Modified flow-state solidified soil based on solid waste base and preparation method of modified flow-state solidified soil

Abstract

The invention discloses modified flow state solidified soil based on a solid waste base and a preparation method of the modified flow state solidified soil. The stabilized soil comprises engineering residue soil, slag, cement, a water reducing agent, wollastonite microfibers subjected to surface modification by a silane coupling agent, an amide monomer, an initiator, an initiator promoter and an early strength agent. Through the synergistic modification effect of in-situ polymerization and wollastonite microfibers, the pressure resistance, crack resistance, toughness and the like of the solidified soil with high solid waste content and high fiber doping amount are remarkably improved. The preparation method is simple, low in cost, convenient to construct and suitable for industrial application.

Description

TECHNICAL FIELD

[0001] The present application relates to a solidified soil, in particular to a modified flowable solidified soil based on solid waste, and a preparation method thereof, and belongs to the technical field of building solid waste resource utilization. BACKGROUND

[0002] The flowable solidified soil technology, as a new type of building material for resource utilization of engineering slag, silt and other solid waste, has broad prospects in roadbed backfilling, pipeline foundation pit backfilling and other engineering applications. However, the traditional flowable solidified soil generally has low early strength, fast time loss of fluidity, easy shrinkage and cracking after hardening, and poor water resistance, which seriously limits its popularization and application in high-standard engineering.

[0003] To overcome these defects, the prior art usually adopts polymer modification or fiber reinforcement, but each method has significant limitations. For example, although the use of externally added polymer emulsion (such as styrene-acrylic emulsion or epoxy resin) can improve the toughness and pore structure of the material to some extent, the interface between the introduced polymer film and the cement hydration product is weak, and the self-volume shrinkage of the film after formation is large, which easily leads to high brittleness of the modified body, interface peeling under dry-wet cycle or external load, and thus aggravates the cracking risk, and the improvement effect on durability is limited. On the other hand, although the direct addition of steel fibers or synthetic fibers can effectively inhibit crack propagation and improve material toughness, the lapping and winding of the fibers in the slurry can seriously damage the rheological properties, resulting in rapid decrease of fluidity, accelerated loss of slump, and difficulty in meeting the process requirements of pumping construction or self-leveling filling, so that the workability and mechanical properties are difficult to coordinate. More fundamentally, the above single modification strategy can only focus on improving a certain aspect of performance, and cannot systematically consider multiple targets such as high fluidity, early strength and high strength, low shrinkage, and excellent durability, especially when facing engineering slag with complex composition and variable properties, the applicability and stability are insufficient.

[0004] Therefore, developing a new collaborative modification technology that can simultaneously optimize workability, mechanical properties and durability has become the key to promoting the high performance and application expansion of flowable solidified soil. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a modified flowable solidified soil based on solid waste. The solidified soil has high toughness and strong crack resistance.

[0006] Another purpose of the present application is to provide a preparation method of a modified flowable solidified soil based on solid waste. The method is simple, low in cost and convenient to apply.

[0007] To achieve the above technical purposes, the present application provides a solid waste base modified fluidized solidified soil, which comprises engineering slag, slag, cement, water reducing agent, wollastonite microfiber surface modified by silane coupling agent, amide monomer, initiator, pro-initiator and early strength agent.

[0008] The modified fluidized solidified soil of the present application realizes the multi-scale synergistic effect of "chemical network strengthening-interface coupling enhancement-pore structure optimization-macroscopic performance improvement" through the synergistic effect of in-situ polymerization and wollastonite microfiber, greatly improving the comprehensive performance of the solidified soil. Among them, the amide monomer is initiated to in-situ polymerize in an alkaline environment, and the generated polymer chain segments preferentially accumulate around the fiber and interpenetrate with the hydration products, building a continuous polymer-hydration product composite network, effectively inhibiting the bleeding channel and pore defects, and improving the overall density and shrinkage control ability of the material; the surface silanol groups of the wollastonite microfiber modified by the silane coupling agent produce chemical bonding with the hydration products and the polymer chain segments, and at the same time the fiber plays a bridging, pulling and pulling energy dissipation role in the process of micro-crack initiation and expansion, thereby significantly improving the crack toughness and shear capacity. That is, the polymer and the fiber realize the dual role of chemical bonding and mechanical anchoring on the micro-interface, so that the system has both densification and durability, and also has toughness and crack resistance.

