Marine corrosion-resistant cementitious materials based on metallurgical solid waste and composite mineralization activators and their preparation methods

Abstract

This invention belongs to the field of building materials technology and discloses a marine corrosion-resistant cementitious material based on metallurgical solid waste and a composite mineralization activator, as well as its preparation method. The raw materials for preparing the marine corrosion-resistant cementitious material, by mass percentage, include 60-89% metallurgical solid waste powder, 10-38% composite mineralization activator, and 0-3% auxiliary components. The marine corrosion-resistant cementitious material provided by this invention uses metallurgical solid waste powder as the main raw material, achieving efficient resource utilization of metallurgical solid waste, reducing dependence on natural resources, and reducing environmental pollution problems caused by solid waste stockpiling, thus exhibiting good environmental and economic benefits. This marine corrosion-resistant cementitious material possesses low heat of hydration, high strength, excellent resistance to chloride ion penetration, freeze-thaw resistance, and chemical corrosion resistance, making it particularly suitable for harsh environments such as marine engineering, effectively extending the service life of engineering structures and reducing maintenance costs.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, and relates to a marine corrosion-resistant cementitious material based on metallurgical solid waste and a composite mineralization activator, and its preparation method. Specifically, it relates to a marine environment corrosion-resistant cementitious material and its preparation method that uses metallurgical industrial solid waste (manganese steel slag, red mud, nickel-iron slag) as the main raw material and is activated by a composite mineralization activator. This material is suitable for concrete structure engineering in seawater erosion environments, including but not limited to seawall revetments, cross-sea bridge pile foundations, offshore wind power foundations, port terminals, and deep-sea drilling platforms, etc., in harsh corrosive environments. Background Technology

[0002] Marine engineering concrete is exposed to high-salt, high-humidity environments for extended periods, facing a dual degradation mechanism of chloride ion penetration and sulfate attack. Studies have shown that chloride ions in seawater... - It penetrates into the concrete through capillaries, when the surface of the reinforcing steel Cl - Concentration exceeding the critical threshold (0.6-0.9 kg / m³) 3 When SO4 is present, it will cause the passivation film to rupture, leading to rust expansion, and SO4 will cause this. 2- It reacts with cement hydration products to form expansive ettringite (3CaO·Al2O3·3CaSO4·32H2O), exacerbating structural cracking. The chloride ion diffusion coefficient of traditional silicate cement is generally higher than 5×10⁻⁶ after 28 days. -12 m 2 / s, and the 180-day sulfate erosion resistance strength loss rate exceeds 30%, which is difficult to meet the long-term life design requirements of cross-sea bridges.

[0003] Existing improvement technologies mainly employ two approaches: one involves incorporating 30-50% slag powder and adding sodium sulfate as an activator, which reduces the chloride ion diffusion coefficient to 3.2 × 10⁻⁶. -12 m 2 / s, but still requires more than 40% cement clinker, and the purity requirements of industrial sodium sulfate lead to a 45% increase in cost; secondly, red mud-based cementitious materials are used, but 10% nano SiO2 needs to be added to improve activity, which increases production cost by 2,000 yuan / ton, and there is a problem of volume instability caused by free alkali metal ions.

[0004] In existing metallurgical solid waste utilization technologies, while compound formulations can achieve high solid waste content, they are limited to the simple superposition of calcium-silicon-aluminum components, making it difficult to synergistically activate the activity of multiple elements such as iron and magnesium. This results in insufficient compressive strength and limited impermeability of the materials. The difference in chemical composition between steel slag and red mud easily leads to a loose structure and high porosity in hydration products, with a still relatively high chloride ion diffusion coefficient. Traditional activators are not adaptable to multi-component systems, and the large amount of unreacted active components left behind not only wastes resources but also causes volume expansion problems in the later stages, further exacerbating pore coarsening and harmful ion penetration. Such materials face durability bottlenecks in the harsh environment of the deep sea and cannot meet the requirements for long-term service.

[0005] Therefore, there is an urgent need to develop a new type of cementitious material that can achieve high content (≥60%) of metallurgical solid waste, and overcome the contradiction between impermeability, volume stability and cost control of existing materials through multi-component synergistic activation technology, so as to meet the stringent durability requirements of marine engineering. Summary of the Invention

[0006] The purpose of this invention is to address the problems of low utilization rate of existing metallurgical solid waste and insufficient marine corrosion resistance, and to provide a marine corrosion-resistant cementitious material based on metallurgical solid waste and composite mineralization activator and its preparation method, thereby solving the technical defects of traditional materials such as poor impermeability, insufficient volume stability and high cost.

