A production method of precision calcined high-strength and durable ordinary portland cement

Abstract

The application relates to the technical field of cement production, and particularly discloses a production method of precision calcined high-strength and high-durability ordinary Portland cement, which comprises the following steps: pretreating limestone, silicon raw materials, aluminum raw materials and iron raw materials, adding a mineralizer, mixing, obtaining cement raw materials, calcining, obtaining cement clinker, uniformly mixing the cement clinker, gypsum, modified metakaolin and reinforcing fillers, and obtaining high-strength and high-durability ordinary Portland cement; through fine pretreatment of raw materials, precision control of the calcining process and synergistic application of composite functional materials, the produced ordinary Portland cement realizes the unity of high strength and high durability, the compressive strength and the flexural strength of the cement are greatly improved, meanwhile, the cement shows excellent sulphate attack resistance and chloride ion penetration resistance, the service life of the matrix in a harsh environment is greatly prolonged, and the method is suitable for high-durability concrete engineering in a severe environment.

Description

Technical Field

[0001] This invention relates to the field of cement production technology, specifically to a method for producing high-strength, durable ordinary Portland cement by precise calcination. Background Technology

[0002] As modern construction engineering continues to develop towards "high, large, heavy, and special" characteristics—namely, the increasing number of high-rise, large-span, heavy-load, and special-functional engineering structures—higher demands are being placed on the performance of building materials and their construction. Ordinary Portland cement, as one of the most widely used cementitious materials, has the advantages of low price and easy availability. Traditional production processes typically pursue high C3S content and high silica ratio to achieve high strength, but this often comes with problems such as high calcination temperature, high energy consumption, large shrinkage, poor resistance to sulfate attack, and poor long-term durability. Furthermore, the strength requirements of its traditional formulations are no longer sufficient to meet the needs of preparing high-strength concrete of C60 and above, limiting its application scope.

[0003] By improving the strength and durability of cement, it is possible to save material usage, contribute to carbon emission reduction, extend the service life of buildings, and reduce construction waste at the source, which aligns with the concept of sustainable development. Chinese patent application CN114920473A discloses a multi-element low-carbon clinker composite cement and its preparation method. This composite cement includes silicate cement clinker, activated kaolin material, slag, limestone, and gypsum. Based on the synergistic hydration of kaolin, limestone, and slag, the clinker content can be as low as 25%. It has the advantages of rapid strength development, good later performance, and dense microstructure, but its early strength is generally average, and durability-related tests have not been conducted. Chinese patent application CN116621477A discloses a method for preparing high-strength silicate bridge-specific cement. This cement includes cement clinker, admixtures, and gypsum. The cement clinker comprises low-alkali limestone, low-alkali quartz, and iron ore. The cement clinker is produced by grinding and calcining raw cement meal. This cement has advantages such as low alkali content, low heat of hydration, good durability, and high flexural and compressive strength. Its main advantage lies in reducing alkali content to inhibit alkali-aggregate reaction and slow down steel corrosion. However, its durability is only moderate, and its energy consumption is high. Chinese patent application CN103553380A discloses a high-volume fly ash cement, comprising 30–70 wt% fly ash, 0.01–10 wt% nano-boehmite, and the balance being silicate cement. It utilizes the small size of the nano-boehmite particles to activate the fly ash through the nano-effect and fill pores, enhancing the interaction between cement particles, promoting early hydration of the cement, and reducing costs. However, due to the large production volume of fly ash, the cement has low early 3-day strength, poor dispersion of nanomaterials, and generally poor durability. Chinese patent application CN118344034A discloses a micro-nano composite silicate cement, comprising the following raw materials in parts by weight: 3045 parts limestone powder, 1824 parts slag powder, 1025 parts fly ash, 215 parts magnesium oxide, 0.55 parts silica fume; and 1535 parts concrete catalyst. It meets the requirements for low-temperature construction and has the advantages of being non-calcinable, environmentally friendly and low-carbon, and having a simple processing technology. However, the non-calcinable process has insufficient cementitious activity, low early strength, and the concrete catalyst is not disclosed. The high admixture content makes the durability unpredictable.

[0004] Therefore, it is of great significance to optimize the strength and durability of ordinary silicate cement by optimizing raw materials, raw material ratios, and introducing precise calcination control technology. Summary of the Invention

[0005] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a method for producing high-strength and durable ordinary silicate cement by precise calcination, which solves the problem of ordinary silicate cement having generally low strength and durability.

