Low-carbon cement and preparation method thereof

Abstract

The invention discloses green low-carbon cement which comprises the following components in parts by weight: 95-100 parts of cement raw material, 2-4 parts of desulfurized gypsum and 2-8 parts of composite modifier, wherein the cement raw material comprises limestone, clay, carbide slag, iron ore powder and coal gangue; the composite modifier comprises fullerene and a carbon nano tube. According to the invention, the composite modifier based on fullerene and carbon nanotubes is introduced into the calcining stage of the cement raw material, so that the calcining temperature can be effectively reduced and the calcining efficiency can be improved while the early and later strength of the cement is ensured; and various industrial wastes such as industrial solid waste coal gangue and carbide slag can be fully utilized, so that the method has remarkable economic and environmental benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to a low-carbon cement and a preparation method thereof. Background Art

[0002] During the production process of portland cement, a large amount of carbon dioxide is generated by the decomposition of calcined limestone (the main component is calcium carbonate), which is one of the main sources of carbon emissions in cement production. During the calcination process of cement clinker, C3S in the cement clinker accounts for about 37-67%, C2S accounts for about 15-30%, C4AF accounts for about 10-18%, and C3A accounts for about 7-15%. The temperature required for the formation of C3S during the calcination of clinker is about 1450°C at the highest, and the temperature required for the formation of C2S to start is only about 800°C, and it reaches the maximum content value at 1100-1200°C. The high-temperature combustion environment in the kiln will cause the nitrogen and oxygen in the air to react to generate nitrogen oxides (such as nitric oxide and nitrogen dioxide). These nitrogen oxides are important pollutants that cause environmental problems such as acid rain and chemical smog. In addition, if the fuel such as coal used in the cement production process has a high sulfur content, sulfur dioxide will also be generated during the combustion process, which is also one of the main pollutants causing acid rain.

[0003] C3S is the mineral component with the highest strength in cement clinker and plays a key role in the development of the early strength of cement. If the calcium-silicon ratio is too low, the content of C3S decreases, which will lead to the slow development of the early strength of cement. Generally speaking, the hydration rate of C3S is relatively fast, and its hydration products can quickly form a cohesive structure, endowing the cement with relatively high early strength. While the hydration rate of C2S is relatively slow and its contribution to strength is small in the early stage. Therefore, when the calcium-silicon ratio is too low, the compressive strength and flexural strength of the cement will both decrease significantly in the early stage (1-3 days).

[0004] Too low calcium-silicon ratio may prolong the setting time of cement. This is because the mineral composition of cement clinker changes, the content of C3S decreases, and the production amount of its hydration product calcium hydroxide also decreases accordingly. Calcium hydroxide can accelerate the hydration process of other minerals in the cement paste. Its reduction will slow down the hydration rate of the entire cement paste, resulting in the prolongation of the initial setting time and final setting time of the cement.

[0005] In terms of long-term strength, although the later strength growth potential of dicalcium silicate is relatively large, due to its slow early strength development, in practical engineering applications, especially for projects with high requirements for early strength, such as the rapid demolding of concrete precast members, etc., it will be adversely affected. And overall, too low calcium-silicon ratio will also make the final strength of the cement lower than that of the cement with a normal calcium-silicon ratio.

[0006] Therefore, developing new low-carbon cement is an urgent task, and reducing the proportion of C3S 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 object of the present invention is to provide a new type of green and low-carbon cement in view of the problems and deficiencies existing in the prior art, which can effectively reduce the calcination temperature, improve the calcination efficiency while ensuring the early and late strength of the cement, and can make full use of industrial solid wastes such as coal gangue and carbide slag, having remarkable economic and environmental benefits.

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

[0009] A green and low-carbon cement, the components and their weight parts include: 95 - 100 parts of cement raw meal, 2 - 4 parts of desulfurized gypsum, and 2 - 8 parts of 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.

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

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

[0012] In the above solution, the fullerene is in the form of black crystal powder, and the number of hydroxyl groups is 24 - 28.

[0013] In the above solution, the outer diameter of the carbon nanotubes is less than 2nm, and the length is 5 - 30um.

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

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

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

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

[0018] In the above solution, the main chemical components of the clay and their mass percentages are as follows: Al2O3 13 - 18%; Fe2O3 4 - 6%, SiO2 65 - 75%, CaO 1 - 2%; the particle size is 45 - 80um.

