Anti-corrosion micro-expansion self-compacting concrete for steel pipe pile and construction method of anti-corrosion micro-expansion self-compacting concrete

Abstract

The invention relates to anti-corrosion micro-expansion self-compacting concrete for a steel pipe pile. Each cubic meter of the concrete is prepared from the following components in parts by mass: 250 to 300 parts of cement, 100 to 120 parts of recycled micro powder, 800 to 830 parts of recycled fine aggregate, 940 to 980 parts of recycled coarse aggregate, 20 to 32 parts of expanding agent, 0.15 to 0.25 part of graphene oxide, 4 to 6 parts of glass fiber, 1.5 to 4 parts of polyformaldehyde fiber, 10 to 13 parts of water reducing agent and 150 to 170 parts of water. The anti-corrosion micro-expansion self-compacting concrete has anti-corrosion, micro-expansion and self-compacting properties, can be suitable for underwater steel pipe pile construction, and remarkably improves the service life and reliability of the steel pipe pile in ocean and water-rich environments.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and in particular to a corrosion-resistant micro-expansion self-compacting concrete for steel pipe piles and its construction method. Background Technology

[0002] Steel pipe piles are a commonly used type of pile in building foundation reinforcement. Compared with other foundation reinforcement methods, they have advantages such as high strength, low cost, fast construction, and minimal impact, making them suitable for construction scenarios with limited space. They can also be used in highway slopes, bridges, docks, offshore wind power, and other fields. Traditional steel pipe piles are filled with ordinary concrete. Ordinary concrete has defects such as poor cohesion, high air content, large autogenous shrinkage, and poor self-compacting properties. There is a lack of special concrete mix proportions and processes for grouting inside steel pipe piles. During construction, it is easy for the concrete to separate from the inner wall of the steel pipe, forming a layer of gaps or cavities. This significantly reduces the bearing capacity of the steel pipe pile and makes it difficult to meet the requirements of corrosion resistance, micro-expansion to compensate for shrinkage, and self-compacting without vibration in marine or water-rich environments. Especially in water-rich strata or marine environments, the interface peeling and bearing capacity reduction caused by pile corrosion are prominent problems, seriously restricting the durability of the structure. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention provides a corrosion-resistant, micro-expansion self-compacting concrete for steel pipe piles, wherein the concrete per m 3 Concrete comprises the following components in the following mass ratios: cement: recycled micro powder: recycled fine aggregate: recycled coarse aggregate: expansion agent: graphene oxide: glass fiber: polyoxymethylene fiber: water-reducing agent: water = 250~300 parts: 100~120 parts: 800~830 parts: 940~980 parts: 20~32 parts: 0.15~0.25 parts: 4~6 parts: 1.5~4 parts: 10~13 parts: 150~170 parts.

[0005] In one embodiment, the cement comprises P·O32.5 or P·O42.5 ordinary Portland cement.

[0006] In one embodiment, the regenerated micro powder is treated with acid and has a particle size of less than 3 μm; the acid treatment includes the following steps: adding the regenerated micro powder to an acid solution and stirring to mix, and then drying it with a combination of hot air and microwave to obtain acid-activated regenerated micro powder.

[0007] In one embodiment, the acid solution includes tannic acid, acetic acid, or hydrochloric acid; the mass concentration of the acid solution is 0.5-1.5%; the hot air-microwave combined drying includes the following steps: using hot air drying at 55-65°C to remove some moisture, and heating at a microwave frequency of 2400-2500MHz to remove the remaining moisture.

[0008] In one embodiment, the fineness modulus of the recycled fine aggregate is 2.3 to 3, the content of fine powder is less than 7%, and the content of mud lumps is less than 2%.

