Preparation method of seawater-corrosion-resistant high-silicon high-iron sulphoaluminate gelling system

Abstract

The invention discloses a preparation method of a seawater-corrosion-resistant high-silicon high-iron sulphoaluminate gelling system, and relates to the technical field of gelling materials for ocean engineering. The method comprises the following three steps: S1, preparing a component A containing a specific mineral composition; S2, preparing a component B containing beta-cyclodextrin and benzotriazole; and S3, mixing the component A, the component B, a coagulation time and activity regulator and a mineral activity admixture according to a ratio, and controlling mixing parameters to a target particle size. Through mineral composition optimization, compact microstructure construction and intelligent targeted anti-corrosion cooperation, the characteristics of low hydration heat, high corrosion resistance and high strength of a gelling system are achieved, temperature cracks are effectively reduced, marine multi-medium corrosion is resisted, the service life of an engineering structure is prolonged, the process is simple and convenient, the cost is controllable, and the method is suitable for large-scale construction.

Description

Technical Field

[0001] This invention relates to the field of cementitious materials for marine engineering, and more specifically to a method for preparing a high-silica, high-iron, sulfoaluminate cementitious system resistant to seawater erosion. Background Technology

[0002] Large-volume concrete structures in marine engineering (such as bridge piers for cross-sea bridges, offshore wind power foundations, and deep-water wharf pile foundations) have long faced the dual severe challenges of concentrated heat release from hydration and the highly corrosive marine environment. Their service life and safety performance are directly related to the overall stability of the project.

[0003] Regarding the heat of hydration, during the hardening process of large-volume concrete, the hydration reaction of traditional cementitious materials releases a large amount of heat, causing the temperature at the center of the structure to reach 60-80℃. Meanwhile, the surface dissipates heat rapidly, creating a huge temperature difference of 20-40℃ between the inside and outside, which in turn generates thermal stress and triggers early cracking. These cracks become rapid penetration channels for corrosive media such as chloride ions and sulfates, accelerating structural deterioration.

[0004] In terms of marine corrosion, the erosion of concrete by the marine environment exhibits the characteristics of multiple coupled deterioration mechanisms: the concentration of chloride ions in seawater is as high as 19 g / L, which penetrates into the interior of concrete and damages the passivation film on the surface of steel bars, leading to steel bar corrosion. The corrosion products expand in volume by 3-6 times, causing concrete cracking and spalling; sulfate ions react with cement hydration products to form ettringite and gypsum, and the volume expansion also causes structural cracking; at the same time, physical and mechanical factors such as carbonation, freeze-thaw cycles, and wave erosion further accelerate the deterioration process of concrete and significantly shorten the service life of engineering projects.

[0005] Traditional silicate cement-based cementitious materials have inherent defects: the hydration process generates a large amount of easily corroded calcium hydroxide, and the internal microstructure contains pores, which facilitate the intrusion of corrosive media. Even though sulfoaluminate cement is gradually being used in marine engineering due to its excellent resistance to sulfate attack, traditional sulfoaluminate cement still suffers from problems such as high early hydration heat release and insufficient density of the cement stone structure. Seawater can easily penetrate the interior through structural pores and react with the reinforcing steel, failing to meet the stringent requirements of marine engineering for cementitious materials with low heat of hydration and high durability.

[0006] To address these issues, numerous studies have been conducted in related fields. For example, patent WO2019152736A1 discloses an alkali-activated cementitious system based on industrial waste such as slag and fly ash. While this system avoids chemical corrosion from chloride ions and sulfates, it suffers from drawbacks such as demanding construction processes (sensitive to alkali activator concentration, modulus, and curing conditions, requiring heat curing), insufficient long-term durability data, high drying shrinkage leading to cracking, and fluctuations in raw material composition affecting the uniformity of the finished product. Patent US20180072433A1 discloses a conventional cement system using composite ultrafine admixtures, which optimizes the pore structure through physical filling and reaction with pozzolanic materials. However, it has extremely high requirements for raw material quality, results in high viscosity and rapid loss of workability in freshly mixed concrete, and the use of ultrafine admixtures and nanomaterials significantly increases production costs, limiting its large-scale engineering application.

[0007] In summary, existing cementing systems struggle to achieve a balanced optimization in terms of low heat of hydration control, long-term resistance to seawater erosion, construction feasibility, and economic efficiency, thus failing to fully meet the high standards required for cementing materials in key marine engineering projects. Therefore, developing a simple, cost-effective, and intelligent long-term corrosion-resistant high-silica, high-iron sulfoaluminate cementing system has become a pressing technical challenge in the field of cementing materials for marine engineering. Summary of the Invention

[0008] To overcome the defects and shortcomings of the existing technology, the present invention provides a method for preparing a high-silica, high-iron sulfoaluminate cementitious system resistant to marine erosion. The purpose of the present invention is to solve the problem that the existing cementitious system is difficult to achieve a balanced optimization in terms of low heat of hydration control, long-term seawater erosion resistance, construction feasibility and economy, and cannot fully meet the high standard requirements of key marine engineering projects for cementitious materials.

[0009] To address the problems existing in the prior art, the present invention is achieved through the following technical solution.

[0010] This invention provides a method for preparing a high-silica, high-iron, sulfoaluminate cementitious system resistant to seawater erosion, comprising the following steps: S1. By mass, take 40-60 parts of calcareous material, 2-15 parts of siliceous material, 4-20 parts of aluminum material, 0-10 parts of iron material, and 10-25 parts of gypsum material, mix them, grind them, press them into cakes, calcine them at 1250℃-1350℃, and grind them again to obtain component A; the mineral composition of component A includes calcium sulfoaluminate, dicalcium silicate, calcium aluminoferrite, free gypsum, and calcium sulfosilicate; S2. After mixing β-cyclodextrin and benzotriazole in a molar ratio of 1:1 to 1:1.5, add reaction aids, put the resulting mixture into a planetary ball mill for thorough grinding, and react the ground product under low temperature vacuum drying conditions. After the constant reaction is complete, component B is obtained. S3. By mass percentage, take 30%-60% of component A, 1%-3% of component B, 2%-15% of setting time and activity regulator, and 30%-60% of mineral active admixture, with the sum of the mass percentages of each component being 100%. Add them to a V-type mixer for mixing. During the mixing process, control the loading coefficient to be 30%-60%, the mixer speed to be 15-30 rpm, and mix for 20-50 minutes until D10≤2.0μm and D90≤40μm, to obtain the high-silica, high-iron, sulfoaluminate gelling system.

