Low-shrinkage hybrid fiber concrete and use method thereof

Abstract

The invention belongs to the technical field of high-performance cement concrete, and particularly relates to low-shrinkage hybrid fiber concrete and a use method thereof. The low-shrinkage hybrid fiber concrete is prepared by mixing cement, fly ash, sand, gravel, steel fibers, synthetic fibers, water and a water reducing agent according to the mass ratio of (410 to 390): (70 to 100): (780 to 750): (900 to 1100): (95 to 65): 1.1: (150 to 160): (8.9 to 7.5). According to the invention, the dispersibility of the steel fibers and the synthetic fibers can be ensured, and the workability of concrete construction is ensured. Hybrid fibers of the concrete have high tensile strength, development of bridge deck concrete cracks is effectively delayed, the fracture resistance of the concrete is improved, the elastic modulus of the concrete is also improved, and therefore the axial tensile strength of the concrete is also obviously improved; meanwhile, the shrinkage performance of the concrete is effectively improved, the durability of the concrete is improved, the service life of the concrete is greatly prolonged, other stress structures of the bridge are effectively protected, and then the overall service life of the bridge is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-performance cement concrete, and particularly relates to a low-shrinkage hybrid fiber concrete and a using method thereof. Background Art

[0002] The application technology of high-performance cement concrete has a history of more than a hundred years, and it is an important building material now and in the future. With the continuous improvement of the strength of concrete in modern architecture, various high-performance concretes have emerged. High-strength concrete and high-performance concrete are constantly being optimized and improved, and the application of fiber concrete has received increasing attention.

[0003] In the prior art, the durability and crack resistance of the concrete for the paving of steel box girder bridges are not ideal enough. The preparation method, transportation method, on-site paving method, curing technology after molding, and adoption of quality control measures of cement concrete all have a great influence on the performance display.

[0004] In order to improve and enhance the durability and crack resistance of the concrete for the paving of steel box girder bridges, it is of extremely important significance to research and improve the concrete mix ratio, reasonable transportation method, on-site paving method, curing technology after molding, strict quality control measures, etc. Summary of the Invention

[0005] The present invention provides a low-shrinkage hybrid fiber concrete and a using method thereof, aiming to improve the durability and crack resistance of the concrete by adding steel fibers and synthetic fibers. At the same time, a novel mixing production technology is adopted to solve the uniform distribution of fibers in the concrete, and the application of the hybrid fiber concrete is implemented and improved through reasonable transportation methods, on-site paving methods, curing technology after molding, strict quality control measures, etc.

[0006] To achieve the above object, the technical solution adopted by the present invention is: A low-shrinkage hybrid fiber concrete, which is composed of cement, fly ash, sand, crushed stone, steel fibers, synthetic fibers, water and water reducing agent mixed in a mass ratio of 410 - 390:70 - 100:780 - 750:900 - 1100:95 - 65:1.1:150 - 160:8.9 - 7.5.

[0007] The crushed stone is composed of crushed stone with a particle size of 5 - 10 mm and crushed stone with a particle size of 10 - 25 mm mixed together.

[0008] The crushed stone with a particle size of 5 - 10 mm and the crushed stone with a particle size of 10 - 25 mm are mixed in a mass ratio of 3 - 4:6 - 7.

[0009] The sand used is river sand, and the particle size of the river sand is 2.6 - 3.05 mm; the synthetic fiber used is polyacrylonitrile fiber.

[0010] The water reducing agent used is a polycarboxylate water reducing agent.

[0011] A method for using low shrinkage hybrid fiber concrete includes the following steps: Step 1: Prepare low shrinkage hybrid fiber concrete and monitor it; Step 2: Transport the low shrinkage hybrid fiber concrete; Transport it according to 4 - 6m 3 per single transport; Step 3: Carry out on - site construction and monitor; Step 4: Cure the low shrinkage hybrid fiber concrete.

