CN113912410A - Preparation method of bionic multifunctional cement-hydrogel composite material - Google Patents
Preparation method of bionic multifunctional cement-hydrogel composite material Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/04—Portland cements
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
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- C04B2111/40—Porous or lightweight materials
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
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Abstract
The invention discloses a preparation method of a bionic multifunctional cement-hydrogel composite material, which comprises the following steps: mixing the cementing material with water to obtain cement paste; freezing the cement paste according to the ice template principle, utilizing a bidirectional freezing gradient to directionally solidify water in the cement paste to form an ice layer, and then storing at low temperature to obtain a cement blank with directional pores and a layered structure; and curing the cement blank in a cement curing environment, demoulding, soaking in a hydrogel solution to fill interlayer pores of the cement blank with the hydrogel solution, and then performing freeze-thaw cycle to prepare the hydrogel. The method is simple, low in cost, controllable in performance and ideal in effect; the obtained composite material has obviously improved toughness and ductility of cement-based materials, and also has the characteristics of light weight, high strength and high specific strength; has excellent heat insulation and sound absorption performance and the characteristics of internal maintenance and self-healing brought by hydrogel.
Description
Technical Field
The invention relates to a preparation method of a cement-based composite material, in particular to a preparation method of a bionic multifunctional cement-hydrogel composite material.
Background
The cement-based material is used as the most widely used building material at home and abroad, and has the advantages of easily available materials, low cost, wide application range and the like. However, the traditional cement-based material has low tensile strength, poor toughness and easy cracking, various crack propagation can occur under the service conditions of long-term use and severe environment, and finally the matrix fails, and particularly under the condition of bearing bending load, the application of the cement-based material is greatly limited by the brittleness and low bending strength. In addition, with the progress and development of society, the demands of high-rise, large-scale and complicated building design on materials are more diversified, and the performances of light weight, heat preservation, heat insulation, sound insulation, water permeability, crack resistance and the like are gradually researched hot spots besides the requirements of continuously improving the strength index and the service time of the building materials.
A plurality of researches show that the tensile strength of a cement matrix can be effectively improved by adding different types and different mixing amounts of fibers. However, due to the property of easy agglomeration of the fibers, uniform distribution of the fibers in the cement matrix is difficult to realize, and the fluidity of the cement paste is reduced after the fibers are added, so that local defects are easily generated, and the loss of comprehensive performance is brought.
The 'brick-mud' structure of the shell pearl layer in biology can also play a role in crack deflection so as to further hinder crack propagation, and the structure has excellent plasticity and toughness and extremely high strong hardness. The high-strength inorganic bricks orderly arranged in the brick-mud structure can be replaced by cement hydration products, and the ice template technology is an effective scheme for preparing bionic bricks. The special mould design is utilized to realize bidirectional freezing gradient, so that cement particles can be directionally arranged and continuously hydrated along with the melting of an ice layer, and the porosity of a particle layer can be reduced because the cement particles are compacted by the driving force generated by the expansion of the solidification volume of ice. After the ice layer is completely melted, the cement particles are basically completely hydrated, and the interlayer gaps left by the ice layer can be consolidated by adding proper mud.
The hydrogel is a material which has excellent flexibility and is well compounded with a cement-based material, and can be used as 'mud' for filling gaps among cement-based materials. Compared with the traditional cement-based material, the cement-hydrogel composite material can effectively improve the mechanical property of the material, reduce the dead weight of the cement-based material while sacrificing the compressive strength within a certain limit, improve the specific strength and has the characteristics of light weight and high strength; free water removed by the hydrogel under normal maintenance or use conditions can further promote the hydration of cement particles, can play an effective role in blocking and repairing the crack initiation and propagation, and has the characteristics of internal maintenance and self-healing. At present, cement-hydrogel composite materials with bending strength close to 10MPa and ultimate strain exceeding 20% are prepared, and have the characteristic of obvious multi-crack cracking. According to the special properties of the hydrogel, the composite material still has the potential of continuously improving the comprehensive performance.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a preparation method of a bionic multifunctional cement-hydrogel composite material with a bionic structure and multiple functions.
