Magnesium-containing low-calcium carbonation cement clinker and method for producing the same

Abstract

The application relates to the technical field of cement-based building materials, in particular to a magnesium-containing low-calcium carbon sequestration cement clinker and a preparation method thereof. The clinker containing C7MS4 and C3S2 is prepared by adopting high-magnesium sandstone and limestone as raw materials and high-temperature calcining and rapid cooling, the carbonation activity of the clinker is enhanced by using the calcium ion dissolution characteristics of the two, the magnesium-containing low-calcium carbon sequestration cement clinker is prepared, a large amount of carbon emissions generated in the production of cement can be reduced, a large amount of CO2 can be stored in the maintenance process, and the low-grade raw materials which are difficult to utilize can be eliminated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cement-based building materials, and particularly relates to a magnesium-containing low-calcium carbon sequestration cement clinker and a preparation method thereof. BACKGROUND

[0002] In recent years, low-carbon development has become a development trend of today's society.

[0003] Environmental problems are increasingly concerned by human beings and society, and in the aspect of industrial production, especially in the building material industry, the production of cement is one of the largest sources of carbon dioxide emissions in the world.

[0004] Reducing carbon emissions in the cement industry is a major problem that needs to be solved in low-carbon development.

[0005] Low-calcium carbon sequestration cement refers to a material that can be hardened to obtain a certain strength under the curing condition of passing CO2 by using the carbonation characteristics of low-calcium calcium silicate minerals, which can replace ordinary Portland cement in some application ranges to alleviate the adverse effects of cement production industry on the environment, and has the characteristics of low carbon and energy saving.

[0006] Compared with C3S minerals, low-calcium calcium silicate minerals CS and C2S minerals have low calcium content and can be generated at a lower temperature, which can reduce carbon emissions in the production process of cement.

[0007] However, the cement product prepared in the carbonation curing process hinders the further diffusion and reaction of carbon dioxide into the product with the generation of carbonation products, thereby causing different carbonation degrees inside and outside the product and easily causing phenomena such as strength reduction or cracking.

[0008] Cement raw material preparation includes calcareous raw materials, siliceous raw materials, correction raw materials, commonly including limestone, bauxite, kaolin, etc., some documents use industrial solid waste fly ash, coal gangue, etc. as raw material to replace part of natural raw material, low calcium carbon sequestration cement containing magnesium is currently in the forefront of research, the prior art CN116553841A discloses a carbon sequestration low calcium high magnesium clinker, which uses high magnesium limestone as raw material to improve its added value, and the prepared clinker mineral composition includes: magnesium pyroxmangite, dicalcium silicate and periclase, the highest carbon sequestration amount can reach 15.9%, and the 24h compressive strength can reach 82.5MPa, the prior art "Enhancing CO2-Cured cementitious binder with Mg-doped γ-C2S from high-Mglimestone" discloses that pure raw materials CaCO3, SiO2 and 4MgCO3·Mg(OH)2·4H2O are used to synthesize low calcium clinker containing magnesium, and the main mineral phase composition of the synthesized clinker is γ-C2S, C7MS4, β-C2S and C3MS2, and the conclusion is that Mg doping can improve the carbonation strength, and the 24h compressive strength of the MS2 sample is close to 120MPa, however, the carbon sequestration amount is reduced, and the carbon sequestration amount of the blank sample MS0 without doping Mg is the highest, which is 14%.

[0009] Sandstone is a commonly used siliceous raw material in cement clinker, however, high magnesium sandstone belongs to low-grade raw material and is almost not developed and utilized. SUMMARY

[0010] To solve the problems in the prior art, the present application provides a low calcium carbon sequestration cement clinker containing magnesium, which is prepared by using high magnesium sandstone and limestone as raw materials, high temperature calcination and rapid cooling to prepare a clinker containing C7MS4 and C3S2, using the calcium ion dissolution characteristics of the two to enhance the carbonation activity of the clinker, and preparing a low calcium carbon sequestration cement clinker containing magnesium, which not only can reduce a large amount of carbon emissions generated in cement production, but also can store a large amount of CO2 in the curing process, and at the same time, can utilize low-grade raw materials.

[0011] Specifically, the preparation method of the low calcium carbon sequestration cement clinker containing magnesium comprises the following steps:

[0012] 1) 25-35 parts of high magnesium sandstone and 65-75 parts of limestone are weighed by weight parts, mixed uniformly, ground, and raw materials are obtained,

[0013] 2) the raw materials are mixed uniformly with water, and are pressed into a cake,

[0014] 3) the raw material cake is calcined, cooled, crushed and finely ground, and the low calcium carbon sequestration cement clinker containing magnesium is obtained.

[0015] Preferably, the high-magnesium sandstone has the following main chemical components and contents: MgO: 3-10%, CaO: 3-10%, SiO2: 70-80%, Al2O3: 3-6%, and Fe2O3: 0-3%.