[0009] In one embodiment, the recycled fine aggregate comprises the following components in parts by weight: 6-10 parts of recycled fine aggregate with a diameter of 4750-2360 μm, 11-15 parts of recycled fine aggregate with a diameter of 2360-1180 μm, 30-34 parts of recycled fine aggregate with a diameter of 1180-600 μm, 26-30 parts of recycled fine aggregate with a diameter of 600-300 μm, 11-15 parts of recycled fine aggregate with a diameter of 300-150 μm, and 9-11 parts of recycled fine aggregate with a diameter of less than 150 μm.

[0010] In one embodiment, the recycled coarse aggregate comprises a continuous gradation of 5-20 mm and an apparent density greater than 2500 kg / m³. 3 The water absorption rate is less than 2.0%, the aggregate crushing value is less than 8%, the mud content is less than 0.3%, and the impurity content is less than 0.5%.

[0011] In one embodiment, the recycled aggregate includes graded crushed stone of 5~9.5mm, 9.5~16mm, and 16~20mm, and is configured according to the mass ratio of 5~9.5mm graded crushed stone: 9.5~16mm graded crushed stone: 16~20mm graded crushed stone in the ratio of (2~3): (4~5): (2~3).

[0012] In one embodiment, the glass fiber comprises a blend of glass fibers of different lengths, with a length of 1-6 mm and a diameter of 10-15 μm.

[0013] In one embodiment, the polyoxymethylene fiber comprises a blend of microfiber and coarse-bundled polyoxymethylene fiber, with a length of 6-12 mm and a crack strength ≥967 MPa; the diameter of the microfiber is 40-80 μm; the diameter of the coarse-bundled polyoxymethylene fiber is 0.5-1.4 mm; and the mass ratio of the microfiber to the coarse-bundled polyoxymethylene fiber is 1:(2-4).

[0014] In one embodiment, the graphene oxide has a sheet diameter of 0.5~5μm, a thickness of 0.8~2.4nm, and a purity of ≥98%. The expansion agent has a limited expansion rate of 0.054-0.06% in water after 7 days; the water reduction agent has a water reduction rate of 20-25%.

[0015] The second aspect of the present invention also provides a construction method for the corrosion-resistant micro-expansion self-compacting concrete used for the steel pipe piles, comprising the following steps: Steel pipe pile fabrication: Before construction, the steel pipe is processed into a steel pipe with internal corrugations. The outer wall of the steel pipe is coated with an anti-corrosion coating. The steel pipe connection is made by sleeve lap welding. Before welding the pile, the vertical axis of the upper and lower pile sections is aligned. After removing the rust from the welding surface, the welding construction is carried out. Drilling: Determine the hole location, drill the hole, clean the sediment and mud inside the hole, and hoist the steel pipe pile; Grouting: After the steel pipe piles are installed, anti-corrosion micro-expansion self-compacting concrete is poured. Filling: Fill the gaps on the outside of the steel pipe with recycled fine aggregate.

[0016] In one embodiment, before the steel pipe piles are fabricated, anti-corrosion micro-expansion self-compacting concrete needs to be prepared, including the following steps: mixing graphene oxide, recycled fine aggregate and water, then adding recycled coarse aggregate, recycled micro powder, expansion agent, glass fiber, water-reducing agent and water to the mixture, vacuuming and stirring under negative pressure to obtain anti-corrosion micro-expansion self-compacting concrete.

[0017] In one embodiment, the negative pressure is controlled to 80~95 kPa and stabilized for 3~10 minutes.

[0018] In one embodiment, during the steel pipe pile manufacturing process, the inner corrugation spacing is 8~12mm and the width is 4~6mm.

[0019] In one embodiment, the sleeve height is not less than 150mm, and the sleeve wall thickness is not less than the steel pipe wall thickness.

[0020] In one embodiment, the weld seam is required to be continuous and full, and incomplete welds or spot welds are not allowed.

