A High-Permeability, Micro-Expansion, Crack-Resistant Concrete, Its Preparation Method and Application

Abstract

This invention belongs to the technical field of backfill materials for subway stations, specifically relating to a high-permeability, micro-expansion, and crack-resistant concrete, its preparation method, and application. The backfill material is composed of the following components: ordinary silicate cement, mineral powder, fly ash, tunnel boring machine slag, fine aggregate from coal gangue, recycled fine aggregate from construction waste, slag, recycled coarse aggregate from construction waste, coarse aggregate from coal gangue, water, calcium sulfoaluminate clinker, steel slag, desulfurized gypsum, acrylic emulsion, butyl acrylate-styrene copolymer latex, polyvinyl alcohol fiber, steel fiber, basalt fiber, cellulose fiber, polycarboxylate superplasticizer, and naphthalene-based superplasticizer. This backfill material possesses self-leveling and self-compacting properties, high permeability resistance, micro-expansion, and good crack resistance, which helps ensure backfill quality and structural safety, improve the station's waterproof performance, reduce the impact on the main structure, improve construction efficiency, reduce station leakage and other disasters, and achieve safe and efficient construction and operation of subway stations.

Description

Technical Field

[0001] This invention belongs to the technical field of backfill materials for subway station trenches, specifically relating to a high-permeability, micro-expansion, crack-resistant concrete and its preparation method and application. Background Technology

[0002] The main structure construction of subway stations generally adopts the open-cut method, which involves excavating layer by layer from the ground down to the design elevation to form a foundation pit before constructing the main structure. As urban underground space development continues to expand deeper, the structural burial depth is increasing, making the backfilling of the narrow, annular space—the "groove"—formed between the station's exterior walls and the foundation pit's supporting slope particularly important. The backfilling of the groove not only serves to transfer water and soil pressure and block groundwater seepage channels, but also has a crucial impact on controlling surface settlement and resisting structural buoyancy, making it a necessary step to ensure the long-term safety and stability of subway stations.

[0003] Traditional backfilling of trenches often uses materials such as plain soil and lime-soil. These materials often face problems in actual engineering, such as difficulty in ensuring uniform compaction, easy softening when exposed to water, large self-weight, and significant post-construction settlement. This can easily lead to water leakage in the backfill area, surface subsidence, and even engineering defects such as lateral deformation of the station structure. On the other hand, using concrete for backfilling has disadvantages such as poor fluidity, limited impermeability, high tendency to shrinkage cracking, high cement consumption, and heavy environmental impact. Summary of the Invention

[0004] The purpose of this invention is to provide a high-permeability, micro-expansion, crack-resistant concrete, its preparation method, and its application, thereby overcoming the shortcomings of the prior art. This backfill material has the characteristics of self-leveling, self-compacting, high permeability, micro-expansion, and good crack resistance, which is conducive to ensuring backfill quality and structural safety, improving the waterproof performance of the station, reducing the impact on the main structure, improving construction efficiency, reducing disasters such as station water leakage, and realizing the safe and efficient construction and operation and maintenance of subway stations.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a highly impermeable, micro-expansion, crack-resistant concrete, which is composed of the following components in parts by weight: 290-390 parts matrix material, 540-710 parts composite fine aggregate, 880-1100 parts composite coarse aggregate, 85-125 parts volume shrinkage improver, 62-123 parts composite crack-resistant and toughening admixture, 8-14 parts composite water-reducing agent, and 300-360 portions of water.

[0006] Furthermore, the matrix material is composed of the following components by weight: 200-250 parts of ordinary Portland cement, 30-50 parts of mineral powder, and 60-90 parts of fly ash; The composite fine aggregate is composed of the following components by weight: 260-320 parts of shield tunnel slag, 180-240 parts of coal gangue fine aggregate, and 100-150 parts of recycled construction waste fine aggregate. The composite coarse aggregate is composed of the following components by weight: 400-480 parts of slag, 280-360 parts of recycled coarse aggregate from construction waste, and 200-260 parts of coarse aggregate from coal gangue. The volume shrinkage improver is composed of the following components by weight: 20-30 parts calcium sulfoaluminate clinker, 40-60 parts steel slag, and 25-35 parts desulfurized gypsum. The composite crack-resistant and toughening admixture is composed of the following components by weight: 20-40 parts of acrylic emulsion, 30-60 parts of butyl acrylate-styrene copolymer latex, 2-4 parts of polyvinyl alcohol fiber, 6-12 parts of steel fiber, 1-2 parts of basalt fiber, and 3-5 parts of cellulose fiber. The composite water-reducing agent is composed of the following components by weight: 3-5 parts of polycarboxylate water-reducing agent and 5-9 parts of naphthalene-based water-reducing agent.

[0007] Ordinary Portland cement is a commonly used material in underground engineering construction, characterized by its stable properties, wide availability, and good mechanical properties. It is also a core cementitious component of traditional concrete. Mineral powder contains a large amount of glassy structure; its active components undergo a secondary hydration reaction with calcium hydroxide, a cement hydration product, generating more reinforcing gel and refining the pore structure. This significantly improves the later-stage strength and durability of cement-based materials and effectively reduces the heat of hydration. Fly ash's microsphere effect acts as a lubricant and filler. Later, the active glassy components react with calcium hydroxide in a pozzolanic reaction, generating gel that fills the pores, improving the workability of fresh concrete, reducing the heat of hydration, and enhancing impermeability and crack resistance. Therefore, this invention uses ordinary Portland cement, mineral powder, and fly ash as cementitious components.

