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CN-122010501-A - Fly ash low-carbon cement and preparation method and application thereof

CN122010501ACN 122010501 ACN122010501 ACN 122010501ACN-122010501-A

Abstract

The invention discloses fly ash low-carbon cement and a preparation method and application thereof, wherein a ternary high-molecular copolymer (poly (acrylic acid-2-acrylamide-2-methylpropanesulfonic acid-N-methylol acrylamide)) is combined with organic weak acid (citric acid) to synergistically excite the activity of the fly ash, so that the efficient replacement of cement clinker is realized; the fly ash low-carbon cement comprises the following components in percentage by mass: cement clinker 25% -60%, fly ash 30% -65%, terpolymer 0.3% -1.2%, organic weak acid 0.1% -0.5%, gypsum 2% -5%, water cement ratio 0.45% -0.55, the invention can realize that the minimum 25% clinker dosage prepares 32.5-grade cement, 45% clinker dosage prepares 42.5-grade cement, and the carbon emission and production cost in the cement production process are obviously reduced, and simultaneously the mechanical property and durability of cement are improved.

Inventors

  • LI JIARUI
  • ZHANG ZUHUA
  • WANG ZILONG
  • HAO YONGCHENG
  • ZHEN YU

Assignees

  • 湖南凝英新材料科技有限公司
  • 鄂尔多斯市兴泽建材有限公司

Dates

Publication Date
20260512
Application Date
20260409

Claims (10)

  1. 1. A fly ash low-carbon cement is characterized by comprising, by mass, 25% -60% of cement clinker, 30% -65% of fly ash, 0.3% -1.2% of a ternary polymer copolymer, 0.1% -0.5% of an organic weak acid and 2% -5% of gypsum, wherein the ternary polymer copolymer is poly (acrylic acid-2-acrylamide-2-methylpropanesulfonic acid-N-methylolacrylamide), the monomer molar ratio of the ternary polymer copolymer is acrylic acid-2-acrylamide-2-methylpropanesulfonic acid-N-methylolacrylamide=3:1:1, the number average molecular weight of the ternary polymer copolymer is 1800-2200, the organic weak acid is citric acid, the sieving residue of a fly ash 45 mu m square-hole sieve is less than or equal to 30%, and the ignition loss is less than or equal to 8.0%.
  2. 2. The fly ash low-carbon cement according to claim 1, wherein the cement clinker is Portland cement clinker, and the mineral composition of the cement clinker is 8-15% by mass of C 3 S 55%-65%、C 2 S 15%-25%、C 3 A 5%-10%、C 4 AF.
  3. 3. The fly ash low-carbon cement according to claim 1, wherein the gypsum is dihydrate gypsum, the purity is more than or equal to 90%, and the screen residue of a square hole screen with the fineness of 80 μm is less than or equal to 10%.
  4. 4. The fly ash low-carbon cement according to claim 1, wherein when preparing the 32.5-grade cement, the mass percentages of the components are 25% -35% of cement clinker, 50% -65% of fly ash, 0.5% -0.8% of ternary polymer copolymer, 0.2% -0.3% of organic weak acid and 2% -4% of gypsum, and when preparing the 42.5-grade cement, the mass percentages of the components are 45% -60% of cement clinker, 30% -45% of fly ash, 0.7% -1.2% of ternary polymer copolymer, 0.3% -0.5% of organic weak acid and 3% -5% of gypsum.
  5. 5. A method for preparing the fly ash low carbon cement according to any one of claims 1 to 4, comprising the steps of: s1, preparing a ternary high polymer, namely adding acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid and N-methylol acrylamide into deionized water according to a molar ratio of 3:1:1, stirring and dissolving, regulating the pH value of a system to 6.5-7.5, adding an initiator ammonium persulfate accounting for 0.8-1.2% of the total mass of monomers and a chain transfer agent sodium bisulfite accounting for 0.4-0.6%, introducing nitrogen for protection, reacting for 3-4 hours at 70-80 ℃, cooling to room temperature, and obtaining a ternary high polymer aqueous solution, and carrying out vacuum drying and crushing for later use; S2, raw material pretreatment, namely respectively crushing cement clinker, fly ash and gypsum, sieving with a 80 mu m square hole sieve for standby, crushing organic weak acid citric acid, and sieving with a 100 mu m square hole sieve for standby; S3, mixing and grinding, namely weighing the pretreated cement clinker, the fly ash, the gypsum, the ternary polymer and the organic weak acid according to the mass percentage of 25-60% of the cement clinker, 30-65% of the fly ash, 0.3-1.2% of the ternary polymer, 0.1-0.5% of the organic weak acid and 2-5% of the gypsum, putting the mixture into a ball mill, controlling the ball milling time to be 30-45min, controlling the ball-material ratio to be 8:1 and the grinding temperature to be less than or equal to 60 ℃ to obtain mixed powder; And S4, molding and curing, namely uniformly mixing the mixed powder obtained in the step 3 with water according to the water-cement ratio of 0.45-0.55, pouring the mixture into a mold, vibrating and molding, carrying out standard curing for 24 hours at the temperature of 20+/-2 ℃ and the relative humidity of more than or equal to 90%, demolding, and continuously curing to a specified age to obtain the fly ash low-carbon cement product.
  6. 6. The preparation method according to claim 5, wherein in the step S1, the deionized water is added in an amount 3-5 times the total mass of the monomers, the vacuum drying temperature is 60-70 ℃, and the drying time is 12-16h.
  7. 7. The method according to claim 5, wherein in step S3, the rotation speed of the ball mill is 200-250r/min, and the specific surface area of the mixed powder is 350-400m 2 /kg.
  8. 8. The method according to claim 5, wherein in the step S4, the frequency of the vibration molding is 50-60Hz, the vibration time is 2-3min, and the specified age is 3 days, 7 days, or 28 days.
  9. 9. Use of the fly ash low carbon cement according to any of claims 1-4 for the preparation of masonry mortar, plastering mortar, concrete components or road base materials.
  10. 10. The use according to claim 9, wherein the amount of the fly ash low carbon cement is 15 to 25% of the total mass of the concrete when used for preparing the concrete member, and 8 to 12% of the total mass of the base material when used for preparing the road base material.