[0011] In a further preferred embodiment, in step S1, the alkalinity coefficient of the mixture formed by the combination of calcareous materials, siliceous materials, aluminum materials, iron materials and gypsum materials is controlled at 0.95-1.15, and the aluminum-sulfur ratio is controlled at 2.5-3.82.

[0012] More preferably, in step S2, the reaction aid is any one of acetone, ethanol, and water.

[0013] More preferably, in step S2, the mass ratio of the mixture formed by mixing the reaction aid with β-cyclodextrin and benzotriazole is 5:100-10:100.

[0014] More preferably, in step S2, the low-temperature vacuum drying conditions refer to a temperature of 40℃-60℃ and a vacuum of 5pa-50pa.

[0015] More preferably, in step S1, the calcareous material is any one or a mixture of any proportion of conventional limestone, high-silicon limestone, and high-silicon, high-calcium industrial waste residue; the calcareous material contains ≥44.00% CaO and ≤15.00% SiO2.

[0016] More preferably, in step S1, the siliceous material is any one or a combination of sandstone, shale and fluorite washing waste in any proportion, wherein the SiO2 content in the siliceous material is ≥70.00%.

[0017] More preferably, in step S1, the ferrous material is non-ferrous metal ash, magnetite, sulfuric acid slag, or copper slag, and the Fe2O3 content in the ferrous material is ≥30.00%; the aluminum material is bauxite, aluminum ash, or high-iron bauxite, wherein the Al2O3 content in the bauxite is ≥50.00%, and the SiO2 content is ≤20%; the Al2O3 content in the aluminum ash is ≥65.00%; and the Al2O3 content in the high-iron bauxite is ≥50.00%, and the Fe2O3 content is ≥15.00%.

[0018] More preferably, in step S1, the gypsum material is dihydrate gypsum, anhydrite, mixed gypsum, desulfurized gypsum, phosphogypsum, or fluorogypsum, wherein the SO3 content is ≥25%.

[0019] More preferably, in step S1, the specific surface area of ​​component A is controlled at 320 m². 2 / kg-380m 2 / kg.

[0020] More preferably, in step S3, the setting time and activity regulator is calcined gypsum, dihydrate gypsum, anhydrite, or a mixed gypsum, with an SO3 content ≥30%.

[0021] More preferably, in step S3, the active admixture is any two or more of fly ash, slag, pozzolanic materials, metakaolin and limestone mixed in any proportion.

[0022] More preferably, the specific surface area of ​​the active admixture is controlled at 400 m². 2 / kg-450m 2 / kg.

[0023] This invention realizes the application of sulfoaluminate cementitious materials in large-volume concrete from three dimensions: reducing chemical erosion weaknesses through mineral composition optimization, constructing a dense microstructure through highly active admixtures and a low water-cement ratio, and providing surface protection for the steel reinforcement structure through intelligent slow-release corrosion inhibitors, thereby providing multiple protections for the entire concrete system, ultimately forming a synergistic corrosion-resistant system of physical barrier + chemical stability + electrochemical protection.

[0024] Firstly, considering the design direction of the main minerals, calcium sulfoaluminate minerals, dicalcium silicate minerals, and aluminoferrite minerals are used to achieve the characteristics of high early strength, good durability, and strong resistance to seawater erosion in the main cementitious material. According to the application scenario, the mineral composition in the clinker is designed by reducing the content of calcium sulfoaluminate, increasing the content of dicalcium silicate, increasing the content of iron phase, and controlling the content of free gypsum. This achieves the early strength support formed by the alternation of high-sulfur ettringite and low-sulfur ettringite. CSH gel has strong adhesion and presents fibrous, network, and can encapsulate and cement the crystalline phases such as AFm and ettringite. Amorphous aluminum glue and iron glue fill the gaps formed by ettringite and other products, resulting in uniform strength development of cement stone. The continuous hydration of gel fills the gaps and improves the density of cement stone, forming an ordered and dense structure of "crystalline phase skeleton + gel phase filling". These hydration products work together to construct the basic structure of cement stone, helping to improve the integrity and strength of the system. Secondly, a multi-mineral synergistic design constructs a composite structure of "high-iron, high-silica calcium sulfoaluminate clinker system + active admixtures + intelligent slow-release corrosion inhibitors": mineral admixtures reduce the concentration of various ions in the system, alleviate the heat release during hydration of the ferroaluminate cement system, and allow early free gypsum to slowly dissolve and react with anhydrous calcium sulfoaluminate to generate low-sulfur ettringite, thereby reducing the early heat release rate and gradually increasing the strength of the cement stone. The reduction of Ca(OH)2 concentration and the organic retarder effectively slow down the early heat release rate and reduce temperature cracks. The active admixtures optimize the gel structure, and the multi-component synergy achieves a comprehensive performance breakthrough of "low heat release, high corrosion resistance, high strength, and low shrinkage".

[0025] Furthermore, in this system, the intelligent slow-release corrosion inhibitor is prepared by mechanical force that micronizes the solid particles and brings them into close contact. With the help of trace solvent molecules, the benzene rings of benzotriazole molecules diffuse into the CD cavity, thereby forming a supramolecular system in which the supramolecular host β-cyclodextrin encapsulates and loads the organic compound benzotriazole (BTA), which has the functions of slowing coagulation and preventing steel corrosion.

[0026] The core of this intelligent release system is a "pH-regulated molecular hydrophilicity / hydrophobicity switch".

[0027] 1) Dormant phase (normal high pH environment, such as concrete pore fluid pH>12.5): At this point, the corrosion inhibitor molecule—benzotriazole-based material—is in a stable state. Its hydrophobic benzene ring moiety is successfully encapsulated within the hydrophobic cavity of the cyclodextrin, forming a stable inclusion complex.

