CN116354664A - Composition for sprayed concrete, preparation method and application thereof - Google Patents
Composition for sprayed concrete, preparation method and application thereof Download PDFInfo
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- 239000011378 shotcrete Substances 0.000 title claims abstract description 73
- 239000000203 mixture Substances 0.000 title claims abstract description 53
- 238000002360 preparation method Methods 0.000 title abstract description 5
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 158
- 239000010959 steel Substances 0.000 claims abstract description 158
- 239000000835 fiber Substances 0.000 claims abstract description 125
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 64
- 239000010881 fly ash Substances 0.000 claims abstract description 34
- 239000004568 cement Substances 0.000 claims abstract description 27
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 27
- 238000004804 winding Methods 0.000 claims abstract description 19
- 239000004566 building material Substances 0.000 claims abstract description 6
- -1 accelerator Substances 0.000 claims abstract description 5
- 238000002156 mixing Methods 0.000 claims description 34
- 238000003756 stirring Methods 0.000 claims description 31
- 238000000034 method Methods 0.000 claims description 22
- 239000004576 sand Substances 0.000 claims description 14
- 239000002245 particle Substances 0.000 claims description 12
- 239000004575 stone Substances 0.000 claims description 11
- 230000000694 effects Effects 0.000 claims description 8
- 239000003054 catalyst Substances 0.000 claims description 6
- 239000013067 intermediate product Substances 0.000 claims description 6
- 229920005646 polycarboxylate Polymers 0.000 claims description 4
- 238000004873 anchoring Methods 0.000 claims description 2
- 239000007787 solid Substances 0.000 claims description 2
- 239000011159 matrix material Substances 0.000 abstract description 15
- 230000008901 benefit Effects 0.000 abstract description 5
- 230000000052 comparative effect Effects 0.000 description 17
- 239000000463 material Substances 0.000 description 12
- 239000004567 concrete Substances 0.000 description 11
- 238000012360 testing method Methods 0.000 description 9
- 238000005520 cutting process Methods 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 238000005452 bending Methods 0.000 description 4
- 238000012545 processing Methods 0.000 description 3
- 230000002787 reinforcement Effects 0.000 description 3
- 239000011435 rock Substances 0.000 description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- 239000011398 Portland cement Substances 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 239000012783 reinforcing fiber Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 229920002748 Basalt fiber Polymers 0.000 description 1
- 244000208060 Lawsonia inermis Species 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000009415 formwork Methods 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 229910052602 gypsum Inorganic materials 0.000 description 1
- 239000010440 gypsum Substances 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000013001 point bending Methods 0.000 description 1
- 229920002239 polyacrylonitrile Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000011150 reinforced concrete Substances 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000012876 topography Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 239000011374 ultra-high-performance concrete Substances 0.000 description 1
- 239000010878 waste rock Substances 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
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00034—Physico-chemical characteristics of the mixtures
- C04B2111/00146—Sprayable or pumpable mixtures
- C04B2111/00155—Sprayable, i.e. concrete-like, materials able to be shaped by spraying instead of by casting, e.g. gunite
-
- 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 sprayed concrete, a preparation method and application thereof, wherein the composition comprises the following components: cement, fly ash, coarse aggregate, fine aggregate, stranded steel fiber, accelerator, water reducer and water, wherein the stranded steel fiber is formed by spirally winding at least two bundles of steel ropes, and the steel ropes are formed by spirally winding at least two strands of steel wires; the average diameter d of the stranded steel fibers is 0.5-0.8mm, and the tensile strength is 1200-1600MPa; the sprayed 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 sprayed concrete, a preparation method and application thereof.
Background
The sprayed concrete is a concrete which is formed by spraying concrete mixture to a sprayed surface at a high speed by means of a spraying machine under the action of air pressure and compacting instantly. Compared with common concrete, the sprayed concrete has higher early strength due to the incorporation of the accelerator, and has the advantages of simple and convenient construction, no formwork support and the like. Currently, shotcrete has been widely applied in the fields of foundation pit slope support, tunnel engineering, underground engineering, structural reinforcement and reconstruction, and the like, and in particular, a tunnel support system mainly based on shotcrete has become a main development trend of future tunnel lining structure design and construction.
