A low-carbon cement and a method for producing the same

Abstract

The application discloses green low-carbon cement, and components and weight percentages of the components are as follows: cement raw material 95-100 parts, desulfurization gypsum 2-4 parts, and composite modifier 2-8 parts; wherein, the cement raw material comprises limestone, clay, carbide slag, iron ore powder and coal gangue; and the composite modifier comprises fullerene and carbon nanotube. The composite modifier based on fullerene and carbon nanotube is introduced into the calcination stage of the cement raw material, so that the calcination temperature can be effectively reduced and the calcination efficiency can be improved while the early and late strength of the cement is ensured; and various industrial wastes such as industrial solid waste coal gangue and carbide slag can be fully utilized, and the application has remarkable economic and environmental benefits.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a low-carbon cement and its preparation method. Background Technology

[0002] In the production of silicate cement, the calcination of limestone (mainly calcium carbonate) decomposes to produce a large amount of carbon dioxide, which is one of the main sources of carbon emissions from cement production. During the calcination of cement clinker, C3S accounts for approximately 37-67%, C2S approximately 15-30%, C4AF approximately 10-18%, and C3A approximately 7-15%. The highest temperature required for C3S formation during clinker calcination is approximately 1450℃, while the initial formation temperature for C2S is only about 800℃, reaching its maximum content at 1100-1200℃. The high-temperature combustion environment inside the kiln causes nitrogen and oxygen in the air to react, producing nitrogen oxides (such as nitric oxide and nitrogen dioxide). These nitrogen oxides are important pollutants contributing to acid rain, chemical smog, and other environmental problems. Furthermore, if the coal or other fuels used in cement production have a high sulfur content, sulfur dioxide will also be produced during combustion, which is also a major pollutant contributing to acid rain.

[0003] C3S is the strongest mineral component in cement clinker and plays a crucial role in the development of early-age strength. A low calcium-silicon ratio reduces C3S content, leading to slow early-age strength development. Generally, C3S hydrates rapidly, and its hydration products quickly form a cohesive structure, imparting high early-age strength to the cement. C2S, on the other hand, hydrates relatively slowly and contributes less to strength in the early stages. Therefore, a low calcium-silicon ratio significantly reduces both compressive and flexural strength in the early stages (1-3 days).

[0004] A low calcium-to-silicon ratio may prolong the setting time of cement. This is because the mineral composition of cement clinker changes, with a decrease in C3S content, which in turn reduces the amount of calcium hydroxide, a hydration product. Calcium hydroxide can accelerate the hydration process of other minerals in cement paste; its reduction slows down the overall hydration rate of the cement paste, thus extending the initial and final setting times of the cement.

[0005] From a long-term strength perspective, although dicalcium silicate has significant potential for increased strength in the later stages, its slow early strength development can negatively impact practical engineering applications, especially in projects with high early strength requirements, such as the rapid demolding of precast concrete components. Furthermore, generally speaking, an excessively low calcium-silica ratio will result in a lower final strength for the cement compared to cement with a normal calcium-silica ratio.

[0006] Therefore, developing new low-carbon cement is an urgent task, and reducing the C3S ratio in the clinker system is one of the most direct and effective ways to prepare low-carbon cement. Summary of the Invention

[0007] The main objective of this invention is to address the problems and shortcomings of existing technologies by providing a new type of green and low-carbon cement that, while ensuring the early and later strength of the cement, effectively reduces the calcination temperature and improves the calcination efficiency. It can also make full use of industrial solid waste such as coal gangue and carbide slag, resulting in significant economic and environmental benefits.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A green, low-carbon cement comprises the following components and their respective weight percentages: 95-100 parts cement raw meal, 2-4 parts desulfurized gypsum, and 2-8 parts composite modifier; wherein the cement raw meal includes limestone, clay, carbide slag, iron ore powder, and coal gangue; and the composite modifier includes fullerene and carbon nanotubes.

[0010] Preferably, the content of the composite modifier is 3 to 5 parts.

[0011] Furthermore, in the composite modifier, the mass ratio of carbon nanotubes to fullerenes is 3-5:100.

[0012] In the above scheme, the fullerene is a black crystalline powder with 24 to 28 hydroxyl groups.

[0013] In the above scheme, the carbon nanotube has an outer diameter of less than 2 nm and a length of 5–30 μm.

[0014] Furthermore, the components and their mass percentages in the cement raw materials include: limestone 16-20%, clay 8-10%, carbide slag 48-51%, iron ore powder 1-3%, and coal gangue 19-21%.

