Waterproof concrete and method for producing the same

Abstract

The application discloses waterproof concrete and a preparation method thereof, relates to the technical field of building materials waterproofing, and aims to overcome the defects that waterproof concrete in the prior art is difficult to have both crack resistance and waterproof durability, shrinkage compensation and component compatibility are insufficient, and leakage is prone to occur. The waterproof concrete comprises the following components: 100 parts of cement, 350-550 parts of aggregate, 35-45 parts of water, 1.2-2.5 parts of a silane-based waterproofing agent, 0.8-1.6 parts of surface modified basalt fiber, 3-6 parts of a delayed magnesium oxide expanding agent, 5-10 parts of micron-grade metakaolin, and 2-5 parts of zeolite powder loaded with lithium silicate; each key component is modified in a targeted manner, and a step-by-step dry mixing and wet mixing process is adopted during preparation. Through the synergistic effect of the components, the waterproof concrete can significantly improve the compactness, compressive strength and crack resistance of the concrete, effectively reduce the drying shrinkage, enhance the waterproof durability, and meet the scene requirements of underground engineering, roof waterproofing and the like.

Description

Technical Field

[0001] This invention relates to the technical field of building materials. More specifically, this invention relates to a waterproof concrete and its preparation method. Background Technology

[0002] In the field of construction engineering, concrete, as a core load-bearing and enclosure material, directly determines the service life and safety of the engineering structure due to its waterproof performance. In underground engineering, water conservancy facilities, roofs, kitchens and bathrooms, concrete structures are constantly exposed to the infiltration and erosion of groundwater, rainwater and other media. After moisture intrusion, it can easily lead to problems such as steel corrosion, concrete carbonation, freeze-thaw damage, etc., which not only reduce the structural load-bearing capacity, but also cause leakage risks, increase later maintenance costs, and even affect the normal use of the project.

[0003] To improve the waterproofing performance of concrete, existing technologies often employ methods such as adding waterproofing agents, optimizing aggregate gradation, and improving construction processes. While traditional waterproofing agents can reduce concrete porosity to some extent, their waterproofing effect tends to diminish over long-term use, making them unsuitable for the long-term impermeability requirements under complex working conditions. Some technologies improve the internal structure of concrete and reduce crack formation by introducing fiber-reinforced materials; however, poor interfacial bonding between fibers and cementitious materials can lead to stress concentration, which in turn affects the overall balance between waterproofing and mechanical properties.

[0004] Furthermore, conventional concrete is prone to volume shrinkage during hydration, forming micro-cracks that become the main channels for water penetration. While existing expansive materials can compensate for shrinkage, the expansion rate is difficult to precisely match with the concrete hydration process. Either insufficient expansion fails to effectively fill the pores, or excessive expansion induces internal stress in the structure, reducing structural stability. Simultaneously, some waterproof concrete formulations suffer from poor component compatibility and complex preparation processes, limiting their construction adaptability and making it difficult to achieve a comprehensive improvement in waterproof performance, mechanical properties, and durability.

[0005] Therefore, it is necessary to design a technical solution that can overcome the above-mentioned defects. Summary of the Invention

[0006] One objective of this invention is to provide a waterproof concrete and its preparation method, which can solve the problems of insufficient impermeability, easy cracking, and poor durability of traditional materials.

[0007] To achieve these objectives and other advantages of the present invention, according to one aspect of the present invention, a waterproof concrete is provided, characterized in that it comprises the following components: 100 parts cement, 350-550 parts aggregate, 35-45 parts water, 1.2-2.5 parts silane waterproofing agent, 0.8-1.6 parts surface-modified basalt fiber, 3-6 parts delayed magnesium oxide expansion agent, 5-10 parts micron-sized metakaolin, and 2-5 parts lithium silicate-loaded zeolite powder; the surface-modified basalt fiber has a length of 15-30 mm, and its surface is pretreated with a silane coupling agent and post-treated with an aluminum salt-phosphate composite solution to form a composite coating; the delayed magnesium oxide expansion agent is obtained by surface treatment of lightly calcined magnesium oxide particles with sodium dihydrogen phosphate solution; the average particle size of the micron-sized metakaolin is 1-5 microns; and the lithium silicate-loaded zeolite powder has a lithium silicate loading of 10-20% of its own mass.

[0008] Further, the surface-modified basalt fiber is prepared by the following method: basalt fiber is immersed in a mixed solution prepared by silane coupling agent, deionized water and anhydrous ethanol at a mass ratio of 1:(4-6):(12-18), and is stirred at a constant temperature of 65-75℃ for 45-60 minutes. Then, it is removed and dried at 120-140℃ to obtain pretreated fiber. The pretreated fiber is then immersed in a composite modification solution containing aluminum salt and phosphate, wherein the mass concentration of aluminum ions in the composite modification solution is 0.5-2% and the mass concentration of phosphate ions is 0.3-1.2%. After immersion for 15-25 minutes, it is removed and heat-treated at 180-220℃ for 20-40 minutes to obtain the surface-modified basalt fiber.

[0009] Further, the delayed magnesium oxide expanding agent is prepared by the following method: lightly calcined magnesium oxide particles are placed in a citric acid aqueous solution with a mass concentration of 0.5-2%, stirred at 50-70°C for 15-30 minutes, filtered and dried to obtain pretreated magnesium oxide; the pretreated magnesium oxide is immersed in a sodium dihydrogen phosphate aqueous solution with a mass concentration of 8-15%, and sodium hexametaphosphate at a mass of 5-10% of sodium dihydrogen phosphate is added as a dispersant, and the reaction is continuously stirred at 75-85°C for 60-120 minutes; the material after the reaction in step two is filtered, and the resulting solid is heat-treated at 180-250°C for 90-150 minutes, cooled and then ground to a specific surface area of ​​400-600 m2 / kg to obtain the delayed magnesium oxide expanding agent.

