CN115196940A - Composite fiber reinforced basic magnesium sulfate cement and preparation method thereof - Google Patents

Composite fiber reinforced basic magnesium sulfate cement and preparation method thereof Download PDF

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CN115196940A
CN115196940A CN202210832743.XA CN202210832743A CN115196940A CN 115196940 A CN115196940 A CN 115196940A CN 202210832743 A CN202210832743 A CN 202210832743A CN 115196940 A CN115196940 A CN 115196940A
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magnesium sulfate
cement
fiber reinforced
volume
magnesium oxide
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宋谦益
刘宜丰
刘联华
游俊杰
杨成
谭达
姜雪
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Southwest Jiaotong University
China Southwest Architectural Design and Research Institute Co Ltd
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Southwest Jiaotong University
China Southwest Architectural Design and Research Institute 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
    • 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
    • C04B28/30Compositions 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 magnesium cements or similar 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
    • C04B14/00Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B14/38Fibrous materials; Whiskers
    • C04B14/46Rock wool ; Ceramic or silicate fibres
    • C04B14/4643Silicates other than zircon
    • 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
    • C04B18/00Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/04Waste materials; Refuse
    • C04B18/18Waste materials; Refuse organic
    • C04B18/24Vegetable refuse, e.g. rice husks, maize-ear refuse; Cellulosic materials, e.g. paper, cork
    • C04B18/26Wood, e.g. sawdust, wood shavings
    • 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
    • C04B2201/00Mortars, concrete or artificial stone characterised by specific physical values
    • C04B2201/50Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
    • 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

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  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
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  • Civil Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)

Abstract

The invention discloses a composite fiber reinforced basic magnesium sulfate cement and a preparation method thereof, wherein the raw materials comprise active magnesium oxide, magnesium sulfate heptahydrate and a modifier; also comprises wood fiber and basalt fiber; the volume of the wood fiber is 0.1-50% of the total volume of the raw materials, the volume fraction is below 50% optimally, and the combustion performance grade of the material is reduced due to overhigh volume; the wood fiber can be made by crushing residual materials in wood processing; the adding volume of the basalt fiber is 0.1-5% of the total volume of the raw materials, the volume fraction is optimally below 5%, and the fluidity and uniformity of slurry are influenced by overhigh volume. The invention has positive significance for developing and utilizing the environment-friendly doping material to improve the performance of the basic magnesium sulfate cement, and the provided cement material has higher mechanical strength, especially rupture strength.

Description

Composite fiber reinforced basic magnesium sulfate cement and preparation method thereof
Technical Field
The invention relates to the technical field of cement preparation, in particular to composite fiber reinforced basic magnesium sulfate cement and a preparation method thereof, and more particularly relates to basalt fiber-wood fiber-composite fiber reinforced basic magnesium sulfate cement and a preparation method thereof.
Background
In the conventional cement industry, the carbon emission is high, and an environmental-friendly substitute for cement needs to be generated due to unprecedented carbon reduction pressure. The magnesium cementing material is a cement material which is gradually developed and improved in recent decades, the magnesium cementing material is used as a green material which can be provided at present, building components such as heat-insulating wallboards and the like manufactured by the magnesium cementing material are widely applied, but the specific mechanical properties, particularly the common working mechanism when the magnesium cementing material is mixed with other environment-friendly materials for use, are not completely clear, and the further popularization of the magnesium cementing material is limited.
