manufacturing / using multiple layers in a given product as needed. The carbonated product can include at least the first / outer / top layer that can be considered as an outer covering according to the product or structure and the second layer that can be called the second / inner / bottom / base layer according to the product or structure. With respect to adhesives (although it is expected that at least the adhesives in this article should be preferably used), aggregates, mixture ratios, additives and other optional components, the composition of the two layers can be different. The layers can also have different thicknesses, and therefore their relative size ratios can be different. The two layers can have different properties, and relative to the second / inner / bottom / base layer, the first / outer / top layer has at least one improved property, which is at least one of wear resistance and freeze-thaw resistance.

[0124] like Figure 2 As shown in , an exemplary embodiment of a carbonated precast concrete product 1 can be composed of two different layers 10, 20 along its thickness. On top is a denser and stronger / more durable precast concrete layer 10. Underneath the top layer 10 is a base layer 20. In one embodiment, the thickness of the top layer 10 can be less than half of the total thickness of the concrete product 1.

[0125] In the embodiment of the top layer: 1) its thickness can be 5mm to 20mm, preferably 6mm to 13mm; 2) it can use the same type of adhesive as the base layer 20; it can also use a different type of adhesive than the base layer 20; 3) if it uses the same type of adhesive as the base layer 20, the top layer 10 can use the same adhesive content as the base layer 20, but with a higher first water: adhesive ratio, and the top layer 10 can also use a larger adhesive content than the base layer 20, but the first water: adhesive ratio is similar to or greater than the latter; such a proportioning practice can be beneficial to improving the wear resistance of the carbonated precast concrete; 4) after the humidification process is completed, it is optionally recommended to apply the above-mentioned surface wetting step to this layer or the entire part of the precast concrete; 5) if the surface wetting step 214 is applied, in order to promote the water absorption process, waterproofing admixtures should not be added to the precast concrete mixture; and 6) it is designed to be a surface for withstanding major losses and tearing during the use of the carbonated precast concrete. Embodiments of the base layer 20 are: 1) adding at least 0.1% binder mass, preferably 1.5% to 2.0% waterproofing admixture; 2) binder content is no greater than the top layer 10 to save material costs; 3) water: binder ratio on a mass / mass basis is lower than the top layer 10 to compensate for the reduced permeability of carbon dioxide gas in the denser top layer 10; and 4) thickness is greater than the thickness of the top layer 10. High dosages of waterproofing admixture can improve both freeze-thaw resistance and water absorption of the base layer 20. It can also provide a dimensionally stable base, which can be important for the durability of a relatively thin top layer.

[0126] In one embodiment, there is provided a method for making a carbonated precast concrete product, the method comprising:

[0127] 1) mixing at least one binder material, aggregate, water and optional additives, preferably, the binder consists of or consists essentially of cement, or comprises a ratio of cement to slag or other carbonatable material of about 1:20 to about 20:1, or a weight ratio of cement to slag or other carbonatable material of about 20:1, or about 15:1, or about 10:1, or about 5:1;

[0128] 1A) mixing at least one binder material, aggregate, water, and optional additives to provide a base mixture, preferably the binder consists of steel slag and / or any other carbonatable material, or consists essentially of steel slag, or comprises a ratio of steel slag to cement of about 1:20 to about 20:1;

[0129] wherein said step 1A) is performed before step 1), simultaneously with step 1), or after step 1);

[0130] 2) shaping the mixed at least one binder material, aggregate, water and optional additives of step 1) to provide a shaped product;

[0131] 2A) shaping the substrate mixture to provide a shaped substrate mixture, wherein step 2A) may be performed before step 2), simultaneously with step 2), or after step 2);

[0132] wherein one or more of step 1) and step 2) and / or step 1A) and step 2A) are optionally repeated, and optionally, each of the mixed at least one binder material, aggregate, water and optional additives may comprise the same or different components in the same or different ratios;

[0133] 3) densifying the shaped product of step 2) and step 2A) into a molded product having a first water:binder ratio;

[0134] 4) demolding the molded product of step 3) having the first water:binder ratio to provide a demolded product;

[0135] 5) conditioning the demoulded product of step 4) to provide a conditioned demoulded product having a reduced amount of water relative to a molded product having a first water:binder ratio; and

[0136] 6) Curing the demoulding product obtained by adjusting the humidity in step 5) with carbon dioxide.

