Highly impermeable self-leveling anti-cracking backfill material, preparation method and application thereof

Abstract

The present application relates to the technical field of subway assembled station vault backfill material, and particularly relates to a high anti-permeability self-leveling anti-cracking backfill material, a preparation method and application thereof. The backfill material takes a small amount of Portland cement clinker and a large amount of multi-source solid waste as main raw materials, and through mineral synergy, grading control and admixture regulation, the material is endowed with good flow performance and self-leveling characteristics. The backfill material provided by the present application has the characteristics of good flow performance, excellent anti-permeability, high toughness and strong anti-cracking ability, which is beneficial to reduce stone body cracks, improve the mechanical properties, anti-permeability and durability of the backfill area, reduce the occurrence of station water leakage disasters, improve the construction efficiency of the station, and realize safe and efficient construction of the subway station.

Description

Technical Field

[0001] This invention relates to the field of backfill materials for prefabricated subway station arches, and particularly to a high-permeability, self-leveling, and crack-resistant backfill material, its preparation method, and its application. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] The construction of subway stations has long relied on the "open-cut and cast-in-place method," which involves excavating the foundation pit and then completing processes such as tying reinforcing bars, erecting formwork, and pouring concrete on-site. This method generally suffers from problems such as low construction efficiency, difficulty in quality control, high safety risks, high resource consumption, significant environmental impact, and long construction periods, and has become a key bottleneck restricting the safe and high-quality construction of subway stations.

[0004] Against this backdrop, prefabricated railway stations have emerged. This construction method involves prefabricating station components in a factory and then transporting them to the site for assembly, offering advantages such as environmental friendliness and high construction efficiency. However, after the main structure of the prefabricated station is assembled, the arch area requires layered backfilling. Traditionally, a 3:7 lime-soil mixture is used as the backfill material, but it suffers from weak mechanical properties, insufficient toughness, and poor impermeability, easily leading to water leakage later on. Furthermore, lime-soil construction requires multiple layers of compaction, a complex and inefficient process. Concrete, on the other hand, suffers from poor fluidity, easy cracking, high environmental impact, and high cost. Therefore, there is an urgent need for a backfill material that combines excellent mechanical properties, high toughness, good impermeability, and meets the requirements of convenient construction, cost-effectiveness, and environmental friendliness for the arch backfilling of prefabricated railway stations. Summary of the Invention

[0005] In view of this, the present invention provides a high-permeability, self-leveling, crack-resistant backfill material, its preparation method, and its application. This backfill material possesses excellent mechanical properties, high toughness, and good permeability resistance, which is beneficial for stabilizing the stress on the station, reducing cracks in the backfill body, improving the overall mechanical properties, toughness, and permeability resistance of the station's backfill area, significantly reducing station water leakage disasters, and achieving safe construction and operation of prefabricated subway stations.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a high impermeability self-leveling crack-resistant backfill material, which is composed of the following raw materials in parts by weight: 475-660 parts of high-performance cementitious component, 860-1060 parts of composite aggregate, 100-170 parts of toughness material, 28-54 parts of crack resistance optimization component, 8-14 parts of leveling control admixture, and 380-460 parts of water. The high-performance cementitious component is composed of the following raw materials in parts by weight: 150-210 parts of silicate cement clinker, 30-50 parts of blast furnace slag, 10-15 parts of gypsum, 70-90 parts of coal gangue powder, 200-260 parts of fly ash, and 15-35 parts of silica fume. The composite aggregate is composed of the following raw materials in parts by weight: 150-190 parts tailings slag, 280-340 parts shield tunnel slag, and 430-530 parts furnace slag. The tough material is composed of the following raw materials in parts by weight: 50-80 parts of waste tire rubber granules, 30-50 parts of styrene-butyl acrylate copolymer latex, and 20-40 parts of waterborne polyurethane. The crack resistance optimization component is composed of the following raw materials in parts by weight: 4-6 parts polyvinyl alcohol fiber, 3-5 parts glass fiber, 1-3 parts steel fiber, and 20-40 parts nano-SiO2. The leveling additive is composed of the following raw materials in parts by weight: 2-4 parts of naphthalene-based water-reducing agent and 6-10 parts of polycarboxylate water-reducing agent.

[0007] Silicate cement clinker is the core component of ordinary silicate cement. It boasts advantages such as wide availability and excellent mechanical properties, making it widely used in underground engineering. Its advantages stem from the designability of its mineral composition and high chemical purity, allowing for customized formulation to produce engineering materials with performance highly matched to project requirements. Blast furnace slag can enhance the long-term strength, density, and durability of cement-based materials, improve resistance to chemical attack, and reduce heat of hydration, while also offering excellent environmental and economic benefits. Gypsum can regulate the setting time of the cement clinker system, preventing rapid setting and ensuring it meets construction requirements. It also participates in hydration reactions, improving the early strength and volume stability of cement.

