Early-high-strength underwater anti-dispersion concrete and preparation method thereof

Abstract

The invention discloses early-strength and high-strength underwater anti-dispersion concrete and a preparation method thereof, and belongs to the technical field of building materials. The concrete realizes the characteristics of high early strength and excellent underwater dispersion resistance by optimizing the material ratio and the preparation process. The preparation method comprises the following steps: proportioning the cement, the nano silicon dioxide, the modified gel, the polypropylene fiber, the marble waste powder, the high-efficiency water reducing agent and the water in parts by mass; dispersing the nano material by adopting high-speed shearing; preparing modified gel to enhance the dispersion resistance; a finished product is obtained through stirring forming and curing. Compared with the traditional concrete, the concrete disclosed by the invention has the advantages that the compressive strength within 3 days reaches 42.3 to 50.5 MPa, the strength within 28 days reaches 65.8 to 78.2 MPa, the underwater anti-dispersion mass loss rate is only 0.6 to 1.2 percent, and the fluidity is 220.5 to 234.1 mm. The method is simple in process, low in cost and suitable for the underwater construction fields of ocean engineering, water conservancy projects and the like, and has remarkable economic and social benefits.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of building materials, and particularly relates to an early high-strength underwater anti-dispersion concrete and a preparation method thereof. BACKGROUND

[0002] Concrete is a composite material that solidifies through the hydration of cement, and its main components include cement, sand, gravel, and water. In the construction industry, concrete is favored due to its ability to be cast into shape as needed, relatively low cost, and durability over long periods of use. In particular, in underwater construction such as the construction of subsea tunnels, piers, bridge foundations, and dams, concrete is an indispensable structural material. However, the underwater environment presents unique challenges to the performance of concrete, including the scouring of water flow, the influence of water pressure, and the inhibition of the hardening process by low temperatures. These factors make it difficult for traditional concrete to be used in underwater applications, and targeted technical improvements are urgently needed. One of the biggest problems faced by concrete during underwater construction is the dispersion phenomenon. When the concrete slurry is cast underwater, the water flow will scour the cement particles and fine aggregates, causing them to disperse into the surrounding environment. This dispersion not only reduces the density of the concrete, but also increases the porosity of the structure after hardening, thereby weakening its compressive strength and durability. For example, in marine engineering, dispersed concrete may not form a uniform structural layer, affecting the stability and safety of subsea facilities. In addition, the low temperature of the underwater environment usually delays the hydration of the cement, causing the setting and hardening time of the concrete to be prolonged. This is particularly disadvantageous for projects that require rapid construction, as insufficient early strength can delay the removal of forms or subsequent construction steps, increasing time and economic costs. Another key requirement is early strength. In modern engineering, especially in underwater projects where time is of the essence or rapid repair is required, concrete must achieve a high compressive strength in a short period of time (such as 1-3 days) to support structural load bearing or speed up construction progress. However, the strength growth rate of traditional concrete is slow, especially under the low temperature conditions of underwater, and this problem is even more pronounced. Therefore, how to achieve early high strength while ensuring anti-dispersion has become a core challenge in the development of underwater concrete technology.

[0003] To combat the dispersion problem in underwater construction, researchers and engineering technicians have developed various anti-dispersion concrete technologies. One common method is to add anti-dispersion agents, such as high molecular polymers (e.g., polycarboxylate superplasticizer), cellulose ethers, or starch derivatives. These additives form a gel network by increasing the viscosity and cohesion of the concrete paste, reducing the loss of cement particles in water. For example, in known anti-dispersion concrete formulations, hydroxyethyl cellulose (HEC) is often used to improve the stability of the paste. However, such anti-dispersion agents often reduce the flowability of the concrete while improving anti-dispersion performance, making it more difficult to pour and construct. In addition, excessive use of anti-dispersion agents can affect the hydration process of cement, hindering the development of early strength.

[0004] To meet the demand for early high strength, existing technologies usually use fast-hardening cement (such as sulphoaluminate cement) or increase the amount of cement to accelerate the growth of strength. Fast-hardening cement can provide higher strength in a shorter time through rapid hydration reaction, while increasing the amount of cement achieves a similar effect by increasing the generation speed of hydration products. In addition, some technologies also combine admixtures, such as accelerators (calcium chloride) or early strength agents (triethanolamine), to further shorten the setting time. However, these methods are not without drawbacks. Fast-hardening cement is expensive and may cause concrete cracking due to excessive heat of hydration in underwater environments; increasing the amount of cement increases material costs and may cause shrinkage cracks, affecting the long-term stability of the structure.

