Magnesium-carbonate-blended sorel cement cured product

Abstract

The purpose of the present invention is to create a Sorel cement cured product in which magnesium carbonate is blended with Sorel cement and to provide a carbon-negative Sorel cement cured product that can be utilized effectively in terms of strength, setting time, and / or water resistance. Provided is a Sorel cement cured product (SCMC) in which magnesium carbonate (MC) is blended with Sorel cement (SC), wherein the blend ratio of magnesium carbonate in the magnesium-carbonate-blended Sorel cement cured product (SCMC) is 10-35 wt% relative to the total weight of Sorel cement (SC) and magnesium carbonate (MC).

Description

Magnesium carbonate-containing Sorel cement hardened body

[0001] The present invention relates to a magnesium carbonate-blended Sorel cement hardened product, an artificial fine aggregate, an artificial coarse aggregate and a concrete material that utilize the Sorel cement hardened product, and a method for producing the magnesium carbonate-blended Sorel cement hardened product.

[0002] It is self-evident that carbon dioxide emitted into the atmosphere is a cause of global warming, which has become a problem in recent years, and reducing carbon dioxide emissions has become a major challenge in protecting the global environment. Therefore, efforts are being made to reduce CO2 emissions through "carbon recycling," which regards CO2 as a resource, separates and captures it, and reuses it in various products and fuels.

[0003] The present inventors have established a method for immobilizing CO2 as magnesium carbonate by reacting magnesium oxide obtained from seawater or brine with CO2 (Patent Documents 1 to 3). However, methods for effectively utilizing the produced magnesium carbonate have not necessarily been fully developed.

[0004] JP 2020-175344 A International Publication Pamphlet WO2021 / 261410 International Publication Pamphlet WO2022 / 030529

[0005] To provide a carbon-negative Sorel cement hardened body which can be effectively used in terms of strength, setting time and / or water resistance by preparing a Sorel cement hardened body by blending magnesium carbonate with Sorel cement at various blending ratios.

[0006] The inventors conducted extensive research and created Sorel cement hardened products by blending magnesium carbonate with Sorel cement in various proportions, and identified the blending ratios that would result in carbon-negative Sorel cement hardened products that could be effectively used in terms of strength, setting time, and / or water resistance. Furthermore, they prepared artificial fine aggregate and concrete materials from the Sorel cement hardened product blended with magnesium carbonate, and evaluated the effect on compressive strength of the Sorel cement hardened products produced by substituting sand in a specified proportion, demonstrating that Sorel cement blended with magnesium carbonate can be used as artificial fine aggregate.

[0007] Specifically, the present invention provides a Sorel cement hardened body (hereinafter also referred to as "SCMC") in which magnesium carbonate (hereinafter also referred to as "MC") is blended with Sorel cement (hereinafter also referred to as "SC"), and the blending ratio of magnesium carbonate is 10 to 35 wt% based on the total weight of the Sorel cement (SC) and the magnesium carbonate (MC).

[0008] In the magnesium carbonate-blended Sorel cement hardened product (SCMC) of the present invention, the composition of the Sorel cement may be a Sorel cement hardened product (SC) in which the molar ratio of magnesium oxide (MgO):magnesium chloride (MgCl2):water (HO) is 3:1:8 to 3:1:11, or 5:1:8 to 5:1:15; however, when the magnesium chloride is magnesium chloride hydrate, the amount of water is adjusted depending on the moisture content of the bound water in the magnesium chloride hydrate.

[0009] In the magnesium carbonate-blended Sorel cement hardened product (SCMC) of the present invention, the magnesium carbonate, the magnesium oxide, and the magnesium chloride may be derived from seawater.

[0010] In the magnesium carbonate-blended Sorel cement hardened body (SCMC) of the present invention, the magnesium carbonate may be produced by grinding the magnesium oxide with a bead mill through gas-solid contact with CO2.

[0011] In the magnesium carbonate-blended Sorel cement hardened body (SCMC) of the present invention, phosphoric acid (hereinafter also referred to as "SP") or citric acid (hereinafter also referred to as "CA") may be added to the magnesium carbonate-blended Sorel cement in order to further extend the setting time.