[0008] Cement hydration produces calcium hydroxide, making the system alkaline. This alkaline environment activates the active silica and alumina in pozzolanic materials, leading to the formation of hydrated calcium silicate gels, which enhance the density and durability of cement materials. This invention adds coal gangue powder, fly ash, and silica fume, primarily composed of aluminosilicate minerals, and fully utilizes the system's cementitious potential by rationally controlling the calcium-silicon ratio and silica-alumina ratio. The active components of coal gangue powder, fly ash, and silica fume react with cement hydration products to form a dense hydrated calcium silicate gel, effectively filling pores and refining the pore structure, thus significantly improving the impermeability of cement-based materials. Simultaneously, by reducing cement dosage, lowering hydration heat, and improving microstructural stress, they effectively inhibit the generation and development of shrinkage cracks, enhancing the material's crack resistance. Experimental results show that the backfill material obtained using the combination of coal gangue powder, fly ash, and silica fume exhibits superior impermeability and toughness.

[0009] This invention uses tailings slag, tunnel boring machine (TBM) slag, and blast furnace slag as aggregates for backfill material. Tailings slag, as an excellent fine aggregate, optimizes the gradation of the backfill, reduces cement usage, and simultaneously achieves resource utilization of tailings solid waste. Using TBM slag enables on-site disposal of engineering waste, significantly reducing the cost of off-site disposal and mitigating environmental burden. The pozzolanic activity of blast furnace slag enhances the later-stage strength of the backfill, and its lightweight and porous nature helps improve the fluidity and stability of the backfill slurry. Through the combination of these three coarse and fine aggregates, the gradation of the backfill can be optimized and controlled, and large-scale solid waste can be utilized for resource recovery and high-value utilization, while significantly reducing the cost of backfill materials. Experimental results show that the backfill material obtained using the combination of tailings slag, TBM slag, and blast furnace slag has superior self-leveling properties.

[0010] This invention incorporates waste tire rubber particles, styrene-butyl acrylate copolymer latex, and waterborne polyurethane to improve the toughness and energy absorption properties of materials at the millimeter and micro / nano scales, respectively. Waste tire rubber particles act as an elastic component in the cement matrix, effectively absorbing and dissipating energy through their large deformation. During crack propagation, they hinder crack development through bridging and plastic deformation, thereby enhancing toughness and energy absorption characteristics. The styrene-butyl acrylate copolymer latex forms a polymer film network within the matrix, bridging cracks and dispersing stress through high ductility, enabling the material to absorb more energy upon failure, significantly improving toughness and energy absorption capacity. After curing, the waterborne polyurethane forms a highly elastic three-dimensional cross-linked network, efficiently absorbing and dissipating external mechanical energy through molecular chain extension and reversible deformation, thus greatly enhancing the material's toughness and energy absorption properties. Experimental results show that the backfill material obtained using the combination of waste tire rubber particles, styrene-butyl acrylate copolymer latex, and waterborne polyurethane exhibits superior toughness and energy absorption properties.

[0011] Furthermore, this invention enhances the crack resistance of materials reinforced with polyvinyl alcohol fibers, glass fibers, steel fibers, and nano-SiO2. Polyvinyl alcohol fibers form a uniformly supported fiber network within the cement matrix, effectively distributing early plastic shrinkage stress and inhibiting the generation and development of microcracks, thereby improving crack resistance. Glass fibers, with their high tensile strength and dispersibility, act as micro-reinforcing ribs in the matrix, bridging cracks in the hardened aggregate and hindering their propagation, thus improving crack resistance. Steel fibers, with their high strength and toughness, effectively bridge macroscopic cracks and withstand significant tensile stress after the aggregate cracks, significantly improving the material's crack resistance and post-cracking toughness. Nano-SiO2, with its extremely high pozzolanic activity and micro-aggregate filling effect, optimizes the interface transition zone and refines the pore structure, enhancing matrix density at the microscopic level and inhibiting microcrack initiation. Experimental results show that the backfill material obtained using the combination of polyvinyl alcohol fibers, glass fibers, steel fibers, and nano-SiO2 exhibits superior toughness and crack resistance.

[0012] This invention enhances the self-leveling properties of materials by incorporating naphthalene-based and polycarboxylate superplasticizers. The naphthalene-based superplasticizer, through adsorption on the surface of cement particles, generates strong electrostatic repulsion, efficiently dispersing the cement particles and releasing free water, thereby reducing water consumption and improving fluidity. The polycarboxylate superplasticizer, through the steric hindrance effect of its polymer comb-like structure and the synergistic effect of electrostatic repulsion, achieves long-term, highly stable dispersion of cement particles, allowing the slurry to maintain excellent fluidity and cohesiveness even at low water-cement ratios, achieving a self-leveling effect without segregation or bleeding. Experimental results show that the backfill material obtained by combining naphthalene-based and polycarboxylate superplasticizers exhibits superior fluidity and self-leveling properties.

