Urban rail transit ballast bed filling steel fiber fine aggregate concrete and preparation method thereof

Abstract

The invention relates to urban rail transit ballast bed filling steel fiber fine aggregate concrete and a preparation method thereof. The urban rail transit ballast bed filling steel fiber fine aggregate concrete is prepared from the following raw materials in parts by weight: 300 to 400 parts of cement, 8 to 20 parts of silica fume, 120 to 200 parts of fly ash, 70 to 100 parts of mineral powder, 160 to 250 parts of water, 7 to 15 parts of water reducing agent, 800 to 1100 parts of sand, 800 to 1000 parts of stone, 10 to 30 parts of steel fiber I and 10 to 30 parts of steel fiber II. The compressive strength, the bending strength and the bending toughness ratio of the steel fiber reinforced concrete are improved, so that the links of manufacturing, binding, mounting and the like of a reinforcing mesh in a concrete filling layer can be canceled by virtue of the mechanical property and the physical enhancement effect of a steel fiber reinforced concrete material under the condition of guaranteeing the bearing capacity of the plate, the production efficiency of the prefabricated plate is improved, and the production cost is reduced. Therefore, the production cost of the precast slab is reduced, and the engineering application requirements of urban rail transit ballast bed filling concrete are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of urban rail transit track engineering, and particularly relates to a steel fiber fine aggregate concrete for filling the roadbed of urban rail transit and a preparation method thereof. Background Art

[0002] This section aims to provide background or context for the embodiments of the present invention described in the claims. The description herein is not admitted to be prior art merely by including it in this section.

[0003] To achieve a more efficient, higher-quality, and more reliable low-carbon track construction path, prefabricated track technology has attracted much attention and has been widely applied to the traditional slab tracks of subway lines in many domestic cities. The track structure consists of parts such as rails, fasteners, track slabs, concrete filling layers, backfill layers, limiting structures, and vibration damping cushions. Although compared with the cast-in-place integral roadbed structure, the traditional slab track structure has simplified the process, improved the construction efficiency, and enhanced the integrity of the roadbed, the construction advantages have not been fully demonstrated because there are still links such as the production, binding, and installation of steel mesh in the concrete filling layer.

[0004] Steel fiber concrete is a new type of multiphase composite material formed by mixing randomly distributed steel fibers into ordinary concrete. These freely distributed steel fibers can effectively hinder the expansion of microcracks and the formation of macro-cracks inside the concrete, and significantly improve the tensile, flexural, impact resistance, and fatigue resistance of the concrete. Although the research on steel fiber concrete has continued for many years and it has been widely used in fields such as construction, highway pavements, municipal engineering, and bridges, the systematic research on steel fiber fine aggregate concrete in urban rail transit, especially as a filling layer material in the slab track structure, is still blank. Summary of the Invention

[0005] The object of the present invention is to provide a steel fiber concrete with a relatively high flexural toughness ratio, a preparation method thereof, and an application in the roadbed of urban rail transit.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] The first aspect of the present invention provides a steel fiber concrete, which comprises raw materials in the following parts by weight: 300-400 parts of cement, 8-20 parts of silica fume, 120-200 parts of fly ash, 70-100 parts of mineral powder, 160-250 parts of water, 7-15 parts of water reducing agent, 800-1100 parts of sand, 800-1000 parts of gravel, 10-30 parts of steel fiber I, and 10-30 parts of steel fiber II; wherein, both steel fiber I and steel fiber II are end-hooked steel fibers, the equivalent diameter of steel fiber I is 0.7-0.8 mm, and the length is 45-55 mm; the equivalent diameter of steel fiber II is 0.7-0.8 mm, and the length is 30-40 mm.

[0008] According to some specific embodiments, the equivalent diameter of the steel fiber I is 0.7 mm, 0.72 mm, 0.74 mm, 0.76 mm, 0.78 mm or 0.8 mm.