[0006] (II) Technical Solution To achieve the above objectives, this invention discloses a method for producing high-strength, durable ordinary Portland cement by precise calcination, comprising the following steps: Step 1: Raw material pretreatment and batching: Limestone, silica raw materials, aluminum raw materials, and iron raw materials are pretreated, mineralizers are added, and they are mixed to obtain cement raw meal; Step 2, Precision Calcination: The raw cement meal is calcined to obtain cement clinker; Step 3, Cement preparation: Mix cement clinker, gypsum, modified metakaolin, and reinforcing filler evenly to obtain high-strength and durable ordinary Portland cement; The reinforcing filler is obtained by grafting silica with nanocellulose.

[0007] As a further aspect of the present invention: the specific process of raw material pretreatment and batching in step one includes the following steps: limestone, silicon raw materials, aluminum raw materials, and iron raw materials are pretreated respectively. The pretreatment is carried out by vertical mill roller pressing process, controlling the material moisture content to ≤1.0%, the particle size of the material after roller pressing to ≤4mm, and the proportion of particles ≤1.5mm to ≥90%. After the treatment is completed, a mineralizer is added, mixed, and fed into a raw meal mill for grinding. The fineness of the raw meal is controlled to be ≤10% of the residue on a 0.08mm square hole sieve. After homogenization, cement raw meal is obtained.

[0008] As a further aspect of the present invention: the mass ratio of limestone, silicon raw material, aluminum raw material, iron raw material and mineralizing agent is 100: (14-25): (4-7): (2-4): (0.3-0.6).

[0009] As a further aspect of the present invention: the limestone mainly provides CaO, and high-quality limestone is selected with a CaCO3 content ≥95%.

[0010] As a further aspect of the present invention: the silicon raw material includes any one or more of sandstone, quartz sand, and diatomaceous earth, wherein the SiO2 content is ≥90%.

[0011] As a further aspect of the present invention: the aluminum raw material includes any one or more of shale, fly ash, and bauxite, wherein the Al2O3 content is ≥35%.

[0012] As a further aspect of the present invention: the iron raw material is iron powder with an Fe2O3 content ≥70%.

[0013] As a further aspect of the present invention: the mineralizing agent is CaF2.

[0014] As a further aspect of the present invention, the specific process of precise calcination in step two includes the following steps: preheating the cement raw meal to a preheating temperature of 850-900℃ with a decomposition rate ≥90%, calcining it in a rotary kiln in stages, with the first stage controlled at a temperature of 950-1250℃ for 8-12 minutes, the second stage calcining at a temperature of 1300-1350℃ for 14-18 minutes, and rapid cooling to below 100℃ within 5 minutes to obtain cement clinker.

[0015] As a further aspect of the present invention: the specific process of cement preparation in step three includes the following steps: grinding cement clinker and gypsum in a ball mill, mixing them evenly in a high-efficiency mixer, adding modified metakaolin and reinforcing filler, wherein the mass ratio of cement clinker, gypsum, modified metakaolin and reinforcing filler is 100:(4-7):(5-9):(1-2), stirring at a stirring rate of 90-120 r / min for 8-10 min, to obtain high-strength durable ordinary Portland cement.

[0016] As a further aspect of the present invention: the reinforcing filler is modified silica-grafted nanocellulose, and its preparation method includes the following steps: A1. Mix dichloromethane, nano-silica, terephthaloyl chloride, and triethylamine evenly and allow them to react. After the reaction is complete, filter the mixture, wash it with dichloromethane, and dry it to obtain modified silica. A2. Mix N,N-dimethylformamide, nanocellulose, and 4-dimethylaminopyridine evenly, then add modified silica, heat to allow the reaction to occur, centrifuge after the reaction is complete, wash with anhydrous ethanol, and dry to obtain silica-grafted nanocellulose. A3. Mix anhydrous ethanol and deionized water at a volume ratio of 9:1 to obtain a mixed solvent. Adjust the pH to 4-5 using glacial acetic acid, then add γ-aminopropyltriethoxysilane and stir for 30 minutes. Add silica-grafted nanocellulose, heat to allow the reaction to occur, and after the reaction is complete, wash with acetone, centrifuge, and dry to obtain modified silica-grafted nanocellulose.

[0017] As a further aspect of the present invention: the mass ratio of dichloromethane, nano-silica, terephthaloyl chloride and triethylamine in A1 is (3500-4000):100:(120-180):(1-2).

[0018] As a further aspect of the present invention: the reaction temperature in A1 is 25-35℃, and the reaction time is 2-4h.

[0019] As a further aspect of the present invention: the mass ratio of N,N-dimethylformamide, nanocellulose, 4-dimethylaminopyridine, and modified silica in A2 is (5000-6000):100:(5-10):(120-150).

[0020] As a further aspect of the present invention: the reaction temperature in A2 is 70-80℃, and the reaction time is 6-8h.

[0021] As a further aspect of the present invention: the mass ratio of the mixed solvent, γ-aminopropyltriethoxysilane, and silica-grafted nanocellulose in A3 is (2500-3000):(15-25):100.

