A large flow state robust C80 concrete and its preparation method and application

Abstract

This invention relates to a high-flow-rate robust C80 concrete, its preparation method, and its applications, and relates to the field of marine floating reinforced concrete structure technology. This C80 concrete, on the one hand, utilizes a quaternary cementitious material combination system to provide a stable driving force for the early and later compressive strength growth of the concrete; on the other hand, by improving the water-reducing agent and introducing cellulose nanofibers as a key nanomaterial, combined with a precisely controlled dispersion process, the cellulose nanofibers form a stable three-dimensional nanofiber network in the water-reducing agent solution. This "network" plays a "physical bridging" and "spatial reinforcement" role in the concrete, significantly improving the concrete's anti-segregation, homogeneity, and cohesion while ensuring ultra-high fluidity. This makes the prepared C80 concrete particularly suitable for high-flow-rate pumping construction of complex structures.

Description

Technical Field

[0001] This invention relates to the field of marine floating reinforced concrete structure technology, and specifically to a high-flow-state robust C80 concrete, its preparation method, and its application. Background Technology

[0002] Floating offshore structures rely on floating structures to achieve stable operation on water, featuring mobility, strong environmental adaptability, and high space utilization. These structures primarily include floating wind turbines, marine ranches, and offshore oil platforms. These floating reinforced concrete structures are characterized by thin walls and dense reinforcement, placing high demands on the workability of the concrete. Furthermore, to ensure the structure can operate in the marine environment, resisting seawater corrosion and steel corrosion, and withstanding fatigue damage caused by long-term wave vibration, high requirements are placed on the concrete's density and durability. Projects often use high-grade concrete, such as UHPC and C80 concrete. However, UHPC has significant drawbacks, including high cost and large shrinkage, while C80 concrete offers distinct advantages.

[0003] To match the characteristics of floating structures, such as thin walls and dense reinforcement, concrete must possess high workability and maintain its workability. Once the cementitious material system is fixed, a high-performance water-reducing agent is needed to prepare high-performance C80 concrete suitable for floating structures. However, existing C80 concrete contains a large amount of powder and is highly sensitive to water-reducing agents, easily leading to incompatibility issues between the water-reducing agent and cement. This results in bleeding, segregation, and delamination of the concrete, causing surface sanding and internal weakness in the floating structure, reducing its strength and impermeability. Furthermore, existing patents generally lack clarity in their water-reducing agent formulations or only briefly mention them, with very little specific research on water-reducing agents suitable for C80 concrete in floating structures. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a high-flow-state robust C80 concrete. This high-flow-state robust C80 concrete focuses on the difficulties encountered in existing floating structures. On the one hand, it meets the high-strength requirements of concrete by selecting a reasonable combination system and dosage of cementitious materials; on the other hand, it ensures high workability and stability of the concrete based on a self-developed cellulose nanofiber reinforced network water-reducing agent. This high-flow-state robust C80 concrete can successfully meet the high-strength concrete requirements of floating structures.

[0005] This invention provides a high-flow-state robust C80 concrete, comprising the following raw materials in the following weight proportions:

[0006] The preparation method of the water-reducing agent includes the following steps: mixing a suspension containing cellulose nanofibers and a dispersant solution, mechanically stirring to form a preliminary suspension, and then ultrasonically treating it to obtain a dispersion containing cellulose nanofibers; mixing a thickener with water and stirring to form a basic colloid; adding the dispersion containing cellulose nanofibers to the basic colloid and stirring; adding a polycarboxylate water-reducing agent and a slow-release slump retainer; adding an auxiliary agent and stirring to obtain the water-reducing agent.

[0007] The aforementioned C80 concrete, on the one hand, provides a stable driving force for the early and later compressive strength growth of concrete through a quaternary cementitious material combination system; on the other hand, by improving the water-reducing agent and introducing cellulose nanofibers as a key nanomaterial, combined with a precisely controlled dispersion process, the cellulose nanofibers form a stable three-dimensional nanofiber network in the water-reducing agent solution. This "network" can play a role in "physical bridging" and "spatial reinforcement" in concrete, significantly improving the concrete's anti-segregation, homogeneity, and cohesion while ensuring ultra-high fluidity. This makes the prepared C80 concrete particularly suitable for high-flow-rate pumping construction of complex structures.

