Method for improving activity of low-calcium carbon sequestration cementing material and product thereof

Abstract

The invention belongs to the technical field of building materials, and particularly relates to a method for improving the activity of a low-calcium carbon sequestration cementing material and a product thereof. The method for improving the activity of the low-calcium carbon sequestration cementing material comprises the following step: doping magnesium salt into the low-calcium carbon sequestration cementing material. The method for improving the activity of the low-calcium carbon-sequestration cementing material is beneficial to improving the reaction activity of the low-calcium carbon-sequestration cementing material and improving the carbon sequestration effect and compressive strength of a low-calcium carbon-sequestration cementing material product.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to a method for improving the activity of low-calcium carbonatable binder and its products. Background Art

[0002] Low Calcium Carbonatable Binder (LCCB) refers to a new type of binder mainly composed of non-hydraulic calcium silicates such as calcium monosilicate (CS) and larnite (C3S2), which can bond other substances into a whole and have certain mechanical strength through spontaneous reaction with carbon dioxide, and has the characteristics of low calcium content and low carbon emission. However, LCCB has problems such as low carbonation reaction activity, low carbon fixation rate, and poor carbonation hardening performance, which need to be solved urgently.

[0003] Therefore, an improved technical solution is needed to address the deficiencies of the above prior art. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for improving the activity of low-calcium carbonatable binder and its products, which helps to solve or improve at least one of the problems of low reaction activity, low carbon fixation rate, and poor carbonation hardening performance of low-calcium carbonatable binder.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A method for improving the activity of low-calcium carbonatable binder, comprising the following steps: adding magnesium salt to the low-calcium carbonatable binder.

[0006] Preferably, the mass ratio of the magnesium salt to the low-calcium carbonatable binder ≤ 12%.

[0007] Preferably, the mass ratio of the magnesium salt to the low-calcium carbonatable binder is 3% - 12%.

[0008] Preferably, the mineral composition of the low-calcium carbonatable binder includes: α-CS, C3S2, and C2AS.

[0009] Preferably, the low-calcium carbonatable binder is prepared by a method comprising the following steps: mixing calcium carbonate, silicon dioxide, and aluminum oxide and calcining, and then cooling to room temperature to obtain the low-calcium carbonatable binder.

[0010] Preferably, the mass percentages of calcium carbonate, silicon dioxide, and aluminum oxide are 14:7:1.

[0011] Preferably, the calcining includes: first heating to 900°C and holding for 30 min, and then heating to 1280 - 1300°C and holding for 120 min.

[0012] Preferably, after the calcination is completed, it is cooled to room temperature within 3 - 5 minutes.

[0013] The present invention also provides a preparation method of a low - calcium carbon - sequestering cementitious material product, which adopts the following technical solution: A preparation method of a low - calcium carbon - sequestering cementitious material product is prepared by the following steps: (1) Mix the low - calcium carbon - sequestering cementitious material with a magnesium salt solution evenly and mold it on a molding device to obtain a pre - formed body; the mass ratio of the magnesium salt in the magnesium salt solution to the low - calcium carbon - sequestering cementitious material ≤ 12%; (2) Place the pre - formed body in a carbonization reactor, introduce a gas containing carbon dioxide, and perform carbonization to obtain the low - calcium carbon - sequestering cementitious material product.

[0014] Preferably, the pressure of the carbonization is 0.2 - 0.4 MPa, the carbonization temperature is 25 - 30 °C, and the carbonization time is 7 - 9 h;

[0015] Preferably, the pressure of the molding is 3 - 5 MPa, and the molding time is 1 - 2 minutes.

[0016] The present invention also provides a low - calcium carbon - sequestering cementitious material product, which adopts the following technical solution: A low - calcium carbon - sequestering cementitious material product is prepared by the method as described above.

[0017] Beneficial effects:

[0018] The method for improving the activity of the low - calcium carbon - sequestering cementitious material of the present invention helps to improve the reaction activity of the low - calcium carbon - sequestering cementitious material and improve the carbon - sequestering effect of the low - calcium carbon - sequestering cementitious material product.