[0022] As a further aspect of the present invention: the reaction temperature in A3 is 70-80℃, and the reaction time is 4-6h.

[0023] As a further aspect of the present invention, the preparation method of the modified metakaolin includes the following steps: drying metakaolin in a drying oven at 110°C for 24 hours, then mixing the dried metakaolin and γ-glycidoxypropyltrimethoxysilane at a mass ratio of 100:9 evenly, placing them in a ball mill for ball milling for 90 minutes, and drying them after ball milling to obtain modified metakaolin.

[0024] (iii) Beneficial technical effects Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In this invention, the pretreatment of raw materials greatly increases the contact area between components by producing extremely fine and uniform raw material particles, making the subsequent solid-phase reaction more complete, rapid and uniform. Furthermore, by controlling the fineness of the raw materials, the high homogeneity of the mixing of each component is further ensured, avoiding uneven clinker quality due to component fluctuations. First, preheating ensures that calcium carbonate is basically decomposed into active calcium oxide before entering the rotary kiln, improving production efficiency. Then, a first-stage calcination generates a large number of primary mineral nuclei with high activity and many defects, avoiding insufficient C2S at high temperatures that would lead to low strength in the later stage. The second-stage calcination promotes the growth of a large number of alite crystals.

[0025] (2) In this invention, terephthaloyl chloride is used to modify the surface of nano-SiO2, introducing acyl chloride onto the surface of nano-SiO2. Then, under the action of the catalyst DMAP, it reacts with the hydroxyl groups on nano-cellulose to form a hybrid network, resulting in an organic-inorganic hybrid reinforcing material, silica-grafted nano-cellulose. γ-aminopropyltriethoxysilane is then used to modify it, introducing amino groups to obtain a reinforcing filler. The introduced amino groups greatly improve the compatibility and reactivity with the cement matrix, forming a strong interaction with the cement hydration product CSH gel. The reinforcing filler can fill the micropores and capillaries in cement stone, making the structure more compact. Nano-cellulose can bridge microcracks, prevent their propagation, consume fracture energy, and significantly improve the toughness and crack resistance of cement stone. Metakaolin is a high-performance pozzolanic material. After modification with γ-glycidyl etheroxypropyltrimethoxysilane, its surface is grafted with epoxy groups and silane groups, improving the dispersibility of metakaolin in cement paste, avoiding agglomeration, and further strengthening the network structure within the system. The active SiO2 and Al2O3 in metakaolin react with Ca(OH)2 produced during cement hydration to generate additional CSH gel, increasing the strength and density of the matrix. The synergistic effect of these two factors further optimizes the pore structure and stress distribution of the matrix, improves its density, effectively blocks external erosion, significantly enhances durability, and simultaneously increases the compressive and flexural strength of the matrix.

[0026] (3) In this invention, through refined pretreatment of raw materials, precise control of the calcination process, and synergistic application of composite functional materials, the produced ordinary silicate cement achieves a balance between high strength and high durability. The compressive and flexural strengths of the cement in the early 3 days and later 28 days are significantly improved, meeting the application requirements of high-strength concrete. At the same time, it exhibits excellent resistance to sulfate attack and chloride ion penetration, greatly extending the service life of the matrix in harsh environments, reducing maintenance costs, and has significant application value and broad engineering application prospects. Detailed Implementation

[0027] To facilitate understanding of the present invention, a more complete description will be provided below. Preferred embodiments of the invention are given below. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0028] Example 1

[0029] A method for preparing modified silica-grafted nanocellulose includes the following steps: A1. Mix dichloromethane, nano-silica, terephthaloyl chloride and triethylamine in a mass ratio of 3500:100:120:1 and react at 25°C for 4 hours. After the reaction is complete, filter, wash with dichloromethane, and dry to obtain modified silica. A2. N,N-dimethylformamide, nanocellulose, and 4-dimethylaminopyridine are mixed evenly, and then modified silica is added. The mass ratio of N,N-dimethylformamide, nanocellulose, 4-dimethylaminopyridine, and modified silica is 5000:100:5:120. The mixture is heated to 70℃ and reacted for 8 hours. After the reaction is completed, the mixture is centrifuged, washed with anhydrous ethanol, and dried to obtain silica-grafted nanocellulose. A3. Anhydrous ethanol and deionized water were mixed evenly at a volume ratio of 9:1 to obtain a mixed solvent. The pH was adjusted to 4 using glacial acetic acid, and then γ-aminopropyltriethoxysilane was added. The mixture was stirred for 30 min, and then silica-grafted nanocellulose was added. The mass ratio of the mixed solvent, γ-aminopropyltriethoxysilane, and silica-grafted nanocellulose was 2500:15:100. The mixture was heated to 70 °C and reacted for 6 h. After the reaction was completed, the mixture was washed with acetone, centrifuged, and dried to obtain modified silica-grafted nanocellulose.

