Marine work concrete resistant to chlorine salt erosion and preparation method thereof

Abstract

The invention discloses marine concrete resistant to chlorine salt erosion and a preparation method thereof, and belongs to the technical field of building materials. The marine concrete is prepared from the following components in parts by mass: 280 to 350 parts of cementing material, 1100 to 1200 parts of aggregate, 150 to 180 parts of mixing water and 2.5 to 4.0 parts of high-efficiency water reducing agent, and the cementing material is prepared from 210 to 270 parts of ordinary Portland cement, 50 to 70 parts of superfine slag powder and 10 to 20 parts of modifier on the basis of the cementing material; on the basis of the modifier, the modifier is prepared from 30 to 45 parts of hexacalcium aluminoferrite, 25 to 35 parts of metaettringite, 20 to 35 parts of tobermorite, 3 to 6 parts of nano attapulgite and 2 to 4 parts of a nano composite material. The components can accelerate the early hydration of cement and the volcanic ash reaction process in the concrete hardening process, so that the concrete can form a compact microstructure in the curing period and cooperate with the curing effect of a hydration product on chloride ions, thereby remarkably improving the chloride ion penetration resistance of the concrete, prolonging the service life of the structure and improving the concrete quality. The method is suitable for port engineering, maritime work structures and buildings in salinized soil areas.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, and more specifically, relates to a type of marine concrete resistant to chloride salt corrosion and its preparation method. Background Technology

[0002] In marine structures, port terminals, roads in saline-alkali areas, and underground engineering projects, concrete is exposed to chloride-containing environments for extended periods. Chloride ions readily penetrate the concrete, causing steel reinforcement corrosion, leading to concrete cracking, spalling, and strength reduction. Once this degradation process occurs, repair is difficult and costly. Existing chloride-resistant measures, such as thickening the protective layer, increasing cement usage, and using organic coatings or corrosion-resistant steel reinforcement, can alleviate the problem to some extent, but they suffer from drawbacks such as complex construction, high costs, or insufficient durability.

[0003] A search revealed existing technologies for improving the chloride resistance of concrete, such as Chinese patent application number 200510101480.1, entitled "A Chloride-Resistant Silicate Cement." The silicate cement disclosed in this patent document comprises 14-94% silicate cement clinker, 5-85% admixtures, 1-10% gypsum, 0-15% additives, and 0-2% chopped fibers. While this improves the chloride resistance of concrete, the high cost of the added additives and fibers, coupled with the large amount of silicate cement clinker used, results in a high overall cost. More importantly, the electrical conductivity of this silicate cement is not significantly reduced.

[0004] For example, Chinese patent application number 201210035581.3, entitled "A Concrete Chloride-Resistant Penetrant and Its Application," utilizes nano-kaolin to modify concrete. However, this chloride-resistant penetrant requires grinding and calcination, which results in high water demand and poor workability of the concrete.

[0005] For example, Chinese patent application number 200610068664.7, entitled "Formulation of a Chloride Ion Penetration Reinforcing Agent for Concrete in Harbor Engineering," discloses a chloride ion penetration reinforcing agent mainly composed of 15-20% ultrafine silica powder, 20-25% metakaolin, 20-25% high-quality fly ash, 5-10% ultrafine nanofibers, and 6% high-efficiency water-reducing agent. Because the raw materials used require a large specific surface area, this increases costs and the amount of high-efficiency water-reducing agent needed, making widespread application difficult.

[0006] Therefore, there is an urgent need to improve the microstructure of materials to develop a new type of marine concrete with excellent resistance to chloride salt corrosion at a lower cost, which can significantly improve the resistance of concrete to chloride salt corrosion and meet the needs of marine engineering and saline soil projects. Summary of the Invention

[0007] To address the shortcomings of existing marine concrete technologies in terms of insufficient resistance to chloride erosion and the need for improved durability, this invention provides a chloride-resistant marine concrete and its preparation method. By optimizing the concrete components and preparation method, this invention improves the concrete's pore structure and accelerates secondary hydration reactions to achieve rapid densification during the early curing stage. It also effectively solidifies chloride ions and significantly enhances resistance to chloride ion penetration, thereby blocking chloride ion penetration pathways and extending the service life of the concrete structure. Furthermore, this method fully utilizes industrial solid waste, reduces production costs, promotes the development of green building materials, and achieves both improved durability and environmental and economic benefits.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a marine concrete resistant to chloride salt corrosion, comprising, based on marine concrete, the following components in parts by weight: 280-350 parts of cementitious material, 1100-1200 parts of aggregate, 150-180 parts of mixing water, and 2.5-4.0 parts of a high-efficiency water-reducing agent, wherein... Based on the cementitious material, the cementitious material comprises the following components in parts by weight: 210-270 parts of ordinary Portland cement, 50-70 parts of slag powder, and 10-20 parts of modifier; Based on the modifier, the modifier comprises the following components in parts by mass: 30-45 parts of calcium hexa-aluminate iron 25-35 parts of calcite 20-35 parts of Tobermorite 3-6 parts of nano-attapulgite 2-4 parts of nanocomposite material.

[0009] As one possible embodiment of the first aspect of the present invention, the cementitious material further includes nano-ettringite and nano-hydrated silica. Based on the cementitious material, the cementitious material comprises 200-260 parts by weight of ordinary silicate cement, 50-70 parts by weight of slag powder, 10-20 parts by weight of modifier, 2.1-4.2 parts by weight of nano-ettringite, and 6.3-10.5 parts by weight of nano-hydrated silica.

