Method for manufacturing in-situ carbonated concrete secondary product

Abstract

The present invention relates to a method for manufacturing an in-situ carbonated concrete secondary product. According to an aspect of the present invention, the method for manufacturing an in-situ carbonated concrete secondary product comprises the steps of: mixing cement, an aggregate, and water; injecting carbon dioxide gas; and further mixing the cement, the aggregate, and the water.

Description

Method for manufacturing in-situ carbonated concrete secondary products

[0001] The present invention relates to a method for manufacturing an in-situ carbonated concrete secondary product, and more specifically, to a method for manufacturing a concrete secondary product having enhanced properties by using carbon dioxide gas in the manufacturing process.

[0002] Over the past three years, greenhouse gas emissions from fossil fuels have reached record highs, accelerating global warming. In response, governments around the world are announcing and implementing various long-term policies for carbon neutrality. Domestically, too, plans such as the 2030 Nationally Determined Contribution (NDC) and the 2050 Long-term Low Greenhouse Gas Emission Development Strategies (LEDS) are being established and implemented to achieve them.

[0003] Carbon neutrality refers to reducing emissions from human activities and increasing absorption to achieve net zero emissions, preventing the rise in greenhouse gas concentrations in the atmosphere. Since eliminating carbon emissions entirely is practically impossible, research is being conducted to capture, store, and reuse carbon already emitted as the most practical way to achieve carbon neutrality. The construction industry is also developing and applying technologies to reduce carbon emissions, such as cement alternatives and carbon capture construction materials.

[0004] Korean Patent No. 10-1619320 discloses a method for manufacturing a concrete secondary product, which includes a step of placing the manufactured concrete secondary product into a curing chamber and injecting carbon dioxide gas into the chamber to cure it. However, this prior art has the disadvantage of requiring the hassle of moving the manufactured heavy concrete and requiring a lot of time and space to perform the process.

[0005] One embodiment of the present invention aims to provide a method for manufacturing a carbonated concrete secondary product using carbon dioxide, which causes environmental problems such as global warming.

[0006] In addition, one embodiment of the present invention aims to provide a method for manufacturing a concrete secondary product that can be carbonated immediately (in-situ) during the manufacturing process without the need to move to a separate carbonation chamber.

[0007] As a technical means for achieving the above-described technical task, according to one aspect of the present invention, a method for manufacturing an in-situ carbonated concrete secondary product includes the steps of mixing cement, aggregate, and water; the step of injecting carbon dioxide gas; the step of further mixing the cement, the aggregate, and the water; the step of injecting the mixed composition into a mold; and the step of compression-molding the composition injected into the mold to form a concrete secondary product.

[0008] According to another aspect of the present invention, the carbon dioxide gas may be injected at 0.1 to 0.7 wt% relative to the weight of the cement.

[0009] According to another aspect of the present invention, the above steps may be performed in a mixer for carbon dioxide injection.

[0010] According to another aspect of the present invention, the carbon dioxide injection mixer may include a carbon dioxide gas tank; a connecting pipe; and a mixer body.

[0011] According to another aspect of the present invention, a heater may be additionally attached to the connecting tube.

[0012] According to another aspect of the present invention, the carbon dioxide injection mixer may additionally include a mass flow meter.

[0013] According to another aspect of the present invention, the weight ratio of the cement and aggregate may be in the range of 1:2.5 to 1:9.

[0014] According to another aspect of the present invention, the water-cement ratio (W / C) may be in the range of 0.25 to 0.7.

[0015] According to any one of the above-described problem solving means of the present invention, the method for manufacturing an in-situ carbonated concrete secondary product according to one embodiment of the present invention stores carbon dioxide gas in the concrete secondary product, thereby reducing the amount of carbon dioxide gas emitted into the atmosphere, thereby having the effect of preventing environmental problems such as global warming.

[0016] In addition, according to any one of the problem solving means of the present invention, the method for manufacturing an in-situ carbonated concrete secondary product according to one embodiment of the present invention enables immediate carbonation by injecting carbon dioxide gas during the mixing process without the need to move the concrete to a separate carbonation chamber, thereby enabling carbonation through a simple process and at low cost.

