Cement clinker for high-speed rail and preparation method thereof

Abstract

The invention discloses cement clinker for high-speed rails and a preparation method thereof, and belongs to the technical field of cement materials. The cement clinker for the high-speed rail is prepared from the following raw materials in parts by mass: 38 to 42 parts of limestone, 8 to 11 parts of wollastonite, 3 to 5 parts of kaolin, 3 to 4 parts of fly ash, 3 to 4 parts of gypsum, 2 to 3 parts of fluorite and 1 to 1.5 parts of modified steel slag, wherein the modified steel slag is steel slag modified by composite acid, and the composite acid accounts for 4-6% of the mass of the steel slag. The cement clinker for the high-speed rail has the characteristics of 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 particularly relates to a cement clinker for high-speed railways and a preparation method thereof. Background Art

[0002] Cement clinker is a semi-finished product obtained by using limestone, clay, and iron-containing raw materials as the main raw materials, proportioning them into raw meal in an appropriate ratio, burning until partially or completely melted, and then cooling. In the cement industry, the most commonly used Portland cement clinker mainly consists of calcium oxide, silicon dioxide, and a small amount of aluminum oxide and iron oxide. The main mineral components are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite.

[0003] In the construction of high-speed railway projects, a large amount of cement is required. To meet the strength and durability requirements of high-speed railways, higher technical requirements and quality standards are imposed on cement. However, in currently commonly used ordinary cement, the proportion of tricalcium silicate (C 3 S) is the highest, approaching 50%, and at the same time, the content of tricalcium aluminate (C 3 A) is relatively high. Therefore, it has high early strength, but large shrinkage and poor durability; while low-heat cement has a relatively high C 2 S content, resulting in low early strength and slow development, which also limits its application.

[0004] Patent CN107555819B discloses a cement for preparing high-speed railway track slabs and a preparation method thereof, including quartz sand, magnesium oxide, kaolin, boric acid, ammonium dihydrogen phosphate, fly ash, mineral fiber, calcium sulfate, and calcium silicate; the preparation method includes 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; (iv) mixing the first mixture, the second mixture, and the third mixture to obtain the cement for preparing high-speed railway track slabs. The cement has the characteristics of low cost, good maintainability, simple operation, good durability, environmental friendliness, and suitability for areas with frequent geological disasters. However, the hydration activity and strength of the cement described in this patent are still relatively low, restricting its application in places and environments with higher requirements. Summary of the Invention

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

[0006] To achieve the above 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 by compound acid, and the compound acid is 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 among 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 cement clinker for high-speed railways, the mass fraction of the modified steel slag is 1 - 1.5 parts. It can be understood that the mass fraction can be any specific value among 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts or any value within the range of 1 - 1.5 parts. In the present invention, the modified steel slag is the steel slag modified by a composite acid, and the composite acid is 4 - 6% of the mass of the steel slag. It can be 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%, 6% or any value within the range of 4 - 6%. In the present invention, the composite acid includes formic acid and acetic acid with a mass ratio of 3:1 - 2:1. It can be understood that the mass ratio can be any specific value among 3:1, 2.5:1, 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 inventor found through a large number of experiments that by adding a certain amount of steel slag modified by a composite acid, especially the steel slag jointly modified by formic acid and acetic acid with a specific mass ratio, the hydration activity and long-term performance of the modified steel slag can be improved. On the one hand, since the acetate ion can optimize the pore size of the cement material and has a good effect on improving the long-term strength of the cement material, and the calcium formate of the hydration product of the formic acid-modified steel slag can significantly promote the hydration of the active minerals in the steel slag and cement, increase the quantity and generation rate of the hydration products, and improve the hydration activity, thereby improving the early strength of the cement material. On the other hand, in-situ pores are generated on the surface of the steel slag particles, increasing the surface roughness and specific surface area of the steel slag particles, enhancing the interlocking effect between the steel slag particles and between the steel slag particles and the hydration products, and forming a more dense microstructure, thereby significantly improving the strength of the cement material. However, the content of the composite acid needs to be strictly controlled. If the content is too much, the steel slag will be corroded excessively, adhesion will occur between the steel slag particles, resulting in steel slag agglomeration, a decrease in activity, and a significant reduction in the early strength of the cement material. And during the long-term hydration process, the hydration expansion of f-CaO will cause the cement material to expand and crack, thereby affecting the durability of the material; if the content is too little, 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 to the second steel slag is 3:1 - 5:1. It can be understood that the mass ratio can be any specific value among 3:1, 4:1, and 5:1 or any value within the range of 3:1 - 5:1. The inventors further found that the hydration activity and strength of steel slags with different particle sizes are different. The content of active components in larger-sized steel slag particles is relatively low, so the hydration activity is low, while the modification effect of smaller-sized steel slag particles is not obvious. Therefore, the present invention combines two steel slags with a specific mass ratio, and after modification, it can simultaneously have 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: (1) Drop the composite acid solution onto the steel slag, stir and react for 2 - 3 h, and then dry to obtain modified steel slag; (2) Crush, grind, and mix limestone, wollastonite, kaolin, fly ash, gypsum, fluorite, and the modified steel slag respectively to obtain cement raw meal; (3) Subject the cement raw meal to primary calcination and secondary calcination in sequence, and then cool to obtain the cement clinker for high-speed rail.

