A high-performance cement clinker based on lithium slag ion doping and crystal form regulation, a preparation method and application thereof

Abstract

The application discloses a kind of high-performance cement clinker based on lithium residue ion doping and crystal form regulation and its preparation method and application, belong to cement building material technical field.The raw material of the cement clinker includes the following mass percentage fraction: lithium residue 20~40%, calcium carbonate 50~70%, dihydrate gypsum 10~20% and di-aluminum oxide 2~6%;The minerals in the cement clinker include: C4A3:20%~35%, C2:50%~65%, C:5%~15%, the remainder is inevitable impurities by mass percentage.After the above raw materials are slurried with water, pressure forming is carried out, two-stage heating is sequentially carried out once sintering, and then quenching is carried out, and the cement clinker is obtained.The cement obtained from the cement clinker has excellent fast-setting and fast-hardening properties, and the compressive strength can reach more than 25MPa at 6h, and the compressive strength at 1d can reach more than 40MPa, which fundamentally solves the technical problems of poor early hydration performance, low strength and reverse shrinkage of high belite sulphoaluminate cement in the prior art.

Description

Technical Field

[0001] This invention relates to a high belite sulfoaluminate cement clinker, specifically to a high-performance cement clinker based on lithium slag ion doping and crystal form control, its preparation method and application, belonging to the field of cement building materials technology. Background Technology

[0002] Lithium is the most important component in modern batteries and a key material for future technological development. Lithium carbonate, a crucial raw material for electric vehicle batteries, is experiencing a continuous increase in both production capacity and consumption. Lithium slag, a byproduct of the lithium carbonate extraction industry, is seeing a rapid increase in both production and inventory due to the industry's rapid growth. According to relevant surveys, domestic lithium slag inventory has already reached 1.2 billion tons and is growing rapidly at a rate of 12 million tons per year. This accumulated lithium slag not only occupies land resources but also poses a serious threat to surrounding soil and water quality due to residual sulfides and harmful elements.

[0003] High belite sulfoaluminate (HB-CSA) cement is a new type of sulfoaluminate cement with β-C2S as the main mineral phase (>50%). Compared with ordinary silicate cement, HB-CSA cement not only has the advantages of significantly reducing clinker calcination temperature and CO2 emissions, but also features low alkalinity and shrinkage compensation, and has lower requirements for raw material grades. Industrial solid wastes commonly found in industrial production, such as Ca-Al-Si-Fe based and CaSO4 based industrial solid wastes, both meet the raw material requirements for HB-CSA clinker in terms of chemical composition.

[0004] However, due to the C4A3 in HB-CSA cement With a lower β-C2S content, HB-CSA undergoes slower overall hydration, losing the rapid hardening and early strength advantage that is most characteristic of sulfoaluminate cement (CSA). Simultaneously, the high β-C2S content and limited hydration activity result in minimal strength development in HB-CSA cement after 7 days. To improve the reactivity of HB-CSA, current technologies primarily employ external ion doping to modify C4A3. The lattice structure and crystal type of C2S promote the formation of c-C4A3. The α-C₂S crystal form is formed and stabilized at room temperature. Lafarge achieves α-C₂S crystal form stability by adding secondary elements to the raw material mixture to enhance the early hydration performance of cement clinker. However, the addition of these trace elements not only increases the production cost of cement clinker but also makes the clinker calcination process relatively complex, increasing the difficulty of industrial production.

[0005] In summary, how to comprehensively utilize lithium slag waste to obtain fast-setting and fast-hardening HB-CSA cement has become a focus of current market attention and is also one of the key technical challenges in realizing the resource utilization of solid waste materials. Summary of the Invention

[0006] To address the problems existing in the prior art, the first objective of this invention is to provide a high-performance cement clinker based on lithium slag ion doping and crystal form control. This cement clinker uses lithium slag as one of the raw materials, utilizing the impurity ions abundant in the lithium slag to control the C4A3 content. The crystal form of C2S, o-C4A3 β-C2S is converted into c-C4A3, which has higher hydration activity. It combines α'-C2S to significantly shorten the setting time of high belite sulfoaluminate cement, thereby effectively promoting the balanced development of early and late strength of cement.