[0015] In the above scheme, the main chemical components and their mass percentages in the coal gangue include: SiO2 50-55%, Al2O3 18-25%, Fe2O3 3-5%, CaO 0-2%; and the particle size is 0.075-0.25mm.

[0016] In the above scheme, the main chemical components and their mass percentages in the carbide slag include: CaO 80-85%, SiO2 3-5%, Al2O3 0-2%; and a particle size of 0.075-0.25 mm.

[0017] In the above scheme, the main chemical components of the limestone and their mass percentages include: CaO 50-55%, MgO 0-3%, SiO2 1-3%; and a particle size of 30-60 μm.

[0018] In the above scheme, the main chemical components of the clay and their mass percentages include: Al2O3 13-18%; Fe2O3 4-6%; SiO2 65-75%; CaO 1-2%; and a particle size of 45-80 μm.

[0019] In the above scheme, the main chemical components of the iron ore powder and their mass percentages include: Fe2O3 40-50%, Fe3O4 15-20%, SiO2 30-40%, Al2O3 5-15%; and the particle size is 50-80 μm.

[0020] In the above scheme, the green low-carbon cement is first obtained by grinding and homogenizing limestone, clay, carbide slag, iron ore powder and coal gangue to obtain cement raw materials; then, a composite modifier is added and calcined to obtain low-calcium silicate cement clinker; finally, desulfurized gypsum is added and ground to obtain the cement.

[0021] Furthermore, the mineral composition and their mass percentage in the low-calcium silicate cement clinker include: C3S 11-30%, C2S 40-65%, C3A 4-10%, and C4AF 9-15%.

[0022] Furthermore, the three ratios of the low-calcium silicate cement clinker are: KH = 0.6-0.8, SM = 2.0-2.2, and IM = 3.0-3.2.

[0023] The above-mentioned method for preparing green and low-carbon cement includes the following steps:

[0024] 1) Weigh the cement raw materials according to the proportions;

[0025] 2) The weighed cement raw materials are homogenized, then a composite modifier is added and calcined, and finally desulfurized gypsum is added and ground; thus, the green low-carbon cement is obtained.

[0026] In the above scheme, the mixing speed in the homogenization step is 30-45 r / min, and the homogenization time is 3-5 min.

[0027] In the above scheme, the calcination temperature is 1200-1300℃ and the time is 15-20min.

[0028] In the above scheme, the grinding speed is 45-50 r / min and the grinding time is 20-30 min.

[0029] Furthermore, the grinding step uses an SM-500 type cement test mill.

[0030] The green and low-carbon cement obtained according to the above scheme has a specific surface area of ​​480-520 m². 2 / kg, while effectively reducing the water consumption for standard consistency (water requirement is below 29%), and taking into account good early strength, etc. The 3-day mortar strength can reach more than 20MPa, and the 28-day mortar strength can reach more than 43MPa.

[0031] The principle of this invention is as follows:

[0032] This invention is the first to propose introducing a composite modifier based on fullerene and carbon nanotubes into the calcination stage of cement raw materials. The corresponding improvement mechanisms include: 1) Combining fullerene and carbon nanotubes helps improve the heat transfer efficiency during cement clinker production, promotes the stability of the calcination process, and helps reduce the calcination temperature of cement clinker, significantly reducing energy consumption and carbon dioxide emissions; 2) Fullerene can also promote the reaction of active components (such as C3S and C2S) in cement clinker with water during subsequent applications, thereby increasing the hydration rate of cement and ensuring the early and later mechanical properties of cement products. Performance; 3) The nanoscale properties of fullerenes enable them to interact with solid waste particles (coal gangue, carbide slag), promoting their uniform dispersion in cement paste and enhancing the overall density of cement; Fullerenes can affect the crystal morphology and structure of cement hydration products, which is beneficial to improving the durability, crack resistance and mechanical properties of cement products; 4) The introduced fullerenes can achieve efficient grinding of solid waste materials such as carbide slag and coal gangue. The resulting powder still has high dispersibility after contact with water, effectively reducing the standard consistency water consumption while increasing the specific surface area of ​​cement and clinker activity.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1) This invention introduces a composite modifier based on fullerene and carbon nanotubes into the calcination stage of cement raw materials, which can effectively reduce the calcination temperature (usually above 1400℃) and improve calcination efficiency while ensuring the early and late strength of cement. In addition, it is beneficial to reduce the amount of water used for standard consistency, which can provide a new approach for the preparation of high-performance cement products.