The main raw material MgO of the magnesian cementing material is MgCO 3 The material is obtained by calcining, but the optimum calcining temperature is only about 700 ℃. According to the industrial data, compared with the PC production process, the energy consumption for producing the magnesium cementing material is reduced by 42.70 percent, and CO is reduced 2 The emission is reduced by 47.37%. The magnesium oxychloride cement and the magnesium sulfate cement are two early-applied magnesium cementing materials, and the main hydration products developed in recent years are novel crystal whisker 5.1.7 phases (5 Mg (OH) 2 ·MgSO 4 ·7H 2 O) combines the advantages of the traditional magnesium cement, overcomes the defect that the main strength phase is 3.1.8 phase (3 Mg (OH) 2 ·MgSO 4 ·8H 2 O) is poor in normal temperature stability and general mechanical property, and is superior to the conventional 5.1.8 phase (5 Mg (OH) in water-resistant and moisture-proof properties 2 ·MgCl 2 ·8H 2 O) magnesium oxychloride cement. The composite fiber reinforced basic magnesium sulfate cement has higher early-age strength, lighter density, and superior mechanical property, water resistance and fire resistance, but as an air-hardening cementing material, the composite fiber reinforced basic magnesium sulfate cement still has wider engineering application range after the toughness is improved.
Fillers are generally chemically inert, but can still indirectly influence the chemical structure of the cement in a positive manner. The incorporation of reinforcing chopped fibers in the cement is one of the best ways in which the toughness and other mechanical properties can be quantitatively analyzed and adjusted. The main inclusions at present are also polymeric fibres based on petrochemical origin (for example polyethylene, polyvinyl alcohol, polyphenylenes, etc.), the non-renewable and non-degradable nature of which has a significant negative impact on the environment. In addition, the lower melting point of the polymer fiber and the toxic and harmful gas released at high temperature have obvious disadvantages on the fire resistance of buildings.
Disclosure of Invention
Based on the technical background, the invention provides the composite fiber reinforced basic magnesium sulfate cement and the preparation method thereof for solving the problems, which have positive significance for developing and utilizing environment-friendly additives to improve the performance of the basic magnesium sulfate cement, and the provided cement material has higher mechanical strength, especially flexural strength.
The invention is realized by the following technical scheme:
a composite fiber reinforced basic magnesium sulfate cement comprises raw materials of active magnesium oxide, magnesium sulfate heptahydrate and a modifier; also comprises wood fiber and basalt fiber; the volume of the wood fiber is 0.1-50% of the total volume of the raw materials, the volume fraction is below 50% optimally, and the combustion performance grade of the material is reduced due to overhigh volume; the wood fiber can be made by crushing residual materials in wood processing; the adding volume of the basalt fiber is 0.1-5% of the total volume of the raw materials, the volume fraction is optimally below 5%, and the fluidity and uniformity of slurry are influenced by overhigh volume.
Further optionally, the volume of the wood fiber added is 10-35% of the total volume of the raw material, and more preferably 25-30%; the adding volume of the basalt fiber is 0.2-0.4% of the total volume of the raw materials.
Further optionally, the length of the basalt fibers is 1mm to 25mm, more preferably 6mm to 12mm.
Further optionally, the basalt fiber monofilament has a diameter of 6 to 50 μm and a density of 2.6g/cm 3 ~2.8g/cm 3 The breaking strength is more than or equal to 1200MPa, and the elastic modulus is more than or equal to 75GPa.
Further optionally, the wood fiber density is 2.5g/cm 3 ~7.0g/cm 3 The water content is 10-30%, and the fineness is 10-40 meshes.
More optionally, the molar ratio of the activated magnesium oxide to the magnesium sulfate heptahydrate is 5 to 10, more preferably 7; the addition amount of the modifier is 0.5-3.5% of the mass fraction of the active magnesium oxide.
Further optionally, the active magnesium oxide source includes light-burned magnesium oxide, and the mass percentage content of the active magnesium oxide in the light-burned magnesium oxide is 55% to 85%.
Further optionally, the modifier is used for inducing modification of a magnesium oxysulfate cement matrix to generate a whisker phase 5.1.7 phase (i.e., in basic magnesium sulfate cement, the main crystal phase is the 5.1.7 phase (the chemical formula of basic magnesium sulfate crystal is 5Mg (OH)) 2 ·MgSO 4 ·7H 2 O (5. 1. 7 phase)); preferably, the modifier is compounded by raw materials including citric acid, sulfate and phosphate.
