Preparation method of high-early-strength low-shrinkage composite Portland cement

Abstract

The invention relates to the technical field of cement materials, in particular to a preparation method of high-early-strength low-shrinkage composite Portland cement, which comprises the following steps: S1, pre-homogenizing limestone, clay and iron powder, grinding and then screening residues to obtain a raw material, preheating the raw material, and calcining and cooling in a rotary kiln to obtain clinker; s2, premixing the early strength agent mother liquor and sodium sulfate, adding triethanolamine, carrying out shearing emulsification treatment, continuously doping a polyether type shrinkage reducing agent and mixing water, and stirring to obtain an admixture mixture; and S3, putting the clinker and gypsum into a ball mill, grinding, transferring into a mixer, sequentially adding slag, silica fume, fly ash, kaolin, magnesium oxide and the dry admixture, mixing, and aging. Mineral components in the clinker react with water to generate hydration products such as hydrated calcium silicate and calcium hydroxide, and the hydration products are filled among cement particles to form a compact structure, so that the strength of the cement is improved.

Description

Technical Field

[0001] The invention relates to the technical field of cement materials, in particular to a method for preparing high-early-strength and low-shrinkage composite silicate cement. Background Art

[0002] The code name of composite silicate cement is P·C. It is a hydraulic cementitious material mainly made of silicate cement clinker, mixed materials, gypsum, etc. The total amount of mixed materials added should be greater than 20% by mass and not more than 50%. Composite silicate cement has the advantages of high strength, good durability, strong impermeability, and good corrosion resistance, but its setting and hardening time is relatively slow and its early strength is low. In addition, composite silicate cement has a small hydration heat and small shrinkage, which is conducive to reducing the cracking and deformation of concrete. At the same time, it has a small water demand, good water retention, and good crack resistance. The concrete it is configured with has good workability and good compatibility with admixtures, which further improves the performance and construction quality of concrete.

[0003] As modern construction projects develop towards high speed, large scale and complexity, higher requirements are placed on the early strength, volume stability and durability of cement-based materials. Although traditional silicate cement has the characteristics of strong versatility, its early strength development is slow, and it cannot meet the needs of shortening the demoulding cycle and improving construction efficiency in scenarios such as winter construction, rapid repair or prefabricated component production. At the same time, the shrinkage problem caused by hydration reaction and water evaporation during the hardening process of traditional silicate cement can easily cause structural cracking, affecting the safety and service life of the project. In order to improve the above defects, domestic and foreign studies have mostly modified cement by adding mineral admixtures such as slag, fly ash, silica fume or chemical admixtures. However, in the prior art, composite cement systems often have the problem that early strength and low shrinkage are difficult to optimize in coordination. Although high-dosage mineral admixtures can reduce hydration heat and shrinkage rate, they may delay early strength development; and when relying solely on chemical admixtures to improve early strength performance, it is easy to cause later strength shrinkage or increased shrinkage rate. Summary of the invention

[0004] In order to solve the problems mentioned in the above background technology, the present invention provides a method for preparing high early strength and low shrinkage composite silicate cement.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing high early strength and low shrinkage composite silicate cement comprises the following steps:

[0007] S1. Pre-homogenize limestone, clay and iron powder, grind to 80-100 μm sieve residue ≤ 12% to obtain raw material, preheat the raw material, put it into a rotary kiln for calcination, and cool it by air cooling to obtain clinker;

[0008] S2, premixing the early strength agent mother solution and sodium sulfate, adding triethanolamine retarder, and subjecting to shear emulsification treatment, transferring to a mixer, and continuing to add a polyether type shrinkage reducing agent and mixing water to stir, to obtain an admixture mixture;

[0009] S3. Put the clinker and gypsum into a planetary ball mill (zirconia balls, Φ3mm) and grind them to a specific surface area of ​​420-440m 2 / kg, transferred to a mixer, slag, silica fume, fly ash, kaolin, magnesium oxide and admixtures were added in sequence, and then the dry mix was aged to obtain high early strength and low shrinkage composite silicate cement.