[0008] In one embodiment, the ultrasonic power of the ultrasonic treatment is 350-450W, the working mode is pulse, and the ultrasonic treatment time is 6-10 minutes.

[0009] In one embodiment, the mass ratio of the suspension containing cellulose nanofibers, the dispersant solution, the thickener, the polycarboxylate superplasticizer, and the slow-release slump retainer is (75-85):(3-5):(20-30):(3500-4500):(1000-1500). The solid content of the suspension containing cellulose nanofibers is 1-1.5%, and the mass percentage of the dispersant in the dispersant solution is 35-45%.

[0010] In one embodiment, the pulse is an ultrasonic treatment for 2 seconds, followed by a 1-second pause, and this cycle is repeated.

[0011] In one embodiment, the dispersant comprises sodium polyacrylate, the thickener comprises hydroxypropyl methylcellulose, the polycarboxylate superplasticizer comprises a TPEG-type polycarboxylate superplasticizer, and the slow-release slump retainer comprises an acrylic acid-hydroxyethyl acrylate-methyl methacrylate terpolymer.

[0012] The above-mentioned acrylic acid-hydroxyethyl acrylate-methyl methacrylate terpolymer is obtained by polymerizing acrylic acid (AA), hydroxyethyl acrylate (HEA), and methyl methacrylate (MMA) dropwise in an aqueous environment with the aid of an initiator (ammonium persulfate (APS)) at a temperature of 60-80°C.

[0013] In one embodiment, the additives include an air-entraining agent, an antifoaming agent, and a pH adjuster. The air-entraining agent includes triterpenoid saponins, the antifoaming agent includes a polyether-modified silicone antifoaming agent, and the pH adjuster includes citric acid.

[0014] In one embodiment, the mass ratio of the suspension containing cellulose nanofibers, dispersant solution, thickener, polycarboxylate superplasticizer, slow-release slump retainer, air-entraining agent, and defoamer is (75-85):(3-5):(20-30):(3500-4500):(1000-1500):(2-3):(25-40).

[0015] In one embodiment, the cement comprises silicate cement, and the fly ash microspheres have an activity index >90%, a loss on ignition <0.3%, a water requirement ratio of 80-90%, and a silica content ≥55%wt. The silica content of the silica ash is ≥95%wt, and the water requirement ratio is <120%. The fine aggregate includes river sand, and the fineness modulus of the river sand is 2.5-2.8; The coarse aggregate includes crushed granite, wherein the parent rock compressive strength of the crushed granite is >100MPa, and the crushing value of the crushed granite is <4%.

[0016] In one embodiment, the strength grade of the cement is P·Ⅱ52.5 or P·O52.5; the fly ash microspheres are global microspheres with a particle size of 0.1-5 micrometers; the quality of the mineral powder is not lower than S95; the granite crushed stone includes small stones and large stones, the particle size of the small stones is 5-10mm, the particle size of the large stones is 10-16mm, and the mass ratio of the small stones to the large stones is 4:6.

[0017] The present invention also provides a method for preparing the aforementioned high-fluidity robust C80 concrete, comprising the following steps: weighing raw materials, sequentially adding coarse aggregate, cementitious material, and fine aggregate, stirring, adding water and water-reducing agent, stirring, and obtaining high-fluidity robust C80 concrete.

[0018] In one embodiment, the cementing material includes: cement, fly ash microspheres, silica fume, and mineral powder.

[0019] In one embodiment, the method for preparing the water-reducing agent includes the following steps: mixing a suspension containing cellulose nanofibers and a dispersant solution, mechanically stirring to form a preliminary suspension, and then subjecting it to ultrasonic treatment to obtain a dispersion containing cellulose nanofibers; mixing a thickener with water and stirring to form a basic colloid; adding the dispersion containing cellulose nanofibers to the basic colloid; adding a polycarboxylate water-reducing agent and a slow-release slump retainer; adding an auxiliary agent; and stirring to obtain the water-reducing agent.

