A cementing material for anti-seepage sealing wall based on soft soil foundation and a preparation method thereof

Abstract

The application discloses a cementing material for anti-seepage sealing wall based on soft soil foundation and belongs to the technical field of underground anti-seepage. The cementing material is composed of the following raw materials in parts by weight: iron tailings 10 parts, silicon-aluminum rich material 50-75 parts, desulfurization ash 15-40 parts, water reducing agent 0.2 part and activator 0.3 part. The cementing slurry is mixed with in-situ soft soil grouting, the slurry has good fluidity and dispersibility, and forms a continuous and dense anti-seepage wall after solidification. The desulfurization ash releases sulfate under alkali activation, reacts with aluminate to form ettringite crystals, produces controllable volume expansion, fills the soft soil pores, reduces the connectivity and improves the impermeability. The application solves the problems of poor uniformity, high construction difficulty, unstable impermeability and the like of traditional anti-seepage walls, has the advantages of strong construction adaptability, continuous wall forming, excellent anti-seepage and the like, and can be widely applied to foundation pit, landfill, contaminated site remediation and underground water isolation engineering and the like.

Description

Technical Field

[0001] This invention relates to the field of underground seepage prevention technology, specifically to a cementitious material for seepage prevention sealing walls and its preparation method. Background Technology

[0002] In foundation pit engineering, landfill seepage prevention, contaminated site remediation, and groundwater isolation projects, seepage-proof sealing walls are typically required to prevent the migration of groundwater or pollutants. Existing seepage-proof sealing walls often take the form of cement-soil mixing walls, diaphragm walls, or bentonite walls, but these generally suffer from high construction costs, complex construction processes, high material consumption, and difficulties in ensuring the uniformity and continuity of the wall. Diaphragm walls, in particular, require high-precision construction equipment; cement-soil mixing walls are easily affected by geological inhomogeneities, resulting in significant fluctuations in wall quality; and bentonite walls, due to the high viscosity of the slurry, are prone to adhesion and deposition in the mixing equipment and slurry delivery pipelines, affecting construction efficiency and the continuity of the wall.

[0003] In practical engineering, seepage-proof sealing walls are often installed in soft strata, such as silty soil or soft soil layers with high water content. These types of soils are characterized by high water content, low strength, high compressibility, and poor structural stability. During wall construction, problems such as uneven mixing, segregation, and insufficient local strength can easily occur, affecting the overall integrity and seepage resistance of the wall. Current technologies typically involve reinforcing the soil by adding cement or other cementitious materials. However, under high water content conditions, traditional cementitious material systems have shortcomings in terms of dispersibility, fluidity, and construction efficiency, making it difficult to simultaneously achieve good construction fluidity, post-curing strength, and low permeability.

[0004] Furthermore, existing cementitious materials often suffer from shrinkage or insufficient filling during the curing process, making it difficult to fully seal soil pores and easily forming microscopic seepage channels in the wall structure, thereby reducing the seepage prevention effect. Therefore, while ensuring good grout fluidity and workability, how to improve the material's ability to fill soil pores and enhance the compactness of the cured structure to improve seepage prevention performance has become a pressing technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a cementitious material system suitable for seepage-proof sealing walls on soft soil foundations, thereby solving the technical problems of high construction costs, poor uniformity of wall formation, and unstable impermeability of existing seepage-proof sealing walls. To achieve the above objective, the cementitious material system provided by this invention includes iron tailings, silica-alumina-rich materials, desulfurization ash, water-reducing agents, and activators. Through synergistic control of the proportions of each component and the reaction process, this cementitious material system exhibits good fluidity and dispersibility in high-moisture-content soft soil environments, enabling it to fully mix with the in-situ soil and form a continuous and dense wall structure during the solidification process.