[0137] Now refer to Figure 3, a method 300 for making a carbonated precast concrete product having a base layer and a top layer is provided. As will be described in more detail below, the method 300 includes: a step 302a of mixing a binder, aggregate, water, admixtures and other additives for the base layer (base mixture), and a step 302b of mixing a binder, aggregate, water, admixtures and other additives for the top layer (top layer or outer layer mixture). A step 304 of molding a concrete product having a base layer from the base mixture and a top layer having a top layer mixture (multi-layer concrete product) to obtain a multi-layer molded intermediate. A step 306 of densifying the multi-layer molded intermediate to obtain a multi-layer densified intermediate. An optional step 308 of initially curing the multi-layer densified intermediate. A step 310 of demolding the multi-layer densified intermediate to obtain a demolded multi-layer intermediate. The demolded multi-layer intermediate has a first water:binder ratio for the base and a second water:binder ratio for the top layer. A step 312 of conditioning the demolded multi-layer intermediate to obtain a conditioned multi-layer article. During conditioning at 312, the water:binder ratio of at least the top layer of the conditioned multilayer article is reduced. In some cases, after the step 312 of conditioning the demolded multilayer intermediate, the water:binder ratios of both the substrate and the top layer are reduced to less than their respective first water:binder ratio and second water:binder ratio. The step 314 of humidifying at least one surface (e.g., the top layer) of the conditioned multilayer article to obtain a humidified multilayer product. After the step 314 of humidifying the top layer, the top layer has a third water:binder ratio greater than the second water:binder ratio. The optional step 316 of air drying the humidified multilayer product. And the step 318 of curing the humidified multilayer product with carbon dioxide. The optional step at Figure 3 Each of steps 302a / 302b to step 318 is described in more detail below.

[0138] Figure 3 Another method 300 for making a double-layer carbonated precast concrete product is shown. The method 300 can be used to make a multi-layer product. The method 300 includes forming a base layer 20 ( Figure 2 ) of the components of the step 302a and the top layer 10 ( Figure 2) is mixed with the components of the base layer 20 at step 302b. As previously described, the base layer mixing step 302a and the top layer mixing step 302b may use different binders, different binder contents, and different water: binder ratios. In addition, the base layer 20 may have a relatively high dosage of waterproofing admixture. It is recommended that an air-entraining admixture be used for the top layer 10 at a dosage that varies with the supplier. However, due to the widespread use of waterproofing admixtures in the base layer 20, an air-entraining admixture may not be necessary in the base layer 20. Optionally, microfibers may be added to the mixture of the top layer 10 at a dosage of 0.2% to 0.5% (based on the total volume of the raw materials). The addition of microfibers may reduce the likelihood of cracking, but may increase the wear resistance of the carbonated precast concrete. In addition, if the surface moistening step 314 is implemented, the top layer 10 may not contain a waterproofing admixture. After batching and mixing, respectively, the top layer 10 mixture and the base layer 20 mixture are conveyed to a forming / molding station. Then the forming step 304 and the densification step 306 by adding the two layers to the mold in the desired amount and order follow. It should be mentioned that the top layer mixture can be added to the mold first or the base layer mixture can be added to the mold first. In order to achieve a strong and durable bond between the two layers 10, 20, the second layer mixture should be added immediately to the leveled but not compacted first layer material. For a better bond between the two layers, other techniques can be implemented, including placing a mesh on top of the first layer or roughening the surface of the first layer before casting the second layer. As described herein with reference to the above reference Figure 1 The step 108 described above optionally performs an initial curing step 308. In addition, as described above with reference to Figure 1 The demoulding step 310 and the moistening step 312 are performed as described in steps 110 and 112. If the top layer 10 contains a cementitious binder such as hydraulic cement, then after the moistening step 312, the precast concrete can be subjected to a carbonation curing step 318 without using a surface moistening step 314. Otherwise, the top layer 10 or the entire precast concrete is subjected to a surface moistening step 314 using the method described above. Due to the addition of a large amount of waterproofing admixture, the base layer 20 can have a very strong hydrophobicity, so that the base layer 20 does not require a surface moistening step 314. After the surface moistening step 314, if necessary, the precast concrete can optionally undergo an air-drying step 316 for a short time before it is subjected to the carbonation curing step 318. The duration of this air-drying stage and the actions taken when the air-drying duration is longer than 1 hour are the same as previously described, for example Figure 1 The precast concrete having a double-layer structure is loaded into the pressure chamber and then subjected to carbonation curing in step 318. The carbonation curing step 318 includes the same parameters for the precast concrete having a double-layer structure as described herein, for example Figure 1The same as those described in step 118.

[0139] In addition to increasing the surface wetting stage, adding a sufficient amount of waterproofing admixture to the precast concrete mixture can also be an effective way to improve the freeze-thaw resistance of carbonated precast concrete. If water or deicing salt solution cannot penetrate into the carbonated precast concrete, freeze-thaw damage can be prevented. By adding a sufficient amount of waterproofing admixture, the water absorption of carbonated precast concrete in a saturated state can be significantly reduced, thereby improving freeze-thaw resistance. Typically, the recommended dosage of waterproofing admixture for precast concrete is less than 0.4% (based on the mass of the binder). Such a low dose of waterproofing admixture may have a very limited effect on the freeze-thaw resistance of concrete. The method disclosed herein can increase the dosage of the waterproofing admixture to 1.0% or more.

[0140] Without adding the above-mentioned surface wetting step, carbonated precast concrete with this high waterproofing admixture dosage can perform well in freeze-thaw tests.