In addition, other auxiliary materials, such as thickening agents, can be added into the raw materials for preparing the composite fiber reinforced basic magnesium sulfate cement. For the thickening agent, hydroxypropyl methylcellulose (HPMC) is added, wherein the mass fraction of the hydroxypropyl methylcellulose accounts for 0.1-1.5% of that of the MgO.
A preparation method of composite fiber reinforced basic magnesium sulfate cement is used for the composite fiber reinforced basic magnesium sulfate cement, and comprises the following steps:
s1: preparing a mixed solution containing magnesium oxide, magnesium sulfate heptahydrate, a modifier, basalt fibers, wood fibers and water; the magnesium oxide contains active magnesium oxide;
s2: curing the mixed solution;
s3: and after curing, carrying out thermal curing treatment, and finally carrying out natural curing to obtain a finished product.
In steps S2 and S3, the fresh mixed solution (pasty sample) may be poured into a mold, and after curing, the mold is removed, and then cured in an environment of a certain humidity and temperature; and then putting the mixture into an environment with certain humidity and temperature for thermal curing, and finally putting the mixture indoors for natural curing to obtain a finished product.
Further optionally, in step S1, the method includes the following steps:
s11: preparing a magnesium sulfate heptahydrate solution, and then adding a modifier or adding the modifier and a thickening agent for mixing to obtain a mixed solution;
s12: sequentially adding basalt fibers and magnesium oxide into the mixed solution in sequence; or simultaneously adding the uniformly mixed magnesium oxide and basalt fiber into the mixed solution;
s13: and continuously adding wood fiber to obtain a mixed solution.
Further optionally, in step S2, the curing process parameters are designed as: the curing humidity is 40-80%, and the temperature is 25-28 ℃; and/or in step S3: the heat curing humidity is more than 80 percent, and the temperature is 35-50 ℃.
More preferably, in step S3, the curing time does not exceed 48h; more preferably, the thermal curing time is more than 48 hours, and the natural curing time is not less than 7 days.
The invention has the following advantages and beneficial effects:
1. the invention has positive significance for developing and utilizing environment-friendly inclusions to further improve BMSC performance by doping wood fibers and basalt fibers as bio-based lightweight fillers and reinforcements on the basis of preparing the basic magnesium sulfate material with the main strength phase of 5.1.7.
2. After the basalt fiber and the wood fiber are doped, a magnesium cement matrix-wood fiber-basalt fiber system is formed in the material, so that a single fiber reinforcement is changed into a composite wood fiber-basalt fiber reinforcement, and the mechanical strength, particularly the breaking strength, of the composite material can be obviously improved. The prepared material has the compressive strength interval of 20-50 MPa, the flexural strength of 5-20 MPa and the tensile strength of 3-20 MPa.
3. The wood fiber has good interface bonding performance in BMSC, and a magnesium cement matrix-wood fiber-basalt fiber system (M-R-B system) is formed in the BMSC material when the wood fiber and the basalt fiber exist simultaneously, so that a single fiber reinforcement is changed into a composite WF-BF reinforcement. Through mechanical test analysis and microscopic observation, the composite reinforcement reduces the probability of interface slippage and interface debonding of BF, reduces BF stress concentration, enables the strength of the composite reinforcement to be obviously superior to that of a single reinforcement only using BF as an adulterant, enables the microscopic damage mechanism of BF to be more deterministic, and reduces the difficulty of improving the mechanical performance of the whole composite material by modifying BF.
4. The material prepared by the invention is a non-combustible material, and the grade of combustion performance can reach the A1 grade of the national standard GB 8624-2012 classification of combustion performance of building materials and products.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1 is a graph comparing the results of flexural strength tests on composite fiber reinforced basic magnesium sulfate cement with different basalt fiber-wood fiber ratios in the examples of the present invention.
FIG. 2 is an SEM image of the morphology of the main product of the composite fiber reinforced basic magnesium sulfate cement (proportioning number 1-10) in the embodiment of the invention
Figure 3 is a typical XRD crystal diffraction pattern of the matrix of BMSC in the composite fiber reinforced basic magnesium sulfate cement of the example of the present invention.