[0006] The key to this invention lies in the controllable volume expansion characteristic of the cementitious material system during the curing process. Desulfurized ash, as the main sulfate source in the system, releases sulfate ions under hydration and alkaline activation conditions. These ions react with the aluminate components in the silicon-aluminum rich material and the calcium and aluminum in the system to generate ettringite crystals (AFt). Due to the large crystal volume of ettringite crystals, their formation process causes volume expansion of the system during the curing stage. In the confined in-situ soil environment, this volume expansion process manifests as a filling effect on the pore structure, thereby reducing pore connectivity and improving the overall density and continuity of the wall structure. Compared with existing technologies, this invention utilizes the controllable volume expansion effect generated during the curing process to effectively fill and reconstruct the pores in soft soil, resulting in a more continuous and dense anti-seepage sealing wall structure, thus significantly improving impermeability. Simultaneously, the system retains good fluidity and construction adaptability, enabling in-situ mixing and grouting for wall formation, reducing construction difficulty and improving engineering applicability.

[0007] This invention is achieved through the following technical solution: The present invention discloses a cementitious material for seepage prevention and sealing walls in soft soil foundations, which is composed of iron tailings, silicon-aluminum rich materials, desulfurization ash, water-reducing agent and activator. After the cementitious material is mixed with water to form a cementitious slurry, it has good fluidity, dispersibility and controllable volume expansion characteristics, and can be fully mixed with in-situ soft soil and solidified to form a continuous and dense structure.

[0008] The cementitious material used in this invention is composed of the following components in parts by weight: 10 portions of iron tailings 50-75 parts of silicon-rich aluminum material 15-40 parts of desulfurization ash 0.2 parts water-reducing agent 0.3 parts of activator A further technical solution of the above-mentioned cementitious material of the present invention is that the mass content of each component of the iron tailings material is as shown in the table below:

[0009] A further technical solution of the above-mentioned cementitious material of the present invention may be that the mass content percentage of each component of the silicon-rich aluminum material is as shown in the table below:

[0010] A further technical solution of the cementitious material described above in this invention may be that the mass content percentage of each component of the desulfurization ash material is as shown in the table below:

[0011] A further technical solution of the above-mentioned cementitious material of the present invention may be that the mass content percentage of each component of the activator is as shown in the table below:

[0012] A further technical solution of the above-mentioned cementitious material of the present invention may be that the water-reducing agent is a polycarboxylate superplasticizer (PCE), the properties of which are shown in the table below:

[0013] A method for preparing a cementitious material for a seepage-proof sealing wall includes the following steps: S1. Dry the iron tailings, silicon-aluminum-rich materials, and desulfurization ash to ensure that the moisture content of the powder raw materials is ≤1%; S2. Weigh out the pretreated iron tailings, silicon-aluminum-rich materials, desulfurization ash, water-reducing agent and activator according to the proportions. S3. Premix the iron tailings, silicon-aluminum-rich materials, desulfurization ash, water-reducing agent and activator to form a uniform powder mixing system. S4. Add water to the powder mixing system and stir to make a slurry, thereby obtaining a cementitious material slurry.

[0014] The beneficial effects of this invention are as follows: This invention utilizes a grouting and mixing method to thoroughly mix the cementitious grout with the in-situ soil, achieving in-situ improvement of weak strata and enhancing the uniformity and integrity of the resulting wall. Simultaneously, the cementitious material system exhibits controllable volume expansion during curing, filling soil pores and reducing pore connectivity. This results in a more continuous and dense wall structure, significantly improving impermeability and effectively preventing the migration of groundwater and pollutants. Furthermore, the cementitious grout system used in this invention possesses excellent fluidity and dispersibility, exhibiting strong construction adaptability, improving construction efficiency, and reducing construction difficulty. Attached Figure Description

[0015] Figure 1 The X-ray diffraction (XRD) pattern of the silt; Figure 2 This is a scanning electron microscope image of the silt. Figure 3 This is a scanning electron microscope image of the cementitious material. Detailed Implementation