The crack resistance and the deformability of the sprayed concrete can be obviously improved by doping a certain volume of fibers into the sprayed concrete. Numerous engineering practices have shown that the addition of reinforcing fibers can greatly increase the failure displacement of shotcrete and that its failure mode will also be converted from brittle fracture failure to ductile failure. Currently, the fibers commonly used to reinforce shotcrete are: steel fibers, basalt fibers, imitation steel fibers, polypropylene fibers, glass fibers, polyacrylonitrile fibers and the like. Among them, steel fiber has been the mainstream reinforcing fiber of shotcrete because of its advantages of good deformability, excellent mechanical properties, and easy mass production. And the wavy steel fibers and the end hook steel fibers are widely applied in China.
CN114956710a discloses a high-performance fly ash sprayed concrete for mudstone tunnels and a preparation method thereof, wherein the high-performance fly ash sprayed concrete comprises 372 parts by mass of cement, 929 parts by mass of medium sand, 929 parts by mass of broken stone, 177 parts by mass of water, 4.13 parts by mass of water reducer and 11.6-24.78 parts by mass of alkali-free liquid accelerator, the volume ratio of the steel fiber is 1-2%, and the mixed admixture comprises 25 parts by mass of fly ash, 10.5 parts by mass of slag powder and 5.5 parts by mass of gypsum. Although the prior art can improve the mechanical property of the traditional sprayed concrete to a certain extent, the prior art has the defects of poor fiber reinforcement effect, low utilization rate of steel fiber property and poor toughness of the sprayed concrete.
For the wavy steel fiber and the end hook type steel fiber applied to sprayed concrete, the geometric shape characteristics of the wavy steel fiber and the end hook type steel fiber are affected, the geometric shape of the wavy steel fiber and the end hook type steel fiber is irregular, and therefore the fiber is obviously agglomerated in the concrete and is not easy to wind and scatter under the condition of higher mixing amount, and the flowing performance of fresh concrete is affected. In addition, the bonding performance between the two steel fibers and the matrix is poor, and the energy consumption cracking resistance effect is mainly shown in the initial stage of crack growth, so that the toughness of the reinforced sprayed concrete is limited.
Therefore, it is necessary to develop a shotcrete which has both good mechanical properties and toughness and can improve the agglomeration of fibers based on the modification of the fiber geometry.
Disclosure of Invention
The invention aims to provide sprayed 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 shotcrete, comprising: cement, fly ash, coarse aggregate, fine aggregate, stranded steel fibers, accelerator, water reducer and water;
the cement comprises, by weight, relative to 300 parts of cement, 40-160 parts of fly ash, 800-1000 parts of coarse aggregate, 800-1000 parts of fine aggregate, 12-32 parts of accelerator, 5-10 parts of water reducer and 120-200 parts of water;
taking the total volume of all components except stranded steel fibers in the composition as a reference, the volume doping amount of the stranded steel fibers is 0.5-1%;
the stranded steel wire type steel fibers are formed by spirally winding at least two bundles of steel ropes, and the steel ropes are formed by spirally winding at least two strands of steel wires; the average diameter d of the stranded steel fibers is 0.5-0.8mm, and the tensile strength is 1200-1600MPa;
the specific surface area of the fly ash is more than or equal to 400m 2 The activity index of the catalyst is more than or equal to 90 percent, the loss on ignition is less than or equal to 5 weight percent, and the water demand ratio is less than or equal to 95 percent.