[0009] According to some specific embodiments, the length of the steel fiber I is 45 mm, 46 mm, 47 mm, 48 mm, 49 mm, 50 mm, 51 mm, 52 mm, 53 mm, 54 mm or 55 mm.

[0010] According to some specific embodiments, the equivalent diameter of the steel fiber II is 0.7 mm, 0.72 mm, 0.74 mm, 0.76 mm, 0.78 mm or 0.8 mm.

[0011] According to some specific embodiments, the length of the steel fiber II is 30 mm, 31 mm, 32 mm, 33 mm, 34 mm, 35 mm, 36 mm, 37 mm, 38 mm, 39 mm or 40 mm.

[0012] According to some specific embodiments, the aspect ratio of the steel fiber I is 65-69, such as 65, 66, 67, 68 or 69, and the tensile strength is 1200-1250 MPa, such as 1200 MPa, 1210 MPa, 1220 MPa, 1230 MPa, 1240 MPa or 1250 MPa; the aspect ratio of the steel fiber II is 43-50, such as 43, 44, 45, 46, 47, 48, 49 or 50, and the tensile strength is 1050-1150 MPa, such as 1050 MPa, 1060 MPa, 1070 MPa, 1080 MPa, 1090 MPa, 1100 MPa, 1110 MPa, 1120 MPa, 1130 MPa, 1140 MPa or 1150 MPa.

[0013] According to some specific embodiments, the cross sections of the steel fiber I and the steel fiber II are circular.

[0014] According to some specific embodiments, the weight parts of the cement are 300 parts, 310 parts, 320 parts, 330 parts, 340 parts, 350 parts, 360 parts, 370 parts, 380 parts, 390 parts or 400 parts.

[0015] According to some specific embodiments, the weight parts of the silica fume are 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts or 20 parts.

[0016] According to some specific embodiments, the weight parts of the fly ash are 120 parts, 130 parts, 140 parts, 150 parts, 160 parts, 170 parts, 180 parts, 190 parts or 200 parts.

[0017] According to some specific embodiments, the weight parts of the blast furnace slag powder are 70 parts, 80 parts, 90 parts or 100 parts.

[0018] According to some specific embodiments, the weight parts of the water are 160 parts, 170 parts, 180 parts, 190 parts, 200 parts, 210 parts, 220 parts, 230 parts, 240 parts or 250 parts.

[0019] According to some specific embodiments, the weight parts of the water reducing agent are 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts or 15 parts.

[0020] According to some specific embodiments, the weight parts of the sand are 800 parts, 810 parts, 820 parts, 830 parts, 840 parts, 850 parts, 860 parts, 870 parts, 880 parts, 890 parts, 900 parts, 910 parts, 920 parts, 930 parts, 940 parts, 950 parts, 960 parts, 970 parts, 980 parts, 990 parts, 1000 parts, 1010 parts, 1020 parts, 1030 parts, 1040 parts, 1050 parts, 1060 parts, 1070 parts, 1080 parts, 1090 parts or 1100 parts.

[0021] According to some specific embodiments, the weight parts of the gravel are 800 parts, 810 parts, 820 parts, 830 parts, 840 parts, 850 parts, 860 parts, 870 parts, 880 parts, 890 parts, 900 parts, 910 parts, 920 parts, 930 parts, 940 parts, 950 parts, 960 parts, 970 parts, 980 parts, 990 parts or 1000 parts.

[0022] According to some specific embodiments, the weight parts of the steel fiber I are 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts or 30 parts.

[0023] According to some specific embodiments, the weight parts of the steel fiber II are 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts or 30 parts.

[0024] According to some specific embodiments, it comprises the following raw materials in parts by weight: 300 - 350 parts of cement, 10 - 18 parts of silica fume, 120 - 140 parts of fly ash, 70 - 90 parts of slag powder, 160 - 180 parts of water, 7 - 15 parts of water reducing agent, 800 - 1000 parts of sand, 800 - 850 parts of gravel, 10 - 15 parts of steel fiber I, and 13 - 18 parts of steel fiber II.

