Magnesium carbonate-soreel cement hardened body

Abstract

The purpose of the present invention is to provide a hardened soileil cement having negative carbon emission, which can be effectively utilized in terms of strength, setting time, and / or water resistance, said hardened soileil cement being obtained by blending magnesium carbonate into soileil cement. Provided is a magnesium carbonate-blended soileil cement hardened body (SCMC) in which magnesium carbonate (MC) is blended in soileil cement (SC), the blending ratio of the magnesium carbonate to the total weight of the soileil cement (SC) and the magnesium carbonate (MC) being 10-35 wt%.

Description

TECHNICAL FIELD

[0001] The present application relates to a magnesium carbonate-composed Sorel cement hardener, an artificial fine aggregate, an artificial coarse aggregate, and a concrete material obtained by using the Sorel cement hardener, and a method for producing a magnesium carbonate-composed Sorel cement hardener. BACKGROUND

[0002] It is obvious that carbon dioxide emitted into the atmosphere is the cause of global warming that has become a problem in recent years, and reduction of the amount of emission of the above-mentioned carbon dioxide has become a major issue for the protection of the global environment. Therefore, measures are taken to suppress the emission of CO2 by capturing CO2 as a resource, separating and recycling it for various products, fuels, and the like, and performing "carbon recycling".

[0003] The present inventors and others have established a method of fixing CO2 by obtaining magnesium oxide from seawater or brine and reacting it with CO2 to produce magnesium carbonate (Patent Documents 1 to 3). However, methods for effectively utilizing the produced magnesium carbonate have not been sufficiently developed.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-175344

[0007] Patent Document 2: International Publication No. WO2021 / 261410

[0008] Patent Document 3: International Publication No. WO2022 / 030529 SUMMARY

[0009] Provided is a negative carbon emission Sorel cement hardener, a Sorel cement hardener in which magnesium carbonate is composed in various composition ratios in Sorel cement, which can be effectively utilized in terms of strength, setting time, and / or water resistance.

[0010] The present inventors and others have conducted intensive research, and have produced a Sorel cement hardener in which magnesium carbonate is composed in various composition ratios in Sorel cement, and have clarified the composition ratio at which a negative carbon emission Sorel cement hardener that can be effectively utilized in terms of strength, setting time, and / or water resistance is achieved. In addition, the Sorel cement hardener composed of magnesium carbonate was prepared into an artificial fine aggregate and a concrete material, and the influence on the compressive strength when a Sorel cement hardener obtained by replacing sand at a prescribed ratio was produced was evaluated, and it was clarified that the magnesium carbonate-composed Sorel cement can be used as an artificial fine aggregate.

[0011] Specifically, the present invention provides a magnesium carbonate-infused Sorel cement hardener (SCMC), which is a Sorel cement hardener (hereinafter also referred to as "SCMC") infused with magnesium carbonate (hereinafter also referred to as "MC"), wherein the proportion of magnesium carbonate in the mixture is 10 to 35 wt% relative to the total weight of Sorel cement (SC) and magnesium carbonate (MC).

[0012] In the magnesium carbonate-combined solidified cement hardener (SCMC) of the present invention, sometimes the solidified cement hardener (SC) is composed of the above-mentioned solidified cement with the molar ratio of magnesium oxide (MgO): magnesium chloride (MgCl2): water (H2O) of 3:1:8 to 3:1:11 or 5:1:8 to 5:1:15; wherein, when the above-mentioned magnesium chloride is magnesium chloride hydrate, the above-mentioned water content is adjusted according to the water content of the bound water of magnesium chloride hydrate.

[0013] In the magnesium carbonate-coated solid cement hardener (SCMC) of the present invention, sometimes the magnesium carbonate, magnesium oxide and magnesium chloride are derived from seawater and are magnesium carbonate-coated solid cement hardeners (SCMC).

[0014] In the magnesium carbonate-based solidified cementitious body (SCMC) of the present invention, the magnesium carbonate is sometimes produced by grinding the magnesium oxide using a bead mill to bring it into gas-solid contact with CO2.

[0015] In the magnesium carbonate-coated solid 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") is sometimes further added to the above-mentioned magnesium carbonate-coated solid cement to prolong the setting time.

