CN112851266A - Ultrahigh-performance concrete with high fiber dispersity and orientation degree and preparation method thereof - Google Patents
Ultrahigh-performance concrete with high fiber dispersity and orientation degree and preparation method thereof Download PDFInfo
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- CN112851266A CN112851266A CN202110238107.XA CN202110238107A CN112851266A CN 112851266 A CN112851266 A CN 112851266A CN 202110238107 A CN202110238107 A CN 202110238107A CN 112851266 A CN112851266 A CN 112851266A
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- 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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- 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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Abstract
The ultra-high performance concrete with high fiber dispersity and orientation degree comprises the following raw materials: cement, silica fume, fine aggregate, polycarboxylate water reducing agent, fiber and water; the mass part ratio of the cement to the silica fume to the polycarboxylate water reducing agent is 75-95: 5-25: 3-5; the volume mixing amount of the fiber in the ultra-high performance concrete is 1-5%; the mass of the water is 0.05-0.10 times of the sum of the mass of the cement, the silica fume and the fine aggregate; after the raw materials of the ultra-high performance concrete are mixed, the slump expansion degree is 260-280 mm. The invention also comprises a preparation method of the ultra-high performance concrete with high fiber dispersity and orientation degree. The ultrahigh-performance concrete has good mechanical property and simple preparation method; the raw materials are easy to obtain and have relatively low price.
Description
Technical Field
The invention relates to an ultra-high performance concrete and a preparation method thereof, in particular to an ultra-high performance concrete doped with fibers and a preparation method thereof.
Background
Infrastructure construction extends to areas such as deep open sea, high saline and alkaline, high temperature extremely cold, has proposed the demand of "faster (construction progress), higher (height length), stronger (intensity toughness), more of a specified duration (durability)" to concrete material. Ultra-high performance concrete (UHPC) is the most ideal material meeting the requirements so far, and has wide application prospect in the fields of bridge engineering, anti-explosion structures, thin-wall structures, architectural decoration, ocean engineering, repair and reinforcement engineering and the like.
Because the water-cement ratio of the ultra-high performance concrete is extremely low, the mixing amount of fine particles such as cement, silica fume and the like is large, the high-efficiency water reducing agent is high in dosage and low in adsorption amount, and the gap liquid is high in viscosity, the freshly mixed ultra-high performance concrete is large in viscosity, large in stirring and pumping resistance, easy to agglomerate in the pouring forming process, and easy to introduce air bubbles, so that the mechanical property is damaged. In order to ensure the excellent mechanical properties of the ultra-high performance concrete, the freshly mixed ultra-high performance concrete is required to have good stability and appropriate plastic viscosity. At present, the viscosity-reducing admixture mainly adopts a high molecular polymer viscosity modifier, such as cellulose ether derivatives, anionic polyacrylamide and the like. By controlling the water migration in the fresh concrete, the segregation of the concrete is reduced, the water retention is improved, the particle flocculation is improved, and the yield stress and the plastic viscosity are improved. However, the use of both water reducing agents and viscosity modifiers has a positive and negative counteracting effect on the rheological parameters of the fresh cement-based material, and the two may have chemical incompatibility problems. Meanwhile, the materials are limited in narrow space, and under the action of a complex microenvironment, the discreteness of test results is large due to the change of raw material compositions and preparation process parameters.
At present, relevant patents related to viscosity reduction technology of high-strength and ultra-high-performance concrete exist, for example, CN103145360A discloses an ultra-high-performance concrete viscosity regulator, and the viscosity reduction effect of the regulator on the concrete is considered from the aspects of powder particle size and gel material grading; CN103613348A discloses ultra-high strength concrete with low viscosity and easy pumping and with the strength of 120MPa, which solves the problems of high viscosity and the like in the concrete pumping process; CN110451885A discloses a viscosity reduction regulation and control method for high-strength and ultrahigh-pumping concrete based on material particle size matching, which can remarkably improve the pumpability and stability of the concrete. However, the above technical solutions only consider the pumping performance and fresh mixing performance of the concrete, and there is no obvious improvement on the fiber distribution in the ultra-high performance concrete.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects in the prior art and providing the ultra-high performance concrete with high fiber dispersity and orientation degree and the preparation method thereof.