[0013] Furthermore, the specific surface area of ​​the silicate cement clinker is 330-380 m². 2 / kg, free calcium oxide content ≤ 1.0%.

[0014] Furthermore, the specific surface area of ​​the blast furnace slag is 400-500 m². 2 / kg, alkalinity coefficient >1.0.

[0015] Furthermore, the particle size of the gypsum satisfies the requirement that the residue on a 0.2 mm square-hole sieve is ≤ 10%.

[0016] Furthermore, the specific surface area of ​​the coal gangue powder and fly ash is 450-550 m². 2 / kg, loss on ignition ≤ 5%.

[0017] Furthermore, the specific surface area of ​​the silica fume is ≥ 15000 m². 2 / kg, SiO2 content ≥ 85%.

[0018] Furthermore, the fineness modulus of the tailings is between 2.2 and 2.8, and the leaching amount of harmful substances meets the requirements for safe groundwater discharge.

[0019] Furthermore, the fineness modulus of the tunnel boring machine excavated soil is between 2.5 and 3.0, and the moisture content is ≤ 30%.

[0020] Furthermore, the slag has a sulfide and sulfate content of ≤ 2.0% and a moisture content of ≤ 5%.

[0021] Furthermore, the waste tire rubber particles have a particle size of 1-2 mm; the styrene-butyl acrylate copolymer latex particles have a particle size of 200-500 nm; and the waterborne polyurethane particles have a particle size of 160-700 nm.

[0022] Furthermore, the elongation at break of the waterborne polyurethane is ≥ 150%.

[0023] Furthermore, the average length of the polyvinyl alcohol fiber is 6-12 mm.

[0024] Furthermore, the average length of the glass fiber is 3-6 mm.

[0025] Furthermore, the average length of the steel fiber is 25-35 mm.

[0026] Furthermore, the effective content of the nano-SiO2 is ≥ 99%.

[0027] Furthermore, the naphthalene-based water-reducing agent is a yellowish-brown powder with a solid content ≥ 99%.

[0028] Furthermore, the water reduction rate of the polycarboxylate superplasticizer is not less than 30%, and the content of effective ingredients is ≥ 99%.

[0029] Furthermore, the water in question is tap water.

[0030] Furthermore, the calcium-silicon ratios of blast furnace slag, coal gangue powder, and fly ash range from 1.4 to 1.6, 0.1 to 0.15, and 0.2 to 0.25, respectively; and the silicon-aluminum ratios range from 2.0 to 2.2, 2.6 to 2.8, and 1.6 to 1.8, respectively.

[0031] In the backfill material provided by this invention, slag, tailings slag, shield tunnel slag (coarse aggregate), fly ash, slag, coal gangue powder (fine filler), silica fume and nano-scale filler nano SiO2 (ultra-fine filler) work together to form a multi-scale particle gradation and dense packing effect. Through multi-level physical filling, the densest packing is formed, which greatly reduces porosity, blocks capillary channels, and improves the impermeability and mechanical properties of the backfill material.

[0032] In the backfill material provided by this invention, a multi-component cementitious system of cement clinker, slag, fly ash, silica fume, coal gangue powder, and gypsum synergistically reacts. The hydration reaction of cement clinker generates calcium hydroxide (CH) and CSH gel, which promotes the reaction of active SiO2 and Al2O3 in slag, fly ash, silica fume, and coal gangue powder with CH to generate additional CSH / CAH gel. Subsequently, SO4 provided by gypsum... 2- It can further activate the activity of slag and fly ash, accelerate the pozzolanic reaction, consume the CH enriched at the aggregate / slurry interface, generate CSH with higher strength, significantly improve interfacial bonding force, and thus improve mechanical properties and impermeability.

[0033] In the backfill material provided by this invention, cement clinker, styrene-butyl acrylate copolymer latex, and waterborne polyurethane work synergistically. The polymer particles adsorb onto the surface of the cement particles, delaying the peak of hydration exothermic reaction and reducing the generation of temperature stress cracks. As the hydration reaction proceeds, the polymer particles aggregate to form a continuous polymer film, which covers the hydration products and aggregate surface, and interpenetrates with CSH gel to form an organic-inorganic interpenetrating network structure, giving the backfill material high toughness and crack resistance. Furthermore, the flexible polyurethane and styrene-butyl acrylate latex film spans microcracks, absorbs energy, and prevents crack propagation. By providing strength through rigid cement hydrates and deformation capacity through flexible polymers, the toughness and flexural strength of the material can be significantly improved. At the same time, due to its film-forming properties, it seals the internal pores, further enhancing impermeability.

