A steel pipe jacking core filling material and its preparation method

Abstract

This application discloses a steel pipe jacking core filling material and its preparation method. The raw materials of the steel pipe jacking core filling material in this application include gel material, coarse aggregate, fine aggregate, wetting and dispersing agent, and water. The weight of the wetting and dispersing agent is 1.0-1.5% of the total mass of the gel material. The wetting and dispersing agent is compounded from maleic anhydride copolymer and organic bisacrylic surfactant. The cementing material includes cement, mineral powder, and fly ash. The molecular structure of the maleic anhydride copolymer is comb-shaped. The molecular weight of the main chain of the maleic anhydride copolymer is 5000-100000 g / mol, and the molecular weight of the side chain of the maleic anhydride copolymer is 100-500 g / mol. The molecular structure of the organic bisacrylic surfactant is comb-shaped. The molecular weight of the main chain of the organic bisacrylic surfactant is 5000-100000 g / mol, and the molecular weight of the side chain of the organic bisacrylic surfactant is 2000-5000 g / mol. The filler material in this application has better fluidity and density properties, and better volume stability, which can meet the dual requirements of mechanical properties and durability of lifting filler materials.

Description

Technical Field

[0001] This invention relates to the field of concrete materials technology, and in particular to a steel pipe jacking filler material and its preparation method. Background Technology

[0002] Steel tube core filling in roof steel structures is a key technical means to improve the overall performance of roof steel structures. Its core function is to enhance the overall integrity of the structure and improve its load-bearing capacity and stability. Specifically, by filling the inside of the steel tubes with core material, local deformation of the steel tubes can be effectively restrained, preventing local buckling of the steel tubes due to external forces and ensuring the structural safety of both the local area and the whole. Under seismic loading, the steel tube core filling structure can dissipate seismic energy through the plastic deformation of the energy-dissipating beam segments, thereby protecting the supporting diagonal members from buckling damage and reducing the impact of seismic loading on the entire roof steel structure. Therefore, this design is particularly important in scenarios with high requirements for structural safety, such as high-rise buildings and irregular roof structures, and is an important support for ensuring the seismic resistance of such buildings. Currently, the materials used for steel pipe core filling in roof steel structures mainly include self-compacting shrinkage-compensating concrete, self-compacting mortar, and fluidized solidified soil. Self-compacting concrete, which can be pumped under pressure into the steel pipe, has advantages such as good fluidity and high density, effectively filling the gaps inside the steel pipe. However, in actual construction, self-compacting concrete is prone to problems such as rapid collapse, insufficient fluidity, and excessive pumping pressure, which can lead to pipe blockage in severe cases, affecting construction efficiency and quality. Self-compacting mortar, compared to self-compacting concrete, has better fluidity and can solve the problem of excessive pumping pressure to some extent. However, self-compacting mortar shrinks significantly after hardening, easily leading to quality defects such as insufficient compaction and detachment from the steel pipe wall, failing to fully utilize the synergistic stress-bearing effect between the core material and the steel pipe. In summary, the construction performance and volume stability of the core material are the core technical challenges in its design and quality control. Furthermore, existing core materials using expansion agents generally suffer from uneven expansion and contraction, further exacerbating potential quality issues. With the increasing demands for quality in engineering construction, the performance requirements for building materials are also rising. For steel pipe jacking fill materials in roof steel structures, in addition to meeting core compressive strength requirements, good durability is also essential to ensure the long-term safety and reliability of the structure after construction. However, current technologies cannot simultaneously meet the comprehensive requirements of construction performance, mechanical properties, and durability, failing to meet the demands of high-quality development in roof steel structure engineering. Therefore, developing a high-flowability, high-stability steel pipe jacking fill material can effectively address the shortcomings of existing technologies and has significant application value and broad prospects in roof steel structure engineering. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this application provides a self-healing steel pipe jacking filler material for thermal stress cracks and its preparation method.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A self-healing steel pipe jacking core filling material for thermal stress cracks, the raw materials include gel material, coarse aggregate, fine aggregate, wetting and dispersing agent and water, the weight of the wetting and dispersing agent is 1.0-1.5% of the total mass of the gel material, the wetting and dispersing agent is compounded by maleic anhydride copolymer and organic twin surfactant, the cementing material includes cement, mineral powder and fly ash; The molecular structure of the maleic anhydride copolymer is comb-shaped, and the side chains of the maleic anhydride copolymer are composed of maleic anhydride units and maleic anhydride derivatives; the molecular structure of the organic twin surfactant is comb-shaped, and the main chain monomer of the organic twin surfactant is polymerized, the side chains of the organic twin surfactant are polyether molecules, and the monomers that polymerize into the main chain of the organic twin surfactant are acrylic acid, methacrylic acid or maleic anhydride.

