CN111302685A - Preparation method of wheat straw fiber reinforced cement board and wheat straw fiber reinforced cement board - Google Patents

Preparation method of wheat straw fiber reinforced cement board and wheat straw fiber reinforced cement board Download PDF

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Publication number
CN111302685A
CN111302685A CN202010107078.9A CN202010107078A CN111302685A CN 111302685 A CN111302685 A CN 111302685A CN 202010107078 A CN202010107078 A CN 202010107078A CN 111302685 A CN111302685 A CN 111302685A
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water
wheat straw
fiber
reinforced cement
fiber reinforced
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吕春粉
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Zhengzhou Zhitao Information Technology Co ltd
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Zhengzhou Zhitao Information Technology Co ltd
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    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B20/00Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
    • C04B20/02Treatment
    • C04B20/026Comminuting, e.g. by grinding or breaking; Defibrillating fibres other than asbestos
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B20/00Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
    • C04B20/02Treatment
    • C04B20/023Chemical treatment
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/02Compositions 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
    • C04B28/04Portland cements
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B40/00Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • C04B40/0028Aspects relating to the mixing step of the mortar preparation
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B40/00Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • C04B40/02Selection of the hardening environment
    • C04B40/024Steam hardening, e.g. in an autoclave
    • C04B40/0245Steam hardening, e.g. in an autoclave including a pre-curing step not involving a steam or autoclave treatment
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20Resistance against chemical, physical or biological attack
    • C04B2111/27Water resistance, e.g. waterproof or water-repellant materials
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20Resistance against chemical, physical or biological attack
    • C04B2111/28Fire resistance, i.e. materials resistant to accidental fires or high temperatures
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20Resistance against chemical, physical or biological attack
    • C04B2111/29Frost-thaw resistance
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02WCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00Technologies for solid waste management
    • Y02W30/50Reuse, recycling or recovery technologies
    • Y02W30/91Use of waste materials as fillers for mortars or concrete

Abstract

The invention relates to a preparation method of a wheat straw fiber reinforced cement board and the wheat straw fiber reinforced cement board, wherein the method comprises the following steps: 1) cutting dried wheat straws into short materials, soaking and softening the short materials by water, and then soaking the short materials by a sodium hydroxide solution to obtain a prepared material; 2) performing steam explosion on the prepared material, and then washing the prepared material to obtain a fiber material; 3) modifying the fiber material by using gamma-aminopropyltriethoxysilane to obtain modified wheat straw fiber; 4) pulping the modified wheat straw fiber to obtain fiber pulp; 5) adding silica fume and metakaolin into the fiber slurry, continuously dispersing, adding a dry material prepared from cement, fly ash and quartz sand and water to prepare a mixed slurry, forming to prepare a wet blank, and carrying out pre-curing, autoclaved curing and drying to obtain the composite material. The obtained wheat straw fiber reinforced cement board has good appearance quality, low water absorption and low wet expansion rate, good water resistance and moisture resistance, high mechanical property, good freeze-thaw resistance, hot water and dry-wet cycle performance and stable property, and can replace the application of wood pulp fiber reinforced cement boards.

Description

Preparation method of wheat straw fiber reinforced cement board and wheat straw fiber reinforced cement board
Technical Field
The invention belongs to the technical field of fiber reinforced cement boards, and particularly relates to a preparation method of a wheat straw fiber reinforced cement board and the wheat straw fiber reinforced cement board.
Background
The fiber reinforced cement board (also called fiber cement board) is a water-hardening artificial board which is prepared by using hardened cement paste or mortar as a base material and fibers as a reinforcing material through the processes of pulping, forming, maintaining, drying and the like; depending on the type of reinforcing fibers used, they can be classified into chrysotile fiber cement boards reinforced with asbestos fibers and non-asbestos fiber cement boards reinforced with other fibers (without asbestos).