[0010] Further, natural zeolite powder is immersed in a lithium silicate solution with a mass concentration of 15-30% and stirred continuously at 60-80°C for 30-60 minutes; then filtered and dried at 120-150°C, and then heat-treated at 280-350°C for 1-2 hours. After cooling, the lithium silicate-loaded zeolite powder is obtained.

[0011] Furthermore, the aggregate includes coarse aggregate and fine aggregate. The coarse aggregate is basalt crushed stone with a particle size of 5-20 mm, and the fine aggregate is natural river sand with a fineness modulus of 2.4-2.8. The mass ratio of the coarse aggregate to the fine aggregate is (2.5-3.5):1.

[0012] Furthermore, the silane waterproofing agent is at least one of isobutyltriethoxysilane and octyltriethoxysilane.

[0013] Furthermore, the loss on ignition of the micron-sized metakaolin is no more than 3%, and its activity index is no less than 105%.

[0014] According to another invention of the present invention, a method for preparing waterproof concrete is also provided, comprising the following steps, based on 100 parts by weight of cement, weighing each component according to the formula: S1: adding cement, micron-sized metakaolin, lithium silicate-loaded zeolite powder and aggregate into a mixing device for a first dry mix of 60-120 seconds to obtain a preliminary dry mix; S2: pre-mixing a silane waterproofing agent with 70-80% of the total mixing water to obtain a diluted waterproofing agent solution; S3: adding the diluted waterproofing agent solution to the preliminary dry mix for a first wet mix of 60-90 seconds to form a uniform slurry; S4: adding surface-modified basalt fiber and delayed magnesium oxide expansion agent to the slurry obtained in S3, and continuing a second wet mix of 90-150 seconds to ensure uniform dispersion of the fiber and expansion agent; S5: adding the remaining mixing water for a final wet mix of 60-120 seconds until a uniform concrete mixture is formed.

[0015] The present invention has at least the following beneficial effects:

[0016] This invention's waterproof concrete achieves simultaneous improvement in waterproof performance and structural stability through synergistic optimization of its components, solving the problems of insufficient impermeability, easy cracking, and poor durability of traditional materials. The synergistic effect of each component effectively refines the internal pore structure, blocks water penetration channels, significantly enhances long-term impermeability, and resists erosion under complex working conditions. It can precisely compensate for concrete hydration shrinkage, inhibit the generation and propagation of micro-cracks, prevent cracks from becoming seepage paths, and balance structural density and mechanical strength. Improved interfacial bonding between components enhances the overall structure's resistance to deformation and extends its service life. Furthermore, the preparation process is simple, the components are highly compatible, and the construction adaptability is strong, making it widely applicable to underground, water conservancy, and other engineering scenarios with high waterproofing requirements, balancing practical value and economic benefits.

[0017] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0018] Figure 1 This is a flowchart of one embodiment of this application. Detailed Implementation

[0019] The present invention will now be described in further detail so that those skilled in the art can implement it based on the description.

[0020] It should be understood that terms such as "having," "comprising," and "including" used in the embodiments of this application do not exclude the presence or addition of one or more other elements or combinations thereof. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of components in a specific posture. If the specific posture changes, the directional indication will also change accordingly. When an element is referred to as "fixed to" or "set on" another element, it can be directly on the other element or may have an intervening element present. When an element is referred to as "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element through an intervening element. Descriptions involving "first," "second," etc., in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0021] It should be noted that the technical solutions of the various embodiments of this application can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this application.

[0022] like Figure 1 As shown, embodiments of this application provide waterproof concrete comprising the following components: 100 parts cement, 350-550 parts aggregate, 35-45 parts water, 1.2-2.5 parts silane waterproofing agent, 0.8-1.6 parts surface-modified basalt fiber, 3-6 parts delayed-action magnesium oxide expansion agent, 5-10 parts micron-sized metakaolin, and 2-5 parts lithium silicate-loaded zeolite powder; the surface-modified basalt fiber has a length of 15-30 mm, and its surface is pretreated with a silane coupling agent and post-treated with an aluminum salt-phosphate composite solution to form a composite coating; the delayed-action magnesium oxide expansion agent is obtained by surface treatment of lightly calcined magnesium oxide particles with sodium dihydrogen phosphate solution; the average particle size of the micron-sized metakaolin is 1-5 microns; in the lithium silicate-loaded zeolite powder, the lithium silicate loading is 10-20% of the zeolite powder's own mass.

[0023] For example, waterproof concrete is a building cementitious material with its own waterproofing capabilities. It can be applied to underground engineering, roof waterproofing, and other scenarios. Its composition includes multiple functional components, which work synergistically to form a complete waterproofing and mechanical support system with a clear and complementary mechanism. Cement, as the core cementitious material, can be selected as PO 42.5 grade ordinary Portland cement, which serves to bind aggregates and other components to form an integral structure. Calcium hydroxide generated during hydration provides the reaction basis for active admixtures, and its dosage is set at 100 parts by weight. Aggregates, as the skeleton structure of concrete, can be selected at 400 or 500 parts, which can improve the compressive strength and volume stability of concrete. Their voids can be filled by cement hydration products and active admixtures, reducing internal leakage channels. The reasonable gradation of coarse and fine aggregates also provides a uniformly distributed carrier for other functional components. Water can be used as a mixing medium, with 38 or 42 parts, corresponding to a water-cement ratio of 0.38-0.42, which meets the conventional requirements for low water-cement ratio in waterproof concrete. It is used to dissolve some additives and fully mix the components. The amount of water must be strictly controlled to avoid affecting the density of the concrete. At the same time, it provides the necessary environment for cement hydration and the reaction between the components. Too much or too little water will destroy the synergistic effect between the components.