The technical scheme is as follows: the preparation method of the bionic multifunctional cement-hydrogel composite material comprises the following steps:
(1) mixing the cementing material with water to obtain cement paste;
(2) freezing the cement paste according to the ice template principle, utilizing a bidirectional freezing gradient to directionally solidify water in the cement paste to form an ice layer, and then storing at low temperature to obtain a cement blank with directional pores and a layered structure;
(3) and placing the cement blank in a cement curing environment, curing for a period of time, demolding, immersing in a hydrogel solution to fill interlayer pores of the cement blank with the hydrogel solution, and then performing freeze-thaw cycle to prepare the hydrogel, thereby obtaining the bionic multifunctional cement-hydrogel composite material.
In the step (1), the water-to-cement ratio in the cement paste is 0.4-1.5, and more preferably 0.4-0.8; the cementing material is selected from ordinary portland cement and silica fume, and preferably contains 10 wt% of silica fume.
Wherein, in the step (1), a thickening agent is added into the cementing material and water, and the addition amount of the thickening agent is 0-1% of the mass of the cement; the thickener is preferably hydroxypropyl methylcellulose. The thickening agent plays a role in improving the consistency of cement paste, and the thickening agent is pre-dissolved in water for 1 day before being mixed so as to ensure complete dissolution and uniform dispersion.
In the step (1), the slurry mixing mode is mechanical stirring, the cementing material is firstly stirred at a medium speed for 1-2 min and uniformly mixed, and after water is added, the stirring is continuously carried out at a medium speed for 3-5 min to mix the cement slurry.
Wherein, the specific process of the step (2) is as follows: and pouring the mixed liquid into the mold, so that the mold only conducts heat through the bottom plate in the liquid nitrogen freezing process to form a bidirectional freezing gradient in the horizontal and vertical directions. Specifically, a copper plate is embedded at the bottom of tubular tetrafluoroethylene and sealed, wedge-shaped solid polydimethylsiloxane is filled in the copper plate in the tetrafluoroethylene, so that the heat of the die is transferred only through the bottom copper plate in the liquid nitrogen freezing process, and a bidirectional freezing gradient in the horizontal direction and the vertical direction is formed.
Wherein, in the step (2), the step of freezing the cement paste comprises the following steps: placing a mould poured with cement paste on a copper column, wherein the diameter of the copper column is slightly smaller than that of a tetrafluoroethylene tube, the upper end of the copper column is in contact with a copper plate at the bottom of the mould, and the lower end of the copper column is immersed in liquid nitrogen to play a role in heat transfer;
in the step (2), the low-temperature storage mode is as follows: and (3) placing the mould subjected to liquid nitrogen freezing treatment in an environment of 2-5 ℃, slowly melting the solidified ice, carrying out hydration reaction with cement particles, reacting for 2-3 days, and gradually hardening the cement in the process, so that the mould can be smoothly demoulded, and the cement blank with directional pores and a layered structure is obtained.
Wherein, in the step (3), the hydrogel solution is filled in interlayer pores of the cement blank by adopting a vacuumizing method; the specific method comprises the following steps: and immersing the hardened cement blank with the oriented interlayer pores into a hydrogel solution, placing the solution in a vacuum dryer, continuously exhausting air to provide a negative pressure environment until the solution is boiled, facilitating the discharge of gas in the cement blank and the entrance of a coagulant, then keeping the solution at a low pressure and standing for 1-2 days to ensure that the pores are completely filled, and drying the cement blank in advance before vacuumizing to remove water, thereby facilitating the immersion of a binder.
In the step (3), the hydrogel solution is a polyvinyl alcohol solution; preferably a polyvinyl alcohol solution with a mass fraction of 10%. The prepared bionic multifunctional cement-hydrogel composite material has excellent mechanical properties, shows good bending resistance and ductility, keeps the characteristics of light weight, high strength and good heat insulation and sound absorption effects of a porous material, and realizes the combination of multiple functions and high toughness of a cement-based material.
In the step (3), the preparation method of the hydrogel comprises the following steps: performing freeze-thaw cycling at a temperature of-30 ℃ to-20 ℃, wherein the freezing time is 8-10 hours, and the thawing time is 2-3 hours.