[0005] In recent years, nanotechnology has also been introduced into the study of underwater concrete. Nano-silica can significantly accelerate the hydration reaction of cement due to its high specific surface area and chemical activity, thereby improving the early strength and density of concrete. However, the uniform dispersibility of nano-materials is poor, and agglomeration easily occurs, leading to unstable effects in concrete. In addition, the preparation and use of nano-materials are costly, limiting their application in practical engineering. Although the above technologies have improved the anti-dispersion and early strength of underwater concrete to some extent, there are still many limitations. First, the compatibility problem of anti-dispersion agent and early strength component is widespread. For example, some high molecular anti-dispersion agents may react with the coagulant, causing fluctuations in concrete performance, and even reducing its final strength. Second, the economy of existing methods is insufficient. The use of fast-hardening cement, nano-materials and high-performance additives significantly increases material costs, making these technologies difficult to be widely used in large-scale engineering. In addition, some processes (such as high temperature curing) are difficult to implement in underwater environments, limiting their practicality. For example, high temperature curing requires additional equipment and energy input, and under low temperature conditions underwater, this method is almost impossible. From the perspective of environmental protection, existing technologies also face challenges. Concrete production is a high-carbon emission industry, and the cement manufacturing process contributes 5-8% of global greenhouse gas emissions. Increasing the amount of cement or relying on special cement solutions further exacerbates environmental burdens. At the same time, waste materials generated by the construction industry (such as marble waste powder, fly ash, etc.) are not fully utilized, resulting in resource waste and additional disposal costs. Therefore, it is of great practical significance to develop a concrete technology that can meet performance requirements and reduce environmental impact.

[0006] The performance and construction of underwater concrete are subject to strict industry standards and regulations. In China, the "Specification for Hydraulic Concrete Construction" (DL / T5144-2015) clearly stipulates the compressive strength, anti-dispersion and construction process requirements of underwater concrete. Internationally, European Standard EN206-1 and the American Concrete Institute (ACI) ACI304R-00 guide also provide detailed specifications for the preparation and performance of underwater concrete. These standards usually require concrete to achieve a certain compressive strength at a certain age (such as 3d or 7d), and to maintain a low dispersion rate during underwater pouring to ensure engineering quality. These regulations provide a technical basis for the research and development of underwater concrete technology, and also highlight the shortcomings of existing methods in meeting standard requirements.

[0007] In summary, the existing underwater anti-dispersion and early high-strength concrete technology still has significant defects in performance stability, economy, construction feasibility, and environmental protection. Specifically: unstable performance: poor compatibility between anti-dispersants and early strength components, leading to fluctuations in concrete performance. high cost: the use of special cement, nanomaterials, and high-performance additives increases material and construction costs. complex construction: high-temperature curing and other processes are difficult to implement in underwater environments, limiting the scope of technology application. environmental burden: high cement consumption and insufficient waste utilization exacerbate resource consumption and carbon emissions.

[0008] Therefore, there is an urgent need for a new type of early high-strength underwater anti-dispersion concrete and its preparation method to overcome the shortcomings of existing technology. The present invention optimizes material ratios and preparation processes, combines the comprehensive utilization of nano-silica, modified gel materials, and waste materials (such as marble waste powder), aiming to achieve the following goals: first, significantly improve the anti-dispersion and early strength of concrete in underwater environments; second, reduce production costs and construction difficulty; third, reduce environmental impact. This innovative technology not only meets the demanding requirements of modern underwater engineering, but also has broad application prospects. SUMMARY

[0009] With the continuous development of engineering technology, especially the increasing application demands in underwater construction fields such as marine engineering and water conservancy engineering, the performance of traditional concrete has been difficult to fully meet the special requirements of modern engineering. Especially in underwater environments, concrete needs to have both anti-dispersion and early high-strength properties to ensure construction quality and structural safety. Therefore, developing a concrete that can maintain stability and quickly obtain high strength in underwater environments has become an important issue in the field of building materials technology. The present invention is proposed in this context, aiming to solve the shortcomings of existing technology and provide an early high-strength underwater anti-dispersion concrete and its preparation method.

[0010] To solve the above problems, the technical scheme adopted by the present invention is as follows.

[0011] The application discloses a preparation method of an early high-strength underwater anti-dispersion concrete, and comprises the following steps: step S1, material proportioning design: preparing the following components according to mass fractions: cement: 80-120 parts, nano silicon dioxide: 3-5 parts, modified gel: 5-10 parts, polypropylene fiber: 0.5-1.5 parts, marble waste powder: 10-20 parts, high-efficiency water reducing agent: 0.5-1 part, and water: 25-45 parts; step S2, nano material dispersion treatment: mixing the nano silicon dioxide, the high-efficiency water reducing agent and the water, stirring in a high-speed shearing machine at 1000-2000 rpm for 5-10 min to form a uniform dispersion liquid; step S3, modified gel treatment: uniformly mixing ethyl acrylate (CAS number: 140-88-5), methacrylic acid (CAS number: 79-41-4), 1, 4-butanediol diacrylate (CAS number: 1070-70-8) and deionized water according to a mass ratio of (4-10):(2-6):(0.1-1):(100-150), adding 0.01-0.2 times of tetramethyl ethylenediamine (CAS number: 110-18-9) of the mass of the ethyl acrylate to synthesize the gel after standing, then adding 0.5-1 times of epoxy methyl acrylate (CAS number: 106-91-2) of the mass of the ethyl acrylate, reacting at 50-60 DEG C under pH 4-5 for 8-12 h to obtain the modified gel; step S4, forming treatment: stirring the dispersion liquid obtained in the step S2, the cement, the polypropylene fiber, the marble waste powder and the modified gel obtained in the step S3 to form a uniform slurry; and step S5, solidification treatment: pouring the slurry obtained in the step S4 into a mold for curing treatment.