[0020] In one embodiment, the mass ratio of the suspension containing cellulose nanofibers, the dispersant solution, the thickener, the polycarboxylate superplasticizer, and the slow-release slump retainer is (75-85):(3-5):(20-30):(3500-4500):(1000-1500); the solid content of the suspension containing cellulose nanofibers is 1-1.5%, and the mass percentage of the dispersant in the dispersant solution is 35-45%. The ultrasonic power of the ultrasonic treatment is 350-450W, the working mode is pulse, and the ultrasonic treatment time is 6-10 minutes.

[0021] The present invention also provides a floating marine structure, the raw material of which includes the aforementioned high-fluidity robust C80 concrete.

[0022] The present invention also provides the application of the aforementioned high-fluidity robust C80 concrete or the aforementioned preparation method in the construction of floating structures at sea.

[0023] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a high-flow-state robust C80 concrete, its preparation method, and its application. This C80 concrete, on the one hand, utilizes a quaternary cementitious material combination system to provide a stable driving force for the early and later compressive strength growth of the concrete; on the other hand, by improving the water-reducing agent and introducing cellulose nanofibers as a key nanomaterial, combined with a precisely controlled dispersion process, the cellulose nanofibers form a stable three-dimensional nanofiber network in the water-reducing agent solution. This "network" can play a "physical bridging" and "spatial reinforcement" role in the concrete, significantly improving the concrete's anti-segregation, homogeneity, and cohesion while ensuring ultra-high fluidity. This makes the prepared C80 concrete particularly suitable for high-flow-state pumping construction of complex structures. Through multiple coupling methods, the prepared C80 concrete exhibits the following characteristics: slump of 220-260 mm, spread of 550-650 mm, air content of 1.0%-2.0%, pressure bleeding rate ≤0.5%, pouring time <10 s, 1-hour spread loss <0 mm, 2-hour spread loss <50 mm, 28-day compressive strength >80 MPa, elastic modulus >38 GPa, and 28-day chloride ion diffusion coefficient <5*10⁻⁶. -12 m 2 / s, 28d impermeability grade > P12. Detailed Implementation

[0024] To facilitate understanding of the present invention, a more complete description will be given below with reference to relevant embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] Unless otherwise specified, all reagents, materials, and equipment used in this embodiment are commercially available; unless otherwise specified, all test methods are conventional test methods in this field.

[0027] Example A robust C80 concrete with high fluidity and its preparation method.

[0028] I. Preparation of water-reducing agents.

[0029] Step 1: Preparation of Cellulose Nanofiber (CNF) Predispersion An ultrasonic cell disruptor was used to completely break up the hydrogen bond aggregates of CNFs at a controlled ambient temperature of 10±20℃, forming a stable and homogeneous colloidal dispersion of nanofibers. The main steps included: 1. Raw materials Cellulose nanofiber (CNF) suspension: solid content 1.0-1.5%, fiber diameter 20-50 nm, length 1-3 μm.

[0030] Dispersant: Sodium polyacrylate (PAAS), molecular weight approximately 5000, 40% aqueous solution.

[0031] Medium: Deionized water.

[0032] 2. Environmental and Equipment Conditions Equipment: Ultrasonic cell disruptor (with low-temperature water bath circulation tank), probe type, power ≥600W; Temperature control: The water bath temperature is maintained at 10±2℃ throughout the process; Container: jacketed beaker or glass reaction flask.

[0033] 3. Chemical / Physical Processes Ultrasonic cavitation and filament depolymerization: [CN·H2O]_aggregates + ultrasonic energy → [CNF]_single or small bundle of fibers·H2O High-intensity ultrasound generates cavitation bubbles in a liquid clock, which are then violently annihilated. The resulting shock waves and microjets mechanically tear apart the hydrogen bonds and van der Waals forces between CNFs, achieving nanoscale dispersion.