The fiber reinforced cement board has the excellent characteristics of fire prevention, insulation, water prevention, moisture prevention, heat insulation, sound insulation, light weight, high strength, simple and convenient construction, good decorative effect, safety, harmlessness, long service life and the like, has a very wide application range, and can be used as a sound absorption and ceiling material because a thin board (with the thickness of 2.5-3.5mm) can be perforated; the conventional board (thickness 4-12mm) can be used as wall and decorative material, such as indoor partition lining board, composite wall panel, outdoor billboard, industrial electric furnace heat insulation board, electrical and electronic power distribution cabinet, transformer partition board, etc.; the thick plate (thickness 13-30mm) and the super-thick plate (thickness 31-100mm) can be used as steel structure floor plates, pavilion floor plates, external wall heat-insulating plates, external wall cladding plates and the like.
In recent years, in order to avoid the occurrence of asbestos-related diseases such as asbestos lung, lung cancer, mesothelioma, etc., research on fiber-reinforced cement boards at home and abroad has been focused on the development of novel substitute fibers, and asbestos-free fiber-reinforced cement boards have been developed, using fiber materials including pulp fibers, glass fibers, synthetic fibers (such as polypropylene fibers, polyvinyl alcohol fibers, aramid fibers), organic and inorganic composite fibers, etc. At present, the chemically treated softwood wood pulp fibers are used more frequently, for example, the wood pulp fibers prepared from the raw materials of the mountain pine, the slash pine and the like are harmless to the human health compared with chrysotile; compared with glass fiber and synthetic fiber, wood pulp fiber belongs to renewable resources and has wide sources. The coniferous wood pulp mainly made of pine wood has moderate fiber length, has better interfacial adhesion with cement after bleaching, can overcome the problem of dry shrinkage of common cement products, and plays a role in strengthening. In the prior art, hardwood (such as eucalyptus) pulp is also used as a raw material to prepare the fiber reinforced cement board, but the hardwood pulp pulping process needs to be further optimized and improved, fiber damage is reduced, and the softwood pulp can be completely replaced.
However, wood resources in China are relatively deficient and scarce, because the coverage rate of forests is not high, the yield of the woods in China is obviously reduced in order to protect the tree resources in forest zones and maintain good ecological environment, and commercial felling is forbidden gradually, and the competition among downstream industries taking the woods as raw materials is intense, so that fiber cement board manufacturers taking wood pulp fibers as reinforcing materials mainly rely on imported wood pulp, the price and the transportation cost are high, and the industrial development and application of green environment-friendly fiber reinforced cement boards are limited.
Disclosure of Invention
The invention aims to provide a preparation method of a wheat straw fiber reinforced cement board.
The second purpose of the invention is to provide a wheat straw fiber reinforced cement board prepared by the preparation method.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a preparation method of a wheat straw fiber reinforced cement board comprises the following steps:
1) cutting dried wheat straws into short materials, soaking and softening the short materials by using water, soaking the short materials for 15-20min by using a sodium hydroxide solution with the mass concentration of 3.0-4.0%, and taking out the short materials to obtain a prepared material;
2) performing steam explosion on the prepared material obtained in the step 1), wherein the steam temperature is 175-; washing the obtained blasting material with water to obtain a fiber material;
3) dissolving gamma-aminopropyltriethoxysilane in an ethanol water solution to prepare a modifier, uniformly mixing the obtained modifier with the fiber material obtained in the step 2), and drying to remove ethanol to obtain modified wheat straw fibers;
4) adding the modified wheat straw fiber obtained in the step 3) into water for pulping and defibering, wherein the pulping degree is 20.0-25.0 DEG SR, and obtaining fiber pulp with the mass concentration of 2.4-2.6%;
5) adding silica fume and metakaolin into the fiber slurry obtained in the step 4), continuously shearing and dispersing for 10-15min, then adding a dry material prepared by mixing cement, fly ash and quartz sand and water to prepare a mixed slurry, then preparing a wet blank through a forming process, and then performing pre-curing, autoclaved curing and drying to obtain the fiber slurry.