[0141] Now refer to Figure 4 The above two-layer structure design can be further extended to a three-layer structure 2 design. The top and bottom of this design are denser and stronger / more durable precast concrete layers 10. Between these two layers is a center layer 30. The precast concrete on the top and bottom layers 10 can be used as described above with reference to Figure 2 The first / outer / top layer 10 of the double-layer precast concrete 1 is prepared in the same manner. The center layer 30 may have the same Figure 2 The raw material source and mix design of the second / inner / bottom / base layer 20 of the double-layer structure design 1 are completely different. Such a sandwich design can bring many benefits to carbonated precast concrete, such as improved flexural properties in addition to improved durability, a well-balanced structure, possible reduction in humidity conditioning and carbonation curing time, and the addition of other desired functions. Figure 3 The manufacturing method 300 of the double-layer carbonated precast concrete shown in FIG. 3 can be used for the three-layer carbonated precast concrete with a slight modification of the molding sequence. Therefore, the multi-layer carbonated precast concrete 2 can be molded to have more than three layers.

[0142] In the following examples, carbonated precast concrete products were formulated using some or all of the raw materials listed below:

[0143] Steel slag: a mixture of EAF and BOF slags (EBH slag) having an average particle size (D50) of 25 μm and an estimated specific gravity of 3.3; wherein the steel slag has a cumulative calcium silicate content of at least about 20%; wherein the steel slag has a calcium oxide content of at least 20%; wherein the steel slag has a silica content of at least about 6%;

[0144] Ordinary Portland cement: Type I;

[0145] Water: tap water;

[0146] Aggregate: crushed stone with a specific gravity of 2.7; 100% passing through a 4.76 mm (No. 4) sieve; 0.25% moisture content and 0.75% water absorption;

[0147] Air entraining admixture (AEA): supplied by BASF, product name MicroAir;

[0148] Water repellent admixture (WRA): supplied by BASF, product name MasterPel 240;

[0149] Hydrated lime: White powder of calcium magnesium tetrahydroxide, supplied by DAP Canada.

[0150] Compressed CO2 in cylinders with a purity of >99.9% is used for carbonation.

[0151] The properties of the carbonated precast concrete produced were evaluated and compared with the ASTM C1372 specification for segmented retaining wall components or the ASTM C936 specification for concrete interlocking paving units. These examples are intended only to demonstrate that the desired properties can be obtained by carbonated precast concrete produced by the method of the present disclosure. Neither the raw materials and processes, nor the products and applications will be limited to those given in the examples.

[0152] Example 1

[0153] Precast concrete samples A were prepared using the mix designs shown in Table 1a and Table 1b below.

[0154] Table 1a : The mixture composition of sample A

[0155]

[0156] Table 1b : Composition of sample A

[0157]

[0158] *: Water:Binder Ratio

[0159] The raw materials were mixed together in a mixer for 5 minutes, molded and densified to the desired density under compaction and vibration. After demoulding, the precast concrete sample A was placed in front of a commercial fan at room temperature at 43 m / s. 3 / min air flow rate for 2 hours to achieve a 50% loss of its initial moisture content. Afterwards, a surface humidification step was performed by completely immersing sample A in water for 1 second to achieve a 189 g / m 2 The surface moistened precast concrete was then air dried at ambient temperature for about 5 minutes before being loaded into a pressure chamber for carbonation curing. Before the carbonation curing began, the weight gain became 172 g / m 2 Carbon dioxide gas adjusted to a pressure of 0.1 MPa (15 psi) was introduced into the sealed pressure chamber. The duration of carbonation curing was set to 24 hours. After carbonation curing, the following properties of the carbonated precast concrete were evaluated:

[0160] Density, water absorption and compressive strength - according to ASTM C140 (ASTM, 2018c);

[0161] Freeze-thaw resistance – according to ASTM C1262;

[0162] Abrasion Resistance – According to ASTM C944.

[0163] During the freeze-thaw resistance test, carbonated precast concrete samples are partially immersed in a 3% NaCl solution and subjected to 40 repeated freeze-thaw cycles, with loose particles collected and the salt solution replaced every 10 cycles. Although ASTM C1372 requires that the cumulative mass loss of segmented concrete retaining wall components after 100 freeze-thaw test cycles is no more than 1%, it is generally believed that this specification is used for concrete retaining walls that are partially immersed in water rather than deicing salt solutions. Due to the complex physical and chemical changes caused by deicing salt solutions, concrete generally experiences faster and more severe deterioration when deicing salts such as NaCl are present during the freeze-thaw process. Due to this difference, many national transportation departments have specified an acceptance standard of no more than 1% cumulative mass loss of concrete retaining walls after 40 freeze-thaw test cycles when 3% NaCl is present. Generally, if carbonated precast concrete can meet this standard, it should easily meet the requirement of no more than 1% mass loss after 100 freeze-thaw test cycles in water.