[0012] The specific method for preparing the low shrinkage hybrid fiber concrete mixture in Step 1 is to directly add it manually on the flat belt; the feeding sequence is: powder materials - fibers - liquid materials; specifically, first add the proportioned sand, gravel, cement, and fly ash and stir and mix them fully for 1 - 2 minutes, then batch - wise and evenly put the proportioned steel fibers and synthetic fibers into the mixer in several times within 1 - 1.5 minutes, continue to stir for 2 - 4 minutes, then add the proportioned water and water reducing agent and stir for 4 - 6 minutes. After the concrete is stirred evenly as a whole, it can be discharged.

[0013] The monitoring of preparing the low shrinkage hybrid fiber concrete in Step 1 includes the inspection of the hybrid fiber content and the inspection during the mixing and pouring process of the hybrid fiber concrete. The specific process is as follows: Inspection of the hybrid fiber content: S1. Take samples at the concrete pouring site to inspect the content of the hybrid fibers; Inspect at least twice per working shift, take three groups of samples each time, and each group of samples is 10L; S2. Inspect by the water washing method; Use the method of washing and collecting steel fibers with water and a magnet to wash out the steel fibers from the concrete at the pouring site. At the same time, the synthetic fibers will float on the water surface. Take them out, wash them, dry them, and then weigh them separately. The deviation of the content of single - sampled steel fibers and steel - like fibers shall not exceed 20% of the proportioned content; the deviation of the average content of the above - mentioned two types of fibers for every three samplings shall not exceed 5% of the proportioned content; Inspection during the mixing and pouring process of the hybrid fiber concrete: Check the quality and dosage of the constituent materials of the hybrid fiber concrete, not less than 2 times per working shift. When the water content changes significantly, increase the number of checks, and adjust the water consumption and material dosage in a timely manner according to the test results. After the hybrid fiber concrete is stirred, check the uniformity, consistency and steel fiber volume ratio of the mixture once per working shift. The hybrid fiber concrete mixture should be evenly mixed, with the same color, and there should be no segregation, bleeding or agglomeration of hybrid fibers. After the concrete is stirred, samples should be taken on-site to detect the slump and air content of the concrete, and observe the cohesiveness and water retention of the concrete mixture.

[0014] The specific method of on-site construction in Step 3 is to lay low-shrinkage hybrid fiber concrete on the bridge deck. The height of the concrete is 5-10 mm higher than the height of the completed bridge deck. The free fall height of the fiber concrete mixture during pouring does not exceed 1.5 m. Then level and compact the concrete. The surface finishing is carried out in two times for the bridge position pouring. The working bridge follows immediately, and the manual finishing is completed on the working bridge.

[0015] The specific method of on-site construction monitoring in Step 3 is to check the slump of the hybrid fiber concrete at the mixing site and the pouring site. Randomly extract specimens for the compressive strength, flexural strength, elastic modulus and axial tension of the concrete at the construction site. The sampling frequency, number of groups and inspection and evaluation are carried out according to the preset requirements.

[0016] The beneficial effects produced by the present invention: (1) The present invention uses low-shrinkage hybrid fiber concrete for the underground bridge deck paving, which greatly improves the service life of the concrete, effectively protects other stress-bearing structures of the bridge, and improves the overall service life of the bridge.

[0017] (2) The low-shrinkage hybrid fiber concrete of the present invention is added with end-structured steel fibers, namely high-performance steel fibers and polypropylene fibers, and is made of raw materials such as PII portland cement, Class I fly ash, medium sand in Zone II, 5-25 mm limestone crushed stone, and polycarboxylate high-performance retarder. Under the mixing method and technology of the present invention, the dispersion of steel fibers and synthetic fibers and the workability of concrete construction are ensured. The hybrid fibers of the concrete have high tensile strength, so they can effectively delay the development of cracks in the bridge deck concrete, improve the flexural resistance of the concrete, and also increase the elastic modulus of the concrete. With the improvement of the flexural resistance and elastic modulus of the concrete, the axial tensile strength of the concrete also increases significantly. At the same time, it also effectively improves the shrinkage performance of the concrete and enhances the durability of the concrete.

[0018] The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly and implement it according to the content of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the drawings. Description of the Drawings

[0019] Figure 1 This is the usage flow chart of the present invention. Specific implementation manners

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] Embodiment 1: The invention provides a low-shrinkage hybrid fiber concrete, which is composed of cement, fly ash, sand, gravel, steel fiber, synthetic fiber, water and water reducer mixed according to a mass ratio of 410-390:70-100:780-750:900-1100:95-65:1.1:150-160:8.9-7.5.