[0016] The magnesium carbonate-based solidified cementitious body (SCMC) of the present invention sometimes has a compressive strength of 20 MPa or more, a setting time of 90 minutes or more, and / or is water resistant and has negative carbon emissions.

[0017] In addition, the present invention provides an artificial fine aggregate prepared by crushing and classifying the above-mentioned magnesium carbonate in combination with Sorel cement hardener (SCMC).

[0018] In addition, the present invention provides an artificial coarse aggregate prepared by crushing and classifying the above-mentioned magnesium carbonate in combination with Sorel cement hardener (SCMC).

[0019] Furthermore, the present invention provides a type of concrete made by using the above-mentioned magnesium carbonate combined with Sorel cement (SCMC) as a binder, adding fine aggregate and coarse aggregate, and further adding phosphoric acid or citric acid as an additive.

[0020] In addition, the present invention provides a method for manufacturing a magnesium carbonate-combined solid cement hardened body (SCMC), characterized in that the magnesium carbonate is mixed in a ratio of 10 to 35 wt% relative to the total weight of solid cement and magnesium carbonate.

[0021] According to the present invention, a carbon-negative Sorel cement hardener can be provided, which is a Sorel cement hardener containing magnesium carbonate in various proportions, and has the characteristics of effectively utilizing strength, setting time, and / or water resistance. Furthermore, artificial fine aggregates and artificial coarse aggregates can be prepared from magnesium carbonate in combination with the Sorel cement hardener, and carbon-negative concrete can be produced by replacing sand in the aforementioned artificial fine aggregates in a specified proportion. Attached Figure Description

[0022] Figure 1 This is a graph representing the evaluation results of the compression strength test based on the compression test of the SCMC cylindrical test specimen.

[0023] Figure 2 This is a graph showing the results of a 7-day water resistance evaluation of SCMC cylindrical test specimens based on a compression test.

[0024] Figure 3 This is a graph showing the test results of the compressive strength of SCMC fine aggregate replacement concrete after 28 days of curing.

[0025] Figure 4 This is a graph showing the results of the compressive strength evaluation of SCMC concrete based on the compressive strength test.

[0026] Figure 5 This is a graph showing the results of the compressive strength test of SCMC concrete (SC3MC15SP5 (3:1:8) and SC3MC15SP1 (3:1:10) after 7 days of water curing.

[0027] Figure 6 This is a graph showing the impact of SCMC concrete on CO2 emissions. Detailed Implementation

[0028] 1. Magnesium carbonate combined with Sorel cement hardener (SCMC)

[0029] One embodiment of the present invention is a magnesium carbonate-infused solid cement hardener (SCMC). More specifically, it is a magnesium carbonate-infused solid cement hardener (SCMC) in which magnesium carbonate (MC) is incorporated into solid cement (SC), wherein the proportion of magnesium carbonate is 10 to 35 wt% relative to the total weight of solid cement (SC) and magnesium carbonate (MC).

[0030] In this specification, magnesium carbonate (MC) includes one or more types of magnesium carbonate selected from Nesquehonite (MgCO3·3H2O), Magnesium hydroxide carbonate (mMgCO3·Mg(OH)2·nH2O (m=3~5, n=3~7)), Dypingite (4MgCO3·Mg(OH)2·5H2O), and Hydromagnesite (4MgCO3·Mg(OH)2·4H2O).

[0031] In this specification, magnesium carbonate-combined Sorel cement hardener (SCMC) includes: a hardener containing a binder of SC and MC; mortar in which part or all of the SCMC artificial fine aggregate or natural fine aggregate is replaced with artificial fine aggregate; and concrete in which part or all of the SCMC artificial fine aggregate and / or artificial coarse aggregate is replaced with natural fine aggregate and / or coarse aggregate, respectively.

[0032] In the invention of the magnesium carbonate-combined solidified cement (SCMC) of the present invention, the composition of the solidified cement, on a molar ratio, is preferably 3:1:8 to 3:1:11 or 5:1:8 to 5:1:15 for magnesium oxide (MgO), magnesium chloride (MgCl2), and water (H2O). However, when magnesium chloride hydrate is used, the amount of water is adjusted according to the moisture content of the bound water of the magnesium chloride hydrate.