[0016] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0017] Any feature disclosed in this specification (including any appended claims and abstract) may be replaced by other equivalent or similar features, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features. Example 1

[0018] A cementitious material for seepage-proof sealing walls in soft soil foundations is prepared from the following raw materials in parts by weight: 10 parts iron tailings, 50 parts silica-alumina rich material, 40 parts desulfurization ash, 0.2 parts water-reducing agent, and 0.3 parts activator, with a constant water-cement ratio of 0.7. First, the iron tailings, silica-alumina rich material, desulfurization ash, water-reducing agent, and activator are weighed according to the proportions, and the powder raw materials are pre-mixed. Then, water is added and stirred for 4 minutes to prepare a uniform cementitious slurry. The flowability of the prepared cementitious slurry is tested: a cylindrical mold with upper and lower diameters of 36 mm and 60 mm respectively, and a height of 80 mm, is placed on a smooth glass plate. The slurry is slowly filled into the mold, and then the mold is raised at a uniform speed. The slump expansion diameter and its vertical diameter of the slurry are measured, and the average value is taken as the slurry flowability. The flowability changes at 0 h, 1 h, and 2 h are tested, and the results are shown in Table 1.

[0019] After completing the flowability test, the volumetric expansion rate of the cementitious material was tested. The test method was in accordance with JC / T313-2019 "Test Method for Expansion Rate of Expansive Cement". The prepared slurry was poured into molds of specified size and cured under standard curing conditions. The volumetric expansion rate was tested at 7 days, 14 days and 28 days. The test results are shown in Table 2.

[0020] Silt from the dredged area of ​​the waterway and port was used as the in-situ soil, with its moisture content constantly controlled at 70%. A cementitious slurry was added at 15% of the silt mass and stirred for 4 minutes to ensure uniform mixing. The prepared mixture was poured into a 40×40×40 mm cubic mold and cured for 7, 14, and 28 days at a temperature of 20±2 ℃ and a relative humidity of approximately 95%. The compressive strength test results are shown in Table 3. After 28 days of curing, the permeability coefficient was determined according to the variable head permeability test method specified in GB / T50123-2019. The test results are shown in Table 4.

[0021] Microstructure analysis was performed on the cured body after 28 days of curing. Figure 1 The XRD pattern of the silt used shows its main mineral composition. Figure 2 The image shows a scanning electron microscope (SEM) image of the original silt, revealing its loose structure and well-developed pores. Figure 3The image shows a scanning electron microscope image of the cementitious material of the present invention after curing. It can be seen that a large number of ettringite crystals are generated and fill the pores, resulting in a dense structure, which confirms the effective sealing effect of controllable volume expansion on the pores. Example 2

[0022] A cementitious material for seepage-proof sealing walls in soft soil foundations is prepared from the following raw materials in parts by weight: 10 parts iron tailings, 55 parts silica-alumina rich material, 35 parts desulfurization ash, 0.2 parts water-reducing agent, and 0.3 parts activator, with a constant water-cement ratio of 0.7. First, the iron tailings, silica-alumina rich material, desulfurization ash, water-reducing agent, and activator are weighed according to the specified ratio, and the powder raw materials are pre-mixed. Then, water is added and stirred for 4 minutes to prepare a uniform cementitious slurry. The flowability of the prepared cementitious slurry is tested: a cylindrical mold with upper and lower diameters of 36 mm and 60 mm respectively, and a height of 80 mm, is placed on a smooth glass plate. The slurry is slowly filled into the mold, and then the mold is raised at a uniform speed. The slump expansion diameter and its vertical diameter of the slurry are measured, and the average value is taken as the slurry flowability. The flowability changes at 0 h, 1 h, and 2 h are tested, and the results are shown in Table 1.

