A seepage-proof concrete for water conservancy and hydropower projects and its preparation method

Abstract

This application relates to a seepage barrier concrete for water conservancy and hydropower projects and its preparation method. The seepage barrier concrete comprises water, polyacrylate emulsion, cementitious materials, coarse aggregate, fine aggregate, water-reducing agent, defoamer, air-entraining agent, synthetic fibers, and unavoidable impurities. The mass ratio of the sum of water and polyacrylate emulsion to the cementitious materials is 0.30–0.40, and the amount of coarse aggregate is 900–1100 kg / m³. 3 The dosage of fine aggregate is 600-850 kg / m³. 3 The sand content is 40%–46%; the dosage of polyacrylate emulsion is 5%–20% of the cementitious material mass; the dosage of water-reducing agent is 0.6%–1.2% of the cementitious material mass; the dosage of defoamer is 0.8%–1.5% of the cementitious material mass; the dosage of air-entraining agent is 0.2%–0.5% of the cementitious material mass; and the dosage of synthetic fiber is 0.5%–2.0% of the total volume of the anti-seepage wall concrete.

Description

Technical Field

[0001] This application relates to the field of water conservancy and hydropower engineering technology, specifically to a seepage-proof wall concrete for water conservancy and hydropower engineering and its preparation method. Background Technology

[0002] Over the past decade, my country has continuously increased its investment in water conservancy and hydropower, and water conservancy and hydropower projects have maintained a high-speed development trend. However, as water conservancy and hydropower construction expands to the west, the deep overburden layers of riverbeds in the western region have gradually become a limitation of existing technologies, making earth-rock dams the only option for dam construction on overburden layers. In particular, with the changing demands for dam construction and the development of dam construction technology, the scale of construction has continued to increase, dams are becoming higher and higher, seepage prevention is becoming deeper and deeper, and the difficulty is becoming greater and greater. Especially for 100-meter-class high dams, if the dam foundation seepage prevention treatment is not up to standard, it will bring great pressure to the later operation and maintenance management. Therefore, effective control of dam foundation seepage and seepage deformation is a prerequisite for ensuring the safety of high earth-rock dams on deep overburden layers.

[0003] Based on domestic and international engineering examples, concrete cutoff walls are currently the most effective means of preventing seepage in deep overburden layers. A commonly used concrete cutoff wall technology involves adding a certain amount of bentonite or clay to conventional concrete to obtain low-strength, low-elasticity plastic concrete. With the development of engineering scale and technology, the practical application of concrete cutoff walls has far exceeded the scope of seepage prevention. It needs to address engineering issues such as erosion control, reinforcement, load-bearing capacity, and underground interception. In particular, as the scale of dam construction continues to increase, the water head or pressure that the cutoff wall bears is increasing, leading to increased internal forces within the wall. Traditional low-strength, low-elasticity plastic concrete can no longer meet the requirements. Ordinary rigid concrete, due to its large elastic modulus, cannot coordinate with the deformation of the foundation, and is prone to stress concentration and failure under load. Summary of the Invention

[0004] The first aspect of this application provides a seepage barrier concrete for water conservancy and hydropower projects. This seepage barrier concrete has the characteristics of low early strength, high later strength, low elastic modulus, small elastic strength ratio, large ultimate deformation, and high seepage resistance. In actual construction, it can improve the crack resistance of the seepage barrier, thereby enhancing the safety of the seepage barrier and ensuring the quality of the project.

[0005] The impermeable wall concrete comprises water, polyacrylate emulsion, cementitious materials, coarse aggregate, fine aggregate, water-reducing agent, defoamer, air-entraining agent, synthetic fibers, and unavoidable impurities; the mass ratio of the sum of water and the polyacrylate emulsion to the cementitious materials is 0.30–0.40, and the amount of coarse aggregate is 900–1100 kg / m³. 3 The amount of fine aggregate used is 600-850 kg / m³. 3The sand content is 40%–46%; the amount of polyacrylate emulsion is 5%–20% of the mass of the cementitious material; the amount of water-reducing agent is 0.6%–1.2% of the mass of the cementitious material; the amount of defoamer is 0.8%–1.5% of the mass of the cementitious material; the amount of air-entraining agent is 0.2%–0.5% of the mass of the cementitious material; and the amount of synthetic fiber is 0.5%–2.0% of the total volume of the impermeable wall concrete.

