Multi-scale hybrid fiber high-toughness concrete and preparation method thereof

Abstract

The invention discloses multi-scale hybrid fiber high-toughness concrete and a preparation method thereof. The multi-scale hybrid fiber high-toughness concrete is prepared from 155 to 165 parts by mass of water, 400 to 450 parts by mass of cement, 30 to 70 parts by mass of fly ash, 1000 to 1100 parts by mass of broken stone, 700 to 750 parts by mass of river sand, 0.65 to 0.75 part by mass of a water reducing agent, 390 to 500 parts by mass of steel fibers, 40 to 50 parts by mass of polypropylene crude fibers and 2 to 6 parts by mass of polypropylene fine fibers. The particle size of the broken stones is 5-10 mm; the steel fiber is an end hook steel fiber, and the diameter of the end hook steel fiber is 0.75 mm; the diameter of the polypropylene crude fiber is 0.75 mm; and the diameter of the polypropylene fine fiber is 0.2 mm. According to the invention, the problem that the existing hybrid fiber concrete is relatively low in breaking strength and toughness indexes is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of high-performance concrete, and particularly relates to a multi-scale hybrid fiber high-toughness concrete and a preparation method thereof. Background Art

[0002] In recent years, China's transportation industry has developed rapidly, and the construction of bridge projects has increased day by day. At the same time, the requirements for structural materials in bridge projects are getting higher and higher. In key parts of road bridges, such as the joints of precast segmental bridge decks, negative moment areas, expansion joints, etc., the joints of precast segmental bridge decks are the main connection parts. The stiffness and structure at the joints are discontinuous, and problems such as cracking and water seepage are likely to occur under the action of loads, resulting in the deterioration of the performance of the bridge deck. The negative moment area of the bridge is extremely prone to cracking under the action of external loads, exposing the steel bars to a humid environment and causing corrosion, which in turn affects the bearing capacity and service life of the bridge. Moreover, the diseases in the negative moment area are likely to be reflected to the bridge deck, threatening the structural safety and service life of the bridge. Therefore, developing high-toughness concrete suitable for vulnerable parts of bridges has become an urgent problem to be solved.

[0003] Under the action of cyclic loads, the flexural toughness of the concrete structure in vulnerable parts of road bridges is a key consideration in engineering design and material selection. Traditional concrete, due to its low flexural tensile strength and high brittleness characteristics, limits its application in key parts of bridges. However, for steel fiber concrete, since the steel fibers are randomly distributed in the concrete matrix, it can effectively prevent the formation of internal cracks in the concrete, significantly improve the ductility and toughness of the concrete, and can significantly increase the service life of vulnerable parts and reduce the maintenance cost. However, due to the high price of the steel fibers themselves, it results in a high application cost in actual projects, affecting its wide application in bridges.

[0004] Compared with steel fiber concrete, hybrid fiber concrete incorporates two or more different scales and different types of fibers in its concrete matrix. Due to the different properties of the fibers, the performance of each fiber can be effectively exerted in the concrete matrix, and they complement each other and make up for each other's deficiencies in different scales and performances. However, for the currently used hybrid fiber concrete, the fibers (such as steel fibers, polyvinyl alcohol fibers, etc.) still have the problem of high cost, and the combined use of steel fibers and micron-scale fibers causes the phenomenon of fiber agglomeration during the construction process of hybrid fiber concrete, which in turn affects the use performance of the concrete. This is also an important problem for the construction application of bridge projects.

[0005] In view of these challenges, the development of new multi-scale hybrid fiber high-toughness concrete materials is crucial for improving the flexural toughness of concrete structures in vulnerable parts of bridges. End-hook steel fibers, polypropylene coarse fibers CPF1, and polypropylene fine fibers CPF2 can effectively limit the development of micro and macro cracks according to their material properties, further improving the problems of reduced bearing capacity and service life caused by the easy cracking of concrete in vulnerable parts of bridges, showing great potential in bridge engineering. Through the design optimization of the composition of a specific aggregate particle size range in the present invention, the hybrid fibers can provide more excellent comprehensive properties than ordinary concrete and steel fiber concrete, thus meeting the requirements of concrete application projects in vulnerable parts of bridges.

