Preparation method of near-zero-magnetism low-heat Portland cement

Abstract

The invention discloses a preparation method of near-zero magnetic low-heat Portland cement. The near-zero magnetic low-heat Portland cement comprises a main body strength component, a magnetic regulation component and a reaction regulation component, the main strength component is P.I Portland cement clinker or white Portland cement clinker; the magnetic regulation and control component comprises the following components in parts by weight: 85-90 parts of hexagonal perovskite ceramic powder and 10-15 parts of a nano silver-graphene composite material; the reaction regulation and control component comprises 30-50 parts by weight of potassium nitrate and 50-70 parts by weight of a carboxyl oxidized beta cyclodextrin-carboxymethyl chitosan composite material; the preparation method comprises the following steps: grinding the magnetic control component and the reaction control component by using a tungsten carbide planetary ball mill, uniformly mixing, and sieving by using a 80-micron sieve; and then grinding the uniformly mixed components and the main body strength component again by using a special tungsten carbide cement grinding system, and uniformly mixing to form graded cement meeting the standard, namely the target near-zero magnetic low-heat portland cement.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a preparation method of near-zero-magnetic low-heat portland cement. BACKGROUND

[0002] Low-magnetic concrete, as a kind of low-magnetic special building material, plays a key role in the fields of astronomical observation, precision instruments and geological exploration. Its main function is to build a closed low-magnetic building environment to ensure the stability of high-end technical equipment and instruments not to be disturbed by external magnetic fields. The conventional low-magnetic concrete structure requires that the residual magnetism of the concrete is not higher than 25 nT. The extremely weak magnetic concrete structure space for original scientific research and exploration requires that the residual magnetism of the concrete is not higher than 0.5 nT.

[0003] The existing invention patent shows that the designed and proposed low-magnetic concrete mix ratio finally realizes the magnetism of the concrete after magnetization of 60 nT. Some scholars optimize the concrete mix ratio and study a series of factors affecting the residual magnetism of the concrete, but the lowest residual magnetism of the concrete reported in the existing literature is 3 nT. In the existing research results, the residual magnetism of the concrete is still relatively high, which cannot achieve the design target of less than 0.5 nT, and the residual magnetism of the prepared concrete is unstable. One of the main raw materials affecting the residual magnetism of the concrete is cement. There are various types of cement, including ordinary portland cement, slag portland cement, pozzolanic portland cement, fly ash portland cement, composite portland cement and white portland cement. The mineral composition of these cements is complex, the content of ferromagnetic minerals is high, and the difference and fluctuation are large. In the cement production process, new iron filings are introduced due to equipment wear and other reasons, which makes the residual magnetism of the hardened cement paste high and fluctuates greatly. The test value at a distance of 2 cm from the 100x100x100 mm hardened paste is usually tens to hundreds of nT, which causes that the near-zero-magnetic concrete with a residual magnetism of less than 0.5 nT cannot be prepared by using conventional cement.

[0004] At the same time, the near-zero-magnetic concrete cannot be mixed with fly ash and other conventional mineral admixtures, the cement content is high, the hydration heat release rate is fast, the temperature rise value of the concrete after pouring is high, and the concrete is prone to cracking. Therefore, it is urgent to solve the problem of high residual magnetism and fast heat release of conventional cement to provide a basis for the construction of large-scale extremely weak magnetic concrete structure. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of near-zero-magnetic low-heat portland cement to solve the problem of high residual magnetism and fast heat release of conventional cement.

[0006] The technical scheme for solving the above technical problems is as follows: a preparation method of near-zero magnetic low-heat portland cement, the near-zero magnetic low-heat portland cement comprising: 93.5-96.5 parts by weight of a main strength component, 3-5 parts by weight of a magnetic control component, and 0.5-1.5 parts by weight of a reaction control component; the main strength component is P*I portland cement clinker or white portland cement clinker; the magnetic control component comprises 85-90 parts by weight of hexagonal perovskite ceramic powder and 10-15 parts by weight of nano silver-graphene composite material; and the reaction control component comprises 30-50 parts by weight of potassium nitrate and 50-70 parts by weight of carboxylic acid β-cyclodextrin-carboxymethyl chitosan composite material.