[0025] Further, it comprises the following raw materials in parts by weight: 300 - 320 parts of cement, 13 - 17 parts of silica fume, 120 - 130 parts of fly ash, 70 - 80 parts of slag powder, 160 - 170 parts of water, 8 - 12 parts of water reducing agent, 850 - 950 parts of sand, 800 - 830 parts of gravel, 10 - 13 parts of steel fiber I, and 13 - 14 parts of steel fiber II.

[0026] According to some specific embodiments, the cement is Portland cement with a strength grade of 42.5.

[0027] According to some specific embodiments, the residue on 45μm square hole sieve of the silica fume is ≤3%, and the SiO2 content is ≥90%.

[0028] According to some specific embodiments, the fly ash is of grade I.

[0029] According to some specific embodiments, the specific surface area of the slag powder is greater than 400m 2 / kg.

[0030] According to some specific embodiments, the water reducing agent is a liquid polycarboxylate superplasticizer with a water reducing rate of ≥25%.

[0031] According to some specific embodiments, the sand is natural sand with a fineness modulus of 2.5 - 3.0 and an apparent density of ≥2500kg / m 3 .

[0032] According to some specific embodiments, the particle size range of the gravel is 4.75 - 20mm, and the apparent density is

[0033] 2800 - 3000kg / m 3 .

[0034] The second aspect of the present invention provides a method for preparing the steel fiber concrete as described above. After mixing the raw materials evenly according to the formula amount, the steel fiber concrete is obtained through casting and curing.

[0035] According to some specific embodiments, the preparation method includes the following steps:

[0036] 1) Weigh cement, silica fume, fly ash, slag powder, water reducing agent, sand, gravel, steel fiber I, steel fiber II and water respectively according to the formula amount;

[0037] 2) Pour the weighed sand and gravel into a forced horizontal shaft mixer, add additional water and stir for 1 - 2 minutes to pre-wet the aggregates;

[0038] 3) Pour the weighed cement, silica fume, fly ash and slag powder into a mortar mixer, and stir with the pre-wetted aggregates for 1 - 2 minutes to mix them evenly;

[0039] 4) Pour the weighed mixing water and water reducing agent into the mixture obtained in step 3) and continue to stir for 4 - 5 minutes;

[0040] 5) Pour the weighed steel fiber I and steel fiber II into the mixture obtained in step 4) and continue to stir for 2 - 3 minutes. After casting and curing, the steel fiber concrete is obtained.

[0041] The third aspect of the present invention provides an application of the steel fiber concrete as described above in the track bed of urban rail transit.

[0042] According to some specific embodiments, the steel fiber concrete is used as the concrete filling layer material of the track bed of urban rail transit.

[0043] Due to the application of the above technical solutions, the present invention has the following advantages compared with the prior art:

[0044] Through the improvement of the raw material ratio of the steel fiber concrete, especially through the combined use of specific types and specific proportions of steel fiber I and steel fiber II, and then cooperating with other raw materials, the compressive strength, flexural strength and flexural toughness ratio of the prepared steel fiber concrete are improved. Furthermore, by virtue of the mechanical properties and physical enhancement effects of the steel fiber concrete material, the production efficiency of precast slabs can be improved by canceling the processes of making, tying and installing the steel mesh in the concrete filling layer while ensuring the bearing capacity of the slab, thereby reducing the production cost of precast slabs and meeting the engineering application requirements of the filling concrete for the track bed of urban rail transit. Specific Embodiments

[0045] Since there are still links such as the production, binding and installation of the steel bar mesh in the concrete filling layer, the construction advantages have not been fully demonstrated. Therefore, in order to further improve the construction efficiency and reduce the difficulty of construction quality control, a new type of assembled track structure has come into the public eye and received extensive attention. The biggest feature of the track bed filling structure of the new type of assembled track structure is the simplification of the construction process. Steel fiber concrete is used as the filling layer material, the arrangement of the steel bar mesh in the filling layer is cancelled, and the intelligent assembly and green and low-carbon construction of the track structure are realized.