In the step 1), the length of the short material is 20-40 mm; the soaking time for soaking and softening by water is 12-16 h. Soaking in water at room temperature. And (4) taking out the obtained product after alkaline leaching, draining the obtained product until the water drops are not in flow, and carrying out subsequent steam explosion operation.
In the step 2), the water washing means that the blasting material is soaked in water for 5-10 hours to fully dissolve out water-soluble substances, and then the blasting material is repeatedly rinsed to be neutral by water.
In step 2), the fiber material is sieved before use. Sieving refers to the removal of excessively finely divided fiber powder. Preferably, the fiber material with the fiber length not less than 2mm is obtained by screening and is ready for use.
In the step 3), the dosage of the gamma-aminopropyl triethoxysilane is 1.0-1.2% of the mass of the fiber material.
In the step 5), the following ingredients are prepared according to the parts by weight: 6-8 parts of modified fiber material, 5-6 parts of silica fume, 48-52 parts of cement, 10-12 parts of metakaolin, 20-22 parts of quartz sand and 5-6 parts of fly ash.
The particle size of the silica fume is 0.05-0.15 μm; the particle size of the metakaolin is 1-3 mu m; the particle size of the quartz sand is 200-300 meshes; the particle size of the fly ash is 300-500 meshes.
The mixed slurry obtained in the step 5) also comprises an auxiliary agent, and the dosage of the auxiliary agent is 0-2.5 parts by weight. The auxiliary agent is any one or combination of a water reducing agent, a release agent, a thickening agent, a waterproof agent and a retarder. The auxiliary agent can be selected according to actual production conditions, and the conventional commercial type in the field can be selected according to requirements.
In the step 5), the temperature of the pre-curing is 60-80 ℃, and the time is 3-5 h; the temperature of the steam pressure curing is 175-185 ℃, the pressure is 0.8-1.2MPa, and the time is 6-8 h.
In the step 5), the water content of the mixed slurry is controlled to be more than or equal to 90%, the water content of the wet blank is controlled to be less than or equal to 32%, and the water content of the plate blank obtained after autoclaved curing is controlled to be less than or equal to 30%.
In the step 5), the drying temperature is 105-110 ℃, and the drying is carried out until the water content of the plate reaches below 7.0%.
The wheat straw fiber reinforced cement board prepared by the preparation method.
The preparation method of the wheat straw fiber reinforced cement board comprises the steps of cutting dry wheat straws into short materials, soaking and softening the short materials by water, and preventing the wheat straws from being excessively crushed into powder after being subjected to steam explosion in a dry state; soaking the wheat straw in 3.0-4.0 wt% concentration sodium hydroxide solution for 15-20min to obtain the material, and soaking the material in alkali solution to permeate into fiber pores and cell walls inside the wheat straw.
The invention carries out steam explosion on the obtained prepared material, wheat straws with alkali liquor enter a steam explosion device, the steam temperature of the steam explosion is controlled to be 175-180 ℃, the explosion pressure is 2.4-2.8MPa, the pressure maintaining time is 4.0-5.0min, the wheat straws are quickly heated to the set temperature by high-temperature steam, sodium hydroxide diffuses and permeates into the fiber cell walls of the wheat straws along with water vapor under high pressure, cellulose, hemicellulose and colloid in the wheat straws are activated under the conditions of high temperature and high pressure to generate alkaline hydrolysis, lignin is softened, the polymerization degree of fiber bundles is reduced, fibers bound by the colloid are gradually loosened, lignin bonded with the cellulose is partially peeled off, the temperature is quickly reduced due to sudden release of pressure during pressure relief, the moistened wheat straws are exploded, raw materials are torn into fine fibers, the cellulose fibers with better strength and toughness after separation and refinement are obtained, and the steam explosion breaks through the wheat straws from inside to outside to prepare fibers, the fiber has high fibrillation rate, good water retention and adsorption. Through the alkaline steam explosion treatment, cellulose and hemicellulose in the wheat straw fiber are degraded, carbohydrate and acid substances are increased, macromolecular carbohydrate is decomposed into micromolecular carbohydrate, biomass with certain viscosity is formed by the macromolecular carbohydrate and activated lignin, the obtained blasting material is washed by water, dissolved substances are removed, and the viscous substances are washed away, so that the pure fiber material is obtained.
