High-performance concrete shield segment and preparation process thereof

Abstract

The application belongs to the technical field of concrete, and particularly relates to high-performance concrete shield segment and a preparation process thereof. The high-performance concrete shield segment comprises anti-permeation concrete and a steel reinforcement cage, and the anti-permeation concrete comprises cement 280-330 parts by mass, gravel 500-570 parts by mass, sand 400-480 parts by mass, fly ash 30-45 parts by mass, steel fiber 20-35 parts by mass, modified biomass carbon 5-18 parts by mass, water reducing agent 5-8 parts by mass, and water 70-90 parts by mass. The modified biomass carbon is obtained by carbonizing biomass with a coarse fiber content of greater than or equal to 30% and then adsorbing calcium lignosulfonate. The biomass is carbonized to form a porous structure, and then calcium lignosulfonate is adsorbed, so that the water-reducing and anti-permeation effects can be achieved. The selected biomass with a high fiber content can release a silicon dioxide component after carbonization, so that the anti-permeation performance is further improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of concrete, and particularly relates to a high-performance concrete shield segment and a preparation process thereof. BACKGROUND

[0002] The shield segment is a main assembly component in shield construction and is also the innermost barrier of a tunnel. The shield segment bears the action of resisting earth pressure, underground water pressure and some special loads. The shield segment is usually made of high-strength anti-permeable concrete. In the shield construction process, the shield machine advances by relying on the jacks against the shield segment, and the shield segment plays a supporting role. After installation, a formed tunnel is formed. The design and construction of the shield segment is one of the key links in tunnel construction, and the quality of the structural design is directly related to the stability, safety and service life of the tunnel.

[0003] The concrete shield segment structure has requirements in terms of anti-permeability grade and itemized durability. In order to meet the requirements of relevant indicators, the existing technology mainly improves the related performance by optimizing the formula, adding fiber, mineral admixture or improving the vibrating and curing process. Patent CN114988813A discloses an anti-permeable concrete for a shield segment and a preparation method thereof, which comprises, by weight fraction: 430-450 parts of Portland cement, 50-58 parts of fly ash, 540-560 parts of sand, 1140-1160 parts of crushed stone, 120-140 parts of water, 100-110 parts of impregnated structural basalt fiber and 20-23 parts of water reducing agent. The impregnated structural basalt fiber is used to improve the impermeability and strength of the concrete. However, the impermeability of this method is not good and needs to be further improved.

[0004] Therefore, it is necessary to provide an improved high-performance concrete shield segment and a preparation process thereof to solve the above problems. SUMMARY

[0005] The application aims to provide a high-performance concrete shield segment and a preparation process thereof. The carbonized biomass absorbs calcium lignosulfonate, and the slow-release synergy of silicon dioxide and calcium lignosulfonate after carbonization of the biomass prolongs the long-term high impermeability and strength.

[0006] To achieve the above-mentioned purpose, the application provides a high-performance concrete shield segment, which comprises anti-permeable concrete and a steel reinforcement cage. The anti-permeable concrete comprises, by mass fraction: 280-330 parts of cement, 500-570 parts of crushed stone, 400-480 parts of sand, 30-45 parts of fly ash, 20-35 parts of steel fiber, 5-18 parts of modified biomass carbon, 5-8 parts of water reducing agent and 70-90 parts of water. The modified biomass carbon is obtained by carbonizing biomass with a coarse fiber content of greater than or equal to 30% and then absorbing calcium lignosulfonate.

[0007] Further, the preparation method of the modified biomass carbon comprises: carbonizing the biomass under the condition of 500-700 DEG C, then crushing and sieving; then adding to the calcium lignosulfonate aqueous solution, then freeze-drying, then crushing and sieving, to obtain the modified biomass carbon.

[0008] Further, the mass fraction of calcium lignosulfonate in the calcium lignosulfonate aqueous solution is 5-12%, and the mass ratio of the carbonized biomass to calcium lignosulfonate is (5-10):1.

[0009] Further, the carbonizing time is 1-3h; the crushing and sieving refers to sieving through 100-200 mesh.

[0010] Further, the biomass comprises one or more of straw, rice husk, hemp rod, wood chips, tree bark, bamboo chips and powder, branches, coconut shell, walnut shell, palm shell, peanut shell and coffee residue.

[0011] Further, the preparation method of the modified biomass carbon further comprises: mixing the freeze-dried product with a silane coupling agent, then drying, crushing and sieving, to obtain the modified biomass carbon.