In a second aspect the invention provides a method of preparing shotcrete using the components of the composition according to the first aspect, comprising:
(1) First mixing the components in the component A to obtain a mixture I; the component A contains cement, fly ash, coarse aggregate, fine aggregate, a water reducer and water;
(2) Carrying out second mixing on the mixture I and stranded steel fibers to obtain a mixture II;
(3) Thirdly mixing the mixture II with an accelerator to obtain the sprayed concrete;
the cement comprises, by weight, 300 parts of cement, 40-160 parts of fly ash, 800-1000 parts of coarse aggregate, 800-1000 parts of fine aggregate, 12-32 parts of accelerator, 5-10 parts of water reducer and 120-200 parts of water;
in the step (1), the specific surface area of the fly ash is more than or equal to 400m 2 The activity index of the catalyst is more than or equal to 90 percent, the loss on ignition is less than or equal to 5 weight percent, and the water demand ratio is less than or equal to 95 percent;
in the step (2), the volume doping amount of the stranded steel fibers is 0.5-1% based on the volume of the mixture I;
in the step (2), the stranded steel fibers are formed by spirally winding at least two bundles of steel ropes, and the steel ropes are formed by spirally winding at least two strands of steel wires; the average diameter d of the stranded steel fiber is 0.5-0.8mm, and the tensile strength is 1200-1600MPa.
A third aspect of the present invention provides shotcrete prepared by the method of the second aspect described above.
A fourth aspect of the invention provides the use of shotcrete as described in the third aspect above 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 end hook type or wave type reinforced concrete, the twisted steel fiber provided by the invention can obviously improve the interface transition area of the fiber-matrix and further improve the pulling resistance in the matrix due to the special geometric structure.
(2) Compared with the traditional steel fiber reinforced sprayed concrete, the stranded steel fiber reinforced sprayed concrete provided by the invention has excellent fiber-matrix bonding performance, and has better strength and limited deformability, higher toughness and wide application prospect under the condition of the same steel fiber volume doping amount.
(3) The stranded steel fiber provided by the invention is preferably obtained from commercial steel strands, and is preferably prepared by a conventional commercial full-automatic cutting machine, so that the mass production of the stranded steel fiber is realized.
Drawings
FIG. 1 is a schematic view of the surface morphology and cross section of a stranded steel fiber;
FIG. 2 is a plot of pull-out load versus slip for steel fibers of inventive example 1 and comparative examples 1-2 in shotcrete;
FIG. 3 is a graph of three-point bending load-deflection contrast for steel fibers of examples 1-3 and comparative examples 1-2 of the present invention in shotcrete.
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.
Unless otherwise specified, 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 shotcrete, comprising: cement, fly ash, coarse aggregate, fine aggregate, stranded steel fibers, accelerator, water reducer and water;
the cement comprises, by weight, relative to 300 parts of cement, 40-160 parts of fly ash, 800-1000 parts of coarse aggregate, 800-1000 parts of fine aggregate, 12-32 parts of accelerator, 5-10 parts of water reducer and 120-200 parts of water;
taking the total volume of all components except stranded steel fibers in the composition as a reference, the volume doping amount of the stranded steel fibers is 0.5-1%;
the stranded steel wire type steel fibers are formed by spirally winding at least two bundles of steel ropes, and the steel ropes are formed by spirally winding at least two strands of steel wires; the average diameter d of the stranded steel fibers is 0.5-0.8mm, and the tensile strength is 1200-1600MPa;
the specific surface area of the fly ash is more than or equal to 400m 2 The activity index of the catalyst is more than or equal to 90 percent, the loss on ignition is less than or equal to 5 weight percent, and the water demand ratio is less than or equal to 95 percent.
The water demand ratio of the fly ash disclosed by the invention is as follows: and the fluidity of the test contrast gum sand is adjusted to be within 145-155 mm, and the fluidity of the test gum sand and the contrast gum sand is measured according to GB/T2419-2016, and the water adding amount ratio when the two reach the specified fluidity range is the water requirement ratio of the fly ash.
The inventor of the invention discovers in the research that when the volume doping amount of the stranded steel fiber is 0.5-1%, the bonding performance of the stranded steel fiber and a matrix is better, and the prepared sprayed concrete has more excellent mechanical property and deformation property.