[0007] In the preparation, the magnetic control component and the reaction control component are ground and mixed uniformly by using a tungsten carbide planetary ball mill, and then screened through an 80-micron sieve; then, the uniformly mixed components and the main strength component are ground and mixed again by using a tungsten carbide special cement grinding system to form a graded cement meeting the standard, which is the target near-zero magnetic low-heat portland cement.

[0008] In the preparation method of the near-zero magnetic low-heat portland cement, preferably, the near-zero magnetic low-heat portland cement comprises 94.0-96.0 parts by weight of the main strength component, 3.4-4.6 parts by weight of the magnetic control component, and 0.8-1.2 parts by weight of the reaction control component; more preferably, the near-zero magnetic low-heat portland cement comprises 95 parts by weight of the main strength component, 4 parts by weight of the magnetic control component, and 1 part by weight of the reaction control component.

[0009] In the preparation method of the near-zero magnetic low-heat portland cement, preferably, the magnetic control component comprises 86-89 parts by weight of hexagonal perovskite ceramic powder and 11-13 parts by weight of nano silver-graphene composite material; and the reaction control component comprises 32-44 parts by weight of potassium nitrate and 55-63 parts by weight of carboxylic acid β-cyclodextrin-carboxymethyl chitosan composite material; more preferably, the magnetic control component comprises 88 parts by weight of hexagonal perovskite ceramic powder and 12 parts by weight of nano silver-graphene composite material; and the reaction control component comprises 40 parts by weight of potassium nitrate and 60 parts by weight of carboxylic acid β-cyclodextrin-carboxymethyl chitosan composite material.

[0010] In the preparation method of the near-zero magnetic low-heat portland cement, preferably, the hexagonal perovskite ceramic powder is prepared by the following method:

[0011] Step 1, Ba8CoNb 5.4 Sb 0.6 O 24 is taken as a reference, and analytical pure barium carbonate, di-niobium pentoxide, di-antimony pentoxide, and cobalt oxalate dihydrate are weighed according to the stoichiometric ratio;

[0012] Step 2, the weighed raw materials are first uniformly dry ground in a tungsten carbide ball mill, then anhydrous ethanol is added, and the grinding is carried out again for not less than 1 hour to fully mix and uniformly mix, and the anhydrous ethanol is mixed in an amount of 10% to 20% of the mass of the raw materials;

[0013] Step 3, the mixed raw materials are placed in a vacuum drying oven for drying, and then placed in an alumina crucible padded with platinum pieces, and sintered at 1250 DEG C for 10 hours;

[0014] Step 4, the raw materials are taken out for secondary grinding, and then placed in a static pressure machine under a pressure of 300 MPa for 30 minutes;

[0015] Step 5, the raw materials are taken out, and heated from room temperature to 550 DEG C at a heating rate of 1.5 DEG C / min, and kept for 4 hours;

[0016] Step 6, then heated to 1400 DEG C at a heating rate of 5 DEG C / min, and calcined for 40 hours;

[0017] Step 7, the raw materials are taken out, ground into powder using a tungsten carbide ball mill, passed through a 120 mu m sieve, and placed in an environment of a temperature of 1150 DEG C and a pressure of 10 GPa for 30 minutes of pressure keeping to obtain the target component: hexagonal perovskite ceramic powder.

[0018] The preparation method of the near-zero magnetic low-heat portland cement is as follows:

[0019] Step 1, prepare a 0.35M ascorbic acid aqueous solution;

[0020] Step 2, add polyvinyl alcohol into the ascorbic acid aqueous solution, and ultrasonic for 30 minutes to obtain a mixed solution 1, and the mixing ratio is that 1.56 mg of polyvinyl alcohol is added into every 10 mL of the ascorbic acid aqueous solution;

[0021] Step 3, add graphene oxide into deionized water to ultrasonic for 3 hours to uniformly mix into a suspension, then add silver nitrate into the suspension, ultrasonic for 1 hour, and heated in a 50 DEG C water bath for 1 hour, and after cooling, a mixed solution 2 is obtained, and the mixing ratio is that 0.021 g of graphene and 0.098 mmol of silver nitrate are added into every 10 mL of the deionized water;

[0022] Step 4, drop the mixed solution 1 into the mixed solution 2 while stirring, and the drop ratio is that the volume ratio of the mixed solution 1 to the mixed solution 2 is 4:15, the drop rate is 10 mL / min, and stirred for 5 hours at 25 DEG C;

[0023] After stirring, the above reaction raw materials are washed with anhydrous ethanol respectively, freeze-dried using a freeze dryer, ground after being taken out using a tungsten carbide ball mill, and passed through a 120-micron sieve to obtain the target component: a nano-silver-graphene composite material.

