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CN-122010473-A - Cement cooling mortar for building outer wall and preparation method thereof

CN122010473ACN 122010473 ACN122010473 ACN 122010473ACN-122010473-A

Abstract

The invention relates to the technical field of building materials, in particular to cement cooling mortar for an external wall of a building and a preparation method thereof, wherein the cement cooling mortar comprises geopolymer cement, modified flax fiber, water-absorbing polymer and water, the geopolymer cement comprises solid powder, toughening fiber and alkali-exciting agent, the solid powder contains Ca 2+ , the modified flax fiber is obtained by loading calcium sulfoaluminate and water glass on the flax fiber and packaging, and the mass percentages of the modified flax fiber, the water-absorbing polymer and the water in the geopolymer cement are respectively 0.3-0.7% of the modified flax fiber, 0.3-1.8% of the water-absorbing polymer and 5-15% of the water. According to laboratory measurement, the cement cooling mortar for the building outer wall provided by the invention realizes surface cooling by evaporating and radiating, and plays a self-repairing function, prevents expansion and recovers strength when cracks appear by toughening and cracking the modified flax fiber, thereby being beneficial to obviously improving durability.

Inventors

  • LIN CHANG
  • WANG FAKANG
  • PENG RUI
  • PAN LISHA
  • XU SHUYING

Assignees

  • 海南大学

Dates

Publication Date
20260512
Application Date
20260228

Claims (10)

  1. 1. A cement cooling mortar for an external wall of a building is characterized by comprising geopolymer cement, modified flax fibers, a water-absorbing polymer and water, wherein the geopolymer cement comprises solid powder, toughening fibers and an alkali-exciting agent, the solid powder contains Ca 2+ , the modified flax fibers are obtained by loading calcium sulfoaluminate and water glass on the flax fibers and packaging, and the mass percentages of the modified flax fibers, the water-absorbing polymer and the water in the geopolymer cement are respectively 0.3-0.7% of the modified flax fibers, 0.3-1.8% of the water-absorbing polymer and 5-15% of the water.
  2. 2. The cement cooling mortar for the building outer wall according to claim 1, wherein the mass ratio of calcium sulfoaluminate to water glass is 1:1, and the solid powder contains slag micropowder with the mass percentage not less than 30%; preferably, the solid powder comprises the following components, by mass, 50% -60% of fly ash, 30% -40% of slag micropowder, 5% -10% of limestone powder and 0.1% -10% of metakaolin; preferably, the particle size of the solid powder is 0.1-2 μm.
  3. 3. The cementitious cooling mortar for building exterior walls according to claim 1, wherein the cellulose content of the flax fiber is not less than 70%, the length is 10-20mm, the diameter is 15-25 μm, the BET is 3-6m 2 /g, the cellulose content of the modified flax fiber is not less than 80%, the BET is 8-12m 2 /g; Preferably, the modified flax fiber is obtained by carrying calcium sulfoaluminate and water glass on the flax fiber and then carrying out compound crosslinking encapsulation on the calcium sulfoaluminate and the water glass through sodium alginate, calcium chloride and aluminum chloride, and further preferably, the loading amount of the calcium sulfoaluminate and the water glass on the flax fiber is 28% -40%, and the thickness of a crosslinking layer obtained after compound crosslinking encapsulation is 0.5-3 mu m; Preferably, a hydrophobic coating is further arranged outside the crosslinking layer, and the hydrophobic coating is formed after being heated and solidified through sodium methyl silicate.
  4. 4. The cementitious cooling mortar for building exterior walls according to claim 1, wherein the volume percentage of the toughening fibers and the solid powder is 1.5% -5%, and the mass percentage of the alkali-activator and the solid powder is 20% -40%.
  5. 5. The cementitious cooling mortar for building exterior walls according to claim 4, wherein the toughening fiber is at least one selected from the group consisting of polyvinyl alcohol fiber, polypropylene fiber, and steel fiber; Preferably, the length of the toughened fiber single fiber is 10-50mm, the diameter of the single fiber is 10-20 mu m, and the tensile strength is 100-5000MPa.
  6. 6. The cementitious cooling mortar for building exterior walls according to claim 4, wherein the alkali-activator is prepared by mixing sodium hydroxide, water glass and water and has a modulus of 1 to 1.2 and a solid content of 42 to 58%.
  7. 7. The cementitious cooling mortar for building exterior walls according to claim 1, wherein the water-absorbing polymer is at least one selected from sodium alginate, hydroxypropyl methylcellulose, and sodium carboxymethylcellulose; Preferably, the water-absorbing polymer is sodium alginate, and the mass percentage of the sodium alginate in the geopolymer cement is 0.5% -1.5%.
  8. 8. A method for preparing the cement cooling mortar for the building outer wall according to any one of claims 1 to 7, which is characterized by comprising the following operation steps: S1, preparing modified flax fibers, namely firstly carrying out alkali dissolution pore-forming on the flax fibers, then carrying out calcium sulfoaluminate and water glass loading, drying, solidifying, packaging and drying again; s2, uniformly mixing solid powder, toughening fibers and solid components of an alkali excitant according to a proportion, then adding a water-absorbing polymer, and uniformly mixing again to obtain a dry mixed material; s3, mixing the liquid component of the alkali-activated agent with water, slowly pouring the mixture into the dry mixture, uniformly stirring to form slurry, and finally, doping the modified flax fibers.
  9. 9. The preparation method of the cement cooling mortar for the building outer wall, which is characterized by comprising the following steps of S1, drying flax fibers before loading calcium sulfoaluminate and water glass, wherein the concrete loading operation comprises the steps of immersing the dried flax fibers in slurry with the mass ratio of the calcium sulfoaluminate to the water glass being 1:1 in vacuum, taking out the slurry after 20-40min, and draining, wherein the viscosity of the slurry is 100-200mPa.s, the calcium sulfoaluminate is calcium sulfoaluminate powder with the D50 not more than 5 mu m, and the water glass is water glass with the modulus of 1 and the solid content not more than 35%; Preferably, in the step S1, the encapsulation comprises composite crosslinking, wherein the concrete operation of the composite crosslinking is that the obtained flax fiber is immersed into a mixed solution of sodium alginate, calcium chloride and aluminum chloride for 20-35S, and is taken out, drained and washed with water, wherein the mass ratio of the sodium alginate to the calcium chloride to the aluminum chloride is 4:10:1; Preferably, in the step S1, the specific operation of alkali dissolution and pore forming is that firstly, flax fibers are soaked in sodium hydroxide solution with the mass percent of 3-5% for at least 3 hours at 50-65 ℃, and then are washed by deionized water and dried.
  10. 10. The method for preparing the cement cooling mortar for the building outer wall according to claim 9, wherein in the step S1, the packaging further comprises the steps of arranging a hydrophobic coating, specifically operating to dip the flax fiber subjected to composite crosslinking into a sodium methyl silicate solution with the mass percentage of 5% for 8-15S, taking out, draining and curing for 10-15min at 80 ℃; preferably, the drying in the step S1 is specifically performed by drying for 4-6 hours at 60 ℃ under vacuum.