The average diameter d of the stranded steel fiber refers to the average diameter of the circumscribed circle of the cross section pattern of the stranded steel fiber.
The inventor of the invention discovers in the research that when the average diameter of the stranded steel fiber is 0.5-0.8mm, the bonding performance of the stranded steel fiber and a matrix is better, and the prepared sprayed concrete has more excellent mechanical property and deformation property.
Preferably, the stranded steel fibers are formed by 7 bundles of steel cords helically wound, and the steel cords are formed by 7 strands of steel wires helically wound.
Preferably, the average length of the stranded steel fibers is 24-60mm.
Preferably, the anchoring length of the stranded steel fibers in the sprayed concrete is 40d-60d.
The middle part in fig. 1 shows the surface topography of the stranded wire type steel fiber preferably provided by the present invention, and the upper left part in fig. 1 shows a schematic cross-sectional view of the stranded wire type steel fiber preferably provided by the present invention, and as can be seen from fig. 1, the stranded wire type steel fibers preferably provided by the present invention are assembled by 7 bundles of steel wire spiral-wound, and the steel wire is formed by 7 strands of steel wire spiral-wound, the average diameter of the stranded wire type steel fiber is represented by d, and the average length is represented by lf; the twisted steel fiber has a plum blossom-shaped cross section, and obvious mechanical engagement teeth exist on the surface, so that the twisted steel fiber has better bonding performance with the sprayed concrete matrix.
The spiral winding angle of the steel wire and the steel wire of the stranded 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 specific processing mode of the stranded steel fiber is not particularly limited, a person skilled in the art can select the specific processing mode according to the technical means known in the art, the preferred specific embodiment is provided by the invention, and the stranded steel fiber 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 fly ash of the invention is a secondary fly ash, and the fly ash contains K 2 O、Na 2 O、CaO、MgO、Fe 2 O 3 、Al 2 O 3 、SiO 2 And SO 3 The content of each component is 39-40wt% of SiO based on the total weight of the fly ash 2 3.05-3.25wt% CaO,29-31wt% Al 2 O 3 3.7 to 3.8wt% of Fe 2 O 3 0.3-0.4wt% MgO,0.8-0.85wt% SO 3 0.3 to 0.35wt% of K 2 O,0.4-0.45wt% Na 2 O。
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 coarse aggregate is crushed stone, and the average particle size of the crushed stone is 5-10mm.
The source of the crushed stone is not particularly limited in the present invention as long as the average particle diameter requirement of the present invention can be satisfied, and those skilled in the art can select according to the crushed stone materials existing in the art.
Preferably, the fine aggregate is sand, and the fineness modulus of the fine aggregate is 3.0 to 2.3.
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.
The aggregate plays roles of filling and framework in the concrete, is in loose granules, improves the durability and stability of the concrete, and is divided into coarse aggregate and fine aggregate according to the particle size. Coarse aggregate refers to sand, stone that acts as a skeleton in concrete and has an average particle size of greater than 4.75mm. The fine aggregate is a building material having an average particle diameter of 4.75mm or less, as opposed to the coarse aggregate.
The common coarse aggregate in concrete is composed of broken stone and pebble, wherein the broken stone is rock particles with the grain size larger than 4.75mm, which are produced by mechanically crushing and sieving natural rock, pebble or mine waste rock. Pebbles are rock particles with a particle size greater than 4.75mm that are formed by natural weathering, water flow handling and sorting, and stacking. The inventors of the present invention found that the mechanical properties and deformation properties of the shotcrete prepared using crushed stone having an average particle size of 5 to 10mm as a coarse aggregate were more excellent.
The granular loose materials with skeleton or filling function of the common fine aggregate in the concrete have average grain diameter below 4.75mm, and can be produced by an impact crusher or a novel efficient sand making machine, and can also be natural sand. The inventors of the present invention found that the mechanical properties and deformation properties of the shotcrete prepared using sand having a fineness modulus of 3.0 to 2.3 as a fine aggregate were more excellent.