[0006] In addition, the anti-seepage wall concrete provided in this application may also have the following additional technical features:

[0007] In one alternative embodiment, the cementitious material comprises cement, silica fume, and fly ash, and the total dosage of the cementitious material is 450–500 kg / m³. 3 The sand content is 40% to 46%; the amount of silica fume in the cementitious material is 3% to 5% of the mass of the cementitious material; the amount of fly ash is 50% to 60% of the mass of the cementitious material.

[0008] In one alternative embodiment, the cement is low-heat or medium-heat silicate cement containing MgO, and the MgO content satisfies: 3.5% ≤ MgO ≤ 5.0%; the silica fume is dense silica fume, and the fly ash is Class F I fly ash.

[0009] In one alternative embodiment, the coarse aggregate comprises a first coarse aggregate with a particle size of 5 to 20 mm and a second coarse aggregate with a particle size of 20 to 40 mm, wherein the ratio of the first coarse aggregate to the second coarse aggregate is 65%:35% to 75%:25%.

[0010] In one alternative embodiment, the porosity of the coarse aggregate is ≤43%; and the fineness modulus of the fine aggregate is 2.8 to 3.2.

[0011] In one optional embodiment, the polyacrylate emulsion has a solids content of 40% to 60%, the water-reducing agent is a retarding polycarboxylate high-performance water-reducing agent, and the water reduction rate of the water-reducing agent is not less than 30%; the defoamer is an organosilicon defoamer; and the air-entraining agent is a foam-stabilizing air-entraining agent.

[0012] In one alternative embodiment, the synthetic fiber is at least one of high-strength, high-modulus chopped polyvinyl alcohol (PVA) fiber, polyvinyl chloride (PE) fiber, and polypropylene (PP) fiber.

[0013] The second aspect of this application provides a method for preparing anti-seepage wall concrete for water conservancy and hydropower projects. This method is used to prepare the anti-seepage wall concrete in the first aspect embodiment, and the method includes the following steps:

[0014] 1) Weigh water, polyacrylate emulsion, cementitious materials, coarse aggregate, fine aggregate, water-reducing agent, defoamer, air-entraining agent and synthetic fiber according to the preset ratio. The cementitious materials include cement, silica fume and fly ash.

[0015] 2) Weigh 2 / 3 of the mixing water, add the water-reducing agent, defoamer, and polyacrylate emulsion to the water and stir evenly to prepare a liquid for later use; weigh 1 / 3 of the mixing water, add the air-entraining agent to the water and stir evenly to prepare a diluted air-entraining agent for later use.

[0016] 3) Add fine aggregate and coarse aggregate to a forced mixer and mix for 30 seconds; then pour cement, silica fume, fly ash and synthetic fiber into a mixing pot and mix for 90-120 seconds; then add the evenly mixed liquid agent in 30-second intervals during the mixing process and continue mixing for 60-90 seconds; finally, add the diluted air-entraining agent in 30-second intervals during the mixing process and continue mixing for 60-90 seconds to make the impermeable wall concrete.

[0017] In one alternative embodiment, after the impermeable wall concrete is made, the slump of the impermeable wall concrete is 160-220 mm, and the compressive strength of the impermeable wall concrete after 90 days of age is greater than 40 MPa and the elastic modulus is less than 25 GPa.

[0018] The beneficial effects of this application are as follows:

[0019] The anti-seepage wall concrete and its preparation method described in this application increase the workability of concrete by incorporating polyacrylate emulsion. After hardening, a flexible mesh film structure is formed in the concrete, improving the system structure of the composite cementitious material and the bonding morphology with aggregates. This enhances the toughness and durability of the concrete with minimal impact on compressive strength. Simultaneously, the elastic modulus of the polyacrylate emulsion is much lower than that of the composite cementitious material system, significantly reducing the elastic modulus of the concrete. Furthermore, through the combined action of defoamer and air-entraining agent, the defoamer eliminates large, unstable air bubbles introduced by the mixing of the polyacrylate emulsion, while the air-entraining agent introduces a large number of small, independent, and stable air bubbles, achieving an air content of 7% ± 1.0% in the concrete. Combined with the material properties of fibers, this significantly reduces early drying shrinkage, effectively lowers the elastic modulus of the concrete, and substantially improves its durability.

