Bamboo fiber reinforced portland cement-based foam material and method of making the same

Abstract

The application discloses a kind of bamboo fiber reinforced Portland cement-based foam material and preparation method thereof, bamboo fiber raw material is first pretreated with alkali combined with EVA emulsion, fermentation pretreatment or acetic acid pretreatment;Portland cement, foam stabilizer, catalyst and pretreated bamboo fiber are premixed, stirred, and a mixture is obtained;Water reducing agent is dissolved in water and added to the mixture, stirred, and a mixed slurry is obtained;Foaming agent is added to the mixed slurry, stirred, and a foaming slurry is obtained;The foaming slurry is injected into a foaming mold, and the foam is formed by standing, film coating, moisture retention, demolding, curing, and the bamboo fiber reinforced Portland cement-based foam material is obtained.The application effectively improves the interface compatibility between bamboo fiber and cement-based by pretreatment method, which can better improve the mechanical strength of Portland cement-based foam material, so as to obtain bamboo fiber reinforced Portland cement-based foam material with the advantages of light weight, high strength, sound insulation, thermal insulation, fireproof, environmental protection and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of manufacturing inorganic thermal insulation materials for building walls, and particularly relates to a bamboo fiber reinforced silicate cement-based foam material and a preparation method thereof. BACKGROUND

[0002] Foamed cement is a new type of lightweight material formed by physical or chemical foaming methods inside the cementitious material containing a large number of closed pores. The main material of foamed cement is cement, with the addition of foaming agent, additive, etc., through mixing, stirring, foaming and pouring into shape. Foamed cement, as a lightweight and high-strength building material, has the advantages of thermal insulation, heat insulation, sound insulation, fire resistance, etc., and is widely used in internal and external wall thermal insulation systems, ground backfilling, fireproof isolation belts, etc. However, foamed cement has the disadvantages of high brittleness, easy cracking and low tensile strength. In order to overcome these shortcomings, steel fibers, glass fibers, etc. are usually used for reinforcement. However, steel fibers have poor corrosion resistance and high cost; glass fibers have high brittleness and are harmful to the human body during production and use. For a long time, many improvement methods have been proposed, among which the addition of an appropriate amount of biomass fibers such as wood fibers to cement is an effective reinforcement method. However, wood growth takes several years, and bamboo is a renewable fast-growing material that is easy to obtain and has low cost. Bamboo fiber, as a natural fiber, has the advantages of being renewable, biodegradable, low cost and high toughness. Moreover, China has abundant bamboo resources, which are easy to obtain. Therefore, bamboo fiber is a potential reinforcing material. Making full use of bamboo to replace wood can effectively overcome the problem of insufficient wood resources. Although bamboo fiber is an excellent fiber reinforcing material, the mechanical properties of the foamed material reinforced by bamboo fiber in the prior art are not ideal, thus limiting the popularization and application of this technology. SUMMARY

[0003] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a bamboo fiber reinforced silicate cement-based foam material with good mechanical properties, light weight, fire resistance and environmental protection, and a preparation method thereof.

[0004] In order to solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0005] A preparation method of a bamboo fiber reinforced silicate cement-based foam material, comprising the following steps:

[0006] (1) Pre-treat the bamboo fiber raw material, the pre-treatment method is alkali combined with EVA emulsion treatment, fermentation treatment or acetic acid treatment; the alkali combined with EVA emulsion treatment is to soak in an alkali solution first and then soak in an ethylene-vinyl acetate copolymer emulsion; the fermentation treatment is to ferment with a fermentation liquid; the acetic acid treatment is to soak in an acetic acid solution;

[0007] (2) Pre-mix silicate cement, foam stabilizer, catalyst and the bamboo fiber pre-treated in step (1), and stir to obtain a mixture;

[0008] (3) dissolving water reducing agent in water, adding the mixture obtained in step (2), stirring, obtaining mixed slurry;

[0009] (4) adding foaming agent into the mixed slurry obtained in step (3), stirring, obtaining foaming slurry;

[0010] (5) injecting the foaming slurry obtained in step (4) into foaming mold, standing for foaming forming, coating for moisture retention, demolding, curing, obtaining bamboo fiber reinforced portland cement-based foaming material.

[0011] The bamboo fiber reinforced portland cement-based foaming material preparation method, preferably, in step (1), the alkali combined EVA emulsion treatment comprises the following steps:

[0012] (1.1) immersing bamboo fiber raw material into alkali solution with mass percentage of 3% to 8% for 8h to 24h, washing, drying, obtaining alkali treated bamboo fiber;

[0013] (1.2) immersing the alkali treated bamboo fiber into ethylene-vinyl acetate copolymer emulsion with mass percentage of 5% to 15% for 24h to 48h, washing, drying, obtaining alkali combined EVA emulsion pretreated bamboo fiber.

