High performance concrete mix for power plants and method of construction thereof

Abstract

The present application relates to the technical field of concrete, in particular to a high-performance concrete mixture for power plants and a construction method thereof. The interface-hydration synergistic regulation technology is adopted, in which cementitious materials, water, river sand and continuously graded gravel are used as the matrix, and poly-carboxylic acid water reducing agent, crystal nucleus slurry A / B and zwitterionic-hydrophobic copolymer brush modified silica particle B are alternately added in stages to pre-coat and synchronously disperse the coarse aggregate, so that the concrete with long-time slump retention, low bleeding, high early and long-term strength, significantly reduced electric flux and chloride ion permeability, improved sulfate erosion resistance and volume stability is obtained under the conventional mixing and pumping conditions. The in-mold temperature, layered pouring thickness, vibration frequency and curing time limit are specified to ensure the engineering implementability and durability, and the concrete is suitable for power plant structures in high-temperature, high-humidity and chlorine-containing environments, and the construction is reliable and the maintenance is convenient.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete, in particular to a high-performance concrete mixture for power plants and a construction method thereof. BACKGROUND

[0002] Power plant structures are long-term exposed to harsh environments such as high temperature, high humidity, and chloride salt corrosion, which puts high requirements on the durability, impermeability, and long-term stability of concrete. Traditional high-performance concrete often relies on high dosage of cementitious materials or complex admixture systems to improve density, but high hydration heat easily leads to temperature cracks, and large amounts of mineral admixtures delay the development of early strength, affecting construction progress. In addition, the adaptability of conventional polycarboxylate superplasticizers and cementitious materials is significantly different, which easily causes large loss of slump over time, bleeding segregation, and other problems, making it difficult to balance the pumping construction performance and durability requirements.

[0003] In terms of regulating the aggregate-paste interface, ordinary concrete has many microcracks and pores in the interfacial transition zone, which becomes the main channel for the invasion of harmful media such as chloride ions and sulfates. Existing technologies attempt to use active fillers such as silica fume and nano-silica to improve the interface structure, but nano-materials are prone to agglomeration and difficult to disperse uniformly, which further exacerbates the workability deterioration; while organic silane hydrophobic agents can reduce the water absorption rate, but they will weaken the adhesion between aggregate and cement paste, leading to a decrease in mechanical properties.

[0004] On the other hand, hydration process regulation mostly relies on the time sequence addition of chemical admixtures, but single early strength agent or nucleating agent is difficult to achieve gradient generation of hydration products and pore refinement. If the nucleation sites are consumed too early, the late hydration dynamics will be insufficient; if the nucleation is delayed, the early strength development will be slow. At the same time, the competitive adsorption of superplasticizers and nucleating agents on the surface of cementitious particles will interfere with the growth orientation of hydration products, causing crystal structure coarsening and a decrease in impermeability. Existing technologies lack effective means for simultaneous regulation of hydration and rheology, making it difficult to ensure smooth construction while achieving ordered optimization of microstructure. SUMMARY

[0005] Therefore, the present application aims to provide a high-performance concrete mixture for power plants and a construction method thereof, to solve the problems of existing power plant concrete that cannot balance high durability and pumping construction performance in high temperature and high humidity environments, weak aggregate-paste interface, inaccurate hydration process control, poor workability due to poor compatibility of admixtures, and insufficient impermeability.

[0006] To achieve the above objectives, the present invention provides a high-performance concrete mix for power plants, comprising the following raw materials: 585 kg of cementitious material, 167-191.2 kg of water, 780 kg of fine aggregate, 1000 kg of pre-coated coarse aggregate, 3-5 kg ​​of polycarboxylate superplasticizer, 13.5-20.7 kg of nucleation slurry A, 12-18 kg of nucleation slurry B, and 0.31-0.625 kg of zwitterionic-hydrophobic copolymer-modified silica particles B.

[0007] The surface of the pre-coated coarse aggregate is provided with a pre-coating layer formed by silica particles B modified by the zwitterionic-hydrophobic copolymer.

[0008] The crystal nucleus slurry A is an aqueous dispersion obtained by wet milling silica sol and calcium hydroxide in water;

[0009] The crystal nucleus slurry B is an aqueous dispersion containing silica sol and calcium hydroxide, and further contains polycarboxylic acid grafted silica particles A;

[0010] The polycarboxylic acid-grafted silica particles A are polycarboxylic acid layers formed on the surface of alkenylated silica particles A by grafting acrylic acid and polyethylene glycol methyl ether methacrylate.

[0011] The alkenylated silica particles A are obtained by treating silica particles A with γ-methacryloxypropyltrimethoxysilane;

[0012] The zwitterionic-hydrophobic copolymer-modified silica particles B are copolymer brushes with sulfobetaine methacrylate units and methyl methacrylate units grafted onto the surface of initiator-modified silica particles B.

[0013] The initiator-modified silica particles B are obtained by first treating silica particles B with 3-aminopropyltriethoxysilane and then grafting 2-bromoisobutyryl bromide.

[0014] Preferably, the cementitious material comprises 420 kg of cement, 120 kg of fly ash, and 45 kg of silica fume.

[0015] Preferably, the fine aggregate is river sand.

[0016] Preferably, the coarse aggregate is continuously graded 5-20mm crushed stone, and the pre-coating dosage is 10-25g of zwitterionic-hydrophobic copolymer-modified silica particles dispersed in 75-90g of deionized water per 1000kg of crushed stone. After spraying, the mixture is mixed with roller for 3min and allowed to stand for 10min to mature.

[0017] Preferably, the preparation ratio of the crystal nucleus slurry A is: 3000-4200g of silica sol, 2400-3300g of calcium hydroxide, 14000-15200g of deionized water, wet milling for 120min.

[0018] Preferably, the preparation ratio of the crystal nucleus slurry B is as follows: 2200-3000g of silica sol, 2400-3300g of calcium hydroxide, and 11000-12000g of deionized water. First, wet mill for 30 minutes, then add 800-1200g of polycarboxylate-grafted silica particles A and 5500-7000g of deionized water and continue wet milling for 90 minutes.