[0033] In this specification, for example, a MC-combined SC hardened body (SCMC) consisting of Sorel cement (MC) with a molar ratio of magnesium oxide: magnesium chloride: water of 3:1:11 and magnesium carbonate (MC) of 25% relative to the total sample is described as "SC3MC25 (3:1:11)". However, when magnesium chloride is MgCl2·6H2O, the water content in each 1 kg of SC3MC25 (3:1:11) sample is calculated as 195.6 g (from MgCl2·6H2O) + 163.0 g (adjustment water) = 358.6 g, which is the amount of water added for adjustment.

[0034] In the invention of the magnesium carbonate-coated solid cement hardener (SCMC) of the present invention, the magnesium carbonate, magnesium oxide and magnesium chloride of the above-mentioned magnesium carbonate, magnesium carbonate and magnesium chloride derived from seawater can be produced and used.

[0035] In the invention of magnesium carbonate combined with Sorel cement hardener (SCMC), the magnesium carbonate is produced by grinding the magnesium oxide using a bead mill to bring it into gas-solid contact with CO2.

[0036] In the invention of the magnesium carbonate-combined Sorel cement hardener (SCMC) of the present invention, phosphoric acid or citric acid can be further added to the above-mentioned magnesium carbonate-combined Sorel cement to prolong the setting time.

[0037] The magnesium carbonate-based solidified cementitious 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 negative carbon emissions.

[0038] The aforementioned setting time refers to the hardening time of concrete from its manufacture until it hardens. Water resistance refers to the compressive strength of the test specimen after it has been aged in water for a specified period, which is the expected strength of 20 MPa or more.

[0039] In this specification, "negative carbon emissions" refers to a state in which the absorption of greenhouse gases, including carbon dioxide (carbonic acid gas), exceeds the emission. Specifically, magnesium carbonate (MC) is produced by grinding magnesium oxide in a bead mill to allow it to come into gas-solid contact with CO2. This MC is then incorporated into Sorel cement (SC) to create magnesium carbonate-sorel cement (SCMC), which is used as a binder in mortar, concrete, fine aggregate, or coarse aggregate, replacing natural fine or coarse aggregate. This process fixes carbon dioxide, thus achieving a negative carbon emission state.

[0040] The magnesium carbonate-infused solid cement hardener (SCMC) of the present invention, as shown in the following examples, has properties exceeding the benchmarks for compressive strength, setting time and / or water resistance, and particularly exhibits a significant improvement in low water resistance in solid cement, and achieves a negative carbon emission state.

[0041] 2.Fine aggregate

[0042] Another embodiment of the present invention is an artificial fine aggregate prepared by crushing and classifying the above-mentioned magnesium carbonate in combination with Sorel cement hardener (SCMC).

[0043] Fine aggregate consists of more than 85% aggregate with a diameter of less than 5 mm.

[0044] The artificial fine aggregate of the present invention can be used in a negative carbon emission manner by replacing part or all of the natural fine aggregate when making mortar or concrete, thereby exceeding the above-mentioned benchmarks for compressive strength, water resistance and / or setting time.

[0045] 3. Coarse aggregate

[0046] Another embodiment of the present invention is an artificial coarse aggregate prepared by crushing and classifying the above-mentioned magnesium carbonate in combination with Sorel cement hardener (SCMC).

[0047] The coarse aggregate consists of more than 85% aggregate with a diameter of 5mm or more.

[0048] The artificial coarse aggregate of the present invention can be used in a negative carbon emission manner by replacing part or all of the natural coarse aggregate during the production of concrete, thereby exceeding the above-mentioned benchmarks for compressive strength, water resistance and / or setting time.

[0049] 4. Concrete

[0050] Another embodiment of the present invention is to make concrete by adding the above-mentioned magnesium carbonate and Sorel cement (SCMC) as a binder to fine aggregates and coarse aggregates, and further adding phosphoric acid or citric acid as an additive.

[0051] Adding additives such as phosphoric acid or citric acid can extend the setting time and improve the workability of concrete.

