An underwater anti-dispersion concrete and a construction method thereof

Abstract

The present application relates to the technical field of concrete, in particular to an underwater anti-dispersion concrete and a construction method thereof. The concrete is prepared by mixing silicate cement, granulated blast furnace slag powder, fly ash, iron oxide yellow powder, medium sand, continuously graded gravel, catechol interval grafting sodium carboxymethyl cellulose, sodium tetraborate decahydrate, polycarboxylic acid water reducing agent, defoaming agent, ferric ammonium citrate and water in steps. The sodium carboxymethyl cellulose for interval grafting is prepared by condensation of sodium carboxymethyl cellulose with specific molecular weight grading and dopamine hydrochloride. The present application realizes the synergistic improvement of fluidity, anti-dispersion and hardening performance in the high mineral admixture system through the time sequence regulation of molecular weight grading, group interval grafting, boron source preposition and iron source postposition, and is suitable for deep water and large volume underwater engineering.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and in particular to an underwater anti-dispersion concrete and its construction method. Background Technology

[0002] Underwater concrete pouring is widely used in water-related projects such as bridge pile foundations, port terminals, and water conservancy dams, and its construction quality directly affects the long-term safety of the structure. Currently, underwater anti-dispersion concrete often uses ordinary sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, or polyacrylamide as thickening / flocculating components to inhibit the loss of cement paste and fine aggregate by improving the cohesiveness of the paste.

[0003] However, this type of technical solution has significant limitations: on the one hand, thickening components can easily lead to excessively high early viscosity peaks in the mixture, increasing pumping resistance, prolonging evacuation time, and even posing a risk of conduit blockage; on the other hand, relying solely on cohesion enhancement is insufficient to balance the slurry retention effect under underwater scouring conditions, often resulting in problems such as large release of suspended solids, significant strength loss after hardening, and insufficient impermeability. Especially in current low-carbon cementitious material systems, the extensive use of admixtures such as slag powder and fly ash further reduces slurry stability. Traditional anti-dispersants are difficult to adapt to systems with high amounts of mineral admixtures, leading to large fluctuations in underwater molding quality and failing to meet the durability requirements of deep-water, large-volume underwater engineering projects. Summary of the Invention

[0004] In view of this, the purpose of this invention is to propose an underwater anti-dispersion concrete and its construction method, so as to avoid the early viscosity peak increase and pumping resistance increase caused by simply increasing the amount of thickener in a low-carbon cementitious system in which a high proportion of slag powder and fly ash replaces cement, while reducing underwater slurry loss, release of suspended solids and loss of strength and impermeability after hardening.

[0005] To achieve the above objectives, this invention provides an underwater anti-dispersion concrete, prepared by stepwise mixing of the following raw materials in parts by weight: 170-210 parts silicate cement, 160-200 parts granulated blast furnace slag powder, 70-100 parts fly ash, 0.35-0.65 parts iron oxide yellow powder, 730-790 parts medium sand, 980-1040 parts continuously graded crushed stone, 1.6-2.4 parts catechol-grafted sodium carboxymethyl cellulose, 0.04-0.08 parts sodium tetraborate decahydrate, 1.6-2.4 parts polycarboxylate superplasticizer, 0.16-0.24 parts concrete defoamer, 0.06-0.12 parts ferric ammonium citrate, and 145-165 parts water; wherein the water includes water used to prepare the borate ester dynamic masking anti-dispersion agent solution, the water-reducing defoaming solution, and the post-ferric coordination solution, as well as the remaining supplementary water.

[0006] The catechol-grafted carboxymethyl cellulose sodium was prepared by a condensation reaction of molecular weight graded carboxymethyl cellulose sodium with dopamine hydrochloride, and the weight-average molecular weight of the molecular weight graded carboxymethyl cellulose sodium was 4 × 10⁻⁶. 5 -8×10 5 The degree of carboxymethyl substitution is 0.65-0.90, and an average of one catechol group is introduced into each 8-18 dehydrated glucose units in the catechol-grafted sodium carboxymethyl cellulose. The stepwise mixing includes: mixing the catechol-grafted sodium carboxymethyl cellulose with a portion of water, then adding the sodium tetraborate decahydrate to form a borate ester dynamic masking anti-dispersant solution; dry mixing the ordinary silicate cement, S95 grade granulated blast furnace slag powder, Class I F fly ash, and iron oxide yellow powder to obtain a dry mix; subsequently, mixing the dry mix sequentially with the borate ester dynamic masking anti-dispersant solution, a water-reducing and defoaming solution containing the polycarboxylate superplasticizer and concrete defoamer, and a post-ferric coordination solution containing the ferric ammonium citrate.

[0007] Preferably, the silicate cement is P·O42.5 ordinary silicate cement.

[0008] Preferably, the continuously graded crushed stone is 5mm-25mm continuously graded crushed stone, and the content of needle-like and flaky particles is not greater than 8%.

[0009] Preferably, the degree of retained carboxymethyl substitution of the catechol-grafted sodium carboxymethyl cellulose is 0.70-0.84.

[0010] Preferably, the catechol-spaced grafted sodium carboxymethyl cellulose is prepared by reacting the molecular weight graded sodium carboxymethyl cellulose with dopamine hydrochloride after activation in 2-morpholine ethanesulfonic acid buffer with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide.

[0011] Preferably, in preparing the catechol-grafted sodium carboxymethyl cellulose, the mass ratio of the molecular weight graded sodium carboxymethyl cellulose, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide and dopamine hydrochloride is 2400:200-360:120-216:160-320.

[0012] Preferably, the borate ester dynamic masking anti-dispersion agent solution is prepared by means of 82-95 parts water, 1.6-2.4 parts catechol-grafted sodium carboxymethyl cellulose and 0.04-0.08 parts sodium tetraborate decahydrate, by mass.

[0013] Preferably, the water-reducing and defoaming solution is prepared by means of 32-48 parts water, 1.6-2.4 parts polycarboxylate superplasticizer and 0.16-0.24 parts concrete defoamer.

[0014] Preferably, the post-ferric coordination solution is prepared by stirring 1 part water and 0.06-0.12 parts ferric ammonium citrate in the dark, by mass fraction.

[0015] Furthermore, the present invention also provides a method for preparing underwater anti-dispersion concrete, comprising the following steps: (1) Disperse sodium carboxymethyl cellulose grafted with catechol in part of water, and then add sodium tetraborate decahydrate to obtain a borate ester dynamic masking anti-dispersant solution; (2) Mix polycarboxylate superplasticizer, concrete defoamer and some water to obtain a water-reducing and defoaming solution; (3) Mix ferric ammonium citrate with some water to obtain a post-ferric complexation solution; (4) Dry mix silicate cement, granulated blast furnace slag powder, fly ash and iron oxide yellow powder, then add medium sand and continuously graded crushed stone and continue to dry mix to obtain dry mix material; (5) Add the borate ester dynamic shielding anti-dispersion agent solution, the remaining water, the water-reducing defoaming solution and the post-iron coordination solution to the dry mix in sequence and stir to obtain underwater anti-dispersion concrete.

[0016] Furthermore, the present invention also provides an underwater construction method for underwater anti-dispersion concrete, comprising the following steps: pouring the underwater anti-dispersion concrete within 15 minutes after mixing; at the start of pouring, ensuring that the distance between the discharge port of the tremie pipe and the bottom surface of the pouring is no more than 300 mm; during continuous pouring, ensuring that the bottom end of the tremie pipe is embedded in the newly poured concrete to a depth of no less than 500 mm; the interruption time at the same pouring point does not exceed 20 minutes; and underwater vibration is not performed during the underwater pouring process.