FIG. 4 is a typical distribution of basalt fibers and wood chips fibers in the composite fiber reinforced basic magnesium sulfate cement in the embodiment of the invention.
Fig. 5 is a typical bonding of a composite fiber reinforced basic magnesium sulfate cement to a substrate in an example of the invention.
FIG. 6 is a typical composite reinforcement microstructure (M-R-B system) in a composite fiber reinforced basic magnesium sulfate cement in an example of the invention.
Fig. 7 is a typical interfacial transition region between wood fiber and a matrix in a composite fiber reinforced basic magnesium sulfate cement according to an embodiment of the present application.
By "exemplary" it is meant that representative microscopic features are observed for the samples prepared in example 2, table 1, under the corresponding basalt fiber-wood fiber formulation.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that: it is not necessary to employ these specific details to practice the present invention. In other instances, well-known materials or methods have not been described in detail in order to avoid obscuring the present invention.
Throughout the specification, reference to "one embodiment," "an embodiment," "one example," or "an example" means: the particular features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment of the invention. Thus, the appearances of the phrase "one embodiment," "an embodiment," "one example" or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and/or sub-combination in one or more embodiments or examples. Further, those of ordinary skill in the art will appreciate that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Example 1
The embodiment provides a composite fiber reinforced basic magnesium sulfate cement which is prepared from light-burned magnesium oxide, magnesium sulfate heptahydrate, a composite modifier, hydroxypropyl methyl cellulose, wood fibers and basalt fibers.
The weight percentage content of the active magnesium oxide in the light-burned magnesium oxide is 55-85%.
The molar ratio of activated magnesium oxide, magnesium sulfate heptahydrate and water is 7.
The addition amount of the composite modifier is 0.5 to 3.5 percent of the mass fraction of the active magnesium oxide; the composite modifier is compounded by citric acid, sulfate and phosphate.
The mixing amount of the hydroxypropyl methyl cellulose is 0.1 to 1.5 percent of the mass fraction of the active magnesium oxide.
The volume of the added wood fiber is 0.1-50% of the total volume of the raw material, and more preferably, the volume of the added wood fiber is 10-35% of the total volume of the raw material. The density of the wood fiber is 2.5g/cm 3 ~7.0g/cm 3 The water content is 10-30%, and the fineness is 10-40 meshes.
The adding volume of the basalt fiber is 0.1-5% of the total volume of the raw materials; more preferably, the adding volume of the basalt fiber is 0.2-0.4% of the total volume of the raw materials. The length of the basalt fiber is 1mm to 25mm, the monofilament diameter of the basalt fiber is 6 mu m to 50 mu m, and the density is 2.6g/cm 3 ~2.8g/cm 3 The breaking strength is more than or equal to 1200MPa, and the elastic modulus is more than or equal to 75GPa.
Example 2
The embodiment provides a preparation method of composite fiber reinforced basic magnesium sulfate cement, which comprises the following steps:
1. experiment raw materials:
light-burned magnesium oxide MgO: the dosage is 200kg/m 3 (ii) a Wherein the mass fraction of the active MgO (alpha-MgO) is 60 percent.
Magnesium sulfate heptahydrate (MgSO) 4 ·7H 2 O): the dosage is 266kg/m 3 To analyze pure chemicals.
Hydroxypropylmethylcellulose (HPMC): the dosage is 1kg/m 3 Adhesive of materialsThe degree is more than or equal to 200,000.
Composite modifier: the dosage is 2.6kg/m 3 (ii) a The main components are citric acid, sulfate and phosphate, and the mass ratio is 2.
Wood fiber: see table 1 for amounts. The density of the wood fiber is 3.5g/cm 3 The water content is 17 percent, and the fineness is 15 meshes to 30 meshes. .
Basalt fiber: see table 1 for amounts. The lengths of the basalt fibers are shown in Table 1, and the monofilament diameter of the basalt fibers is 17 μm, and the density is 2.66g/cm 3 The breaking strength is 1200MPa, and the elastic modulus is 75GPa.
