CN116354665A - Composition for ultra-high performance concrete, preparation method and application thereof - Google Patents
Composition for ultra-high performance concrete, preparation method and application thereof Download PDFInfo
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- 239000011374 ultra-high-performance concrete Substances 0.000 title claims abstract description 68
- 239000000203 mixture Substances 0.000 title claims abstract description 53
- 238000002360 preparation method Methods 0.000 title abstract description 5
- 239000000835 fiber Substances 0.000 claims abstract description 113
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 106
- 239000010959 steel Substances 0.000 claims abstract description 106
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 62
- 229910021487 silica fume Inorganic materials 0.000 claims abstract description 29
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 28
- 239000004568 cement Substances 0.000 claims abstract description 27
- 238000004804 winding Methods 0.000 claims abstract description 11
- 238000002156 mixing Methods 0.000 claims description 27
- 238000011282 treatment Methods 0.000 claims description 26
- 238000000034 method Methods 0.000 claims description 21
- 238000003756 stirring Methods 0.000 claims description 21
- 239000004567 concrete Substances 0.000 claims description 13
- 230000000694 effects Effects 0.000 claims description 10
- 238000000465 moulding Methods 0.000 claims description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical group O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 8
- 239000004576 sand Substances 0.000 claims description 8
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 6
- 239000013067 intermediate product Substances 0.000 claims description 6
- 229920005646 polycarboxylate Polymers 0.000 claims description 6
- 238000011418 maintenance treatment Methods 0.000 claims description 3
- 238000004873 anchoring Methods 0.000 claims description 2
- 238000005266 casting Methods 0.000 claims description 2
- 239000007787 solid Substances 0.000 claims description 2
- 239000004035 construction material Substances 0.000 claims 1
- 239000011159 matrix material Substances 0.000 abstract description 18
- 230000008901 benefit Effects 0.000 abstract description 7
- 239000004566 building material Substances 0.000 abstract description 4
- 230000000052 comparative effect Effects 0.000 description 23
- 239000000463 material Substances 0.000 description 12
- 238000005452 bending Methods 0.000 description 8
- 239000002994 raw material Substances 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- 102000002151 Microfilament Proteins Human genes 0.000 description 4
- 108010040897 Microfilament Proteins Proteins 0.000 description 4
- 238000005520 cutting process Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 210000003632 microfilament Anatomy 0.000 description 4
- 230000007704 transition Effects 0.000 description 4
- 239000002245 particle Substances 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- 239000012783 reinforcing fiber Substances 0.000 description 3
- 239000011398 Portland cement Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000011031 large-scale manufacturing process Methods 0.000 description 2
- 244000208060 Lawsonia inermis Species 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000011210 fiber-reinforced concrete Substances 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
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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
-
- 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
-
- 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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
The invention relates to the technical field of building materials, and discloses a composition for ultra-high performance concrete, the ultra-high performance concrete, a preparation method and application thereof, wherein the composition comprises the following components: cement, silica fume, fine aggregate, threaded steel fibers, a water reducing agent and water, wherein the threaded steel fibers are formed by spirally winding at least two steel wires, the average diameter d of the threaded steel fibers is 0.2-0.4mm, and the tensile strength is 1100-1600MPa. The ultra-high performance concrete provided by the invention has stronger adhesion with the matrix and more excellent mechanical property and deformation property. Has good economic benefit and wider application prospect.
Description
Technical Field
The invention relates to the technical field of building materials, in particular to a composition for ultra-high-performance concrete, the ultra-high-performance concrete, and a preparation method and application thereof.
Background
Since the 90s of the last century, ultra-high performance concrete has been widely focused on its excellent mechanical and durability properties, and has become the cement-based composite material with the most innovative and practical properties internationally at present, and has been widely practiced and applied in the fields of bridge engineering, building engineering, protection engineering, etc.
Compared with common concrete, the ultra-high performance concrete is based on an evenly distributed ultra-fine compact system, and the compact filling among the components is realized according to the principle of maximum bulk density. Meanwhile, by doping mineral admixtures such as silica fume, the interface transition area between the cement matrix and the aggregate is as compact as cement paste. In addition, by adding the fiber, the mechanical property and the deformability of the fiber-matrix are further improved by utilizing the bridging effect of the fiber-matrix.