[0012] The preparation method realizes the synergistic targets of rapid reinforcement, low dispersion and good fluidity in an underwater environment through a composite idea of "multi-scale reinforcement + chemical network stabilization + process kinetics optimization". The core lies in early strength excitation of the nano silicon dioxide, three-dimensional locking of the modified gel, toughening bridging of the polypropylene fiber and filling activation of the marble waste powder, which jointly construct a dense and tough cement matrix under the conditions of high-speed shearing and precise curing.

[0013] Material proportioning design mechanism: cement provides the main cementitious framework, relying on hydration reaction to generate C-S-H gel and CH crystals, to provide a reaction platform for subsequent nano-activation and gel network. Nano-silica 3-5 parts as 10-35 nm particles act as heterogeneous crystal nuclei, reduce the nucleation energy barrier and have secondary pozzolanic reaction with CH, generating a large amount of C-S-H in a short time, bringing early strength jump and filling nanopores. Modified gel is formed by copolymerization of ethyl acrylate-methyl methacrylate and crosslinking by epoxy groups to form a dense three-dimensional network, which can wrap cement particles and aggregates with high cohesive force, significantly inhibiting particle loss caused by water flow erosion. Polypropylene fibers construct a random distribution of bridging system at the micron scale, preventing rapid crack tip propagation and bearing tensile load, improving toughness and integrity. Marble waste powder 10-20 parts has more than 90% calcium carbonate and ≤50 µm particle size, which can improve the particle size distribution, provide additional nucleation sites and form interfacial bonds between part of the surface active components and hydration products, taking into account environmental protection and densification. High efficiency water reducing agent reduces the surface tension of the system through electrostatic repulsion and steric hindrance dispersion effect, so that the water-cement ratio is reduced while maintaining fluidity, creating conditions for high strength and workability. Water not only meets the hydration demand but also realizes low water-binder ratio with the help of water reducing agent, ensuring early reaction rate and late pore structure optimization. Key process step mechanism: high-speed shear dispersion, a shear rate of 1000-2000 rpm provides >10 4 s -1Shear gradient, quickly overcome the van der Waals forces between nanoparticles and water-reducing agent to form a stable sol, to avoid agglomeration and sedimentation, so as to realize uniform dispersion and activity maximization. Modified gel synthesis, weak acid pH 4-5 and 50-60 ℃ conditions prompt ring-opening addition of epoxy group methacrylate, tetramethyl ethylenediamine to initiate free radical copolymerization, both containing flexible ether chain and rigid ester bond crosslinking network, showing high viscoelasticity and chemical stability, can be quickly coated and bonded solid particles underwater. Multi-component forming, when the nanodispersion liquid is stirred with cement, fiber, waste powder and gel, the shear-bending composite flow field further breaks the potential agglomeration, and the nanoparticles are adsorbed on the surface of the cement, and the gel and the fiber are interlaced into an interlocking framework, so that the slurry has excellent dispersion resistance while maintaining a flow degree of 220-234 mm. Sealing-wet curing, the high humidity sealing of 8-14h in early stage provides moisture and temperature protection for nanofilling and gel network consolidation; Subsequent 30-40 ℃, 90-95% RH continues to maintain for 14d, so that secondary hydration and epoxy crosslinking fully proceed, and finally form a high-density, low-porosity and fiber-reinforced composite structure. Multi-scale synergistic reinforcement path, nanoscale: SiO2 filling micropore + crystal nucleus excitation, 3d strength reaches 42-50 MPa, and the late strength is further improved. Micron level: waste powder and hydration products together to densify the slurry and provide alkali excitation sites, reduce the risk of hydration heat concentration. Millimeter level: PP fiber across the microcrack, improve the tensile and anti-scour toughness, and form a "chemical lock + physical chain" double stability with the gel network. Performance-mechanism correspondence: compressive strength: nanocrystal nucleus and pozzolanic effect make the 28d strength stable at 66-78 MPa, which is 20%-30% higher than that of the system without nano. Dispersion resistance: gel barrier + fiber bridging makes the underwater mass loss rate only 0.6-1.2%, which is far lower than the conventional 5%-10%. Flow degree: water-reducing agent-nano synergistic maintains high flow state without excessive water, meeting the complex underwater pouring requirements. Innovation and application value summary: This method constructs a chemical-physical double stable system with "nano activation-gel locking-fiber toughening-waste powder resource utilization", realizes high early strength, low dispersion and excellent construction performance under underwater conditions, and greatly saves energy and reduces carbon through waste utilization and normal temperature and humidity curing, which has significant engineering popularization potential.