The invention dissolves gamma-aminopropyl triethoxy silane in ethanol water solution to prepare modifier, and the modifier and the obtained fiber material are evenly mixed and dried to remove ethanol, thus obtaining the modified wheat straw fiber. The fiber material is modified by gamma-aminopropyltriethoxysilane, so that the hydrophilicity of the wheat straw fiber is reduced, the water-retaining property of the fiber is improved, and the alkali resistance and the interface bonding force with a cement matrix are enhanced. The ethanol water is adopted as the solvent, which is beneficial to the hydrolysis of the gamma-aminopropyl triethoxysilane and the spreading on the fiber surface, the dosage of the gamma-aminopropyl triethoxysilane is saved, the subsequent process is prevented from being influenced, and the used ethanol can be recycled.
The modified wheat straw fiber is added into water for pulping and defibering, the pulping degree and the fiber pulp concentration are controlled, the fiber in the obtained fiber pulp is uniformly dispersed and has good brooming degree, the subsequent adsorption of cement particles and hydration products thereof is facilitated, the binding force between material layers is improved, and the layering phenomenon is inhibited.
According to the invention, the silica fume and the metakaolin are added into the obtained fiber slurry, and the shearing and the dispersion are continued for 10-15min, so that a part of superfine materials of the silica fume and the metakaolin are firstly adsorbed on the surface of the fiber, the adsorption effect of the fiber on cement particles is enhanced, and then the dry material prepared by mixing the cement, the fly ash and the quartz sand and water are added to prepare the mixed slurry. Metakaolin can also rapidly react with calcium hydroxide generated by cement hydration to generate viscous mixtures such as ettringite, calcium silicate gel and the like, so that the interface bonding strength of the fiber and the base material is improved; meanwhile, the alkalinity of the cement base material can be reduced, the damage effect on the self structure of the wheat straw fiber is reduced, and the reinforcing effect of the fiber is improved. The quartz sand is used as the fine aggregate of the cement base material, and the fly ash is used as the mineral admixture for improving the strength and the mechanical property of the plate. The mixed slurry is made into a wet blank through a forming process, and then the wet blank is subjected to pre-curing, autoclaved curing and drying to obtain the plate, wherein the pre-curing and autoclaved curing parameters are scientifically and reasonably designed, and the obtained plate has stable properties and high quality.
The invention takes cement as a base material, modified wheat straw fiber as a reinforcing material, silica fume and metakaolin as fillers, quartz sand as fine aggregate and fly ash as a mineral admixture, and the surface of the obtained wheat straw fiber reinforced cement board (original board) finished product has no phenomena of crack, delamination, peeling and bubbling, and has no obvious corner drop and edge drop, thereby meeting the requirement of appearance quality. The detection shows that the water absorption rate of the obtained board is below 15.86 percent, the hygroexpansion rate is below 0.1 percent, which indicates that the combination between the wheat straw fiber reinforced material and the matrix in the board is tighter, the porosity is small, the board is not easy to absorb water, and the board has better water resistance and moisture resistance; the incombustibility of the obtained plate meets the requirement of GB 8624 incombustibility A, and after the water impermeability test lasts for 24 hours, no water drops appear on the bottom surface of the plate, so that the water impermeability requirement is met. In a mechanical property detection test, the water saturation breaking strength of the obtained plate is not lower than 13MPa, and the R3-level strength requirements of A-type and B-type plates are met; the impact strength is not lower than 1.8kJ/m3Meets the C3-grade strength requirement of the plate with the thickness e less than or equal to 14 mm. In an anti-freezing test, after 100 times of freeze-thaw cycles, the water-saturated breaking strength of the obtained plate is still more than 11.52MPa, the breaking strength ratio is more than 83.72%, the strength loss is small, and the plate has good anti-freezing performance; in a hot water test, the water saturation breaking strength of the obtained plate is still more than 10.31MPa, the breaking strength ratio is more than 74.39%, the strength loss is small, and the plate has good damp-heat resistance stability; in a soaking-drying test, the obtained board has the water saturation breaking strength of more than 11.79MPa, the breaking strength ratio of more than 85.68 percent, small strength loss and good dry and wet resistance stability. The obtained wheat straw fiber reinforced cement board has excellent comprehensive performance and can replace the application of the existing wood pulp fiber reinforced cement board.