[0008] Furthermore, this invention employs shield tunneling slag, coal gangue fine aggregate, and recycled construction waste fine aggregate as the graded fine aggregate in the material system. Shield tunneling slag typically contains clay components, which helps improve the water retention and cohesiveness of the mixture, reduces segregation, and enables the resource utilization of the project's own waste, reducing off-site disposal costs and environmental impact. The porous structure of the coal gangue fine aggregate reduces the apparent density of the concrete and provides a high-value-added utilization method for bulk industrial solid waste coal gangue, reducing the consumption of natural sand and gravel. The angular particles of the recycled construction waste fine aggregate help improve the mechanical strength of the concrete when added in small amounts; its utilization transforms urban demolition waste into resources, aligning with the concept of a circular economy. Experimental results show that the concrete obtained using the above combination has superior workability and mechanical properties.

[0009] Furthermore, this invention uses slag, recycled construction waste coarse aggregate, and coal gangue coarse aggregate as coarse aggregates for concrete. Slag has a good particle size distribution and relatively light weight, which helps optimize the concrete's skeleton structure and reduce overall density. It also enables the resource utilization of industrial by-products, reducing land occupation and environmental pollution. The high angularity and surface roughness of recycled construction waste coarse aggregate are beneficial for improving the compressive strength and shear strength of concrete, transforming urban demolition waste into valuable resources and saving on natural stone consumption. Coal gangue coarse aggregate is porous, allowing for the preparation of lightweight concrete with certain thermal insulation effects. It also provides a large-scale disposal method for coal gangue, a major solid waste, reducing the pressure on natural resource extraction. Through the combination of these three coarse aggregates, the gradation optimization and control of backfill material can be achieved, along with the resource utilization and high-value utilization of major solid waste, while reducing backfill material costs. Experimental results show that the backfill material obtained using the above combination has superior self-leveling properties.

[0010] Furthermore, this invention incorporates calcium sulfoaluminate clinker, steel slag, and desulfurized gypsum to improve the shrinkage characteristics of the backfill material. During hydration, calcium sulfoaluminate clinker rapidly generates a large amount of ettringite, resulting in controllable volume expansion, effectively compensating for the chemical shrinkage and drying shrinkage of the backfill material. Steel slag contains free calcium oxide (f-CaO) and periclase (MgO), which slowly generate calcium hydroxide and magnesium hydroxide in the later stages of hydration, producing delayed volume expansion. Desulfurized gypsum, as a sulfate activator, reacts with the aluminum phase in the cementitious material to generate the expansive product ettringite, increasing solid volume and reducing porosity by promoting hydration. Therefore, this invention uses a composite of the above three materials to provide volume expansion stress in the early, middle, and late stages of the reaction. Experimental results show that the backfill material obtained using the above combination exhibits micro-volume expansion characteristics.

[0011] Furthermore, this invention enhances the impermeability and crack resistance of the material by adding acrylate emulsion, butyl acrylate-styrene copolymer latex, polyvinyl alcohol fiber, steel fiber, basalt fiber, and cellulose fiber. The acrylate emulsion forms a continuous polymer film in the cement pores, filling capillaries and bridging microcracks, thus blocking some seepage channels and improving toughness. The butyl acrylate-styrene copolymer latex forms a flexible polymer film that effectively seals pores and imparts higher deformability to the matrix to alleviate stress, thereby inhibiting the generation and development of microcracks. During the plastic stage and early hardening stage of concrete, polyvinyl alcohol fiber effectively blocks aggregate settlement and moisture evaporation paths through a large number of uniformly distributed fibers, thereby inhibiting the generation and development of primary microcracks. Steel fiber has a high elastic modulus and tensile strength, enabling it to cross cracks in hardened concrete and transfer stress, thereby improving the material's crack resistance and post-cracking toughness. Basalt fiber has good adhesion to the cement matrix, acting as a bridge and crack inhibitor during microcrack propagation, thus refining cracks and improving impermeability. Cellulose fibers' unique hydrophilicity and three-dimensional distribution structure effectively absorb moisture, reduce plastic shrinkage, and inhibit the formation of early plastic cracks through weak but widespread fiber bridging. Polyvinyl alcohol fibers can form a uniformly supported fiber network in the cement matrix, effectively distributing early plastic shrinkage stress, inhibiting the generation and development of microcracks, and thus improving crack resistance. Experimental results show that the backfill material obtained by using the above combination has superior impermeability and crack resistance.

