High performance cement composite material containing steel slag and method for preparing the same

Abstract

The application belongs to the technical field of cement composite materials, and particularly relates to a high-performance cement composite material containing steel slag and a preparation method thereof, which comprises the following components in parts by weight: 90-100 parts of sulphoaluminate cement, 15-20 parts of modified steel slag, 15-20 parts of modified fly ash, 10-15 parts of mineral powder, 2-3 parts of silicon dioxide, 3-5 parts of carboxyl styrene emulsion, 1.0-1.5 parts of polypropylene fiber, 0.05-0.08 parts of boric acid, 1.5-2.5 parts of polycarboxylic acid superplasticizer and 30-35 parts of mixing water; wherein the modified steel slag is obtained through normal-pressure saturated steam activation, atomization spraying of a mixed silane solution and low-temperature mechanical-chemical ball milling and ladder-type thermal curing; and the modified fly ash is obtained through mechanical-chemical calcification activation and dry-process amino silane grafting. The application effectively improves the mechanical strength, crack resistance and durability of the composite material, and realizes high-value utilization of the steel slag and fly ash.

Description

Technical Field

[0001] This invention relates to the field of cement composite materials technology, specifically to a high-performance cement composite material containing steel slag and its preparation method. Background Technology

[0002] As the most widely used building material, cement-based materials have always been a key research focus in this field, particularly in improving their performance and utilizing industrial solid waste resources. Steel slag, a major solid waste generated during steel smelting, has a huge annual output, but its poor volume stability and low activity severely restrict its large-scale application in cement concrete. Fly ash, a byproduct of coal-fired power plants, has been widely used in cement concrete, but its insufficient early activity and weak interfacial bonding with the cement matrix still need improvement. Therefore, how to effectively modify steel slag and fly ash to enhance their utilization value and enable them to play a synergistic reinforcing role in cement-based materials has become a pressing technical challenge in this field.

[0003] CN107935419B discloses a modified steel slag cement, which only uses a single silane coupling agent to perform simple surface modification of steel slag. This cannot fundamentally solve the stability defects of steel slag, and it does not involve the modification of fly ash. When steel slag and fly ash are compounded, problems such as activity mismatch and poor interfacial compatibility easily occur, making it difficult to form a synergistic effect. The mechanical strength improvement of the prepared cement composite material at all ages is limited, and the risk of cracking is high. CN115583813A discloses a mineral powder-fly ash-steel slag system concrete composite admixture, which only treats steel slag and fly ash through ultrafine grinding process without deep activation and interfacial modification. Although it improves the fineness of the powder to a certain extent, it cannot effectively dissolve the free calcium oxide in steel slag or break the inert glassy phase of fly ash. The improvement of solid waste activity after modification is limited, and the interfacial bonding with the cement matrix is ​​weak. The prepared composite material has high drying shrinkage rate in the later stage, poor resistance to chloride ion penetration, and insufficient long-term volume stability.

[0004] Therefore, developing a high-strength, high-impermeability, low-shrinkage, and excellent crack-resistant high-performance cement composite material containing steel slag is of great practical significance for promoting the efficient resource utilization of industrial solid waste and upgrading the performance of cement-based materials. Summary of the Invention

[0005] To address the problems of existing technologies, this invention provides a high-performance cement composite material containing steel slag and its preparation method. The steel slag is modified through atmospheric pressure saturated steam activation, spray premixing, low-temperature mechanochemical grafting, and stepped thermosetting. Simultaneously, fly ash is modified through mechanochemical calcification activation and dry-process aminosilane grafting. Then, sulfoaluminate cement, modified steel slag, modified fly ash, mineral powder, silica, carboxylated styrene-butadiene emulsion, polypropylene fiber, boric acid, polycarboxylate superplasticizer, and mixing water are dry-mixed in proportion, followed by fiber dispersion, liquid mixing, blending, molding, and curing. This yields a high-performance cement composite material containing steel slag with high compressive strength, high flexural strength, low shrinkage, high impermeability, and high crack resistance.