[0014] The bamboo fiber reinforced portland cement-based foaming material preparation method, preferably, in step (1.1), the alkali solution is sodium hydroxide solution or potassium hydroxide solution, the washing is washing with water until the pH of washing waste water is greater than or equal to 6, and the drying is drying at 60℃ to 75℃ until the mass change is not more than 1g per 4h; in step (1.2), the washing is washing with water until the pH of washing waste water is greater than or equal to 6, and the drying is drying at 60℃ to 75℃ until the mass change is not more than 1g per 4h.

[0015] The bamboo fiber reinforced portland cement-based foaming material preparation method, preferably, in step (1), the fermentation liquid comprises water, flour, yeast and wine starter, and the mass ratio of the bamboo fiber raw material to water, flour, yeast and wine starter is 50:25 to 40:0.7 to 2:0.5 to 1.5:1 to 2.5, and is further preferably 50:30:1:1:2, and the fermentation is anaerobic fermentation.

[0016] The bamboo fiber reinforced portland cement-based foaming material preparation method, preferably, in step (1), the fermentation temperature is 4℃ to 45℃, and is further preferably 20℃ to 25℃, the fermentation time is 24h to 48h, after the fermentation is completed, the washing is washing with water until the washing waste water is clear, and then the drying is drying at 60℃ to 75℃ until the mass change is not more than 1g per 4h; the yeast is activated with water at 30℃ to 35℃ for 10min to 15min before use.

[0017] The bamboo fiber reinforced Portland cement-based foam material preparation method, preferably, in step (1), the mass percentage of the acetic acid solution is 5% to 10%.

[0018] The bamboo fiber reinforced Portland cement-based foam material preparation method, preferably, in step (1), the soaking time of the acetic acid solution is 8h to 24h, and after the acetic acid solution soaking is completed, water is washed until the pH of the washing wastewater is greater than or equal to 6, and then drying is performed at 60°C to 75°C for 4h, and the weight change is not more than 1g.

[0019] The bamboo fiber reinforced Portland cement-based foam material preparation method, preferably, the foaming agent is 25% to 35% hydrogen peroxide solution, the foam stabilizer is calcium stearate, the water reducing agent is polycarboxylic acid, the catalyst is manganese dioxide, and the size of the bamboo fiber raw material is 20 mesh to 80 mesh, and each component includes, by mass fraction:

[0020] Portland cement 100 parts to 200 parts;

[0021] Bamboo fiber 4 parts to 10 parts;

[0022] Hydrogen peroxide solution 2.75 parts to 3.5 parts;

[0023] Calcium stearate 1 part to 5 parts;

[0024] Manganese dioxide 0.25 parts to 0.35 parts;

[0025] Polycarboxylic acid 0.1 parts to 0.2 parts;

[0026] Water 50 parts to 100 parts.

[0027] The bamboo fiber reinforced Portland cement-based foam material preparation method, preferably, the bamboo fiber is 6 to 8 parts, and the hydrogen peroxide solution is 3 parts to 3.25 parts.

[0028] The bamboo fiber reinforced Portland cement-based foam material preparation method, preferably, in step (2), the stirring speed is 300 r / min to 500 r / min, and the stirring time is 5 min to 10 min;

[0029] In step (3), the stirring speed is 600 r / min to 800 r / min, and the stirring time is 1 min to 2 min;

[0030] In step (4), the stirring speed is 1000 r / min to 1500 r / min, and the stirring time is 5s to 10s;

[0031] In step (5), the film is removed after being moisturized for 1-3 days, and the curing is natural curing by spraying water at regular intervals for 7-28 days.

[0032] As a general technical concept, the present application also provides a bamboo fiber reinforced silicate cement-based foam material prepared by the above preparation method.

[0033] Compared with the prior art, the present application has the following advantages:

[0034] (1) The preparation method of the bamboo fiber reinforced silicate cement-based foam material of the present application adds bamboo fiber to cement. The bamboo fiber has high strength and good toughness, forms a three-dimensional network structure in the cement, can improve the stress concentration problem, bear tensile stress, effectively improve the strength of the cement, and improve the generation and propagation of cracks. Since the main components of bamboo fiber include cellulose, hemicellulose, lignin, wax and pectin, these components are easily hydrolyzed in the alkaline environment of the cement-based material to form insoluble calcium saccharate covering the surface of the cement particles, hindering the hydration of the cement and reducing the interfacial compatibility of the bamboo fiber and the cement-based material. The present application effectively improves the interfacial compatibility between the bamboo fiber and the cement-based material by any one of the pretreatment methods of alkali combined with EVA emulsion treatment, fermentation treatment and acetic acid treatment, and can better improve the mechanical strength of the silicate cement-based foam material. The three pretreatment methods of bamboo fiber in the present application have their own advantages, and compared with bamboo fiber without pretreatment, they can significantly enhance the mechanical properties of the silicate cement-based foam material. Specifically, alkali treatment removes surface lignin, pectin and other components, which can improve the interfacial adhesion between the fiber and the cement matrix, reduce the water absorption of the fiber, and reduce the risk of material cracking and damage to the porous structure. The emulsion coating treatment forms a polymer film on the surface of the fiber, which can isolate water to greatly reduce the water absorption rate, buffer the shrinkage stress of the cement, and improve the bending resistance and toughness of the material. Fermentation treatment can remove impurities by microbial degradation to improve the porosity of the fiber and enhance the bonding force, and is environmentally friendly without chemical residues. Acetic acid treatment is a mild chemical modification that is more environmentally friendly, can clean the fiber surface, slightly improves the interfacial bonding force while retaining most of the strength of the fiber, and avoids fiber agglomeration.

[0035] (2) The preparation method of the present application uses bamboo fiber to cooperate with silicate cement. Bamboo fiber is a renewable and inexpensive raw material with a wide range of sources. It not only provides mechanical strength for cement foam materials, but also reduces the cost of cement foam materials. Bamboo fiber is light in weight and highly compatible with the lightweight requirements of foam materials. Bamboo fiber is a natural plant fiber and can be biodegraded. The present application uses bamboo fiber as a reinforcing material, which is green and environmentally friendly, conducive to sustainable development, widens the application of biomass materials in the field of construction, and has good application value.

[0036] (3) The preparation method of the present application takes silicate cement as a base material, and the prepared bamboo fiber reinforced silicate cement-based foam material is a non-combustible material, has good fire resistance, and reaches non-combustible level. When used as a thermal insulation material, the fire resistance is far superior to that of the widely used polyphenyl board plastering system, extruded board and polyurethane insulation board. Compared with the use of organic synthetic adhesives such as urea-formaldehyde resin and phenol-formaldehyde resin, the present application uses silicate cement as a cementing material, which solves the problem of harmful gas release of organic synthetic adhesives, and also solves the problems of resource constraints and high cost of organic synthetic adhesives.

[0037] (4) The bamboo fiber reinforced silicate cement-based foam material prepared by the preparation method of the present application has the advantages of light weight, high strength, sound insulation, thermal insulation, fireproofing, environmental protection and the like. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 Figure 1 is a SEM surface morphology diagram of the bamboo fiber reinforced silicate cement-based foam material of Example 1 of the present application, wherein (a) is untreated bamboo fiber, (b) is alkali treated bamboo fiber, and (c) is alkali combined with EVA treated bamboo fiber. DETAILED DESCRIPTION

[0039] The present application will be further described below in combination with the drawings of the specification and specific preferred embodiments, but the protection scope of the present application is not limited thereby. In the following examples, if not specifically stated, the raw materials and instruments used are commercially available, wherein the silicate cement is ordinary portland cement P.O 52.5, purchased from Zhucheng Jiuli Building Material Co., Ltd.; calcium stearate powder is purchased from Tianjin Zhonglian Chemical Reagent Co., Ltd., with a calcium content of 6.5%±0.5% and a specification of 250g / bottle; polycarboxylic acid powder is purchased from Shanxi Feike New Material Technology Co., Ltd., FK-A type, with a specification of 1kg / bag. Ethylene-vinyl acetate copolymer emulsion is purchased from Guangzhou Zhonggao Chemical Co., Ltd., with a solid content of ≥55% and a viscosity of 2500cps-3700cps, 1kg / bottle; yeast is purchased from Angel Yeast Co., Ltd., 5g / bag; distiller's yeast is purchased from Angel Yeast Co., Ltd., 8g / bag; alkali solution is sodium hydroxide solution, and flour is ordinary wheat flour.