[0006] Currently, existing hybrid fiber concrete (such as the Chinese patent with publication number CN105585294A) has a flexural strength of only 6.0 to 6.9 MPa after 28 days of standard curing, and the toughness indexes I5, I 10 、I 20 are 7.2, 12.3, and 18.4 respectively, which are relatively low, restricting its application in structures. And existing experimental studies have shown that the hybrid fiber concrete used in this technology has poor service life performance under load cycling conditions.

[0007] The concrete of the present invention exhibits excellent flexural performance in vulnerable parts of bridges, and its compressive strength range after 28 days of standard curing is 60 MPa to 80 MPa, the flexural strength reaches 11.25 Mpa, and the toughness indexes I5, I 10 、I 20 are 16.57, 23.72, and 30.72 respectively, having high flexural toughness and being sufficient to meet the strength requirements of most bridge engineering structures. Summary of the Invention

[0008] To overcome the defects of the existing technology, a multi-scale hybrid fiber high-toughness concrete and its preparation method are provided to solve the problem that the flexural strength and toughness indexes of existing hybrid fiber concrete are relatively low.

[0009] To achieve the above object, a multi-scale hybrid fiber high-toughness concrete is provided, which includes 155 - 165 parts by mass of water, 400 - 450 parts by mass of cement, 30 - 70 parts by mass of fly ash, 1000 - 1100 parts by mass of crushed stone, 700 - 750 parts by mass of river sand, 0.65 - 0.75 parts by mass of water reducing agent, 390 - 500 parts by mass of steel fibers, 40 - 50 parts by mass of polypropylene coarse fibers, and 2 - 6 parts by mass of polypropylene fine fibers;

[0010] The particle size of the crushed stone is 5 - 10 mm;

[0011] The steel fiber is an end-hooked steel fiber, and the diameter of the end-hooked steel fiber is 0.75 mm;

[0012] The diameter of the polypropylene coarse fiber is 0.75 mm;

[0013] The diameter of the polypropylene fine fiber is 0.2 mm.

[0014] Furthermore, the fineness modulus of the river sand is 2.85.

[0015] Furthermore, the water reducing agent is a polycarboxylate high-performance water reducing agent.

[0016] Furthermore, the cement is 52.5-grade ordinary portland cement.

[0017] Furthermore, the fly ash is Class I fly ash.

[0018] The present invention provides a method for preparing multi-scale hybrid fiber high-toughness concrete, comprising the following steps:

[0019] Dry-mix 400-450 parts by mass of cement, 30-70 parts by mass of fly ash, 1000-1100 parts by mass of crushed stone, and 700-750 parts by mass of river sand evenly to obtain a powder material;

[0020] Add 155-165 parts by mass of water and 0.65-0.75 parts by mass of water reducing agent to the powder material and stir evenly to obtain a wet material;

[0021] Add 390-500 parts by mass of steel fiber, 40-50 parts by mass of polypropylene coarse fiber, and 2-6 parts by mass of polypropylene fine fiber to the wet material and stir evenly to prepare multi-scale hybrid fiber high-toughness concrete.

[0022] The beneficial effects of the present invention are as follows. The multi-scale hybrid fiber high-toughness concrete of the present invention improves the performance of concrete through the synergistic cooperation of adding multi-scale ternary fibers and coarse aggregates within a specific particle size range. Among them, the effects of the three fibers on the concrete show a "positive effect", which not only reduces the material cost but also improves the flexural strength, flexural toughness and splitting tensile strength of the concrete structure, greatly enhances the energy absorption capacity of the concrete, better restricts the development of cracks, and significantly improves the service life of the concrete. Moreover, the concrete of the present invention has good fluidity, can achieve the pumping effect at the concrete pouring site, and greatly saves the construction labor cost.