[0164] For comparison purposes, conventional carbonated precast concrete sample B was made with the same formulation as sample A but lacking the surface moistening step. Its moisture loss due to conditioning was 56%. Its physical-mechanical properties and durability after carbonation curing were also evaluated.

[0165] Table 1c: Key physical-mechanical properties and durability of surface-enhanced carbonated precast concrete and conventional carbonated precast concrete

[0166]

[0167] Table 2 : ASTM C1372 Specification for Segmental Retaining Wall Elements

[0168]

[0169] The test results of both sample A and sample B are summarized in Table 1c. The test results obtained are compared with the ASTM C1372 specification (Table 2). Due to the surface strengthening process through the surface wetting process, sample A has much better freeze-thaw resistance and wear resistance than sample B. In the absence of the surface wetting step, carbonated precast concrete cannot be accepted for segmented retaining wall applications due to its poor freeze-thaw resistance, although its other properties meet the requirements of ASTM C1372. The surface strengthening effect has made sample A meet all the requirements of ASTM C1372 for concrete segmented retaining walls.

[0170] The moisture content of precast concrete was monitored at different stages of the sample manufacturing process and the results are shown in Figure 5 At the end of the conditioning process, about 50% of the initial moisture of the precast concrete had evaporated. The surface humidification process brought some water back to the precast concrete, resulting in a moisture loss of about 40% of its initial moisture content. It is not the change in the average moisture content, but the change in the moisture content distribution after the surface humidification process that significantly improves the internal quality and surface quality or freeze-thaw resistance of the carbonated precast concrete. The moisture content of the conditioned sample B was measured along its thickness and the results are shown in Figure 6 From the top surface to the bottom of sample B, the moisture content is distributed like a slightly skewed bell curve. In its center, the moisture content is 3%. As a result of the fan-assisted humidification process, this moisture content continues to decrease on the way from the center to the outer surface. In the outermost part of sample B, the moisture content is reduced to as low as 1%. Such low moisture content makes the carbonation curing of precast concrete incomplete, because the carbonation reaction requires sufficient water as a reactant. This incomplete carbonation curing on the outer surface, in turn, creates a fragile surface of the carbonated precast concrete. This is why both the freeze-thaw resistance and the wear resistance of sample B are very poor.

[0171] Through the surface wetting process, the moisture content distribution along the thickness of the precast concrete is completely improved. Figure 6As shown in , after being immersed in water, the difference in moisture content between the center and the outer surface of the precast concrete is reduced to less than 0.5%. This indicates that the moisture distribution across the thickness of the sample is more uniform. More importantly, after taking the surface wetting process, the moisture content of the outer surface of the precast concrete is increased from the initial 1% to about 4%. In fact, a moisture content of about 4% is considered to be the optimal value for precast concrete to achieve the maximum degree of carbonation curing. With the help of sufficient amounts of moisture on and near the outer surface of the precast concrete, the carbonation reaction achieves its highest potential. Therefore, the internal quality and surface quality of the carbonated precast concrete are improved. This is why sample A has much greater resistance to both freeze-thaw and wear deformation than sample B.

[0172] Example 2

[0173] Precast concrete samples were made using the formulation and manufacturing method of Example 1, but the surface wetting method was changed. After the conditioned precast concrete samples were conditioned with a fan for 2 hours, they were immersed in a 5% cement (i.e., the same Portland cement as described in the above mix composition) slurry (Sample C) or a 5% slaked lime slurry (Sample D) for 1 second instead of being immersed in water. The moisture loss caused by the conditioning of Sample C and Sample D was 56% and 55%, respectively. After the surface wetting step was completed, their weight gains were 248 g / m 2 and 234g / m 2 The surface moistened samples were then air dried for about 6 minutes and then subjected to carbonation curing at a pressure of 0.1 MPa (15 psi) for 24 hours. The freeze-thaw resistance and abrasion resistance of the carbonated precast concrete samples were evaluated in the same manner as Sample A, and the results are recorded in Table 3. Compared with the test results of conventional carbonated precast concrete (Sample B in Table 1), the improvement in freeze-thaw resistance and abrasion resistance is obvious with the proposed surface moistening step.

[0174] Table 3 : Freeze-thaw resistance and abrasion resistance of surface-strengthened carbonated precast concrete

[0175]

[0176] Example 3

[0177] Precast concrete samples were made using the formulation and manufacturing method of Example 1, but with an increased duration of surface wetting. Instead of immersing in water for 1 second, the conditioned precast concrete samples were immersed in water for 3 seconds (Sample E) or 5 seconds (Sample F). After conditioning in front of the fan for 2 hours, Sample E and Sample F lost 55% and 54% of their initial moisture content, respectively. After the surface wetting step, they achieved 231 g / m 2 and 222g / m 2After about 6 minutes of air drying after surface wetting, it was cured for 24 hours with carbon dioxide gas adjusted to a pressure of 0.1 MPa (15 psi). The wear resistance of the carbonated precast concrete samples was evaluated in the same manner as sample A, and the results are recorded in Table 4. Compared with the test results of conventional carbonated precast concrete (sample B in Table 1), the improvement in wear resistance is obvious with the added surface wetting step.