[0019] Preferably, the silica sol is of the type LudoxHS-40.

[0020] Preferably, the average particle size of the silica particles A is 15 nm, and the average particle size of the silica particles B is 350 nm.

[0021] Preferably, the preparation of the polycarboxylic acid grafted silica particles A includes: alkenylating 6000g of silica particles A with γ-methacryloyloxypropyltrimethoxysilane, and then reacting them in an aqueous phase with 900-1500g of acrylic acid, 1800-3000g of polyethylene glycol methyl ether methacrylate and 10-20g of ammonium persulfate at 60°C for 100-150min to obtain the grafted product.

[0022] Preferably, the preparation of the zwitterionic-hydrophobic copolymer-modified silica particles B includes: introducing 2500g of silica particles B with 3-aminopropyltriethoxysilane into an amino group, reacting it with 2-bromoisobutyryl bromide to obtain an initiator-modified surface; and reacting 800-1200g of sulfobetaine methacrylate and 90-150g of methyl methacrylate at 35°C for 40-60min under the catalysis of methanol / water system, cuprous bromide / sodium bromide / pentamethyldiethylenetriamine to obtain a surface copolymer brush.

[0023] Preferably, the mixing steps of the high-performance concrete mix for power plants are as follows: Add 420 kg of cement, 120 kg of fly ash, 45 kg of silica fume, 78 kg of fine aggregate, 135-148 kg of deionized water, and 1.5-2.5 kg of the first-stage polycarboxylate superplasticizer to the mixer in sequence, and mix at 120 rpm for 60 seconds; add 8.5-12.5 kg of crystal nucleus slurry B, and mix at 120 rpm for 90 seconds; add 12-18 kg of crystal nucleus slurry A, and mix at 120 rpm for 60 seconds and let stand for 60 seconds; then add 1.5-2.5 kg of the second-stage polycarboxylate superplasticizer and 30-40 kg of deionized water, and mix at 120 rpm for 60 seconds; add 3.5-5.5 kg of crystal nucleus slurry B and crystal nucleus slurry A... 1.5-2.7 kg of fine aggregate and 1000 kg of pre-coated crushed stone were added, and stirred at 120 rpm for 90 s. Simultaneously, 300-600 g of silica particles B modified with the zwitterionic-hydrophobic copolymer and dispersed in 2000-3200 g of deionized water were sprayed in and stirred at 60 rpm for 120 s. 120 g of air-entraining agent was added and stirred at 60 rpm for 60 s to obtain high-performance concrete mix for power plants.

[0024] This invention also provides a construction method for high-performance concrete mix for power plants, comprising the following steps: the mix is ​​poured into the formwork within 60 minutes of leaving the mixer, the formwork temperature is 10-28℃, it is poured in layers of 200-300mm, immersion vibration is performed at ≥120Hz, the vibration point spacing is ≤1.5×vibration radius, until it no longer settles significantly, the surface is smoothed 2-3 times before initial setting, and it is covered and kept moist within 30 minutes after pouring, and continuously cured for ≥7 days.

[0025] The beneficial effects of this invention are:

[0026] This invention pre-modifies the aggregate surface using a zwitterionic-hydrophobic copolymer brush, significantly reducing the aggregate-paste interfacial energy, enhancing the cement paste's encapsulation and wetting ability of the aggregate, and effectively inhibiting the formation of microcracks and capillary channels in the interfacial transition zone. This modified layer allows for dynamic adjustment of the interfacial water film thickness during concrete mixing, reducing bleeding and segregation caused by localized water accumulation, and improving the density and chemical stability of the hardened interfacial zone, thereby significantly improving resistance to chloride ion penetration and sulfate attack.

[0027] By adding polycarboxylate superplasticizer and two types of nucleation slurry in stages and alternately, precise timing control of the hydration process is achieved. In the initial stage, nucleation sites preferentially occupy the active sites on the surface of the gel particles, promoting the uniform precipitation of hydration products; in the middle stage, the continuous supply of nuclei prevents the coarsening of products during the hydration deceleration period, ensuring the continuous growth of the gel phase; in the later stage, the supplementary dispersion effect of the superplasticizer further optimizes the pore structure. This synergistic mechanism enables the hydration products to exhibit a gradient densification arrangement without sacrificing fluidity, significantly improving early strength development and long-term durability.

[0028] Polyethylene glycol segment-grafted silica particles exert a dual stabilizing effect in the slurry through steric hindrance and electrostatic repulsion. Their hydrophilic flexible chains can adsorb a large number of free water molecules, reducing water evaporation and migration paths, and ensuring that the mixture maintains its plasticity for a long time. At the same time, this design prevents the nanoparticles from agglomerating due to their high surface energy, allowing them to fully fill the pores between cementitious particles and form an interpenetrating network with hydration products, further enhancing the mechanical properties and impermeability of concrete.

[0029] The hierarchical gradation system of dual-scale silica achieves gradient filling of pores at the micro to nano scales. Fine particles preferentially occupy gel pores, optimizing the bulk density of early hydration products; while coarse particles act as skeletal nodes in later hydration, bridging the gel phase and aggregate to form a continuous reinforcing phase. This multi-scale synergistic effect effectively blocks the transport channels of harmful media, enabling concrete to maintain high volume stability and low permeability even under harsh environments. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0031] Figure 1 This is a flowchart of the mixing steps for the high-performance concrete mix for power plants according to the present invention.

[0032] Figure 2 The X-ray spectra of the 28-day milled samples prepared from the mixtures of Example 2 and Comparative Examples 1-6 of this invention are shown below.

