Cement clinker for high-speed rail and preparation method thereof

Abstract

A cement clinker for high-speed rail and its preparation method belong to the technical field of cement materials. The cement clinker comprises the following raw materials by weight: 38-42 parts limestone, 8-11 parts wollastonite, 3-5 parts kaolin, 3-4 parts fly ash, 3-4 parts gypsum, 2-3 parts fluorite, and 1-1.5 parts modified steel slag; the modified steel slag is steel slag modified with a composite acid, and the composite acid accounts for 4-6% of the slag mass. The cement clinker for high-speed rail has high hydration activity, high early and long-term strength, and good durability.

Description

Technical Field

[0001] The present invention belongs to the technical field of cement materials, and in particular relates to cement clinker for high-speed rail and a preparation method thereof. Background Art

[0002] Cement clinker is a semi-finished product made from limestone, clay, and iron as primary raw materials. This raw meal is mixed in appropriate proportions, burned until partially or completely molten, and then cooled. In the cement industry, the most commonly used Portland cement clinker primarily consists of calcium oxide, silicon dioxide, and small amounts of aluminum oxide and iron oxide. Its primary mineral components are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite.

[0003] High-speed railway construction requires large quantities of cement. To meet the required strength and durability, cement has higher technical requirements and quality standards. However, currently used ordinary cement contains tricalcium silicate (C3S) at a maximum concentration of nearly 50%, along with a high content of tricalcium aluminate (C3A). This results in high early strength but also significant shrinkage and poor durability. Low-heat cement, due to its high C2S content, also exhibits low early strength and slow development, limiting its application.

[0004] Patent CN107555819B discloses a cement for making high-speed rail track slabs and a method for making the same. The cement comprises quartz sand, magnesium oxide, kaolin, boric acid, ammonium dihydrogen phosphate, fly ash, mineral fiber, calcium sulfate, and calcium silicate. The method comprises the following steps: (i) mixing quartz sand, magnesium oxide, kaolin, and calcium silicate to obtain a first mixture; (ii) mixing quartz sand, calcium sulfate, mineral fiber, and fly ash to obtain a second mixture; (iii) mixing quartz sand, boric acid, and ammonium dihydrogen phosphate to obtain a third mixture; and (iv) mixing the first, second, and third mixtures to obtain the cement for making high-speed rail track slabs. The cement has the advantages of low cost, good maintainability, simple operation, good durability, environmental friendliness, and suitability for areas prone to geological disasters. However, the cement described in this patent still has relatively low hydration activity and strength, limiting its application in demanding locations and environments. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a cement clinker for high-speed rail and a preparation method thereof, wherein the cement clinker for high-speed rail has the characteristics of high hydration activity, high early and long-term strength, and good durability.

[0006] To achieve the above-mentioned object, according to one aspect of the present invention, there is provided a cement clinker for high-speed rail, comprising the following raw materials in parts by mass: 38-42 parts of limestone, 8-11 parts of wollastonite, 3-5 parts of kaolin, 3-4 parts of fly ash, 3-4 parts of gypsum, 2-3 parts of fluorite and 1-1.5 parts of modified steel slag; wherein the modified steel slag is steel slag modified with a composite acid, and the composite acid accounts for 4-6% of the mass of the steel slag.

[0007] In the present invention, in the cement clinker for high-speed rail, the mass fraction of limestone is 38-42 parts. It can be understood that its mass fraction can be any specific value among 38 parts, 39 parts, 40 parts, 41 parts, 42 parts or any value within the range of 38-42 parts.

[0008] In the present invention, in the cement clinker for high-speed rail, the mass fraction of wollastonite is 8-11 parts. It can be understood that its mass fraction can be any specific value among 8 parts, 9 parts, 10 parts, 11 parts or any value within the range of 8-11 parts.

[0009] In the present invention, in the cement clinker for high-speed rail, the mass fraction of kaolin is 3-5 parts. It can be understood that its mass fraction can be any specific value among 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts or any value within the range of 3-5 parts.

[0010] In the present invention, in the cement clinker for high-speed rail, the mass fraction of fly ash is 3-4 parts. It can be understood that its mass fraction can be any specific value among 3 parts, 3.2 parts, 3.4 parts, 3.6 parts, 3.8 parts, 4 parts or any value within the range of 3-4 parts.