[0030] Example 2

[0031] A method for preparing modified silica-grafted nanocellulose includes the following steps: A1. Mix dichloromethane, nano silica, terephthaloyl chloride and triethylamine in a mass ratio of 3800:100:150:1.5 until homogeneous. React at 30°C for 3 hours. After the reaction is complete, filter, wash with dichloromethane, and dry to obtain modified silica. A2. N,N-dimethylformamide, nanocellulose, and 4-dimethylaminopyridine are mixed evenly, and then modified silica is added. The mass ratio of N,N-dimethylformamide, nanocellulose, 4-dimethylaminopyridine, and modified silica is 5500:100:8:140. The mixture is heated to 75°C and reacted for 7 hours. After the reaction is completed, the mixture is centrifuged, washed with anhydrous ethanol, and dried to obtain silica-grafted nanocellulose. A3. Anhydrous ethanol and deionized water were mixed evenly at a volume ratio of 9:1 to obtain a mixed solvent. The pH was adjusted to 4.5 using glacial acetic acid. γ-aminopropyltriethoxysilane was then added and stirred for 30 min. Silica-grafted nanocellulose was then added, with the mass ratio of the mixed solvent, γ-aminopropyltriethoxysilane, and silica-grafted nanocellulose being 2800:20:100. The mixture was heated to 75℃ and reacted for 5 h. After the reaction was completed, the nanocellulose was washed with acetone, centrifuged, and dried to obtain modified silica-grafted nanocellulose.

[0032] Example 3

[0033] A method for preparing modified silica-grafted nanocellulose includes the following steps: A1. Mix dichloromethane, nano-silica, terephthaloyl chloride and triethylamine in a mass ratio of 4000:100:180:2 evenly, react at 35°C for 2 hours, filter after reaction, wash with dichloromethane, and dry to obtain modified silica. A2. Mix N,N-dimethylformamide, nanocellulose, and 4-dimethylaminopyridine evenly, then add modified silica. The mass ratio of N,N-dimethylformamide, nanocellulose, 4-dimethylaminopyridine, and modified silica is 6000:100:10:150. Heat the mixture to 80℃ and react for 6 hours. After the reaction is complete, centrifuge, wash with anhydrous ethanol, and dry to obtain silica-grafted nanocellulose. A3. Anhydrous ethanol and deionized water were mixed evenly at a volume ratio of 9:1 to obtain a mixed solvent. The pH was adjusted to 5 using glacial acetic acid, and then γ-aminopropyltriethoxysilane was added. The mixture was stirred for 30 min, and then silica-grafted nanocellulose was added. The mass ratio of the mixed solvent, γ-aminopropyltriethoxysilane, and silica-grafted nanocellulose was 3000:25:100. The mixture was heated and reacted at 80℃ for 4 h. After the reaction was completed, the mixture was washed with acetone, centrifuged, and dried to obtain modified silica-grafted nanocellulose.

[0034] Example 4

[0035] A method for producing high-strength, durable ordinary Portland cement by precise calcination includes the following steps: Step 1: Raw material pretreatment and batching: Limestone, quartz sand, fly ash, and iron powder in a mass ratio of 100:14:4:2:0.3 are pretreated separately. The pretreatment is carried out using a vertical mill roller pressing process, controlling the material moisture content to ≤1.0%, and the particle size of the material after roller pressing to ≤4mm, with the proportion of particles ≤1.5mm being ≥90%. After the treatment, mineralizer CaF2 is added, mixed, and fed into a raw meal mill for grinding, controlling the fineness of the raw meal to ≤10% residue on a 0.08mm square hole sieve, homogenizing, and obtaining cement raw meal; Step 2, Precise Calcination: Preheat the cement raw meal to 850℃, with a decomposition rate ≥90%. Calcinate it in stages in a rotary kiln. The first stage is controlled at 950℃ and calcined for 12 minutes. The second stage is calcined at 1300℃ for 18 minutes. Then, rapidly cool it to below 100℃ within 5 minutes to obtain cement clinker. Step 3: Cement preparation: Cement clinker and gypsum are ground in a ball mill and then mixed evenly in a high-efficiency mixer. Modified metakaolin and reinforcing filler are added, with the mass ratio of cement clinker, gypsum, modified metakaolin and reinforcing filler being 100:4:5:1. The mixture is stirred at a speed of 90 r / min for 8 min to obtain high-strength and durable ordinary Portland cement.

[0036] The preparation method of the reinforcing filler in this embodiment is completely consistent with the preparation method of the reinforcing filler in Example 1.