[0016] Preferably, the limestone has the following main chemical components and contents: CaO: 50-56%, SiO2: 1-5%, MgO: 0-3%, Al2O3: 0-3%, and Fe2O3: 0-2%.

[0017] Preferably, the clinker has the following main chemical components and contents: CaO: 55-63%, SiO2: 33-38%, MgO: 2-4%, and Al2O3: 1-3%.

[0018] Preferably, the raw material has a particle size of less than 45 microns, and the water addition amount is 8-12% of the mass of the raw material.

[0019] Preferably, the calcination temperature is 1260-1340℃, and the calcination time is 2.5-3h.

[0020] Preferably, the cooling is performed by rapid cooling.

[0021] Preferably, the clinker has a particle size of less than or equal to 75 microns, and the fine grinding time is 10-30min.

[0022] The application also relates to a magnesium-containing low-calcium carbon sequestration cement clinker, which is prepared by the above method.

[0023] Preferably, the mineral composition of the clinker mainly includes low-calcium minerals gamma-C2S, beta-C2S, C3S2, and magnesium-containing minerals C7MS4, wherein the mass content of C3S2 is 6-30%, and the mass content of C7MS4 is 5%-35%. The application shows that the raw material ratio and the calcination temperature have a significant influence on the solid-phase reaction and the mineral phase composition of the clinker. Magnesium-containing minerals such as C3MS2, C2MS2, C7MS4, and calcium silicate minerals will be converted with each other according to different raw materials and processes. The clinker prepared by the raw material and the process of the application contains C7MS4 and C3S2, and has a better carbon sequestration effect.

[0024] Unless otherwise specified, the application is calculated and characterized by mass parts.

[0025] The application has the following technical advantages:

[0026] 1. The main components of the clinker prepared by the application are C2S, C3S2, and magnesium-containing mineral C7MS4, which has the characteristics of low calcium and high strength, saves traditional cement production raw materials, improves the utilization rate of low-grade industrial raw materials, has a low calcination temperature, a simple sintering process, convenient batching, low cost, and a simple sintering process,

[0027] 2. The clinker utilizes the C7MS4 mineral generated from the Mg component contained in the high-magnesium sandstone, which can enhance the calcium ion dissolution characteristics of the clinker in the carbonization process, enhance the carbonization activity of the clinker, and synergistically enhance the carbonization performance of the cement with C3S2, realize CO2 mineralization sequestration, and thus obtain a high-strength magnesium-containing low-calcium carbon sequestration cement clinker. DETAILED DESCRIPTION

[0028] To characterize the technical effects of the present application, the clinker is prepared and detected. In the test process, the clinker and water are mixed uniformly according to a water-binder ratio of 0.1, the sample is molded into a cylinder with a diameter of 20 mm and a height of 20 mm by pressing, and carbonization is carried out under the conditions of a humidity of 75%, a temperature of 25°C, and a CO2 partial pressure of 0.3 MPa for 24 h. The carbonized test block is tested for compressive strength on a universal testing machine, the broken test block after testing is measured for carbon sequestration rate, the carbon sequestration rate is determined by the calcination method, about 10 g of the sample is calcined at 300°C and 850°C for 1.5 h, the mass loss percentage of the original sample weight is calculated, and the mineral composition quantitative analysis is performed on the XRD pattern by Highscore Plus. Example 1

[0029] The preparation method of the clinker comprises the following steps:

[0030] 1) 30 parts of high-magnesium sandstone and 70 parts of limestone are weighed according to weight parts, mixed uniformly, and ground to a particle size of less than 45 μm to obtain a raw material,

[0031] 2) the raw material is mixed with 10% of water based on the mass of the raw material, and is pressed and molded to obtain a raw material cake,

[0032] 3) the raw material cake is calcined at 1300°C for 3 h, is rapidly cooled, is broken, and is finely ground to a particle size of ≤75 μm, and thus the clinker is obtained.

[0033] After detection, the mineral phase of the clinker includes γ-C2S2 5.5%, C7MS4 11.5%, β-C2S1 5.2%, C3S2 25.7%, Akermanite 22.1%, the 24 h compressive strength is 136.3 MPa, and the carbon sequestration rate is 14.8%. Example 2

[0034] The preparation method of the clinker comprises the following steps:

[0035] 1) 35 parts of high-magnesium sandstone and 65 parts of limestone are weighed according to weight parts, mixed uniformly, and ground to a particle size of less than 45 μm to obtain a raw material,

[0036] 2) the raw material is mixed with 10% of water based on the mass of the raw material, and is pressed and molded to obtain a raw material cake,

[0037] 3) calcining the raw material cake at 1340℃ for 3h, quenching, crushing, and fine grinding to a particle size of ≤75μm to obtain the clinker.