[0052] 5. Method for manufacturing magnesium carbonate-based solidified cementitious composite (SCMC)

[0053] Another embodiment of the present invention is a method for manufacturing a magnesium carbonate-based hardened Sorel cement (SCMC) with a magnesium carbonate content of 10 to 35 wt% relative to the total weight of Sorel cement and magnesium carbonate.

[0054] In the invention of the method for manufacturing magnesium carbonate-combined solidified cement (SCMC), the composition of the solidified cement, in molar ratio, is preferably 3:1:8 to 3:1:11 or 5:1:8 to 5:1:15 for magnesium oxide (MgO), magnesium chloride (MgCl2), and water (H2O). When magnesium chloride hydrate is used, the amount of water is adjusted according to the moisture content of the bound water in the magnesium chloride hydrate.

[0055] In the invention of the method for manufacturing magnesium carbonate-coated solid cement hardener (SCMC) of the present invention, the magnesium carbonate, magnesium oxide and magnesium chloride of the above-mentioned magnesium carbonate, magnesium carbonate and magnesium chloride derived from seawater can be produced and used.

[0056] In the invention of the method for manufacturing magnesium carbonate combined with Sorel cement hardened body (SCMC), the magnesium carbonate is produced by grinding the magnesium oxide using a bead mill to bring it into gas-solid contact with CO2.

[0057] In the invention of the method for manufacturing magnesium carbonate-combined Sorel cement hardened body (SCMC), phosphoric acid or citric acid can be further added to the above-mentioned magnesium carbonate-combined Sorel cement to prolong the setting time.

[0058] Example

[0059] The present invention will be described in more detail below with examples and comparative examples. Appropriate modifications may be made without departing from the spirit of the invention. Therefore, the scope of the invention is not to be limited by the specific examples shown below.

[0060] 1. Magnesium carbonate (MC) used in the experiment

[0061] (1) Preparation of magnesium carbonate (MC) by CO2 mineralization using a bead mill

[0062] A continuous grinding unit (hereinafter, bead mill: SDA1, Ashizawa Finetech Co., Ltd.) was used to grind MgO obtained by thermally decomposing MgCl2·2H2O from seawater (actually brine source) under two conditions: 430°C and 520°C. Simultaneously, 100% CO2 gas was introduced into the main body. The MgO feeding rate was 450 g / h, and the grinding beads used were alumina beads with a particle size of 3 mm. Ethanol was selected as the grinding aid and added at a ratio of 0.36 wt% relative to the MgO feeding amount. The powder ground by the bead mill could be ground to a uniform particle size of approximately 5 μm within one cycle.

[0063] MC obtained by CO2 mineralization using a bead mill contains 4MgCO3·Mg(OH)2·5H2O, MgCO3·3H2O, or 4MgCO3·Mg(OH)2·4H2O. As an example, MCs were prepared with 26.5 mol% MgCO3·3H2O and 73.5 mol% 4MgCO3·Mg(OH)2·5H2O or 4MgCO3·Mg(OH)2·4H2O.

[0064] (2) Preparation of amorphous magnesium carbonate (AMC) with hydromagnesia as the main component

[0065] AMCs based on hydromagnesite were prepared by liquid-phase stirring for compression testing. As an example, MCs with MgCO3·3H2O and 4MgCO3·Mg(OH)2·5H2O or 4MgCO3·Mg(OH)2·4H2O were used, with 6.9 mol% and 93.1 mol% respectively.

[0066] (3) Commercially available MgCl2 and MC

[0067] In some experiments, MgCl2 and MC not derived from seawater were used instead of MgCl2 and MC produced by Hayashi Chun-Yaku Kogyo Co., Ltd. (4MgCO3·Mg(OH)2·5H2O) for the experiments.

[0068] 2. Evaluation method for the performance of magnesium carbonate combined with Sorel cement hardened body

[0069] The performance of magnesium carbonate combined with Sorel cement hardened body (SCMC) was evaluated using the following methods.