[0012] Further, the sand has a fineness modulus of 2.3-3.3, and the broken stone is 5-25mm grade broken stone.

[0013] The application further provides a preparation process of the high-performance concrete shield segment, comprising the following steps:

[0014] S1, concrete preparation: preparing concrete according to the raw material ratio of the impermeable concrete;

[0015] S2, reinforcing cage preparation and installation: preparing a segment mold, brushing a release agent, processing a segment reinforcing cage, hoisting into the mold for positioning and installation;

[0016] S4, concrete pouring and vibrating: pouring the concrete obtained in step S1 into the mold, vibrating, to form a pouring body;

[0017] S5, curing and demolding: curing the pouring body, to obtain a shield segment.

[0018] Further, the curing refers to first steam curing or natural curing until the compressive strength of the concrete reaches 20MPa, then hoisting to a water curing pool for curing for 7-28 days.

[0019] Compared with the prior art, the above technical scheme conceived by the application has the following beneficial effects:

[0020] 1. This invention carbonizes biomass to form a porous structure, which then absorbs calcium lignosulfonate, achieving water-reducing and anti-seepage properties. The high-fiber biomass released silica after carbonization, further improving anti-seepage properties and strength. Furthermore, the biochar itself can increase the strength and hardness of concrete while also reducing shrinkage and permeability.

[0021] 2. Increase the adsorption capacity of calcium lignosulfonate and the specific surface area of ​​modified biomass carbon through freeze drying, thereby improving the mixing effect with cement and other powders and improving the impermeability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a process flow chart for preparing high-performance concrete shield segments of the present invention. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0024] The present invention provides a high-performance concrete shield segment, comprising impermeable concrete and a steel cage. The impermeable concrete comprises, by mass, 280-330 parts of cement, 500-570 parts of crushed stone, 400-480 parts of sand, 30-45 parts of fly ash, 20-35 parts of steel fiber, 5-18 parts of modified biomass carbon, 5-8 parts of water reducer, and 70-90 parts of water. The modified biomass carbon is obtained by carbonizing biomass with a crude fiber content of 30% or more and then adsorbing calcium lignosulfonate.

[0025] The use of biomass with a high fiber content has high carbonization residue and porosity, which is conducive to the adsorption of calcium lignosulfonate and plays a long-term anti-seepage role through slow release; and the biomass charcoal itself can also increase the strength and hardness of concrete, while also reducing the shrinkage and permeability of concrete.

[0026] Furthermore, the modified biomass carbon preparation method includes: carbonizing the biomass at 500-700°C, then pulverizing and screening; then adding the biomass to an aqueous solution of calcium lignosulfonate, freeze-drying, and further pulverizing and screening to obtain the modified biomass carbon. Freeze-drying increases the adsorption capacity of calcium lignosulfonate and the specific surface area of ​​the modified biomass carbon, thereby improving its contact with powders such as cement and enhancing its impermeability.

[0027] Furthermore, the mass fraction of calcium lignosulfonate in the calcium lignosulfonate aqueous solution is 5-12%, and the mass ratio of the carbonized biomass to calcium lignosulfonate is (5-10):1.

[0028] Furthermore, the carbonization treatment time is 1-3 hours; the crushing and screening refers to passing through a 100-200 mesh sieve.

[0029] Furthermore, the biomass includes one or more of straw, rice husks, hemp stalks, wood chips, bark, bamboo chips and powder, tree branches, coconut shells, walnut shells, palm shells, peanut shells, and coffee grounds. Rice husks are preferred, as they contain a certain amount of silica, which helps to increase the strength of concrete and improves its anti-seepage effect through a slow-release process.

[0030] Furthermore, the modified biomass carbon preparation method further includes: mixing the freeze-dried product with a silane coupling agent, and then drying, crushing, and screening to obtain the modified biomass carbon. The silane coupling agent improves the hydrophobicity of the modified biomass carbon, thereby improving the anti-seepage effect.

[0031] The silane coupling agent is KH550, hexadecyltrimethoxysilane, etc.

[0032] Furthermore, the fineness modulus of the sand is 2.3-3.3, and the gravel is 5-25 mm grade gravel.

[0033] like Figure 1 The present invention also provides a process for preparing a high-performance concrete shield segment as described in any one of the above, comprising the following steps:

[0034] S1. Concrete preparation: preparing concrete according to the raw material ratio of the anti-seepage concrete;

[0035] S2. Fabrication and installation of steel cage: Prepare the segment mold, apply mold release agent, and process the segment steel cage, then hoist it into the mold for positioning and installation;

[0036] S4, concrete pouring and vibrating: pouring the concrete obtained in step S1 into the mold and vibrating to form a casting body;

[0037] S5. Curing and demoulding: curing the cast body to obtain shield segments.

