CN115417643B - High-cracking-resistance fiber concrete and preparation method and application thereof - Google Patents
High-cracking-resistance fiber concrete and preparation method and application thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/04—Portland cements
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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
- C04B16/00—Use of organic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of organic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B16/04—Macromolecular compounds
- C04B16/06—Macromolecular compounds fibrous
- C04B16/0616—Macromolecular compounds fibrous from polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
- C04B16/0625—Polyalkenes, e.g. polyethylene
- C04B16/0633—Polypropylene
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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
- C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
- C04B24/24—Macromolecular compounds
- C04B24/26—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- C04B24/2641—Polyacrylates; Polymethacrylates
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F216/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical
- C08F216/02—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical by an alcohol radical
- C08F216/04—Acyclic compounds
- C08F216/08—Allyl alcohol
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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
- C04B2103/40—Surface-active agents, dispersants
- C04B2103/408—Dispersants
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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
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/34—Non-shrinking or non-cracking materials
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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
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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- Y—GENERAL 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
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Abstract
The invention provides high-cracking-resistance fiber concrete which is prepared from the following components in parts by weight: 6-8 parts of polypropylene fiber, 130-150 parts of water, 320-340 parts of P.O42.5 cement, 550-570 parts of sand, 1200-1400 parts of coarse aggregate, 6-7 parts of water reducer and 0.2-0.5 part of dispersing agent. Aiming at the agglomeration problem of fiber concrete in actual preparation, the applicant proposes a set of innovative preparation process, mainly 'changing into one new'. Instead, the stirring process of fiber concrete is improved, the limit is to clearly limit the mixing amount of polypropylene fibers, and the preparation of novel dispersing agents is new. Compared with plain concrete, the concrete has 65% raised cracking resistance, raised freeze thawing resistance, raised chloride ion permeation resistance, raised carbonization resistance and other raised performance.
Description
Technical Field
The invention belongs to the technical field of engineering, and particularly relates to high-cracking-resistance fiber concrete and a preparation method and application thereof.
Background
The polypropylene engineering fiber is an artificial synthetic fiber applied to construction engineering. In 1984, the U.S. military successfully developed the first concrete polypropylene fiber (fibermash) in the world in concert with concrete specialists of synthetic industry companies to solve the problem of shatter resistance of concrete in the ground hit by military. To date, fibermash has become an increasingly important admixture in construction, road and bridge, water supply and drainage, ports and geotechnical engineering with good engineering performance and low cost. The polypropylene fiber is divided into fiber yarn and fiber net, and is used as a flexible fiber for more than 20 years in modern engineering, and has good engineering performance and no serious accident. Compared with the traditional steel fiber, the stirring and pumping do not need special machinery, the engineering performance is similar, the manufacturing cost is lower, and the method has wide application prospect.
Polypropylene is a flexible fiber with high strength and low elastic modulus. Polypropylene fiber concrete is a composite material that incorporates a small amount of chopped polypropylene fibers to enhance or improve certain properties of the concrete. A large number of indoor tests and engineering practices prove that the polypropylene fiber concrete has the advantages of inhibiting plastic shrinkage cracks, along with good impact resistance, bending fatigue resistance, good loosening resistance, high residual strength, good impermeability, increased tensile and bending strength, good weather aging resistance, good freeze thawing resistance and the like. By utilizing the advantages, the polypropylene fiber concrete is widely applied to projects such as basements of high-rise buildings, sewage pools of sewage treatment plants, harbor road surfaces, expressway road surfaces, wharf goods yards, underground caverns, slope protection and the like, and has good effects. The polypropylene fiber is added into the concrete, so that the service life of the concrete can be effectively prolonged, and the brittle failure of the concrete can be compensated. It can raise tensile strength and flexural strength of concrete, and its toughness can reduce crack produced by initial shrinkage of concrete. The road surface added with polypropylene fiber in road engineering is wear-resistant compared with the common road surface. In waterproof and underground engineering, polypropylene is effectively impermeable because of effective reduction of cracks in concrete. In fact, the addition of flexible polypropylene fibers to the rigid concrete can integrally improve the comprehensive performance of the concrete engineering, and the 'hardness and softness combination' of the concrete is realized.