[0028] The corrosion inhibitor is "locked" in the cyclodextrin and fixed in the cement matrix, so it will not be ineffectively lost or cause unnecessary side reactions with other cement components.

[0029] 2) Activation and release phase (carbonization of corrosion-retarding concrete occurs, pH decreases locally): When concrete carbonization or chloride ion infiltration causes steel reinforcement to begin to corrode, the microenvironment on the steel reinforcement surface becomes acidic (pH can drop below 9). Under acidic conditions, the nitrogen atom in BTA molecules combines with a hydrogen ion and a calcium ion, becoming a positively charged cation.

[0030] This protonation process greatly enhances the hydrophilicity of the molecules. The hydrophobic molecules, which were originally tightly bound to the hydrophobic cavity of the cyclodextrin, become hydrophilic ions. According to the principle of "like dissolves like," the hydrophobic environment exerts a strong repulsive force on the bound molecules. The inclusion effect between the corrosion inhibitor molecules and the cyclodextrin is disrupted, causing the BTA to detach from the cyclodextrin cavity. The corrosion inhibitor is then intelligently released near the steel reinforcement, encapsulating areas prone to corrosion.

[0031] 3) The stage where it takes effect: The released corrosion inhibitor molecules are quickly adsorbed on the active anodic region of the steel bar surface, forming a monomolecular protective film that effectively prevents the continued dissolution of iron ions, thereby inhibiting the corrosion process.

[0032] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1. Constructing a synergistic corrosion-resistant system to achieve a multi-layered protective closed loop: This invention forms a synergistic corrosion-resistant system of "physical barrier + chemical stability + electrochemical protection" from three core dimensions: mineral composition optimization, microstructure densification, and intelligent protection empowerment, comprehensively solving the corrosion problem of cementitious materials in marine environments. By precisely controlling the proportion of minerals such as calcium sulfoaluminate, dicalcium silicate, and calcium aluminoferrite in high-silica and high-iron sulfoaluminate cement clinker, the chemical weaknesses susceptible to corrosion are reduced; with the synergistic effect of highly active admixtures and low water-cement ratio, an ordered and dense structure of "crystalline phase skeleton + gel phase filling" is constructed—fibrous and network-like CSH gel encapsulates and binds crystalline phases such as AFm and ettringite, while amorphous aluminum and iron gels fill the pores, significantly reducing the penetration channels of corrosive media; intelligent slow-release corrosion inhibitors provide targeted electrochemical protection for steel bars. The three form a protective closed loop, which is significantly superior to traditional cementitious systems with a single protection mechanism.

[0033] 2. Outstanding Low Heat of Hydration Characteristics, Solving the Problem of Temperature Cracks: Addressing the issue of temperature difference cracks caused by concentrated heat of hydration in large-volume concrete, this invention achieves low heat release regulation through multi-component synergistic design. On one hand, it optimizes the clinker mineral composition, reducing the content of calcium sulfoaluminate and increasing the content of dicalcium silicate and iron phase, thus reducing the early-stage heat release peak. On the other hand, the introduction of mineral admixtures reduces the ion concentration of the system, allowing early-stage free gypsum to slowly dissolve and react with anhydrous calcium sulfoaluminate to generate low-sulfur ettringite, slowing down the heat release rate. Simultaneously, it reduces the Ca(OH)2 concentration and further mitigates early-stage heat release through organic retarding. Actual measured data show that the cementitious system of this invention has a minimum 1-day heat of hydration of only 182.6 J / g and a maximum 28-day heat of hydration of 270.1 J / g, far lower than the traditional aluminoferrite cement system (comparative example, 302.5 J / g hydration heat at 128 days). This effectively controls the internal and external temperature differences within a safe range, reduces the occurrence of temperature cracks, and solves the industry pain point of high early-stage heat release in traditional sulfoaluminate cement.

[0034] 3. Stable and balanced strength development with excellent long-term performance: The cementitious system of this invention achieves a balanced development characteristic of early-stage strength support and continuous strength growth in later stages. The 1-day compressive strength is ≥32.5 MPa, meeting the early construction load-bearing requirements; the 28-day compressive strength reaches a maximum of 58.6 MPa, significantly higher than the standard requirement of 42.5 MPa, and superior to traditional cement systems (comparative example: 128-day compressive strength 52.9 MPa). The stability of strength growth stems from the synergistic hydration of mineral components: the mineral composition of high-silica and high-iron clinker ensures a solid foundation for early strength, while the active admixtures continuously undergo pozzolanic reactions during hydration, generating more CSH gel, continuously filling pores and creating a dense structure, achieving long-term strength improvement. Simultaneously, the 28-day free expansion rate of the system is controlled at 0.02%-0.05%, meeting standard requirements and eliminating the risk of shrinkage, avoiding structural cracking due to volume deformation and ensuring the long-term stability of the project.

[0035] 4. Intelligent Targeted Corrosion Prevention, Extending Structural Service Life: The intelligent slow-release corrosion inhibitor of this invention adopts an inclusion supramolecular system of β-cyclodextrin and benzotriazole (BTA), possessing intelligent characteristics of "pH response-targeted release-precise protection". In the normal high pH environment of concrete (pore fluid pH>12.5), the hydrophobic benzene ring of BTA is encapsulated by the hydrophobic cavity of cyclodextrin, forming a stable inclusion complex, avoiding ineffective loss and side reactions; when concrete carbonization or chloride ion intrusion leads to acidification of the microenvironment on the surface of steel reinforcement (pH≤9), the BTA molecule is protonated and transformed into a hydrophilic cation, which is destroyed by the inclusion effect of cyclodextrin, and is released to the corrosion site in a targeted manner, rapidly adsorbing to form a monomolecular protective film, preventing the dissolution of iron ions. This mechanism significantly improves the utilization rate of corrosion inhibitors. Compared with the system without the addition of intelligent slow-release corrosion inhibitors (comparative example, corrosion resistance coefficient of 1.02 at 328 days), the corrosion resistance coefficient of this invention reaches up to 1.19 at 28 days, which significantly enhances the resistance to marine corrosive media such as chloride ions and sulfates, effectively delays steel corrosion and concrete deterioration, and greatly extends the service life of marine engineering structures.