[0017] In addition, according to any one of the problem solving means of the present invention, a concrete secondary product using the method for manufacturing an in-situ carbonated concrete secondary product according to one embodiment of the present invention has the advantage of having enhanced flexural strength and compressive strength.

[0018] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention belongs from the description below.

[0019] FIG. 1 is a result of analyzing the particle size distribution of a cement raw material used in a method for manufacturing an in-situ carbonated concrete secondary product according to one embodiment of the present invention using a particle size analyzer (PSA).

[0020] Figure 2 shows the results of measuring basic properties of cement raw materials using an X-ray diffraction analyzer.

[0021] Figure 3 is a schematic diagram of a mixer for carbon dioxide injection according to one embodiment of the present invention.

[0022] FIG. 4 shows temperature conditions calculated for curing a mixture of cement, aggregate, water, and carbon dioxide gas after pouring it into a mold in manufacturing a concrete secondary product sample according to one embodiment of the present invention, according to KS F 4419.

[0023] FIG. 5 is a photograph of a laboratory-scale press used in manufacturing a concrete secondary product sample according to one embodiment of the present invention.

[0024] Figure 6 shows the results of a flexural strength test on a concrete secondary product according to one embodiment of the present invention.

[0025] Figure 7 shows the results of a compressive strength test on a concrete secondary product according to one embodiment of the present invention.

[0026] Figure 8 shows the results of X-ray diffraction analysis at 7 days of age for a concrete secondary product according to one embodiment of the present invention.

[0027] Fig. 9 is a photograph showing the appearance of a secondary concrete product according to one embodiment of the present invention.

[0028] Below, with reference to the attached drawings, embodiments of the present invention are described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, irrelevant parts have been omitted for clarity of description, and similar reference numerals have been used throughout the specification to indicate similar elements.

[0029] Throughout the specification, when a part is said to be "connected" to another part, this includes not only cases where it is "directly connected," but also cases where it is "indirectly connected" with other members or elements intervening. Furthermore, when a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated. Furthermore, when a component is expressed in the singular, it includes cases where it includes plural, unless otherwise explicitly stated.

[0030] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for illustrating embodiments of the present invention are illustrative and are not intended to limit the present invention to the details depicted. Furthermore, in describing the present invention, if a detailed description of a related known technology is deemed to unnecessarily obscure the gist of the present invention, such detailed description will be omitted.

[0031] When interpreting components, it is interpreted as including the error range even if there is no separate explicit description.

[0032] Although terms like "first," "second," etc. are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another. Accordingly, a first component referred to below may also be a second component within the technical scope of the present invention.

[0033] The individual features of the various embodiments of the present invention can be partially or wholly combined or combined with each other, and as can be fully understood by those skilled in the art, various technical connections and operations are possible, and each embodiment can be implemented independently of each other or can be implemented together in a related relationship.

[0034] Meanwhile, the tentative effects that can be expected by the technical features of the present invention that are not specifically mentioned in the specification of the present invention are treated as described in the specification, and the present embodiment is provided to more completely explain the present invention to a person having average knowledge in the art, and the contents shown in the drawings may be expressed exaggeratedly compared to the actual implementation of the invention, and a detailed description of a configuration that is judged to unnecessarily obscure the gist of the present invention is omitted or briefly described.

[0035] The present invention will be described in detail with reference to the attached drawings below.

[0036] According to one aspect of the present invention, a method for manufacturing an in-situ carbonated concrete secondary product is configured to include a step of mixing cement, aggregate, and water; a step of injecting carbon dioxide gas; and a step of further mixing the cement, the aggregate, and the water.

[0037] The steps for mixing cement, aggregate, and water are not limited to a specific mixing method, and any method commonly used to form concrete may be employed without limitation. For example, machine mixing may be used, and each material may be introduced simultaneously, or the aggregate, cement, and water may be mixed in that order. Alternatively, the aggregate and cement may be first dry mixed, and then water may be added to perform water mixing.

[0038] The above aggregate may be fine aggregate (fine aggregate) with a particle size of 5 mm or less or coarse aggregate with a particle size of 5 mm or more, and may be mixed and used as needed.