[0037] Example 5

[0038] A method for producing high-strength, durable ordinary Portland cement by precise calcination includes the following steps: Step 1: Raw material pretreatment and batching: Limestone, quartz sand, fly ash, and iron powder in a mass ratio of 100:18:5:2.5:0.4 are pretreated separately. The pretreatment is carried out using a vertical mill roller pressing process, controlling the material moisture content to ≤1.0%, and the particle size of the material after roller pressing to ≤4mm, with the proportion of particles ≤1.5mm being ≥90%. After the treatment, mineralizer CaF2 is added, mixed, and fed into a raw meal mill for grinding, controlling the fineness of the raw meal to ≤10% residue on a 0.08mm square hole sieve, homogenizing, and obtaining cement raw meal; Step 2, Precise Calcination: Preheat the cement raw meal to 870℃, with a decomposition rate ≥90%. Calcinate it in stages in a rotary kiln. The first stage is controlled at 1050℃ for 9 minutes, and the second stage is calcined at 1320℃ for 15 minutes. Then, rapidly cool it to below 100℃ within 5 minutes to obtain cement clinker. Step 3, Cement Preparation: Cement clinker and gypsum are ground into powder in a ball mill, and then mixed evenly in a high-efficiency mixer. Modified metakaolin and reinforcing filler are added. The mass ratio of cement clinker, gypsum, modified metakaolin and reinforcing filler is 100:5:6:1.4. The mixture is stirred at a stirring speed of 105 r / min for 9 min to obtain high-strength and durable ordinary Portland cement.

[0039] The preparation method of the reinforcing filler in this embodiment is completely consistent with the preparation method of the reinforcing filler in Example 2.

[0040] Example 6

[0041] A method for producing high-strength, durable ordinary Portland cement by precise calcination includes the following steps: Step 1: Raw material pretreatment and batching: Limestone, quartz sand, fly ash, and iron powder in a mass ratio of 100:18:5:2.5:0.4 are pretreated separately. The pretreatment is carried out using a vertical mill roller pressing process, controlling the material moisture content to ≤1.0%, and the particle size of the material after roller pressing to ≤4mm, with the proportion of particles ≤1.5mm being ≥90%. After the treatment, mineralizer CaF2 is added, mixed, and fed into a raw meal mill for grinding, controlling the fineness of the raw meal to ≤10% residue on a 0.08mm square hole sieve, homogenizing, and obtaining cement raw meal; Step 2, Precise Calcination: Preheat the cement raw meal to 870℃, with a decomposition rate ≥90%. Calcinate it in stages in a rotary kiln. The first stage is controlled at 1050℃ for 9 minutes, and the second stage is calcined at 1320℃ for 15 minutes. Then, rapidly cool it to below 100℃ within 5 minutes to obtain cement clinker. Step 3, Cement Preparation: Cement clinker and gypsum are ground into powder in a ball mill, and then mixed evenly in a high-efficiency mixer. Modified metakaolin and reinforcing filler are added. The mass ratio of cement clinker, gypsum, modified metakaolin and reinforcing filler is 100:5:7:1.8. The mixture is stirred at a speed of 105 r / min for 9 min to obtain high-strength and durable ordinary Portland cement.

[0042] The preparation method of the reinforcing filler in this embodiment is completely consistent with the preparation method of the reinforcing filler in Example 2.

[0043] Example 7

[0044] A method for producing high-strength, durable ordinary Portland cement by precise calcination includes the following steps: Step 1: Raw material pretreatment and batching: Limestone, quartz sand, fly ash, and iron powder in a mass ratio of 100:21:6:3:0.5 are pretreated separately. The pretreatment is carried out using a vertical mill roller pressing process, controlling the material moisture content to ≤1.0%, and the particle size of the material after roller pressing to ≤4mm, with the proportion of particles ≤1.5mm being ≥90%. After the treatment is completed, mineralizer CaF2 is added, mixed, and fed into a raw meal mill for grinding. The fineness of the raw meal is controlled to be ≤10% residue on a 0.08mm square hole sieve. After homogenization, cement raw meal is obtained. Step 2, Precise Calcination: Preheat the cement raw meal to 880℃, with a decomposition rate ≥90%. Calcinate it in stages in a rotary kiln. The first stage is controlled at 1150℃ for 9 minutes, and the second stage is calcined at 1320℃ for 16 minutes. Then, rapidly cool it to below 100℃ within 5 minutes to obtain cement clinker. Step 3, Cement Preparation: Cement clinker and gypsum are ground into powder in a ball mill, and then mixed evenly in a high-efficiency mixer. Modified metakaolin and reinforcing filler are added. The mass ratio of cement clinker, gypsum, modified metakaolin and reinforcing filler is 100:5:7:1.8. The mixture is stirred at a speed of 105 r / min for 9 min to obtain high-strength and durable ordinary Portland cement.