[0023] The multi-scale hybrid fiber high-toughness concrete of the present invention reduces the material cost and significantly improves the basic mechanical properties of the concrete, especially the flexural toughness, by optimizing the raw material mix ratio and adding appropriate amounts of SF, CPF1, and CPF2, and can effectively solve the problem of easy damage to key parts in bridge engineering. The multi-scale hybrid fiber concrete of the present invention can be preferably applied to vulnerable parts (such as expansion joints, negative moment areas, etc.) in bridge engineering, and can significantly improve the safety and service life of bridge structures. Detailed implementation manners

[0024] The following further elaborates on the present application in conjunction with embodiments. It can be understood that the specific embodiments described herein are only used to explain the relevant invention and not to limit the invention.

[0025] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The following will elaborate on the present application in conjunction with embodiments.

[0026] The present invention provides a multi-scale hybrid fiber high-toughness concrete, which includes 155-165 parts by mass of water, 400-450 parts by mass of cement, 30-70 parts by mass of fly ash, 1000-1100 parts by mass of crushed stone, 700-750 parts by mass of river sand, 0.65-0.75 parts by mass of water reducer, 390-500 parts by mass of steel fiber, 40-50 parts by mass of polypropylene coarse fiber, and 2-6 parts by mass of polypropylene fine fiber.

[0027] The particle size of the crushed stone is 5-10 mm.

[0028] In this embodiment, a ternary limit is formed by the steel fiber, polypropylene coarse fiber, and polypropylene fine fiber. Among them, the steel fiber is an end-hooked steel fiber. The diameter of the end-hooked steel fiber is 0.75 mm. The diameter of the polypropylene coarse fiber is 0.75 mm. The diameter of the polypropylene fine fiber is 0.2 mm.

[0029] The multi-scale hybrid fiber high-toughness concrete of the present invention uses ordinary Portland cement as the main cementitious material, and selects crushed stones with a particle size range of 5-10 mm for the preparation of concrete. The crushed stones with a smaller particle size (5-10 mm) are more evenly distributed in the concrete, can better fill the voids, and the crushed stones with a smaller particle size enable the cement paste to better fill the voids between the aggregates, forming a more compact bonding structure, which helps to enhance the crack resistance of the concrete. When the concrete is subjected to a bending load, the internal stress distribution is more uniform, reducing the possibility of local stress concentration. Under the action of the bending load, due to the smaller particle size of the crushed stones and the increase in the amount of crushed stones, the crack propagation path is more tortuous in the concrete with smaller particle size crushed stones because there are more interfaces between the aggregates, and the cracks need to bypass more aggregates to propagate. This tortuous crack propagation path can absorb more energy, and there is an interfacial transition zone between the aggregates and the cement paste in the concrete, and the strength of this area is usually lower than the strength of the aggregates and the cement paste itself. The smaller particle size crushed stones can increase the contact area between the aggregates and the cement paste, thereby possibly improving the performance of the interfacial transition zone and increasing the overall strength of the concrete. When the strength of the interfacial transition zone is increased, the concrete can better resist the formation and propagation of cracks under the action of a bending load, thereby improving the flexural toughness.

[0030] In contrast, the crushed stones with a larger particle size may lead to insufficient filling of the cement paste, larger voids inside the concrete, and weakened bonding force between the aggregates, thereby reducing the flexural toughness of the concrete. Therefore, the multi-scale hybrid fiber high-toughness concrete of the present invention uses crushed stones with a particle size range of 5-10 mm.

[0031] The multi-scale hybrid fiber high-toughness concrete of the present invention selects end-hooked steel fiber SF, polypropylene coarse fiber CPF1, and polypropylene fine fiber CPF2 for ternary hybrid preparation of high-toughness concrete. Specifically, the end-hooked steel fiber, with its high strength (1200 MPa) and special hooked shape, plays an effective strengthening role in the concrete. The hooked shape can increase the bond strength between the fiber and the concrete and improve the pull-out resistance of the fiber. When the concrete is subjected to an external force, the end-hooked steel fiber can transfer stress and disperse the energy at the crack, preventing the further propagation of the crack, and can effectively improve the bending performance of the concrete throughout the bending process.