[0039] The above cement, aggregate, and water may be mixed in an appropriate ratio depending on the characteristics of the concrete secondary product to be manufactured. The weight ratio of the cement and aggregate may range, for example, from 1:2.5 to 1:9, preferably from 1:2.5 to 1:6. Within the above range, the concrete interlocking block for road pavement may have properties suitable for use.

[0040] In one embodiment of the present invention, the water-cement ratio (W / C) may be in the range of 0.25 to 0.7, preferably in the range of 0.25 to 0.5. The water-cement ratio (W / C) is the weight ratio of water to the weight of cement used in the concrete mix. If the W / C ratio is low, the strength and durability are high, but workability may be somewhat reduced, and if the W / C ratio is too high, the number of pores in the concrete increases, which may weaken the strength.

[0041] A method for manufacturing a secondary concrete product according to one embodiment of the present invention comprises injecting carbon dioxide gas into mixed cement, aggregate, and water, whereby Ca(OH)2 and CaO react with carbon dioxide to convert into stable CaCO3, and the manufactured secondary concrete product has SiO2-CaCO3-H2O and is carbonated. Accordingly, the pH of the secondary concrete product is lowered, so that the strong alkalinity is somewhat neutralized, and the carbon dioxide gas is stored within the secondary concrete product.

[0042] The carbon dioxide gas may be injected at a concentration of 0.1 to 0.7 wt% relative to the weight of the cement. More specifically, the concentration may be 0.1 to 0.3 wt%. Within the above range, the environmental pollution prevention effect and the property enhancement effect of the secondary concrete product, as intended by the present invention, can be maximized.

[0043] The above steps for producing a secondary concrete product according to one embodiment of the present invention may be performed within a carbon dioxide injection mixer. Since a series of steps are performed simultaneously within a single mixer (an in-situ process), there is no need to move the product to a separate carbonation chamber, simplifying the process, reducing spatial constraints, and enabling carbonation at a low cost.

[0044] The above carbon dioxide injection mixer may include a carbon dioxide gas cylinder; a connecting pipe; and a mixer body. The gas cylinder is connected to the mixer body through the connecting pipe, and the mixer is designed to maintain a completely sealed environment to prevent the gas from leaking into the air.

[0045] In one embodiment, the connecting pipe may have an additional heater attached to prevent gas loss due to temperature differences with the outside during the movement of carbon dioxide gas from the gas tank to the mixer.

[0046] In addition, the above-mentioned carbon dioxide injection mixer may additionally include a mass flow meter. If the above-mentioned mass flow meter is additionally included, there is an advantage in that carbon dioxide gas can be stably injected at a constant concentration.

[0047] According to another aspect of the present invention, a concrete secondary product can be manufactured according to a method for manufacturing an in-situ carbonated concrete secondary product according to one embodiment of the present invention. The manufactured concrete secondary product can have improved flexural strength, compressive strength, etc., due to the carbonation treatment promoting the formation of hydrates such as CaCO3 crystals and CSH.

[0048] Example

[0049] Experimental Example 1: Analysis of the composition, particle size, and crystal phase of raw materials (cement)

[0050] Ordinary Portland Cement (OPC) of domestic H company was used for manufacturing in-situ carbonated secondary concrete products. In the case of carbon dioxide, high-purity carbon dioxide gas in a gaseous state was used because it was deemed most suitable for the process conducted in this study among solid, liquid, and gaseous states, and high-purity (CO299.999%) gas was used to inject at a stable concentration. In order to analyze the basic properties of the cement used in the study, a microstructural analysis was performed through chemical composition, particle size analysis, and crystal phase measurement. For chemical composition analysis, basic oxide analysis was performed using an X-ray fluorescence spectrometer (XRF, Supermini 200, Rigaku, JAPAN), and the results are shown in Table 1 below. To analyze the particle size distribution of raw materials, a particle size analyzer (PSA, LA-950V2, Horiba, JAPAN) was used, and to analyze the crystal phase, an X-ray diffraction analyzer (XRD, D8 Advance A25 Plus, Bruker, USA) was used to measure the basic properties of the raw materials. The particle size distribution analysis results are shown in Fig. 1. The X-ray diffraction analysis measurement results were analyzed using the PDF-2 database of the 'International Center for Diffraction Data (ICDD)' and the 'Inorganic Crystal Structure Database (ICSD)' of the X'Pert Highscore software. The results are shown in Fig. 2, and these results were used for subsequent sample preparation and crystal phase analysis.