[0178] Table 4 :Abrasion resistance of surface-strengthened carbonated precast concrete

[0179]

[0180] Example 4

[0181] Precast concrete samples were made using the formulation and manufacturing method of Example 1, but the surface wetting method was changed. The conditioned precast concrete samples were immersed in 25% cement slurry (Sample G) or 25% slaked lime slurry (Sample H) or 25% steel slag slurry (Sample I) for 1 second instead of in water. After conditioning in front of a fan for 2 hours, Sample G, Sample H and Sample I lost 47%, 50% and 51% of their initial moisture content, respectively. After the surface wetting step, they achieved 213 g / m 2 , 268g / m 2 and 258g / m 2 Weight gain. After about 6 minutes of air drying after surface wetting, it was cured for 24 hours with carbon dioxide gas under 0.1MPa (15psi) pressure. The wear resistance of the carbonated precast concrete samples was evaluated in the same manner as sample A, and the results are recorded in Table 5. Compared with the wear test results of conventional carbonated precast concrete (sample B in Table 1), the improvement in wear resistance is obvious in the case of the increased surface wetting step. In addition, the use of steel slag slurry is more effective in improving the wear resistance of carbonated precast concrete than using cement slurry or slaked lime slurry.

[0182] Table 5 :Abrasion resistance of surface-strengthened carbonated precast concrete

[0183]

[0184] Example 5

[0185] Precast concrete samples were prepared with the mix design shown below:

[0186] Table 6a : Mixed design of samples J, K, L and M

[0187]

[0188] Table 6b : Composition of samples J, K, L and M

[0189]

[0190] *: Water:Binder Ratio

[0191] The raw materials are mixed together, molded, and then densified to the desired density. After demoulding, the precast concrete samples are placed in front of a commercial fan at room temperature at 43 m / s. 3 / min air flow rate for 2 hours. This conditioning process caused a 53% water reduction for both samples J and K, and a 49% water reduction for both samples L and M. Afterwards, the surface of the precast concrete sample J was humidified by completely immersing it in water for 5 seconds, achieving a 245 g / m 2 Precast concrete samples K, L and M were surface wetted by complete immersion in 25% cement slurry, 25% steel slag slurry and 25% slaked lime slurry for 5 seconds, respectively, to achieve 283 g / m 2 , 295g / m 2 and 305g / m 2 The weight gain of the precast concrete sample after surface moistening is then air-dried for about 10 minutes at ambient temperature and then loaded into a pressure chamber for carbonation curing. Carbon dioxide gas adjusted to a pressure of 0.1 MPa (15 psi) is introduced into a sealed pressure chamber. The duration of carbonation curing is set to 24 hours. After carbonation curing, the density, water absorption, compressive strength and freeze-thaw resistance of the carbonated precast concrete sample are evaluated according to the method described in Example 1. The results obtained are recorded in Table 6c. Compared with the ASTM C 1372 specification shown in Table 2, samples J, K, L and M can all be accepted for retaining wall applications. Compared with conventional carbonated precast concrete (sample B in Table 1), with the help of a surface moistening step, they have much greater freeze-thaw resistance. In addition, immersion in cement slurry or water gives carbonated precast concrete greater freeze-thaw resistance than immersion in slag slurry or slaked lime slurry. Furthermore, if the freeze-thaw test results of Sample J are compared with those of Sample A in Table 1, immersion in water for 5 seconds gives the carbonated precast concrete greater freeze-thaw resistance than immersion in water for only 1 second.

[0192] Table 6c : Key physical-mechanical properties and durability of surface-enhanced carbonated precast concrete

[0193]

[0194] Example 6

[0195] Precast concrete sample N was prepared with the mix design shown below. The main features of this mix design are the increased water-repellent admixture (WRA) dosage from the conventional 0.2% to 0.4% to 2.0%, and a binary binder system (combination use of steel slag and ordinary Portland cement).

[0196] Table 7a : Mixed design of sample N

[0197]

[0198] Table 7b : Composition of sample N

[0199]

[0200] *: Water:Binder Ratio

[0201] The raw materials were mixed together, molded, and then densified to the desired density. After demoulding, the precast concrete sample N was placed in front of a commercial fan at room temperature at 43 m / s. 3 / minute air flow humidification for 30 minutes, thereby causing 21% water loss. Afterwards, the precast concrete sample is immediately loaded into the pressure chamber for carbonation curing, and surface humidification is not applied to it. Carbon dioxide gas adjusted to 0.1MPa (15psi) pressure is introduced into the sealed pressure chamber. The duration of carbonation curing is set to 24 hours. After carbonation curing, the density, water absorption, compressive strength, freeze-thaw resistance and wear resistance of the carbonated precast concrete sample are evaluated according to the method described in Example 1. The results obtained are recorded in Table 7c. Compared with the ASTM C1372 specification shown in Table 2, sample N can be well accepted for retaining wall applications. Compared with conventional carbonated precast concrete (sample B in Table 1), it has much better freeze-thaw resistance. Compared with carbonated precast concrete (sample A in Table 1, samples C and D in Table 3, and samples J, K, L and M in Table 6c) treated with surface humidification, it has better freeze-thaw resistance. Unfortunately, if the wear test results in Table 7c are compared to the wear resistance of Sample B in Table 1, no improvement in wear resistance is obtained with the high dosage of water repellent admixture.