[0007] The present invention adopts the following technical solution:

[0008] A marine corrosion-resistant cementitious material based on metallurgical solid waste and a composite mineralization activator is disclosed. The raw materials for preparing the marine corrosion-resistant cementitious material, by mass percentage, have a total mass percentage of 100% for each component, including 60-89% metallurgical solid waste powder, 10-38% composite mineralization activator, and 0-3% auxiliary components. First, the metallurgical solid waste powder is added to a mixing device, then an appropriate amount of water is added, followed by the composite mineralization activator. After stirring evenly, the auxiliary components are added, and then an appropriate amount of water is added a second time. The mixture is stirred evenly again, with the total amount of water added being 40-60% of the total mass of each component.

[0009] Preferably, the metallurgical solid waste powder includes manganese steel slag powder, red mud, and nickel iron slag, with a mass ratio of (3-5):(2-4):1.

[0010] Preferably, the specific surface area of ​​the metallurgical solid waste powder is ≥500m² / kg, wherein the CaO content of the manganese steel slag powder is ≥40%, the Fe2O3 content of the red mud is ≥15%, and the MgO content of the nickel-iron slag is 8-12%.

[0011] Preferably, the composite mineralization activator is a mixture of calcined glauconite and calcined alunite in a mass ratio of (1.5-2):1, with a calcination temperature of 600-700℃ and a calcination time of 1-2 hours.

[0012] Furthermore, the calcined calcium sulfate ore is natural calcium sulfate ore that has been calcined at 650℃, and the effective sulfate content is ≥85%.

[0013] Preferably, the auxiliary components include borax and hydroxypropyl methylcellulose ether in a mass ratio of (0.5-1.5):(0.3-1.5).

[0014] Furthermore, the mass ratio of the manganese steel slag powder to the red mud is 3:2, and the amount of nickel iron slag added is 10-15% of the total solid waste mass.

[0015] According to a specific embodiment of the present invention, the marine corrosion-resistant cementitious material contains 1-2% nano-alumina by mass of the composite mineralization activator.

[0016] The preparation method of the above-mentioned marine corrosion-resistant cementitious material according to a specific embodiment of the present invention includes the following steps:

[0017] The metallurgical solid waste powder is composed of 60-89% by mass, 10-38% by mass, a composite mineralization activator, and 0-3% by mass. The metallurgical solid waste powder is a compound of manganese steel slag powder, red mud, and nickel iron slag in a mass ratio of (3-5):(2-4):1. The composite mineralization activator is a compound of calcined calcium mirabilite and calcined alunite in a mass ratio of (1.5-2):1.

[0018] Specific preparation methods include:

[0019] First, add metallurgical solid waste powder to a mixing device, add an appropriate amount of water, then add a composite mineralization activator, stir evenly, then add auxiliary components, stir at a speed of 70-100 r / min for 10-20 minutes, then add an appropriate amount of water a second time, continue to mix evenly, maintain a speed of 70-100 r / min and continue stirring for 5-10 minutes to obtain the cementitious material. The total amount of water added is 40-60% of the sum of the mass of each component.

[0020] Compared with the prior art, the beneficial effects of the present invention include:

[0021] The marine corrosion-resistant cementitious material provided by this invention uses metallurgical solid waste powder as the main raw material, realizing the efficient resource utilization of metallurgical solid waste, reducing dependence on natural resources, and reducing environmental pollution caused by solid waste stockpiling, thus achieving good environmental and economic benefits. By rationally proportioning manganese steel slag powder, red mud, and nickel-iron slag, and controlling their specific surface area and chemical composition, a synergistic effect is achieved among the metallurgical solid waste powders, providing a good foundation for the cementitious material's cementitious performance. The composite mineralization activator is a compound of calcined calcium sulfate ore treated under specific proportions and calcination conditions with calcined alunite, and the addition of nano-alumina effectively activates the activity of the metallurgical solid waste powder, improving the hydration reaction rate and degree of the cementitious material, thereby enhancing the material's early and later strength. The rational combination of borax and hydroxypropyl methylcellulose ether in the auxiliary components further improves the workability and durability of the cementitious material. This marine corrosion-resistant cementitious material has low heat of hydration, high strength, and excellent resistance to chloride ion penetration, freeze-thaw cycles, and chemical corrosion. It is particularly suitable for harsh environments such as marine engineering, and can effectively extend the service life of engineering structures and reduce maintenance costs.