[0021] In one embodiment, the drilling method includes dry drilling, wet drilling, or pneumatic drilling; during the drilling process, if a collapsed soil layer is encountered, mud circulation for wall protection or casing drilling is used.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. Recycled aggregates are derived from construction waste such as bricks and old mortar. They have many pores and a high water absorption rate. After vacuum negative pressure treatment, it is beneficial for the air bubbles in the recycled aggregates to be discharged, which helps to open up some of the blocked pores. Cement and recycled micro powder slurry can be fully penetrated and filled. Aggregates treated with negative pressure grouting have lower porosity, denser structure, and higher mechanical properties.

[0023] 2. The aggregate structure of recycled concrete contains many pores, which can easily lead to low strength and poor corrosion resistance. Short glass fibers, with their micron-sized diameter, can penetrate deep into the aggregate pores and microcracks, achieving a "pinning effect" for reinforcement and toughening. They also influence the formation and distribution of CSH (carbon silicate sulfide), and the reaction products can fill these micropores, improving the overall durability of the concrete (including corrosion resistance). Furthermore, the high toughness of polyoxymethylene (POM) organic fibers and the high modulus of glass fibers complement each other, enhancing the overall corrosion resistance of the system. A combination of microfiber POM and coarse-bundle POM fibers is used, where the microfibers provide extreme crack resistance and the coarse bundles provide macroscopic toughening, strengthening the structural toughness and improving its mechanical and corrosion resistance.

[0024] 3. Tannic acid-modified recycled micro powder: Through the complexation effect of tannic acid, polyphenol functional groups are attached to the surface of recycled micro powder. The adsorption effect of polyphenol functional groups is used to improve the bonding performance between recycled micro powder and cement. The strength and durability of concrete prepared by using modified recycled micro powder are improved. Attached Figure Description

[0025] Figure 1 A flowchart illustrating the construction method for corrosion-resistant micro-expansion self-compacting concrete steel pipe piles. Detailed Implementation

[0026] To facilitate understanding of the present invention, a more complete description will be given below with reference to relevant embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] The present invention does not limit the source of the raw materials used. Unless otherwise specified, the raw materials used in the present invention are all commercially available products in this technical field.

[0029] The recycled micro powder used in the embodiments of the present invention conforms to the industry standard "Recycled Micro Powder for Concrete and Mortar" (JG / T573); the recycled fine aggregate used conforms to the national standard "Recycled Fine Aggregate for Concrete and Mortar" (GB / T 25176); and the recycled coarse aggregate used conforms to Class I or Class II of the national standard "Recycled Coarse Aggregate for Concrete" (GB / T 25177).

[0030] Example 1 per m 3 The corrosion-resistant micro-expansion self-compacting concrete includes: 290 kg of P·O42.5 ordinary Portland cement, 110 kg of recycled micro powder, 810 kg of recycled fine aggregate, 960 kg of recycled coarse aggregate, 28 kg of expansion agent, 0.2 kg of graphene oxide, 5 kg of glass fiber, 3 parts of polyoxymethylene fiber, 12 kg of water-reducing agent, and 157 kg of water.

[0031] The regenerated micro powder is treated with acid. The treatment method is as follows: the regenerated micro powder is added to a 0.8% tannic acid solution and stirred and mixed. After hot air-microwave combined drying, acid-activated regenerated micro powder is obtained. The hot air-microwave combined drying involves first drying with hot air at 60℃ to remove most of the moisture, and then heating at a microwave frequency of 2450MHz to quickly remove the residual moisture.

[0032] The recycled fine aggregate gradation consists of the following sizes and weights of gravel: 8 parts recycled fine aggregate of 4750~2360μm, 13 parts recycled fine aggregate of 2360~1180μm, 31 parts recycled fine aggregate of 1180~600μm, 28 parts recycled fine aggregate of 600~300μm, 11 parts recycled fine aggregate of 300~150μm, and 9 parts recycled fine aggregate of less than 150μm.