[0024] Silyl-based waterproofing agent is an organosilicon-based waterproofing additive. Isobutyltriethoxysilane or octyltriethoxysilane can be selected, and the addition amount can be set at 1.8 parts or 2.2 parts. It can penetrate into the capillary walls formed by cement hydration products, reacting with the hydroxyl groups in the hydration products to form a hydrophobic film. Simultaneously, it can synergistically work with lithium silicate released from zeolite powder loaded with lithium silicate, further strengthening the waterproof barrier of the capillaries and reducing the water absorption rate of concrete. Surface-modified basalt fiber is a surface-treated inorganic fiber, with a length of 20 mm or 25 mm. Its surface is pretreated with a silane coupling agent and post-treated with an aluminum salt-phosphate composite solution to form a composite coating, which can enhance the adhesion to the cement matrix and inhibit crack formation. The addition amount can be set at 1.0 part or 1.4 parts. The fiber can cross micro-cracks and disperse stress, forming a crack-resistant synergy with delayed magnesium oxide expansion agent, preventing crack propagation and damage to the waterproof structure.

[0025] Delayed-expansion magnesium oxide (MEO) can produce moderate expansion to compensate for concrete shrinkage. The addition amount can be set at 4 or 5 parts. It is prepared by surface treatment of lightly calcined magnesium oxide particles with sodium dihydrogen phosphate solution. Its delayed expansion characteristics can match the cement hydration process, playing a role in the later stages of concrete setting and hardening, compensating for drying shrinkage and hydration shrinkage, reducing porosity. Simultaneously, the micro-stress generated by expansion can promote the bonding between active admixtures and cement hydration products, preventing cracks in concrete due to shrinkage. Micron-sized metakaolin is an active admixture with an average particle size of 2 or 3 microns. The addition amount can be set at 6 or 8 parts. It can undergo a secondary hydration reaction with calcium hydroxide generated during cement hydration, producing cementitious products that fill the internal pores of concrete, increasing density. Its small particle size can fill the gaps between cement hydration products and aggregates, forming a gradient filling effect with lithium silicate-loaded zeolite powder, further densifying the internal structure.

[0026] Lithium silicate-loaded zeolite powder is a modified admixture that uses natural zeolite powder as a carrier to load lithium silicate. The addition amount can be set to 3 or 4 parts, and the lithium silicate loading can be 15% or 18% of the zeolite powder's own mass. The porous structure of the zeolite powder can adsorb and slowly release lithium silicate. Lithium silicate not only reacts with hydration products to enhance structural density but also complements the hydrophobic film of silane-based waterproofing agents, improving long-term waterproofing performance. Simultaneously, the zeolite powder itself can act as an inert filler, synergistically optimizing the internal gradation of concrete with metakaolin. The surface-modified basalt fiber composite coating improves the compatibility between the fiber and the cement matrix, reduces fiber agglomeration during mixing, ensures uniform fiber dispersion to fully exert its reinforcing and crack-resistant effect, and avoids the formation of localized weak areas due to fiber aggregation. The surface treatment of the delayed magnesium oxide expansion agent can adjust the expansion rate, allowing it to exert its expansion effect in the later stages of concrete setting and hardening, precisely compensating for shrinkage. Combined with the crack-resistant effect of the fiber, this forms a synergistic mechanism of "expansion compensation - crack inhibition." The micron-sized metakaolin, with a particle size controlled within the 1-5 micron range, can better fill the voids between cement hydration products, complementing the porous filling properties of zeolite powder and enhancing the density of concrete. This provides a good structural foundation for the waterproofing agent to function effectively. The lithium silicate loading in the lithium-loaded zeolite powder is controlled at 10-20%, ensuring the slow release of lithium silicate. This creates a synergistic effect with the silane-based waterproofing agent, providing long-term and short-term waterproofing benefits and maintaining the concrete's waterproof performance over the long term. The components work together synergistically, enhancing the overall performance of concrete from three dimensions: structural density, waterproofing barrier, and crack resistance compensation.

[0027] In existing technologies, waterproof concrete often improves its performance by adding ordinary waterproofing agents and fibers. However, ordinary waterproofing agents are easily lost during hydration, fibers have poor adhesion to the cement matrix, and the expansion timing of the expansion agent is difficult to match the shrinkage process of the concrete, leading to cracks and insufficient waterproofing durability, which can cause leakage problems in underground engineering. This embodiment, through the rational combination of various functional components and modification treatments, utilizes a silane-based waterproofing agent with strong stability and resistance to loss, modified basalt fibers with tight adhesion to the matrix, and a delayed expansion agent to precisely compensate for shrinkage. The synergistic effect of these components improves the density and crack resistance of the concrete. Compared with existing technologies, this effectively improves waterproofing durability, solves the leakage problem caused by cracks, and forms a more reasonable technical solution.

[0028] In another embodiment, the surface-modified basalt fiber is prepared by the following method: basalt fiber is immersed in a mixed solution prepared by silane coupling agent, deionized water and anhydrous ethanol at a mass ratio of 1:(4-6):(12-18), and is treated with constant temperature stirring at 65-75°C for 45-60 minutes. The fiber is then removed and dried at 120-140°C to obtain pretreated fiber. The pretreated fiber is then immersed in a composite modification solution containing aluminum salt and phosphate, wherein the mass concentration of aluminum ions in the composite modification solution is 0.5-2% and the mass concentration of phosphate ions is 0.3-1.2%. After immersion for 15-25 minutes, the fiber is removed and heat-treated at 180-220°C for 20-40 minutes to obtain the surface-modified basalt fiber.