[0022] 1. The marine corrosion-resistant cementitious material of this invention has high strength and long-term impermeability, with a compressive strength ≥55MPa after 90 days of seawater curing and a chloride ion diffusion coefficient ≤1.5×10⁻⁶. -12 m 2 / s, with a strength loss rate of <5% after 150 freeze-thaw cycles, significantly improving the durability of marine engineering structures while reducing maintenance costs.

[0023] 2. The composite mineralization activator of the present invention synergistically activates the activity of Ca, Fe and Al in manganese steel slag and red mud to form a composite structure of ettringite and layered double hydroxides (Mg-Al-Cl LDHs), with a chloride ion binding rate of ≥70%, effectively inhibiting steel corrosion, achieving an early strength of 50MPa in 28 days without subsequent shrinkage.

[0024] 3. This invention replaces more than 60% of traditional cement raw materials with metallurgical solid waste, reduces limestone consumption by 1.2 tons per ton of material, reduces CO2 emissions by 75%, and lowers production costs by 20-30% compared to ordinary silicate cement, thus combining environmental protection and economic benefits. Attached Figure Description

[0025] Figure 1 Scanning electron microscope (SEM) images of the material with an MgO content of 8-12%;

[0026] Figure 2 This is a scanning electron microscope image of the material when the MgO content is >12%. Detailed Implementation

[0027] The technical solutions of the present invention will be further described in detail below with reference to embodiments. For the sake of simplicity, it is impossible to exhaustively list all alternative technical features and implementation schemes included in the present invention. Therefore, those skilled in the art should understand that any technical feature and implementation scheme within this embodiment does not limit the scope of protection of the present invention. The scope of protection includes all alternative technical features and implementation schemes adopted by those skilled in the art without creative effort. Specifically, any implementation scheme obtained by replacing any technical feature in the present invention or combining any two or more technical features provided by the present invention should be within the scope of protection of the present invention. Where specific techniques and conditions are not specified in the embodiments, they shall be performed in accordance with the techniques and conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0028] Manganese steel slag powder refers to the powder material obtained by grinding the waste slag generated during the smelting of manganese alloy steel or high manganese steel. It mainly originates from the electric arc furnace (EAF) or basic oxygen furnace (BOF) smelting processes in the steel industry. In smelting manganese alloy steel, a certain amount of metallic manganese or ferromanganese alloy is added as alloying elements to achieve the required mechanical properties (such as high strength, high toughness, and wear resistance). The slag and flux generated during the smelting process mainly consist of calcium silicate, iron and manganese oxides, etc. After cooling, crushing, magnetic separation (recovering scrap iron), and then grinding to the specified fineness, manganese steel slag powder is obtained.

[0029] Compared with traditional steel slag, manganese steel slag has a unique mineral composition and activity due to its higher content of manganese oxides (MnO, etc.). This invention utilizes its high CaO content (≥40%) as the main source of calcium and alkaline activation conditions. At the same time, elements such as manganese and iron can also participate in the reaction under the action of a composite activator, which plays a positive role in the formation of a dense microstructure.

[0030] Nickel-iron slag, also known as nickel slag, is an industrial waste generated during the production of nickel-iron alloy using the RKEF (Rotary Kiln-Electric Furnace) process, also known as the "rotary kiln-electric arc furnace" method. This process is currently the mainstream technology for pyrometallurgical smelting of laterite nickel ore. The specific process is as follows: laterite nickel ore with high moisture content is dried and pre-reduced in a rotary kiln, then fed into an electric arc furnace for high-temperature smelting. Nickel and some iron in the ore are reduced and melted into a nickel-iron alloy liquid, while gangue components in the ore (such as SiO2, MgO, CaO, Al2O3) react with the flux to form slag that floats to the surface. After separating from the molten metal, it is quenched (granulated) with water or air-cooled to form nickel-iron slag.