[0033] Figure 3 The infrared spectrum of polycarboxylate-grafted silica particles A in Example 2 of this invention;

[0034] Figure 4 The infrared spectrum of the zwitterionic-hydrophobic copolymer brush-modified silica particles B in Example 2 of this invention is shown. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0036] Example 1:

[0037] Step S1: Preparation of alkenylated silica particles A

[0038] 10500g of anhydrous ethanol, 4500g of deionized water, and 6000g of silica particles A (average particle size 15nm) were added sequentially to the reaction vessel. Mechanical stirring was started and the speed was set to 300rpm. Then, 90g of γ-methacryloyloxypropyltrimethoxysilane was added, and glacial acetic acid was added dropwise to finely adjust the pH of the reaction solution to 4.0. The reaction system was heated to 40°C and stirred at a constant speed for 90min at this temperature. After the reaction was completed, the mixture was filtered and separated. The filter cake was washed three times with anhydrous ethanol and dried at 60°C and a vacuum of 100Pa for 360min to obtain alkenylated silica particles A.

[0039] Step S2: Preparation of polycarboxylate-grafted silica particles A

[0040] 7500g of deionized water, 900g of acrylic acid, 1800g of polyethylene glycol methyl ether methacrylate (number average molecular weight 950) and 10g of ammonium persulfate were added to a reaction vessel. The system temperature was 25°C, and the mixture was stirred at 300 rpm. Nitrogen was purged for 20 min to ensure an oxygen-free environment. Then, 6000g of alkenylated silica particles A were added, and the system temperature was raised to 60°C. The reaction was carried out at this temperature for 100 min while stirring at 300 rpm. After the reaction was completed, the mixture was separated by filtration and dried at 60°C and a vacuum of 100 Pa for 360 min to obtain polycarboxylate grafted silica particles A.

[0041] Step S3: Preparation of initiator-modified silica particles B

[0042] In a reaction vessel, 5000g of anhydrous ethanol and 2500g of silica particles B (average particle size 350nm) were added and dispersed evenly. 60g of 3-aminopropyltriethoxysilane was added, and the mixture was stirred at 40°C and 300rpm for 120min. After the reaction was completed, the mixture was filtered and washed three times with anhydrous ethanol to obtain aminated silica B. The aminated silica B was redispersed in 3500g of dichloromethane, and 100g of triethylamine was added as an acid absorbent. The system was placed in an ice-water bath and the temperature was kept below 5°C. 64g of 2-bromoisobutyryl bromide was added dropwise. After the addition was completed, the mixture was stirred at 5°C for 60min, then the temperature was raised to 25°C and the mixture was reacted for another 60min. After the reaction was completed, the mixture was filtered and the product was washed three times with diethyl ether. The product was dried at 40°C and 100Pa vacuum for 240min to obtain initiator-modified silica particles B.

[0043] Step S4: Preparation of zwitterionic-hydrophobic copolymer-modified silica particles B

[0044] In a nitrogen-environment reactor, 5000g methanol, 5000g deionized water, 800g sulfobetaine methacrylate, 90g methyl methacrylate, 6g cuprous bromide, 24g sodium bromide, 10g pentamethyldiethylenetriamine, and 2500g initiator-modified silica particles B were added sequentially. The mixture was stirred at 300 rpm for 40 min at 35°C. The reaction solution was then transferred to a dialysis bag and dialyzed in flowing deionized water for 48 h. After filtration, the solution was dried at 60°C and a vacuum of 100 Pa for 360 min to obtain zwitterionic-hydrophobic copolymer brush-modified silica particles B.

[0045] Step S5: Preparation of nucleus slurry A

[0046] Add 3000g of silica sol (Ludox HS-40), 2400g of calcium hydroxide, 14000g of deionized water, and 3000g of zirconia grinding balls (half 10mm and half 3mm in diameter) to the ball mill jar. Fix the ball mill jar on a planetary ball mill, set the speed to 300rpm, and wet mill for 120min. After ball milling, filter the slurry with a 200-mesh standard sieve to remove large particles that have not been crushed and grinding balls, and obtain crystal nucleus slurry A.

[0047] Step S6: Preparation of crystal nucleus slurry B

[0048] Add 2200g of silica sol (Ludox HS-40), 2400g of calcium hydroxide, 11000g of deionized water and 3000g of zirconium oxide grinding balls to a ball milling jar, and ball mill at 300rpm for 30min. Under continuous ball milling conditions, add 800g of polycarboxylate-grafted silica particles A and 5500g of deionized water to the jar, and continue ball milling for 90min to obtain crystal nucleus slurry B.

[0049] Step S7: Pre-coating the surface of the crushed stone

[0050] Take 1000kg of crushed stone (continuous gradation 5-20mm), place it in a mixer, disperse 10g of zwitterionic-hydrophobic copolymer brush-modified silica particles B in 90g of deionized water, and spray it evenly onto the surface of the rolling aggregate through a spray gun. Mix the roller at 20rpm for 3min, and then let it stand and mature for 10min to pre-coat the crushed stone.

[0051] Step S8: Preparation of concrete mix

[0052] Add 420 kg of cement (PO 52.5R), 120 kg of fly ash (Grade F), 45 kg of silica fume (industrial grade microsilica, median particle size 0.15 μm), 78 kg of river sand (fineness modulus 2.6), 135 kg of deionized water, and 1.5 kg of polycarboxylate superplasticizer (PCA-I type, solid content 40%) to a forced mixer in sequence, and stir at 120 rpm for 60 s; add 8.5 kg of nucleation slurry B, and maintain stirring at 120 rpm for 90 s; add 12 kg of nucleation slurry A, stir at 120 rpm for 60 s, and let stand for 60 s; then add 1.5 kg of polycarboxylate superplasticizer. Carboxylic acid water-reducing agent (PCA-I type, solid content 40%) and 30 kg of deionized water were stirred at 120 rpm for 60 s; 3.5 kg of crystal nucleus slurry B and 1.5 kg of crystal nucleus slurry A were added, and stirred at 120 rpm for 90 s; 702 kg of river sand (fineness modulus 2.6) and 1000 kg of pre-coated crushed stone were added, and 300 g of zwitterionic-hydrophobic copolymer brush-modified silica particles B were dispersed in 2000 g of deionized water and sprayed in; the mixture was stirred at 60 rpm for 120 s; 120 g of air-entraining agent (Sika AER) was added, and stirred at 60 rpm for 60 s to obtain high-performance concrete mix for power plants.

