Pervious concrete material based on shield waste soil and preparation method

Abstract

The invention relates to the field of concrete. The problems that in the prior art, the shield waste soil resource utilization rate is low, and the pervious concrete pore structure is difficult to accurately control are solved. Surface modified shield waste soil coarse aggregate and degradable pore-forming agent particles are adopted as core components, the bonding performance of the aggregate is improved through gamma-aminopropyltriethoxysilane surface modification, a corn starch-based double-layer cross-linked structure pore-forming agent is designed to achieve staged degradation, the degradation rate constant in the early stage is 0.04-0.08 d <-1 >, the degradation rate constant in the later stage is 0.12-0.18 d <-1 >, and the pore-forming agent has the advantages that the pore-forming effect is good; the water-permeable concrete is prepared by matching components such as a cementing material and water. According to the material, the resource utilization rate of waste soil is remarkably improved, the bonding strength of aggregate and cement paste is improved by 30-60%, the stable degradation rate of the pore-forming agent is kept to be smaller than 5% 48 hours before concrete pouring, the shell degradation rate reaches 25-35% in the third-seventh day, the total degradation rate reaches 70-85% in the seventh-28th day, an accurate and controllable communicated pore network is formed, and the material is suitable for engineering application such as sponge city construction and road pavement.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of concrete materials, in particular to a kind of pervious concrete material based on shield waste soil and preparation method. BACKGROUND

[0002] Under the background of the rapid development of urban underground space, shield method is widely used in subway, tunnel, comprehensive pipe gallery and other large infrastructure construction, and a large amount of shield waste soil not only occupies land resources, but also causes potential pollution to the environment. At the same time, the demand for pervious concrete materials in urban rainwater management system increases significantly, which plays a key role in urban roads, squares, sidewalks and sponge city infrastructure, and requires excellent water permeability, mechanical strength and durability, and can maintain the stability and connectivity of pore structure in complex environment for a long time. Therefore, how to build a pervious concrete system with structural bearing capacity and water regulation function has become the core demand to promote the construction of urban green infrastructure. Under this application background, if the high value utilization of shield waste soil can be realized and the pore structure of concrete can be precisely controlled, it will not only help to improve the functional performance and service life of the material, but also significantly reduce the engineering cost and environmental burden, and promote the integration development between shield construction and ecological building materials. Therefore, the development of a kind of pervious concrete material based on shield waste soil not only meets the development direction of green and low-carbon urban construction, but also has important significance for perfecting the solid waste resource recycling system and improving the performance of urban infrastructure.

[0003] Although some current researches try to use shield waste soil in the field of building materials, and some researches are committed to optimizing the pore structure of pervious concrete, there are still obvious deficiencies in the efficient utilization of shield waste soil in pervious concrete and the precise control of its pore structure. For example, the patent with publication number CN109293318B discloses a kind of pervious concrete, which proposes the idea of using slag, but fails to effectively solve the controllability problem of the pore structure of pervious concrete, resulting in unstable water permeability and mechanical properties in practical application. The fundamental reason is that the shield waste soil has complex composition, high water content and uneven particle distribution, which may cause fluctuation of aggregate performance when directly used. Traditional pore forming methods mainly rely on physical foaming or single degradation mechanism, which is difficult to realize the systematic control of pore structure in formation time, connectivity and spatial distribution. Therefore, the existing material system generally lacks in-depth design of coupling between aggregate modification and pore forming agent function, which leads to the difficulty in balancing the structural compactness and permeability function of the obtained concrete, limiting the application space of shield waste soil in high-performance pervious concrete, and restricting its popularization potential in sustainable urban construction. SUMMARY

[0004] (1) Technical problems solved

[0005] The application aims to provide a shield waste soil-based pervious concrete material and a preparation method, and solve the technical problems of resource utilization of shield waste soil and accurate control of the pore structure of the pervious concrete.

[0006] (2) Technical solutions

[0007] To achieve the above-mentioned purpose, the application provides the following technical solutions:

[0008] A shield waste soil-based pervious concrete material comprises the following components by weight: surface-modified shield waste soil coarse aggregate 85-95 parts, degradable pore-forming agent particles 5.0-15 parts, cementitious material 15-35 parts, water 10-25 parts, additive 0.5-1.5 parts, and fine aggregate 1.0-3.0 parts.

[0009] The surface-modified shield waste soil coarse aggregate is obtained by surface modification of the shield waste soil coarse aggregate with gamma-aminopropyltriethoxysilane.

[0010] The mineral composition of the shield waste soil coarse aggregate comprises: quartz content 15.0-35.0 wt%, feldspar content 10.0-25.0 wt%, and total clay mineral content 40.0-60.0 wt%, wherein the content of montmorillonite is not more than 20.0 wt% of the total clay mineral content.

[0011] The degradable pore-forming agent particles are spherical particles with a double-layer crosslinked structure design, wherein the inner core is modified with high-crosslinking-degree glutaraldehyde to provide structural stability, and the outer shell is modified with low-crosslinking-degree glutaraldehyde to realize staged degradation, and the particles are prepared by rotary granulation molding.

[0012] Further, the mass ratio of the shield waste soil coarse aggregate and the degradable pore-forming agent particles is (85-95):(5-15).

[0013] The application adopts surface modification of shield waste soil coarse aggregate and degradable pore-forming agent particles to design a preparation method of a porous concrete, which is mainly used for enhancing the structural stability and pore regulation performance of the porous concrete. The technical scheme performs surface modification treatment on the shield waste soil coarse aggregate by using gamma-aminopropyl triethoxysilane, significantly improves the interface compatibility of the waste soil aggregate and the cementing material, and solves the bonding performance defect problem caused by the insufficient surface activity of the traditional waste soil material. The formation of the surface modification layer constructs an organic silicon modified network structure on the surface of the aggregate, enhances the chemical bonding action of the aggregate and the cement paste, and provides a reliable mechanical support basis for the porous concrete. The degradable pore-forming agent particles adopt a double-layer cross-linking structure design of a corn starch substrate, the high cross-linking degree glutaraldehyde modification of the inner core ensures the structural integrity of the particles in the process of concrete pouring and early hardening, avoids the uneven pore distribution problem caused by the easy damage of the traditional pore-forming material, and the low cross-linking degree glutaraldehyde modification of the outer shell realizes a phased controllable degradation mechanism, so that the pore-forming process is coordinated with the development of the concrete strength. The synergistic mechanism of the surface modified aggregate and the double-layer structure pore-forming agent is that the enhanced interface bonding performance provided by the modified aggregate creates a good matrix environment for the stable existence of the pore-forming agent particles, and the phased degradation process of the pore-forming agent fully utilizes the structural support provided by the modified aggregate, forming the organic unity of the mechanical performance and the water permeability. The reasonable proportioning of the silicate and clay minerals such as quartz and feldspar in the shield waste soil coarse aggregate provides rich reactive sites for the surface modification, and the control of the content of montmorillonite avoids the adverse effect of excessive swelling on the stability of the material, ensuring the durability and reliability of the modification effect.

[0014] Further, the degradable pore-forming agent particles adopt a double-layer cross-linking structure design, the cross-linking degree of the inner core is 15.0-20.0%, the cross-linking degree of the outer shell is 6.0-10.0%, the average size of the inner core is 2.0-6.0mm, and the total size of the outer shell after coating is 2.5-8.0mm, which maintains the structural stability within 48 hours after the concrete is poured, and the degradation rate is less than 5%; the outer shell starts to degrade from the 3rd to the 7th day, and the degradation rate reaches 25-35%; the inner core is fully degraded from the 7th to the 28th day, and the total degradation rate reaches 70-85%; and the degradation kinetics is divided into two stages: the rate constant k1 of the early stage is 0.04-0.08d-1, and the rate constant k2 of the later stage is 0.12-0.18d-1.

[0015] Further, the preparation method of the shield waste soil coarse aggregate comprises the following steps in sequence: firstly, the waste soil is dehydrated, and then a silty clay base material with a water content of 15-25% is obtained by passing through a 5mm square hole screen; then, a compound curing agent prepared by mixing 42.5-grade ordinary portland cement, II-grade quicklime and F-class fly ash at a mass ratio of 1:(0.8-1.2):(0.9-1.1) is added, and the liquid index is adjusted to 0.2-0.6 by adjusting the mixing water; then, the mixture is stirred in a double-shaft forced mixer at a speed of 350-450rpm for 20-40 minutes, and then 5-20mm ellipsoidal particles are prepared by using an 8-12MPa roller-type granulator; then, the particles are cured at 20-30℃ and a relative humidity of 85-95% for 7-28 days, and an atomization curing system is used instead of direct spraying of a carbonate buffer solution; finally, the shield waste soil coarse aggregate is obtained after screening and grading.

[0016] Further, the average size of the shield waste soil coarse aggregate is 8.0-20.0mm.