[0014] Preferably, the cement in step S1 is type II Portland cement (CAS No.: 65997-15-1), and the specific surface area is ≥2800 cm 2 / g; the particle size of the nanosilica in step S1 is 10-35 nm, and the specific surface area is ≥185 m 2 / g.

[0015] Preferably, the parameters of the polypropylene fibers in step S1 are as follows: length 8-12 mm, diameter 20-40 μm, tensile strength ≥ 400 MPa; the parameters of the marble waste powder in step S1 are as follows: mass percentage content of calcium carbonate not less than 90%, average particle size ≤ 50 μm.

[0016] Preferably, the superplasticizer in step S1 is polycarboxylic ether (CAS No. 51798-33-5), sodium lignosulfonate (CAS No. 8061-51-6) or sodium gluconate (CAS No. 527-07-1).

[0017] Preferably, the synthesis temperature of the gel in step S3 is 40-60 ℃, and the synthesis time of the gel is 15-20 min.

[0018] Preferably, the stirring mode in step S4 is as follows: stirring in a planetary mixer at 40-60 rpm for 8-12 min.

[0019] Preferably, the parameters of the curing treatment in step S5 are as follows: sealed curing at room temperature for 8-14 h, and humidity control at 90-95%.

[0020] Preferably, after curing, demolding is performed, and curing is continued for 14 d, the curing temperature is 30-40 ℃, and the curing humidity is controlled at 90-95%.

[0021] An early high-strength underwater anti-dispersion concrete is obtained by the preparation method described above.

[0022] The copolymerization mechanism is as follows: free radical copolymerization of ethyl acrylate, methacrylic acid and 1,4-butanediol diacrylate occurs under the initiation of tetramethyl ethylenediamine: initiation step, tetramethyl ethylenediamine decomposes to generate free radicals; growth step, monomer molecules gradually add to form polymer chains; termination step, free radicals combine or disperse to terminate the reaction. Crosslinking mechanism of epoxy modification: the addition of epoxy methacrylate realizes further modification of the polymer network. Under weak acidic conditions at pH 4-5 and a temperature of 50-60 ℃, ring-opening reaction of the epoxy group occurs. This crosslinking reaction forms a three-dimensional network structure with high cohesion and chemical stability, which can effectively wrap cement particles and aggregates, and significantly improve the anti-dispersion performance.

[0023] Compared with the prior art, the present application has the beneficial effects that: the present application discloses an early high-strength underwater anti-dispersion concrete and a preparation method thereof, and belongs to the technical field of building materials. The prior art has the problems of concrete dispersion, slow strength development, etc. in underwater construction, which leads to great construction difficulty, unstable quality, prolonged construction period and increased cost, and seriously restricts the rapid development of fields such as marine engineering and water conservancy engineering. The present application successfully overcomes the limitations of the prior art by optimizing the material ratio and preparation process, realizes the characteristics of high early strength and excellent underwater anti-dispersion performance, and provides a high-performance, environmentally friendly and economical concrete material for the field of underwater construction. The beneficial effects of the present application are described in detail from multiple dimensions as follows.

[0024] (1) High early strength

[0025] The compressive strength of the concrete of the present application reaches 42.3-50.5 MPa within 3d, and the 28d strength reaches 65.8-78.2 MPa. Compared with traditional concrete, the early strength is increased by 30%-50%, and the late strength is increased by 20%-30%. This significant improvement is mainly due to the addition of nano-silicon dioxide, and its action mechanism is as follows: crystal nucleus effect: nano-silicon dioxide particles (specific surface area ≥185 m 2 / g) as heterogeneous crystal nucleus, reduce the nucleation potential barrier of hydration products, promote the generation of calcium silicate hydrate (C-S-H gel) and calcium hydroxide (CH crystal), and accelerate the hydration reaction process of cement. Pozzolanic effect: nano-silicon dioxide reacts with CH produced by cement hydration to generate secondary hydration products, further enhancing the strength of concrete. Filling effect: nano-silicon dioxide fills the micropores in cement stone, reduces the porosity, and improves the compactness, thereby significantly improving the mechanical properties. Through high-speed shear dispersion technology (stirring speed 1000-2000 rpm), nano-silicon dioxide is uniformly distributed in the concrete, avoiding agglomeration, and ensuring its performance to fully play. This characteristic enables the concrete to quickly reach the design strength in underwater construction, shortens the construction period, and improves the engineering efficiency.