[0035] 2) Compared with traditional cement, the green and low-carbon cement of the present invention can effectively guarantee and further improve early and later strength, and at the same time can make extensive use of idle resources such as solid waste, which has significant economic and environmental benefits.

[0036] 3) The preparation method involved in this invention is relatively simple, easy to operate, low in preparation cost, and environmentally friendly, making it suitable for widespread application. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0038] In the following examples, the fullerene used is a black crystalline powder with 24-28 hydroxyl groups, an oxygen content of 42.41 wt%, a carbon content of 38.12 wt%, a hydrogen content of 2.97 wt%, and a molecular formula of C2. 60 (OH) n H₂O; carbon nanotubes with an outer diameter of less than 2 nm, a length of 5–30 μm, and a packing density of 0.018 g / cm³. 3 .

[0039] The chemical composition of the limestone, clay, iron ore powder, coal gangue, and carbide slag used is shown in Table 1.

[0040] Table 1 Chemical composition of raw materials (%)

[0041] name Loss on ignition <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO limestone 38.75 2.42 0.31 0.19 53.13 0.57 clay 5.27 70.25 14.72 5.48 1.41 0.92 Iron ore powder / 34.42 11.53 48.27 3.53 0.09 Coal gangue 16.67 52.37 22.23 3.77 1.76 0.32 calcium carbide slag / 3.08 1.9 0.13 84.83 /

[0042] Example 1

[0043] A green, low-carbon cement is prepared by the following steps:

[0044] 1) Preparation of green and low-carbon cement raw materials;

[0045] Based on the design of the low-calcium silicate cement clinker system, the three ratios of the clinker are KH=0.72, SM=2.1, and IM=3.2. Combining the chemical composition of the raw materials used (limestone, clay, iron ore powder, and coal gangue) (see Table 1), the designed raw material mass ratio (%) is: limestone 17.79%, clay 9.22%, carbide slag 50.55%, iron ore powder 1.72%, and coal gangue 20.72%. According to the raw material ratio, the limestone, clay, iron ore powder, and other raw materials that have been ground to a fineness of (15±2)% residue on a 0.08mm square hole sieve are weighed and homogenized in a mixer for 4 minutes (mixer speed 30r / min).

[0046] 2) Preparation of cement clinker;

[0047] Before calcination, 3 parts of composite modifier (mass ratio of carbon nanotubes to fullerenes of 5:100) were added to the homogenized raw meal (95 parts by weight, the same below). The meal was calcined at 1300℃ (heating rate of 10℃ / min) to partially melt and form clinker. The calcination time was 16min, and low-calcium silicate cement clinker was obtained.

[0048] 3) Grinding of cement clinker;

[0049] The obtained low-calcium silicate cement clinker and 4 parts of desulfurized gypsum were mixed evenly and then fed into a cement test mill. The mixture was ground for 25 minutes at a mill speed of 48 r / min to obtain the green low-carbon cement (specific surface area of ​​495 m²). 2 / kg).

[0050] The compressive strength of mortar samples prepared with low-carbon cement was tested according to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Mortar blocks of 40mm×40mm×160mm were prepared by mixing with a water-cement ratio of 0.5 and cured according to standard. The compressive strengths at 3 days and 28 days were measured to be 20.7MPa and 43.3MPa, respectively.

[0051] A standard water requirement test for cement consistency was conducted, and the water requirement was found to be 29%.

[0052] Example 2

[0053] A green, low-carbon cement is prepared by the following steps:

[0054] 1) Preparation of green and low-carbon cement raw materials;

[0055] Based on the design of the low-calcium silicate cement clinker system, the three ratios of the clinker were KH = 0.72, SM = 2.1, and IM = 3.2. Considering the chemical composition of the raw materials used—limestone, clay, iron ore powder, and coal gangue (see Table 1)—the designed raw material mass ratio (%) was: limestone 17.79%, clay 9.22%, carbide slag 50.55%, iron ore powder 1.72%, and coal gangue 20.72%. According to the raw material ratio, limestone, clay, iron ore powder, and other raw materials, ground to a fineness of (15±2)% residue on a 0.08mm square-hole sieve, were weighed and homogenized in a mixer for 4 minutes (mixer speed 30 r / min).