[0034] Electrostatic and steric stability CNF-OH (surface) + PAAS-COO - Na + →CNF-O...Na + ... - OOC-PAAS Sodium polyacrylate (PAAS) is adsorbed onto the negatively charged CNF surface via Na-ion bridging. Its polymer chains extend in water, and through the dual effects of electrostatic repulsion and steric hindrance, it prevents the filaments from re-aggregating.

[0035] 4. Operating Procedures and Control Points Premix: Add deionized water, CNF slurry and PAAS to a jacketed beaker, and premix with a mechanical stirrer at 500 rpm for 2 minutes to form a preliminary suspension; Ultrasonic processing: Immerse the ultrasonic probe 1-2 cm below the page, set the ultrasonic power to 400W, the working mode to pulse (on for 2 seconds, off for 1 second), and the total processing time is 8 minutes.

[0036] Endpoint determination and storage: The obtained CNF predispersant should be a homogeneous, slightly opalescent, viscous colloid without obvious particle texture. It should be prepared and used immediately, or sealed and stored at 4°C for no more than 24 hours.

[0037] Step 2: Compounding of the main water-reducing agent system (integration of CNF network) A stable CNF dispersion is orderly compounded with a polymeric thickener, a polycarboxylic acid mother liquor, and a slump retainer to construct a "nanofiber-polymer" synergistic network. The main steps include: 1. Materials used: CNF predispersant: prepared from the first step; High molecular weight thickener: Hydroxypropyl methylcellulose (HPMC), viscosity 80,000 mPa·s; Polycarboxylate superplasticizer mother liquor: TPEG type, solid content 40%, water reduction rate ≥30%; Slow-release slump retainer: Acrylic acid-hydroxyethyl acrylate-methyl methacrylate terpolymer, containing ester groups, solid content 30%; Deionized water.

[0038] 2. Environment and Equipment: Equipment: 500mL reaction vessel with a constant temperature jacket and frame-type stirring paddle.

[0039] Temperature: Maintain a temperature of 25±1℃ throughout the entire process.

[0040] Stirring: Stepless speed adjustment is available, from low to medium speed.

[0041] 3. Chemical and physical processes: HPMC Dissolution and Primary Network Formation: HPMC molecular chains hydrate and stretch, forming a long-chain physical entanglement network that provides the basic viscosity.

[0042] CNF-HPMC secondary network construction: CNF-OH (filaments) + HO-HPMC (molecular chain) → CNF-OH...O-HPMC (strong hydrogen bond) The abundant hydroxyl groups on the CNF surface form dense hydrogen bond crosslinking points with the hydroxyl groups and ether oxygen bonds on the HPMC chains. A single CNF can simultaneously connect multiple HPMC chains, forming an enhanced three-dimensional network structure with "filaments as nodes and polymer chains as connectors," resulting in a significant improvement in the system's viscoelasticity and stability.

[0043] Mild integration of polymers: Polycarboxylic acid and slump retainer molecules are physically mixed with the above-mentioned network through diffusion, and their polar groups such as carboxyl groups may also form weak hydrogen bonds with CNF, achieving functional integration.

[0044] 4. Operating procedures and key control points: Basic colloid preparation: Add deionized water to the reactor and heat to 30°C. Slowly sprinkle HPMC powder in while stirring at 300 rpm. After the addition is complete, increase the speed to 600 rpm and disperse for 30 minutes until a transparent and homogeneous colloid is formed. Cool down to 25°C.

[0045] CNF network introduction: Adjust the stirring speed to 400 rpm and slowly add all the CNF pre-dispersion liquid dropwise. After the addition is complete, maintain this stirring speed for 45 minutes. The viscosity will increase significantly during this stage, which is a sign of network formation.

[0046] Functional main agent compounding: While maintaining 25℃ and 300rpm, slowly add the following in sequence: a. Polycarboxylate superplasticizer mother liquor; b. Slow-release slump retainer.

[0047] Each ingredient should be added within approximately 10 minutes. After addition, continue stirring for 60 minutes to ensure complete homogenization of the system. High-speed stirring should be avoided during this stage to prevent shearing damage to the CNF network.