[0026] (2) Excellent underwater anti-dispersion performance

[0027] The underwater dispersion resistance quality loss rate of the concrete is only 0.6-1.2%, while the traditional concrete is usually more than 5%-10%, which shows significant dispersion resistance advantage. This performance is mainly due to the synergistic effect of modified gel and polypropylene fiber: modified gel: by copolymerization of ethyl acrylate, methacrylic acid and 1,4-butanediol diacrylate, and modification by epoxy methacrylate, a high cohesive force gel material is prepared. The modified gel forms a gel network in the concrete, effectively wrapping the cement particles and fine aggregate, reducing the loss of materials caused by water erosion. Polypropylene fiber: fiber parameters are length 8-12mm, diameter 20-40μm, tensile strength ≥400MPa, forming a three-dimensional network structure in the concrete, enhancing the crack resistance and integrity, further preventing dispersion. This "double protection" system ensures the stability and integrity of the concrete during underwater pouring and hardening process, providing reliable guarantee for complex underwater environment.

[0028] (3) suitable fluidity

[0029] The fluidity of the concrete is 220.5-234.1mm, which is much better than the traditional underwater concrete (usually 180-200mm), ensuring good construction performance. This advantage is due to the following factors: high efficiency water reducing agent: using polycarboxylic acid ether, sodium lignosulfonate or sodium gluconate as high efficiency water reducing agent, which can significantly reduce the water-cement ratio and improve the fluidity of the paste, while not affecting the strength development. Nanometer silica dispersion liquid: prepared by high-speed shearing dispersion technology, which ensures uniform distribution of nanoparticles and avoids agglomeration, further improving the fluidity of the paste. The suitable fluidity makes the concrete easy to operate during underwater pouring, which can fully fill the formwork and gaps, improving the construction quality and efficiency.

[0030] (4) simple process and low cost

[0031] The preparation method of the present application includes material ratio design, nanometer material dispersion, modified gel preparation, molding and curing steps, and the process flow is clear and easy to operate, which is easy to industrialize. The specific advantages are as follows: high-speed shearing dispersion technology: effectively disperses nanometer silica, simple process, no need for complex equipment. Modified gel preparation: by copolymerization and modification steps, the preparation process is easy to control. Waste resource utilization: using marble waste powder (calcium carbonate content ≥90%, average particle size ≤50μm) as a component, which plays the role of filler and active component, not only reduces the production cost, but also realizes the high value utilization of industrial waste, which meets the concept of circular economy. Through process optimization and waste utilization, the production cost of the present application is significantly reduced, which lays an economic foundation for large-scale application.

[0032] (5) wide application range

[0033] The concrete of the present application is suitable for various underwater construction scenes, including: marine engineering: submarine tunnel, wharf, artificial island, etc. Water conservancy engineering: dam, bridge foundation, river restoration, etc. Underground engineering: subway, underwater pipeline, etc. Its excellent dispersion resistance and early high strength characteristics ensure that the concrete hardens quickly and maintains structural stability in complex underwater environments, meeting the stringent requirements of modern engineering for high-performance concrete.

[0034] (6) Significant economic and social benefits

[0035] The popularization and application of the concrete of the present application bring significant economic and social benefits: Economic benefits: Improve engineering quality: excellent dispersion resistance and high strength reduce construction quality problems, reduce maintenance and repair costs. Shorten the construction period: early high strength characteristics accelerate the construction progress, save time cost. Reduce material cost: waste utilization and optimized proportioning reduce raw material cost. Social benefits: Environmental protection: using marble waste powder reduces waste discharge and environmental pollution, conforms to the concept of green building and sustainable development. Safety: high-performance concrete improves the safety and durability of underwater engineering. Technological progress: promote building material technology innovation, provide new technical support for related industries.

[0036] Compared with the prior art, the present application has the following advantages: Performance improvement: early strength and dispersion resistance far exceed the prior art, meeting the stringent requirements of underwater construction. Cost control: waste utilization and process optimization reduce production cost and improve economic benefit. Environmental protection: reduce waste discharge, meet environmental protection requirements. Construction convenience: suitable fluidity, easy to pour, reduce construction difficulty.

[0037] With the rapid development of marine engineering, water conservancy engineering and other fields, the demand for high-performance underwater concrete is increasing. The present application has broad market prospects due to its excellent performance and economy: Market demand: in the next 10 years, the global underwater concrete market is expected to grow at an average annual rate of 5%-8%. Competitive advantage: performance, cost and environmental protection, occupying a favorable position in the market. Application potential: can be widely used in domestic and foreign underwater engineering projects.

[0038] In summary, compared with the prior art, the present application has the following advantages: early strength, underwater dispersion resistance, fluidity, process simplicity, cost control, application range and economic and social benefits. Through the synergistic effect of nano-silica, modified gel, polypropylene fiber and marble waste powder, combined with optimized preparation process, the present application develops a kind of high-performance, environmentally friendly and economical early high-strength underwater dispersion-resistant concrete, which provides an innovative material solution for underwater construction field. Its popularization and application will promote the technological progress and sustainable development of related industries, and bring significant economic and social benefits. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1is a transmission electron microscope image of the homogeneous dispersion prepared in Example 1.