The steel fiber has the advantages of excellent mechanical property, good deformability, convenience for large-scale production and the like, and becomes the first choice reinforcing fiber of various cement-based materials. Wherein, for ultra-high performance concrete, microfilament steel fiber is generally selected as the reinforcing fiber. For the microfilament steel fiber, the cross section is circular, the diameter is more than 0.1mm-0.3mm, the length is generally 5mm-25mm, the tensile strength is generally more than 2000MPa, and the fiber shape mainly comprises straight, wavy, end hook shape and the like. At present, straight fibers, end hook type steel fibers and the like are widely applied in China.
CN112851266a discloses an ultra-high performance concrete with high fiber dispersity and orientation degree, and a preparation method thereof, the raw materials of the ultra-high performance concrete with high fiber dispersity and orientation degree comprise: cement, silica fume, fine aggregate, polycarboxylate water reducer, fiber and water; the cement, the silica fume and the polycarboxylate water reducer are prepared from the following components in parts by mass: 5-25:3-5; the volume doping amount of the fiber in the ultra-high performance concrete is 1-5%; the mass of water is 0.05 to 0.10 times of the sum of the masses of cement, silica fume and fine aggregate; after the raw materials of the ultra-high performance concrete are mixed, the slump expansion is 260-280mm. Although the prior art can improve the mechanical property of the ultra-high performance concrete to a certain extent and reduce the production cost, the prior art has the defects of poor steel fiber reinforcement effect and low fiber utilization efficiency.
For copper-plated microfilament steel fibers and end hook type steel fibers applied to ultra-high performance concrete, a plurality of technical problems still exist to be solved. Wherein, for the common copper-plated microfilament steel fiber, the interface bonding performance with the ultra-high performance concrete is poor, and the strength exerting rate is only 10-25%. For the end hook type steel fiber, the fiber is easy to agglomerate in concrete under the condition of higher doping amount due to the special geometric structure. Meanwhile, after the reinforcing fibers are doped, the ultra-high performance concrete still has the defects of insignificant toughness improving effect, higher required fiber doping amount and the like.
Therefore, it is necessary to develop a steel fiber capable of further improving the mechanical and deformation properties of the ultra-high performance concrete and further reducing the production cost of the ultra-high performance concrete.
Disclosure of Invention
The invention aims to provide ultra-high performance concrete which has strong adhesion with a matrix and excellent mechanical property and deformability.
In order to achieve the above object, a first aspect of the present invention provides a composition for ultra-high performance concrete, comprising: cement, silica fume, fine aggregate, threaded steel fibers, a water reducing agent and water;
the content of the silica fume is 20-40 parts by weight, the content of the fine aggregate is 80-120 parts by weight, the content of the water reducing agent is 2-3 parts by weight, and the content of the water is 18-24 parts by weight relative to 100 parts by weight of the cement;
the volume doping amount of the threaded steel fiber is 0.5-3% based on the total volume of all components except the threaded steel fiber in the composition;
the threaded steel fiber is formed by spirally winding at least two steel wires, the average diameter d of the threaded steel fiber is 0.2-0.4mm, and the tensile strength is 1100-1600MPa;
the specific surface area of the silica fume is more than or equal to 18000m 2 /kg，SiO 2 The content is more than or equal to 95wt percent, and the 28d activity index is more than or equal to 105 percent.
In a second aspect the invention provides a method of preparing ultra-high performance concrete using the components of the composition of the first aspect, comprising:
(1) First mixing the components in the component A to obtain a mixture I; the component A contains cement, silica fume, fine aggregate, a water reducing agent and water;
(2) Carrying out second mixing on the mixture I and the threaded steel fibers to obtain a mixture II;
(3) Sequentially carrying out pouring molding treatment and maintenance treatment on the mixture II to obtain the ultra-high performance concrete;
the amount of the silica fume is 20-40 parts by weight, the amount of the fine aggregate is 80-120 parts by weight, the amount of the water reducing agent is 2-3 parts by weight, and the amount of the water is 18-24 parts by weight relative to 100 parts by weight of the cement;
in the step (1), the specific surface area of the silica fume is more than or equal to 18000m 2 /kg，SiO 2 The content is more than or equal to 95wt percent, and the 28d activity index is more than or equal to 105 percent;
in the step (2), the volume doping amount of the threaded steel fibers is 0.5-3% based on the volume of the mixture I;
in the step (2), the threaded steel fiber is formed by spirally winding at least two steel wires, and the average diameter d of the threaded steel fiber is 0.2-0.4mm, and the tensile strength is 1100-1600MPa.