[0036] 5. Strong raw material adaptability and significant advantages in construction and economy: This invention is compatible with industrial waste residues (such as aluminum ash residue, sulfuric acid residue, desulfurization gypsum, slag, etc.) in terms of raw material selection. Calcareous materials can be selected from conventional limestone, high-silica limestone and high-silica and high-calcium industrial waste residues. Siliceous materials can be selected from industrial by-products such as fluorite washing waste residues, which not only reduces raw material costs, but also realizes the resource utilization of solid waste, which is in line with the development trend of green building materials. In terms of construction performance, the system controls particle size distribution (D10≤2.0μm, D90≤40μm) through mixing with a V-type mixer, resulting in good workability of fresh concrete. No special curing conditions are required. Compared with the alkali-activated system of patent WO2019152736A1 (which requires heat curing and has a demanding construction process), it is more suitable for large-scale on-site construction. Compared with the ultrafine admixture system of patent US20180072433A1 (which requires a high-efficiency water-reducing agent and is costly), this invention does not rely on nanomaterials or expensive ultrafine admixtures, thus controlling production costs while ensuring performance and possessing stronger engineering application feasibility.

[0037] 6. Comprehensive corrosion resistance, adaptable to complex marine environments: Addressing the multiple coupled degradation mechanisms of chloride ion corrosion, sulfate corrosion, carbonization, and freeze-thaw cycles in marine environments, this invention achieves comprehensive corrosion resistance enhancement. The system's dense microstructure reduces the intrusion of corrosive media, and the high-silicon, high-iron clinker mineral composition prevents CSH gel decalcification and inhibits excessive expansion of ettringite and gypsum. The intelligent slow-release corrosion inhibitor specifically addresses steel reinforcement corrosion, achieving a 28-day corrosion resistance coefficient ≥1.10, with a maximum of 1.19, superior to systems without added admixtures (Comparative Example 2, corrosion resistance coefficient 1.05) and without added corrosion inhibitors (Comparative Example 3, corrosion resistance coefficient 1.02). This characteristic enables the cementitious system of this invention to adapt to different marine environments (including freeze-thaw cycle scenarios in cold sea areas), effectively resisting the synergistic damage of multiple corrosive factors and solving the major problem of insufficient durability of traditional cementitious materials in complex marine corrosive environments. Attached Figure Description

[0038] Figure 1 This is a scanning electron microscope image of the hydration products of the gelation system in Example 1 of the present invention; Figure 2 The lithofacies of component A in Example 1 of this invention Figure 1 .

[0039] Figure 3 The lithofacies of component A in Example 1 of this invention Figure 2 . Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0041] Example 1 As a preferred embodiment of the present invention, this embodiment provides a method for preparing a high-silica, high-iron sulfoaluminate cementitious system resistant to seawater erosion, comprising the following steps: S1. By mass, select 45 parts limestone (CaO = 54%, SiO2 = 0.62%), 10 parts sandstone (SiO2 = 70.25%), 15 parts aluminum slag ash (Al2O3 = 68.23%, SiO2 = 2.12%), 10 parts sulfuric acid slag (F2O3 = 45.31%), and 20 parts fluorogypsum (SO3 = 31.25%). Mix them to form mixture a. When selecting materials, control the basicity coefficient of mixture a to be 0.95 and the sulfur-aluminum ratio to be 3.82. After grinding mixture a, press it into cakes, calcine it at 1280℃, and grind it again to obtain component A, as follows. Figure 1 , Figure 2 and Figure 3 As shown; the main mineral composition of mixture a after calcination is calcium sulfoaluminate, dicalcium silicate, calcium aluminoferrite, free gypsum, and calcium sulfosilicate; the specific surface area of ​​component A is controlled at 350 m². 2 / kg.

[0042] S2. After mixing β-cyclodextrin and benzotriazole in a molar ratio of 1:1, add 5% acetone (by mass of the mixture) as a reaction aid. Place the mixture of acetone, β-cyclodextrin and benzotriazole into a planetary ball mill and grind for 30 minutes. The resulting paste or powder is dried at 40°C and 50 Pa vacuum for 10 hours until the reaction is complete, yielding component B.

[0043] S3. By mass percentage, take 51% of component A, 1% of component B, 5% of setting time and activity regulator, and 43% of mineral active admixture; add them to a V-type mixer for mixing. During the mixing process, control the loading coefficient to 30%, the mixer speed to 15 rpm, mix for 20 minutes, and control the particle size distribution D10=1.58μm, D90=37.9μm; thus obtaining the seawater erosion resistant high-silica high-iron sulfoaluminate cementitious system.

[0044] The setting time and activity regulator used was calcined gypsum, with an SO3 content of 31.20%. The mineral active admixtures were slag and limestone, with the specific surface area of ​​the mineral active admixtures controlled at 400 m². 2 / kg.

[0045] Example 2 As another preferred embodiment of the present invention, this embodiment provides a method for preparing a high-silica, high-iron sulfoaluminate cementitious system resistant to seawater erosion, comprising the following steps: S1. By mass, select 60 parts limestone (CaO = 44.00%, SiO2 = 15.01%), 2 parts fluorite washing waste (SiO2 = 82.10%), 17 parts bauxite (Al2O3 = 68.23%, SiO2 = 2.12%), 8 parts copper slag (F2O3 = 42.15%), and 13 parts phosphogypsum (SO3 = 42.14%); mix them to form mixture a. When selecting materials, control the basicity coefficient of mixture a to be 1.02 and the sulfur-aluminum ratio to be 2.21. After grinding mixture a, press it into cakes, calcine it at 1250℃, and grind it again to obtain component A. The main mineral composition of mixture a after calcination is calcium sulfoaluminate, dicalcium silicate, calcium aluminoferrite, free gypsum, and calcium sulfosilicate. The specific surface area of ​​component A is controlled at 358 m². 2 / kg.

[0046] S2. After mixing β-cyclodextrin and benzotriazole in a molar ratio of 1:1.5, 10% of the mass of ethanol of the mixture of β-cyclodextrin and benzotriazole was added as a reaction aid. The mixture of ethanol, β-cyclodextrin and benzotriazole was placed in a planetary ball mill and ground for 150 min. The resulting paste was dried at 60℃ and 5 Pa vacuum for 18 h until the reaction was complete, yielding component B.