[0005] In one embodiment, the raw materials for producing the single-unit steel pipe jacking filler material include 400-600 kg of gel material, 940-1030 kg of coarse aggregate, 810-900 kg of fine aggregate, 160-180 kg of water, 120-180 kg of ordinary silicate cement, 168-252 kg of mineral powder, and 112-168 kg of fly ash; the molecular weight of the maleic anhydride copolymer backbone is 5000-100000 g / mol, the molecular weight of the maleic anhydride copolymer side chain is 100-500 g / mol, the molecular weight of the organic twin surfactant backbone is 5000-100000 g / mol, and the molecular weight of the organic twin surfactant side chain is 2000-5000 g / mol.

[0006] In one embodiment, the cement is 42.5 grade silicate cement that meets the standard requirements.

[0007] In one embodiment, the mineral powder is S95 grade or higher slag powder with a 28-day activity index of not less than 105%.

[0008] In one embodiment, the fly ash is Class I fly ash with an activity index of not less than 85% after 28 days.

[0009] In one embodiment, the fine aggregate is continuously graded manufactured sand or natural sand with a fineness modulus of 2.6 to 2.8 and a distribution modulus of no more than 0.2; the coarse aggregate is continuously graded crushed stone with a maximum particle size of no more than 10 mm.

[0010] This application also provides a method for preparing the above-mentioned steel pipe jacking core filling material, including the following steps: Weigh the gel material, coarse aggregate, fine aggregate, wetting and dispersing agent, and water by weight. After mixing the wetting and dispersing agent and water evenly, add them together with the gel material to the mixer and mechanically stir for 100-120 seconds. Then add the coarse aggregate and fine aggregate and continue mechanically stirring for 2-3 minutes to obtain the steel pipe lifting core filling material.

[0011] Compared with the prior art, this application has at least the following beneficial effects: This application uses a wetting and dispersing agent in the raw materials of the steel pipe jacking core filling material. The polar groups such as sulfonic acid group and carboxyl group in the wetting and dispersing agent molecule reduce the surface tension of the liquid and improve the wetting performance of the liquid on the solid surface. At the same time, the wetting and dispersing agent molecule can be adsorbed by different fine particles, and disperse the cementitious material through the electrostatic repulsion between molecules. Its comb-like molecular structure prevents the particles from agglomerating. Under the action of stirring, the cementitious material system is in a fully dispersed state. Different types of cementitious materials can effectively undergo hydration reaction at different times. The cementitious materials in this application include not only mineral powder and fly ash, but also cement. The quality of cement, mineral powder and fly ash for producing single-cubic-meter steel pipe lifting core filling materials is set. This can enhance the workability of concrete with a low water-cement ratio, improve the workability and compaction of the core filling materials. Compared with conventional self-compacting concrete, which uses mineral powder and fly ash as a double admixture and the admixture dosage can only reach 45%, the mineral powder and fly ash in this application are further increased. Under the action of the above-mentioned wetting and dispersing agents, the workability of the mixture system can be significantly improved. This application uses coarse and fine aggregates controlled by the distribution modulus and with continuous gradation. Compared with ordinary concrete coarse and fine aggregates, it has a denser packing density and continuous gradation. The intermeshing effect between its particles is greatly reduced, and it often exhibits higher fluidity in the mixture system. It can increase the fluidity of the mixture without increasing the amount of cementitious materials, while maintaining the stability of the mixture volume. During the hydration of the cementitious material in this application, the overall hydration rate of the cementitious material system is reduced due to the high content of fly ash and mineral powder. In the early stage of hydration, the hydration of minerals such as C3S in cement mainly produces CSH gel and Ca(OH)2, forming a hardened gel with many capillaries. Ca(OH)2 crystallizes and expands, inverting the shrinkage in the later stage. The large amount of fly ash and mineral powder in the cementitious material system contains a large amount of SiO2. Al2O3 reacts with calcium hydroxide produced by cement hydration to form more CSH gel in the pores, reducing the enrichment of easily soluble Ca(OH)2, thereby reducing shrinkage. At the same time, the longer hydration reaction time of fly ash slows down the hydration reaction of the cementitious material, reduces the plastic shrinkage due to thermal stress inversion, and improves volume stability. In addition, the combined use of mineral powder and fly ash optimizes the stability of the paste through a synergistic effect, jointly inhibiting the shrinkage after the mixture hardens.