Detailed Description
The present invention will be further described with reference to the following embodiments.
In a specific embodiment, the used dry wheat straws are purchased from local farmers, have the water content of 15-20 percent and are cleaned of impurities such as soil, dust, weeds and the like before use.
In a specific embodiment, the cement is commercially availableOrdinary portland cement, strength grade 42.5 #. The used silica fume is a commercial product, and the particle size is 0.05-0.15 μm. The metakaolin is a commercial product and is prepared by calcining metakaolin at 800 deg.C for 4 hr, and has average particle diameter of not more than 1.0 μm and specific gravity of 2.58g/cm3The activity is 35-40%. The quartz sand is a commercial product with the grain diameter of 200-300 meshes and SiO2The content is more than 99.6 percent. The fly ash is a commercial product, the particle size is 300-500 meshes, and the density is 2.29g/cm3
In the specific embodiment, the forming process comprises a sheet-making method, extrusion dehydration and compression forming.
Example 1
The preparation method of the wheat straw fiber reinforced cement board of the embodiment comprises the following steps:
1) cutting dried wheat straws into short materials with the length of 20-40mm, soaking the short materials with clear water for 12 hours at room temperature to soften the short materials, then soaking the short materials with sodium hydroxide solution with the mass concentration of 4.0% for 15 minutes, taking out the short materials, draining the short materials until water drops do not flow down as strands, and obtaining a prepared material;
2) placing the prepared material obtained in the step 1) in a steam explosion device for steam explosion, wherein the steam temperature is 175 ℃, the explosion pressure is 2.8MPa, the pressure maintaining time is 4.5min, and then discharging the material to obtain the explosive material; soaking the blasting material in water for 10h to fully dissolve out water-soluble substances (including water-soluble colloid), repeatedly rinsing with water to neutrality without adhesion between fibers, and sieving to obtain fiber material with length of 2-5 mm;
3) dissolving gamma-aminopropyltriethoxysilane in an ethanol water solution (the mass ratio of ethanol to water is 82:8) to prepare a modifier with the mass concentration of 10%, uniformly mixing the obtained modifier with the fiber material obtained in the step 2), and drying to remove ethanol (ethanol is recycled and reused) to obtain modified wheat straw fibers; wherein the dosage of the gamma-aminopropyl triethoxysilane is 1.1 percent of the mass of the fiber material;
4) adding the modified wheat straw fiber obtained in the step 3) into water for pulping and defibering, wherein the pulping degree is 21.0 DEG SR, and obtaining fiber pulp with the mass concentration of 2.5%;
5) the materials are prepared according to the following parts by weight: 6.5 parts of modified wheat straw fiber, 5.5 parts of silica fume, 52 parts of cement, 10 parts of metakaolin, 21 parts of quartz sand and 5 parts of fly ash;
adding silica fume and metakaolin into the fiber slurry obtained in the step 4), continuously shearing and dispersing for 10min, then adding a dry material prepared by mixing cement, fly ash and quartz sand and water to prepare a mixed slurry, and controlling the water content of the mixed slurry to be more than or equal to 90%; then a wet blank is prepared by a forming process (a copying method), and the water content of the wet blank is controlled to be less than or equal to 32 percent; pre-curing for 5h at the temperature of 60 ℃, then performing autoclaved curing for 8h at the temperature of 185 ℃ and the pressure of 0.8MPa (controlling the water content of the plate blank obtained after the autoclaved curing to be less than or equal to 30%), and drying at the temperature of 105 ℃ until the water content of the plate reaches less than 7.0%, thus obtaining the wheat straw fiber reinforced cement plate.