[0011] In the present invention, in the cement clinker for high-speed rail, the mass fraction of gypsum is 3-4 parts. It can be understood that its mass fraction can be any specific value among 3 parts, 3.2 parts, 3.4 parts, 3.6 parts, 3.8 parts, 4 parts or any value within the range of 3-4 parts.

[0012] In the present invention, in the cement clinker for high-speed rail, the mass fraction of fluorite is 2-3 parts. It can be understood that its mass fraction can be any specific value of 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3 parts, or any value within the range of 2-3 parts.

[0013] In the present invention, in the high-speed rail cement clinker, the mass fraction of modified steel slag is 1-1.5 parts. It is understood that its mass fraction can be any specific value among 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, and 1.5 parts, or any value within the range of 1-1.5 parts. In the present invention, the modified steel slag is steel slag modified with a composite acid, and the composite acid accounts for 4-6% of the mass of the steel slag. It is understood that it can be any specific value among 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5.0%, 5.2%, 5.4%, 5.6%, 5.8%, and 6%, or any value within the range of 4-6%. In the present invention, the composite acid includes formic acid and acetic acid in a mass ratio of 3:1-2:1. It is understood that its mass ratio can be any specific value among 3:1, 2.5:1, and 2:1, or any value within the range of 3:1-2:1.

[0014] An important inventive point of the present invention is that the inventors have found through a large number of experiments that by adding a certain amount of composite acid-modified steel slag, especially formic acid and acetic acid co-modified steel slag in a specific mass ratio, the hydration activity and long-term performance of the modified steel slag can be improved. On the one hand, because acetate can optimize the pore size of cement materials, it has a good improvement effect on the long-term strength of cement materials, and the hydration product of formic acid-modified steel slag, calcium formate, can significantly promote the hydration of active minerals in steel slag and cement, increase the number and generation rate of hydration products, improve hydration activity, and thus improve the early strength of cement materials. On the other hand, in-situ pores are generated on the surface of steel slag particles, which increases the surface roughness and specific surface area of steel slag particles, thereby enhancing the intercalation between steel slag particles and between steel slag particles and hydration products, forming a more compact microstructure, thereby significantly improving the strength of cement materials. However, the content of the composite acid needs to be strictly controlled. If the content is too high, the steel slag will be excessively corroded, and adhesion will occur between the steel slag particles, resulting in steel slag agglomeration, reduced activity, and significantly reduced the early strength of the cement material. In addition, during the long-term hydration process, the hydration expansion of f-CaO will cause expansion and cracking of the cement material, thereby affecting the durability of the material. If the content is too low, the modification effect is not obvious, and the hydration activity and strength of the material are both low.

[0015] In the present invention, the steel slag includes a first steel slag with an average particle size of 40-70 μm and a second steel slag with an average particle size of 20-30 μm. In the present invention, the mass ratio of the first steel slag and the second steel slag is 3:1-5:1. It can be understood that the mass ratio can be any specific value of 3:1, 4:1, 5:1 or any value within the range of 3:1-5:1. The inventors further discovered that the hydration activity and strength of steel slags of different particle sizes are different. The content of active ingredients in steel slag particles with larger particle sizes is lower, so the hydration activity is low, while the modification effect of steel slag particles with smaller particle sizes is not obvious. Therefore, the two steel slags of a specific mass ratio in the present invention are compounded, and after modification, they can have both high hydration activity and strength.

[0016] According to another aspect of the present invention, there is also provided a method for preparing the above-mentioned cement clinker for high-speed rail, comprising the following steps:

[0017] (1) Add the composite acid solution dropwise to the steel slag, stir and react for 2-3 hours, and dry to obtain modified steel slag;

[0018] (2) crushing and grinding limestone, wollastonite, kaolin, fly ash, gypsum, fluorite and modified steel slag respectively, and mixing them uniformly to obtain cement raw material;

[0019] (3) The cement raw material is subjected to primary calcination and secondary calcination in sequence, and cooled to obtain the cement clinker for high-speed rail.