[0017] Further, the preparation method of the double-layer structure of the pore-forming agent particles comprises the following steps: firstly, corn starch is dried to a water content of ≤3%, mixed with water at a mass ratio of 1:(2.5-3.5), and then subjected to gelatinization treatment by stirring at 75-85℃ for 30-40 minutes; after the gelatinization liquid is cooled to 50-60℃, 0.3-0.5% of glutaraldehyde based on the mass of the dry starch is added to perform an inner core crosslinking reaction, the pH value is controlled to be 6.5-7.0, and the reaction is performed at a constant temperature for 100-120 minutes; after the reaction is completed, 0.4-0.5% of sodium sulfite based on the mass of the dry starch is added to terminate the reaction; then, the reaction product is formed into an inner core particle by using a rotary granulator with a screen aperture of 4-9mm and a rotation speed of 25-45rpm; after the inner core particle is dried to a water content of ≤3%, it is immersed in a starch gelatinization liquid containing 0.1-0.2% of glutaraldehyde to perform outer shell coating, the coating thickness is 0.2-0.5mm, and the reaction is performed at 50-60℃ for 30-45 minutes; finally, the reaction product is dried at 55-65℃ for 2-3 hours until the water content is ≤5%, and the pore-forming agent particles with a double-layer crosslinking structure are collected.

[0018] Further, the cementing material is composed of 42.5-grade ordinary portland cement and F-class fly ash at a mass ratio of 1:(0.15-0.45), and the hydration product contains 15.0-25.0wt% of calcium hydroxide, 8.0-15.0wt% of ettringite, 40.0-55.0wt% of hydrated calcium silicate gel, and the balance of unreacted cement.

[0019] Further, the additive agent comprises a retarder, and the retarder is selected from sodium citrate.

[0020] Further, the preparation method of the surface modified shield waste soil coarse aggregate comprises the following steps: firstly, the solidified and cured aggregate is washed with deionized water to remove the surface loose particles and soluble salt, and is dried at 40-50 DEG C for 1-2 hours; then, a mass fraction of 2-5% of γ-aminopropyl triethoxysilane ethanol solution is prepared, and the pH is adjusted to 4.0-5.0 to promote the hydrolysis of silane; then, the aggregate is immersed in the solution, the liquid-solid ratio is set to 3:1-5:1, and the treatment is carried out at 40-60 DEG C for 2-4 hours; after the treatment, the aggregate is dried at 50-60 DEG C for 2 hours to make the silane molecules condense on the surface of the aggregate to form a stable organic silicon modified layer, and the bonding strength of the aggregate with the cement paste can be increased by 30-60% compared with the untreated aggregate.

[0021] Further, the fine aggregate is natural sand, and the fineness modulus is 2.3-3.0.

[0022] The application adopts a double-layer cross-linking structure pore-forming agent particle and a compound curing agent to treat shield waste soil coarse aggregate to cooperatively design a preparation method mainly used for enhancing the pore regulation performance and structural stability of the pervious concrete. The technical scheme realizes the accurate time sequence control of the pore-forming process through the double-layer structure design of the glutaraldehyde cross-linking modified corn starch-based pore-forming agent particle, the high cross-linking degree structure of the inner core provides stable structural support in the early stage of concrete pouring to ensure that the early strength development is not disturbed, and the low cross-linking degree structure of the outer shell starts to degrade after the concrete is basically hardened to form the initial pore network, and then the sufficient degradation of the inner core completes the construction of the final interconnected pores, and the staged degradation mechanism avoids the structural defect problem caused by the synchronous degradation of the traditional pore-forming material. The shield waste soil coarse aggregate is treated by the compound curing agent of the 42.5 grade ordinary portland cement, the grade II quicklime and the F type fly ash to realize the cementation transformation of the waste soil, wherein the cement provides the main cementing strength, the quicklime promotes the stabilization reaction of the clay mineral, and the F type fly ash enhances the pozzolanic activity, and the three cooperate to form the artificial aggregate with good mechanical properties. The surface modification treatment adopts the hydrolysis condensation reaction of the gamma-aminopropyl triethoxysilane under acidic conditions to form an organic silicon modified layer on the surface of the aggregate, which significantly improves the interfacial bonding performance of the aggregate and the cementing material. The compound use of the 42.5 grade ordinary portland cement and the F type fly ash in the cementing material fully gives play to the complementary advantages of the two, the rapid hydration of the cement provides the early strength, the pozzolanic reaction of the fly ash continuously improves the interface structure in the later stage, and the coexistence of the multi-phase such as calcium hydroxide, ettringite and hydrated calcium silicate gel in the hydration product provides a suitable chemical environment for the stable existence and orderly degradation of the pore-forming agent particle. The addition of the sodium citrate retarder delays the hydration rate of the cementing material to provide a sufficient time window for the positioning of the pore-forming agent particle and the full compaction of the concrete, which ensures the uniform distribution of the pore structure. The reasonable grading of the natural sand fine aggregate fills the gap between the coarse aggregate and the double-layer pore-forming agent particle to form a hierarchical pore structure system, which realizes the optimized balance between the water permeability and the mechanical properties.

[0023] The application further discloses a preparation method of a pervious concrete material based on shield waste soil, which comprises the following steps:

[0024] S1. Pre-mixing the surface modified shield waste soil coarse aggregate and the degradable pore-forming agent particle in a dry state for 3-6 minutes;

[0025] S2. Adding the cementing material, and dry mixing for 5-10 minutes to form a continuous coating layer on the surface of the aggregate;

[0026] S3. Dissolving the additive in water to form a solution, slowly adding the solution into the above mixture at a rate of 50-100 mL / min, stirring at a speed of 250-350 rpm, and stirring for 10-18 minutes until the slump of the mixture reaches 80-120 mm;

[0027] S4. Pouring the mixture into a mold and vibrating it with a vibrating table at a frequency of 50-80 Hz for 45-90 seconds, and maintaining the system temperature at 25-35°C through a circulating water bath during the stirring process;

[0028] S5. Curing under standard curing conditions of temperature 20±2°C and relative humidity ≥95% to the design age, the pore-forming agent particles remain stable to provide early strength development for the concrete in the first 48 hours, the shell gradually degrades to form initial pores in the 3rd-7th day, and the core fully degrades to form the final interconnected pore network in the 7th-28th day.

[0029] The application adopts a preparation method of surface modified shield waste soil coarse aggregate and degradable pore-forming agent particles in cooperation, and is mainly used for enhancing the water permeability and strength performance of the water permeable concrete material. The design purpose of the technical scheme mainly embodies three core aspects of resource utilization, pore structure optimization and performance coordination. From the perspective of resource utilization, the shield waste soil, as a large amount of waste generated in the process of urban underground engineering construction, is used as a coarse aggregate after surface modification treatment, which not only solves the disposal problem of the waste soil, but also provides an economically feasible raw material source for the water permeable concrete, and realizes the high-value utilization of the waste. The surface modification treatment can improve the surface properties of the shield waste soil and improve the interfacial bonding performance with the cementitious material, laying a foundation for the subsequent strength development. From the perspective of pore structure design, the introduction of the degradable pore-forming agent particles is a key technical means to realize the water permeability, and the unique staged degradation mechanism makes the pore formation process have time sequence and controllability. The stable period of 48 hours provides necessary support for the early strength development of the concrete, avoiding the early strength loss problem that may be caused by the traditional pore-forming method. The gradual degradation of the shell in the 3-7 days forms the initial pore, which creates conditions for the preliminary establishment of the water permeability. The sufficient degradation of the core in the 7-28 days forms the final connected pore network, ensuring that the water permeable concrete has excellent water permeability. The precise control of the preparation process parameters embodies the synergistic effect among the multi-component materials. The premixing in the dry state ensures the uniform distribution of the surface modified shield waste soil coarse aggregate and the degradable pore-forming agent particles. The addition of the cementitious material and the dry mixing process form a continuous coating layer on the surface of the aggregate, enhancing the interfacial bonding strength. The slow addition of the admixture solution and the controlled stirring speed ensure the uniformity and workability of the mixture. The vibration compaction process ensures the density of the concrete, and the precise control of the temperature and humidity provides the most suitable environmental conditions for the synergistic effect of the components. This multi-component synergistic design makes the strength contribution of the surface modified shield waste soil coarse aggregate and the water permeability function of the degradable pore-forming agent particles realize organic unity, ensuring the structural integrity of the water permeable concrete and obtaining excellent water permeability. At the same time, through the staged pore formation mechanism, the contradiction between the early strength and the water permeability is avoided, realizing the coordinated optimization of the performance, and finally forming a high-performance water permeable concrete material with good strength and water permeability.

[0030] (3)Beneficial technical effects

[0031] 1. The application realizes the dual goals of high-value utilization of waste and performance improvement of water permeable concrete through the synergistic effect of surface modified shield waste soil coarse aggregate and degradable pore-forming agent particles, effectively solving the technical problem that the early strength and water permeability of traditional water permeable concrete are difficult to consider.

[0032] 2. The application realizes the phased pore formation and coordinated development of strength by the synergistic design of the double-layer cross-linked pore-forming agent particles and the compound curing agent for treating waste soil, and solves the technical bottleneck that the traditional pervious concrete cannot simultaneously consider the early strength loss and pore uniformity. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The microstructure morphology diagram of the pervious concrete prepared in Example 1 of the application at the 20th day after pouring is completed.

