Cement with low thermal expansion coefficient and production method thereof

Abstract

The invention discloses cement with low heat and low expansion coefficient and its production method, belongs to the field of building materials, cement with low heat and low expansion coefficient includes aggregate and additive, aggregate includes silicate cement, granulated blast furnace slag, coal gangue powder, calcium sulfate powder, gypsum; additive includes grinding aid, nano-microsphere emulsion, auxiliary agent, wherein the mass of grinding aid is 0.2% of the total mass of aggregate, the addition amount of nano-microsphere emulsion accounts for 3-5% of the total mass of aggregate, and the diameter of nano-microsphere in the nano-microsphere emulsion is 60-70nm; the preparation method of cement with low heat and low expansion coefficient of the present invention utilizes modeling and the combination of hardware and software such as speed sensor and laser sensor to monitor the running state of the stirring motor of the reactor during shearing, and ensures to have good shearing effect. The low heat and low expansion coefficient cement prepared by the present invention has high compressive and flexural strength, and has low shrinkage rate.

Description

Technical Field

[0001] The invention belongs to the field of building materials and relates to cement with low thermal expansion coefficient and a production method thereof. Background Art

[0002] The hydraulic cementitious material with low hydration heat and low expansion properties made by grinding granulated blast furnace slag as the main component and adding appropriate amounts of silicate cement clinker and gypsum is called low-heat and low-expansion cement. It is mainly suitable for concrete and large-volume concrete that require lower hydration heat and shrinkage compensation. It is also suitable for projects that require anti-seepage and resistance to sulfate erosion.

[0003] Existing low-heat and low-expansion cement is used to compensate for shrinkage of concrete by adding expansive agents. Although the expansive agent can compensate for the shrinkage of cement, there is a problem of compatibility between the expansive agent and cement and other additives. For example, the expansion effect varies depending on the type and amount of water reducer, pumping agent, and cement. It is necessary to conduct trial mixing of shrinkage compensating concrete based on the raw materials on the construction site. This not only increases the difficulty and cost of using low-heat and low-expansion cement, but also the shrinkage compensation effect of cement is unstable. Summary of the invention

[0004] The purpose of the present invention is to provide cement with low heat and low expansion coefficient and a production method thereof, so as to solve the problem that the existing low heat and low expansion cement is used to compensate for the shrinkage of concrete by adding an expansion agent, and the expansion agent has compatibility with cement and other additives during use, which makes the shrinkage compensation effect of the expansion agent unstable.

[0005] The technical solution adopted by the present invention is as follows:

[0006] Cement with low thermal expansion coefficient includes aggregate and additives, wherein the aggregate includes the following components in parts by weight: 80-90 parts of silicate cement, 15-20 parts of granulated blast furnace slag, 10-15 parts of coal gangue powder, 5-10 parts of calcium alum powder, and 5-8 parts of gypsum;

[0007] The additives include grinding aids, nano-microsphere emulsions, and additives, wherein the mass of the grinding aids is 0.2% of the total mass of the aggregate, the amount of the nano-microsphere emulsion added is 3-5% of the total mass of the aggregate, and the diameter of the nano-microspheres in the nano-microsphere emulsion is 60-70nm;

[0008] The surface of the grinding aid has a negative charge, and the surface of the nano-microsphere emulsion has a positive charge;

[0009] The nano-microsphere emulsion comprises a continuous phase and a dispersed phase, and the mass ratio of the dispersed phase to the continuous phase is 1:35-45;

[0010] The continuous phase of the nano-microsphere emulsion comprises the following components: dodecylpyridinium ammonium chloride and butyl acetate, wherein the mass ratio of dodecylpyridinium ammonium chloride to butyl acetate is 1:10;

[0011] The dispersed phase of the nano-microsphere emulsion comprises the following components: an amphiphilic comb-shaped polymer, 2-hydroxy-3-methacryloyloxypropyl trimethyl ammonium chloride, N,N-dimethyl acrylamide, methacryloyl ethyl sulfon betaine, a crosslinking agent, an initiator, and water. The mass ratio of the amphiphilic comb-shaped polymer: 2-hydroxy-3-methacryloyloxypropyl trimethyl ammonium chloride: N,N-dimethyl acrylamide: methacryloyl ethyl sulfon betaine: crosslinking agent: initiator: water is 15-20: 15-20: 6-10: 3-5: 2-4: 2-2.4: 100-120.

[0012] In the present invention, silicate cement, granulated blast furnace slag and gypsum are basic raw materials of low thermal and low expansion coefficient cement. On this basis, the present invention adds calcium alum powder and coal gangue powder. Alum stone forms calcium alum stone under the stimulation of alkali-sulfate, so that the strength of cement stone is well developed; the chemical composition of coal gangue powder is similar to that of cement clinker, and can replace part of cement raw materials, reduce production cost and improve production efficiency. In addition, coal gangue powder can also improve the compressive strength and ductility of cement blocks, so that cement products have more strength and plasticity.

[0013] The invention uses a grinding aid with a negative charge on the surface and a nano-microsphere emulsion with a positive charge on the surface. The nano-microspheres in the nano-microsphere emulsion can absorb water and swell to replace the existing swelling agent; the positively charged nano-microspheres are adsorbed on the aggregate particles with a negative charge on the surface after passing through the grinding aid powder, and the adjacent aggregate particles repel each other because of the same charge on the surface, thereby avoiding the aggregation of the aggregate particles. The surface of the aggregate particles is coated with microspheres, and the surface of the microspheres is smooth, so that the friction between the aggregate particles and other fillers, aids or solutions is small, the flow resistance is small, and thus the overall fluidity of the cement slurry is good. The two properties replace The function of the existing water reducer; in the case of having the above functions, the microspheres of the present invention have high elasticity. When the cement shrinks, since the emulsion microspheres are dispersed between the aggregate particles, the cement shrinks and the microspheres will undergo elastic deformation under the extrusion state. When the cement shrinks and squeezes the internal structure, the microspheres attached to the surface of the aggregate can resist the compression force, which compensates for the cement shrinkage. In addition, the elastic microspheres are located between the gaps between the aggregate particles. When the cement is subjected to compression force, rigid stress will not be generated between the aggregate particles to cause cracks, which solves the problem of cracking caused by water shrinkage in the prior art and compensates for the shrinkage of the cement.

