CN109279835B - Bionic cement with directional porous structure and preparation method thereof - Google Patents
Bionic cement with directional porous structure and preparation method thereof Download PDFInfo
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Images
Classifications
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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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
The invention relates to the field of porous cement, in particular to bionic cement which is mainly used as a building material and has a directional porous structure and a preparation method thereof. The bionic cement has a porous structure, the porosity of the bionic cement is 10% -90%, the pore diameter is 0.5-500 μm, and pore channels are preferentially arranged along a specific direction. The preparation method of the cement comprises three steps of slurry preparation, freezing casting and blank maintenance, wherein the mass ratio of water to cement powder in the slurry is 0.25-3. The bionic cement has excellent properties of light weight, high specific strength and specific stiffness, heat preservation and insulation, sound insulation and noise reduction, fire prevention, difficult cracking and the like, particularly has good water permeability, air permeability and mechanical properties along the pore channel direction, and the properties can be effectively controlled by adjusting the slurry proportion and the preparation process. The preparation method of the bionic cement has the advantages of simple process, short flow, low cost, energy conservation, environmental protection and suitability for large-scale production.
Description
Technical Field
The invention relates to the field of porous cement, in particular to bionic cement which is mainly used as a building material and has a directional porous structure and a preparation method thereof.
Background
With the gradual rise of high-rise, large-scale and modern buildings, on the premise of meeting the mechanical property required by safe service, the development of novel building materials with light weight, heat preservation, crack prevention and sound insulation has important significance for realizing the safe, efficient, energy-saving and light-weight design of the buildings. For example, compared with the conventional wall material, the cement foam brick has excellent properties such as light weight, heat preservation, sound insulation and the like due to the porous structure, and has the advantages of high strength, fire resistance and the like compared with a resin heat preservation material, so that the cement foam brick is widely applied to the field of buildings (particularly as a brick for a non-load-bearing wall). In addition, with the development of the integrated process of the economic society and the urban and rural areas in China, the problems of urban 'heat island effect', underground water level reduction, serious road surface water accumulation and the like become more prominent, and the problems are related to poor water permeability of the traditional road surface to a great extent. Compared with the traditional pavement, the permeable pavement has good permeability due to the micro porous structure, so that the tendency of urban ' heat island effect ' and urban underground water resource attenuation year by year is favorably relieved, the timely permeation of the surface gathered water can be promoted in rainy days, and convenience is brought to people's trip while the load of an urban drainage system is reduced. Therefore, the porous cement can be used as building materials such as foam bricks, permeable bricks and the like, and has wide market requirements and application prospects in the field of building engineering such as walls, pavements and the like.
However, the cellular structure in the conventional porous cement is disordered and isotropic, and the uniformity of the size and distribution of the pore channels is poor, so that the conventional porous cement has the advantages of heat preservation, sound insulation, light weight and the like, but the cement has good mechanical properties, so that the limitations that the properties of heat preservation, sound insulation, light weight and the like cannot be compatible with the mechanical properties of strength, rigidity and the like are reflected. In particular, the performance advantages of conventional porous cements cannot be exploited by focusing on certain specific orientations due to the isotropic microstructure. However, under actual service conditions, the performance of the porous cement is often applied only in certain specific directions (such as strength in the load-bearing direction and thermal insulation in the heat conduction direction). Therefore, the performance characteristics of the conventional porous cement still have a large deviation from the practical application requirements. In addition, the distribution and orientation of the pores in the conventional porous cement are random and have poor continuity, so the water permeability and air permeability of the conventional porous cement still need to be further improved.