[0019] The low - calcium carbon - sequestering cementitious material product of the present invention has high compressive strength, and the increased proportion of the compressive strength can reach more than 60%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. Among them:

[0021] Figure 1 It is the XRD refined graph of the low - calcium carbon - sequestering cementitious material prepared in step (1) of Example 1;

[0022] Figure 2 It is the XRD graph of the low - calcium carbon - sequestering cementitious material products of Examples 1 - 4 and Comparative Example 1;

[0023] Figure 3 It is the nuclear magnetic resonance spectrum of the low - calcium carbon - sequestering cementitious material products of Examples 1 - 4 and Comparative Example 1. Among them, (a) is the pore distribution diagram; (b) is the porosity diagram;

[0024] Figure 4 SEM images of the low-calcium carbon-fixing cementitious material products of Examples 1-4 and Comparative Example 1;

[0025] Figure 5 Infrared images of the low-calcium carbon-fixing cementitious material products of Examples 1-4 and Comparative Example 1. Detailed implementation manners

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0027] The present invention will be described in detail below in conjunction with embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0028] Aiming at at least one of the problems of low reaction activity, low carbon fixation rate and poor carbonation hardening performance existing in the current low-calcium carbon-fixing cementitious materials, the present invention provides a method for improving the activity of low-calcium carbon-fixing cementitious materials.

[0029] The method for improving the activity of the low-calcium carbon-fixing cementitious material in the embodiment of the present invention includes the following steps: adding a magnesium salt to the low-calcium carbon-fixing cementitious material. By adding a magnesium salt to the low-calcium carbon-fixing cementitious material, the reaction activity, carbon fixation amount and compressive strength after carbonation hardening of the low-calcium carbon-fixing cementitious material can be effectively improved.

[0030] In a preferred embodiment of the method for improving the activity of the low-calcium carbon-fixing cementitious material in the embodiment of the present invention, the mass ratio of the magnesium salt to the low-calcium carbon-fixing cementitious material ≤ 12%.

[0031] Preferably, the mass ratio of the magnesium salt to the low-calcium carbon-fixing cementitious material is 3%-12% (for example, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11% or 12%).

[0032] More preferably, the mass ratio of the magnesium salt to the low-calcium carbon-fixing cementitious material is 9%.

[0033] In a preferred embodiment of the method for improving the activity of the low-calcium carbon-fixing cementitious material in the embodiment of the present invention, the mineral composition of the low-calcium carbon-fixing cementitious material includes: α-CS, C3S2 and C2AS.

[0034] In a preferred embodiment of the method for improving the activity of the low-calcium carbon-fixing cementitious material in the embodiment of the present invention, the low-calcium carbon-fixing cementitious material is prepared by a method including the following steps: combining calcium carbonate, silicon dioxide and alumina and calcining and cooling to room temperature to obtain the low-calcium carbon-fixing cementitious material.

[0035] In a preferred embodiment of the method for improving the activity of a low-calcium carbon-fixing cementitious material according to an embodiment of the present invention, the mass ratio of calcium carbonate, silicon dioxide, and alumina is 14:7:1.

[0036] In a preferred embodiment of the method for improving the activity of a low-calcium carbon-fixing cementitious material according to an embodiment of the present invention, the calcination includes: first heating to 900 °C and holding for 30 min, and then heating to 1280 °C - 1300 °C (for example, 1280 °C, 1290 °C, or 1300 °C, etc.) and holding for 120 min.

[0037] Preferably, after the calcination is completed, it is cooled to room temperature (rapidly cooled to room temperature) within 3 - 5 min (for example, 3 min, 3.5 min, 4 min, 4.5 min, or 5 min).

[0038] The present invention provides a method for preparing a low-calcium carbon-fixing cementitious material product. The method for preparing the low-calcium carbon-fixing cementitious material product according to an embodiment of the present invention is prepared by using the following method: (1) uniformly mixing the low-calcium carbon-fixing cementitious material with a magnesium salt solution, and forming on a forming device to obtain a preform; the mass ratio of the magnesium salt in the magnesium salt solution to the low-calcium carbon-fixing cementitious material ≤ 12%; (2) placing the preform in a carbonization reactor, introducing a gas containing carbon dioxide, and carbonizing to obtain the low-calcium carbon-fixing cementitious material product.

[0039] Preferably, the mass ratio of water in the magnesium salt solution to the low-calcium carbon-fixing cementitious material is 10%.