[0029] For example, the preparation of surface-modified basalt fibers can be carried out according to the following process: First, a pretreatment mixed solution is prepared, wherein the silane coupling agent can be KH550 or KH560, which is an auxiliary agent that can enhance the compatibility between inorganic and organic materials; deionized water is high-purity water to avoid impurities affecting the treatment effect; and anhydrous ethanol is used as a solvent to promote the dissolution of the silane coupling agent. The mass ratio of the three can be 1:5:15 or 1:4.5:16. The three are thoroughly stirred and mixed evenly before use. Basalt fibers are immersed in the above-mentioned mixed solution. Basalt fibers are inorganic fibers made by melting and drawing basalt and have high strength and high temperature resistance. During the immersion process, it is ensured that the fibers are completely coated with the solution. Then, the solution is placed in a constant temperature environment of 68°C or 72°C and continuously stirred for 50 or 55 minutes using a stirring device. The stirring rate can be controlled at about 50 rpm to allow the silane coupling agent to be fully grafted onto the fiber surface. The fibers are then removed and dried in a drying device at 130°C or 135°C to remove the residual solution from the fiber surface, resulting in pretreated fibers. This pretreatment step can improve the surface activity of the fibers and lay the foundation for the subsequent formation of composite coatings. Next, a composite modification solution is prepared. The aluminum salt can be aluminum sulfate or aluminum chloride, and the phosphate can be ammonium dihydrogen phosphate or disodium hydrogen phosphate. Both are dissolved in deionized water to form a composite modification solution, in which the mass concentration of aluminum ions can be set to 1.0% or 1.5%, and the mass concentration of phosphate ions can be set to 0.6% or 0.9%. The pretreated fiber is immersed in the composite modification solution to ensure that the fiber is fully wetted. After immersion for 20 or 22 minutes, it is taken out and placed in a heat treatment device at 190°C or 210°C for curing for 30 or 35 minutes. During the curing process, the aluminum salt and phosphate react to form a composite coating that adheres tightly to the fiber surface, and finally, surface-modified basalt fiber is obtained. This composite coating can further enhance the adhesion between the fiber and the cement matrix, and at the same time improve the corrosion resistance of the fiber.

[0030] Ordinary basalt fibers have a smooth surface and poor compatibility with cementitious matrices. Direct addition leads to agglomeration and weak bonding, failing to fully exert their reinforcing and crack-resistant effects. Some treatment methods use only a single silane coupling agent, resulting in insufficient coating stability and easy fiber detachment in hydration environments. This embodiment employs a two-step process: first, surface activity is enhanced using a silane coupling agent, and then a composite coating is formed using aluminum salts and phosphates. This dual modification optimizes the bonding effect between the fiber and the matrix, resulting in a more stable coating that can maintain the reinforcing effect of the fiber for a long time. Compared with existing technologies, this effectively solves the problems of fiber agglomeration and detachment, improving the overall performance of concrete.

[0031] In another embodiment, the delayed magnesium oxide expanding agent is prepared by the following method: Lightly calcined magnesium oxide particles are placed in a 0.5-2% (w / w) citric acid aqueous solution and stirred at 50-70°C for 15-30 minutes. The mixture is then filtered and dried to obtain pretreated magnesium oxide. The pretreated magnesium oxide is then immersed in an 8-15% (w / w) sodium dihydrogen phosphate aqueous solution, with 5-10% (w / w) sodium hexametaphosphate added as a dispersant. The mixture is stirred continuously at 75-85°C for 60-120 minutes. The material from step two is filtered, and the resulting solid is heat-treated at 180-250°C for 90-150 minutes. After cooling, it is ground to a specific surface area of ​​400-600 m². 2 / kg, thus obtaining the delayed magnesium oxide expanding agent.

[0032] For example, the preparation of delayed magnesium oxide expansion agent can be carried out by the following steps: First, select lightly calcined magnesium oxide particles. Lightly calcined magnesium oxide is active magnesium oxide made by low-temperature calcination of magnesite and has a certain expansion potential. Place it in a citric acid aqueous solution with a mass concentration of 1.0% or 1.5%. The citric acid aqueous solution can slightly corrode the surface of the magnesium oxide particles and improve the surface activity. In an environment of 55°C or 65°C, continuously stir the particles for 20 minutes or 25 minutes using a stirring device. The stirring rate is controlled at about 60 rpm to ensure that the particle surface is fully in contact with the solution. Then, filter out the solid particles through a filtration device and dry them in a drying device to constant weight to obtain pretreated magnesium oxide. Next, a sodium dihydrogen phosphate aqueous solution is prepared, with a mass concentration of 10% or 12%. Sodium dihydrogen phosphate can form a coating on the surface of magnesium oxide to regulate the expansion rate. Simultaneously, sodium hexametaphosphate (6% or 8% by mass of sodium dihydrogen phosphate) is added to the solution as a dispersant. Sodium hexametaphosphate prevents magnesium oxide particles from agglomerating and improves reaction uniformity. The pretreated magnesium oxide is immersed in this solution and continuously stirred at 80°C for 90 or 100 minutes to ensure a uniform coating formation on the particle surface. After the reaction is complete, the solid material is separated by filtration and placed in a heat treatment device for heat treatment at 200°C or 230°C for 120 or 130 minutes to stabilize the coating structure. After cooling to room temperature, it is ground to a specific surface area of ​​450 m² / kg or 550 m² / kg, ultimately yielding a delayed-expansion magnesium oxide agent. This agent can slowly expand in the later stages of concrete setting, precisely compensating for shrinkage.