[0006] The technical solution of the present invention to solve the above problems is as follows: A high-performance cement composite material containing steel slag comprises the following components in parts by weight: 90-100 parts of sulfoaluminate cement, 15-20 parts of modified steel slag, 15-20 parts of modified fly ash, 10-15 parts of mineral powder, 2-3 parts of silica, 3-5 parts of carboxylated styrene-butadiene emulsion, 1.0-1.5 parts of polypropylene fiber, 0.05-0.08 parts of boric acid, 1.5-2.5 parts of polycarboxylate superplasticizer, and 30-35 parts of mixing water; The method for preparing the modified steel slag is as follows: Step S1: Crush and grind the steel slag to a particle size < 0.075 mm and a specific surface area ≥ 450 m². 2 / kg, treated with saturated steam at 95-105℃ and normal pressure for 5-6 hours, and then post-treated to obtain activated steel slag; Step S2: Atomize the mixed silane solution and spray it onto activated steel slag that is stirred at 5-10℃, then ball mill it in stages to obtain spray-treated steel slag; Step S3: The spray-treated steel slag is sequentially kept at 75-85℃ for 1.5-2.5h, 115-125℃ for 1-2h, and 135-145℃ for 20-40min, and then cooled to room temperature to obtain modified steel slag.

[0007] Further, the mixed silane solution in step S2 is composed of KH560, KH570 and deionized water in a mass ratio of 2-2.5:1-1.5:3-4.

[0008] Furthermore, the mass ratio of the activated steel slag and the mixed silane solution in step S2 is 100:6-8.

[0009] Furthermore, the preparation method of the modified fly ash is as follows: Step a: Dry mix fly ash, calcium hydroxide, and anhydrous gypsum, add water in batches and ball mill, controlling the material temperature to ≤60℃ during ball milling, and obtain activated fly ash after post-treatment; Step b: Atomize and spray the KH550 solution onto the activated fly ash, mix for 15-20 minutes, and then keep it at 75-85℃ for 50-70 minutes and 105-115℃ for 50-70 minutes in sequence to obtain modified fly ash.

[0010] Furthermore, the mass ratio of fly ash, calcium hydroxide, and anhydrous gypsum in step a is 100:5-8:2-4.

[0011] Furthermore, the solvent of the KH550 solution in step b is a mixture of anhydrous ethanol and water with a volume ratio of 93-97:5, and the mass fraction of KH550 in the KH550 solution is 30-40%.

[0012] Furthermore, the mass ratio of activated fly ash to KH550 in step b is 100:2-3.

[0013] A method for preparing a high-performance cement composite material containing steel slag includes the following steps: dry mixing sulfoaluminate cement, modified steel slag, modified fly ash, mineral powder, silica, and boric acid, then adding polypropylene fiber and stirring evenly to obtain a dry mixture, then mixing carboxylated styrene-butadiene emulsion, polycarboxylate superplasticizer, and mixing water to obtain a mixed liquid, adding the mixed liquid to the dry mixture and stirring at low speed first, then stirring at high speed, and finally molding and curing to obtain the final product.

[0014] Furthermore, the low-speed stirring is 15-25 rpm for 55-65 seconds, and the high-speed stirring is 35-45 rpm for 120-150 seconds.