[0034] Figure 2 The XRD phase analysis diagram of the shield waste soil coarse aggregate prepared in Example 1 of the application.

[0035] Figure 3 The comparison diagram of the compressive strength and the number of freeze-thaw cycles of the examples and the comparative examples of the application.

[0036] Figure 4 The comparison diagram of the water permeability coefficient and the effective porosity of the examples and the comparative examples of the application.

[0037] Figure 5 The comprehensive comparison diagram of the abrasion loss rate and the freeze-thaw resistance of the examples and the comparative examples of the application.

[0038] Figure 6 The radar diagram of the comprehensive performance of the examples and the comparative examples of the application.

[0039] Figure 7 The series performance optimization trend diagram of the examples of the application. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the examples of the application clearer, the technical scheme in the examples of the application will be described clearly and completely below in combination with the drawings in the examples of the application.

[0041] Example 1

[0042] A pervious concrete material based on shield waste soil, comprising the following components by weight: surface modified shield waste soil coarse aggregate 90 parts, degradable pore-forming agent particles 8.0 parts, cementing material 25 parts, water 18 parts, additive 1.0 part and fine aggregate 2.0 part;

[0043] The surface modified shield waste soil coarse aggregate is obtained by surface modification of the shield waste soil coarse aggregate with gamma-aminopropyl triethoxysilane;

[0044] The mineral composition of the shield waste soil coarse aggregate is: quartz content 25.0wt%, feldspar content 17.5wt%, total amount of clay minerals 50.0wt%, wherein the content of montmorillonite does not exceed 15.0wt% of the total amount of clay minerals;

[0045] The degradable pore-forming agent particle is a spherical particle with a double-layer cross-linking structure design, in which the inner core is modified by glutaraldehyde with high cross-linking degree to provide structural stability, and the shell is modified by glutaraldehyde with low cross-linking degree to realize staged degradation, and is prepared by a rotary granulation forming method.

[0046] The mass ratio of the shield waste soil coarse aggregate and the degradable pore-forming agent particle in this embodiment is 90:8.

[0047] Further, the degradable pore-forming agent particle has a double-layer cross-linking structure design, the cross-linking degree of the inner core is 17.5%, the cross-linking degree of the shell is 8.0%, the average size of the inner core is 4.0 mm, and the total size of the shell after coating is 5.2 mm, which maintains structural stability within 48 hours after concrete pouring, and the degradation rate is less than 5%; the shell starts to degrade from the 3rd to 7th day, and the degradation rate reaches 30%; the inner core is fully degraded from the 7th to 28th day, and the total degradation rate reaches 80%; and the degradation kinetics is divided into two stages: the rate constant k1 of the early stage is 0.06 d-1, and the rate constant k2 of the later stage is 0.15 d-1.

[0048] The preparation method of the shield waste soil coarse aggregate in this embodiment includes the following steps performed in sequence: first, the waste soil is dehydrated, and then a silty clay base material with a water content of 20% is obtained through a 5 mm square hole screen; then, a compound curing agent prepared by mixing 42.5-grade ordinary portland cement, grade II quicklime and F-class fly ash at a mass ratio of 1:1.0:1.0 is added, and the liquid index is adjusted to 0.4 by adjusting the mixing water; then, the mixture is stirred in a double-shaft forced mixer at a speed of 400 rpm for 30 minutes, and then 12 mm ellipsoidal particles are prepared by a 10 MPa roller granulator; then, the particles are cured at 25°C and a relative humidity of 90% for 14 days, and an atomization curing system is used instead of direct spraying of carbonate buffer solution; finally, after screening and grading, the shield waste soil coarse aggregate is obtained.

[0049] The average size of the shield waste soil coarse aggregate in this embodiment is 14.0 mm.

[0050] The double-layer structure preparation method of the pore-forming agent particles of the embodiment comprises the following steps: firstly, corn starch is dried to a water content of ≤3%, mixed with water at a mass ratio of 1:3.0, and subjected to gelatinization treatment by stirring at 80°C for 35 minutes; after the gelatinization liquid is cooled to 55°C, 0.4% of glutaraldehyde by mass of dry starch is added to perform inner core crosslinking reaction, the pH value is controlled to be 6.8, and the constant temperature reaction is performed for 110 minutes; after the reaction is completed, 0.45% of sodium sulfite by mass of dry starch is added to terminate the reaction; then, the reaction product is formed into inner core particles by a rotary granulator with a sieve aperture of 6.5 mm and a rotating speed of 35 rpm; after the inner core particles are dried to a water content of ≤3%, the inner core particles are immersed in a starch gelatinization liquid containing 0.15% of glutaraldehyde to perform outer shell coating, the coating thickness is 0.35 mm, and the reaction is performed at 55°C for 37 minutes; finally, the particles are dried at 60°C for 2.5 hours until the water content is ≤5%, and the pore-forming agent particles with a double-layer crosslinking structure are collected.

[0051] The cementitious material of the embodiment is composed of 42.5-grade ordinary portland cement and F-class fly ash at a mass ratio of 1:0.3, and the hydration product contains 20.0wt% of calcium hydroxide, 11.5wt% of ettringite, 47.5wt% of calcium silicate gel, and the balance of unreacted cement.

[0052] The additive of the embodiment comprises a retarder, and the retarder is selected from sodium citrate.

[0053] The preparation method of the surface-modified shield waste soil coarse aggregate of the embodiment comprises the following steps: firstly, the aggregate after solidification and curing is washed with deionized water to remove surface loose particles and soluble salt, and is dried at 45°C for 1.5 hours; then, a mass fraction of 3.5% of γ-aminopropyl triethoxysilane ethanol solution is prepared, and the pH value is adjusted to 4.5 to promote silane hydrolysis; then, the aggregate is immersed in the solution, the liquid-solid ratio is set to 4:1, and the treatment is performed at 50°C for 3 hours; after the treatment is completed, the aggregate is dried at 55°C for 1.5 hours to make the silane molecules condense on the surface of the aggregate to form a stable organic silicon modified layer, and the bonding strength of the aggregate to the cement paste after the treatment can be increased by 45% compared with that of the untreated aggregate.

[0054] The fine aggregate of the embodiment is natural sand with a fineness modulus of 2.65.

[0055] The preparation method of the water-permeable concrete material based on shield waste soil of the embodiment comprises the following steps:

[0056] S1. The surface-modified shield waste soil coarse aggregate and the degradable pore-forming agent particles are pre-mixed in a dry state for 4.5 minutes;

[0057] S2. The cementitious material is added, and dry mixing is performed for 7.5 minutes to form a continuous coating layer on the surface of the aggregate;

[0058] S3. Dissolve the admixture in water to form a solution, slowly add the above mixture at a rate of 75 mL / min, stirring speed is 300 rpm, stirring for 14 minutes until the slump of the mixture reaches 100 mm;

[0059] S4. Pour the mixture into a mold, use a vibrating table with a vibration frequency of 65 Hz to compact it, the vibration time is 67 seconds, and the system temperature is maintained at 30°C by circulating water bath during stirring;

[0060] S5. Under the standard curing conditions of temperature 20±2℃ and relative humidity ≥95%, curing to the design age, the pore-forming agent particles remain stable to provide early strength development for the concrete in the first 48 hours, the shell gradually degrades to form initial pores in the 3rd to 7th day, and the core fully degrades to form the final interconnected pore network in the 7th to 28th day.

[0061] Example 1 uses relatively conservative medium parameter configuration, pursuing stability and reliability. This scheme selects a medium pore-forming agent dosage of 8.0 parts, a moderate amount of cementitious material of 25 parts, to ensure that the concrete has good mechanical properties. The coarse aggregate is of medium size of 14.0 mm, the surface modification treatment uses a medium concentration of 3.5% silane solution, and the treatment is carried out at a temperature of 50℃ for 3 hours, obtaining a 45% improvement in bonding strength. The pore-forming agent is designed as a medium cross-linking degree combination (core 17.5%, shell 8.0%), and the degradation process is relatively mild, with a total degradation rate of 80%. The process parameters of this example are all selected in the middle of the range, the stirring speed is 400 rpm, the curing temperature is 25℃, the vibration frequency is 65 Hz, the overall scheme is mature and stable, and is suitable for use as a standard formula.

[0062] Example 2

[0063] A kind of water permeable concrete material based on shield waste soil, comprising the following components by weight: surface modified shield waste soil coarse aggregate 88 parts, degradable pore-forming agent particles 12.0 parts, cementitious material 20 parts, water 22 parts, admixture 0.7 parts and fine aggregate 1.5 parts;

[0064] The surface modified shield waste soil coarse aggregate is obtained by surface modification of shield waste soil coarse aggregate with γ-aminopropyl triethoxysilane;

[0065] The mineral composition of the shield waste soil coarse aggregate is: quartz content 18.0 wt%, feldspar content 22.0 wt%, total clay mineral content 55.0 wt%, wherein the montmorillonite content is not more than 12.0 wt% of the total clay mineral content;

[0066] The degradable pore-forming agent particle is a spherical particle with a double-layer cross-linking structure design, in which the inner core is modified by glutaraldehyde with high cross-linking degree to provide structural stability, and the shell is modified by glutaraldehyde with low cross-linking degree to realize staged degradation, and is prepared by rotary granulation molding.