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

[0020] In the above solution, for the green and low - carbon cement, first, limestone, clay, carbide slag, iron ore powder, and coal gangue are ground and homogenized to obtain cement raw meal; then, a composite modifier is added for calcination to obtain low - calcium silicate cement clinker, and finally, desulfurized gypsum is added for grinding to obtain the product.

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

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

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

[0024] 1) Weigh the cement raw meal according to the ratio;

[0025] 2) Homogenize the weighed cement raw meal, then add a composite modifier for calcination, and finally add desulfurized gypsum for grinding; thus, the green and low - carbon cement is obtained.

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

[0027] In the above solution, the temperature used for calcination is 1200 - 1300°C, and the time is 15 - 20min.

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

[0029] Furthermore, the SM - 500 type cement test mill is used in the grinding step.

[0030] For the green and low - carbon cement obtained according to the above solution, its specific surface area reaches 480 - 520m 2 / kg, and at the same time, it can effectively reduce the standard consistency water demand (the water demand is below 29%), and take into account good early strength, etc. The 3-day mortar strength can reach more than 20 MPa, and the 28-day mortar strength can reach more than 43 MPa.

[0031] The principle of the present invention is as follows:

[0032] The present invention first proposes to introduce a composite modifier based on fullerenes and carbon nanotubes into the calcination stage of cement raw meal. The corresponding improvement mechanisms include: 1) Combining fullerenes and carbon nanotubes is beneficial to improving the heat conduction efficiency during the production process of cement clinker, promoting the stability of the burning process, and facilitating the reduction of the burning temperature of cement clinker, significantly reducing energy consumption and carbon dioxide emissions; 2) Fullerenes can also promote the reaction of active components (such as C3S and C2S) in cement clinker with water during subsequent application processes, thereby improving the hydration rate of cement and ensuring the mechanical properties of cement products in the early and late stages; 3) The nano-scale characteristics of fullerenes enable them to interact with solid waste particles (coal gangue, carbide slag), promoting their uniform dispersion in the cement paste, which is beneficial to enhancing the overall compactness 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 the high-efficiency grinding of carbide slag, coal gangue and other solid waste materials. The obtained powder still has high dispersibility after encountering water. On the premise of increasing the specific surface area of cement and the activity of clinker, it can effectively reduce the standard consistency water demand.

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

[0034] 1) The present invention introduces a composite modifier based on fullerenes and carbon nanotubes into the calcination stage of cement raw meal, which can effectively reduce the calcination temperature (usually above 1400°C) while ensuring the early and late strength of cement, improving the calcination efficiency; In addition, it is beneficial to reduce the standard consistency water demand, providing a new idea 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 ensure and further improve the early and late strength, and at the same time can make a large amount of use of idle resources such as solid waste, with significant economic and environmental benefits;

[0036] 3) The preparation method involved in the present invention is relatively simple, easy to operate, has a low preparation cost, and is environmentally friendly, and is suitable for popularization and application. Specific embodiments

[0037] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following further details the present invention in conjunction with embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0038] In the following examples, the fullerene used is in the form of black crystal powder, with the number of hydroxyl groups being 24 - 28, the oxygen content being 42.41 wt%, the carbon content being 38.12 wt%, the hydrogen content being 2.97 wt%, and the molecular formula being C 60 (OH) n ﹒H2O; the outer diameter of the carbon nanotubes is less than 2 nm, the length is 5 - 30 um, and the bulk density is 0.018 g / cm 3 。

[0039] The chemical components of the limestone, clay, iron ore powder, coal gangue, and carbide slag used are 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 and low - carbon cement, and its preparation method includes the following steps:

[0044] 1) Preparation of the raw meal for green and low - carbon cement;

[0045] According to the low - calcium silicate cement clinker system, the three modulus values of the clinker are designed as KH = 0.72, SM = 2.1, IM = 3.2. Combining with the chemical components of the raw materials limestone, clay, iron ore powder, and coal gangue used (see Table 1), the mass ratio of the raw meal (%) is designed as: limestone 17.79%, clay 9.22%, carbide slag 50.55%, iron ore powder 1.72%, coal gangue 20.72%; according to the raw meal ratio, weigh the raw materials such as limestone, clay, and iron ore powder that have been ground to a fineness of (15 ± 2)% residue on a 0.08 mm square hole sieve, and homogenize them in a mixer for 4 min (mixer speed 30 r / min);