[0053] Example 2:

[0054] Step S1: Preparation of alkenylated silica particles A

[0055] 10500g of anhydrous ethanol, 4500g of deionized water, and 6000g of silica particles A (average particle size 15nm) were added sequentially to the reaction vessel. Mechanical stirring was started and the speed was set to 300rpm. Then, 120g of γ-methacryloyloxypropyltrimethoxysilane was added, and glacial acetic acid was added dropwise to finely adjust the pH of the reaction solution to 4.0. The reaction system was heated to 40°C and stirred at a constant speed for 120min at this temperature. After the reaction was completed, the mixture was separated by vacuum filtration. The filter cake was washed three times with anhydrous ethanol and dried at 60°C and a vacuum of 100Pa for 360min to obtain alkenylated silica particles A.

[0056] Step S2: Preparation of polycarboxylate-grafted silica particles A

[0057] 7500g of deionized water, 1200g of acrylic acid, 2400g of polyethylene glycol methyl ether methacrylate (number average molecular weight 950) and 15g of ammonium persulfate were added to a reaction vessel. The system temperature was 25°C, and the mixture was stirred at 300 rpm. Nitrogen was purged for 20 min to ensure an oxygen-free environment. Then, 6000g of alkenylated silica particles A were added, and the system temperature was raised to 60°C. The reaction was carried out at this temperature for 120 min while stirring at 300 rpm. After the reaction was completed, the mixture was separated by filtration and dried at 60°C and a vacuum of 100 Pa for 360 min to obtain polycarboxylate grafted silica particles A.

[0058] Step S3: Preparation of initiator-modified silica particles B

[0059] In a reaction vessel, 5000g of anhydrous ethanol and 2500g of silica particles B (average particle size 350nm) were added and dispersed evenly. 75g of 3-aminopropyltriethoxysilane was added, and the mixture was stirred at 40°C and 300rpm for 120min. After the reaction was completed, the mixture was filtered and washed three times with anhydrous ethanol to obtain aminated silica B. The aminated silica B was redispersed in 3500g of dichloromethane, and 120g of triethylamine was added as an acid absorbent. The system was placed in an ice-water bath and the temperature was kept below 5°C. 80g of 2-bromoisobutyryl bromide was added dropwise. After the addition was completed, the mixture was stirred at 5°C for 60min, and then the temperature was raised to 25°C and reacted for another 60min. After the reaction was completed, the mixture was filtered and the product was washed three times with diethyl ether. The product was dried at 40°C and a vacuum of 100Pa for 240min to obtain initiator-modified silica particles B.

[0060] Step S4: Preparation of zwitterionic-hydrophobic copolymer-modified silica particles B

[0061] In a nitrogen-environment reactor, 5000g methanol, 5000g deionized water, 1000g sulfobetaine methacrylate, 120g methyl methacrylate, 8g cuprous bromide, 30g sodium bromide, 12g pentamethyldiethylenetriamine, and 2500g initiator-modified silica particles B were added sequentially. The mixture was stirred at 300rpm for 45min at 35°C. The reaction solution was then transferred to a dialysis bag and dialyzed in flowing deionized water for 48h. After filtration, the solution was dried at 60°C and a vacuum of 100Pa for 360min to obtain zwitterionic-hydrophobic copolymer brush-modified silica particles B.

[0062] Step S5: Preparation of nucleus slurry A

[0063] Add 3600g of silica sol (Ludox HS-40), 2800g of calcium hydroxide, 14600g of deionized water, and 3000g of zirconia grinding balls (half 10mm and half 3mm in diameter) to the ball mill jar. Fix the ball mill jar on a planetary ball mill, set the speed to 300rpm, and wet mill for 120min. After ball milling, filter the slurry with a 200-mesh standard sieve to remove large particles that have not been crushed and grinding balls, and obtain crystal nucleus slurry A.

[0064] Step S6: Preparation of crystal nucleus slurry B

[0065] Add 2500g of silica sol (Ludox HS-40), 2800g of calcium hydroxide, 11500g of deionized water and 3000g of zirconia grinding balls to a ball milling jar, and ball mill at 300rpm for 30min. Under continuous ball milling conditions, add 1000g of polycarboxylate-grafted silica particles A and 6200g of deionized water to the jar, and continue ball milling for 90min to obtain crystal nucleus slurry B.

[0066] Step S7: Pre-coating the surface of the crushed stone

[0067] Take 1000kg of crushed stone (continuous gradation 5-20mm), place it in a mixer, disperse 15g of zwitterionic-hydrophobic copolymer brush-modified silica particles B in 85g of deionized water, and spray it evenly onto the surface of the rolling aggregate through a spray gun. Mix the roller at 20rpm for 3min, and then let it stand and mature for 10min to pre-coat the crushed stone.

[0068] Step S8: Preparation of concrete mix

[0069] Add 420 kg of cement (PO 52.5R), 120 kg of fly ash (Grade F), 45 kg of silica fume (industrial grade microsilica, median particle size 0.15 μm), 78 kg of river sand (fineness modulus 2.6), 141 kg of deionized water, and 2 kg of polycarboxylate superplasticizer (PCA-I type, solid content 40%) to a forced mixer in sequence, and mix at 120 rpm for 60 s; add 10.5 kg of nucleation slurry B, and maintain mixing at 120 rpm for 90 s; add 15 kg of nucleation slurry A, and mix at 120 rpm for 60 s, then let stand for 60 s; finally, add 2 kg of polycarboxylate superplasticizer. Acid-reducing water-reducing agent (PCA-I type, solid content 40%) and 35 kg of deionized water were stirred at 120 rpm for 60 s; 4.5 kg of crystal nucleus slurry B and 2.1 kg of crystal nucleus slurry A were added, and stirred at 120 rpm for 90 s; 702 kg of river sand (fineness modulus 2.6) and 1000 kg of pre-coated crushed stone were added, and 435 g of zwitterionic-hydrophobic copolymer brush-modified silica particles B were dispersed in 2465 g of deionized water and sprayed in; the mixture was adjusted to 60 rpm and stirred for 120 s; 120 g of air-entraining agent (Sika AER) was added, and stirred at 60 rpm for 60 s to obtain high-performance concrete mix for power plants.