[0056] 2) Preparation of cement clinker;

[0057] Before calcination, 3 parts of composite modifier (the mass ratio of carbon nanotubes to fullerenes is 5:100) were added to the homogenized raw meal (95 parts). The meal was then calcined at 1280℃ (heating rate of 10℃ / min) to partially melt and form clinker. The calcination time was 16 min, and low-calcium silicate cement clinker was obtained.

[0058] 3) Grinding of cement clinker;

[0059] The obtained low-calcium silicate cement clinker and 4 parts of desulfurized gypsum were mixed evenly and then fed into a cement test mill. The mixture was ground for 25 minutes at a mill speed of 48 r / min to obtain the green low-carbon cement (specific surface area of ​​497 m²). 2 / kg).

[0060] The compressive strength of mortar samples prepared with low-carbon cement was tested according to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Mortar blocks of 40mm×40mm×160mm were prepared by mixing with a water-cement ratio of 0.5 and cured according to standard. The compressive strengths at 3 days and 28 days were measured to be 23.1 MPa and 45.9 MPa, respectively.

[0061] A standard water requirement test for cement consistency was conducted, and the water requirement was found to be 27%.

[0062] Example 3

[0063] A green, low-carbon cement is prepared by the following steps:

[0064] 1) Preparation of green and low-carbon cement raw materials;

[0065] Based on the design of the low-calcium silicate cement clinker system, the three ratios of the clinker are KH=0.72, SM=2.1, and IM=3.2. Combining the chemical composition of the raw materials used (limestone, clay, iron ore powder, and coal gangue) (see Table 1), the designed raw material mass ratio (%) is: limestone 17.79%, clay 9.22%, carbide slag 50.55%, iron ore powder 1.72%, and coal gangue 20.72%. According to the raw material ratio, the limestone, clay, iron ore powder, and other raw materials that have been ground to a fineness of (15±2)% residue on a 0.08mm square hole sieve are weighed and homogenized in a mixer for 4 minutes (mixer speed 30r / min).

[0066] 2) Preparation of cement clinker;

[0067] Before calcination, 5 parts of the homogenized raw meal (95 parts) were mixed with a composite modifier (the mass ratio of carbon nanotubes to fullerenes was 5:100). The mixture was then calcined at 1250℃ (heating rate of 10℃ / min) to partially melt and form clinker. The calcination time was 16 min, which yielded low-calcium silicate cement clinker.

[0068] 3) Grinding of cement clinker;

[0069] The obtained low-calcium silicate cement clinker and 4 parts of desulfurized gypsum were mixed evenly and then fed into a cement test mill. The mixture was ground for 25 minutes at a mill speed of 48 r / min to obtain the green low-carbon cement (specific surface area of ​​495 m²). 2 / kg).

[0070] The compressive strength of mortar samples prepared with low-carbon cement was tested according to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Mortar blocks of 40mm×40mm×160mm were prepared by mixing with a water-cement ratio of 0.5 and cured according to standard. The compressive strengths at 3 days and 28 days were measured to be 25.3 MPa and 47.2 MPa, respectively.

[0071] A standard water requirement test for cement consistency was conducted, and the water requirement was found to be 24%.

[0072] Example 4

[0073] A green, low-carbon cement is prepared by the following steps:

[0074] 1) Preparation of green and low-carbon cement raw materials;

[0075] Based on the design of the low-calcium silicate cement clinker system, the three ratios of the clinker were KH = 0.72, SM = 2.1, and IM = 3.2. Considering the chemical composition of the raw materials used—limestone, clay, iron ore powder, and coal gangue (see Table 1)—the designed raw material mass ratio (%) was: limestone 17.79%, clay 9.22%, carbide slag 50.55%, iron ore powder 1.72%, and coal gangue 20.72%. According to the raw material ratio, limestone, clay, iron ore powder, and other raw materials, ground to a fineness of (15±2)% residue on a 0.08mm square-hole sieve, were weighed and homogenized in a mixer for 4 minutes (mixer speed 30 r / min).

[0076] 2) Preparation of cement clinker;

[0077] Before calcination, 6 parts of composite modifier (the mass ratio of carbon nanotubes to fullerenes is 5:100) were added to the homogenized raw meal (95 parts). The mixture was then calcined at 1220℃ (heating rate of 10℃ / min) to partially melt and form clinker. The calcination time was 16 min, which yielded low-calcium silicate cement clinker.