[0040] Example 1

[0041] A preparation method of a bamboo fiber reinforced silicate cement-based foam material of the present application, comprising the following steps:

[0042] (1) The bamboo fiber raw material is pretreated by alkali combined with EVA (ethylene-vinyl acetate copolymer) emulsion treatment, and the specific steps include:

[0043] (1.1) immerse the bamboo fiber raw material of 60 mesh to 80 mesh into an alkali solution with a mass percentage of 5%, soak for 24 hours at room temperature, then wash with distilled water until the pH of the washing wastewater is ≥6, the acidity and alkalinity are neutral, and put into an oven at 75°C until dry (4 hours of weight change not more than 1 g), to obtain the alkali treated bamboo fiber;

[0044] (1.2) immerse the alkali treated bamboo fiber into an ethylene-vinyl acetate copolymer emulsion with a mass percentage of 10% to form an EVA coating layer, soak for 24 hours, then wash with distilled water until the pH of the washing wastewater is ≥6, the acidity and alkalinity are neutral, to wash away the excess emulsion, and put into an oven at 60°C until dry (4 hours of weight change not more than 1 g), to obtain the bamboo fiber pretreated by alkali combined with EVA emulsion;

[0045] (2) pre-mix the portland cement, bamboo fiber, foam stabilizer, and catalyst for 2 minutes, then stir with a stirrer at 300 r / min for 5 minutes to obtain the mixture;

[0046] (3) completely dissolve the water reducing agent in water, and add it into the mixture in small amounts for multiple times, and stir at a speed of 600 r / min for 1 minute to obtain a uniform mixed slurry;

[0047] (4) quickly add the foaming agent into the mixed slurry, and stir with a stirrer at 1200 r / min for 5-10 seconds to obtain a foaming slurry;

[0048] (5) quickly inject the foaming slurry into a foaming mold, and let it stand to form, then cover the surface of the sample with a plastic film to prevent water evaporation, demold after foaming and forming for 1 day, cut off the part of the sample that exceeds the upper edge of the mold, and naturally maintain by spraying water at regular intervals for 7 days, to obtain the bamboo fiber reinforced portland cement based foaming material.

[0049] In this embodiment, the foaming agent is 30% hydrogen peroxide solution, the foam stabilizer is calcium stearate, the water reducing agent is polycarboxylic acid powder, and the catalyst is manganese dioxide powder, and each component includes, by mass fraction:

[0050] 100 parts of ordinary portland cement;

[0051] 8 parts of bamboo fiber;

[0052] 3 parts of 30% hydrogen peroxide (H2O2) solution;

[0053] 1 part of calcium stearate powder;

[0054] 0.25 parts of manganese dioxide (MnO2) powder;

[0055] 0.1 parts of polycarboxylic acid powder;

[0056] 50 parts of water.

[0057] Example 2

[0058] A method for preparing the bamboo fiber reinforced Portland cement-based foam material of the present application, comprising the following steps:

[0059] (1) pretreating the bamboo fiber raw material, the pretreatment method being alkali combined with EVA emulsion treatment, the specific steps comprising:

[0060] (1.1) immersing the bamboo fiber raw material of 60-80 mesh into an alkali solution with a mass percentage of 5%, soaking at room temperature for 24 h, then washing with distilled water until the pH of the washing wastewater is ≥6, and placing in an oven at 75°C to dry to absolute dryness (4 h weight change not more than 1 g), to obtain the alkali treated bamboo fiber;

[0061] (1.2) immersing the alkali treated bamboo fiber into an ethylene-vinyl acetate copolymer emulsion with a mass percentage of 10% to form an EVA coating layer, soaking for 24 h, then washing with distilled water until the pH of the washing wastewater is neutral, to wash off the excess emulsion, and placing in an oven at 60°C to dry to absolute dryness (4 h weight change not more than 1 g), to obtain the bamboo fiber pretreated by alkali combined with EVA emulsion;

[0062] (2) pre-mixing the Portland cement, bamboo fiber, foam stabilizer, and catalyst for 2 min, then stirring with a stirrer at 300 r / min for 5 min, to obtain the mixed material;

[0063] (3) completely dissolving the water reducing agent in water, and adding it into the mixed material in small amounts for multiple times, stirring at a speed of 600 r / min for 1 min, to obtain the uniform mixed slurry;

[0064] (4) quickly adding the foaming agent into the mixed slurry, and stirring with a stirrer at 1200 r / min for 5-10 s, to obtain the foaming slurry;

[0065] (5) quickly injecting the foaming slurry into the foaming mold, standing for foaming and molding, then covering plastic film on the surface of the sample to prevent water evaporation, demolding after foaming and molding for 1 day, cutting off the part of the sample above the upper edge of the mold, and naturally curing by spraying water at regular time for 7 days, to obtain the product.

[0066] In this example, the foaming agent is 30% hydrogen peroxide solution, the foam stabilizer is calcium stearate, the water reducing agent is polycarboxylic acid powder, and the catalyst is manganese dioxide powder, each component includes, by mass parts:

[0067] Portland cement 100 parts;

[0068] Bamboo fiber 6 parts;

[0069] 30% hydrogen peroxide (H2O2) solution 3 parts;

[0070] Calcium stearate powder 1 part;

[0071] Manganese dioxide (MnO2) powder 0.25 parts;

[0072] Polycarboxylic acid powder 0.1 parts;

[0073] Water 50 parts.

