CN109111149B - Fiber shrinkage-reducing anti-cracking agent and preparation method thereof - Google Patents
Fiber shrinkage-reducing anti-cracking agent and preparation method thereof Download PDFInfo
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- CN109111149B CN109111149B CN201811214144.1A CN201811214144A CN109111149B CN 109111149 B CN109111149 B CN 109111149B CN 201811214144 A CN201811214144 A CN 201811214144A CN 109111149 B CN109111149 B CN 109111149B
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/0028—Aspects relating to the mixing step of the mortar preparation
- C04B40/0039—Premixtures of ingredients
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/60—Agents for protection against chemical, physical or biological attack
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Abstract
The invention discloses a fiber shrinkage reducing and crack resisting agent and a preparation method thereof, wherein the fiber shrinkage reducing and crack resisting agent comprises the following components in percentage by mass: 1 to 2.5 percent of microporous fiber, 0.5 to 1 percent of shrinkage reducing component, 30 to 45 percent of alum stone powder, 20 to 30 percent of coal gangue powder and 30 to 40 percent of gypsum; the shrinkage reducing component is formed by mixing a methyl vinyl ether-maleic anhydride copolymer and polyether polyol according to the mass ratio of 1: 1.5-2.5; the surface of the microporous fiber is provided with a plurality of micropores, and the spray drying method is used for absorbing the shrinkage reducing component in the micropores. The invention uses three anti-crack materials in a compounding way, and improves the anti-crack capability of the concrete structure in a combined way: the shrinkage reducing component is adsorbed on the microporous fiber and plays a role in slowly releasing and reducing shrinkage when the concrete is hydrated; the combination of the microporous fiber and the set cement is tighter, and the early tensile strength of the concrete is increased; the coal gangue powder, the alum stone powder and the gypsum generate expansion products to compensate the concrete shrinkage.
Description
Technical Field
The invention relates to the field of anti-cracking additives for concrete structures, and particularly provides a fiber shrinkage-reducing anti-cracking agent and a preparation method thereof.
Background
With the increasing number of construction projects, the problem of concrete shrinkage cracking is increasingly prominent, and the durability, the bearing capacity and the waterproof performance of concrete are seriously influenced. The concrete structure has three main causes of generating cracks: firstly, the cracks are caused by external loads and are most common, and mainly have the problems of unreasonable structural design, insufficient safety coefficient, no consideration of construction possibility, insufficient structural rigidity and the like; secondly, the crack is caused by the secondary stress of the structure, and the crack is caused by the secondary stress at certain parts because the actual working state of the concrete structure is in or out of the conventional calculation or the crack is not considered comprehensively; and the deformation stress is caused, mainly structural deformation caused by factors such as temperature, shrinkage, steel bar corrosion, uneven settlement and the like, when the deformation is restrained, stress is generated, and when the stress exceeds the tensile strength of the concrete, cracks are generated.
In order to avoid concrete cracking, the prior art mainly adopts methods of optimizing the mix proportion design of concrete, increasing the reinforcement ratio, reducing the hydration heat of concrete, adding fibers and expanding agents and the like. At present, most projects apply expanding agents or fibers to improve the compactness of concrete, play a role in compensating shrinkage and prevent the cracking of the concrete.
Engineering fibers are widely favored as reinforcing materials for concrete structures. The addition of a certain amount of fibers in the concrete can effectively limit the occurrence and the development of primary cracks formed by the concrete in early stages (plastic stage and hardening stage) due to segregation, bleeding, chemical shrinkage and other factors, and reduce the number and the size of the primary cracks. The fiber reinforced concrete can effectively improve the impact resistance, bending resistance and crack resistance of the cement concrete. Compared with the traditional steel wire mesh reinforced material, the material has the advantages of light weight, chemical corrosion resistance, and convenient and safe use. However, the traditional engineering fiber has the defects of poor dispersibility, poor adhesion with a matrix and the like, and the application is limited.