[0034] In the backfill material provided by this invention, polyvinyl alcohol fiber, glass fiber, and steel fiber work together to toughen the material. Polyvinyl alcohol fiber (with a small diameter, hydrophilic properties, and good adhesion to the cement matrix) plays a role in the early plastic shrinkage stage, preventing the generation and propagation of microcracks. Steel fiber bears the main tensile stress in the later hardening stage and bridges macroscopic cracks. Glass fiber is between polyvinyl alcohol fiber and steel fiber, reinforcing the overall network. The three types of fibers control cracks at different scales and stages, which can significantly improve the toughness and crack resistance of the material.

[0035] In a second aspect, the present invention provides a method for preparing a high-permeability, self-leveling, crack-resistant backfill material as described in the first aspect, comprising: (1) Silicate cement clinker, blast furnace slag, gypsum, coal gangue powder, fly ash, silica fume, tailings slag, shield tunnel slag, furnace slag, nano-SiO2, naphthalene-based water-reducing agent, polycarboxylate water-reducing agent and water are mixed evenly to obtain the backfill material matrix material; (2) Add waste tire rubber particles, styrene-butyl acrylate copolymer latex, waterborne polyurethane, polyvinyl alcohol fiber, glass fiber and steel fiber to the backfill material matrix material and stir evenly to obtain the final product.

[0036] Further, in step (1), the mixture is stirred at 100-200 rpm for 2-10 min; preferably at 150 rpm for 3 min.

[0037] Further, in step (2), the mixture is stirred at 200-300 rpm for 3-5 min; preferably at 300 rpm for 4 min.

[0038] Thirdly, the present invention provides the application of the high impermeability self-leveling and crack-resistant backfill material described in the first aspect in the backfilling project of the arch of a subway prefabricated station.

[0039] The core performance indicators of backfill materials suitable for prefabricated railway station arch backfill are as follows: slump ≥ 200 mm, spread ≥ 600 mm, 1.75 g / cm³. 3 Density ≥ 1.65 g / cm³ 3 Initial setting time ≥ 5 h, compressive strength at 3 days and 28 days ≥ 5 MPa and 14 MPa respectively, 28-day flexural-compression ratio ≥ 0.30, 28-day impermeability pressure ≥ 0.7 MPa, total crack area per unit area ≤ 50 mm 2 / m 2 The performance parameters of embodiments 1-6 of the present invention all conform to the above-mentioned range.

[0040] Compared with the prior art, the present invention has achieved the following beneficial effects: This invention provides a high-permeability, self-leveling, and crack-resistant backfill material for the arched roof of prefabricated subway stations. Using a small amount of silicate cement clinker and a large amount of multi-source solid waste as main raw materials, the material exhibits good flowability and self-leveling properties through mineral synergy, gradation control, and admixture regulation. The backfill material incorporates various functional admixtures, improving its permeability and crack resistance, reducing cracks in the aggregate, enhancing the mechanical properties, permeability, and durability of the backfill area, reducing the occurrence of station leakage disasters, improving station construction efficiency, and achieving safe and efficient subway station construction.

[0041] This invention utilizes a large amount of solid waste to prepare high-performance backfill materials, realizing high-value utilization of solid waste resources. The materials have excellent working performance and impermeability, while also having low cost and environmental impact. Detailed Implementation

[0042] 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 herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0043] In the following embodiments, the parameters of each component are as follows: The average specific surface area of ​​the silicate cement clinker is 365 m². 2 / kg, with a free calcium oxide content of 0.32%; The average specific surface area of ​​the blast furnace slag is 470 m². 2 / kg, with an alkalinity coefficient of 1.157; The gypsum particle size was 4.6% when sieved through a 0.2 mm square-hole sieve. The average specific surface area of ​​the coal gangue powder and fly ash is 470 m². 2 / kg and 520 m2 / kg, with losses on ignition of 4.56% and 3.72%, respectively; The specific surface area of ​​the silica fume is 18643 m². 2 / kg, SiO2 content ≥ 85%; The fineness modulus of the tailings is 2.25; The fineness modulus of the tunnel boring machine excavated soil is 2.63, and the moisture content is 22%. The slag has a sulfide and sulfate content of 1.42% and a moisture content of 3.5%. The average particle size of the waste tire rubber granules is 2 mm; The average particle size of the styrene-butyl acrylate copolymer latex particles is 355 nm, and the average particle size of the waterborne polyurethane particles is 476 nm.

[0044] The elongation at break of the waterborne polyurethane is 160%. The average length of the polyvinyl alcohol fiber is 9 mm; The average length of the glass fiber is 4 mm; The average length of the steel fiber is 30 mm; The effective material content of the nano-SiO2 is 99.8%; The naphthalene-based water-reducing agent is a yellowish-brown powder with a solid content of 99.6%. The polycarboxylate superplasticizer has a water reduction rate of 36% and an effective ingredient content of 99.7%. The water in question is tap water.