[0007] The second objective of this invention is to provide a method for preparing high-performance cement clinker based on lithium slag ion doping and crystal structure control. This method first improves the density of the raw meal cake through high-pressure cold pressing, and then employs a two-stage calcination process to obtain the final product. The first calcination process primarily decomposes the carbonates in the raw meal, while the second calcination process mainly improves the clinker crystal structure through the impurities in the lithium slag, thereby effectively enhancing the hydration activity of the cement clinker.

[0008] The third objective of this invention is to provide an application of high-performance cement clinker based on lithium slag ion doping and crystal form control for the preparation of high-belite sulfoaluminate cement. Based on the characteristics of the obtained cement clinker, its use in the preparation of high-belite sulfoaluminate cement can significantly improve its comprehensive mechanical properties. Testing shows that the high-belite sulfoaluminate cement obtained from this cement clinker exhibits excellent rapid setting and hardening properties, with an initial setting time of less than 10 minutes and a final setting time of less than 20 minutes. Furthermore, its compressive strength reaches over 25 MPa at 6 hours and over 40 MPa at 1 day, fundamentally solving the technical problems of poor early hydration performance and low strength in existing high-belite sulfoaluminate cement.

[0009] To achieve the above technical objectives, this invention provides a high-performance cement clinker based on lithium slag ion doping and crystal form control. The raw materials of the cement clinker include the following components by mass percentage: 20-40% lithium slag, 50-60% calcium carbonate, 10-20% gypsum dihydrate, and 2-8% aluminum oxide.

[0010] The minerals in the cement clinker, by mass percentage, include: C4A3 20%~40%, C2 50%~65%, C 5% to 15%, with the remainder being unavoidable impurities.

[0011] As a preferred embodiment, the raw materials of the cement clinker include the following components by mass percentage: 20-30% lithium slag, 50-60% calcium carbonate, 12-18% gypsum dihydrate and 5-6% aluminum oxide.

[0012] The raw materials used in the technical solutions provided in this invention must strictly adhere to the above requirements. Specifically, the raw meal design aims to minimize the use of aluminous materials, gypsum, and calcium oxide, while maximizing lithium slag utilization. Therefore, the C2S content in the clinker mineral phase is designed to be 50-65%. In the high belite sulfoaluminate cement clinker (HB-CSA), all silica and iron oxide are provided by lithium slag. Furthermore, the lithium slag also provides some calcium oxide and sulfur trioxide, as well as regulating C4A3. and C2 Impurity ions in the crystal form. If the lithium slag content is below this range, on the one hand, C2 The content will decrease, failing to meet the phase composition range of high belite sulfoaluminate cement clinker, and the utilization rate of lithium slag is low; on the other hand, with the decrease in lithium slag content, the content of impurity ions that regulate mineral crystal form decreases, so as not to achieve the purpose of regulating mineral phase crystal form.

[0013] The main function of calcium carbonate is to supplement the CaO required for the clinker firing reaction. If the CaO content is too low, calcium aluminum feldspar will be present in the clinker phase, reducing the compressive strength of the cement. If the CaO content is too high, free CaO will be present in the clinker phase, which can easily cause the cement to set too quickly.

[0014] The main function of gypsum dihydrate is to supplement the SO3 and CaO required for the clinker firing reaction. If the SO3 content is too low, the target amount of C4A3 cannot be generated. If the SO3 content is too high, there will be a large amount of free CaSO4 in the clinker phase, which will affect the setting of cement and the growth of its later strength.

[0015] The main function of aluminum oxide is to supplement the Al2O3 required for the clinker calcination reaction. If the Al2O3 content is too low, the target amount of C4A3 cannot be generated. If the Al2O3 content is too high, it will increase the production cost of cement clinker.

[0016] As a preferred embodiment, the minerals in the cement clinker also include 0% to 3% C4AF by mass percentage.

[0017] This invention also provides a method for preparing high-performance cement clinker based on lithium slag ion doping and crystal form control, comprising: grinding and sieving cement clinker raw materials sequentially, drying them thoroughly and mixing them evenly to obtain raw meal powder; mixing the raw meal powder with water to form a slurry, pressing it in a mold, drying it thoroughly to obtain raw meal cake; placing the raw meal cake in a muffle furnace for a first heating and calcination, and after the carbonates in the raw meal cake are completely decomposed, performing a second heating and calcination, and then rapidly cooling it to room temperature after calcination to obtain the final product.