[0046] Through the improvement of the raw material ratio of the steel fiber concrete, especially through the combined use of specific types and specific proportions of steel fiber Ⅰ and steel fiber Ⅱ, and then working synergistically with other raw materials, the compressive strength, flexural strength and flexural toughness ratio of the prepared steel fiber concrete are improved. Furthermore, by virtue of the mechanical properties and physical enhancement effect of the steel fiber concrete material, the links such as the production, binding and installation of the steel bar mesh in the concrete filling layer can be cancelled while ensuring the bearing capacity of the slab, the production efficiency of the precast slab can be improved, and further the production cost of the precast slab can be reduced, meeting the engineering application requirements of the filling concrete for the urban rail transit track bed.

[0047] Furthermore, the present invention has the following advantages:

[0048] 1. Based on the fiber reinforcement theory, the present invention mixes different types and dosages of steel fibers, and at the same time incorporates admixtures such as silica fume, fly ash and blast furnace slag powder, increasing the matrix viscosity and improving the reinforcement and toughening effect of the steel fibers. The prepared concrete has good performance, solves the problem of insufficient toughness of the concrete, reduces the cement consumption, lowers the production cost, and is conducive to sustainable development.

[0049] 2. The present invention greatly reduces the difficulty of construction quality control, improves the filling layer pouring efficiency by about 3 times, and improves the comprehensive construction progress by about 2 times.

[0050] 3. The present invention can save more than 10 processes, reduce the material consumption, reduce the labor employment quantity by about 70%, and has good economic effects.

[0051] In the following text, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the embodiments of the present invention. Therefore, the description is considered to be exemplary in nature rather than restrictive.

[0052] The present invention will be further described below in conjunction with embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions adopted in the embodiments can be further adjusted according to different requirements of specific uses. The implementation conditions not specified are conventional conditions in the industry. For example, the conditions for concrete pouring, forming and curing can be carried out according to the conventional conditions in the art. The technical features involved in each implementation mode of the present invention can be combined with each other as long as they do not conflict with each other.

[0053] Unless otherwise specified in this article, the preparation methods and detection methods involved in the following examples or comparative examples refer to the prior art. Unless otherwise specified in the following examples, all raw materials are obtained through commercial purchase or prepared by conventional methods in the art.

[0054] Among them, in the following examples and comparative examples, the raw materials used are as follows:

[0055] The selected cement is Portland cement conforming to GB175-2023 "Common Portland Cement", with a strength grade of 42.5.

[0056] The selected fly ash is fly ash conforming to GBT1596-2017 "Fly Ash Used in Cement and Concrete", with a grade of Class I.

[0057] The selected blast furnace slag powder complies with GB / T 18046-2017 "Ground Granulated Blast Furnace Slag for Use in Cement, Mortar and Concrete", with a specific surface area greater than 400 m 2 / kg.

[0058] The selected silica fume is silica fume conforming to GB27690-2023 "Silica Fume for Mortar and Concrete". The selected silica fume has a residue on a 45μm square hole sieve of ≤3%, and a SiO2 content of ≥90%.

[0059] The selected sand is natural sand, with a fineness modulus of 2.5 - 3.0 and an apparent density of ≥2500 kg / m 3 .

[0060] The selected crushed stone has a particle size range of 4.75 - 20 mm and an apparent density of 2900 kg / m 3 .

[0061] The selected water reducing agent is a liquid polycarboxylate superplasticizer, with a water reducing rate of ≥25%.

[0062] The selected steel fibers are end-hooked steel fibers. Steel fiber I has an equivalent diameter of 0.75 mm, a length of 50 mm, a length-diameter ratio of 67, a tensile strength of 1230 Mpa, and a circular cross-section; Steel fiber II has an equivalent diameter of 0.75 mm, a length of 35 mm, a length-diameter ratio of 47, a tensile strength of 1100 Mpa, and a circular cross-section.