[0022] In the low-shrinkage hybrid fiber concrete of the present invention, the steel fiber and the hybrid fiber are mixed with cement, fly ash, sand, gravel, water and water reducer by adopting the ratio of the present technical solution, which can ensure the dispersibility of the steel fiber and the synthetic fiber and ensure the workability of concrete construction. The hybrid fiber adopts this ratio, so that the prepared concrete has a high tensile strength, thus effectively delaying the development of cracks in the bridge deck concrete, improving the flexural resistance of the concrete, and also increasing the elastic modulus of the concrete. With the flexural resistance and elastic modulus of the concrete, the axial tensile strength of the concrete is also significantly increased; at the same time, the shrinkage performance of the concrete is effectively improved, and the durability of the concrete is improved. The steel fiber in this embodiment is an end-structured steel fiber, that is, a high-performance steel fiber.

[0023] The cement in this embodiment is PII portland cement, which has slow setting and hardening, low early strength, fast later strength growth, and good corrosion resistance.

[0024] In some embodiments, the gravel is composed of gravel with a particle size of 5-10 mm and gravel with a particle size of 10-25 mm mixed.

[0025] Further, the gravel with a particle size of 5-10 mm and the gravel with a particle size of 10-25 mm are mixed according to a mass ratio of 3-4:6-7.

[0026] In some embodiments, preferably, the sand used is river sand with a particle size of 2.6-3.0 mm; the synthetic fiber used is polyacrylonitrile fiber. Specifically in application, particle sizes such as 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm, etc. can be selected.

[0027] In some embodiments, the water reducing agent used is a polycarboxylate water reducing agent, which has the characteristics of high-efficiency slump retention and setting retardation. However, the water reduction rate of the water reducing agent should not be lower than 25%, and it should be harmless to concrete and steel.

[0028] The high-performance polycarboxylate water reducing agent is a water reducing agent based on a polymer synthesized from carboxyl unsaturated monomers and other monomers, with a high water reduction rate and good slump retention performance. Compared with other water reducing agents, when preparing high-strength concrete and high-durability concrete, the high-performance water reducing agent adsorbs at the interface of cement particles and forms an electric double layer, generating an electrostatic repulsive force, which strongly disperses the cement particles among the cement particles and prevents the dispersed particles from aggregating, destroying the viscous structure of the cement paste and diluting it. The mutual sliding ability between the dispersed cement particles increases, reducing the yield stress and plastic viscosity of the concrete mixture. Therefore, under the condition of greatly reducing the water-cement ratio, the fluidity increases. It promotes the full hydration of cement, improves the internal structure and interfacial adhesion of the cement stone, maintains and increases the workability, and prepares high-strength and high-workability steel fiber concrete, with obvious technical advantages and high cost performance.

[0029] Example Two: Refer to Figure 1 , a method for using a low-shrinkage hybrid fiber concrete of the present invention, includes the following steps: Step 1: Prepare low-shrinkage hybrid fiber concrete and monitor it; The specific method for preparing the low-shrinkage hybrid fiber mixture is to directly add it manually on the flat belt; when adding, add it evenly to ensure that the fibers are loose and even when added; the feeding sequence: powder materials - fibers - liquid materials; adopt the dry mixing method, that is, first add the proportioned sand, gravel, cement, and fly ash and stir and mix them fully for 1 - 2 minutes, then add the proportioned steel fibers and synthetic fibers in batches and evenly several times into the mixer within 1 - 1.5 minutes, continue to stir for 2 - 4 minutes, then add the proportioned water and water reducing agent and stir for 4 - 6 minutes. After the concrete is stirred evenly as a whole, it can be discharged. There should be no phenomenon of powder materials and fibers forming lumps in the mixture. After stirring is completed, no water or admixture can be added to the mixture.