[0012] The magnesium carbonate-blended Sorel cement hardened body (SCMC) of the present invention may have a compressive strength of 20 MPa or more, a setting time of 90 minutes or more, and / or may be water resistant and carbon negative.

[0013] The present invention also provides an artificial fine aggregate obtained by pulverizing and classifying the above-mentioned magnesium carbonate-blended Sorel cement hardened body (SCMC).

[0014] The present invention also provides an artificial coarse aggregate obtained by pulverizing and classifying the above-mentioned magnesium carbonate-blended Sorel cement hardened product (SCMC).

[0015] Furthermore, the present invention provides concrete prepared by using the above-mentioned magnesium carbonate-blended Sorel cement (SCMC) as a binder, adding fine aggregate and coarse aggregate, and optionally adding phosphoric acid or citric acid as an additive.

[0016] The present invention also provides a method for producing hardened Sorel cement containing magnesium carbonate (SCMC), characterized in that the blending ratio of magnesium carbonate is 10 to 35 wt % based on the total weight of Sorel cement and magnesium carbonate.

[0017] According to the present invention, a Sorel cement hardened body can be prepared by blending magnesium carbonate with Sorel cement in various blending ratios, and the hardened body can be provided as a carbon-negative body having effectively usable properties such as strength, setting time, and / or water resistance. Furthermore, artificial fine aggregate and artificial coarse aggregate can be prepared from the Sorel cement hardened body blended with magnesium carbonate, and carbon-negative concrete can be produced by replacing sand with the artificial fine aggregate in a predetermined ratio.

[0018] FIG. 1 shows the evaluation results of a compressive strength test conducted by a compression test on an SCMC cylindrical specimen. FIG. 2 shows the results of a 7-day water resistance evaluation conducted by a compression test on an SCMC cylindrical specimen. FIG. 3 shows the results of a compressive strength test on SCMC fine aggregate-substituted concrete after 28 days of curing. FIG. 4 shows the results of a compressive strength evaluation conducted by a compressive strength test on SCMC concrete. FIG. 5 shows the results of a compressive strength test on SCMC concrete (SC3MC15SP5 (3:1:8) and SC3MC15SP1 (3:1:10)) after 7 days of underwater curing. FIG. 6 shows the effect of SCMC concrete on CO2 emissions.

[0019] 1. Magnesium Carbonate-Blended Sorel Cement Hardened Product (SCMC) One embodiment of the present invention is a magnesium carbonate-blended Sorel Cement Hardened Product (SCMC). More specifically, it is a magnesium carbonate-blended Sorel Cement Hardened Product (SCMC) in which magnesium carbonate (MC) is blended with Sorel Cement (SC), and the blending ratio of magnesium carbonate is 10 to 35 wt % based on the total weight of the Sorel Cement (SC) and the magnesium carbonate (MC).

[0020] In this specification, magnesium carbonate (MC) includes one or more magnesium carbonates selected from the group consisting of nesquehonite (MgCO3.3H2O), basic magnesium carbonate (mMgCO3.Mg(OH)2.nH2O (m = 3 to 5, n = 3 to 7)), dypingite (4MgCO3.Mg(OH)2.5H2O), and hydromagnesite (4MgCO3.Mg(OH)2.4H2O).

[0021] In this specification, the term "magnesium carbonate-blended Sorel cement hardened body (SCMC)" includes a hardened body of a binder blended with SC and MC, mortar in which some or all of the SCMC artificial fine aggregate or natural fine aggregate has been replaced with artificial fine aggregate, and concrete in which some or all of the SCMC artificial fine aggregate and / or artificial coarse aggregate has been replaced with natural fine aggregate and / or coarse aggregate, respectively.

[0022] In the invention of the magnesium carbonate-blended Sorel cement hardened product (SCMC), the composition of the Sorel cement is preferably such that the molar ratio of magnesium oxide (MgO):magnesium chloride (MgCl2):water (HO) is 3:1:8 to 3:1:11, or 5:1:8 to 5:1:15. However, when magnesium chloride hydrate is used as the magnesium chloride, the amount of water is adjusted depending on the moisture content of the bound water in the magnesium chloride hydrate.