Compared with porous materials with isotropic tissue structures, porous biomaterials in nature (such as bones, woods and the like) often have pore channel structures preferentially arranged along a specific direction, so that anisotropic performance characteristics are shown, and particularly, the porous biomaterials have optimal mechanical properties along a stress direction. The bionic cement with the directional porous structure is designed and prepared by simulating the microstructure of a natural biological material, so that the problems of the traditional porous cement are expected to be solved, the performance of the porous cement is obviously improved, and the actual application requirements are better met. As a new porous material preparation technology, the freeze casting process utilizes the ice crystals growing along the solidification direction of water-based slurry in the directional solidification process to gradually extrude powder and additives mixed in the slurry between ice layers, thereby realizing the directional arrangement of the slurry. The process can effectively control the microstructure of the finally obtained porous material by adjusting the concentration of the slurry, the cooling speed, the types and the content of the additives and the like. The porous material with the oriented structure can be prepared by a freezing casting process, the volume fraction, the size, the shape and the like of the pore channel can be manually controlled by adjusting the preparation process, the process is simple, energy is saved, the environment is protected, and the prepared porous material can realize higher porosity and excellent mechanical property. Therefore, the freezing casting process provides an effective way for preparing the novel directional porous bionic cement.
Chinese patent (publication No. CN103739306A) discloses a preparation method of directional porous special cement, which comprises four steps of preparation of cement-based slurry, preparation of a frozen blank body, preparation of a cement-based porous biscuit by a freeze drying method and maintenance of the biscuit. Chinese patent (publication No. CN106892674A) discloses a method for preparing gradient directional porous cement based on a two-phase pore former system freeze molding technology, which is characterized in that cement powder and a mixed solution based on a two-phase pore former system are stirred and mixed into a uniform system, and then the uniform system is subjected to freeze molding, freeze drying and maintenance in sequence to obtain a gradient directional porous cement material. Chinese patent (publication No. CN107619226A) discloses a porous cement membrane and a preparation method and application thereof, wherein the preparation process comprises the following steps: 1) mechanically stirring and mixing deionized water, a dispersing agent and a binder, adding cement powder and performing ball milling to obtain cement-based slurry; 2) degassing the slurry, injecting the slurry into a self-made mold for directional freezing molding, removing the slurry after the slurry is frozen, and then freezing and drying to obtain a cement biscuit; 3) and curing the cement biscuit, and then washing and cleaning to obtain the porous cement membrane with the oriented lamellar pore canal structure.
It can be known from analysis of the existing method for preparing porous cement based on the freeze casting technology that, although the pore channels in the cement can be arranged preferentially according to a certain orientation, the preparation process is multiple, the flow is long, the process is complex, especially, the frozen cement slurry prepared by freeze casting needs to be subjected to vacuum freeze drying treatment to obtain a cement biscuit, the step is not only low in efficiency and long in time consumption, but also needs to consume a large amount of energy, cannot meet the requirements of energy conservation and environmental protection, and meanwhile, the size of the prepared cement biscuit is strictly limited, so that the method is difficult to be used for producing large-size porous cement, and the preparation cost of the porous cement is remarkably increased, therefore, the method is very unsuitable for large-scale industrial production. In addition, because the moisture in the cement blank is removed in the freeze drying process, the subsequent curing of the porous cement needs to reapply the moisture, which not only increases the preparation process of the porous cement and prolongs the production period, but also influences the curing process of the porous cement and reduces the strength and rigidity of the finally obtained porous cement.
Disclosure of Invention
The invention aims at providing a preparation method of bionic cement with an oriented porous structure, and aims at preparing novel bionic cement with the oriented porous structure and excellent performances of light weight, high specific strength, high specific rigidity, heat insulation, sound insulation, noise reduction, water permeability, crack prevention and the like based on a freeze casting technology.
In order to achieve the above purpose, the technical solution adopted by the invention is as follows:
the bionic cement with oriented porous structure has porous structure, porosity of 10-90% and pore size of 0.5-500 microns, and pores in the cement are arranged preferentially in the freezing direction during preparation.
The preparation method of the bionic cement with the directional porous structure comprises the following steps:
1) preparing slurry: uniformly mixing cement powder, water and an additive to obtain uniformly dispersed cement slurry;
2) freezing and casting: treating the slurry by using a freezing casting process to enable water in the slurry to be directionally solidified, so that cement powder and additives are squeezed between ice layers to be directionally arranged;
3) and (3) maintaining the blank body: and slowly melting the solidified cement slurry to obtain a shaped porous cement blank, and curing the blank to obtain the bionic cement with the directional porous structure.