[0014] The nano-emulsion microspheres are wrapped on the outside of the aggregate particles, which is equivalent to the modification of the aggregate particles, rather than just using their own water absorption properties to achieve the effect of compensating cement shrinkage. Therefore, the present invention uses a grinding aid with a negative charge on the surface and a nano-microsphere emulsion with a positive charge on the surface, which can replace the existing expansion agent and water reducer. It not only relies on the performance of the microspheres themselves, but also relies on the charge adsorption effect. It is not affected by aggregates and cement additives, has versatility, and does not produce adaptability problems. It solves the problem that the existing low-heat and low-expansion cement seeks to compensate for shrinkage by adding expansion agents. The expansion agent has adaptability problems with cement and other additives during use, making the expansion agent shrinkage compensation effect unstable. Although the nano-emulsion microspheres in the present invention have a significant and stable effect on compensating cement shrinkage, compared with inorganic expansion agents, the mechanical strength of the nano-emulsion microspheres is lower. Therefore, the present invention has made improvements on aggregates, adding calcium alum powder and coal gangue powder to make up for this defect. In the present invention, the grinding aid is wrapped around the outside of the aggregate particles, not relying on the attraction between charges, but mainly through surface adsorption. Therefore, the charge of the aggregate particles has no direct relationship with the use of the grinding aid.

[0015] The nano-microsphere emulsion of the present invention is different from the existing nano-microspheres. The nano-microspheres of the present invention have the function of water absorption and expansion, and have high adhesion and high elasticity. Therefore, the present invention relates to a new nano-emulsion microsphere formula, which uses an amphiphilic comb-shaped high molecular polymer as a macromolecular material, which is equivalent to the base material of the nano-microspheres. The amphiphilic comb-shaped high molecular polymer is also called a comb-type amphiphilic polymer. The comb-type amphiphilic polymer is a special type of amphiphilic polymer, which is composed of a main chain with a plurality of side chains of different numbers and different molecular structures, has a comb-like structure, a regular structure and controllable composition, and has the basic characteristics of an amphiphilic polymer. The comb-type amphiphilic polymer macromolecule can be adsorbed on the surface of particles through the effects of ion pairs, hydrogen bonds and intermolecular forces to form a directional adsorption layer, thereby changing the surface properties of the particles, achieving the effects of improving wettability, dispersion and dispersion stability. The present invention uses 2-hydroxy-3-methacryloxypropyltrimethylammonium chloride, N,N-dimethylacrylamide and methacryloylethylsulfobetaine as polymerization monomers.

[0016] 2-Hydroxy-3-methacryloyloxypropyltrimethylammonium chloride is a cationic monomer that provides positive charge for the microspheres. 2-Hydroxy-3-methacryloyloxypropyltrimethylammonium chloride has a large molecular weight and structure and a strong stereo configuration, so it has a high tensile strength. In addition, 2-Hydroxy-3-methacryloyloxypropyltrimethylammonium chloride contains an acryloyloxy group, which can improve the compatibility with the polymer and improve the interface compatibility and dispersibility of the polymer.

[0017] The two hydrogen atoms on the amide nitrogen of N,N-dimethylacrylamide are replaced by methyl groups. The hydrolysis stability of the copolymer is significantly improved compared with that of acrylamide. The active double bonds in the molecule make it easy to self-polymerize or copolymerize with other monomers.

[0018] Methacryloylethyl sulfobetaine, also known as 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, has a positive charge in its molecular structure. It is a quaternary ammonium salt with high water solubility and good surface active properties. It can reduce surface tension at the liquid interface and increase the permeability and stability of the solution.

[0019] The dispersed phase liquid of the present invention is sheared by the continuous phase liquid into a plurality of droplets with an oil-in-water structure, and the macromolecular material in the droplets reacts with the monomers through cross-linking to prepare microspheres with positively charged functional groups and a three-dimensional network structure; the butyl acetate in the continuous phase of the present invention is an organic solvent, and dodecylpyridinium chloride is a surfactant. The amount of the surfactant added will affect the diameter of the microspheres, and therefore, in order to obtain nano-scale microspheres, the present invention limits the amount of the surfactant used.

[0020] The present invention limits the proportion of each component. When the proportion is small, the performance of the cement with low thermal expansion coefficient obtained is better than that of the prior art. The cement with low thermal expansion coefficient obtained by the present invention has stable compensatory shrinkage performance, a large specific surface area, and meets the requirements of GB2938 cement standard.

[0021] Furthermore, the mass ratio of the amphiphilic comb-shaped polymer: 2-hydroxy-3-methacryloxypropyltrimethylammonium chloride: N,N-dimethylacrylamide: methacryloylethyl sulfobetaine: crosslinking agent: initiator: water is 20:20:8:3:4:2.4:100.

[0022] The present invention optimizes the optimal ratio of each component in the dispersed phase, so that the elasticity, water absorption expansion and adhesion of the prepared microspheres reach the best that can be achieved by the present invention.

[0023] Furthermore, the aggregate comprises the following components in parts by weight: 90 parts of silicate cement, 20 parts of granulated blast furnace slag, 13 parts of coal gangue powder, 10 parts of calcium alum powder, and 8 parts of gypsum. The amount of the nano-microsphere emulsion added accounts for 4% of the total mass of the aggregate, and the mass ratio of the dispersed phase to the continuous phase in the nano-microsphere emulsion is 1:42.

[0024] The invention optimizes the optimal proportion of aggregates based on the dispersed phase with the optimal proportion.

[0025] Furthermore, the additives include rust inhibitor, antifreeze agent, early strength agent, colorant, and waterproofing agent, wherein the mass of the rust inhibitor is 0.1% of the total mass of the aggregate, the mass of the antifreeze agent is 3% of the total mass of the aggregate, the mass of the early strength agent is 1% of the total mass of the aggregate, the mass of the colorant is 0.2% of the total mass of the aggregate, and the mass of the waterproofing agent is 0.3% of the total mass of the aggregate.

[0026] Furthermore, the grinding aid is a polycarboxylic acid polymer compound; the granulated blast furnace slag is a molten material with silicate and aluminosilicate as main components obtained when smelting pig iron in a blast furnace; and the gypsum is a natural ore with calcium sulfate dihydrate as main component.

[0027] The production method of the cement with low thermal expansion coefficient comprises the following steps:

[0028] S1. Preparation of aggregate

[0029] Coarse grinding: Mix silicate cement, granulated blast furnace slag, coal gangue powder, calcium sulfate powder and gypsum and put them into the coarse grinding system for grinding to obtain a uniformly mixed coarse aggregate;

[0030] Fine grinding: Coarse aggregate is mixed with a grinding aid with negative charge on the surface and added into the fine grinding system for fine grinding to obtain fine aggregate with negative charge on the surface. The specific surface area of ​​the fine aggregate is 480-630m 2 / kg;

[0031] S2. Preparation of nano-microsphere emulsion

[0032] Prepare the continuous phase: under nitrogen, stir and mix dodecylpyridinium chloride and butyl acetate to form a continuous phase homogeneous liquid;

[0033] Preparation of dispersed phase: adding a certain amount of water to a reaction container, slowly adding an amphiphilic comb-like polymer while stirring, heating to 100°C after stirring for 30 minutes, and continuing to stir to obtain an amphiphilic comb-like polymer solution; firstly adding water to 2-hydroxy-3-methacryloxypropyltrimethylammonium chloride, N,N-dimethylacrylamide, methacryloylethylsulfobetaine, and an initiator, mixing evenly, heating to 50-60°C, and heating while stirring, after 30 minutes, adding the above amphiphilic comb-like polymer solution, and continuously stirring at 50-60°C for 2 hours to obtain a dispersed phase liquid;

[0034] Shearing: Pump the continuous phase homogeneous liquid and the dispersed phase liquid into the reactor, stir the materials at a stirring speed of 600 rpm to achieve shearing, and heat while stirring after the continuous phase homogeneous liquid and the dispersed phase liquid are fed. After heating to 60°C, add the crosslinking agent, continue stirring at 400 rpm to carry out the crosslinking reaction, continue the reaction for 3-4 hours, stop stirring, and obtain a nano-microsphere emulsion with a positive charge on the surface;

[0035] S3. Preparation of additives: Prepare corresponding cement additives according to the use environment.