[0023] After completing the flowability test, the volumetric expansion rate of the cementitious material was tested. The test method was in accordance with JC / T313-2019 "Test Method for Expansion Rate of Expansive Cement". The prepared slurry was poured into molds of specified size and cured under standard curing conditions. The volumetric expansion rate was tested at 7 days, 14 days and 28 days. The test results are shown in Table 2.

[0024] Silt from the dredged area of ​​the waterway and port was used as the in-situ soil, with its moisture content constantly controlled at 70%. A cementitious slurry was added at 15% of the silt mass and stirred for 4 minutes to ensure uniform mixing. The prepared mixture was poured into a 40×40×40 mm cubic mold and cured for 7, 14, and 28 days at a temperature of 20±2 ℃ and a relative humidity of approximately 95%. The compressive strength test results are shown in Table 3. After 28 days of curing, the permeability coefficient was determined according to the variable head permeability test method specified in GB / T50123-2019. The test results are shown in Table 4. Example 3

[0025] A cementitious material for seepage-proof sealing walls in soft soil foundations is prepared from the following raw materials in parts by weight: 10 parts iron tailings, 60 parts silica-alumina rich material, 30 parts desulfurization ash, 0.2 parts water-reducing agent, and 0.3 parts activator, with a constant water-cement ratio of 0.7. First, the iron tailings, silica-alumina rich material, desulfurization ash, water-reducing agent, and activator are weighed according to the proportions, and the powder raw materials are pre-mixed. Then, water is added and stirred for 4 minutes to prepare a uniform cementitious slurry. The flowability of the prepared cementitious slurry is tested: a cylindrical mold with upper and lower diameters of 36 mm and 60 mm respectively, and a height of 80 mm, is placed on a smooth glass plate. The slurry is slowly filled into the mold, and then the mold is raised at a uniform speed. The slump expansion diameter and its vertical diameter of the slurry are measured, and the average value is taken as the slurry flowability. The flowability changes at 0 h, 1 h, and 2 h are tested, and the results are shown in Table 1.

[0026] After completing the flowability test, the volumetric expansion rate of the cementitious material was tested. The test method was in accordance with JC / T313-2019 "Test Method for Expansion Rate of Expansive Cement". The prepared slurry was poured into molds of specified size and cured under standard curing conditions. The volumetric expansion rate was tested at 7 days, 14 days and 28 days. The test results are shown in Table 2.

[0027] Silt from the dredged area of ​​the waterway and port was used as the in-situ soil, with its moisture content constantly controlled at 70%. A cementitious slurry was added at 15% of the silt mass and stirred for 4 minutes to ensure uniform mixing. The prepared mixture was poured into a 40×40×40 mm cubic mold and cured for 7, 14, and 28 days at a temperature of 20±2 ℃ and a relative humidity of approximately 95%. The compressive strength test results are shown in Table 3. After 28 days of curing, the permeability coefficient was determined according to the variable head permeability test method specified in GB / T50123-2019. The test results are shown in Table 4. Example 4

[0028] A cementitious material for seepage-proof sealing walls in soft soil foundations is prepared from the following raw materials in parts by weight: 10 parts iron tailings, 65 parts silica-alumina rich material, 25 parts desulfurization ash, 0.2 parts water-reducing agent, and 0.3 parts activator, with a constant water-cement ratio of 0.7. First, the iron tailings, silica-alumina rich material, desulfurization ash, water-reducing agent, and activator are weighed according to the specified ratio, and the powder raw materials are pre-mixed. Then, water is added and stirred for 4 minutes to prepare a uniform cementitious slurry. The flowability of the prepared cementitious slurry is tested: a cylindrical mold with upper and lower diameters of 36 mm and 60 mm respectively, and a height of 80 mm, is placed on a smooth glass plate. The slurry is slowly filled into the mold, and then the mold is raised at a uniform speed. The slump expansion diameter and its vertical diameter of the slurry are measured, and the average value is taken as the slurry flowability. The flowability changes at 0 h, 1 h, and 2 h are tested, and the results are shown in Table 1.