[0010] As one possible embodiment of the first aspect of the present invention, based on a nanocomposite material, the nanocomposite material added to the modifier, based on the nanocomposite material, comprises the following components in parts by mass: 35-45 parts of calcium acetate 25-35 parts sodium silicate 20-25 parts of methyl allyl alcohol polyoxyethylene ether (HPEG2400) 5-8 parts maleic anhydride 1-2 parts potassium persulfate 1-2 parts of sodium propylene sulfonate Sodium hydroxide 2-3 parts.

[0011] As one possible embodiment of the first aspect of the present invention, the method for preparing the nanocomposite material includes the following steps: Step 1: Prepare aqueous solutions of potassium persulfate, calcium acetate, and sodium silicate; Step 2: Add water to the reaction vessel, and then add HPEG2400, maleic anhydride and sodium propylene sulfonate in sequence while stirring; Step 3: Raise the temperature of the solution in the reactor to 80℃±2℃, add a potassium persulfate aqueous solution accounting for 50% of the total amount of potassium persulfate, and keep the reaction at this temperature for 1~1.5 hours; Step 4: Simultaneously start the dropping program through different dropping channels to drop the remaining 50% of potassium persulfate aqueous solution, all of the calcium acetate aqueous solution, and all of the sodium silicate aqueous solution. The dropping rate of the potassium persulfate aqueous solution is controlled at 0.15~0.18 parts / hour, the dropping rate of the calcium acetate aqueous solution is controlled at 1.7~4.5 parts / hour, and the dropping rate of the sodium silicate aqueous solution is controlled at 1.3~3.5 parts / hour. Step 5: After the addition is complete, maintain the temperature for 4-6 hours to allow the reaction to proceed; Step 6: Centrifuge to separate the solids and perform low-temperature vacuum drying.

[0012] As one possible embodiment of the first aspect of the present invention, in step 6, the centrifugation speed is 8000~10000 r / min, the centrifugation time is 15~20 minutes, the drying temperature is 40℃~50℃, and the drying time is 8~12 hours.

[0013] As one possible embodiment of the first aspect of the present invention, the meta-calcite is obtained by dehydrating calcite at 90°C to 105°C for 1 to 3 hours.

[0014] As one possible embodiment of the first aspect of the present invention, the tobermorite is at least one of 0.9 nm, 1.1 nm, and 1.4 nm tobermorite.

[0015] As one possible embodiment of the first aspect of the present invention, the modifier is prepared by adding hexacalcium aluminoferrite, metacalcium aluminate, tobermorite nanoattapulgite, and nanocomposite material into a ball mill and grinding at a speed of 300~400 r / min for 2~3 hours until the specific surface area of ​​the material reaches 350m² / kg~450m² / kg, thereby obtaining the modifier for marine concrete resistant to chloride salt corrosion.

[0016] As one possible embodiment of the first aspect of the present invention, the high-efficiency water-reducing agent is selected from polycarboxylate high-efficiency water-reducing agents.

[0017] A second aspect of the present invention provides a method for preparing the above-mentioned marine concrete, comprising the following steps: Step 1: Mix the modifier with a portion of the high-efficiency water-reducing agent, add a portion of mixing water, and disperse using an ultrasonic disperser to prepare a pre-dispersion of the modifier. Step 2: Add the cementitious materials and aggregates to the mixer and dry mix to ensure the solid raw materials are evenly mixed; Step 3: Add the modifier dispersion prepared in Step 1 and some of the mixing water to the mixer, stir, then add the remaining high-efficiency water-reducing agent and the remaining mixing water, and continue stirring to form a concrete mixture. Step 4: Pour the concrete mixture into the mold, vibrate it, and after pouring, cure and demold to obtain marine concrete resistant to chloride salt corrosion.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) This invention optimizes the composition and proportion of marine concrete, especially by adding a modifier with a specific formula, to construct a dual chloride-fixing system of chemical curing and physical adsorption, achieving curing efficiency far exceeding traditional technologies. On one hand, the hydration products of hexacalcium aluminoferrite (hydrated calcium aluminate and hydrated calcium ferrite) added to the modifier react chemically with chloride ions to generate stable chloroaluminate (Friedel salt), achieving chemical locking of chloride ions. On the other hand, the microporous structure of tobermorite, the nanopores (pore size 5~20nm) of nano-attapulgite, and the sulfonic acid groups (-SO3) of the nanocomposite materials... - The free chloride ions are further fixed through physical adsorption. Under the dual mechanism, the free chloride ion content (mass ratio of cementitious materials) of concrete after 90 days is ≤0.06%, which is far lower than the critical concentration for steel corrosion (0.15%~0.20%). After 180 days of immersion in 5% NaCl solution, the steel corrosion rate is ≤0.03%, which can protect the stability of the passivation film on the steel for a long time.

[0019] Furthermore, to further enhance the chloride erosion resistance of the resulting marine concrete, ultrafine admixtures containing nano-calcite and nano-hydrated calcium silicate are introduced. Combined with the synergistic effect of active components and hydration products, this improves the concrete's pore structure, accelerates secondary hydration for rapid densification during the early curing stage, effectively solidifies chloride ions, and significantly enhances resistance to chloride ion penetration. This blocks chloride ion penetration pathways, extends the service life of the concrete structure, and effectively meets the needs of marine engineering and saline soil projects. In practical applications in marine engineering, ports, and saline soil environments, it significantly slows down the corrosion of steel reinforcement by chloride ions, thereby reducing the likelihood of cracking and spalling. Compared to ordinary concrete, the marine concrete of this invention extends the service life by 20-30 years, reduces maintenance frequency and costs, and has significant economic and social benefits.