In the preparation method of the bionic cement with the oriented porous structure, in the step 1), the cement powder is one or more of portland cement, ordinary portland cement, pozzolana portland cement, fly ash portland cement, slag portland cement and composite portland cement, and the mass ratio of water in the slurry to the cement powder is 0.25-3.
The preparation method of the bionic cement with the oriented porous structure comprises the following steps that in the step 1), the additive comprises one or more than one of a water reducing agent, a thickening agent and a retarder; wherein the water reducing agent is one or more of a polycarboxylic acid high-performance water reducing agent, a melamine high-efficiency water reducing agent, a sulfamate high-efficiency water reducing agent, a naphthalene high-efficiency water reducing agent and a calcium lignosulfonate water reducing agent, and the addition amount of the water reducing agent is 0-3% of the mass of the cement powder; the thickening agent is one or more of cellulose ether, hydroxypropyl methylcellulose, polyurethane thickening agent and polyacrylate thickening agent, and the addition amount is 0-3% of the mass of the cement powder; the retarder is one or more of citric acid, tartaric acid, salicylic acid, sodium gluconate and sodium tripolyphosphate, and the addition amount of the retarder is 0-2% of the mass of the cement powder.
The preparation method of the bionic cement with the directional porous structure comprises the following steps of 1), mechanically stirring or ball milling is adopted as a mixing process of the cement slurry; the stirring speed of mechanical stirring is 5-500 rpm, and the stirring time is more than 3 min; the ball milling speed is 10-600 rpm, the ball milling time is more than 5min, and the mass ratio of the grinding balls to the slurry is more than 0.05.
The preparation method of the bionic cement with the directional porous structure comprises the following steps in step 2): pouring the uniformly mixed slurry into a mould, cooling one end of the mould to ensure that water in the slurry is directionally solidified from bottom to top along the mould, and gradually squeezing cement powder and additives in the slurry to be between ice layers by ice crystals growing along the solidification direction so as to ensure that the cement powder and the additives are directionally arranged; the cooling of the mold is achieved by connecting the mold to a copper plate with one end immersed in a coolant, which is liquid nitrogen or dry ice.
In the step 3), the slow melting of the solidified cement slurry is to take the solidified cement slurry off the cooling copper plate and place the cooled cement slurry in an environment of 0-30 ℃ to slowly melt ice in the solidified slurry, and the cement is gradually hardened in the process, so that the directional porous structure is stored to obtain the shaped porous cement blank.
In the step 3), the maintenance of the cement blank is realized by placing the cement blank in an air environment or water with the temperature of more than 0 ℃ and the relative humidity of more than 90 percent, and the maintenance time is not less than 1 day; the cement blank is gradually hardened in the curing process, and finally the bionic cement with the directional porous structure is obtained.
The design idea of the invention is as follows:
the porous cement is prepared by taking the cement powder, the water and the additive as raw materials, and taking the water as the pore-forming agent, so that the porous cement is simple and easy to obtain the raw materials, is non-toxic and harmless, and has low price. The invention adopts a freeze casting process to realize the directionally arranged pore channel structure in the porous cement, and the freeze casting process utilizes the displacement action generated between adjacent ice layers in the directional icing process of the water in the water-based slurry to ensure that the cement powder and the additive mixed in the cement slurry are directionally arranged, thereby finally forming the directional pore channel structure in the porous cement. The invention can effectively control the microstructure and the performance of the porous cement by adjusting the preparation processes such as the concentration of the slurry, the cooling speed, the types and the content of the additives and the like. The porous cement has the tissue structure design similar to that of biological materials such as bones, woods and the like, and the pore channels of the porous cement are preferentially arranged in the cement along a specific direction, so that the performance advantage of the porous cement can be exerted in a certain specific direction. Particularly, on the premise of ensuring the performances of cracking resistance, fire resistance and the like, the porous cement has the optimal performances of heat preservation, heat insulation, sound insulation, noise reduction and the like in the direction perpendicular to the pore channel, and has the optimal mechanical properties of strength, rigidity and the like, and water permeability and air permeability in the direction parallel to the pore channel, so that the porous cement has excellent comprehensive performance. According to the preparation method of the bionic cement with the directional porous structure, the setting of the cement blank is realized by utilizing the self-generated hardening process of the solidified cement slurry in the melting process, and the vacuum freeze drying treatment is not needed, so that the preparation cost is low, the process is simple, the working procedures are few, the flow is short, the efficiency is high, the energy is saved, the environment is protected, the prepared porous cement has no size limitation, and the cement blank can be better maintained, so that the performance of the porous cement can be better ensured. Therefore, the preparation method of the bionic cement with the directional porous structure is suitable for industrial production.