[0012] Furthermore, this invention adds polycarboxylate superplasticizer and naphthalene-based superplasticizer to improve the fluidity of concrete and impart self-leveling properties. The polycarboxylate superplasticizer efficiently disperses cement particles through the steric hindrance effect of its molecular structure, thereby reducing the water-cement ratio and giving the concrete high fluidity and excellent slump retention, achieving self-leveling and self-compacting properties. The naphthalene-based superplasticizer mainly relies on electrostatic repulsion to disperse cement particles, releasing trapped free water and thus improving the initial fluidity of the concrete. Experimental results show that the backfill material obtained using the above combination has superior fluidity and self-leveling properties.

[0013] In some other embodiments, the average particle size of ordinary silicate cement is ≤40μm; The specific surface area of ​​the mineral powder is 400-500 m² / kg, and the alkalinity coefficient is >1.0; The specific surface area of ​​fly ash is 450-550 m² / kg, and the loss on ignition is ≤5%.

[0014] In some other implementations, the fineness modulus of the tunnel boring machine excavation soil is between 2.5 and 3.0, and the moisture content is ≤30%. The water absorption rate of fine aggregate from coal gangue is ≤8%, and the sulfide content is ≤1%. The water absorption rate of recycled fine aggregate from construction waste is ≤8%, and the content of particles with a particle size of less than 75μm is ≤5%.

[0015] In some other embodiments, the slag has a sulfide and sulfate content of ≤2.0% and a moisture content of ≤5%; The crushing index of recycled coarse aggregate from construction waste is ≤30%, the water absorption rate is ≤5%, and the impurity content is ≤1%. The crushing index of coal gangue coarse aggregate is ≤30%, the water absorption rate is ≤5%, and the sulfide content is ≤1%. The water is tap water.

[0016] In some other embodiments, the alkali content of the calcium sulfoaluminate clinker is ≤0.6%; The mesh size of steel slag or desulfurized gypsum is 325-425 mesh; The average length of polyvinyl alcohol fibers is 10-20 mm; The average length of the steel fibers is 25-35 mm.

[0017] In some other embodiments, the average length of the basalt fibers is 12-18 mm; The average length of cellulose fibers is 2-3 mm.

[0018] In some other embodiments, the water reduction rate of the polycarboxylate superplasticizer is not less than 30%, and the content of the effective ingredient is ≥99%; The solid content of naphthalene-based water-reducing agents is ≥99%.

[0019] In a second aspect, the present invention provides a method for preparing the high impermeability, micro-expansion, and crack-resistant concrete described in the first aspect, comprising the following steps: (1) Stir and mix slag, recycled coarse aggregate from construction waste and coarse aggregate from coal gangue to obtain the first mixture; add shield tunnel slag, fine aggregate from coal gangue and recycled fine aggregate from construction waste during the stirring process of the first mixture to obtain the second mixture; then add ordinary silicate cement, mineral powder, fly ash, calcium sulfoaluminate clinker, steel slag and desulfurized gypsum to stir and mix to obtain the third mixture; finally add polyvinyl alcohol fiber, steel fiber, basalt fiber and cellulose fiber and stir evenly to obtain concrete dry powder material. (2) Mix water, polycarboxylate superplasticizer and naphthalene superplasticizer evenly, add them to the dry concrete powder and mix evenly to obtain wet concrete material; (3) Add the acrylic emulsion and butyl acrylate-styrene copolymer latex to the wet concrete and stir evenly to obtain high impermeability, micro-expansion and crack-resistant concrete.

[0020] In some other embodiments, in step (1), the stirring speed of the first mixture, the second mixture and the third mixture is 60-120 rpm / min; the stirring speed of the concrete dry powder material is 150-300 rpm / min, and the time is 2-4 min. In step (2), the stirring speed is 100-200 rpm / min and the time is 2-4 min; In step (3), the stirring speed is 150-250 rpm / min and the time is 3-5 min.

[0021] Thirdly, the present invention provides the application of the high impermeability, micro-expansion and crack-resistant concrete described in the first aspect in the backfilling project of trenches.

[0022] The beneficial effects of this invention are: (1) The high-permeability, micro-expansion, crack-resistant concrete for backfilling underground engineering trenches provided by this invention uses ordinary silicate cement and mineral admixtures as the main cementitious components, and incorporates a large amount of industrial solid waste and recycled building aggregates. By optimizing particle size distribution, controlling hydration reaction, and using composite functional admixtures, the material possesses excellent workability and self-leveling and self-compacting properties. No vibration is required during construction, simplifying the process and improving backfilling efficiency. By introducing an admixture system with micro-expansion, crack resistance, and impermeability enhancement effects, the volume stability and impermeability of the material during the hardening process are significantly improved. It can effectively compensate for shrinkage and inhibit crack formation, thereby ensuring close contact between the backfill and the main structure, enhancing waterproofing, reducing leakage risk, and providing reliable protection for the long-term safe operation of subway stations.