[0036] The present invention stirs the material at a stirring speed of 600 rpm to achieve shearing, and in combination with the ratio of each component (such as the amount of surfactant added), a nanometer-level nano-microsphere emulsion can be obtained. The nanometer-level microspheres and each component in the aggregate produce two-level gradations, one level is the particle size of each component in the aggregate, which is generally micrometer-level; the other level is nanometer-level; the micrometer-nanometer two-level gradation forms a close stacking, which can effectively improve the density of cement, the cement has a strong ability to bind water, effectively controls free water, effectively ensures the stability of cement slurry, and avoids obvious sedimentation of cement slurry.

[0037] Furthermore, the content of nano-microspheres with positive charges on the surface in the nano-microsphere emulsion with positive charges on the surface is 50-52%.

[0038] Furthermore, the initiator is potassium persulfate / tetramethylethylenediamine, and the cross-linking agent is acrylamide acetaldehyde dimethyl acetal.

[0039] Furthermore, the amphiphilic comb-shaped high molecular polymer is a quaternary ammonium salt modified amino-terminated hyperbranched polymer.

[0040] Furthermore, the shearing process in step S2 includes monitoring the working state of the stirring motor in the reactor, and the specific steps of the monitoring method are as follows:

[0041] A. Obtain the motor running speed of the motor, and install a speed sensor on the stirring shaft close to the stirring motor to obtain the output speed of the stirring motor;

[0042] B. Install a laser sensor on the mounting frame of the reactor to measure the actual stirring speed of the stirring blade in the reactor;

[0043] C. Construct the speed operation model of the stirring motor based on the liquid viscosity. The specific steps are as follows:

[0044] Obtaining the initial viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture when stirring begins and the final viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture when heated to 60°C;

[0045] Pre-configure liquids of the two viscosities according to the initial viscosity and final viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture, obtain the motor operating speed, output speed and actual stirring speed of the stirring motor in the liquids of the two viscosities, take the actual stirring speed as a reference, obtain the motor operating speed and output speed when the actual stirring speed is 600rpm, correct the motor operating speed and output speed according to the difference between the actual stirring speed and the motor operating speed and output speed, obtain the corrected data of the motor operating speed and output speed when the actual stirring speed is 600rpm under the two viscosities, and establish a speed operation model of the stirring motor in the above two liquids of the two viscosities;

[0046] F. According to the speed operation model of the stirring motor in the above two viscosities of the liquid in step C, the threshold of the operating speed and the threshold of the output speed of the stirring motor of the reactor in the shearing process of the continuous phase homogeneous liquid and the dispersed phase liquid mixture in step S2 are obtained, the operating speed and the output speed corresponding to the initial viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture are the highest values, and the operating speed and the output speed corresponding to the final viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture are the lowest values;

[0047] According to the threshold of the operating speed and the threshold of the output speed of the reactor stirring motor in step D, the operating speed range and the output speed range of the reactor stirring motor in the shearing process of the continuous phase homogeneous liquid and the dispersed phase liquid mixture in step S2 are obtained, thereby realizing the monitoring of the operating state of the reactor stirring motor during the shearing process; when the operating speed or the output speed of the reactor stirring motor exceeds the threshold, it means that the actual stirring speed does not match the target speed.

[0048] During the preparation process of nano-microsphere emulsion, high-speed stirring and shearing are required. High-speed stirring has very high requirements on the stirring motor. It is necessary to ensure that the continuous phase homogeneous liquid and the dispersed phase liquid mixture can be sheared at a speed of 600rpm. The running speed of the stirring motor is 600rpm, but affected by the viscosity of the stirring liquid, the actual stirring speed of the stirring blade on the liquid will be lower than 600rpm; therefore, the present invention combines the viscosity of the liquid to correct the running speed of the stirring motor. The viscosity of the liquid will gradually decrease during the high-speed stirring process. The smaller the viscosity of the liquid, the smaller the resistance to the stirring blade, and the smaller the impact on the speed. The viscosity of the liquid cannot be accurately measured in real time during the high-speed stirring process. Therefore, the present invention uses the initial viscosity and final viscosity of the liquid as reference data, and through modeling The speed threshold of the running motor (including the best speed and the lowest speed) is determined with reference to the two viscosities. During the shearing process of the present invention, it is necessary to monitor whether the speed of the stirring motor is within this range. If it is not within this range, it means that the shearing speed is not 600rpm, and the stirring motor needs to be alarmed and handled in time. In the actual monitoring process, since there may be wear or connection problems between the stirring shaft and the stirring motor, the present invention also uses the speed of the stirring shaft as the output speed of the stirring motor, and determines the threshold of the output speed through modeling. The output speed range and the operating speed range are combined to simultaneously realize the monitoring of the operating status of the stirring motor of the reactor during the shearing process. Once the speed is abnormal, it can be discovered in time to ensure that the shearing effect is optimal and nano-scale microspheres are obtained.

[0049] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0050] 1. The cement with low thermal expansion coefficient of the present invention adds calcium alum powder and coal gangue powder to the aggregate. The alum stone forms calcium alum stone under the stimulation of alkali-sulfate, so that the strength of cement stone is well developed; the chemical composition of coal gangue powder is similar to that of cement clinker, and can replace part of cement raw materials, reduce production costs, and improve production efficiency. In addition, coal gangue powder can also improve the compressive strength and ductility of cement blocks, so that cement products have more strength and plasticity;

[0051] 2. The microspheres in the cement with low thermal expansion coefficient of the present invention have high elasticity. When the cement shrinks, the latex microspheres are dispersed between the aggregate particles. The cement shrinks because the microspheres undergo elastic deformation under extrusion. When the cement shrinks and squeezes the internal structure, the microspheres attached to the surface of the aggregate can resist the compression force, which compensates for the cement shrinkage. In addition, the elastic microspheres are located between the gaps between the aggregate particles. When the cement is subjected to compression force, rigid stress will not be generated between the aggregate particles to cause cracks, which solves the problem of cracking caused by water shrinkage in the prior art and compensates for the shrinkage of the cement.