Description

Fly ash low-carbon cement and preparation method and application thereof Technical Field The invention belongs to the technical field of cement, and particularly relates to fly ash low-carbon cement and a preparation method and application thereof. Background Cement is an indispensable basic material in the building industry, but a large amount of resources such as limestone, coal and the like are consumed in the production process, and about 0.85 ton of carbon dioxide is discharged per 1 ton of cement clinker produced, so that the cement is one of the main carbon emission sources worldwide. The low-carbonization transformation in the cement industry has become a necessary trend, reduces the consumption of cement clinker, improves the recycling utilization rate of industrial solid waste, and is a key path for realizing the low-carbon development in the cement industry. The fly ash is industrial solid waste generated in the coal-fired power generation process of the thermal power plant, the annual emission is huge, and if a large amount of fly ash is piled up, not only can land resources be occupied, but also the pollution of the atmosphere and the water body can be caused. The main chemical components of the fly ash are SiO 2、Al2O3、Fe2O3 and the like, and the fly ash has certain potential activity, can be used as a cement mixed material to replace part of cement clinker, can realize the recycling of solid waste, and can reduce the carbon emission and the production cost of cement production. However, the activity of the fly ash is lower, the glass body structure of the fly ash is compact, the clinker substitution rate is usually not more than 20% in the conventional use, and if the substitution rate is blindly improved, the mechanical property and durability of the cement are obviously reduced, so that the engineering use requirement cannot be met. In order to improve the activity of the fly ash, the prior art mainly adopts physical excitation, chemical excitation or composite excitation and other modes. Physical excitation (such as mechanical grinding) can reduce the particle size of the fly ash and increase the specific surface area, but has higher energy consumption and limited excitation effect, and chemical excitation is the most widely used mode at present, and commonly used excitation agents comprise alkaline excitation agents (such as sodium hydroxide and water glass) and acidic excitation agents (such as organic weak acid). Although the alkaline excitant can effectively excite the activity of the fly ash, the alkaline excitant has the problems of strong corrosiveness, high cost, easy to cause poor cement volume stability and the like, and the organic weak acid excitant (such as citric acid and tartaric acid) has low corrosiveness and moderate cost, but has limited excitation effect when being singly used, and is difficult to realize the substitution of clinker with high proportion. In recent years, the application of high molecular polymers in cement-based materials is focused gradually, and partial researches adopt binary high molecular copolymers (such as polyacrylic acid-acrylamide copolymers) to assist in exciting the activity of the fly ash, but the binary copolymers have limited functional group types, poor combination ability and synergistic excitation effect with the fly ash, and can not realize the preparation of qualified 32.5-grade cement with clinker substitution rate of more than 25 percent. For example, the Chinese patent application CN112174553A discloses a composite activated low-calcium fly ash cement and a preparation method thereof, and adopts an alkaline activator and a mineral admixture to compositely activate the fly ash, but the problems of strong corrosiveness of the alkaline activator, low clinker substitution rate (not more than 30 percent), poor cement performance stability and the like exist. In addition, the patent does not use a high molecular copolymer as an activator, and cannot meet the requirements of high-proportion clinker substitution and low carbonization. Disclosure of Invention The invention aims to overcome the technical defects of low activity of fly ash, limited clinker substitution rate, high carbon emission, poor effect of an exciting agent and the like in the prior art, and provides fly ash low-carbon cement and a preparation method and application thereof. In order to solve the technical problems, the invention is realized by the following technical scheme: The invention provides fly ash low-carbon cement which comprises, by mass, 25% -60% of cement clinker, 30% -65% of fly ash, 0.3% -1.2% of a ternary polymer copolymer, 0.1% -0.5% of an organic weak acid and 2% -5% of gypsum, wherein the ternary polymer copolymer is poly (acrylic acid-2-acrylamide-2-methylpropanesulfonic acid-N-methylolacrylamide), the monomer molar ratio of the ternary polymer copolymer is acrylic acid-2-acrylamide-2-methylpropanesulfonic acid-N-methylolacrylamide=3:1:1, the number a