[0023] In this specification, for example, an MC-blended SC hardened body (SCMC) made by blending Sorel cement (MC) with a molar ratio of magnesium oxide:magnesium chloride:water of 3:1:11 and 25% magnesium carbonate (MC) relative to the entire sample is expressed as "SC3MC25 (3:1:11)." However, when MgCl.6H.sub.2O is used as the magnesium chloride, the amount of water in a 1 kg sample of SC3MC25 (3:1:11) is calculated as 195.6 g (from MgCl.6H.sub.2O) + 163.0 g (water for adjustment) = 358.6 g, and the amount of water to be added is adjusted accordingly.

[0024] In the invention of the magnesium carbonate-blended Sorel cement hardened body (SCMC) of the present invention, a magnesium carbonate-blended Sorel cement hardened body (SCMC) in which the magnesium carbonate, magnesium oxide, and magnesium chloride are derived from seawater can be produced and used.

[0025] In the invention of the magnesium carbonate-blended Sorel cement hardened body (SCMC) of the present invention, the magnesium carbonate can be produced by grinding the magnesium oxide with a bead mill through gas-solid contact with CO2.

[0026] In the invention of the magnesium carbonate-blended Sorel cement hardened body (SCMC) of the present invention, phosphoric acid or citric acid can be added to the magnesium carbonate-blended Sorel cement to extend the setting time.

[0027] The magnesium carbonate-blended Sorel cement hardened body (SCMC) of the present invention has a compressive strength of 20 MPa or more, a setting time of 90 minutes or more, and / or improved water resistance, and is carbon negative.

[0028] The setting time refers to the time it takes for the concrete to harden after being produced, and water resistance refers to the desired compressive strength of 20 MPa or more after a test specimen has been cured in water for a specified period of time.

[0029] In this specification, "carbon negative" refers to a state in which the amount of greenhouse gases, including carbon dioxide (carbon dioxide), absorbed is greater than the amount emitted. That is, magnesium carbonate (MC), which is produced by grinding magnesium oxide in a bead mill and subjecting it to gas-solid contact with CO2, is blended with Sorel cement (SC), and magnesium carbonate-blended Sorel cement (SCMC) is used as a binder to produce mortar, concrete, fine aggregate, or coarse aggregate. By replacing natural fine aggregate or coarse aggregate with this magnesium carbonate, a carbon-negative state can be achieved.

[0030] As shown in the examples below, the magnesium carbonate-blended Sorel cement hardened product (SCMC) of the present invention has performance that exceeds the standards for compressive strength, setting time and / or water resistance, and in particular, it has a significant improvement effect on the low water resistance of Sorel cement, and achieves a carbon negative state.

[0031] 2. Fine Aggregate Another embodiment of the present invention is an artificial fine aggregate obtained by pulverizing and classifying the magnesium carbonate-blended Sorel cement hardened body (SCMC).

[0032] The fine aggregate has a diameter of less than 5 mm and 85% or more of the aggregate is fine aggregate.

[0033] The artificial fine aggregate of the present invention can be used in a carbon-negative manner by replacing part or all of the natural fine aggregate in making mortar or concrete, thereby exceeding the above standards for compressive strength, water resistance and / or setting time.

[0034] 3. Coarse Aggregate Another embodiment of the present invention is an artificial coarse aggregate obtained by pulverizing and classifying the above-mentioned magnesium carbonate-blended Sorel cement hardened body (SCMC).

[0035] At least 85% of the coarse aggregate has a diameter of 5 mm or more.

[0036] The artificial coarse aggregate of the present invention can be used in a carbon-negative manner to replace part or all of the natural coarse aggregate in making concrete, thereby exceeding the above standards for compressive strength, water resistance and / or setting time.

[0037] 4. Concrete Another embodiment of the present invention is concrete made by using the above-mentioned Sorel cement mixed with magnesium carbonate (SCMC) as a binder, adding fine aggregate and coarse aggregate, and optionally adding phosphoric acid or citric acid as an additive.