A third aspect of the present invention provides ultra-high performance concrete prepared by the method of the second aspect described above.
A fourth aspect of the invention provides the use of the ultra-high performance concrete of the third aspect in a building material.
Compared with the prior art, the technical scheme provided by the invention has at least the following advantages:
(1) Compared with the traditional reinforced fiber, the reinforced fiber of the ultra-high performance concrete has the advantages that the surface is rough and obvious mechanical engagement teeth exist due to the special geometric structure, the interface transition area of the fiber-matrix can be obviously improved, and the bonding performance between the fiber and the matrix can be further improved.
(2) Compared with the traditional fiber reinforced ultra-high performance concrete, the threaded steel fiber reinforced ultra-high performance concrete provided by the invention has better bearing capacity and deformation performance, higher toughness and wide application prospect.
(3) The threaded steel fiber is preferably obtained from a commercial superfine diameter steel wire rope, a conventional commercial full-automatic numerical control steel wire rope cutting machine is preferably adopted, the large-scale production of the threaded steel fiber is realized, and compared with the traditional reinforced steel fiber, the threaded steel fiber has the advantages of convenience in obtaining materials, convenience in production and the like, and has good economic benefits.
Drawings
FIG. 1 is a schematic view of the surface morphology and cross section of a threaded steel fiber;
FIG. 2 is a microscopic morphology of a threaded steel fiber-matrix interface transition region;
FIG. 3 is a plot of pull-out load versus slip for the steel fibers of inventive example 1 and comparative examples 1-2 in ultra-high performance concrete;
FIG. 4 is a graph comparing bending load-deflection of ultra-high performance concrete of example 1 of the present invention with that of comparative examples 1-2.
Detailed Description
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
It should be noted that, in the aspects of the present invention, the present invention is described only once in one aspect thereof without repeated description with respect to the same components or terms in the aspects, and those skilled in the art should not understand the limitation of the present invention.
The average particle diameters described in the present invention all represent average diameters.
As described above, the first aspect of the present invention provides a composition for ultra-high performance concrete, comprising: cement, silica fume, fine aggregate, threaded steel fibers, a water reducing agent and water;
the content of the silica fume is 20-40 parts by weight, the content of the fine aggregate is 80-120 parts by weight, the content of the water reducing agent is 2-3 parts by weight, and the content of the water is 18-24 parts by weight relative to 100 parts by weight of the cement;
the volume doping amount of the threaded steel fiber is 0.5-3% based on the total volume of all components except the threaded steel fiber in the composition;
the threaded steel fiber is formed by spirally winding at least two steel wires, the average diameter d of the threaded steel fiber is 0.2-0.4mm, and the tensile strength is 1100-1600MPa;
the specific surface area of the silica fume is more than or equal to 18000m 2 /kg，SiO 2 The content is more than or equal to 95wt percent, and the 28d activity index is more than or equal to 105 percent.
Preferably, the threaded steel fibers are incorporated in an amount of 1 to 3% by volume based on the total volume of the components of the composition excluding the threaded steel fibers. The inventor of the invention discovers that under the preferable condition, the bonding performance of the threaded steel fiber and the matrix is better, and the prepared ultra-high performance concrete has more excellent mechanical property and deformation property.
The average diameter d of the threaded steel fiber refers to the average diameter of the circumscribed circle of the cross-section pattern of the threaded steel fiber.
The inventor of the invention discovers in the research that when the average diameter of the threaded steel fiber is 0.2-0.4mm, the bonding performance of the threaded steel fiber and a matrix is better, and the prepared ultra-high performance concrete has more excellent mechanical property and deformation property.
Preferably, the threaded steel fibers are formed by spirally winding 7 strands of steel wires.
Preferably, the average length of the threaded steel fibers is 10-18mm.
Preferably, the anchoring length of the threaded steel fiber in the ultra-high performance concrete is 40d-60d. The inventor of the present invention found that under the preferred conditions, the bonding property of the threaded steel fiber and the matrix is better.
FIG. 1 shows the surface morphology (left) and cross-sectional view (right) of a threaded steel fiber preferably provided by the invention, and FIG. 2 shows the microscopic morphology of a threaded steel fiber-matrix interface transition region preferably provided by the invention; as can be seen from fig. 1 and 2, the threaded steel fiber provided by the invention is preferably formed by combining 7 steel wires in a spiral winding manner, has a rough surface and obvious mechanical engagement teeth, and therefore has better bonding performance with an ultra-high performance concrete matrix.