[0048] Step 3: Fine-tuning of functional additives and product standardization In a stable network system that has been established, functional microbubbles are introduced and stabilized to obtain a standard product. The main steps are as follows: 1. Raw materials used: Air-entraining agent: triterpenoid saponins, solid powder.

[0049] Defoamer: Polyether-modified silicone emulsion.

[0050] pH adjuster: citric acid, 10% aqueous solution.

[0051] 2. Environment and Process: Additives: Maintain a temperature of 25°C and reduce the stirring speed to 150 rpm. Add the triterpenoid saponin powder and stir for 15 minutes to ensure it is fully dissolved and effective. Slowly add the polyether-modified silicone defoamer and stir for 20 minutes. Adjust the pH of the system to 6.8-7.2 with citric acid solution.

[0052] Volume adjustment and homogenization: Add deionized water. Stir at 100 rpm for 30 minutes to ensure absolute homogenization.

[0053] In this embodiment, the mass ratio of the suspension containing cellulose nanofibers, the dispersant solution, the thickener, the polycarboxylate superplasticizer, the slow-release slump retainer, the air-entraining agent, and the defoamer is (75-85):(3-5):(20-30):(3500-4500):(1000-1500):(2-3):(25-40). The solid content of the suspension containing cellulose nanofibers is 1-1.5%, and the mass percentage of the dispersant in the dispersant solution is 35-45%.

[0054] The water-reducing agent prepared through the above steps can perform the following functions in C80 concrete: Anti-segregation: CNF network can firmly lock in the moisture and fine particles in the slurry, and there is no obvious bleeding or slurry separation at the aggregate edge even when the spread is >700mm.

[0055] Flowability and pumpability: Polycarboxylate provides strong dispersing power, and CNF network provides lubrication and support, allowing concrete to flow smoothly in the pump pipe with a uniform and stable flow rate, making it less prone to pipe blockage or intermittent flow.

[0056] Hardening properties: CNF can serve as a microfiber reinforcing phase, potentially improving the early crack resistance and toughness of concrete.

[0057] II. Preparation of a high-flow-state robust C80 concrete.

[0058] (1) Weigh all the raw materials in the mix proportion; (2) Add crushed stone (coarse aggregate) - cementitious material - sand (fine aggregate) in sequence, stir for 20 seconds, add water and water-reducing agent, and stir for 3 minutes; (3) Obtain freshly mixed concrete, test its workability, and simultaneously mold relevant specimens.

[0059] The cement selected should be Portland cement of strength grade P·Ⅱ52.5 or P·O52.5; the fly ash microspheres should be global microspheres of 0.1-5 micrometers, with an activity index greater than 90%, loss on ignition less than 0.3%, water requirement ratio between 80-90%, and silica content not less than 55%wt; the silica fume should have a silica content not less than 95%wt and a water requirement ratio <120%; the mineral powder should be mineral powder of quality not lower than S95 grade. The fine aggregate is river sand with a fineness modulus between 2.5 and 2.8; the coarse aggregate is granite crushed stone with a parent rock compressive strength > 100 MPa. The crushed stone particles are 5-10 mm and 10-16 mm in size, produced by impact crusher. The mass ratio of large to small stones is 6:4 during use, and the crushing value of the crushed stone is less than 4%.

[0060] Application Example 1 High-fluidity robust C80 concrete was prepared according to the preparation method of the embodiment. The specific steps are as follows.

[0061] I. Preparation of water-reducing agent, taking the preparation of 10kg with a solid content of 20% as an example: Step 1: CNF and Dispersion Add 720g of deionized water, 80g of CNF stock (1% solid content) and 4g of PASS (40%) solution to a jacketed beaker. Premix with a mechanical stirrer at 500rpm for 2min to form a preliminary suspension. Immerse the ultrasonic probe 1-2cm below the liquid surface, set the ultrasonic power to 400W, and the working mode to pulse (on for 2s, off for 1s). The total processing time is 8min. Obtain the CNF and dispersion. It should be prepared and used immediately, or sealed and stored at 4℃ for no more than 24h.