[0017] The beneficial effects of this invention are: (1) The present invention uses a weight-average molecular weight of 4×10 5 -8×10 5 Sodium carboxymethyl cellulose with a molecular weight grade of 0.65-0.90 and carboxymethyl substitution degree, and catechol groups introduced at intervals of 8-18 dehydrated glucose units, avoids the early over-thickening caused by the excessively wide molecular chain distribution of traditional thickeners. It also utilizes the underwater dynamic cross-linking characteristics of catechol groups to reduce the underwater loss to 0.5%-1.1% and the suspended solids content to as low as 54-119 mg / L while maintaining excellent fluidity of 530-565 mm slump spread and 9.8-16.9 s air-draining time.

[0018] (2) By pre-forming borate ester dynamic shielding with sodium tetraborate decahydrate and post-triggering coordination crosslinking with ferric ammonium citrate, combined with the spatial distribution optimization of iron oxide yellow powder dry mixing and pre-dispersion, a synergistic effect of low-resistance transport in the initial stage of mixing and rapid anti-dispersion after water discharge was achieved. Data shows that this scheme achieves an underwater compressive strength of 39.6-47.6 MPa after 28 days, with a water-land strength retention rate of 89.4%-95.8%, which is 2.3%-9.0% higher than the comparative example 4 without boron source and 4.7%-11.3% higher than the comparative example 5 with iron source pre-positioned, effectively solving the industry problem of the trade-off between fluidity and anti-dispersion.

[0019] (3) The composite iron source design of dry-mixed pre-dispersion of iron oxide yellow and post-positioned iron source significantly improves the impermeability of hardened concrete. Detailed Implementation

[0020] 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.

[0021] The sodium carboxymethyl cellulose used in the specific implementation method is C104977 type sodium carboxymethyl cellulose from Shanghai Aladdin Biochemical Technology Co., Ltd., with a weight-average molecular weight of 7×10⁻⁶. 5 The degree of carboxymethyl substitution is 0.9. Ferric ammonium citrate is Shanghai Aladdin Biochemical Technology Co., Ltd.'s A100170 type ferric ammonium citrate, with an iron content of 21.5 wt%. Iron oxide yellow is Lanxess Chemical's BAYFERROX 920 type iron oxide yellow powder. Polycarboxylate superplasticizer is Jiangsu Subote New Material Co., Ltd.'s PCA-300P type powdered polycarboxylate superplasticizer. Concrete defoamer is Jiangsu Subote New Material Co., Ltd.'s SBT-PXP(Ⅲ) type concrete defoamer. Silicate cement is Anhui Conch Cement Co., Ltd.'s Conch brand P·O42.5 ordinary silicate cement, conforming to GB175-2023 "General Silicate Cement". Granulated blast furnace slag powder is S95 grade granulated blast furnace slag powder conforming to GB / T18046-2017 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete". The fly ash is Class I, F type, conforming to GB / T1596-2017 "Fly Ash for Cement and Concrete". The fineness modulus of the medium sand is 2.6, and the mud content is not greater than 1%. The crushed stone is 5mm-25mm continuously graded crushed stone, and the content of needle-like and flaky particles is not greater than 8%.

[0022] Example 1: I. Preparation of Sodium Carboxymethyl Cellulose Based on Molecular Weight Fraction Add 200,000 g of deionized water to a mechanically stirred reactor. Stir at 200 rpm at 25°C, and add 4,000 g of sodium carboxymethyl cellulose in eight portions of 500 g each over 40 min. After the addition is complete, continue stirring at 200 rpm for 8 h. Then filter through an 80-mesh sieve, ensuring the undispersed matter on the sieve does not exceed 4 g. Cool the filtrate to 10°C, and add 75,000 g of anhydrous ethanol over 30 min. Stir at 150 rpm at 10°C for 30 min. After standing for 60 min, separate and discard the first precipitate using a 200-mesh filter. Add 97,200 g of anhydrous ethanol to the resulting filtrate over 40 min, and stir at 150 rpm at 10°C for 40 min. After standing for 120 min, collect the second precipitate using a 200-mesh filter. The second precipitate was washed twice with 20,000 g of 70% ethanol aqueous solution, and then dried for 12 h at 40 °C under a vacuum not exceeding -0.08 MPa to obtain molecular weight fractionated sodium carboxymethyl cellulose. Its weight-average molecular weight was determined by aqueous gel permeation chromatography using 0.1 mol / L sodium nitrate aqueous solution as the mobile phase and calibrated with pullulan polysaccharide standard. The determined weight-average molecular weight was 6.2 × 10⁻⁶. 5 The degree of carboxymethyl substitution was determined by acid-base titration and found to be 0.86.

[0023] II. Preparation of sodium carboxymethyl cellulose grafted onto catechol spacer 120,000 g of 50 mmol / L, pH 5.5 2-morpholine ethanesulfonic acid buffer, 2400 g of molecular weight fractionated sodium carboxymethyl cellulose, and 12 g of ascorbic acid were added to the reactor. The mixture was stirred at 150 rpm for 60 min at 25 °C, and nitrogen gas was purged for 30 min. Subsequently, 252 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 152 g of N-hydroxysuccinimide were added, and the mixture was activated at 150 rpm for 60 min at 25 °C and pH 5.5. 228 g of dopamine hydrochloride was dissolved in 12,000 g of 50 mmol / L, pH 5.5 2-morpholine ethanesulfonic acid buffer and added to the reactor over 30 min. The reaction was continued at 25 °C for 18 h. During the reaction, the pH was measured every 30 min, and the pH was maintained at 5.2-5.8 using 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide solution. After the reaction, the reaction solution was purified using an ultrafiltration membrane with a molecular weight cutoff of 100 kDa. The small molecule salt, unreacted monomers, and free condensing agent were replaced six times with 300,000 g of deionized water. The purified product was dried at 40°C under a vacuum not exceeding -0.08 MPa until the water content was less than 5%, yielding catechol-grafted sodium carboxymethyl cellulose. The degree of carboxymethyl substitution was determined by acid-base titration, and found to be 0.79. The amount of catechol groups introduced was determined by UV-Vis spectrophotometry. Calculation using a dopamine hydrochloride standard curve showed that an average of one catechol group was introduced for every 12 dehydrated glucose units.

[0024] III. Preparation of Admixtures for Underwater Anti-Dispersion Concrete Add 90,000 g of water to the first mixing container and stir at 300 rpm at 25°C. Add 2,000 g of catechol-grafted sodium carboxymethyl cellulose in four portions of 500 g each over 20 minutes. After adding all materials, continue stirring at 300 rpm for 30 minutes, then at 150 rpm for 120 minutes. Dissolve 60 g of sodium tetraborate decahydrate in 1,000 g of water and add it to the first mixing container over 10 minutes. Continue stirring at 150 rpm for 30 minutes to obtain a borate ester dynamic masking anti-dispersant solution. Add 43,000 g of water, 2,000 g of polycarboxylate superplasticizer powder, and 200 g of concrete defoamer to the second mixing container and stir at 150 rpm for 10 minutes to obtain a water-reducing and defoaming solution. Add 1000g of water and 90g of ferric ammonium citrate to the third stirring container, stir at 150r / min for 10min in the dark to obtain the post-iron coordination solution.

[0025] IV. Preparation of Underwater Anti-Dispersion Concrete Add 190 kg of ordinary Portland cement, 180 kg of S95 grade granulated blast furnace slag powder, 80 kg of Class I F fly ash, and 500 g of iron oxide yellow powder to a concrete mixer and dry mix for 90 seconds; then add 760 kg of medium sand and 1010 kg of continuously graded crushed stone and continue dry mixing for 60 seconds; add 93060 g of borate ester dynamic masking anti-dispersion agent solution and 20000 g of water to the dry mix within 30 seconds and mix for 60 seconds; then add 45200 g of water-reducing and defoaming solution within 30 seconds and continue mixing for 90 seconds; finally, add 1090 g of post-ferric complexation solution within 15 seconds and continue mixing for 45 seconds to obtain underwater anti-dispersion concrete.