[0052] 3. The cement with low thermal expansion coefficient of the present invention uses a grinding aid with negative charge on the surface and a nano-microsphere emulsion with positive charge on the surface. The nano-microspheres in the nano-microsphere emulsion can absorb water and swell to replace the existing expansion agent; the positively charged nano-microspheres are adsorbed on the aggregate particles with negative charge on the surface after passing through the grinding aid powder, and the adjacent aggregate particles repel each other because of the same charge on the surface, thereby avoiding the aggregation between the aggregate particles. The surface of the aggregate particles is coated with microspheres, and the surface of the microspheres is smooth, so that the friction between the aggregate particles and other fillers, boosters or solutions is small, the flow resistance is small, and the overall fluidity of the cement slurry is good. The two properties replace the role of the existing water reducer;

[0053] 4. The preparation method of the cement with low thermal expansion coefficient of the present invention is to stir the material at a stirring speed of 600 rpm to achieve shearing, and to obtain a nanometer-scale nano-microsphere emulsion in combination with the ratio of each component (such as the amount of surfactant added). The nanometer-scale microspheres and each component in the aggregate produce two-level gradation, one level is the particle size of each component in the aggregate, generally at the micrometer level; the other level is at the nanometer level; the micrometer and nanometer two-level gradation forms a close stacking, which can effectively improve the density of the cement, the cement has a strong ability to bind water, effectively controls free water, effectively ensures the stability of the cement slurry, and avoids obvious sedimentation of the cement slurry;

[0054] 5. The method for preparing cement with low thermal expansion coefficient of the present invention uses a combination of modeling and hardware such as rotation speed sensors and laser sensors and software to monitor the operating state of the stirring motor of the reactor during the shearing process to ensure a good shearing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative work, among which:

[0056] Figure 1 Schematic diagram of the surface changes of bone particles before and after grinding of the present invention;

[0057] Figure 2 is a schematic diagram of the surface charge of the bone particles after grinding in the present invention;

[0058] Figure 3 is a scanning electron microscope photograph (SEM) of the nanosphere emulsion in Example 1 of the present invention;

[0059] Figure 4 is a scanning electron microscope photograph (SEM) of the cement slurry in Example 1 of the present invention;

[0060] Figure 5 is a scanning electron microscope photograph (SEM) of the cement slurry during hardening and shrinkage in Example 1 of the present invention;

[0061] Figure 6 is a scanning electron microscope photograph (SEM) of the nanosphere emulsion in Example 6 of the present invention;

[0062] Figure 7 is a scanning electron microscope photograph (SEM) of the nanosphere emulsion in Example 7 of the present invention;

[0063] Figure 8 is a scanning electron microscope photograph (SEM) of the nano-microsphere emulsion in Comparative Example 4 of the present invention;

[0064] Fig. 9 is a scanning electron microscope photograph (SEM) of the nanosphere emulsion in Comparative Example 5 of the present invention;

[0065] Fig.10 It is a scanning electron microscope photograph (SEM) of the nano-microsphere emulsion in Comparative Example 6 of the present invention. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0067] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0068] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0069] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0070] Example 1

[0071] The low thermal expansion coefficient cement and its production method provided by the preferred embodiment of the present invention include aggregate and additives, wherein the aggregate includes the following components in parts by weight: 90 parts of silicate cement, 20 parts of granulated blast furnace slag, 13 parts of coal gangue powder, 10 parts of calcium alum powder, and 8 parts of gypsum; based on the total mass of the aggregate being 100g, the aggregate and the additive are accurately weighed in this embodiment;

[0072] The additives include grinding aids, nano-microsphere emulsions, and additives, wherein the mass of the grinding aids is 0.2% of the total mass of the aggregate, and the amount of the nano-microsphere emulsion added is 4% of the total mass of the aggregate;

[0073] The surface of the grinding aid has a negative charge, and the surface of the nano-microsphere emulsion has a positive charge;

[0074] The nano-microsphere emulsion comprises a continuous phase and a dispersed phase, and the mass ratio of the dispersed phase to the continuous phase is 1:42;

[0075] The continuous phase of the nano-microsphere emulsion comprises the following components: dodecylpyridinium ammonium chloride and butyl acetate, wherein the mass ratio of dodecylpyridinium ammonium chloride to butyl acetate is 1:10;

[0076] The dispersed phase of the nano-microsphere emulsion comprises the following components: an amphiphilic comb-shaped polymer, 2-hydroxy-3-methacryloxypropyl trimethyl ammonium chloride, N,N-dimethyl acrylamide, methacryloyl ethyl sulfon betaine, a cross-linking agent, an initiator, and water, wherein the mass ratio of the amphiphilic comb-shaped polymer: 2-hydroxy-3-methacryloxypropyl trimethyl ammonium chloride: N,N-dimethyl acrylamide: methacryloyl ethyl sulfon betaine: cross-linking agent: initiator: water is 20:20:8:3:4:2.4:100;

[0077] The additives include rust inhibitor, antifreeze agent, early strength agent, colorant, and waterproof agent, wherein the mass of rust inhibitor is 0.1% of the total mass of aggregate, the mass of antifreeze agent is 3% of the total mass of aggregate, the mass of early strength agent is 1% of the total mass of aggregate, the mass of colorant is 0.2% of the total mass of aggregate, and the mass of waterproof agent is 0.3% of the total mass of aggregate;

[0078] The grinding aid is a polycarboxylic acid polymer compound; the granulated blast furnace slag is a molten material with silicate and aluminosilicate as main components obtained when smelting pig iron in a blast furnace; and the gypsum is a natural ore with calcium sulfate dihydrate as main component.

[0079] The initiator is potassium persulfate / tetramethylethylenediamine, and the cross-linking agent is acrylamide acetaldehyde dimethyl acetal;

[0080] The amphiphilic comb-shaped macromolecular polymer is a quaternary ammonium salt-modified amino-terminated hyperbranched polymer;

[0081] Based on the above content, the production method of cement with low thermal expansion coefficient in this embodiment comprises the following steps:

[0082] S1. Preparation of aggregate

[0083] Coarse grinding: Mix silicate cement, granulated blast furnace slag, coal gangue powder, calcium sulfate powder and gypsum and put them into the coarse grinding system for grinding to obtain a uniformly mixed coarse aggregate;

[0084] Fine grinding: Mix the coarse aggregate with a grinding aid with a negative charge on the surface and add it to the fine grinding system for fine grinding;

[0085] S2. Preparation of nano-microsphere emulsion

[0086] Prepare the continuous phase: under nitrogen, stir and mix dodecylpyridinium chloride and butyl acetate to form a continuous phase homogeneous liquid;