[0067] The mass ratio of the shield waste soil coarse aggregate and the degradable pore-forming agent particle in this embodiment is 88:12.

[0068] Further, the degradable pore-forming agent particle adopts a double-layer cross-linking structure design, the cross-linking degree of the inner core is 19.5%, the cross-linking degree of the shell is 6.5%, the average size of the inner core is 3.0 mm, and the total size of the shell after coating is 4.0 mm, which maintains structural stability within 48 hours after concrete pouring, and the degradation rate is less than 5%; the shell starts to degrade on the 37th day, and the degradation rate reaches 32%; the inner core is fully degraded within 7-28 days, and the total degradation rate reaches 85%; and the degradation kinetics is divided into two stages: the rate constant k1 of the early stage is 0.05 d-1, and the rate constant k2 of the later stage is 0.16 d-1.

[0069] The preparation method of the shield waste soil coarse aggregate in this embodiment includes the following steps performed in sequence: first, the waste soil is dehydrated, and then a silty clay base material with a water content of 18% is obtained through a 5 mm square hole screen; then, a compound curing agent prepared by mixing 42.5-grade ordinary portland cement, II-grade quicklime and F-class fly ash at a mass ratio of 1:0.9:1.1 is added, and the liquid index is adjusted to 0.3 by adjusting the mixing water; then, the mixture is stirred in a double-shaft forced mixer at a speed of 380 rpm for 25 minutes, and then 8 mm ellipsoidal particles are prepared by a 9 MPa roller granulator; then, the particles are cured at 22°C and a relative humidity of 88% for 21 days, and an atomization curing system is used instead of direct spraying of carbonate buffer; finally, after screening and grading, the shield waste soil coarse aggregate is obtained.

[0070] The average size of the shield waste soil coarse aggregate in this embodiment is 10.5 mm.

[0071] The double-layer structure preparation method of the pore-forming agent particles of the embodiment comprises the following steps: firstly, dry the corn starch to a water content of ≤3%, mix with water at a mass ratio of 1:2.8, and perform gelatinization treatment by stirring at 77°C for 32 minutes; after the gelatinization liquid is cooled to 52°C, add 0.35% of glutaraldehyde based on the mass of dry starch to perform inner core crosslinking reaction, control the pH value to be 6.6, and perform constant temperature reaction for 105 minutes; after the reaction is completed, add 0.42% of sodium sulfite based on the mass of dry starch to terminate the reaction; then, the reaction product is formed into inner core particles by a rotary granulator with a sieve aperture of 5 mm and a rotating speed of 30 rpm; after the inner core particles are dried to a water content of ≤3%, they are immersed in a starch gelatinization liquid containing 0.12% of glutaraldehyde to perform outer shell coating, the coating thickness is 0.25 mm, and the reaction is performed at 52°C for 33 minutes; finally, drying is performed at 57°C for 2.2 hours until the water content is ≤5%, and the pore-forming agent particles with a double-layer crosslinked structure are collected.

[0072] The cementitious material of the embodiment is composed of 42.5-grade ordinary portland cement and F-class fly ash at a mass ratio of 1:0.2, and the hydration product contains 22.5wt% of calcium hydroxide, 9.5wt% of ettringite, 52.0wt% of calcium silicate gel, and the balance of unreacted cement.

[0073] The admixture of the embodiment comprises a retarder, and the retarder is selected from sodium citrate.

[0074] The preparation method of the surface-modified shield waste soil coarse aggregate of the embodiment comprises the following steps: firstly, the aggregate after solidification and curing is washed with deionized water to remove surface loose particles and soluble salts, and is dried at 42°C for 1.2 hours; then, a mass fraction of 2.5% of γ-aminopropyltriethoxysilane ethanol solution is prepared, and the pH value is adjusted to 4.2 to promote silane hydrolysis; then, the aggregate is immersed in the solution, the liquid-solid ratio is set to 3.5:1, and treatment is performed at 45°C for 2.5 hours; after the treatment is completed, the aggregate is dried at 52°C for 1.3 hours to make the silane molecules condense on the surface of the aggregate to form a stable organic silicon modified layer, and the bonding strength of the aggregate to the cement paste after the treatment can be increased by 35% compared with that of the untreated aggregate.

[0075] The fine aggregate of the embodiment is natural sand with a fineness modulus of 2.4.

[0076] The preparation method of a kind of water permeable concrete material based on shield waste soil of the embodiment comprises the following steps:

[0077] S1. The surface-modified shield waste soil coarse aggregate and the degradable pore-forming agent particles are pre-mixed in a dry state for 3.5 minutes;

[0078] S2. The cementitious material is added, and dry mixing is performed for 6 minutes to form a continuous coating layer on the surface of the aggregate;

[0079] S3. Dissolve the admixture in water to form a solution, slowly add the above mixture at a rate of 60 mL / min, stirring speed is 270 rpm, stirring for 12 minutes until the slump of the mixture reaches 90 mm;

[0080] S4. Pour the mixture into a mold, use a vibrating table with a vibration frequency of 55 Hz to compact it, the vibration time is 55 seconds, and the stirring process is maintained by circulating water bath to maintain the system temperature at 27°C;

[0081] S5. Under the standard curing conditions of temperature 20±2℃ and relative humidity ≥95%, maintain until the design age, the pore-forming agent particles remain stable for the first 48 hours to provide early strength development for the concrete, the shell gradually degrades to form initial pores on the 37th day, and the core fully degrades to form the final interconnected pore network on the 728th day.

[0082] Example 2 is specifically designed for high water permeability performance, using a higher dosage of pore-forming agent 12.0 parts, combined with a relatively lower dosage of cementitious material 20 parts, aiming to maximize the porosity. The coarse aggregate is selected to be smaller in size, 10.5 mm, to increase the specific surface area, and the pore-forming agent particles are also smaller in total size, 4.0 mm, which is beneficial to form a more uniform pore distribution. The surface modification uses relatively mild conditions (2.5% silane concentration, 45°C treatment), avoiding excessive modification affecting water permeability. The degradation kinetics design of this example is more aggressive, with a shell cross-linking degree reduced to 6.5%, ensuring the rapid formation of water permeable channels, and a total degradation rate of 85%. The process parameters are selected under relatively mild conditions, with a stirring speed of 270 rpm and a vibration frequency of 55 Hz, focusing on ensuring the integrity of the pore structure.

[0083] Example 3

[0084] A water permeable concrete material based on shield waste soil, comprising the following components by weight: surface modified shield waste soil coarse aggregate 93 parts, degradable pore-forming agent particles 6.5 parts, cementitious material 32 parts, water 15 parts, admixture 1.3 parts, and fine aggregate 2.8 parts;

[0085] The surface modified shield waste soil coarse aggregate is obtained by surface modification of shield waste soil coarse aggregate with γ-aminopropyl triethoxysilane;

[0086] The mineral composition of the shield waste soil coarse aggregate is: quartz content 30.0 wt%, feldspar content 13.0 wt%, total clay mineral content 45.0 wt%, and the montmorillonite content is not more than 18.0 wt% of the total clay mineral content;

[0087] The degradable pore-forming agent particle is a spherical particle with corn starch as a base material and a double-layer cross-linking structure design, wherein the inner core adopts high cross-linking degree glutaraldehyde modification to provide structural stability, and the shell adopts low cross-linking degree glutaraldehyde modification to realize staged degradation, and is prepared by rotary granulation molding.

[0088] The mass ratio of the shield waste soil coarse aggregate and the degradable pore-forming agent particle in this embodiment is 93:6.5.

[0089] Further, the degradable pore-forming agent particle adopts a double-layer cross-linking structure design, the cross-linking degree of the inner core is 16.0%, the cross-linking degree of the shell is 9.5%, the average size of the inner core is 5.5mm, and the total size of the shell after coating is 7.5mm, which maintains structural stability within 48 hours after concrete pouring, and the degradation rate is less than 5%; the shell starts to degrade on the 37th day, and the degradation rate reaches 28%; the inner core is fully degraded on the 728th day, and the total degradation rate reaches 75%; and the degradation kinetics is divided into two stages: the rate constant k1 of the early stage is 0.07d-1, and the rate constant k2 of the later stage is 0.13d-1.

[0090] The preparation method of the shield waste soil coarse aggregate in this embodiment includes the following steps performed in sequence: first, the waste soil is dehydrated, and then a silty clay base material with a water content of 23% is obtained through a 5mm square hole screen; then, a compound curing agent prepared by mixing 42.5-grade ordinary portland cement, II-grade quicklime and F-class fly ash at a mass ratio of 1:1.1:0.95 is added, and the liquid index is adjusted to 0.5 by adjusting the mixing water; then, the mixture is stirred in a double-shaft forced mixer at a speed of 420rpm for 35 minutes, and then 16mm ellipsoidal particles are prepared by a 11MPa roller granulator; then, the particles are cured at 28℃ and a relative humidity of 92% for 10 days, and an atomization curing system is used instead of direct spraying of carbonate buffer solution; finally, after screening and grading, the shield waste soil coarse aggregate is obtained.