[0047] S3. By mass percentage, take 30% of component A, 1.4% of component B, 8.6% of setting time and activity regulator, and 60% of mineral active admixture; add them to a V-type mixer for mixing. During the mixing process, control the loading coefficient to be 43%, the mixer speed to be 30 rpm, mix for 40 min, and control the particle size distribution D10=1.41μm, D90=32.56μm; thus obtaining the seawater erosion resistant high-silica, high-iron, sulfoaluminate cementitious system.

[0048] The setting time and activity regulator used was anhydrite, with an SO3 content of 41.12%. The mineral active admixtures were metakaolin and fly ash, with the specific surface area of ​​the mineral active admixtures controlled at 450 m². 2 / kg.

[0049] Example 3 As another preferred embodiment of the present invention, this embodiment provides a method for preparing a high-silica, high-iron sulfoaluminate cementitious system resistant to seawater erosion, comprising the following steps: S1. By mass, select 40 parts of white clay (CaO = 51.01%, SiO2 = 16.2%), 13 parts of shale (SiO2 = 71.23%), 20 parts of bauxite (Al2O3 = 59.12%, SiO2 = 2.12%), 2 parts of magnetite (F2O3 = 49.47%), and 25 parts of anhydrite (SO3 = 49.56%); mix them to form mixture a. When selecting materials, control the basicity coefficient of mixture a to be 1.15 and the sulfur-aluminum ratio to be 2.12. After grinding mixture a, press it into cakes, calcine it at 1350℃, and grind it again to obtain component A. The main mineral composition of mixture a after calcination is calcium sulfoaluminate, dicalcium silicate, calcium aluminoferrite, free gypsum, and calcium sulfosilicate. The specific surface area of ​​component A is controlled at 326 m². 2 / kg.

[0050] S2. After mixing β-cyclodextrin and benzotriazole in a molar ratio of 1:1.2, add 5% water (by mass of the mixture) as a reaction aid. Place the mixture of water, β-cyclodextrin and benzotriazole into a planetary ball mill and grind for 120 min. The resulting paste is dried at 50°C and 40 Pa vacuum for 24 h until the reaction is complete, yielding component B.

[0051] S3. By mass percentage, take 60% of component A, 1.5% of component B, 2% of setting time and activity regulator, and 36.5% of mineral active admixture; add them to a V-type mixer for mixing. During the mixing process, control the loading coefficient to 60%, the mixer speed to 22 rpm, mix for 50 min, and control the particle size distribution D10=1.59μm, D90=38.42μm; thus obtaining the seawater erosion resistant high-silica, high-iron, sulfoaluminate cementitious system.

[0052] The setting time and activity regulator used was mixed gypsum with an SO3 content of 38.12%. The mineral active admixtures were Hainan volcanic ash and slag, with the specific surface area of ​​the mineral active admixtures controlled at 420 m². 2 / kg.

[0053] Example 4 As another preferred embodiment of the present invention, this embodiment provides a method for preparing a high-silica, high-iron sulfoaluminate cementitious system resistant to seawater erosion, comprising the following steps: S1. By mass, select 57 parts of carbide slag (CaO = 67.02%, SiO2 = 8.20%), 13 parts of sandstone (SiO2 = 75.55%), 20 parts of iron-aluminate bauxite (Al2O3 = 53.45%, Fe2O3 content = 22.42%, SiO2 = 2.12%), and 10 parts of desulfurized gypsum (SO3 = 45.95%); mix them to form mixture a. When selecting materials, control the basicity coefficient of mixture a to be 1.00 and the sulfur-aluminum ratio to be 2.52. After grinding mixture a, press it into cakes, calcine it at 1300℃, and grind it again to obtain component A. The main mineral composition of mixture a after calcination is calcium sulfoaluminate, dicalcium silicate, calcium iron-aluminate, free gypsum, and calcium sulfosilicate. The specific surface area of ​​component A is controlled at 360 m². 2 / kg.

[0054] S2. After mixing β-cyclodextrin and benzotriazole in a molar ratio of 1:1.3, add 8% acetone by mass of the mixture as a reaction aid. Place the mixture of acetone, β-cyclodextrin and benzotriazole into a planetary ball mill and grind for 100 min. The resulting paste or powder is dried at 42℃ and 25 Pa vacuum for 24 h until the reaction is complete, yielding component B.

[0055] S3. By mass percentage, take 47% of component A, 2% of component B, 12% of setting time and activity regulator, and 39% of mineral active admixture; add them to a V-type mixer for mixing. During the mixing process, control the loading coefficient to be 51%, the mixer speed to be 15 rpm, mix for 22 minutes, and control the particle size distribution D10=1.45μm, D90=33.11μm; thus obtaining the seawater erosion resistant high-silica, high-iron, sulfoaluminate cementitious system.

[0056] The setting time and activity regulator used was mixed gypsum with an SO3 content of 45.95%. The mineral active admixtures were Hainan volcanic ash and limestone, with the specific surface area of ​​the mineral active admixtures controlled at 400 m². 2 / kg.

[0057] Example 5 As another preferred embodiment of the present invention, this embodiment provides a method for preparing a high-silica, high-iron sulfoaluminate cementitious system resistant to seawater erosion, comprising the following steps: S1. By mass, select 55 parts of high-silica limestone (CaO = 48.50%, SiO2 = 12.30%), 15 parts of sandstone (SiO2 = 78.60%), 4 parts of bauxite (Al2O3 = 52.10%, SiO2 = 18.30%), 5 parts of magnetite (Fe2O3 = 47.80%), and 18 parts of desulfurized gypsum (SO3 = 38.70%); mix them to form mixture a. When selecting materials, control the basicity coefficient of mixture a to be 1.05 and the sulfur-aluminum ratio to be 2.5. After grinding mixture a, press it into cakes, calcine it at 1320℃, and grind it to obtain component A. The main mineral composition of mixture a after calcination is calcium sulfoaluminate, dicalcium silicate, calcium aluminoferrite, free gypsum, and calcium sulfosilicate. The specific surface area of ​​component A is controlled at 380 m² / kg.