Example 2
The preparation method of the wheat straw fiber reinforced cement board of the embodiment comprises the following steps:
1) cutting dried wheat straws into short materials with the length of 20-40mm, soaking the short materials for 14h at room temperature for softening, soaking the short materials for 18min by using a sodium hydroxide solution with the mass concentration of 3.5%, taking out the short materials, draining the short materials until water drops do not flow down as strands, and obtaining a prepared material;
2) placing the prepared material obtained in the step 1) in a steam explosion device for steam explosion, wherein the steam temperature is 180 ℃, the explosion pressure is 2.4MPa, the pressure maintaining time is 5.0min, and then discharging the material to obtain the explosive material; soaking the blasting material in water for 10h to fully dissolve out water-soluble substances (including water-soluble colloid), repeatedly rinsing with water to neutrality without adhesion between fibers, and sieving to obtain fiber material with length of 2-5 mm;
3) dissolving gamma-aminopropyltriethoxysilane in an ethanol water solution (the mass ratio of ethanol to water is 82:8) to prepare a modifier with the mass concentration of 10%, uniformly mixing the obtained modifier with the fiber material obtained in the step 2), and drying to remove ethanol (ethanol is recycled and reused) to obtain modified wheat straw fibers; wherein the dosage of the gamma-aminopropyl triethoxysilane is 1.0 percent of the mass of the fiber material;
4) adding the modified wheat straw fiber obtained in the step 3) into water for pulping and defibering, wherein the pulping degree is 22.0 DEG SR, and obtaining fiber pulp with the mass concentration of 2.4%;
5) the materials are prepared according to the following parts by weight: 7 parts of modified wheat straw fiber, 6 parts of silica fume, 50 parts of cement, 11 parts of metakaolin, 20 parts of quartz sand and 6 parts of fly ash;
adding silica fume and metakaolin into the fiber slurry obtained in the step 4), continuously shearing and dispersing for 10min, then adding a dry material prepared by mixing cement, fly ash and quartz sand and water to prepare a mixed slurry, and controlling the water content of the mixed slurry to be more than or equal to 90%; and then preparing a wet blank by a forming process (a copying method), pre-curing for 4h at the temperature of 70 ℃, then performing autoclaved curing for 6h at the temperature of 180 ℃ and the pressure of 1.0MPa (controlling the water content of the plate blank obtained after the autoclaved curing to be less than or equal to 30%), and then drying at the temperature of 105 ℃ until the water content of the plate reaches below 7.0%, thus obtaining the wheat straw fiber reinforced cement plate.