[0020] Meanwhile, this invention features a simple process and readily available raw materials, making it suitable for large-scale engineering applications. In terms of raw material selection, it fully utilizes industrial byproducts such as slag powder as admixtures, reducing cement clinker consumption and lowering energy usage and carbon dioxide emissions during production. This technology not only aligns with the development direction of green building materials but also enables the resource utilization of solid waste, reduces environmental pollution, and promotes the sustainable development of the construction industry, offering significant environmental and economic benefits. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] In coastal areas, port projects, and saline soil regions, concrete structures are exposed to chloride-containing environments for extended periods, making them highly susceptible to chloride ion penetration and steel reinforcement corrosion, leading to decreased structural durability and shortened service life. Existing technologies typically improve concrete's resistance to chloride erosion by reducing the water-cement ratio, introducing mineral admixtures, or applying surface coatings, but these methods still have the following shortcomings: (1) Chloride ions are easily penetrated: Traditional concrete has a high porosity and a non-dense microstructure in the early curing stage, so chloride ions can easily enter the interior through capillaries.

[0023] (2) Insufficient durability: Some mineral admixtures react slowly and are difficult to form an effective barrier in the early stage, resulting in insufficient performance of chloride salt resistance.

[0024] (3) Limited service life: In a highly corrosive environment, conventional concrete still cannot guarantee a long service life.

[0025] Therefore, traditional concrete must be improved to address the problem of chloride erosion. Existing technologies have proposed three main categories of chloride-resistant concrete, but all have corresponding drawbacks, primarily as follows: Structural protection solutions reduce the contact between chloride ions and steel bars by thickening the concrete protective layer, covering the steel bars or concrete surface with organic coatings, and using corrosion-resistant steel bars such as stainless steel. However, these methods have drawbacks such as complex construction procedures, significantly increased costs (e.g., stainless steel steel bars cost 3-5 times more than ordinary steel bars), and easy aging and failure of the coating, making them difficult to widely apply in large-scale projects.

[0026] Mix design optimization: This involves improving the density of the concrete's microstructure by reducing the water-cement ratio, increasing cement content, and incorporating mineral admixtures such as fly ash and slag. However, reducing the water-cement ratio leads to a decrease in concrete workability, requiring an additional increase in the dosage of high-efficiency water-reducing agents. Furthermore, the pozzolanic reaction rate of mineral admixtures (such as fly ash) is slow, making it difficult to form an effective impermeable barrier in the early stages. In environments with high chloride concentrations and rapid erosion, the problem of insufficient early chloride resistance is particularly prominent.

[0027] Admixture modification: Introducing chloride ion curing agents (such as layered bimetallic hydroxide LDH, aluminum-rich phase materials) to fix chloride ions through chemical bonding or physical adsorption. However, existing curing agents often have problems such as poor compatibility with cement hydration systems (e.g., some LDHs are structurally unstable in strongly alkaline environments) and curing efficiency being greatly affected by environmental factors (such as temperature and ionic strength), making it difficult to achieve long-term stable chloride salt resistance.

[0028] Research has revealed that existing chloride-resistant concrete technologies typically suffer from shortcomings such as insufficient early-stage structural density, limited chloride ion curing capacity, and short service life. The chloride-resistant marine concrete proposed in this invention, through optimized design of its components and proportions, enables the rapid formation of a dense microstructure in the early stages of concrete hardening and exhibits strong chloride ion curing properties, thereby significantly enhancing the concrete's resistance to chloride ion corrosion and meeting the application requirements of marine engineering and saline-alkali land projects.

[0029] Specifically, the chloride-resistant marine concrete of the present invention, based on marine concrete, comprises the following components in parts by weight: 280-350 parts of cementitious material, 1100-1200 parts of aggregate, 150-180 parts of mixing water, and 2.5-4.0 parts of high-efficiency water-reducing agent.

[0030] The composition and proportions of the above components are further explained in detail below: Cementitious material: The cementitious material used in this invention, based on the cementitious material, comprises the following components in parts by mass: 210-270 parts of ordinary Portland cement 50-70 parts of slag powder 10-20 parts of modifier.

[0031] The ordinary Portland cement used has a P·O 42.5 or higher, and its technical indicators are: initial setting time ≥45min, final setting time ≤600min, and 3d compressive strength ≥17MPa. The slag powder is of grade S95, and its technical indicators are: specific surface area ≥400m² / kg, 28d activity index ≥95%, and loss on ignition ≤1.0%.

[0032] Based on the modifier, the modifier comprises the following components in parts by mass: 30-45 parts of calcium hexa-aluminate iron 25-35 parts of calcite 20-35 parts of Tobermorite 3-6 parts of nano-attapulgite 2-4 parts of nanocomposite material.

[0033] The purity of the calcium aluminoferrite is ≥90%, the particle size is ≤10μm, and the early hydration heat release rate (3d) is ≥250J / g; The aforementioned meta-calcite is composed of calcite (stoichiometric formula: 3CaO) Al2O3 3CaSO4 Place 32H2O) in a forced-air drying oven and dehydrate at 90℃~105℃ for 1~3 hours (preferably at 100℃ for 2 hours). Control the crystal water content of ettringite after dehydration to be 8~12%. After cooling to room temperature, pulverize to a particle size ≤5μm to obtain ettringite powder. The tobermullite is at least one of the following crystal forms with a crystal interplanar spacing of 0.9 nm, 1.1 nm, and 1.4 nm, preferably the 1.1 nm crystal form, and has a specific surface area ≥300 m² / g; The nano-attapulgite has a particle size of 50~100nm, and after surface modification with 1%~3% silane coupling agent (KH-550), its dispersibility is ≤0.5% and its agglomeration rate is ≤0.5%. Based on nanocomposite materials, the nanocomposite materials comprise the following components in parts by mass: 35-45 parts of calcium acetate 25-35 parts sodium silicate Methyl allyl alcohol polyoxyethylene ether (HPEG2400) 20-25 parts 5-8 parts maleic anhydride 1-2 parts potassium persulfate 1-2 parts of sodium propylene sulfonate Sodium hydroxide 2-3 parts.