The hollow or porous fiber is processed into a hollow or porous shape, so that the contact area with the cement paste can be increased to improve the bonding strength and the crack resistance, but the problem of agglomeration among the fibers cannot be avoided all the time, so that the fibers cannot be uniformly dispersed in the concrete or mortar material, and the crack resistance is greatly reduced. The effect of improving the local tensile strength of the concrete through the fiber alone on the whole crack resistance is limited, and cracks generated by external environmental effects such as temperature shrinkage, drying shrinkage and loading cannot be effectively resisted. The anti-cracking admixture which comprises anti-cracking fibers and shrinkage reducing components and is used in a composite mode exists in the market, the inherent defects of the fibers in a cement-based system cannot be overcome only by simply mixing two anti-cracking materials together, and the two anti-cracking materials cannot form a synergistic anti-cracking effect, so that the anti-cracking effect is limited.
Chinese patent CN106927713A is an anti-crack and anti-seepage additive for marine concrete, which is composed of the following substances by weight percentage: 3 to 6 percent of shrinkage reducing agent, 1 to 3 percent of tackifying and water retaining agent, 5 to 8 percent of anti-cracking substance, 30 to 60 percent of expanding agent, 1 to 2 percent of complexing agent, 5 to 8 percent of water reducing agent, 0.01 to 1 percent of retarder, 0.01 to 0.02 percent of defoaming agent and the balance of fine filler; the anti-cracking substance is prepared from basalt fibers, aromatic polyamide fibers and basic magnesium sulfate whiskers according to the weight ratio of 5-8: 2-3: 1. The invention can make the marine concrete more compact, reduce the generation of concrete gaps and cracks, strengthen the anti-cracking and anti-seepage performance of the marine concrete, effectively utilize industrial waste residues, and is beneficial to saving resources and protecting the environment. The patent uses the combined action of an anti-cracking substance, an expanding agent and a shrinkage reducing agent to resist cracking, but the fiber has the defects of poor dispersibility, poor adhesion with a matrix and the like, so that the stability of the anti-cracking effect is poor, and the fiber is directly mixed with raw materials such as the shrinkage reducing agent and the like, so that the anti-cracking effect is not limited due to the fact that the fiber does not have a synergistic anti-cracking effect.
Chinese patent CN200610005255.2 discloses an application of hollow porous fiber in rigid self-waterproof concrete, the hollow porous fiber is polypropylene reinforced fiber, the cross section of the fiber has a hollow structure with 3-9 holes, the hollowness is more than 20%, the void ratio of the fiber is more than 98%, the diameter of the fiber is 20-50 μm, and the strength of the fiber is 20-50 μm>500N/mm2Modulus of elasticity>3500N/mm2An elongation of 15-30%, a length of 6-25 mm, a fiber number of 76-200 million/kg, and a density>0.70g/cm3. Compared with the existing polypropylene fiber, the hollow fiber in the patent has lower density, and cannot increase the dead weight of a concrete structure; the concrete product has the advantages of improving the tensile strength and toughness of the concrete product, improving the durability such as impact resistance, impermeability and frost resistance of the concrete product, further improving the waterproof capability of the structural rigidity self-waterproof concrete, reducing the occurrence of diseases such as steel bar corrosion and leakage of an internal structure caused by cracks, and greatly prolonging the service life and the maintenance period of the structure. However, because the fibers are easy to agglomerate, the fibers cannot be uniformly dispersed in the concrete or mortar material, the anti-cracking effect is greatly reduced, and the stability is poor.
Disclosure of Invention
Aiming at the defects of the technology, the invention aims to provide a fiber shrinkage-reducing anti-cracking agent which is compounded by using a plurality of anti-cracking materials, has the synergy and can greatly improve the anti-cracking capability of a concrete structure.