[0046] 2) Preparation of cement clinker;

[0047] Before calcination, add 3 parts of a composite modifier (the mass ratio of carbon nanotubes to fullerene is 5:100) to the homogenized raw meal (95 parts; by weight, the same below), and calcine it at 1300 °C (heating rate 10 °C / min) until it partially melts to form clinker. The calcination time is 16 min, and thus low - calcium silicate cement clinker is obtained;

[0048] 3) Grinding of cement clinker;

[0049] Mix the obtained low - calcium silicate cement clinker and 4 parts of desulfurized gypsum evenly, and then put them into a cement test mill and grind for 25 min at a mill speed of 48 r / min, thus obtaining the said green and low - carbon cement (specific surface area 495 m 2 / kg).

[0050] The compressive strength test was carried out on the mortar specimens prepared from low-carbon cement according to GB / T 17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Mortar specimens with dimensions of 40mm×40mm×160mm were prepared by mixing at a water-cement ratio of 0.5, cured according to the standard, and the compressive strengths at 3d and 28d were measured to be 20.7MPa and 43.3MPa respectively.

[0051] The standard water requirement for cement consistency was tested, and the water requirement was measured to be 29%.

[0052] Example 2

[0053] A green low-carbon cement, the preparation method of which comprises the following steps:

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

[0055] According to the low-calcium silicate cement clinker system, the three modulus values of the clinker were designed as KH = 0.72, SM = 2.1, IM = 3.2. Combining the chemical components of the raw materials limestone, clay, iron ore powder, and coal gangue used (see Table 1), the mass ratio of the raw meal (%) was designed as: limestone 17.79%, clay 9.22%, carbide slag 50.55%, iron ore powder 1.72%, coal gangue 20.72%; according to the raw meal ratio, the raw materials such as limestone, clay, and iron ore powder that had been ground to a fineness of (15±2)% residue on a 0.08mm square hole sieve were weighed, homogenized in a mixer for 4 min (mixer rotation speed 30 r / min),

[0056] 2) Preparation of cement clinker;

[0057] Before calcination, 3 parts of a composite modifier (mass ratio of carbon nanotubes to fullerenes is 5:100) were added to the homogenized raw meal (95 parts), and calcined at 1280 °C (heating rate 10 °C / min) until partial melting to form clinker. The calcination time was 16 min, and thus 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 put into a cement test mill, and ground for 25 min at a mill rotation speed of 48 r / min, thus obtaining the said green low-carbon cement (specific surface area 497m 2 / kg).

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

[0061] The standard water requirement for cement consistency was tested, and the water requirement was measured to be 27%.

[0062] Example 3

[0063] A green low-carbon cement, the preparation method thereof comprises the following steps:

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

[0065] According to the low-calcium silicate cement clinker system, the three modulus values of the clinker were designed as KH = 0.72, SM = 2.1, IM = 3.2. Combining with the chemical components of the raw materials limestone, clay, iron ore powder, and coal gangue used (see Table 1), the mass ratio of the raw meal was designed as follows (%): limestone 17.79%, clay 9.22%, carbide slag 50.55%, iron ore powder 1.72%, coal gangue 20.72%; according to the raw meal ratio, raw materials such as limestone, clay, and iron ore powder that had been ground to a fineness of (15±2)% residue on a 0.08mm square hole sieve were weighed, and were homogenized in a mixer for 4 minutes (the mixer rotation speed was 30r / min);

[0066] 2) Preparation of cement clinker;

[0067] Before calcination, 5 parts of a composite modifier (the mass ratio of carbon nanotubes to fullerenes was 5:100) were added to 95 parts of the homogenized raw meal, and were calcined at 1250°C (the heating rate was 10°C / min) until partial melting to form clinker. The calcination time was 16 minutes, and thus low-calcium silicate cement clinker was obtained;

[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 put into a cement test mill, and were ground for 25 minutes at a mill rotation speed of 48r / min, and thus the said green low-carbon cement was prepared (the specific surface area was 495m 2 / kg).

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

[0071] The standard water consumption for cement consistency is tested, and the water demand is measured to be 24%.

