Preparation method of sulphoaluminate cement clinker

Abstract

The invention discloses a preparation method of sulphoaluminate cement clinker, and belongs to the technical field of materials. According to the sulphoaluminate cement clinker, limestone, anhydrite, bauxite, fly ash and harmless aluminum slag are used as raw materials, and industrial fluorite waste residues with the CaF2 content being 75-80 wt% are used as mineralizing agents; the amount of the industrial fluorite waste residues accounts for 0.08-1.2 wt% of the total amount of the raw materials; the preparation method of the sulphoaluminate cement clinker comprises the following steps: matching and weighing the raw materials according to the chemical composition, adding the fluorite waste residue to prepare a raw material, and carrying out ball milling and calcining to obtain the clinker. The early strength of the sulphoaluminate cement clinker is improved by externally doping a certain amount of fluorite waste residues into the sulphoaluminate cement raw material, meanwhile, the later strength can be prevented from being reduced without doping limestone or using other modification methods, and the performance of the sulphoaluminate cement is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of materials, and particularly relates to a method for preparing sulphoaluminate cement clinker. Background Art

[0002] The main mineral phases of sulphoaluminate cement clinker are anhydrous calcium sulphoaluminate (C4A3S), dicalcium silicate (C2S) and iron phase, and the CaO content is controlled in the range of 38-48%. Compared with ordinary Portland cement, its firing temperature is reduced by 150-200°C, and carbon emissions are reduced by 20-50%, highlighting the green advantages of the low-calcium cementitious system. After adding appropriate amounts of gypsum and limestone, the cement exhibits high early strength, rapid setting and hardening, and strong resistance to sulfate erosion, making it particularly suitable for marine engineering and low-temperature construction scenarios. Microstructural analysis shows that the rapid formation of calcium aluminoferrite (AFt) in its hydration products imparts excellent durability, but the slowdown in strength growth and potential shrinkage in the later period still need to be overcome through mineral phase regulation and hydration process optimization.

[0003] A large amount of fluorite waste slag derived from the fluorine chemical industry is rich in calcium fluoride (CaF2) resources, and its landfill disposal not only causes environmental pollution but also leads to a waste of fluorine resources. CaF2 plays a significant role in cement clinker production as a mineralizer: it can effectively improve the burnability of raw materials and enhance the quality of clinker by promoting the decomposition of carbonate and aluminosilicate minerals, accelerating the volatilization of alkali metal oxides and the breaking of silicon-oxygen bonds. Existing research focuses on the modification of ordinary Portland cement by CaF2, while its mechanism of influence on the burning process of sulphoaluminate cement is still unclear. Although some studies have attempted to prepare alite-sulphoaluminate cement by introducing CaF2, this type of system leads to mineral phase reconstruction due to excessive C3S content, which is manifested as an increase in standard consistency water demand and reduced engineering applicability. In addition, the high CaO content deviates from the low-carbon development orientation. It is urgent to explore new paths for the synergistic utilization of fluorine resources and the greening of sulphoaluminate cement.

[0004] Therefore, providing a sulphoaluminate cement clinker that not only ensures its high early strength but also avoids the shrinkage of the later strength without the need for other modification methods, so that the later strength increases steadily and meets engineering applications has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing sulphoaluminate cement clinker, so as to solve the problems of uncoordinated early and late strength development, late strength shrinkage, poor engineering applicability and the like of ordinary sulphoaluminate cement.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] The invention discloses a method for preparing sulphoaluminate cement clinker. The sulphoaluminate cement clinker uses limestone, anhydrite, bauxite, fly ash and harmless aluminum slag as raw materials, and uses industrial fluorite waste slag as a mineralizer. The content of CaF2 in the industrial fluorite waste slag is 75-80 wt%, and the amount of the industrial fluorite waste slag accounts for 0.08-1.2 wt% of the total raw material amount.