Example 3
The preparation method of the wheat straw fiber reinforced cement board of the embodiment comprises the following steps:
1) cutting dried wheat straws into short materials with the length of 20-40mm, soaking the short materials with clear water for 16h at room temperature to soften the short materials, then soaking the short materials with sodium hydroxide solution with the mass concentration of 3.0% for 20min, taking out the short materials, draining the short materials until water drops do not flow down as strands, and obtaining a prepared material;
2) placing the prepared material obtained in the step 1) in a steam explosion device for steam explosion, wherein the steam temperature is 180 ℃, the explosion pressure is 2.6MPa, the pressure maintaining time is 4.0min, and then discharging the material to obtain the explosive material; soaking the blasting material in water for 10h to fully dissolve out water-soluble substances (including water-soluble colloid), repeatedly rinsing with water to neutrality without adhesion between fibers, and sieving to obtain fiber material with length of 2-5 mm;
3) dissolving gamma-aminopropyltriethoxysilane in an ethanol water solution (the mass ratio of ethanol to water is 82:8) to prepare a modifier with the mass concentration of 10%, uniformly mixing the obtained modifier with the fiber material obtained in the step 2), and drying to remove ethanol (ethanol is recycled and reused) to obtain modified wheat straw fibers; wherein the dosage of the gamma-aminopropyl triethoxysilane is 1.2 percent of the mass of the fiber material;
4) adding the modified wheat straw fiber obtained in the step 3) into water for pulping and defibering, wherein the pulping degree is 23.0 DEG SR, and obtaining fiber pulp with the mass concentration of 2.6%;
5) the materials are prepared according to the following parts by weight: 7.5 parts of modified wheat straw fiber, 5 parts of silica fume, 48 parts of cement, 12 parts of metakaolin, 22 parts of quartz sand and 5.5 parts of fly ash;
adding silica fume and metakaolin into the fiber slurry obtained in the step 4), continuously shearing and dispersing for 10min, then adding a dry material prepared by mixing cement, fly ash and quartz sand and water to prepare a mixed slurry, and controlling the water content of the mixed slurry to be more than or equal to 90%; then a wet blank is prepared by a forming process (a copying method), and the water content of the wet blank is controlled to be less than or equal to 32 percent; pre-curing for 3h at the temperature of 80 ℃, then performing autoclaved curing for 6h at the temperature of 175 ℃ and the pressure of 1.2MPa (controlling the water content of the plate blank obtained after the autoclaved curing to be less than or equal to 30%), and drying at the temperature of 105 ℃ until the water content of the plate reaches less than 7.0%, thus obtaining the wheat straw fiber reinforced cement plate.
The wheat straw fiber-reinforced cement boards obtained in examples 1 to 3 were subjected to the following procedure in accordance with section 1 of JC/T412.1 fiber cement panel: the results of the performance test conducted on the asbestos-free fiber cement slabs are shown in Table 1.
TABLE 1 results of measuring the properties of the wheat straw fiber-reinforced cement boards obtained in examples 1 to 3
As can be seen from Table 1, the wheat straw fiber reinforced cement board (raw board) finished products obtained in examples 1-3 have no cracks, delamination, peeling and bubbling phenomena on the surface, have no obvious corner drop and edge drop, and meet the requirements of appearance quality; the design requirements for the thickness of the sheets of examples 1 to 3 were 10mm, and the apparent density of the sheets was 1.4g/cm2In the actual measurement result, the thickness and the apparent density are not lower than the design requirements, and the dimensional deviation is within the specified range. The detection shows that the water absorption rate of the obtained plate is below 15.86 percent, and the wet expansion rate is 0.1% below, this shows that the wheat straw fiber reinforced cement board of the invention has the advantages of tight combination between the wheat straw fiber reinforced material and the matrix, small porosity, difficult water absorption, and good water and moisture resistance; the incombustibility of the obtained plate meets the requirement of GB 8624 incombustibility A, and after the water impermeability test lasts for 24 hours, no water drops appear on the bottom surface of the plate, so that the water impermeability requirement is met. In a mechanical property detection test, the water saturation breaking strength of the plate obtained in the examples 1-3 is respectively 13.76MPa, 14.05MPa and 14.68MPa, which are not lower than 13MPa, and the R3-level strength requirements of the A-type plate and the B-type plate are met; the impact strength is respectively 2.08kJ/m3、2.16kJ/m3、2.19kJ/m3Are not less than 1.8kJ/m3Meets the C3-grade strength requirement of the plate with the thickness e less than or equal to 14 mm. In an anti-freezing test, after 100 times of freeze-thaw cycles, the water-saturated breaking strength of the obtained plate is still more than 11.52MPa, the breaking strength ratio is more than 83.72%, the strength loss is small, and the plate has good anti-freezing performance; in a hot water test, the water saturation breaking strength of the obtained plate is still more than 10.31MPa, the breaking strength ratio is more than 74.39%, the strength loss is small, and the plate has good damp-heat resistance stability; in a soaking-drying test, the obtained board has the water saturation breaking strength of more than 11.79MPa, the breaking strength ratio of more than 85.68 percent, small strength loss and good dry and wet resistance stability.