[0038] Furthermore, the curing refers to first steam curing or natural curing until the compressive strength of the concrete reaches 20MPa, and then hoisting it to a water curing tank for curing for 7-28 days.

[0039] Example 1

[0040] A high-performance concrete shield segment comprises anti-permeation concrete and a reinforcement cage, the anti-permeation concrete comprises cement 300 parts by mass, crushed stone 550 parts by mass, sand 420 parts by mass, fly ash 36 parts by mass, steel fiber 28 parts by mass, modified biomass carbon 12 parts by mass, water reducing agent calcium lignosulfonate 6 parts by mass, and water 80 parts by mass.

[0041] The preparation method of the modified biomass carbon comprises: carbonizing rice husks at 550 DEG C in an air atmosphere, then crushing to pass through a 100-mesh sieve to obtain biomass carbon; then adding to 8wt% calcium lignosulfonate aqueous solution and mixing uniformly, the mass ratio of the biomass carbon to the calcium lignosulfonate being 6:1, then freeze-drying at-40 DEG C for 36h, and then crushing to pass through a 100-mesh sieve to obtain the modified biomass carbon.

[0042] The steel fiber has a length of 50mm and a diameter of 0.75mm. The reinforcement cage is provided with inner reinforcement The auxiliary reinforcement comprises standing reinforcement, reinforcing reinforcement, spiral reinforcement, and waist reinforcement.

[0043] The preparation process of the high-performance concrete shield segment comprises the following steps:

[0044] S1, concrete preparation: mixing raw materials according to the proportion of the anti-permeation concrete to prepare concrete;

[0045] S2, reinforcement cage preparation and installation: preparing a segment mold, brushing a release agent, processing a segment reinforcement cage, and hoisting the reinforcement cage into the mold for positioning and installation;

[0046] S4, concrete pouring and vibrating: pouring the concrete obtained in step S1 into the mold and vibrating to form a pouring body;

[0047] S5, curing and demolding: naturally curing the pouring body until the compressive strength of the concrete reaches 20MPa, then hoisting the pouring body to a water curing pool for curing for 28 days to obtain the shield segment.

[0048] Example 2

[0049] The difference between example 1 and example 2 is that the mass concentration of the calcium lignosulfonate aqueous solution is 5wt%, and the other conditions are the same as those in example 1, which will not be repeated here.

[0050] Example 3

[0051] The difference between example 1 and example 3 is that the mass concentration of the calcium lignosulfonate aqueous solution is 12wt%, and the other conditions are the same as those in example 1, which will not be repeated here.

[0052] Example 4

[0053] The difference from Example 1 is that the mass ratio of biomass carbon to calcium lignosulfonate is 10:1. The rest is the same as Example 1 and will not be repeated here.

[0054] Example 5

[0055] The difference from Example 1 is that the modified biochar preparation method includes: carbonizing rice husks at 550°C in an air atmosphere, then pulverizing through a 100-mesh sieve to obtain biochar; then adding the husks to an 8 wt% aqueous solution of calcium lignosulfonate and mixing uniformly, with the mass ratio of biochar to calcium lignosulfonate being 6:1; soaking for 1 hour, followed by solid-liquid separation, drying, and then pulverizing through a 100-mesh sieve to obtain the modified biochar. Other steps are the same as in Example 1 and are not further described here.

[0056] Example 6

[0057] The difference from Example 1 is that rice husks are replaced with coconut shells. Other details are the same as in Example 1 and will not be repeated here.

[0058] Comparative Example 1

[0059] The difference from Example 1 is that a high-performance concrete shield segment includes impermeable concrete and a steel cage. The impermeable concrete comprises, by weight, 300 parts cement, 550 parts crushed stone, 420 parts sand, 36 parts fly ash, 28 parts steel fiber, 6 parts water reducer, and 80 parts water. All other aspects are the same as in Example 1 and are not further described here.

[0060] Comparative Example 2

[0061] The difference from Example 1 is that the modified biomass carbon preparation method includes: carbonizing rice husks at 550°C in air, and then crushing them through a 100-mesh sieve to obtain biomass carbon. Other steps are the same as in Example 1 and will not be repeated here.