[0023] (2) This invention transforms a large amount of industrial solid waste and construction waste into key components of high-performance backfill materials, realizing the large-scale and high-value utilization of solid waste resources. This not only reduces material costs but also conforms to the green and low-carbon building concept, resulting in significant economic and environmental benefits. The core performance indicators proposed by this invention for backfill materials suitable for tunnel lining walls are as follows: slump ≥ 180 mm, spread ≥ 600 mm, initial setting time ≥ 4 h, volume change rate ≥ 0.05% in 28 days, seepage pressure ≥ 0.8 MPa in 28 days, compressive strength in 3 days, 7 days and 28 days greater than 7 MPa, 12 MPa and 20 MPa respectively, flexural-compression ratio in 28 days ≥ 0.30, and total crack area per unit area ≤ 50 mm² / m². Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 The images show the effects of backfilling the fertilizer trench before and after in Embodiment 1 of the present invention, where a represents the fertilizer trench before backfilling and b represents the fertilizer trench after backfilling. Detailed Implementation

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] The butyl acrylate-styrene copolymer latex has been published in the following paper: Zhang CY, Wang J, Zhang SF, Hou XW, Kong XM. Damping performance of hardened cement pastes containing styrene-butyl acrylate polymers with varied glass transition temperature and surface charges[J]. Cement&Concrete Composites, 2024, 145:105312.

[0028] Coal gangue fine aggregate is prepared by crushing and screening, which involves raw coal gangue → crushing → screening to obtain the required particle size; construction waste recycled fine aggregate is first crushed and screened: construction waste (mainly waste concrete) → crushing → screening, and then impurities are separated by air separation, magnetic separation, water washing and other methods to remove impurities such as waste wood, plastic and metal.

[0029] The preparation methods for coarse and fine aggregates are the same, differing only in parameters such as crushing and screening. Coal gangue coarse aggregate is prepared using a crushing and screening method, obtaining the desired particle size through raw coal gangue → crushing → screening; recycled construction waste coarse aggregate first undergoes crushing and screening: construction waste (mainly waste concrete) → crushing → screening, followed by impurity separation, removing impurities such as waste wood, plastic, and metal through air separation, magnetic separation, and water washing.

[0030] As mentioned earlier, existing backfill materials suffer from numerous drawbacks, such as difficulty in ensuring compaction, softening upon contact with water, high weight, and susceptibility to settlement. These drawbacks lead to severe water leakage problems in the later stages, often causing trench leakage, ground subsidence, and even lateral deformation of the main structure under pressure. Furthermore, concrete materials suffer from poor fluidity, insufficient impermeability, susceptibility to shrinkage cracking, and significant environmental emissions. To address these issues, this invention proposes a highly impermeable, micro-expansion, crack-resistant concrete for backfilling trenches in underground engineering projects.

[0031] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0032] Example 1 A high-permeability, micro-expansion, crack-resistant concrete, composed of the following by weight parts: ordinary silicate cement: mineral powder: fly ash: tunnel boring machine slag: coal gangue fine aggregate: recycled construction waste fine aggregate: slag: recycled construction waste coarse aggregate: coal gangue coarse aggregate: water: calcium sulfoaluminate clinker: steel slag: desulfurized gypsum: acrylate emulsion: butyl acrylate-styrene copolymer latex: polyvinyl alcohol fiber: steel fiber: basalt fiber: cellulose fiber: polycarboxylate superplasticizer: naphthalene-based superplasticizer = 225:30: 90: 290: 180: 125: 440: 360: 200: 360: 25: 40: 35: 30: 60: 2: 12: 1.5: 3: 4: 5.

[0033] The preparation method of the above-mentioned high impermeability, micro-expansion, and crack-resistant concrete includes the following steps: (1) Stir the slag, recycled coarse aggregate from construction waste and coarse aggregate from coal gangue at a rate of 80 rpm / min. During the stirring process, add shield tunnel slag, fine aggregate from coal gangue and recycled fine aggregate from construction waste. Then add ordinary silicate cement, mineral powder, fly ash, calcium sulfoaluminate clinker, steel slag and desulfurized gypsum. Finally, add polyvinyl alcohol fiber, steel fiber, basalt fiber and cellulose fiber. Stir at a rate of 180 rpm / min for 3 min to obtain concrete dry powder material.

[0034] (2) After uniformly mixing water, polycarboxylate superplasticizer and naphthalene superplasticizer, add them to the dry concrete powder material and stir at 150 rpm / min for 3 min to obtain wet concrete material; then add acrylate emulsion and butyl acrylate-styrene copolymer latex to the wet concrete material and stir at 200 rpm / min for 4 min to obtain a high impermeability micro-expansion crack-resistant concrete for backfilling underground engineering trenches.

[0035] Example 2 A high-permeability, micro-expansion, crack-resistant concrete, composed of the following by weight parts: ordinary silicate cement: mineral powder: fly ash: tunnel boring machine slag: coal gangue fine aggregate: recycled construction waste fine aggregate: slag: recycled construction waste coarse aggregate: coal gangue coarse aggregate: water: calcium sulfoaluminate clinker: steel slag: desulfurized gypsum: acrylate emulsion: butyl acrylate-styrene copolymer latex: polyvinyl alcohol fiber: steel fiber: basalt fiber: cellulose fiber: polycarboxylate superplasticizer: naphthalene-based superplasticizer = 200:40:90:320:210:100:480:320:230:330:25:60:25:20:45:3:12:1:3:5:5.