Compared with the prior materials and technologies, the invention has the following advantages and beneficial effects:
(1) the bionic cement with the oriented porous structure has the advantages of simple raw materials, low price, energy conservation, environmental protection, no toxicity and harm by using water as a pore-forming agent, and easy obtainment.
(2) The pore channel structures in the bionic cement with the oriented porous structure are preferentially arranged along a specific direction, so that the bionic cement has excellent properties of light weight, high specific strength, high specific stiffness, heat preservation and insulation, sound insulation and noise reduction, fire prevention, difficulty in cracking and the like, particularly has good water permeability, air permeability and mechanical properties along the pore channel direction, and the properties can be effectively controlled by adjusting the slurry proportion and the preparation process.
(3) The preparation method of the bionic cement with the directional porous structure does not need vacuum freeze drying treatment, has simple process, short flow, low cost, high efficiency, energy conservation and environmental protection, and the prepared porous cement has no size limitation and is suitable for large-scale production.
(4) The bionic cement can be used as building materials such as foam bricks, permeable bricks and the like, and has considerable application prospect in the field of building engineering such as walls, pavements and the like.
Drawings
Fig. 1 is a scanning electron micrograph of biomimetic cement with an oriented porous structure prepared by using a slurry with a mass ratio of water to cement powder of 0.4 in example 1.
Fig. 2 is a scanning electron micrograph of biomimetic cement with an oriented porous structure prepared by using a slurry with a mass ratio of water to cement powder of 0.7 in example 2.
FIG. 3 is a scanning electron micrograph of a biomimetic cement with an oriented porous structure prepared by a slurry with a mass ratio of water to cement powder of 1.1 in example 3.
Detailed Description
In the specific implementation process, the bionic cement with the oriented porous structure has a porous structure, the porosity of the bionic cement is 10% -90%, preferably 25% -75%, the pore diameter is 0.5-500 μm, preferably 5-300 μm, and pore channels are preferentially arranged in the cement along a specific direction. The preparation process of the porous cement comprises three steps of slurry preparation, freezing casting and green body maintenance, wherein the mass ratio of water to cement powder in the slurry is 0.25-3.
The present invention will be further illustrated by the following examples, which are to be construed as merely illustrative and not limitative of the remainder of the disclosure.
Example 1:
in this example, the slurry having a mass ratio of water to cement powder of 0.4 was used to prepare the biomimetic cement having an oriented porous structure. The raw materials comprise ordinary portland cement powder (fineness is 80 μm, the balance is 0.9 wt%, and specific surface area is 342 m)2Per kg), water and a polycarboxylic acid high-performance water reducing agent, and the specific preparation process comprises the following steps:
1) preparation of slurry
750g of ordinary portland cement powder, 300g of water and 3g of DH-4005 type polycarboxylic acid high-performance water reducing agent are weighed and added into a 1000mL plastic wide-mouth bottle for mechanical stirring, the stirring speed is 100rpm, and the stirring time is 30min, so that the uniformly dispersed cement slurry is obtained.
2) Chill casting
Pouring the uniformly stirred slurry into a cuboid polymethyl methacrylate mould with the inner cavity size of 30mm multiplied by 70mm, sealing the lower end of the mould by a polydimethylsiloxane base with the inclination angle of 25 degrees, placing the mould on a square copper plate, connecting the copper plate with a copper rod with one end immersed in liquid nitrogen, cooling the copper plate to ensure that water in the slurry is directionally solidified from bottom to top along the mould, and gradually squeezing the slurry to the ice layers along ice crystals growing in the solidification direction, thereby realizing the directional arrangement of the slurry.