[0074] Example 3

[0075] A method for preparing a bamboo fiber reinforced Portland cement-based foam material of the present application, comprising the following steps:

[0076] (1) Pretreating the bamboo fiber raw material, the pretreatment method being alkali combined with EVA emulsion treatment, and the specific steps comprising:

[0077] (1.1) Immersing the bamboo fiber raw material of 60-80 mesh into an alkali solution with a mass percentage of 5%, soaking at room temperature for 24 h, then washing with distilled water until the pH of the washing wastewater is ≥6, and placing in an oven at 75°C to dry to absolute dryness (4 h weight change not more than 1 g), to obtain the alkali treated bamboo fiber;

[0078] (1.2) Immersing the alkali treated bamboo fiber into an ethylene-vinyl acetate copolymer emulsion with a mass percentage of 10% to form an EVA coating layer, soaking for 24 h, then washing with distilled water until the pH of the washing wastewater is neutral, to wash off the excess emulsion, and placing in an oven at 60°C to dry to absolute dryness (4 h weight change not more than 1 g), to obtain the bamboo fiber pretreated by alkali combined with EVA emulsion;

[0079] (2) Pre-mixing the Portland cement, bamboo fiber, foam stabilizer, and catalyst for 2 min, then stirring with a stirrer at 300 r / min for 5 min, to obtain the mixed material;

[0080] (3) Dissolving the water reducing agent completely in water, and adding it into the mixed material in small amounts multiple times, stirring at a speed of 600 r / min for 1 min, to obtain a uniform mixed slurry;

[0081] (4) Quickly adding the foaming agent into the mixed slurry, and stirring with a stirrer at 1200 r / min for 5-10 s, to obtain a foaming slurry;

[0082] (5) Quickly injecting the foaming slurry into a foaming mold, standing for foaming and molding, then covering the surface of the sample with a plastic film to prevent water evaporation, demolding after foaming and molding for 1 day, cutting off the part of the sample above the upper edge of the mold, and naturally curing by spraying water at regular intervals for 7 days, to obtain the bamboo fiber reinforced Portland cement-based foam material.

[0083] In this embodiment, the foaming agent is 30% hydrogen peroxide solution, the foam stabilizer is calcium stearate, the water reducing agent is polycarboxylic acid powder, the catalyst is manganese dioxide powder, and each component includes, by mass fraction:

[0084] Ordinary Portland cement 100 parts;

[0085] Bamboo fiber 10 parts;

[0086] 30% hydrogen peroxide (H2O2) solution 3 parts;

[0087] Calcium stearate powder 1 part;

[0088] Manganese dioxide (MnO2) powder 0.25 parts;

[0089] Polycarboxylic acid powder 0.1 parts;

[0090] Water 50 parts.

[0091] Example 4

[0092] A method for preparing a bamboo fiber reinforced Portland cement-based foamed material of the present application, comprising the following steps:

[0093] (1) The bamboo fiber raw material is pretreated by fermentation treatment, i.e. soaked in fermentation liquid; the fermentation liquid includes water, flour, yeast and wine starter. In this embodiment, 60-80 mesh bamboo fiber raw material is mixed with water, flour, yeast and wine starter in a mass ratio of 50:30:1:1:2, stirred uniformly, and then loaded into a container for anaerobic fermentation at room temperature (optimally 20-25°C) for 48 h. After fermentation, the material is washed with distilled water until the washing wastewater is clear, and then placed in an oven at 75°C until dry (4 h weight change not more than 1 g). The yeast needs to be activated with 35°C distilled water for 10 min before use.

[0094] (2) The Portland cement, bamboo fiber, foam stabilizer and catalyst are pre-mixed for 2 min, then stirred with a stirrer at 300 r / min for 5 min to obtain a mixture;

[0095] (3) The water reducing agent is completely dissolved in water and added to the mixture in small amounts several times, and stirred at a speed of 600 r / min for 1 min to obtain a uniform mixed slurry;

[0096] (4) The foaming agent is quickly added to the mixed slurry, and stirred with a stirrer at 1200 r / min for 5-10 s to obtain a foamed slurry;

[0097] (5) The foaming slurry is quickly injected into the foaming mold, and is left to foam and form. Then, a plastic film is covered on the surface of the sample to prevent moisture evaporation. After 1 day of foaming and forming, the sample is demolded, the part exceeding the upper edge of the mold is cut off, and the sample is naturally cured by spraying water at regular time for 7 days, to obtain the bamboo fiber reinforced Portland cement-based foaming material.