[0017] In the present invention, in step (1), the composite acid solution is dropped onto the steel slag, stirred and reacted for 2 - 3 h, and then dried to obtain modified steel slag. In the present invention, the preparation method of the composite acid solution comprises the following steps: Mix formic acid and acetic acid in proportion, add absolute ethanol and stir evenly to obtain a composite acid solution with a mass concentration of 80 - 85%. In the present invention, in step (1), the dropping rate is 1 - 2 s / drop. The reason for using absolute ethanol instead of water as the solvent 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.

[0018] In the present invention, in step (2), limestone, wollastonite, kaolin, fly ash, gypsum, fluorite, and the modified steel slag are respectively crushed, ground, and mixed evenly to obtain cement raw meal. In the present invention, in step (2), the fineness of the cement raw meal is controlled such that the residue on a 80 μm square-hole sieve is 15 ± 2 wt%.

[0019] In the present invention, in step (3), the cement raw meal is subjected to primary calcination and secondary calcination in sequence, and then cooled to obtain the cement clinker for high-speed rail. In the present invention, in step (3), the condition for the primary calcination is calcination at 1350 - 1400 °C for 30 - 35 min. In the present invention, in step (3), the condition for the secondary calcination is calcination at 1450 °C for 40 - 45 min. Preferably, the heating rate for the primary calcination is 5 - 15 °C / min, and the heating rate for the secondary calcination is 5 - 15 °C / min. Preferably, the cooling is rapid air cooling, and more preferably, it is cooled to room temperature by blowing air with a blower, and the rotational speed of the blower is 3000 - 3500 r / min.

[0020] The inventor of the present invention found that by controlling the calcination conditions, especially through calcination under two specific conditions, it is ensured that all components of the cement fully undergo chemical reactions, with less residual f-CaO in the clinker, which is beneficial to 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 C 3 S crystal form transforms into the M1 type, thereby enhancing the strength of the cement clinker.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In the present invention, by adding a certain amount of steel slag modified by a composite acid, especially steel slag modified by formic acid and acetic acid with a specific mass ratio, the two synergistically improve the hydration activity and long-term performance of the modified steel slag. On the one hand, since acetate ions can optimize the pore size of the cement material and have a good effect on improving the long-term strength of the cement material, and calcium formate, the hydration product of formic acid-modified steel slag, can significantly promote the hydration of active minerals in the 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 interlocking effect between steel slag particles and between steel slag particles and hydration products, forming a more dense microstructure, thereby significantly improving the strength of the cement material.

[0022] (2) The present invention uses two kinds of steel slag with a specific mass ratio for compounding, and after modification, it can simultaneously have high hydration activity and strength, 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.

[0023] (3) The preparation method of the present invention ensures that all components of the cement fully undergo chemical reactions by controlling the calcination conditions, especially through two calcinations under specific conditions, with less residual f-CaO in the clinker, which is beneficial to 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 C 3The crystal form of S is transformed into the M1 type, thereby enhancing the strength of the cement clinker. Detailed implementation manners

[0024] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meanings understood by those skilled in the art for the present invention. In case of conflicts, the definitions in this specification shall prevail.

[0025] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0026] In this article, when describing the embodiments or examples, it should be understood that they are not used to limit the present invention to these embodiments or examples. On the contrary, all alternatives, improvements, and equivalents of the methods and materials described in the present invention can be covered within the scope defined by the claims.

[0027] In this article, for the sake of brevity of description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there are no contradictions in the combinations of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0028] 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 by a composite acid, and the composite acid is 4 - 6% of the mass of the steel slag.

[0029] In the present invention, the composite acid comprises formic acid and acetic acid with a mass ratio of 3:1 - 2:1.