[0032] The polypropylene coarse fiber, with its high tensile strength (620 MPa) and good dispersibility, plays a role in strengthening and crack resistance in the concrete, and can reduce the generation of early plastic shrinkage and dry shrinkage cracks in the concrete. In the later stage of the development of the bending cracks in the concrete, relying on its larger diameter and deformation ability, it can cooperate with the steel fiber to effectively limit the development of macroscopic cracks.

[0033] Polypropylene fine fibers, with their small diameter (0.2 mm) and a certain dosage, form a dense fiber network in concrete. This dense fiber network can effectively prevent the expansion of internal microcracks in concrete, improving the crack resistance and flexural toughness of concrete before the peak load.

[0034] The multi-scale hybrid fiber high-toughness concrete of the present invention hybridizes three types of fibers, which can not only give full play to the strengthening and crack resistance effects of high-modulus and high-strength fibers, but also play the role of early toughening of low-modulus and high-elongation fibers, synergistically improving the flexural toughness of concrete before, during, and after bending.

[0035] The hooked-end steel fiber SF, polypropylene coarse fiber CPF1, and polypropylene fine fiber CPF2 used in the multi-scale hybrid fiber high-toughness concrete of the present invention have diameters of 0.75 mm, 0.75 mm, and 0.2 mm respectively, and their aspect ratios are adjusted according to requirements. The aggregate particle size range is 5 - 10 mm. The smaller-sized crushed stones make the distribution of fibers in concrete more uniform and dense, so it is easier to form good bonding with the aggregates. This tight bonding structure helps the fibers play a better bridging role when the concrete is subjected to bending loads. Moreover, the smaller-sized crushed stones can increase the contact area between the fibers and the aggregates, thereby improving the performance of the interfacial transition zone. This helps enhance the bonding force between the fibers and the aggregates, thus enhancing the flexural toughness of concrete. When cracks expand and cause fiber pull-out, the smaller-sized crushed stones can provide better anchoring, reducing premature fiber pull-out and increasing the energy consumption during the pull-out process, thereby improving the flexural toughness of concrete.

[0036] The multi-scale hybrid fiber high-toughness concrete of the present invention adopts ternary fiber hybridization for strengthening. The ternary fiber hybridization, combining the characteristics of high strength and low modulus, high elongation, can play different roles at different stages of concrete bending, significantly improving the flexural bearing capacity and flexural toughness of concrete throughout the bending process. The crack expansion of the multi-scale hybrid fiber high-toughness concrete of the present invention is hindered. The tortuous crack path absorbs more energy, effectively preventing crack expansion and improving the durability and service life of concrete.

[0037] The multi-scale hybrid fiber high-toughness concrete of the present invention has a high energy consumption for fiber pull-out. The smaller-sized crushed stones provide better anchoring for the fibers, reducing premature fiber pull-out. Moreover, the stress between fibers with a certain aspect ratio can be effectively transmitted, giving full play to the characteristics of each fiber, increasing the energy consumption of pull-out, and enhancing the flexural toughness of concrete.

[0038] The particle size of the crushed stone in the multi-scale hybrid fiber high-toughness concrete of the present invention is 5-10 mm. The crushed stone is evenly distributed and tightly fills the voids, enhancing the crack resistance of the concrete and improving the overall strength of the concrete. The small-sized crushed stone makes the internal stress distribution of the concrete more uniform, reduces local stress concentration, and improves stability.

[0039] The multi-scale hybrid fiber high-toughness concrete of the present invention improves the performance of the interfacial transition zone and enhances the bonding force between the fibers and the aggregate by increasing the contact area between the aggregate and the paste.