[0012] After hydration, the continuously graded aggregates are filled with coarse and fine particles, which reduces the porosity of the system to a low level, reduces the shrinkage of the cementitious materials, and the tightly packed aggregates form a rigid skeleton for the entire mixture system, limiting the free shrinkage of the cement paste through compressibility. Compared to self-compacting concrete, the filler material of this invention has better fluidity and compaction properties, and can effectively complete the filling in the complex environment of steel pipes; compared with self-compacting mortar, the filler material has better volume stability; the filler material of this application can be made without adding fibers, expansion agents and other components, thus meeting the dual requirements of mechanical properties and durability of steel pipe jacking filler materials. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below through specific embodiments. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0014] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0015] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms and should not be construed as indicating or implying relative importance. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0016] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical connection or internal connection between two components. They can be direct connection or indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0017] To better understand the technical solution of the present invention, the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0018] In the examples and comparative examples, the raw materials used include: a gel material composed of cement, mineral powder and fly ash, fine aggregate, coarse aggregate, water, a wetting and dispersing agent or a polycarboxylate superplasticizer.

[0019] The cement is 42.5 grade Portland cement that meets the standard requirements; the mineral powder is S95 grade or above slag powder with a 28-day activity index of not less than 105%; the fly ash is Grade I fly ash with a 28-day activity index of not less than 85%; the fine aggregate is fine aggregate 1 or fine aggregate 2, where fine aggregate 1 is continuously graded manufactured sand or natural sand with a fineness modulus of 2.6~2.8 and a distribution modulus of not more than 0.2; fine aggregate 2 is natural sand with a fineness modulus of 2.6~2.8 and natural gradation; the coarse aggregate is coarse aggregate 1 or coarse aggregate, where coarse aggregate 1 is continuously graded crushed stone with a maximum particle size of not more than 10mm; and coarse aggregate 2 is 5-20mm crushed stone with ordinary gradation. The wetting and dispersing agent is a compound of maleic anhydride copolymer and organic twin surfactant. The cementing material includes ordinary silicate cement, mineral powder, and fly ash. The maleic anhydride copolymer has a comb-like molecular structure, with a main chain molecular weight of 5000-100000 g / mol and a side chain molecular weight of 100-500 g / mol. The side chain is composed of maleic anhydride units and maleic anhydride derivatives. The organic twin surfactant also has a comb-like molecular structure, with a main chain molecular weight of 5000-100000 g / mol and a side chain molecular weight of 2000-5000 g / mol. The main chain is polymerized from monomers such as acrylic acid, methacrylic acid, or maleic anhydride, and the side chain is a polyether molecule. Example

[0020] A steel pipe jacking filler material is prepared through the following steps: After mixing 6.0 kg of wetting and dispersing agent with 160 kg of water, add it together with 120 kg of cement, 168 kg of mineral powder, and 112 kg of fly ash into a mixer and mechanically mix for 120 seconds. Then add 900 kg of fine aggregate 1 and 940 kg of coarse aggregate 1 and mechanically mix for 2-3 minutes to ensure that all components in the cementitious material and the coarse and fine aggregates are evenly dispersed, thus obtaining the steel pipe jacking core filling material.

[0021] Comparative Example 1: A steel pipe jacking filler material is prepared through the following steps: After mixing 6.0 kg of polycarboxylate superplasticizer with 160 kg of water, add it to a mixer along with 120 kg of cement, 168 kg of mineral powder, and 112 kg of fly ash. Mechanically mix for 120 seconds. Then add 900 kg of fine aggregate 1 and 940 kg of coarse aggregate 1 and mechanically mix for 2-3 minutes to ensure that all components in the cementitious material and the coarse and fine aggregates are evenly dispersed, thus obtaining the steel pipe jacking core filling material in the example.

[0022] Comparative Example 2: A steel pipe jacking filler material is prepared through the following steps: After mixing 6.0 kg of polycarboxylate superplasticizer with 160 kg of water, add it to a mixer along with 120 kg of cement, 168 kg of mineral powder, and 112 kg of fly ash. Mechanically mix for 120 seconds. Then add 900 kg of fine aggregate 2 and 940 kg of coarse aggregate 2 and mechanically mix for 2-3 minutes to ensure that all components in the cementitious material and the coarse and fine aggregates are evenly dispersed, thus obtaining the steel pipe jacking core filling material in the example.

[0023] Comparative Example 3: A steel pipe jacking filler material is prepared through the following steps: After mixing 6.0 kg of polycarboxylate superplasticizer with 160 kg of water, add it to a mixer along with 280 kg of cement, 72 kg of mineral powder, and 48 kg of fly ash. Mechanically mix for 120 seconds. Then add 900 kg of fine aggregate 1 and 940 kg of coarse aggregate 1 and mechanically mix for 2-3 minutes to ensure that all components in the cementitious material and the coarse and fine aggregates are evenly dispersed, thus obtaining the steel pipe jacking core filling material in the example.

[0024] Table 1: Raw material formulations of different core-filling materials in Examples and Comparative Examples 1-3 (unit: kg / m³)

[0025] After preparing Examples 1-3 and Comparative Examples 1-3 using the above methods, the performance of the filler materials was tested according to the test methods specified in the current standards. The results are shown in Table 2 below.

[0026] Table 2 shows the performance indicators of the different filler materials mentioned above.