[0072] Example 4

[0073] A green and low-carbon cement, and its preparation method includes the following steps:

[0074] 1) Preparation of the raw meal for green and low-carbon cement;

[0075] According to the low-calcium silicate cement clinker system, the three modulus values of the clinker are designed as KH = 0.72, SM = 2.1, and IM = 3.2. Combining with the chemical components of the raw materials limestone, clay, iron ore powder, and coal gangue used (see Table 1), the mass ratio of the raw meal (%) is designed as: limestone 17.79%, clay 9.22%, carbide slag 50.55%, iron ore powder 1.72%, and coal gangue 20.72%; according to the raw meal ratio, weigh the raw materials such as limestone, clay, and iron ore powder that have been ground to a fineness of (15 ± 2)% residue on a 0.08 mm square hole sieve, homogenize in a mixer for 4 min (mixer speed 30 r / min),

[0076] 2) Preparation of cement clinker;

[0077] Before calcination, add 6 parts of a composite modifier (mass ratio of carbon nanotubes to fullerenes is 5:100) to the homogenized raw meal (95 parts), and calcine at 1220 °C (heating rate is 10 °C / min) to partially melt and form clinker. The calcination time is 16 min, and low-calcium silicate cement clinker is obtained;

[0078] 3) Grinding of cement clinker;

[0079] Mix the obtained low-calcium silicate cement clinker and 4 parts of desulfurized gypsum evenly, and put them into a cement test mill. Grind for 25 min at a mill speed of 48 r / min to obtain the green and low-carbon cement (specific surface area is 497 m 2 / kg).

[0080] According to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)", the compressive strength test is carried out on the mortar specimens prepared from the low-carbon cement. Mix with a water-cement ratio of 0.5 to make 40 mm × 40 mm × 160 mm mortar test blocks, cure according to the standard, and measure the 3d and 28d compressive strengths to be 24.1 MPa and 46.1 MPa respectively.

[0081] The standard water consumption for cement consistency is tested, and the water demand is measured to be 26%.

[0082] Comparative Example 1

[0083] A green and low-carbon cement, and its preparation method comprises the following steps:

[0084] 1) Preparation of the raw meal for green and low-carbon cement;

[0085] Based on the low-calcium silicate cement clinker system, the three modulus values of the clinker are designed as KH = 0.72, SM = 2.1, and IM = 3.2. Combining with the chemical components of the raw materials limestone, clay, iron ore powder, and coal gangue used (see Table 1), the mass ratio of the raw meal (%) is designed as: limestone 17.79%, clay 9.22%, carbide slag 50.55%, iron ore powder 1.72%, and coal gangue 20.72%. According to the raw meal ratio, weigh the raw materials such as limestone, clay, and iron ore powder that have been ground to a fineness of (15 ± 2)% residue on a 0.08 mm square hole sieve. After homogenizing in a mixer for 4 minutes (mixer rotation speed 30 r / min),

[0086] 2) Preparation of cement clinker;

[0087] Weigh 95 parts of the homogenized raw meal and calcine it at 1300 °C (heating rate 10 °C / min) until it is partially melted to form clinker. The calcination time is 16 minutes, and thus low-calcium silicate cement clinker is obtained;

[0088] 3) Grinding of cement clinker;

[0089] Add 4 parts of desulfurized gypsum to the obtained low-calcium silicate cement clinker, and then add 5 parts of a composite modifier (mass ratio of carbon nanotubes to fullerenes is 5:100). After mixing evenly, put it into a cement test mill and grind it for 25 minutes at a mill rotation speed of 48 r / min, and thus the said green and low-carbon cement is prepared (specific surface area is 496 m 2 / kg).

[0090] Carry out a compressive strength experiment on the mortar specimen prepared from the low-carbon cement in accordance with GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Prepare a mortar test block of 40 mm × 40 mm × 160 mm by mixing at a water-cement ratio of 0.5, and cure it according to the standard. Measure the compressive strengths at 3 d and 28 d to be 14.9 MPa and 34.7 MPa respectively.

[0091] Carry out a test on the standard water requirement for cement consistency, and the measured water requirement is 31%.

[0092] Comparative Example 2

[0093] A green and low-carbon cement, and its preparation method comprises the following steps:

[0094] 1) Preparation of the raw meal for green and low-carbon cement;

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

[0096] 2) Preparation of cement clinker;

[0097] Before calcination, add 8 parts of fullerene (without adding carbon nanotubes) to the homogenized raw meal (95 parts), and calcine it at 1200 °C (heating rate is 10 °C / min) to make it partially molten to form clinker. The calcination time is 16 minutes, and the low-calcium silicate cement clinker is obtained.