[0040] Figure 2 is a scanning electron microscope image of the modified gel prepared in Example 1.

[0041] Figure 3 is a photograph of the slurry prepared in Example 1. DETAILED DESCRIPTION

[0042] The present application is described in detail below with specific examples, but the purpose and object of these exemplary embodiments are only to exemplify the present application, and do not constitute any form of any limitation on the actual scope of protection of the present application, nor limit the scope of protection of the present application. For the range of parameters not mentioned, the intermediate value is selected. Meanwhile, for the mass percentage or weight percentage not explicitly stated or mentioned, it generally refers to the final concentration after addition.

[0043] Example 1

[0044] Material ratio: prepared according to mass fraction (unit: g): type II Portland cement (specific surface area 2800 cm 2 / g) 80 g, nano-silica (particle size 10 nm, specific surface area 185 m 2 / g) 3 g, modified gel 5 g, polypropylene fiber (length 8 mm, diameter 20 μm, tensile strength 400 MPa) 0.5 g, marble waste powder (calcium carbonate content 90%, average particle size 50 μm) 10 g, polycarboxylate ether superplasticizer 0.5 g, water 25 g.

[0045] Nano-material dispersion: mix nano-silica, polycarboxylate ether superplasticizer and water, stir in a high-speed shearing machine at 1000 rpm for 5 min to form a homogeneous dispersion, as shown in Figure 1 .

[0046] Modified gel preparation: mix ethyl acrylate 4 g, methacrylic acid 2 g, 1,4-butanediol diacrylate 0.1 g, deionized water 100 g, after standing, add tetramethyl ethylenediamine 0.04 g (0.01 times the mass of ethyl acrylate), react at 40 °C for 15 min to synthesize the gel; then add epoxy methacrylate 2 g (0.5 times the mass of ethyl acrylate), react at pH 4, 50 °C for 8 h to obtain modified gel 5 g, as shown in Figure 2 .

[0047] Molding: mix the dispersion with cement, polypropylene fiber, marble waste powder and modified gel in a planetary mixer at 40 rpm for 8 min to form a homogeneous slurry, as shown in Figure 3 .

[0048] Curing: The paste was injected into the mold, sealed and cured at room temperature for 8h, 90% humidity; continued curing for 14d after demolding, 30℃, 90% humidity.

[0049] Examples 2-18: Refer to the process flow of Example 1, adjust the partial ratio or process parameters, see Table 1 and Table 2. The ratio covers the end point values (such as cement 80g, 120g, nano-silica 3g, 5g, etc.) and intermediate values (such as cement 90g, 100g, 110g) of all components and process parameters in the claims, and the modified gel ratio is designed according to the end point and intermediate value of the mass ratio of 4:2:0.1:100 to 10:6:1:150.

[0050] Table 1 Material ratio and process parameters of Examples 1-9 (unit: g)

[0051]

[0052]

[0053] Table 2 Material ratio and process parameters of Examples 10-18 (unit: g)

[0054]

[0055]

[0056] The modified gel ratio (Examples 1-18) The modified gel ratio is designed as 4:2:0.1:100 to 10:6:1:150 (mass ratio of ethyl acrylate:methacrylic acid:1,4-butanediol diacrylate:deionized water), and the specific ratio is as follows (unit: g): Example 1, 7, 13: ethyl acrylate 4 g, methacrylic acid 2 g, 1,4-butanediol diacrylate 0.1 g, deionized water 100 g, tetramethyl ethylenediamine 0.04 g, epoxy methacrylate 2 g. Example 2, 8, 14: ethyl acrylate 6 g, methacrylic acid 3 g, 1,4-butanediol diacrylate 0.4 g, deionized water 120 g, tetramethyl ethylenediamine 0.12 g, epoxy methacrylate 3 g. Example 3, 9, 15: ethyl acrylate 7 g, methacrylic acid 4 g, 1,4-butanediol diacrylate 0.5 g, deionized water 125 g, tetramethyl ethylenediamine 0.14 g, epoxy methacrylate 3.5 g. Example 4, 10, 16: ethyl acrylate 8 g, methacrylic acid 5 g, 1,4-butanediol diacrylate 0.7 g, deionized water 130 g, tetramethyl ethylenediamine 0.16 g, epoxy methacrylate 4 g. Example 5, 11, 17: ethyl acrylate 9 g, methacrylic acid 5.5 g, 1,4-butanediol diacrylate 0.9 g, deionized water 140 g, tetramethyl ethylenediamine 0.18 g, epoxy methacrylate 4.5 g. Example 6, 12, 18: ethyl acrylate 10 g, methacrylic acid 6 g, 1,4-butanediol diacrylate 1 g, deionized water 150 g, tetramethyl ethylenediamine 0.2 g, epoxy methacrylate 5 g.