[0015] The present invention has the following beneficial effects: First, this invention modifies steel slag through a three-step synergistic process and simultaneously modifies fly ash through a two-step synergistic process. The two modification processes are highly integrated and complementary in terms of technical route. In the preparation of modified steel slag, step S1 uses atmospheric pressure saturated steam activation, utilizing 95-105℃ steam to fully hydrate the free calcium oxide in the steel slag to eliminate the risk of expansion. At the same time, hydrothermal etching increases the surface active hydroxyl groups, providing reaction sites for subsequent chemical grafting. In step S2, KH560 and KH570 mixed silanes are uniformly coated onto the surface of the steel slag through atomized spraying. Under low-temperature stirring and segmented ball milling conditions at 5-10℃, mechanical force is used to promote the hydrolysis and condensation of silanes to form Si-OM covalent bonds, while avoiding premature ring opening of epoxy groups and thermal polymerization of double bonds. In step S3, the residual silanes are deeply condensed through stepped thermosetting at 75-85℃, 115-125℃, and 135-145℃, forming a stable and dense siloxane network. In the preparation of modified fly ash, step a involves mechanochemical calcification and activation of fly ash with calcium hydroxide and anhydrous gypsum under fractional atomized water and low-temperature ball milling conditions, generating CSH gel in situ, which significantly improves the pozzolanic activity of fly ash and increases surface reaction sites. Step b involves atomizing and spraying KH550 solution and then performing stepwise thermosetting at 75-85℃ and 105-115℃ to covalently graft amino groups onto the fly ash surface, forming a Si-O-Si anchoring layer. The modified steel slag surface contains epoxy functional groups, and the modified fly ash surface contains amino functional groups. Under the bridging of carboxylated styrene-butadiene emulsion, they form a ternary chemical bonding network of "epoxy-amino-carboxyl": esterification crosslinking of epoxy and carboxyl groups, hydrogen bonding of amino and carboxyl groups, and interaction between amino and cement hydration products Ca. 2+ The coordination effect of the two materials synergistically constructs a multi-level, multi-type chemical cross-linking system from steel slag to fly ash to polymer emulsion. The two modified materials produce significant synergistic effects in spatial scale, chemical bonding and hydration induction, which synergistically improves the compressive and flexural strength of the composite material at all ages, and synergistically reduces water penetration height, chloride ion migration coefficient, drying shrinkage and crack area, achieving a reinforcement effect of 1+1>2.

[0016] Secondly, the various raw material components of this invention form a multi-scale, multi-mechanism synergistic enhancement system. Sulfoaluminate cement, as an early-strength, low-alkali matrix, provides rapidly developing initial strength. Modified steel slag and modified fly ash, as coarse and fine active micro-aggregates respectively, not only physically fill the dense matrix but also chemically crosslink with carboxylated styrene-butadiene emulsion through surface functional groups, transforming traditional inert fillers into active interface reinforcements. Carboxylated styrene-butadiene emulsion forms a film in the alkaline environment of cement hydration, where its carboxyl groups react with the epoxy groups of modified steel slag and the amino groups of modified fly ash to form a flexible organic-inorganic hybrid network, effectively buffering drying shrinkage stress and impact energy. Simultaneously, it forms a dual crack-resistant mechanism of chemical bonding and physical crack resistance through physical bridging with polypropylene fibers. Nano-silica fills nanoscale capillaries and consumes Ca(OH)2 through pozzolanic reaction to generate additional CSH gel, further refining the pore structure. Boric acid regulates the setting time of sulfoaluminate cement, ensuring the construction operation window and uniform fiber dispersion. Polycarboxylate superplasticizer reduces water consumption and improves slurry fluidity and matrix density. The above components are fully mixed under a specific mixing process. Low-speed stirring ensures uniform wetting of the powder and prevents fiber agglomeration, while high-speed stirring promotes full contact between the components. Ultimately, a complete performance enhancement system is formed, from nanopore filling and micron interface strengthening to macro crack control. This gives the cement composite material high strength, high impermeability, low shrinkage, and excellent crack toughness, making it suitable for high-performance repair, waterproofing and impermeability, marine engineering, sewage treatment, and other special building materials fields. Attached Figure Description