[0010] Furthermore, the preheating temperature in step S1 is 850-860°C, the calcination temperature in the rotary kiln is 1450-1480°C, the calcination time is 40-50min, and the cooling rate is >600°C / min.

[0011] Furthermore, in step S1, the mass ratio of limestone, clay and iron powder is (73-75):(22-23):(2-5).

[0012] Furthermore, in step S2, the speed of the shear emulsification treatment is 3000-4000 rpm, the treatment time is 15-20 min, the stirring speed is 100-200 rpm, and the stirring time is 5-15 min.

[0013] Furthermore, in step S2, the mass ratio of the early strength agent mother solution, sodium sulfate, triethanolamine, polyether shrinkage reducing agent and mixing water is (6-7): (0.4-0.5): (0.05-0.06): (7-8): (20-30).

[0014] Furthermore, the early strength agent mother solution in step S2 is prepared by the following steps:

[0015] A1. Dissolve lithium molybdate in excess water at 60°C, stir for 30-40 minutes, add aluminum nitrate solution dropwise, control the pH value to 3.3-3.7, evaporate in a water bath at 80-90°C until a colloid is formed, heat to 600-650°C at a rate of 5°C / min, keep warm for 4-5 hours, cool and then use a ball mill (zirconia balls, Φ3mm) for 4-6 hours to obtain a modified lithium aluminum molybdate porous powder;

[0016] A2, adding tannic acid and concentrated sulfuric acid into a reactor, stirring and reacting at a speed of 200-300 rpm in an oil bath at 108-112°C for 5-6 hours, after the reaction, cooling to 10°C in an ice water bath, adding NaOH solution to neutralize to a pH value of 7.0, adding zinc chloride solution, and complexing at a constant temperature of 60-65°C for 2-3 hours, collecting the precipitate by centrifugation, and drying to obtain a tannic acid carrier;

[0017] A3. Add the porous powder and tannic acid carrier into water and perform ultrasonic treatment at a frequency of 30-40 kHz for 20-30 min to obtain a mother solution of the early strength agent.

[0018] Furthermore, in step S3, the rotating speed of the mixer is 40-50 rpm, the temperature of the cement out of the mill is ≤110° C., the aging time is 36 hours, the aging temperature is 18-22° C., and the aging humidity is ≥90%.

[0019] Furthermore, in step A1, the mass ratio of lithium molybdate to aluminum nitrate solution is (0.8-0.9):(5-7), and the concentration of aluminum nitrate solution is 1-1.5 mol / L.

[0020] Furthermore, in step A2, the mass ratio of tannic acid, concentrated sulfuric acid and zinc chloride solution is (4-5):(25-27):(2.4-2.6), and the mass ratio of porous powder, tannic acid carrier and water is (3-3.5):(1-1.2):8.

[0021] Beneficial effects of the present invention:

[0022] 1. In the technical solution of the present invention, the modified lithium aluminum molybdate porous powder is formed by sol-gel and high-temperature calcination to form a layered perovskite-derived structure with three-dimensional through-mesopores and high specific surface area. High-temperature calcination induces the formation of [MoO4] 2- Tetrahedron and [AlO6] 9- The perovskite-like structure of octahedral corner-connected structures can undergo topological ion exchange in a hydration environment. The modified lithium aluminum molybdate porous powder forms powder particles with a porous structure, which is conducive to the adsorption and release of calcium ions in cement hydration products and promotes the hydration reaction. At the same time, the lithium, aluminum, molybdenum and other elements in lithium aluminum molybdate affect the structure and properties of cement hydration products through ion exchange and complexation.

[0023] 2. In the technical solution of the present invention, the tannic acid carrier is prepared by sulfonating tannic acid and Zn 2 + After coordination, a stable octahedral complex is formed, which is anchored on the surface of the porous powder through π-π stacking to form a pH-responsive slow-release system. When the pH value of the system increases, the Zn-O coordination bond breaks, and the Si-O-Si network in the CSH gel is coordinated and cross-linked, which enhances the early polymerization degree of CSH, helps to improve the stability and durability of the early strength agent, and improves the early strength of silicate cement.