For the crack resistance of concrete, the engineering community gives a great deal of attention, and Wang Tiemeng teaches that the normal concrete works well to control the harmful cracks of the concrete structure. A large number of practical projects reflect that in the modern design and construction of concrete with continuously improved concrete grade and large area and volume, many conditions are difficult to meet, and the original concrete crack resistance measures need to be further improved.
The anti-cracking performance of the concrete structure can be improved by doping the fiber into the concrete, and the fiber of the common concrete structure comprises steel fiber, polypropylene fiber and the mixed doping among the fibers, wherein the polypropylene fiber has an obvious effect of reducing the plastic crack of the concrete. The plastic crack reducing effect of the polypropylene fiber on concrete is more than 70%; yang Shicong and Wang Fumin are subjected to early crack resistance tests on different fiber mortars under the regulations of fiber concrete technical regulations and concrete structure durability design construction guidelines, and the researches show that: cement: sand: water: the area reduction rate of the first nominal crack is 68.30% under the condition that the fiber mixing ratio is 1:1.5:0.5:0.6, which shows that the doping ratio is 0.6Kg/m 3 The polypropylene fibers delay the cracking time and the maximum crack width of the cement mortar.
However, in concrete production, the dispersibility of the fibers in the concrete is extremely important. Even if the mechanical properties and ageing resistance of the fibers are good, if the fibers cannot be well dispersed in concrete in actual mixing, isotropy cannot be formed in the concrete, and the mechanical properties cannot be uniform, so that the structure cannot fully play a role. If the entangled and agglomerated fibers are obviously present in the concrete, the addition of fibers to the concrete is not beneficial, but rather detrimental. The fiber cannot be well dispersed in the concrete, isotropy cannot be formed in the concrete, mechanical properties tend to be uniform, the structure cannot fully play a role, and a phenomenon of agglomeration is obviously formed in the concrete by winding.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to provide high-cracking-resistance fiber concrete, which can enhance the cracking resistance of the concrete and the durability of the concrete, improve the cracking resistance of a concrete building and improve the freezing and thawing damage resistance of the concrete in alpine regions by adding polymer fibers into the concrete and using specific dispersing agents.
The invention also provides a preparation method of the fiber concrete, and the dispersibility of the polymer fibers in the concrete is ensured by adopting a specific feeding sequence.
The invention also provides application of the fiber concrete in the technical field of engineering.
In order to achieve the above purpose, the present invention provides the following technical solutions:
the high-cracking-resistance fiber concrete is prepared from the following components in parts by weight: 6-8 parts of polypropylene fiber, 130-150 parts of water, 320-340 parts of P.O 42.5.5 cement, 550-570 parts of sand, 1200-1400 parts of coarse aggregate, 6-7 parts of water reducer and 0.2-0.5 part of dispersing agent.
Preferably, the coarse aggregate is limestone. Preferably, the coarse aggregate comprises 380-400 parts of coarse aggregate with the particle size of 5-20mm and 910-930 parts of coarse aggregate with the particle size of 16-31.5 mm. The matching can meet the compaction theory, and can also prevent cracks from cracking. The grading proportion is the marble: medium stone: small stone=47:38:15, crushed stone crush value 15.7%, mud content 0.1%; the bulk density of the wool is 2641kg/m 3 。
Preferably, the water reducing agent is a bleed air water reducing agent, preferably a GH-6 high efficiency water reducing agent (bleed air type).
Preferably, the addition amount of the polypropylene fiber is 0.8 percent of the volume fraction of the concrete wet material. When the volume fraction is less than 0.8%, the freeze-thawing resistance of the fiber concrete is increased along with the increase of the mixing amount of the polypropylene fibers, and the mixing of the polypropylene fibers plays a role in air entraining in the concrete; when the addition amount is more than 0.8%, the frost resistance of the concrete is rather lowered, and the reason is probably because the fiber is excessively doped, so that the fiber is agglomerated in the mixing process, and the performance of the concrete is lowered. The concrete wet material is formed by mixing and stirring water, P.O 42.5.5 cement, sand, coarse aggregate, a water reducing agent and a dispersing agent.