[0009] As a preferred scheme, the modified fluidized solidified soil comprises the following components by mass:

[0010] Engineering slag 1000-1500 parts;

[0011] Slag 500-1200 parts;

[0012] Cement 300-600 parts;

[0013] Water reducing agent 1-5 parts;

[0014] Wollastonite microfiber surface modified by silane coupling agent 40-180 parts;

[0015] Amide monomer 20-50 parts;

[0016] Initiator 0.5-3 parts;

[0017] Pro-initiator 2-8 parts;

[0018] Early strength agent 0.5-3 parts.

[0019] The above raw material ratio can make the comprehensive performance of the flowable solidified soil reach the best state. The amount of the amide monomer directly affects the density and integrity of the in-situ generated polymer network. When the amount is lower than the optimal demand of the system, the generated polyacrylamide molecular chain is too short, the network is sparse, and it cannot effectively bridge and wrap the wollastonite microfiber and cementation product, resulting in insufficient reinforcement effect, limited improvement of material toughness, and difficulty in effectively inhibiting shrinkage. When the amount is too high, excessive crosslinking polymerization reaction will generate a too thick polymer film, which will destroy the uniformity of the material structure, increase the brittleness, and even cause macro cracking. The amount of wollastonite microfiber determines the density and effectiveness of the microskeleton formed in the slurry. When the amount is too low, the number of fibers is insufficient, and it cannot effectively form a network in the matrix, and its toughening and crack resistance effect is minimal. When the amount is too high, although the theoretical enhancement potential increases, the large specific surface area will adsorb a large amount of free water, seriously damaging the rheological properties of the slurry, resulting in a sharp increase in viscosity and a sharp decrease in fluidity. More seriously, excessive fibers are easily entangled and agglomerated due to van der Waals force, forming stress concentration points in the matrix and becoming a performance defect. The synergistic effect of the amide monomer and the wollastonite microfiber exceeds the simple addition of the individual effects of each component. The wollastonite microfiber modified by the silane coupling agent has a surface rich in functional groups that can form strong hydrogen bonds or covalent bonds with the polymer molecular chain. Under the optimal amount ratio, the in-situ polymerized polyacrylamide long chain can be tightly anchored to the surface of the wollastonite fiber and the hydration product around it through chemical bonding and physical entanglement. The flexible polymer phase effectively transfers the load to the rigid wollastonite fiber, fully utilizes its high modulus and high strength characteristics, and together withstands external force, achieving a balance between rigidity and toughness, greatly improving the flexural strength and fracture toughness of the material. The three-dimensionally distributed wollastonite fiber network provides physical constraints for the shrinkage of the polymer film, significantly reducing the overall drying shrinkage caused by the volume change of the polymer phase, effectively avoiding the risk of shrinkage cracking, and appropriately adsorbing the polymer molecular chain on the fiber surface to improve the dispersibility of the fiber to some extent, alleviate the loss of fluidity caused by the addition of fibers, so that the system can maintain good workability while obtaining excellent mechanical properties.

[0020] As a preferred scheme, the modified flowable solidified soil comprises the following components by mass:

[0021] Engineering slag 1200-1400 parts;

[0022] Slag 800-1000 parts;

[0023] Cement 400-500 parts;

[0024] Water reducing agent 2-4 parts;

[0025] 50~150 parts of silicate microfiber surface modified by silane coupling agent;

[0026] 24~30 parts of amide monomer;

[0027] 1~2 parts of initiator;

[0028] 3~6 parts of pro-initiator;

[0029] 1~2 parts of early strength agent.

[0030] The further preferred composition ratio can make the comprehensive performance of the solidified soil reach the best state.

[0031] As a preferred scheme, the silicate microfiber surface modified by silane coupling agent is obtained by surface modification treatment of silicate microfiber impregnated with silane coupling agent solution.

[0032] As a preferred scheme, the silane coupling agent is KH-570.

[0033] As a preferred scheme, the impregnation condition is that the temperature is room temperature~70℃, and the time is 30~50min.

[0034] As a preferred scheme, the length-diameter ratio of the silicate microfiber surface modified by silane coupling agent is 20~30:1.

[0035] As a preferred scheme, the engineering slag soil is soil and gravel, construction waste including concrete fragments and waste bricks, minerals including quartz clay kaolin, etc.

[0036] As a preferred scheme, the water reducing agent is polycarboxylic acid water reducing agent.

[0037] As a preferred scheme, the amide monomer is acrylamide.

[0038] As a preferred scheme, the initiator is ammonium persulfate.

[0039] As a preferred scheme, the pro-initiator is tetramethyl ethylenediamine.

[0040] As a preferred scheme, the early strength agent is a chloride-based early strength agent.

[0041] The application also provides a preparation method of modified fluidized solidified soil based on solid waste.