[0038] Additives such as phosphoric acid or citric acid can be added to extend the setting time and improve the workability of the concrete.

[0039] 5. Method for producing hardened Sorel cement containing magnesium carbonate (SCMC) Another embodiment of the present invention is a method for producing hardened Sorel cement containing magnesium carbonate (SCMC) in which the blending ratio of magnesium carbonate is 10 to 35 wt % based on the total weight of Sorel cement and magnesium carbonate.

[0040] In the method for producing a magnesium carbonate-blended Sorel cement hardened product (SCMC) of the present invention, the composition of the Sorel cement is preferably a molar ratio of magnesium oxide (MgO):magnesium chloride (MgCl2):water (HO) of 3:1:8 to 3:1:11, or 5:1:8 to 5:1:15. However, when magnesium chloride hydrate is used as the magnesium chloride, the amount of water is adjusted depending on the moisture content of the bound water in the magnesium chloride hydrate.

[0041] In the method for producing a magnesium carbonate-blended Sorel cement hardened product (SCMC) of the present invention, a magnesium carbonate-blended Sorel cement hardened product (SCMC) in which the magnesium carbonate, magnesium oxide, and magnesium chloride are derived from seawater can be produced and used.

[0042] In the method for producing a magnesium carbonate-blended Sorel cement hardened body (SCMC) of the present invention, the magnesium carbonate can be produced by grinding the magnesium oxide with a bead mill and subjecting it to gas-solid contact with CO2.

[0043] In the method for producing a magnesium carbonate-blended Sorel cement hardened body (SCMC) of the present invention, phosphoric acid or citric acid can be optionally added to the magnesium carbonate-blended Sorel cement to extend the setting time.

[0044] The present invention will be explained in more detail below with reference to examples and comparative examples, but modifications can be made as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0045] 1. Magnesium Carbonate (MC) Used in the Experiment (1) Obtaining Magnesium Carbonate (MC) by CO Mineralization Using a Bead Mill Using a continuous grinding device (hereinafter referred to as the bead mill: SDA1, Ashizawa Finetech Co., Ltd.), MgCl2·2H2O derived from actual brine from seawater was thermally decomposed at two conditions, 430°C and 520°C, to form MgO, which was then ground with the bead mill while 100% CO2 gas was introduced into the main body. The MgO feeding rate was 450 g / h, and the packed beads were alumina beads with a particle size of 3 mm. Ethanol was selected as a grinding aid and added at a rate of 0.36 wt% of the MgO input. The powder ground through the bead mill could be ground to a uniform particle size of approximately 5 μm in one cycle.

[0046] MCs obtained by CO mineralization using a bead mill include 4MgCO3·Mg(OH)2·5H2O, MgCO3·3H2O, and 4MgCO3·Mg(OH)2·4H2O. As an example, MCs were used in which MgCO3·3H2O and 4MgCO3·Mg(OH)2·5H2O or 4MgCO3·Mg(OH)2·4H2O were used at 26.5 mol% and 73.5 mol%, respectively.

[0047] (2) Obtaining amorphous magnesium carbonate (AMC) composed mainly of hydromagnesite. AMC composed mainly of hydromagnesite was prepared by liquid-phase stirring and subjected to compression tests. As an example, MC containing 6.9 mol% MgCO3·3H2O and 4MgCO3·Mg(OH)2·5H2O or 4MgCO3·Mg(OH)2·4H2O was used.

[0048] (3) Commercially available MgCl2 and MC In some experiments, MgCl2 and MC (4MgCO3.Mg(OH)2.5H2O) manufactured by Hayashi Pure Chemical Industries, Ltd. were purchased and used in the experiments, rather than MgCl2 and MC derived from seawater.

[0049] 2. Evaluation method for performance of hardened Sorel cement containing magnesium carbonate The performance of hardened Sorel cement containing magnesium carbonate (SCMC) was evaluated by the following method.

[0050] (1) Preparation of specimen: Add the missing H2O to MgCl2·6H2O and mix to prepare an MgCl2 slurry, then add MgO and mix. Finally, add MC and mix in a concrete mixer until it becomes similar to fresh concrete. Then, to measure the compressive strength, fill a cylindrical mold 100 mm high and 50 mm in diameter while removing air bubbles. After curing in air for 7 days, the strength of the 7-day-old SCMC is measured by a compression test.