TABLE 1 basalt fiber-wood fiber formulation table
Figure BDA0003749044150000051
Figure BDA0003749044150000061
2. Preparation procedure
S1: mgSO (MgSO) will 4 ·7H 2 Preparing uniform solution from O and water according to the proportion, adding the compound modifier and the hydroxypropyl methyl cellulose, and uniformly stirring to obtain mixed solution I;
s2: adding basalt fibers into the mixed solution I and uniformly stirring; adding MgO powder, and continuously stirring uniformly, specifically, stirring at a low speed of 60r/min for 2min by using a planetary stirrer, and then stirring at a medium speed of 200r/min for 2min to obtain a mixed solution II;
s3: adding wood fiber into the mixed solution II, and stirring and mixing until a uniform fresh mixture (paste) is obtained;
s4: pouring the fresh mixture sample obtained in the step S3 into a mold, demolding after curing for about 24 hours, and then curing for 25 hours in an environment with the humidity of 40-80% and the temperature of 25-28 ℃;
s5: after curing, placing the mixture into an environment with the humidity of 80% and the temperature of 35-50 ℃ for thermal curing for 50 hours; finally, placing the mixture in a room for natural maintenance for 28 days to obtain a finished product.
Example 3
Evaluation of composite fiber reinforced basic magnesium sulfate Cement prepared in example 2
1. Density contrast test
As shown in table 1 of example 2, the results of the density test of the composite fiber reinforced basic magnesium sulfate cement with different basalt fiber-wood fiber ratios are compared, and it can be seen from the table that:
the BMSC density is obviously reduced by adding WF and BF at the same time, and the BMSC density is not greatly influenced by only adding BF. For samples not incorporating WF, the density ranged from 1441.0kg/m 3 To 1499.1kg/m 3 In the meantime. For samples incorporating WF, the density range was smaller, with a density range of 1274.7kg/m 3 To 1391.9kg/m 3 In the meantime.
2. And (3) compressive strength comparison test:
as shown in table 1 of example 2, the results of the compressive strength test of the composite fiber reinforced basic magnesium sulfate cement with different basalt fiber-wood fiber ratios are compared, and it can be seen from the table that:
for the sample doped with WF, the volume fraction of BF and the fiber length have little influence, the compressive strength range distribution is 34.5-36.2 MPa, and the change is small. For samples without added WF, the compressive strength is generally lower than for samples with added WF, ranging from 31.8 to 39.0 MPa.
3. And (3) flexural strength comparison test:
as shown in table 1 of example 2, the results of the flexural strength test of the composite fiber reinforced basic magnesium sulfate cement with different basalt fiber-wood fiber ratios are shown in the comparative graph, and it can be seen from the graph that:
the samples with WF incorporation and without WF incorporation exhibited diametrically opposite characteristics with respect to flexural strength, and the flexural strength of BMSC samples with both WF and BF was significantly better than that of the samples with BF alone. In the samples doped with WF, the flexural strength was enhanced with the increase of BF volume fraction, and the flexural strength of the samples with 0.2% BF volume fraction was improved by about 90% compared with that of the samples not doped with BF, as shown in FIG. 1 (a), while the level of flexural strength of the samples doped with different BF lengths was not changed much with the same BF volume fraction, and the flexural strength of the samples doped with BF length of 6mm was improved by 80% or more compared with that of the samples not doped with BF, as shown in FIG. 1 (b).
Such properties again illustrate the complex strengthening mechanism of WF in combination with BF in BMSC materials.
4. Fracture morphology contrast test:
as shown in FIG. 2, SEM images of the characteristic hydration products of all sample numbers (1-10) in the basalt fiber-wood fiber formulation chart of example 2 are shown. FIG. two illustrates that a large number of needle-like crystal structures were observed in the samples of all sample numbers in example 2, the crystal structures of the cylinders were intertwined, and covering with floc products was also observed on the surface; the needle-like crystal region was enlarged to find that the crystal was not a single cylinder but a prism having a regular cross section. Compared with the related literature, the morphological characteristics of the crystal structure are consistent with the characteristics of the 5.1.7 phase of the product.