[0018] Lithium slag, as a raw material for high-belite sulfoaluminate cement clinker, can reduce the amount of limestone and bauxite used in cement production, thereby reducing carbon dioxide emissions and cement production costs. During clinker sintering, the ions in the lithium slag act as mineralizers and crystal stabilizers, significantly lowering the formation temperature of clinker minerals and stabilizing the highly active c-C4A3. And α'-C2S. Further, highly active c-C4A3 Upon contact with water, it reacts rapidly, generating a large amount of early hydration products such as ettringite, which is the main source of cement's rapid setting and hardening characteristics. The hydration activity of α'-C2S is intermediate between that of C4A3. Between β-C2S and β-C2S, it serves as an intermediate hydrated mineral phase, filling the strength growth trough between early and late strength, and successfully preparing cement clinker with rapid hardening, early strength, stable growth, and no shrinkage.

[0019] As a preferred embodiment, the particle size of the cement clinker after grinding and sieving is 80 μm.

[0020] As a preferred embodiment, the thorough drying process is as follows: drying in an oven at 100~110℃ for 12~36 hours until the weight is constant.

[0021] As a preferred embodiment, the preparation process of the raw material cake is as follows: 15wt% water ion water is added to the raw material powder and mixed evenly, and then placed in a mold and pressed into shape at 20~30MPa to obtain the cake.

[0022] As a preferred embodiment, the sintering process is as follows: the temperature is increased from room temperature to 850-950℃ at a rate of 3-5℃ / min, and held at that temperature for 0.5-1.5 hours.

[0023] As a preferred embodiment, the secondary sintering process is as follows: the temperature is increased from 850~950℃ to 1250~1350℃ at a rate of 3~5℃ / min, and held for 1~2 hours; the rapid cooling method is air cooling at room temperature.

[0024] The sintering process is one of the key technical features of this invention. The primary heating and calcination stage serves to fully decompose the calcium carbonate in the raw materials at a relatively low temperature, preventing the subsequent high-temperature stage from causing a loose clinker structure due to gas generation from carbonate decomposition. The secondary heating and calcination stage, after the carbonates are completely decomposed, rapidly raises the temperature to a higher target firing temperature of 1250-1350℃. This stepped heating strategy ensures the optimal temperature for the main minerals C2S and C4A3. It forms efficiently and purely at the optimal temperature.

[0025] This invention also provides an application of high-performance cement clinker based on lithium slag ion doping and crystal form control, for the preparation of high belite sulfoaluminate cement.

[0026] As a preferred embodiment, the preparation process of the high belite sulfoaluminate cement is as follows: the cement clinker described in claim 1 or 2 is crushed and then gypsum is added, followed by grinding and sieving to obtain the cement.

[0027] As a preferred embodiment, the amount of gypsum added is 3 to 8 wt% of the cement clinker.

[0028] As a preferred embodiment, the grinding method is planetary ball milling, with the following conditions: the ratio of small, medium and large grinding balls is 4~6:2~3:1~2, the ball-to-material ratio is 1~3:1, the revolution speed is 200~300 r / min, and the ball milling time is 30~60 min.

[0029] The technical solution provided by this invention uses lithium slag to perform ion doping and crystal form control on HB-CSA. The lithium slag contains ions such as Li, K, Na, Mg, B, and Fe. This invention utilizes the ions in the lithium slag as mineralizing agents and crystal form stabilizers to control the core mineral phase C2 in high-belite sulfoaluminate cement clinker at the crystal lattice scale. and C4A3 Targeted regulation is implemented. K, Na, and Fe ions from lithium slag enter C4A3 through solid solution. The c-C4A3 has been stabilized. Under high SO3 conditions, Li, Mg, and B dissolve into C2S, inducing lattice distortion and stabilizing α'-C2S. The hydration reactivity of α'-C2S is intermediate between that of C4A3. Between β-C2S and β-C2S, it serves as an intermediate hydrated mineral phase, filling the trough in strength growth between early and late strength, thus constructing an ideal mineral system with rapid hardening, early strength, and stable strength growth, solving the problems of low early strength and weak strength growth in traditional high belite sulfoaluminate cement.