The technical scheme adopted by the invention for solving the technical problems is as follows: the ultra-high performance concrete with high fiber dispersion degree and orientation degree comprises the following raw materials: cement, silica fume, fine aggregate, polycarboxylate water reducing agent, fiber and water; the mass part ratio of the cement to the silica fume to the polycarboxylate water reducing agent is 75-95: 5-25: 3-5; the volume mixing amount of the fiber in the ultra-high performance concrete is 1-5%; the mass of the water is 0.05-0.10 times of the sum of the mass of the cement, the silica fume and the fine aggregate; after the raw materials of the ultra-high performance concrete are mixed, the slump expansion degree is 260-280 mm.
Preferably, the mass part ratio of the cement to the silica fume to the polycarboxylate water reducing agent is 80-90: 10-20: 3-5.
Preferably, the volume mixing amount of the fiber in the ultra-high performance concrete is 2-3%.
Preferably, the mass of the water is 0.06-0.08 times of the sum of the mass of the cement, the silica fume and the fine aggregate.
Preferably, the cement is portland cement or ordinary portland cement.
Preferably, the silica fume has a specific surface area of 10000m2More than kg.
Preferably, the mass of the fine aggregate is 0.9-1.1 times of the sum of the mass of the cement and the mass of the silica fume.
Preferably, the fine aggregate is natural river sand and/or machine-made sand, and the fineness modulus of the fine aggregate is 2.2-1.6.
More preferably, the natural river sand accounts for 70-75 wt% of the fine aggregate, and the rest fine aggregate is machine-made sand.
Preferably, the polycarboxylate water reducing agent is a liquid polycarboxylate water reducing agent with the solid content of 20-25% and the water reducing rate of more than 70%.
Preferably, the fibers are steel fibers and/or organic fibers, the length of the fibers is 3-20 mm, and the diameter of the fibers is 0.01-0.6 mm.
The preparation method of the ultrahigh-performance concrete with high fiber dispersity and orientation degree comprises the following steps:
(1) placing cement, silica fume and fine aggregate into a stirrer, and stirring for 2-4 minutes at a low speed; the cement, the silica fume and the fine aggregate are basically and uniformly stirred through low-grade stirring;
(2) mixing water with a polycarboxylate water reducing agent to obtain a mixture; adding part of the mixture into a stirrer, and stirring for 3-5 minutes at a low speed; the fluidity occurs at this time;
(3) adding the rest mixture into a stirrer, and stirring for 3-5 minutes at low grade; stable fluidity occurs at this time;
(4) uniformly adding the fibers into the stirrer for 40-70 seconds under the condition of low-grade stirring; after the addition is finished, stirring for 1-2 minutes by using a medium grade, and then stirring for 1-2 minutes by using a high grade;
(5) measuring slump expansion, and supplementing a polycarboxylate water reducing agent until the slump expansion is 260-280 mm to obtain freshly mixed ultrahigh-performance concrete;
(6) loading the freshly mixed ultrahigh-performance concrete and pouring for forming, wherein the concrete is automatically filled into a concrete mold in the pouring process; placing the obtained concrete and the mould in a curing room for 20-26 hours, removing the mould, and placing in normal-temperature water for standard curing for 28-30 days; the humidity of the curing room is more than 90%, and the temperature is 18-22 ℃.
Fresh-mixed ultra-high performance concrete is a typical non-Newtonian fluid, and the dispersion characteristics and the structural construction process of each component material in suspension determine the microstructure and the macroscopic performance of the hardened cement-based material. Wherein the dispersion and orientation characteristics of the fibers will control the development of tensile strength and toughness in ultra-high performance concrete. The inventor finds out through research that the rheological property of the fresh-mixed ultra-high performance concrete determines the flow velocity gradient of the fiber in a fluid medium and the dispersion and orientation characteristics of the fiber: the larger the viscosity of the freshly mixed ultrahigh-performance concrete is, the larger the dragging force provided by the fluid medium to the fiber in the moving process is, so that the rotation degree of the fiber in the matrix is influenced, and further the bearing direction orientation of the fiber and the reinforcing and toughening effects of the fiber on the ultrahigh-performance concrete are influenced. The method regulates and controls the mechanical property of the ultra-high performance concrete by controlling the rheological property in the process of mixing the concrete. On the premise of ensuring the stability of the freshly mixed ultrahigh-performance concrete, the dispersion and orientation of the fibers are greatly improved, and the strength and toughness of the hardened ultrahigh-performance concrete are obviously improved.
Preferably, the part of the mixture in the step (2) is 85-90% of the total amount of the mixture; the amount of the polycarboxylate water reducing agent added in the step (5) is 0-2% of the total amount of the polycarboxylate water reducing agent.