Preferably, the dispersing agent is a sodium polyacrylate-allyl alcohol solution, and the preparation method comprises the following steps:
1) Mixing sodium bisulphite and water according to the volume ratio of 1 (20-30), stirring and dissolving, heating to 60-70 ℃, and beginning to dropwise add a mixture of acrylic acid and allyl alcohol to obtain a first mixed solution;
preferably, the addition amount of the mixture of the acrylic acid and the allyl alcohol is 5-10% by volume of the mixed solution of the sodium bisulphite and the water, and the volume ratio of the acrylic acid to the allyl alcohol is 1:3.
2) Adding an aqueous solution of ammonium persulfate into the first mixed solution, continuing to perform heat preservation reaction, cooling to 30-40 ℃, and neutralizing with an aqueous solution of sodium hydroxide until the pH value is 7-8 to obtain a viscous low-molecular-weight sodium polyacrylate-allyl alcohol solution.
Preferably, the mass concentration of the ammonium persulfate aqueous solution is 20-30%, and the addition amount is 5% of the volume fraction of the first mixed solution.
Preferably, the incubation time is 90min.
Preferably, in the sodium polyacrylate-acrylate solution, the average molecular weight of the polymer is 4.6X10 4 。
The reaction mechanism of the preparation process is as follows:
the main reaction: acrylic acid and allyl alcohol are subjected to copolymerization reaction, ammonium persulfate is used as an initiator to generate an acrylic acid-allyl alcohol copolymer, and the acrylic acid-allyl alcohol copolymer and sodium hydroxide are reacted to generate sodium polyacrylate-allyl alcohol, wherein the reaction formula is as follows:
side reaction: the acrylic acid is heated and polymerized in water by using ammonium persulfate as an initiator, and the generated polymer is neutralized by sodium hydroxide to obtain sodium polyacrylate, and the sodium polyacrylate and the allyl alcohol generate sodium polyacrylate-allyl alcohol under the action of ammonium persulfate, wherein the reaction formula is as follows:
compared with the existing dispersing agent, the self-made dispersing agent provided by the invention does not have a single product to play a dispersing role, and polyacrylic acid, sodium polyacrylate, acrylic acid-allyl alcohol copolymer and sodium polyacrylate-allyl alcohol in the dispersing agent can play a dispersing effect, so that the dispersing capability of the dispersing agent is greatly improved.
As to the preparation method of the fiber concrete, the applicant research finds that: establishing a correct stirring regime has a great effect on improving the quality of the fibre concrete. Compared with the traditional concrete stirring technology, the method has the advantages that uneven fiber distribution needs to be prevented in the stirring process, and fiber agglomeration is avoided. In general, the order of addition, the stirring time, the type of stirrer and the shape and quantity of the fibers all affect whether the fibers are agglomerated or not, and further, the quality of the concrete is lost on different scales. The applicant adopts an innovative novel process to stir the fiber concrete, comprising the following steps:
(1) Mixing and stirring the sand, the coarse aggregate and the cement for 50-60 s to obtain a first mixture;
(2) Mixing water, a water reducing agent and a dispersing agent to obtain a mixed solution;
(3) Adding 2/3 of the mixed solution into the first mixture obtained in the step (1), stirring for 40-50 s, then adding polypropylene fibers, stirring for 30s, checking whether agglomerations exist, and scattering if so, so as to obtain a second mixture;
(4) And adding the rest 1/3 of the mixed solution into the second mixture, and stirring for 1-2 min to obtain the fiber concrete.
The fiber concrete obtained by adopting the improved preparation process can be more uniformly distributed in the concrete, and the strength of the fiber concrete is improved by 10-20% compared with that of the concrete stirred by adopting a conventional stirring method. Fiber concrete requires a longer time to mix than typical concrete for a mixing time of 2-3 minutes, typically 4-6 minutes for optimal mixing time. The above 4 to 6 minutes are the total stirring time, that is, the time required for steps (1) to (4).