[0024] 3. In the technical solution of the present invention, the porous powder and tannic acid carrier in the early strength agent mother liquor can promote the hydration reaction by adsorbing and releasing calcium ions in cement hydration products, and can also affect the structure and distribution of cement hydration products to generate more hydration products that contribute to strength. After adding the early strength agent mother liquor, the early strength of concrete is significantly improved, the curing period is greatly shortened, and the construction progress is accelerated.

[0025] 4. In the technical solution of the present invention, the early strength agent mother liquor can also improve the durability of concrete. By affecting the structure and distribution of cement hydration products, the porous powder and tannic acid carrier improve the density and impermeability of concrete. The increase in density reduces the penetration of moisture and harmful substances, and the increase in impermeability prevents the invasion of corrosive ions such as chloride ions, thereby extending the service life of concrete.

[0026] 5. In the technical solution of the present invention, sodium sulfate, triethanolamine retarder and polyether shrinkage reducing agent in the admixture adjust the setting time of cement, reduce shrinkage and improve early strength through synergistic effect. Sodium sulfate promotes the hydration reaction. Triethanolamine retarder delays the setting time of cement and improves construction performance. Polyether shrinkage reducing agent reduces the shrinkage by reducing the surface tension of cement paste and reducing the evaporation and migration of water.

[0027] 6. During the cement hydration process, the mineral components in the clinker react with water to generate hydration products such as calcium silicate hydrate (CSH gel) and calcium hydroxide. The hydration products fill between cement particles to form a compact structure and provide cement strength. At the same time, the addition of mixed materials further improves the performance of cement. Slag and silica fume can participate in the hydration reaction to generate more hydration products. Fly ash is used as a filler to improve the density and strength of cement. Kaolin and magnesium oxide adjust the structure and performance of cement hydration products through their specific chemical properties. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Unless otherwise specified, the raw materials used in the present invention are all conventional products purchased from the market.

[0030] Preparation Example 1

[0031] The early strength agent mother solution comprises the following steps to prepare:

[0032] A1. Dissolve 0.8 kg of lithium molybdate in 10 kg of water at 60 ° C, stir for 30 min, add 7 kg of 1 mol / L aluminum nitrate (Al(NO3)3·9H2O) solution dropwise, control the pH value to 3.3, evaporate in a water bath at 80 ° C until a colloid is formed, heat to 600 ° C at a rate of 5 ° C / min, keep warm for 4 h, cool and use a ball mill (zirconia balls, Φ3 mm) for 4 h to obtain a porous powder;

[0033] A2, 4 kg of tannic acid and 25 kg of concentrated sulfuric acid (98%) were added to a reactor, and the mixture was stirred at 200 rpm in an oil bath at 108°C for 5 h. After the reaction was completed, the mixture was cooled to 10°C in an ice-water bath, and a NaOH solution was added to neutralize the mixture until the pH value reached 7.0. 2.4 kg of zinc chloride solution was added, and the mixture was subjected to constant temperature complexation at 60°C for 2 h. The precipitate was collected by centrifugation and dried to obtain a brown powder.

[0034] A3. Add 3 kg of porous powder and 1 kg of brown powder into 8 kg of water and treat with ultrasound at a frequency of 30 kHz for 20 min to obtain a mother solution of the early strength agent.

[0035] Preparation Example 2

[0036] The early strength agent mother solution comprises the following steps to prepare:

[0037] A1. Dissolve 0.85 kg of lithium molybdate in 10 kg of water at 60 ° C, stir for 35 min, add 6.2 kg of 1.2 mol / L aluminum nitrate (Al(NO3)3·9H2O) solution dropwise, control the pH value to 3.5, evaporate in a water bath at 85 ° C until colloid is formed, heat to 625 ° C at a rate of 5 ° C / min, keep warm for 4.5 h, cool and use a ball mill (zirconia ball, Φ3 mm) for 5 h to obtain a porous powder;

[0038] A2, 4.5kg of tannic acid and 26kg of concentrated sulfuric acid (98%) were added to a reactor, and the mixture was stirred at 250rpm in an oil bath at 110°C for 5.5h. After the reaction was completed, the mixture was cooled to 10°C in an ice-water bath, and a NaOH solution was added to neutralize the mixture until the pH value reached 7.0. 2.5kg of zinc chloride solution was added, and the mixture was subjected to constant temperature complexation at 62°C for 2.5h. The precipitate was collected by centrifugation and dried to obtain a brown powder;

[0039] A3. Add 3.2 kg of porous powder and 1.1 kg of brown powder into 8 kg of water and treat with ultrasound at a frequency of 35 kHz for 25 min to obtain a mother solution of the early strength agent.