[0040] In a preferred embodiment of the method for preparing the low-calcium carbon-fixing cementitious material product of the present invention, the carbonization pressure is 0.2 - 0.4 MPa (for example, 0.2 MPa, 0.25 MPa, 0.3 MPa, 0.35 MPa, or 0.4 MPa), the carbonization temperature is 25 - 30 °C (for example, 25 °C, 26 °C, 27 °C, 28 °C, 29 °C, or 30 °C), and the carbonization time is 7 - 9 h (for example, 7 h, 7.5 h, 8 h, 8.5 h, or 9 h).

[0041] Preferably, the forming pressure is 3 - 5 MPa (for example, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, or 5 MPa), and the forming time is 1 - 2 min (for example, 1 min, 1.2 min, 1.4 min, 1.6 min, 1.8 min, or 2 min).

[0042] More preferably, the size of the preform is 20 mm × 20 mm × 20 mm.

[0043] The present invention also provides a low-calcium carbon-fixing cementitious material product, and the low-calcium carbon-fixing cementitious material product according to an embodiment of the present invention is prepared by using the method described above.

[0044] The compressive strength of the low-calcium carbon-fixing cementitious material product of the present invention is significantly improved compared to the low-calcium carbon-fixing cementitious material.

[0045] The method for improving the activity of the low-calcium carbon-fixing cementitious material, the low-calcium carbon-fixing cementitious material product and its preparation method of the present invention will be described in detail below through specific examples.

[0046] Sources of the main raw materials used in the following examples: Calcium carbonate comes from Tianjin Hongyan Reagent Factory, and silicon dioxide and alumina come from Tianjin Kemiou Chemical Reagent Co., Ltd., all of which are pure chemical reagents for analysis.

[0047] Example 1

[0048] The method for improving the activity of the low-calcium carbon-fixing cementitious material in this example: Add magnesium nitrate to the low-calcium carbon-fixing cementitious material, and the mass ratio of magnesium nitrate to the low-calcium carbon-fixing cementitious material is 3:100.

[0049] The preparation method of the low-calcium carbon-fixing cementitious material product in this example includes the following steps:

[0050] (1) Mix calcium carbonate, silicon dioxide and alumina with a mass ratio of 14:7:1 and calcine (first heat up to 900 °C and hold for 30 min, then heat up to 1290 °C and hold for 120 min); cool to room temperature within 4 min after the calcination ends to obtain the low-calcium carbon-fixing cementitious material;

[0051] (2) By mass fraction, stir 100 parts of the low-calcium solid cementitious material prepared in step (1) with a magnesium nitrate solution (the magnesium nitrate solution is obtained by fully dissolving 3 parts of magnesium nitrate in 10 parts of tap water), and then form it on a forming device (pressure 4 MPa, time 1.5 min) to obtain a preform (size 20 mm × 20 mm × 20 mm);

[0052] (3) Put the preform into a carbonization reactor for carbonization (carbonization conditions: carbon dioxide concentration 99.9%, carbonization pressure 0.3 MPa, carbonization time 8 h, carbonization temperature 28 °C). After the carbonization ends, the low-calcium carbon-fixing cementitious material product of this example (hereinafter referred to as M1) is obtained.

[0053] Example 2

[0054] The method for improving the activity of the low-calcium carbon-fixing cementitious material in this example: Add magnesium nitrate to the low-calcium carbon-fixing cementitious material, and the mass ratio of magnesium nitrate to the low-calcium carbon-fixing cementitious material is 6:100.

[0055] The preparation method of the low-calcium carbon-fixing cementitious material product in this example includes the following steps:

[0056] (1) Mix calcium carbonate, silica, and alumina in a mass ratio of 14:7:1 and calcine (first heat up to 900 °C and hold for 30 min, then heat up to 1290 °C and hold for 120 min); cool to room temperature within 4 min after the calcination ends to obtain a low-calcium carbon-fixing cementitious material;

[0057] (2) By mass parts, mix 100 parts of the low-calcium solid cementitious material prepared in step (1) with a magnesium nitrate solution (the magnesium nitrate solution is obtained by fully dissolving 6 parts of magnesium nitrate in 10 parts of tap water) evenly and then form it on a forming device (pressure 4 MPa, time 1.5 min) to obtain a preform (size 20 mm × 20 mm × 20 mm);

[0058] (3) Put the preform into a carbonization reactor for carbonization (carbonization conditions: carbon dioxide concentration 99.9%, carbonization pressure 0.3 MPa, carbonization time 8 h, carbonization temperature 28 °C). After the carbonization ends, the low-calcium carbon-fixing cementitious material product of this example (hereinafter referred to as M2) is obtained.