[0057] Comparative Examples 1-16 verify the necessity of each component and process condition by missing key components, replacing components, or exceeding / being lower than the scope of the claims. The ratio and process parameters are shown in Table 3 and Table 4.

[0058] Comparative Examples 2-16 adjust part of the ratio or process parameters with reference to the process flow of Example 1, and the specific ratio and process parameters are shown in Table 4 and Table 5. The design of the comparative examples includes: missing key components (nano silicon dioxide, modified gel, polypropylene fiber, marble waste powder, high efficiency water reducing agent), replacing the modified gel with unmodified gel, replacing epoxy methacrylate with other components, exceeding or being lower than the parameter range.

[0059] Table 3 Material ratio and process parameters of Comparative Examples 1-8 (unit: g)

[0060]

[0061]

[0062] Table 4 Material ratio and process parameters of Comparative Examples 9-16 (unit: g)

[0063]

[0064]

[0065] Comparative Example 4 (unmodified gel): ethyl acrylate 4 g, methacrylic acid 2 g, 1,4-butanediol diacrylate 0.1 g, deionized water 100 g, tetramethyl ethylenediamine 0.04 g, reaction temperature 40 °C, time 15 min, no epoxy methacrylate modification step. Comparative Example 8: ethyl acrylate 4 g, methacrylic acid 2 g, 1,4-butanediol diacrylate 0.1 g, deionized water 100 g, tetramethyl ethylenediamine 0.04 g, epoxy methacrylate 0 g, reaction pH 4, temperature 50 °C, time 8 h.

[0066] To verify the performance of the early high-strength underwater anti-dispersion concrete prepared in Examples 1-18 and Comparative Examples 1-16, the following test methods are used, referring to national standards and related literature.

[0067] Compressive strength test

[0068] Method: According to the “Standard Test Methods for Physical and Mechanical Properties of Concrete” (GB / T50081-2019), the prepared concrete test pieces (size 100 mm x 100 mm x 100 mm) are cured under specified curing conditions (curing time, temperature, humidity of examples and comparative examples), and the compressive strength at 3d and 28d is tested respectively. Use a universal testing machine (model: WEW-1000D), loading rate 0.5 MPa / s, record the maximum load at the time of test piece failure, calculate the compressive strength (unit: MPa). Each group of test pieces is tested 3 times, and the average value is taken, with 1 decimal place. Reference: “Maohua Zhang; Danan Ma; Daocheng Zhou. Scouring erosion resistance of nano-marine concrete under four-factor coupling. Journal of Building Engineering 2025, 103.”.

[0069] Anti-dispersion test

[0070] Method: Refer to the "Test Method of Underwater Non-dispersive Concrete" (Iman Ali Hussein, Mansour Ghalehnovi, The impact of colloidal nanosilica (CNS) and polypropylene fibers (PP) on the properties of recycled concrete aggregate self-compacting concrete (SCC), Case Studies in Construction Materials, Volume 22, 2025, e04424), the prepared concrete slurry (200 g) is injected into a beaker containing 1000 mL of deionized water, simulating an underwater environment, stirring at 300 rpm for 10 min, then filtering, drying and weighing the residual solid mass, and calculating the mass loss rate (%). Mass loss rate = (initial mass - residual mass) / initial mass x 100%. Each group is tested 3 times, and the average value is taken, with 1 decimal place.

[0071] Slump test

[0072] Method: According to the "Technical Specification for Application of Concrete Admixtures" (GB50119-2013), the initial fluidity of the concrete slurry is tested using a fluidity test device (conical mold, top diameter 100 mm, bottom diameter 200 mm, height 300 mm). Pour the slurry into the conical mold, and after lifting the mold, measure the maximum expansion diameter of the slurry on the horizontal plane (unit: mm). Each group is tested 3 times, and the average value is taken, with 1 decimal place.

[0073] Test results

[0074] The following are the test results of Examples 1-18 and Comparative Examples 1-16.

[0075] Table 5 Test results of Examples 1-9

[0076]

[0077] Table 6 Test results of Examples 10-18

[0078]

[0079]

[0080] Table 7 Test results of Comparative Examples 1-8

[0081]