[0026] V. Underwater Construction Methods After the concrete is mixed, it should be poured within 15 minutes. At the start of pouring, the distance between the outlet of the tremie pipe and the bottom surface of the concrete should not exceed 300mm. During continuous pouring, the bottom of the tremie pipe should be embedded in the newly poured concrete to a depth of not less than 500mm. The interruption time at the same pouring point should not exceed 20 minutes. Underwater vibration should not be performed during the underwater pouring process. After pouring, allow the concrete to stand in the original water environment for more than 24 hours, and then continue underwater curing according to the engineering design requirements.

[0027] Example 2: I. Preparation of Sodium Carboxymethyl Cellulose Based on Molecular Weight Fraction Add 200,000 g of deionized water to a mechanically stirred reactor. Stir at 200 rpm at 25°C, and add 4,000 g of sodium carboxymethyl cellulose in eight portions of 500 g each over 40 min. After the addition is complete, continue stirring at 200 rpm for 8 h. Then filter through an 80-mesh sieve, ensuring the undispersed matter on the sieve does not exceed 4 g. Cool the filtrate to 10°C, and add 85,000 g of anhydrous ethanol over 30 min. Stir at 150 rpm at 10°C for 30 min. After standing for 60 min, separate and discard the first precipitate using a 200-mesh filter. Add 110,000 g of anhydrous ethanol to the resulting filtrate over 40 min, and stir at 150 rpm at 10°C for 40 min. After standing for 120 min, collect the second precipitate using a 200-mesh filter. The second precipitate was washed twice with 20,000 g of 70% ethanol aqueous solution, and then dried at 40℃ and a vacuum degree not exceeding -0.08 MPa for 12 h to obtain molecular weight fractionated sodium carboxymethyl cellulose. Its weight-average molecular weight was determined by aqueous gel permeation chromatography using 0.1 mol / L sodium nitrate aqueous solution as the mobile phase and calibrated with pullulan polysaccharide standard. The determined weight-average molecular weight was 4.5 × 10⁻⁶. 5 The degree of carboxymethyl substitution was determined by acid-base titration and found to be 0.84.

[0028] II. Preparation of sodium carboxymethyl cellulose grafted onto catechol spacer 120,000 g of 50 mmol / L, pH 5.5 2-morpholine ethanesulfonic acid buffer, 2400 g of molecular weight fractionated sodium carboxymethyl cellulose, and 12 g of ascorbic acid were added to the reactor. The mixture was stirred at 150 rpm for 60 min at 25 °C, and nitrogen gas was purged for 30 min. Subsequently, 200 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 120 g of N-hydroxysuccinimide were added, and the mixture was activated at 150 rpm for 60 min at 25 °C and pH 5.5. 160 g of dopamine hydrochloride was dissolved in 12,000 g of 50 mmol / L, pH 5.5 2-morpholine ethanesulfonic acid buffer and added to the reactor over 30 min. The reaction was continued at 25 °C for 18 h. During the reaction, the pH was measured every 30 min, and the pH was controlled at 5.2-5.8 using 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide solution. After the reaction, the reaction solution was purified using an ultrafiltration membrane with a molecular weight cutoff of 100 kDa. The small molecule salt, unreacted monomers, and free condensing agent were replaced six times with 300,000 g of deionized water. The purified product was dried at 40°C under a vacuum not exceeding -0.08 MPa until the water content was less than 5%, yielding catechol-grafted sodium carboxymethyl cellulose. The degree of carboxymethyl substitution was determined by acid-base titration, and found to be 0.78. The amount of catechol groups introduced was determined by UV-Vis spectrophotometry. Calculation using a dopamine hydrochloride standard curve showed that an average of one catechol group was introduced for every 18 dehydrated glucose units.

[0029] III. Preparation of Admixtures for Underwater Anti-Dispersion Concrete Add 82,000 g of water to the first mixing container and stir at 300 rpm at 25°C. Add 1,600 g of catechol-grafted sodium carboxymethyl cellulose in four portions over 20 minutes, 400 g each time. After all additions are complete, continue stirring at 300 rpm for 30 minutes, then at 150 rpm for 120 minutes. Dissolve 40 g of sodium tetraborate decahydrate in 1,000 g of water and add it to the first mixing container over 10 minutes. Continue stirring at 150 rpm for 30 minutes to obtain a borate ester dynamic masking anti-dispersant solution. Add 48,000 g of water, 2,400 g of polycarboxylate superplasticizer powder, and 160 g of concrete defoamer to the second mixing container and stir at 150 rpm for 10 minutes to obtain a water-reducing and defoaming solution. Add 1000g of water and 60g of ferric ammonium citrate to the third stirring container, stir at 150r / min for 10min in the dark to obtain the post-iron coordination solution.

[0030] IV. Preparation of Underwater Anti-Dispersion Concrete Add 210 kg of ordinary Portland cement, 160 kg of S95 grade granulated blast furnace slag powder, 70 kg of Class I F fly ash, and 350 g of iron oxide yellow powder to a concrete mixer and dry mix for 90 seconds; then add 790 kg of medium sand and 980 kg of continuously graded crushed stone and continue dry mixing for 60 seconds; add 84,640 g of borate ester dynamic masking anti-dispersion agent solution and 26,000 g of water to the dry mix within 30 seconds and mix for 60 seconds; then add 50,560 g of water-reducing and defoaming solution within 30 seconds and continue mixing for 90 seconds; finally, add 1,060 g of post-ferric complexation solution within 15 seconds and continue mixing for 45 seconds to obtain underwater anti-dispersion concrete.

[0031] V. Underwater Construction Methods After the concrete is mixed, it should be poured within 15 minutes. At the start of pouring, the distance between the outlet of the tremie pipe and the bottom surface of the concrete should not exceed 300mm. During continuous pouring, the bottom of the tremie pipe should be embedded in the newly poured concrete to a depth of not less than 500mm. The interruption time at the same pouring point should not exceed 20 minutes. Underwater vibration should not be performed during the underwater pouring process. After pouring, allow the concrete to stand in the original water environment for more than 24 hours, and then continue underwater curing according to the engineering design requirements.

[0032] Example 3: I. Preparation of Sodium Carboxymethyl Cellulose Based on Molecular Weight Fraction Add 200,000 g of deionized water to a mechanically stirred reactor. Stir at 200 rpm at 25°C, and add 4,000 g of sodium carboxymethyl cellulose in eight portions of 500 g each over 40 min. After the addition is complete, continue stirring at 200 rpm for 8 h. Then filter through an 80-mesh sieve, ensuring the undispersed matter on the sieve does not exceed 4 g. Cool the filtrate to 10°C, and add 65,000 g of anhydrous ethanol over 30 min. Stir at 150 rpm at 10°C for 30 min. After standing for 60 min, separate and discard the first precipitate using a 200-mesh filter. Add 86,000 g of anhydrous ethanol to the resulting filtrate over 40 min, and stir at 150 rpm at 10°C for 40 min. After standing for 120 min, collect the second precipitate using a 200-mesh filter. The second precipitate was washed twice with 20,000 g of 70% ethanol aqueous solution, and then dried at 40℃ and a vacuum degree not exceeding -0.08 MPa for 12 h to obtain molecular weight fractionated sodium carboxymethyl cellulose. Its weight-average molecular weight was determined by aqueous gel permeation chromatography using 0.1 mol / L sodium nitrate aqueous solution as the mobile phase and calibrated with pullulan polysaccharide standard. The determined weight-average molecular weight was 7.6 × 10⁻⁶. 5 The degree of carboxymethyl substitution was determined by acid-base titration and found to be 0.88.