[0024] The preparation method of the near-zero magnetic low-heat Portland cement according to the present application is as follows:

[0025] Step 1: A 0.05M, PH=6.8 sodium phosphate buffer solution is prepared, and β-cyclodextrin is ultrasonically mixed in the buffer solution to obtain a mixed solution 1, with a mixing ratio of 90mL of the buffer solution per gram of β-cyclodextrin.

[0026] Step 2: 0.1mmol / g of 2,2,6,6-tetramethylpiperidine oxide is ultrasonically dissolved in the mixed solution 1, heated at 60°C for 0.5 hours, and cooled to obtain a mixed solution 2, with a mass ratio of 2,2,6,6-tetramethylpiperidine oxide to β-cyclodextrin of 4:25.

[0027] Step 3: 80wt%, 10mmol of sodium chlorite is dissolved in the mixed solution 2, heated at 40°C for 1 hour, and cooled to obtain a mixed solution 3, with a mass ratio of sodium chlorite to β-cyclodextrin of 113:100.

[0028] Step 4: 1mmol / g of sodium hypochlorite solution is added to the mixed solution 3, stirred at 25°C for 24 hours, and a mixed solution 4 is obtained, with a volume ratio of the sodium hypochlorite solution to the mixed solution 3 of 74:100.

[0029] Step 5: The mixed solution 4 is dialyzed until the conductivity does not change, freeze-dried, then washed with ethanol, and the filtrate is tested with silver nitrate until there is no chlorine ion, and dried at 60°C to obtain carboxyl-oxidized β-cyclodextrin.

[0030] Step 6: Carboxymethyl chitosan is placed in deionized water, ultrasonically mixed for 30 minutes, and carboxyl-oxidized β-cyclodextrin, 1-ethyl-(3-dimethylaminopropyl) carbonyl diimide, and N-hydroxysuccinimide are added, the PH is adjusted to neutral, and the mixture is heated at 30°C and stirred simultaneously for 10 hours, with a ratio of 0.272g of carboxymethyl chitosan, 0.3g of carboxyl-oxidized β-cyclodextrin, 1mmol of 1-ethyl-(3-dimethylaminopropyl) carbonyl diimide, and 1mmol of N-hydroxysuccinimide added to every 10mL of deionized water to obtain an initial component.

[0031] Step 7: The above components are freeze-dried, then ground using a tungsten carbide ball mill, and passed through a 120-micron sieve to obtain the target component: a carboxyl-oxidized β-cyclodextrin-carboxymethyl chitosan composite material.

[0032] The beneficial effects of the present application are:

[0033] 1. The remanence test value of a common 100x100x100mm hardened cement paste is usually tens to hundreds of nT at 2cm, the remanence value is high and unstable, the near-zero magnetic low-heat cement has a stable remanence test value less than 0.5nT under the same test conditions, which can provide support for the construction of extremely weak magnetic concrete structures;

[0034] 2. Compared with ordinary cement, the near-zero magnetic low-heat cement has a low hydration heat peak value, the hydration heat peak appears at a delayed time, which can effectively reduce the risk of temperature shrinkage and cracking of low-magnetic concrete without mineral admixtures, while the unit cumulative heat total amount remains unchanged, by reducing the early hydration heat release rate, improving the pore structure of concrete, reducing harmful pores formed due to temperature, and further improving the compressive strength of low-magnetic concrete. DETAILED DESCRIPTION

[0035] The embodiments described herein are specific embodiments of the present application, used to illustrate the concept of the present application, and are explanatory and exemplary, and should not be interpreted as limiting the embodiments of the present application and the scope of the present application. In addition to the embodiments described herein, those skilled in the art can also employ other technical solutions based on the disclosure of the claims and the specification of the present application, which include technical solutions that make any obvious substitutions and modifications to the embodiments described herein.

[0036] The raw materials used in the embodiments of the present application are as follows:

[0037] 1. P.I Portland cement clinker, P.I 42.5 Portland cement clinker produced by Hebei Zhongkebei Gong Test Instrument Co., Ltd.