[0033] Recycled coarse aggregate consists of stones of the following sizes and weight proportions: graded crushed stone of 5~9.5mm, 9.5~16mm, and 16~20mm, and should be used in a mass ratio of 3:4:3.

[0034] Glass fiber includes three length sizes: 6mm, 9mm, and 6mm, with a volume ratio of 3:4:3. The diameter of the glass fiber is 10~15μm.

[0035] Polyoxymethylene (POM) fiber comes in three length sizes: 6mm, 8mm, and 12mm. It is composed of microfiber POM and coarse fiber bundles, with a mass ratio of 1:3.

[0036] Construction method of corrosion-resistant micro-expansion self-compacting concrete steel pipe piles (see...) Figure 1 ), including the following steps: 1. Preparation of anti-corrosion micro-expansion self-compacting concrete: First, add graphene oxide, recycled fine aggregate, and 20-30% of the required water to the mixer and mix for 1 minute. Then, add recycled coarse aggregate, recycled micro powder, expansion agent, glass fiber, remaining water, and water-reducing agent to the mixer and mix for 1 minute. Start the vacuum pump to remove air, and at the same time start the mixer to mix under negative pressure. Control the negative pressure to 85-90 kPa and stabilize the pressure for 5-8 minutes to obtain anti-corrosion micro-expansion self-compacting concrete.

[0037] 2. Steel pipe pile fabrication: Before construction, the steel pipes must be processed into steel pipes with internal corrugations (10.0mm spacing, 5.0mm width), and the outer wall of the steel pipes should be coated with an anti-corrosion coating; the steel pipe joints should be connected by sleeve lap welding, the sleeve height should not be less than 150mm, the sleeve wall thickness should not be less than the steel pipe wall thickness, and before welding the pile joints, the vertical axis of the upper and lower pile sections should be aligned, and the rust on the welding surface should be removed before welding construction; the weld should be continuous and full, and incomplete welding and spot welding are not allowed.

[0038] 3. Before drilling, determine the hole location according to the design requirements and select dry drilling, wet drilling or pneumatic drilling according to the actual situation. If the soil layer that collapses during the drilling process is encountered, it is advisable to use mud circulation for wall protection or follow-through drilling. After the hole is completed, clean the sediment and mud in the hole and then hoist the steel pipe pile.

[0039] 4. After the steel pipe piles are installed and pass the acceptance inspection according to standard 5.10 of GB 50202, the anti-corrosion micro-expansion self-compacting concrete pouring construction shall be carried out.

[0040] 5. Fill the gaps on the outside of the steel pipe with recycled fine aggregate.

[0041] Example 2 per m 3 The corrosion-resistant micro-expansion self-compacting concrete includes: 300 kg of P·O42.5 ordinary Portland cement, 100 kg of recycled micro powder, 810 kg of recycled fine aggregate, 960 kg of recycled coarse aggregate, 25 kg of expansion agent, 0.2 kg of graphene oxide, 6 kg of glass fiber, 2.5 parts of polyoxymethylene fiber, 12 kg of water-reducing agent, and 162 kg of water.

[0042] The method for treating recycled micronized acid, the gradation composition of recycled coarse aggregate and recycled fine aggregate, and the composition of fibers are the same as in Example 1.

[0043] The construction method for corrosion-resistant micro-expansion self-compacting concrete steel pipe piles is the same as that in Example 1, except that the raw materials are replaced with those in this example.

[0044] Example 3 per m 3 The corrosion-resistant micro-expansion self-compacting concrete includes: 250 kg of P·O32.5 ordinary Portland cement, 120 kg of recycled micro powder, 810 kg of recycled fine aggregate, 960 kg of recycled coarse aggregate, 32 kg of expansion agent, 0.2 kg of graphene oxide, 3 kg of glass fiber, 4 parts of polyoxymethylene fiber, 12 kg of water-reducing agent, and 170 kg of water.