Preferably, the low-grade stirring speed is 105-110 r/min, the medium-grade stirring speed is 190-200 r/min, and the high-grade stirring speed is 290-300 r/min.
The inventor finds that the addition of a large amount of ultrafine powder particles into the ultrahigh-performance concrete can improve the bulk density of the ultrahigh-performance concrete, reduce the porosity and improve the mechanical property, however, the powder particles have small particle size, large specific surface area and high surface free energy, not only can improve the water demand of the ultrahigh-performance concrete, but also can easily flocculate to lock part of water and the water reducing agent, and influence the dispersibility of fine particles, the water reducing and dispersing effects of the water reducing agent, and the working performance and even the hardening performance of the ultrahigh-performance concrete. In addition, although the high-efficiency polycarboxylate water reducer used in the ultra-high performance concrete can obviously reduce the water demand and the water-cement ratio by the generated electrostatic repulsion and steric hindrance effect and reduce flocculation of the gelled material to a certain extent, the viscosity of the ultra-high performance concrete is greatly increased due to the high concentration of the liquid phase of the polycarboxylic acid in the high-efficiency polycarboxylate water reducer, so that the problems of fiber agglomeration and hole introduction are caused.
Based on the research, the invention provides the ultra-high performance concrete which has excellent tensile and anti-fracture performance and is obtained by improving the stacking characteristic of the ultra-high performance concrete through adjusting the gradation of the raw material particles of the ultra-high performance concrete on the premise of not influencing the using amount of the cementing material and the water-cement ratio in the ultra-high performance concrete, controlling the rheological property of the ultra-high performance concrete by utilizing the filling effect of the silica fume, the pozzolan reaction and the water reducing and dispersing effects of the high-efficiency water reducing agent, uniformly distributing the fibers in the ultra-high performance concrete, having the orientation characteristic which is favorable for bearing, and improving the effective utilization rate of the fibers, so that the reinforcing, toughening and anti-cracking effects of the fibers on the ultra-high performance concrete are improved, the bearing direction is optimized, and.
The invention is simple and easy to operate, low in cost, high in efficiency, strong in compatibility with other components of concrete, and widely applicable to various projects, such as large-span and river-crossing bridges, thin-wall and light roofs, repair projects and the like, improves the cracking resistance, toughness and durability of a concrete structure, prolongs the service life of the concrete structure, and provides guarantee for the quality of ultra-high performance concrete materials and projects.
The invention has the beneficial effects that: compared with the similar technology at home and abroad, (1) the ultra-high performance concrete provided by the invention has high dispersion degree and orientation degree of fibers, good working performance, low viscosity, small shrinkage and good mechanical property; (2) the preparation method adopted by the invention is simple, convenient to operate and strong in applicability; (3) the raw materials adopted by the invention are all conventional materials required in the preparation process of the ultra-high performance concrete, and are easy to obtain and relatively low in price.
Drawings
FIG. 1 is a fracture plot obtained by tensile fracture of a comparative example of the present invention;
FIG. 2 is a fracture plot obtained by tensile fracture of example 2 of the present invention;
FIG. 3 is a fracture plot obtained by tensile fracture of inventive example 5;
FIG. 4 is a cross-sectional fiber distribution plot of a comparative example of the present invention;
FIG. 5 is a cross-sectional fiber distribution of example 2 of the present invention;
FIG. 6 is a cross-sectional fiber distribution of example 5 of the present invention;
FIG. 7 is a flexural stress-strain curve of the ultra-high performance concrete obtained in example 2 of the present invention and a comparative example;
FIG. 8 is a tensile stress-strain curve of the ultra-high performance concrete obtained in example 2 of the present invention and the comparative example.
Detailed Description
The present invention will be further described with reference to the following examples and the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The starting materials used in the examples of the present invention were all obtained from conventional commercial sources.
Table 1 shows the raw material composition of the ultra-high performance concrete of examples 1 to 5 of the present invention and comparative examples; wherein the amounts of cement, silica fume, natural river sand, superfine machine-made sand, water and polycarboxylate water reducing agent are expressed by mass parts; the dosage of the steel fiber is expressed by volume mixing amount of the steel fiber in the ultra-high performance concrete. Table 2 shows properties of the raw materials of the ultra-high performance concrete of examples 1 to 5 of the present invention and comparative examples.