[0063] Example 1

[0064] The steel fiber concrete prepared in this embodiment has the raw material proportions as shown in Table 1, with the unit being kg / m 3 .

[0065] Table 1

[0066] Cement Fly ash Ground granulated blast-furnace slag Silica fume Sand Crushed stone Water reducing agent Steel fiber Ⅰ Steel fiber Ⅱ Water 300 120 70 15 890 800 10 10 13 160

[0067] The preparation method is as follows: Prepare the above components in proportion. Pour the weighed sand and gravel into a forced horizontal shaft mixer, add additional water and stir for 1 - 2 minutes to pre-wet the aggregate. Secondly, pour the weighed Portland cement, silica fume, fly ash, and mineral powder into a mortar mixer and stir with the aggregate for 1 - 2 minutes to make it evenly mixed. Then, pour the weighed mixing water and water reducer into the obtained mixture at the same time and continue to stir for 4 - 5 minutes. Finally, pour the weighed steel fibers into the obtained mixture and continue to stir for 2 - 3 minutes. After casting, forming, and curing, steel fiber concrete with a relatively high flexural toughness ratio is obtained.

[0068] Example 2

[0069] The steel fiber concrete prepared in this embodiment has the raw material proportions as shown in Table 2, with the unit being kg / m 3 .

[0070] Table 2

[0071] Cement Fly ash Ground granulated blast-furnace slag Silica fume Sand Crushed stone Water reducing agent Steel fiber Ⅰ Steel fiber Ⅱ Water 300 120 70 15 890 800 10 12 13 160

[0072] The preparation method is as follows: Prepare the above components in proportion. Pour the weighed sand and gravel into a forced horizontal shaft mixer, add additional water and stir for 1 - 2 minutes to pre-wet the aggregate. Secondly, pour the weighed Portland cement, silica fume, fly ash, and mineral powder into a mortar mixer and stir with the aggregate for 1 - 2 minutes to make it evenly mixed. Then, pour the weighed mixing water and water reducer into the obtained mixture at the same time and continue to stir for 4 - 5 minutes. Finally, pour the weighed steel fibers into the obtained mixture and continue to stir for 2 - 3 minutes. After casting, forming, and curing, steel fiber concrete with a relatively high flexural toughness ratio is obtained.

[0073] Example 3

[0074] The steel fiber concrete prepared in this embodiment has the raw material proportions as shown in Table 3, with the unit being kg / m 3 .

[0075] Table 3

[0076] Cement Fly ash Ground granulated blast-furnace slag Silica fume Sand Crushed stone Water reducing agent Steel fiber Ⅰ Steel fiber Ⅱ Water 300 120 70 15 890 800 10 13 14 160

[0077] The preparation method is as follows: Prepare the above components in proportion. Pour the weighed sand and gravel into a forced horizontal-axis mixer, add additional water and stir for 1 - 2 minutes to pre-wet the aggregate. Secondly, pour the weighed portland cement, silica fume, fly ash, and mineral powder into a mortar mixer and stir with the aggregate for 1 - 2 minutes to mix them evenly. Then, pour the weighed mixing water and water reducer into the obtained mixture simultaneously and continue to stir for 4 - 5 minutes. Finally, pour the weighed steel fiber into the obtained mixture and continue to stir for 2 - 3 minutes. After casting, forming, and curing, steel fiber concrete with a relatively high flexural toughness ratio is obtained.

[0078] Control Example 1

[0079] For the steel fiber concrete prepared in this control example, the raw material proportions are shown in Table 4, with the unit being kg / m 3 .

[0080] Table 4

[0081]

[0082]

[0083] The preparation method is as follows: Prepare the above components in proportion. Pour the weighed sand and gravel into a forced horizontal-axis mixer, add additional water and stir for 1 - 2 minutes to pre-wet the aggregate. Secondly, pour the weighed portland cement, silica fume, fly ash, and mineral powder into a mortar mixer and stir with the aggregate for 1 - 2 minutes to mix them evenly. Then, pour the weighed mixing water and water reducer into the obtained mixture simultaneously and continue to stir for 4 - 5 minutes. Finally, pour the weighed steel fiber into the obtained mixture and continue to stir for 2 - 3 minutes. After casting, forming, and curing, steel fiber concrete is obtained.