[0030] Compared with existing technologies, the superior technical effects of the technical solution provided by this invention are as follows:

[0031] 1) The high belite sulfoaluminate cement clinker provided by this invention uses lithium slag as one of the raw materials, and utilizes the impurity ions rich in lithium slag to regulate C4A3. The crystal form of C2S, o-C4A3 β-C2S is converted into c-C4A3, which has higher hydration activity. and α' H -C2S significantly shortens the setting time of high belite sulfoaluminate cement, thereby effectively promoting the balanced development of early and late strength of cement.

[0032] 2) In the preparation method provided by the present invention, the density of the raw meal cake is first improved by high pressure cold pressing, and then a two-stage calcination process is adopted to obtain the product. The first heating calcination process mainly decomposes the carbonate in the raw meal, and the second heating calcination process mainly improves the clinker crystal form by the impurity ions in the lithium slag, thereby effectively improving the hydration activity of cement clinker.

[0033] 3) In the technical solution provided by this invention, based on the characteristics of the cement clinker obtained above, its use in preparing high belite sulfoaluminate cement can significantly improve its comprehensive mechanical properties. Testing shows that the high belite sulfoaluminate cement obtained from this cement clinker exhibits excellent rapid setting and hardening properties, with an initial setting time of less than 10 minutes and a final setting time of less than 20 minutes. Furthermore, its compressive strength reaches over 25 MPa at 6 hours and over 40 MPa at 1 day, fundamentally solving the technical problems of poor early hydration performance and low strength in existing high belite sulfoaluminate cement. Attached Figure Description

[0034] Figure 1 The XRD pattern of the cement clinker obtained in Example 1 of this invention;

[0035] Figure 2 The XRD pattern of the cement clinker obtained in Example 2 of this invention;

[0036] Figure 3 The XRD pattern of the cement clinker obtained in Comparative Example 1 of this invention;

[0037] Figure 4 The image shows the XRD pattern of the cement clinker obtained in Comparative Example 2 of this invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying tables. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] The chemical composition of the lithium slag used in the embodiments and comparative examples provided by this invention is shown in Table 1.

[0040]

[0041] Example 1

[0042] This embodiment provides a high-performance cement clinker based on lithium slag ion doping and crystal form control, and its specific preparation process is as follows:

[0043] 1) Weigh out 56.13% calcium carbonate, 13.11% gypsum dihydrate, 25.20% lithium slag and 5.55% aluminum oxide by mass percentage, grind the above raw materials into powder using a planetary ball mill until they completely pass through an 80 μm sieve, and dry them thoroughly in a 105 ℃ forced-air drying oven for 24 h to obtain raw meal powder;

[0044] 2) After mixing and preparing the raw material powder with 15wt% deionized water, press it into a 50 mm × 8 mm cylinder using a steel clamp with a molding pressure of about 25 MPa, and then dry it thoroughly in a 105 ℃ forced-air drying oven for 24 h.

[0045] 3) Place the formed raw meal into a muffle furnace and raise the temperature from room temperature to 900℃ at a rate of 5℃ / min and hold for 30 minutes to fully decompose the calcium carbonate in the raw meal. Then raise the temperature of the silicon molybdenum rod muffle furnace to 1300℃ and hold for 1 hour. After the holding time is over, the test cake is quickly taken out and rapidly cooled to room temperature using an electric fan to obtain high belite sulfoaluminate cement clinker.

[0046] The present invention also conducted XRD tests on the obtained high-belite sulfoaluminate cement clinker, and the results are shown in Table 2 and... Figure 1 As shown.

[0047]

[0048] In this embodiment, the obtained cement clinker is mixed with gypsum to prepare high belite sulfoaluminate cement. The specific process is as follows: the cement clinker is crushed by a jaw crusher, then further ground by a pulverizer, and 6.40 wt% anhydrous gypsum is added. Then it is placed in a vertical planetary ball mill for grinding. The ball mill has a small, medium and large ball ratio of 5:3:2, a ball-to-material ratio of 2:1, a revolution speed of 300 r / min, and a ball milling time of 30 min. After the powder is cooled, it is passed through an 80 μm sieve to obtain high belite sulfoaluminate cement.