[0091] The average size of the shield waste soil coarse aggregate in this embodiment is 17.5mm.

[0092] The double-layer structure preparation method of the pore-forming agent particles of the embodiment comprises the following steps: firstly, dry the corn starch to a water content of ≤3%, mix with water at a mass ratio of 1:3.3, and perform gelatinization treatment by stirring at 83°C for 38 minutes; after the gelatinization liquid is cooled to 58°C, add 0.45% of glutaraldehyde by mass of dry starch for inner core crosslinking reaction, control the pH value to be 7.0, and perform constant temperature reaction for 115 minutes; after the reaction is completed, add 0.48% of sodium sulfite by mass of dry starch to terminate the reaction; then, the reaction product is formed into inner core particles by a rotary granulator with a sieve aperture of 8 mm and a rotating speed of 40 rpm; after the inner core particles are dried to a water content of ≤3%, they are immersed in a starch gelatinization liquid containing 0.18% of glutaraldehyde for shell coating, the coating thickness is 0.45 mm, and the reaction is performed at 58°C for 42 minutes; finally, drying is performed at 63°C for 2.8 hours until the water content is ≤5%, and the pore-forming agent particles with a double-layer crosslinked structure are collected.

[0093] The cementitious material of the embodiment is composed of 42.5-grade ordinary portland cement and F-class fly ash at a mass ratio of 1:0.4, and the hydration product contains 18.0wt% of calcium hydroxide, 13.0wt% of ettringite, 44.0wt% of calcium silicate gel, and the balance of unreacted cement.

[0094] The admixture of the embodiment comprises a retarder, and the retarder is selected from sodium citrate.

[0095] The preparation method of the surface-modified shield waste soil coarse aggregate of the embodiment comprises the following steps: firstly, the aggregate after solidification and curing is washed with deionized water to remove surface loose particles and soluble salts, and is dried at 48°C for 1.8 hours; then, a γ-aminopropyltriethoxysilane ethanol solution with a mass fraction of 4.5% is prepared, and the pH value is adjusted to 4.8 to promote silane hydrolysis; then, the aggregate is immersed in the solution, the liquid-solid ratio is set to 4.5:1, and treatment is performed at 58°C for 3.5 hours; after the treatment is completed, the aggregate is dried at 58°C for 1.8 hours to make the silane molecules condense on the surface of the aggregate to form a stable organic silicon modified layer, and the bonding strength of the aggregate to the cement paste after the treatment can be increased by 55% compared with that of the untreated aggregate.

[0096] The fine aggregate of the embodiment is natural sand with a fineness modulus of 2.9.

[0097] The preparation method of a kind of water permeable concrete material based on shield waste soil of the embodiment comprises the following steps:

[0098] S1. The surface-modified shield waste soil coarse aggregate and the degradable pore-forming agent particles are pre-mixed in a dry state for 5.5 minutes;

[0099] S2. The cementitious material is added, and dry mixing is performed for 9 minutes to form a continuous coating layer on the surface of the aggregate;

[0100] S3. Dissolve the admixture in water to form a solution, slowly add the above mixture at a rate of 90 mL / min, the stirring speed is 330 rpm, and stir for 16 minutes until the slump of the mixture reaches 110 mm;

[0101] S4. Pour the mixture into a mold, and use a vibrating table with a vibration frequency of 75 Hz to compact the mixture, the vibration time is 80 seconds, and the system temperature is maintained at 33°C by circulating water bath during the stirring process;

[0102] S5. Maintain the standard curing conditions at a temperature of 20±2°C and a relative humidity of ≥95% until the design age, the pore-forming agent particles remain stable to provide early strength development for the concrete in the first 48 hours, the shell gradually degrades to form initial pores on the 37th day, and the core fully degrades to form the final interconnected pore network on the 728th day.

[0103] Example 3 focuses on the optimization of strength performance, using a high cementitious material dosage of 32 parts with a lower pore-forming agent dosage of 6.5 parts to maximize mechanical performance while ensuring certain water permeability. The coarse aggregate is selected to be larger in size, 17.5 mm, to provide better skeleton effect, and the surface modification is performed using a higher concentration of 4.5% silane solution at 58°C for 3.5 hours to obtain a significant bond strength improvement of 55%. The pore-forming agent is designed with large-sized particles (7.5 mm total size), moderate core cross-linking degree (16.0%), and higher shell cross-linking degree (9.5%) to ensure early strength development. This example selects higher process parameters, stirring speed of 330 rpm and vibration frequency of 75 Hz, to fully utilize the advantages of high cementitious material dosage, which is suitable for application scenarios with higher strength requirements.

[0104] Example 4

[0105] A water permeable concrete material based on shield waste soil, comprising the following components by weight: surface modified shield waste soil coarse aggregate 86 parts, degradable pore-forming agent particles 13.5 parts, cementitious material 28 parts, water 24 parts, admixture 1.4 parts, and fine aggregate 1.2 parts;

[0106] The surface modified shield waste soil coarse aggregate is obtained by surface modification of shield waste soil coarse aggregate with γ-aminopropyl triethoxysilane;

[0107] The mineral composition of the shield waste soil coarse aggregate is: quartz content 32.0 wt%, feldspar content 20.0 wt%, total clay mineral content 42.0 wt%, and the content of montmorillonite is not more than 8.0 wt% of the total clay mineral content;

[0108] The degradable pore-forming agent particle is a spherical particle with a double-layer cross-linking structure design, in which the inner core is modified by glutaraldehyde with high cross-linking degree to provide structural stability, and the shell is modified by glutaraldehyde with low cross-linking degree to realize staged degradation, and is prepared by a rotary granulator.

[0109] The mass ratio of the shield waste soil coarse aggregate and the degradable pore-forming agent particle in this embodiment is 86:13.5.

[0110] Further, the degradable pore-forming agent particle has a double-layer cross-linking structure design, the cross-linking degree of the inner core is 18.5%, the cross-linking degree of the shell is 7.5%, the average size of the inner core is 2.5 mm, and the total size of the shell after coating is 3.2 mm, which maintains structural stability within 48 hours after concrete pouring, and the degradation rate is less than 5%; the shell starts to degrade on the 37th day, and the degradation rate reaches 34%; the inner core is fully degraded on the 728th day, and the total degradation rate reaches 88%; and the degradation kinetics is divided into two stages: the rate constant k1 of the early stage is 0.045 d-1, and the rate constant k2 of the later stage is 0.17 d-1.

[0111] The preparation method of the shield waste soil coarse aggregate in this embodiment includes the following steps performed in sequence: first, the waste soil is dehydrated, and then a silty clay base material with a water content of 16% is obtained through a 5 mm square hole screen; then, a compound curing agent prepared by mixing 42.5-grade ordinary portland cement, II-grade quicklime and F-class fly ash at a mass ratio of 1:0.85:1.05 is added, and the liquid index is adjusted to 0.25 by adjusting the mixing water; then, the mixture is stirred in a double-shaft forced mixer at a speed of 360 rpm for 22 minutes, and then 6 mm ellipsoidal particles are prepared by an 8.5 MPa roller granulator; then, the particles are cured at 24℃ and a relative humidity of 87% for 25 days, and an atomization curing system is used instead of direct spraying of carbonate buffer solution; finally, after screening and grading, the shield waste soil coarse aggregate is obtained.

[0112] The average size of the shield waste soil coarse aggregate in this embodiment is 9.5 mm.

[0113] The double-layer structure preparation method of the pore-forming agent particles of the embodiment comprises the following steps: firstly, dry the corn starch to a water content of ≤3%, mix it with water at a mass ratio of 1:2.6, and perform gelatinization treatment by stirring at 76°C for 31 minutes; after the gelatinization liquid is cooled to 51°C, add 0.32% of glutaraldehyde by mass of dry starch to perform inner core crosslinking reaction, control the pH value to be 6.7, and perform constant temperature reaction for 102 minutes; after the reaction is completed, add 0.41% of sodium sulfite by mass of dry starch to terminate the reaction; then, the reaction product is formed into inner core particles by a rotary granulator with a sieve aperture of 4.5 mm and a rotating speed of 28 rpm; after the inner core particles are dried to a water content of ≤3%, they are immersed in a starch gelatinization liquid containing 0.11% of glutaraldehyde to perform outer shell coating, the coating thickness is 0.22 mm, and the reaction is performed at 51°C for 31 minutes; finally, drying is performed at 56°C for 2.1 hours until the water content is ≤5%, and the pore-forming agent particles with a double-layer crosslinking structure are collected.

[0114] The cementitious material of the embodiment is composed of 42.5-grade ordinary portland cement and F-class fly ash at a mass ratio of 1:0.35, and the hydration product contains 24.0wt% of calcium hydroxide, 10.5wt% of ettringite, 49.5wt% of calcium silicate gel, and the balance of unreacted cement.

[0115] The admixture of the embodiment comprises a retarder, and the retarder is selected from sodium citrate.