[0059] Example 3

[0060] The method for improving the activity of the low-calcium carbon-fixing cementitious material in this example: Add magnesium nitrate to the low-calcium carbon-fixing cementitious material, and the mass ratio of magnesium nitrate to the low-calcium carbon-fixing cementitious material is 9:100.

[0061] The preparation method of the low-calcium carbon-fixing cementitious material product in this example includes the following steps:

[0062] (1) Mix calcium carbonate, silica, and alumina in a mass ratio of 14:7:1 and calcine (first heat up to 900 °C and hold for 30 min, then heat up to 1290 °C and hold for 120 min); cool to room temperature within 4 min after the calcination ends to obtain a low-calcium carbon-fixing cementitious material;

[0063] (2) By mass parts, mix 100 parts of the low-calcium solid cementitious material prepared in step (1) with a magnesium nitrate solution (the magnesium nitrate solution is obtained by fully dissolving 9 parts of magnesium nitrate in 10 parts of tap water) evenly and then form it on a forming device (pressure 4 MPa, time 1.5 min) to obtain a preform (size 20 mm × 20 mm × 20 mm);

[0064] (3) Put the preform into a carbonization reactor for carbonization (carbonization conditions: carbon dioxide concentration 99.9%, carbonization pressure 0.3 MPa, carbonization time 8 h, carbonization temperature 28 °C). After the carbonization ends, the low-calcium carbon-fixing cementitious material product of this example (hereinafter referred to as M3) is obtained.

[0065] Example 4

[0066] Method for improving the activity of low-calcium carbon-fixing cementitious materials in this embodiment: Add magnesium nitrate to the low-calcium carbon-fixing cementitious materials, and the mass ratio of magnesium nitrate to the low-calcium carbon-fixing cementitious materials is 12:100.

[0067] Preparation method of the low-calcium carbon-fixing cementitious material product in this embodiment includes the following steps:

[0068] (1) Combine calcium carbonate, silicon dioxide, and alumina with a mass ratio of 14:7:1 and calcine (first heat up to 900 °C and hold for 30 min, then heat up to 1290 °C and hold for 120 min); cool to room temperature within 4 min after the calcination ends to obtain low-calcium carbon-fixing cementitious materials;

[0069] (2) By mass fraction, stir 100 parts of the low-calcium solid cementitious materials prepared in step (1) evenly with a magnesium nitrate solution (the magnesium nitrate solution is obtained by fully dissolving 12 parts of magnesium nitrate in 10 parts of tap water), and then form it on a molding device (pressure 4 MPa, time 1.5 min) to obtain a preform (size 20 mm × 20 mm × 20 mm);

[0070] (3) Put the preform into a carbonization reactor for carbonization (carbonization conditions: carbon dioxide concentration 99.9%, carbonization pressure 0.3 MPa, carbonization time 8 h, carbonization temperature 28 °C). After the carbonization ends, the low-calcium carbon-fixing cementitious material product of this embodiment (hereinafter referred to as M4) is obtained.

[0071] Comparative Example 1

[0072] Preparation method of the low-calcium carbon-fixing cementitious material product in this comparative example includes the following steps:

[0073] (1) Combine calcium carbonate, silicon dioxide, and alumina with a mass ratio of 14:7:1 and calcine (first heat up to 900 °C and hold for 30 min, then heat up to 1290 °C and hold for 120 min); cool to room temperature within 4 min after the calcination ends to obtain low-calcium carbon-fixing cementitious materials;

[0074] (2) By mass fraction, stir 100 parts of the low-calcium solid cementitious materials prepared in step (1) evenly with 10 parts of water, and then form it on a molding device (pressure 4 MPa, time 1.5 min) to obtain a preform (size 20 mm × 20 mm × 20 mm);

[0075] (3) Put the preform into a carbonization reactor for carbonization (carbonization conditions: carbon dioxide concentration 99.9%, carbonization pressure 0.3 MPa, carbonization time 8 h, carbonization temperature 28 °C). After the carbonization ends, the low-calcium carbon-fixing cementitious material product of this comparative example (hereinafter referred to as M0) is obtained.