[0045] The method for treating recycled micronized acid, the gradation composition of recycled coarse aggregate and recycled fine aggregate, and the composition of fibers are the same as in Example 1.

[0046] The construction method for corrosion-resistant micro-expansion self-compacting concrete steel pipe piles is the same as that in Example 1, except that the raw materials are replaced with those in this example.

[0047] Comparative Example 1 (Regenerated micro powder without tannic acid treatment) The construction method of the anti-corrosion micro-expansion self-compacting concrete and steel pipe piles in Comparative Example 1 differs from that in Example 1 only in that the recycled micro powder used has not undergone acid treatment.

[0048] The test methods for slump, slump spread, spread time, compressive strength, and free expansion rate under 28-day closed environment tests of anti-corrosion micro-expansion self-compacting concrete for steel pipe piles in the examples and comparative examples are as follows: (1) The slump, slump spread and spread time tests were conducted in accordance with the China Engineering Construction Standardization Association standard "Technical Specification for Application of Self-Compacting Concrete" (CECS203). (2) The compressive strength test shall be conducted in accordance with the national standard "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T50081); (3) The air content test shall be conducted in accordance with the national standard "Standard for Test Methods of Performance of Ordinary Concrete Mixtures" (GB / T50080); (4) The free expansion rate test and chloride ion penetration resistance test under 28-day closed environment shall be conducted in accordance with the national standard "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete" (GB / T 50082).

[0049] The test results are shown in Table 1: Table 1 Performance test results of corrosion-resistant micro-expansion self-compacting concrete

[0050] As can be seen from the results in Table 1, the concrete prepared in Examples 1-3 is significantly better than that in Comparative Example 1 in terms of slump, slump spread, spread time, compressive strength, air content, free expansion rate in a closed environment, and resistance to chloride ion penetration. It is evident that the concrete prepared in Comparative Example 1, which did not use tannic acid to treat the recycled micro powder, has poor fluidity, high water demand, high air content, low strength, and poor corrosion resistance.

[0051] Ordinary concrete undergoes chemical shrinkage and drying shrinkage during hardening. Inside steel pipe piles, the concrete is tightly encased in a steel pipe, under strong constraint. When the concrete shrinks, the steel pipe restricts it. This constraint stress generates tensile stress within the concrete, making it prone to cracking. These cracks not only severely reduce the integrity and strength of the concrete but also provide pathways for external corrosive media (such as chloride ions), corroding the pipe wall and significantly reducing durability. Furthermore, due to the shrinkage of the concrete, it separates from the inner wall of the steel pipe, forming a gap or cavity. This causes a significant decrease in the bearing capacity of the steel pipe pile and local instability: under immense pressure, the vacant area of ​​the steel pipe loses the support of the internal concrete, making it prone to local buckling (collapse) and leading to pile failure. This invention achieves a micro-expansion effect by adding an expansive agent. By optimizing the concrete mix ratio, it reduces the porosity within the concrete, decreasing the penetration channels for corrosive media (such as chloride ions and sulfates), thereby slowing down the corrosion process.

[0052] In summary, this invention provides a special concrete for steel pipe piles with good corrosion resistance, micro-expansion and self-compacting properties, as well as its construction method, to solve the problems of poor cohesion, high air content, large autogenous shrinkage, insufficient self-compacting degree and resource waste of traditional cast-in-place concrete. It realizes the efficient utilization of construction solid waste, is applicable to underwater steel pipe pile construction, and significantly improves the service life and reliability of steel pipe piles in marine and water-rich environments.

[0053] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0054] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A corrosion-resistant, micro-expansion, self-compacting concrete for steel pipe piles, characterized in that, per m 3 Concrete comprises the following components in the indicated mass proportions: Cement: Recycled micro powder: Recycled fine aggregate: Recycled coarse aggregate: Expansion agent: Graphene oxide: Glass fiber: Polyoxymethylene fiber: Water-reducing agent: Water = 250~300 parts: 100~120 parts: 800~830 parts: 940~980 parts: 20~32 parts: 0.15~0.25 parts: 4~6 parts: 1.5~4 parts: 10~13 parts: 150~170 parts.