[0045] The preparation method of the reinforcing filler in this embodiment is completely consistent with the preparation method of the reinforcing filler in Example 2.

[0046] Example 8

[0047] A method for producing high-strength, durable ordinary Portland cement by precise calcination includes the following steps: Step 1: Raw material pretreatment and batching: Limestone, quartz sand, fly ash, and iron powder in a mass ratio of 100:25:7:4:0.6 are pretreated separately. The pretreatment is carried out using a vertical mill roller pressing process, controlling the material moisture content to ≤1.0%, and the particle size of the material after roller pressing to ≤4mm, with the proportion of particles ≤1.5mm being ≥90%. After the treatment is completed, mineralizer CaF2 is added, mixed, and fed into a raw meal mill for grinding. The fineness of the raw meal is controlled to be ≤10% residue on a 0.08mm square hole sieve. After homogenization, cement raw meal is obtained. Step 2, Precise Calcination: Preheat the cement raw meal to 900℃, with a decomposition rate ≥90%. Calcinate it in stages in a rotary kiln. The first stage is controlled at 1250℃ for 8 minutes, and the second stage is calcined at 1350℃ for 14 minutes. Then, rapidly cool it to below 100℃ within 5 minutes to obtain cement clinker. Step 3: Cement preparation: Cement clinker and gypsum are ground in a ball mill and then mixed evenly in a high-efficiency mixer. Modified metakaolin and reinforcing filler are added, with the mass ratio of cement clinker, gypsum, modified metakaolin and reinforcing filler being 100:7:9:2. The mixture is stirred at a speed of 120 r / min for 10 min to obtain high-strength and durable ordinary Portland cement.

[0048] The preparation method of the reinforcing filler in this embodiment is completely consistent with the preparation method of the reinforcing filler in Example 3.

[0049] Comparative Example 1 A method for producing high-strength and durable ordinary silicate cement by precision calcination is completely consistent with the method for producing high-strength and durable ordinary silicate cement in Example 7. The difference is that the modified silica-grafted nanocellulose is replaced in equal amounts with a mixed filler of nanocellulose and nanosilica in a mass ratio of 2:3.

[0050] Comparative Example 2 A method for producing high-strength, durable ordinary Portland cement by precise calcination includes the following steps: Step 1: Raw material pretreatment and batching: Limestone, quartz sand, fly ash, and iron powder in a mass ratio of 100:21:6:3:0.5 are pretreated separately. The pretreatment is carried out using a vertical mill roller pressing process, controlling the material moisture content to ≤1.0%, and the particle size of the material after roller pressing to ≤4mm, with the proportion of particles ≤1.5mm being ≥90%. After the treatment is completed, mineralizer CaF2 is added, mixed, and fed into a raw meal mill for grinding. The fineness of the raw meal is controlled to be ≤10% residue on a 0.08mm square hole sieve. After homogenization, cement raw meal is obtained. Step 2, Calcination: The cement raw meal is calcined in sections in a rotary kiln at a temperature of 1320℃ for 25 minutes, followed by rapid cooling to below 100℃ within 5 minutes to obtain cement clinker. Step 3, Cement Preparation: Cement clinker and gypsum are ground into powder in a ball mill, and then mixed evenly in a high-efficiency mixer. Modified metakaolin and reinforcing filler are added. The mass ratio of cement clinker, gypsum, modified metakaolin and reinforcing filler is 100:5:6:1.8. The mixture is stirred at a stirring speed of 105 r / min for 9 min to obtain high-strength and durable ordinary Portland cement.

[0051] The preparation method of the reinforcing filler in this comparative example is completely consistent with the preparation method of the reinforcing filler in Example 2.

[0052] Comparative Example 3 A method for producing high-strength, durable ordinary Portland cement by precise calcination includes the following steps: Step 1, Ingredients: Mix limestone, quartz sand, fly ash, iron powder, and mineralizer CaF2 in a mass ratio of 100:21:6:3:0.5 to obtain cement raw materials; Step 2, Precise Calcination: Preheat the cement raw meal to 880℃, with a decomposition rate ≥90%. Calcinate it in stages in a rotary kiln. The first stage is controlled at 1150℃ for 9 minutes, and the second stage is calcined at 1320℃ for 16 minutes. Then, rapidly cool it to below 100℃ within 5 minutes to obtain cement clinker. Step 3, Cement Preparation: Cement clinker and gypsum are ground into powder in a ball mill, and then mixed evenly in a high-efficiency mixer. Modified metakaolin and reinforcing filler are added. The mass ratio of cement clinker, gypsum, modified metakaolin and reinforcing filler is 100:5:6:1.8. The mixture is stirred at a stirring speed of 105 r / min for 9 min to obtain high-strength and durable ordinary Portland cement.