Comparative example
The comparative example adopts the mixing proportion of standard ultra-high performance concrete, does not mix any mineral admixture (silica fume), adopts pure cement as a cementing material, adopts river sand and fine-grained machine-made sand as fine aggregate to improve the particle stacking density, uses a liquid high-efficiency water reducing agent (polycarboxylate water reducing agent), adopts steel fiber with the volume mixing amount of 2 percent, and is prepared by adopting the preparation method of the conventional ultra-high performance concrete.
Example 1
The cementing material of the ultra-high performance concrete with high fiber dispersity and orientation degree is cement and silica fume, the silica fume with the mass fraction of 5% is used for replacing part of the cement, river sand and machine-made sand are used as fine aggregate to improve the stacking density, and a liquid high-efficiency water reducing agent (polycarboxylate water reducing agent) is used and the volume mixing amount of steel fiber is 2%. The slump spread of the freshly mixed ultrahigh-performance concrete was 265 mm.
The preparation method of the ultra-high performance concrete with high fiber dispersity and orientation degree in the embodiment is as follows:
(1) placing cement, silica fume and fine aggregate into a stirrer, and stirring for 2 minutes at a low speed;
(2) mixing water with a polycarboxylate water reducing agent to obtain a mixture; adding 87% of the mixture into a stirrer, and stirring for 3 minutes at a low speed;
(3) adding the rest mixture into a stirrer, and stirring for 3 minutes at a low gear;
(4) under the condition of low-grade stirring, uniformly adding the fibers into the stirrer within 60 seconds; after the addition is finished, stirring for 1 minute by using a medium grade, and then stirring for 1 minute by using a high grade;
(5) measuring slump expansion, and supplementing a polycarboxylate water reducing agent with the total dosage of 0.5 percent of the polycarboxylate water reducing agent to obtain the freshly mixed ultrahigh-performance concrete;
(6) loading the freshly mixed ultrahigh-performance concrete and pouring for forming, wherein the concrete is automatically filled into a concrete mold in the pouring process; placing the obtained concrete and the mould in a curing chamber together, placing for 24 hours, removing the mould, and placing in normal temperature water for standard curing for 28 days; the humidity of the curing chamber is 95%, and the temperature is 20 ℃.
In the preparation process, the low-grade stirring speed is 107r/min, the medium-grade stirring speed is 198r/min, and the high-grade stirring speed is 295 r/min.
Example 2
The cementing material of the ultra-high performance concrete with high fiber dispersity and orientation degree is cement and silica fume, the silica fume with the mass fraction of 10% is used for replacing part of the cement, river sand and machine-made sand are used as fine aggregate to improve the stacking density, and a liquid high-efficiency water reducing agent (polycarboxylate water reducing agent) is used and the volume mixing amount is 2% of steel fiber. The slump expansion of the freshly mixed ultrahigh-performance concrete was 272 mm.
The preparation method of the ultra-high performance concrete with high fiber dispersity and orientation degree in the embodiment is as follows:
(1) placing cement, silica fume and fine aggregate into a stirrer, and stirring for 3 minutes at a low speed;
(2) mixing water with a polycarboxylate water reducing agent to obtain a mixture; adding 90% of the mixture into a stirrer, and stirring for 4 minutes at a low speed;
(3) adding the rest mixture into a stirrer, and stirring for 4 minutes at a low gear;
(4) uniformly adding the fibers into the stirrer within 58 seconds under the condition of low-grade stirring; after the addition is finished, stirring for 1.5 minutes by using a middle grade, and then stirring for 1.5 minutes by using a high grade;
(5) measuring slump expansion, and supplementing a polycarboxylate water reducing agent with the total dosage of 0.2 percent of the polycarboxylate water reducing agent to obtain the freshly mixed ultrahigh-performance concrete;
(6) loading the freshly mixed ultrahigh-performance concrete and pouring for forming, wherein the concrete is automatically filled into a concrete mold in the pouring process; placing the obtained concrete and the mould in a curing chamber together, placing for 23 hours, removing the mould, and placing in normal temperature water for standard curing for 30 days; the humidity of the curing chamber is 96%, and the temperature is 21 ℃.
In the preparation process, the low-grade stirring speed is 108r/min, the medium-grade stirring speed is 194r/min, and the high-grade stirring speed is 290 r/min.