[0040] The multi-scale hybrid fiber high-toughness concrete of the present invention uses polypropylene coarse fibers to replace part of the steel fibers with the same diameter to effectively control macroscopic cracks, significantly reducing the material cost while increasing the toughness of the concrete.

[0041] The multi-scale hybrid fiber high-toughness concrete of the present invention improves the performance of the concrete through the synergistic cooperation of adding multi-scale ternary fibers and coarse aggregates in a specific particle size range. Among them, the three fibers have a "positive effect" on the concrete, improving the flexural strength, flexural toughness, and splitting tensile strength of the concrete structure while reducing the material cost, greatly enhancing the energy absorption capacity of the concrete, better restricting the development of cracks, and significantly increasing the service life of the concrete. Moreover, the concrete of the present invention has good fluidity, can achieve the pumping effect at the concrete pouring site, and greatly saves the construction labor cost. The multi-scale hybrid fiber concrete of the present invention can be well applied in vulnerable parts of bridge engineering (such as expansion joints, negative moment areas, etc.), can significantly improve the safety and service life of the bridge structure, and has good practical application value and popularization value.

[0042] As a preferred embodiment, the fineness modulus of the river sand is 2.85.

[0043] As a preferred embodiment, the water reducing agent is a polycarboxylate high-performance water reducing agent.

[0044] As a preferred embodiment, the cement is 52.5-grade ordinary Portland cement.

[0045] As a preferred embodiment, the fly ash is Class I fly ash.

[0046] The present invention provides a preparation method for multi-scale hybrid fiber high-toughness concrete, comprising the following steps:

[0047] S1. Dry-mix 400-450 parts by mass of cement, 30-70 parts by mass of fly ash, 1000-1100 parts by mass of crushed stone, and 700-750 parts by mass of river sand evenly to obtain a powder material.

[0048] Weigh various raw materials accurately according to the above mix ratio, and pour the gelling material, coarse aggregate and fine aggregate into a concrete mixer for dry mixing for 30 - 60 s to obtain powder materials.

[0049] S2. Add 155 - 165 parts by mass of water and 0.65 - 0.75 parts by mass of water reducer to the powder materials and stir evenly to obtain wet materials.

[0050] Slowly add water and high-performance water reducer to the powder materials, and continue mixing for 60 - 90 s to obtain wet materials.

[0051] S3. Add 390 - 500 parts by mass of steel fibers, 40 - 50 parts by mass of polypropylene coarse fibers, and 2 - 6 parts by mass of polypropylene fine fibers to the wet materials and stir evenly to prepare multi-scale hybrid fiber high-toughness concrete.

[0052] Slowly add polypropylene coarse fiber CPF1, polypropylene fine fiber CPF2, and steel fiber SF to the wet materials respectively. After adding each kind, stir for 30 - 60 seconds and then add another fiber. Cure for 28 days under standard curing conditions to obtain multi-scale hybrid fiber high-toughness concrete applicable to vulnerable parts of road bridges based on hybrid fibers.

[0053] To further illustrate the performance characteristics of the multi-scale hybrid fiber high-toughness concrete of the present invention, the following examples and comparative examples are given for detailed description.

[0054] Example 1

[0055] This example provides a multi-scale hybrid fiber high-toughness concrete, and the specific component mix ratio is shown in Table 1 below.

[0056] Table 1. Mix ratio of multi-scale hybrid fiber high-toughness concrete in Example 1

[0057]

[0058] Among them: The coarse aggregate is ordinary crushed stone, with a continuous grading of 5 - 10 mm and a crushing value index of 5% - 18%;

[0059] The fly ash is Class I fly ash;

[0060] The fine aggregate is natural river sand, and the fineness modulus of the fine aggregate is 2.85;

[0061] The water reducer is a polycarboxylate high-performance water reducer with a water reduction rate ≥ 25% produced by Beijing Muhu Admixture Co., Ltd.;

[0062] The cement is ordinary Portland cement (P·O 52.5) with a strength grade of 52.5 produced by Jiyuan Zhonglian Cement Group Co., Ltd.