[0020] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Detailed Implementation

[0021] To better understand the technical solution of this application, the embodiments of this application will be described in detail.

[0022] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0023] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0024] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0025] With the development of engineering scale and technology, the actual application of concrete cutoff walls has far exceeded the scope of seepage prevention. It is necessary to take into account engineering problems such as erosion prevention, reinforcement, load bearing and underground interception. In particular, as the scale of dam construction continues to increase, the water head or pressure that the cutoff wall bears is increasing, and the internal forces of the wall are increasing. Traditional low-strength and low-elasticity plastic concrete can no longer meet the requirements. Ordinary rigid concrete, due to its large elastic modulus, cannot coordinate with the deformation of the foundation and is prone to stress concentration and failure when bearing loads.

[0026] Taking the Xiaolangdi Hydropower Station in my country as an example, the concrete design strength of the right bank cutoff wall of the Xiaolangdi main dam is 35 MPa, making it the highest strength cutoff wall in my country to date. Initially, ordinary concrete was used, but its high early strength (30.7 MPa at 5 days and 44.7 MPa at 23 days) made drilling joint holes extremely difficult. During construction, slow-setting high-strength concrete was used, alleviating the difficulties caused by the excessively high strength of the wall concrete and setting a new record for cutoff wall depth at the time (82m). Considering the technical performance of cutoff wall concrete with depths exceeding 100m that have been built or are under construction in my country in recent years, dam cutoff wall concrete exhibits a unique strength development pattern. For high dams with deep walls, the design generally requires a 28-day compressive strength of no more than 25 MPa, a 90-day compressive strength of no less than 40 MPa, and a 90-day elastic modulus of no more than 25 GPa. This high-strength, low-elasticity concrete wall material is a typical example of concrete with low early strength, high later strength, and low elastic modulus. Concrete exhibits a slow increase in early-stage strength followed by a rapid increase in later-stage strength, which is the opposite of the strength development pattern of ordinary concrete. This is especially true as the government increases investment in infrastructure and places greater emphasis on environmental protection, leading to the widespread use of manufactured sand and crushed stone. Using manufactured sand and crushed stone in concrete formulation further complicates the process of reducing the elastic modulus of concrete. Therefore, the commonly used technical approach is to minimize the elastic modulus while maintaining overall strength.

[0027] In this regard, the present application provides a method for preparing anti-seepage wall concrete for water conservancy and hydropower projects. The anti-seepage wall concrete has the characteristics of low early strength, high later strength, low elastic modulus, small elastic strength ratio, large ultimate deformation, and high impermeability. In actual construction, it can improve the crack resistance of the anti-seepage wall, thereby greatly enhancing the safety of the anti-seepage wall and ensuring the quality of the project.

[0028] The first aspect of this application provides a seepage barrier concrete for water conservancy and hydropower projects. The seepage barrier concrete comprises water, polyacrylate emulsion, cementitious materials, coarse aggregate, fine aggregate, water-reducing agent, defoamer, air-entraining agent, synthetic fibers, and unavoidable impurities. The mass ratio of the sum of water and polyacrylate emulsion to the cementitious materials is 0.30–0.40, and the amount of coarse aggregate is 900–1100 kg / m³. 3 The dosage of fine aggregate is 600-850 kg / m³. 3 The sand content is 40%–46%; the dosage of polyacrylate emulsion is 5%–20% of the cementitious material mass; the dosage of water-reducing agent is 0.6%–1.2% of the cementitious material mass; the dosage of defoamer is 0.8%–1.5% of the cementitious material mass; the dosage of air-entraining agent is 0.2%–0.5% of the cementitious material mass; and the dosage of synthetic fiber is 0.5%–2.0% of the total volume of the anti-seepage wall concrete.

[0029] This anti-seepage wall concrete incorporates a certain proportion of polyacrylate emulsion, increasing its workability. After hardening, it forms a flexible mesh-like film structure within the concrete, improving the bonding between the composite cementitious material system and aggregates. This enhances the concrete's toughness and durability with minimal impact on compressive strength. Simultaneously, the elastic modulus of the polyacrylate emulsion is significantly lower than that of the composite cementitious material system, substantially reducing the concrete's elastic modulus. Furthermore, the combined action of defoamers and air-entraining agents eliminates large, unstable air bubbles introduced during polyacrylate emulsion mixing, while the air-entraining agent introduces numerous small, independent, and stable air bubbles, achieving an air content of 7% ± 1.0%. Combined with the material properties of fibers, this significantly reduces early drying shrinkage, effectively lowers the concrete's elastic modulus, and substantially improves its durability.