[0034] The hexacalcium aluminoferrite (C6AF) in the modifier of this invention has high early hydration activity, and meta-calcite can be rapidly regenerated into ettringite (AFt) in the hydration environment. The two active components can react rapidly in the early stage of cement hydration, releasing a large amount of calcium and aluminum ions and heat of hydration, which significantly accelerates the hydration process of cement clinker and the pozzolanic reaction of admixtures such as slag powder. Compared with the "slow early reaction" defect of traditional mineral admixtures (such as fly ash), this process can increase the 3-day hydration degree of concrete by 25% to 30%, which can not only rapidly improve the early compressive strength (3-day strength is 20% to 25% higher than that of ordinary concrete), but also effectively shorten the standard curing time, allowing the concrete to form a dense structure in the early stage of service and have the ability to resist chloride salt erosion in advance, which is suitable for the actual needs of "rapid construction and early erosion resistance" in marine engineering and port engineering.

[0035] Furthermore, the modifier of this invention also incorporates nanocomposite materials. Through the synergistic effect of active component hydration and nanomaterial filling, multi-scale optimization of the concrete microstructure is achieved, forming a dense microstructure that blocks chloride ion erosion pathways from the source. The hydration products of hexacalcium aluminoferrite and metacalcite rapidly fill early capillary pores, while the pozzolanic reaction between tobermorite and slag powder continuously generates additional CSH gel. Nano-attapulgite and nanocomposite materials further refine the hydration product particles and fill micropores. Ultimately, the resulting concrete has a total porosity of ≤18% after 28 days, and the proportion of macropores (pore size >50nm) is reduced from 15%~20% in ordinary concrete to below 8%, forming a continuous and dense cementitious product layer that completely blocks the penetration channels of chloride ions and other corrosive media, thereby fundamentally improving impermeability and durability.

[0036] Furthermore, the slag powder in the admixture reacts with calcium ions during hydration to generate more byproducts, filling and optimizing the capillary structure of the concrete. The pore size distribution shifts from large pores to medium and small pores, reducing porosity and lengthening the diffusion path and decreasing the diffusion rate of chloride ions in the concrete. Through this multi-scale pore structure regulation, the density and durability of the concrete are significantly improved.

[0037] Furthermore, the method for preparing the nanocomposite material of the present invention using the above components and proportions is as follows: Step 1: Prepare 20% potassium persulfate aqueous solution, 20% calcium acetate aqueous solution, and 20% sodium silicate aqueous solution separately for later use; Step 2: Add deionized water (calculated based on 30% solid content of nanocomposite material) to a reaction vessel equipped with a stirring device (speed controlled at 300~500r / min), a temperature control device and a dropping funnel. While stirring, add the specified mass parts of HPEG2400, maleic anhydride and sodium propylene sulfonate in sequence, and stir until completely dissolved to form a homogeneous solution. Step 3: Raise the temperature of the solution in the reactor to 80℃±2℃, and after maintaining the temperature, add a potassium persulfate aqueous solution accounting for 50% of the total amount of potassium persulfate. Keep the temperature for 1 hour to initiate the polymerization reaction. Step 4: Simultaneously add the solutions using different dropping funnels, adding the remaining 50% potassium persulfate aqueous solution, all of the calcium acetate aqueous solution, and all of the sodium silicate aqueous solution respectively. The dropping rate of the potassium persulfate aqueous solution is controlled at 0.15~0.18 parts / hour (based on the mass of potassium persulfate solids), the dropping rate of the calcium acetate aqueous solution is controlled at 1.7~4.5 parts / hour (based on the mass of calcium acetate solids), and the dropping rate of the sodium silicate aqueous solution is controlled at 1.3~3.5 parts / hour (based on the mass of sodium silicate solids). During the dropping process, maintain the reaction temperature stable at 80℃±2℃. Step 5: After the addition is complete, continue to keep the reaction at a warm temperature for 4-6 hours (preferably 5 hours) to ensure a complete reaction; Step 6: Transfer the reaction product to a centrifuge and centrifuge at 8000~10000 r / min for 15~20 minutes to collect the solid component; place the solid component in a vacuum drying oven at 40℃~50℃ and dry for 8~12 hours (preferably 10 hours), then pulverize and pass through an 800-mesh sieve to obtain nanocomposite powder.

[0038] As a further design of the present invention, nano-calcite and nano-hydrated calcium silicate are added to the cementitious material to further improve the chloride ion penetration resistance of marine concrete. Specifically, based on the cementitious material, the cementitious material of the present invention comprises the following components in parts by weight: 200-260 parts of ordinary Portland cement 50-70 parts of slag powder 10-20 parts of modifier Nano-calcite 2.1~4.2 parts 6.3 to 10.5 parts of nano-hydrated calcium silicate.