[0063] The aspect ratio of the steel fiber is 66, the diameter is 0.75 mm, its tensile strength is 1100 MPa, the elastic modulus is 210 GPa, and it is from Zhitai Steel Fiber Manufacturing Co., Ltd.

[0064] The aspect ratio of CPF1 is 40, the diameter is 0.75 mm, its tensile strength is 620 MPa, the elastic modulus is 7.8 GPa, and it is from Zhitai Steel Fiber Manufacturing Co., Ltd.

[0065] The aspect ratio of the steel fiber is 75, the diameter is 0.2 mm, its tensile strength is 560 MPa, the elastic modulus is 7.8 GPa, and it is from Zhitai Steel Fiber Manufacturing Co., Ltd.

[0066] Select raw materials according to the raw material ratio in Table 1. Pour the cementitious material, coarse aggregate and fine aggregate into a concrete mixer and dry mix for 30 - 60 s, then slowly add water and high-performance water reducer, and continue mixing for 60 - 90 s. Then slowly add polypropylene coarse fiber CPF1, polypropylene fine fiber CPF2, and steel fiber SF respectively. After adding each one, it is necessary to stir for 30 - 60 seconds before adding another fiber, thus obtaining multi-scale hybrid fiber high-toughness concrete applicable to vulnerable parts of road bridges based on hybrid fibers, and its mechanical property technical indicators are listed in Table 4.

[0067] Example 2

[0068] This example provides a multi-scale hybrid fiber high-toughness concrete, and the specific component mix ratio is shown in Table 2 below.

[0069] Table 2. Mix ratio of multi-scale hybrid fiber high-toughness concrete in Example 2

[0070]

[0071] Among them: The coarse aggregate is ordinary crushed stone, with a continuous grading of 5 - 10 mm and a crushing value index of 5% - 18%;

[0072] The fly ash is Class I fly ash;

[0073] The fine aggregate is natural river sand, and the fineness modulus of the fine aggregate is 2.85;

[0074] The water reducer is a polycarboxylate high-performance water reducer with a water reduction rate ≥ 25% produced by Beijing Muhu Admixture Co., Ltd.;

[0075] The cement is ordinary Portland cement (P·O 52.5) with a strength grade of 52.5 produced by Jiyuan Zhonglian Cement Group Co., Ltd.

[0076] The aspect ratio of the steel fiber is 66, the diameter is 0.75 mm, its tensile strength is 1100 MPa, the elastic modulus is 210 GPa, and it is from Zhitai Steel Fiber Manufacturing Co., Ltd.

[0077] The aspect ratio of CPF1 is 66, the diameter is 0.75 mm, its tensile strength is 620 MPa, the elastic modulus is 7.8 GPa, and it is from Zhitai Steel Fiber Manufacturing Co., Ltd.

[0078] The aspect ratio of the steel fiber is 60, the diameter is 0.2 mm, its tensile strength is 560 MPa, the elastic modulus is 7.8 GPa, and it is from Zhitai Steel Fiber Manufacturing Co., Ltd.

[0079] Select raw materials according to the raw material ratio in Table 1. Pour the cementitious material, coarse aggregate and fine aggregate into a concrete mixer and dry mix for 30 - 60 s, then slowly add water and high-performance water reducer, and continue to mix for 60 - 90 s. Then slowly add polypropylene coarse fiber CPF1, polypropylene fine fiber CPF2, and steel fiber SF respectively. After adding each one, it is necessary to stir for 30 - 60 seconds before adding another fiber, and then the multi-scale hybrid fiber high-toughness concrete applicable to vulnerable parts of road bridges based on hybrid fibers can be obtained. Its mechanical property technical indicators are listed in Table 4.

[0080] Example 3

[0081] This example provides a multi-scale hybrid fiber high-toughness concrete. The specific component mix ratio is shown in Table 3 below.