[0030] In one specific embodiment, the cementitious material includes cement, silica fume, and fly ash, and the total amount of cementitious material is 450–500 kg / m³. 3 The sand content is 40%–46%; the silica fume content in the cementitious material is 3%–5% of the cementitious material mass; the fly ash content is 50%–60% of the cementitious material mass.

[0031] This embodiment utilizes a large amount of high-quality Grade I fly ash, which significantly reduces the early strength of concrete. Simultaneously, the combined synergistic effect of fly ash and silica fume fully activates the admixtures. The large amount of SiO2 in the admixtures participates in the secondary hydration of cement, ensuring a significant increase in later-stage strength. This results in a significant improvement in the tensile strength and ultimate tensile value of the concrete, while the elastic modulus remains essentially unchanged or slightly decreases, further enhancing the concrete's crack resistance. The impermeable wall concrete prepared using a material combination of high-magnesium low-heat or medium-heat silicate cement, silica fume, fly ash, polyacrylate emulsion, defoamer and air-entraining agent, and fiber exhibits low early-stage hydration heat and shrinkage. While its 28-day compressive strength is low, the increase in compressive strength after 28 days is substantial, reaching over 40 MPa at 90 days. The compressive elastic modulus at 90 days is less than 25 GPa, and durability is significantly improved, making it far superior to impermeable wall concrete prepared using existing technologies.

[0032] Specifically, the cement is P.LH42.5 low-heat silicate cement or P.MH42.5 medium-heat silicate cement, which meets the technical requirements of "Medium-heat Silicate Cement and Low-heat Silicate Cement" (GB / T200-2017), with a MgO content of 3.5% ≤ 5.0%. High-magnesium low-heat or medium-heat cement with low heat of hydration in the early stage is used to offset the volume shrinkage of the anti-seepage wall concrete during the cooling stage, reduce early drying shrinkage, and increase the early environmental adaptability of the anti-seepage wall concrete. A design age of 90 days is adopted to make full use of the later strength of low-heat or medium-heat silicate cement.

[0033] Furthermore, the silica fume used is a dense silica fume that meets the technical requirements of the "Technical Specification for Silica Fume Admixture in Hydraulic Concrete" (DL / T5777-2018). The incorporation of silica fume can significantly improve the bonding strength of concrete, reduce bleeding and segregation, reduce the coarser pores in the concrete, and improve the durability of the concrete. In addition, the incorporation of silica fume increases the volume of the concrete paste, which can further improve the deformation capacity of the concrete and increase the later strength of the concrete, while relatively reducing the elastic modulus.

[0034] The fly ash used is Class F, Grade I fly ash, which meets the technical requirements of the "Technical Specification for Fly Ash Admixture in Hydraulic Concrete" (DL / T 5055-2007). By adding a large amount of high-quality Grade I fly ash to concrete, the workability of the concrete is increased. Utilizing the characteristic that fly ash participates in secondary hydration later, while reducing the early strength of the concrete, its long-term strength and impermeability are improved, and the drying shrinkage of the concrete is reduced, without increasing the elastic modulus of the concrete.

[0035] In one specific embodiment, the coarse aggregate is produced by crushing excavated material through an aggregate production and processing system. It is available in two sizes: 5–20 mm and 20–40 mm, with a ratio of 65%:35%–75%:25%. The performance of the coarse aggregate meets the relevant technical requirements for aggregates in the "Specification for Construction of Hydraulic Concrete" (DL / T 5144-2015), and it does not pose a potential alkali reactivity hazard, with a porosity ≤43%. The fine aggregate is manufactured sand produced by crushing excavated material through an aggregate production and processing system, with a fineness modulus of 2.8–3.2. Its performance meets the relevant technical requirements for aggregates in the "Specification for Construction of Hydraulic Concrete" (DL / T 5144-2015), and it does not pose a potential alkali reactivity hazard.