[0036] The preparation method of the above-mentioned high impermeability, micro-expansion, and crack-resistant concrete includes the following steps: (1) Stir the slag, recycled coarse aggregate from construction waste and coarse aggregate from coal gangue at a rate of 80 rpm / min. During the stirring process, add shield tunnel slag, fine aggregate from coal gangue and recycled fine aggregate from construction waste. Then add ordinary silicate cement, mineral powder, fly ash, calcium sulfoaluminate clinker, steel slag and desulfurized gypsum. Finally, add polyvinyl alcohol fiber, steel fiber, basalt fiber and cellulose fiber. Stir at a rate of 180 rpm / min for 3 min to obtain concrete dry powder material.

[0037] (2) After uniformly mixing water, polycarboxylate superplasticizer and naphthalene superplasticizer, add them to the dry concrete powder material and stir at 150 rpm / min for 3 min to obtain wet concrete material; then add acrylic emulsion and butyl acrylate-styrene copolymer latex to the wet concrete material and stir at 200 rpm / min for 4 min to obtain a high impermeability micro-expansion crack-resistant concrete for backfilling underground engineering trenches.

[0038] Example 3 A high-permeability, micro-expansion, crack-resistant concrete, composed of the following by weight parts: ordinary silicate cement: mineral powder: fly ash: tunnel boring machine slag: coal gangue fine aggregate: recycled construction waste fine aggregate: slag: recycled construction waste coarse aggregate: coal gangue coarse aggregate: water: calcium sulfoaluminate clinker: steel slag: desulfurized gypsum: acrylate emulsion: butyl acrylate-styrene copolymer latex: polyvinyl alcohol fiber: steel fiber: basalt fiber: cellulose fiber: polycarboxylate superplasticizer: naphthalene-based superplasticizer = 200:50:75:290:240:100:440:320:200:300:30:50:30:40:30:4:6:2:5:4:9.

[0039] The preparation method of the above-mentioned high impermeability, micro-expansion, and crack-resistant concrete includes the following steps: (1) Stir the slag, recycled coarse aggregate from construction waste and coarse aggregate from coal gangue at a rate of 80 rpm / min. During the stirring process, add shield tunnel slag, fine aggregate from coal gangue and recycled fine aggregate from construction waste. Then add ordinary silicate cement, mineral powder, fly ash, calcium sulfoaluminate clinker, steel slag and desulfurized gypsum. Finally, add polyvinyl alcohol fiber, steel fiber, basalt fiber and cellulose fiber. Stir at a rate of 180 rpm / min for 3 min to obtain concrete dry powder material.

[0040] (2) After uniformly mixing water, polycarboxylate superplasticizer and naphthalene superplasticizer, add them to the dry concrete powder material and stir at 150 rpm / min for 3 min to obtain wet concrete material; then add acrylate emulsion and butyl acrylate-styrene copolymer latex to the wet concrete material and stir at 200 rpm / min for 4 min to obtain a high impermeability micro-expansion crack-resistant concrete for backfilling underground engineering trenches.

[0041] Example 4 A high-permeability, micro-expansion, crack-resistant concrete, composed of the following by weight parts: ordinary silicate cement: mineral powder: fly ash: tunnel boring machine slag: coal gangue fine aggregate: recycled construction waste fine aggregate: slag: recycled construction waste coarse aggregate: coal gangue coarse aggregate: water: calcium sulfoaluminate clinker: steel slag: desulfurized gypsum: acrylate emulsion: butyl acrylate-styrene copolymer latex: polyvinyl alcohol fiber: steel fiber: basalt fiber: cellulose fiber: polycarboxylate superplasticizer: naphthalene-based superplasticizer = 250:30:75:260:210:150:400:360:260:330:20:50:30:20:60:2:9:1.5:4:3:7.

[0042] The preparation method of the above-mentioned high impermeability, micro-expansion, and crack-resistant concrete includes the following steps: (1) Stir the slag, recycled coarse aggregate from construction waste and coarse aggregate from coal gangue at a rate of 80 rpm / min. During the stirring process, add shield tunnel slag, fine aggregate from coal gangue and recycled fine aggregate from construction waste. Then add ordinary silicate cement, mineral powder, fly ash, calcium sulfoaluminate clinker, steel slag and desulfurized gypsum. Finally, add polyvinyl alcohol fiber, steel fiber, basalt fiber and cellulose fiber. Stir at a rate of 180 rpm / min for 3 min to obtain concrete dry powder material.

[0043] (2) After uniformly mixing water, polycarboxylate superplasticizer and naphthalene superplasticizer, add them to the dry concrete powder material and stir at 150 rpm / min for 3 min to obtain wet concrete material; then add acrylate emulsion and butyl acrylate-styrene copolymer latex to the wet concrete material and stir at 200 rpm / min for 4 min to obtain a high impermeability micro-expansion crack-resistant concrete for backfilling underground engineering trenches.

[0044] Example 5 A high-permeability, micro-expansion, crack-resistant concrete, composed of the following by weight parts: ordinary silicate cement: mineral powder: fly ash: tunnel boring machine slag: coal gangue fine aggregate: recycled construction waste fine aggregate: slag: recycled construction waste coarse aggregate: coal gangue coarse aggregate: water: calcium sulfoaluminate clinker: steel slag: desulfurized gypsum: acrylate emulsion: butyl acrylate-styrene copolymer latex: polyvinyl alcohol fiber: steel fiber: basalt fiber: cellulose fiber: polycarboxylate superplasticizer: naphthalene-based superplasticizer = 225:40:60:320:180:125:480:280:230:300:30:60:25:30:45:3:9:1:4:5:7.