[0098] In the embodiment, the foaming agent is 30% hydrogen peroxide solution, the foam stabilizer is calcium stearate, the water reducing agent is polycarboxylic acid powder, and the catalyst is manganese dioxide powder. Each component includes the following by mass fraction:

[0099] 100 parts of ordinary Portland cement;

[0100] 10 parts of bamboo fiber;

[0101] 3 parts of 30% hydrogen peroxide (H2O2) solution;

[0102] 1 part of calcium stearate powder;

[0103] 0.25 parts of manganese dioxide (MnO2) powder;

[0104] 0.1 parts of polycarboxylic acid powder;

[0105] 50 parts of water.

[0106] Example 5

[0107] A method for preparing the bamboo fiber reinforced Portland cement-based foaming material of the present application includes the following steps:

[0108] (1) The bamboo fiber raw material is pretreated by acetic acid treatment, that is, soaked in an acetic acid solution. The specific steps include: 60-80 mesh bamboo fiber raw material is soaked in an acetic acid solution with a mass percentage of 5% for 24 h at room temperature, and then taken out, washed with distilled water until the pH of the washing wastewater is ≥6, and the acidity and alkalinity are neutral. After that, the water is drained, and the material is placed in a 75°C oven to dry to absolute dryness (4 h weight change not more than 1 g);

[0109] (2) The Portland cement, bamboo fiber, foam stabilizer and catalyst are premixed for 2 min, and then stirred by a stirrer at 300 r / min for 5 min to obtain a mixture;

[0110] (3) The water reducing agent is completely dissolved in water, and then added to the mixture in small amounts for several times, and stirred at a speed of 600 r / min for 1 min to obtain a uniform mixed slurry;

[0111] (4) The foaming agent is quickly added to the mixed slurry, and stirred by a stirrer at 1200 r / min for 5-10 s to obtain a foaming slurry;

[0112] (5) The foaming slurry is quickly injected into the foaming mold, and is left to foam and form. Then, a plastic film is covered on the surface of the sample to prevent moisture evaporation. After 1 day of foaming and forming, the sample is demolded, the part above the upper edge of the mold is cut off, and the sample is naturally cured by spraying water at regular time for 7 days, to obtain the bamboo fiber reinforced portland cement-based foaming material.

[0113] In the embodiment, the foaming agent is 30% hydrogen peroxide solution, the foam stabilizer is calcium stearate, the water reducing agent is polycarboxylic acid powder, and the catalyst is manganese dioxide powder. Each component includes, by mass fraction:

[0114] 100 parts of ordinary portland cement;

[0115] 4 parts of bamboo fiber;

[0116] 3 parts of 30% hydrogen peroxide (H2O2) solution;

[0117] 1 part of calcium stearate powder;

[0118] 0.25 parts of manganese dioxide (MnO2) powder;

[0119] 0.1 parts of polycarboxylic acid powder;

[0120] 50 parts of water.

[0121] Comparative Example 1

[0122] A preparation method of a portland cement-based foaming material, the steps of which are basically the same as those of Example 1, and the only difference is that the bamboo fiber is not used in the raw material components.

[0123] Comparative Example 2

[0124] A preparation method of a portland cement-based foaming material, the steps of which are basically the same as those of Example 1, and the only difference is that the bamboo fiber used in the raw material components is 4 parts of bamboo fiber raw material without pretreatment.

[0125] Performance characterization:

[0126] The surface morphology of the untreated bamboo fiber and the bamboo fiber after alkali treatment in step (1.1) and alkali combined with EVA emulsion treatment in step (1.2) of Example 1 was observed by scanning electron microscope, and the results are shown in Figure 1 Figure 1 ​Figure (a) is the surface morphology of the untreated bamboo fiber at 600 times magnification. It can be seen that the surface of the bamboo fiber presents a rough structure and is attached with a large amount of impurities. The irregular surface structure and impurities will reduce the bonding force between the bamboo fiber and the cement base, thereby affecting the overall performance of the composite material. Figure (b) is the surface morphology of the bamboo fiber treated by the alkali solution at 600 times magnification. It can be seen from the figure that the treatment of the alkali solution can effectively reduce the surface impurities and the like of the bamboo fiber, and the removal of the waxy layer makes the fiber bundle of the bamboo fiber more obvious, and the bamboo fiber presents obvious gullies. This indicates that the alkali treatment can dissolve the hemicellulose, pectin and impurities in the bamboo fiber, increase the roughness of the surface of the bamboo fiber, improve the contact surface between the bamboo fiber and the cement base, and thus promote the interfacial adhesion between the bamboo fiber and the cement base material. Figure (c) is the surface morphology of the bamboo fiber coated by the alkali and the EVA emulsion at 1000 times magnification. After the EVA emulsion coating, a homogeneous polymer film is formed on the surface of the bamboo fiber. This film can reduce the surface defects of the bamboo fiber and effectively prevent the migration of erosive ions, reduce the dissolution of the components in the bamboo fiber that hinder the cement hydration reaction, thereby reducing the delay or inhibition effect of the components in the bamboo fiber on the cement hydration, improving the interfacial compatibility between the bamboo fiber and the cement, and improving the mechanical properties of the composite material.