Preferably, the accelerator is an alkali-free accelerator.
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 shotcrete using the components of the composition of the first aspect described above, comprising:
(1) First mixing the components in the component A to obtain a mixture I; the component A contains cement, fly ash, coarse aggregate, fine aggregate, a water reducer and water;
(2) Carrying out second mixing on the mixture I and stranded steel fibers to obtain a mixture II;
(3) Thirdly mixing the mixture II with an accelerator to obtain the sprayed concrete;
the cement comprises, by weight, 300 parts of cement, 40-160 parts of fly ash, 800-1000 parts of coarse aggregate, 800-1000 parts of fine aggregate, 12-32 parts of accelerator, 5-10 parts of water reducer and 120-200 parts of water;
in step (1), theThe specific surface area of the fly ash is more than or equal to 400m 2 The activity index of the catalyst is more than or equal to 90 percent, the loss on ignition is less than or equal to 5 weight percent, and the water demand ratio is less than or equal to 95 percent;
in the step (2), the volume doping amount of the stranded steel fibers is 0.5-1% based on the volume of the mixture I;
in the step (2), the stranded steel fibers are formed by spirally winding at least two bundles of steel ropes, and the steel ropes are formed by spirally winding at least two strands of steel wires; the average diameter d of the stranded steel fiber is 0.5-0.8mm, and the tensile strength is 1200-1600MPa.
Preferably, in step (1), the water-gel ratio of the mixture I is between 0.40 and 0.45:1. the water-cement ratio refers to the ratio of the weight of water to the total weight of cement and fly ash in the mixture I.
Preferably, in step (1), the conditions of the first mixing include: the stirring speed is 55-70rpm and the stirring time is 180-240s.
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 components except for an accelerator, a water reducing agent and 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: first, the stranded steel fibers are continuously added to the system formed with the mixture I under the first stirring condition for not more than 90 seconds, and then the second mixing is performed. The inventor of the invention finds that under the preferable condition, the bonding performance of the stranded steel fiber and the matrix is better, and the prepared sprayed concrete has more excellent mechanical property and deformation property.
Preferably, in step (2), the conditions of the second mixing include: the stirring speed is 110-130rpm, and the stirring time is 60-90s.
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 addition of the stranded steel fibers is completed.
Preferably, in step (3), the conditions of the third mixing include: the stirring speed is 55-70rpm, and the stirring time is 30-60s.
As previously described, a third aspect of the present invention provides shotcrete prepared by the method of the second aspect.
As previously mentioned, a fourth aspect of the invention provides the use of the shotcrete according to the third aspect in a building material.
The invention will be described in detail below by way of examples. In the following embodiments, a fully-automatic numerical control steel wire rope cutting machine is adopted to cut steel fiber raw materials;
the stranded steel fibers formed by spirally winding 7 bundles of steel cords, and the steel cords formed by spirally winding 7 strands of steel wires, are referred to as: 7*7 stranded steel fibers;
the stranded wire type steel fiber formed by spirally winding 3 bundles of steel wire, and the steel wire formed by spirally winding 3 bundles of steel wire, is referred to as: 3*3 stranded steel fibers;
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, fly ash, coarse aggregate and fine aggregate into a stirrer and stirring at 60rpm for 210s to obtain a mixed material, uniformly mixing a water reducer and water, and then carrying out first mixing (stirring speed is 60rpm and time is 210 s) with the mixed material to obtain a mixture I;
(2) Continuously and uniformly adding stranded steel fibers into a system formed by the stranded 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 80 seconds) to obtain a mixture II;
(3) And thirdly mixing the mixture II with an accelerator (stirring speed is 60rpm, time is 45 s) to obtain sprayed concrete.
Example 2
The procedure was followed, similar to that of example 1, except that: and (3) adjusting the volume doping amount of the stranded steel fiber I in the step (2) from 0.75% to 0.5%.