[0040] Preparation Example 3

[0041] The early strength agent mother solution comprises the following steps to prepare:

[0042] A1. Dissolve 0.9 kg lithium molybdate in 10 kg water at 60 °C, stir for 40 min, add 7 kg 1.5 mol / L aluminum nitrate (Al(NO3)3·9H2O) solution dropwise, control the pH value to 3.7, evaporate in a 90 °C water bath until a colloid is formed, heat to 650 °C at a rate of 5 °C / min, keep warm for 5 h, cool and then ball mill for 6 h using a ball mill (zirconia balls, Φ3 mm) to obtain a porous powder;

[0043] A2, 5kg of tannic acid and 27kg of concentrated sulfuric acid (98%) were added to a reactor, and the mixture was stirred at 300rpm for 6h in an oil bath at 112°C. After the reaction, the mixture was cooled to 10°C in an ice-water bath, and a NaOH solution was added to neutralize the mixture until the pH value reached 7.0. 2.6kg of zinc chloride solution was added, and the mixture was subjected to constant temperature complexation at 65°C for 3h. The precipitate was collected by centrifugation and dried to obtain a brown powder;

[0044] A3. Add 3.5 kg of porous powder and 1.2 kg of brown powder into 8 kg of water and treat with ultrasound at a frequency of 40 kHz for 30 min to obtain a mother solution of the early strength agent.

[0045] Example 1

[0046] A method for preparing high early strength and low shrinkage composite silicate cement comprises the following steps:

[0047] S1, pre-homogenize 7.3kg limestone, 2.2kg clay and 0.2kg iron powder, grind and sieve out the residue to obtain raw material, preheat the raw material to 850°C, put it into a rotary kiln and calcine it at 1450°C for 40min, cool it to room temperature by air cooling process, and the cooling rate is 650°C / min to obtain clinker;

[0048] S2, premix 6kg of the early strength agent mother solution prepared in Preparation Example 1 and 0.4kg of sodium sulfate, add 0.05kg of triethanolamine, shear and emulsify at a speed of 3000rpm for 15min, transfer to a mixer, continue to add 7kg of polyether shrinkage reducing agent and 20kg of mixing water, stir at a speed of 100rpm for 5min, and obtain an admixture mixture;

[0049] S3. Put 55% clinker and 5% gypsum into a ball mill according to mass percentage, grind them, and then transfer them to a mixer. Add 18% slag, 6% silica fume, 10% fly ash, 2.7% kaolin, 0.3% magnesium oxide and 3% admixture dry mix in sequence, mix and age, and obtain high early strength and low shrinkage composite silicate cement.

[0050] Example 2

[0051] A method for preparing high early strength and low shrinkage composite silicate cement comprises the following steps:

[0052] S1, pre-homogenize 7.4kg limestone, 2.25kg clay and 0.35kg iron powder, grind and sieve out the residue to obtain raw material, preheat the raw material to 855°C, put it into a rotary kiln and calcine it at 1460°C for 45min, cool it to room temperature by air cooling quenching process, and the cooling rate is 650°C / min to obtain clinker;

[0053] S2, pre-mix 6.5kg of the early strength agent mother solution prepared in Preparation Example 2 and 0.45kg of sodium sulfate, add 0.05kg of triethanolamine, shear and emulsify at a speed of 3500rpm for 18min, transfer to a mixer, continue to add 7.5kg of polyether shrinkage reducing agent and 25kg of mixing water, stir at a speed of 150rpm for 10min, and obtain an admixture mixture;

[0054] S3. Put 65% clinker and 5% gypsum into a ball mill according to mass percentage, grind them, and then transfer them to a mixer. Add 15% slag, 9% silica fume, 3.9% fly ash, 4% kaolin, 0.1% magnesium oxide and 1% admixture dry mix in sequence, mix and age, and obtain high early strength and low shrinkage composite silicate cement.