In the step (3), the composite material curing method comprises the following steps: and placing the cement-hydrogel composite material in an environment with the temperature of 20-25 ℃ and the relative humidity of 95-100% for curing, wherein the curing time can be selected from 4-28 days, and finally obtaining the cement-hydrogel composite material with the bionic structure and the multifunctional characteristics.
The working principle is as follows: through the design of a bionic brick-mud structure, on one hand, the orderly arranged cement particles are compacted to generate fewer pores after hydration, and hydration products are compact and have higher strength; on the other hand, the hydrogel is filled between the particle layers, so that the hydration products between the layers can be connected, the toughness of the cement matrix is improved, and meanwhile, a porous structure formed by the hydrogel after dehydration has good heat preservation, insulation and sound absorption effects.
Has the advantages that: compared with the prior art, the invention has the following remarkable effects: (1) the preparation of a 'brick-mud' bionic structure is realized, the mechanical property of the cement-based material is obviously improved, the bending strength and the ultimate strain of the bionic structure exceed the level of the traditional cement-based material, the bionic structure further shows the characteristic of multi-joint cracking, and the bionic structure has certain deformation capacity under the condition of bearing bending load. (2) The characteristics of light weight, high strength and good heat insulation and sound absorption effects of the porous material are reserved, the combination of multiple functions and high strength and toughness of the cement-based material is realized, the comprehensive performance of the cement-hydrogel composite material can be effectively controlled by adjusting the slurry proportion, the ice template freezing rate and the type and parameters of the filling material mud, and the development and application prospects are wide. (3) The preparation method has the advantages that the preparation process of the multifunctional cement-based material is simplified based on the improvement of the microstructure on the cement-based material, the raw materials are simple and easy to obtain, the cost is low, the production process is green and environment-friendly, the process is simple, and the efficiency is high.
Drawings
FIG. 1 is a topographic map of a biomimetic multifunctional cement-hydrogel composite material according to example 1 of the present invention;
FIG. 2 is a topographic map of the biomimetic multifunctional cement-hydrogel composite of example 2 of the present invention;
FIG. 3 is a topographic map of the biomimetic multifunctional cement-hydrogel composite material of embodiment 5 of the present invention.
Detailed Description
The present invention is described in further detail below.
Example 1
In this example, a bionic multifunctional cement-hydrogel composite material was prepared using a slurry ratio of water to a gelling material of 1.5 by mass. The raw materials used include: ordinary portland cement: P.O 42.5.5, specific surface area 342m2Per kg; silica fume: specific surface area 2X 104m2Per kg; thickening agent: hydroxypropyl methylcellulose, hereinafter referred to as HPMC, having a viscosity of 100000Pa · s; polyvinyl alcohol: PVA is abbreviated as follows, and the molecular weight is 80000-100000; deionized water. The preparation process comprises the following steps:
(1) weighing 225g of ordinary portland cement, 25g of silica fume, 375g of water and 2.25g of hydroxypropyl methyl cellulose, adding the hydroxypropyl methyl cellulose into the water 1 day ahead of time, and continuously stirring until the mixture is fully dissolved and uniform; adding the gelled material into a stirrer with the volume of 1L, mechanically stirring at the speed of 300rpm for 1min, uniformly mixing, adding the hydroxypropyl methyl cellulose solution, and continuously stirring at medium speed for 3 min.
(2) Pouring the stirred slurry into a tetrafluoroethylene mold with an inner diameter of 50 multiplied by 50mm and a bottom embedded with a copper plate, wherein wedge-shaped polydimethylsiloxane with an inclination angle of 18 degrees is arranged below the mold; one end of a copper column is immersed in liquid nitrogen, the other end of the copper column is in contact with a copper bottom plate of the mold, the heat transfer of the copper column is utilized to enable water in the slurry to generate a bidirectional freezing gradient, and ice crystals growing along the solidification direction gradually squeeze the slurry between ice layers, so that the directional arrangement of cement particles and pores is realized.