[0076] Experimental Example

[0077] 1. XRD tests were conducted on the low-calcium carbonation cementitious material prepared in step (1) of Example 1 and the low-calcium carbonation cementitious material products of Examples 1-4 and Comparative Example 1:

[0078] Test method: The carbonated sample (any one of M0 - M4) was ground in a mortar until it passed through a 200-mesh sieve. The mineral composition of the obtained powder sample was analyzed using a rotating anode X-ray diffractometer (SmartLab, Japan). The scanning angle range was set to 10 - 80°, the scanning speed was 5° / min, and Cu target was selected as the target material.

[0079] After obtaining the XRD pattern of the low-calcium carbonation cementitious material prepared in step (1) of Example 1, it was refined and the mineral composition was calculated; the results are as Figure 1 shown. Its mineral composition includes 62.10% α-CS, 25.70% C3S2, and 12.20% C2AS.

[0080] The XRD patterns of the low-calcium carbonation cementitious material products of Examples 1-4 and Comparative Example 1 are as Figure 2 shown; Figure 2 diffraction peaks of α-CS, C3S2, C2AS, calcite, aragonite, and Mg(NO3)2 appeared. Compared with the blank group M0, Mg(NO3)2 diffraction peaks appeared in M1 - M4, and their intensities gradually increased. The carbonation products include calcite and aragonite.

[0081] 2. LF NMR tests were conducted on the low-calcium carbonation cementitious material products of Examples 1-4 and Comparative Example 1:

[0082] Test method: A low-field nuclear magnetic resonance spectrometer (MesoMR 12-060V, China) was used to analyze the pore size distribution of the carbonated samples. Before the test, the dried carbonated sample (any one of M0 - M4) was placed in a plastic cup and vacuum saturated with water at 50°C for 24 h.

[0083] Figure 3 are the nuclear magnetic resonance spectra of the low-calcium carbonation cementitious materials of Examples 1-4 and Comparative Example 1; among them, (a) is the pore distribution diagram; (b) is the porosity diagram.

[0084] It can be seen from Figure 3 that: after adding different concentrations of Mg(NO3)2, the macropores (1 - 10 μm) decreased significantly, indicating that Mg(NO3)2 effectively promoted the formation of carbonation products to fill the macropores. The porosities of M0 to M4 were 18.44%, 17.16%, 15.13%, 14.16%, and 14.58% respectively. It should be noted that the porosity gradually decreased from M0 to M3, but the porosity of M4 increased, indicating that excessive Mg(NO3)2 would inhibit the carbonation process.

[0085] 3. SEM tests were conducted on the low-calcium carbonation cementitious material products of Examples 1-4 and Comparative Example 1:

[0086] Test method: Take thin slices from the carbonized samples (any one of M0-M4), pour and mold them with epoxy resin. Use a scanning electron microscope (Merlin Compact, Germany) for microscopic morphology analysis. The attached facilities, including the OXFOFD energy spectrometer and the electron backscatter diffraction instrument, are used to capture secondary electron and backscattered electron images at acceleration voltages of 15 kV and 20 kV, respectively.

[0087] The test results are as Figure 4 shown.

[0088] It can be seen from Figure 4 that: compared with M0 without Mg(NO3)2, the incorporation of Mg(NO3)2 leads to an increase in carbonation products. The phenomenon of dense packing of carbonation products effectively reduces the porosity of the carbonized samples, thereby improving the compressive strength.

[0089] 4. FTIR tests were conducted on the low-calcium carbonation cementitious material products of Examples 1-4 and Comparative Example 1:

[0090] Test method: Use a synchronous thermal-transmission-reflection spectroscopy test system (STA8000 Frontier, USA) to conduct FTIR analysis on the carbonized samples (any one of M0-M4). The scanning range is between 400 and 4000 cm -1 -1.

[0091] The test results are as Figure 5 shown.

[0092] It can be seen from Figure 5 that: compared with the low-calcium carbonation cementitious material sample before carbonation, a new strong absorption peak appears in the range of 1391 to 1446 cm -1 -1, which is the characteristic absorption peak of v 3 of CaCO3 crystals, representing the asymmetric stretching vibration of the C-O bond. At 875 cm -1 -1, the characteristic absorption peak of v 2 of CaCO3 crystals is obvious and sharp, which is related to the out-of-plane deformation vibration of the C-O bond. In addition, the absorption band appearing at 1077 cm -1 -1 is the antisymmetric stretching vibration absorption of Si-O-Si. This absorption band shifts to a higher wavenumber, indicating the formation of highly polymerized silica gel. Therefore, Mg(NO3)2 has a positive effect on the carbonation degree of the low-calcium carbonation cementitious material.