[0202] Table 7c : Key physical-mechanical properties and durability of carbonated precast concrete with high dosage of waterproofing admixture

[0203]

[0204] Example 7

[0205] A layered structure with a binary binder composition comprising 90% steel slag and 10% ordinary Portland cement was used for the manufacture of Sample O. The carbonated precast concrete was designed for concrete paving materials or similar applications. The top layer of Sample O was 6 mm thick. Its base layer was 24 mm to 45 mm thick, varying with the desired property test. The mix design of Sample O is shown below:

[0206] Table 8a : Mixed design for sample O

[0207]

[0208] Table 8b : Composition of sample O

[0209]

[0210] *: Water:Binder Ratio

[0211] The concrete mixes for the top layer and the base layer were prepared separately. After all the raw materials were mixed together, the base layer mix was molded into a mold and leveled, and then the top layer mix was added. The molded material was then densified to the desired density by compaction and vibration. After demoulding, the precast concrete sample O was placed in front of a commercial fan at room temperature at 43 m / s. 3 / min air flow rate for 2 hours, thereby achieving a 36% water reduction. Afterwards, the surface of the precast concrete sample O was humidified by immersing the top layer of the precast concrete sample in water for 3 seconds, thereby achieving a 84g / m 2 The surface moistened precast concrete was then air dried at ambient temperature for about 10 minutes and then loaded into a pressure chamber for carbonation curing. Carbon dioxide gas adjusted to a pressure of 0.1 MPa (15 psi) was introduced into the sealed pressure chamber. The duration of carbonation curing was set to 24 hours. After carbonation curing, the following properties of the carbonated precast concrete were evaluated:

[0212] Density, moisture content, water absorption and compressive strength – according to ASTM C140;

[0213] Freeze-thaw resistance – per ASTM C1645, using 3% NaCl solution;

[0214] Abrasion Resistance – According to ASTM C944.

[0215] For comparison purposes, a single-layer carbonated precast concrete sample P was manufactured with a mix design very close to the mix design of the base layer of sample O, the only difference being that the mix of sample P had an initial water:binder ratio of 0.11, while the mix of the base layer of sample O had a water:binder ratio of 0.13. Sample P was manufactured following the same formulation and manufacturing method as sample N. Prior to carbonate curing, sample P was heated to 43 m / s at room temperature in front of a commercial fan. 3 / minute air flow rate for 2 hours, resulting in a 26% water reduction. The properties of Sample P were evaluated using the same test method used for Sample O. The test results for both Sample O and Sample P are summarized in Table 8c. The test results obtained were then compared with the ASTM C936 specification for concrete paving materials shown in Table 9.

[0216] ASTM C936 specifies the sandblasting method (ASTM C418) for measuring the abrasion resistance of concrete paving materials. Faced with the complexity and usability issues of ASTM C418, an alternative method, ASTM C944, was selected to evaluate the abrasion resistance of Samples O and P.

[0217] To judge the wear resistance quality of Sample O and Sample P, commercial concrete paving materials were sourced from Home Depot, including 4 types of concrete interlocking pavement elements and 5 different types of paving slabs. The purchased concrete paving materials were tested for wear resistance according to ASTM C944. Among the commercial concrete paving materials tested, the lowest mass loss due to wear was selected as the benchmark for evaluating the wear resistance of Sample O and Sample P, which is shown in Table 9.

[0218] Sample P lacking a lamellar structure has very poor wear resistance. After the wear test, its mass loss is 25 times higher than that of sample O. Sample P also has slightly lower strength than sample O, but has better water absorption and freeze-thaw resistance. Compared with the ASTM C936 specification and the best wear resistance of commercial concrete paving materials shown in Table 9, sample P cannot be accepted for concrete paving material applications, mainly because of its poor wear resistance. On the contrary, sample O has a wear resistance almost equivalent to that of the best grade of commercial concrete paving materials (Table 9) due to the combination of a lamellar structure and the surface strengthening effect of surface wetting. Its water absorption, strength and freeze-thaw resistance meet the requirements of ASTM C936. Obviously, sample O is very suitable for concrete paving material applications.