As shown in fig. 3, the XRD spectrum of the matrix in the typical composite fiber reinforced basic magnesium sulfate cement of example 2 is shown. FIG. 3 illustrates the main phases in the BMSC matrix in example 2, the main products in the 28-day-old BMSC matrix are phases 5.1.7, mgO, mg (OH) 2 And MgCO 3 The hydration product did not form crystals such as the 3.1.8 phase, indicating that the primary strength phase of the basic magnesium sulphate material prepared in example 2 was the 5.1.7 phase.
FIG. 4 illustrates the distribution of BF in BMSC matrix, which illustrates that the effect of the previous dispersion pretreatment is ideal, and the phenomenon that WF and BF are interlaced together in the mixing process, thereby causing uneven distribution, does not occur.
BF as an inorganic fiber with good corrosion resistance has good bonding performance in BMSC materials, as shown in figure 5, the connection between BF and a substrate is tight, large defects are not found, and obvious chemical damage of BF is not found on the surface; and simultaneously, hydration products are generated on the surface of the fiber reinforcement, so that the bonding capability of the fiber reinforcement and the matrix can be further enhanced to form a strong bonding interface, and the interface can effectively transfer stress. This phenomenon indicates that there is some mechanism for the combination of WF and BF, which limits the form of BF failure, and this is beneficial to the positive significance of controlling the overall mechanical properties of BF-BMSC components, such as plates, by adjusting the mechanical properties of BF.
Thus, SEM test of 1,000x on microstructure areas where both WF and BF were present, revealed that the substrate, WF and BF were very tightly bound together, as shown in FIG. 6, that the three formed a stable structural system, and that both WF and BF were found to be coated with very many products, such as Mg (OH) 2 And 5.1.7 phase crystals, are more tightly connected with the matrix, so that the whole stress can be better transmitted. The addition of WF causes a fiber crosslinking effect to be formed between the matrix and BF, which is similar to that in a thermoplastic composite material, and a tight connection of a magnesium cement matrix-wood fiber-basalt fiber system (M-R-B system) is formed; the single fiber reinforcement is changed into the composite WF-BF reinforcement, the probability of interface slippage and interface debonding of BF is reduced, the BF stress concentration phenomenon is reduced, and the strength of the reinforcement is enhanced. After the performance of the reinforcement is improved, the ratio of the interfacial force to the strength of the reinforcement is reduced, the probability of failure from the interface is increased under the action of load, additional energy is consumed for generating an interface crack, the total fracture energy is increased, and the mechanical performance of the composite material is improved. The presence of WF improves the brittle fracture characteristics of BF itself in the matrix, and this can also effectively explain the phenomenon that the fracture resistance is greatly improved after WF is doped in the fiber magnesium cement.
The bonding performance of WF itself to the substrate is also very excellent, as shown in FIG. 7, no obvious interfacial transition region is observed between WF and the substrate in the observation range of 5,000x, and the WF and the substrate are compact and have no obvious pores. When the size is enlarged to about 30,000x, an obvious Interface Transition Zone (ITZ) can be found, and the interface transition zone is good, which indicates that the BMSC and the plant material have good mixing compatibility.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only examples of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (11)

1. The composite fiber reinforced basic magnesium sulfate cement is characterized by also comprising wood fibers and basalt fibers, wherein the raw materials comprise active magnesium oxide, magnesium sulfate heptahydrate and a modifier;
the adding volume of the wood fiber is 0.1-50% of the total volume of the raw materials, and the adding volume of the basalt fiber is 0.1-5% of the total volume of the raw materials.
2. The composite fiber reinforced basic magnesium sulfate cement as claimed in claim 1, wherein the addition volume of the wood fiber is 10-35% of the total volume of the raw materials, and the addition volume of the basalt fiber is 0.2-0.4% of the total volume of the raw materials.