[0084] Control Example 2

[0085] For the steel fiber concrete prepared in this control example, the raw material proportions are shown in Table 5, with the unit being kg / m 3 .

[0086] Table 5

[0087] Cement Fly ash Ground granulated blast-furnace slag Silica fume Sand Crushed stone Water reducing agent Steel fiber Ⅰ Water 300 120 70 15 890 800 10 25 160

[0088] The preparation method is as follows: Prepare the above-mentioned components in proportion. Pour the weighed sand and gravel into a forced horizontal-axis mixer, add additional water and stir for 1 - 2 minutes to pre-wet the aggregate. Secondly, pour the weighed Portland cement, silica fume, fly ash, and mineral powder into a mortar mixer and stir with the aggregate for 1 - 2 minutes to make them evenly mixed. Then, pour the weighed mixing water and water reducer into the obtained mixture at the same time and continue to stir for 4 - 5 minutes. Finally, pour the weighed steel fiber into the obtained mixture and continue to stir for 2 - 3 minutes. After casting, forming, and curing, steel fiber concrete is obtained.

[0089] Comparative Example 3

[0090] For the steel fiber concrete prepared in this comparative example, the raw material proportions are shown in Table 6, and the unit is kg / m 3 。

[0091] Table 6

[0092] Cement Fly ash Ground granulated blast-furnace slag Silica fume Sand Crushed stone Water reducing agent Steel fiber Ⅰ Water 300 120 70 15 890 800 10 27 160

[0093] The preparation method is as follows: Prepare the above-mentioned components in proportion. Pour the weighed sand and gravel into a forced horizontal-axis mixer, add additional water and stir for 1 - 2 minutes to pre-wet the aggregate. Secondly, pour the weighed Portland cement, silica fume, fly ash, and mineral powder into a mortar mixer and stir with the aggregate for 1 - 2 minutes to make them evenly mixed. Then, pour the weighed mixing water and water reducer into the obtained mixture at the same time and continue to stir for 4 - 5 minutes. Finally, pour the weighed steel fiber into the obtained mixture and continue to stir for 2 - 3 minutes. After casting, forming, and curing, steel fiber concrete is obtained.

[0094] Comparative Example 4

[0095] For the steel fiber concrete prepared in this comparative example, the raw material proportions are shown in Table 7, and the unit is kg / m 3 。

[0096] Table 7

[0097] Cement Fly ash Ground granulated blast-furnace slag Silica fume Sand Crushed stone Water reducing agent Steel fiber Ⅱ Water 300 120 70 15 890 800 10 23 160

[0098] The preparation method is as follows: Prepare the above-mentioned components in proportion. Pour the weighed sand and gravel into a forced horizontal-axis mixer, add additional water and stir for 1 - 2 minutes to pre-wet the aggregate. Secondly, pour the weighed Portland cement, silica fume, fly ash, and mineral powder into a mortar mixer and stir with the aggregate for 1 - 2 minutes to make them evenly mixed. Then, pour the weighed mixing water and water reducer into the obtained mixture at the same time and continue to stir for 4 - 5 minutes. Finally, pour the weighed steel fiber into the obtained mixture and continue to stir for 2 - 3 minutes. After casting, forming, and curing, steel fiber concrete is obtained.

[0099] Comparative Example 5

[0100] For the steel fiber concrete prepared in this comparative example, the raw material proportions are shown in Table 8, with the unit being kg / m 3 .