[0062] Step 2: Compounding of the main water-reducing agent system (integration of CNF network) Add 1200g of deionized water to the reactor and heat to 30℃. Slowly sprinkle in 24g of HPMC powder while stirring at 300rpm. After the addition is complete, increase the speed to 600rpm and disperse for 30min until a transparent, homogeneous colloid is formed. Then, cool to 25℃. Next, adjust the speed to 400rpm and slowly add all of the CNF pre-dispersion solution dropwise. After the addition is complete, stir for 45min. Maintaining 25℃ and 300rpm, add 4000g of polycarboxylate superplasticizer stock solution and 1200g of slow-release slump retainer in sequence. Continue stirring for 60min to ensure complete homogenization of the system.

[0063] Step 3: Fine-tuning of functional additives and product standardization Maintain a temperature of 25°C, reduce the stirring speed to 150 rpm, add 2.4 g of triterpenoid saponin powder, and stir for 15 minutes to ensure complete dissolution. Slowly add 32 g of polyether-modified silicone defoamer and stir for 20 minutes. Adjust the pH of the system to between 6.8 and 7.2 using a 10% citric acid solution (estimated to require 16 g). Add deionized water to bring the total mass to 10 kg, and stir at 100 rpm for 30 minutes to ensure absolute homogeneity.

[0064] The final product was 10 kg of water-reducing agent with 20% solid content.

[0065] In this embodiment, the mass ratio of the suspension containing cellulose nanofibers, the dispersant solution, the thickener, the polycarboxylate superplasticizer, the slow-release slump retainer, the air-entraining agent, and the defoamer is 80:4:24:4000:1200:2.4:32.

[0066] II. Preparation of robust C80 concrete with high fluidity.

[0067] 1. Weigh out 300 parts of cement, 150 parts of fly ash microspheres, 90 parts of mineral powder, 60 parts of silica fume, 875 parts of crushed stone (large stone: small stone mass ratio = 6:4), 746 parts of sand, 162 parts of water, and 7 parts of water-reducing agent. 2. Add crushed stone (coarse aggregate) - cementitious material - sand (fine aggregate) in sequence, stir for 20 seconds, add water and water-reducing agent, and stir for 3 minutes; 3. Obtain freshly mixed concrete, test its workability, and simultaneously mold relevant test specimens.

[0068] Example 2 1. Weigh out 300 parts of cement, 150 parts of fly ash microspheres, 90 parts of mineral powder, 60 parts of silica fume, 875 parts of crushed stone (large stone: small stone mass ratio = 6:4), 746 parts of sand, 162 parts of water, and 9 parts of water-reducing agent. 2. Add crushed stone, cementitious material, and sand in sequence, stir for 20 seconds, add water and water-reducing agent (ordinary polycarboxylate water-reducing agent), and stir for 3 minutes; 3. Obtain freshly mixed concrete, test its workability, and simultaneously mold relevant test specimens.

[0069] In this embodiment, the materials of cement, fly ash microspheres, mineral powder, silica fume, crushed stone, and sand are the same as in application embodiment 1, and the water-reducing agent used is a common polycarboxylate water-reducing agent.

[0070] Experimental Example The fresh mix performance of the C80 high-strength concrete prepared by applying Examples 1 and 2 is shown in Table 1, and the hardening performance is shown in Table 2.

[0071] Table 1 Performance of Freshly Mixed Materials

[0072] Table 2 Hardening properties

[0073] As can be seen from the comparison of Tables 1 and 2, the new water-reducing agent outperforms the ordinary polycarboxylate water-reducing agent in all aspects while ensuring the performance of C80 concrete, especially in terms of workability retention.

[0074] As can be seen from the comparison of Tables 1 and 2, the new water-reducing agent, while ensuring the performance of C80 concrete, has better later-stage strength and durability than ordinary polycarboxylate water-reducing agents, further highlighting the advanced nature of the configuration technology proposed in this patent.