[0017] Figure 1 The graph shows the compressive and flexural strength results of different samples at different ages; Figure 2 The graph shows the water seepage height results for different samples. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] All raw materials used in the following examples are commercially available products. Sulfoaluminate cement was purchased from Zhengzhou Zhengjin Building Materials Co., Ltd.; steel slag, 80-120 mesh, 99% purity, from Lingshou County Baiyi Mineral Products Processing Plant; fly ash, Grade I fly ash, 325 mesh, from Hebei Huishun Mining Co., Ltd.; mineral powder, S95 grade, from Hebei Huishun Mining Co., Ltd.; silica, 15nm particle size, 99.6% silica content, from Greenlink (Jining) Chemical Technology Co., Ltd.; carboxylated styrene-butadiene emulsion, 46% solid content, model 3618, from Nanjing Yaojie Energy Saving Technology Co., Ltd.; polypropylene fiber, 6mm length, 25μm thickness, from Shandong Taicheng Fiber Co., Ltd.; polycarboxylate superplasticizer, 98% solid content, from Jinan Jianhui Chemical Co., Ltd.; mixing water, conforming to JGJ 63-2006 "Standard for Water Used in Concrete"; anhydrous gypsum purchased from Shandong Longbang Gypsum Products Co., Ltd.

[0020] Example 1 A high-performance cement composite material containing steel slag comprises the following components in parts by weight: 90 parts of sulfoaluminate cement, 15 parts of modified steel slag, 15 parts of modified fly ash, 10 parts of mineral powder, 2 parts of silica, 3 parts of carboxylated styrene-butadiene emulsion, 1.0 part of polypropylene fiber, 0.05 parts of boric acid, 1.5 parts of polycarboxylate superplasticizer, and 30 parts of mixing water. The method for preparing the modified steel slag is as follows: Step S1: Crush and grind the steel slag to a particle size < 0.075 mm and a specific surface area ≥ 450 m². 2 / kg, treated with saturated steam at 95℃ and normal pressure for 5h, and dried at 80℃ to constant weight to obtain activated steel slag; Step S2: The mixed silane solution is atomized and sprayed onto activated steel slag stirred at 5°C at a rotation speed of 20 rpm. Then it is transferred to a planetary ball mill jar with zirconia balls, 5 mm in diameter, and a ball-to-material mass ratio of 8:1. The ball milling program is as follows: 300 rpm for 10 min, intermittent cooling for 5 min, 350 rpm for 10 min, intermittent cooling for 5 min, and 300 rpm for 10 min. The material temperature is controlled to be ≤55°C during ball milling to obtain spray-treated steel slag. The mixed silane solution is composed of KH560, KH570 and deionized water in a mass ratio of 2:1:3. The mass ratio of activated steel slag to mixed silane solution is 100:6. Step S3: Spray-treated steel slag is sequentially kept at 75℃ for 1.5h, 115℃ for 1h, and 135℃ for 20min, and then naturally cooled to room temperature to obtain modified steel slag.

[0021] The modified fly ash is prepared as follows: Step a: Dry mix fly ash, calcium hydroxide, and anhydrous gypsum to obtain a mixture. Add water in three stages and atomize and ball mill. Use zirconia balls with a diameter of 10 mm and a ball-to-material mass ratio of 6:1. The first addition of water accounts for 8% of the mass of the mixture, and the ball milling is carried out at 300 rpm for 10 minutes. The second addition of water accounts for 7% of the mass of the mixture, and the ball milling is carried out at 350 rpm for 15 minutes. The third addition of water accounts for 5% of the mass of the mixture, and the ball milling is carried out at 300 rpm for 10 minutes. During ball milling, control the material temperature to ≤60℃. Dry at 80℃ until the moisture content is <1% to obtain activated fly ash. The mass ratio of fly ash, calcium hydroxide, and anhydrous gypsum is 100:5:2. Step b: Atomize and spray the KH550 solution onto the activated fly ash, mix for 15 minutes, and then heat at 75℃ for 50 minutes and 105℃ for 50 minutes in sequence to obtain modified fly ash. The solvent of the KH550 solution is a mixture of anhydrous ethanol and water with a volume ratio of 93:5. The mass fraction of KH550 in the KH550 solution is 30%, and the mass ratio of activated fly ash to KH550 is 100:2.