[0030] The monitoring of preparing the low-shrinkage hybrid fiber concrete in Step 1 includes the inspection of the hybrid fiber content and the inspection during the mixing and pouring process of the hybrid fiber concrete. The specific process is as follows: Inspection of the hybrid fiber content: S1. Take samples at the concrete pouring site to inspect the content of the hybrid fibers; Inspect at least twice per working shift, take three groups of samples each time, and each group of samples is 10L; S2. Inspect by the water washing method; The method of collecting steel fibers from concrete by washing with water and magnets is to take samples at the pouring site and wash them out. At the same time, synthetic fibers will float on the water surface. Take them out, wash and dry them, and then weigh them separately. The content deviation of single-sampled steel fibers and steel fiber-like fibers shall not exceed 20% of the mixing ratio dosage; for every three samples or more, the deviation of the average content of the above two types of fibers shall not exceed 5% of the mixing ratio dosage. Inspection during the mixing and pouring process of hybrid fiber concrete: Inspect the quality and dosage of the constituent materials of hybrid fiber concrete, not less than 2 times per working shift. When the water content changes significantly, increase the number of inspections, and adjust the water consumption and material dosage in a timely manner according to the test results. After the hybrid fiber concrete is stirred, check the uniformity, consistency and steel fiber volume ratio of the mixture once per working shift. The hybrid fiber concrete mixture should be evenly mixed, with the same color, and there should be no segregation, bleeding or agglomeration of hybrid fibers; after the concrete is stirred, samples should be taken at the construction site to test the slump and air content of the concrete, and observe the cohesion and water retention of the concrete mixture.

[0031] Step 2: Transportation of low-shrinkage hybrid fiber concrete; The mixing time of hybrid fiber concrete per 1 m 3 is about 5 minutes. Considering the loss of the working performance of the concrete per unit time and the paving construction rate on site, adopt the measure of single transportation of 4 - 6 m 3 to ensure that the construction is completed within 1.5 hours of the working performance of the concrete and meet the on-site construction rate; Step 3: On-site construction and monitoring; Specifically: For the transportation of the bridge deck paving concrete, all use cranes to transport the concrete to the bridge deck and lay it manually. The height of the laid concrete should be 5 - 10 mm higher than the completed bridge deck height. First, level and compact it with two flat vibrators, and then level and compact it with a vibrating beam. The power of the flat vibrator is small, and covering about 100 mm of the already vibrated part can avoid the occurrence of vertical working joints. The free fall height of the fiber concrete mixture during pouring does not exceed 1.5 m. The concrete is initially leveled manually and vibrated by combining a flat vibrator and a vibrating beam. The vibration duration is based on the concrete not emitting bubbles, and then a three-roller steel drum is used to roll and lift the slurry. During leveling, the steel fibers should not be exposed on the surface. The surface finishing is carried out in two times. For the bridge position pouring, use a 12 m wide vibrating beam combined with a flat vibrator for paving and leveling. The working bridge follows closely, and the manual plastering is completed on the working bridge. When arranging a 12 m wide vibrating beam combined with a flat vibrator, adjust the height according to the formwork elevation. During the vibration process, keep the flat vibrator at the same height as the formwork to ensure the concrete pouring elevation. When vibrating and constructing, the excitation force provided by the equipment should not be too large, and the vibration time should not be too long to avoid the phenomenon of sparse distribution at the top and dense distribution at the bottom of the steel fibers in the bridge deck.

[0032] During in-situ casting, vibration shall be carried out evenly without omission or over-vibration until the concrete surface shows slight slurry oozing, and then it shall be leveled immediately. It shall be ensured that all parts of the concrete are vibrated evenly and sufficiently. During the casting process, for the parts with local surface defects, manual plastering repair shall be carried out using the working bridge erected on the tracks on both sides of the casting surface. There shall be no defects on the surface after plastering. While plastering, use an aluminum alloy straightedge to detect the flatness of the surface after forming in a timely manner. If the flatness does not meet the requirements, it shall be dealt with immediately.

[0033] The specific method for on-site construction monitoring is to check the slump of the hybrid fiber concrete at the mixing site and the pouring site; randomly extract specimens for compressive strength, flexural strength, elastic modulus, and axial tension of the concrete at the construction site. The sampling frequency, number of groups, and inspection and evaluation shall be carried out in accordance with the "Technical Specification for Application of Fiber Reinforced Concrete" JGJ / T 221-2010 and the requirements of the engineering design documents.