[0098] 3) Grinding of cement clinker;

[0099] Add the obtained low-calcium silicate cement clinker and 4 parts of desulfurized gypsum, mix them evenly and then put them into a cement test mill, and grind them for 25 minutes at a mill speed of 48 r / min to obtain the green and low-carbon cement (specific surface area is 495 m 2 / kg).

[0100] Carry out the compressive strength test on the mortar specimens prepared from the low-carbon cement according to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Make mortar test blocks of 40 mm × 40 mm × 160 mm by mixing with a water-cement ratio of 0.5, cure them according to the standard, and measure the compressive strengths at 3 days and 28 days to be 14.3 MPa and 35.8 MPa respectively.

[0101] Carry out the test on the standard water requirement for cement consistency, and the measured water requirement is 32%.

[0102] Comparative Example 3

[0103] A green and low-carbon cement, and its preparation method includes the following steps:

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

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

[0106] 2) Preparation of cement clinker;

[0107] Before calcination, add 5 parts of a composite modifier (the mass ratio of carbon nanotubes to fullerenes is 20:80) to the homogenized raw meal (95 parts), and calcine it at 1200 °C (the heating rate is 10 °C / min) until it is partially melted to form clinker. The calcination time is 16 minutes, and the low-calcium silicate cement clinker is obtained;

[0108] 3) Grinding of cement clinker;

[0109] Add 4 parts of desulfurized gypsum to the obtained low-calcium silicate cement clinker, mix evenly and put it into a cement test mill, and grind it for 25 minutes at a mill speed of 48 r / min to obtain the green low-carbon cement (specific surface area is 498 m 2 / kg).

[0110] Carry out a compressive strength experiment on the mortar specimens prepared from the low-carbon cement according to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Prepare mortar specimens of 40mm×40mm×160mm by mixing with a water-cement ratio of 0.5, cure them according to the standard, and measure the 3d and 28d compressive strengths to be 15.7 MPa and 37.2 MPa respectively.

[0111] Carry out a test on the standard water requirement for cement consistency, and the measured water requirement is 30%.

[0112] The present invention is not limited to the above embodiments. For those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and retouches can be made, and these improvements and retouches are also regarded as within the protection scope of the present invention. The content not described in detail in this specification belongs to the well-known prior art of those skilled in the art.

Claims

1. A low-carbon cement, characterized in that, The components and their weight parts include: 95 - 100 parts of cement raw meal, 2 - 4 parts of desulfurized gypsum, and 2 - 8 parts of composite modifier; among them, the cement raw meal contains limestone, clay, carbide slag, iron ore powder, and coal gangue; the composite modifier contains fullerene and carbon nanotubes.

2. The low-carbon cement according to claim 1, wherein, In the said composite modifier, the mass ratio of carbon nanotubes to fullerene is 3 - 5:

100.

3. The low-carbon cement according to claim 1, wherein In the said cement raw meal, the components and their mass percentages include: 16 - 20% of limestone, 8 - 10% of clay, 48 - 51% of carbide slag, 1 - 3% of iron ore powder, and 19 - 21% of coal gangue.

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

5. The low-carbon cement according to claim 1, wherein The said low - carbon cement is obtained by first grinding and homogenizing limestone, clay, carbide slag, iron ore powder, and coal gangue to prepare cement raw meal; then adding the composite modifier for calcination, and finally adding desulfurized gypsum for grinding.

6. The low-carbon cement according to claim 5, characterized in that, In the said low - calcium silicate cement clinker, the mineral compositions and their mass percentages include: 11 - 30% of C3S, 40 - 65% of C2S, 4 - 10% of C3A, and 9 - 15% of C4AF.

7. The preparation method of the low-carbon cement according to any one of claims 1 to 6, characterized in that, It includes the following steps: 1) Weigh the cement raw meal according to the ratio. 2) Grind and homogenize the weighed cement raw meal, then add the composite modifier for calcination, and finally add desulfurized gypsum for grinding; thus obtaining the said low - carbon cement.

8. The preparation method according to claim 6, characterized in that, The temperature used for the said high - temperature calcination is 1200 - 1300°C, and the time is 15 - 20min.

9. The preparation method according to claim 6, characterized in that, The grinding speed used in the said grinding step is 45 - 50r / min, and the grinding time is 20 - 30min.