3) Maintaining the blank
And taking the solidified cement slurry from the copper plate, placing the solidified cement slurry in an environment at 7 ℃ to slowly melt the solidified cement slurry, taking the cement blank out of the mold after the solidified cement slurry is placed for one day, and placing the cement blank in an environment with room temperature and 95% relative humidity for curing for 3 days, wherein the cement blank is gradually hardened in the curing process.
The bionic cement with the directional porous structure can be prepared by the process, and the microstructure of the bionic cement is shown in figure 1. As shown in fig. 1, the bionic cement includes a large number of oriented tunnels with uniform pore diameters besides the circular holes with different sizes inherent in cement materials, and the circular holes are also elongated along the tunnel direction. The porosity of the bionic cement is about 20.5%, and the average pore diameter is about 55.2 μm.
Example 2:
in this example, the slurry having a mass ratio of water to cement powder of 0.7 was used to prepare the biomimetic cement having an oriented porous structure. The raw materials used are the same as in example 1, and the specific preparation process is as follows:
1) preparation of slurry
Weighing 400g of ordinary portland cement powder, 280g of water and 1g of DH-4005 type polycarboxylic acid high-performance water reducing agent, adding the materials into a 1000mL plastic wide-mouth bottle, adding 6 zirconia grinding balls with the diameters of 3mm, 6mm, 10mm and 12mm into the bottle, sealing the wide-mouth bottle cap with the bottle cap, and placing the bottle cap on a roller ball mill for ball milling. The ball milling speed is 150rpm, the ball milling time is 10min, and the mass ratio of the milling balls to the slurry is 0.5, so that the uniformly dispersed cement slurry is obtained.
2) Chill casting
This operation differs from step 2) of example 1 in that the cooling medium for the copper bar is dry ice.
3) Maintaining the blank
And taking the solidified cement slurry from the copper plate, placing the solidified cement slurry in an environment at 15 ℃ to slowly melt the solidified cement slurry, placing the solidified cement slurry for 10 hours, taking the cement blank out of the mold, placing the cement blank in water at room temperature for curing, wherein the curing time is 20 days, and the cement blank is gradually hardened in the curing process.
The bionic cement with the directional porous structure can be prepared by the process, and the microstructure of the bionic cement is shown in figure 2. As shown in FIG. 2, the bionic cement contains a large number of oriented channels with uniform pore size, the porosity of the oriented channels is about 41.3%, and the average pore size of the oriented channels is about 74.8 μm.
Example 3:
in this example, a slurry having a mass ratio of water to cement powder of 1.1 was used to prepare a biomimetic cement having an oriented porous structure. The raw materials comprise fly ash portland cement powder (fineness is 80 microns, the rest is 1.6 wt%, and the specific surface area is 315 m)2Per kg), water and hydroxypropyl methylcellulose powder (average particle size 180 μm), the specific preparation process is as follows:
1) preparation of slurry
333.3g of ordinary portland cement powder, 300g of water and 1.3g of hydroxypropyl methyl cellulose powder are weighed and added into a 1000mL plastic jar for mechanical stirring, the stirring speed is 30rpm, and the stirring time is 1h, so that the uniformly dispersed cement slurry is obtained.
2) Chill casting
This procedure is the same as in step 2) of example 1.
3) Maintaining the blank
And taking the solidified cement slurry from the copper plate, placing the solidified cement slurry in an environment at 3 ℃ to slowly melt the solidified cement slurry, taking the cement blank out of the mold after placing for one day, placing the cement blank in water at the temperature of 5 ℃ for curing for one month, and gradually hardening the cement blank in the curing process.
The bionic cement with the directional porous structure can be prepared by the process, and the microstructure of the bionic cement is shown in figure 3. As shown in FIG. 3, the bionic cement contains a large number of oriented channels with uniform pore size, the porosity of the oriented channels is about 52.8%, and the average pore size of the oriented channels is about 86.5 μm.