[0127] The foamed materials prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to strength tests, and the test results are shown in Table 1.

[0128] Table 1 Strength test results of the foamed materials prepared in Examples 1-5 and Comparative Examples 1-2

[0129]

[0130] As can be seen from Table 1, the compressive strength and bending strength of the foamed materials without bamboo fiber in Comparative Example 1 or without pretreatment of the bamboo fiber in Comparative Example 2 are obviously lower than those of the foamed materials reinforced by the pretreated bamboo fiber in Examples 1-5. Because the pretreatment can remove the easily degradable components and impurities in the bamboo, reduce the moisture absorption, and at the same time improve the surface properties and the interfacial bonding force with the matrix, the bamboo fiber can be more uniformly dispersed in the bamboo fiber reinforced foamed cement material, and fully play a reinforcing role, so that the mechanical properties, crack resistance and durability of the final product are significantly improved. The bamboo fiber reinforced foamed material prepared by the method of the present application has a density of 450-550 kg / m 3 , and a 7-day strength greater than the requirement of JG / T-266-2011 "Foamed Concrete" (dry density of 400-600 kg / m 3 , strength ≤1.5 MPa), which has great market prospects.

[0131] Although the comparative example 2 uses 4 parts of unpretreated bamboo fibers to reinforce the foamed material, the bending strength of the final product is still not as good as that of the foamed material without bamboo fibers in the comparative example 1. The main reason is that when the bamboo fibers are not pretreated, the natural components such as hemicellulose and lignin in the bamboo are easily degraded, which not only reduces the structural stability of the bamboo itself, but also interferes with the matrix reaction such as cement hydration and weakens the interfacial bonding force. In addition, its strong water absorption property easily leads to cracking and deformation of the product due to dry and wet shrinkage, shortening the service life. Therefore, the bending strength of the foamed material reinforced by the untreated bamboo fibers in the comparative example 2 is still not as good as that of the foamed material without bamboo fibers in the comparative example 1.

[0132] During the test, when the load approaches the ultimate strength, the crack of the test piece of the comparative example 1 rapidly propagates, and with the increase of the load, the crack penetration and peeling phenomenon gradually appear, until the complete loss of bearing capacity, and the test piece is completely destroyed.

[0133] As can be seen from the comparison between the example 2 and the example 1, with the increase of the amount of bamboo fibers, the compressive strength and bending strength of the foamed material are obviously improved, the strength of the corresponding test piece is gradually improved, the number of cracks and the penetration phenomenon are reduced, and the integrity of the test piece is good after reaching the ultimate load. The result is because the addition of bamboo fibers enhances the tensile stress of the cement-based material, and the random distribution of bamboo fibers in the cement-based material effectively inhibits the generation and propagation of cracks, improves the failure mode of the cement material, and thus improves the strength of the test piece. As can be seen from the comparison between the example 3 and the example 1, the amount of pretreated bamboo fibers is not the more the better. The amount of bamboo fibers is too low or too high, which has adverse effects on the performance of the Portland cement-based foamed material. When the amount of bamboo fibers is too low in the preparation of foamed cement material, the fibers are difficult to form a "supporting" structure inside, which cannot fully improve the brittleness of the cement matrix, and is also easy to cause cracking after hardening due to temperature changes, slight vibration and the like. In addition, the mechanical properties such as bending and compression are limited, which is difficult to meet the bearing and performance requirements of scenarios such as partition wall board and roof insulation layer. When the amount of bamboo fibers is too high, it is easy to cause fiber aggregation, which destroys the uniformity of the cement slurry, causes irregular bubble distribution and internal voids during foaming, and increases the viscosity of the slurry, which affects the effect of the foaming agent and the molding, and finally leads to unstable volume density and decreased compactness of the foamed cement.

[0134] Although the present application is disclosed with the preferred embodiments as above, it is not intended to limit the present application. Any skilled person in the art can make many possible changes and modifications to the technical solutions of the present application, or modify equivalent embodiments with equivalent changes, without departing from the spirit and technical solutions of the present application. Therefore, any simple modification, equivalent replacement, equivalent change and modification of the above examples made according to the technical essence of the present application, which does not depart from the technical solutions of the present application, still belongs to the protection scope of the technical solutions of the present application.