[0020] In the present invention, in step (1), the composite acid solution is added dropwise to the steel slag, stirred to react for 2-3 hours, and dried to obtain modified steel slag. In the present invention, the preparation method of the composite acid solution comprises the following steps: evenly mixing formic acid and acetic acid in proportion, adding anhydrous ethanol and stirring evenly to obtain a composite acid solution with a mass concentration of 80-85%. In the present invention, in step (1), the dropwise addition speed is 1-2 seconds per drop. The reason why anhydrous ethanol is used as a solvent instead of water in the present invention is to minimize the hydration reaction of active minerals in the steel slag during the modification process, reduce the loss of active components therein, and thus ensure the activity of the steel slag.

[0021] In the present invention, in step (2), limestone, wollastonite, kaolin, fly ash, gypsum, fluorite, and modified steel slag are crushed, ground, and uniformly mixed to obtain cement raw material. In the present invention, in step (2), the fineness of the cement raw material is such that the sieve residue on an 80 μm square hole sieve is controlled to be 15±2 wt%.

[0022] In the present invention, in step (3), the cement raw material is sequentially subjected to primary calcination and secondary calcination, and cooled to obtain the cement clinker for high-speed rail. In the present invention, in step (3), the conditions for the primary calcination are calcination at 1350-1400°C for 30-35 minutes. In the present invention, in step (3), the conditions for the secondary calcination are calcination at 1450°C for 40-45 minutes. Preferably, the heating rate of the primary calcination is 5-15°C / min, and the heating rate of the secondary calcination is 5-15°C / min. Preferably, the cooling is rapid cooling with air, and more preferably, rapid cooling to room temperature is performed by using a blower, and the speed of the blower is 3000-3500r / min.

[0023] The inventors discovered that by controlling calcination conditions, specifically performing two calcinations under specific conditions, they ensured that the chemical reactions of the cement components were fully complete, resulting in minimal residual f-CaO in the clinker. This facilitated the development of mineral crystals within the cement clinker, resulting in a cement clinker with uniform crystal distribution, appropriate size, and clear boundaries. Furthermore, the two calcinations under specific conditions ensured that the C3S crystal form in the clinker transformed to the M1 form, thereby enhancing the strength of the cement clinker.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention modifies steel slag by adding a certain amount of composite acid, particularly formic acid and acetic acid in a specific mass ratio, to the modified steel slag. The two acids synergistically improve the hydration activity and long-term performance of the modified steel slag. On the one hand, because acetate can optimize the pore size of cement materials, it has a good effect on improving the long-term strength of cement materials. The hydration product of formic acid-modified steel slag, calcium formate, can significantly promote the hydration of active minerals in steel slag and cement, thereby improving the early strength of cement materials. On the other hand, the rough surface of the modified steel slag enhances the intercalation between steel slag particles and between steel slag particles and hydration products, forming a more compact microstructure, thereby significantly improving the strength of cement materials.

[0026] (2) The present invention uses two types of steel slag in a specific mass ratio for compounding, and after modification, it can have high hydration activity and strength at the same time, so that the cement clinker for high-speed rail has the characteristics of high hydration activity, high early and long-term strength, and good durability.

[0027] (3) The preparation method of the present invention ensures that the chemical reactions of the various components of the cement are fully carried out by controlling the calcination conditions, particularly by calcining under two specific conditions. This results in less residual f-CaO in the clinker, which is beneficial for promoting the development of mineral crystals in the cement clinker, thereby forming a cement clinker with uniform crystal distribution, appropriate size, and clear boundaries. At the same time, the two calcinations under specific conditions ensure that the crystal form of C3S in the clinker transforms to the M1 type, thereby improving the strength of the cement clinker. DETAILED DESCRIPTION

[0028] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0029] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0030] Herein, when describing embodiments or examples, it should be understood that they are not intended to limit the present invention to these embodiments or examples. On the contrary, all alternatives, modifications and equivalents of the methods and materials described herein are encompassed within the scope defined by the claims.