In summary, the applicant has conducted intensive studies on the agglomeration problem of fiber concrete in actual preparation, and has concluded an innovative preparation process, mainly "change to a limit. Instead, the stirring process of fiber concrete is improved, the limit is to clearly limit the mixing amount of polypropylene fibers, and the preparation of novel dispersing agents is new.
The invention also provides application of the fiber concrete in the technical field of engineering, and the fiber concrete is particularly suitable for constructing an airport runway pavement.
Compared with a common airport pavement: with the high-speed development of aviation industry in China, airports are required to bear heavy passenger transport and freight transport tasks, and the most main pavement structural form of civil aviation airport application in China is a concrete pavement. However, since the concrete material is a brittle material, when the concrete material is subjected to a great impact during the take-off and landing of an aircraft and a strong friction between the wheels and the airfield pavement, cracks are extremely easily generated on the concrete pavement, so that the durability is reduced and the service life is greatly shortened. Therefore, the brittleness of the concrete is improved by adding fiber materials, and the cracking resistance and the impact resistance of the concrete are improved to a certain extent. Aiming at the condition that the airport temperature in winter in north is too low, the frost cracking resistance of the concrete material can be greatly improved after the fiber is added into the concrete material for brittleness enhancement.
Compared with a fiber airfield pavement: in concrete production, the dispersibility of fibers in concrete is of exceptional importance. Even if the mechanical property of the fiber is good, the aging resistance is good, but if the fiber cannot be well dispersed in the concrete in actual mixing, the concrete cannot form isotropy, the mechanical property cannot tend to be uniform, the structure cannot fully play a role, and if the fiber which is clustered obviously exists in the concrete, the fiber is added into the concrete, so that the fiber is not beneficial, but is harmful. The fiber concrete agglomeration phenomenon can be greatly improved by stirring and adding the dispersing agent through the improved preparation process, so that the fiber is really beneficial to the concrete.
The cracking resistance mechanism of the fiber concrete is as follows:
the toughening mechanism of the fiber aggregate is explained so far that after the first crack of the cement matrix occurs, the fiber can bear larger load if the pullout resistance of the fiber is larger than the load when the first crack occurs. In the split section the "cement matrix is not able to withstand any stretching" and the fibres carry the full load on the composite. As the load on the composite increases, the fibers will transfer additional stress to the cement matrix through the bonding stress. If these bond stresses do not exceed the bond strength, more cracks will occur in the cement matrix. This increased cracking process continues until either the fibers are broken or the bond strength fails, resulting in the fibers being pulled out.
According to the constraint action of the fiber on the occurrence and development of concrete cracks, the crack strength of the original materials with defects and cracks in the concrete can be improved due to the fact that after the fiber is added into the concrete, the toughness of the concrete is increased, the size of the crack is reduced or the stress concentration coefficient of the crack tip is reduced. This is a theoretical explanation of the reason why the incorporation of fibers can improve the crack resistance of concrete.
The fiber concrete of the invention has the following freeze-thawing damage prevention mechanism:
in the water saturation state of the concrete, at a certain freezing temperature, water in the capillary holes is frozen, and the water in the gelatinization holes is in a supercooled state. The water is frozen to form ice, so that the concrete expands; in addition, since water molecules in a supercooled state in the gel pores permeate to the interface of ice in the pressure capillary pores, a permeation pressure is generated in the capillary pores again. Therefore, when the concrete in a saturated state is frozen, the capillary pore wall of the concrete is simultaneously subjected to expansion and permeation 2 pressures, the concrete is cracked when the 2 pressures exceed the tensile strength of the concrete, the cracks in the concrete are mutually communicated after repeated freezing and thawing cycles, the strength of the cracks is gradually reduced, and finally the cracks are even completely lost, so that the concrete is damaged from the outside to the inside. And a certain amount of uniformly distributed polypropylene fibers are added into the concrete, and the existence of the fibers can delay the freeze-thawing cycle effect, so that a crack stress concentration zone is expanded into the concrete matrix, and cracks caused by early plastic cracking and frost heaving pressure of the concrete are restrained, thereby further delaying the deterioration of the freeze-thawing effect on the concrete performance.