Example 3
The cementing material of the ultra-high performance concrete with high fiber dispersity and orientation degree is cement and silica fume, 15% of silica fume is used for replacing part of the cement, river sand and machine-made sand are used as fine aggregate to improve the bulk density, and a liquid high-efficiency water reducing agent (polycarboxylate water reducing agent) is used and the volume mixing amount of steel fiber is 2%. The slump spread of the freshly mixed ultrahigh-performance concrete was 279 mm.
The preparation method of the ultra-high performance concrete with high fiber dispersity and orientation degree is the same as that of the concrete in the embodiment 1.
Example 4
The cementing material of the ultra-high performance concrete with high fiber dispersity and orientation degree is cement and silica fume, the silica fume with the mass fraction of 20% is used for replacing part of the cement, river sand and machine-made sand are used as fine aggregate to improve the stacking density, and a liquid high-efficiency water reducing agent (polycarboxylate water reducing agent) is used and the volume mixing amount of steel fiber is 2%. The slump expansion of the freshly mixed ultrahigh-performance concrete was 276 mm.
The preparation method of the ultra-high performance concrete with high fiber dispersity and orientation degree is the same as that of the concrete in the embodiment 1.
Example 5
The cementing material of the ultra-high performance concrete with high fiber dispersity and orientation degree is cement and silica fume, the silica fume with the mass fraction of 25% is used for replacing part of the cement, river sand and superfine machine-made sand are used as fine aggregate to improve the bulk density, and a liquid high-efficiency water reducing agent (polycarboxylate water reducing agent) is used, and the volume mixing amount of the steel fiber is 2%. The slump spread of freshly mixed ultrahigh-performance concrete was 268 mm.
The preparation method of the ultra-high performance concrete with high fiber dispersity and orientation degree is the same as that of the concrete in the example 2.
TABLE 1 ultra high Performance concrete mix proportions for examples 1-5 and comparative examples
TABLE 2 raw Material Properties of examples 1-5 and comparative examples
Detection and analysis
(1) The ultra-high performance concrete of examples 1 to 5 was subjected to comparative tests for workability and mechanical properties (slump extension was measured according to ASTM C230/C230M, yield stress and viscosity of ultra-high performance concrete were determined by ConTech 5 rheometer, compressive strength was measured according to ASTM C109, bending resistance was measured according to ASTM C1609, tensile properties were measured according to the dogbone pull method) with comparative examples, and the test results are shown in Table 3 and FIGS. 1 to 8.
Fig. 1 to 3 are fracture diagrams obtained by tensile fracture of comparative example, example 2 and example 5, respectively, and it can be seen from the diagrams that the degree of fiber orientation in example 2 is high, the degree of fiber orientation in example 5 is high, and the degree of fiber orientation in comparative example is low.
Fig. 4 to 6 are cross-sectional fiber distribution diagrams of comparative examples, example 2 and example 5, respectively, in which white dot-shaped or strip-shaped regions are fiber cross-sections, and it can be seen that the fiber cross-sections in the comparative examples are both dot-shaped and strip-shaped, and the fiber distribution in the region of the right middle part is less, indicating that the fiber orientation is not uniform and the dispersion is not uniform enough; in the embodiment 2, the cross sections of the fibers are all in a round point shape and are uniformly distributed, which shows that the fibers have excellent orientation and dispersibility; in example 5, the fibers have a uniform distribution with a cross section of a dot or a rice grain shape, and the orientation and dispersibility of the fibers are satisfactory.
TABLE 3 fresh mix performance and hardening performance test results of ultra high performance concrete
As can be seen from table 3, fig. 1-8: the plastic viscosity of the ultra-high performance concrete obtained in the examples 1 to 5 of the invention is lower than that of the comparative example, the fiber dispersion coefficient, the orientation coefficient, the tensile strength, the flexural strength and the flexural toughness of the ultra-high performance concrete are higher than those of the comparative example, especially in the examples 2 to 4 doped with 10 to 20 percent of silica fume, the fiber dispersion and the orientation coefficient are obviously improved, the mechanical property is greatly improved, and the invention has obvious technical effect. However, when silica fume was incorporated in a large amount (example 5), the effect of improving the fiber dispersion and orientation factor and the mechanical properties began to decrease.
Claims (10)
1. The ultra-high performance concrete with high fiber dispersity and orientation degree is characterized by comprising the following raw materials: cement, silica fume, fine aggregate, polycarboxylate water reducing agent, fiber and water; the mass part ratio of the cement to the silica fume to the polycarboxylate water reducing agent is 75-95: 5-25: 3-5; the volume mixing amount of the fiber in the ultra-high performance concrete is 1-5%; the mass of the water is 0.05-0.10 times of the sum of the mass of the cement, the silica fume and the fine aggregate; after the raw materials of the ultra-high performance concrete are mixed, the slump expansion degree is 260-280 mm.