[0042] As a preferred scheme, the liquid-solid mass ratio in the slurry is 0.3-0.8:1.

[0043] As a preferred scheme, the concentration of the amide monomer solution is 200-300 g / L.

[0044] As a preferred scheme, the concentration of the initiator solution is 6-9 g / L.

[0045] As a preferred scheme, the concentration of the promoter solution is 1-3 g / L.

[0046] Compared with the prior art, the present application has the following beneficial effects:

[0047] (1) By means of the "in-situ polymerization gradient initiation + fiber surface directional modification" process, the fiber-polymer compatibility problem is solved, and the comprehensive performance of the flow state solidified soil is significantly improved, not only in the aspects of strength, toughness and durability, but also in the aspect of rheological properties, the thixotropic thickening problem caused by the fiber is effectively alleviated, and the operability and mechanical properties are considered at the same time.

[0048] (2) The preparation method is simple, low in cost and convenient to apply, and the engineering waste and slag are fully utilized as main raw materials, the resource utilization rate of solid waste is effectively improved (the utilization rate is increased to 85%), and "waste into treasure" is realized. DETAILED DESCRIPTION

[0049] The technical solutions of the present application will be described in detail below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0050] The engineering waste used in the present application is the spoil produced in the tunnel construction process of a certain subway station, the slag is a by-product produced in the ironmaking process of a certain blast furnace iron plant, the polycarboxylic acid water reducing agent is Hua Xuan PC-3008, and the wollastonite microfiber is a papermaking grade wollastonite mineral fiber produced by Jiangxi Oute.

[0051] Example 1

[0052] At room temperature, the wollastonite microfiber was immersed in a 5wt% KH-570 silane coupling agent ethanol solution for 60 min, and then dried at 60℃ to obtain the wollastonite microfiber surface modified by the silane coupling agent.

[0053] Preparation of raw materials: cement 400 parts, construction waste 1400 parts, slag 800 parts, polycarboxylic acid water reducing agent 2 parts, calcium chloride early strength agent 1 part, acrylamide 24 parts, ammonium persulfate 1 part, tetramethyl ethylenediamine 3 parts, silane coupling agent surface modified wollastonite microfiber 100 parts, and water 1200 parts.

[0054] The acrylamide, ammonium persulfate, and tetramethyl ethylenediamine were respectively prepared into acrylamide aqueous solution with a concentration of 300 g / L, ammonium persulfate aqueous solution with a concentration of 9 g / L, and tetramethyl ethylenediamine aqueous solution with a concentration of 3 g / L using the above water, and the remaining water was reserved.

[0055] First, the cement, slag, and silane coupling agent surface modified wollastonite microfiber were added to the construction waste, stirred and mixed for 30 s, then the above acrylamide aqueous solution, ammonium persulfate aqueous solution, and tetramethyl ethylenediamine aqueous solution were sequentially added, mixed uniformly, and then the above remaining water, water reducing agent, and early strength agent were added, and stirred and mixed uniformly to obtain a slurry. The slurry was injected into a mold to form a solidified soil.

[0056] Example 2

[0057] The solidified soil was prepared by the method of Example 1, except that the raw material composition was: cement 400 parts, construction waste 1400 parts, slag 800 parts, polycarboxylic acid water reducing agent 2 parts, chloride-based early strength agent 1 part, acrylamide 48 parts, ammonium persulfate 2 parts, tetramethyl ethylenediamine 6 parts, silane coupling agent surface modified wollastonite microfiber 150 parts, and water 1200 parts.

[0058] Example 3

[0059] The solidified soil was prepared by the method of Example 1, except that the raw material composition was: cement 400 parts, construction waste 1400 parts, slag 800 parts, polycarboxylic acid water reducing agent 2 parts, chloride-based early strength agent 1 part, acrylamide 48 parts, ammonium persulfate 2 parts, tetramethyl ethylenediamine 6 parts, silane coupling agent surface modified wollastonite microfiber 200 parts, and water 1200 parts.

[0060] Example 4

[0061] The solidified soil was prepared by the method of Example 1, except that the raw material composition was: cement 400 parts, construction waste 1400 parts, slag 800 parts, polycarboxylic acid water reducing agent 2 parts, chloride-based early strength agent 1 part, acrylamide 72 parts, ammonium persulfate 3 parts, tetramethyl ethylenediamine 9 parts, silane coupling agent surface modified wollastonite microfiber 150 parts, and water 1200 parts.

[0062] Comparative Example 1

[0063] Preparation of raw materials: cement 400 parts, construction waste 1200 parts, slag 800 parts, polycarboxylic acid water reducing agent 2 parts, chloride-based early strength agent 1 part, water 1200 parts.