[0070] (1) Preparation of test subjects

[0071] After adding H2O (to a lesser amount than MgCl2·6H2O) to prepare a MgCl2 slurry, MgO was added and mixed. Finally, MC was added and mixed in a concrete mixer until it reached the consistency of raw concrete. Then, to determine the compressive strength, air bubbles were eliminated by degassing while filling a cylindrical mold with a height of 100 mm and a diameter of 50 mm. After air curing for 7 days, the strength of SCMC at 7 days of age was determined by compression testing.

[0072] (2) Compression strength test

[0073] The compressive strength test of the magnesium carbonate-coated Sorel cement hardened specimen was conducted using a universal testing machine (UH-X (1000kN): Shimadzu Corporation) after 7 days of air curing. The test speed was 0.60 (N / mm²). 2 The compressive strength was calculated using a cross-sectional area of ​​1963.5 mm² / second. 2 .

[0074] The compressive strength benchmark according to JIS A 1108, i.e., the compressive strength of concrete, is 20 N / mm². 2 (=MPa) is used as the target benchmark.

[0075] (3) Determination of setting time

[0076] To investigate the setting time of concrete containing SCMC binder, a mixture of SCMC mortar (SCMC binder, water, and sand) was prepared, and the initial setting time of the SCMC mortar was determined by the Vicat test (specified in JIS R 5201).

[0077] (4) Water resistance test

[0078] For the SCMC hardened body used as the test subject, the compressive strength of the specimens cured in air in a constant temperature chamber for a specified time (e.g., 7 days) and the specimens cured in air in a constant temperature chamber for a specified time (e.g., 2 days) and then cured in water for a specified time (e.g., 5 days) are determined by a compressive strength test. The compressive strength of the specimens cured in water, or the degree of reduction in compressive strength, is evaluated to assess the water resistance of the SCMC hardened body.

[0079] 3. Manufacturing of Artificial Fine Aggregate (AFA)

[0080] (1) Study on the proportion of SCMC fine aggregate components

[0081] MgO, MgCl2 and H2O, which are used as raw materials for SC, are mixed to make a compounded SC paste. Then, MC is added and the mixture is further mixed. The paste is poured into a mold and cured to harden it. The hardened body obtained is used as the SCMC test body and compression test is performed.

[0082] The relationship between the names of the test specimens and the SC molar ratios of each component of MgO, MgCl2, and H2O is shown in Table 1.

[0083]

[0084] result

[0085] The results of the compression test of the above test specimens are shown in... Figure 1 .according to Figure 1 The following insights can be drawn.

[0086] 1) The more magnesium carbonate (MC), the higher the compressive strength of SCMC. On the other hand, the more MC added, the worse the workability (processability: setting time) becomes, so the maximum MC addition rate is considered to be around 35%. However, the higher the addition rate, the more carbon dioxide can be absorbed.

[0087] 2) Compared to the molar ratio of MgO:MgCl2:H2O, the higher the proportion of MgO or the lower the proportion of H2O, the higher the strength.

[0088] 3) The SCMC test specimen of (Nakagaki) showed approximately twice the strength of the SCMC test specimen of (Lin) (under the same molar ratio).

[0089] (2) Evaluation of the water resistance of SCMC test specimens

[0090] Curing method for water resistance test specimens: For test specimens (i) cured in air in a constant temperature chamber for 7 days as air curing test specimens, and (ii) cured in air in a constant temperature chamber for 2 days and then cured in water for 5 days as water curing test specimens, the compressive strength was measured to evaluate the water resistance of the test specimens.

[0091] result

[0092] The results are shown in Figure 2The 7-day compressive strengths of (Forest) SC3, SC3MC25, and SC3MC35A as test specimens were compared after curing in air and water. The compressive strengths of SC3 and SC3MC after 5 days of water curing decreased by approximately 80% and 50%, respectively, compared to the test specimens cured in air. The significant strength reduction was due to the low water resistance of Sorel cement binder (SC3). On the other hand, the reduction rate was suppressed by adding MC.

[0093] (3) Evaluation of SCMC artificial fine aggregate

[0094] SCMC cubes are manufactured by crushing them using a hammer crusher and adjusting the particle size through screening. Particles with a size of 0.075mm to 4.75mm are used as SCMC artificial fine aggregate.