[0030] In the present invention, 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.

[0031] In the present invention, the mass ratio of the first steel slag to the second steel slag is 3:1 - 5:1.

[0032] The present invention also provides a preparation method of the above-mentioned cement clinker for high-speed rail, comprising the following steps: (1) Drop the composite acid solution into the steel slag, stir and react for 2 - 3 h, and then dry to obtain the modified steel slag; (2) Crush, grind, and mix limestone, wollastonite, kaolin, fly ash, gypsum, fluorite, and modified steel slag evenly to obtain cement raw meal. (3) Calcinate the cement raw meal through primary calcination and secondary calcination in sequence, and then cool it to obtain the cement clinker for high-speed rail.

[0033] In the present invention, in step (1), the preparation method of the composite acid solution includes the following steps: Mix formic acid and acetic acid evenly in proportion, add absolute ethanol and stir evenly to obtain a composite acid solution with a mass concentration of 80 - 85%.

[0034] In the present invention, in step (1), the dropping rate is 1 - 2 s / drop.

[0035] In the present invention, in step (2), the fineness of the cement raw meal is controlled such that the residue on a 80μm square-hole sieve is 15 ± 2 wt%.

[0036] In the present invention, in step (3), the conditions for primary calcination are calcination at 1350 - 1400 °C for 30 - 35 min.

[0037] In the present invention, in step (3), the conditions for secondary calcination are calcination at 1450 °C for 40 - 45 min.

[0038] The present invention will be described in detail below through examples. It should be understood that the following examples are only used to further explain and illustrate the content of the present invention by way of example, and are not used to limit the present invention. Among them, Example 1 is the best example of the present invention.

[0039] The chemical additives used in the examples and comparative examples of the present invention are all commercially available, and the specific information is as follows: Limestone: particle size 40 - 80 mm, purchased from Shandong Zhongxin Calcium Industry Co., Ltd.; Wollastonite: 80 mesh, Xinyu Southern 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, absolute 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.

[0040] Example 1 A kind of cement clinker for high-speed railway described in this embodiment comprises raw materials in the following mass parts: 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 by composite acid, and the composite acid is 5% of the mass of the steel slag; the composite acid comprises formic acid and acetic acid with a mass ratio of 2.5:1, the steel slag comprises first steel slag with an average particle size of 40 - 70 μm and 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.

[0041] The preparation method of the cement clinker for high-speed railway comprises the following steps: (1) Mix formic acid and acetic acid evenly according to the proportion, add absolute ethanol and stir evenly to obtain a composite acid solution with a mass concentration of 82%; drop the composite acid solution into the first steel slag and the second steel slag, control the dropping speed at 1 s / drop, stir and react for 2.5 h, and dry to obtain the modified steel slag; (2) Crush, grind and mix limestone, wollastonite, kaolin, fly ash, gypsum, fluorite and modified steel slag respectively to obtain cement raw meal; control the fineness of the cement raw meal so that the residue on a 80-μm square-hole sieve is controlled at 15 ± 2 wt%; (3) Calcinate the cement raw meal once and then twice in sequence, and use a blower to blow air for rapid cooling to room temperature. The rotational speed of the blower is 3000 r / min to obtain the cement clinker for high-speed railway. Among them, the conditions for the first calcination are calcination at 1350 °C for 35 min with a heating rate of 10 °C / min; the conditions for the second calcination are calcination at 1450 °C for 40 min with a heating rate of 10 °C / min.

[0042] Example 2 A kind of cement clinker for high-speed railway described in this embodiment comprises raw materials in the following mass parts: 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 by composite acid, and the composite acid is 6% of the mass of the steel slag; the composite acid comprises formic acid and acetic acid with a mass ratio of 3:1, the steel slag comprises first steel slag with an average particle size of 40 - 70 μm and 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.

[0043] The preparation method of the cement clinker for high-speed railway comprises the following steps: (1) Mix formic acid and acetic acid evenly according to the proportion, add absolute ethanol and stir evenly to obtain a composite acid solution with a mass concentration of 85%; drop the composite acid solution into the first steel slag and the second steel slag, control the dropping speed at 2 s / drop, stir and react for 3 h, and dry to obtain the modified steel slag; (2) Crush, grind, and mix limestone, wollastonite, kaolin, fly ash, gypsum, fluorite, and modified steel slag evenly to obtain raw cement material; control the residue on a 80μm square-hole sieve of the raw cement material to be within 15±2wt%. (3) Conduct primary calcination and secondary calcination on the raw cement material in sequence, and use a blower to blow air for rapid cooling to room temperature. The rotational speed of the blower is 3500r / min to obtain the cement clinker for high-speed rail. Among them, the conditions for primary calcination are calcination at 1350°C for 30min with a heating rate of 15°C / min; the conditions for secondary calcination are calcination at 1450°C for 45min with a heating rate of 15°C / min.