[0087] Preparation of dispersed phase: adding a certain amount of water to a reaction container, slowly adding an amphiphilic comb-like polymer while stirring, heating to 100°C after stirring for 30 minutes, and continuing to stir to obtain an amphiphilic comb-like polymer solution; firstly adding water to 2-hydroxy-3-methacryloxypropyltrimethylammonium chloride, N,N-dimethylacrylamide, methacryloylethylsulfobetaine, and an initiator, mixing evenly, heating to 50-60°C, and heating while stirring, after 30 minutes, adding the above amphiphilic comb-like polymer solution, and continuously stirring at 50-60°C for 2 hours to obtain a dispersed phase liquid;

[0088] Shearing: Pump the continuous phase homogeneous liquid and the dispersed phase liquid into the reactor, stir the materials at a stirring speed of 600 rpm to achieve shearing, and heat while stirring after the continuous phase homogeneous liquid and the dispersed phase liquid are fed. After heating to 60°C, add the crosslinking agent, continue stirring at 400 rpm to carry out the crosslinking reaction, continue the reaction for 3-4 hours, stop stirring, and obtain a nano-microsphere emulsion with a positive charge on the surface;

[0089] S3. Preparation of additives: Prepare corresponding cement additives according to the use environment.

[0090] In this embodiment, the specific surface area of ​​fine aggregate reaches 630m 2 / kg, the content of nano-microspheres with positive charges on the surface in the nano-microsphere emulsion reaches 52%; the diameter of the nano-microspheres in the nano-microsphere emulsion is 60-70nm.

[0091] Figure 1 is a schematic diagram of the surface changes of the bone particles before and after grinding of the present invention, Figure 2 is a schematic diagram of the surface charge of the bone particles after grinding in the present invention, Figure 2 The black part in the middle represents the aggregate particles, which are painted black in the present invention for the purpose of differentiation; Figure 3 is a scanning electron microscope photo (SEM) of the nanosphere emulsion in this Example 1, Figure 4 The microstructure diagram (SEM) of the present embodiment when it is prepared into cement slurry according to the existing cement slurry preparation method (water-cement ratio is 0.5) is shown in FIG. Figure 5 Schematic diagram of the microstructure (SEM) of the cement slurry prepared in this example when it hardens and shrinks (microsphere expansion); Figure 4 It can be seen that a large number of microspheres are distributed in the cement slurry, indicating that the microspheres in the nano-microsphere emulsion of the present invention have good adhesion; Figure 5 It can be seen that when the cement slurry hardens and shrinks, the diameter of the microspheres increases significantly, indicating that the microspheres can expand and play a role in compensating for the shrinkage.

[0092] Combination Figure 3It can be seen that the microspheres in the nano-microsphere emulsion of this embodiment are densely packed, have a high microsphere content, have a regularly spherical structure, and are evenly distributed within a particle size range of 60-70 nm.

[0093] Micron-sized microspheres were prepared according to the components of the nano-microsphere emulsion of the present invention. The microspheres were not broken under the pressure condition of 10g of induction force. When the pressure was reduced to no pressure condition, the particle size of the microspheres recovered to the original state, indicating that the microspheres in the nano-microsphere emulsion of the present invention had good elasticity.

[0094] Example 2

[0095] This embodiment is based on Example 1, and is different from Example 1 in that the aggregate includes the following components in parts by weight: 80 parts of Portland cement, 15 parts of granulated blast furnace slag, 10 parts of coal gangue powder, 5 parts of calcium alum powder, and 5 parts of gypsum; based on the total mass of the aggregate being 100 g, the aggregate and additives are accurately weighed in this embodiment; the other components and preparation methods are the same as those in Example 1, and will not be elaborated on herein.

[0096] The specific surface area of ​​the fine aggregate in this embodiment reaches 480m 2 / kg.

[0097] Example 3

[0098] This embodiment is based on Example 1, and is different from Example 1 in that the aggregate includes the following components in parts by weight: 85 parts of Portland cement, 17.5 parts of granulated blast furnace slag, 12.5 parts of coal gangue powder, 7.5 parts of calcium alum powder, and 6.5 parts of gypsum; based on the total mass of the aggregate being 100 g, the aggregate and additives are accurately weighed in this embodiment; the other components and preparation methods are the same as those in Example 1, and will not be elaborated on herein.

[0099] The specific surface area of ​​the fine aggregate in this embodiment reaches 550m 2 / kg.

[0100] Example 4

[0101] This embodiment is based on the embodiment 1, but different from the embodiment 1 in that the amount of the nano-microsphere emulsion added in this embodiment accounts for 3% of the total amount of aggregate.

[0102] Example 5

[0103] This embodiment is based on the embodiment 1, but different from the embodiment 1 in that the amount of the nano-microsphere emulsion added in this embodiment accounts for 5% of the total amount of aggregate.

[0104] Example 6

[0105] This embodiment is based on the embodiment 1, but is different from the embodiment 1 in that the mass ratio of the dispersed phase to the continuous phase in the nanosphere emulsion of this embodiment is 1:35. Figure 6 The scanning electron microscope (SEM) photograph of the nanosphere emulsion of this embodiment shows that the content of nanospheres with positive charges on the surface of the nanosphere emulsion reaches 50%, 60-70 nm. Figure 6 It can be seen that as the amount of continuous phase added decreases, the concentration of the dispersed phase in the continuous phase increases, and the obtained microspheres are adhered and the number decreases.

[0106] Example 7

[0107] This embodiment is based on the embodiment 1, but is different from the embodiment 1 in that the mass ratio of the dispersed phase to the continuous phase in the nano-microsphere emulsion of this embodiment is 1:45. Figure 7 The scanning electron microscope (SEM) image of the nanosphere emulsion of this example is shown in FIG.

[0108] In this embodiment, the content of nano-microspheres with positive charge on the surface of the nano-microsphere emulsion reaches 51.5%, 60-70nm. The dispersion of microspheres increases, and the distribution of microspheres becomes uneven, and some microspheres will stick and deform. The amount of microspheres contained in the nano-microsphere emulsion is relatively reduced compared with Example 1.