[0095] Prepare SCMC fine aggregate, natural sand, natural stone, water, and additives. Mix the SCMC fine aggregate, natural sand, and natural stone, then add water and additives and mix thoroughly. Use a plastic mold to prepare cylindrical test specimens. The proportions of SCMC fine aggregate, natural sand, natural stone, water, and additives for the cylindrical test specimens (Mix0 to Mix4) are shown in Table 2. Perform compression tests on the test specimens (Mix0 to Mix4) to determine their compressive strength.

[0096]

[0097] result

[0098] The results of the 28-day compressive strength determination of concrete replaced with SCMC fine aggregate are shown below. Figure 3 As a result, concrete obtained by replacing 6% of sand with SCMC fine aggregate achieved a strength of over 20 MPa. Furthermore, it was shown that SC3MC35A exhibited even higher strength when 4% of the sand in the concrete was replaced. Additionally, it was demonstrated that increasing the amount of MC within the SCMC fine aggregate could potentially improve both the concrete strength and CO2 fixation.

[0099] (4) Recommended values ​​for the formulation of artificial fine aggregate (AFA)

[0100] Based on the above results, the recommended values ​​for the formulation of artificial fine aggregate (AFA) are as follows: MgO:MgCl2:H2O ratio of 3:1:11 to 3:1:8, MC mass ratio of 5% to 35%, and CO2 fixation of approximately 18 kg / ton to approximately 125 kg / ton (Table 3).

[0101]

[0102] Furthermore, recommended values ​​for the amount of AFA in concrete are shown in Table 4. This indicates that by increasing the MC ratio in the additive, the replacement rate can exceed 6 vol%.

[0103]

[0104] 4. Optimization of molar ratio (SC3 vs. SC5): Research on the blending of Sorel cement hardened bodies with compressive strength above 20 MPa

[0105] MC was added to Sorel cement, which is made by blending and mixing MgO, MgCl2 and H2O, to prepare a mixed SCMC binder. The improvement of compressive strength, hardening time and water resistance was studied and evaluated.

[0106] The experiment recorded the proportions of each component of the adhesive and the amount of additives corresponding to the names of the test pieces listed in Tables 5 and 6.

[0107]

[0108]

[0109] result

[0110] The effect of varying the proportions of Sorel cement (MgO, MgCl2, H2O) and MC in the SCMC concrete obtained by using materials from the Nakagaki Research Laboratory (MgO, MgCl2, MC (AMC in this case)) on compressive strength is shown in the figure. Figure 4 .

[0111] In the Sorel cement molar ratio of MgO:MgCl2:H2O, SC3MC15 (3:1:8) and SC5MC15 (5:1:9) with less water can achieve very high strengths of over 50MPa.

[0112] In the test specimens with higher water content (SC3MC15SP1 (3:1:11), SC5MC15SP5 (5:1:10), SC5MC15SP2 (5:1:11), etc.), although surface cracks appeared, a compressive strength of 20 MPa, exceeding the target strength, was obtained. However, SC3MC15 (3:1:11) was below the target strength.

[0113] Based on the results of using materials from the Nakagaki Research Laboratory, it is considered that the optimal range for SCMC formulation is 3:1:8 to 3:1:11 and 5:1:8 to 5:1:15.

[0114] 5. Evaluation of the impact on setting time

[0115] To investigate the setting time of concrete containing SCMC binder, a mixture of SCMC mortar (SCMC binder, water, and sand) was prepared. The results of the initial setting time of the SCMC mortar determined using the Vicat test are shown in Table 7. It should be noted that additives such as sodium monophosphate (SP) and citric acid (CA) phosphoric acid (PA) were added to prolong the setting time.

[0116]

[0117] It can be seen that the setting time of mortar with added SC3 (3:1:8) is 130 minutes, which exceeds the target setting time of 90 minutes. However, the setting time of mortar with added AMC produced by Nakagaki Laboratory (SC3MC15 (3:1:8) and SC5MC15 (5:1:9)) is shortened to less than 20 minutes.