[0078] 3) Grinding of cement clinker;

[0079] The obtained low-calcium silicate cement clinker and 4 parts of desulfurized gypsum were mixed evenly and then fed into a cement test mill. The mixture was ground for 25 minutes at a mill speed of 48 r / min to obtain the green low-carbon cement (specific surface area of ​​497 m²). 2 / kg).

[0080] The compressive strength of mortar samples prepared with low-carbon cement was tested according to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Mortar blocks of 40mm×40mm×160mm were prepared by mixing with a water-cement ratio of 0.5 and cured according to standard. The compressive strengths at 3 days and 28 days were measured to be 24.1 MPa and 46.1 MPa, respectively.

[0081] A standard water requirement test for cement consistency was conducted, and the water requirement was found to be 26%.

[0082] Comparative Example 1

[0083] A green, low-carbon cement is prepared by the following steps:

[0084] 1) Preparation of green and low-carbon cement raw materials;

[0085] Based on the design of the low-calcium silicate cement clinker system, the three ratios of the clinker were KH = 0.72, SM = 2.1, and IM = 3.2. Considering the chemical composition of the raw materials used—limestone, clay, iron ore powder, and coal gangue (see Table 1)—the designed raw material mass ratio (%) was: limestone 17.79%, clay 9.22%, carbide slag 50.55%, iron ore powder 1.72%, and coal gangue 20.72%. According to the raw material ratio, limestone, clay, iron ore powder, and other raw materials, ground to a fineness of (15±2)% residue on a 0.08mm square-hole sieve, were weighed and homogenized in a mixer for 4 minutes (mixer speed 30 r / min).

[0086] 2) Preparation of cement clinker;

[0087] Weigh 95 parts of the homogenized raw meal and calcine it at 1300℃ (heating rate of 10℃ / min) to partially melt it into clinker. The calcination time is 16min, and low-calcium silicate cement clinker is obtained.

[0088] 3) Grinding of cement clinker;

[0089] The obtained low-calcium silicate cement clinker was mixed with 4 parts desulfurized gypsum and 5 parts composite modifier (carbon nanotubes to fullerenes in a mass ratio of 5:100). After thorough mixing, the mixture was fed into a cement test mill and ground for 25 minutes at a mill speed of 48 r / min to obtain the green low-carbon cement (specific surface area of ​​496 m²). 2 / kg).

[0090] The compressive strength of mortar samples prepared with low-carbon cement was tested according to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Mortar blocks of 40mm×40mm×160mm were prepared by mixing with a water-cement ratio of 0.5 and cured according to standard. The compressive strengths at 3 days and 28 days were measured to be 14.9 MPa and 34.7 MPa, respectively.

[0091] A standard water requirement test for cement consistency was conducted, and the water requirement was found to be 31%.

[0092] Comparative Example 2

[0093] A green, low-carbon cement is prepared by the following steps:

[0094] 1) Preparation of green and low-carbon cement raw materials;

[0095] Based on the design of the low-calcium silicate cement clinker system, the three ratios of the clinker are KH=0.72, SM=2.1, and IM=3.2. Combining the chemical composition of the raw materials used (limestone, clay, iron ore powder, and coal gangue) (see Table 1), the designed raw material mass ratio (%) is: limestone 17.79%, clay 9.22%, carbide slag 50.55%, iron ore powder 1.72%, and coal gangue 20.72%. According to the raw material ratio, the limestone, clay, iron ore powder, and other raw materials that have been ground to a fineness of (15±2)% residue on a 0.08mm square hole sieve are weighed and homogenized in a mixer for 4 minutes (mixer speed 30r / min).

[0096] 2) Preparation of cement clinker;

[0097] Before calcination, 8 parts of fullerene (without carbon nanotubes) were added to the homogenized raw meal (95 parts). The meal was then calcined at 1200℃ (heating rate of 10℃ / min) to partially melt and form clinker. The calcination time was 16 min, which yielded low-calcium silicate cement clinker.

[0098] 3) Grinding of cement clinker;

[0099] The obtained low-calcium silicate cement clinker was mixed with 4 parts of desulfurized gypsum, and then fed into a cement test mill. The mixture was ground for 25 minutes at a mill speed of 48 r / min to obtain the green low-carbon cement (specific surface area of ​​495 m²). 2 / kg).

[0100] The compressive strength of mortar samples prepared with low-carbon cement was tested according to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Mortar blocks of 40mm×40mm×160mm were prepared by mixing with a water-cement ratio of 0.5 and cured according to standard. The compressive strengths at 3 days and 28 days were measured to be 14.3MPa and 35.8MPa, respectively.