[0033] Ordinary magnesium oxide expanding agents expand rapidly, easily generating excessive expansion stress in the early stages of concrete, leading to cracking. Furthermore, the lack of an effective coating on the surface makes the expansion effect difficult to control, failing to adapt to the concrete's setting and hardening process and affecting waterproofing performance. This embodiment, through a two-step treatment and coating modification, combined with a dispersant to improve reaction uniformity, effectively regulates the expansion rate, matching the expansion timing with the concrete shrinkage process. Simultaneously, it enhances the stability of the expanding agent. Compared to existing technologies, this avoids early expansion cracking problems and improves the volume stability and waterproofing effect of the concrete.

[0034] In another embodiment, natural zeolite powder is immersed in a lithium silicate solution with a mass concentration of 15-30% and stirred continuously at 60-80°C for 30-60 minutes; then filtered and dried at 120-150°C, and then heat-treated at 280-350°C for 1-2 hours, and cooled to obtain the lithium silicate-loaded zeolite powder.

[0035] For example, the preparation of lithium silicate-loaded zeolite powder can be carried out according to the following procedure: First, natural zeolite powder is selected. Natural zeolite powder is a porous aluminosilicate mineral with good adsorption properties and can be used as a carrier to load functional substances. It is immersed in a lithium silicate solution with a mass concentration of 20% or 25%. Lithium silicate has good water resistance and can be loaded into the pores of zeolite powder through adsorption. Under an environment of 65°C or 75°C, it is continuously stirred for 35 minutes or 45 minutes using a stirring device, with the stirring rate controlled at about 45 rpm, so that the lithium silicate can fully penetrate into the pores of the zeolite powder. After stirring, the solid material is filtered out using a filtration device to remove excess lithium silicate solution adhering to the surface. It is then placed in a drying device and dried at 130°C or 140°C to remove moisture from the material, so that the lithium silicate is initially fixed in the pores. The dried material is then placed in a heat treatment device and heat-treated at 300°C or 320°C for 1.5 hours. Heat treatment can enhance the bonding force between lithium silicate and zeolite powder carrier and prevent rapid loss during use. After cooling to room temperature, lithium silicate-loaded zeolite powder is obtained. This zeolite powder can slowly release lithium silicate in concrete and play a long-term waterproof role. At the same time, the porous structure of zeolite powder can fill the internal pores of concrete and improve the density.

[0036] In existing technologies, lithium silicate added directly to concrete is prone to rapid reaction and loss, failing to maintain its waterproofing effect in the long term. Some load-bearing materials have weak carrier adsorption capacity and low loading capacity, resulting in insufficient waterproofing durability and difficulty in meeting long-term waterproofing requirements. This embodiment uses natural zeolite powder as a carrier. Its porous structure increases the lithium silicate loading capacity. Combined with drying and heat treatment to enhance bonding strength, it allows for the slow release of lithium silicate, extending the waterproofing time compared to existing technologies. Simultaneously, the zeolite powder also acts as a filler, synergistically improving the density and waterproofing performance of the concrete.

[0037] In another embodiment, the aggregate includes coarse aggregate and fine aggregate, wherein the coarse aggregate is basalt crushed stone with a particle size of 5-20 mm, and the fine aggregate is natural river sand with a fineness modulus of 2.4-2.8, and the mass ratio of the coarse aggregate to the fine aggregate is (2.5-3.5):1.

[0038] For example, aggregate is a crucial component of concrete, serving as a supporting framework. It can be divided into coarse aggregate and fine aggregate. The coarse aggregate can be basalt crushed stone with a particle size of 8-15 mm. Basalt crushed stone possesses high strength, high wear resistance, and good chemical stability, which can improve the compressive strength and durability of concrete, making it suitable for waterproofing projects with high strength requirements. The fine aggregate can be natural river sand with a fineness modulus of 2.6. The fineness modulus is an indicator of the coarseness of sand. Natural river sand in the range of 2.4-2.8 has good gradation, can fill the voids between coarse aggregate, and improve the workability of concrete. Natural river sand is clean in texture and has low impurity content, so it will not adversely affect the hydration reaction of concrete. The mass ratio of coarse aggregate to fine aggregate can be selected as 3:1 or 3.2:1. A reasonable ratio can optimize the aggregate gradation, maximize the filling of voids, reduce the internal porosity of concrete, improve density, and thus enhance waterproof performance and compressive strength. It can also prevent the concrete structure from becoming loose and leaking due to improper aggregate ratio.

[0039] This embodiment uses basalt crushed stone and well-graded natural river sand. By optimizing the ratio of coarse and fine aggregates, the internal porosity is reduced and the density of concrete is improved. At the same time, the basalt crushed stone enhances the structural strength. Compared with the existing technology, it effectively reduces leakage channels and balances strength and waterproof performance.

[0040] In another embodiment, the silane waterproofing agent is at least one of isobutyltriethoxysilane and octyltriethoxysilane.

[0041] For example, silane-based waterproofing agents are organosilicon-based waterproofing additives that can penetrate into the concrete and react with hydration products to form a hydrophobic film, improving the waterproofing performance of the concrete. The type of agent can be isobutyltriethoxysilane or octyltriethoxysilane. Isobutyltriethoxysilane has excellent penetration ability, reaching deep into the concrete, and the formed hydrophobic film is highly stable and not easily affected by environmental factors, making it suitable for waterproofing projects in damp underground environments. Octyltriethoxysilane has excellent hydrophobic effects, effectively reducing the water absorption rate of concrete, and has good compatibility with the cement matrix, without affecting the setting and hardening process of the concrete. This type of waterproofing agent can react with the hydroxyl groups in the concrete hydration products to form a dense hydrophobic film on the capillary walls, blocking water penetration without clogging the capillaries or affecting the breathability of the concrete. It can prevent freeze-thaw damage caused by internal moisture accumulation in the concrete, improving durability. The addition amount is controlled within the range of 1.2-2.5 parts, and the appropriate dosage can be selected according to the waterproofing requirements to ensure the waterproofing effect without affecting the concrete strength due to excessive addition.