The spiral winding angle of the steel wire of the threaded steel fiber is not particularly limited, and a person skilled in the art can select according to the existing raw materials in the art, and the present invention is not described herein again, and the person skilled in the art should not understand the limitation of the present invention.
The invention provides a preferred specific embodiment, which is obtained by cutting raw materials meeting the requirements of the invention by using a commercially available full-automatic numerical control steel wire rope cutting machine as cutting processing equipment.
Preferably, the cement is selected from at least one of p o, 42.5, p o, 52.5.
P o 42.5.5 in the present invention represents Portland cement having a strength grade of 42.5, and p o 52.5.5 in the present invention represents Portland cement having a strength grade of 52.5.
Preferably, the fine aggregate is sand, and the average particle diameter of the sand is not more than 2.36mm.
The source of the sand is not particularly limited, and may be natural river sand or machine-made sand, as long as the sand is within the average particle size range required by the present invention.
Preferably, the water reducer is a polycarboxylate water reducer, the water reducing rate of the polycarboxylate water reducer is more than or equal to 25%, and the solid content is 20-25wt%.
The source of the water is not particularly limited, so long as the water can meet the requirements of JGJ 63-2006 Water Standard for concrete.
As previously mentioned, a second aspect of the present invention provides a method of preparing ultra-high performance concrete using the components of the composition of the first aspect, comprising:
(1) First mixing the components in the component A to obtain a mixture I; the component A contains cement, silica fume, fine aggregate, a water reducing agent and water;
(2) Carrying out second mixing on the mixture I and the threaded steel fibers to obtain a mixture II;
(3) Sequentially carrying out pouring molding treatment and maintenance treatment on the mixture II to obtain the ultra-high performance concrete;
the amount of the silica fume is 20-40 parts by weight, the amount of the fine aggregate is 80-120 parts by weight, the amount of the water reducing agent is 2-3 parts by weight, and the amount of the water is 18-24 parts by weight relative to 100 parts by weight of the cement;
in the step (1), the specific surface area of the silica fume is more than or equal to 18000m 2 /kg，SiO 2 The content is more than or equal to 95wt percent, and the 28d activity index is more than or equal to 105 percent;
in the step (2), the volume doping amount of the threaded steel fibers is 0.5-3% based on the volume of the mixture I;
in the step (2), the threaded steel fiber is formed by spirally winding at least two steel wires, and the average diameter d of the threaded steel fiber is 0.2-0.4mm, and the tensile strength is 1100-1600MPa.
Preferably, the water-gel ratio of the mixture I is 0.16-0.20:1.
in the present invention, the water-cement ratio refers to the ratio of the weight of water in the mixture I to the total weight of cement and silica fume.
Preferably, in step (1), the conditions of the first mixing include: the stirring speed is 55-70rpm, and the stirring time is 300-360s.
According to a preferred embodiment, the method of step (1) comprises: and firstly, carrying out first contact on the water reducer and the water to obtain an intermediate product, and then carrying out first mixing on the intermediate product and the rest components in the component A.
According to another preferred embodiment, the method of step (1) comprises: firstly, carrying out second contact on the components except the water reducing agent and the water in the component A to obtain a mixed material, carrying out first contact on the water reducing agent and the water to obtain an intermediate product, and carrying out first mixing on the intermediate product and the mixed material.
The specific conditions of the first contact and the second contact are not particularly limited, so long as the materials can be uniformly mixed, the invention is not described herein, and the person skilled in the art should not understand the limitation of the invention.
Preferably, the method of step (2) comprises: firstly, continuously adding the threaded steel fibers into a system formed by the mixture I under a first stirring condition, wherein the adding time is not more than 90 seconds, and then carrying out the second mixing to obtain the mixture II.
Preferably, in step (2), the conditions of the second mixing include: the stirring speed is 110-130rpm, and the stirring time is 240-300s.
Preferably, the stirring rate of the first stirring is the same as the stirring rate of the second mixing.
The second mixing time is calculated from the time when the threaded steel fiber is added.
According to a preferred embodiment, in step (3), the operation of curing treatment comprises: sequentially carrying out first curing treatment and second curing treatment on the concrete block obtained after casting molding treatment; the temperature of the first curing treatment is 18-22 ℃, the time is 24-48h, and the relative humidity is more than or equal to 95%; the second curing treatment is carried out in water, the temperature is 18-22 ℃ and the time is 26-30d.