The fiber shrinkage-reducing crack-resistant agent comprises the following components in percentage by mass: 1 to 2.5 percent of microporous fiber, 0.5 to 1 percent of shrinkage reducing component, 30 to 45 percent of alum stone powder, 20 to 30 percent of coal gangue powder and 30 to 40 percent of gypsum; the surface of the microporous fiber is provided with a plurality of micropores; the shrinkage reducing component is formed by mixing methyl vinyl ether-maleic anhydride copolymer and polyether polyol according to the mass ratio of 1: 1.5-2.5, and is adsorbed in micropores on the surface of the microporous fiber by using a spray drying method.
The invention adopts the microporous fiber absorbed with the shrinkage reducing component, wherein the shrinkage reducing component is dissolved in a small amount in the stirring process of concrete or mortar, a layer of hydrophilic film is formed on the surface of the porous fiber, the dispersibility of the fiber in the concrete or mortar is improved, the alkalinity of the solution is gradually enhanced along with the hydration reaction, the shrinkage reducing component is completely dissolved and dispersed in the cement paste, the brittleness of hardened cement stone is improved, and the surface tension of the pore solution is reduced, so that the effect of slowly releasing, reducing and cracking is achieved; the combination of the microporous fiber and the set cement is tighter, and the early tensile strength of the concrete is increased; the coal gangue powder, the alum stone powder and the gypsum generate expansion products to compensate the concrete shrinkage; the cooperation of multiple anti-cracking components greatly improves the anti-cracking effect of the concrete.
Preferably, the microporous fiber is one or more of the following fibers: polypropylene fibers, polyvinyl alcohol fibers, polyester fibers, polyamide fibers, basalt fibers.
Further preferably, the diameter of the microporous fiber is 60-80 μm, the diameter of the solid body part of the middle fiber is 40-60 μm, the thickness of the microporous part of the outer layer is 20 μm, the micropores are cylindrical, the axes of the micropores are perpendicular to the axes of the fiber, the pore diameter is 15-20 μm, the number of the micropores contained in each 1mm length of the fiber is 100-240, and the micropores are not communicated with each other.
Preferably, Al of the alunite powder2O3The content is 30-40%, and the specific surface area is 200-400 m2And/kg, the residue on a 1.18mm sieve is 0-0.5%.
Preferably, the coal gangue powder is formed by grinding spontaneous combustion coal gangue powder, and the specific surface area is 400-600 m2The activity index of the material is 50 to 80 percent in 28 days.
Preferably, the gypsum is one or more of desulfurized gypsum, dihydrate gypsum and anhydrite.
Further preferably, the gypsum has a purity of 75-98%, and SO3The content is 50% -55%, and the specific surface area is 300-500 m2/kg。
The invention also provides a preparation method of the fiber shrinkage-reducing anti-cracking agent, which comprises the following steps:
(1) weighing the components according to a set proportion, firstly adding the microporous fibers into a dry material bin of a spray dryer, turning on an air heater to heat air to 120-160 ℃, turning on an air blower, uniformly feeding the microporous fibers in the dry material bin into a spray drying chamber through hot air of a hot air distributor, and dispersing and spirally rotating the microporous fibers by airflow; mixing the methyl vinyl ether-maleic anhydride copolymer with polyether polyol according to the mass ratio of 1: 1.5-2.5 to obtain a shrinkage reducing component, and uniformly stirring the shrinkage reducing component and a 50% ethanol solution according to the mass ratio of 1:5 to prepare a liquid material; pouring the liquid material into a constant-temperature feeding tank, heating and keeping the temperature of the liquid material at 60-90 ℃, opening a liquid material conveying pipe, conveying the liquid material to a two-fluid atomization nozzle at the top of a spray drying chamber, and atomizing the shrinkage reducing component into particles with the diameter of 10-15 mu m; the rotating hot air flow fully mixes the microporous fiber and the liquid material prepared by the shrinkage reducing component, the micropores distributed on the surface layer of the fiber fully adsorb atomized particles, the high-temperature air volatilizes the water and the ethanol in the liquid material, and the fiber becomes a carrier of the shrinkage reducing component; mixing and drying for 10min, opening a discharge port of a drying chamber, and separating the microporous fibers adsorbed with the shrinkage reducing components by a cyclone separator;
(2) and putting the microporous fiber adsorbed with the shrinkage reducing components, coal gangue powder, alum stone powder and gypsum into a dry powder mixer, and mixing for 15min to obtain a finished product of the fiber shrinkage reducing anti-cracking agent.