[0039] This invention significantly accelerates the secondary hydration reaction process in the cementitious system by adding nano-ettringite and nano-hydrated calcium silicate to the cementitious material, using them as crystal nuclei. The high specific surface area of ​​the introduced nanomaterials promotes the large-scale formation of CSH gel and ettringite, forming a continuous and dense cementitious product layer that effectively seals chloride ion channels, fundamentally improving the concrete's resistance to chloride salt erosion.

[0040] Aggregate: The aggregate used in this invention includes crushed stone and medium sand, with a mass ratio of medium sand to crushed stone of 1:(1.5~1.8).

[0041] The crushed stone is a continuous gradation of 5~20mm, and its technical indicators are: crushing index ≤10%, needle-like and flaky particle content ≤5%, mud content ≤1.0%, and apparent density ≥2600kg / m³. The fineness modulus of the medium sand is 2.3~3.0, and its technical indicators are: mud content ≤3.0%, mud lump content ≤1.0%, soundness ≤8%, and apparent density ≥2500kg / m³.

[0042] Mixing water: The mixing water used in this invention is drinking water, and its technical indicators are: conforming to the "Standard for Water Used in Concrete" GB / T 14684, pH≥6.5, chloride ion content≤200mg / L.

[0043] High-efficiency water-reducing agent: The high-efficiency water-reducing agent used in this invention is polycarboxylate high-efficiency water-reducing agent, whose technical indicators are: water reduction rate ≥25%, slump loss rate ≤15% in 2 hours, no chloride salts, and no rusting effect on steel bars.

[0044] The method for preparing the modifier using the above-mentioned components and proportions is as follows: Add 30-45 parts by weight of hexacalcium aluminoferrite, 25-35 parts of metacalcium aluminate, 20-35 parts of tobermorite, 3-6 parts of nano-attapulgite, and 2-4 parts of nanocomposite material into a ball mill. Use agate balls as the grinding media (ball-to-material ratio 5:1) and grind at 300-400 r / min for 2-3 hours until the specific surface area of ​​the material reaches 350 m² / kg-450 m² / kg to obtain the modified concrete for resisting chloride salt erosion.

[0045] It should be noted that this invention adds a modifier to the concrete components and optimizes the composition and ratio of the modifier. On the one hand, it utilizes the high early hydration activity of hexacalcium aluminoferrite in the modifier, which can rapidly generate hydrated calcium aluminate and hydrated calcium ferrite. On the other hand, by adding meta-calcite, it utilizes its regeneration into ettringite during hydration, which, together with tobermorite, synergistically fills the capillary pores inside the concrete, resulting in a 7-day chloride ion diffusion coefficient (RCM method) of ≤6×10⁻⁶. -12 m 2 / s, compared to ordinary concrete (12~15×10 -12 m 2 The permeability of chloride salts was reduced by more than 50%, and the early resistance to chloride salt penetration was significantly improved.

[0046] Meanwhile, the hydration products of hexacalcium aluminoferrite can further react with chloride ions to form stable chloroaluminate, achieving chemical curing and further improving the early-stage curing effect of concrete against chloride ions. The added nano-attapulgite's nanopores (pore size controlled at 5~20 nm) and the sulfonic acid groups (-SO3) in the nanocomposite material further enhance the effect. - Chloride ions are fixed by physical adsorption. The content of free chloride ions (by mass of cementitious materials) is ≤0.06% after 90 days, which is far lower than the critical concentration for steel corrosion (0.15%~0.20%). This means that efficient chloride fixation is achieved by using a dual mechanism of chemical curing and physical adsorption, which improves the chloride ion curing efficiency.

[0047] Furthermore, the tobermorite added to the modifier can subsequently react with slag powder in the concrete cementitious material to generate additional CSH gel through a pozzolanic reaction. Nano-attapulgite further refines the cement hydration product particles, resulting in a 28-day total porosity of ≤18% for the concrete, with macropores (pore size >50nm) accounting for ≤8%. This results in a dense microstructure, significantly lower than ordinary concrete (macropores account for 15%~20%), fundamentally blocking chloride ion penetration channels. Adding the modifier of this invention accelerates early cement hydration, increasing the 3-day compressive strength of the concrete by 20%~25% and the 28-day compressive strength by 10%~15% compared to ordinary concrete. After soaking in a 5% NaCl solution for 180 days, the steel corrosion rate is ≤0.03%, structural durability is improved by more than 30%, and service life is extended by 20~30 years.

[0048] The method for preparing the chloride-resistant marine concrete of the present invention is as follows: Step 1: Raw material pretreatment; Mix the modifier with a portion of the high-efficiency water-reducing agent, add some mixing water, and disperse using an ultrasonic disperser (power 500W, frequency 25kHz) for 10-15 minutes to form a pre-dispersion of the modifier, thus preventing the modifier from agglomerating. Step 2: Mix the dry ingredients; Add the cementitious materials and aggregates to the forced concrete mixer and dry mix for 1-2 minutes to ensure that the solid raw materials are evenly mixed. Step 3: Wet mixing stage; Add the pre-dispersed modifier liquid and some of the mixing water prepared in step one to the mixer and stir for 2-3 minutes; then add the remaining high-efficiency water-reducing agent and mixing water, and continue stirring for 3-4 minutes to form a uniform concrete mixture. Step 4: Pouring and Curing; The concrete mixture is poured into the mold and vibrated for 20-30 seconds with an immersion vibrator (frequency 50-60Hz) until no air bubbles overflow from the surface. After pouring, the concrete is immediately covered with plastic film to keep it moist. It is then cured in an environment with a temperature of 20℃±2℃ and a relative humidity of ≥90% for 24 hours before demolding. After demolding, it is cured according to standard for 28 days to obtain marine concrete resistant to chloride salt corrosion.