[0031] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0032] The present invention provides a cement clinker for high-speed rail, comprising the following raw materials in parts by mass: 38-42 parts of limestone, 8-11 parts of wollastonite, 3-5 parts of kaolin, 3-4 parts of fly ash, 3-4 parts of gypsum, 2-3 parts of fluorite and 1-1.5 parts of modified steel slag; wherein the modified steel slag is steel slag modified with a composite acid, and the composite acid accounts for 4-6% of the mass of the steel slag.

[0033] In the present invention, the composite acid comprises formic acid and acetic acid in a mass ratio of 3:1-2:1.

[0034] In the present invention, the steel slag includes a first steel slag with an average particle size of 40-70 μm and a second steel slag with an average particle size of 20-30 μm.

[0035] In the present invention, the mass ratio of the first steel slag to the second steel slag is 3:1-5:1.

[0036] The present invention also provides a method for preparing the above-mentioned cement clinker for high-speed rail, comprising the following steps:

[0037] (1) Add the composite acid solution dropwise to the steel slag, stir and react for 2-3 hours, and dry to obtain modified steel slag;

[0038] (2) crushing and grinding limestone, wollastonite, kaolin, fly ash, gypsum, fluorite and modified steel slag respectively, and mixing them uniformly to obtain cement raw material;

[0039] (3) The cement raw material is subjected to primary calcination and secondary calcination in sequence, and cooled to obtain the cement clinker for high-speed rail.

[0040] In the present invention, in step (1), the method for preparing the composite acid solution comprises the following steps: mixing formic acid and acetic acid in proportion, adding anhydrous ethanol and stirring evenly to obtain a composite acid solution with a mass concentration of 80-85%.

[0041] In the present invention, in step (1), the dropping speed is 1-2 s / drop.

[0042] In the present invention, in step (2), the fineness of the cement raw material is such that the residue on an 80 μm square hole sieve is controlled to be 15±2 wt%.

[0043] In the present invention, in step (3), the conditions for the primary calcination are calcination at 1350-1400° C. for 30-35 minutes.

[0044] In the present invention, in step (3), the secondary calcination is carried out at 1450° C. for 40-45 minutes.

[0045] The present invention will be described in detail below by way of examples. It should be understood that the following examples are merely provided to further illustrate and describe the present invention, and are not intended to limit the present invention. Among them, Example 1 is the most preferred embodiment of the present invention.

[0046] The chemical additives used in the examples and comparative examples of the present invention are all commercially available, and their specific information is as follows:

[0047] Limestone: particle size 40-80 mm, purchased from Shandong CITIC Calcium Industry Co., Ltd.; wollastonite: 80 mesh, Xinyu Nanfang wollastonite Co., Ltd.; kaolin: 325 mesh, purchased from Longyan Kaolin Co., Ltd.; fly ash: average particle size 10-100 μm, purchased from Guangdong Xinze Building Materials Co., Ltd.; gypsum: purchased from Hubei Longyuan Gypsum Co., Ltd.; fluorite: purchased from Hubei Tuolunzhi Technology Co., Ltd.; formic acid, acetic acid, anhydrous ethanol: purchased from Aladdin Reagent Co., Ltd.; first steel slag: average particle size 20-30 μm, purchased from Shandong Tai'an Iron and Steel Co., Ltd.; second steel slag: average particle size 20-30 μm, purchased from Shandong Tai'an Iron and Steel Co., Ltd.

[0048] Example 1

[0049] The cement clinker for high-speed rail described in this embodiment includes the following raw materials in parts by mass: 40 parts of limestone, 10 parts of wollastonite, 4 parts of kaolin, 4 parts of fly ash, 4 parts of gypsum, 3 parts of fluorite and 1.2 parts of modified steel slag; wherein the modified steel slag is steel slag modified with a composite acid, and the composite acid accounts for 5% of the mass of the steel slag; the composite acid includes formic acid and acetic acid in a mass ratio of 2.5:1, and the steel slag includes a first steel slag with an average particle size of 40-70 μm and a second steel slag with an average particle size of 20-30 μm, and the mass ratio of the first steel slag to the second steel slag is 4:1.