[0045] The preparation method of the above-mentioned high impermeability, micro-expansion, and crack-resistant concrete includes the following steps: (1) Stir the slag, recycled coarse aggregate from construction waste and coarse aggregate from coal gangue at a rate of 80 rpm / min. During the stirring process, add shield tunnel slag, fine aggregate from coal gangue and recycled fine aggregate from construction waste. Then add ordinary silicate cement, mineral powder, fly ash, calcium sulfoaluminate clinker, steel slag and desulfurized gypsum. Finally, add polyvinyl alcohol fiber, steel fiber, basalt fiber and cellulose fiber. Stir at a rate of 180 rpm / min for 3 min to obtain concrete dry powder material.

[0046] (2) After uniformly mixing water, polycarboxylate superplasticizer and naphthalene superplasticizer, add them to the dry concrete powder material and stir at 150 rpm / min for 3 min to obtain wet concrete material; then add acrylate emulsion and butyl acrylate-styrene copolymer latex to the wet concrete material and stir at 200 rpm / min for 4 min to obtain a high impermeability micro-expansion crack-resistant concrete for backfilling underground engineering trenches.

[0047] Example 6 A high-permeability, micro-expansion, crack-resistant concrete, composed of the following by weight parts: ordinary silicate cement: mineral powder: fly ash: tunnel boring machine slag: coal gangue fine aggregate: recycled construction waste fine aggregate: slag: recycled construction waste coarse aggregate: coal gangue coarse aggregate: water: calcium sulfoaluminate clinker: steel slag: desulfurized gypsum: acrylate emulsion: butyl acrylate-styrene copolymer latex: polyvinyl alcohol fiber: steel fiber: basalt fiber: cellulose fiber: polycarboxylate superplasticizer: naphthalene-based superplasticizer = 250:50:60:260:240:150:400:280:260:360:20:40:35:40:30:4:6:2:5:3:9.

[0048] The preparation method of the above-mentioned high impermeability, micro-expansion, and crack-resistant concrete includes the following steps: (1) Stir the slag, recycled coarse aggregate from construction waste and coarse aggregate from coal gangue at a rate of 80 rpm / min. During the stirring process, add shield tunnel slag, fine aggregate from coal gangue and recycled fine aggregate from construction waste. Then add ordinary silicate cement, mineral powder, fly ash, calcium sulfoaluminate clinker, steel slag and desulfurized gypsum. Finally, add polyvinyl alcohol fiber, steel fiber, basalt fiber and cellulose fiber. Stir at a rate of 180 rpm / min for 3 minutes to obtain concrete dry powder material.

[0049] (2) After uniformly mixing water, polycarboxylate superplasticizer and naphthalene superplasticizer, add them to the dry concrete powder material and stir at 150 rpm / min for 3 min to obtain wet concrete material; then add acrylate emulsion and butyl acrylate-styrene copolymer latex to the wet concrete material and stir at 200 rpm / min for 4 min to obtain a high impermeability micro-expansion crack-resistant concrete for backfilling underground engineering trenches.

[0050] Comparative Example 1 The difference from Example 5 is that no mineral powder and fly ash were added, while the other materials and steps are the same as in Example 5.

[0051] Comparative Example 2 The difference from Example 5 is that shield tunneling slag, coal gangue fine aggregate, and recycled construction waste fine aggregate were not added; the other materials and steps are the same as in Example 5.

[0052] Comparative Example 3 The difference from Example 5 is that no slag, recycled coarse aggregate from construction waste, or coarse aggregate from coal gangue were added; all other materials and steps were the same as in Example 5.

[0053] Comparative Example 4 The difference from Example 5 is that calcium sulfoaluminate clinker, steel slag and desulfurization gypsum were not added, while the other materials and steps were the same as in Example 5.

[0054] Comparative Example 5 The difference from Example 5 is that acrylate emulsion, butyl acrylate-styrene copolymer latex, polyvinyl alcohol fiber, steel fiber, basalt fiber and cellulose fiber were not added, while the other materials and steps were the same as in Example 5.

[0055] Comparative Example 6 The difference from Example 5 is that no polycarboxylate superplasticizer and naphthalene-based superplasticizer were added; the other materials and steps were the same as in Example 5.

[0056] Comparative Example 7 The difference from Example 5 is that calcium sulfoaluminate clinker was not added, while the other materials and steps are the same as in Example 5.

[0057] Comparative Example 8 The difference from Example 5 is that steel slag and desulfurization gypsum were not added, while the other materials and steps were the same as in Example 5.

[0058] Comparative Example 9 The difference from Example 5 is that acrylate emulsion and butyl acrylate-styrene copolymer latex were not added, while the other materials and steps were the same as in Example 5.

[0059] Comparative Example 10 The difference from Example 5 is that polyvinyl alcohol fiber, steel fiber, basalt fiber and cellulose fiber were not added, while the other materials and steps were the same as in Example 5.