[0062] The shield segments were tested for impermeability according to GB / T 22082, "Precast Concrete Lining Segments." The compressive strength of the impermeable concrete (i.e., the concrete pipe obtained by direct curing by removing the steel cage according to S1 and S5) was tested according to GB / T50081-2019, "Standard for Test Methods for Physical and Mechanical Properties of Concrete."

[0063] Table 1 Performance test results of examples and comparative examples

[0064] Sample 28d compressive strength (MPa) Maximum water pressure (MPa) Maximum water pressure penetration depth (mm) Example 1 58.9 2.6 30.6 Example 2 56.7 2.6 35.2 Example 3 58.6 2.6 32.1 Example 4 55.3 2.2 30.2 Example 5 56.1 2.6 36.8 Example 6 57.5 2.2 28.9 Comparative Example 1 54.4 2.0 55.8 Comparative Example 2 54.8 2.0 50.6

[0065] As shown in Table 1, varying the mass concentration of the calcium lignosulfonate aqueous solution results in changes in compressive strength and water penetration depth. However, since the mass ratio of biomass carbon to calcium lignosulfonate remains constant, the strength and water penetration depth are not significantly affected. When the mass ratio increases, that is, when the amount of calcium lignosulfonate used decreases, the compressive strength decreases, and the maximum water penetration pressure decreases. When solid-liquid separation and drying are used, the calcium lignosulfonate loading decreases, and the specific surface area decreases, resulting in a decrease in compressive strength and an increase in water penetration depth. When coconut shells are used, the silica content decreases, resulting in a decrease in strength and a decrease in maximum water penetration pressure. When no modified biomass is added, both the compressive strength and maximum water penetration pressure decrease, indicating a deterioration in water penetration performance. When the modified biomass does not adsorb calcium lignosulfonate, water penetration performance also decreases, demonstrating that the present invention can improve water penetration performance by loading and slowly releasing calcium lignosulfonate.

[0066] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high performance concrete shield segment, characterized in that: The invention comprises an impermeable concrete and a steel cage. The impermeable concrete comprises, by weight, 280-330 parts of cement, 500-570 parts of crushed stone, 400-480 parts of sand, 30-45 parts of fly ash, 20-35 parts of steel fiber, 5-18 parts of modified biomass carbon, 5-8 parts of water reducer, and 70-90 parts of water. The modified biomass carbon is obtained by carbonizing biomass with a crude fiber content of 30% or more and then adsorbing calcium lignosulfonate. The modified biomass carbon preparation method comprises: carbonizing the biomass at 550° C., then pulverizing the biomass through a 100-200 mesh sieve; then adding the biomass to an aqueous solution of calcium lignosulfonate, freeze-drying the solution, and then pulverizing the solution through a 100-200 mesh sieve to obtain the modified biomass carbon; the mass fraction of calcium lignosulfonate in the aqueous solution of calcium lignosulfonate is 8-12%; and the mass ratio of the carbonized biomass to the calcium lignosulfonate is (5-10):

1.

2. The high performance concrete shield segment according to claim 1, characterized in that: The carbonization treatment time is 1-3 hours.

3. The high performance concrete shield segment according to claim 1, characterized in that: The biomass includes one or more of straw, rice husk, hemp stalk, wood chips, bark, bamboo chips and bamboo powder, branches, coconut shells, walnut shells, palm shells, peanut shells, and coffee grounds.

4. The high performance concrete shield segment according to claim 1, characterized in that: The preparation method of the modified biomass carbon further comprises: mixing the freeze-dried product with a silane coupling agent, and then drying, crushing and sieving the mixture to obtain the modified biomass carbon.

5. The high performance concrete shield segment according to claim 1, characterized in that: The fineness modulus of the sand is 2.3-3.3, and the crushed stone is 5-25 mm grade crushed stone.

6. A process for preparing a high performance concrete shield segment according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Concrete preparation: preparing concrete according to the raw material ratio of the anti-seepage concrete; S2. Fabrication and installation of steel cage: Prepare the segment mold, apply mold release agent, and process the segment steel cage, then hoist it into the mold for positioning and installation; S4, concrete pouring and vibrating: pouring the concrete obtained in step S1 into the mold, vibrating, and forming a casting body; S5. Curing and demoulding: curing the cast body to obtain shield segments.

7. The preparation process according to claim 6, characterized in that: The curing refers to steam curing or natural curing until the compressive strength of the concrete reaches 20MPa, and then hoisting it to a water curing tank for curing for 7-28 days.

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