[0008] The preparation method of the sulphoaluminate cement clinker comprises the following steps:

[0009] S1. Dry and crush each raw material separately and store them in warehouse;

[0010] S2. The raw materials are mixed and weighed according to their chemical composition, and fluorite waste residue is added to make raw meal, which is then ball-milled and calcined in a new dry kiln to obtain clinker.

[0011] In some embodiments of the present invention, the decomposition furnace temperature is controlled at 900°C, and the calcination temperature is controlled at 1250-1350°C.

[0012] In some embodiments of the present invention, the chemical composition of cement clinker includes:

[0013] SiO2 7.90~8.80%

[0014] Al2O3 31.20~32.00%

[0015] Fe2O3 2.50~4.00%

[0016] CaO 42.00~43.10%

[0017] MgO 1.20~2.00%

[0018] SO3 9.50~10.50%

[0019] f-CaO 0~1.00%

[0020] f-CaSO4 2.00~5.00%.

[0021] In some embodiments of the present invention, the chemical composition of cement clinker includes:

[0022] SiO2 8.20~8.70%

[0023] Al2O3 31.40~32.00%

[0024] Fe2O3 2.60~4.00%

[0025] CaO 42.50~43.10%

[0026] MgO 1.40~2.00%

[0027] SO3 9.90~10.40%

[0028] f-CaO 0.30~0.80%

[0029] f-CaSO4 3.00~4.00%.

[0030] In some embodiments of the present invention, the amount of industrial fluorite waste slag accounts for 0.06 to 0.8 wt % of the total raw material.

[0031] In some embodiments of the present invention, the CaF2 content of industrial fluorite waste slag is 78 wt%, and the amount of industrial fluorite waste slag accounts for 0.6 wt% of the total raw material.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention, scientifically designed and ingeniously conceived, aims to improve the performance of sulfoaluminate cement clinker by utilizing fluorite waste slag, while simultaneously avoiding significant changes in the mineral composition and maintaining good working performance. By adding an appropriate amount of fluorite waste slag to the sulfoaluminate cement raw meal, the early strength of the sulfoaluminate cement clinker is increased while avoiding later strength reduction without the need for limestone addition or other modification methods, thereby improving the performance of the sulfoaluminate cement.

[0034] The clinker prepared by the present invention can be used to prepare sulphoaluminate cement with high early strength and steadily increasing late strength. The 3h compressive strength reaches 16.0MPa and the 28d compressive strength reaches 62.2MPa, solving the problem of unbalanced development of early strength and late strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the X-ray diffraction pattern of sulphoaluminate cement clinker. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] The limestone, anhydrite, bauxite, fly ash and harmless aluminum slag used in the embodiments of the present invention are all common raw materials used in cement industry production. The CaF2 content of the industrial fluorite waste slag is 75%.

[0038] Table 1 Main chemical composition of raw materials (wt%)

[0039] name <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO <![CDATA[SO3]]> LOI limestone 4.77 0.31 0.19 51.96 0.84 0.00 41.91 Anhydrite 2.63 0.36 0.59 35.38 2.00 46.96 10.26 Bauxite 8.18 74.06 1.18 0.14 0.77 0.00 12.15 fly ash 51.21 20.06 5.12 4.16 1.19 1.11 14.70 Harmless aluminum slag 3.24 76.68 0.20 5.56 2.09 0.54 -2.35

[0040] Examples and Comparative Examples

[0041] Table 2 Ingredients

[0042]

[0043]

[0044] The preparation method of the cement clinker of embodiment and comparative example is as follows:

[0045] S1. Dry and crush each raw material separately and store them in warehouse;

[0046] S2. The raw materials are mixed and weighed according to their chemical composition, and fluorite waste residue is added to make raw meal, which is then ball-milled and calcined in a new dry kiln to obtain clinker; the decomposition furnace temperature is controlled at 900°C, and the calcination temperature is controlled at 1250-1350°C.