[0070] Example 3:

[0071] Step S1: Preparation of alkenylated silica particles A

[0072] 10500g of anhydrous ethanol, 4500g of deionized water, and 6000g of silica particles A (average particle size 15nm) were added sequentially to the reaction vessel. Mechanical stirring was started and the speed was set to 300rpm. Then, 150g of γ-methacryloyloxypropyltrimethoxysilane was added, and glacial acetic acid was added dropwise to finely adjust the pH of the reaction solution to 4.0. The reaction system was heated to 40°C and stirred at a constant speed for 150min at this temperature. After the reaction was completed, the mixture was filtered and separated. The filter cake was washed three times with anhydrous ethanol and dried at 60°C and a vacuum of 100Pa for 360min to obtain alkenylated silica particles A.

[0073] Step S2: Preparation of polycarboxylate-grafted silica particles A

[0074] 7500g deionized water, 1500g acrylic acid, 3000g polyethylene glycol methyl ether methacrylate (number average molecular weight 950) and 20g ammonium persulfate were added to a reaction vessel. The system temperature was 25°C, and the mixture was stirred at 300 rpm. Nitrogen was purged for 20 min to ensure an oxygen-free environment. Then, 6000g of alkenylated silica particles A were added, and the system temperature was raised to 60°C. The reaction was carried out at this temperature for 150 min while stirring at 300 rpm. After the reaction was completed, the mixture was separated by filtration and dried at 60°C and a vacuum of 100 Pa for 360 min to obtain polycarboxylate grafted silica particles A.

[0075] Step S3: Preparation of initiator-modified silica particles B

[0076] In a reaction vessel, 5000g of anhydrous ethanol and 2500g of silica particles B (average particle size 350nm) were added and dispersed evenly. 90g of 3-aminopropyltriethoxysilane was added, and the mixture was stirred at 40°C and 300rpm for 120min. After the reaction was completed, the mixture was filtered and washed three times with anhydrous ethanol to obtain aminated silica B. The aminated silica B was redispersed in 3500g of dichloromethane, and 140g of triethylamine was added as an acid absorbent. The system was placed in an ice-water bath and the temperature was kept below 5°C. 96g of 2-bromoisobutyryl bromide was added dropwise. After the addition was completed, the mixture was stirred at 5°C for 60min, then the temperature was raised to 25°C and the mixture was reacted for another 60min. After the reaction was completed, the mixture was filtered and the product was washed three times with diethyl ether. The product was dried at 40°C and a vacuum of 100Pa for 240min to obtain initiator-modified silica particles B.

[0077] Step S4: Preparation of zwitterionic-hydrophobic copolymer-modified silica particles B

[0078] In a nitrogen-environment reactor, 5000g methanol, 5000g deionized water, 1200g sulfobetaine methacrylate, 150g methyl methacrylate, 10g cuprous bromide, 36g sodium bromide, 14g pentamethyldiethylenetriamine, and 2500g initiator-modified silica particles B were added sequentially. The mixture was stirred at 300rpm for 60min at 35°C. The reaction solution was then transferred to a dialysis bag and dialyzed in flowing deionized water for 48h. After filtration, the solution was dried at 60°C and a vacuum of 100Pa for 360min to obtain zwitterionic-hydrophobic copolymer brush-modified silica particles B.

[0079] Step S5: Preparation of nucleus slurry A

[0080] Add 4200g of silica sol (Ludox HS-40), 3300g of calcium hydroxide, 15200g of deionized water, and 3000g of zirconia grinding balls (half 10mm and half 3mm in diameter) to the ball mill jar. Fix the ball mill jar on a planetary ball mill, set the speed to 300rpm, and wet mill for 120min. After ball milling, filter the slurry with a 200-mesh standard sieve to remove large particles that have not been crushed and grinding balls, and obtain crystal nucleus slurry A.

[0081] Step S6: Preparation of crystal nucleus slurry B

[0082] Add 3000g of silica sol (Ludox HS-40), 3300g of calcium hydroxide, 12000g of deionized water and 3000g of zirconium oxide grinding balls to a ball milling jar, and ball mill at 300rpm for 30min. Under continuous ball milling conditions, add 1200g of polycarboxylate-grafted silica particles A and 7000g of deionized water to the jar, and continue ball milling for 90min to obtain crystal nucleus slurry B.

[0083] Step S7: Pre-coating the surface of the crushed stone

[0084] Take 1000kg of crushed stone (continuous gradation 5-20mm), place it in a mixer, disperse 25g of zwitterionic-hydrophobic copolymer brush-modified silica particles B in 75g of deionized water, and spray it evenly onto the surface of the rolling aggregate through a spray gun. Mix the roller at 20rpm for 3min, and then let it stand and mature for 10min to pre-coat the crushed stone.