The embodiment result shows that the preparation method of the bionic cement with the directional porous structure does not need vacuum freeze drying treatment, has simple process, short flow, low cost, high efficiency, energy conservation and environmental protection, and the prepared porous cement has no size limitation. Meanwhile, the bionic cement with the directional porous structure prepared based on the freeze casting technology has excellent properties of light weight, high specific strength, high specific rigidity, heat preservation and insulation, sound insulation and noise reduction, fire prevention, difficult cracking and the like, particularly shows good water permeability, air permeability and mechanical properties along the pore channel direction, and the performance of the cement can be effectively controlled by adjusting the slurry proportion and the preparation process. Therefore, the bionic cement can be used as building materials such as foam bricks, permeable bricks and the like, and has considerable application prospect in the field of building engineering such as walls, pavements and the like.
Claims (4)
1. The preparation method of the bionic cement with the oriented porous structure is characterized in that the cement has the porous structure, the porosity of the cement is 10% -90%, the pore diameter is 0.5-500 mu m, and pore channels are preferentially arranged in the cement along the freezing direction during preparation;
the method comprises the following steps:
1) preparing slurry: uniformly mixing cement powder, water and an additive to obtain uniformly dispersed cement slurry;
2) freezing and casting: treating the slurry by using a freezing casting process to enable water in the slurry to be directionally solidified, so that cement powder and additives are squeezed between ice layers to be directionally arranged;
3) and (3) maintaining the blank body: slowly melting the solidified cement slurry to obtain a shaped porous cement blank, and curing the blank to obtain bionic cement with a directional porous structure; in the step 3), the solidified cement slurry is slowly melted by taking the solidified cement slurry off the cooling copper plate and then placing the cooled copper plate in an environment at 0-30 ℃ to slowly melt ice in the solidified slurry, and cement is gradually hardened in the process, so that a directional porous structure is stored to obtain a shaped porous cement blank;
in the step 1), the cement powder is more than one of portland cement, ordinary portland cement, pozzolana portland cement, fly ash portland cement, slag portland cement and composite portland cement, and the mass ratio of water to the cement powder in the slurry is 0.25-3;
in the step 1), the additive comprises more than one of a water reducing agent, a thickening agent and a retarder; wherein the water reducing agent is more than one of a polycarboxylic acid high-performance water reducing agent, a melamine high-efficiency water reducing agent, a sulfamate high-efficiency water reducing agent, a naphthalene high-efficiency water reducing agent and a calcium lignosulfonate water reducing agent, and the addition amount of the water reducing agent is 0-3% of the mass of the cement powder; the thickening agent is more than one of cellulose ether, polyurethane thickening agent and polyacrylate thickening agent, and the addition amount is 0-3% of the mass of the cement powder; the retarder is more than one of citric acid, tartaric acid, salicylic acid, sodium gluconate and sodium tripolyphosphate, and the addition amount of the retarder is 0-2% of the mass of the cement powder.
2. The method for preparing bionic cement with an oriented porous structure according to claim 1, wherein in the step 1), the mixing process of the cement slurry is mechanical stirring or ball milling; the stirring speed of mechanical stirring is 5-500 rpm, and the stirring time is more than 3 min; the ball milling speed is 10-600 rpm, the ball milling time is more than 5min, and the mass ratio of the grinding balls to the slurry is more than 0.05.
3. The method for preparing bionic cement with an oriented porous structure according to claim 1, wherein in the step 2), the freeze casting process comprises the following steps: pouring the uniformly mixed slurry into a mould, cooling one end of the mould to ensure that water in the slurry is directionally solidified from bottom to top along the mould, and gradually squeezing cement powder and additives in the slurry to be between ice layers by ice crystals growing along the solidification direction so as to ensure that the cement powder and the additives are directionally arranged; the cooling of the mold is achieved by connecting the mold to a copper plate with one end immersed in a coolant, which is liquid nitrogen or dry ice.
4. The method for preparing bionic cement with an oriented porous structure according to claim 1, wherein in the step 3), the cement body is maintained in an air environment or water with the temperature of more than 0 ℃ and the relative humidity of more than 90%, and the maintenance time is not less than 1 day; the cement blank is gradually hardened in the curing process, and finally the bionic cement with the directional porous structure is obtained.
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