The invention uses a spray dryer to atomize the shrinkage reducing component into particles smaller than the pore diameter of the surface layer of the microporous fiber, so that the microporous fiber becomes a carrier of the shrinkage reducing component and fully absorbs the shrinkage reducing component; after the microporous fibers fully dispersed in the drying chamber adsorb the shrinkage reducing components on the surfaces, the electrostatic action on the original fiber surfaces disappears, and the microporous fibers are not easy to wind and agglomerate in the production and use processes. The fiber shrinkage reducing and anti-cracking agent is applied to concrete, shrinkage reducing components are gradually released along with the increase of the alkalinity of a solution in the hydration process of the concrete, the shrinkage pressure caused by the water loss of capillary pores when the concrete is hardened is reduced, the fiber shrinkage reducing and anti-cracking agent plays respective roles in different periods and mechanisms of the concrete shrinkage by using three shrinkage reducing and anti-cracking materials, and the comprehensive anti-cracking effect of the whole process of the concrete is achieved: the organic shrinkage reducing component reduces the surface tension of the concrete pore solution and reduces plastic shrinkage and chemical shrinkage; the combination of the microporous fiber and the set cement is tighter, and the early tensile strength of the concrete is increased; the coal gangue powder, the alum stone powder and the gypsum generate expansion products to compensate the concrete shrinkage.
Detailed Description
The fiber shrinkage-reducing and crack-resisting agent provided by the embodiment of the invention comprises the following components in percentage by mass: 1 to 2.5 percent of microporous fiber, 0.5 to 1 percent of shrinkage reducing component, 30 to 45 percent of alum stone powder, 20 to 30 percent of coal gangue powder and 30 to 40 percent of gypsum; the surface of the microporous fiber is provided with a plurality of micropores; the shrinkage reducing component is formed by mixing a methyl vinyl ether-maleic anhydride copolymer and polyether polyol according to the mass ratio of 1: 1.5-2.5, and the shrinkage reducing component is adsorbed in micropores on the surface of the microporous fiber by using a spray drying method.
The technical solutions of the present invention are described in detail and fully below with reference to the following embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention. Equivalent changes or substitutions of method, process route, function and the like by those skilled in the art according to the following embodiments are within the scope of the present invention.
Example 1
The fiber shrinkage-reducing crack-resistant agent of the embodiment is weighed according to the following mixture ratio in percentage by mass:
2.5 percent of microporous fiber is polypropylene fiber. The diameter of the micropore fiber is 60 mu m, the diameter of the solid body part of the middle fiber is 40 mu m, the thickness of the micropore part of the outer layer is 20 mu m, the micropore is cylindrical, the axis of the micropore is vertical to the axis of the fiber, the aperture is 15 mu m, each 1mm length of the fiber contains 120 micropores, and the micropores are not communicated with each other;
the shrinkage reducing component is 0.8 percent and is formed by mixing methyl vinyl ether-maleic anhydride copolymer and polyether polyol according to the mass ratio of 1: 1.5;
45% of alunite powder and Al of alunite powder2O3The content is 30 percent, and the specific surface area is 400m2Per kg, the residue on a 1.18mm sieve is 0 percent;
20 percent of coal gangue powder is formed by grinding spontaneous combustion coal gangue, and the specific surface area is 600m2Activity index 80% in 28 days per kg.