[0051] MgOAl2O3SiO2P2O5SO3K2OCaOFe2O3Others3.264.7019.401.124.061.1262.303.220.82

[0052] (Unit: wt%)

[0053]

[0054] As a result of particle size distribution analysis, the average particle size of the sample was found to be 25 ㎛, and the particle size distribution was measured to be distributed into two groups of 0.35 ㎛ and 15 ㎛.

[0055] Through X-ray diffraction analysis, the crystals of the raw materials were measured to be C2S (Belite, 2CaO·SiO2), C3S (Alite, 3CaO·SiO2), C3A (Aluminate, 3CaO·Al2O3), C4AF (Ferrite, Ca2(Al,Fe)2O5), and Gypsum. These results were consistent with the main constituent minerals of ordinary Portland cement, and it was determined that there was no problem in using it as a raw material.

[0056] As an aggregate for manufacturing a concrete secondary product sample according to one embodiment of the present invention, S Company's standard sand (ISO standard sand Standard Sand (EN 196-1)) was used, and the experiment was conducted under conditions in which the granulation ratio was kept constant.

[0057]

[0058] Manufacturing Example 1: Manufacturing of a mixer for carbon dioxide injection

[0059] To apply in-situ carbonation technology to secondary concrete products, an experiment was conducted by selecting a method of injecting carbon dioxide gas during material mixing. A mixer for carbon dioxide injection was designed with a device capable of quantitatively injecting CO2 gas to inject carbon dioxide gas during mixing, and its schematic is shown in Figure 3. A mass flow controller (MFC) was connected to enable quantitative injection of CO2 gas to maintain a constant gas concentration and experimental environment. A mixer cover was designed to prevent carbon dioxide gas from escaping into the air during mixing, and was made of 2 cm thick acrylic considering the pressure during carbon dioxide gas injection. Rubber seals were attached to all gaps to maintain a completely sealed environment, and a heater was attached to the gas pipe to prevent gas loss due to temperature differences with the outside during the gas transfer from the gas tank to the mixer.

[0060]

[0061] Manufacturing Example 2: Manufacturing of In-situ Carbonated Concrete Secondary Product Samples

[0062] To investigate the properties compared to the existing mix when injecting carbon dioxide during mixing, the amount of carbon dioxide injected was controlled to 0, 0.1, 0.3, 0.5, and 0.7% based on the mass of cement. Since carbon dioxide gas is in a gaseous state and has a unit of volume, the molar mass of CO2 was considered and replaced with the weight based on the weight of cement. The cement:aggregate ratio was controlled to 1:3, and the water-cement ratio (W / C) was 0.35, and the mixing ratio is shown in Table 2.

[0063] Sample*Cement (g)Aggregate (g)W / CCO2(wt%)IB-04501,3500.350IB-0.14501,3500.350.1IB-0.34501,3500.350.3IB-0.54501,3500.350.5IB-0.74501,3500.350.7

[0064] *) Sample name 'IB' is abbreviation of interlocking Block

[0065]

[0066] Concrete interlocking blocks for sidewalks were selected as the secondary concrete product to which this mix will be applied, and the manufacturing and property tests were performed in accordance with KS F 4419 (Concrete interlocking blocks for sidewalks). Before manufacturing concrete interlocking blocks, 4 × 4 × 16 cm square specimens and 5 × 5 × 5 cm cubic specimens (paste) were made to investigate the basic properties and chemical reactions, and preliminary experiments were conducted using the same mix. When making samples, the mixing ratio was as follows: cement and aggregate were put into a mixer bowl, dry mixed, then water was added and mixed for 30 seconds, followed by mixing while injecting carbon dioxide for 30 seconds according to the mix ratio, and then additional mixing for 60 seconds. The total mixing time was set to 2 minutes. In the case of paste specimens, since they do not contain aggregates, dry mixing was excluded and mixing was performed in the same order thereafter. After pouring the mixed dough into the mold, it was cured at high temperature for 9.5 hours within the temperature range required by KS F 4419, and then air-cured (23±1℃) until testing. The temperature range required by KS standards is 500 accumulated temperature, and the calculated results are shown in Figure 4.