[0044] Example 3 A cement clinker for high-speed rail in this example 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; among them, the modified steel slag is steel slag modified by compound acid, and the compound acid is 4% of the mass of the steel slag; the compound acid includes formic acid and acetic acid with a mass ratio of 2:1, and the steel slag includes first steel slag with an average particle size of 40-70μm and second steel slag with an average particle size of 20-30μm, and the mass ratio of the first steel slag to the second steel slag is 3:1.

[0045] The preparation method of the cement clinker for high-speed rail includes the following steps: (1) Mix formic acid and acetic acid evenly in proportion, add absolute ethanol and stir evenly to obtain a compound acid solution with a mass concentration of 80%; drop the compound acid solution into the first steel slag and the second steel slag, control the dropping speed to be 1s / drop, stir and react for 2h, and dry to obtain modified steel slag; (2) Crush, grind, and mix limestone, wollastonite, kaolin, fly ash, gypsum, fluorite, and modified steel slag evenly to obtain raw cement material; control the residue on a 80μm square-hole sieve of the raw cement material to be within 15±2wt%. (3) Conduct primary calcination and secondary calcination on the raw cement material in sequence, and use a blower to blow air for rapid cooling to room temperature. The rotational speed of the blower is 3000r / min to obtain the cement clinker for high-speed rail. Among them, the conditions for primary calcination are calcination at 1400°C for 35min with a heating rate of 5°C / min; the conditions for secondary calcination are calcination at 1450°C for 40min with a heating rate of 10°C / min.

[0046] Comparative Example 1 The preparation method of the cement clinker for high-speed rail in this comparative example is the same as that of Example 1, except that the compound acid is 8% of the mass of the steel slag.

[0047] Comparative Example 2 The preparation method of the cement clinker for high-speed rail described in this comparative example is the same as that of Example 1, except that the composite acid is 2% of the mass of the steel slag.

[0048] Comparative Example 3 The preparation method of the cement clinker for high-speed rail described in this comparative example is the same as that of Example 1, except that the composite acid includes formic acid and acetic acid with a mass ratio of 1:1.

[0049] Comparative Example 4 The preparation method of the cement clinker for high-speed rail described in this comparative example is the same as that of Example 1, except that the composite acid includes formic acid and acetic acid with a mass ratio of 5:1.

[0050] Comparative Example 5 The preparation method of the cement clinker for high-speed rail described in this comparative example is the same as that of Example 1, except that the mass ratio of the first steel slag to the second steel slag is 1:1.

[0051] Comparative Example 6 The preparation method of the cement clinker for high-speed rail described in this comparative example is the same as that of Example 1, except that the mass ratio of the first steel slag to the second steel slag is 8:1.

[0052] Comparative Example 7 The preparation method of the cement clinker for high-speed rail described in this comparative example is the same as that of Example 1, except that step (3) is: calcining the cement raw meal, and rapidly cooling it to room temperature by blowing air with a blower, the rotational speed of the blower is 3000 r / min, to obtain the cement clinker for high-speed rail. Among them, the conditions for the calcination are calcining at 1350 °C for 75 min, and the heating rate is 5 °C / min.

[0053] Performance Test The cement clinkers described in Examples 1-3 and Comparative Examples 1-7 were subjected to performance tests according to the following method, and the specific results are shown in Table 1.

[0054] Content of f-CaO in cement clinker: Using strontium nitrate as a catalyst and phenolphthalein as an indicator, reacting the sample with glycerol anhydrous ethanol solution at 160 - 170 °C to generate calcium glycerolate, and titrating with benzoic acid anhydrous ethanol standard titration solution. Calculate the content of f-CaO in the cement clinker according to the volume of the benzoic acid anhydrous ethanol standard titration solution consumed during the titration.

[0055] Table 1 Performance Data of Cement Clinkers in Examples 1-3 and Comparative Examples 1-7 。

[0056] 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 during the long-term hydration process, the cement is not prone to expansion and cracking and has good durability.

[0057] The cement clinkers described in Examples 1-3 and Comparative Examples 1-7 were subjected to performance tests according to the following method, and the specific results are shown in Table 2.

[0058] Setting time: Tested in accordance with Standard GB / T1346-2011.