According to another preferred embodiment, in the step (3), the mixture II is cast and molded by a mold molding method to obtain a concrete block, the concrete block is subjected to the first curing treatment together with a mold, and then the mold is removed to obtain a first curing block, and then the first curing block is subjected to the second curing treatment to obtain the ultra-high performance concrete.
As previously mentioned, a third aspect of the present invention provides ultra-high performance concrete prepared by the method of the second aspect described above.
As previously mentioned, a fourth aspect of the present invention provides the use of the ultra-high performance concrete of the third aspect in a building material.
The invention will be described in detail below by way of examples. In the following examples, a fully automatic numerical control wire rope cutter was used to cut the steel fiber raw material.
In the following examples, the raw materials were all commercially available, and specific sources of the raw materials are shown in table 1, unless otherwise specified.
In the examples below, the types and amounts of the components are listed in Table 2.
TABLE 1
In the following examples and comparative examples, 1kg was represented per part or per part by weight.
Example 1
(1) Placing cement, silica fume and fine aggregate in a stirrer and stirring at 60rpm for 180s to obtain a mixed material, uniformly mixing a water reducing agent and water, and then carrying out first mixing (the stirring speed is 60rpm and the time is 320 s) with the mixed material to obtain a mixture I;
(2) Continuously and uniformly adding the threaded steel fibers into a system formed by the threaded steel fibers and the mixture I, wherein the adding time is not more than 90 seconds, and then carrying out second mixing (the stirring speed is 120rpm, and the time is 260 seconds) to obtain a mixture II;
(3) Pouring the mixture II in a mould for pouring molding treatment, placing the obtained concrete block and the mould in a curing chamber for first curing treatment (the temperature is 20 ℃, the time is 24h, the relative humidity is 95%), removing the mould, and placing the concrete block and the mould in water for second curing treatment (the temperature is 20 ℃ and the time is 28 d) to obtain the ultra-high performance concrete.
Example 2
(1) Placing cement, silica fume and fine aggregate in a stirrer and stirring for 180s at 55rpm to obtain a mixed material, uniformly mixing a water reducing agent and water, and then carrying out first mixing (the stirring speed is 55rpm and the time is 300 s) with the mixed material to obtain a mixture I;
(2) Continuously and uniformly adding the threaded steel fibers into a system formed by the mixture I for no more than 90 seconds, and then carrying out second mixing (stirring speed is 110rpm, and time is 240 seconds) to obtain a mixture II;
(3) Pouring the mixture II in a mould for pouring molding treatment, placing the obtained concrete block and the mould in a curing chamber for first curing treatment (the temperature is 18 ℃, the time is 36h, the relative humidity is 95%), removing the mould, and placing the concrete block and the mould in water for second curing treatment (the temperature is 18 ℃ and the time is 26 d) to obtain the ultra-high performance concrete.
Example 3
(1) Placing cement, silica fume and fine aggregate in a stirrer and stirring at 70rpm for 180s to obtain a mixed material, uniformly mixing a water reducing agent and water, and then carrying out first mixing (the stirring speed is 70rpm and the time is 360 s) with the mixed material to obtain a mixture I;
(2) Continuously and uniformly adding the threaded steel fibers into a system formed by the mixture I for no more than 90 seconds, and then carrying out second mixing (the stirring speed is 130rpm, and the time is 300 seconds) to obtain a mixture II;
(3) Pouring the mixture II in a mould for pouring molding treatment, placing the obtained concrete block and the mould in a curing chamber for first curing treatment (the temperature is 22 ℃, the time is 48h, the relative humidity is 95%), removing the mould, and placing the concrete block and the mould in water for second curing treatment (the temperature is 22 ℃ and the time is 30 d) to obtain the ultra-high performance concrete.
Example 4
This example was carried out using a procedure similar to example 1, except that: and replacing the threaded steel fiber I with the threaded steel fiber II with the same volume doping amount.
And preparing the ultra-high performance concrete.
Example 5
This example was carried out using a procedure similar to example 1, except that: the volume doping amount of the threaded steel fiber I is adjusted from 2% to 0.5%.
And preparing the ultra-high performance concrete.
Comparative example 1
This comparative example was carried out using a procedure similar to that of example 1, substituting the threaded steel fibers I with equal volume amounts of straight steel fibers.