[0036] In one specific embodiment, the polyacrylate emulsion has a solids content of 40% to 60%. The incorporation of the polyacrylate emulsion can wet and lubricate the artificial aggregate, compensating for the shortcomings of manufactured sand's angularity and rough surface, overcoming the adverse effects of its irregular shape, and increasing the fluidity, cohesiveness, and water retention of concrete. Simultaneously, the elastic modulus of the polyacrylate emulsion is much lower than that of the composite cementitious material system, significantly reducing the elastic modulus of concrete.

[0037] The water-reducing agent is a retarded polycarboxylate high-performance water-reducing agent that meets the technical requirements of "Concrete Admixtures" (GB 8076-2008) and has a water reduction rate of not less than 30%. The use of a high water reduction rate retarded polycarboxylate high-performance water-reducing agent reduces the unit water consumption of concrete, reduces the amount of cement, and reduces the elastic modulus of concrete.

[0038] The defoamer is an organosilicon defoamer whose performance meets the technical requirements of "Organosilicon Defoamers" (GB / T 26527-2011); the air-entraining agent is a foam-stabilizing air-entraining agent whose performance meets the technical requirements of "Concrete Admixtures" (GB 8076-2008). The combination of an organosilicon defoamer and a foam-stabilizing air-entraining agent eliminates large, unstable air bubbles introduced by the mixing of polyacrylate emulsions, and introduces a large number of tiny, independent, and stable small air bubbles, achieving an air content of 7% ± 1.0% in the concrete. These tiny, independent, and stable air bubbles significantly improve the workability of the concrete mixture and have excellent slump retention, effectively reducing the elastic modulus of the concrete while improving its durability.

[0039] In one specific embodiment, the synthetic fiber is high-strength, high-modulus, short-cut polyvinyl alcohol (PVA) fiber or one or more of polyvinyl (PE) and polypropylene (PP) fibers. By incorporating fibers that are well-suited to concrete, the problem of excessive early drying shrinkage in the anti-seepage wall concrete due to high air content is reduced, the formation of early shrinkage cracks is decreased, and the durability of the concrete is significantly improved.

[0040] The second aspect of this application provides a method for preparing anti-seepage wall concrete for water conservancy and hydropower projects. This method is used to prepare the anti-seepage wall concrete in the first aspect embodiment, and the method includes the following steps:

[0041] 1) Weigh water, polyacrylate emulsion, cementitious materials, coarse aggregate, fine aggregate, water-reducing agent, defoamer, air-entraining agent and synthetic fiber according to the preset ratio. Cementitious materials include cement, silica fume and fly ash.

[0042] 2) Weigh 2 / 3 of the mixing water, add the water-reducing agent, defoamer, and polyacrylate emulsion to the water and stir evenly to prepare a liquid for later use; weigh 1 / 3 of the mixing water, add the air-entraining agent to the water and stir evenly to prepare a diluted air-entraining agent for later use.

[0043] 3) Add fine and coarse aggregates to a forced mixer and mix for 30 seconds; then pour cement, silica fume, fly ash, and synthetic fibers into a mixing pot and mix for 90–120 seconds; next, add the uniformly mixed liquid agent evenly over 30 seconds during the mixing process, and continue mixing for 60–90 seconds; finally, add the diluted air-entraining agent evenly over 30 seconds during the mixing process, and continue mixing for 60–90 seconds to produce the impermeable wall concrete. Pour the mixed concrete into molds and cure at 20–25°C for no less than 24 hours before demolding, and then cure according to standard for 90 days.

[0044] The anti-seepage wall concrete prepared according to this method has a slump of 160-220mm and a 28-day compressive strength of less than 25MPa. However, the strength increase after 28 days is relatively large, and the strength after 90 days can reach more than 40MPa. However, its elastic modulus is less than 25GPa. When used in actual construction, it can improve the crack resistance of the anti-seepage wall and play an important role in improving the safety of the project.

[0045] The technical solution of this application will be further described below with reference to more specific embodiments:

[0046] A certain hydropower station reservoir adopts an asphalt concrete core rockfill dam with a maximum dam height exceeding 100m. The dam body cover layer adopts a fully enclosed concrete cutoff wall for seepage prevention. The cutoff wall is 1.2m thick and has a maximum depth of approximately 120m. The physical properties of the cutoff wall concrete construction include: concrete slump of 18-22cm, spread of 35-50cm, slump retention time of 150mm or more for no less than 1 hour, compressive strength at 28 days ≤25MPa, compressive strength at 90 days ≥40MPa, elastic modulus not greater than 25GPa, impermeability grade ≥W10, and frost resistance grade ≥F100.