[0064] First, add cement, slag to the construction waste and stir for 30s, then add water, water reducing agent and early strength agent after mixing evenly, continue to stir evenly to get slurry, pour the slurry into the mold to form solidified soil.

[0065] Comparative Example 2

[0066] Preparation of raw materials: cement 400 parts, construction waste 1200 parts, slag 800 parts, polycarboxylic acid water reducing agent 2 parts, early strength agent 1 part, acrylamide 24 parts, ammonium persulfate 1 part, tetramethyl ethylenediamine 3 parts, water 1200 parts.

[0067] Solidified soil is prepared by using the raw materials of this comparative example according to the method of Example 1.

[0068] Comparative Example 3

[0069] Preparation of raw materials: cement 400 parts, construction waste 1200 parts, slag 800 parts, polycarboxylic acid water reducing agent 2 parts, early strength agent 1 part, acrylamide 48 parts, ammonium persulfate 2 parts, tetramethyl ethylenediamine 6 parts, water 1200 parts.

[0070] Solidified soil is prepared by using the raw materials of this comparative example according to the method of Comparative Example 2.

[0071] Comparative Example 4

[0072] Preparation of raw materials: cement 400 parts, construction waste 1200 parts, slag 800 parts, polycarboxylic acid water reducing agent 2 parts, early strength agent 1 part, wollastonite microfiber surface modified by silane coupling agent 100 parts, water 1200 parts.

[0073] First, add cement, slag and wollastonite microfiber surface modified by silane coupling agent to the construction waste and stir for 30s, then add water, water reducing agent and early strength agent after mixing evenly, continue to stir evenly to get slurry, pour the slurry into the mold to form solidified soil.

[0074] Comparative Example 5

[0075] Preparation of raw materials: cement 400 parts, construction waste 1200 parts, slag 800 parts, polycarboxylic acid water reducing agent 2 parts, early strength agent 1 part, wollastonite microfiber surface modified by silane coupling agent 150 parts, water 1200 parts.

[0076] First, add cement, slag and wollastonite microfiber surface modified by silane coupling agent to the construction waste and stir for 30s, then add water, water reducing agent and early strength agent after mixing evenly, continue to stir evenly to get slurry, pour the slurry into the mold to form solidified soil.

[0077] The cured soil prepared in each of the above embodiments and comparative examples was subjected to performance testing, and the results are shown in Tables 1-4. Among them, the mechanical performance testing refers to the standard GB / T 50081-2019 for testing the physical and mechanical properties of concrete; the durability performance testing refers to GB / T 50082-2024 for long-term performance and durability of ordinary concrete; the working performance testing refers to the standard GB / T 50080-2016 for testing the performance of ordinary concrete mixture; and the rheological performance testing over time refers to ISO / TR 20659-1:2024.

[0078]

[0079]

[0080]

[0081]

[0082] The performance test results show that the benchmark system (Comparative Example 1) has a loose structure, a 28 d compressive strength of only 4.8 MPa, a shear strength of 200 kPa, a dry shrinkage strain of up to 520 με, a strength loss rate of 28% under dry-wet cycles, and insufficient durability. The use of in-situ polymerization alone (Comparative Examples 2 and 3) or the incorporation of wollastonite microfibers alone (Comparative Examples 4 and 5) improves the performance to some extent, but the overall improvement effect is limited. In contrast, the use of the synergistic modification system (Embodiments 1 and 2) of the present application can achieve excellent comprehensive performance, wherein the compressive strength of Embodiment 1 is 7.4 MPa, the shear strength is 510 kPa, the dry shrinkage strain is reduced to 310 με, and the dry-wet cycle loss rate is only 12%; under the synergistic effect of a high dose, the compressive strength of Embodiment 2 is further increased to 8.2 MPa, the shear strength is 580 kPa, the dry shrinkage strain is reduced to 280 με, and the dry-wet cycle loss rate is only 10%. At the same time, the initial setting time of the two synergistic modification systems is maintained at 370-390 min, the final setting time is 715-730 min, ensuring the operability of construction, and the fluidity is maintained at 305-320 mm, meeting the pumping and pouring requirements of flowable solidified soil.