[0085] Step S8: Preparation of concrete mix

[0086] Add 420 kg of cement (PO 52.5R), 120 kg of fly ash (Grade F), 45 kg of silica fume (industrial grade microsilica, median particle size 0.15 μm), 78 kg of river sand (fineness modulus 2.6), 148 kg of deionized water, and 2.5 kg of polycarboxylate superplasticizer (PCA-I type, solid content 40%) to a forced mixer in sequence, and mix at 120 rpm for 60 s; add 12.5 kg of nucleation slurry B, and maintain mixing at 120 rpm for 90 s; add 18 kg of nucleation slurry A, and mix at 120 rpm for 60 s, then let stand for 60 s; finally add 2.5 kg of... Polycarboxylate superplasticizer (PCA-I type, solid content 40%) was mixed with 40 kg of deionized water at 120 rpm for 60 s; 5.5 kg of nucleation slurry B and 2.7 kg of nucleation slurry A were added, and the mixture was stirred at 120 rpm for 90 s; 702 kg of river sand (fineness modulus 2.6) and 1000 kg of pre-coated crushed stone were added, and 600 g of zwitterionic-hydrophobic copolymer brush-modified silica particles B were dispersed in 3200 g of deionized water and sprayed in; the mixture was stirred at 60 rpm for 120 s; 120 g of air-entraining agent (Sika AER) was added, and the mixture was stirred at 60 rpm for 60 s to obtain high-performance concrete mix for power plants.

[0087] Comparative Example 1:

[0088] The difference between Comparative Example 1 and Example 2 is that: in step S7, the crushed stone surface is not pre-coated, and in S8, crushed stone is used directly. The other conditions are the same as in Example 2.

[0089] Comparative Example 2:

[0090] The difference between Comparative Example 2 and Example 2 is that in step S8, all the crystal nucleus slurry A and crystal nucleus slurry B were combined into a single initial addition, and the polycarboxylate superplasticizer was not added alternately in stages and in small amounts as in Example 2. The other conditions were the same as in Example 2.

[0091] Comparative Example 3:

[0092] The difference between Comparative Example 3 and Example 2 is that: in step S4, sulfobetaine methacrylate is not added, and only methyl methacrylate is polymerized on the surface of initiator-modified silica particles B to form a hydrophobic copolymer brush. The other conditions are the same as in Example 2.

[0093] Comparative Example 4:

[0094] The difference between Comparative Example 4 and Example 2 is that in step S2, all of the polyethylene glycol methyl ether methacrylate was replaced with an equal mass of methyl methacrylate to prepare polycarboxylate-grafted silica particles A, while the other conditions were the same as in Example 2.

[0095] Comparative Example 5:

[0096] The difference between Comparative Example 5 and Example 2 is that the silica particles A and B in the raw materials are interchanged. That is, the silica particles B prepared in step S2 are polycarboxylate grafted silica particles, and the silica particles A modified with zwitterionic-hydrophobic copolymer are prepared in step S4. The other conditions are the same as in Example 2.

[0097] Comparative Example 6:

[0098] The difference between Comparative Example 6 and Example 2 is that in step S8, the addition is carried out in stages, but in each stage, the polycarboxylate superplasticizer is added first, followed by the crystal nucleus slurry A and crystal nucleus slurry B. The order of addition is the opposite of that in Example 2, while the other conditions are the same as those in Example 2.

[0099] Performance testing:

[0100] Sample preparation: The mixture was cast into 3 cubes of 150mm and 3 prisms of 100mm×100mm×400mm. In addition, 6 discs of φ100mm×50mm were prepared for ion penetration testing. After demolding, the samples were cured at 20±2°C and RH 96±1% for the specified age.

[0101] Slump: According to GB / T50080-2016, the test room temperature is 20±2°C. The initial value is measured within 5 minutes after mixing. A standard slump cone (100mm at the top, 200mm at the bottom, and 300mm in height) is placed on a wet steel plate. The material is loaded in three layers, and each layer is tamped evenly 25 times. The cone is lifted for 5-10 seconds, and the slump is read in mm. The remaining mixture is covered with a film and sealed, and left to stand for 60 minutes. The cone forming, cone lifting, and reading are repeated, and the slump is recorded after 60 minutes. The results are shown in Table 1.

[0102] Gas content and apparent density: According to GB / T50080-2016, after the pressure method gas content meter is qualified, the mixture is loaded into a graduated cylinder in two layers, the mouth surface is scraped flat, standard pressure is applied and the gas content % is read. After correction by the instrument coefficient, the mass of the mixture is weighed in a container of known volume to calculate the apparent density. The results are shown in Table 1.

[0103] Water bleeding rate: According to GB / T50080-2016, take the mixture and put it into a transparent graduated cylinder, scrape the mouth surface level, cover with a film to prevent evaporation, and let it stand at 20±2°C. Collect the water bleeding every 10 min and read the volume until 120 min. Calculate the cumulative water bleeding rate (%) according to the standard. The results are shown in Table 1.

[0104] Compressive strength: According to GB / T50081-2019, 150 mm cubes were tested on a 2000 kN press at 1 day and 28 days of age; the loading rate was 0.8 MPa / s, and the test was stopped when the failure occurred. The average of the three samples was recorded. The results are shown in Table 1.

[0105] Splitting tensile strength: According to GB / T50081-2019, a 28d cube was taken, and steel bars were placed symmetrically for loading at a rate of 0.04-0.06 MPa / s until failure; the average of 3 samples was taken and recorded. The results are shown in Table 1.

[0106] Chloride ion penetration resistance: According to the GB / T50082-2024 electric flux method, a φ100mm×50mm circular disc was sealed with epoxy at both ends and vacuum-saturated with water. The specimen was clamped between a 0.3mol / L NaOH chamber and a 3.0% NaCl chamber, and a 60V DC current was applied for 6h. The current A was recorded every 30min and the electric flux C was obtained by integration. The results are shown in Table 1.

[0107] X-ray diffraction: 28-day ground samples (<80μm) were tested on an X-ray diffractometer with 2θ = 5-70° and a step of 0.02°.

[0108] Infrared spectroscopy: Samples were prepared using the KBr pellet method, at 4000-400 cm⁻¹ -1 Scan, resolution 4cm -1 .