And preparing the ultra-high performance concrete.
Comparative example 2
This comparative example was conducted using a procedure similar to example 1, except that: and replacing the threaded steel fiber I with end hook type steel fiber with equal volume doping amount.
And preparing the ultra-high performance concrete.
Comparative example 3
This comparative example was conducted using a procedure similar to example 1, except that: the volume doping amount of the threaded steel fiber I is adjusted from 2% to 3.5%.
And preparing the ultra-high performance concrete.
Comparative example 4
This comparative example was conducted using a procedure similar to example 1, except that: the silica fume I was replaced with an equal weight of silica fume II.
And preparing the ultra-high performance concrete.
Comparative example 5
This comparative example was conducted using a procedure similar to example 1, except that: the amount of fine aggregate in the composition is adjusted.
And preparing the ultra-high performance concrete.
TABLE 2
Test case
The ultra-high performance concrete prepared in each example and comparative example was subjected to performance test.
The bending strength testing method comprises the following steps: reference is made to GB 50081-2019 for a bending performance test using an MTS Landmark type tester manufactured by Meter Industrial systems, inc. of America. The results are shown in Table 3.
The compressive strength testing method comprises the following steps: reference is made to GB 50081-2019 for testing using an INSTRON model 1346 universal materials testing machine manufactured by INSTRON corporation, england. The results are shown in Table 3.
The pull-out load test method comprises the following steps: reference "Wu Zemei. Multiscale study of interfacial adhesion properties of fibers to matrix in ultra-high performance concrete [ D ]. University of henna, 2017." uniaxial tensile properties were tested using an MTS Landmark tester manufactured by american mest industrial systems limited.
Fig. 3 shows a plot of pull-out load-slip comparison of the steel fibers of inventive example 1 and comparative examples 1-2 in ultra-high performance concrete.
The bending load testing method comprises the following steps: reference is made to GB 50081-2019 for a bending performance test using an MTS Landmark type tester manufactured by Meter Industrial systems, inc. of America.
FIG. 4 shows a bending load-deflection comparison graph of ultra-high performance concrete of inventive example 1 and comparative examples 1-2.
TABLE 3 Table 3
| Flexural Strength (MPa) | Compressive strength (MPa) | |
| Example 1 | 52.5 | 165.8 |
| Example 2 | 50.7 | 159.3 |
| Example 3 | 51.9 | 162.1 |
| Example 4 | 48.7 | 143.8 |
| Example 5 | 39.8 | 130.6 |
| Comparative example 1 | 35.7 | 131.7 |
| Comparative example 2 | 39.3 | 129.5 |
| Comparative example 3 | 44.2 | 134.6 |
| Comparative example 4 | 39.9 | 131.2 |
| Comparative example 5 | 43.1 | 137.6 |
As can be seen from the results in Table 3, the ultra-high performance concrete prepared in examples 1 to 4 provided by the present invention has significantly better flexural strength and compressive strength than the comparative examples. In addition, in example 5, under the condition of 0.5% by volume of the mixing amount, the prepared ultra-high performance concrete has the effect equivalent to that of the comparative example (the volume mixing amount of the steel fiber is 2%) in terms of mechanical strength indexes such as bending resistance, compression resistance and the like.
Therefore, under the condition of not reducing the mechanical property, the threaded steel fiber reinforced ultra-high performance concrete provided by the invention can obviously reduce the consumption of steel fibers, reduce the production cost and has higher economic value than the traditional steel fiber reinforced concrete system.
As can be seen from fig. 3, the threaded section steel fiber has more excellent interfacial adhesion with the matrix than the conventional straight fiber and end hook fiber. In particular, the peak extraction load between the thread-shaped steel fiber and the matrix can respectively reach 8.31 and 1.76 times of that between the traditional straight fiber and the end hook fiber, and the peak load corresponding sliding between the thread-shaped steel fiber and the matrix can respectively reach 1.63 and 2.59 times of that between the traditional straight fiber and the end hook fiber.
As can be seen from fig. 4, the ultra-high performance concrete reinforced by the threaded steel fiber has better bending resistance under the condition of the same fiber volume doping amount, and the ultra-high performance concrete reinforced by the threaded steel fiber has more excellent deformability. In particular, the flexural strength of the ultra-high performance concrete after being reinforced by the threaded steel fibers can respectively reach 1.47 times and 1.34 times of that of the traditional straight fiber and end hook fiber reinforced test piece.