Claims

1. A method for the production of a bamboo fiber reinforced silicate cement-based foam material, characterized in that, Comprise the following steps: (1) the bamboo fiber raw material is pretreated, the pretreatment mode is alkali combined with EVA emulsion treatment, fermentation treatment or acetic acid treatment; the alkali combined with EVA emulsion treatment is first soaked with alkali solution, then soaked with ethylene-vinyl acetate copolymer emulsion; the fermentation treatment is fermented by using fermentation liquor; the acetic acid treatment is soaked by using acetic acid solution; (2) the silicate cement, foam stabilizer, catalyst and the bamboo fiber pretreated in step (1) are premixed, stirred, and the mixture is obtained; (3) the water reducing agent is dissolved in water, added to the mixture obtained in step (2), stirred, and the mixed slurry is obtained; (4) the foaming agent is added to the mixed slurry obtained in step (3), stirred, and the foaming slurry is obtained; (5) the foaming slurry obtained in step (4) is injected into a foaming mold, foamed and formed by standing, coated and moisturized, demolded, and cured, and the bamboo fiber reinforced silicate cement-based foaming material is obtained; In step (1), the alkali combined with EVA emulsion treatment comprises the following steps: (1.1) the bamboo fiber raw material with a size of 60-80 mesh is soaked in an alkali solution with a mass percentage of 3-8% for 8-24 hours, washed, dried, and the bamboo fiber treated with alkali is obtained; (1.2) the bamboo fiber treated with alkali is soaked in an ethylene-vinyl acetate copolymer emulsion with a mass percentage of 5-15% for 24-48 hours, washed, dried, and the bamboo fiber pretreated with alkali combined with EVA emulsion is obtained; The fermentation liquor comprises water, flour, yeast and wine starter, and the mass ratio of the bamboo fiber raw material to water, flour, yeast and wine starter is 50:25-40:0.7-2:0.5-1.5:1-2.5, the fermentation is anaerobic fermentation, the temperature of the fermentation is 4-45°C, and the time of the fermentation is 24-48 hours; The mass percentage of the acetic acid solution is 5-10%, the temperature of the acetic acid solution soaking is room temperature, and the time of the acetic acid solution soaking is 8-24 hours; In step (1.1), the alkali solution is sodium hydroxide solution or potassium hydroxide solution, the washing is washing with water until the pH of the washing wastewater is greater than or equal to 6, and the drying is drying at 60-75°C until the mass change is not more than 1g per 4 hours; In step (1.2), the washing is washing with water until the pH of the washing wastewater is greater than or equal to 6, and the drying is drying at 60-75°C until the mass change is not more than 1g per 4 hours.

2. The method for preparing bamboo fiber reinforced silicate cement-based foamed material according to claim 1, characterized in that, In step (1), after the fermentation is completed, the washing wastewater is clarified by washing with water, and then dried at 60-75°C until the weight change is not more than 1g per 4 hours; the yeast is activated in water at 30-35°C for 10-15 minutes before use.

3. The method for preparing bamboo fiber reinforced silicate cement-based foamed material according to claim 1, characterized in that, In step (1), after the acetic acid solution soaking is completed, the washing wastewater is clarified by washing with water until the pH is greater than or equal to 6, and then dried at 60-75°C until the weight change is not more than 1g per 4 hours.

4. The method for producing a bamboo fiber-reinforced silicate cement-based foam material according to any one of claims 1 to 3, characterized by, The foaming agent is 25-35% hydrogen peroxide solution, the foam stabilizer is calcium stearate, the water reducing agent is polycarboxylic acid, and the catalyst is manganese dioxide, and each component comprises, by mass fraction: Silicate cement 100-200 parts; Bamboo fiber 4-10 parts; hydrogen peroxide solution 2.75 to 3.5 parts; calcium stearate 1 to 5 parts; manganese dioxide 0.25 to 0.35 parts; polycarboxylic acid 0.1 to 0.2 parts; water 50 to 100 parts; The size of the bamboo fiber raw material subjected to the fermentation treatment or acetic acid treatment is 20 to 80 mesh.

5. The method for preparing a bamboo fiber reinforced silicate cement-based foam material according to any one of claims 1 to 3, characterized in that, In step (2), the stirring speed is 300 to 500 r / min, and the stirring time is 5 to 10 min. In step (3), the stirring speed is 600 to 800 r / min, and the stirring time is 1 to 2 min. In step (4), the stirring speed is 1000 to 1500 r / min, and the stirring time is 5 to 10 s. In step (5), the film is removed after being moisturized for 1 to 3 days, and the curing is natural curing by spraying water at regular intervals for 7 to 28 days.

6. A bamboo fiber reinforced silicate cement-based foam material prepared by the preparation method according to any one of claims 1 to 5.

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