[0051] (2) Compressive strength test The compressive strength test of the resulting magnesium carbonate mixed Sorel cement hardened specimen is carried out after 7 days of air curing using a universal testing machine (UH-X (1000kN): Shimadzu Corporation). The test speed is 0.60 (N / mm 2 ) / sec., and the cross-sectional area of ​​1963.5 mm 2 was adopted.

[0052] The compressive strength standard for concrete in JIS A 1108 is 20 N / mm 2 (= MPa) was used as the target standard.

[0053] (3) Measurement of Setting Time In order to investigate the setting time of concrete containing SCMC binder, a mixture of SCMC mortar (a mixture of SCMC binder, water, and sand) is prepared, and the initial setting time of the SCMC mortar is determined by the Vicat test (specified in JIS R 5201).

[0054] (4) Water resistance test For the SCMC hardened specimen, a sample is cured in air in a constant temperature room for a predetermined period (e.g., 7 days) and a sample is cured in water for a predetermined period (e.g., 5 days) after curing in air in a constant temperature room for a predetermined period (e.g., 2 days). The compressive strength is measured in a compressive strength test, and the compressive strength of the sample cured in water or the degree of decrease in compressive strength is evaluated to evaluate the water resistance of the SCMC hardened specimen.

[0055] 3. Manufacturing of Artificial Fine Aggregate (AFA) (1) Investigation of the blending ratio of components of SCMC fine aggregate The SC raw materials MgO, MgCl2 and H2O were mixed and kneaded to make SC paste, then MC was added, the mixture was further kneaded and placed in a formwork, and cured to harden. This was used as an SCMC specimen and subjected to compression tests. The relationship between the name of the specimen and the SC molar ratio of each component of MgO, MgCl2 and H2O is shown in Table 1.

[0056]

[0057] Results The results of the compression tests on the above specimens are shown in Figure 1. The following can be said from Figure 1: 1) The more magnesium carbonate (MC) was added, the higher the compressive strength of the SCMC. On the other hand, the more MC added, the lower the workability (workability: setting time), so the maximum MC addition rate is thought to be around 35%. However, the higher the addition rate, the more carbon dioxide can be absorbed. 2) Compared to the molar ratio of MgO:MgCl2:H2O, the higher the MgO ratio or the lower the H2O ratio, the higher the strength. 3) Nakagaki's SCMC specimen demonstrated strength that was about twice as high as Hayashi's SCMC specimen (under conditions where the molar ratios were equivalent).

[0058] (2) Evaluation of Water Resistance of SCMC Specimens The water-resistant specimens were cured using the following curing methods: (i) air-cured specimens, which were cured in the air in a temperature-controlled room for 7 days; and (ii) underwater-cured specimens, which were cured in the air in a temperature-controlled room for 2 days and then underwater for 5 days. The compressive strength of the specimens was measured to evaluate their water resistance.

[0059] Results The results are shown in Figure 2. Test specimens (Hayashi) SC3, SC3MC25, and SC3MC35A were compared for their 7-day compressive strength when cured in air and water. The compressive strength of SC3 and SC3MC cured in water for 5 days was reduced by approximately 80% and 50%, respectively, compared to those cured in air. The strength of the Sorel cement binder alone (SC3) was significantly reduced due to its low water resistance. On the other hand, the rate of reduction could be reduced by adding MC.

[0060] (3) Evaluation of SCMC Artificial Fine Aggregate SCMC cubes were produced, crushed with a hammer crusher, and sieved to adjust the particle size. Pieces with particle sizes of 0.075 mm to 4.75 mm were used as SCMC artificial fine aggregate.

[0061] SCMC fine aggregate, natural sand, natural stone, water, and additives were prepared. After mixing the SCMC fine aggregate, natural sand, and natural stone, water and additives were added and mixed thoroughly to create cylindrical specimens in plastic mode. The blending ratios of SCMC fine aggregate, natural sand, natural stone, water, and additives for the cylindrical specimens Mix 0 to Mix 4 are shown in Table 2. Compression tests were conducted on these specimens Mix 0 to Mix 4 to measure their compressive strength.