The sprayed concrete is prepared.
Example 3
The procedure was followed, similar to that of example 1, except that: and (3) adjusting the volume doping amount of the stranded steel fiber I in the step (2) from 0.75% to 1.0%.
The sprayed concrete is prepared.
Example 4
(1) Placing cement, fly ash, coarse aggregate and fine aggregate in a stirrer and stirring at 55rpm for 210s 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 stirring time is 180 s) with the mixed material to obtain a mixture I;
(2) Continuously and uniformly adding stranded steel fibers into a system formed by the stranded 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 110rpm, and the time is 60 seconds) to obtain a mixture II; and (5) obtaining the sprayed concrete.
(3) The mixture II was mixed with an accelerator for a third time (stirring rate: 55rpm, time: 30 s) to obtain shotcrete.
Example 5
(1) Placing cement, fly ash, coarse aggregate and fine aggregate into a stirrer and stirring at 70rpm for 210s 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 stirring time is 240 s) with the mixed material to obtain a mixture I;
(2) Continuously and uniformly adding stranded steel fibers into a system formed by the stranded 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 130rpm, and the time is 90 seconds) to obtain a mixture II;
(3) And thirdly mixing the mixture II with an accelerator (stirring speed is 70rpm, time is 60 s) to obtain sprayed concrete.
Example 6
This example was carried out using a procedure similar to example 1, except that: and replacing the stranded steel fiber I with the stranded steel fiber II with the equal volume doping amount.
The sprayed concrete is prepared.
Example 7
This example was carried out using a procedure similar to example 1, except that: in this embodiment, the time for adding the stranded steel fiber in the step (2) is controlled to be 120s, specifically:
step (2): the twisted steel fiber was continuously and uniformly added to the system formed with the mixture I, and the addition time was controlled to be 120s, and then a second mixing (stirring rate of 120rpm, time 210 s) was performed to obtain a mixture II.
The sprayed concrete is prepared.
Comparative example 1
This comparative example was carried out using a procedure similar to that of example 1, substituting stranded steel fibers I with end hook steel fibers of equal volume loading.
The sprayed concrete is prepared.
Comparative example 2
This comparative example was conducted using a procedure similar to example 1, except that: and replacing the stranded steel fiber I with the wavy steel fiber with equal volume doping amount.
The sprayed concrete is prepared.
Comparative example 3
This comparative example was conducted using a procedure similar to example 1, except that: the volume doping amount of the stranded steel fiber I is adjusted from 0.75% to 1.5%.
The sprayed concrete is prepared.
Comparative example 4
This comparative example was conducted using a procedure similar to example 1, except that: the fly ash I is replaced by the fly ash II with equal weight parts.
The sprayed concrete is prepared.
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.
The sprayed concrete is prepared.
TABLE 2
Test case
The sprayed 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 2.
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 2.
The pull-out load test method comprises the following steps: reference is made to "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. 2 shows a plot of pull-out load versus slip for steel fibers of inventive example 1 and comparative examples 1-2 in shotcrete.
FIG. 3 shows a graph of bending load-deflection contrast for sprayed concrete of examples 1-3 of the present invention versus comparative examples 1-2.
TABLE 3 Table 3
As can be seen from the results in Table 3, the sprayed concrete prepared by the technical scheme provided by the invention has significantly better flexural strength and compressive strength than the comparative examples.
As can be seen from FIG. 2, compared with the traditional straight steel fibers and end hook fibers, the stranded steel fibers provided by the invention have more excellent interface bonding performance with the sprayed concrete matrix. In particular, the pulling resistance between the stranded steel fiber and the sprayed concrete matrix can be respectively 6.51 and 1.86 times of that of the traditional straight steel fiber and the end hook steel fiber, and the peak load corresponding sliding between the threaded steel fiber and the matrix can be respectively 1.93 and 2.84 times of that of the traditional straight steel fiber and the end hook steel fiber.