[0053] The preparation method of the reinforcing filler in this comparative example is completely consistent with the preparation method of the reinforcing filler in Example 2.

[0054] The preparation method of modified metakaolin in the embodiments and comparative examples of the present invention includes the following steps: drying metakaolin in a drying oven at 110°C for 24 hours, then mixing the dried metakaolin and γ-glycidoxypropyltrimethoxysilane at a mass ratio of 100:9 evenly, placing them in a ball mill for ball milling for 90 minutes, and drying them after ball milling to obtain modified metakaolin.

[0055] The nano-silica used in the examples and comparative examples of this invention was purchased from Jiangsu Lianyungang Pengrui Chemical Co., Ltd., with an average particle size of 15 nm; the metakaolin was purchased from Lingshou County Shifeng Mining Processing Plant, with product number SF-GP and a particle size of 1250 mesh; the nanocellulose was purchased from Guilin Qihong Technology Co., Ltd.; and the other reagents were commercially available.

[0056] The silicate cements prepared in Examples 4-8 and Comparative Examples 1-3 were ground to a specific surface area of ​​approximately 350 m². 2 / kg, relevant tests were conducted, and the tests are as follows: (1) Strength test: The test standard is GB / T 17671-2021 "Test method for strength of cement mortar (ISO method)". Cement mortar specimens of 40mm×40mm×160mm (cement: standard sand: water = 1:3:0.5) were prepared according to the standard. After curing under standard curing conditions (temperature 20±1°C, relative humidity ≥90%) for 3d and 28d respectively, the flexural strength and compressive strength were determined by universal testing machine. The compressive strength and flexural strength at 3d and 28d were recorded. (2) Durability test 1) Resistance to sulfate attack: The test standard is GB / T 749-2008 "Test method for resistance to sulfate attack of cement". Cement mortar specimens of 40mm×40mm×160mm (cement: standard sand: water = 1:3:0.5) were prepared according to the standard. After curing under standard curing conditions (temperature 20±1°C, relative humidity ≥90%) for 28 days, the cement mortar specimens of 28 days age were immersed in 5% Na2SO4 solution and clean water respectively. After 30 days, the flexural strength of the specimens immersed in the solution and clean water was measured. The corrosion resistance coefficient (K) was used for evaluation. K = strength of specimen cured in sulfate solution / strength of specimen cured in clean water at the same time × 100%. The higher the K value, the stronger the corrosion resistance. 2) Chloride ion diffusion resistance: The test adopted the chloride ion diffusion coefficient test method in NT BUILD 492 standard. Cement mortar specimens of 40mm×40mm×160mm (cement:standard sand:water=1:3:0.5) were prepared according to the standard. After curing under standard curing conditions (temperature 20±1°C, relative humidity ≥90%) for 28 days, the cement mortar specimens of 28 days age were immersed in 3.5% sodium chloride solution and kept at a constant temperature of 35°C. After immersion for 28 days, the specimens were taken out and their chloride ion diffusion depth was measured. The chloride ion diffusion coefficient was calculated by electrochemical analysis. The test results are shown in Table 1: Table 1 The test results in Table 1 show that the silicate cements corresponding to Examples 4-8 have high strength, good durability, and long service life. The corrosion resistance coefficient K of Examples 4-8 is higher than 90%, significantly better than the comparative examples, demonstrating excellent erosion resistance and excellent matrix density, effectively blocking the migration channels of chloride ions. In Comparative Example 1, a simple mixture of nano-silica and nano-cellulose was used instead of modified silica-grafted nano-cellulose as a reinforcing filler. Compared with Example 7, the silicate cement prepared showed poor dispersibility and compatibility, resulting in a significant reduction in overall performance. This indicates that the filler is firmly bonded to the cement matrix through chemical bonds, forming a highly efficient organic-inorganic hybrid reinforcing network that can both inhibit microcrack propagation and promote hydration, thereby significantly improving mechanical properties. In Comparative Example 2, the cement was not precisely calcined in stages, but rather subjected to single high-temperature calcination. This made it difficult to accurately control the crystal development and microstructure of key minerals such as C3S and C2S, resulting in loose gel arrangement, weak interfacial bonding, and a reduction in the strength and durability of the silicate cement. In Comparative Example 3, no pretreatment was performed on the raw materials, resulting in poor homogenization of cement raw materials, uneven distribution of hydration products, obvious interfacial gaps, loose structure, and poor overall performance.

[0057] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for the production of precision calcined high strength durable Portland cement, characterized by: Includes the following steps: Step 1: Raw material pretreatment and batching: Limestone, silica raw materials, aluminum raw materials, and iron raw materials are pretreated, mineralizers are added, and they are mixed to obtain cement raw meal; Step 2, Precision Calcination: The raw cement meal is calcined to obtain cement clinker; Step 3, Cement preparation: Mix cement clinker, gypsum, modified metakaolin, and reinforcing filler evenly to obtain high-strength and durable ordinary Portland cement; The reinforcing filler is obtained by grafting silica with nanocellulose.