[0033] II. Preparation of sodium carboxymethyl cellulose grafted onto catechol spacer 120,000 g of 50 mmol / L, pH 5.5 2-morpholine ethanesulfonic acid buffer, 2400 g of molecular weight fractionated sodium carboxymethyl cellulose, and 12 g of ascorbic acid were added to the reactor. The mixture was stirred at 150 rpm for 60 min at 25 °C, and nitrogen gas was purged for 30 min. Subsequently, 360 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 216 g of N-hydroxysuccinimide were added, and the mixture was activated at 150 rpm for 60 min at 25 °C and pH 5.5. 320 g of dopamine hydrochloride was dissolved in 12,000 g of 50 mmol / L, pH 5.5 2-morpholine ethanesulfonic acid buffer and added to the reactor over 30 min. The reaction was continued at 25 °C for 18 h. During the reaction, the pH was measured every 30 min, and the pH was controlled at 5.2-5.8 using 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide solution. After the reaction, the reaction solution was purified using an ultrafiltration membrane with a molecular weight cutoff of 100 kDa. The small molecule salt, unreacted monomers, and free condensing agent were replaced six times with 300,000 g of deionized water. The purified product was dried at 40°C under a vacuum not exceeding -0.08 MPa until the water content was less than 5%, yielding catechol-grafted sodium carboxymethyl cellulose. The degree of carboxymethyl substitution was determined by acid-base titration, and found to be 0.73. The amount of catechol groups introduced was determined by UV-Vis spectrophotometry. Calculation using a dopamine hydrochloride standard curve showed that an average of one catechol group was introduced for every eight dehydrated glucose units.

[0034] III. Preparation of Admixtures for Underwater Anti-Dispersion Concrete Add 95,000 g of water to the first mixing container and stir at 300 rpm at 25°C. Add 2,400 g of catechol-grafted sodium carboxymethyl cellulose in four portions (600 g each) over 20 minutes. After adding all materials, continue stirring at 300 rpm for 30 minutes, then at 150 rpm for 120 minutes. Dissolve 80 g of sodium tetraborate decahydrate in 1,000 g of water and add it to the first mixing container over 10 minutes. Continue stirring at 150 rpm for 30 minutes to obtain a borate ester dynamic masking anti-dispersant solution. Add 32,000 g of water, 2,000 g of polycarboxylate superplasticizer powder, and 240 g of concrete defoamer to the second mixing container and stir at 150 rpm for 10 minutes to obtain a water-reducing and defoaming solution. Add 1000g of water and 120g of ferric ammonium citrate to the third stirring container, stir at 150r / min for 10min in the dark to obtain the post-iron coordination solution.

[0035] IV. Preparation of Underwater Anti-Dispersion Concrete Add 170 kg of ordinary Portland cement, 200 kg of S95 grade granulated blast furnace slag powder, 100 kg of Class I F fly ash, and 650 g of iron oxide yellow powder to a concrete mixer and dry mix for 90 seconds; then add 730 kg of medium sand and 1040 kg of continuously graded crushed stone and continue dry mixing for 60 seconds; add 98480 g of borate ester dynamic masking anti-dispersion agent solution and 19000 g of water to the dry mix within 30 seconds and mix for 60 seconds; then add 34240 g of water-reducing and defoaming solution within 30 seconds and continue mixing for 90 seconds; finally, add 1120 g of post-ferric complexation solution within 15 seconds and continue mixing for 45 seconds to obtain underwater anti-dispersion concrete.

[0036] V. Underwater Construction Methods After the concrete is mixed, it should be poured within 15 minutes. At the start of pouring, the distance between the outlet of the tremie pipe and the bottom surface of the concrete should not exceed 300mm. During continuous pouring, the bottom of the tremie pipe should be embedded in the newly poured concrete to a depth of not less than 500mm. The interruption time at the same pouring point should not exceed 20 minutes. Underwater vibration should not be performed during the underwater pouring process. After pouring, allow the concrete to stand in the original water environment for more than 24 hours, and then continue underwater curing according to the engineering design requirements.

[0037] Example 4: I. Preparation of Sodium Carboxymethyl Cellulose Based on Molecular Weight Fraction Add 200,000 g of deionized water to a mechanically stirred reactor. Stir at 200 rpm at 25°C, and add 4,000 g of sodium carboxymethyl cellulose in eight portions of 500 g each over 40 min. After the addition is complete, continue stirring at 200 rpm for 8 h. Then filter through an 80-mesh sieve, ensuring the undispersed matter on the sieve does not exceed 4 g. Cool the filtrate to 10°C, and add 80,000 g of anhydrous ethanol over 30 min. Stir at 150 rpm at 10°C for 30 min. After standing for 60 min, separate and discard the first precipitate using a 200-mesh filter. Add 105,000 g of anhydrous ethanol to the resulting filtrate over 40 min, and stir at 150 rpm at 10°C for 40 min. After standing for 120 min, collect the second precipitate using a 200-mesh filter. The second precipitate was washed twice with 20,000 g of 70% ethanol aqueous solution, and then dried at 40℃ and a vacuum degree not exceeding -0.08 MPa for 12 h to obtain molecular weight fractionated sodium carboxymethyl cellulose. Its weight-average molecular weight was determined by aqueous gel permeation chromatography using 0.1 mol / L sodium nitrate aqueous solution as the mobile phase and calibrated with pullulan polysaccharide standard. The determined weight-average molecular weight was 5.3 × 10⁻⁶. 5 The degree of carboxymethyl substitution was determined by acid-base titration and found to be 0.82.

[0038] II. Preparation of sodium carboxymethyl cellulose grafted onto catechol spacer 120,000 g of 50 mmol / L, pH 5.5 2-morpholine ethanesulfonic acid buffer, 2400 g of molecular weight fractionated sodium carboxymethyl cellulose, and 12 g of ascorbic acid were added to the reactor. The mixture was stirred at 150 rpm for 60 min at 25 °C, and nitrogen gas was purged for 30 min. Subsequently, 220 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 132 g of N-hydroxysuccinimide were added, and the mixture was activated at 150 rpm for 60 min at 25 °C and pH 5.5. 190 g of dopamine hydrochloride was dissolved in 12,000 g of 50 mmol / L, pH 5.5 2-morpholine ethanesulfonic acid buffer and added to the reactor over 30 min. The reaction was continued at 25 °C for 18 h. During the reaction, the pH was measured every 30 min, and the pH was controlled at 5.2-5.8 using 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide solution. After the reaction, the reaction solution was purified using an ultrafiltration membrane with a molecular weight cutoff of 100 kDa. The small molecule salt, unreacted monomers, and free condensing agent were replaced six times with 300,000 g of deionized water. The purified product was dried at 40°C under a vacuum not exceeding -0.08 MPa until the water content was less than 5%, yielding catechol-grafted sodium carboxymethyl cellulose. The degree of carboxymethyl substitution was determined by acid-base titration, and found to be 0.76. The amount of catechol groups introduced was determined by UV-Vis spectrophotometry. Calculation using a dopamine hydrochloride standard curve showed that an average of one catechol group was introduced for every 15 dehydrated glucose units.