[0038] The clinker mineral phase includes γ-C2S 38.7%, C7MS 411.6%, β-C2S 21.4%, C3S 28.3%, Akermanite 20%, 24h compressive strength 138.7MPa, and carbon fixation rate 16.2%.

[0039] Comparative Example 1

[0040] The preparation method of the clinker comprises the following steps:

[0041] 1) 10 parts of high-magnesium sandstone, 20 parts of kaolin, and 70 parts of limestone are weighed by weight parts, mixed uniformly, and ground to a particle size of less than 45μm to obtain a raw material,

[0042] 2) the raw material is mixed with 10% of water by weight of the raw material, and is pressed into a raw material cake,

[0043] 3) the raw material cake is calcined at 1300℃ for 3h, quenched, crushed, and fine ground to a particle size of ≤75μm to obtain the clinker.

[0044] The clinker mineral phase includes γ-C2S 50.2%, C7MS 43.2%, β-C2S 30.3%, C3MS 24.9%, Akermanite 11.4%, 24h compressive strength 95.6MPa, and carbon fixation rate 12.1%.

[0045] Comparative Example 2

[0046] The preparation method of the clinker comprises the following steps:

[0047] 1) 30 parts of high-magnesium sandstone and 70 parts of limestone are weighed by weight parts, mixed uniformly, and ground to a particle size of less than 45μm to obtain a raw material,

[0048] 2) the raw material is mixed with 10% of water by weight of the raw material, and is pressed into a raw material cake,

[0049] 3) the raw material cake is calcined at 1450℃ for 3h, quenched, crushed, and fine ground to a particle size of ≤75μm to obtain the clinker.

[0050] The clinker mineral phase includes γ-C2S 10.2%, β-C2S 35.0%, C3S 45.5%, C3A 9.3%, 24h compressive strength 75.4MPa, and carbon fixation rate 9.6%.

[0051] Comparative Example 3

[0052] The preparation method of the clinker comprises the following steps:

[0053] 1) 30 parts of sandstone and 70 parts of limestone by weight are mixed uniformly, and are ground to a particle size of less than 45 μm to obtain raw meal,

[0054] 2) The raw meal is mixed with water at 10% of the mass of the raw meal, and is pressed to form a raw meal cake,

[0055] 3) The raw meal cake is calcined at 1300°C for 3 h, is rapidly cooled, is broken, and is finely ground to a particle size of ≤75 μm, and is obtained.

[0056] It is detected that the mineral phase of the clinker includes γ-C2S 5.6%, C7MS 436.5%, β-C2S 47.3%, Akermanite 10.6%, the 24 h compressive strength is 88.9 MPa, and the carbon fixation rate is 11.7%.

[0057] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A magnesium-containing, low-calcium, carbon-fixing cement clinker, characterized in that, The preparation method includes the following steps: 1) Weigh out 25-35 parts by weight of high-magnesium sandstone and 65-75 parts by weight of limestone, mix them evenly, and grind them to obtain raw material. 2) Mix the raw materials with water evenly, press and shape to obtain raw material cakes. 3) Calcine the raw material cake at 1260-1340℃ for 2.5-3 hours, cool, crush, and grind finely to obtain clinker. The mineral composition of clinker is mainly low-calcium minerals γ-C2S, β-C2S, C3S2 and magnesium-containing mineral C7MS4, of which the mass content of C3S2 is 6-30% and the mass content of C7MS4 is 5%-35%.

2. The magnesium-containing low-calcium carbon-fixing cement clinker according to claim 1, characterized in that, The main chemical components and contents of the high magnesium sandstone are: MgO: 3-10%, CaO: 3-10%, SiO2: 70-80%, Al2O3: 3-6%, Fe2O3: 0-3%.

3. The magnesium-containing low-calcium carbon-fixing cement clinker according to claim 1, characterized in that, The main chemical components and contents of the limestone are: CaO: 50-56%, SiO2: 1-5%, MgO: 0-3%, Al2O3: 0-3%, Fe2O3: 0-2%.

4. The magnesium-containing low-calcium carbon-fixing cement clinker according to claim 1, characterized in that, The main chemical components and contents of the clinker are: CaO 55-63%, SiO2 33-38%, MgO 2-4%, Al2O3 1-3%.

5. The magnesium-containing low-calcium carbon-fixing cement clinker according to claim 1, characterized in that, The raw material has a particle size of less than 75 micrometers, and the amount of water added is 8-12% of the raw material mass.

6. The magnesium-containing low-calcium carbon-fixing cement clinker according to claim 1, characterized in that, The cooling method is rapid cooling.

7. The magnesium-containing low-calcium carbon-fixing cement clinker according to claim 1, characterized in that, The clinker has a particle size ≤75μm and a fine grinding time of 10-30min.