[0047] The flexural strength and compressive strength of the clinker were measured according to the test method described in GB / T 37125-2018. The results are shown in Table 3:

[0048] Table 3 Physical properties of sulphoaluminate cement clinker

[0049]

[0050] Comparison results show that Examples 1 and 2 have significant advantages in both early and late strength. This is because Examples 1 and 2 generate a certain amount of tricalcium silicate while maintaining a relatively high content of dicalcium silicate. Consequently, the early strength gain rate is large, and the late strength can also develop steadily.

[0051] Sulphoaluminate cement was prepared with 88% clinker and 12% anhydrite. The mechanical properties of the cement were tested according to the test method described in GB / T 20472-2006. The mechanical properties are shown in Table 4.

[0052] Table 4 Mechanical properties of sulphoaluminate cement

[0053]

[0054] As can be seen from Table 4, the mechanical properties of the cements of Examples 1 and 2 are significantly improved. Comparative Example 1 still has a decline in flexural performance and a slow increase in late strength, while the flexural strength of Example 1 does not shrink, and the 28d flexural strength reaches 9.4MPa. The 3h compressive strength of Example 1 is more than three times higher than that of Comparative Example 1, and the 28d strength is 7.4MPa higher than that of Comparative Example 1. Since the amount of fluorite waste residue added in Example 2 is reduced, the improvement in cement performance is weaker than that in Example 1, but it can also improve the early strength and steadily improve the late strength. This shows that the early strength of sulphoaluminate cement clinker can be improved by the method of the present invention, and the late flexural and compressive strength can be prevented from shrinking without the addition of limestone or the use of other modification methods, thereby improving the performance of sulphoaluminate cement.

[0055] The above is only a preferred embodiment of the invention and does not impose any formal limitation on the invention. Based on the technical essence of the invention and within the spirit and principles of the invention, any simple modification, equivalent replacement and improvement of the above embodiment shall still fall within the scope of protection of the technical solution of the invention.

Claims

1. A method for preparing sulphoaluminate cement clinker, characterized in that: The sulphoaluminate cement clinker is made of limestone, anhydrite, bauxite, fly ash and harmless aluminum slag as raw materials, and industrial fluorite waste slag is used as a mineralizer; wherein the CaF2 content of the industrial fluorite waste slag is 75-80wt%, and the amount of the industrial fluorite waste slag accounts for 0.08-1.2wt% of the total raw materials; The preparation method comprises the following steps: S1. Dry and crush each raw material separately and store them in warehouse; S2. The raw materials are mixed and weighed according to their chemical composition, and fluorite waste residue is added to make raw meal, which is then ball-milled and calcined in a new dry kiln to obtain clinker.

2. The method for preparing sulphoaluminate cement clinker according to claim 1, wherein The chemical composition of cement clinker includes: SiO2 7.90~8.80% Al2O3 31.20~32.00% Fe2O3 2.50~4.00% CaO 42.00~43.10% MgO 1.20~2.00% SO3 9.50~10.50% f-CaO 0~1.00% f-CaSO4 2.00~5.00%.

3. The method for preparing sulphoaluminate cement clinker according to claim 1, wherein: The chemical composition of cement clinker includes: SiO2 8.20~8.70% Al2O3 31.40~32.00% Fe2O3 2.60~4.00% CaO 42.50~43.10% MgO 1.40~2.00% SO3 9.90~10.40%. f-CaO 0.30~0.80% f-CaSO4 3.00~4.00%.

4. The method for preparing sulphoaluminate cement clinker according to claim 1, wherein: The amount of industrial fluorite waste residue added to the total raw material is 0.6-0.8wt%.

5. The method for preparing sulphoaluminate cement clinker according to claim 1, wherein: The CaF2 content of industrial fluorite waste slag is 78.0wt%, and the amount of industrial fluorite waste slag accounts for 0.6wt% of the total raw material.

6. The method for preparing sulphoaluminate cement clinker according to claim 1, wherein: The decomposition furnace temperature is controlled at 900°C, and the calcination temperature is controlled at 1250-1350°C.

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