[0118] The mixtures SC3MC15CA5 (3:1:8) and SC3MC15CA5Hyd. (3:1:8), with 5% CA added at a (MC+SC) mass ratio, achieved setting times of 45 minutes and 110 minutes, respectively. The mixtures with 5% SP added at a (MC+SC) mass ratio (e.g., SC3MC15SP5 (3:1:8)) did not show an effect on extending the setting time. On the other hand, by adding 1% phosphoric acid (PA) at a (MC+SC) weight ratio, increasing the particle size of AMC to 150–300 μm, the hardening times of SC3MC15PA1 (3:1:8) and SC5MC15PA1 (5:1:8), obtained using AMC from the Nakagaki Laboratory, were extended to 108 minutes and 80 minutes, respectively.

[0119] 6. Evaluation of water resistance

[0120] The effects of SC3MC15SP5 (3:1:8) and SC3MC15SP1 (3:1:10) on the compressive strength of specimens cured in air for 7 days, as well as specimens cured in air for 7 days and in water for 7 days, were investigated. The results are presented in... Figure 5 .

[0121] Although the compressive strength of SC3MC15SP5 (3:1:8) and SC3MC15SP1 (3:1:10) after 7 days of water curing decreased to 84% and 92% respectively compared with the air-cured specimens, they still showed a higher strength than the target strength of 20 MPa.

[0122] 7. Evaluation of Negative Carbon Emissions

[0123] The carbon dioxide (CO2) emissions of the SC3MC25 sample (3:1:11) using SCMC binder were calculated. The calculated CO2 emissions were -39.2 kg / m³. 3 For concrete with negative carbon emissions ( Figure 6 ).

Claims

1. A magnesium carbonate-infused Sorel cement hardener SCMC, which is a Sorel cement hardener SCMC infused with magnesium carbonate MC, wherein the proportion of magnesium carbonate MC relative to the total weight of Sorel cement SC and magnesium carbonate MC is 10-35 wt%. Here, Sorel cement is also referred to as "SC", magnesium carbonate is also referred to as "MC", and magnesium carbonate-infused Sorel cement hardener is also referred to as "SCMC".

2. The magnesium carbonate-based solidified cement hardener SCMC according to claim 1, wherein, The composition of the Sorel cement, in molar ratio, is 3:1:8 to 3:1:11 or 5:1:8 to 5:1:15 for magnesium oxide (MgO), magnesium chloride (MgCl2), and water (H2O). In the case where the magnesium chloride is magnesium chloride hydrate, the amount of water is adjusted according to the moisture content of the bound water of the magnesium chloride hydrate.

3. The magnesium carbonate-based solidified cement hardener SCMC according to claim 2, wherein, The magnesium carbonate, magnesium oxide, and magnesium chloride are derived from seawater.

4. The magnesium carbonate-based solidified cement hardener SCMC according to claim 1, wherein, The magnesium carbonate is produced by grinding magnesium oxide using a bead mill to bring it into gas-solid contact with CO2.

5. The magnesium carbonate-based solidified cement hardener SCMC according to claim 1, wherein, Sodium phosphate or citric acid is further added to the magnesium carbonate-based Sorel cement according to claim 1 to prolong the setting time.

6. The magnesium carbonate-based solidified cement hardener SCMC according to claim 1, wherein, It has a compressive strength of 20 MPa or higher, a setting time of 90 minutes or higher, and / or is water-resistant and has negative carbon emissions.

7. An artificial fine aggregate, which is prepared by crushing and classifying magnesium carbonate according to any one of claims 1 to 6 in combination with Sorel cement hardener SCMC.

8. An artificial coarse aggregate, which is prepared by crushing and classifying magnesium carbonate according to any one of claims 1 to 6 in combination with Sorel cement hardener SCMC.

9. A type of concrete, which is made by using magnesium carbonate as a binder and Sorel cement (SCMC) as a binder, as described in any one of claims 1 to 6, adding fine aggregate and coarse aggregate, and further adding phosphoric acid or citric acid as an additive.

10. A method for manufacturing a magnesium carbonate-based solidified cementitious body (SCMC), characterized in that, As a proportion of magnesium carbonate, it is 10 to 35 wt% relative to the total weight of Sorel cement and magnesium carbonate.

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