In conclusion, the ultra-high performance concrete provided by the invention has stronger adhesion with the matrix and more excellent mechanical property and deformation property. Has good economic benefit and wider application prospect.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.
Claims (10)
1. A composition for ultra-high performance concrete, characterized in that the composition comprises: cement, silica fume, fine aggregate, threaded steel fibers, a water reducing agent and water;
the content of the silica fume is 20-40 parts by weight, the content of the fine aggregate is 80-120 parts by weight, the content of the water reducing agent is 2-3 parts by weight, and the content of the water is 18-24 parts by weight relative to 100 parts by weight of the cement;
the volume doping amount of the threaded steel fiber is 0.5-3% based on the total volume of all components except the threaded steel fiber in the composition;
the threaded steel fiber is formed by spirally winding at least two steel wires, the average diameter d of the threaded steel fiber is 0.2-0.4mm, and the tensile strength is 1100-1600MPa;
the specific surface area of the silica fume is more than or equal to 18000m 2 /kg，SiO 2 The content is more than or equal to 95wt percent, and the 28d activity index is more than or equal to 105 percent.
2. The composition of claim 1, wherein the threaded steel fibers are formed by spiral winding of 7 strands of steel wire.
3. The composition of claim 1 or 2, wherein the threaded steel fibers have an average length of 10-18mm; and/or the number of the groups of groups,
the anchoring length of the threaded steel fiber in the ultra-high performance concrete is 40d-60d.
4. A composition according to any one of claims 1 to 3, wherein the cement is selected from at least one of po 42.5, p o 52.5; and/or the number of the groups of groups,
the fine aggregate is sand, and the average grain diameter of the sand is not more than 2.36mm; and/or the number of the groups of groups,
the water reducer is a polycarboxylate water reducer, the water reducing rate of the polycarboxylate water reducer is more than or equal to 25%, and the solid content is 20-25wt%.
5. A method for preparing ultra-high performance concrete, characterized in that it is carried out using the components of the composition according to any one of claims 1 to 4, comprising:
(1) First mixing the components in the component A to obtain a mixture I; the component A contains cement, silica fume, fine aggregate, a water reducing agent and water;
(2) Carrying out second mixing on the mixture I and the threaded steel fibers to obtain a mixture II;
(3) Sequentially carrying out pouring molding treatment and maintenance treatment on the mixture II to obtain the ultra-high performance concrete;
the amount of the silica fume is 20-40 parts by weight, the amount of the fine aggregate is 80-120 parts by weight, the amount of the water reducing agent is 2-3 parts by weight, and the amount of the water is 18-24 parts by weight relative to 100 parts by weight of the cement;
in the step (1), the specific surface area of the silica fume is more than or equal to 18000m 2 /kg，SiO 2 The content is more than or equal to 95wt percent, and the 28d activity index is more than or equal to 105 percent;
in the step (2), the volume doping amount of the threaded steel fibers is 0.5-3% based on the volume of the mixture I;
in the step (2), the threaded steel fiber is formed by spirally winding at least two steel wires, and the average diameter d of the threaded steel fiber is 0.2-0.4mm, and the tensile strength is 1100-1600MPa.
6. The process according to claim 5, wherein in step (1), the mixture I has a water to gel ratio of 0.16 to 0.20:1, a step of; and/or the number of the groups of groups,
in step (1), the first mixing conditions include: stirring speed is 55-70rpm, and stirring time is 300-360s; and/or the number of the groups of groups,
the method of step (1) comprises: and firstly, carrying out first contact on the water reducer and the water to obtain an intermediate product, and then carrying out first mixing on the intermediate product and the rest components in the component A.
7. The method of claim 5 or 6, wherein in step (2), the conditions of the second mixing include: the stirring speed is 110-130rpm, and the stirring time is 240-300s.
8. The method according to any one of claims 5 to 7, wherein in step (3), the operation of curing treatment comprises: sequentially carrying out first curing treatment and second curing treatment on the concrete block obtained after casting molding treatment; the temperature of the first curing treatment is 18-22 ℃, the time is 24-48h, and the relative humidity is more than or equal to 95%; the second curing treatment is carried out in water, the temperature is 18-22 ℃ and the time is 26-30d.
9. Ultra-high performance concrete prepared by the method of any one of claims 5-8.
10. Use of the ultra-high performance concrete of claim 9 in construction materials.
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