[0034] Step Four: Curing of low-shrinkage hybrid fiber concrete; The early strength of the hybrid fiber concrete is relatively high, so it is necessary to strengthen the early curing of the concrete and strictly implement the specified curing system. The low-shrinkage hybrid fiber concrete shall be watered and cured in a timely manner after initial setting and covered with geotextiles to keep it in a moist state. Sewage or water harmful to the concrete and its strength development shall not be used for curing, and the curing period shall be no less than 14 days. During the curing period, the concrete shall not be subjected to external forces. During the concrete curing period, focus on strengthening the control of the humidity and temperature of the concrete, minimize the exposure time of the surface concrete as much as possible, arrange special personnel to check the tight coverage of the geotextiles to ensure complete coverage, and prevent the surface temperature of the concrete from changing violently due to environmental factors.

[0035] Example Three: Comparative experiment The hybrid fibers and other raw materials in the concrete are incorporated at the mass dosage of the proportioning. The total cementitious materials are designed to be 500 kg / m 3 , and the designed bulk density is 2500 kg / m 3 , and the water reducing agent is 1.6% of the total cementitious materials.

[0036] Table 1 Mix proportion trial mix of C50 hybrid fiber concrete (kg / m 3 )

[0037] In the above table, No. 1-2 are the mix proportions of a certain municipal design institute, and No. 3-4 are the design mix proportions of the laboratory of the present invention.

[0038] Table 2 Performance data of concrete mixtures

[0039] It can be seen from the test results of the above mix ratio that appropriate increase in some cementitious materials and appropriate reduction in the dosage of steel fibers have achieved good results. Moreover, the dosage of the admixture has also been reduced from 1.9% to 1.5%, and the properties of the mixture can fully meet the requirements of on-site pumping construction.

[0040] The main purpose of adding hybrid fibers is to inhibit the generation and expansion of cracks at different structural levels. At the same time, the fibers complement each other in terms of performance, thus changing the multi-level properties of concrete, learning from each other's strengths and compensating for each other's weaknesses, and exerting the "positive hybrid effect" at different levels and loading stages to enhance concrete. The specific manifestations are as follows: a. Improving the tensile strength or flexural strength; b. Improving the impact strength; c. Controlling the crack expansion and changing the failure mode by the ductility after the matrix cracks; d. Changing the rheological properties or fluidity of the fresh mixture.

[0041] If the volume fraction of hybrid fibers is too small, it cannot achieve the strengthening effect. If it is too large, it will not only fail to strengthen, but will instead reduce the inherent strength of the matrix. Increasing the fiber content can improve many properties of cement or concrete after hardening, but it also reduces the fluidity of their mixtures at the initial preparation stage. Seriously, it is difficult to evenly disperse the reinforcing fibers in the matrix, and it is easy to cause the setting time of the matrix to become longer or even unable to solidify, thus reducing the original strength of the matrix. It can only play a positive role when incorporated into concrete in a suitable proportion. It can be seen from the data in Table 1 and Table 2 that when using the raw materials at the construction site and applying the mix ratio designed by the design institute, due to the relatively high proportion of hybrid fibers in the recommended mix ratio, the workability and fluidity of the concrete mixture are seriously affected, and it is difficult to meet the requirements of pumping construction. After optimizing and adjusting the mix ratio, the construction performance of the mixture has been greatly improved, meeting the construction requirements.