2. A method of producing precisely calcined high strength and durable Portland cement as claimed in claim 1, wherein: The specific process of raw material pretreatment and batching in step one includes the following steps: limestone, silicon raw materials, aluminum raw materials, and iron raw materials are pretreated respectively. The pretreatment is carried out by vertical mill roller pressing process, controlling the material moisture content to ≤1.0%, the particle size of the material after roller pressing to ≤4mm, and the proportion of particles ≤1.5mm to ≥90%. After the treatment is completed, a mineralizer is added, mixed, and fed into a raw meal mill for grinding. The fineness of the raw meal is controlled to be ≤10% residue on a 0.08mm square hole sieve. After homogenization, cement raw meal is obtained.

3. A method of producing precisely calcined high strength and durable Portland cement as claimed in claim 1, wherein: The mass ratio of limestone, silicon raw materials, aluminum raw materials, iron raw materials, and mineralizing agent is 100:(14-25):(4-7):(2-4):(0.3-0.6).

4. A method of producing precisely calcined high strength and durable Portland cement as claimed in claim 1, wherein: The specific process of precise calcination in step two includes the following steps: preheating the cement raw meal to a temperature of 850-900℃ with a decomposition rate of ≥90%, calcining it in stages in a rotary kiln, controlling the temperature of the first stage at 950-1250℃ for 8-12 minutes, calcining the second stage at 1300-1350℃ for 14-18 minutes, and then rapidly cooling it to below 100℃ within 5 minutes to obtain cement clinker.

5. A method of producing precisely calcined high strength and durable Portland cement as claimed in claim 1, wherein: The specific process of cement preparation in step three includes the following steps: Cement clinker and gypsum are ground into powder in a ball mill, mixed evenly in a high-efficiency mixer, and then modified metakaolin and reinforcing filler are added. The mass ratio of cement clinker, gypsum, modified metakaolin and reinforcing filler is 100:(4-7):(5-9):(1-2). The mixture is stirred at a stirring speed of 90-120 r / min for 8-10 min to obtain high-strength and durable ordinary Portland cement.

6. A method of producing precisely calcined high strength and durable Portland cement as claimed in claim 1, wherein: The reinforcing filler is modified silica-grafted nanocellulose, and its preparation method includes the following steps: A1. Mix dichloromethane, nano-silica, terephthaloyl chloride, and triethylamine evenly and allow them to react. After the reaction is complete, filter, wash, and dry to obtain modified silica. A2. Mix N,N-dimethylformamide, nanocellulose, and 4-dimethylaminopyridine evenly, then add modified silica, heat to allow the reaction to occur, and after the reaction is complete, centrifuge, wash, and dry to obtain silica-grafted nanocellulose. A3. Mix anhydrous ethanol and deionized water at a volume ratio of 9:1 to obtain a mixed solvent. Adjust the pH to 4-5 using glacial acetic acid, then add γ-aminopropyltriethoxysilane and stir for 30 min. Add silica-grafted nanocellulose, heat to allow the reaction to occur, and after the reaction is complete, wash, centrifuge, and dry to obtain modified silica-grafted nanocellulose.

7. A method of producing precisely calcined high strength and durable Portland cement as claimed in claim 6, wherein: The mass ratio of dichloromethane, nano-silica, terephthaloyl chloride, and triethylamine in A1 is (3500-4000):100:(120-180):(1-2), the reaction temperature is 25-35℃, and the reaction time is 2-4h.

8. The method for producing high-strength, durable ordinary Portland cement by precision calcination according to claim 6, characterized in that: The mass ratio of N,N-dimethylformamide, nanocellulose, 4-dimethylaminopyridine, and modified silica in A2 is (5000-6000):100:(5-10):(120-150), the reaction temperature is 70-80℃, and the reaction time is 6-8h.

9. The method for producing high-strength, durable ordinary Portland cement by precision calcination according to claim 6, characterized in that: The mass ratio of the mixed solvent, γ-aminopropyltriethoxysilane, and silica-grafted nanocellulose in A3 is (2500-3000):(15-25):100, the reaction temperature is 70-80℃, and the reaction time is 4-6h.

10. The method for producing high-strength, durable ordinary Portland cement by precise calcination according to claim 1, characterized in that: The preparation method of the modified metakaolin includes the following steps: drying metakaolin in a drying oven at 110℃ for 24h, then mixing the dried metakaolin and γ-glycidoxypropyltrimethoxysilane at a mass ratio of 100:9 evenly, placing them in a ball mill for ball milling for 90min, and drying them after ball milling to obtain modified metakaolin.

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