[0045] The calcium-to-silicon ratios of the blast furnace slag, coal gangue powder, and fly ash are 1.486, 0.108, and 0.223, respectively, and the silicon-to-aluminum ratios are 2.014, 2.549, and 1.668, respectively.

[0046] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0047] Example 1 A high-permeability, self-leveling, and crack-resistant backfill material, by weight, comprises: silicate cement clinker: blast furnace slag: gypsum: coal gangue powder: fly ash: silica fume: tailings slag: tunnel boring machine slag: furnace slag: waste tire rubber granules: styrene-butyl acrylate copolymer latex: waterborne polyurethane: polyvinyl alcohol fiber: glass fiber: steel fiber: nano-SiO2: naphthalene-based water-reducing agent: polycarboxylate water-reducing agent: water = 150: 50: 10: 90: 230: 15: 170: 280: 530: 65: 30: 30: 4: 5: 2: 30: 2: 10: 420.

[0048] The backfill material preparation method includes the following steps: (1) Silicate cement clinker, blast furnace slag, gypsum, coal gangue powder, fly ash, silica fume, tailings slag, shield tunnel slag, furnace slag, nano-SiO2, naphthalene-based water-reducing agent, polycarboxylate water-reducing agent and water are mixed and stirred at 150 rpm for 3 min to obtain the backfill material matrix material.

[0049] (2) Add waste tire rubber particles, styrene-butyl acrylate copolymer latex, waterborne polyurethane, polyvinyl alcohol fiber, glass fiber and steel fiber to the backfill material matrix and stir at 300 rpm for 4 min to obtain the final product.

[0050] Example 2 A high-permeability, self-leveling, and crack-resistant backfill material, by weight, comprises: silicate cement clinker: blast furnace slag: gypsum: coal gangue powder: fly ash: silica fume: tailings slag: tunnel boring machine slag: furnace slag: waste tire rubber granules: styrene-butyl acrylate copolymer latex: waterborne polyurethane: polyvinyl alcohol fiber: glass fiber: steel fiber: nano-SiO2: naphthalene-based water-reducing agent: polycarboxylate water-reducing agent: water = 180: 40: 12.5: 90: 200: 25: 190: 340: 480: 50: 40: 20: 5: 4: 2: 40: 3: 6: 460.

[0051] The backfill material preparation method includes the following steps: (1) Silicate cement clinker, blast furnace slag, gypsum, coal gangue powder, fly ash, silica fume, tailings slag, shield tunnel slag, furnace slag, nano-SiO2, naphthalene-based water-reducing agent, polycarboxylate water-reducing agent and water are mixed and stirred at 150 rpm for 3 min to obtain the backfill material matrix material.

[0052] (2) Waste tire rubber particles, styrene-butyl acrylate copolymer latex, waterborne polyurethane, polyvinyl alcohol fiber, glass fiber and steel fiber are added to the backfill material matrix and stirred at 300 rpm for 4 min to obtain a high impermeability self-leveling crack-resistant backfill material for the arch of the subway prefabricated station.

[0053] Example 3 A high-permeability, self-leveling, and crack-resistant backfill material, by weight, comprises: silicate cement clinker: blast furnace slag: gypsum: coal gangue powder: fly ash: silica fume: tailings slag: tunnel boring machine slag: furnace slag: waste tire rubber granules: styrene-butyl acrylate copolymer latex: waterborne polyurethane: polyvinyl alcohol fiber: glass fiber: steel fiber: nano-SiO2: naphthalene-based water-reducing agent: polycarboxylate water-reducing agent: water = 150: 30: 15: 80: 260: 35: 170: 310: 430: 80: 50: 20: 6: 4: 1: 20: 3: 10: 420.

[0054] The method for preparing backfill material includes the following steps: (1) Silicate cement clinker, blast furnace slag, gypsum, coal gangue powder, fly ash, silica fume, tailings slag, shield tunnel slag, furnace slag, nano-SiO2, naphthalene-based water-reducing agent, polycarboxylate water-reducing agent and water are mixed and stirred at 150 rpm for 3 min to obtain the backfill material matrix material.

[0055] (2) Add waste tire rubber particles, styrene-butyl acrylate copolymer latex, waterborne polyurethane, polyvinyl alcohol fiber, glass fiber and steel fiber to the backfill material matrix and stir at 300 rpm for 4 min to obtain the final product.

[0056] Example 4 A high-permeability, self-leveling, and crack-resistant backfill material, by weight, comprises: silicate cement clinker: blast furnace slag: gypsum: coal gangue powder: fly ash: silica fume: tailings slag: tunnel boring machine slag: furnace slag: waste tire rubber granules: styrene-butyl acrylate copolymer latex: waterborne polyurethane: polyvinyl alcohol fiber: glass fiber: steel fiber: nano-SiO2: naphthalene-based water-reducing agent: polycarboxylate water-reducing agent: water = 210: 30: 12.5: 80: 230: 25: 150: 280: 530: 50: 40: 40: 4: 5: 3: 40: 4: 8: 380.