[0029] After completing the flowability test, the volumetric expansion rate of the cementitious material was tested. The test method was in accordance with JC / T313-2019 "Test Method for Expansion Rate of Expansive Cement". The prepared slurry was poured into molds of specified size and cured under standard curing conditions. The volumetric expansion rate was tested at 7 days, 14 days and 28 days. The test results are shown in Table 2.

[0030] Silt from the dredged area of ​​the waterway and port was used as the in-situ soil, with its moisture content constantly controlled at 70%. A cementitious slurry was added at 15% of the silt mass and stirred for 4 minutes to ensure uniform mixing. The prepared mixture was poured into a 40×40×40 mm cubic mold and cured for 7, 14, and 28 days at a temperature of 20±2 ℃ and a relative humidity of approximately 95%. The compressive strength test results are shown in Table 3. After 28 days of curing, the permeability coefficient was determined according to the variable head permeability test method specified in GB / T50123-2019. The test results are shown in Table 4. Example 5

[0031] A cementitious material for seepage-proof sealing walls in soft soil foundations is prepared from the following raw materials in parts by weight: 10 parts iron tailings, 70 parts silica-alumina rich material, 20 parts desulfurization ash, 0.2 parts water-reducing agent, and 0.3 parts activator, with a constant water-cement ratio of 0.7. First, the iron tailings, silica-alumina rich material, desulfurization ash, water-reducing agent, and activator are weighed according to the proportions, and the powder raw materials are pre-mixed. Then, water is added and stirred for 4 minutes to prepare a uniform cementitious slurry. The flowability of the prepared cementitious slurry is tested: a cylindrical mold with upper and lower diameters of 36 mm and 60 mm respectively, and a height of 80 mm, is placed on a smooth glass plate. The slurry is slowly filled into the mold, and then the mold is raised at a uniform speed. The slump expansion diameter and its vertical diameter of the slurry are measured, and the average value is taken as the slurry flowability. The flowability changes at 0 h, 1 h, and 2 h are tested, and the results are shown in Table 1.

[0032] After completing the flowability test, the volumetric expansion rate of the cementitious material was tested. The test method was in accordance with JC / T313-2019 "Test Method for Expansion Rate of Expansive Cement". The prepared slurry was poured into molds of specified size and cured under standard curing conditions. The volumetric expansion rate was tested at 7 days, 14 days and 28 days. The test results are shown in Table 2.

[0033] Silt from the dredged area of ​​the waterway and port was used as the in-situ soil, with its moisture content constantly controlled at 70%. A cementitious slurry was added at 15% of the silt mass and stirred for 4 minutes to ensure uniform mixing. The prepared mixture was poured into a 40×40×40 mm cubic mold and cured for 7, 14, and 28 days at a temperature of 20±2 ℃ and a relative humidity of approximately 95%. The compressive strength test results are shown in Table 3. After 28 days of curing, the permeability coefficient was determined according to the variable head permeability test method specified in GB / T50123-2019. The test results are shown in Table 4. Example 6

[0034] A cementitious material for seepage-proof sealing walls in soft soil foundations is prepared from the following raw materials in parts by weight: 10 parts iron tailings, 75 parts silica-alumina rich material, 15 parts desulfurization ash, 0.2 parts water-reducing agent, and 0.3 parts activator, with a constant water-cement ratio of 0.7. First, the iron tailings, silica-alumina rich material, desulfurization ash, water-reducing agent, and activator are weighed according to the proportions, and the powder raw materials are pre-mixed. Then, water is added and stirred for 4 minutes to prepare a uniform cementitious slurry. The flowability of the prepared cementitious slurry is tested: a cylindrical mold with upper and lower diameters of 36 mm and 60 mm respectively, and a height of 80 mm, is placed on a smooth glass plate. The slurry is slowly filled into the mold, and then the mold is raised at a uniform speed. The slump expansion diameter and its vertical diameter of the slurry are measured, and the average value is taken as the slurry flowability. The flowability changes at 0 h, 1 h, and 2 h are tested, and the results are shown in Table 1.