[0082] Table 3. Mix ratio of multi-scale hybrid fiber high-toughness concrete in Example 3

[0083]

[0084] Among them: The coarse aggregate is ordinary crushed stone, with a continuous gradation of 5 - 10 mm and a crushing value index of 5% - 18%;

[0085] The fly ash is Class I fly ash;

[0086] The fine aggregate is natural river sand, and the fineness modulus of the fine aggregate is 2.85;

[0087] The water reducer is a polycarboxylate high-performance water reducer with a water reduction rate ≥ 25% produced by Beijing Muhu Admixture Co., Ltd.;

[0088] The cement is ordinary Portland cement (P·O 52.5) with a strength grade of 52.5 produced by Jiyuan Zhonglian Cement Group Co., Ltd.

[0089] The aspect ratio of the steel fiber is 66, the diameter is 0.75 mm, its tensile strength is 1100 MPa, the elastic modulus is 210 GPa, and it is from Zhitai Steel Fiber Manufacturing Co., Ltd.

[0090] The aspect ratio of CPF1 is 66, the diameter is 0.75 mm, its tensile strength is 620 MPa, the elastic modulus is 7.8 GPa, and it is from Zhitai Steel Fiber Manufacturing Co., Ltd.

[0091] The aspect ratio of the steel fiber is 60, the diameter is 0.2 mm, its tensile strength is 560 MPa, and the elastic modulus is 7.8 GPa. It is from Zhitai Steel Fiber Manufacturing Co., Ltd.

[0092] Select raw materials according to the raw material ratio in Table 1. Pour the cementitious material, coarse aggregate, and fine aggregate into a concrete mixer and dry mix for 30 - 60 s. Then slowly add water and high-performance water reducer, and continue mixing for 60 - 90 s. Then slowly add polypropylene coarse fiber CPF1, polypropylene fine fiber CPF2, and steel fiber SF respectively. After adding each type, stir for 30 - 60 seconds before adding another fiber, thus obtaining multi-scale hybrid fiber high-toughness concrete applicable to vulnerable parts of road bridges. Its mechanical property technical indicators are listed in Table 4.

[0093] Comparative Example 1

[0094] The difference between this comparative example and Example 1 is that steel fiber SF, polypropylene coarse fiber CPF1, and polypropylene fine fiber CPF2 are omitted. Its mechanical property technical indicators are listed in Table 5.

[0095] Comparative Example 2

[0096] The difference between this comparative example and Example 1 is that polypropylene coarse fiber CPF1 and polypropylene fine fiber CPF2 are omitted, and the steel fiber SF is adjusted to 117 kg / m 3 , and its mechanical property technical indicators are listed in Table 5.

[0097] Comparative Example 3

[0098] The difference between this comparative example and Example 1 is that polypropylene fine fiber CPF2 is omitted, and the steel fiber SF is adjusted to 39 kg / m 3 , and polypropylene coarse fiber CPF1 is 9 kg / m 3 , and its mechanical property technical indicators are listed in Table 5.

[0099] Table 4. Performance indicators of multi-scale hybrid fiber high-toughness concrete

[0100]

[0101] Table 5. Performance indicators of ordinary concrete, steel fiber concrete, and steel-polypropylene hybrid fiber concrete

[0102]

[0103] Table 4 description: The multi-scale hybrid fiber concrete prepared at a relatively low cost has good compressive strength, splitting tensile strength, flexural strength and flexural toughness. On the basis of ordinary concrete, increasing a certain material cost makes it have good mechanical property indexes and has good engineering application value.

[0104] Table 5 description: Compared with the ordinary concrete of Comparative Example 1, although the cost of the multi-scale hybrid fiber concrete of the present invention increases by 400 - 600 yuan / m 3 , its splitting tensile strength and flexural strength are respectively increased by 54.4% - 91.3% and 85.1% - 115.55%, and the mechanical properties of the concrete are significantly improved.