[0109] Table 1 Performance Test Results

[0110]

[0111] Data Analysis:

[0112] As can be seen from the data in Examples 1–3 in Table 1, the mixture prepared by this invention has significant advantages in maintaining fluidity, resisting bleeding, early strength, and density. This is mainly due to the staged, small-volume addition of two types of nucleation slurry and polycarboxylate superplasticizer in alternating combinations, which allows the hydration products to obtain more uniform nucleation sites in the early stage. Combined with the reduction of aggregate-slurry interfacial energy by zwitterionic-hydrophobic brushes, the formation of microcracks and capillary bleeding channels in the interfacial transition zone is significantly suppressed. At the same time, the steric hindrance and hydrophilicity of polyethylene glycol segments ensure the stable dispersion of particles during the mixing process without sacrificing the fluidity of the mixture. The hierarchical gradation of silica with two particle sizes plays a role in pore filling and skeleton-gel complementarity in the later stage of hydration, thereby simultaneously improving splitting tensile strength and resistance to ionic intrusion. This system can achieve a balance of workability, strength, and durability within the conventional process window without relying on extreme admixture dosages, meeting the dual requirements of durability and pumpability for power plant structures.

[0113] As can be seen from the data in Example 2 and Comparative Example 1 in Table 1, after removing the pre-coating on the crushed stone surface, the fluidity of the mixture continued to decrease while bleeding increased. The main reason is that the interfacial energy was not reduced, resulting in insufficient wetting and bonding of the paste on the aggregate surface. This easily leads to the formation of a weak concrete interface transition zone and induces capillary upwelling channels, thereby amplifying slump decay and electrical flux. Therefore, it is evident that the extremely low dose of zwitterionic-hydrophobic brush pre-coating produces a synergistic effect in interface control, balancing slump retention and impermeability.

[0114] As can be seen from the data in Example 2 and Comparative Example 2 in Table 1, after changing the nucleation slurry to a one-time initial addition, both early and late strength were damaged, and slump retention deteriorated. The main reason is that the nucleation-growth process changed from continuous nucleation supply to instantaneous nucleation supply, which limited crystal growth and pore structure optimization, and caused competitive adsorption with the water-reducing agent. It is evident that staged, small-dose alternating addition has a significant synergistic effect on maintaining hydration kinetics and rheological stability.

[0115] As can be seen from the data in Example 2 and Comparative Example 3 in Table 1, when only the hydrophobic brush is retained and the zwitterionic monomer is missing, the initial fluidity is considerable, but the slump retention decreases and the resistance to ion intrusion deteriorates. The main reason is that without the charged hydrophilic group, the interfacial electric bilayer regulation and the stability of the adsorbed water film are insufficient, making it easier for micro-phase separation and electrical conduction channels to occur in the later stages of mixing. It can be seen that the zwitterionic-hydrophobic bicomponent exhibits a synergistic effect of 1+1>2 in terms of interfacial shielding and slump retention.

[0116] As can be seen from the data in Example 2 and Comparative Example 4 in Table 1, replacing polyethylene glycol methyl ether methacrylate with methyl methacrylate significantly weakens the dispersion and slump retention capabilities, leading to a decrease in density and strength. The main reason is that the loss of hydrophilic flexible segments reduces the steric hindrance stability and hydration ion shielding ability of the particle-slurry mixture, making it difficult to optimize the pore structure. This indicates that polyethylene glycol segments play a crucial synergistic role in achieving both dispersion and density objectives.

[0117] As can be seen from the data in Table 1 for Example 2 and Comparative Example 5, the balance of workability, strength, and durability was disrupted after the A / B particle size systems were interchanged. The main reason for this is that the timing matching of hierarchical filling and nucleation-growth was disrupted, resulting in insufficient early-stage occupancy by fine particles and difficulty for coarse particles to effectively reinforce the framework in the later stages. This indicates that the gradation sequence of dual-scale silica has a synergistic amplification effect on the formation of a dense, continuous phase.

[0118] As can be seen from the data in Table 1 for Example 2 and Comparative Example 6, when the feeding order is reversed to water-reducing agent first and then crystal nuclei, the early strength and slump retention are both lower than in Example 2. The main reason is that the water-reducing agent preferentially forms an adsorption layer, weakening the adhesion and continued supply capacity of crystal nuclei, and reducing the hydration nucleation efficiency. This indicates that the alternation of crystal nuclei and water-reducing agents is crucial for early structural control and rheological stability.

[0119] fromFigure 2 It can be seen that Example 2 exhibits a stronger CSH amorphous peak at 28-34°, while the Ca(OH)2 peaks at 18.1° and 34.1° are significantly weakened, and the ettringite peaks at 9.1° and other locations are also relatively low. In Comparative Examples 1, 4, 5, and 6, the intensity of the Ca(OH)2 and ettringite peaks generally increases, and a weak residual silicate peak is visible near 32°, indicating insufficient densification of the hydration products. Overall, Example 2 shows more complete hydration and a denser pore structure.

[0120] from Figure 3 It can be seen that 1730 / 1705cm -1 The carbonyl bimodal distribution clearly characterizes the coexistence of the ester group of polyethylene glycol dimethacrylate and the carboxylic acid group of polyacrylic acid, at 1100 and 1045 cm⁻¹. -1 The strong band formed is the coupling absorption of Si-O-Si and polyether COC, at 3430 cm⁻¹. -1 The broadband corresponds to the carboxyl group / OH group of adsorbed water, 2955 / 288 cm⁻¹ -1 The hydrocarbon group is CH, and the values ​​are 950 and 800 cm. -1 Identify the symmetrical stretching of Si-OH and Si-O-Si respectively; and simultaneously measure 1560 / 1410 cm⁻¹. -1 The weak bands suggest the presence of a small amount of carboxylate groups, indicating that the silica surface has been successfully grafted with polymers containing carboxylic acid and polyether segments.

[0121] from Figure 4 It can be seen that the sample is 1730cm. -1 Strong absorption at 1705cm -1 Shoulder peak characterizes ester groups; 1220 / 1185cm -1 -SO3 - Double peaks and 1100cm -1 Wide-strength Si-O-Si main band (with 1040cm) -1 (Shoulder) jointly indicates the coexistence of a sulfobetaine / methyl methacrylate copolymer brush and a silica skeleton; 950-970cm -1 The absorption is attributed to Si-OH and quaternary ammonium-related vibrations; 2950 / 2924 / 2870 cm⁻¹ -1 Hydrocarbon group C–H, 800cm -1 The Si–O–Si symmetric stretching is observed; this indicates that the surface modification of silica B by the zwitterionic-hydrophobic copolymer brush has been achieved.