[0047] The raw materials are as follows: cement is low-heat silicate cement with an MgO content of 4.02%; coarse aggregate is crushed limestone from engineering excavation, composed of small stones (5-20mm) and medium stones (20-40mm), and does not pose a potential alkali reactivity hazard; fine aggregate is crushed limestone from engineering excavation, with a fineness modulus of 2.8, belonging to Zone II medium sand, and does not pose a potential alkali reactivity hazard; polyacrylate emulsion has a solids content of 43%; silica fume is dense silica fume; fly ash is Class F, Grade I fly ash; water-reducing agent is a retarding polycarboxylate high-performance water-reducing agent with a water reduction rate of 32%; defoamer is an organosilicon defoamer; air-entraining agent is a foam-stabilizing air-entraining agent; fiber is PVA fiber; water is tap water. All raw materials meet the relevant specifications for hydropower engineering.

[0048] Concrete mix proportion tests were conducted based on the concrete design parameters of the anti-seepage wall of the engineering dam. As a comparison, Examples 1-2 and Comparative Examples 1-2 are provided below.

[0049] Example 1: The concrete for the dam's anti-seepage wall has the following components:

[0050]

[0051] Examples 1 and 2 are two preferred embodiments of this application.

[0052] Comparative Example 1 is the concrete mix proportion for the anti-seepage wall under the existing technical route. The difference between Comparative Example 1 and the embodiment is that all low-heat silicate cement is replaced with ordinary silicate cement, and polypropylene emulsion, silica fume, defoamer, and PVA fiber are not added. The remaining parameters are slightly adjusted according to the fresh concrete performance.

[0053] Comparative Example 2 is a seepage-proof wall concrete prepared using low-heat silicate cement under the existing technical route. The difference between Comparative Example 2 and Comparative Example 1 is that all ordinary silicate cement is replaced with low-heat silicate cement, and the remaining parameters are slightly adjusted according to the fresh concrete performance.

[0054] The mixing performance, mechanical properties, and durability of concrete were tested in accordance with the "Test Procedure for Hydraulic Concrete" (DL / T 5150-2017).

[0055]

[0056] The test results of Examples 1 and 2 show that the anti-seepage wall concrete prepared by the two preferred schemes of the present invention can meet the design requirements and have a high safety margin.

[0057] The test results of Examples 1 and 2 and Comparative Example 1 show that the anti-seepage wall concrete prepared in this invention has slightly better fluidity than the anti-seepage wall concrete prepared by the prior art using "ordinary Portland cement + 30% fly ash" as the core. The 28-day compressive strength is significantly reduced, the 90-day compressive strength is slightly higher, the 90-day elastic modulus is significantly reduced, the 90-day axial tensile strength and the 90-day ultimate tensile value are significantly increased, and the 90-day impermeability grade and 90-day frost resistance grade are both greatly improved.

[0058] The test results of Examples 1 and 2 and Comparative Example 2 show that the anti-seepage wall concrete prepared in this invention has slightly better fluidity, slightly lower 28-day compressive strength, slightly higher 90-day compressive strength, significantly lower 90-day elastic modulus, significantly higher 90-day axial tensile strength and 90-day ultimate tensile value, and significantly improved 90-day impermeability grade and 90-day frost resistance grade compared to the existing anti-seepage wall concrete prepared with "low-heat silicate cement + 30% fly ash admixture".

[0059] The test results of Comparative Example 1 and Comparative Example 2 show that when using the existing technical solution to prepare anti-seepage wall concrete with a 90-day compressive strength that meets the design requirements, the 28-day compressive strength and 90-day elastic modulus do not meet the design requirements. In particular, the concrete prepared with low-heat silicate cement has lower 28-day compressive strength and 90-day elastic modulus than that prepared with ordinary silicate cement.