[0050] The method for preparing cement clinker for high-speed rail comprises the following steps:

[0051] (1) Formic acid and acetic acid were mixed in proportion, and anhydrous ethanol was added and stirred to obtain a composite acid solution with a mass concentration of 82%; the composite acid solution was added dropwise to the first steel slag and the second steel slag at a dropping speed of 1 s / drop, stirred and reacted for 2.5 h, and dried to obtain a modified steel slag;

[0052] (2) crushing and grinding limestone, wollastonite, kaolin, fly ash, gypsum, fluorite and modified steel slag respectively, and mixing them uniformly to obtain cement raw material; controlling the fineness of the cement raw material to control the sieve residue of 80 μm square hole sieve to be 15±2wt%;

[0053] (3) The cement raw material is subjected to primary calcination and secondary calcination in sequence, and rapidly cooled to room temperature by a blower at a speed of 3000 r / min to obtain the high-speed rail cement clinker. The primary calcination is performed at 1350°C for 35 minutes at a heating rate of 10°C / min; the secondary calcination is performed at 1450°C for 40 minutes at a heating rate of 10°C / min.

[0054] Example 2

[0055] The cement clinker for high-speed rail described in this embodiment includes the following raw materials in parts by mass: 42 parts of limestone, 11 parts of wollastonite, 5 parts of kaolin, 4 parts of fly ash, 4 parts of gypsum, 3 parts of fluorite and 1.5 parts of modified steel slag; wherein the modified steel slag is steel slag modified with a composite acid, and the composite acid accounts for 6% of the mass of the steel slag; the composite acid includes formic acid and acetic acid in a mass ratio of 3:1, and the steel slag includes a first steel slag with an average particle size of 40-70 μm and a second steel slag with an average particle size of 20-30 μm, and the mass ratio of the first steel slag to the second steel slag is 5:1.

[0056] The method for preparing cement clinker for high-speed rail comprises the following steps:

[0057] (1) Formic acid and acetic acid were mixed in proportion, and anhydrous ethanol was added and stirred to obtain a composite acid solution with a mass concentration of 85%; the composite acid solution was added dropwise to the first steel slag and the second steel slag at a dropping speed of 2s / drop, stirred and reacted for 3h, and dried to obtain a modified steel slag;

[0058] (2) crushing and grinding limestone, wollastonite, kaolin, fly ash, gypsum, fluorite and modified steel slag respectively, and mixing them uniformly to obtain cement raw material; controlling the fineness of the cement raw material to control the sieve residue of 80 μm square hole sieve to be 15±2wt%;

[0059] (3) The cement raw material is subjected to primary calcination and secondary calcination in sequence, and rapidly cooled to room temperature by a blower at a speed of 3500 r / min to obtain the high-speed rail cement clinker. The primary calcination is performed at 1350°C for 30 minutes at a heating rate of 15°C / min; the secondary calcination is performed at 1450°C for 45 minutes at a heating rate of 15°C / min.

[0060] Example 3

[0061] The cement clinker for high-speed rail described in this embodiment includes the following raw materials in parts by mass: 38 parts of limestone, 8 parts of wollastonite, 3 parts of kaolin, 3 parts of fly ash, 3 parts of gypsum, 2 parts of fluorite and 1 part of modified steel slag; wherein the modified steel slag is steel slag modified with a composite acid, and the composite acid accounts for 4% of the mass of the steel slag; the composite acid includes formic acid and acetic acid in a mass ratio of 2:1, and the steel slag includes a first steel slag with an average particle size of 40-70 μm and a second steel slag with an average particle size of 20-30 μm, and the mass ratio of the first steel slag to the second steel slag is 3:1.

[0062] The method for preparing cement clinker for high-speed rail comprises the following steps:

[0063] (1) Formic acid and acetic acid were mixed in proportion, and anhydrous ethanol was added and stirred to obtain a composite acid solution with a mass concentration of 80%; the composite acid solution was added dropwise to the first steel slag and the second steel slag at a dropping speed of 1 s / drop, stirred and reacted for 2 h, and dried to obtain a modified steel slag;

[0064] (2) crushing and grinding limestone, wollastonite, kaolin, fly ash, gypsum, fluorite and modified steel slag respectively, and mixing them uniformly to obtain cement raw material; controlling the fineness of the cement raw material to control the sieve residue of 80 μm square hole sieve to be 15±2wt%;

[0065] (3) The cement raw material is subjected to primary calcination and secondary calcination in sequence, and rapidly cooled to room temperature by a blower at a speed of 3000 r / min to obtain the high-speed rail cement clinker. The primary calcination is performed at 1400°C for 35 minutes at a heating rate of 5°C / min; the secondary calcination is performed at 1450°C for 40 minutes at a heating rate of 10°C / min.