[0101] Table 8

[0102] Cement Fly ash Ground granulated blast-furnace slag Silica fume Sand Crushed stone Water reducing agent Steel fiber Ⅱ Water 300 120 70 15 890 800 10 25 160

[0103] The preparation method is as follows: Prepare the above components in proportion. Pour the weighed sand and gravel into a forced horizontal shaft mixer, add additional water and stir for 1 - 2 minutes to pre-wet the aggregate. Secondly, pour the weighed portland cement, silica fume, fly ash, and mineral powder into a mortar mixer and stir with the aggregate for 1 - 2 minutes to mix them evenly. Then, pour the weighed mixing water and water reducer into the obtained mixture simultaneously and continue to stir for 4 - 5 minutes. Finally, pour the weighed steel fibers into the obtained mixture and continue to stir for 2 - 3 minutes. After casting, forming, and curing, steel fiber concrete is obtained.

[0104] Comparative Example 6

[0105] For the steel fiber concrete prepared in this comparative example, the raw material proportions are shown in Table 9, with the unit being kg / m 3 .

[0106] Table 9

[0107] Cement Fly ash Ground granulated blast-furnace slag Silica fume Sand Crushed stone Water reducing agent Steel fiber Ⅱ Water 300 120 70 15 890 800 10 27 160

[0108] The preparation method is as follows: Prepare the above components in proportion. Pour the weighed sand and gravel into a forced horizontal shaft mixer, add additional water and stir for 1 - 2 minutes to pre-wet the aggregate. Secondly, pour the weighed portland cement, silica fume, fly ash, and mineral powder into a mortar mixer and stir with the aggregate for 1 - 2 minutes to mix them evenly. Then, pour the weighed mixing water and water reducer into the obtained mixture simultaneously and continue to stir for 4 - 5 minutes. Finally, pour the weighed steel fibers into the obtained mixture and continue to stir for 2 - 3 minutes. After casting, forming, and curing, steel fiber concrete is obtained.

[0109] According to the standards "Standard Test Method for Mechanical Properties of Ordinary Concrete" GB / T 50081-2016, "Steel Fiber Reinforced Concrete" JGT 472-2015, and ASTM C1609 / C1609M-12: Standard Test Method for Flexural Performance of Fiber Reinforced Concrete (Using Beam with Third Point Loading), the compressive strength, flexural performance, and flexural toughness ratio of the steel fiber reinforced concrete in Examples 1 to 3 and the steel fiber reinforced concrete in Comparative Examples 1 to 6 were measured. The test specimens were 100×100×100 mm cube specimens and 150×150×550 mm rectangular prism specimens respectively. The measurement results are shown in Table 10.

[0110] Table 10

[0111] Group Flexural strength at 28 days / MPa Compressive strength at 28 days / MPa Flexural toughness ratio / % Control Example 1 4.87 42.52 35.3 Control Example 2 5.07 44.53 37.2 Control Example 3 5.33 45.92 42.7 Control Example 4 4.78 43.58 38.6 Control Example 5 5.34 43.91 41.2 Control Example 6 5.61 45.23 45.5 Example 1 5.35 45.32 69.7 Example 2 5.27 47.29 72.4 Example 3 5.45 48.53 71.3

[0112] It can be seen from the data in Table 10 that after 28 days of standard curing, the compressive strength of the steel fiber reinforced concrete prepared by the present invention reaches more than 45 MPa, the flexural strength reaches more than 5 MPa, and the flexural toughness ratio reaches more than 69%. Therefore, the mechanical properties of the steel fiber reinforced concrete prepared by the present invention meet the engineering application requirements of the filling concrete for urban rail transit ballast beds. In addition, it can be seen from the test results of Comparative Examples 1 to 6 that the flexural toughness ratio of the steel fiber reinforced concrete material with a single steel fiber incorporated is significantly reduced and can no longer meet the mechanical property requirements of the filling concrete for urban rail transit ballast beds.

[0113] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An urban rail transit roadbed filled with steel fiber fine stone concrete, characterized in that: The invention comprises the following raw materials in parts by weight: 300-400 parts of cement, 8-20 parts of silica fume, 120-200 parts of fly ash, 70-100 parts of mineral powder, 160-250 parts of water, 7-15 parts of water reducer, 800-1100 parts of sand, 800-1000 parts of gravel, 10-30 parts of steel fiber I and 10-30 parts of steel fiber II; wherein, both steel fiber I and steel fiber II are end hook type steel fibers, the equivalent diameter of steel fiber I is 0.7-0.8 mm and the length is 45-55 mm; the equivalent diameter of steel fiber II is 0.7-0.8 mm and the length is 30-40 mm.