[0057] The preparation method and application of backfill materials include the following steps: (1) Silicate cement clinker, blast furnace slag, gypsum, coal gangue powder, fly ash, silica fume, tailings slag, shield tunnel slag, furnace slag, nano-SiO2, naphthalene-based water-reducing agent, polycarboxylate water-reducing agent and water are mixed and stirred at 150 rpm for 3 min to obtain the backfill material matrix material.

[0058] (2) Add waste tire rubber particles, styrene-butyl acrylate copolymer latex, waterborne polyurethane, polyvinyl alcohol fiber, glass fiber and steel fiber to the backfill material matrix and stir at 300 rpm for 4 min to obtain the final product.

[0059] Example 5 A high-permeability, self-leveling, and crack-resistant backfill material, by weight, comprises: silicate cement clinker: blast furnace slag: gypsum: coal gangue powder: fly ash: silica fume: tailings slag: tunnel boring machine slag: furnace slag: waste tire rubber granules: styrene-butyl acrylate copolymer latex: waterborne polyurethane: polyvinyl alcohol fiber: glass fiber: steel fiber: nano-SiO2: naphthalene-based water-reducing agent: polycarboxylate water-reducing agent: water = 180: 50: 10: 70: 260: 15: 150: 340: 480: 65: 50: 30: 6: 3: 1: 20: 2: 8: 460.

[0060] The backfill material preparation method includes the following steps: (1) Silicate cement clinker, blast furnace slag, gypsum, coal gangue powder, fly ash, silica fume, tailings slag, shield tunnel slag, furnace slag, nano-SiO2, naphthalene-based water-reducing agent, polycarboxylate water-reducing agent and water are mixed and stirred at 150 rpm for 3 min to obtain the backfill material matrix material.

[0061] (2) Add waste tire rubber particles, styrene-butyl acrylate copolymer latex, waterborne polyurethane, polyvinyl alcohol fiber, glass fiber and steel fiber to the backfill material matrix and stir at 300 rpm for 4 min to obtain the final product.

[0062] Example 6 A high-permeability, self-leveling, and crack-resistant backfill material, by weight, comprises: silicate cement clinker: blast furnace slag: gypsum: coal gangue powder: fly ash: silica fume: tailings slag: tunnel boring machine slag: furnace slag: waste tire rubber granules: styrene-butyl acrylate copolymer latex: waterborne polyurethane: polyvinyl alcohol fiber: glass fiber: steel fiber: nano-SiO2: naphthalene-based water-reducing agent: polycarboxylate water-reducing agent: water = 210: 40: 15: 70: 200: 35: 190: 310: 430: 80: 30: 40: 5: 3: 3: 30: 4: 6: 380.

[0063] The backfill material preparation method includes the following steps: (1) Silicate cement clinker, blast furnace slag, gypsum, coal gangue powder, fly ash, silica fume, tailings slag, shield tunnel slag, furnace slag, nano-SiO2, naphthalene-based water-reducing agent, polycarboxylate water-reducing agent and water are mixed and stirred at 150 rpm for 3 min to obtain the backfill material matrix material.

[0064] (2) Add waste tire rubber particles, styrene-butyl acrylate copolymer latex, waterborne polyurethane, polyvinyl alcohol fiber, glass fiber and steel fiber to the backfill material matrix and stir at 300 rpm for 4 min to obtain the final product.

[0065] Comparative Example 1 The difference from Example 2 is that coal gangue powder, fly ash and silica fume were not added, while the other materials and steps were the same as in Example 2.

[0066] Comparative Example 2 The difference from Example 2 is that tailings slag, tunnel boring machine slag and furnace slag were not added, while the other materials and steps were the same as in Example 2.

[0067] Comparative Example 3 The difference from Example 2 is that waste tire rubber particles, styrene-butyl acrylate copolymer latex and waterborne polyurethane were not added, while the other materials and steps were the same as in Example 2.

[0068] Comparative Example 4 The difference from Example 2 is that polyvinyl alcohol fiber, glass fiber, steel fiber and nano-SiO2 were not added, while the other materials and steps were the same as in Example 2.

[0069] Comparative Example 5 The difference from Example 2 is that no naphthalene-based water-reducing agent or polycarboxylate water-reducing agent was added; all other materials and steps were the same as in Example 2.

[0070] Comparative Example 6 The difference from Example 2 is that the amounts of coal gangue powder, fly ash and silica fume are different, at 45 parts, 300 parts and 10 parts respectively, while the other materials and steps are the same as in Example 2.