[0055] Example 3

[0056] A method for preparing high early strength and low shrinkage composite silicate cement comprises the following steps:

[0057] S1, pre-homogenize 7.5kg limestone, 2.3kg clay and 0.5kg iron powder, grind and sieve out the residue to obtain raw material, preheat the raw material to 860°C, put it into a rotary kiln and calcine it at 1480°C for 50min, cool it to room temperature by air cooling quenching process, and the cooling rate is 700°C / min to obtain clinker;

[0058] S2, pre-mix 7kg of the early strength agent mother solution prepared in Preparation Example 3 and 0.5kg of sodium sulfate, add 0.06kg of triethanolamine, shear and emulsify at a speed of 4000rpm for 20min, transfer to a mixer, continue to add 8kg of polyether shrinkage reducing agent and 30kg of mixing water, and stir at a speed of 200rpm for 15min to obtain an admixture mixture;

[0059] S3. Put 60% clinker and 6.5% gypsum into a ball mill according to mass percentage, grind them, and then transfer them to a mixer. Add 16.5% slag, 7.5% silica fume, 6.5% fly ash, 2.5% kaolin, 0.2% magnesium oxide and 2% admixture dry mix in sequence, mix and age, and obtain high early strength and low shrinkage composite silicate cement.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 1 is that lithium molybdate replaces the early strength agent mother solution prepared in the preparation example, and the remaining steps are the same as those in Example 1.

[0062] Comparative Example 2

[0063] The difference between this comparative example and Example 2 is that aluminum nitrate replaces the early strength agent mother solution prepared in the preparation example, and the remaining steps are the same as those in Example 2.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 3 is that tannic acid is used instead of the early strength agent mother solution prepared in the preparation example, and the remaining steps are the same as those in Example 3.

[0066] Comparative Example 4

[0067] The difference between this comparative example and Example 1 is that calcium chloride replaces the early strength agent mother solution prepared in the preparation example, and the remaining steps are the same as those in Example 1.

[0068] Comparative Example 5

[0069] The difference between this comparative example and Example 2 is that sodium sulfate replaces the early strength agent mother solution prepared in the preparation example, and the remaining steps are the same as those in Example 2.

[0070] With reference to GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)", 1 kg of cement and standard ISO sand prepared in Examples 1-3 and Comparative Examples 1-5 were respectively poured into a planetary mortar mixer, dry mixed at 140 rpm for 5 s, water was slowly added, stirred at low speed (285 rpm) for 30 s, paused for 30 s, scraped off the blade attachments, and stirred at high speed (1250 rpm) for 30 s, poured into a 40×40×160 mm triple mold for vibration molding, with an amplitude of 0.75 mm, a frequency of 60 Hz, and 120 vibrations. The mass ratio of cement: standard ISO sand: water was 1:3:0.5. The mold was removed after 24 hours and transferred to a standard curing box (20±1°C, RH≥95%) until the test age (3d, 7d, 28d) to obtain a cement mortar specimen. Take 3 specimens from each group and place them in a pressure testing machine (YES-300). Use a compressive fixture to load them until they fail. Record the peak load and calculate the compressive strength R. c , Among them, R c is the compressive strength, MPa; F c is the failure load, N; A is the compressive area, 1600mm 2 The results are shown in Table 1:

[0071] Table 1. Compressive strength of Examples 1-3 and Comparative Examples 1-5

[0072]

[0073]

[0074] 1 kg of cement, standard sand and water prepared in Examples 1-3 and Comparative Examples 1-5 were respectively injected into a 25×25×280 mm shrinkage test mold at a mass ratio of 1:1:0.35, vibrated and compacted, demolded after 24 hours, and moved into a constant temperature and humidity chamber (20±2°C, RH 60±5%). After demolding, the initial length L0 was measured, and the length L was measured according to the age (3d, 7d, 28d). t , calculate the drying shrinkage ε, L g The effective length of the specimen is 250 mm, ×10 -6 The results are shown in Table 2:

[0075] Table 2. Drying shrinkage of Examples 1-3 and Comparative Examples 1-5

[0076]

[0077]

[0078] With reference to GB / T 50082-2024 "Standard for Test Methods for Long-term Performance and Durability of Concrete", Φ100×50 mm cylindrical specimens of Examples 1-3 and Comparative Examples 1-5 were prepared respectively, and after demolding for 24 h, they were immersed in a standard curing room, and after 28 d of curing, they were vacuum saturated with water, installed in a test tank, injected with 3% NaCl (negative electrode) and 0.3 mol / L NaOH (positive electrode), applied 60 V DC, recorded the amount of electricity passed for 6 h, recorded the current value, and calculated the total electric flux, Q=900(I0+2I 30 +2I 60 +…+I 360 ), where I t is the current at t minutes, A. The results are shown in Table 3:

[0079] Table 3. Drying shrinkage of Examples 1-3 and Comparative Examples 1-5

[0080] sample Total electric flux Q (Coulomb) Example 1 820 Example 2 780 Example 3 750 Comparative Example 1 1580 Comparative Example 2 2040 Comparative Example 3 2300 Comparative Example 4 3820 Comparative Example 5 1980

[0081] As shown in Table 1, the compressive strengths of Examples 1-3 at 3 days, 7 days and 28 days are relatively high, showing good early strength and late strength development, which may be due to the fact that the early strength agent mother liquor prepared in the preparation example effectively promotes the hydration reaction of cement, forms more hydration products, and thus improves the compressive strength of cement. In Comparative Examples 1-5, in which lithium molybdate, aluminum nitrate, tannic acid, calcium chloride and sodium sulfate are used instead of the early strength agent mother liquor, the compressive strengths are significantly lower than those of the examples, which may be because these single compounds cannot comprehensively promote the hydration reaction of cement like the early strength agent mother liquor, resulting in a reduction in the amount of hydration products generated and a decrease in compressive strength.

[0082] As shown in Table 2, the drying shrinkage rates of Examples 1-3 at 3 days, 7 days and 28 days are relatively low, showing good anti-shrinkage performance, which may be due to the synergistic effect of the porous powder and the brown powder in the early strength agent mother solution, which reduces the porosity in the cement paste, thereby reducing the drying shrinkage rate. The drying shrinkage rates of Comparative Examples 1-5 are generally higher than those of the examples, especially Comparative Examples 1, 2, 3 and 4, which may be because a single compound cannot effectively reduce the porosity in the cement paste like the early strength agent mother solution, resulting in an increase in the drying shrinkage rate.

[0083] As shown in Table 3, the total electric flux of Examples 1-3 is relatively low, showing good anti-permeability, which may be because the early strength agent mother solution promotes the cement hydration reaction, forming a denser cement paste structure, thereby improving the anti-permeability. The total electric flux of Comparative Examples 1-5 is significantly higher than that of the examples, especially Comparative Example 4, which may be because a single compound cannot effectively promote the cement hydration reaction like the early strength agent mother solution, resulting in a loose cement paste structure and reduced anti-permeability.

[0084] In summary, the early strength agent mother liquor prepared in the preparation example plays an important role in the high early strength and low shrinkage composite silicate cement. By promoting cement hydration reaction, reducing porosity and improving impermeability, the early strength agent mother liquor significantly improves the early strength and later strength development, anti-shrinkage performance and impermeability of cement.

[0085] In the description of the specification, the description with reference to the terms "preparation example", "embodiment", "various embodiments" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or preparation example are included in at least one embodiment or preparation example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or preparation example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or preparation examples in a suitable manner.