[0122] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A high performance concrete mix for power plants, characterized by, comprising cementitious materials 585 kg, water 167-191.2 kg, fine aggregate 780 kg, pre-coated coarse aggregate 1000 kg, polycarboxylate superplasticizer 3-5 kg, crystal nucleus slurry A 13.5-20.7 kg, crystal nucleus slurry B 12-18 kg, and zwitterionic-hydrophobic copolymer brush modified silica particle B 0.31-0.625 kg; the pre-coated coarse aggregate is provided with a pre-coating layer formed by the zwitterionic-hydrophobic copolymer brush modified silica particle B; the crystal nucleus slurry A is a water dispersion of silica sol and calcium hydroxide obtained by wet milling in water; the crystal nucleus slurry B is a water dispersion containing silica sol and calcium hydroxide, and further containing polycarboxylate grafted silica particle A; the polycarboxylate grafted silica particle A is a polycarboxylate layer formed by grafting acrylic acid and polyethylene glycol methyl ether methacrylate onto the surface of alkenylated silica particle A; the zwitterionic-hydrophobic copolymer brush modified silica particle B is a copolymer brush containing sulfobetaine methacrylate unit and methyl methacrylate unit grafted onto the surface of initiator modified silica particle B; the average particle size of the silica particle A is 15 nm, and the average particle size of the silica particle B is 350 nm; the mixing procedure of the high performance concrete mixture for power plant is as follows: adding cementitious materials 585 kg, fine aggregate 78 kg, deionized water 135-148 kg, and first-stage polycarboxylate superplasticizer 1.5-2.5 kg into a mixer in sequence, stirring at 120 rpm for 60 s; adding crystal nucleus slurry B 8.5-12.5 kg, stirring at 120 rpm for 90 s; adding crystal nucleus slurry A 12-18 kg, stirring at 120 rpm for 60 s and standing for 60 s; adding second-stage polycarboxylate superplasticizer 1.5-2.5 kg and deionized water 30-40 kg, stirring at 120 rpm for 60 s; adding crystal nucleus slurry B 3.5-5.5 kg and crystal nucleus slurry A 1.5-2.7 kg, stirring at 120 rpm for 90 s; adding fine aggregate 702 kg and pre-coated coarse aggregate 1000 kg at the same time, and spraying zwitterionic-hydrophobic copolymer brush modified silica particle B 300-600 g dispersed in deionized water 2000-3200 g, stirring at 60 rpm for 120 s; adding air entraining agent 120 g, stirring at 60 rpm for 60 s, to obtain the high performance concrete mixture for power plant.

2. The high performance concrete mix for power plants according to claim 1, characterized in that, The cementitious materials comprise 420 kg of cement, 120 kg of fly ash, and 45 kg of silica fume; and the fine aggregate is river sand.

3. The high performance concrete mix for power plants according to claim 1, characterized in that, The coarse aggregate is continuously graded 5-20 mm gravel, and the pre-coating amount is 10-25 g of zwitterionic-hydrophobic copolymer brush modified silica particle B dispersed in 75-90 g of deionized water per 1000 kg of coarse aggregate, and the spraying is followed by drum mixing for 3 min and standing for 10 min.

4. The high performance concrete mix for power plants according to claim 1, wherein The preparation ratio of the crystal nucleus slurry A is: 3000-4200 g of silica sol, 2400-3300 g of calcium hydroxide, and 14000-15200 g of deionized water, and wet grinding for 120 min.

5. The high performance concrete mix for power plants according to claim 1, wherein The preparation ratio of the crystal nucleus slurry B is: 2200-3000 g of silica sol, 2400-3300 g of calcium hydroxide, and 11000-12000 g of deionized water, wet grinding for 30 min first, then adding 800-1200 g of polycarboxylic acid grafted silica particles A and 5500-7000 g of deionized water and continuing wet grinding for 90 min.

6. The high performance concrete mix for power plants according to claim 1, wherein The silica sol is of the model Ludox HS-40.

7. The high performance concrete mix for power plants according to claim 1, wherein The preparation of the polycarboxylic acid grafted silica particles A comprises: alkylating 6000 g of silica particles A with γ-methacryloxypropyltrimethoxysilane, and then reacting 900-1500 g of acrylic acid, 1800-3000 g of polyethylene glycol methyl ether methacrylate and 10-20 g of ammonium persulfate in an aqueous phase at 60°C for 100-150 min to obtain a grafting product.

8. The high performance concrete mix for power plants according to claim 1, wherein The preparation of the zwitterionic-hydrophobic copolymer brush modified silica particles B comprises: introducing amino groups into 2500 g of silica particles B with 3-aminopropyltriethoxysilane, and then reacting with 2-bromoisobutyryl bromide to obtain an initiator modified surface; in a methanol / water system, under the catalysis of cuprous bromide / sodium bromide / pentamethyldiethylene triamine, reacting 800-1200 g of sulfobetaine methacrylate and 90-150 g of methyl methacrylate at 35°C for 40-60 min to obtain a surface copolymer brush.

9. A method of placing high performance concrete mixtures for power plants according to any one of claims 1-8, characterized in that, The following steps are included: The mixed material is placed into the mold within 60 min, the temperature is 10-28°C, the pouring is layered and the pouring height is 200-300 mm, the vibration is inserted type and the vibration frequency is ≥120 Hz, the vibration point spacing is ≤1.5 times the vibration radius, until no significant sinking occurs, the surface is troweled 2-3 times before initial setting, the pouring is covered and moisturized within 30 min after pouring, and the continuous curing is ≥7 d. The following steps are included:

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