[0060] The performance testing method is as follows: 1. The slump test shall be conducted in accordance with the slump test method in GB / T 50080-2016 "Standard for Test Method of Performance of Ordinary Concrete Mixture". The test instruments are slump cone (100mm diameter at the top, 200mm diameter at the bottom, and 300mm in height), tamping rod and ruler.

[0061] 2. The spreadability test was conducted according to the method in GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures".

[0062] 3. The initial setting time test was conducted according to the setting time test method in GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixture". The test instrument used was a penetration resistance meter and a standard sieve. The initial setting time was determined by measuring the penetration resistance value at regular intervals and plotting a curve.

[0063] 4. The water permeability test shall be conducted in accordance with the water permeability test method in GB / T 50082-2024 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", and the test instrument shall be a concrete permeability meter.

[0064] 5. Shrinkage rate shall be determined according to the method in GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete".

[0065] 6. Compressive strength and flexural strength tests were conducted in accordance with GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0066] 7. Flexural-compression ratio: The compressive strength and flexural strength of the material are tested according to the methods in GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", and the flexural-compression ratio is calculated by dividing the flexural strength by the compressive strength.

[0067] 8. The total cracked area per unit area shall be tested according to the method in GB / T 50082-2024 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete".

[0068] The working performance of each embodiment and comparative example was tested, including slump, spread, initial setting time, 28-day volume change rate, and 28-day impermeability pressure. The results are shown in Table 1. The mechanical properties, toughness, and early cracking performance (24 hours after casting) of each embodiment and comparative example were evaluated, including 3-day compressive strength, 7-day compressive strength, 28-day compressive strength, 28-day flexural-compression ratio, and total crack area per unit area. The results are shown in Table 2.

[0069] Table 1 Performance Test Results

[0070] Table 2. Test results of mechanical properties, toughness, and early cracking performance.

[0071] As can be seen from Tables 1 and 2, all embodiments exhibit an excellent balance of comprehensive performance: suitable flow properties and setting time, certain micro-expansion characteristics, excellent impermeability and mechanical properties, and good toughness and crack resistance. Among them, Embodiment 5 has the best comprehensive performance.

[0072] Compared with Example 5, Comparative Example 1, due to the absence of mineral powder and fly ash, showed increased slump and spread, prolonged setting time, and reduced impermeability, micro-expansion characteristics, mechanical properties, and toughness.

[0073] Compared with Example 5, Comparative Example 2, due to the absence of shield tunnel slag, coal gangue fine aggregate and recycled construction waste fine aggregate, showed significantly improved flowability, extended setting time, and slightly reduced impermeability, compressive strength and toughness.

[0074] Compared with Example 5, Comparative Example 3, due to the absence of slag, recycled coarse aggregate from construction waste, and coarse aggregate from coal gangue, showed a significant increase in slump, spread, and setting time, while its impermeability, compressive strength, and toughness were significantly reduced.

[0075] Compared with Example 5, Comparative Example 4 did not include calcium sulfoaluminate clinker, steel slag, and desulfurized gypsum, resulting in a change from slight volume expansion to volume contraction. At the same time, the setting time was slightly prolonged, the flow properties were slightly improved, and the compressive strength and toughness were slightly reduced.

[0076] Compared with Example 5, Comparative Example 5 did not include acrylate emulsion, butyl acrylate-styrene copolymer latex, polyvinyl alcohol fiber, steel fiber, basalt fiber and cellulose fiber, resulting in a decrease in the material's impermeability and mechanical properties, a significant decrease in the flexural-compression ratio, a substantial increase in the total cracked area per unit area, and an improvement in flowability.

[0077] Compared with Example 5, Comparative Example 6, due to the absence of polycarboxylate superplasticizer and naphthalene-based superplasticizer, resulted in a significant decrease in slump and spread, while the compressive strength was slightly improved.

[0078] Compared with Example 5, Comparative Example 7 did not include calcium sulfoaluminate clinker, resulting in a slight increase in flowability, a change from slight volume expansion to volume contraction, and a slight decrease in compressive strength.

[0079] Compared with Example 5, Comparative Example 8 did not include steel slag and desulfurized gypsum, resulting in increased slump and spread. The material changed from slight volume expansion to volume contraction, and its mechanical properties and toughness were reduced.

[0080] Compared with Example 5, Comparative Example 9, due to the absence of acrylate emulsion and butyl acrylate-styrene copolymer latex, showed a slight decrease in material flowability, a decrease in impermeability and toughness, and a slight increase in compressive strength.