3. The composite fiber reinforced basic magnesium sulfate cement as claimed in claim 1, wherein the length of the basalt fiber is 1mm to 25mm.
4. The composite fiber reinforced basic magnesium sulfate cement as claimed in claim 1, wherein the basalt fiber monofilament has a diameter of 6 to 50 μm and a density of 2.6g/cm 3 ~2.8g/cm 3 The breaking strength is more than or equal to 1200MPa, and the elastic modulus is more than or equal to 75GPa.
5. The composite fiber reinforced basic magnesium sulfate cement of claim 1, wherein the wood fiber density is 2.5g/cm 3 ~7.0g/cm 3 The water content is 10-30%, and the fineness is 10-40 meshes.
6. The composite fiber reinforced basic magnesium sulfate cement as claimed in any one of claims 1 to 5, wherein the molar ratio of the activated magnesium oxide to the magnesium sulfate heptahydrate is 5 to 10; the addition amount of the modifier is 0.5-3.5% of the mass fraction of the active magnesium oxide.
7. The composite fiber reinforced basic magnesium sulfate cement as claimed in claim 6, wherein the active magnesium oxide source comprises lightly calcined magnesium oxide, and the mass percentage of the active magnesium oxide in the lightly calcined magnesium oxide is 55-85%.
8. The basic magnesium sulfate cement as claimed in claim 6, wherein the modifier is used to induce modification of the magnesium oxysulfate cement matrix to produce whisker phase 5.1.7; preferably, the modifier is compounded by raw materials including citric acid, sulfate and phosphate.
9. A method of producing a composite fibre reinforced basic magnesium sulphate cement as claimed in any one of claims 1 to 8, comprising the steps of:
s1: preparing a mixed solution containing magnesium oxide, magnesium sulfate heptahydrate, a modifier, basalt fibers, wood fibers and water; the magnesium oxide contains active magnesium oxide;
s2: curing the mixed solution;
s3: and after curing, carrying out thermal curing treatment, and finally carrying out natural curing to obtain a finished product.
10. The method for preparing the composite fiber reinforced basic magnesium sulfate cement as claimed in claim 9, wherein the step S1 comprises the following steps:
s11: preparing a magnesium sulfate heptahydrate solution, and then adding a modifier or adding the modifier and a thickening agent for mixing to obtain a mixed solution;
s12: sequentially adding basalt fibers and magnesium oxide into the mixed solution in sequence; or simultaneously adding the uniformly mixed magnesium oxide and basalt fiber into the mixed solution;
s13: and continuously adding wood fiber to obtain a mixed solution.
11. The method for preparing the composite fiber reinforced basic magnesium sulfate cement as claimed in claim 9,
in step S2, the curing process parameters are designed as follows: the curing humidity is 40-80%, and the temperature is 25-28 ℃;
and/or in step S3: the heat curing humidity is more than 80 percent, and the temperature is 35-50 ℃.
CN202210832743.XA 2022-07-15 2022-07-15 Composite fiber reinforced basic magnesium sulfate cement and preparation method thereof Pending CN115196940A (en)

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CN109704604A (en) * 2019-02-25 2019-05-03 北京科技大学 A kind of modified magnesium oxysulfide concrete and preparation method thereof
CN110746174A (en) * 2019-11-14 2020-02-04 福建省德锐新材有限公司 A-grade fireproof mineral board and preparation method thereof
CN111635211A (en) * 2020-05-29 2020-09-08 安徽埃科博秸秆科技有限公司 Plant fiber cement board and preparation method thereof
US20210292236A1 (en) * 2020-03-19 2021-09-23 Jiangsu Langyue New Materials Technology Co., Ltd. Reinforced and toughened mgo substrate, preparation method thereof and composite board having the substrate
CN113860844A (en) * 2021-09-13 2021-12-31 安徽省建筑科学研究设计院 Solid waste regenerated magnesium oxysulfate composite material and preparation method thereof

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CN110746174A (en) * 2019-11-14 2020-02-04 福建省德锐新材有限公司 A-grade fireproof mineral board and preparation method thereof
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