[0031] Lateritic nickel ore is rich in magnesium, so a significant characteristic of nickel-iron slag is its high MgO content (typically 8%-20%). This invention specifically selects nickel-iron slag with an MgO content of 8-12% to utilize its MgO component. Under the sulfate and aluminate environment provided by the composite activator, MgO can participate in the formation of substances such as magnesium aluminum spinel (MgAl2O4) or, more importantly, layered bimetallic hydroxides (LDHs, such as Mg-Al-Cl LDHs). The LDH structure can effectively "capture" and solidify chloride ions in the environment, which is one of the key mechanisms for achieving an extremely low chloride ion diffusion coefficient in this invention. This solves the stability problems that MgO may cause in traditional materials, turning a potential hazard into a benefit.

[0032] The manganese steel slag powder of this invention must meet the following requirements: specific surface area ≥ 500 m² / kg, CaO content ≥ 40%. A high specific surface area increases the contact area with the activator, accelerating the reaction, optimizing porosity, and synergistically improving impermeability with nano-Al₂O₃. High CaO content provides an alkaline environment, facilitates the formation of ettringite to support early strength of ≥ 50 MPa at 28 days, and also prevents later strength reduction. The red mud contains ≥ 15% Fe₂O₃, which, under the action of the composite activator, can be converted into an iron-cemented phase to improve density (freeze-thaw loss rate < 5%). 3+ It can complex with chloride ions (combination rate ≥70%) and react with nickel-iron slag MgO to form Mg-Fe-Al LDHs to resist seawater corrosion (strength > 58MPa); the MgO content of nickel-iron slag needs to be controlled at 8-12%, which is a necessary condition for the formation of Mg-Al-Cl LDHs, and can prevent expansion or insufficient formation. The LDHs nanosheets can also be interspersed with ettringite network to block cracks, so that the cementitious material reaches a strength of 65MPa after 10 months. Traditional cement does not have this structure, so the chloride ion diffusion coefficient is much higher.

[0033] The mixing order in this invention must not be reversed. In the relevant processes, the operation must be carried out in the order of "first adding metallurgical solid waste powder, then adding composite mineralization activator, and finally adding auxiliary components," with each step having a clear scientific purpose. Adding the metallurgical solid waste powder first is to establish an alkaline environment with a pH > 12.5, dissolving the Ca in it. 2+ SiO4 4- Plasma lays the foundation for subsequent activation reactions. If the order is reversed, allowing the activator to directly contact the liquid phase, it will trigger local over-reaction, generating amorphous products that block active sites. For example, in Example 2, when the order was reversed, the intensity decreased by 9.8% after 28 days. The subsequently added composite mineralization activator can allow the calcined calcium sulfate ore (providing SO4) to react in an alkaline medium. 2- ) and calcined alunite (providing Al) 3+ Gradually release ions, which react with the Ca dissolved from the solid waste. 2+ Mg 2+The synergistic formation of ettringite and LDHs framework is achieved, and the activator must contain 1-2% premixed nano-alumina by mass to ensure preferential dispersion of nanoparticles in the system and prevent them from being encapsulated and deactivated by solid waste. Finally, among the auxiliary components added, borax can form [B4O5(OH)4] under highly alkaline conditions. 2- The complex extends the initial setting time of C3A in manganese steel slag from 5 min to 45 min. HPMC needs to be added in the later stage of ion release to prevent its chain coiling at temperatures above 40℃, which would lead to a 50% loss in viscosity.

[0034] like Figure 1 As shown, this invention controls the MgO content in nickel-iron slag to be 8-12%, and under the sulfate and aluminate environment provided by the composite activator, MgO reacts with Ca... 2+ Al 3+ The synergistic formation of Mg-Al-Cl LDHs layered double hydroxides exhibits a typical lamellar morphology, effectively capturing and solidifying chloride ions with a chloride ion binding rate ≥70%; while... Figure 2 As shown, when the MgO content in nickel-iron slag exceeds 12% (e.g., 15% in Comparative Example 3-3), a stable LDH layered structure cannot be formed, resulting in a significant increase in microporosity, leading to an 18% loss in compressive strength and a decrease in impermeability. Simultaneously, the 1-2% nano-alumina added to the composite mineralization activator can act as crystal nuclei, promoting LDH crystal growth and improving structural stability. Without the addition of nano-alumina (Comparative Example 4-1), the chloride ion diffusion coefficient increases to 2.7 × 10⁻⁶. -12 m² / s.