As can be seen from FIG. 3, after the sprayed concrete is reinforced by the stranded steel fibers provided by the invention under the condition of the same fiber volume doping amount, the flexural resistance of the sprayed concrete is obviously better than that of a sprayed concrete test piece reinforced by the traditional straight steel fibers and end hook type steel fibers. In particular, the bending strength of the sprayed concrete after 28 days of reinforcement by the threaded steel fibers can respectively reach 1.47 times and 1.34 times of that of the traditional straight steel fiber and end hook steel fiber reinforced test piece.
In conclusion, the sprayed 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 shotcrete, the composition comprising: cement, fly ash, coarse aggregate, fine aggregate, stranded steel fibers, accelerator, water reducer and water;
the cement comprises, by weight, relative to 300 parts of cement, 40-160 parts of fly ash, 800-1000 parts of coarse aggregate, 800-1000 parts of fine aggregate, 12-32 parts of accelerator, 5-10 parts of water reducer and 120-200 parts of water;
taking the total volume of all components except stranded steel fibers in the composition as a reference, the volume doping amount of the stranded steel fibers is 0.5-1%;
the stranded steel wire type steel fibers are formed by spirally winding at least two bundles of steel ropes, and the steel ropes are formed by spirally winding at least two strands of steel wires; the average diameter d of the stranded steel fibers is 0.5-0.8mm, and the tensile strength is 1200-1600MPa;
the specific surface area of the fly ash is more than or equal to 400m 2 The activity index of the catalyst is more than or equal to 90 percent, the loss on ignition is less than or equal to 5 weight percent, and the water demand ratio is less than or equal to 95 percent.
2. The composition of claim 1, wherein the stranded steel fibers are formed from 7 bundles of steel cord helically wound and the steel cord is formed from 7 strands of steel cord helically wound.
3. The composition of claim 1 or 2, wherein the stranded steel fibers have an average length of 24-60mm; and/or the number of the groups of groups,
the anchoring length of the stranded steel fibers in the sprayed 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 coarse aggregate is crushed stone, and the average particle size of the crushed stone is 5-10mm; and/or the number of the groups of groups,
the fine aggregate is sand, and the fineness modulus of the fine aggregate is 3.0-2.3; and/or the number of the groups of groups,
the accelerator is an alkali-free accelerator; 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 shotcrete, 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, fly ash, coarse aggregate, fine aggregate, a water reducer and water;
(2) Carrying out second mixing on the mixture I and stranded steel fibers to obtain a mixture II;
(3) Thirdly mixing the mixture II with an accelerator to obtain the sprayed concrete;
the cement comprises, by weight, 300 parts of cement, 40-160 parts of fly ash, 800-1000 parts of coarse aggregate, 800-1000 parts of fine aggregate, 12-32 parts of accelerator, 5-10 parts of water reducer and 120-200 parts of water;
in the step (1), the specific surface area of the fly ash is more than or equal to 400m 2 The activity index of the catalyst is more than or equal to 90 percent, the loss on ignition is less than or equal to 5 weight percent, and the water demand ratio is less than or equal to 95 percent;
in the step (2), the volume doping amount of the stranded steel fibers is 0.5-1% based on the volume of the mixture I;
in the step (2), the stranded steel fibers are formed by spirally winding at least two bundles of steel ropes, and the steel ropes are formed by spirally winding at least two strands of steel wires; the average diameter d of the stranded steel fiber is 0.5-0.8mm, and the tensile strength is 1200-1600MPa.
6. The process according to claim 5, wherein in step (1), the water-gel ratio of the mixture I is from 0.40 to 0.45:1, 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 180-240s; 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 60-90s.
8. The method of any one of claims 5-7, wherein in step (3), the third mixing conditions comprise: the stirring speed is 55-70rpm, and the stirring time is 30-60s.
9. A shotcrete produced by the method of any one of claims 5 to 8.
10. Use of the shotcrete according to claim 9 in building materials.
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