[0049] The specific surface area of ​​high-belite sulfoaluminate cement was tested using a Bosch specific surface area and air permeability meter. The standard consistency water requirement and setting time of high-belite sulfoaluminate cement were determined according to GB / T "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". The compressive strength of high-belite sulfoaluminate cement was tested using 20×20×20 mm cube specimens at a water-cement ratio of 0.4. The test results are shown in Table 3.

[0050]

[0051] Figure 1 The XRD pattern of the cement clinker in this embodiment is obtained by... Figure 1 It can be seen that the main mineral phases of the cement clinker in Example 1 include C2S and C4A3. And f-CaSO4 and some trace minerals, including C2S including two crystal forms, β-C2S and α-C2S, C4A3 Including c-C4A3 and o-C4A3 Two crystal forms were observed. Quantitative analysis revealed the main mineral phase contents of the cement clinker, as shown in Table 2, including 40.80% β-C2S, 18.50% α-C2S, and 11.00% c-C4A3. 19.60%o- C4A3 The composition was 7.20% f-CaSO4 and 0.70% C4AF. Table 3 shows that the initial setting time of HB-CSA prepared by adding 8 wt% anhydrous gypsum was 8 min, the final setting time was 18 min, and the compressive strength at 6 h and 1 d reached 28.50 MPa and 43.30 MPa, respectively. This is mainly due to the K, Na, Fe and other ions in the lithium slag entering C4A3 through solid solution. The c-C4A3 has been stabilized. Highly active c-C4A3 and o-C4A3 Upon contact with water, it rapidly reacts with anhydrous gypsum to produce a large amount of early hydration products such as ettringite. Under high SO3 conditions, α'-C2S, stabilized by the solid solution of Li, Mg, and B ions, serves as an intermediate hydration mineral phase, filling the gap in C4A3. The strength growth trough between β-C2S and β-C2S resulted in a stable strength increase, with the compressive strength increasing to 55.10 MPa at 3 days and 72.90 MPa at 7 days. Towards the later stages of hydration, as β-C2S begins to hydrate, the compressive strength reaches 91.50 MPa at 28 days.

[0052] Example 2

[0053] This embodiment provides a high-performance cement clinker based on lithium slag ion doping and crystal form control, and its specific preparation process is as follows:

[0054] 1) Weigh out 56.13% calcium carbonate, 13.11% gypsum dihydrate, 25.20% lithium slag and 5.55% aluminum oxide by mass percentage, grind the above raw materials into powder using a planetary ball mill until they completely pass through an 80 μm sieve, and dry them thoroughly in a 105 ℃ forced-air drying oven for 24 h to obtain raw meal powder;

[0055] 2) After mixing and preparing the raw material powder with 15wt% deionized water, press it into a 50 mm × 8 mm cylinder using a steel clamp with a molding pressure of about 25 MPa, and then dry it thoroughly in a 105 ℃ forced-air drying oven for 24 h.

[0056] 3) Place the formed raw meal into a muffle furnace and raise the temperature from room temperature to 900℃ at a rate of 5℃ / min and hold for 30 min to fully decompose the calcium carbonate in the raw meal. Then raise the temperature of the silicon molybdenum rod muffle furnace to 1350℃ and hold for 1 hour. After the holding time is over, the test cake is quickly taken out and cooled to room temperature by electric fan to obtain high belite sulfoaluminate cement clinker.

[0057] The present invention also conducted XRD tests on the obtained high-belite sulfoaluminate cement clinker, and the results are shown in Table 4 and... Figure 2 As shown.

[0058]

[0059] In this embodiment, the obtained cement clinker is mixed with gypsum to prepare high belite sulfoaluminate cement. The specific process is as follows: the cement clinker is crushed by a jaw crusher, then further ground by a pulverizer, and 7.50 wt% anhydrous is added. Then it is placed in a vertical planetary ball mill for grinding. The ball mill has a small, medium and large grinding ball ratio of 5:3:2, a ball-to-material ratio of 2:1, a revolution speed of 300 r / min, and a ball milling time of 30 min. After the powder is cooled, it is passed through an 80 μm sieve to obtain high belite sulfoaluminate cement.

[0060] The specific surface area of ​​high belite sulfoaluminate cement was tested using a Bosch specific surface area and air permeability meter. The standard consistency water requirement and setting time of high belite sulfoaluminate cement were determined according to GB / T "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". The compressive strength of high belite sulfoaluminate cement was tested using 20×20×20 mm cube specimens at a water-cement ratio of 0.4. The test results are shown in Table 5.