[0116] The preparation method of the surface-modified shield waste soil coarse aggregate of the embodiment comprises the following steps: firstly, the aggregate after solidification and curing is washed with deionized water to remove surface loose particles and soluble salts, and is dried at 43°C for 1.3 hours; then, a γ-aminopropyltriethoxysilane ethanol solution with a mass fraction of 3.0% is prepared, and the pH value is adjusted to 4.3 to promote silane hydrolysis; then, the aggregate is immersed in the solution, the liquid-solid ratio is set to 3.8:1, and treatment is performed at 47°C for 2.8 hours; after the treatment is completed, the aggregate is dried at 53°C for 1.4 hours to make the silane molecules condense on the surface of the aggregate to form a stable organic silicon modified layer, and the bonding strength of the aggregate to the cement paste after the treatment can be increased by 40% compared with that of the untreated aggregate.

[0117] The fine aggregate of the embodiment is natural sand with a fineness modulus of 2.5.

[0118] The preparation method of a kind of permeable concrete material based on shield waste soil of the embodiment comprises the following steps:

[0119] S1. The surface-modified shield waste soil coarse aggregate and the degradable pore-forming agent particles are pre-mixed in a dry state for 4 minutes;

[0120] S2. The cementitious material is added, and dry mixing is performed for 8 minutes to form a continuous coating layer on the surface of the aggregate;

[0121] S3. Dissolve the admixture in water to form a solution, slowly add the above mixture at a rate of 85 mL / min, stirring speed is 280 rpm, stirring for 15 minutes until the slump of the mixture reaches 95 mm;

[0122] S4. Pour the mixture into a mold, use a vibrating table with a vibration frequency of 60 Hz to vibrate and compact, the vibration time is 70 seconds, and the stirring process maintains the system temperature at 28°C through a circulating water bath;

[0123] S5. Under the standard curing conditions of temperature 20±2℃ and relative humidity ≥95%, maintain until the design age, the pore-forming agent particles remain stable for the first 48 hours to provide early strength development for the concrete, the shell gradually degrades to form initial porosity on the 37th day, and the core fully degrades to form the final interconnected pore network on the 728th day.

[0124] Example 4 uses the balanced optimization design concept to achieve the best balance between water permeability and strength by fine-tuning the proportions of each component. The amount of pore-forming agent is 13.5 parts, close to the upper limit, but with medium to high cementitious material of 28 parts, through optimized mineral composition (high quartz content of 32.0%, low montmorillonite content of 8.0%) and precise cross-linking degree control (core 18.5%, shell 7.5%) to achieve synergistic effect. The coarse aggregate is selected to be smaller in size, 9.5mm, combined with small size pore-forming agent particles (3.2mm) to form a multi-level pore structure. The degradation kinetics design of this example is the most aggressive, with a late rate constant of 0.17d-1 and a total degradation rate of up to 88%, ensuring the formation of an efficient interconnected pore network. The process parameters are moderately configured, with an emphasis on precise control, suitable for engineering applications with higher comprehensive performance requirements.

[0125] Comparative Example 1: Basically the same as Example 1, the difference is that the surface-modified shield waste soil coarse aggregate is directly replaced by the shield waste soil coarse aggregate without surface modification treatment, i.e. omitting the surface modification treatment step of γ-aminopropyl triethoxysilane, and directly using the shield waste soil coarse aggregate after curing and maintenance and grading by screen.

[0126] Comparative Example 2: Basically the same as Example 1, the difference is that the degradable pore-forming agent particles are replaced by a single-layer cross-linked structure design instead of a double-layer cross-linked structure, specifically, corn starch is dried to a moisture content of ≤3%, then mixed with water at a mass ratio of 1:3.0, and pasted at 80℃ for 35 minutes, then when the pasting liquid is cooled to 55℃, 0.4% of glutaraldehyde based on the dry starch mass is added for uniform cross-linking reaction, the pH value is controlled at 6.8, and the reaction is carried out at a constant temperature of 110 minutes, then 0.45% of sodium sulfite based on the dry starch mass is added to terminate the reaction, then single-layer cross-linked pore-forming agent particles are formed by a rotary granulator.

[0127] Comparative Example 3: substantially the same as Example 1, except that the surface modifier is 3-aminopropyltrimethoxysilane instead of γ-aminopropyltriethoxysilane, and the surface modification method is to prepare a 3.5% by mass 3-aminopropyltrimethoxysilane ethanol solution, adjust the pH to 4.5, immerse the aggregate in the solution, set the liquid-to-solid ratio to 4:1, and treat at 50°C for 3 hours, and then dry at 55°C for 1.5 hours.

[0128] Comparative Example 4: substantially the same as Example 1, except that the substrate of the degradable pore-forming agent particles is potato starch instead of corn starch, and the preparation method is to dry the potato starch to a water content of ≤3%, mix with water at a mass ratio of 1:3.0, and perform gelatinization treatment at 78°C for 33 minutes, and the remaining steps of the preparation of the double-layer crosslinked structure remain the same, with the same amount of glutaraldehyde and reaction conditions.

[0129] Comparative Example 5: substantially the same as Example 1, except that the composition of the solidification agent for the shield waste soil coarse aggregate is changed to use only ordinary Portland cement of grade 42.5, without adding quicklime of grade II and fly ash of class F, and the amount of the solidification agent is calculated at 12% of the dry soil mass, and the remaining preparation process conditions remain unchanged.

[0130] Comparative Example 6: substantially the same as Example 1, except that the degradable pore-forming agent particles are formed using a traditional drop granulation method instead of a rotary granulation molding method, specifically by dropping the starch paste after crosslinking into a 0.5% CaCl2 solution at a rate of 2 mL / min to form ionically gelled irregular spherical particles, which are then washed with deionized water and dried.

[0131] Comparative Example 7: substantially the same as Example 1, except that the composition of the cementitious material is changed to a combination of ordinary Portland cement of grade 42.5 and slag powder at a mass ratio of 1:0.3, instead of the original combination of cement and fly ash of class F, and the specific surface area of the slag powder is 400±20 m 2 / kg, and the activity index is not less than 75%.

[0132] Comparative Example 8: substantially the same as Example 1, except that the crosslinking agent for the degradable pore-forming agent particles is epichlorohydrin instead of glutaraldehyde, and the preparation method is to add 0.6% of epichlorohydrin based on the dry starch mass after the starch gelatinization solution is cooled to 55°C, control the pH to 8.5, and react for 90 minutes at a constant temperature, and then adjust the pH to neutral with dilute hydrochloric acid.

[0133] Comparative Example 9: substantially the same as Example 1, except that the curing method for the shield waste soil coarse aggregate is natural air drying instead of an atomization curing system, specifically by air drying the granulated particles in an outdoor natural environment at an ambient temperature of 15-35°C and a relative humidity of 40-80%, for a curing time of 14 days without artificial humidity control.

[0134] Comparative Example 10: substantially the same as Example 1, except that the inner core of the degradable pore-forming agent particles has a cross-linking degree of 8.0%, the outer shell has a cross-linking degree of 15.0%, and the preparation method is adjusted accordingly, i.e., 0.15% glutaraldehyde is added to the dry starch during the cross-linking of the inner core, and a starch paste containing 0.3% glutaraldehyde is used during the coating of the outer shell, and the remaining preparation conditions remain unchanged.

[0135] Performance test:

[0136] Water permeability test: the test object is a test block of permeable concrete material based on shield waste soil, with a size of 150mm x 150mm x 150mm cubic test piece. The test purpose is to evaluate the permeability coefficient and permeability performance stability of the material, which is the most core functional index of permeable concrete. The test principle is based on Darcy's law, which calculates the permeability coefficient by measuring the water flow per unit area of material per unit time under the action of a certain water pressure difference. The experimental method uses a constant water head permeability test, installs the test piece in the permeameter, applies a constant water head of 0.1 MPa, records the flow and seepage time under stable seepage state, and monitors the water temperature change for temperature correction. The standards are GB / T 25993-2010 "Permeable Pavement Brick and Permeable Pavement Panel" and CJJ / T 135-2009 "Permeable Cement Concrete Pavement Technical Specification". Key parameters include test temperature 20±2℃, relative humidity 60±5%, water head height 100mm, test time not less than 10 minutes, and not less than 6 test pieces per group. Data processing is calculated according to the formula K=QL / (AHt), where Q is the permeable amount, L is the thickness of the test piece, A is the permeable area, H is the water head height, and t is the permeable time, and the results are taken as the logarithmic average value and the coefficient of variation is evaluated.

[0137] Compressive strength performance test: the test object is a 100mmx100mmx100mm cube standard specimen prepared based on the pervious concrete material of shield waste soil, and the test is carried out after standard curing for 28 days. The test purpose is to evaluate the bearing capacity and structural integrity of the material to ensure that the strength requirements of road engineering are met. The test principle is based on the failure mechanism of the material under uniaxial compression load, and the maximum bearing capacity is determined by gradually increasing the pressure until the specimen is destroyed. The experimental method adopts a pressure testing machine to continuously and uniformly load at a constant loading rate of 0.5-0.8MPa / s until the specimen is destroyed, and the maximum load value at the time of destruction is recorded, while the failure mode and crack development mode are observed. The standards are GB / T 50081-2019 "Standard Test Methods for Physical and Mechanical Properties of Concrete" and ASTM C39 / C39M-2018 "Standard Test Methods for Compressive Strength of Cylindrical Concrete Specimens". Key parameters include test environment temperature 20±2℃, relative humidity 60±5%, specimen moisture state saturated surface dry, loading speed 0.6±0.1MPa / s, and the number of specimens in each group is not less than 3 and not more than 6. Data processing uses the formula of compressive strength fc=P / A, where P is the failure load and A is the pressure area, the results are taken as the arithmetic mean value and the standard deviation is calculated, and the abnormal values exceeding the average value±15% are removed and recalculated.