[0109] Example 8

[0110] Based on the above embodiment, the shearing process in step S2 includes monitoring the working state of the stirring motor in the reactor, and the specific steps of the monitoring method are as follows:

[0111] A. Obtain the motor running speed of the motor, and install a speed sensor on the stirring shaft close to the stirring motor to obtain the output speed of the stirring motor;

[0112] B. Install a laser sensor on the mounting frame of the reactor to measure the actual stirring speed of the stirring blade in the reactor;

[0113] C. Construct the speed operation model of the stirring motor based on the liquid viscosity. The specific steps are as follows:

[0114] Obtaining the initial viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture when stirring begins and the final viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture when heated to 60°C;

[0115] Pre-configure liquids of the two viscosities according to the initial viscosity and final viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture, obtain the motor operating speed, output speed and actual stirring speed of the stirring motor in the liquids of the two viscosities, take the actual stirring speed as a reference, obtain the motor operating speed and output speed when the actual stirring speed is 600rpm, correct the motor operating speed and output speed according to the difference between the actual stirring speed and the motor operating speed and output speed, obtain the corrected data of the motor operating speed and output speed when the actual stirring speed is 600rpm under the two viscosities, and establish a speed operation model of the stirring motor in the above two liquids of the two viscosities;

[0116] G. According to the speed operation model of the stirring motor in the above two viscosities of the liquid in step C, the threshold of the operating speed and the threshold of the output speed of the stirring motor of the reactor in the shearing process of the continuous phase homogeneous liquid and the dispersed phase liquid mixture in step S2 are obtained, the operating speed and the output speed corresponding to the initial viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture are the highest values, and the operating speed and the output speed corresponding to the final viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture are the lowest values;

[0117] According to the threshold of the operating speed and the threshold of the output speed of the reactor stirring motor in step D, the operating speed range and the output speed range of the reactor stirring motor in the shearing process of the continuous phase homogeneous liquid and the dispersed phase liquid mixture in step S2 are obtained, thereby realizing the monitoring of the operating state of the reactor stirring motor during the shearing process.

[0118] During the preparation process of nano-microsphere emulsion, high-speed stirring and shearing are required. High-speed stirring has very high requirements on the stirring motor. It is necessary to ensure that the continuous phase homogeneous liquid and the dispersed phase liquid mixture can be sheared at a speed of 600rpm. The running speed of the stirring motor is 600rpm, but affected by the viscosity of the stirring liquid, the actual stirring speed of the stirring blade on the liquid will be lower than 600rpm; therefore, the present invention combines the viscosity of the liquid to correct the running speed of the stirring motor. The viscosity of the liquid will gradually decrease during the high-speed stirring process. The smaller the viscosity of the liquid, the smaller the resistance to the stirring blade, and the smaller the impact on the speed. The viscosity of the liquid cannot be accurately measured in real time during the high-speed stirring process. Therefore, the present invention uses the initial viscosity and final viscosity of the liquid as reference data , the speed threshold of the running motor (including the best speed and the lowest speed) is determined by modeling with reference to the two viscosities. During the shearing process of the present invention, it is necessary to monitor whether the speed of the stirring motor is within this range. If it is not within this range, it means that the shearing speed is not 600rpm, and the stirring motor needs to be alarmed and processed in time; in the actual monitoring process, since there may be wear or connection problems between the stirring shaft and the stirring motor, the present invention also uses the speed of the stirring shaft as the output speed of the stirring motor, and determines the threshold of the output speed through modeling. Combined with the output speed range and the operating speed range, the operating status of the reactor stirring motor during the shearing process is monitored at the same time. Once the speed is abnormal, it can be discovered in time to ensure that the shearing effect is optimal.

[0119] Comparative Example 1

[0120] Based on Example 1, the difference between this comparative example and Example 1 is that the mass of the grinding aid is 0.1% of the total mass of the aggregate. If the amount of the grinding aid is too low, the negative charge on the surface of the aggregate particles is unevenly distributed, and the attached microspheres are also unevenly distributed.

[0121] Comparative Example 2

[0122] Based on Example 1, the difference between this comparative example and Example 1 is that the mass of the grinding aid is 0.3% of the total mass of the aggregate. Excessive grinding aids will not only fail to improve the grinding effect of cement, but will also have many negative effects, for example: excessive grinding aids will react with other components in cement, reduce the strength and durability of cement, and affect its service life; excessive use of cement grinding aids will increase the cost of cement production.

[0123] Comparative Example 3

[0124] On the basis of Example 1, this comparative example is different from Example 1 in that this comparative example does not use a grinding aid to grind the aggregate, and there is no grinding aid to coat the aggregate particles. The surface of the aggregate particles cannot be uniformly charged with negative charges, so the charge distribution of the aggregate is uneven. Microspheres with positive charges adhere to the surfaces of some negatively charged aggregates, and the surfaces of some positively charged aggregates cannot adsorb the microspheres, so that the microspheres cannot be evenly distributed among the particles; in addition, the aggregates that have not been ground with a grinding aid include particles with opposite charges on the surfaces. The particles with opposite charges will be adsorbed and agglomerated, affecting the dispersibility of the aggregates, and further affecting the mechanical strength of the cement slurry.

[0125] Comparative Example 4

[0126] Based on Example 1, this comparative example is different from Example 1 in that the nano-microsphere emulsion of this comparative example does not contain an amphiphilic comb-like polymer. The obtained nano-microspheres are irregular in shape, have poor water absorption and swelling effects, and have uneven charge distribution on the surface of the microspheres, which affects the adhesion between the nano-microspheres and the aggregate particles. The scanning electron microscope (SEM) of the nano-microsphere emulsion of this comparative example is shown in FIG. Figure 8 As shown, the microspheres in the obtained nanoemulsion microspheres are irregular in shape.

[0127] Comparative Example 5

[0128] Based on Example 1, the difference between this comparative example and Example 1 is that the nano-microsphere emulsion of this comparative example does not contain N, N-dimethyl acrylamide. The scanning electron microscope photo (SEM) of the nano-microsphere emulsion of this comparative example is as follows: Fig. 9 As shown, the microspheres in the obtained nanoemulsion microspheres are irregular in shape and unevenly distributed.

[0129] Comparative Example 6

[0130] Based on Example 1, the difference between this comparative example and Example 1 is that the nano-microsphere emulsion of this comparative example does not contain methacryloylethyl sulfobetaine. The scanning electron microscope photo (SEM) of the nano-microsphere emulsion of this comparative example is as follows: Fig.10 As shown, the microspheres in the obtained nanoemulsion microspheres are irregular in shape and unevenly distributed.

[0131] Comparative Example 7

[0132] Based on Example 1, this comparative example is different from Example 1 in that the amount of nano-microsphere emulsion added in this comparative example accounts for 2% of the total amount of aggregate.

[0133] Comparative Example 8

[0134] Based on Example 1, the difference between this comparative example and Example 1 is that the amount of nano-microsphere emulsion added in this comparative example accounts for 6% of the total amount of aggregate. If the nano-microsphere emulsion is excessive, the mechanical strength of cement will be relatively reduced.

[0135] Comparative Example 9

[0136] This example is based on Example 1, and is different from Example 1 in that the mass ratio of the dispersed phase to the continuous phase in the nano-microsphere emulsion of this comparative example is 1:30. The dispersed phase has poor fluidity in the mobile phase and cannot be fully sheared, so the obtained microspheres are not only small in quantity but also too close to each other and stick to each other, affecting the shape of the microspheres, making the microspheres irregular in shape.