[0081] Compared with Example 5, Comparative Example 10 did not include polyvinyl alcohol fiber, steel fiber, basalt fiber and cellulose fiber, resulting in a significant decrease in the toughness and crack resistance of the material, a reduction in mechanical properties and micro-expansion effect, and an improvement in flowability.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A highly impermeable, micro-expansion, crack-resistant concrete, characterized in that, It consists of the following components in parts by weight: The matrix material consists of 290-390 parts, composite fine aggregate of 540-710 parts, composite coarse aggregate of 880-1100 parts, volume shrinkage improver of 85-125 parts, composite crack-resistant and toughening admixture of 62-123 parts, composite water-reducing agent of 8-14 parts, and water of 300-360 parts. The volume shrinkage improver is composed of calcium sulfoaluminate clinker, steel slag and desulfurized gypsum in a mass ratio of (20-30):(40-60):(25-35); The composite crack-resistant and toughening additive is composed of acrylate emulsion, butyl acrylate-styrene copolymer latex, polyvinyl alcohol fiber, steel fiber, basalt fiber and cellulose fiber in a mass ratio of (20-40):(30-60):(2-4):(6-12):(1-2):(3-5).

2. The high impermeability and micro-expansion crack-resistant concrete according to claim 1, characterized in that, The matrix material is composed of ordinary silicate cement, mineral powder and fly ash mixed in a mass ratio of (200-250):(30-50):(60-90); Alternatively, the composite fine aggregate is composed of shield tunnel slag, coal gangue fine aggregate, and recycled construction waste fine aggregate mixed in a mass ratio of (260-320):(180-240):(100-150); Alternatively, the composite coarse aggregate is composed of slag, recycled coarse aggregate from construction waste, and coarse aggregate from coal gangue in a mass ratio of (400-480):(280-360):(200-260); Alternatively, the composite water-reducing agent is composed of polycarboxylate water-reducing agent and naphthalene-based water-reducing agent mixed in a mass ratio of (3-5):(5-9).

3. The high impermeability and micro-expansion crack-resistant concrete according to claim 2, characterized in that, The average particle size of the ordinary silicate cement is ≤40μm; The specific surface area of ​​the mineral powder is 400-500 m² / kg, and the alkalinity coefficient is >1.0; The fly ash has a specific surface area of ​​450-550 m² / kg and a loss on ignition of ≤5%.

4. The high impermeability and micro-expansion crack-resistant concrete according to claim 2, characterized in that, The fineness modulus of the tunnel boring machine excavated soil is between 2.5 and 3.0, and the moisture content is ≤30%. The water absorption rate of the coal gangue fine aggregate is ≤8%, and the sulfide content is ≤1%. The water absorption rate of the recycled fine aggregate from construction waste is ≤8%, and the content of particles with a particle size of less than 75μm is ≤5%.

5. The high impermeability and micro-expansion crack-resistant concrete according to claim 2, characterized in that, The slag has a sulfide and sulfate content of ≤2.0% and a moisture content of ≤5%. The crushing index of the recycled coarse aggregate from construction waste is ≤30%, the water absorption rate is ≤5%, and the impurity content is ≤1%. The crushing index of the coal gangue coarse aggregate is ≤30%, the water absorption rate is ≤5%, and the sulfide content is ≤1%. The water in question is tap water.

6. The high impermeability and micro-expansion crack-resistant concrete according to claim 2, characterized in that, The alkali content of the calcium sulfoaluminate clinker is ≤0.6%; The steel slag or desulfurized gypsum has a mesh size of 325-425 mesh; The average length of the polyvinyl alcohol fiber is 10-20 mm; The average length of the steel fibers is 25-35 mm.

7. The high impermeability and micro-expansion crack-resistant concrete according to claim 2, characterized in that, The average length of the basalt fibers is 12-18 mm; The average length of the cellulose fibers is 2-3 mm; The water reduction rate of the polycarboxylate superplasticizer is not less than 30%, and the content of effective ingredients is ≥99%. The solid content of the naphthalene-based water-reducing agent is ≥99%.

8. A method for preparing high-permeability, micro-expansion, crack-resistant concrete according to any one of claims 1-7, characterized in that, Includes the following steps: (1) Stir and mix slag, recycled coarse aggregate from construction waste and coarse aggregate from coal gangue to obtain the first mixture; add shield tunnel slag, fine aggregate from coal gangue and recycled fine aggregate from construction waste during the stirring process of the first mixture to obtain the second mixture; then add ordinary silicate cement, mineral powder, fly ash, calcium sulfoaluminate clinker, steel slag and desulfurized gypsum to stir and mix to obtain the third mixture; finally add polyvinyl alcohol fiber, steel fiber, basalt fiber and cellulose fiber and stir evenly to obtain concrete dry powder material. (2) Mix water, polycarboxylate superplasticizer and naphthalene superplasticizer evenly, add them to the dry concrete powder and mix evenly to obtain wet concrete material; (3) Add the acrylic emulsion and butyl acrylate-styrene copolymer latex to the wet concrete and stir evenly to obtain high impermeability, micro-expansion and crack-resistant concrete.

9. A method for preparing high-permeability, micro-expansion, crack-resistant concrete as described in claim 8, characterized in that, In step (1), the mixing speed of the first mixture, the second mixture and the third mixture is 60-120 rpm / min; the mixing speed of the concrete dry powder material is 150-300 rpm / min, and the time is 2-4 min. In step (2), the stirring speed is 100-200 rpm / min and the time is 2-4 min; In step (3), the stirring speed is 150-250 rpm / min and the time is 3-5 min.

10. The application of the high impermeability, micro-expansion and crack-resistant concrete according to any one of claims 1-7 in backfilling projects of trenches.

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