[0039] III. Preparation of Admixtures for Underwater Anti-Dispersion Concrete Add 90,000 g of water to the first mixing container and stir at 300 rpm at 25°C. Add 2,200 g of catechol-grafted sodium carboxymethyl cellulose in four portions of 550 g each over 20 minutes. After all additions are complete, continue stirring at 300 rpm for 30 minutes, then at 150 rpm for 120 minutes. Dissolve 80 g of sodium tetraborate decahydrate in 1,000 g of water and add it to the first mixing container over 10 minutes. Continue stirring at 150 rpm for 30 minutes to obtain a borate ester dynamic masking anti-dispersant solution. Add 38,000 g of water, 1,800 g of polycarboxylate superplasticizer powder, and 200 g of concrete defoamer to the second mixing container and stir at 150 rpm for 10 minutes to obtain a water-reducing and defoaming solution. Add 1000g of water and 70g of ferric ammonium citrate to the third stirring container, stir at 150r / min for 10min in the dark to obtain the post-iron coordination solution.

[0040] IV. Preparation of Underwater Anti-Dispersion Concrete Add 185 kg of ordinary Portland cement, 200 kg of S95 grade granulated blast furnace slag powder, 75 kg of Class I F fly ash, and 550 g of iron oxide yellow powder to a concrete mixer and dry mix for 90 seconds; then add 750 kg of medium sand and 1020 kg of continuously graded crushed stone and continue dry mixing for 60 seconds; add 93280 g of borate ester dynamic masking anti-dispersion agent solution and 22000 g of water to the dry mix within 30 seconds and mix for 60 seconds; then add 40000 g of water-reducing and defoaming solution within 30 seconds and continue mixing for 90 seconds; finally, add 1070 g of post-ferric complexation solution within 15 seconds and continue mixing for 45 seconds to obtain underwater anti-dispersion concrete.

[0041] V. Underwater Construction Methods After the concrete is mixed, it should be poured within 15 minutes. At the start of pouring, the distance between the outlet of the tremie pipe and the bottom surface of the concrete should not exceed 300mm. During continuous pouring, the bottom of the tremie pipe should be embedded in the newly poured concrete to a depth of not less than 500mm. The interruption time at the same pouring point should not exceed 20 minutes. Underwater vibration should not be performed during the underwater pouring process. After pouring, allow the concrete to stand in the original water environment for more than 24 hours, and then continue underwater curing according to the engineering design requirements.

[0042] Example 5: I. Preparation of Sodium Carboxymethyl Cellulose Based on Molecular Weight Fraction Add 200,000 g of deionized water to a mechanically stirred reactor. Stir at 200 rpm at 25°C, and add 4,000 g of sodium carboxymethyl cellulose in eight portions of 500 g each over 40 min. After the addition is complete, continue stirring at 200 rpm for 8 h. Then filter through an 80-mesh sieve, ensuring the undispersed matter on the sieve does not exceed 4 g. Cool the filtrate to 10°C, add 70,000 g of anhydrous ethanol over 30 min, and stir at 150 rpm for 30 min at 10°C. After standing for 60 min, separate and discard the first precipitate using a 200-mesh filter. Add another 90,000 g of anhydrous ethanol to the resulting filtrate over 40 min, and stir at 150 rpm for 40 min at 10°C. After standing for 120 min, collect the second precipitate using a 200-mesh filter. The second precipitate was washed twice with 20,000 g of 70% ethanol aqueous solution, and then dried at 40℃ and a vacuum degree not exceeding -0.08 MPa for 12 h to obtain molecular weight fractionated sodium carboxymethyl cellulose. Its weight-average molecular weight was determined by aqueous gel permeation chromatography using 0.1 mol / L sodium nitrate aqueous solution as the mobile phase and calibrated with pullulan polysaccharide standard. The determined weight-average molecular weight was 6.8 × 10⁻⁶. 5 The degree of carboxymethyl substitution was determined by acid-base titration and found to be 0.85.

[0043] II. Preparation of sodium carboxymethyl cellulose grafted onto catechol spacer 120,000 g of 50 mmol / L, pH 5.5 2-morpholine ethanesulfonic acid buffer, 2400 g of molecular weight fractionated sodium carboxymethyl cellulose, and 12 g of ascorbic acid were added to the reactor. The mixture was stirred at 150 rpm for 60 min at 25 °C, and nitrogen gas was purged for 30 min. Subsequently, 300 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 180 g of N-hydroxysuccinimide were added, and the mixture was activated by stirring at 150 rpm for 60 min at 25 °C and pH 5.5. 270 g of dopamine hydrochloride was dissolved in 12,000 g of 50 mmol / L, pH 5.5 2-morpholine ethanesulfonic acid buffer and added to the reactor over 30 min. The reaction was continued at 25 °C for 18 h. During the reaction, the pH was measured every 30 min, and the pH was controlled at 5.2-5.8 using 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide solution. After the reaction, the reaction solution was purified using an ultrafiltration membrane with a molecular weight cutoff of 100 kDa. The small molecule salt, unreacted monomers, and free condensing agent were replaced six times with 300,000 g of deionized water. The purified product was dried at 40°C under a vacuum not exceeding -0.08 MPa until the water content was less than 5%, yielding catechol-grafted sodium carboxymethyl cellulose. The degree of carboxymethyl substitution was determined by acid-base titration to be 0.75. The amount of catechol groups introduced was determined by UV-Vis spectrophotometry. Calculation using a dopamine hydrochloride standard curve showed that an average of one catechol group was introduced for every 10 dehydrated glucose units.

[0044] III. Preparation of Admixtures for Underwater Anti-Dispersion Concrete Add 86,000 g of water to the first mixing container and stir at 300 rpm at 25°C. Add 1,800 g of catechol-grafted sodium carboxymethyl cellulose in four portions of 450 g each over 20 minutes. After all additions are complete, continue stirring at 300 rpm for 30 minutes, then at 150 rpm for 120 minutes. Dissolve 50 g of sodium tetraborate decahydrate in 1,000 g of water and add it to the first mixing container over 10 minutes. Continue stirring at 150 rpm for 30 minutes to obtain a borate ester dynamic masking anti-dispersant solution. Add 45,000 g of water, 2,200 g of polycarboxylate superplasticizer powder, and 220 g of concrete defoamer to the second mixing container and stir at 150 rpm for 10 minutes to obtain a water-reducing and defoaming solution. Add 1000g of water and 110g of ferric ammonium citrate to the third stirring container, stir at 150r / min for 10min in the dark to obtain the post-iron coordination solution.

[0045] IV. Preparation of Underwater Anti-Dispersion Concrete Add 200 kg of ordinary Portland cement, 170 kg of S95 grade granulated blast furnace slag powder, 90 kg of Class I F fly ash, and 450 g of iron oxide yellow powder to a concrete mixer and dry mix for 90 seconds; then add 780 kg of medium sand and 1000 kg of continuously graded crushed stone and continue dry mixing for 60 seconds; add 88850 g of borate ester dynamic masking anti-dispersion agent solution and 26000 g of water to the dry mix within 30 seconds and mix for 60 seconds; then add 47420 g of water-reducing and defoaming solution within 30 seconds and continue mixing for 90 seconds; finally, add 1110 g of post-ferric complexation solution within 15 seconds and continue mixing for 45 seconds to obtain underwater anti-dispersion concrete.

[0046] V. Underwater Construction Methods After the concrete is mixed, it should be poured within 15 minutes. At the start of pouring, the distance between the outlet of the tremie pipe and the bottom surface of the concrete should not exceed 300mm. During continuous pouring, the bottom of the tremie pipe should be embedded in the newly poured concrete to a depth of not less than 500mm. The interruption time at the same pouring point should not exceed 20 minutes. Underwater vibration should not be performed during the underwater pouring process. After pouring, allow the concrete to stand in the original water environment for more than 24 hours, and then continue underwater curing according to the engineering design requirements.