[0083] In addition, the rheological performance test results further prove the advantages of the synergistic effect of the present application. The benchmark system (Comparative Example 1) has a yield stress of about 45 Pa and a plastic viscosity of about 0.38 Pa·s at the initial time (0 min), and gradually increases over time at 30 min and 60 min. After using in-situ polymerization alone (Comparative Examples 2 and 3), the initial yield stress and plastic viscosity are reduced due to the synergistic dispersion and lubrication effect of the polycarboxylate superplasticizer and the polymer segment, and the fluidity is improved, but the improvement effect is not good. However, the yield stress and plastic viscosity are significantly increased by adding wollastonite microfibers alone (Comparative Examples 4 and 5), and the fluidity of the system decreases significantly with time, showing a strong thixotropic thickening effect. In contrast, the yield stress of the present application scheme (Examples 1 and 2) is 50-55 Pa and the plastic viscosity is 0.40-0.42 Pa·s at the initial time, which is between the effects of in-situ polymerization and fibers alone, indicating that the polymer segment weakens the excessive thickening caused by the fibers while maintaining dispersion and lubrication; at 30 min and 60 min, the yield stress and viscosity of the synergistic system increase within the workable range, ensuring the pumpability and fillability of the flowable solidified soil. Examples 3 and 4 show that the performance of the solidified soil is relatively lower when the preferred component ratio of the present application is not used, but it is still better than that of the comparative examples.

[0084] In summary, the flowable solidified soil prepared by the "in-situ polymerization + wollastonite microfiber synergistic modification" system of the present application not only shows significant improvement in strength, toughness and durability, but also effectively alleviates the thixotropic thickening problem caused by the fibers in the rheological properties, achieving the balance between workability and mechanical properties.

[0085] Various modifications to these examples will be readily apparent to those skilled in the art, and general principles defined herein can be applied to other examples without departing from the spirit or scope of the application. Accordingly, the present application is not to be limited to the examples shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A solid waste-based modified fluidified soil stabilization, characterized in that: The modified fluidized solidified soil based on solid waste includes engineering slag, slag, cement, water reducing agent, silicate microfiber surface modified by silane coupling agent, amide monomer, initiator, pro-initiator and early strength agent.

2. A solid waste based modified flowable soil stabilizer according to claim 1, characterized in that: The modified fluidized solidified soil based on solid waste includes the following components by mass fraction: Engineering slag 1000-1500 parts; Slag 500-1200 parts; Cement 300-600 parts; Water reducing agent 1-5 parts; Silicate microfiber surface modified by silane coupling agent 40-180 parts; Amide monomer 20-50 parts; Initiator 0.5-3 parts; Pro-initiator 2-8 parts; Early strength agent 0.5-3 parts.

3. A solid waste based modified flowable soil stabilizer according to claim 1 or 2, characterized in that: The modified fluidized solidified soil based on solid waste includes the following components by mass fraction: Engineering slag 1200-1400 parts; Slag 800-1000 parts; Cement 400-500 parts; Water reducing agent 2-4 parts; Silicate microfiber surface modified by silane coupling agent 50-150 parts; Amide monomer 24-30 parts; Initiator 1-2 parts; Pro-initiator 3-6 parts; Early strength agent 1-2 parts.

4. A solid waste based modified flowable soil stabilization material according to claim 1, characterized in that: The silicate microfiber surface modified by silane coupling agent is obtained by immersing the silicate microfiber in a silane coupling agent solution.

5. The modified fluidized solidified soil based on solid waste according to claim 4, wherein: The silane coupling agent is KH-570; The mass concentration of the silane coupling agent solution is 1.5%-5%; The immersion conditions are room temperature-70°C and 30-50 min.

6. A solid waste based modified flowable soil stabilizer according to claim 1, 4 or 5, characterized in that: The aspect ratio of the silicate microfiber surface modified by silane coupling agent is 20-30:

1.

7. The modified fluidized solidified soil based on solid waste according to claim 1, wherein: The water reducing agent is polycarboxylic acid water reducing agent; The amide monomer is acrylamide; The initiator is ammonium persulfate; The pro-initiator is tetramethyl ethylenediamine; The early strength agent is chloride-based early strength agent.

8. A method of producing a modified flowable soil solidified on the basis of solid waste according to any one of claims 1 to 7, characterized in that: The amide monomer solution, initiator solution and pro-initiator solution are added to the mixture of engineering slag, slag, cement and silicate microfiber, and then water, water reducing agent and early strength agent are added to obtain a slurry.

9. A method of producing a modified flowable soil solidified soil based on solid waste according to claim 8, characterized in that: The liquid-solid mass ratio in the slurry is 0.3-0.8:

1.

10. The preparation method of the modified fluidized solidified soil based on solid waste according to claim 8 or 9, wherein: The concentration of the amide monomer solution is 200-300 g / L; The concentration of the initiator solution is 6-9 g / L; The concentration of the pro-initiator solution is 1-3 g / L.

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