[0038] 2. White Portland cement clinker, 42.5 white Portland cement clinker produced by Lingshou County Shuangshi Mineral Product Processing Factory.

[0039] 3. Potassium nitrate, AR analytical pure, purchased from Guangdong Small Chemical Co., Ltd.

[0040] 4. Hexagonal perovskite ceramic powder, prepared according to the following method:

[0041] Step 1, Ba8CoNb 5.4 Sb 0.6 O 24 as a reference, the analytical pure barium carbonate, di-niobium pentoxide, di-antimony pentoxide, and cobalt oxalate dihydrate were weighed according to the stoichiometric ratio;

[0042] Step 2, the weighed raw materials are first uniformly dry ground in a tungsten carbide ball mill, then anhydrous ethanol is added, and the mixture is ground again for not less than 1 hour to fully mix and uniformly distribute the anhydrous ethanol, and the amount of the anhydrous ethanol is 10% to 20% of the mass of the raw materials;

[0043] Step 3, the mixed raw materials are placed in a vacuum drying oven for drying, and then placed in an alumina crucible padded with platinum pieces, and sintered at 1250°C for 10 hours;

[0044] Step 4, the raw materials are taken out for secondary grinding, and then placed in a static pressure machine for pressure maintaining at 300MPa for 30 minutes;

[0045] Step 5, the raw materials are taken out, and heated from room temperature to 550°C at a heating rate of 1.5°C / min, and kept at 550°C for 4 hours;

[0046] Step 6, then heated to 1400°C at a heating rate of 5°C / min, and calcined for 40 hours;

[0047] Step 7, the raw materials are taken out, ground into powder using a tungsten carbide ball mill, and passed through a 120μm sieve, and then placed in an environment at a temperature of 1150°C and a pressure of 10GPa for pressure maintaining and temperature maintaining for 30 minutes to obtain the target component: hexagonal perovskite ceramic powder.

[0048] 5. A nano-silver-graphene composite material is prepared according to the following method:

[0049] Step 1, prepare a 0.35M ascorbic acid aqueous solution;

[0050] Step 2, add polyvinyl alcohol to the ascorbic acid aqueous solution, and ultrasonically treat for 30 minutes to obtain a mixed solution 1, and the addition ratio is 1.56mg of polyvinyl alcohol per 10mL of the ascorbic acid aqueous solution;

[0051] Step 3, add graphene oxide to deionized water, and ultrasonically treat for 3 hours to obtain a suspension, then add silver nitrate to the suspension, and ultrasonically treat for 1 hour, and heat in a 50°C water bath for 1 hour, and then cool to obtain a mixed solution 2, and the addition ratio is 0.021g of graphene and 0.098mmol of silver nitrate per 10mL of the deionized water;

[0052] Step 4, drop the mixed solution 1 into the mixed solution 2 while stirring, and the drop ratio is that the volume ratio of the mixed solution 1 to the mixed solution 2 is 4:15, and the drop rate is 10mL / min, and stir for 5 hours at 25°C;

[0053] Step 5, after stirring, wash the above reaction raw materials with anhydrous ethanol, and freeze-dry using a freeze dryer, and then grind using a tungsten carbide ball mill, and pass through a 120μm sieve to obtain the target component: a nano-silver-graphene composite material.

[0054] 6. A carboxy-oxidized β-cyclodextrin-carboxymethyl chitosan composite material prepared according to the following method:

[0055] Step 1, prepare a 0.05M, PH=6.8 sodium phosphate buffer solution, ultrasonic mix β-cyclodextrin in the buffer solution to obtain mixed solution 1, the addition ratio is 90mL buffer solution per gram of β-cyclodextrin;

[0056] Step 2, ultrasonic 0.1mmol / g of 2,2,6,6-tetramethylpiperidine oxide into mixed solution 1, 60℃ water bath heating 0.5h, after cooling to obtain mixed solution 2, the mass ratio of 2,2,6,6-tetramethylpiperidine oxide and β-cyclodextrin is 4:25;

[0057] Step 3, 80wt%, 10mmol of sodium chlorite is dissolved in mixed solution 2, 40℃ water bath heating 1h, after cooling to obtain mixed solution 3, the mass ratio of sodium chlorite and β-cyclodextrin is 113:100;