[0062]

[0063] Results Figure 3 shows the results of measuring the 28-day compressive strength of concrete substituted with SCMC fine aggregate. As a result, concrete in which 6% of the sand was replaced with SCMC fine aggregate achieved a strength of over 20 MPa. It was also shown that when 4% of the sand in concrete was replaced with SC3MC35A, the strength was higher. It was also shown that increasing the amount of MC in SCMC fine aggregate could improve the strength and CO2 fixation amount of concrete.

[0064] (4) Recommended Mixing Values ​​for the Production of Artificial Fine Aggregate (AFA) From the above results, it was suggested that the recommended mixing values ​​for the production of artificial fine aggregate (AFA) are an MgO:MgCl2:H2O ratio of 3:1:11 to 3:1:8, an MC mass ratio of 5% to 35%, and a CO2 fixation amount of approximately 18 kg / ton to approximately 125 kg / ton (Table 3).

[0065]

[0066] Furthermore, the recommended amount of AFA contained in concrete is shown in Table 4. It was suggested that by increasing the MC ratio with the additive, the replacement ratio can exceed 6 vol%.

[0067]

[0068] 4. Optimization of molar ratio (SC3 vs. SC5): Study of the composition of Sorel cement hardened body that can achieve compressive strength of 20 MPa or more. MgO, MgCl2, and H2O were mixed and kneaded to form Sorel cement, which was then mixed with MC to create an SCMC binder. The compressive strength, hardening time, and degree of improvement in water resistance were studied and evaluated. In the experiment, the amounts of each binder component and additives added for the test specimen names listed in Tables 5 and 6 are listed.

[0069]

[0070]

[0071] Results Figure 4 shows the effect on compressive strength of the SCMC concrete made with materials from the Nakagaki Laboratory (MgO, MgCl, MC (AMC in this case)) when the amount of each component of the Sorel cement (MgO, MgCl, HO) and MC was changed.

[0072] Among the Sorel cements with a molar ratio of MgO:MgCl2:H20, SC3MC15 (3:1:8) and SC5MC15 (5:1:9) with low water content were able to achieve extremely high strength of over 50 MPa.

[0073] Although cracks were observed on the surface of specimens with a high water content (SC3MC15SP1 (3:1:11), SC5MC15SP5 (5:1:10), SC5MC15SP2 (5:1:11), etc.), a compressive strength exceeding the target strength of 20 MPa was achieved. However, SC3MC15 (3:1:11) fell short of the target strength.

[0074] Based on the results using materials from the Nakagaki Laboratory, it was considered preferable to set the SCMC blending ranges to 3:1:8 to 3:1:11 and 5:1:8 to 5:1:15.

[0075] 5. Evaluation of the effect on setting time To investigate the setting time of concrete containing SCMC binder, SCMC mortar (a mixture of SCMC binder, water, and sand) was prepared. The initial setting time of the SCMC mortar was determined by a Vicat test, and the results are shown in Table 7. In order to extend the setting time, additives such as sodium monophosphate (SP), citric acid (CA), and phosphoric acid (PA) were added.

[0076]

[0077] The setting time of the mortar containing SC3 (3:1:8) was 130 minutes, exceeding the target setting time of 90 minutes. However, the setting time of the mortar containing AMC (SC3MC15 (3:1:8), SC5MC15 (5:1:9)) produced by Nakagaki Laboratory was reduced to less than 20 minutes.

[0078] The addition of 5% CA by weight (MC+SC) to mixes SC3MC15CA5 (3:1:8) and SC3MC15CA5Hyd. (3:1:8) extended the setting times to 45 and 110 minutes, respectively. Addition of 5% additive SP (e.g., SC3MC15SP5 (3:1:8)) did not extend the setting time. On the other hand, the addition of 1% phosphoric acid (PA) by weight (MC+SC) and increasing the particle size of AMC to 150-300 μm extended the setting times of SC3MC15PA1 (3:1:8) and SC5MC15PA1 (5:1:8) using AMC from the Nakagaki Laboratory to 108 and 80 minutes, respectively.