31.7 percent of gypsum is desulfurized gypsum. The purity of the gypsum is 98%, SO3The content is 55 percent, and the specific surface area is 500m2/kg。
The preparation method comprises the following steps: (1) weighing the components according to a set ratio, adding the microporous fibers into a dry material bin of a spray dryer, turning on an air heater to heat the air to 120 ℃, turning on an air blower, uniformly feeding the microporous fibers in the dry material bin into a spray drying chamber through hot air of a hot air distributor, and dispersing and spirally rotating the microporous fibers by air flow; mixing a methyl vinyl ether-maleic anhydride copolymer and polyether polyol according to a mass ratio of 1:1.5 to obtain a shrinkage reducing component, adding the shrinkage reducing component and the polyether polyol into a 50% ethanol solution which is 5 times of the mass of the shrinkage reducing component, uniformly stirring to prepare a liquid material, pouring the liquid material into a constant-temperature feeding tank, heating, keeping the temperature of the liquid material at 90 ℃, opening a liquid material conveying pipe, conveying the liquid material to a two-fluid atomization nozzle at the top of a spray drying chamber, and atomizing the shrinkage reducing component into particles with the diameter of 10 mu m; the rotating hot air flow fully mixes the microporous fiber and the solution prepared by the shrinkage reducing component, the micropores distributed on the surface layer of the fiber fully adsorb atomized particles, the high-temperature air volatilizes the water and the ethanol in the solution, and the fiber becomes a carrier of the shrinkage reducing component; after mixing and drying for 20min, opening a discharge port of the drying chamber, and separating the microporous fibers adsorbed with the shrinkage reducing components by a cyclone separator. (2) And putting the microporous fiber adsorbed with the shrinkage reducing components, coal gangue powder, alum stone powder and gypsum into a dry powder mixer, and mixing for 15min to obtain a finished product of the fiber shrinkage reducing anti-cracking agent.
Example 2
The fiber shrinkage-reducing crack-resistant agent of the embodiment is weighed according to the following mixture ratio in percentage by mass:
1.5 percent of microporous fiber is polyester fiber. The diameter of the micropore fiber is 50 microns, the diameter of the solid body part of the middle fiber is 30 microns, the thickness of the micropore part of the outer layer is 20 microns, the micropore is cylindrical, the axis of the micropore is vertical to the axis of the fiber, the aperture is 18 microns, the number of micropores contained in each 1mm length fiber is 180, and the micropores are not communicated with each other;
the shrinkage reducing component is 1 percent and is formed by mixing methyl vinyl ether-maleic anhydride copolymer and polyether polyol according to the mass ratio of 1: 2;
35% of alunite powder and Al of alunite powder2O3The content is 35 percent, and the specific surface area is 300m2Per kg, the residue on a 1.18mm sieve is 0-0.2%;
25 percent of coal gangue powder is formed by grinding spontaneous combustion coal gangue, and the specific surface area is 500m2Activity index 65% in 28 days per kg.
37.5 percent of gypsum is dihydrate gypsum. The purity of the gypsum is 80%, SO3The content is 52 percent, and the specific surface area is 400m2/kg。
After the above materials were weighed, the preparation method was the same as that of example 1 except that the temperature of the heated air was changed to 140 ℃, the temperature of the liquid material was changed to 80 ℃, the particle size of the atomized particles of the shrinkage component was reduced to 12 μm, and the mixing and drying time was 15min, and other steps and processes were the same as those of example 1.