[0042] In another embodiment, the loss on ignition of the micron-sized metakaolin is no more than 3%, and its activity index is no less than 105%.

[0043] For example, micron-sized metakaolin is an active admixture made from kaolin through low-temperature calcination and activation. It possesses high pozzolanic activity and can undergo a secondary hydration reaction with calcium hydroxide in cement hydration products to generate cementitious products that fill the internal pores of concrete, increasing its density. Its average particle size is controlled within the range of 1-5 microns, with 2 or 3 microns being suitable. The fine particle size better fills the tiny gaps between cement hydration products, reducing leakage channels and simultaneously improving the compressive strength and bonding performance of concrete. Loss on ignition (LOI) refers to the mass loss of metakaolin at high temperatures, which can be controlled to be no more than 2.5%. A lower LOI indicates higher purity and fewer impurities in the metakaolin, preventing impurities from affecting the hydration reaction. The activity index, a measure of its pozzolanic activity, can be controlled to be no less than 108%. A higher activity index ensures sufficient reaction with calcium hydroxide to generate enough cementitious products, effectively optimizing the internal structure of concrete, enhancing waterproofing performance and durability, and making it suitable for waterproof concrete projects with high density requirements.

[0044] The embodiments of this application also provide a method for preparing waterproof concrete, which includes the following steps, based on 100 parts by weight of cement: S1: cement, micron-sized metakaolin, lithium silicate-loaded zeolite powder, and aggregate are added to a mixing device for a first dry mix of 60-120 seconds to obtain a preliminary dry mix; S2: silane waterproofing agent is pre-mixed with 70-80% of the total mixing water to obtain a diluted waterproofing agent solution; S3: the diluted waterproofing agent solution is added to the preliminary dry mix for a first wet mix of 60-90 seconds to form a uniform slurry; S4: surface-modified basalt fiber and delayed magnesium oxide expansion agent are added to the slurry obtained in S3, and a second wet mix is ​​performed for 90-150 seconds to ensure uniform dispersion of the fiber and expansion agent; S5: the remaining mixing water is added for a final wet mix of 60-120 seconds until a uniform concrete mixture is formed.

[0045] For example, taking 100 parts by weight of cement as a baseline, each raw material component is weighed according to the above-mentioned proportioning requirements. The preparation process can be carried out in the following steps: First, cement, micron-sized metakaolin, lithium silicate-loaded zeolite powder, and aggregate are added to a forced mixing device. The forced mixing device has a strong mixing force, which can ensure that the dry materials are fully and evenly mixed for the first dry mixing operation. The mixing time can be controlled at 80 or 100 seconds. During the dry mixing process, each powder component can be evenly adhered to the surface of the aggregate, avoiding local aggregation during subsequent wet mixing, and obtaining a uniformly mixed preliminary dry mix. Second, the silane waterproofing agent is pre-mixed with 75% or 78% of the total mixing water, which is the 35-45 parts specified above. The mixture is slowly stirred to fully dissolve the waterproofing agent in the water, obtaining a diluted waterproofing agent solution. Pre-dilution can avoid excessively high local concentrations when the waterproofing agent is directly added, which would affect its compatibility with other components. The third step involves slowly adding the diluted waterproofing agent solution to the initial dry mix, starting the mixing equipment for the first wet mix. The mixing time is controlled at 70 or 80 seconds to allow the dry mix to fully absorb water and form a uniform slurry. At this point, the waterproofing agent is evenly dispersed in the slurry, initially exerting its water-repellent effect. The fourth step involves adding surface-modified basalt fibers and delayed-release magnesium oxide expansion agent to the resulting slurry, continuing the second wet mix. The mixing time is controlled at 120 or 130 seconds. During the mixing process, the mixing rate needs to be controlled to prevent fiber clumping and ensure that the fibers and expansion agent are evenly dispersed in the slurry. The fibers can initially exert their crack-resistant effect, while the expansion agent is evenly distributed and awaits subsequent expansion. The fifth step involves adding the remaining mixing water, which should be 22% or 25% of the total water volume, for the final wet mix. The mixing time is controlled at 90 or 100 seconds until a uniform, fine, and workable concrete mixture is formed. The final wet mix ensures that all components are fully integrated, improving the overall homogeneity of the concrete.

[0046] This embodiment adopts a step-by-step dry and wet mixing method, optimizes the order of material addition and mixing time, ensures that each component is evenly dispersed, the waterproofing agent plays its full role, and the fiber and expansion agent are evenly distributed. Compared with the existing technology, it improves the homogeneity of the concrete mixture, makes the internal structure more compact, and makes the mechanical and waterproof properties more stable.

[0047] The following is a description of a specific embodiment.

[0048] I. Formula Design for Experimental and Control Groups

[0049] (a) Experimental Group (EX)