[0075] Example 3 I. Preparation of water-reducing agent, taking 10kg as an example Step 1: CNF raw material ready for use CNF stock solution (1% solids content) is prepared directly without ultrasonic dispersion or PAAS addition.

[0076] Step 2: Compounding of the main water-reducing agent system (CNF added directly) (1) Add water to the reactor: 1920g of deionized water (to compensate for the 720g of water not used in step one, so as to balance the total amount).

[0077] (2) HPMC dispersion: Heat to 30°C, slowly sprinkle 24g HPMC powder while stirring at 300rpm, and after adding, increase the speed to 600rpm and disperse for 30min until a transparent colloid is formed, then cool to 25°C.

[0078] (3) Add CNF: Keep at 400 rpm and directly add 80g CNF raw slurry (1% solid content) and stir for 45 min (at this time, flocculent aggregates can be seen).

[0079] (4) Add functional main agent: Keep at 25℃ and 300rpm, add 4000g of polycarboxylate superplasticizer mother liquor and 1200g of slow-release slump retainer in sequence (add each for 10min), and continue stirring for 60min after the addition is complete.

[0080] Step 3: Addition of functional additives and volume adjustment (1) Induction: Reduce to 150 rpm, add 2.4 g of triterpenoid saponin powder, and stir for 15 min.

[0081] (2) Defoaming: Slowly add 32g of polyether modified silicone defoamer and stir for 20min.

[0082] (3) Adjust pH: Use 10% citric acid solution (about 16g) to adjust pH to 6.8-7.2.

[0083] (4) Homogenize to a constant volume: Add deionized water to a total mass of 10 kg and stir at 100 rpm for 30 min.

[0084] II. Preparation of C80 concrete.

[0085] 1. Weigh out 300 parts of cement, 150 parts of fly ash microspheres, 90 parts of mineral powder, 60 parts of silica fume, 875 parts of crushed stone (large stone: small stone = 6:4), 746 parts of sand, 162 parts of water, and 13 parts of water-reducing agent. 2. Add crushed stone, cementitious material, and sand in sequence, stir for 20 seconds, add water and water-reducing agent, and stir for 3 minutes; 3. Obtain freshly mixed concrete, test its workability, and simultaneously mold relevant test specimens.

[0086] The test results of the water-reducing agent prepared by the above steps in concrete are shown in the table below: Table 3 Performance of Freshly Mixed Food

[0087] Table 4 Hardening properties

[0088] As can be seen from the comparison of Examples 1-3, the water-reducing agent prepared without the dispersion process is not only less effective than the new water-reducing agent, but also has a lower performance compared with the ordinary polycarboxylate water-reducing agent. The main reason is that without the dispersion process, the CNF water-reducing agent prepared has agglomeration, which causes the water-reducing agent to lose its function.

[0089] As can be seen from the comparison of Examples 1-3, the novel water-reducing agent prepared by the method proposed in this patent fully disperses CNF, enabling it to exert a bridging network effect in the water-reducing agent, and the concrete prepared has good workability.

[0090] The C80 concrete of the present invention has the following significant technical advantages: (1) The nanocellulose network construction technology has been extended from special concrete (UHPC / underwater concrete) to the field of general-purpose high-performance concrete water-reducing agent, which solves the technical problem that conventional water-reducing agents cannot take into account both fluidity and anti-segregation properties under high water reduction rate.

[0091] (2) A “rigid-flexible” CNF-HPMC double hydrogen bond crosslinking network was proposed and constructed. The network uses rigid CNF as the skeleton node and flexible HPMC as the connecting chain. It achieves synergistic effect through dense hydrogen bonds, which significantly enhances the structural viscosity and water-locking ability of the slurry, which is different from the “density difference three-dimensional skeleton” and “flocculator-filled structure” in the prior art.

[0092] (3) A three-step precision construction and protection process was developed. High-quality CNF structural units were obtained through ultrasonic pre-dispersion, efficient network formation was promoted through stepwise composite and low-speed cross-linking, and the network integrity of the final product was protected through low-speed homogenization, thus ensuring the engineering realization of the microstructure design.