Description

Cement cooling mortar for building outer wall and preparation method thereof Technical Field The invention relates to the technical field of building materials, in particular to cement cooling mortar for an external wall of a building and a preparation method thereof. Background The cement mortar is the most common protective structure layer of the building outer wall, can form a physical barrier when being coated on the building outer wall, resists wind and rain erosion, ultraviolet radiation and temperature difference change, prevents the wall from cracking, is impervious and waterproof, reduces reinforcement corrosion and freeze thawing damage caused by moisture permeation, and prolongs the service life of the wall. In the background of global warming, in order to cope with extreme climates, the demand for energy-saving cement cooling mortar with a cooling function is increasing. In the prior art, cement mortar capable of continuously cooling the surface and realizing the purpose of energy saving is mainly subjected to heat regulation and control by adopting the following principles that (1) SiC or Al 2O3 nano particles are doped for radiating heat to space through an atmospheric window to realize passive refrigeration, (2) anatase titanium dioxide or infrared reflection pigment is doped for reflecting sunlight with 400-2500nm wave band selectively, (3) evaporation cooling, medium capable of containing a large amount of water such as zeolite, modified diatomite and the like is doped for realizing water slow release by capillary action, continuous cooling is realized at 4-7 ℃ in an environment with RH being less than or equal to 50%, and (4) phase change energy storage temperature adjustment is realized by doping a phase change material for realizing reversible phase change in a 28-32 ℃ interval, and then heat flow is buffered. Among them, the evaporative cooling mode has low cost, strong extreme environmental adaptability and dynamic responsiveness, and therefore has received extensive attention. However, the cyclic dryness moistening in the evaporation cooling mode is easy to cause mortar microcrack, the strength loss is remarkable, the durability is poor, and the system is obviously inferior to the systems such as reflection cooling, phase change energy storage temperature adjustment and the like. For this purpose, the present application is proposed. Disclosure of Invention In view of the defects in the prior art, the invention provides cement cooling mortar for an external wall of a building and a preparation method thereof, which are used for solving the problems that the prior art is easy to cause mortar microcrack, remarkable in strength loss and poor in durability due to cyclic dryness moistening. In order to achieve the above purpose, the main technical scheme adopted by the invention comprises the following steps: On one hand, the invention provides cement cooling mortar for an outer wall of a building, which comprises geopolymer cement, modified flax fibers, a water-absorbing polymer and water, wherein the geopolymer cement comprises solid powder, toughening fibers and an alkali-exciting agent, the solid powder contains Ca 2+, the modified flax fibers are obtained by loading calcium sulfoaluminate and water glass on the flax fibers and packaging, and the mass percentages of the modified flax fibers, the water-absorbing polymer and the water in the geopolymer cement are respectively 0.3-0.7% of the modified flax fibers, 0.3-1.8% of the water-absorbing polymer and 5-15% of the water. The modified flax fiber utilizes the natural macroporous structure to guide water, provides an evaporation surface, absorbs water when the water-absorbing polymer is high in humidity and releases water when the water-absorbing polymer is low in humidity, and the modified flax fiber and the water-absorbing polymer jointly act to construct a water storage, water guide and evaporation system to exert an active evaporation cooling function. More importantly, the modified flax fiber is doped into geopolymer cement according to Sup>A given proportion, the surface temperature is reduced by utilizing evaporation efficiency with Sup>A water-absorbing polymer, on one hand, the inherent bridging toughening effect of the fiber can be exerted to prevent the formation of shrinkage cracks, on the other hand, calcium sulfoaluminate and water glass are broken and exposed when the cracks are generated, at the moment, moisture in the water-absorbing polymer or environment enters, CSup>A 2+ and Sup>A strong alkali environment provided by the geopolymer cement are just optimal conditions for the reaction of the water glass and the calcium sulfoaluminate, the calcium sulfoaluminate rapidly reacts with CSup>A 2+ when meeting water to generate ettringite, then the water glass and the geopolymer cement are greatly expanded to fill the cracks, N-A-S-H gel (sodium alumino silicate gel, also called geopolymer gel) is rapidly generated by the r