[0049] This invention also provides applications of the aforementioned marine concrete, specifically for use in marine environments with high humidity and high salinity (Cl). - Concentration ≥1.5%), saline soil (Cl - It can maintain its excellent performance in construction under conditions of concentration ≥0.5% and freezing-thaw cycles (-20℃~20℃), and can meet the engineering needs of various harsh environments such as ports, marine engineering, and saline soil areas.

[0050] Furthermore, by replacing part of the cement clinker with slag powder in the concrete composition, carbon dioxide emissions during the cement production process are reduced. The designed modifiers are made from conventional industrial materials, and their preparation process does not require high-temperature or high-pressure equipment, resulting in a 30%–40% cost reduction compared to LDH-type curing agents, making them suitable for large-scale industrial production and engineering applications.

[0051] The marine concrete of the present invention will be described in detail below with reference to specific implementation examples.

[0052] Example 1 1.1 Preparation of Modifier Weigh the following raw materials according to mass percentages: 35 parts of calcium aluminoferrite, 30 parts of calcium ferroaluminate (dehydrated at 100℃ for 2 hours), 28 parts of 1.1nm tobermorite, 5 parts of nano-attapulgite, and 4 parts of nano-composite material; add the above raw materials to a ball mill at a ball-to-material ratio of 5:1, at a speed of 350 r / min, and grind for 2.5 hours to obtain a modifier with a specific surface area of ​​400 m² / kg.

[0053] The preparation of the nanocomposite material involved 40 parts calcium acetate, 30 parts sodium silicate, 22 parts HPEG2400, 6 parts maleic anhydride, 1.5 parts potassium persulfate, 1.5 parts sodium propylene sulfonate, and 2.5 parts sodium hydroxide. The method of this invention was used for preparation, with the key process parameters as follows: the stirring speed was controlled at 400 r / min; the potassium persulfate aqueous solution was added at a rate of 0.16 parts / hour (based on the solid mass of potassium persulfate), the calcium acetate aqueous solution was added at a rate of 3 parts / hour (based on the solid mass of calcium acetate), and the sodium silicate aqueous solution was added at a rate of 2 parts / hour (based on the solid mass of sodium silicate); the reaction was maintained at a constant temperature for 5 hours after addition; during centrifugation, the centrifugation speed was 9000 r / min, the vacuum drying temperature was 45℃, and the drying time was 10 hours. After pulverization, the powder was passed through an 800-mesh sieve to obtain the nanocomposite material powder.

[0054] 1.2 Concrete Preparation Raw material proportions: Based on concrete, it includes the following components in parts by mass: 320 parts of cementitious material, 1150 parts of aggregate, 165 parts of mixing water and 3.2 parts of high-efficiency water-reducing agent; Specifically, based on the cementitious material, the cementitious material includes the following components in parts by weight: 240 parts of P·O 42.5 cement, 64 parts of slag powder, and 16 parts of modifier; Based on aggregate, the aggregate consists of the following components by mass: 1150 parts crushed stone and 700 parts medium sand.

[0055] The above components are prepared according to the steps of this invention. The key process parameters are: ultrasonic dispersion time 12 minutes; vibrator frequency 55Hz, vibration for 25 seconds; standard curing for 28 days.

[0056] The properties of the obtained concrete were tested, and the test results are shown in Table 1.

[0057] Example 2 2.1 Preparation of Modifier Weigh the raw materials according to the following mass percentages: 40 parts of calcium aluminoferrite, 28 parts of calcium ferroaluminate (dehydrated at 95℃ for 2.5 hours), 30 parts of 0.9nm+1.1nm tobermorite (mass ratio 1:1), 4 parts of nano-attapulgite, and 3 parts of nano-composite materials. Add the above raw materials to a ball mill with a ball-to-material ratio of 5:1, a ball milling speed of 380 r / min, and grind for 2 hours to obtain a specific surface area of ​​380 m² / kg.

[0058] Preparation of nanocomposite materials: 42 parts calcium acetate, 28 parts sodium silicate, 23 parts HPEG2400, 7 parts maleic anhydride, 1.8 parts potassium persulfate, 1.2 parts sodium propylene sulfonate, and 2.8 parts sodium hydroxide were prepared using the method of this invention. Key process parameters were as follows: During stirring, the rotation speed was controlled at 400 r / min; the dropping rate of the potassium persulfate aqueous solution was controlled at 0.15 parts / hour (based on the mass of potassium persulfate solids), the dropping rate of the calcium acetate aqueous solution was controlled at 1.7 parts / hour (based on the mass of calcium acetate solids), and the dropping rate of the sodium silicate aqueous solution was controlled at 1.3 parts / hour (based on the mass of sodium silicate solids); the reaction was maintained at a constant temperature for 5 hours after the addition; during centrifugation, the centrifugation speed was 10000 r / min, the vacuum drying temperature was 50℃, and the drying time was 10 hours. After pulverization, the nanocomposite material powder was obtained by passing it through an 800-mesh sieve.

[0059] 2.2 Concrete Preparation Raw material proportions: Based on concrete, it includes the following components in parts by mass: 290 parts of cementitious material, 1100 parts of aggregate, 180 parts of mixing water, and 4.0 parts of high-efficiency water-reducing agent; Specifically, based on the cementitious material, the cementitious material includes the following components in parts by weight: 234 parts P·O 42.5 cement, 62 parts slag powder, 15 parts modifier, 3 parts nano-ettringite and 6 parts nano-hydrated silica. Based on aggregate, the aggregate consists of the following components by mass: 1180 parts crushed stone and 680 parts medium sand.