[0058] S2. After mixing β-cyclodextrin and benzotriazole in a molar ratio of 1:1.1, 7% ethanol (by mass of the mixture of β-cyclodextrin and benzotriazole) was added as a reaction aid. The mixture of ethanol, β-cyclodextrin and benzotriazole was placed in a planetary ball mill and ground for 90 min. The resulting paste was dried at 48°C and 30 Pa vacuum for 16 h until the reaction was complete, yielding component B.

[0059] S3. By mass percentage, take 40% of component A, 3% of component B, 15% of setting time and activity regulator, and 42% of mineral active admixture; add them to a V-type mixer for mixing. During the mixing process, control the loading coefficient to 45%, the mixer speed to 25 rpm, and mix for 30 minutes. Control the particle size distribution to D10=1.62μm and D90=38.5μm; thus obtaining the seawater erosion resistant high-silica, high-iron, sulfoaluminate cementitious system.

[0060] The setting time and activity regulator used is gypsum dihydrate with an SO3 content of 35.60%. The mineral active admixtures are fly ash and metakaolin, and the specific surface area of ​​the mineral active admixtures is controlled at 430 m² / kg.

[0061] Example 6 As another preferred embodiment of the present invention, this embodiment provides a method for preparing a high-silica, high-iron sulfoaluminate cementitious system resistant to seawater erosion, comprising the following steps: S1. By mass, select 48 parts of calcium carbide slag (CaO = 62.30%, SiO2 = 10.50%), 15 parts of shale (SiO2 = 73.80%), 10 parts of aluminum ash slag (Al2O3 = 68.50%, SiO2 = 12.10%), and 22 parts of phosphogypsum (SO3 = 41.30%); mix them to form mixture a. When selecting materials, control the basicity coefficient of mixture a to be 1.08 and the sulfur-aluminum ratio to be 3.2. After grinding mixture a, press it into cakes, calcine it at 1270℃, and grind it to obtain component A. The main mineral composition of mixture a after calcination is calcium sulfoaluminate, dicalcium silicate, calcium aluminoferrite, free gypsum, and calcium sulfosilicate. The specific surface area of ​​component A is controlled at 320 m² / kg.

[0062] S2. After mixing β-cyclodextrin and benzotriazole in a molar ratio of 1:1.4, add 6% water (by mass of the mixture) as a reaction aid. Place the mixture of water, β-cyclodextrin and benzotriazole into a planetary ball mill and grind for 80 min. The ground powder is then dried at 55℃ and 15 Pa vacuum for 14 h until the reaction is complete, yielding component B.

[0063] S3. By mass percentage, take 45% of component A, 2% of component B, 8% of setting time and activity regulator, and 45% of mineral active admixture; add them to a V-type mixer for mixing. During the mixing process, control the loading coefficient to 50%, the mixer speed to 20 rpm, and mix for 35 minutes. Control the particle size distribution D10=1.51μm and D90=36.8μm; thus obtaining the seawater erosion resistant high-silica, high-iron, sulfoaluminate cementitious system.

[0064] The setting time and activity regulator used was mixed gypsum with an SO3 content of 36.80%. The mineral active admixtures were slag and pozzolanic materials, and the specific surface area of ​​the mineral active admixtures was controlled at 410 m² / kg.

[0065] Example 7 As another preferred embodiment of the present invention, this embodiment provides a method for preparing a high-silica, high-iron sulfoaluminate cementitious system resistant to seawater erosion, comprising the following steps: S1. By mass, select 60 parts of limestone (CaO = 53.80%, SiO2 = 8.60%), 8 parts of fluorite beneficiation waste (SiO2 = 71.50%), 4 parts of high-iron bauxite (Al2O3 = 51.20%, Fe2O3 = 18.70%, SiO2 = 16.30%), 10 parts of copper slag (Fe2O3 = 45.60%), and 15 parts of anhydrite (SO3 = 43.20%); mix them to form mixture a. When selecting materials, control the basicity coefficient of mixture a to be 1.12 and the sulfur-aluminum ratio to be 3.82. After grinding mixture a, press it into cakes, calcine it at 1330℃, and grind it again to obtain component A. The main mineral composition of mixture a after calcination is calcium sulfoaluminate, dicalcium silicate, calcium aluminoferrite, free gypsum, and calcium sulfosilicate. The specific surface area of ​​component A is controlled at 365 m² / kg.

[0066] S2. After mixing β-cyclodextrin and benzotriazole in a molar ratio of 1:1.2, 9% of the mass of acetone was added as a reaction aid. The mixture of acetone, β-cyclodextrin and benzotriazole was placed in a planetary ball mill and ground for 110 min. The resulting paste was dried at 45°C and 45 Pa vacuum for 12 h until the reaction was complete, yielding component B.

[0067] S3. By mass percentage, take 55% of component A, 3% of component B, 4% of setting time and activity regulator, and 38% of mineral active admixture; add them to a V-type mixer for mixing. During the mixing process, control the loading coefficient to 55%, the mixer speed to 28 rpm, mix for 45 minutes, and control the particle size distribution D10=1.48μm, D90=39.2μm; thus obtaining the seawater erosion resistant high-silica high-iron sulfoaluminate cementitious system.

[0068] The setting time and activity regulator used was calcined gypsum with an SO3 content of 33.40%. The mineral active admixtures were limestone and metakaolin, and the specific surface area of ​​the mineral active admixtures was controlled at 440 m² / kg.

[0069] Example 8 As another preferred embodiment of the present invention, this embodiment provides a method for preparing a high-silica, high-iron sulfoaluminate cementitious system resistant to seawater erosion, comprising the following steps: S1. By mass, select 45 parts of white clay (CaO = 50.20%, SiO2 = 13.80%), 12 parts of sandstone (SiO2 = 75.30%), 18 parts of aluminum slag (Al2O3 = 66.70%, SiO2 = 14.50%), 3 parts of non-ferrous metal slag (Fe2O3 = 38.90%), and 20 parts of fluorogypsum (SO3 = 35.80%); mix them to form mixture a. When selecting materials, control the basicity coefficient of mixture a to be 1.00 and the sulfur-aluminum ratio to be 3.0. After grinding mixture a, press it into cakes, calcine it at 1290℃, and grind it again to obtain component A. The main mineral composition of mixture a after calcination is calcium sulfoaluminate, dicalcium silicate, calcium aluminoferrite, free gypsum, and calcium sulfosilicate. The specific surface area of ​​component A is controlled at 345 m² / kg.