Claims (9)

1. A preparation method of a wheat straw fiber reinforced cement board is characterized by comprising the following steps: the method comprises the following steps:
1) cutting dried wheat straws into short materials, soaking and softening the short materials by using water, soaking the short materials for 15-20min by using a sodium hydroxide solution with the mass concentration of 3.0-4.0%, and taking out the short materials to obtain a prepared material;
2) performing steam explosion on the prepared material obtained in the step 1), wherein the steam temperature is 175-; washing the obtained blasting material with water to obtain a fiber material;
3) dissolving gamma-aminopropyltriethoxysilane in an ethanol water solution to prepare a modifier, uniformly mixing the obtained modifier with the fiber material obtained in the step 2), and drying to remove ethanol to obtain modified wheat straw fibers;
4) adding the modified wheat straw fiber obtained in the step 3) into water for pulping and defibering, wherein the pulping degree is 20.0-25.0 DEG SR, and obtaining fiber pulp with the mass concentration of 2.4-2.6%;
5) adding silica fume and metakaolin into the fiber slurry obtained in the step 4), continuously shearing and dispersing for 10-15min, then adding a dry material prepared by mixing cement, fly ash and quartz sand and water to prepare a mixed slurry, then preparing a wet blank through a forming process, and then performing pre-curing, autoclaved curing and drying to obtain the fiber slurry.
2. The method for preparing a wheat straw fiber reinforced cement board as claimed in claim 1, wherein: in the step 1), the length of the short material is 20-40 mm; the soaking time for soaking and softening by water is 12-16 h.
3. The method for preparing a wheat straw fiber reinforced cement board as claimed in claim 1, wherein: in the step 2), the water washing means that the blasting material is soaked in water for 5-10 hours to fully dissolve out water-soluble substances, and then the blasting material is repeatedly rinsed to be neutral by water.
4. The method for preparing a wheat straw fiber reinforced cement board as claimed in claim 1, wherein: in the step 3), the dosage of the gamma-aminopropyl triethoxysilane is 1.0-1.2% of the mass of the fiber material.
5. The method for preparing a wheat straw fiber reinforced cement board as claimed in claim 1, wherein: in the step 5), the following ingredients are prepared according to the parts by weight: 6-8 parts of modified wheat straw fiber, 5-6 parts of silica fume, 48-52 parts of cement, 10-12 parts of metakaolin, 20-22 parts of quartz sand and 5-6 parts of fly ash.
6. The method for preparing a wheat straw fiber reinforced cement board as claimed in claim 1, wherein: in the step 5), the temperature of the pre-curing is 60-80 ℃, and the time is 3-5 h; the temperature of the steam pressure curing is 175-185 ℃, the pressure is 0.8-1.2MPa, and the time is 6-8 h.
7. The method for preparing a wheat straw fiber reinforced cement board as claimed in claim 1, wherein: in the step 5), the water content of the mixed slurry is controlled to be more than or equal to 90%, the water content of the wet blank is controlled to be less than or equal to 32%, and the water content of the plate blank obtained after autoclaved curing is controlled to be less than or equal to 30%.
8. The method for preparing a wheat straw fiber reinforced cement board as claimed in claim 1, wherein: in the step 5), the drying temperature is 105-110 ℃, and the drying is carried out until the water content of the plate reaches below 7.0%.
9. A straw fiber reinforced cement board prepared by the preparation method of any one of claims 1 to 8.
CN202010107078.9A 2020-02-21 2020-02-21 Preparation method of wheat straw fiber reinforced cement board and wheat straw fiber reinforced cement board Withdrawn CN111302685A (en)

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Application publication date: 20200619