2. The urban rail transit roadbed filled with steel fiber fine stone concrete according to claim 1, characterized in that: The aspect ratio of the steel fiber I is 65-69, and the tensile strength is 1200-1250 MPa; the aspect ratio of the steel fiber II is 43-50, and the tensile strength is 1050-1150 MPa.

3. The urban rail transit roadbed filled with steel fiber fine stone concrete according to claim 1 or 2, characterized in that: The cross sections of the steel fibers I and II are circular.

4. The urban rail transit roadbed filled with steel fiber fine stone concrete according to claim 1, characterized in that: The invention comprises the following raw materials in parts by weight: 300-350 parts of cement, 10-18 parts of silica fume, 120-140 parts of fly ash, 70-90 parts of mineral powder, 160-180 parts of water, 7-15 parts of water reducing agent, 800-1000 parts of sand, 800-850 parts of gravel, 10-15 parts of steel fiber I and 13-18 parts of steel fiber II.

5. The urban rail transit roadbed filled with steel fiber fine stone concrete according to claim 4, characterized in that: The invention comprises the following raw materials in parts by weight: 300-320 parts of cement, 13-17 parts of silica fume, 120-130 parts of fly ash, 70-80 parts of mineral powder, 160-170 parts of water, 8-12 parts of water reducing agent, 850-950 parts of sand, 800-830 parts of gravel, 10-13 parts of steel fiber I and 13-14 parts of steel fiber II.

6. The urban rail transit roadbed filled with steel fiber fine stone concrete according to claim 1, 4 or 5, characterized in that: The cement is silicate cement with a strength grade of 42.5; and / or, The silica fume has a 45 μm square hole sieve residue rate of ≤3% and a SiO2 content of ≥90%; and / or, The grade of the fly ash is Grade I; and / or, The specific surface area of ​​the mineral powder is greater than 400m 2 / kg; and / or, The water reducing agent is a liquid polycarboxylic acid high performance water reducing agent, and the water reducing rate is ≥ 25%; and / or, The sand is natural sand with a fineness modulus of 2.5-3.0 and an apparent density of ≥2500kg / m 3 and / or, The particle size of the stone is in the range of 4.75-20mm, and the apparent density is 2800-3000kg / m 3 .

7. A method for preparing a steel fiber fine stone concrete filled with an urban rail transit roadbed as claimed in any one of claims 1 to 6, characterized in that: The raw materials are mixed evenly according to the formula, and then poured, formed and cured to obtain the urban rail transit roadbed filled with steel fiber fine stone concrete.

8. The preparation method according to claim 7, characterized in that: The steps include: 1) Weigh cement, silica fume, fly ash, mineral powder, water reducing agent, sand, gravel, steel fiber I, steel fiber II and water according to the formula; 2) Pour the weighed sand and gravel into a forced horizontal shaft mixer, add additional water and stir for 1-2 minutes to pre-wet the aggregate; 3) Pour the weighed cement, silica fume, fly ash and mineral powder into the mortar mixer and mix them together with the pre-wetted aggregate for 1-2 minutes to make them evenly mixed; 4) Pour the weighed mixing water and water reducing agent into the mixture obtained in step 3) and continue stirring for 4-5 minutes; 5) Pour the weighed steel fiber I and steel fiber II into the mixture obtained in step 4) and continue stirring for 2-3 minutes. After casting and curing, steel fiber concrete is obtained.

9. Use of the steel fiber concrete according to any one of claims 1 to 6 in the roadbed of urban rail transit.

10. The use according to claim 9, characterized in that: The steel fiber concrete is used as the concrete filling layer material of the urban rail transit roadbed.