[0060] The above components were prepared according to the steps of the present invention, and the key process parameters for preparation were the same as in Example 1.

[0061] The properties of the obtained concrete were tested, and the test results are shown in Table 1.

[0062] Example 3 3.1 Preparation of Modifier Weigh the following raw materials according to mass percentages: 30 parts of calcium aluminoferrite, 25 parts of calcium ferroaluminate (dehydrated at 100℃ for 2 hours), 20 parts of 1.1nm tobermorite, 3 parts of nano-attapulgite, and 2 parts of nano-composite material. Add the above raw materials to a ball mill with a ball-to-material ratio of 5:1, a rotation speed of 300 r / min, and grind for 2 hours to obtain a modifier with a specific surface area of ​​355 m² / kg.

[0063] The preparation of the nanocomposite material involved 35 parts calcium acetate, 25 parts sodium silicate, 20 parts HPEG2400, 5 parts maleic anhydride, 1 part potassium persulfate, 1 part sodium propylene sulfonate, and 2 parts sodium hydroxide, prepared using the method of this invention. Key process parameters were as follows: the stirring speed was controlled at 300 r / min; the dropping rate of the potassium persulfate aqueous solution was controlled at 0.18 parts / hour (based on the solid mass of potassium persulfate), the dropping rate of the calcium acetate aqueous solution was controlled at 4.5 parts / hour (based on the solid mass of calcium acetate), and the dropping rate of the sodium silicate aqueous solution was controlled at 3.5 parts / hour (based on the solid mass of sodium silicate); during centrifugation, the centrifugation speed was 8000 r / min, the vacuum drying temperature was 40℃, and the drying time was 8 hours. After pulverization, the powder was passed through an 800-mesh sieve to obtain the nanocomposite material powder.

[0064] 3.2 Concrete Preparation Raw material proportions: Based on concrete, it includes the following components in parts by mass: 280 parts of cementitious material, 1150 parts of aggregate, 165 parts of mixing water and 3.2 parts of high-efficiency water-reducing agent; Specifically, based on the cementitious material, the cementitious material includes the following components in parts by weight: 204 parts P·O 42.5 cement, 54 parts slag powder, 13 parts modifier, 3 parts nano-ettringite and 6 parts nano-hydrated silica. Based on aggregate, the aggregate consists of the following components by mass: 1150 parts crushed stone and 700 parts medium sand.

[0065] The above components were prepared according to the steps of the present invention, and the key process parameters for preparation were the same as in Example 1.

[0066] The properties of the obtained concrete were tested, and the test results are shown in Table 1.

[0067] Example 4 4.1 Preparation of Modifier Weigh the following raw materials according to mass percentages: 45 parts calcium aluminoferrite, 35 parts calcium ferroaluminate (dehydrated at 100℃ for 2 hours), 35 parts 1.1 nm tobermorite, 6 parts nano-attapulgite, and 2.5 parts nano-composite material. Add the above raw materials to a ball mill with a ball-to-material ratio of 5:1, a rotation speed of 500 r / min, and grind for 3 hours to obtain a modifier with a specific surface area of ​​445 m² / kg.

[0068] The nanocomposite material was prepared using the method of this invention, comprising 45 parts calcium acetate, 35 parts sodium silicate, 25 parts HPEG2400, 8 parts maleic anhydride, 2 parts potassium persulfate, 2 parts sodium propylene sulfonate, and 3 parts sodium hydroxide. The key process parameters were as follows: the stirring speed was controlled at 500 r / min; the dropping rate of the potassium persulfate aqueous solution was controlled at 0.17 parts / hour (based on the solid mass of potassium persulfate), the dropping rate of the calcium acetate aqueous solution was controlled at 3.5 parts / hour (based on the solid mass of calcium acetate), and the dropping rate of the sodium silicate aqueous solution was controlled at 2.5 parts / hour (based on the solid mass of sodium silicate); during centrifugation, the centrifugation speed was 10000 r / min, the vacuum drying temperature was 50℃, and the drying time was 12 hours. After pulverization, the powder was passed through an 800-mesh sieve to obtain the nanocomposite material powder.

[0069] 4.2 Concrete Preparation Raw material proportions: Based on concrete, it includes the following components in parts by mass: 350 parts cementitious material, 1200 parts aggregate, 150 parts mixing water, and 2.5 parts high-efficiency water-reducing agent; Specifically, based on the cementitious material, the cementitious material includes the following components in parts by weight: 255 parts P·O 42.5 cement, 68 parts slag powder, 16 parts modifier, 3 parts nano-calcite and 8 parts nano-hydrated silica. Based on aggregate, the aggregate consists of the following components by mass: 1150 parts crushed stone and 700 parts medium sand.

[0070] The above components were prepared according to the steps of the present invention, and the key process parameters for preparation were the same as in Example 1.

[0071] The properties of the obtained concrete were tested, and the test results are shown in Table 1.

[0072] Comparative Example 1 This comparative example is ordinary chloride-resistant concrete, and its preparation method is as follows: The following mixture was prepared using conventional processes: 350 parts of P·O 42.5 cement, 80 parts of fly ash, 15 parts of LDH curing agent, 1150 parts of crushed stone, 700 parts of medium sand, 3.5 parts of water-reducing agent, and 170 parts of mixing water.

[0073] Table 1 Performance test data of marine concrete obtained from the examples and comparative examples

[0074] As shown in Table 1, the concrete of the present invention is significantly superior to the prior art in terms of compressive strength, resistance to chloride ion penetration, and chloride fixation efficiency.