[0067] Flexural strength, compressive strength, and absorption were measured using 4 × 4 × 16 cm square cylindrical test specimens, and each test was performed at ages of 1, 3, 7, and 28 days according to KS L ISO 679 (Test method for strength of cement). In the case of 5 × 5 × 5 cm cubic test specimens, they were made with paste excluding aggregates, and these were crushed at ages of 1, 3, 7, and 28 days for X-ray diffraction analysis for crystal phase analysis. After crushing, the moisture in the sample was completely removed to stop hydration in order to maintain the state of the age until the test. The hydration stop method used in this experiment was a solvent exchange method using isopropyl alcohol, and the sample was stored in the solvent until the X-ray diffraction analysis measurement.

[0068] Based on the results of the preliminary experiment, mock-up scale concrete interlocking blocks (I-shaped regular sidewalk blocks, 20 × 10 × 6 cm) were manufactured. Since actual concrete interlocking manufacturing sites use vibrating press equipment to apply high pressure to the blocks during block forming, a laboratory-scale press was manufactured and used for block manufacturing.

[0069]

[0070] Experimental Example 2: Flexural strength, compressive strength, and water absorption test results of in-situ carbonated secondary concrete product samples.

[0071] In order to analyze the properties of concrete specimens according to the amount of carbon dioxide injected before block production, a 4×4×16 cm square mold was produced and tests on flexural strength, compressive strength, and water absorption were performed at different ages.

[0072] The results of the flexural strength test (Fig. 6) showed a higher strength tendency than the existing mix at carbon dioxide injection amounts of 0.1 and 0.3%, and a slightly lower strength tendency than the existing mix at 0.5 and 0.7%, but it was found to satisfy the flexural strength standard specified in KS F 4419.

[0073] The results of the compressive strength test (Fig. 7) were the same as the results of the flexural strength test, showing higher strength than the sample without carbon dioxide injection up to 0.1 and 0.3%, and from 0.5% onwards, the strength decreased as the injection amount increased compared to the existing sample. Although there is no standard stipulated in KS F 4419 for compressive strength, the strength enhancement effect was shown when the carbon dioxide injection amount was adjusted within the optimal range, confirming the possibility of applying the in-situ carbonation technology to secondary construction products other than concrete interlocking blocks.

[0074] The results of the absorption rate test (Table 3) showed a tendency for the absorption rate to decrease as the amount of carbon dioxide injected increased, but all mixtures satisfied the absorption rate standard presented in KS F 4419, so it was determined that there would be no problem in producing secondary products for carbon dioxide injection construction.

[0075] Sample Absorption rate (%)W*_wet (g)W_dry (g)IB-07.7572.27531.12IB-0.18.1574.90531.59IB-0.38.3586.63541.84IB-0.58.6572.44526.96IB-0.78.9569.88523.17

[0076] *) W: Weight

[0077]

[0078] Experimental Example 3: Crystallinity Analysis Results of In-situ Carbonated Concrete Secondary Product Samples

[0079] To analyze the chemical properties and crystallinity changes occurring inside the specimens when carbon dioxide was injected into the secondary concrete product, 5 × 5 × 5 cm cubic specimens were produced. The specimens were made into pastes excluding aggregates for X-ray diffraction analysis, and were crushed to a size of 63 ㎛ or less according to each age and kept in a state of hydration arrest until analysis before being used for measurements.