[0070] S2. After mixing β-cyclodextrin and benzotriazole in a molar ratio of 1:1.3, 8% ethanol (by mass of the mixture of β-cyclodextrin and benzotriazole) was added as a reaction aid. The mixture of ethanol, β-cyclodextrin and benzotriazole was placed in a planetary ball mill and ground for 70 min. The ground powder was dried at 52℃ and 20 Pa vacuum for 19 h until the reaction was complete, yielding component B.

[0071] S3. By mass percentage, take 35% of component A, 2% of component B, 10% of setting time and activity regulator, and 53% of mineral active admixture; add them to a V-type mixer for mixing. During the mixing process, control the loading coefficient to 40%, the mixer speed to 22 rpm, mix for 38 minutes, and control the particle size distribution D10=1.55μm, D90=37.3μm; thus obtaining the seawater erosion resistant high-silica high-iron sulfoaluminate cementitious system.

[0072] The setting time and activity regulator used is anhydrite, with an SO3 content of 39.60%. The mineral active admixtures are fly ash and slag, and the specific surface area of ​​the mineral active admixtures is controlled at 425 m² / kg.

[0073] Comparative Example 1 To highlight the performance proposed in this invention, this comparative example is provided, in which conventional aluminoferrite cement clinker is used to replace component A in Example 3 to prepare a cementitious system.

[0074] Comparative Example 2 To highlight the performance proposed in this invention, this comparative example is provided, using the gelling system prepared in Example 3 without the addition of mineral active admixtures.

[0075] Comparative Example 3 To highlight the performance proposed in this invention, this comparative example is provided, using the gelling system prepared in Example 3 without the addition of the intelligent slow-release corrosion inhibitor.

[0076] Experimental Example 1 According to Examples 1-4 and Comparative Examples 1-3 above, the performance was tested in accordance with the relevant provisions of GB / T45920-2025 Aluminoferrite Cement. The test method for the heat of hydration of cement was the isothermal calorimetry method of GB / T12959-2024 Determination of Heat of Hydration of Cement. The specific test results for compressive strength, 28-day free expansion rate, and 28-day erosion resistance coefficient are shown in Table 1.

[0077] Table 1 shows the physical property parameters of the cementitious system.

[0078] According to the data in the table above, under the same technical solution, although the early strength of Examples 1-4 was slightly inferior to the control sample, the strength growth was more stable, and the later strength was significantly better than the control sample. This indicates that during the hydration process, the mineral hydration effect of cementitious clinker and other materials can be reasonably utilized due to the different retarders, mineral admixtures, and intelligent slow-release corrosion inhibitors. By adopting a mineral component design and adjusting the calcium sulfoaluminate content in the clinker, the hydration process of ferroaluminate stabilizes the structure of ettringite crystals. During the iron phase hydration process, iron-containing ettringite is formed, changing the crystal structure of ettringite and enabling it to form dense hydration products in the early stage. Simultaneously, the dicalcium silicate content in the clinker is controlled, and the CSH gel content is coordinated. The ettringite crystals grow in a needle-like and columnar shape, interpenetrating with the CSH gel. The active admixtures are used to form more CSH cement under the alkaline activation of gypsum and alkaline substance hydration products, gradually enhancing the density of the hydration products and improving the resistance to seawater erosion. The standard also has clear provisions for expansion performance, especially the control of anhydrous calcium sulfoaluminate content and adjustment in Example 1. The high alumina slag content of the retarder and active admixture, combined with the dicalcium silicate content, achieves a micro-expansion effect of hydration products. The examples control the clinker mineral composition and the content of active mineral admixtures. Based on the theory of crystallization pressure in supersaturated solutions, the solid phase volume of sulfoaluminate minerals expands due to crystallization pressure. As the minerals formed during clinker hydration and the hydration of active admixtures gradually fill the spaces between ettringite crystals, compensating for the volume shrinkage caused by crystal water loss, the expansion effect is more pronounced compared to the comparative example. In Example 3, which uses high-silicon, high-iron sulfoaluminate clinker, appropriately increasing the dicalcium silicate content reduces the intensity of the hydration reaction of the clinker mineral components. Although the early strength is slightly inferior, it can synergistically hydrate with the active admixtures, thereby reducing the heat release of the hydration reaction compared to the comparative example. This reduces temperature cracks in large-volume concrete caused by temperature rise during construction, thus improving the durability of the concrete. Furthermore, in Example 4, due to the high content of anhydrous calcium sulfoaluminate and the reasonable proportion of active admixtures, the slow-release effect of the intelligent slow-release corrosion inhibitor also improves the cement stone's resistance to seawater ion corrosion.

[0079] For Example 1 Figure 1 Scanning electron microscopy analysis of cement specimens revealed that ettringite crystals grew radially or in bundles, interspersed within the CSH gel matrix. This needle-like crystal structure acts as a "microfiber reinforcement," filling pores and increasing the matrix density. The rough surface of the CSH gel forms flocculent inclusions that surround and intersect the ettringite, creating a continuous cementitious phase. Furthermore, small amounts of aluminum and iron binders fill the voids, further enhancing the density of the structure. Figure 2 and Figure 3In Example 1, the high-silica and high-iron sulfoaluminate cement clinker, compared to ordinary sulfoaluminate cement clinker, exhibits fewer overall clinker pores, and many are spherical. This indicates that the clinker system is not a completely solid-phase reaction in the traditional sense. The high-silica and high-iron components result in a partial liquid phase in the clinker, ensuring a more uniform mineral distribution and a reasonable reaction rate. Early hydration is not intense, while later hydration continues. The anhydrous calcium sulfoaluminate mineral phase particles are small, with a size of 3-10 μm, which is larger than the mineral size (2-3 μm) of ordinary sulfoaluminate cement clinker. This effectively slows down the hydration reaction rate of calcium sulfoaluminate; while the B ore particles are uniform in size and evenly distributed with anhydrous calcium sulfoaluminate ore, with a size between 5μm and 10μm. Compared with the smaller B ore size in ordinary sulfoaluminate cement clinker, this is conducive to the hydration reaction of dicalcium silicate; and there are significantly more white mesophase aluminoferrite minerals, which surround the B ore and anhydrous calcium sulfoaluminate. During the crushing and grinding process, they are easy to grind, providing early hydration reaction aluminate in the cementitious material, and developing in coordination with the hydration reaction rate of calcium sulfoaluminate and dicalcium silicate, thus enhancing the density of cement stone.