[0047] Comparative Example 1: The difference from Example 1 is that in the third step, 2000g of catechol-grafted sodium carboxymethyl cellulose is replaced with 2000g of sodium carboxymethyl cellulose, and the preparation of catechol-grafted sodium carboxymethyl cellulose in the second step of Example 1 is omitted; 90000g of water is still added to the first stirring vessel, and the mixture is stirred at 300r / min at 25°C. 2000g of sodium carboxymethyl cellulose is added in the same manner as in the third step of Example 1, followed by 1000g of an aqueous solution of 60g of sodium tetraborate decahydrate, to obtain the anti-dispersant solution. All other conditions are the same as in Example 1.

[0048] Comparative Example 2: The difference from Example 1 is that: in the first step, the two-stage anhydrous ethanol fractionation precipitation is not performed; the sodium carboxymethyl cellulose is dissolved in 200,000 g of deionized water, filtered through an 80-mesh sieve, and dried at 40°C and a vacuum degree not exceeding -0.08 MPa, and then directly used as the sodium carboxymethyl cellulose in the subsequent second step; the second, third, fourth, and fifth steps are all carried out according to Example 1. The remaining conditions are the same as in Example 1.

[0049] Comparative Example 3: The difference from Example 1 is that in the second step, the amount of dopamine hydrochloride was adjusted from 228g to 456g, the amount of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride was adjusted from 252g to 504g, and the amount of N-hydroxysuccinimide was adjusted from 152g to 304g, so that the amount of catechol groups introduced was converted by UV-Vis spectrophotometry to an average of 1 catechol group introduced for every 5 dehydrated glucose units. All other conditions were the same as in Example 1.

[0050] Comparative Example 4: The difference from Example 1 is that in step 3, 60g of sodium tetraborate decahydrate is not added; instead, 60g of sodium tetraborate decahydrate is replaced with 60g of water. The total mass of other substances added to the first stirring container and the anti-dispersant solution added in step 4 remains unchanged. All other conditions are the same as in Example 1.

[0051] Comparative Example 5: The difference from Example 1 is as follows: After obtaining 1090g of post-iron coordination solution in the third step, this 1090g of post-iron coordination solution is immediately added to the first stirring vessel after the preparation of the borate ester dynamic masking anti-dispersant solution, and stirring is continued at 150r / min for 30min; in the fourth step, no more 1090g of post-iron coordination solution is added, and the corresponding 1090g of liquid in the fourth step is added together with the borate ester dynamic masking anti-dispersant solution. The remaining conditions are the same as in Example 1.

[0052] Comparative Example 6: The difference from Example 1 is that in step four, 500g of iron oxide yellow powder is not added; instead, 500g of Grade I F-type fly ash is replaced. Ordinary silicate cement, S95 grade granulated blast furnace slag powder, the original 80kg of Grade I F-type fly ash, and the newly added 500g of Grade I F-type fly ash are dry-mixed together for 90 seconds. All other conditions are the same as in Example 1.

[0053] Comparative Example 7: The difference from Example 1 is that in the third step, 90g of ferric ammonium citrate is not added; instead, 90g of ferric ammonium citrate is replaced with 90g of water. 1090g of water is added to the third stirring container, and the mixture is stirred at 150r / min for 10min in the dark as the last liquid added. All other conditions are the same as in Example 1.

[0054] Comparative Example 8: The difference from Example 1 is that in step four, the 500g of iron oxide yellow powder is not dry-mixed with ordinary silicate cement, S95 grade granulated blast furnace slag powder, and Class I F fly ash during the dry powder stage. Instead, the 500g of iron oxide yellow powder is added to the third mixing container, mixed with 1000g of water and 90g of ferric ammonium citrate in the dark at 150r / min for 10min, and then added to the concrete mixer in the last 15s of step four. The remaining conditions are the same as in Example 1.

[0055] Performance testing: The underwater anti-dispersion concretes obtained in Examples 1-5 and Comparative Examples 1-8 were used as test samples. All samples used the same batch of ordinary Portland cement, S95 grade granulated blast furnace slag powder, Class I F fly ash, medium sand, continuously graded crushed stone, polycarboxylate superplasticizer powder, concrete defoamer, ferric ammonium citrate, iron oxide yellow powder, and water. The mixing environment temperature was controlled at 20℃, the relative humidity at 60%, and the concrete mixer capacity was 60L. The quantities were weighed proportionally according to the mix proportions in each example or comparative example, with a single mixing volume of 30L for each group of samples. The mixing completion time was recorded immediately after mixing, and all performance tests of the mixtures began within 15 minutes of mixing completion. Underwater molded specimens were formed in a water tank at a temperature of 20℃ and a depth of 500mm. Concrete was poured into a 100mm×100mm×100mm mold placed at the bottom of the water tank through a 50mm inner diameter guide pipe. The outlet of the guide pipe was no more than 30mm from the bottom of the mold. No vibration was used during the molding process. After molding, the specimens were left to stand in the original water environment for 24 hours before demolding and then cured in water at 20℃ until the specified age. Land-based molded specimens were made using molds of the same specifications, prepared according to GB / T50081-2019, and cured according to standard specifications.

[0056] Molecular weight, degree of carboxymethyl substitution, and catechol grafting spacer: The catechol spacer obtained in Examples 1-5 and the second step of Comparative Examples 2 and 3 was used for intrinsic characterization by grafting sodium carboxymethyl cellulose. Weight-average molecular weight was determined by aqueous gel permeation chromatography. 20 mg of dried sample was weighed, and 10 mL of 0.1 mol / L sodium nitrate aqueous solution was added. The sample was allowed to swell at 25 °C for 12 h, then stirred at 100 r / min for 30 min. The solution was filtered through a 0.45 μm aqueous filter membrane. The column temperature was 35 °C, the mobile phase was 0.1 mol / L sodium nitrate aqueous solution, the flow rate was 0.5 mL / min, and the injection volume was 100 μL. The weight-average molecular weight was 1.0 × 10⁻⁶. 5 2.0×10 5 4.0×10 5 8.0×10 5 and 1.0×10 6A calibration curve was established using pullulan polysaccharide standards. The degree of carboxymethyl substitution was determined by acid-base titration. 1.0000 g of dried sample was weighed, dispersed in 75 mL of 95% ethanol, acidified with 5 mL of nitric acid, filtered, washed, and then reacted with 0.4000 mol / L sodium hydroxide standard solution. The solution was then back-titrated with 0.4000 mol / L hydrochloric acid standard solution. The determination was performed in triplicate, and the average value was taken. The grafting interval of catechol was determined using UV-Vis spectrophotometry according to the instrument requirements of GB / T 9721-2006 "General Rules for Molecular Absorption Spectrophotometry of Chemical Reagents (UV and Visible Part)". 20 mg of dried sample was weighed and dissolved in 100 mL of pH 5.5 2-morpholine ethanesulfonic acid buffer. The absorbance was measured at 280 nm. The catechol group content was converted using the dopamine hydrochloride standard curve, and the average number of dehydrated glucose units corresponding to each catechol group was calculated.

[0057] Slump spread and inverted slump cone emptying time: The slump spread and inverted slump cone emptying time of the mixtures in Examples 1-5 and Comparative Examples 1-8 were tested according to GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". After mixing, the mixture was covered with a damp cloth and allowed to stand for 15 minutes before testing. For the slump spread test, a slump meter was used. The base plate was pre-wetted and wiped dry. Concrete was poured into the slump cone in one go, without tamping or vibration. The time to lift the cone was controlled at 3 seconds. Immediately after lifting the cone, the expansion diameter in two mutually perpendicular directions was measured, and the average value was taken as the slump spread, accurate to 5 mm. In the inverted slump cone emptying time test, the slump cone was inverted and fixed, the bottom opening was sealed, and concrete was poured in all at once. The bottom opening was opened, and timing was started simultaneously. The time required for the concrete to completely empty was taken as the inverted slump cone emptying time, accurate to 0.1 seconds.