[0027] The above test methods are all test methods stipulated by national and industry standards, and there are no special features or special explanations.

[0028] Results Analysis Based on the examples and comparative examples 1-3, and referring to the data in Table 2, it can be seen that the steel pipe jacking filler material prepared according to the method of the present invention has better fluidity and faster flow speed compared to comparative examples 1-3, possesses lower plastic viscosity, and exhibits a higher 14-day restricted expansion rate after hardening. It can address the shrinkage compensation level of concrete without adding an expansion agent, while its 90-day drying shrinkage rate is less than 200 × 10⁻⁶. -6 It belongs to low-shrinkage concrete, which greatly improves the volume stability of concrete.

[0029] Application: The high-flowability, high-volume-stability steel pipe jacking filler material described in this invention has been successfully applied in a real-world project (steel pipe columns on the roof of the upper structure of Shanghai East Railway Station, with a factory expansion of 600×600mm and an on-site expansion of 600×600mm; the inverted emptying time was <5s; a fixed pump was used during pumping, and the maximum pump pressure at the jacking point was only 2.0MPa). This fully verifies the superior properties of this filler material, such as low viscosity and high flowability. Furthermore, subsequent cutting verification of the test column showed that the filler inside the pipe was dense, uniform, and without voids. The practical application further demonstrates the reliability of this filler material. Compared to ordinary self-compacting concrete, this material has good encapsulation and anti-segregation properties, while also having lower plastic viscosity, a certain ability to compensate for shrinkage in the later stages, and high volume stability. It effectively solves the problem of balancing workability and long-term durability in jacking concrete projects.

[0030] In summary, the steel pipe filling material of this invention has higher fluidity and compaction performance than ordinary self-compacting concrete, and also has the characteristic of compensating for shrinkage. It can effectively compensate for the self-shrinkage of the filling material in the steel pipe, significantly reduce the drying shrinkage rate, solve the construction and durability problems of jacking materials, and ensure the compactness of the steel pipe.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A steel pipe jacking core filling material, characterized in that, The raw materials include gelling materials, coarse aggregates, fine aggregates, wetting and dispersing agents, and water. The weight of the wetting and dispersing agent is 1.0-1.5% of the total mass of the gelling materials. The wetting and dispersing agent is a compound of maleic anhydride copolymer and organic twin surfactant. The gelling materials include cement, mineral powder, and fly ash. The molecular structure of the maleic anhydride copolymer is comb-shaped, and the side chains of the maleic anhydride copolymer are composed of maleic anhydride units and maleic anhydride derivatives; the molecular structure of the organic twin surfactant is comb-shaped, and the main chain monomer of the organic twin surfactant is polymerized, the side chains of the organic twin surfactant are polyether molecules, and the monomers that polymerize into the main chain of the organic twin surfactant are acrylic acid, methacrylic acid or maleic anhydride.

2. The steel pipe jacking filler material according to claim 1, characterized in that, The raw materials for producing single-unit steel pipe jacking filler material include 400-600 kg of gel material, 940-1030 kg of coarse aggregate, 810-900 kg of fine aggregate, 160-180 kg of water, 120-180 kg of ordinary silicate cement, 168-252 kg of mineral powder, and 112-168 kg of fly ash; the molecular weight of the maleic anhydride copolymer main chain is 5000-100000 g / mol, the molecular weight of the maleic anhydride copolymer side chain is 100-500 g / mol, the molecular weight of the organic twin surfactant main chain is 5000-100000 g / mol, and the molecular weight of the organic twin surfactant side chain is 2000-5000 g / mol.

3. The steel pipe jacking filler material according to claim 2, characterized in that, The cement is grade 42.5 silicate cement that meets the standard requirements.

4. The steel pipe jacking filler material according to claim 2, characterized in that, The mineral powder is S95 grade or higher slag powder with an activity index of not less than 105% after 28 days.

5. The steel pipe jacking filler material according to claim 2, characterized in that, The fly ash is Class I fly ash with an activity index of not less than 85% after 28 days.

6. The steel pipe jacking filler material according to claim 2, characterized in that, The fine aggregate is continuously graded manufactured sand or natural sand with a fineness modulus of 2.6 to 2.8 and a distribution modulus of no more than 0.2; the coarse aggregate is continuously graded crushed stone with a maximum particle size of no more than 10 mm.

7. A method for preparing a steel pipe jacking core filling material as described in any one of claims 2-6, characterized in that, Includes the following steps: Weigh the gel material, coarse aggregate, fine aggregate, wetting and dispersing agent, and water by weight. After mixing the wetting and dispersing agent and water evenly, add them together with the gel material to the mixer and mechanically stir for 100-120 seconds. Then add the coarse aggregate and fine aggregate and continue mechanically stirring for 2-3 minutes to obtain the steel pipe lifting core filling material.

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