[0035] In the following examples, the amount of water added is not strictly required and can be adjusted according to the actual situation during implementation. The total amount of water added is 40-60% of the sum of the masses of each component of the cementitious material. Example 1

[0036] (1) Raw material preparation

[0037] Metallurgical solid waste powder: Weigh 50% (mass percentage) of manganese steel slag powder (CaO content 42%, specific surface area 520 m² / kg), 20% (mass percentage) of red mud (Fe₂O₃ content 16%, specific surface area 510 m² / kg), and 10% (mass percentage) of nickel-iron slag (MgO content 10%, specific surface area 530 m² / kg), and mix thoroughly. The total mass percentage of metallurgical solid waste powder is 80%.

[0038] Composite mineralization activator: Natural calcium sulfate ore is calcined at 650℃ for 1.5 hours to obtain calcined calcium sulfate ore with an effective sulfate content of 86%. It is then compounded with calcined alunite ore calcined at 650℃ for 1.5 hours at a mass ratio of 1.8:1, and 1.5% nano alumina is added. The composite mineralization activator accounts for 18.7% of the total mass.

[0039] Auxiliary components: Weigh 0.8% (mass percentage) of borax and 0.5% (mass percentage) of hydroxypropyl methylcellulose ether, with a mass ratio of 1.6:1, and the auxiliary components account for 1.3% of the total mass.

[0040] (2) The preparation process is as follows:

[0041] Add the prepared 80% metallurgical solid waste powder to a mixing device, add an appropriate amount of water, and stir at 80 r / min for 5 minutes; then add 18.7% composite mineralization activator and continue stirring at 80 r / min for 5 minutes; finally add 1.3% auxiliary components and stir at 80 r / min for 15 minutes; then add an appropriate amount of water and continue stirring at 80 r / min for 8 minutes until the mixture is homogeneous, thus obtaining a marine corrosion-resistant cementitious material.

[0042] (3) Performance testing:

[0043] ①The heat of hydration of marine corrosion-resistant cementitious materials was tested according to the heat of solution method in GB / T 12959-2008 "Determination of Heat of Hydration of Cement".

[0044] ②According to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)" (now GB / T17671-2021), the flexural strength and compressive strength of marine corrosion-resistant cementitious materials were tested after curing in seawater for 3 days and 28 days, and the compressive strength after curing in seawater for 3 months and 10 months was recorded.

[0045] ③ The compressive strength loss rate of marine corrosion-resistant cementitious materials was determined by conducting freeze-thaw tests on them according to the methods in GB / T50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete".

[0046] ④ The chloride ion diffusion coefficient of marine corrosion-resistant cementitious materials was tested according to the Rapid Chloride Ion Migration Coefficient Method (RCM Method) in GB / T50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete".

[0047] ⑤ Prepare test blocks according to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)" (now GB / T17671-2021), conduct alkali corrosion resistance test in 5% sodium hydroxide solution, and test compressive strength after 3 months.

[0048] ⑥ Prepare test blocks according to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)" (now GB / T17671-2021), conduct sulfate corrosion resistance test in 5% sodium sulfate solution, and test compressive strength after 3 months.

[0049] (4) The test results are as follows:

[0050] Heat of hydration over 3 days <180kJ / kg;

[0051] 7-day heat of hydration <210kJ / kg;

[0052] 3-day flexural strength in seawater: 5.8 MPa;

[0053] Flexural strength in seawater after 28 days: 8.1 MPa;

[0054] Seawater compressive strength after 3 days: 29.4 MPa;

[0055] Seawater compressive strength after 28 days: 53.0 MPa;

[0056] Seawater compressive strength after 3 months: 59.5 MPa;

[0057] Seawater compressive strength after 10 months: 65.0 MPa;

[0058] Chloride ion diffusion coefficient: 1.3 × 10⁻⁶ -12 m² / s;

[0059] Compressive strength loss rate after 150 freeze-thaw cycles: 4.6%;

[0060] Compressive strength after 3 months of alkali corrosion resistance: 58.5 MPa;

[0061] Compressive strength against sulfate corrosion after 3 months: 59.8 MPa. Example 2

[0062] (1) Raw material preparation

[0063] Metallurgical solid waste powder: 30% (mass percentage) of manganese steel slag powder (CaO content 43%, specific surface area 500m² / kg), 20% (mass percentage) of red mud (Fe2O3 content 18%, specific surface area 520m² / kg), and 10% (mass percentage) of nickel iron slag (MgO content 9%, specific surface area 550m² / kg), totaling 60%.