[0080] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a high-silica, high-ferrous sulfoaluminate cementitious system resistant to seawater erosion, characterized in that: Includes the following steps, S1. By mass, take 40-60 parts of calcareous material, 2-15 parts of siliceous material, 4-20 parts of aluminum material, 0-10 parts of iron material, and 10-25 parts of gypsum material, mix them, grind them, press them into cakes, calcine them at 1250℃-1350℃, and grind them again to obtain component A; the mineral composition of component A includes calcium sulfoaluminate, dicalcium silicate, calcium aluminoferrite, free gypsum, and calcium sulfosilicate; S2. After mixing β-cyclodextrin and benzotriazole in a molar ratio of 1:1-1:1.5, add reaction aids, put the resulting mixture into a planetary ball mill for thorough grinding, and react the ground product under low temperature vacuum drying conditions. After the constant reaction is complete, component B is obtained. S3. By mass percentage, take 30%-60% of component A, 1%-3% of component B, 2%-15% of setting time and activity regulator, and 30%-60% of mineral active admixture, with the sum of the mass percentages of each component being 100%. Add them to a V-type mixer for mixing. During the mixing process, control the loading coefficient to be 30%-60%, the mixer speed to be 15-30 rpm, and mix for 20-50 minutes until D10≤2.0μm and D90≤40μm, to obtain the high-silica, high-iron, sulfoaluminate gelling system.

2. The preparation method of the seawater-resistant high-silica, high-iron, sulfoaluminate cementitious system as described in claim 1, characterized in that: In step S1, the alkalinity coefficient of the mixture formed by the combination of selected calcareous materials, siliceous materials, aluminum materials, iron materials and gypsum materials is controlled between 0.95 and 1.15, and the aluminum-sulfur ratio is controlled between 2.5 and 3.

82.

3. The preparation method of the seawater-resistant high-silica, high-iron, sulfoaluminate cementitious system as described in claim 1, characterized in that: In step S2, the reaction aid is any one of acetone, ethanol, and water.

4. A method for preparing a high-silica, high-iron, sulfoaluminate cementitious system resistant to seawater erosion as described in any one of claims 1-3, characterized in that: In step S2, the mass ratio of the mixture formed by mixing the reaction aid with β-cyclodextrin and benzotriazole is 5:100-10:

100.

5. A method for preparing a high-silica, high-iron, sulfoaluminate cementitious system resistant to seawater erosion as described in any one of claims 1-3, characterized in that: In step S2, the low-temperature vacuum drying conditions refer to a temperature of 40℃-60℃ and a vacuum of 5pa-50pa.

6. A method for preparing a high-silica, high-iron, sulfoaluminate cementitious system resistant to seawater erosion as described in any one of claims 1-3, characterized in that: In step S1, the calcareous material is any one or a mixture of any proportions of conventional limestone, high-silicon limestone, and high-silicon, high-calcium industrial waste residue; the calcareous material contains ≥44.00% CaO and ≤15.00% SiO2.

7. A method for preparing a high-silica, high-iron sulfoaluminate cementitious system resistant to seawater erosion as described in any one of claims 1-3, characterized in that: In step S1, the siliceous material is any one or a combination of sandstone, shale and fluorite washing waste in any proportion, wherein the SiO2 content in the siliceous material is ≥70.00%.

8. A method for preparing a high-silica, high-iron, sulfoaluminate cementitious system resistant to seawater erosion as described in any one of claims 1-3, characterized in that: In step S1, the ferrous material is non-ferrous metal ash slag, magnetite, sulfuric acid slag, or copper slag, and the Fe2O3 content in the ferrous material is ≥30.00%; the aluminum material is bauxite, aluminum ash slag, or high-iron bauxite, wherein the Al2O3 content in bauxite is ≥50.00%, and the SiO2 content is ≤20%; the Al2O3 content in aluminum ash slag is ≥65.00%; and the Al2O3 content in high-iron bauxite is ≥50.00%, and the Fe2O3 content is ≥15.00%.

9. A method for preparing a high-silica, high-iron, sulfoaluminate cementitious system resistant to seawater erosion as described in any one of claims 1-3, characterized in that: In step S1, the gypsum material is dihydrate gypsum, anhydrite, mixed gypsum, desulfurized gypsum, phosphogypsum, or fluorogypsum, wherein the SO3 content is ≥25%.

10. A method for preparing a high-silica, high-iron sulfoaluminate cementitious system resistant to seawater erosion as described in any one of claims 1-3, characterized in that: In step S1, the specific surface area of ​​component A is controlled at 320 m². 2 / kg-380m 2 / kg.

11. A method for preparing a high-silica, high-iron, sulfoaluminate cementitious system resistant to seawater erosion as described in any one of claims 1-3, characterized in that: In step S3, the setting time and activity regulator are calcined gypsum, dihydrate gypsum, anhydrite, or mixed gypsum, with an SO3 content ≥30%.

12. A method for preparing a high-silica, high-iron, sulfoaluminate cementitious system resistant to seawater erosion as described in any one of claims 1-3, characterized in that: In step S3, the active admixture is any two or more of the following materials mixed in any proportion: fly ash, slag, pozzolanic materials, metakaolin, and limestone.

13. The method for preparing a high-silica, high-iron, sulfoaluminate cementitious system resistant to seawater erosion as described in claim 12, characterized in that: The specific surface area of ​​the active admixture is controlled at 400 m². 2 / kg-450m 2 / kg.

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