[0035] After completing the flowability test, the volumetric expansion rate of the cementitious material was tested. The test method was in accordance with JC / T313-2019 "Test Method for Expansion Rate of Expansive Cement". The prepared slurry was poured into molds of specified size and cured under standard curing conditions. The volumetric expansion rate was tested at 7 days, 14 days and 28 days. The test results are shown in Table 2.

[0036] Silt from the dredged area of ​​the waterway and port was used as the in-situ soil, with its moisture content constantly controlled at 70%. A cementitious slurry was added at 15% of the silt mass and stirred for 4 minutes to ensure uniform mixing. The prepared mixture was poured into a 40×40×40 mm cubic mold and cured for 7, 14, and 28 days at a temperature of 20±2 ℃ and a relative humidity of approximately 95%. The compressive strength test results are shown in Table 3. After 28 days of curing, the permeability coefficient was determined according to the variable head permeability test method specified in GB / T50123-2019. The test results are shown in Table 4.

[0037]

[0038]

[0039]

[0040]

[0041] As shown in Tables 1-4, the cementitious material system of this invention possesses good fluidity, controllable volume expansion characteristics, and superior mechanical and impermeability properties. Specifically, the grout maintains good fluidity under different mixing ratios, meeting the requirements of in-situ grouting construction. During the curing process, the system undergoes moderate volume expansion, which is beneficial for filling soil pores and improving structural density. With increasing curing age, the compressive strength of the cured body continuously increases, and all embodiments exhibit low permeability coefficients. The results indicate that this invention achieves comprehensive optimization of fluidity, strength, and impermeability through the synergistic effect between its components, meeting the application requirements of seepage prevention and sealing wall projects in soft soil foundations.

[0042] The basic teachings of the invention have been described, and many extensions and variations will be readily apparent to those skilled in the art. Since the invention disclosed in the specification can be practiced in other specific forms without departing from the spirit or general characteristics of the invention, and some of these specific forms have been pointed out, the embodiments disclosed in the specification should be considered illustrative rather than limiting. The scope of the invention is defined by the appended claims, not by the foregoing description, and all modifications of equal meaning and scope falling within the claims are included within their scope.

Claims

1. A cementitious material for use in seepage-proof sealing walls, characterized in that, The cementitious material is prepared from the following raw materials in the indicated weight fractions: 10 portions of iron tailings; 50-75 parts of silicon-rich aluminum material; 15-40 parts of desulfurization ash; 0.2 parts water-reducing agent; 0.3 parts of activator.

2. The cementitious material according to claim 1, characterized in that, The percentage of mass content of each component in the iron tailings is shown in the table below:

3. The cementitious material according to claim 1, characterized in that, The percentage of mass content of each component in the silicon-rich aluminum material is shown in the table below:

4. The cementitious material according to claim 1, characterized in that, The percentage of each component in the desulfurization ash is shown in the table below:

5. The cementitious material according to claim 1, characterized in that, The percentage mass content of each component of the activator is shown in the table below:

6. The cementitious material for a seepage-proof sealing wall according to claim 1, characterized in that, The preparation method of the cementitious material includes the following steps: S1. Dry the iron tailings, silicon-aluminum-rich materials, and desulfurization ash to ensure that the moisture content of the powder raw materials is ≤1%; S2. Weigh out the pretreated iron tailings, silicon-aluminum-rich materials, desulfurization ash, water-reducing agent and activator according to the proportions. S3. Premix the iron tailings, silicon-aluminum-rich materials, desulfurization ash, water-reducing agent and activator to form a uniform powder mixing system. S4. Add water to the powder mixing system and stir to make a slurry, thereby obtaining a cementitious material slurry.

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