[0138] Porosity and Pore Size Distribution Test: The test object is irregular small block samples of pervious concrete material based on shield waste soil, with a size of about 10 mm x 10 mm x 10 mm, taken from the center of the standard test piece to avoid boundary effects. The purpose of the test is to quantitatively analyze the pore structure characteristics of the material, including total porosity, effective porosity, pore size distribution and pore connectivity, to provide microstructure support for the pervious performance. The test principle is based on the mercury intrusion method, which uses the non-wetting properties of mercury to press mercury into pores of different sizes by gradually increasing the pressure, and calculates the pore size distribution according to the Washburn equation relationship between pressure and pore size. The experimental method uses a mercury porosimeter. First, the sample is dried at 110°C for 24 hours to a constant weight, then degassed under vacuum conditions, loaded into the sample cell for low pressure mercury filling (0-0.2 MPa) and high pressure mercury filling (0.2-200 MPa) test, and the relationship curve between the cumulative amount of mercury intrusion and the pressure is recorded. The standard is GB / T 21650.1-2008 "Determination of Pore Size Distribution and Porosity of Solid Materials by Mercury Intrusion and Gas Adsorption - Part 1: Mercury Intrusion Method" and ASTM D4404-2018 "Standard Test Method for Determining Pore Volume and Pore Size Distribution of Materials Using Mercury Intrusion". Key parameters include test temperature 23±2℃, mercury surface tension 0.485 N / m, mercury-solid contact angle 130°, pressure range 0.1-200 MPa, pressure step size set according to logarithmic series. Data processing uses the Washburn equation D = 4y cos θ / P to calculate the pore size, where y is the surface tension of mercury, θ is the contact angle, P is the pressure, and the total porosity is calculated by the ratio of mercury intrusion volume to sample volume, and the results are expressed as pore size distribution curve and cumulative porosity curve.

[0139] Freeze-thaw cycle resistance test: The test object is a 100mm x 100mm x 400mm prism specimen made of permeable concrete material based on shield waste soil, which is cured for 28 days and saturated in water for 48 hours before testing. The purpose of the test is to evaluate the durability and structural stability of the material under repeated freeze-thaw action in cold regions, ensuring long-term performance. The test principle is based on the damage mechanism of internal stress generated by the volume expansion of water freezing in the pores to the material structure, simulating the effect of actual climate conditions through repeated freeze-thaw cycles. The experimental method uses a rapid freeze-thaw testing machine, which freezes the saturated specimen at -18±2℃ for 4 hours, then melts it in 4±2℃ water for 4 hours as one cycle, and continues for 300 freeze-thaw cycles. The dynamic elastic modulus, mass loss and appearance change of the specimen are measured every 25 cycles. The standards are GB / T 50082-2009 "Standard Test Methods for Long-term Performance and Durability of Ordinary Concrete" and ASTM C666 / C666M-2015 "Standard Test Methods for Resistance of Concrete to Rapid Freeze-Thaw Cycling". Key parameters include freezing temperature -18±2℃, thawing temperature 4±2℃, freezing and thawing time each 4±0.5 hours, specimen saturation not less than 90%, dynamic elastic modulus test frequency range 2000-5000Hz. Data processing uses relative dynamic elastic modulus Pc=(fn / f0)2x100% and mass loss rate AW=(W0-Wn) / W0x100% to calculate, where fn and f0 are the transverse fundamental frequency after n cycles and the initial value, respectively, and Wn and W0 are the mass after n cycles and the initial mass, respectively. The freeze-thaw resistance is evaluated by the number of cycles when the relative dynamic elastic modulus decreases to 60%.

[0140] Abrasion resistance test: The test object is a disc-shaped specimen with a diameter of 150 mm and a thickness of 50 mm prepared from the permeable concrete material based on shield waste soil. The surface of the specimen should be smooth and free of obvious defects. The purpose of the test is to evaluate the durability of the material surface under mechanical abrasion, simulating the wear of pavement materials under traffic load. The test principle is based on the abrasive effect of abrasive materials on the surface of the material under certain pressure and rotation speed. The abrasion resistance is evaluated by measuring the mass or thickness change before and after abrasion. The experimental method uses a modified Los Angeles abrasion tester. A load of 20±1 kg is applied to the surface of the specimen, and the specimen is rotated at a speed of 75±5 r / min. Standard quartz sand is used as abrasive material, and the total number of revolutions for abrasion is 1000. The mass change of the specimen is measured every 200 revolutions, and the mass loss curve during abrasion is recorded. The standards are JC / T 446-2000 "Concrete pavement brick" and ASTM C944 / C944M-2012 "Standard test method for abrasion resistance of concrete or mortar surfaces". The key parameters include test environment temperature 20±5℃, relative humidity 45-75%, applied load 20±1 kg, rotation speed 75±5 r / min, abrasive material 0.3-0.6 mm standard quartz sand, abrasion path diameter 120 mm, and specimen surface flatness deviation not more than 0.5 mm. Data processing uses the formula Ma=(m0-mn) / A to calculate the abrasion rate, where m0 and mn are the mass before and after abrasion, respectively, and A is the abrasion area. The result is expressed in g / cm 2 , and the abrasion rate is calculated and the abrasion-time relationship curve is plotted to evaluate the abrasion resistance grade of the material.

[0141] The performance of the concrete mixed with examples 1-4 and comparative examples 1-10 is summarized in Table 1. It can be seen from the table that the shield waste soil coarse aggregate without surface modification treatment lacks effective interface bonding improvement measures, resulting in a decrease in the bonding strength between the aggregate and the cementitious material. At the same time, the hydrophilicity of the aggregate surface is enhanced, making the interface transition zone more prone to micro-cracks, thereby affecting the overall mechanical properties and durability performance. The pore-forming agent with a single-layer cross-linking structure lacks a gradient release mechanism during the degradation process, resulting in an uneven and uncontrollable pore formation process, which leads to a decrease in the connectivity and stability of the pore structure, thereby affecting the consistency of the water permeability performance and the overall strength of the material. Using different types of silane coupling agents will change the effect of surface modification, especially the difference in functional group structure will affect the chemical bonding strength and interface stability with the matrix material, thereby reducing the modification effect to some extent. Replacing the starch-based material type will affect the gelatinization characteristics, cross-linking reaction activity and degradation behavior of the pore-forming agent. The difference in molecular structure of different starches leads to changes in the pore characteristics and distribution pattern formed finally, thereby affecting the balance of water permeability performance and mechanical properties. The simplified curing agent composition lacks the synergistic effect of a multi-component cementitious system, and cannot fully play the complementary role of different cementitious materials, resulting in limitations in curing effect and long-term stability. The traditional granulation process is difficult to achieve precise control of the shape and size of the particles, resulting in a decrease in the uniformity and consistency of the pore-forming agent particles, affecting the regularity of the final pore structure and the stability of the performance. Changes in the cementitious material system will affect the hydration reaction process and product composition. The activity difference and reaction mechanism change of different admixtures may lead to changes in the strength development law and durability performance. The reaction mechanism and cross-linking efficiency difference of different cross-linking agents will affect the structural stability and degradation controllability of the pore-forming agent, thereby affecting the timing of pore formation and the final material performance. The fluctuation of environmental factors and unstable curing effect under natural curing conditions will affect the uniformity and consistency of the final performance of the material, especially the lack of humidity and temperature control may lead to an increase in performance dispersion. Changes in the cross-linking degree ratio will affect the matching of the inner and outer structures of the pore-forming agent and the degradation gradient control effect. An inappropriate cross-linking degree combination may lead to an uncoordinated pore formation process and a decrease in the final performance.