(3) And (3) placing the solidified mould into an environment at 5 ℃ for low-temperature storage for 2d to slowly melt ice, then curing for 6 days under the curing conditions that the temperature is 20 ℃ and the humidity is 95%, taking out the blank from the mould, immersing the blank into an ethanol solution for 1 day, drying at 40 ℃ for 3 days, immersing the blank into a 10 wt% PVA aqueous solution, performing vacuum air suction, and keeping the pressure low for 1 day to ensure that pores are filled. Then, freeze-thaw cycle is carried out, the mixture is frozen at minus 30 ℃ for 8 hours and then placed at normal temperature for 3 hours, and the process is repeated for three times.
The bionic multifunctional cement-hydrogel composite material in the embodiment has a large hydrogel ratio, a large ice layer thickness and a small cement layer thickness, and a layered structure is uniform and flat before pore filling, as shown in fig. 1.
Example 2
In this example, a bionic multifunctional cement-hydrogel composite material was prepared using a slurry ratio of water to a cementitious material of 0.8 by mass. The raw materials used include: ordinary portland cement: P.O 42.5.5, specific surface area 342m2Per kg; silica fume: specific surface area 2X 104m2Per kg; thickening agent: HPMC with viscosity of 100000Pa · s; PVA, molecular weight 80000-100000; deionized water. The preparation process comprises the following steps:
(1) weighing 225g of ordinary portland cement, 25g of silica fume, 200g of water and 2.25g of hydroxypropyl methyl cellulose, adding the hydroxypropyl methyl cellulose into the water 1 day ahead of time, and continuously stirring until the mixture is fully dissolved and uniform; adding the gelled material into a stirrer with the volume of 1L, mechanically stirring at the speed of 300rpm for 1min, uniformly mixing, adding the hydroxypropyl methyl cellulose solution, and continuously stirring at medium speed for 3 min.
(2) Pouring the stirred slurry into a tetrafluoroethylene mold with an inner diameter of 50 multiplied by 50mm and a bottom embedded with a copper plate, wherein wedge-shaped polydimethylsiloxane with an inclination angle of 18 degrees is arranged below the mold; one end of a copper column is immersed in liquid nitrogen, the other end of the copper column is in contact with a copper bottom plate of the mold, the heat transfer of the copper column is utilized to enable water in the slurry to generate a bidirectional freezing gradient, and ice crystals growing along the solidification direction gradually squeeze the slurry between ice layers, so that the directional arrangement of cement particles and pores is realized.
(3) And (3) placing the solidified mould into an environment at 5 ℃ for low-temperature storage for 2d to slowly melt ice, then curing for 4 days under the curing conditions that the temperature is 20 ℃ and the humidity is 95%, taking out the blank from the mould, immersing the blank into an ethanol solution for 1 day, drying at 40 ℃ for 3 days, immersing the blank into a 10 wt% PVA aqueous solution, performing vacuum air suction, and keeping the pressure low for 1 day to ensure that pores are filled. Then, freeze-thaw cycle is carried out, the mixture is frozen at-20 ℃ for 10 hours and then placed at normal temperature for 2 hours, and the process is repeated for three times.
(4) And (3) placing the filled cement-hydrogel composite material for 7 days at normal temperature and normal pressure until strength test is carried out.
The bionic multifunctional cement-hydrogel composite material in the embodiment has a compact structure before pore filling, the thickness of the cement particle sheet is large, the interlayer gap is small, as shown in fig. 2, the ductility of the composite material is good, the ultimate bending strain can reach 4.83%, and the bending strength is 1.88 MPa.
Example 3
In this example, a bionic multifunctional cement-hydrogel composite material was prepared using a slurry ratio of water to a cementitious material of 0.6 by mass. The raw materials used include: ordinary portland cement: P.O 42.5.5, specific surface area 342m2Per kg; silica fume: specific surface area 2X 104m2Per kg; thickening agent: HPMC with viscosity of 100000Pa · s; PVA, molecular weight 80000-100000; deionized water. The preparation process comprises the following steps:
(1) weighing 225g of ordinary portland cement, 25g of silica fume, 200g of water and 2.25g of hydroxypropyl methyl cellulose, adding the hydroxypropyl methyl cellulose into the water 1 day ahead of time, and continuously stirring until the mixture is fully dissolved and uniform; adding the gelled material into a stirrer with the volume of 1L, mechanically stirring at the speed of 300rpm for 1min, uniformly mixing, adding the hydroxypropyl methyl cellulose solution, and continuously stirring at medium speed for 3 min.