[0058] Step 4, add 1mmol / g of sodium hypochlorite solution to mixed solution 3, stir at 25℃ for 24h, to obtain mixed solution 4, the volume ratio of sodium hypochlorite solution and mixed solution 3 is 74:100;

[0059] Step 5, dialysis of mixed solution 4 until the conductivity does not change, freeze-drying, then washed with ethanol, the filtrate is tested with silver nitrate until no chloride ion, dried at 60℃, to obtain carboxy-oxidized β-cyclodextrin;

[0060] Step 6, carboxymethyl chitosan is placed in deionized water, ultrasonic mixing for 30min, add carboxy-oxidized β-cyclodextrin, 1-ethyl-(3-dimethylaminopropyl) carbonyl diimide, N-hydroxysuccinimide, adjust the PH to neutral, 30℃ water bath heating and synchronous stirring for 10h, the ratio is 0.272g carboxymethyl chitosan, 0.3g carboxy-oxidized β-cyclodextrin, 1mmol of 1-ethyl-(3-dimethylaminopropyl) carbonyl diimide, 1mmol of N-hydroxysuccinimide per 10mL deionized water, to obtain the initial components;

[0061] Step 7, freeze-drying the above components, then use tungsten carbide ball mill to grind, pass through 120μm sieve, to obtain the target component: carboxy-oxidized β-cyclodextrin-carboxymethyl chitosan composite material.

[0062] For the magnetic regulation component, the hexagonal perovskite ceramic powder has low remanence and high magnetic stability; the nano silver-graphene can form a conductive network in the slurry, so that the weak magnetic field decays quickly.

[0063] For the reaction control component, potassium nitrate is often used to delay the hydration heat peak, but when combined with carboxyl oxidized β-cyclodextrin-chitosan, it can form a stable complex shell in the early hydration stage, inhibit the ion diffusion rate, and thus both reduce the temperature and optimize the pore structure. Carboxyl oxidized β-cyclodextrin-chitosan: not only controls the release of ions, but also chelates trace iron magnetic impurity ions (Fe 2 + / Fe 3+ ), reducing the magnetic source.

[0064] The magnetic control component is prepared according to the following weight ratio, identified by CTKZF1.

[0065] Magnetic regulation component number Hexagonal perovskite ceramic powder Nano-silver-graphene composite material CTKZF1 85 parts by weight 15 parts by weight CTKZF2 90 parts by weight 10 parts by weight CTKZF3 86 parts by weight 13 parts by weight CTKZF4 89 parts by weight 11 parts by weight CTKZF5 88 parts by weight 12 parts by weight CTKZF6 88 parts by weight 0 CTKZF7 0 12 parts by weight

[0066] The reaction control component is prepared according to the following weight ratio, identified by FYTKZF.

[0067]

[0068] Example 1

[0069] The main strength component is 95 parts by weight of white Portland cement clinker, the magnetic control component is 4 parts by weight (specifically CTKZF1), and the reaction control component is 1 part by weight (specifically FYTKZF1). During preparation: use a tungsten carbide planetary ball mill to grind and mix the magnetic control component and the reaction control component uniformly, and pass through an 80 μm sieve; then use a tungsten carbide special cement grinding system to grind and mix the uniformly mixed components with the main strength component again to form a graded cement that meets the standard, which is the target near-zero magnetic low-heat Portland cement.

[0070] Example 2

[0071] The main strength component is 95 parts by weight, the magnetic control component is 4 parts by weight (specifically CTKZF2), and the reaction control component is 1 part by weight (specifically FYTKZF2). The rest is the same as Example 1.

[0072] Example 3

[0073] The main strength component is 95 parts by weight, the magnetic control component is 4 parts by weight (specifically CTKZF3), and the reaction control component is 1 part by weight (specifically FYTKZF3). The rest is the same as Example 1.

[0074] Example 4

[0075] The main strength component is 95 parts by weight, the magnetic control component is 4 parts by weight (specifically CTKZF4), and the reaction control component is 1 part by weight (specifically FYTKZF4). The rest is the same as Example 1.

[0076] Example 5

[0077] Main body strength component 95 parts by weight, magnetic regulation component 4 parts by weight (specifically CTKZF5), reaction regulation component 1 part by weight (specifically FYTKZF5). The rest is the same as Example 1.