2. The ultra-high performance concrete of high degree of fiber dispersion and orientation according to claim 1, wherein the cement is portland cement or ordinary portland cement; the specific surface area of the silica fume is 10000m2More than kg.
3. The ultra-high performance concrete with high fiber dispersity and orientation degree according to claim 1, wherein the mass of the fine aggregate is 0.9-1.1 times of the sum of the mass of cement and silica fume; the fine aggregate is natural river sand and/or machine-made sand, and the fineness modulus of the fine aggregate is 2.2-1.6.
4. The ultrahigh-performance concrete with high fiber dispersity and orientation according to claim 3, wherein the natural river sand accounts for 70-75 wt% of the fine aggregate, and the rest of the fine aggregate is machine-made sand.
5. The ultrahigh-performance concrete with high fiber dispersity and orientation degree according to any one of claims 1 to 4, wherein the polycarboxylate water reducer is a liquid polycarboxylate water reducer with a solid content of 20-25% and a water reduction rate of more than 70%.
6. The ultra-high performance concrete with high degree of fiber dispersion and orientation according to any one of claims 1 to 4, wherein the fibers are steel fibers and/or organic fibers, and have a length of 3 to 20mm and a diameter of 0.01 to 0.6 mm.
7. The ultra-high performance concrete with high degree of fiber dispersion and orientation according to claim 5, wherein the fibers are steel fibers and/or organic fibers, and have a length of 3 to 20mm and a diameter of 0.01 to 0.6 mm.
8. The ultra-high performance concrete with high fiber dispersity and orientation degree and the preparation method thereof according to any one of claims 1 to 7 are characterized by comprising the following steps:
(1) placing cement, silica fume and fine aggregate into a stirrer, and stirring for 2-4 minutes at a low speed;
(2) mixing water with a polycarboxylate water reducing agent to obtain a mixture; adding part of the mixture into a stirrer, and stirring for 3-5 minutes at a low speed;
(3) adding the rest mixture into a stirrer, and stirring for 3-5 minutes at low grade;
(4) uniformly adding the fibers into the stirrer for 40-70 seconds under the condition of low-grade stirring; after the addition is finished, stirring for 1-2 minutes by using a medium grade, and then stirring for 1-2 minutes by using a high grade;
(5) measuring slump expansion, and supplementing a polycarboxylate water reducing agent until the slump expansion is 260-280 mm to obtain freshly mixed ultrahigh-performance concrete;
(6) loading the freshly mixed ultrahigh-performance concrete and pouring for forming, wherein the concrete is automatically filled into a concrete mold in the pouring process; placing the obtained concrete and the mould in a curing room for 20-26 hours, removing the mould, and placing in normal-temperature water for standard curing for 28-30 days; the humidity of the curing room is more than 90%, and the temperature is 18-22 ℃.
9. The ultra-high performance concrete with high fiber dispersity and orientation degree and the preparation method thereof according to claim 8 are characterized in that the part of the mixed material in the step (2) is 85% -90% of the total amount of the mixed material; the amount of the polycarboxylate water reducing agent added in the step (5) is 0-2% of the total amount of the polycarboxylate water reducing agent.
10. The ultra-high performance concrete with high fiber dispersity and orientation degree and the preparation method thereof according to claim 8 or 9 are characterized in that the low-grade stirring speed is 105-110 r/min, the medium-grade stirring speed is 190-200 r/min, and the high-grade stirring speed is 290-300 r/min.
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| CN113387643A (en) * | 2021-06-10 | 2021-09-14 | 上海交通大学设计研究总院有限公司 | High-toughness concrete and preparation method thereof |
| CN117658566A (en) * | 2023-11-16 | 2024-03-08 | 中铁二十五局集团第三工程有限公司 | Straight pump concrete and preparation method and application thereof |
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| CN113387643A (en) * | 2021-06-10 | 2021-09-14 | 上海交通大学设计研究总院有限公司 | High-toughness concrete and preparation method thereof |
| CN117658566A (en) * | 2023-11-16 | 2024-03-08 | 中铁二十五局集团第三工程有限公司 | Straight pump concrete and preparation method and application thereof |
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