[0082] Table 8 Test results of Comparative Examples 9-16

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[0085] Result analysis: compressive strength: the 3d compressive strength of examples 1-18 ranges from 42.3-50.5MPa, and the 28d compressive strength ranges from 65.8-78.2MPa, which is significantly higher than that of comparative examples 1-16 (3d: 29.8-35.6MPa, 28d: 49.5-57.2MPa). This indicates that the synergistic effect of nanosilica, modified gel, polypropylene fiber and marble waste powder significantly improves the early and late strength of concrete. The absence of any key component (such as comparative examples 1-3, 5-7) or the deviation of process parameters from the range (such as comparative examples 9-16) leads to a decrease in strength. Anti-dispersion: the mass loss rate of examples 1-18 ranges from 0.6-1.2%, which is much lower than that of comparative examples 1-16 (3.1-4.0%). The addition of modified gel and polypropylene fiber effectively reduces the dispersion of concrete in underwater environment, and the absence of these components (such as comparative examples 3, 5) or the use of unmodified gel (such as comparative examples 4, 8) significantly increases the mass loss rate. Fluidity: the fluidity of examples 1-18 ranges from 220.5-234.1mm, which is better than that of comparative examples 1-16 (204.7-211.5mm). The dispersion effect of high-efficiency water reducer and nanosilica improves the fluidity of the slurry, and the absence of high-efficiency water reducer (such as comparative example 7) or the deviation of parameters from the range (such as comparative examples 9-12) leads to a decrease in fluidity. Examples 1-18 exhibit excellent compressive strength, anti-dispersion and fluidity by optimizing the ratio and process parameters, which verifies the necessity of each component and process condition in the claims. Comparative examples 1-16 show poor performance by missing key components, replacing components or deviating from the parameter range, which highlights the unique advantages of the formula of the present application. The synergistic effect of nanosilica and modified gel significantly improves the mechanical properties and underwater anti-dispersion of concrete, the addition of marble waste powder realizes the resource utilization, and the optimization of process parameters ensures the construction performance.

[0086] The above is a further detailed description of the present application in combination with specific embodiments, which cannot be considered as limiting the specific embodiments of the present application to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or replacements can be made, which should be considered as belonging to the protection scope determined by the claims submitted by the present application.

Claims

1. A method for preparing early-strength, high-strength, underwater anti-dispersion concrete, characterized in that: The process includes the following steps: Step S1: Material proportioning design: Prepare the following components by mass: cement: 80-120 parts, nano silica: 3-5 parts, modified gel: 5-10 parts, polypropylene fiber: 0.5-1.5 parts, marble waste powder: 10-20 parts, high-efficiency water-reducing agent: 0.5-1 part, water: 25-45 parts; Step S2: Nanomaterial dispersion treatment: Mix nano silica, high-efficiency water-reducing agent and water, and stir in a high-speed shear press at 1000-2000 rpm for 5-10 minutes to form a uniform dispersion; Step S3: Modified gel treatment: Mix ethyl acrylate, methacrylic acid, 1,4-butanediol diacrylate and... Ionized water was mixed at a mass ratio of (4-10):(2-6):(0.1-1):(100-150), and after standing, tetramethylethylenediamine (0.01-0.2 times the mass of ethyl acrylate) was added to synthesize gel. Then, epoxy methacrylate (0.5-1 times the mass of ethyl acrylate) was added, and the mixture was reacted at pH 4-5 and 50-60℃ for 8-12 hours to obtain modified gel. Step S4: Molding treatment: The dispersion obtained in step S2 was stirred with cement, polypropylene fiber, marble waste powder and the modified gel obtained in step S3 to form a uniform slurry. Step S5: Curing treatment: The slurry obtained in step S4 was injected into a mold for curing treatment.

2. The method for preparing early-strength, high-strength underwater anti-dispersion concrete according to claim 1, characterized in that: The cement used in step S1 is Type II Portland cement with a specific surface area ≥ 2800 cm². 2 / g; The nano-silica in step S1 has a particle size of 10-35nm and a specific surface area ≥185m². 2 / g.

3. The method for preparing early-strength underwater anti-dispersion concrete according to claim 1, characterized in that: The parameters of the polypropylene fiber in step S1 are as follows: length 8-12mm, diameter 20-40μm, tensile strength ≥400MPa; the parameters of the marble waste powder in step S1 are as follows: calcium carbonate content by mass percentage not less than 90%, average particle size ≤50μm.

4. The method for preparing early-strength underwater anti-dispersion concrete according to claim 1, characterized in that: In step S1, the high-efficiency water-reducing agent is polycarboxylate ether, sodium lignosulfonate, or sodium gluconate.

5. The method for preparing early-strength underwater anti-dispersion concrete according to claim 1, characterized in that: In step S3, the gel is synthesized at a temperature of 40-60℃ for 15-20 minutes.

6. The method for preparing early-strength underwater anti-dispersion concrete according to claim 1, characterized in that: The mixing method in step S4 is as follows: Mix at 40-60 rpm for 8-12 minutes in a planetary mixer.

7. The method for preparing early-strength underwater anti-dispersion concrete according to claim 1, characterized in that: The parameters for the curing treatment in step S5 are as follows: sealed curing at room temperature for 8-14 hours, with humidity controlled at 90-95%.

8. The method for preparing early-strength underwater anti-dispersion concrete according to claim 7, characterized in that: After curing, demold and continue curing for 14 days at a temperature of 30-40℃ and a humidity of 90%-95%.

9. A high-strength, early-stage underwater anti-dispersion concrete, characterized in that, The aforementioned high-strength underwater anti-dispersion concrete is obtained by the preparation method described in any one of claims 1-8.

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