[0078] Example 6

[0079] Main body strength component 95 parts by weight, magnetic regulation component 4 parts by weight (specifically CTKZF6), reaction regulation component 1 part by weight (specifically FYTKZF6). The rest is the same as Example 1.

[0080] Example 7

[0081] Main body strength component 95 parts by weight, magnetic regulation component 4 parts by weight (specifically CTKZF7), reaction regulation component 1 part by weight (specifically FYTKZF7). The rest is the same as Example 1.

[0082] Example 8

[0083] Main body strength component 96.5 parts by weight, magnetic regulation component 3 parts by weight (specifically CTKZF5), reaction regulation component 1.5 parts by weight (specifically FYTKZF5). The rest is the same as Example 1.

[0084] Example 9

[0085] Main body strength component 93.5 parts by weight, magnetic regulation component 5 parts by weight (specifically CTKZF5), reaction regulation component 0.5 parts by weight (specifically FYTKZF5). The rest is the same as Example 1.

[0086] Example 10

[0087] Main body strength component 96 parts by weight, magnetic regulation component 3.4 parts by weight (specifically CTKZF5), reaction regulation component 1.2 parts by weight (specifically FYTKZF5). The rest is the same as Example 1.

[0088] Example 11

[0089] Main body strength component 94 parts by weight, magnetic regulation component 4.6 parts by weight (specifically CTKZF5), reaction regulation component 0.8 parts by weight (specifically FYTKZF5). The rest is the same as Example 1.

[0090] Example 12

[0091] Main body strength component 95 parts by weight, magnetic regulation component 0 parts by weight (specifically CTKZF5), reaction regulation component 0 parts by weight (specifically FYTKZF5). The rest is the same as Example 1.

[0092] Example 13

[0093] Main strength component 95 parts by weight, magnetic regulation component 0 parts by weight (specifically CTKZF5), reaction regulation component 1 part by weight (specifically FYTKZF5). The rest is the same as Example 1.

[0094] Example 14

[0095] Main strength component 95 parts by weight, magnetic regulation component 4 parts by weight (specifically CTKZF5), reaction regulation component 0 parts by weight (specifically FYTKZF5). The rest is the same as Example 1.

[0096] Example 15

[0097] Main strength component 93.5 parts by weight, magnetic regulation component 5 parts by weight (specifically CTKZF5), inert filler 1 part by weight (specifically gypsum powder). The rest is the same as Example 1.

[0098] Example 16

[0099] Main strength component 95 parts by weight, which is P·I Portland cement clinker, magnetic regulation component 4 parts by weight (specifically CTKZF5), reaction regulation component 1 part by weight (specifically FYTKZF5). The rest is the same as Example 1.

[0100] Example 17

[0101] Main strength component 96 parts by weight, which is P·I Portland cement clinker, magnetic regulation component 3.4 parts by weight (specifically CTKZF5), reaction regulation component 1.2 parts by weight (specifically FYTKZF5). The rest is the same as Example 1.

[0102] Example 18

[0103] Main strength component 94 parts by weight, which is P·I Portland cement clinker, magnetic regulation component 4.6 parts by weight (specifically CTKZF5), reaction regulation component 0.8 parts by weight (specifically FYTKZF5). The rest is the same as Example 1.

[0104] Performance test

[0105] The cement neat paste and concrete are prepared according to the mixing ratio in the following Table 1. The cement is the near-zero magnetic low-heat Portland cement described in Examples 1 to 18 above, and the quartzite and quartz sand are commercially available products that meet the requirements.

[0106] Table 1 Sample mixing ratio

[0107]

[0108] The isothermal calorimetry method is used to test the heat release of fresh cement paste, and the test temperature is 40℃. At the same time, cement paste and concrete test blocks are prepared, and the size of the test blocks is 100x100x100mm. After the cement paste test block is hardened for 3 days, the residual magnetism value at a distance of 2cm from the surface of the test block is tested using a fluxgate sensor. After the concrete test block is hardened for 28 days, its compressive strength is tested. The test results are shown in Table 2.

[0109]

[0110]

[0111]

[0112] Example 5 and Example 14 near-zero magnetic low-heat portland cement are used to prepare concrete according to the proportions in Table 1, and the size of the test blocks is 100x100x100mm. The curing is carried out according to the following methods. 1. Regular curing: placed at room temperature for 28d. 2. High-temperature dry heat curing: conditions: 60℃ dry heat box, continuous heat preservation for 28d, indoor relative humidity <20%. After the curing is completed, the residual magnetism value is detected.