[0042] Table 3 Concrete mechanical property data

[0043] Relevant literature studies have shown that in steel fiber and polyacrylonitrile fiber hybrid reinforced concrete, the enhancement of the flexural strength of fiber concrete is mainly contributed by steel fibers, and polyacrylonitrile fibers only assist in changing the internal structure of concrete, and have little direct enhancement effect on concrete. The main reason for polyacrylonitrile fibers to improve the initial flexural cracking strength of concrete is to reduce the internal cracks in concrete at the initial hardening stage and optimize the internal structure of concrete, and they have little contribution to the hardened concrete before cracking under load. In addition, the density of polyacrylonitrile fibers is relatively small, and they can "support" the aggregates when floating during vibration. After being mixed with steel fibers, they can also "support" the steel fibers, making the steel fibers better and more evenly dispersed into the interior of concrete, so that a large number of steel fibers will not sink to the bottom of the specimen. During the test, the side fiber concrete during specimen molding is used as the tensile zone, which greatly increases the number of steel fibers in the tensile zone of concrete during the test, reduces the fiber spacing, and correspondingly increases the enhancement effect on concrete.

[0044] It can be seen from the mechanical property data of steel fiber concrete with two different shapes in the above table that when the volume fraction of steel fiber in the hybrid fiber incorporated into the concrete is 0.83% and the volume fraction of synthetic fiber is 0.10%, the flexural strength and axial tensile strength of the concrete can be effectively improved.

[0045] The mechanical properties of the concrete mixed with the optimized mix ratio can meet the design requirements.

[0046] Table 4 Durability performance data of concrete

[0047] It can be seen from the above table that the elastic modulus of the fiber after incorporation is relatively higher than that of the matrix in the initial setting stage, increasing the tensile strength of the plastic and hardened initial composite body, which can effectively inhibit the generation and development of early shrinkage cracks in the concrete, reduce the porosity of the concrete, especially inhibit the generation of connected cracks; at the same time, the fiber reduces the water loss area of the matrix and makes it difficult for water to migrate, thus reducing the capillary tension formed by capillary water loss shrinkage and improving the impermeability of the concrete. In addition, the addition of the fiber effectively inhibits the development of internal cracks, improves the crack resistance effect of the concrete, and the chloride ion penetration coefficient at 28 days is lower than 4.0×10 -12 , achieving the effect of improving the chloride ion erosion resistance of the concrete. The fibers are randomly distributed in three dimensions in the cement matrix, forming a network support structure, which can effectively prevent and inhibit the sinking of aggregates and slow down the evaporation of surface water in the concrete matrix; a large number of fibers evenly distributed in the matrix can bear the stress generated by the volume deformation of the cement matrix and reduce the shrinkage of the cement matrix. It is precisely by inhibiting the volume deformation of the cement matrix, weakening the stress concentration effect, and reducing its shrinkage that are all less than the design specified values.

[0048] It can be seen from the durability performance data of steel fiber concrete with two different shapes in the above table that the durability performance parameters of the concrete mixed with the optimized mix ratio can meet the design requirements. Comparing the two different shapes of steel fibers, the shrinkage rate of the concrete with end-hooked fibers is less than that of the wave-shear-shaped fibers. This may be because the uneven surface of the wave-shaped steel fibers increases the frictional force of dispersion, and the dispersion effect is worse than that of the end-hooked fibers within the same mixing time, resulting in uneven distribution in the concrete and making it difficult to effectively inhibit the shrinkage of the concrete matrix.

[0049] Without conflict, those skilled in the art can combine the relevant technical features in the above examples according to the actual situation to achieve the corresponding technical effects. The specific combinations are not elaborated one by one here.

[0050] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship, movement conditions, etc. between components in a specific posture (as shown in the attached drawings). If the specific posture changes, the directional indications will also change accordingly.

[0051] In addition, the descriptions involving "first", "second", etc. in the present invention are only for descriptive purposes and cannot be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature.

[0052] As described above, these are only the preferred embodiments of the present invention. The present invention will not be limited to these embodiments shown herein, but rather should conform to the broadest scope consistent with the principles and novel features disclosed herein. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solutions of the present invention.

Claims

1. A low shrinkage hybrid fiber concrete, characterized in that: It comprises cement, fly ash, sand, crushed stone, steel fiber, synthetic fiber, water and water reducing agent in a mass ratio of 410-390:70-100:780-750:900-1100:95-65:1.1:150-160:8.9-7.

5.

2. A low shrinkage hybrid fiber concrete as claimed in claim 1, characterized in that: The crushed stone is a mixture of crushed stones with a particle size of 5 to 10 mm and crushed stones with a particle size of 10 to 25 mm.