[0066] Comparative Example 1

[0067] The preparation method of cement clinker for high-speed rail described in this comparative example is the same as that in Example 1, except that the composite acid accounts for 8% of the mass of the steel slag.

[0068] Comparative Example 2

[0069] The preparation method of cement clinker for high-speed rail described in this comparative example is the same as that in Example 1, except that the composite acid accounts for 2% of the mass of the steel slag.

[0070] Comparative Example 3

[0071] The preparation method of cement clinker for high-speed rail described in this comparative example is the same as that in Example 1, except that the composite acid comprises formic acid and acetic acid in a mass ratio of 1:1.

[0072] Comparative Example 4

[0073] The preparation method of the cement clinker for high-speed rail described in this comparative example is the same as that in Example 1, except that the composite acid comprises formic acid and acetic acid in a mass ratio of 5:1.

[0074] Comparative Example 5

[0075] The preparation method of cement clinker for high-speed rail described in this comparative example is the same as that in Example 1, except that the mass ratio of the first steel slag to the second steel slag is 1:1.

[0076] Comparative Example 6

[0077] The preparation method of cement clinker for high-speed rail described in this comparative example is the same as that in Example 1, except that the mass ratio of the first steel slag to the second steel slag is 8:1.

[0078] Comparative Example 7

[0079] The method for preparing high-speed rail cement clinker described in this comparative example is the same as that in Example 1, except that step (3) comprises calcining the cement raw material and rapidly cooling it to room temperature using a blower at a speed of 3000 r / min to obtain the high-speed rail cement clinker. The calcination conditions are calcination at 1350°C for 75 min and a heating rate of 5°C / min.

[0080] Performance Testing

[0081] The cement clinkers described in Examples 1-3 and Comparative Examples 1-7 were subjected to performance tests according to the following methods. The specific results are shown in Table 1.

[0082] f-CaO content in cement clinker: Using strontium nitrate as a catalyst and phenolphthalein as an indicator, react the sample with an ethanolic glycerol solution at 160-170°C to generate calcium glycerol. Titrate with a standard ethanolic benzoic acid solution. Calculate the f-CaO content in the cement clinker based on the volume of the ethanolic benzoic acid solution consumed during the titration.

[0083] Table 1 Cement clinker performance data in Examples 1-3 and Comparative Examples 1-7

[0084] .

[0085] As can be seen from Table 1, the f-CaO content in the cement clinkers described in Examples 1-3 of the present invention is relatively low, indicating that the cement is not prone to expansion and cracking during long-term hydration and has good durability.

[0086] The cement clinkers described in Examples 1-3 and Comparative Examples 1-7 were subjected to performance tests according to the following methods. The specific results are shown in Table 2.

[0087] Setting time: tested in accordance with standard GB / T1346-2011.

[0088] Flexural strength and compressive strength: According to the standard GB / T17671-2021, the strength performance of cement was tested after curing for 3 days, 28 days and 90 days respectively.

[0089] Table 2 Cement performance data in Examples 1-3 and Comparative Examples 1-7

[0090] .