[0061]

[0062] Figure 2 As shown, the main mineral phases of the cement clinker in Example 2 include C2S and C4A3. And f-CaSO4 and some trace minerals, including C2S including two crystal forms, β-C2S and α-C2S, C4A3 Including c-C4A3$ and o-C4A3 Two crystal forms. Quantitative analysis revealed the main mineral phase contents of the cement clinker, as shown in Table 4, including 41.20% β-C2S, 21.70% α-C2S, and 9.50% c-C4A3. 20.00%o-C4A3 The composition was 5.60% f-CaSO4 and 0.10% C4AF. Table 5 shows that the initial setting time of HB-CSA prepared by adding 5 wt% anhydrous gypsum was 9 min, the final setting time was 19 min, and the compressive strength at 6 h and 1 d reached 26.40 MPa and 41.30 MPa, respectively. This is mainly due to the K, Na, Fe and other ions in the lithium slag entering C4A3 through solid solution. The c-C4A3 has been stabilized. Highly active c-C4A3 and o-C4A3 Upon contact with water, it rapidly reacts with anhydrous gypsum to produce a large amount of early hydration products such as ettringite. Under high SO3 conditions, α'-C2S, stabilized by the solid solution of Li, Mg, and B ions, serves as an intermediate hydration mineral phase, filling the gap in C4A3. The strength growth trough between β-C2S and β-C2S resulted in a stable strength increase, with the compressive strength increasing to 53.60 MPa at 3 days and 69.80 MPa at 7 days. Towards the later stages of hydration, as β-C2S begins to hydrate, the compressive strength reaches 86.30 MPa at 28 days.

[0063] Comparative Example 1

[0064] This comparative example provides a high-performance cement clinker based on lithium slag ion doping and crystal form control, and its specific preparation process is as follows:

[0065] 1) Weigh out 56.13% calcium carbonate, 13.11% gypsum dihydrate, 25.20% lithium slag and 5.55% aluminum oxide by mass percentage, grind the above raw materials into powder using a planetary ball mill until they completely pass through an 80 μm sieve, and dry them thoroughly in a 105 ℃ forced-air drying oven for 24 h to obtain raw meal powder;

[0066] 2) After mixing and preparing the raw material powder with 15wt% deionized water, press it into a 50 mm × 8 mm cylinder using a steel clamp with a molding pressure of about 25 MPa, and then dry it thoroughly in a 105 ℃ forced-air drying oven for 24 h.

[0067] 3) Place the formed raw meal into a muffle furnace and raise the temperature from room temperature to 900℃ at a rate of 5℃ / min and hold for 30 minutes to fully decompose the calcium carbonate in the raw meal. Then raise the temperature of the silicon molybdenum rod muffle furnace to 1250℃ and hold for 1 hour. After the holding time is over, the test cake is quickly taken out and rapidly cooled to room temperature using an electric fan to obtain high belite sulfoaluminate cement clinker.

[0068] The present invention also conducted XRD tests on the obtained high-belite sulfoaluminate cement clinker, and the results are shown in Table 6 and... Figure 3 As shown.

[0069]

[0070] This comparative example also involves mixing the obtained cement clinker with gypsum to prepare high belite sulfoaluminate cement. The specific process is as follows: the cement clinker is crushed by a jaw crusher, then further ground by a pulverizer, and 4.0 wt% anhydrous is added. Subsequently, it is placed in a vertical planetary ball mill for grinding. The ball mill has a small, medium and large ball ratio of 5:3:2, a ball-to-material ratio of 2:1, a revolution speed of 300 r / min, and a ball milling time of 30 min. After the powder is cooled, it is passed through an 80 μm sieve to obtain high belite sulfoaluminate cement.

[0071] The specific surface area of ​​high-belite sulfoaluminate cement was tested using a Bosch specific surface area and air permeability meter. The standard consistency water requirement and setting time of high-belite sulfoaluminate cement were determined according to GB / T "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". The compressive strength of high-belite sulfoaluminate cement was tested using 20×20×20 mm cube specimens at a water-cement ratio of 0.4. The test results are shown in Table 7.