(2) Pouring the stirred slurry into a tetrafluoroethylene mold with an inner diameter of 50 multiplied by 50mm and a bottom embedded with a copper plate, wherein wedge-shaped polydimethylsiloxane with an inclination angle of 18 degrees is arranged below the mold; one end of a copper column is immersed in liquid nitrogen, the other end of the copper column is in contact with a copper bottom plate of the mold, the heat transfer of the copper column is utilized to enable water in the slurry to generate a bidirectional freezing gradient, and ice crystals growing along the solidification direction gradually squeeze the slurry between ice layers, so that the directional arrangement of cement particles and pores is realized.
(3) And (3) storing the solidified mould at a low temperature of 5 ℃ for 2 days to slowly melt ice, and then soaking in water for curing, wherein the curing conditions are as follows: and (3) curing at 25 ℃ and 100% relative humidity for 4 days, taking the blank out of the mold, immersing the blank in an ethanol solution for 1 day, drying the blank for 3 days at 40 ℃, immersing the blank in a 10 wt% PVA aqueous solution, performing vacuum pumping, and keeping the pressure low for 1 day to ensure that the pores are filled. Then, freeze-thaw cycle is carried out, the mixture is frozen at-20 ℃ for 10 hours and then placed at normal temperature for 2 hours, and the process is repeated for three times.
(4) And (3) placing the filled cement-hydrogel composite material for 20 days at normal temperature and normal pressure until strength test is carried out.
The bionic multifunctional cement-hydrogel material in the embodiment has a compact structure before pore filling, large lamella thickness of cement particles, small interlayer gaps, ideal filling effect, long standing time after filling, further development of strength in a hydrogel system, bending strength of 3.36MPa and bending strain of 2.8%.
Example 4
In this example, a bionic multifunctional cement-hydrogel composite material was prepared using a slurry ratio of water to a cementitious material of 0.6 by mass. The raw materials used include: ordinary portland cement: P.O 42.5.5, specific surface area 342m2Per kg; silica fume: specific surface area 2X 104m2Per kg; thickening agent: HPMC with viscosity of 100000Pa · s; PVA, molecular weight 80000-100000; deionized water. The preparation process comprises the following steps:
(1) weighing 225g of ordinary portland cement, 25g of silica fume, 200g of water and 0.45g of hydroxypropyl methyl cellulose, adding the hydroxypropyl methyl cellulose into the water 1 day ahead of time, and continuously stirring until the mixture is fully dissolved and uniform; adding the gelled material into a stirrer with the volume of 1L, mechanically stirring at the speed of 300rpm for 1min, uniformly mixing, adding the hydroxypropyl methyl cellulose solution, and continuously stirring at medium speed for 3 min.
(2) Pouring the stirred slurry into a tetrafluoroethylene mold with an inner diameter of 50 multiplied by 50mm and a bottom embedded with a copper plate, wherein wedge-shaped polydimethylsiloxane with an inclination angle of 18 degrees is arranged below the mold; one end of a copper column is immersed in liquid nitrogen, the other end of the copper column is in contact with a copper bottom plate of the mold, the heat transfer of the copper column is utilized to enable water in the slurry to generate a bidirectional freezing gradient, and ice crystals growing along the solidification direction gradually squeeze the slurry between ice layers, so that the directional arrangement of cement particles and pores is realized.
(3) And (3) storing the solidified mould at a low temperature of 5 ℃ for 2 days to slowly melt ice, and then soaking in water for curing, wherein the curing conditions are as follows: the temperature is 25 ℃, and the relative humidity is 100%; and after 28 days of maintenance, taking the blank out of the mold, immersing the blank into an ethanol solution for 1 day, drying the blank for 3 days at 40 ℃, immersing the blank into a 10 wt% PVA aqueous solution, vacuumizing, and keeping the pressure low for 1 day to ensure that the pores are filled. Then, freeze-thaw cycle is carried out, the mixture is frozen at-30 ℃ for 10 hours and then placed at normal temperature for 3 hours, and the process is repeated for three times.