[0064] Composite mineralization activator: calcined calcium mirabilite (calcined at 650℃ for 2 hours, sulfate content 85%) and calcined alunite are compounded at a ratio of 1.5:1, with 1% nano alumina added, for a total proportion of 37%.

[0065] Auxiliary components: 1.5% borax (by weight) + 1.5% hydroxypropyl methylcellulose ether (by weight) (ratio 1.5:1), totaling 3%.

[0066] (2) According to the modified preparation method of Example 1, metallurgical solid waste powder is added and stirred for 5 minutes, an appropriate amount of water is added, then a composite mineralization activator is added and stirred for 5 minutes, finally auxiliary components are added and stirred for 15 minutes, an appropriate amount of water is added and stirred for 8 minutes to obtain marine corrosion resistant cementitious material.

[0067] According to the above raw material composition, the mixing order was changed to "first add the composite mineralization activator, then add the metallurgical solid waste powder, and finally add the auxiliary components". The remaining preparation conditions were the same as in Example 1. The 28-day compressive strength was tested to be 47.8 MPa, which is 9.8% lower than the 53 MPa in Example 1, verifying the technical effect that the mixing order cannot be reversed.

[0068] Performance testing was performed based on the performance testing method of Example 1.

[0069] The test results are as follows:

[0070] Heat of hydration over 3 days <180kJ / kg;

[0071] 7-day heat of hydration <210kJ / kg;

[0072] 3-day flexural strength in seawater: 7.1 MPa;

[0073] Flexural strength in seawater after 28 days: 11.5 MPa;

[0074] Seawater compressive strength after 3 days: 28.9 MPa;

[0075] Seawater compressive strength after 28 days: 47.8 MPa;

[0076] Seawater compressive strength after 3 months: 55.9 MPa;

[0077] Seawater compressive strength after 10 months: 61.4 MPa;

[0078] Chloride ion diffusion coefficient: 1.4 × 10⁻⁶ -12 m² / s;

[0079] After being cured in seawater for 10 months, the steel bars showed no rust and no weight loss.

[0080] Compressive strength loss rate after 150 freeze-thaw cycles: 4.7%;

[0081] Compressive strength after 3 months of alkali corrosion resistance: 55.7 MPa;

[0082] Compressive strength against sulfate corrosion after 3 months: 56.2 MPa. Example 3

[0083] This embodiment provides a marine corrosion-resistant cementitious material, composed of the following raw materials by mass fraction:

[0084] (1) Raw material preparation

[0085] Metallurgical solid waste powder: 45% (mass percentage) of manganese steel slag powder (CaO content 41%, specific surface area 540m² / kg), 30% (mass percentage) of red mud (Fe₂O₃ content 17%, specific surface area 500m² / kg), and 14% (mass percentage) of nickel-iron slag (MgO content 11%, specific surface area 510m² / kg), accounting for a total of 89%.

[0086] Composite mineralization activator: calcined calcium mirabilite (calcined at 700℃ for 1 hour) and calcined alunite are compounded in a 2:1 ratio, with 2% nano alumina added, for a total proportion of 10%.

[0087] Auxiliary components: 0.5% borax (by weight) + 0.5% hydroxypropyl methylcellulose ether (by weight) (ratio 1:1), total percentage 1%.

[0088] (2) The marine corrosion-resistant cementitious material was prepared by following the preparation method in Example 1.

[0089] Performance testing was performed based on the performance testing method of Example 1.

[0090] Heat of hydration over 3 days <180kJ / kg;

[0091] 7-day heat of hydration <210kJ / kg;

[0092] 3-day flexural strength in seawater: 5.6 MPa;

[0093] Flexural strength in seawater after 28 days: 8.9 MPa;

[0094] Seawater compressive strength after 3 days: 27.3 MPa;

[0095] Seawater compressive strength after 28 days: 51.5 MPa;

[0096] Seawater compressive strength after 3 months: 58.0 MPa;

[0097] Seawater compressive strength after 10 months: 63.4 MPa;

[0098] Chloride ion diffusion coefficient: 1.4 × 10⁻⁶ -12 m² / s;

[0099] After being cured in seawater for 10 months, the steel bars showed no rust and no weight loss.