The technical scheme provided by the invention has at least the beneficial effects that:
the invention provides high-cracking-resistance fiber concrete, which is characterized in that polypropylene fibers are added into the concrete to enhance the cracking resistance and durability of the concrete, improve the cracking resistance of a concrete building and improve the freeze thawing damage resistance of the concrete in alpine regions; compared with plain concrete, the concrete doped with the fiber has 65% improved cracking resistance, and has improved freezing and thawing resistance, chloride ion permeation resistance, carbonization resistance and the like.
Aiming at the agglomeration problem of fiber concrete in actual preparation, the applicant proposes a set of innovative preparation process, mainly 'changing into one new'. Instead, the stirring process of fiber concrete is improved, the limit is to clearly limit the mixing amount of polypropylene fibers, and the preparation of novel dispersing agents is new.
Drawings
FIG. 1 is a flow chart of a method for preparing the fiber concrete with high cracking resistance.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in further detail below.
The physical parameters of the polypropylene fibers used in the examples are shown in table 1:
TABLE 1
| Project | Characteristic parameter | Project | Characteristic parameter |
| Density of | 0.9 | Fiber length | 16～19mm |
| Water absorption rate | 0 | Modulus of elasticity/MPa | 3500 |
| Tensile strength/MPa | 350～770 | Acid and alkali resistance | Very good |
| Melting Point/. Degree.C | 162 | Dispersibility of | Good quality |
| Ignition point/. Degree.C | 590 | Safety (for human body) | Good quality |
Example 1
The high-cracking-resistance fiber concrete is prepared from the following components in parts by weight: 6 parts of polypropylene fiber, 135 parts of water, 330 parts of P.O 42.5.5 cement, 550 parts of sand, 380 parts of coarse aggregate with the particle size of 5-20mm, 910 parts of coarse aggregate with the particle size of 16-31.5mm, 6 parts of GH-6 high-efficiency water reducer (air entraining type) and 0.2 part of dispersing agent. Wherein the addition amount of the polypropylene fiber is 0.8% of the wet volume of the concrete.
Wherein the dispersing agent is sodium polyacrylate-allyl alcohol solution, and the preparation method comprises the following steps:
1) Mixing sodium bisulphite and water according to the volume ratio of 1:25, stirring and dissolving, heating to 65 ℃, and beginning to dropwise add a mixture of acrylic acid and allyl alcohol to obtain a first mixed solution;
wherein the volume ratio of the mixture of the acrylic acid and the allyl alcohol is 1:3, and the addition amount of the mixture of the acrylic acid and the allyl alcohol is 6 percent of the mixed solution of the sodium bisulphite and the water;
2) And adding an aqueous solution of ammonium persulfate with the mass concentration of 25% into the first mixed solution, wherein the addition amount is 5% of the volume fraction of the first mixed solution. And (3) continuing the heat preservation reaction after the dripping is finished, cooling to 35 ℃ after 90min, and neutralizing with sodium hydroxide aqueous solution until the pH value is 7.5 to obtain a viscous sodium polyacrylate-allyl alcohol solution with low molecular weight.
The preparation process flow chart of the fiber concrete is shown in fig. 1, and specifically comprises the following steps:
(1) Mixing and stirring the sand, the coarse aggregate and the cement for 55s to obtain a first mixture;
(2) Mixing water, a water reducing agent and a dispersing agent to obtain a mixed solution;
(3) Adding 2/3 of the mixed solution into the first mixture obtained in the step (1), stirring for 45s, then adding polypropylene fibers, stirring for 30s, checking whether agglomerations exist, and scattering if so, so as to obtain a second mixture;
(4) And adding the rest 1/3 of the mixed solution into the second mixture, and stirring for 1min to obtain the fiber concrete.
Comparative example 1
A common commercially available dispersant (30% by mass of a polyacrylic acid solution) was used, and no polypropylene fiber was added, and other raw materials and preparation procedures were the same as in example 1.
Comparative example 2
The polypropylene fiber was added using a common commercially available dispersant (30% by mass of a polyacrylic acid solution), and the other raw materials and the preparation process were the same as in example 1.