[0060] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A type of seepage-proof concrete for water conservancy and hydropower projects, characterized in that, The impermeable wall concrete comprises water, polyacrylate emulsion, cementitious materials, coarse aggregate, fine aggregate, water-reducing agent, defoamer, air-entraining agent, synthetic fibers, and unavoidable impurities; the mass ratio of the sum of water and the polyacrylate emulsion to the cementitious materials is 0.30–0.40, and the amount of coarse aggregate is 900–1100 kg / m³. 3 The amount of fine aggregate used is 600-850 kg / m³. 3 The sand content is 40%–46%; the amount of polyacrylate emulsion is 5%–20% of the mass of the cementitious material; the amount of water-reducing agent is 0.6%–1.2% of the mass of the cementitious material; the amount of defoamer is 0.8%–1.5% of the mass of the cementitious material; the amount of air-entraining agent is 0.2%–0.5% of the mass of the cementitious material; and the amount of synthetic fiber is 0.5%–2.0% of the total volume of the impermeable wall concrete.

2. The anti-seepage concrete for water conservancy and hydropower projects according to claim 1, characterized in that, The cementitious material includes cement, silica fume, and fly ash, and the total dosage of the cementitious material is 450–500 kg / m³. 3 The sand content is 40% to 46%; the amount of silica fume in the cementitious material is 3% to 5% of the mass of the cementitious material; the amount of fly ash is 50% to 60% of the mass of the cementitious material.

3. The anti-seepage concrete for water conservancy and hydropower projects according to claim 2, characterized in that, The cement is low-heat or medium-heat silicate cement, and the cement contains MgO, with the MgO content satisfying: 3.5% ≤ MgO ≤ 5.0%; the silica fume is dense silica fume, and the fly ash is Class F I fly ash.

4. The anti-seepage concrete for water conservancy and hydropower projects according to any one of claims 1-3, characterized in that, The coarse aggregate includes a first coarse aggregate with a particle size of 5-20 mm and a second coarse aggregate with a particle size of 20-40 mm, and the ratio of the first coarse aggregate to the second coarse aggregate is 65%:35%-75%:25%.

5. The anti-seepage concrete for water conservancy and hydropower projects according to claim 4, characterized in that, The porosity of the coarse aggregate is ≤43%; the fineness modulus of the fine aggregate is 2.8 to 3.

2.

6. The anti-seepage concrete for water conservancy and hydropower projects according to any one of claims 1-3 or 5, characterized in that, The polyacrylate emulsion has a solids content of 40% to 60%, the water-reducing agent is a retarding polycarboxylate high-performance water-reducing agent, and the water reduction rate of the water-reducing agent is not less than 30%; the defoamer is an organosilicon defoamer; and the air-entraining agent is a foam-stabilizing air-entraining agent.

7. The anti-seepage concrete for water conservancy and hydropower projects according to any one of claims 1-3 or 5, characterized in that, The synthetic fiber is at least one of high-strength, high-modulus, short-cut polyvinyl alcohol (PVA) fiber, polyvinyl chloride (PE) fiber, and polypropylene (PP) fiber.

8. A method for preparing anti-seepage wall concrete for water conservancy and hydropower projects, used to prepare anti-seepage wall concrete according to any one of claims 1-7, characterized in that, The method for preparing the impermeable wall concrete includes the following steps: 1) Weigh water, polyacrylate emulsion, cementitious materials, coarse aggregate, fine aggregate, water-reducing agent, defoamer, air-entraining agent and synthetic fiber according to the preset ratio. The cementitious materials include cement, silica fume and fly ash. 2) Weigh 2 / 3 of the mixing water, add the water-reducing agent, defoamer, and polyacrylate emulsion to the water and stir evenly to prepare a liquid for later use; weigh 1 / 3 of the mixing water, add the air-entraining agent to the water and stir evenly to prepare a diluted air-entraining agent for later use. 3) Add fine aggregate and coarse aggregate to a forced mixer and mix for 30 seconds; then pour cement, silica fume, fly ash and synthetic fiber into a mixing pot and mix for 90-120 seconds; then add the evenly mixed liquid agent in 30-second intervals during the mixing process and continue mixing for 60-90 seconds; finally, add the diluted air-entraining agent in 30-second intervals during the mixing process and continue mixing for 60-90 seconds to make the impermeable wall concrete.

9. The method for preparing anti-seepage wall concrete for water conservancy and hydropower projects according to claim 8, characterized in that, After the impermeable wall concrete is made, the slump of the impermeable wall concrete is 160-220 mm, and the compressive strength of the impermeable wall concrete after 90 days of age is greater than 40 MPa and the elastic modulus is less than 25 GPa.

Images