[0059] Flexural strength and compressive strength: Cured for 3 days, 28 days, and 90 days respectively in accordance with Standard GB / T17671-2021 to test the strength performance of the cement.

[0060] Table 2 Cement performance data in Examples 1-3 and Comparative Examples 1-7

[0061] As can be seen from Table 2, the flexural strength and compressive strength of the cement described in Examples 1-3 of the present invention at different days are relatively high. Among them, the 3d compressive strength of the cement in Example 1 exceeds 37 MPa, the 28d compressive strength exceeds 68 MPa, and the 90d compressive strength exceeds 83 MPa. By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the mass content of the composite acid in Comparative Examples 1 and 2 is too high or too low, and its short-term and long-term flexural strength and compressive strength are significantly reduced, indicating that the content of the composite acid needs to be strictly controlled. Too high or too low content will affect the modification effect, and thus affect the hydration activity and strength. By comparing Example 1 with Comparative Examples 3 and 4, it can be seen that the proportion of formic acid in the composite acid in Comparative Example 3 is too low, and its short-term strength decreases significantly. The proportion of acetic acid in Comparative Example 4 is too low, and its long-term strength decreases significantly, indicating that the proportion relationship between the two in the composite acid is crucial for the activity and strength. The change in the proportion will reduce the synergistic effect of the two, thus affecting the performance. By comparing Example 1 with Comparative Examples 5 and 6, it can be seen that the mass ratio of the first steel slag and the second steel slag in Comparative Examples 5 and 6 is different, and their short-term and long-term strengths are significantly reduced, indicating that there is a synergistic effect between the two different particle size steel slags, jointly improving the cement activity and strength. By comparing Example 1 with Comparative Example 7, it can be seen that the calcination conditions in Comparative Example 7 are different, and its activity and strength are affected, indicating that the secondary calcination conditions of the present invention can improve the performance of the cement more than the primary calcination.

[0062] It can be seen that in the present invention, by adding a certain amount of steel slag modified by a composite acid, especially steel slag modified by formic acid and acetic acid with a specific mass ratio, the two synergistically improve the hydration activity and long-term performance of the modified steel slag. On the one hand, since acetate ions can optimize the pore size of cement materials and have a good promoting effect on the long-term compressive strength of cement materials, and calcium formate, the hydration product of formic acid-modified steel slag, 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 interlocking effect between steel slag particles and between steel slag particles and hydration products, forming a denser microstructure, thereby significantly increasing the compressive strength of cement materials. In addition, the present invention uses two kinds of steel slag with a specific mass ratio for compounding, and after modification, it can simultaneously have high hydration activity and compressive strength, 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.

[0063] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly explaining the present invention, rather than limitations on the implementation modes of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made on the basis of the above description. It is impossible to enumerate all the implementation modes here. Any obvious changes or variations derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A cement clinker for high-speed railway, characterized in that: The invention comprises the following raw materials in parts by weight: 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 by composite acid, and the composite acid accounts for 4-6% of the mass of the steel slag.

2. The cement clinker for high-speed railway according to claim 1, characterized in that: The composite acid comprises formic acid and acetic acid in a mass ratio of 3:1-2:

1.

3. The cement clinker for high-speed railway according to claim 1, characterized in that: The steel slag includes a first steel slag having an average particle size of 40-70 μm and a second steel slag having an average particle size of 20-30 μm.

4. The cement clinker for high-speed railway according to claim 3, characterized in that: The mass ratio of the first steel slag to the second steel slag is 3:1-5:

1.

5. A method for preparing cement clinker for high-speed railway according to any one of claims 1 to 4, characterized in that: The steps include: (1) adding the composite acid solution dropwise to the steel slag, stirring to react for 2-3 hours, and drying to obtain modified steel slag; (2) crushing and grinding limestone, wollastonite, kaolin, fly ash, gypsum, fluorite and modified steel slag respectively, and mixing them evenly 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.

6. A method for preparing cement clinker for high-speed railway according to claim 5, 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%.

7. A method for preparing cement clinker for high-speed railway according to claim 5, characterized in that: In step (1), the dropping speed is 1-2 s / drop.

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

9. A method for preparing cement clinker for high-speed railway according to claim 5, characterized in that: In step (3), the conditions for the first calcination are calcination at 1350-1400° C. for 30-35 min.

10. A method for preparing cement clinker for high-speed rail according to claim 5, characterized in that: In step (3), the secondary calcination is carried out at 1450° C. for 40-45 min.

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