Example 3
The fiber shrinkage-reducing crack-resistant agent of the embodiment is weighed according to the following mixture ratio in percentage by mass:
1% of microporous fiber is polyester fiber. The diameter of the micropore fiber is 80 microns, the diameter of the solid body part of the middle fiber is 60 microns, the thickness of the micropore part of the outer layer is 20 microns, the micropore is cylindrical, the axis of the micropore is vertical to the axis of the fiber, the aperture is 20 microns, the number of the micropores contained in each 1mm length fiber is 200, and the micropores are not communicated with each other;
the shrinkage reducing component is 1 percent and is formed by mixing methyl vinyl ether-maleic anhydride copolymer and polyether polyol according to the mass ratio of 1: 1.5-2.5;
30% of alunite powder and Al of alunite powder2O3The content is 40 percent, and the specific surface area is 200m2Per kg, the residue on a 1.18mm sieve is 0.5 percent;
28 percent of coal gangue powder is formed by grinding spontaneous combustion coal gangue, and the specific surface area is 400m2Activity index 50% in 28 days per kg.
40% of gypsum is natural anhydrite. The purity of the gypsum is 75%, SO3The content is 55 percent, and the specific surface area is 300m2/kg。
After the above materials were weighed, the preparation method was the same as that of example 1 except that the temperature of the heated air was changed to 160 ℃, the temperature of the liquid material was changed to 60 ℃, the particle size of the atomized particles of the shrinkage component was reduced to 15 μm, and the mixing and drying time was 10 min.
Example 4
Compared with the embodiment 1, the diameter of the microporous fiber of the embodiment is 60 μm, the diameter of the solid body part of the middle fiber is 50 μm, the thickness of the microporous part of the outer layer is 10 μm, the micropores are cylindrical, the axes of the micropores are vertical to the axes of the fiber, the pore diameter is 5 μm, the number of the micropores contained in the fiber with the length of 1mm is 70, the micropores are not communicated with each other, and the rest is the same as the embodiment 1.
Example 5
In comparison with example 1, Al in the alunite powder of this example2O3The content is 20 percent, and the specific surface area is 200m2Per kg, 0% screen residue on a 1.18mm sieve, the same as in example 1.
Example 6
Compared with the embodiment 1, the coal gangue powder of the embodiment is formed by grinding the spontaneous combustion coal gangue powder, and the specific surface area is 300m2Perkg, 28 day activity index 50%, otherwise the same as in example 1.
Example 7
In comparison with example 1, dihydrate gypsum was used as the gypsum in this example, and the purity of gypsum was 62%, SO3The content is 48 percent, and the specific surface area is 200m2Kg, other examples1 are identical.
Comparative example 1
In comparison with example 1, the shrinkage reducing component of this comparative example does not contain a methyl vinyl ether-maleic anhydride copolymer, and only a polyether polyol is used, the other being the same as in example 1.
Comparative example 2
Compared with the embodiment 1, the shrinkage reducing component of the comparative example is formed by mixing the methyl vinyl ether-maleic anhydride copolymer and the polyether polyol according to the mass ratio of 1:1, and the rest is the same as the embodiment 1.
Comparative example 3
In comparison with example 1, this comparative example uses a common polypropylene fiber having a fiber diameter of 60 μm without a microporous layer, and is otherwise the same as example 1.
Comparative example 4
Compared with example 1, the comparative example comprises the following components in percentage by mass: 5% of microporous fiber, 0.5% of shrinkage reducing component, 45% of alunite powder, 29.5% of coal gangue powder and 29.5% of gypsum; the rest is the same as in example 1.
Comparative example 5
The shrinkage reducing agent of this comparative example was glycerol, which was used as the shrinkage reducing agent of example 1, and the other examples were the same as example 1.
Comparative example 6
Compared with the example 1, the anti-cracking agent of the comparative example has the same components as the example 1, and the preparation method comprises the following steps: directly putting the shrinkage reducing component, the microporous fiber, the coal gangue powder, the alum stone powder and the gypsum into a dry powder mixer, and mixing for 15min to obtain a finished product of the fiber shrinkage reducing anti-cracking agent.