[0219] Table 8c : Key physical-mechanical properties and durability of layered carbonated precast concrete and its single-layer counterpart

[0220]

[0221] Table 9 : ASTM C936 Specification for Interlocking Concrete Pavement Elements and Optimal Abrasion Resistance of Commercial Concrete Paving Materials

[0222]

[0223] It can be found from Table 8c that after 28 freeze-thaw test cycles, Sample O has a greater mass loss than Sample P. Such a result may be due to the use of a high dose of waterproofing admixture in Sample P. Although the top surface of Sample O is strengthened by the added surface wetting step, this surface strengthening effect may not be as effective as a high dose of waterproofing admixture in terms of freeze-thaw resistance. Nevertheless, the mass loss caused by freeze-thaw of Sample O is still within the maximum allowable amount of the ASTM standard for concrete paving materials.

[0224] Example 8

[0225] The layered structure was used for the manufacture of Sample Q, with steel slag as the sole binder. The carbonated precast concrete was designed for use in concrete paving materials or similar applications. The top layer of Sample Q was 6 mm thick. Its base layer was 24 mm to 45 mm thick, varying with the desired property test. The precast concrete samples were prepared with the mix design shown below:

[0226] Table 10a : Mixed design of sample Q

[0227]

[0228] Table 10b :Composition of sample Q

[0229]

[0230] *: Water:Binder Ratio

[0231] The concrete mixes for the top layer and the base layer were prepared separately. After all the raw materials were mixed together, the base layer mix was molded into a mold and leveled, and then the top layer mix was added. The molded material was then densified to the desired density under compaction and vibration. After demoulding, the precast concrete sample Q was placed in front of a commercial fan at room temperature at 43 m / s. 3 / min air flow rate for 2 hours, thereby losing 41% of its initial moisture content. Afterwards, the surface of the precast concrete was humidified by immersing the top layer in water for 3 seconds, achieving 103 g / m 2The precast concrete with surface moistening was then air-dried at ambient temperature for about 10 minutes and then loaded into a pressure chamber for carbonation curing. Carbon dioxide gas adjusted to a pressure of 0.1 MPa (15 psi) was introduced into the sealed pressure chamber. The duration of carbonation curing was 24 hours. After carbonation curing, the physical-mechanical properties and durability of the carbonated precast concrete were evaluated as described in Example 7.

[0232] For comparison purposes, a single-layer carbonated precast concrete sample R was made with the same formulation as the base layer of sample Q, but without the surface humidification step. 3 After conditioning for 2 hours at an air flow rate of 1 / min, sample R lost 47% of its initial moisture content. Its properties were also evaluated. The test results for both sample Q and sample R are summarized in Table 10c.

[0233] Lacking a laminar structure and a surface wetting step, sample R has very poor wear resistance. After the wear test, its mass loss is 9 times higher than that of sample Q. Sample R also has a greater water absorption than sample Q, although its strength is similar to sample Q and its freeze-thaw resistance is slightly better. Compared with the ASTM C936 specification and the best wear resistance of commercial concrete paving materials shown in Table 9, sample R cannot be accepted for concrete paving material applications, mainly because of its poor wear resistance. On the contrary, sample Q has a wear resistance that is better than the best grade of commercial concrete paving materials (Table 9) due to the combination of a laminar structure and the surface strengthening effect of surface wetting. Its water absorption, strength and freeze-thaw resistance meet the requirements of ASTM C936. Obviously, sample Q is very suitable for concrete paving material applications.

[0234] Table 10c : Key physical-mechanical properties and durability of layered carbonated precast concrete and its single-layer counterpart

[0235]

[0236] References

[0237] The following references are all incorporated herein by reference in their entirety.

[0238] ACI Committee.(2008).201.2R-08: Guide to Durable ConcreteDurability.Michigan, US: American Concrete Institute.

[0239] ASTM.(2017).Standard Specffication for Dry-Cast Segmental RetainingWall Units(Vol.ASTM C1372-17).West Conshohocken,PA:ASTM International.

[0240] ASTM.(2018a).Standard Specification for Solid Concrete InterlockingPaving Units(Vol.ASTM C936 / C936M-18).West Conshohocken,PA:ASTM International.

[0241] ASTM.(2018b).Standard Test Method for Evaluating the Freeze-ThawDurabliity of Dry-Cast Segmental Retaining Wall Units and Related ConcreteUnits(Vol.ASTM C1262 / C1262M-18).West Conshohocken,PA:ASTM International.

[0242] ASTM.(2018c).Standard Test Methods for Sampling and Testing ConcreteMasonry Units and Related Units(Vol.ASTM C140 / C140M-18).West Conshohocken,PA:ASTM International.ASTM.(2019a).Standard Test Method for Abrasion Resistanceof Concrete or Mortar Surfaces by the Rotating-Cutter Method(Vol.ASTM C944 / C944M-19).West Conshohocken,PA:ASTM International.

[0243] ASTM.(2019b).Standard Test Method for Freeze-thaw and De-icing SaltDurabliity of Solid Concrete Interlocking Paving Units(Vol.ASTM C1645-19).West Conshohocken.PA:ASTM International.