[0137] Comparative Example 10

[0138] This example is based on Example 1, and is different from Example 1 in that the mass ratio of the dispersed phase to the continuous phase in the nano-microsphere emulsion of this comparative example is 1:50. After the dispersed phase is mixed with the mobile phase, the proportion of the dispersed phase is small, the microspheres produced after shearing are over-dispersed and unevenly arranged, and the amount of microspheres contained in the nano-microsphere emulsion is relatively reduced.

[0139] Comparative Example 11

[0140] The patent CN201010616980.X, a micro-expansion low-heat silicate cement, is used as a comparative technology of the present invention.

[0141] Performance Testing

[0142] 1. Cement expansion rate detection

[0143] According to the JC313-82 expansive cement expansion rate test method, the linear expansion performance of the cement prepared in Examples 1-7 and Comparative Examples 1-11 was tested. The results are shown in Table 1.

[0144] Table 1 Test results of cement expansion performance at different ages

[0145]

[0146]

[0147] GB2938 cement standard requires that the linear expansion rate should meet the following requirements: 1d shall not be less than 0.05%, 7d shall not be less than 0.10%, and 28d shall not be greater than 0.60%. Examples 1-7 of the present invention all meet the requirements, and the linear expansion rate in Comparative Example 1 is different from the cement standard requirements, indicating that the expansion performance of the cement of the present invention is better than that of Comparative Example 11, indicating that the expansion performance of the low-heat and low-expansion cement of the present invention is better than the currently disclosed technology under the condition of meeting the requirements.

[0148] 2. Cement strength test

[0149] According to the cement strength testing method in GB2938 cement standard requirements, the compressive strength and flexural strength performance tests of the cements prepared in Examples 1-7 and Comparative Examples 1-11 at various ages were performed. The results are shown in Table 2.

[0150] Table 2 Performance test results of compressive strength and flexural strength of cement at various ages

[0151]

[0152]

[0153] Combined with Table 1 and Table 2, Example 1 of the present invention is the best ratio. The amount of nanosphere emulsion affects the flexural strength of cement. As the amount of nanosphere emulsion gradually increases, the flexural strength of cement will also gradually increase. When the amount of nanosphere emulsion increases to a certain amount, the linear expansion rate of cement tends to be stable, but the flexural strength and compressive strength of cement will tend to decrease. After exceeding a certain amount, the amount of nanosphere emulsion added is excessive. For example, in Comparative Example 8, the flexural strength and compressive strength of cement decrease to be basically the same as the prior art, without significant changes. Therefore, the present invention limits the amount of nanosphere emulsion, among which Example 1 is the best. The compressive and flexural strengths of the cement of the present invention meet the requirements of GB2938 cement standard. The requirements of GB2938 cement standard are shown in Table 3;

[0154] Table 3 GB2938 cement standard requirements

[0155]

[0156] Combining the data in Table 2 and Table 3, it can be seen that the compressive strength and flexural strength of the cement of the present invention meet the requirements of GB2938 cement standard and have significant improvements compared with the prior art.

[0157] 3. Test block drying shrinkage test

[0158] The cement with low thermal expansion coefficient mentioned in Examples 1-7 of the present invention and Comparative Examples 1-11 was prepared into cement test blocks according to the same water-cement ratio. After the test blocks were cured for 28 days, the test blocks were taken out, the surface moisture was wiped off, and then the test blocks were placed in a constant temperature and humidity environment for drying. The surfaces of all the test blocks were observed for cracks and the drying shrinkage rates of the test blocks in Examples 1-7 were determined. The cement test blocks corresponding to Examples 1-7 of the present invention had no cracks, and the test blocks corresponding to Comparative Examples 1, 2, 3, and 7 had a small number of fine cracks on their surfaces. The curing environment of the cement test blocks should be kept at a constant temperature and humidity as much as possible, the temperature should be controlled at about 20°C, and the humidity should be kept above 90%. The test blocks can be covered with a wet cloth or placed in water for curing.

[0159] The drying shrinkage of the cement test blocks corresponding to Examples 1-7 of the present invention is 0.05%-0.072%, all less than 0.1%, meeting the cement standard. The drying shrinkage of the cement test block in Example 1 can reach 0.05%, indicating that the present invention has a low drying shrinkage rate after adding nano-microsphere emulsion, strong anti-shrinkage performance, and effectively prevents cracking during cement hardening.

[0160] In summary, the low heat and low expansion coefficient cement prepared by the present invention has high compressive and flexural strength, low shrinkage rate, strong shrinkage resistance, and can effectively prevent cracking; the nano-microsphere emulsion prepared by the present invention has good adhesion to aggregate particles and has certain expansion performance and elasticity. The production method of preparing low heat and low expansion coefficient cement of the present invention monitors the operating state of the stirring motor during the shearing process to ensure the best shearing effect, thereby obtaining the nano-microsphere emulsion and low heat and low expansion cement with the best performance.

[0161] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made by any technician familiar with the field within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. Cement with low thermal expansion coefficient, characterized in that: The invention is composed of aggregate and additives, wherein the aggregate is composed of the following components in parts by weight: 90 parts of silicate cement, 20 parts of granulated blast furnace slag, 13 parts of coal gangue powder, 10 parts of calcium alum powder, and 8 parts of gypsum; The additives include grinding aids, nano-microsphere emulsions, and additives, wherein the mass of the grinding aids is 0.2% of the total mass of the aggregate, the amount of the nano-microsphere emulsion added is 4% of the total mass of the aggregate, and the diameter of the nano-microspheres in the nano-microsphere emulsion is 60-70nm; The surface of the grinding aid has a negative charge, and the grinding aid is a polycarboxylic acid polymer compound; the surface of the nano-microsphere emulsion has a positive charge; The nano-microsphere emulsion comprises a continuous phase and a dispersed phase, and the mass ratio of the dispersed phase to the continuous phase is 1:42; The continuous phase of the nano-microsphere emulsion comprises the following components: dodecylpyridinium ammonium chloride and butyl acetate, wherein the mass ratio of dodecylpyridinium ammonium chloride to butyl acetate is 1:10; The dispersed phase of the nano-microsphere emulsion comprises the following components: an amphiphilic comb-shaped polymer, 2-hydroxy-3-methacryloxypropyl trimethyl ammonium chloride, N,N-dimethyl acrylamide, methacryloyl ethyl sulfon betaine, a crosslinking agent, an initiator, and water. The mass ratio of the amphiphilic comb-shaped polymer: 2-hydroxy-3-methacryloxypropyl trimethyl ammonium chloride: N,N-dimethyl acrylamide: methacryloyl ethyl sulfon betaine: crosslinking agent: initiator: water is 20:20:8:3:4:2.4:100; the amphiphilic comb-shaped polymer is a quaternary ammonium salt modified amino-terminated hyperbranched polymer; The nano-microsphere emulsion is prepared by the following method: Prepare the continuous phase: under nitrogen, stir and mix dodecylpyridinium chloride and butyl acetate to form a continuous phase homogeneous liquid; Preparation of dispersed phase: adding a certain amount of water to a reaction container, slowly adding an amphiphilic comb-like polymer while stirring, heating to 100°C after stirring for 30 minutes, and continuing to stir to obtain an amphiphilic comb-like polymer solution; firstly adding water to 2-hydroxy-3-methacryloxypropyltrimethylammonium chloride, N,N-dimethylacrylamide, methacryloylethylsulfobetaine, and an initiator, mixing them uniformly, heating to 50-60°C, and heating while stirring, after 30 minutes, adding the above-mentioned amphiphilic comb-like polymer solution, and continuously stirring at 50-60°C for 2 hours to obtain a dispersed phase liquid; Shearing: Pump the continuous phase homogeneous liquid and the dispersed phase liquid into the reactor, stir the materials at a stirring speed of 600 rpm to achieve shearing, and heat while stirring after the continuous phase homogeneous liquid and the dispersed phase liquid are fed. After heating to 60°C, add the crosslinking agent, continue stirring at 400 rpm to carry out the crosslinking reaction, continue the reaction for 3-4 hours, stop stirring, and obtain a nano-microsphere emulsion with a positive charge on the surface; The aggregate is prepared by the following method: Coarse grinding: Mix silicate cement, granulated blast furnace slag, coal gangue powder, calcium sulfate powder and gypsum and put them into the coarse grinding system for grinding to obtain a uniformly mixed coarse aggregate; Fine grinding: Coarse aggregate is mixed with a grinding aid with negative charge on the surface and added into the fine grinding system for fine grinding to obtain fine aggregate with negative charge on the surface. The specific surface area of ​​the fine aggregate is 480-630m 2 / kg.