[0093] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0094] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A mass flow stable robust C80 concrete, characterized in that, The raw materials include the following parts by weight: The preparation method of the water-reducing agent includes the following steps: mixing a suspension containing cellulose nanofibers and a dispersant solution, mechanically stirring to form a preliminary suspension, and then ultrasonically treating it to obtain a dispersion containing cellulose nanofibers; mixing a thickener with water and stirring to form a basic colloid; adding the dispersion containing cellulose nanofibers to the basic colloid and stirring; adding a polycarboxylate water-reducing agent and a slow-release slump retainer; adding an auxiliary agent and stirring to obtain the water-reducing agent.

2. The mass flow regime robust C80 concrete according to claim 1, characterized in that, The ultrasonic power of the ultrasonic treatment is 350-450W, the working mode is pulse, and the ultrasonic treatment time is 6-10 minutes.

3. The high-flow-state robust C80 concrete according to claim 1, characterized in that, The mass ratio of the suspension containing cellulose nanofibers, dispersant solution, thickener, polycarboxylate superplasticizer, and slow-release slump retainer is (75-85):(3-5):(20-30):(3500-4500):(1000-1500). The solid content of the suspension containing cellulose nanofibers is 1-1.5%, and the mass percentage of the dispersant in the dispersant solution is 35-45%.

4. The high-flow-state robust C80 concrete according to claim 1, characterized in that, The dispersant includes sodium polyacrylate, the thickener includes hydroxypropyl methylcellulose, the polycarboxylate superplasticizer includes TPEG-type polycarboxylate superplasticizer, and the slow-release slump retainer includes a copolymer of acrylate-hydroxyethyl acrylate-methyl methacrylate.

5. The high-flow-state robust C80 concrete according to claim 1, characterized in that, The cement includes silicate cement, and the fly ash microspheres have an activity index >90%, a loss on ignition <0.3%, a water requirement ratio of 80-90%, and a silica content ≥55%wt. The silica content of the silica ash is ≥95%wt, and the water requirement ratio is <120%. The fine aggregate includes river sand, and the fineness modulus of the river sand is 2.5-2.8; The coarse aggregate includes crushed granite, wherein the parent rock compressive strength of the crushed granite is >100MPa, and the crushing value of the crushed granite is <4%.

6. The method for preparing high-flow-state robust C80 concrete according to any one of claims 1-5, characterized in that, The process includes the following steps: weighing the raw materials, adding coarse aggregate, cementitious material, and fine aggregate in sequence, stirring, adding water and water-reducing agent, stirring again, and obtaining high-fluidity robust C80 concrete.

7. The method for preparing high-flow-state robust C80 concrete according to claim 6, characterized in that, The preparation method of the water-reducing agent includes the following steps: mixing a suspension containing cellulose nanofibers and a dispersant solution, mechanically stirring to form a preliminary suspension, and then ultrasonically treating it to obtain a dispersion containing cellulose nanofibers; mixing a thickener with water and stirring to form a basic colloid; adding the dispersion containing cellulose nanofibers to the basic colloid, stirring, adding a polycarboxylate water-reducing agent and a slow-release slump retainer, adding an auxiliary agent, and stirring to obtain the water-reducing agent.

8. The method for preparing high-flow-state robust C80 concrete according to claim 6, characterized in that, The mass ratio of the suspension containing cellulose nanofibers, the dispersant solution, the thickener, the polycarboxylate superplasticizer, and the slow-release slump retainer is (75-85):(3-5):(20-30):(3500-4500):(1000-1500); the solid content of the suspension containing cellulose nanofibers is 1-1.5%, and the mass percentage of the dispersant in the dispersant solution is 35-45%. The ultrasonic power of the ultrasonic treatment is 350-450W, the working mode is pulse, and the ultrasonic treatment time is 6-10 minutes.

9. A floating structure for marine construction, characterized in that, The building materials include the high-fluidity robust C80 concrete as described in any one of claims 1-5.

10. The application of the high-fluidity robust C80 concrete of any one of claims 1-5 or the preparation method of any one of claims 6-8 in the construction of floating structures at sea.

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