[0244] CSA.(2005).CSA A231.2Precast concrete paving slabs / Precast concretepavers.Toronto,Ontario:CSA.

[0245] Environmental Protection Agency.(1995).AP 42-Compilation of AirPollutant Emission Factors,5 th Edition,Volume 1.Research Triangle Park,NC:U.S.Environmental Protection Agency.

[0246] Patel,H.,Bland,C.,&Poole,A.(1995).The microstructure of concretecured at elevated temperatures.Cement and Concrete Research,25(3),485-490.

[0247] Zhang,D.,Ghouleh,Z.,&Shao,Y.(2017).Review on carbonation curing ofcement-based materials.Journal of CO2 Utilization,21,119-131.

[0248] doi:10.1016 / j.jcou.2017.07.003.

Claims

1. A method for producing a carbonated precast concrete product, comprising: obtaining a mixture comprising at least one binder material, aggregate, and water; molding the mixture into a molded intermediate; demolding the molded intermediate to obtain a demolded intermediate having a first water:binder ratio; conditioning the demoulded intermediate to provide a conditioned product having a second water:binder ratio that is less than the first water:binder ratio of the demoulded intermediate, wherein after the conditioning, the conditioned product has a first moisture content difference between an exterior moisture content at an exterior surface of the carbonated precast concrete product and an interior moisture content at a center of the precast concrete product; moistening at least one surface of the conditioned article with an aqueous medium, thereby causing the conditioned article to gain weight and providing a moistened product, wherein after the moistening, the moistened product has a second moisture content difference between the outer moisture content and the inner moisture content, the second moisture content difference being less than the first moisture content difference; as well as The humidified product is cured with carbon dioxide to obtain the carbonated precast concrete product.

2. The method according to claim 1, wherein the first moisture content difference is up to 2 / 3 of the total moisture content of the mixture, and the second moisture content is up to 1 / 8 of the total moisture content.

3. The method of claim 1 or 2, wherein the moisturizing comprises moisturizing the at least one surface of the conditioned article until the second moisture content difference is 30% or less of the first moisture content difference.

4. The method of any one of claims 1 to 3, wherein the first moisture content difference is at least about 2%, and the second moisture content difference is at most about 0.5%.

5. The method of any one of claims 1 to 4, wherein the conditioning the demoulded intermediate comprises conditioning the demoulded intermediate until 20 wt% to 70 wt% of the initial moisture content of the demoulded intermediate is removed.

6. The method according to any one of claims 1 to 5, wherein the moistening of the at least one surface comprises applying the aqueous medium using an application method selected from the following: partially or completely immersing the at least one surface in an aqueous liquid; spraying the aqueous medium onto the at least one surface; or applying the aqueous medium to the at least one surface using a roller device.

7. The method of any one of claims 1 to 6, wherein moisturizing the at least one surface of the conditioned article comprises moisturizing the at least one surface until the conditioned article achieves a relative humidity of at least 10 g / m 2 of weight gain.

8. The method of any one of claims 1 to 7, wherein applying the aqueous medium comprises applying water, a water-based solution, and / or a water-based slurry on the at least one surface.

9. The method of any one of claims 1 to 8, wherein applying the aqueous medium comprises applying the aqueous medium at a temperature of 15°C to 25°C.

10. The method according to any one of claims 1 to 9, wherein obtaining the mixture comprises: obtaining a dry portion having at least one aggregate material and at least one binder material and a liquid portion having water; and mixing the dry portion with the liquid portion to obtain the mixture.

11. The method of claim 10, comprising mixing an additive with the dry portion and the liquid portion.

12. The method of claim 11 comprising mixing microfibers with the dry fraction.

13. The method according to any one of claims 1 to 12, wherein obtaining the mixture comprises obtaining the mixture with the at least one binder material, the at least one binder material being non-gelled.

14. The method according to any one of claims 1 to 13, wherein obtaining the mixture comprises obtaining the mixture with the at least one binder, the at least one binder comprising steel slag and cement, the weight ratio of steel slag to cement being 1:20 to 20:

1.

15. The method according to any one of claims 1 to 14, wherein obtaining the mixture comprises obtaining the mixture having the aggregate in a weight ratio of 0.3 to 0.8 to the total weight of the mixture.

16. The method according to claim 13 or 15, wherein obtaining the mixture comprises obtaining the mixture in which a weight ratio of the additive to the total weight of the mixture is 0.005 to 0.

010.

17. The method according to any one of claims 1 to 16, wherein obtaining the mixture comprises obtaining the mixture comprising an admixture.

18. The method of claim 17, wherein the admixture is a waterproofing admixture.

19. The method according to claim 18, wherein the admixture is a plasticizer, a superplasticizer or a polycarboxylate-based water reducer.

20. The method according to any one of claims 1 to 19, wherein molding the mixture comprises shaping the mixture into a shaped intermediate.

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