[0101] A standard water requirement test for cement consistency was conducted, and the water requirement was found to be 32%.

[0102] Comparative Example 3

[0103] A green, low-carbon cement is prepared by the following steps:

[0104] 1) Preparation of green and low-carbon cement raw materials;

[0105] Based on the design of the low-calcium silicate cement clinker system, the three ratios of the clinker are KH=0.72, SM=2.1, and IM=3.2. Combining the chemical composition of the raw materials used (limestone, clay, iron ore powder, and coal gangue) (see Table 1), the designed raw material mass ratio (%) is: limestone 17.79%, clay 9.22%, carbide slag 50.55%, iron ore powder 1.72%, and coal gangue 20.72%. According to the raw material ratio, the limestone, clay, iron ore powder, and other raw materials that have been ground to a fineness of (15±2)% residue on a 0.08mm square hole sieve are weighed and homogenized in a mixer for 4 minutes (mixer speed 30r / min).

[0106] 2) Preparation of cement clinker;

[0107] Before calcination, 5 parts of composite modifier (mass ratio of carbon nanotubes to fullerenes of 20:80) were added to the homogenized raw meal (95 parts). The mixture was then calcined at 1200℃ (heating rate of 10℃ / min) to partially melt and form clinker. The calcination time was 16 min, which yielded low-calcium silicate cement clinker.

[0108] 3) Grinding of cement clinker;

[0109] The obtained low-calcium silicate cement clinker was mixed with 4 parts of desulfurized gypsum, and then fed into a cement test mill. The mixture was ground for 25 minutes at a mill speed of 48 r / min to obtain the green low-carbon cement (specific surface area of ​​498 m²). 2 / kg).

[0110] The compressive strength of mortar samples prepared with low-carbon cement was tested according to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Mortar blocks of 40mm×40mm×160mm were prepared by mixing with a water-cement ratio of 0.5 and cured according to standard. The compressive strengths at 3 days and 28 days were measured to be 15.7 MPa and 37.2 MPa, respectively.

[0111] A standard water requirement test for cement consistency was conducted, and the water requirement was found to be 30%.

[0112] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A low-carbon cement, characterized in that, The components and their respective weight percentages include: 95-100 parts cement raw meal, 2-4 parts desulfurized gypsum, and 2-8 parts composite modifier; wherein, the cement raw meal includes limestone, clay, carbide slag, iron ore powder, and coal gangue; the composite modifier includes fullerene and carbon nanotubes. In the composite modifier, the mass ratio of carbon nanotubes to fullerenes is 3~5:100; The low-carbon cement is first prepared by grinding and homogenizing limestone, clay, carbide slag, iron ore powder, and coal gangue to prepare cement raw materials; then, a composite modifier is added and calcined to obtain low-calcium silicate cement clinker; finally, desulfurized gypsum is added and ground to obtain the final product.

2. The low-carbon cement according to claim 1, characterized in that, The cement raw materials include the following components and their mass percentages: limestone 16-20%, clay 8-10%, carbide slag 48-51%, iron ore powder 1-3%, and coal gangue 19-21%.

3. The low-carbon cement according to claim 1, characterized in that, The main chemical components and their mass percentages in the coal gangue include: SiO2 50~55%, Al2O3 18~25%, Fe2O3 3~5%, CaO 0~2%; and a particle size of 0.075~0.25mm. The main chemical components and their mass percentages in the carbide slag include: CaO 80~85%, SiO2 3~5%, Al2O3 0~2%; and a particle size of 0.075~0.25mm.

4. The low-carbon cement according to claim 1, characterized in that, The mineral composition and their mass percentage in the low-calcium silicate cement clinker include: C3S 11~30%, C2S 40~65%, C3A 4~10%, and C4AF 9~15%.

5. The method for preparing low-carbon cement according to any one of claims 1 to 4, characterized in that, Includes the following steps: 1) Weigh the cement raw materials according to the proportions; 2) The weighed cement raw meal is ground and homogenized, then a composite modifier is added and calcined, and finally desulfurized gypsum is added and ground; thus, the low-carbon cement is obtained.

6. The preparation method according to claim 5, characterized in that, The calcination is carried out at a temperature of 1200~1300℃ for 15~20 minutes.

7. The preparation method according to claim 5, characterized in that, The grinding step uses a grinding speed of 45~50 r / min and a grinding time of 20~30 min.