[0100] Compressive strength loss rate after 150 freeze-thaw cycles: 4.9%;

[0101] Compressive strength after 3 months of alkali corrosion resistance: 57.8 MPa;

[0102] Compressive strength against seawater corrosion after 3 months: 58.2 MPa.

[0103] Comparative Example 1

[0104] This comparative example provides a common silicate cement, which is purchased from Dalian Tianrui Cement Co., Ltd. as common silicate cement PO52.5.

[0105] Performance testing was performed based on the performance testing method of Example 1.

[0106] Test results:

[0107] Heat of hydration over 3 days > 250 kJ / kg;

[0108] 7-day heat of hydration > 300 kJ / kg;

[0109] 3-day flexural strength in seawater: 5.2 MPa;

[0110] Flexural strength in seawater after 28 days: 8.7 MPa;

[0111] Seawater compressive strength after 3 days: 25.0 MPa;

[0112] Seawater compressive strength after 28 days: 47.3 MPa;

[0113] Seawater compressive strength after 3 months: 44.3 MPa;

[0114] Seawater compressive strength after 10 months: 40.4 MPa;

[0115] Chloride ion diffusion coefficient: 8.3 × 10⁻⁶ -12 m² / s.

[0116] Compared with Comparative Example 1 (ordinary silicate cement), the marine corrosion-resistant cementitious material of Example 1 has the following advantages:

[0117] 1. Lower heat of hydration: The 3-day heat of hydration of Example 1 is <180 kJ / kg, and the 7-day heat of hydration is <210 kJ / kg; while the 3-day heat of hydration of Comparative Example 1 is >250 kJ / kg, and the 7-day heat of hydration is >300 kJ / kg. Lower heat of hydration helps reduce the risk of cracking in large-volume concrete due to temperature stress and improves the durability of concrete.

[0118] 2. Improved early compressive strength: The 3-day compressive strength of seawater in Example 1 was 29.4 MPa, which was higher than that of Comparative Example 1 (25.0 MPa). This indicates that the material in Example 1 can form strength more quickly in the early stage, which is beneficial to shorten the construction cycle and improve project efficiency.

[0119] 3. Continuous and higher long-term compressive strength: In Example 1, the seawater compressive strength after 28 days was 53.0 MPa, after 90 days it was 59.5 MPa, and after 10 months it was 65.0 MPa; in Comparative Example 1, the seawater compressive strength after 28 days was 47.3 MPa, after 90 days it was 44.3 MPa, and after 10 months it was 40.4 MPa. The material in Example 1 showed a significant increase in long-term strength, which was much higher than that in Comparative Example 1, indicating that it has better long-term mechanical properties and durability.

[0120] 4. Better flexural strength performance: Although the 28-day flexural strength (8.7 MPa) of Comparative Example 1 is slightly higher than that of Example 1 (8.1 MPa), the 3-day flexural strength (5.8 MPa) of Example 1 is higher than that of Comparative Example 1 (5.2 MPa). Moreover, in terms of the overall strength growth trend, the strength of Example 1 is more balanced and stable.

[0121] 5. Lower chloride ion diffusion coefficient: The chloride ion diffusion coefficient in Example 1 is 1.3 × 10⁻⁶. -12 m 2 / s, far lower than the 8.3×10 in Comparative Example 1. -12 m 2 / s. The lower chloride ion diffusion coefficient means that the material of Example 1 has better resistance to chloride ion penetration, effectively preventing steel corrosion and improving the durability of concrete structures in marine environments.

[0122] 6. Superior freeze-thaw resistance: The compressive strength loss rate of Example 1 after 150 freeze-thaw cycles was 4.6%, while Comparative Example 1 did not mention this data. However, the freeze-thaw resistance of ordinary Portland cement is generally relatively poor. The lower compressive strength loss rate of Example 1 indicates that it has better freeze-thaw resistance and is suitable for marine engineering in cold regions.