[0058] Underwater anti-dispersion: The underwater anti-dispersion of Examples 1-5 and Comparative Examples 1-8 was conducted according to the underwater anti-dispersion test method for cement concrete mixtures in JTG 3420-2020 "Test Procedures for Cement and Cement Concrete in Highway Engineering" (T 0537-2020). For the loss test, water was added to a 500mm depth in a 550mm high, 400mm diameter iron bucket. A wide-mouthed container with a known mass and a volume of 1500mL was placed at the bottom of the bucket. Approximately 2000g of concrete mixed for 15 minutes was weighed and allowed to fall freely from the water surface into the underwater container. After standing for 5 minutes, the container was removed, the surface water of the concrete was drained, and the concrete was weighed. This process was repeated three times, and the average loss was calculated. For the suspended solids content and pH test, add 800 mL of water to a 1000 mL beaker, divide 500 g of concrete into 10 equal parts, and let them fall slowly and freely from the water surface within 10-20 seconds. After standing for 3 minutes, take 600 mL of the upper layer of water without stirring the water sample; this is used to determine the suspended solids content according to the gravimetric method of GB / T 11901.

[0059] 28-day underwater compressive strength and 28-day water-land compressive strength retention rate: Underwater and land-based molded specimens from Examples 1-5 and Comparative Examples 1-8 were tested for compressive strength according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". For each sample, six underwater-molded 100mm×100mm×100mm cube specimens and six land-based 100mm×100mm×100mm cube specimens were prepared. Three were used for 7-day compressive strength testing, and three for 28-day compressive strength testing. This table focuses on recording the 28-day results. After reaching the required age, the specimens were removed from the 20℃ curing water, surface water was wiped off, the flatness of the bearing surface was checked, and the specimens were placed in the center of the pressure testing machine. A continuous and uniform loading rate of 0.6 MPa / s was applied until failure. The maximum failure load was recorded and converted to compressive strength. The 28-day underwater and land compressive strength retention rate is calculated by dividing the 28-day underwater molding compressive strength by the 28-day land molding compressive strength and then multiplying by 100%.

[0060] Water permeability resistance: The water permeability resistance of underwater-formed concrete in Examples 1-5 and Comparative Examples 1-8 was tested according to GB / T50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete". Six frustum-shaped permeability test specimens with an upper diameter of 175 mm, a lower diameter of 185 mm, and a height of 150 mm were prepared for each sample using an underwater conduit molding method. After molding, the specimens were left to stand in the original water environment for 24 hours before demolding and then cured in water at 20℃ for 28 days. Before the test, the specimens were removed, their surfaces were dried, and the sides were sealed with sealant. They were then placed in the permeability tester mold. The test water pressure started at 0.1 MPa and increased by 0.1 MPa every 8 hours until water seepage appeared at the end faces of three specimens or the pressure reached 1.2 MPa. Specimens without end face seepage were split open after the test, and the seepage height was measured. The average seepage height of the six specimens was taken as the evaluation value of water permeability resistance.

[0061] Table 1 Performance Test Results Example 1 6.5 0.79 12 530 12.4 0.8 82 42.8 92.6 16.85 Example 2 4.7 0.78 18 565 9.8 1.1 119 39.6 89.4 22.70 Example 3 8.0 0.73 8 500 16.9 0.5 54 47.6 95.8 11.90 Example 4 5.5 0.76 15 510 15.7 0.7 76 44.2 93.8 13.55 Example 5 7.2 0.75 10 550 10.9 0.8 88 43.7 94.4 14.20 Comparative Example 1 — — — 535 11.1 1.7 182 35.8 80.3 35.60 Comparative Example 2 7.4 0.82 12 505 15.6 1.3 143 39.0 86.8 28.45 Comparative Example 3 7.0 0.66 5 455 24.2 0.9 96 40.5 88.1 25.90 Comparative Example 4 6.5 0.79 12 470 21.7 1.1 124 38.7 86.9 29.70 Comparative Example 5 6.5 0.79 12 445 28.4 1.2 135 37.9 84.7 32.15 Comparative Example 6 6.5 0.79 12 530 12.0 1.2 131 39.2 87.5 27.80 Comparative Example 7 6.5 0.79 12 540 10.7 1.4 148 38.1 84.9 31.50 Comparative Example 8 6.5 0.79 12 515 13.5 1.1 116 40.1 88.4 25.65

[0062] Note: Comparative Example 1 did not prepare sodium carboxymethyl cellulose grafted with catechol spacers, therefore the weight-average molecular weight, degree of carboxymethyl substitution, and catechol grafting spacers of the grafted products are not filled in.

[0063] As shown in Table 1, when ordinary sodium carboxymethyl cellulose was used as the anti-dispersion component in Comparative Example 1, the initial slump expansion of the mixture was 535 mm, and the emptying time of the inverted slump cone was 11.1 s, indicating that it still had a certain degree of fluidity. However, its underwater loss reached 1.7%, the suspended solids content reached 182 mg / L, the 28-day underwater compressive strength was only 35.8 MPa, the 28-day water-land compressive strength retention rate was 80.3%, and the seepage height was 35.60 mm. This indicates that ordinary sodium carboxymethyl cellulose mainly improves the stability of the slurry by thickening, and has limited effect on slurry retention, strength retention, and anti-seepage performance under underwater scouring conditions.

[0064] Compared with Comparative Example 1, Example 1 used catechol-grafted sodium carboxymethyl cellulose with a weight-average molecular weight of 6.5×10^5, a retained carboxymethyl substitution degree of 0.79, and a catechol grafting interval of 12 dehydrated glucose units. It was combined with the pre-addition of sodium tetraborate decahydrate, the post-addition of ferric ammonium citrate, and the dry-mixing pre-dispersion of iron oxide yellow powder. This reduced the underwater loss to 0.8%, the suspended solids content to 82 mg / L, the 28-day underwater compressive strength to 42.8 MPa, the 28-day water-land compressive strength retention rate to 92.6%, and the water seepage height to 16.85 mm. This shows that the catechol-grafted modification and the combination of boron source, iron source and iron oxide yellow can improve the underwater anti-dispersion and hardened compactness of concrete while basically maintaining the construction fluidity.

[0065] Comparative Example 2 also prepared catechol-grafted sodium carboxymethyl cellulose, and its weight-average molecular weight was 7.4 × 10⁻⁶. 5 The carboxymethyl substitution degree was retained at 0.82, and the catechol grafting interval was 12 dehydrated glucose units. However, due to the lack of molecular weight classification, the initial slump spread decreased to 505 mm, the emptying time was extended to 15.6 s, and the underwater loss and suspended solids content were 1.3% and 143 mg / L, respectively, both inferior to Example 1. This indicates that catechol grafting alone is not sufficient to obtain the best overall performance. The molecular weight distribution control of sodium carboxymethyl cellulose before grafting has an important impact on the balance between flowability and anti-dispersion.

[0066] Comparative Example 3 shortened the catechol grafting interval to 5 dehydrated glucose units, reduced the retained carboxymethyl substitution degree to 0.66, and had an underwater loss of 0.9% and a suspended solids content of 96 mg / L. Although it still showed some anti-dispersion effect, the initial slump expansion was reduced to 455 mm, the drainage time was extended to 24.2 s, the 28-day water and land compressive strength retention rate was only 88.1%, and the water seepage height was 25.90 mm. This indicates that if the amount of catechol groups introduced is too high, it may cause the mixing system to thicken prematurely or coagulate locally, which is not conducive to the casting of the conduit, uniform molding, and the performance of the later stage.