[0079] 6. Evaluation of Water Resistance The effects on compressive strength of SC3MC15SP5 (3:1:8) and SC3MC15SP1 (3:1:10) cured in air for 7 days, and cured in air and underwater for 7 days were examined. The results are shown in Figure 5.

[0080] The compressive strength of SC3MC15SP5 (3:1:8) and SC3MC15SP1 (3:1:10) cured in water after 7 days was 84% ​​and 92%, respectively, compared to that of those cured in air, but still showed a strength higher than the target strength of 20 MPa.

[0081] 7. Carbon Negative Evaluation The carbon dioxide (CO2) emissions were calculated for the sample SC3MC25 (3:1:11) using the SCMC binder. The result was -39.2 kg / m 3 It was estimated that the CO2 emissions would be 100% of the total, making it carbon-negative concrete (Figure 6).

Claims

1. A hardened sorel cement (hereinafter also referred to as "SCMC") comprising sorel cement (hereinafter also referred to as "SC") and magnesium carbonate (hereinafter also referred to as "MC"), wherein the ratio of magnesium carbonate is 10 to 35 wt% of the total weight of sorel cement (SC) and magnesium carbonate (MC), and the magnesium carbonate includes amorphous magnesium carbonate.

2. The magnesium carbonate-containing sorrel cement hardened body (SCMC) according to Claim 1, wherein the amorphous magnesium carbonate comprises nesquehonite and hydromagnesite.

3. The composition of the aforementioned sorel cement is, in molar ratio, magnesium oxide (MgO):magnesium chloride (MgCl 2 ): Water (H 2 A magnesium carbonate-containing sorrel cement hardened body (SCMC) according to claim 1, wherein the amounts of each of O) are 3:1:8 to 3:1:11, or 5:1:8 to 5:1:15; However, if the magnesium chloride is magnesium chloride hydrate, the amount of water is adjusted by the water content of the bound water in the magnesium chloride hydrate.

4. The magnesium carbonate-containing sorrel cement hardened body (SCMC) according to claim 3, wherein the magnesium carbonate, magnesium oxide, and magnesium chloride are derived from seawater.

5. The aforementioned magnesium carbonate is obtained by grinding magnesium oxide with a bead mill, resulting in CO 2 A magnesium carbonate-containing sorrel cement hardened body (SCMC) according to claim 1, produced by gas-solid contact.

6. The magnesium carbonate-containing sorrel cement hardened body (SCMC) according to claim 1, wherein phosphoric acid or citric acid is added to further extend the setting time.

7. A magnesium carbonate-containing sorrel cement hardened body (SCMC) according to claim 1, having a compressive strength of 20 MPa or more, a setting time of 90 minutes or more, and / or being water-resistant, and being carbon-negative.

8. The magnesium carbonate-containing sorrel cement hardened body (SCMC) according to Claim 1, characterized in that the particle size of the magnesium carbonate is in the range of 150 to 300 μm.

9. Artificial fine aggregate obtained by crushing and classifying the magnesium carbonate-containing sorrel cement hardened body (SCMC) according to any one of claims 1 to 8.

10. Artificial coarse aggregate obtained by crushing and classifying the magnesium carbonate-containing sorrel cement hardened body (SCMC) according to any one of claims 1 to 8.

11. Concrete prepared using magnesium carbonate-containing sorrel cement (SCMC) as described in any one of claims 1 to 8 as a binder, with fine aggregate and coarse aggregate added, and optionally with phosphoric acid or citric acid added as an additive.

12. A method for producing a magnesium carbonate-containing sorrel cement hardened body (SCMC), characterized in that the magnesium carbonate contains amorphous magnesium carbonate, and the magnesium carbonate is blended in an amount of 10 to 35 wt% relative to the total weight of sorrel cement and magnesium carbonate.

13. The amorphous magnesium carbonate contains magnesium oxide CO 2 The manufacturing method according to claim 12, characterized in that it is produced by bringing it into contact with and grinding magnesium oxide with a bead mill.