[0093] 5. Carbon sequestration rate and compressive strength tests of the low-calcium carbonation cementitious material products of Examples 1-4 and Comparative Example 1:

[0094] Testing method: Take about 15 mg of carbonized sample (any one of M0 - M4), and conduct a thermogravimetric experiment using a synchronous thermal - trans - reflectance spectroscopy test system (STA8000 Frontier, USA). The test temperature range is set to 50 - 950 °C, and the heating rate is 10 °C / min.

[0095] Use a fully automatic pressure testing machine (WDW - 200, China) controlled by a microcomputer to test the compressive strength of the carbonized sample. The loading rate is 1 kN / s, with three samples in each group, and the average value is taken after multiple tests.

[0096] The test results are shown in Table 1 below:

[0097] Table 1 Test results of carbon fixation rate and compressive strength

[0098]

[0099] It can be seen from Table 1 that compared with Comparative Example 1 (only doped with tap water), Examples 1, 2, 3, and 4 of the present invention can significantly improve the carbon fixation amount and carbonization hardening ability of the low - calcium carbon - fixing cementitious material after doping with magnesium nitrate, showing carbonization reaction activity. Among them, the carbon fixation rate of the low - calcium carbon - fixing cementitious material in Example 3 of the present invention is increased by 58.14% compared with Comparative Example 1, and the compressive strength is increased by 60.25% compared with Comparative Example 1.

[0100] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for improving the activity of a low-calcium carbon-fixing cementitious material, characterized in that, It includes the following steps: adding a magnesium salt to the low-calcium carbon-fixing cementitious material.

2. The method for improving the activity of the low-calcium carbon-fixing cementitious material according to claim 1, characterized in that, The mass ratio of the magnesium salt to the low-calcium carbon-fixing cementitious material is ≤12%.

3. The method for improving the activity of the low-calcium carbonation cementitious material according to claim 2, characterized in that, The mass ratio of the magnesium salt to the low-calcium carbon-fixing cementitious material is 3%-12%.

4. The method for improving the activity of the low-calcium carbonation cementitious material according to claim 1, wherein The mineral composition of the low-calcium carbon-fixing cementitious material includes: α-CS, C3S2 and C2AS.

5. The method for improving the activity of the low-calcium carbon-fixing cementitious material as described in claim 4, wherein the low-calcium carbon-fixing cementitious material is prepared by a method including the following steps: Mix calcium carbonate, silicon dioxide and alumina and calcine them, and cool to room temperature to obtain the low-calcium carbon-fixing cementitious material.

6. The method for improving the activity of the low-calcium carbonation cementitious material according to claim 5, characterized in that, The mass percentages of the calcium carbonate, silicon dioxide and alumina are 14:7:

1.

7. The method for improving the activity of the low-calcium carbonation cementitious material according to claim 5, wherein the calcination comprises: First, heat up to 900°C and hold for 30 min, then heat up to 1280-1300°C and hold for 120 min; Preferably, after the calcination is completed, cool to room temperature within 3-5 min.

8. A preparation method of a low-calcium carbon-fixing cementitious material product, characterized in that, It is prepared by a method including the following steps: (1) Mix the low-calcium carbon-fixing cementitious material and the magnesium salt solution evenly, and form them on a forming device to obtain a preform; the mass ratio of the magnesium salt in the magnesium salt solution to the low-calcium carbon-fixing cementitious material is ≤12%; (2) Place the preform in a carbonization reactor, introduce a gas containing carbon dioxide, and carry out carbonization to obtain the low-calcium carbon-fixing cementitious material product.

9. The preparation method of the low-calcium carbon-fixing cementitious material product according to claim 8, characterized in that, The pressure of the carbonization is 0.2-0.4 MPa, the carbonization temperature is 25-30°C, and the carbonization time is 7-9 h; Preferably, the pressure of the forming is 3-5 MPa, and the forming time is 1-2 min.

10. A low-calcium carbon-fixing cementitious material product, characterized in that, The low-calcium carbon-fixing cementitious material product is prepared by the method as described in claim 8 or 9.

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