[0080] X-ray diffraction analysis was performed using the IB-0 sample, which was not injected with carbon dioxide, and the IB-0.3 sample, which showed the highest strength trend compared to the IB-0 sample, which was not injected with carbon dioxide in the strength test results of the prismatic specimens described above. To show the difference in crystal phase between the two samples, the X-ray diffraction analysis results at 7 days, when the difference was most pronounced, are shown in Fig. 8. Portlandite (Ca(OH)2), calcite (CaCO3), larnite (Ca2SiO4), zeolite, and ettringite crystals were observed in both samples regardless of carbon dioxide injection, and these crystals are the main minerals that commonly appear in cement specimens. Among them, active formation of portlandite crystals was observed in both samples. In addition, the formed larnite is a type of C2S, a basic mineral of cement, and it seems that the residual C2S crystals that did not fully react were measured, as the size of the C2S peak was significantly reduced compared to the cement X-ray diffraction analysis pattern. Although there appears to be little difference in the types of crystals formed depending on the carbon dioxide injection, the amount of residual larnite decreases significantly as the amount of carbon dioxide injected increases. This suggests that carbon dioxide injection promotes the reaction of C2S, a basic cement mineral, more actively than in the existing sample, promoting the formation of hydration products such as CSH, resulting in higher strength.

[0081]

[0082] Experimental Example 4: Compressive strength test results of concrete interlocking blocks.

[0083] Based on the results of the preliminary experiments conducted previously, specimens measuring 20 × 10 × 6 cm were manufactured. To manufacture blocks using the same method as actual field equipment, a laboratory-scale press was manufactured in-house, and experiments were conducted using the IB-0 sample mixture to select the optimal pressing load. Blocks were manufactured in units of 500 kg within the minimum and maximum load ranges of the manufactured press, and the optimal pressing load was selected through compressive strength measurements at 1 day, and the results are shown in Table 4.

[0084] Weight (kg)2,0002,5003,0003,5004,0004,500C.S* (MPa)19.721.925.329.132.933.1

[0085] *) CS: Compressive strength

[0086]

[0087] The experimental results showed that the higher the pressurizing load, the higher the compressive strength. However, when a load of 4,500 kg or more was applied, moisture inside the sample leaked out of the mold. Therefore, 4,000 kg was selected as the optimal pressurizing load and blocks were manufactured.

[0088] Concrete interlocking blocks were manufactured using the optimal press load and the same mixing ratio as in the pre-experimental experiment. The measured flexural and compressive strength results were identical to the pre-experimental results. Furthermore, the blocks exhibited the same visual appearance regardless of whether carbon dioxide was injected (Fig. 9).

[0089] In other words, when carbon dioxide is injected within the optimal range, higher strength can be achieved compared to conventional mixes. Even beyond the optimal range, strength tendencies similar to conventional mixes were observed. Therefore, through additional experiments to select mixing conditions based on diverse field conditions, the potential application of in-situ carbonation technology to various secondary concrete products was confirmed.

[0090] The present invention can be applied to various industrial fields that utilize concrete. For example, it can be utilized in the construction and civil engineering industries.

Claims

1. Step of mixing cement, aggregate and water; Step of injecting carbon dioxide gas; Additionally, a step of mixing the cement, the aggregate, and the water; A step of injecting the mixed composition into a mold; and Comprising a step of forming a secondary concrete product by compression molding the composition injected into the mold. Method for manufacturing in-situ carbonated secondary concrete products.

2. In the first paragraph, the carbon dioxide gas is injected at 0.1 to 0.7 wt% relative to the weight of the cement. Method for manufacturing in-situ carbonated secondary concrete products.

3. In the first paragraph, the steps are performed in a mixer for carbon dioxide injection. Method for manufacturing in-situ carbonated secondary concrete products.

4. In the third paragraph, the carbon dioxide injection mixer carbon dioxide gas cylinder; connector; and Including a mixer body, Method for manufacturing in-situ carbonated secondary concrete products.

5. In the fourth paragraph, a heater is additionally attached to the connecting pipe. Method for manufacturing in-situ carbonated secondary concrete products.

6. In paragraph 4, the carbon dioxide injection mixer Including an additional mass flow meter, Method for manufacturing in-situ carbonated secondary concrete products.

7. In paragraph 1, the weight ratio of the cement and aggregate is 1:2.5 to 1:

9. Method for manufacturing in-situ carbonated secondary concrete products.

8. In paragraph 1, the water-cement ratio (W / C) is 0.25 to 0.

7. Method for manufacturing in-situ carbonated secondary concrete products.

9. A secondary concrete product manufactured according to any one of the manufacturing methods in clauses 1 to 8.

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