[0086] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing high early strength and low shrinkage composite silicate cement, characterized in that: The following steps are involved: S1. Pre-homogenize limestone, clay and iron powder, grind and sieve out the residue to obtain raw material, preheat the raw material, put it into a rotary kiln for calcination, and cool it by air cooling to obtain clinker; S2, premix the early strength agent mother solution and sodium sulfate, add triethanolamine, and after shearing and emulsification, transfer to a mixer, continue to add a polyether shrinkage reducing agent and mixing water, and stir to obtain an admixture mixture; S3. Put the clinker and gypsum into a ball mill, grind them, transfer them to a mixer, add slag, silica fume, fly ash, kaolin, magnesium oxide and admixture dry mix in sequence, mix and age, and obtain high early strength and low shrinkage composite silicate cement.

2. The method for preparing high early strength and low shrinkage composite silicate cement according to claim 1, characterized in that: The mass percentage of each component is: 55-65% of silicate clinker, 15-18% of slag, 6-9% of silica fume, 3-10% of fly ash, 1-4% of kaolin, 5-8% of gypsum, 0.1-0.3% of magnesium oxide and 1-3% of admixture mixture.

3. The method for preparing high early strength and low shrinkage composite silicate cement according to claim 1, characterized in that: The preheating temperature in step S1 is 850-860° C., the calcination temperature in the rotary kiln is 1450-1480° C., the calcination time is 40-50 min, and the cooling rate is >600° C. / min.

4. The method for preparing high early strength and low shrinkage composite silicate cement according to claim 1, characterized in that: The mass ratio of limestone, clay and iron powder in step S1 is (73-75): (22-23): (2-5).

5. The method for preparing high early strength and low shrinkage composite silicate cement according to claim 1, characterized in that: In step S2, the shear emulsification treatment speed is 3000-4000 rpm, the treatment time is 15-20 min, the stirring speed is 100-200 rpm, and the stirring time is 5-15 min.

6. The method for preparing high early strength and low shrinkage composite silicate cement according to claim 1, characterized in that: In step S2, the mass ratio of the early strength agent mother solution, sodium sulfate, triethanolamine, polyether shrinkage reducing agent and mixing water is (6-7): (0.4-0.5): (0.05-0.06): (7-8): (20-30).

7. The method for preparing high early strength and low shrinkage composite silicate cement according to claim 1, characterized in that: The early strength agent mother solution in step S2 is prepared by the following steps: A1. Dissolve lithium molybdate in 60℃ water, stir for 30-40min, add aluminum nitrate solution dropwise, control the pH value to 3.3-3.7, evaporate in a water bath at 80-90℃ until colloid is formed, heat to 600-650℃, keep warm for 4-5h, cool and then ball mill for 4-6h to obtain modified lithium aluminum molybdate porous powder; A2, adding tannic acid and concentrated sulfuric acid into a reactor, stirring and reacting in an oil bath at 108-112°C for 5-6 hours, after the reaction, cooling to 10°C in an ice water bath, adding NaOH solution to neutralize to a pH value of 7.0, adding zinc chloride solution, constant temperature complexing at 60-65°C for 2-3 hours, centrifuging and collecting the precipitate, and drying to obtain a tannic acid carrier; A3. Add the porous powder and tannic acid carrier into water and perform ultrasonic treatment at a frequency of 30-40 kHz for 20-30 min to obtain a mother solution of the early strength agent.

8. The method for preparing high early strength and low shrinkage composite silicate cement according to claim 1, characterized in that: In step S3, the rotating speed of the mixer is 40-50 rpm, the temperature of the cement out of the mill is ≤110° C., the aging time is 36 hours, the aging temperature is 18-22° C., and the aging humidity is ≥90%.

9. The method for preparing high early strength and low shrinkage composite silicate cement according to claim 7, characterized in that: In step A1, the mass ratio of lithium molybdate to aluminum nitrate solution is (0.8-0.9):(5-7), and the concentration of aluminum nitrate solution is 1-1.5 mol / L.

10. The method for preparing high early strength and low shrinkage composite silicate cement according to claim 7, characterized in that: The mass ratio of tannic acid, concentrated sulfuric acid and zinc chloride solution in step A2 is (4-5):(25-27):(2.4-2.6), and the mass ratio of porous powder, tannic acid carrier and water in step A3 is (3-3.5):(1-1.2):8.

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