[0071] Comparative Example 7 The difference from Example 2 is that the amounts of tailings slag, shield tunneling slag and furnace slag are different, at 100 parts, 400 parts and 350 parts respectively, while the other materials and steps are the same as in Example 2.

[0072] Comparative Example 8 The difference from Example 2 is that the amounts of waste tire rubber granules, styrene-butyl acrylate copolymer latex, and waterborne polyurethane are different, at 30 parts, 20 parts, and 60 parts, respectively. The other materials and steps are the same as in Example 2.

[0073] Comparative Example 9 The difference from Example 2 is that the amounts of polyvinyl alcohol fiber, glass fiber, steel fiber and nano-SiO2 are different, at 3 parts, 2 parts, 5 parts and 15 parts respectively, while the other materials and steps are the same as in Example 2.

[0074] Comparative Example 10 The difference from Example 2 is that the amounts of naphthalene-based water-reducing agent and polycarboxylate water-reducing agent are different, at 7 parts and 3 parts respectively, while the other materials and steps are the same as in Example 2.

[0075] Comparative Example 11 The difference from Example 2 is that the lengths of the polyvinyl alcohol fiber and the steel fiber are different, being 4 mm and 10 mm respectively, while the other materials and steps are the same as in Example 2.

[0076] Comparative Example 12 The difference from Example 2 is that the amount of glass fiber used is different, at 8 parts, while the other materials and steps are the same as in Example 2.

[0077] 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 Methods of Performance of Ordinary Concrete Mixtures". The test instruments are a slump cone (100 mm in diameter at the top, 200 mm in diameter at the bottom, and 300 mm in height), a tamping rod, and a ruler; the spread test shall be conducted in accordance with the method in GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures".

[0078] 2. Density testing was conducted according to the methods in GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0079] 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.

[0080] 4. 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".

[0081] 5. 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.

[0082] 6. 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.

[0083] 7. 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".

[0084] The working performance of each embodiment and comparative example was tested, including slump, spread, density, and initial setting time. The results are shown in Table 1. The mechanical properties, impermeability, toughness, and early cracking performance (24 h after casting) of each embodiment and comparative example were evaluated, including 3-day compressive strength, 28-day compressive strength, 28-day flexural-compression ratio, 28-day impermeability pressure, and total crack area per unit area. The results are shown in Table 2.

[0085] Table 1. Test results of the working performance of high impermeability self-leveling and crack-resistant backfill material

[0086] Table 2 Test results of mechanical properties, impermeability, toughness and early cracking performance of high impermeability self-leveling crack-resistant backfill material

[0087] Table 1-2 shows that by comparing the data of Example 2 and Comparative Example 1, the addition of coal gangue powder, fly ash and silica fume slightly reduces the fluidity and density of the material, while improving its mechanical properties, impermeability, toughness and crack resistance. By comparing the data of Example 2 and Comparative Example 6, it can be seen that when the amount of coal gangue powder, fly ash and silica fume is outside the range given in this invention, it has a significant adverse effect on the fluidity, initial setting time, mechanical properties and impermeability of the material.

[0088] Comparing the data from Example 2 and Comparative Example 2, it is evident that the addition of tailings slag, tunnel boring machine (TBM) slag, and furnace slag improves the workability of the material, enhances its compressive strength and impermeability, and reduces the crack area. In Comparative Example 2, without the addition of aggregate, the fluidity significantly increases, causing the slump and spread test results to far exceed the normal range. The obtained data cannot reflect the actual workability of the concrete and therefore lacks engineering reference value. Comparing the data from Example 2 and Comparative Example 7, it is evident that when the amounts of tailings slag, TBM slag, and furnace slag are outside the range given in this invention, the initial setting time, mechanical properties, flexural-compression ratio, impermeability, and crack resistance of the material are all reduced.

[0089] Comparing the data from Example 2 and Comparative Example 3, it can be seen that the addition of waste tire rubber particles, styrene-butyl acrylate copolymer latex, and waterborne polyurethane reduced the mechanical properties of the material, but significantly improved its toughness and crack resistance. Comparing the data from Example 2 and Comparative Example 8, it can be seen that when the amounts of waste tire rubber particles, styrene-butyl acrylate copolymer latex, and waterborne polyurethane are outside the range given in this invention, the material's fluidity, initial setting time, mechanical properties, and impermeability pressure are slightly reduced, the crack area increases, and the flexural-to-pressure ratio decreases significantly.