[0050] The experimental formulation was strictly prepared according to all technical requirements, with each component parameter uniquely determined and free of multiple defects, ensuring the complete realization of the synergistic effect of each component. The specific formulation was based on 100 parts by weight of cement: PO 42.5 grade ordinary Portland cement was selected; 420 parts of aggregate, of which coarse aggregate was basalt crushed stone with a particle size of 8-15 mm, and fine aggregate was natural river sand with a fineness modulus of 2.6, with a coarse-to-fine aggregate mass ratio of 3:1; 40 parts of water; 2.0 parts of isobutyltriethoxysilane was selected as the silane waterproofing agent; and 1.2 parts of surface-modified basalt fiber, 22 mm in length, pretreated with KH550 silane coupling agent (mixed solution mass ratio 1:5:15, constant temperature stirring at 68℃ for 50 minutes, then at 130℃). Drying) and post-treatment with aluminum salt-phosphate composite solution (aluminum ion mass concentration 1.2%, phosphate ion mass concentration 0.7%, impregnation for 20 minutes, curing at 200℃ for 30 minutes); 4.5 parts of delayed magnesium oxide expansion agent, made from lightly calcined magnesium oxide particles pretreated with 1.2% citric acid aqueous solution (stirred at 60℃ for 22 minutes), reacted with 12% sodium dihydrogen phosphate aqueous solution (with 7% sodium hexametaphosphate added) at 80℃ for 90 minutes, heat-treated at 220℃ for 120 minutes, and ground to a specific surface area of ​​500 m². 2 / kg; 7 parts of micron-sized metakaolin with an average particle size of 2.5 microns, a loss on ignition of 2.2%, and an activity index of 110%; 3.5 parts of lithium silicate-loaded zeolite powder with a lithium silicate loading of 16%, prepared by stirring in a 22% lithium silicate solution at 70°C for 40 minutes, drying at 135°C, and heat-treating at 310°C for 1.5 hours. The preparation process strictly followed a step-by-step dry-mixing and wet-mixing process: the first dry mixing for 90 seconds, premixing the waterproofing agent with 75% water, the first wet mixing for 75 seconds, adding the fiber and expanding agent, followed by a second wet mixing for 120 seconds, and finally adding the remaining water and wet mixing for 90 seconds.

[0051] (II) Control Group

[0052] The control group was based on the experimental group's formula, except for the absence of one or more of the following: surface-modified basalt fiber, delayed magnesium oxide expansion agent, and lithium silicate-supported zeolite powder. The remaining components and preparation process were completely identical to the experimental group.

[0053] CK1: Lacking surface-modified basalt fiber, the remaining components and processes are the same as the experimental group;

[0054] CK2: Lacking delayed magnesium oxide expanding agent, the remaining components and processes are the same as the experimental group;

[0055] CK3: Zeolite powder lacking lithium silicate loading, with other components and processes the same as the experimental group;

[0056] CK4: It lacks both surface-modified basalt fiber and delayed magnesium oxide expansion agent, while the other components and processes are the same as the experimental group;

[0057] CK5: It lacks surface-modified basalt fiber, delayed magnesium oxide expansion agent, and lithium silicate-loaded zeolite powder. The remaining components and processes are the same as those in the experimental group.

[0058] II. Performance Parameter Testing Methods

[0059] After all concrete mixtures were formed, they were cured for 28 days under standard curing conditions (temperature 20±2℃, relative humidity ≥95%). Indicators strongly correlated with the core performance of waterproof concrete were selected for testing. The results are shown in Table 1. All test methods complied with national standards and industry specifications.

[0060] 1. Compressive strength: According to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", 150mm×150mm×150mm cubic specimens were used to test the compressive strength after 28 days of curing.

[0061] 2. Permeability resistance grade: According to GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", a frustum-shaped specimen with a top diameter of 175mm, a bottom diameter of 185mm, and a height of 150mm was used. The pressure was increased stepwise, with each pressure maintained for 8 hours, until water seepage appeared on the end face of the specimen. The pressure at this time was recorded as the basis for the permeability resistance grade.

[0062] 3. Drying shrinkage rate: According to GB / T 50082-2009, a 100mm×100mm×515mm prism test block was used to test the drying shrinkage rate after 28 days of curing and 28 days of placement in an environment with a temperature of 20±2℃ and a relative humidity of 60±5%.

[0063] 4. Crack resistance grade: According to CECS 13-2009 "Standard for Test Methods of Fiber Reinforced Concrete", the plate restraint method was used to prepare 800mm×600mm×100mm plate test blocks. The number and width of surface cracks of the test blocks were observed within 28 days of curing to evaluate the crack resistance grade.

[0064] Table 1 Performance Test Results Statistics

[0065]

[0066] Note: Crack resistance grades range from L-Ⅲ to L-Ⅶ, with higher values ​​indicating poorer crack resistance; impermeability grades range from P4 to P12, with higher values ​​indicating better impermeability.

[0067] IV. Conclusion

[0068] As shown in Table 1, the experimental group exhibited significantly better performance than all control groups in all aspects, and the more types of key components were missing, the more pronounced the performance decline. The experimental group achieved the highest 28-day compressive strength and impermeability grade, the lowest drying shrinkage rate, and the best crack resistance grade, demonstrating the synergistic effect of surface-modified basalt fiber, delayed-action magnesium oxide expansion agent, lithium silicate-loaded zeolite powder, and other components. Specifically, surface-modified basalt fiber primarily enhances the compressive strength and crack resistance of concrete; its absence (CK1) leads to a decrease in compressive strength, a worse crack resistance grade, and increased susceptibility to cracks, resulting in a decline in impermeability. The delayed-action magnesium oxide expansion agent's core function is to compensate for drying shrinkage; its absence (CK2) significantly increases the drying shrinkage rate, increases internal porosity, and causes a simultaneous decline in both compressive and impermeability properties. Lithium silicate-loaded zeolite powder strengthens the waterproof barrier and structural density; its absence (CK3) significantly weakens impermeability and slightly increases the shrinkage rate. When two or more key components are missing simultaneously (CK4, CK5), the performance degradation exhibits a cumulative effect. In particular, when all three components are missing, the compressive strength, impermeability, crack resistance, and shrinkage performance of the concrete all reach their worst levels. This further confirms the indispensability of the three key components in the overall technical solution and the important significance of the synergistic effect of each component in improving the comprehensive performance of waterproof concrete. In summary, this technical solution is not simply a matter of stacking surface-modified basalt fiber, delayed-release magnesium oxide expansion agent, and lithium silicate-loaded zeolite powder. Instead, it involves targeted modification of each component, optimization of the component ratio and preparation process, to create a synergistic system between the three key components, cement, aggregate, silane-based waterproofing agent, and micron-sized metakaolin. The surface-modified basalt fiber undergoes double surface treatment, enhancing its adhesion to the cement matrix and effectively inhibiting crack initiation and propagation. The delayed-release magnesium oxide expansion agent, through surface coating, precisely exerts its expansion effect in the later stages of concrete setting and hardening, compensating for drying shrinkage and reducing internal porosity. The lithium silicate-loaded zeolite powder slowly releases lithium silicate, forming a complementary waterproof barrier with the silane-based waterproofing agent, while simultaneously synergistically optimizing the internal structural density with micron-sized metakaolin. This synergistic effect of the three components simultaneously improves performance in four dimensions: crack resistance, shrinkage compensation, waterproof barrier, and structural density, solving the technical challenge of existing technologies where single-component modification cannot simultaneously address multiple performance aspects.