[0072]

[0073] Figure 3 The results show that the main mineral phases of the cement clinker in Comparative Example 1 include C2S and C4A3. And f-CaSO4 and some trace minerals, including C2S including two crystal forms, β-C2S and α-C2S, C4A3 Including c-C4A3 and o-C4A3 Two crystal forms were observed. Quantitative analysis revealed the main mineral phase contents of the cement clinker, as shown in Table 2, including 58.50% β-C₂S, 0.9% α-C₂S, and 10.90% c-C₄A₃. 16.70%o-C4A3 , 8.30% f-CaSO4, 0.10% C4AF.

[0074] Table 7 shows that the initial setting time of HB-CSA prepared by adding 4 wt% anhydrous gypsum was 7 min, and the final setting time was 16 min. This is attributed to the fact that K, Na, Fe ions from lithium slag enter C4A3 through solid solution. The c-C4A3 has been stabilized. Highly active c-C4A3 and o-C4A3 Upon contact with water, it rapidly reacts with anhydrous gypsum to generate a large amount of early hydration products such as ettringite. In Comparative Example 1, the compressive strength of the cement reached 29.70 MPa at 6 hours and 46.90 MPa at 1 day. At a calcination temperature of 1250℃, due to the presence of only 0.9% α'-C2S, the compressive strength increased to 44.30 MPa at 3 days and 47.90 MPa at 7 days, respectively, with a relatively small increase in compressive strength in the later stages.

[0075] Comparative Example 2

[0076] This comparative example provides a high-performance cement clinker based on lithium slag ion doping and crystal form control, and its specific preparation process is as follows:

[0077] 1) Weigh out 57.32% calcium carbonate, 16.38% gypsum dihydrate, 13.94% silicon dioxide, 11.04% aluminum oxide and 0.59% ferric oxide by mass percentage, grind the above raw materials into powder using a planetary ball mill until they completely pass through an 80 μm sieve, and dry them thoroughly in a 105 ℃ forced-air drying oven for 24 h to obtain raw meal powder;

[0078] 2) After mixing and preparing the raw material powder with 15wt% deionized water, press it into a 50 mm × 8 mm cylinder using a steel clamp with a molding pressure of about 25 MPa, and then dry it thoroughly in a 105 ℃ forced-air drying oven for 24 h.

[0079] 3) Place the formed raw meal into a muffle furnace and raise the temperature from room temperature to 900℃ at a rate of 5℃ / min and hold for 30 minutes to fully decompose the calcium carbonate in the raw meal. Then raise the temperature of the silicon molybdenum rod muffle furnace to 1300℃ and hold for 1 hour. After the holding time is over, the test cake is quickly taken out and rapidly cooled to room temperature using an electric fan to obtain high belite sulfoaluminate cement clinker.

[0080] The present invention also conducted XRD tests on the obtained high-belite sulfoaluminate cement clinker, and the results are shown in Table 8 and... Figure 4 As shown.

[0081]

[0082] This comparative example also involves mixing the obtained cement clinker with gypsum to prepare high belite sulfoaluminate cement. The specific process is as follows: the cement clinker is crushed by a jaw crusher, then further ground by a pulverizer, and 5.80 wt% anhydrous gypsum is added. Subsequently, it is placed in a vertical planetary ball mill for grinding. The ball mill has a small, medium and large ball ratio of 5:3:2, a ball-to-material ratio of 2:1, a revolution speed of 300 r / min, and a grinding time of 30 min. After the powder is cooled, it is passed through an 80 μm sieve to obtain high belite sulfoaluminate cement.

[0083] The specific surface area of ​​high-belite sulfoaluminate cement was tested using a Bosch specific surface area and air permeability meter. The standard consistency water requirement and setting time of high-belite sulfoaluminate cement were determined according to GB / T "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". The compressive strength of high-belite sulfoaluminate cement was tested using 20×20×20 mm cube specimens at a water-cement ratio of 0.4. The test results are shown in Table 9.