[0091] As shown in Table 2, the flexural strength and compressive strength of the cement under different days described in the embodiments of the present invention 1-3 are all higher, and the cement 3d compressive strength of embodiment 1 exceeds 37MPa, and 28d compressive strength exceeds 68MPa, and 90d compressive strength exceeds 83MPa. As shown in Example 1 and Comparative Examples 1 and 2, the composite acid in Comparative Examples 1 and 2 accounts for slag mass content on the high side or on the low side, and its short-term and long-term flexural strength and compressive strength are all significantly reduced, illustrating that the content of composite acid needs strict control, and content on the high side or on the low side all can affect modification effect, and then affect hydration activity and intensity. As shown in Example 1 and Comparative Examples 3 and 4, the proportion of formic acid in the composite acid in Comparative Example 3 is on the low side, and its short-term strength obviously decreases, and the proportion of acetic acid in Comparative Example 4 is on the low side, and its long-term strength obviously decreases, illustrating that the proportional relationship of the two in composite acid is key for activity and intensity impact, and proportional change can reduce the synergistic effect of the two, thereby affecting performance. As shown in Example 1 and Comparative Examples 5 and 6, the different mass ratios of the first and second slags in Comparative Examples 5 and 6 significantly reduced both the short-term and long-term strengths, indicating a synergistic effect between the two slags of different particle sizes, which together improved the activity and strength of the cement. As shown in Example 1 and Comparative Example 7, the different calcination conditions in Comparative Example 7 affected both the activity and strength, demonstrating that the secondary calcination conditions of the present invention can further improve cement performance compared to primary calcination.

[0092] As can be seen from this, the present invention is by adding a certain amount of composite acid modified steel slag, particularly formic acid and acetic acid co-modified steel slag of a specific mass ratio, and the two collaborate to enhance the hydration activity and long-term performance of the modified steel slag. On the one hand, due to the acetic acid radical can optimize the pore size of the cement material, the long-term compressive strength of the cement material is preferably enhanced, and the hydration product calcium formate of the formic acid modified steel slag can significantly promote the hydration of active minerals in steel slag and cement, thereby enhancing the early strength of the cement material. On the other hand, the rough surface of the modified steel slag enhances the intercalation between the steel slag particles, the steel slag particles and the hydration product, and forms a more compact microstructure, thereby significantly improving the compressive strength of the cement material. In addition, the present invention adopts two kinds of steel slags of a specific mass ratio to be composited, and after modification, it can be made to have higher hydration activity and compressive strength simultaneously, so that the high-speed iron cement clinker has the characteristics of high hydration activity, high early and long-term strength, and good durability.

[0093] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A cement clinker for high-speed rail, characterized in that: The invention comprises the following raw materials in parts by mass: 38-42 parts of limestone, 8-11 parts of wollastonite, 3-5 parts of kaolin, 3-4 parts of fly ash, 3-4 parts of gypsum, 2-3 parts of fluorite and 1-1.5 parts of modified steel slag; wherein the modified steel slag is steel slag modified with a composite acid, and the composite acid accounts for 4-6% of the mass of the steel slag; the composite acid comprises formic acid and acetic acid in a mass ratio of 3:1-2:1; the steel slag comprises a first steel slag with an average particle size of 40-70 μm and a second steel slag with an average particle size of 20-30 μm; and the mass ratio of the first steel slag to the second steel slag is 3:1-5:

1.

2. A method for preparing cement clinker for high-speed rail according to claim 1, characterized in that: The steps include: (1) Add the composite acid solution dropwise to the steel slag, stir and react for 2-3 hours, and dry to obtain modified steel slag; (2) crushing and grinding limestone, wollastonite, kaolin, fly ash, gypsum, fluorite and modified steel slag respectively, and mixing them uniformly to obtain cement raw material; (3) The cement raw material is subjected to primary calcination and secondary calcination in sequence, and cooled to obtain the cement clinker for high-speed rail.

3. A method for preparing cement clinker for high-speed rail according to claim 2, characterized in that: In step (1), the preparation method of the composite acid solution comprises the following steps: mixing formic acid and acetic acid in proportion, adding anhydrous ethanol and stirring evenly to obtain a composite acid solution with a mass concentration of 80-85%.

4. A method for preparing cement clinker for high-speed rail according to claim 2, characterized in that: In step (1), the dropping speed is 1-2 s / drop.

5. A method for preparing cement clinker for high-speed rail according to claim 2, characterized in that: In step (2), the fineness of the cement raw material is such that the residue on an 80 μm square hole sieve is controlled at 15±2 wt%.

6. A method for preparing cement clinker for high-speed rail according to claim 2, characterized in that: In step (3), the conditions for the primary calcination are calcination at 1350-1400°C for 30-35 minutes.

7. A method for preparing cement clinker for high-speed rail according to claim 2, characterized in that: In step (3), the secondary calcination is carried out at 1450° C. for 40-45 minutes.