(4) And (3) placing the filled cement-hydrogel composite material for 9 days at normal temperature and normal pressure until strength test is carried out.
The bionic multifunctional cement-hydrogel composite material under the embodiment has the advantages of basically complete strength development before pore filling, compact structure, optimal effect after hydrogel filling, highest ductility, ultimate bending strain up to 24.28% and bending strength up to 3.94 MPa.
Example 5
In this example, a bionic multifunctional cement-hydrogel composite material was prepared using a slurry ratio of water to a cementitious material of 0.4 by mass. The raw materials used include: ordinary portland cement: P.O 42.5.5, specific surface area 342m2Per kg; silica fume: specific surface area 2X 104m2Per kg; thickening agent: HPMC with viscosity of 100000Pa · s; PVA, molecular weight 80000-100000; deionized water. The preparation process comprises the following steps:
(1) weighing 225g of ordinary portland cement, 25g of silica fume and 200g of water; the gelled material was added to a 1L capacity blender and mechanically stirred at 300rpm for 1min, followed by addition of water and continued stirring at medium speed for 3 min.
(2) Pouring the stirred slurry into a tetrafluoroethylene mold with an inner diameter of 50 multiplied by 50mm and a bottom embedded with a copper plate, wherein wedge-shaped polydimethylsiloxane with an inclination angle of 18 degrees is arranged below the mold; one end of a copper column is immersed in liquid nitrogen, the other end of the copper column is in contact with a copper bottom plate of the mold, the heat transfer of the copper column is utilized to enable water in the slurry to generate a bidirectional freezing gradient, and ice crystals growing along the solidification direction gradually squeeze the slurry between ice layers, so that the directional arrangement of cement particles and pores is realized.
(3) And (3) storing the solidified mould at a low temperature of 5 ℃ for 2 days to slowly melt ice, and then soaking in water for curing, wherein the curing conditions are as follows: and (3) curing at 25 ℃ and 100% relative humidity for 28 days, taking the blank out of the mold, immersing the blank in an ethanol solution for 1 day, drying the blank for 3 days at 40 ℃, immersing the blank in a 10 wt% PVA aqueous solution, performing vacuum pumping, and keeping the pressure low for 1 day to ensure that the pores are filled. Then, freeze-thaw cycle is carried out, the mixture is frozen at minus 30 ℃ for 8 hours and then placed at normal temperature for 3 hours, and the process is repeated for three times.
(4) And (3) placing the filled cement-hydrogel composite material for 14 days at normal temperature and normal pressure until strength test is carried out.
The bionic multifunctional cement-hydrogel composite material in the embodiment has compact structure before pore filling, the thickness of the cement particle sheet layer is large, and almost no visible interlayer gap exists, as shown in figure 3, so that the bionic multifunctional cement-hydrogel composite material has the best strength characteristic, the bending strength can reach 9.86MPa, and the limit strain is 1.05%.
Comparative example 1
The bionic multifunctional cement-hydrogel composite material is prepared by using a slurry mixture ratio of 0.8 mass ratio of water to the cementing material. The raw materials used include: ordinary portland cement: P.O 42.5.5, specific surface area 342m2Per kg; silica fume: specific surface area 2X 104m2Per kg; thickening agent: HPMC with viscosity of 100000Pa · s; deionized water. The preparation process comprises the following steps:
(1) weighing 225g of ordinary portland cement, 25g of silica fume, 200g of water and 2.25g of hydroxypropyl methyl cellulose, adding the hydroxypropyl methyl cellulose into the water 1 day ahead of time, and continuously stirring until the mixture is fully dissolved and uniform; adding the gelled material into a stirrer with the volume of 1L, mechanically stirring at the speed of 300rpm for 1min, uniformly mixing, adding the hydroxypropyl methyl cellulose solution, and continuously stirring at medium speed for 3 min.