[0084]

[0085] Figure 4 The results show that the main mineral phases of the cement clinker in Comparative Example 2 include C2S and C4A3. And f-CaSO4 and some trace minerals, including C2S including two crystal forms, β-C2S and α-C2S, C4A3 Including c-C4A3 and o-C4A3 Two crystal forms. Quantitative analysis revealed the main mineral phase contents of the cement clinker, as shown in Table 8, including 55.30% β-C₂S, 3.30% α'-C₂S, and 2.40% c-C₄A₃. 27.50%o-C4A3 7.50% f-CaSO4, 0.40% C4AF. Because cement clinker contains only 2.40% c-C4A3. The HB-CSA prepared by adding 6 wt% anhydrous gypsum had an initial setting time of 49 min, a final setting time of 201 min, and a 1-day compressive strength of only 7.90 MPa. This is mainly due to the lack of K, Na, and other ion-stabilized, highly reactive c-C4A3. Due to the lack of ionic solid solution stabilizers such as Li, Mg, and B, the cement clinker in Comparative Example 2 contained only 3.30% α'-C2S. The compressive strength at 3d and 7d increased to 32.90 MPa and 33.80 MPa, respectively, while the compressive strength at 28d only reached 38.60 MPa.

Claims

1. A high-performance cement clinker based on lithium slag ion doping and crystal form control, characterized in that: The raw materials of the cement clinker are composed of the following components by mass percentage: lithium slag 20-40%, calcium carbonate 50-60%, gypsum dihydrate 10-20%, and alumina 2-6%; The minerals in the cement clinker, by mass percentage, include: C4A3S: 20%–35%, C2S: 50%–65%, C2S: 5%–15%, with the remainder being unavoidable impurities; The cement clinker contains c-C4A3 as 9.5-11% of the mineral mass and α'-C2S as 18.5-21.7% of the mineral mass. The preparation process of the cement clinker includes: grinding and sieving the cement clinker raw materials in sequence, drying them thoroughly and mixing them evenly to obtain raw meal powder; mixing the raw meal powder with water to form a slurry, pressing it into shape in a mold, drying it thoroughly to obtain raw meal cake; placing the raw meal cake in a muffle furnace for a first heating and calcination, and after the carbonates in the raw meal cake are completely decomposed, performing a second heating and calcination, and then rapidly cooling it to room temperature after calcination to obtain the final product. The secondary heating and calcination process is as follows: the temperature is increased from 850~950℃ to 1250~1350℃ at a rate of 3~5℃ / min, and held for 1~2 hours; the rapid cooling is air cooling at room temperature.

2. The high-performance cement clinker based on lithium slag ion doping and crystal form control according to claim 1, characterized in that: The minerals in the cement clinker also include 0% to 3% C4AF by mass percentage.

3. The high-performance cement clinker based on lithium slag ion doping and crystal form control according to claim 1, characterized in that: The particle size of the cement clinker raw material after grinding and sieving is 80μm; the process of thorough drying is as follows: drying in an oven at 100~110℃ for 12~36h until the weight is constant.

4. The high-performance cement clinker based on lithium slag ion doping and crystal form control according to claim 1, characterized in that: The preparation process of the raw material cake is as follows: 15wt% deionized water is added to the raw material powder and mixed evenly, and then placed in a mold and pressed into shape at 20~30MPa to obtain the cake.

5. The high-performance cement clinker based on lithium slag ion doping and crystal form control according to claim 1, characterized in that: The process of heating and calcining is as follows: the temperature is increased from room temperature to 850-950℃ at a rate of 3-5℃ / min, and then held for 0.5-1.5 hours.

6. The application of a high-performance cement clinker based on lithium slag ion doping and crystal form control as described in claim 1 or 2, characterized in that: Used to prepare high belite sulfoaluminate cement.

7. The application of a high-performance cement clinker based on lithium slag ion doping and crystal form control according to claim 6, characterized in that: The preparation process of the high belite sulfoaluminate cement is as follows: after crushing the cement clinker as described in claim 1 or 2, anhydrous gypsum is added, and the mixture is then ground and sieved in sequence to obtain the cement.

8. The application of a high-performance cement clinker based on lithium slag ion doping and crystal form control according to claim 7, characterized in that: The amount of anhydrous gypsum added is 3-8 wt% of cement clinker; the grinding method is planetary ball milling, with the following conditions: the ratio of small, medium and large grinding balls is 4-6:2-3:1-2, the ball-to-material ratio is 1-3:1, the revolution speed is 200-300 r / min, and the ball milling time is 30-60 min.

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