2. The low thermal expansion coefficient cement according to claim 1, characterized in that: The additives include rust inhibitor, antifreeze agent, early strength agent, colorant and waterproof agent, wherein the mass of rust inhibitor is 0.1% of the total mass of aggregate, the mass of antifreeze agent is 3% of the total mass of aggregate, the mass of early strength agent is 1% of the total mass of aggregate, the mass of colorant is 0.2% of the total mass of aggregate, and the mass of waterproof agent is 0.3% of the total mass of aggregate.

3. The low thermal expansion coefficient cement according to claim 1, characterized in that: The gypsum is a natural ore with calcium sulfate dihydrate as the main component.

4. The method for producing cement with low thermal expansion coefficient according to claim 1, characterized in that: The following steps are involved: S1. Preparation of aggregate Coarse grinding: Mix silicate cement, granulated blast furnace slag, coal gangue powder, calcium sulfate powder and gypsum and put them into the coarse grinding system for grinding to obtain a uniformly mixed coarse aggregate; Fine grinding: Coarse aggregate is mixed with a grinding aid with negative charge on the surface and added into the fine grinding system for fine grinding to obtain fine aggregate with negative charge on the surface. The specific surface area of ​​the fine aggregate is 480-630m 2 / kg; S2. Preparation of nano-microsphere emulsion Prepare the continuous phase: under nitrogen, stir and mix dodecylpyridinium chloride and butyl acetate to form a continuous phase homogeneous liquid; Preparation of dispersed phase: adding a certain amount of water to a reaction container, slowly adding an amphiphilic comb-like polymer while stirring, heating to 100°C after stirring for 30 minutes, and continuing to stir to obtain an amphiphilic comb-like polymer solution; firstly adding water to 2-hydroxy-3-methacryloxypropyltrimethylammonium chloride, N,N-dimethylacrylamide, methacryloylethylsulfobetaine, and an initiator, mixing them uniformly, heating to 50-60°C, and heating while stirring, after 30 minutes, adding the above-mentioned amphiphilic comb-like polymer solution, and continuously stirring at 50-60°C for 2 hours to obtain a dispersed phase liquid; Shearing: Pump the continuous phase homogeneous liquid and the dispersed phase liquid into the reactor, stir the materials at a stirring speed of 600 rpm to achieve shearing, and heat while stirring after the continuous phase homogeneous liquid and the dispersed phase liquid are fed. After heating to 60°C, add the crosslinking agent, continue stirring at 400 rpm to carry out the crosslinking reaction, continue the reaction for 3-4 hours, stop stirring, and obtain a nano-microsphere emulsion with a positive charge on the surface; S3. Preparation of additives: Prepare corresponding cement additives according to the use environment.

5. The cement with low thermal expansion coefficient and the production method thereof according to claim 4, characterized in that: The content of nano-microspheres with positive charges on the surface in the nano-microsphere emulsion with positive charges on the surface is 50-52%.

6. The method for producing cement with low thermal expansion coefficient according to claim 4, characterized in that: The initiator is potassium persulfate / tetramethylethylenediamine, and the cross-linking agent is acrylamide acetaldehyde dimethyl acetal.

7. The method for producing cement with low thermal expansion coefficient according to claim 4, characterized in that: The shearing process of step S2 includes monitoring the working state of the stirring motor in the reactor. The specific steps of the monitoring method are as follows: A. Obtain the motor running speed of the motor, and install a speed sensor on the stirring shaft close to the stirring motor to obtain the output speed of the stirring motor; B. Install a laser sensor on the mounting frame of the reactor to measure the actual stirring speed of the stirring blade in the reactor; C. Construct the speed operation model of the stirring motor based on the liquid viscosity. The specific steps are as follows: Obtaining the initial viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture when stirring begins and the final viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture when heated to 60°C; Pre-configure liquids of the two viscosities according to the initial viscosity and final viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture, obtain the motor operating speed, output speed and actual stirring speed of the stirring motor in the liquids of the two viscosities, take the actual stirring speed as a reference, obtain the motor operating speed and output speed when the actual stirring speed is 600rpm, correct the motor operating speed and output speed according to the difference between the actual stirring speed and the motor operating speed and output speed, obtain the corrected data of the motor operating speed and output speed when the actual stirring speed is 600rpm under the two viscosities, and establish a speed operation model of the stirring motor in the above two liquids of the two viscosities; D. According to the speed operation model of the stirring motor in the above two viscosities of the liquid in step C, the threshold of the operating speed and the threshold of the output speed of the stirring motor of the reactor in the shearing process of the continuous phase homogeneous liquid and the dispersed phase liquid mixture in step S2 are obtained, the operating speed and the output speed corresponding to the initial viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture are the highest values, and the operating speed and the output speed corresponding to the final viscosity of the continuous phase homogeneous liquid and the dispersed phase liquid mixture are the lowest values; E. According to the threshold of the operating speed and the threshold of the output speed of the reactor stirring motor in step D, the operating speed range and the output speed range of the reactor stirring motor in the shearing process of the continuous phase homogeneous liquid and the dispersed phase liquid mixture in step S2 are obtained, thereby realizing the monitoring of the operating state of the reactor stirring motor during the shearing process.

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