[0123] 7. Good resistance to chemical corrosion: In Example 1, after a 3-month alkali corrosion test in a 5% sodium hydroxide solution, the compressive strength was 58.5 MPa, and after a 3-month sulfate corrosion test in a 5% sodium sulfate solution, the compressive strength was 59.8 MPa. This indicates that the material has good resistance to chemicals such as alkalis and sulfates and can maintain stable performance in complex marine chemical environments.

[0124] Comparative Example 2: Solid Waste Component Simplification Experiment (Verifying the Necessity of Compound Formulation)

[0125] Table 1. Raw material composition and key indicator test data for Example 1 and Comparative Example 2

[0126]

[0127] Conclusion: A single solid waste cannot simultaneously achieve strength formation (CaO), impermeability (Fe2O3), and ion solidification (MgO).

[0128] Comparative Example 3: Breakthrough Test of Key Component Threshold (Verification of Content Critical Point)

[0129] Table 2. Raw material composition and key indicator test data for Example 1 and Comparative Example 3

[0130]

[0131] Comparative Example 4: Comparative Experiment of Initiator Modification (Verifying the Effect of Nano-Alumina)

[0132] Table 3. Raw material composition and key indicator test data for Example 1 and Comparative Example 4

[0133]

[0134] Comparative Example 5: Functional Verification Test of Auxiliary Components

[0135] Table 4. Raw material composition and key indicator test data for Example 1 and Comparative Example 5

[0136]

[0137] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A marine corrosion resistant cementitious material based on metallurgical solid waste and complex mineralization activator, characterized in that, The raw materials for preparing the marine corrosion-resistant cementitious material include, in percentage by mass, 60-89% of metallurgical solid waste powder, 10-38% of composite mineralization activator, and 0-3% of auxiliary components, with the sum of the percentage by mass of each component being 100%, and the amount of the auxiliary components not being 0; the metallurgical solid waste powder is first added to a stirring device, an appropriate amount of water is added, the composite mineralization activator is then added, the auxiliary components are added after uniform stirring, and then an appropriate amount of water is added for the second time, followed by uniform mixing, with the total amount of water being 40-60% of the sum of the masses of the components; The metallurgical solid waste powder includes manganese steel slag powder, red mud, and nickel-iron slag, with the mass ratio of the three being (3-5):(2-4):1; The specific surface area of the metallurgical solid waste powder is ≥500 m 2 / kg, wherein the CaO content of the manganese slag powder is ≥40%, the Fe2O3 content of the red mud is ≥15%, and the MgO content of the nickel-iron slag is 8-12%. The composite mineralization activator is compounded from calcined glauber's salt and calcined alunite at a mass ratio of (1.5-2):1, with the calcining temperature being 600-700 DEG C and the calcining time being 1-2 hours; The auxiliary components include borax and hydroxypropyl methyl cellulose ether, with the mass ratio being (0.5-1.5):(0.3-1.5).

2. The metallurgical solid waste and complex mineralization activator based marine corrosion resistant cementitious material as claimed in claim 1, wherein, The calcined glauber's salt is natural glauber's salt treated by calcination at 600-750 DEG C, with the effective content of sulfate being greater than or equal to 85%.

3. The metallurgical solid waste and complex mineralization activator based marine corrosion resistant cementitious material as claimed in claim 1, wherein, The mass ratio of the manganese steel slag powder to the red mud is 3:2, and the amount of the nickel-iron slag is 10-15% of the total solid waste.

4. The metallurgical solid waste and complex mineralization activator based marine corrosion resistant cementitious material as claimed in claim 1, wherein, The composite mineralization activator is added with 1-2% of nano-aluminum oxide based on the total mass of the composite mineralization activator.

5. A method of producing a marine corrosion resistant cementitious material as claimed in any one of claims 1 to 4, characterised in that, The method includes the following steps: 60-89% of metallurgical solid waste powder, 10-38% of composite mineralization activator, and 0-3% of auxiliary components are mixed in the following order: the metallurgical solid waste powder is first added to a stirring device, an appropriate amount of water is added, the composite mineralization activator is then added, the auxiliary components are added after uniform stirring, and the stirring is performed at a speed of 70-100 r / min for 10-20 minutes, and then an appropriate amount of water is added for the second time, followed by uniform mixing, to obtain the cementitious material.

6. The method for preparing the marine corrosion-resistant cementitious material according to claim 5, characterized in that, The uniform mixing after the second addition of water is performed at a speed of 70-100 r / min for 5-10 minutes.

Images