2. The anti-corrosion micro-expansion self-compacting concrete for steel pipe piles according to claim 1, characterized in that, The cement includes P·O32.5 or P·O42.5 ordinary Portland cement.

3. The anti-corrosion micro-expansion self-compacting concrete for steel pipe piles according to claim 1, characterized in that, The regenerated micro powder is treated with acid and has a particle size of less than 3 μm. The acid treatment includes the following steps: adding the regenerated micro powder to an acid solution and stirring to mix, followed by hot air-microwave combined drying to obtain acid-activated regenerated micro powder.

4. The anti-corrosion micro-expansion self-compacting concrete for steel pipe piles according to claim 3, characterized in that, The acid solution includes tannic acid, acetic acid, or hydrochloric acid; the mass concentration of the acid solution is 0.5~1.5%; the hot air-microwave combined drying includes the following steps: using hot air drying at 55~65℃ to remove some moisture, and heating at a microwave frequency of 2400~2500MHz to remove the remaining moisture.

5. The anti-corrosion micro-expansion self-compacting concrete for steel pipe piles according to claim 1, characterized in that, The fineness modulus of the recycled fine aggregate is 2.3~3, the content of micro powder is less than 7%, and the content of clay lumps is less than 2%.

6. The anti-corrosion micro-expansion self-compacting concrete for steel pipe piles according to claim 1, characterized in that, The recycled coarse aggregate comprises a continuous gradation of 5-20 mm and has an apparent density greater than 2500 kg / m³. 3 The water absorption rate is less than 2.0%, the aggregate crushing value is less than 8%, the mud content is less than 0.3%, and the impurity content is less than 0.5%.

7. The anti-corrosion micro-expansion self-compacting concrete for steel pipe piles according to claim 1, characterized in that, The glass fiber comprises a blend of glass fibers of different lengths, with a length of 1~6mm and a diameter of 10~15μm.

8. The anti-corrosion micro-expansion self-compacting concrete for steel pipe piles according to claim 1, characterized in that, The polyoxymethylene fiber comprises a blend of microfiber and coarse bundled polyoxymethylene fiber, with a length of 6-12 mm and a crack resistance ≥967 MPa. The diameter of the microfiber polyoxymethylene fiber is 40~80μm; The diameter of the coarse bundles of polyoxymethylene fibers is 0.5~1.4 mm; The mass ratio of the microfiber polyoxymethylene fiber to the coarse bundle polyoxymethylene fiber is 1:(2~4).

9. The anti-corrosion micro-expansion self-compacting concrete for steel pipe piles according to claim 1, characterized in that, The graphene oxide has a sheet diameter of 0.5~5μm, a thickness of 0.8~2.4nm, and a purity of ≥98%. The expansion agent has a limited expansion rate of 0.054-0.06% in water after 7 days; the water reduction agent has a water reduction rate of 20-25%.

10. The construction method of corrosion-resistant micro-expansion self-compacting concrete for steel pipe piles as described in claims 1-9, characterized in that, Includes the following steps: Steel pipe pile fabrication: Before construction, the steel pipe is processed into a steel pipe with internal corrugations. The outer wall of the steel pipe is coated with an anti-corrosion coating. The steel pipe connection is made by sleeve lap welding. Before welding the pile, the vertical axis of the upper and lower pile sections is aligned. After removing the rust from the welding surface, the welding construction is carried out. Drilling: Determine the hole location, drill the hole, clean the sediment and mud inside the hole, and hoist the steel pipe pile; Grouting: After the steel pipe piles are installed, anti-corrosion micro-expansion self-compacting concrete is poured. Filling: Fill the gaps on the outside of the steel pipe with recycled fine aggregate.

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