The crack resistance agents prepared in the above examples and comparative examples were incorporated into concrete and tested for workability, mechanical properties, and crack resistance. Slump is carried out according to GB/T50080-2016 Standard for Performance test methods of common concrete mixtures; the compression strength and the flexural strength of the concrete are according to GB/T50081-2002 Standard of mechanical property test methods of common concrete, and the size of a test piece is the standard size specified in the standard; the early crack resistance performance test is carried out according to appendix A in T/CECS 10001-2017 crack-resistant and impervious composite material used in concrete. The blank group is not added with an anti-cracking agent as a control group, the anti-cracking agent addition amount of the examples and the comparative examples accounts for 10% of the total mass of the cementing material, the fly ash is replaced by equal mass, and the types and the proportions of the raw materials used in the performance comparison test are shown in table 1.
TABLE 1 concrete ratio (unit Kg/m) of crack resistance agent3)
The test results of the tested concrete of the anti-cracking agent are shown in table 2, and the test results in table 2 show that, compared with the blank group, when the fiber shrinkage reducing and anti-cracking agent provided by the embodiment of the invention is applied to the concrete, no adverse effect is caused on the slump, the compressive strength is kept consistent, and the early and middle flexural strengths are increased; the average cracking area of each crack and the number of cracking cracks in unit area are obviously reduced, the crack reduction coefficient is more than 100 percent, and the crack resistance effect is obvious. Because the spray drying method is adopted in the embodiment of the invention, after the shrinkage reducing component is fully adsorbed on the surface of the microporous fiber, the electrostatic action on the original fiber surface disappears, and the microporous fiber is not easy to wind and agglomerate in the production and use process. The invention uses the swelling agent with proper proportion to be matched with the microporous fiber absorbed with the shrinkage reducing component, wherein the shrinkage reducing component is dissolved in a small amount in the process of stirring the concrete or the mortar, a layer of hydrophilic film is formed on the surface of the porous fiber, the dispersibility of the fiber in the concrete or the mortar is improved, the alkalinity of the solution is gradually enhanced along with the hydration reaction, the shrinkage reducing component is gradually released and dispersed into the cement paste, the brittleness of hardened cement stone is improved, the surface tension of the pore solution is reduced, and the plastic shrinkage and the chemical shrinkage are reduced, so that the effects of slowly releasing, reducing shrinkage and cracking are achieved; the combination of the microporous fiber and the set cement is tighter, and the early tensile strength of the concrete is increased; the coal gangue powder, the alum stone powder and the gypsum generate expansion products to compensate the concrete shrinkage; the cooperation of multiple anti-cracking components greatly improves the anti-cracking effect of the concrete.
Table 2: test result of crack resistance agent tested concrete index
By comparing the embodiment 1 with the embodiments 4 to 7 independently, it can be seen that the anti-cracking effect can be improved to a greater extent by using the microporous fibers, the gangue powder, the alum powder and the gypsum which are optimized by the invention, and no adverse effect is caused on other performances. Compared with the comparative examples 1-5, the anti-cracking effect of the composite material can be obviously reduced by changing the shrinkage reducing component, the anti-cracking fiber, the raw material composition or the mixture ratio in the composite material compared with the example 1, which shows that the anti-cracking effect of various anti-cracking components in the composite material can be greatly reduced by changing any raw material or mixture ratio under the proper mixture ratio. In the comparative example 6, the concrete is prepared by directly mixing a plurality of raw materials, the porous fiber is not easy to be uniformly dispersed in the concrete, the absorption effect of the shrinkage reducing component on the porous fiber is poor, the shrinkage reducing component cannot be gradually released, and the fiber is easy to agglomerate in the mixing process, so that the anti-cracking effect is poor.