[0142] From Figure 1 It can be observed that the water permeable concrete prepared in example 1 of the present application presents a uniform pore structure at the 20th day after pouring, at which time part of the pore-forming agent particles have not yet completely degraded, indicating that the double-layer cross-linking structure design achieves a controllable gradient degradation effect, providing an effective guarantee for the gradual formation and stabilization of pores. Figure 2 The XRD phase analysis results show that the shield waste soil coarse aggregate is mainly composed of mineral phases such as quartz (Q), illite (I), montmorillonite (M) and calcite (C), among which quartz has the highest content and good crystallinity, providing a good mineralogical basis for the waste soil as a concrete coarse aggregate. Figure 3The compressive strength and freeze-thaw cycle resistance of the application are compared and analyzed, and the results show that the mechanical properties and durability of the application are significantly better than those of the comparative examples, achieving a good balance between strength and freeze-thaw resistance, and verifying the synergistic effect of the surface modified shield waste soil coarse aggregate and the optimized cementitious material system. Figure 4 The relationship between the water permeability coefficient and the effective porosity of the application is compared, which reveals that the application can ensure water permeability while achieving higher porosity utilization efficiency, indicating that the combination of double-layer crosslinking pore-forming agent technology and surface modification technology effectively improves the connectivity and stability of the pore structure. Figure 5 The comprehensive comparison of the abrasion loss rate and freeze-thaw resistance of the application further confirms the overall advantage of the application in durability, and each example shows lower abrasion loss rate and better freeze-thaw resistance, reflecting the overall superiority of the technical solution. Figure 6 The radar chart of the comprehensive performance of the application intuitively shows the overall improvement of the application in water permeability, mechanical properties, durability and other dimensions compared with the comparative examples, forming a more full and balanced performance distribution pattern. Figure 7 The performance optimization trend chart of the application shows that through the adjustment and combination of different technical parameters, the application realizes the systematic optimization and improvement of the performance of the pervious concrete material, providing reliable technical support and theoretical basis for the engineering application of high-performance pervious concrete material based on shield waste soil.

[0143] Table 1 Performance of concrete of examples 1-4 and comparative examples 1-10

[0144]

[0145] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the application and not to limit it, although the application has been described in detail with reference to the above examples, those skilled in the art should understand that: any equivalent structural transformation made within the concept of the application, using the contents of the application specification and drawings, should be covered within the protection scope of the claims of the application.

Claims

1. A permeable concrete material based on shield waste soil, characterized in that: The invention comprises the following components in parts by weight: 85-95 parts of surface-modified shield waste soil coarse aggregate, 5.0-15 parts of degradable pore-forming agent particles, 15-35 parts of cementitious material, 10-25 parts of water, 0.5-1.5 parts of admixture and 1.0-3.0 parts of fine aggregate; The surface-modified shield waste soil coarse aggregate is obtained by surface-modifying shield waste soil coarse aggregate with γ-aminopropyltriethoxysilane; The mineral composition of the shield waste soil coarse aggregate is as follows: quartz content 15.0-35.0wt%, feldspar content 10.0-25.0wt%, total clay mineral content 40.0-60.0wt%, wherein the montmorillonite content does not exceed 20.0wt% of the total clay mineral content; The degradable pore-forming agent particles are spherical particles with corn starch as the base material and a double-layer cross-linked structure design. The inner core is modified with high-crosslinking glutaraldehyde to provide structural stability, and the outer shell is modified with low-crosslinking glutaraldehyde to achieve staged degradation. They are prepared by rotary granulation molding.

2. The permeable concrete material based on shield waste soil according to claim 1, characterized in that: The mass ratio of the shield waste soil coarse aggregate and the degradable pore-forming agent particles is (85-95):(5-15).

3. The permeable concrete material based on shield waste soil according to claim 1, characterized in that: The degradable pore-forming agent particles adopt a double-layer cross-linked structure design, with a core cross-linking degree of 15.0-20.0% and a shell cross-linking degree of 6.0-10.0%. The average size of the core is 2.0-6.0 mm, and the total size after the shell is coated is 2.5-8.0 mm. The structure maintains stability within the first 48 hours after concrete pouring, and the degradation rate is less than 5%. The shell begins to degrade from the 3rd to the 7th day, and the degradation rate reaches 25-35%. The core is fully degraded from the 7th to the 28th day, and the total degradation rate reaches 70-85%. The degradation kinetics are divided into two stages: the rate constant k1 in the early 0-7 days is 0.04-0.08 d -1 The rate constant k2 was 0.12~0.18 d in the later 7~28 days. -1 .

4. The permeable concrete material based on shield waste soil according to claim 1, characterized in that: The method for preparing shield waste soil coarse aggregate comprises the following steps: first, dehydrating the waste soil and passing it through a 5mm square hole sieve to obtain a silty clay base material with a moisture content of 15-25%; then adding a compound curing agent prepared by 42.5 grade ordinary Portland cement, II grade quicklime and F class fly ash in a mass ratio of 1:(0.8-1.2):(0.9-1.1), and adjusting the mixing water so that the liquid index reaches 0.2-0.6; then stirring at a speed of 350-450 rpm for 20-40 minutes in a double-shaft forced mixer, and then preparing 5-20 mm ellipsoidal particles through an 8-12 MPa double-roll granulator; then curing at 20-30° C. and a relative humidity of 85-95% for 7-28 days, using an atomization curing system instead of directly spraying a carbonate buffer solution; and finally, obtaining the shield waste soil coarse aggregate after sieving.

5. The permeable concrete material based on shield waste soil according to claim 1, characterized in that: The modified polyurethane emulsion preparation method is as follows: 20 to 50 parts of fluorine-containing polyol, 24 to 75 parts of isocyanate and 80 to 120 parts of N,N-dimethylformamide are added to a reaction kettle in parts by weight, and reacted at 60 to 80° C. for 2 to 4 hours to obtain a prepolymer, and then 5 to 10 parts of a chain extender are added to the prepolymer, stirred evenly, and reacted at 100 to 140° C. for 1 to 2 hours to obtain the modified polyurethane emulsion.

6. The permeable concrete material based on shield waste soil according to claim 1, characterized in that: The average size of the shield waste soil coarse aggregate is 8.0-20.0 mm.

7. The permeable concrete material based on shield waste soil according to claim 1, characterized in that: The preparation method of the double-layer structure of the pore-forming agent particles comprises the following steps: first, drying corn starch to a moisture content of ≤3%, mixing it with water in a mass ratio of 1:(2.5-3.5), and stirring at 75-85° C. for 30-40 minutes for gelatinization; after the gelatinization liquid is cooled to 50-60° C., adding glutaraldehyde at a mass of 0.3-0.5% of the mass of the dry starch to carry out a core cross-linking reaction, controlling the pH value to 6.5-7.0, and reacting at a constant temperature for 100-120 minutes; after the reaction is completed, adding 0.4-0.5% of the mass of the dry starch to form a pore-forming agent; The reaction is terminated by adding % sodium sulfite; the reaction product is then formed into core particles by a rotary granulator with a sieve aperture of 4-9 mm and a rotation speed of 25-45 rpm; the core particles are dried to a moisture content of ≤3%, and then immersed in a starch gelatinization solution containing 0.1-0.2% glutaraldehyde for shell coating with a coating thickness of 0.2-0.5 mm, and reacted at 50-60° C. for 30-45 minutes; finally, dried at 55-65° C. for 2-3 hours to a moisture content of ≤5%, and pore-forming agent particles with a double-layer cross-linked structure are collected.

8. The permeable concrete material based on shield waste soil according to claim 1, characterized in that: The cementitious material is composed of 42.5 grade ordinary Portland cement and Class F fly ash in a mass ratio of 1:(0.15-0.45), and the hydration product contains 15.0-25.0 wt% of calcium hydroxide, 8.0-15.0 wt% of ettringite, 40.0-55.0 wt% of hydrated calcium silicate gel, and the balance is unreacted cement; The admixture includes a retarder, and the retarder is selected from sodium citrate; The fine aggregate is natural sand with a fineness modulus of 2.3 to 3.

0.

9. The permeable concrete material based on shield waste soil according to claim 1, characterized in that: The method for preparing surface-modified shield waste soil coarse aggregate comprises the following steps: first, rinsing the cured aggregate with deionized water to remove loose particles and soluble salts on the surface, and drying at 40-50°C for 1-2 hours; then preparing a 2-5% by mass γ-aminopropyltriethoxysilane ethanol solution, adjusting the pH to 4.0-5.0 to promote silane hydrolysis; then immersing the aggregate in the solution with a liquid-to-solid ratio of 3:1-5:1, and treating at 40-60°C for 2-4 hours; and after treatment, drying at 50-60°C for 2 hours to allow silane molecules to condense on the aggregate surface to form a stable organosilicon modified layer. After this treatment, the bonding strength between the aggregate and cement paste can be increased by 30-60% compared with untreated aggregate.

10. A method for preparing permeable concrete according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Premix the surface-modified shield waste soil coarse aggregate and the biodegradable pore-forming agent particles in a dry state for 3 to 6 minutes; S2. Add cementitious material and dry mix for 5 to 10 minutes to form a continuous coating on the aggregate surface; S3. The admixture was dissolved in water to form a solution, and the mixture was slowly added at a rate of 50 to 100 mL / min, with a stirring speed of 250 to 350 rpm, and stirred for 10 to 18 minutes until the slump of the mixture reached 80 to 120 mm; S4. The mixture was cast and compacted using a vibration table with a vibration frequency of 50 to 80 Hz, and the vibration time was 45 to 90 seconds. The stirring process was maintained at a temperature of 25 to 35 ° C by a circulating water bath; S5. Curing to the design age under standard curing conditions of temperature 20±2°C and relative humidity ≥95%. The pore-forming agent particles remain stable for the first 48 hours to provide early strength development for the concrete. The outer shell gradually degrades to form initial pores from the 3rd to the 7th day. The inner core is fully degraded to form the final interconnected pore network from the 7th to the 28th day.

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