[0113] Residual magnetization value Conventional curing High-temperature dry curing Example 5 0.15 0.16 Example 14 0.15 0.27

[0114] The performance of the above examples is verified as follows:

[0115] 1. The reaction control component maintains the stability of the low magnetic value under high temperature conditions, and has a synergistic effect with the magnetic control component. The data prove that the combination of the reaction control component and the magnetic control component can maintain the stability of the low magnetism, while the single component will degrade.

[0116] 2. The conventional means of reducing hydration heat (such as adding inert fillers) will sacrifice the early strength. The data of the present application show that the hydration heat peak value decreases (2.92mW / g of Example 5 vs 11.31 of Example 12), but the strength is improved (38.8MPa vs 33.7MPa).

[0117] The above disclosed technical features are not limited to the disclosed combinations with other features, and other combinations between technical features can also be made by those skilled in the art according to the purpose of the application, and the purpose of the application is achieved.

Claims

1. A method for preparing near-zero magnetic low-heat silicate cement, characterized in that, The near-zero magnetic low-heat silicate cement comprises: 93.5–96.5 parts by weight of the main strength component, 3–5 parts by weight of the magnetic regulation component, and 0.5–1.5 parts by weight of the reaction regulation component; the main strength component is P·I silicate cement clinker or white silicate cement clinker; the magnetic regulation component comprises 85–90 parts by weight of hexagonal perovskite ceramic powder and 10–15 parts by weight of nano-silver-graphene composite material; the reaction regulation component comprises 30–50 parts by weight of potassium nitrate and 50–70 parts by weight of carboxyl-oxidized β-cyclodextrin-carboxymethyl chitosan composite material. During preparation: The magnetic control component and the reaction control component are ground and mixed evenly using a tungsten carbide planetary ball mill and passed through an 80μm sieve; then the mixed components and the main strength component are ground and mixed evenly again using a tungsten carbide special cement grinding system to form a graded cement that meets the standard. The graded cement is the target near-zero magnetic low-heat silicate cement.

2. The method for preparing near-zero magnetic low-heat silicate cement according to claim 1, characterized in that, The near-zero magnetic low-heat silicate cement comprises: 94.0–96.0 parts by weight of main strength component, 3.4–4.6 parts by weight of magnetic regulation component, and 0.8–1.2 parts by weight of reaction regulation component.

3. The method for preparing near-zero magnetic low-heat silicate cement according to claim 2, characterized in that, The near-zero magnetic low-heat silicate cement comprises: 95 parts by weight of main strength component, 4 parts by weight of magnetic regulation component, and 1 part by weight of reaction regulation component.

4. The method for preparing near-zero magnetic low-heat silicate cement according to claim 1, characterized in that, The magnetic control component includes 86-89 parts by weight of hexagonal perovskite ceramic powder and 11-13 parts by weight of nano-silver-graphene composite material; the reaction control component includes 32-44 parts by weight of potassium nitrate and 55-63 parts by weight of carboxyl-oxidized β-cyclodextrin-carboxymethyl chitosan composite material.

5. The method for preparing near-zero magnetic low-heat silicate cement according to claim 4, characterized in that, The magnetic control component includes 88 parts by weight of hexagonal perovskite ceramic powder and 12 parts by weight of nano-silver-graphene composite material; the reaction control component includes 40 parts by weight of potassium nitrate and 60 parts by weight of carboxyl-oxidized β-cyclodextrin-carboxymethyl chitosan composite material.

6. The method for preparing near-zero magnetic low-heat silicate cement according to claim 1, characterized in that, Hexagonal perovskite ceramic powder was prepared by the following method: Step 1, using Ba8CoNb 5.4 Sb 0.6 O 24 Based on the standard, weigh the analytical grade barium carbonate, niobium pentoxide, antimony pentoxide, and cobalt oxalate dihydrate according to the stoichiometric ratio. Step 2: First, dry grind the weighed raw materials evenly in a tungsten carbide ball mill. Then, add anhydrous ethanol and grind again for at least 1 hour to ensure thorough mixing. The amount of anhydrous ethanol should be 10% to 20% of the raw material mass. Step 3: The mixed raw materials are dried in a vacuum drying oven, and then placed in an alumina crucible lined with platinum sheets and sintered at 1250°C for 10 hours. Step 4: Take out the raw material and grind it a second time, then place it in a static press and hold it under pressure of 300MPa for 30 minutes; Step 5: Remove the raw material and heat it from room temperature to 550°C at a rate of 1.5°C / min, and keep it at that temperature for 4 hours. Step 6, then raise the temperature to 1400℃ at a rate of 5℃ / min and calcine for 40 hours; Step 7: Take out the raw material, grind it into powder using a tungsten carbide ball mill, pass it through a 120μm sieve, and place it in an environment with a temperature of 1150℃ and a pressure of 10GPa for 30 minutes to obtain the target component: hexagonal perovskite ceramic powder.