The results of the performance test of the prepared concrete are shown in tables 2 to 4:
table 2 compressive strength of concrete
TABLE 3 flexural Strength of concrete
TABLE 4 mass of test pieces after every 25 freeze-thawing cycles under the anti-cracking measure
The test results show that after the dispersing agent is added into the fiber concrete, the fibers can be uniformly dispersed into the concrete, so that the mechanical property of the concrete is improved. However, the bonding strength between the fiber and the cement and mortar bodies is slightly weakened due to the wrapping of the dispersant on the fiber surface.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.
Claims (3)
1. The high-cracking-resistance fiber concrete is characterized by being prepared from the following components in parts by weight: 6-8 parts of polypropylene fiber, 130-150 parts of water, 320-340 parts of P.O42.5 cement, 550-570 parts of sand, 1200-1400 parts of coarse aggregate, 6-7 parts of water reducer and 0.2-0.5 part of dispersing agent;
the coarse aggregate comprises 380-400 parts of coarse aggregate with the particle size of 5-20mm and 910-930 parts of coarse aggregate with the particle size of 16-31.5 mm; the coarse aggregate is made of limestone;
the addition amount of the polypropylene fiber is 0.8 percent of the volume fraction of the concrete wet material;
the dispersing agent is sodium polyacrylate-allyl alcohol solution, and the preparation method comprises the following steps:
1) Mixing sodium bisulphite and water according to the volume ratio of 1 (20-30), stirring and dissolving, heating to 60-70 ℃, and beginning to dropwise add a mixture of acrylic acid and allyl alcohol to obtain a first mixed solution; the addition amount of the mixture of the acrylic acid and the allyl alcohol is 5-10% by volume of the mixed solution of the sodium bisulphite and the water, and the volume ratio of the acrylic acid to the allyl alcohol is 1:3;
2) Adding an aqueous solution of ammonium persulfate into the first mixed solution, continuing to perform heat preservation reaction, cooling to 30-40 ℃, and neutralizing with an aqueous solution of sodium hydroxide until the pH value is 7-8 to obtain a viscous low-molecular-weight sodium polyacrylate-allyl alcohol solution; the mass concentration of the ammonium persulfate aqueous solution is 20-30%, the addition amount is 5% of the volume fraction of the first mixed solution, and the heat preservation reaction time is 90min;
the preparation method of the fiber concrete with high cracking resistance comprises the following steps:
(1) Mixing and stirring the sand, the coarse aggregate and the cement for 50-60 s to obtain a first mixture;
(2) Mixing water, a water reducing agent and a dispersing agent to obtain a mixed solution;
(3) Adding 2/3 of the mixed solution into the first mixture obtained in the step (1), stirring for 40-50 s, then adding polypropylene fibers, stirring for 30s, checking whether agglomerations exist, and scattering if so, so as to obtain a second mixture;
(4) Adding the rest 1/3 mixed solution into the second mixture, and stirring for 1-2 min to obtain the fiber concrete;
the total time of the steps (1) to (4) is 4-6 minutes.
2. The high crack resistant fiber concrete of claim 1 wherein the water reducing agent is a bleed air water reducing agent.
3. Use of the high fracture resistance fiber concrete of claim 1 or 2 in the field of engineering technology.
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| CN101249397A (en) * | 2008-03-10 | 2008-08-27 | 江苏飞翔化工股份有限公司 | Preparation of amphiprotic high molecular type surfactant for promoting papermaking rubber coating agent aging |
| CN112047670A (en) * | 2020-07-21 | 2020-12-08 | 甘肃省地震局（中国地震局兰州地震研究所） | C40 polypropylene fiber-doped anti-freezing concrete and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101249397A (en) * | 2008-03-10 | 2008-08-27 | 江苏飞翔化工股份有限公司 | Preparation of amphiprotic high molecular type surfactant for promoting papermaking rubber coating agent aging |
| CN112047670A (en) * | 2020-07-21 | 2020-12-08 | 甘肃省地震局（中国地震局兰州地震研究所） | C40 polypropylene fiber-doped anti-freezing concrete and preparation method thereof |
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| 张光华.《水处理化学品制备与应用指南》.中国石化出版社,2003,第136-137页. * |
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