[0090] Comparing the data from Example 2 and Comparative Example 4, it is evident that the addition of polyvinyl alcohol fiber, glass fiber, steel fiber, and nano-SiO2 improved the mechanical properties and toughness of the material and significantly reduced the crack area. Comparing the data from Example 2 and Comparative Example 9, it is evident that when the amounts of polyvinyl alcohol fiber, glass fiber, steel fiber, and nano-SiO2 were outside the range given in this invention, it adversely affected the initial setting time, mechanical properties, and impermeability of the material, while significantly reducing toughness and crack resistance. Comparing the data from Example 2 and Comparative Example 11, it is evident that when the lengths of polyvinyl alcohol fiber and steel fiber were outside the range given in this invention, the compressive strength and flexural-to-compression ratio of the material decreased, and the crack area significantly increased. Comparing the data from Example 2 and Comparative Example 12, it is evident that when the amount of glass fiber was outside the range given in this invention, both the mechanical properties and impermeability of the material significantly decreased.

[0091] Comparing the data from Example 2 and Comparative Example 5, it can be seen that the addition of naphthalene-based water-reducing agent and polycarboxylate water-reducing agent mainly improves the flow properties of the material; comparing the data from Example 2 and Comparative Example 10, it can be seen that when the amount of naphthalene-based water-reducing agent and polycarboxylate water-reducing agent is outside the range given in this invention, the slump and spread of the material decrease significantly.

[0092] 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 high-permeability, self-leveling, crack-resistant backfill material, characterized in that, It is composed of the following raw materials in parts by weight: 475-660 parts of high-performance cementitious component, 860-1060 parts of composite aggregate, 100-170 parts of toughening material, 28-54 parts of crack resistance optimization component, 8-14 parts of leveling control admixture, and 380-460 parts of water. The high-performance cementitious component is composed of the following raw materials in parts by weight: 150-210 parts of silicate cement clinker, 30-50 parts of blast furnace slag, 10-15 parts of gypsum, 70-90 parts of coal gangue powder, 200-260 parts of fly ash, and 15-35 parts of silica fume. The composite aggregate is composed of the following raw materials in parts by weight: 150-190 parts tailings slag, 280-340 parts shield tunnel slag, and 430-530 parts furnace slag. The tough material is composed of the following raw materials in parts by weight: 50-80 parts of waste tire rubber granules, 30-50 parts of styrene-butyl acrylate copolymer latex, and 20-40 parts of waterborne polyurethane. The crack resistance optimization component is composed of the following raw materials in parts by weight: 4-6 parts polyvinyl alcohol fiber, 3-5 parts glass fiber, 1-3 parts steel fiber, and 20-40 parts nano-SiO2. The leveling additive is composed of the following raw materials in parts by weight: 2-4 parts of naphthalene-based water-reducing agent and 6-10 parts of polycarboxylate water-reducing agent; The average length of the polyvinyl alcohol fiber is 6-12 mm; the average length of the steel fiber is 25-35 mm.

2. The backfill material as described in claim 1, characterized in that, The specific surface area of ​​the silicate cement clinker is 330-380 m². 2 / kg; or, the specific surface area of ​​the blast furnace slag is 400-500 m². 2 / kg.

3. The backfill material as described in claim 1, characterized in that, The gypsum particle size meets the requirement that the residue on a 0.2 mm square-hole sieve is ≤ 10%; or, the specific surface area of ​​the coal gangue powder and fly ash is 450-550 m². 2 / kg.

4. The backfill material as described in claim 1, characterized in that, The specific surface area of ​​the silica fume is ≥ 15000 m². 2 / kg; or, the fineness modulus of the tailings slag is between 2.2 and 2.8; or, the fineness modulus of the shield tunnel slag is between 2.5 and 3.0, and the moisture content is ≤ 30%.

5. The backfill material as described in claim 1, characterized in that, The slag has a sulfide and sulfate content of ≤2.0% and a moisture content of ≤5%; or, the elongation at break of the waterborne polyurethane is ≥150%.

6. The backfill material as described in claim 1, characterized in that, The particle size of the waste tire rubber granules is 1-2 mm; or, the average length of the glass fiber is 3-6 mm.

7. The method for preparing the high impermeability self-leveling and crack-resistant backfill material according to any one of claims 1 to 6, characterized in that, include: (1) Silicate cement clinker, blast furnace slag, gypsum, coal gangue powder, fly ash, silica fume, tailings slag, shield tunnel slag, furnace slag, nano-SiO2, naphthalene-based water-reducing agent, polycarboxylate water-reducing agent and water are mixed evenly to obtain the backfill material matrix material; (2) Add waste tire rubber particles, styrene-butyl acrylate copolymer latex, waterborne polyurethane, polyvinyl alcohol fiber, glass fiber and steel fiber to the backfill material matrix material and stir evenly to obtain the final product.

8. The preparation method according to claim 7, characterized in that, In step (1), stir at 100-200 rpm for 2-10 min.

9. The preparation method according to claim 7, characterized in that, In step (2), stir at 200-300 rpm for 3-5 minutes.

10. The application of the high impermeability self-leveling and crack-resistant backfill material as described in any one of claims 1 to 6 in the backfilling project of the arch of a subway prefabricated station.

Images