[0067] Further comparison of Example 1 with Comparative Examples 4 and 5 shows that, under the same intrinsic parameters of the grafted product, after removing sodium tetraborate decahydrate from Comparative Example 4, the slump expansion decreased from 530 mm to 470 mm, the evacuation time increased from 12.4 s to 21.7 s, the underwater loss increased to 1.1%, and the 28-day underwater compressive strength decreased to 38.7 MPa. In Comparative Example 5, after adding ferric ammonium citrate to the anti-dispersant solution in advance, the slump expansion further decreased to 445 mm, the evacuation time increased to 28.4 s, and the 28-day underwater compressive strength decreased to 37.9 MPa. This indicates that the pre-addition of sodium tetraborate decahydrate and the post-addition of ferric ammonium citrate are not simply changes in the order of feeding, but rather help to reduce the flow resistance in the initial stage of mixing and avoid excessive coagulation of the system before underwater casting.

[0068] Comparing Example 1 with Comparative Examples 6, 7, and 8, it can be seen that after removing the iron oxide yellow powder, removing the ferric ammonium citrate, or replacing the iron oxide yellow powder with a wet post-addition method, the underwater loss increased to 1.2%, 1.4%, and 1.1%, respectively; the suspended solids content increased to 131 mg / L, 148 mg / L, and 116 mg / L, respectively; and the seepage height increased to 27.80 mm, 31.50 mm, and 25.65 mm, respectively. This indicates that the combination of dry pre-dispersion of iron oxide yellow powder and post-addition of ferric ammonium citrate is beneficial to improving the slurry retention effect near the cementitious material particles and the impermeability and compactness after underwater molding.

[0069] Examples 1-5 all employed a combination of sodium carboxymethyl cellulose, sodium tetraborate decahydrate, ferric ammonium citrate, and iron oxide yellow powder grafted with catechol as a spacer. However, due to differences in the weight-average molecular weight of the grafted products, the catechol grafting interval, and the dosage of added components, the performance varied. Example 2 exhibited the highest initial slump spread (565 mm) and the shortest emptying time (9.8 s), indicating that a lower anti-dispersant dosage, a larger grafting interval, and a higher water-reducing agent dosage are beneficial for improving construction fluidity. However, its underwater loss, suspended solids content, and seepage height were relatively high. Example 3 used a weight-average molecular weight of 8.0 × 10⁻⁶. 5 The grafted product, which retains a carboxymethyl substitution degree of 0.73 and a catechol grafting interval of 8 dehydrated glucose units, and is combined with a higher amount of antidispersant, sodium tetraborate decahydrate, ferric ammonium citrate, and iron oxide yellow powder, reduces underwater loss to 0.5%, suspended solids content to 54 mg / L, increases 28-day underwater compressive strength to 47.6 MPa, maintains 28-day water-land compressive strength retention rate of 95.8%, and reduces seepage height to 11.90 mm, exhibiting the best comprehensive performance in underwater antidispersion, strength retention, and impermeability.

[0070] Examples 4 and 5 were modified by adjusting the proportion of boron source, the proportion of iron source, and the amount of iron oxide yellow. The underwater loss was 0.7% and 0.8%, respectively. The 28-day water and land compressive strength retention rates were 93.8% and 94.4%, respectively. The water penetration heights were 13.55 mm and 14.20 mm, respectively. This shows that the present invention can still maintain good comprehensive performance within a certain range of formula fluctuations.

[0071] 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, 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. An underwater anti-dispersion concrete, characterized in that, The following raw materials, by weight, are mixed stepwise to obtain the following: 170-210 parts silicate cement, 160-200 parts granulated blast furnace slag powder, 70-100 parts fly ash, 0.35-0.65 parts iron oxide yellow powder, 730-790 parts medium sand, 980-1040 parts continuously graded crushed stone, 1.6-2.4 parts catechol-grafted sodium carboxymethyl cellulose, 0.04-0.08 parts sodium tetraborate decahydrate, 1.6-2.4 parts polycarboxylate superplasticizer, 0.16-0.24 parts concrete defoamer, 0.06-0.12 parts ferric ammonium citrate, and 145-165 parts water. The catechol-grafted carboxymethyl cellulose sodium was prepared by a condensation reaction of molecular weight graded carboxymethyl cellulose sodium with dopamine hydrochloride, and the weight-average molecular weight of the molecular weight graded carboxymethyl cellulose sodium was 4 × 10⁻⁶. 5 -8×10 5 The degree of carboxymethyl substitution is 0.65-0.90, and an average of one catechol group is introduced into each 8-18 dehydrated glucose units in the catechol-grafted sodium carboxymethyl cellulose. The stepwise mixing includes: mixing the catechol-grafted sodium carboxymethyl cellulose with a portion of water, then adding the sodium tetraborate decahydrate to form a borate ester dynamic masking anti-dispersant solution; dry mixing the ordinary silicate cement, S95 grade granulated blast furnace slag powder, Class I F fly ash, and iron oxide yellow powder to obtain a dry mix; subsequently, mixing the dry mix sequentially with the borate ester dynamic masking anti-dispersant solution, a water-reducing and defoaming solution containing the polycarboxylate superplasticizer and concrete defoamer, and a post-ferric coordination solution containing the ferric ammonium citrate.

2. The underwater anti-dispersion concrete according to claim 1, characterized in that, The silicate cement is P·O42.5 ordinary silicate cement.

3. The underwater anti-dispersion concrete according to claim 1, characterized in that, The continuously graded crushed stone is 5mm-25mm continuously graded crushed stone, and the content of needle-like and flaky particles is not greater than 8%.

4. The underwater anti-dispersion concrete according to claim 1, characterized in that, The degree of retained carboxymethyl substitution of the catechol-grafted sodium carboxymethyl cellulose is 0.70-0.

84.

5. The underwater anti-dispersion concrete according to claim 1, characterized in that, The catechol-spaced grafted carboxymethyl cellulose sodium is prepared by reacting the molecular weight graded carboxymethyl cellulose sodium in 2-morpholine ethanesulfonic acid buffer with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, followed by dopamine hydrochloride.

6. The underwater anti-dispersion concrete according to claim 5, characterized in that, When preparing the catechol-grafted sodium carboxymethyl cellulose, the mass ratio of the molecular weight graded sodium carboxymethyl cellulose, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide and dopamine hydrochloride is 2400:200-360:120-216:160-320.

7. The underwater anti-dispersion concrete according to claim 1, characterized in that, The borate ester dynamic masking anti-dispersion agent solution is prepared by means of 82-95 parts water, 1.6-2.4 parts catechol-grafted sodium carboxymethyl cellulose and 0.04-0.08 parts sodium tetraborate decahydrate, by weight.

8. The underwater anti-dispersion concrete according to claim 1, characterized in that, The water-reducing and defoaming solution is prepared by mass fractions of 32-48 parts water, 1.6-2.4 parts polycarboxylate superplasticizer, and 0.16-0.24 parts concrete defoamer.

9. The underwater anti-dispersion concrete according to claim 1, characterized in that, The post-ferric coordination solution was prepared by stirring 1 part water and 0.06-0.12 parts ferric ammonium citrate in the dark, by mass fraction.

10. An underwater construction method for underwater anti-dispersion concrete according to any one of claims 1-9, characterized in that, The process includes the following steps: after the underwater anti-dispersion concrete is mixed, it is poured within 15 minutes; at the start of pouring, the distance between the outlet of the guide pipe and the bottom surface of the pouring is no more than 300mm; during continuous pouring, the bottom end of the guide pipe is embedded in the newly poured concrete to a depth of no less than 500mm; the interruption time at the same pouring point does not exceed 20 minutes. Underwater vibration is not performed during the underwater pouring process.