3. A low shrinkage hybrid fiber concrete as claimed in claim 2, characterized in that: The crushed stones with a particle size of 5 to 10 mm and 10 to 25 mm are mixed in a mass ratio of 3 to 4:6 to 7.

4. The low shrinkage hybrid fiber concrete according to claim 1, characterized in that: The sand used is river sand, and the particle size of the river sand is 2.6-3.05 mm; the synthetic fiber used is polyacrylonitrile fiber.

5. The low shrinkage hybrid fiber concrete according to claim 1, characterized in that: The water reducing agent used is a polycarboxylic acid water reducing agent.

6. A method for using the low shrinkage hybrid fiber concrete according to any one of claims 1 to 5, characterized in that: The following steps are included: Step 1: Preparation and monitoring of low shrinkage hybrid fiber concrete; Step 2: Transportation of low shrinkage hybrid fiber concrete; According to single transport 4-6m 3 to transport; Step 3: On-site construction and monitoring; Step 4: Curing of low shrinkage hybrid fiber concrete.

7. The method for using the low shrinkage hybrid fiber concrete according to claim 6, characterized in that: The specific method for preparing the low shrinkage mixed fiber mixture in step 1 is to manually add it directly on the flat belt; the feeding sequence is: powder material - fiber - liquid material; specifically, first add the proportion of sand, gravel, cement, and fly ash and stir and mix them for 1 to 2 minutes, then add the proportion of steel fiber and synthetic fiber into the mixer several times in batches within 1 to 1.5 minutes, continue to stir for 2 to 4 minutes, then add the proportion of water and water reducing agent and stir for 4 to 6 minutes, and discharge the material after the concrete is stirred evenly as a whole.

8. The method for using the low shrinkage hybrid fiber concrete according to claim 6, characterized in that: The monitoring of preparing low shrinkage hybrid fiber concrete in step 1 includes hybrid fiber dosage inspection and hybrid fiber concrete inspection during mixing and pouring. The specific process is as follows: Mixed fiber content test: S1. The amount of mixed fiber is sampled and tested at the concrete pouring site; Each work shift shall be inspected at least twice, and three groups of samples shall be taken each time, and each group of samples shall be 10L; S2, tested by water washing method; The steel fibers are collected from the concrete by using a water-washing magnet to collect the steel fibers. The synthetic fibers will float on the water surface. They are taken out, cleaned, dried and weighed separately. The deviation of the steel fiber and imitation steel fiber content in a single sample shall not exceed 20% of the proportion of the mixed amount; the deviation of the average value of the two fiber contents in every three samples shall not exceed 5% of the proportion of the mixed amount; Inspection of hybrid fiber concrete during mixing and pouring: Check the quality and amount of the constituent materials of the hybrid fiber concrete at least twice per work shift. When there is a significant change in the water content, increase the number of times and adjust the water consumption and material consumption in time according to the test results. After the hybrid fiber concrete is mixed, check the uniformity, consistency and steel fiber volume ratio of the mixture once per work shift. The hybrid fiber concrete mixture should be mixed evenly, with a uniform color, without segregation, bleeding, and mixed fiber agglomeration. After the concrete mixing is completed, samples should be taken at the construction site to test the slump and air content of the concrete, and observe the cohesiveness and water retention of the concrete mixture.

9. The method for using the low shrinkage hybrid fiber concrete according to claim 6, characterized in that: The specific method of on-site construction of step three is to lay low shrinkage hybrid fiber concrete on the bridge deck, the concrete height is 5-10mm higher than the completed bridge deck height, and the free height of the fiber concrete mixture poured does not exceed 1.5m; then the concrete is leveled and compacted; the bridge position is poured in two times; the working bridge follows closely, and the manual finishing is completed on the working bridge.

10. The method for using the low shrinkage hybrid fiber concrete according to claim 6, characterized in that: The method of on-site construction monitoring in step three is specifically to check the slump of mixed fiber concrete at the mixing site and the pouring site; randomly select concrete compression, flexural strength, elastic modulus and axial tension test pieces at the construction site, and the sampling frequency, number of groups and inspection and evaluation are carried out according to preset requirements.

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