(2) Pouring the stirred slurry into a tetrafluoroethylene mold with an inner diameter of 50 multiplied by 50mm and a bottom embedded with a copper plate, wherein wedge-shaped polydimethylsiloxane with an inclination angle of 18 degrees is arranged below the mold; one end of a copper column is immersed in liquid nitrogen, the other end of the copper column is in contact with a copper bottom plate of the mold, the heat transfer of the copper column is utilized to enable water in the slurry to generate a bidirectional freezing gradient, and ice crystals growing along the solidification direction gradually squeeze the slurry between ice layers, so that the directional arrangement of cement particles and pores is realized.
(3) And (3) storing the solidified mould at a low temperature of 5 ℃ for 2 days to slowly melt ice, and then soaking in water for curing, wherein the curing conditions are as follows: maintaining at 25 deg.C and relative humidity of 100% for 28 days, taking out the blank from the mold, soaking in ethanol solution for 1 day, and oven drying at 40 deg.C for 3 days.
The comparison example provides a comparison of the water cement ratio of 0.8 and the bending resistance of the cement paste filled with anhydrous gel, the limit strain of the comparison example is 0.48%, and the bending strength can reach 2.52 MPa.
Claims (10)
1. A preparation method of a bionic multifunctional cement-hydrogel composite material is characterized by comprising the following steps:
(1) mixing the cementing material with water to obtain cement paste;
(2) freezing the cement paste according to the ice template principle, utilizing a bidirectional freezing gradient to directionally solidify water in the cement paste to form an ice layer, and then storing at low temperature to obtain a cement blank with directional pores and a layered structure;
(3) and curing the cement blank in a cement curing environment, demoulding, soaking in a hydrogel solution to fill interlayer pores of the cement blank with the hydrogel solution, and then performing freeze-thaw cycle to prepare hydrogel to obtain the bionic multifunctional cement-hydrogel composite material.
2. The preparation method of the bionic multifunctional cement-hydrogel composite material as claimed in claim 1, wherein in the step (1), the water-to-gel ratio in the cement paste is 0.4-1.5.
3. The preparation method of the bionic multifunctional cement-hydrogel composite material as claimed in claim 1, wherein in the step (1), a thickener is added into the gelled material and water, and the addition amount of the thickener is 0-1% of the mass of the gelled material.
4. The preparation method of the bionic multifunctional cement-hydrogel composite material as claimed in claim 1, wherein the specific process of the step (2) is as follows: and pouring the mixed liquid into the mold, so that the mold only conducts heat through the bottom plate in the liquid nitrogen freezing process to form a bidirectional freezing gradient in the horizontal and vertical directions.
5. The method for preparing a bionic multifunctional cement-hydrogel composite material as claimed in claim 1, wherein the bottom of the mold used for freezing the mixed solution by using the ice template principle has a base with an inclined angle.
6. The preparation method of the bionic multifunctional cement-hydrogel composite material as claimed in claim 1, wherein in the step (2), the low-temperature storage mode is as follows: and (3) placing the mould subjected to liquid nitrogen freezing treatment in a low-temperature environment, so that the solidified ice is slowly melted and undergoes hydration reaction with cement particles.
7. The method for preparing a bionic multifunctional cement-hydrogel composite material as claimed in claim 1, wherein in the step (3), the hydrogel solution is filled in the interlayer pores of the cement body by a vacuum pumping method.
8. The preparation method of the bionic multifunctional cement-hydrogel composite material as claimed in claim 1, wherein the vacuum pumping method comprises the following specific steps: and (3) immersing the hardened cement blank with the oriented interlayer pores into the hydrogel solution, placing the solution in a vacuum drier, continuously exhausting air to provide a negative pressure environment until the solution is boiled, and then standing at a low pressure.
9. The preparation method of the bionic multifunctional cement-hydrogel composite material as claimed in claim 1, wherein in the step (3), the preparation method of the hydrogel comprises the following steps: performing freeze-thaw cycling at a temperature of-30 ℃ to-20 ℃, wherein the freezing time is 8-10 hours, and the thawing time is 2-3 hours.
10. The preparation method of the bionic multifunctional cement-hydrogel composite material as claimed in claim 1, wherein in the step (3), the curing manner is as follows: and curing the mixture in an environment with the temperature of 20-25 ℃ and the relative humidity of 95-100% for 4-28 days.
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