Having shown and described the basic principles, essential features and advantages of the invention, while embodiments of the invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (7)
1. The fiber shrinkage-reducing crack-resistant agent is characterized by comprising the following components in percentage by mass: 1 to 2.5 percent of microporous fiber, 0.5 to 1 percent of shrinkage reducing component, 30 to 45 percent of alum stone powder, 20 to 30 percent of coal gangue powder and 30 to 40 percent of gypsum; the surface of the microporous fiber is provided with a plurality of micropores; the shrinkage reducing component is formed by mixing methyl vinyl ether-maleic anhydride copolymer and polyether polyol according to the mass ratio of 1: 1.5-2.5, and is adsorbed in micropores on the surface of the microporous fiber by using a spray drying method; the diameter of the microporous fiber is 60-80 microns, the diameter of the solid body part of the middle fiber is 40-60 microns, the thickness of the microporous part of the outer layer is 20 microns, the micropores are cylindrical, the axis of the micropores is perpendicular to the axis of the fiber, the aperture of the micropores is 15-20 microns, the number of the micropores contained in each 1mm length of the fiber is 100-240, and the micropores are not communicated with one another.
2. The agent for reducing and cracking fiber according to claim 1, wherein the microporous fiber is one or more of the following fibers: polypropylene fibers, polyvinyl alcohol fibers, polyester fibers, polyamide fibers, basalt fibers.
3. The agent for reducing and cracking fiber according to claim 1, wherein Al of alunite powder2O3The content is 30-40%, and the specific surface area is 200-400 m2And/kg, the residue on a 1.18mm sieve is 0-0.5%.
4. The fiber shrinkage-reducing and crack-resisting agent according to claim 1, wherein the coal gangue powder is formed by grinding spontaneous combustion coal gangue powder, and the specific surface area of the coal gangue powder is 400-600 m2The activity index of the material is 50 to 80 percent in 28 days.
5. The agent according to claim 1, wherein the gypsum is one or more of desulfurized gypsum, dihydrate gypsum and anhydrite.
6. The fiber shrinkage and crack resistance reducing agent according to claim 5, wherein the gypsum has a purity of 75-98%, SO3The content is 50% -55%, and the specific surface area is 300-500 m2/kg。
7. The process for preparing the fiber shrinkage and crack reducing agent of any one of claims 1 to 6, comprising the steps of:
(1) weighing the components according to a set proportion, firstly adding the microporous fibers into a dry material bin of a spray dryer, turning on an air heater to heat air to 120-160 ℃, turning on an air blower, uniformly feeding the microporous fibers in the dry material bin into a spray drying chamber through hot air of a hot air distributor, and dispersing and spirally rotating the microporous fibers by airflow; mixing the methyl vinyl ether-maleic anhydride copolymer with polyether polyol according to the mass ratio of 1: 1.5-2.5 to obtain a shrinkage reducing component, and uniformly stirring the shrinkage reducing component and a 50% ethanol solution according to the mass ratio of 1:5 to prepare a liquid material; pouring the liquid material into a constant-temperature feeding tank, heating and keeping the temperature of the liquid material at 60-90 ℃, opening a liquid material conveying pipe, conveying the liquid material to a two-fluid atomization nozzle at the top of a spray drying chamber, and atomizing the shrinkage reducing component into particles with the diameter of 10-15 mu m; the rotating hot air flow fully mixes the microporous fiber and the liquid material prepared by the shrinkage reducing component, the micropores distributed on the surface layer of the fiber fully adsorb atomized particles, the high-temperature air volatilizes the water and the ethanol in the liquid material, and the fiber becomes a carrier of the shrinkage reducing component; mixing and drying for 10min, opening a discharge port of a drying chamber, and separating the microporous fibers adsorbed with the shrinkage reducing components by a cyclone separator;
(2) and putting the microporous fiber adsorbed with the shrinkage reducing components, coal gangue powder, alum stone powder and gypsum into a dry powder mixer, and mixing for 15min to obtain a finished product of the fiber shrinkage reducing anti-cracking agent.
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| CN100999393A (en) * | 2006-01-10 | 2007-07-18 | 深圳市海川实业股份有限公司 | Application of hollow porous fiber in plastering cement substrate material |
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