[0105] Compared with the multi-scale hybrid fiber high-toughness concrete of the present invention, the compressive strength, splitting tensile strength, flexural strength and flexural toughness of the steel fiber concrete of the ordinary concrete of Comparative Example 2 are not significantly improved, while its cost increases by 35% - 81.2%, and its application value is significantly lower than that of the multi-scale hybrid fiber concrete.

[0106] Compared with the steel-polypropylene coarse fiber concrete of Comparative Example 3, it can be seen that under the condition of similar material costs, the multi-scale hybrid fiber high-toughness concrete of the present invention has a better improvement effect on the compressive strength, splitting tensile strength, flexural strength and flexural toughness of the concrete. It can be seen that a reasonable combination of multi-scale fibers can give full play to the characteristics of various fibers, thereby improving the comprehensive performance of the concrete.

[0107] The multi-scale hybrid fiber high-toughness concrete of the present invention has a multi-scale hybrid fiber high-toughness concrete with low cost and excellent mechanical properties. Applying it to vulnerable parts such as bridge expansion joints and negative moment areas can effectively improve the service life of the bridge and reduce the maintenance cost, and has high economic benefits.

[0108] The multi-scale hybrid fiber high-toughness concrete and its preparation method provided by the present invention reduce the material cost and significantly improve the basic mechanical properties of the concrete, especially the flexural toughness, by optimizing the raw material mix ratio and adding appropriate amounts of SF, CPF1, and CPF2. It can effectively solve the problem of easy damage to key parts in bridge engineering and has broad application prospects.

[0109] The above description is only the preferred embodiments of the present application and the description of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the technical solutions formed by mutually replacing the above features with the technical features (but not limited to) having similar functions disclosed in the present application.

Claims

1. A multi-scale hybrid fiber high-toughness concrete, characterized in that, Comprising 155 - 165 parts by mass of water, 400 - 450 parts by mass of cement, 30 - 70 parts by mass of fly ash, 1000 - 1100 parts by mass of crushed stone, 700 - 750 parts by mass of river sand, 0.65 - 0.75 parts by mass of water reducing agent, 390 - 500 parts by mass of steel fiber, 40 - 50 parts by mass of polypropylene coarse fiber, 2 - 6 parts by mass of polypropylene fine fiber; The particle size of the crushed stone is 5 - 10 mm; The steel fiber is end - hooked steel fiber, and the diameter of the end - hooked steel fiber is 0.75 mm; The diameter of the polypropylene coarse fiber is 0.75 mm; The diameter of the polypropylene fine fiber is 0.2 mm.

2. The multi-scale hybrid fiber high-toughness concrete according to claim 1, wherein The fineness modulus of the river sand is 2.

85.

3. The multi-scale hybrid fiber high-toughness concrete according to claim 1, wherein The water reducing agent is polycarboxylate high - performance water reducing agent.

4. The multi-scale hybrid fiber high-toughness concrete according to claim 1, characterized in that, The cement is 52.5 - grade ordinary Portland cement.

5. The multi-scale hybrid fiber high-toughness concrete according to claim 1, characterized in that The fly ash is Class - I fly ash.

6. A preparation method of the multi-scale hybrid fiber high-toughness concrete according to any one of claims 1 to 5, characterized in that, Comprising the following steps: Dry - mix 400 - 450 parts by mass of cement, 30 - 70 parts by mass of fly ash, 1000 - 1100 parts by mass of crushed stone, 700 - 750 parts by mass of river sand evenly to obtain powder materials; Add 155 - 165 parts by mass of water and 0.65 - 0.75 parts by mass of water reducing agent into the powder materials and stir evenly to obtain wet materials; Add 390 - 500 parts by mass of steel fiber, 40 - 50 parts by mass of polypropylene coarse fiber, 2 - 6 parts by mass of polypropylene fine fiber into the wet materials and stir evenly to prepare multi - scale hybrid fiber high - toughness concrete.

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