7. The method for preparing near-zero magnetic low-heat silicate cement according to claim 1, characterized in that, The nano-silver-graphene composite material was prepared by the following method: Step 1: Prepare a 0.35M ascorbic acid aqueous solution; Step 2: Add polyvinyl alcohol to the ascorbic acid aqueous solution and sonicate for 30 minutes to obtain mixed solution 1. The addition ratio is 1.56 mg of polyvinyl alcohol per 10 mL of ascorbic acid aqueous solution. Step 3: Add graphene oxide to deionized water and sonicate for 3 hours to form a suspension. Then add silver nitrate to the suspension, sonicate for 1 hour, heat in a 50°C water bath for 1 hour, and cool to obtain mixed solution 2. The doping ratio is 0.021g of graphene and 0.098mmol of silver nitrate per 10mL of deionized water. Step 4: While stirring, add mixed solution 1 dropwise to mixed solution 2 at a volume ratio of mixed solution 1: mixed solution 2 = 4:15, with a dropping rate of 10 mL / min, and stir at 25°C for 5 hours. Step 5: After stirring, wash the above reaction raw materials with anhydrous ethanol, freeze dry them using a freeze dryer, take them out and grind them with a tungsten carbide ball mill, and pass them through a 120μm sieve to obtain the target component: nano-silver-graphene composite material.

8. The method for preparing near-zero magnetic low-heat silicate cement according to claim 1, characterized in that, The carboxyl-oxidized β-cyclodextrin-carboxymethyl chitosan composite material was prepared by the following method: Step 1: Prepare a 0.05M sodium phosphate buffer solution with pH=6.

8. Dissolve β-cyclodextrin in the buffer solution by ultrasonic mixing to obtain mixed solution 1. The addition ratio is 90mL of buffer solution per gram of β-cyclodextrin. Step 2: 0.1 mmol / g of 2,2,6,6-tetramethylpiperidine oxide was ultrasonically dissolved in mixed solution 1, heated in a water bath at 60°C for 0.5 hours, and cooled to obtain mixed solution 2, in which the mass ratio of 2,2,6,6-tetramethylpiperidine oxide to β-cyclodextrin was 4:

25. Step 3: Dissolve 80 wt% and 10 mmol of sodium chlorite in mixed solution 2, heat in a water bath at 40°C for 1 hour, and cool to obtain mixed solution 3. The mass ratio of sodium chlorite to β-cyclodextrin is 113:

100. Step 4: Add 1 mmol / g sodium hypochlorite solution to mixed solution 3 and stir at 25°C for 24 hours to obtain mixed solution 4. The volume ratio of sodium hypochlorite solution to mixed solution 3 is 74:

100. Step 5: Dialyze mixed solution 4 until the conductivity does not change, freeze dry, then wash with ethanol, test the filtrate with silver nitrate until no chloride ions are present, and dry at 60°C to obtain carboxylated β-cyclodextrin; Step 6: Place carboxymethyl chitosan in deionized water and sonicate for 30 minutes. Add carboxylated β-cyclodextrin, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and N-hydroxysuccinimide. Adjust the pH to neutral. Heat in a 30°C water bath with simultaneous stirring for 10 hours. The ratio is 0.272g carboxymethyl chitosan, 0.3g carboxylated β-cyclodextrin, 1mmol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and 1mmol of N-hydroxysuccinimide per 10mL of deionized water to obtain the initial components. Step 7: Freeze-dry the above components, then grind them using a tungsten carbide ball mill and pass them through a 120 μm sieve to obtain the target component: carboxylated β-cyclodextrin-carboxymethyl chitosan composite material.

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