[0075] In summary, the concrete of this invention exhibits excellent resistance to chloride erosion and strong environmental adaptability, making it widely applicable in port engineering, marine structures, and construction in saline-alkali soil areas. In these complex environments, traditional concrete often suffers a shortened lifespan due to chloride ion penetration, while this invention effectively extends the service life of structures and reduces maintenance and reinforcement costs. Furthermore, the process is simple, the raw materials are readily available, making it suitable for large-scale engineering applications and offering significant economic and social benefits.

[0076] The present invention and its embodiments have been described above illustratively. This description is not restrictive and is only one embodiment of the present invention. The actual structure is not limited to this. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A type of marine concrete resistant to chloride salt corrosion, characterized in that, Based on marine concrete, it comprises the following components by weight: 280-350 parts cementitious materials, 1100-1200 parts aggregate, 150-180 parts mixing water, and 2.5-4.0 parts high-efficiency water-reducing agent. Based on the cementitious material, the cementitious material comprises the following components in parts by weight: 210-270 parts of ordinary Portland cement, 50-70 parts of slag powder, and 10-20 parts of modifier; Based on the modifier, the modifier comprises the following components in parts by mass: 30-45 parts of calcium hexa-aluminate iron 25-35 parts of calcite 20-35 parts of Tobermorite 3-6 parts of nano-attapulgite 2-4 parts of nanocomposite material.

2. The marine concrete according to claim 1, characterized in that, The cementitious material also includes nano-ettringite and nano-hydrated silica. Based on the cementitious material, the cementitious material contains 200-260 parts by weight of ordinary silicate cement, 50-70 parts by weight of slag powder, 10-20 parts by weight of modifier, 2.1-4.2 parts by weight of nano-ettringite, and 6.3-10.5 parts by weight of nano-hydrated silica.

3. The marine concrete according to claim 1, characterized in that, Based on nanocomposite materials, the nanocomposite materials added to the modifier, based on nanocomposite materials, comprise the following components in parts by mass: 35-45 parts of calcium acetate 25-35 parts sodium silicate 20-25 parts of methyl allyl alcohol polyoxyethylene ether (HPEG2400) 5-8 parts maleic anhydride 1-2 parts potassium persulfate 1-2 parts of sodium propylene sulfonate Sodium hydroxide 2-3 parts.

4. The marine concrete according to claim 3, characterized in that, The preparation method of the nanocomposite material includes the following steps: Step 1: Prepare aqueous solutions of potassium persulfate, calcium acetate, and sodium silicate; Step 2: Add water to the reaction vessel, and then add HPEG2400, maleic anhydride and sodium propylene sulfonate in sequence while stirring; Step 3: Raise the temperature of the solution in the reactor to 80℃±2℃, add a potassium persulfate aqueous solution accounting for 50% of the total amount of potassium persulfate, and keep the reaction at this temperature for 1~1.5 hours; Step 4: Simultaneously start the dropping program through different dropping channels to drop the remaining 50% of potassium persulfate aqueous solution, all of the calcium acetate aqueous solution, and all of the sodium silicate aqueous solution. The dropping rate of the potassium persulfate aqueous solution is controlled at 0.15~0.18 parts / hour, the dropping rate of the calcium acetate aqueous solution is controlled at 1.7~4.5 parts / hour, and the dropping rate of the sodium silicate aqueous solution is controlled at 1.3~3.5 parts / hour. Step 5: After the addition is complete, maintain the temperature for 4-6 hours to allow the reaction to proceed; Step 6: Centrifuge to separate the solids and perform low-temperature vacuum drying.

5. The marine concrete according to claim 3, characterized in that, In step 6, the centrifugation speed is 8000~10000 r / min, the centrifugation time is 15~20 minutes, the drying temperature is 40℃~50℃, and the drying time is 8~12 hours.

6. The marine concrete according to any one of claims 1-4, characterized in that, The calcite is obtained by dehydrating calcite at 90℃~105℃ for 1~3 hours.

7. The marine concrete according to any one of claims 1-4, characterized in that, The tobermulite is at least one of 0.9 nm, 1.1 nm, and 1.4 nm tobermulite.

8. The marine concrete according to any one of claims 1-4, characterized in that, The modifier is prepared by adding hexacalcium aluminoferrite, metacalcium aluminate, tobermorite nanoattapulgite, and nanocomposite materials into a ball mill and grinding them at a speed of 300~400 r / min for 2~3 hours until the specific surface area of ​​the material reaches 350m² / kg~450m² / kg, thus obtaining the modifier for marine concrete resistant to chloride salt corrosion.

9. The marine concrete according to any one of claims 1-4, characterized in that, The high-efficiency water-reducing agent is selected from polycarboxylate high-efficiency water-reducing agents.

10. The method for preparing marine concrete according to any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Mix the modifier with a portion of the high-efficiency water-reducing agent, add a portion of mixing water, and disperse using an ultrasonic disperser to prepare a pre-dispersion of the modifier. Step 2: Add the cementitious materials and aggregates to the mixer and dry mix to ensure the solid raw materials are evenly mixed; Step 3: Add the modifier dispersion prepared in Step 1 and some of the mixing water to the mixer, stir, then add the remaining high-efficiency water-reducing agent and the remaining mixing water, and continue stirring to form a concrete mixture. Step 4: Pour the concrete mixture into the mold, vibrate it, and after pouring, cure and demold to obtain marine concrete resistant to chloride salt corrosion.

Images