[0069] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. Waterproof concrete, characterized in that, It includes the following components: 100 parts cement, 350-550 parts aggregate, 35-45 parts water, 1.2-2.5 parts silane waterproofing agent, 0.8-1.6 parts surface-modified basalt fiber, 3-6 parts delayed magnesium oxide expansion agent, 5-10 parts micron-sized metakaolin, and 2-5 parts lithium silicate-loaded zeolite powder; The surface-modified basalt fiber has a length of 15-30 mm, and its surface is pretreated with silane coupling agent and post-treated with aluminum salt-phosphate composite solution to form a composite coating. The delayed magnesium oxide expanding agent is prepared by surface treatment of lightly calcined magnesium oxide particles with sodium dihydrogen phosphate solution; The average particle size of the micron-sized metakaolin is 1-5 microns. In the lithium silicate-loaded zeolite powder, the lithium silicate loading is 10-20% of the zeolite powder's own mass.

2. The waterproof concrete as described in claim 1, characterized in that, The surface-modified basalt fiber is prepared by the following method: Basalt fibers are immersed in a mixed solution prepared by silane coupling agent, deionized water and anhydrous ethanol in a mass ratio of 1:(4-6):(12-18), and are stirred at a constant temperature of 65-75℃ for 45-60 minutes. Then they are taken out and dried at 120-140℃ to obtain pretreated fibers. The pretreated fiber is immersed in a composite modification solution containing aluminum salt and phosphate, wherein the mass concentration of aluminum ions in the composite modification solution is 0.5-2% and the mass concentration of phosphate ions is 0.3-1.2%. After immersion for 15-25 minutes, it is taken out and heat-treated and cured at 180-220℃ for 20-40 minutes to obtain the surface-modified basalt fiber.

3. The waterproof concrete as described in claim 1, characterized in that, The delayed magnesium oxide expanding agent is prepared by the following method: Lightly calcined magnesium oxide particles are placed in a 0.5-2% citric acid aqueous solution and stirred at 50-70℃ for 15-30 minutes. After filtration and drying, pretreated magnesium oxide is obtained. The pretreated magnesium oxide is immersed in an aqueous solution of sodium dihydrogen phosphate with a mass concentration of 8-15%, and sodium hexametaphosphate with a mass of 5-10% of sodium dihydrogen phosphate is added as a dispersant. The mixture is stirred continuously at 75-85°C for 60-120 minutes. The material after the reaction in step two is filtered, and the resulting solid is heat-treated at 180-250℃ for 90-150 minutes. After cooling, it is ground to a specific surface area of ​​400-600 m². 2 / kg, thus obtaining the delayed magnesium oxide expanding agent.

4. The waterproof concrete as described in claim 1, characterized in that, Natural zeolite powder is immersed in a lithium silicate solution with a mass concentration of 15-30% and stirred continuously at 60-80°C for 30-60 minutes; then filtered and dried at 120-150°C, and then heat-treated at 280-350°C for 1-2 hours. After cooling, the lithium silicate-loaded zeolite powder is obtained.

5. The waterproof concrete as described in claim 1, characterized in that, The aggregate includes coarse aggregate and fine aggregate. The coarse aggregate is basalt crushed stone with a particle size of 5-20 mm, and the fine aggregate is natural river sand with a fineness modulus of 2.4-2.

8. The mass ratio of coarse aggregate to fine aggregate is (2.5-3.5):

1.

6. The waterproof concrete as described in claim 1, characterized in that, The silane waterproofing agent is at least one of isobutyltriethoxysilane and octyltriethoxysilane.

7. The waterproof concrete as described in claim 1, characterized in that, The loss on ignition of the micron-sized metakaolin is no more than 3%, and its activity index is no less than 105%.

8. A method for preparing waterproof concrete as described in any one of claims 1-7, characterized in that, Weigh each component according to the formula, based on 100 parts by weight of cement, and include the following steps: S1: Add cement, micron-sized metakaolin, lithium silicate-loaded zeolite powder and aggregate to the mixing equipment for the first dry mixing. The mixing time is 60-120 seconds to obtain the preliminary dry mix. S2: Premix the silane waterproofing agent with 70-80% of the total mixing water to prepare a diluted waterproofing agent solution; S3: Add the diluted waterproofing agent solution to the preliminary dry mix and perform the first wet mix, stirring for 60-90 seconds to form a uniform slurry; S4: Add surface-modified basalt fiber and delayed magnesium oxide expansion agent to the slurry obtained in S3, and continue the second wet mixing. Stir for 90-150 seconds to ensure that the fiber and expansion agent are evenly dispersed. S5: Add the remaining mixing water and perform final wet mixing. Stir for 60-120 seconds until a homogeneous concrete mixture is formed.

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