[0022] The above-mentioned method for preparing high-performance cement composite materials containing steel slag includes the following steps: (1) Dry mixing: Add sulfoaluminate cement, modified steel slag, modified fly ash, mineral powder, silica and boric acid into a forced mixer and dry mix for 120 seconds; (2) Fiber dispersion: Add polypropylene fiber to the dry mix and continue stirring for 180s until it is evenly dispersed to obtain the dry mix; (3) Liquid mixing: Mix carboxylated styrene-butadiene emulsion, polycarboxylate superplasticizer and mixing water, and stir at low speed of 20 rpm for 60 s until uniform liquid is obtained; (4) Mixing: Add the mixed liquid to the dry mixture, stir at low speed first, then stir at high speed to obtain the mixture. The low speed stirring is 15 rpm for 55 seconds, and the high speed stirring is 35 rpm for 120 seconds. (5) Molding and curing: Pour, vibrate and smooth the mixture, and cure it at 20℃ and relative humidity ≥95% until the specified age.

[0023] Example 2 A high-performance cement composite material containing steel slag comprises the following components in parts by weight: 100 parts of sulfoaluminate cement, 20 parts of modified steel slag, 20 parts of modified fly ash, 15 parts of mineral powder, 3 parts of silica, 5 parts of carboxylated styrene-butadiene emulsion, 1.5 parts of polypropylene fiber, 0.08 parts of boric acid, 2.5 parts of polycarboxylate superplasticizer, and 35 parts of mixing water. The method for preparing the modified steel slag is as follows: Step S1: Crush and grind the steel slag to a particle size < 0.075 mm and a specific surface area ≥ 450 m².2 / kg, treated with saturated steam at 105℃ and normal pressure for 6h, and dried at 80℃ to constant weight to obtain activated steel slag; Step S2: The mixed silane solution is atomized and sprayed onto activated steel slag stirred at 10℃ at a speed of 20 rpm. Then it is transferred to a planetary ball mill jar with zirconia balls, 5 mm in diameter, and a ball-to-material mass ratio of 8:1. The ball milling program is as follows: 300 rpm for 10 min, intermittent cooling for 5 min, 350 rpm for 10 min, intermittent cooling for 5 min, and 300 rpm for 10 min. The material temperature is controlled to be ≤55℃ during ball milling to obtain spray-treated steel slag. The mixed silane solution is composed of KH560, KH570 and deionized water in a mass ratio of 2.5:1.5:4. The mass ratio of activated steel slag to mixed silane solution is 100:8. Step S3: Spray-treated steel slag is sequentially kept at 85℃ for 2.5h, 125℃ for 2h, and 145℃ for 40min, and then naturally cooled to room temperature to obtain modified steel slag.

[0024] The modified fly ash is prepared as follows: Step a: Dry mix fly ash, calcium hydroxide, and anhydrous gypsum to obtain a mixture. Add water in three stages and atomize and ball mill. Use zirconia balls with a diameter of 10 mm and a ball-to-material mass ratio of 6:1. The first addition of water accounts for 12% of the mass of the mixture, and the ball milling is carried out at 300 rpm for 10 minutes. The second addition of water accounts for 10% of the mass of the mixture, and the ball milling is carried out at 350 rpm for 15 minutes. The third addition of water accounts for 8% of the mass of the mixture, and the ball milling is carried out at 300 rpm for 10 minutes. During ball milling, control the material temperature to ≤60℃. Dry at 80℃ until the moisture content is <1% to obtain activated fly ash. The mass ratio of fly ash, calcium hydroxide, and anhydrous gypsum is 100:8:4. Step b: Atomize and spray the KH550 solution onto the activated fly ash, mix for 20 minutes, and then keep it at 85℃ for 70 minutes and 115℃ for 70 minutes in sequence to obtain modified fly ash. The solvent of the KH550 solution is a mixture of anhydrous ethanol and water with a volume ratio of 97:5. The mass fraction of KH550 in the KH550 solution is 40%, and the mass ratio of activated fly ash to KH550 is 100:3.

[0025] The preparation method of the high-performance cement composite material containing steel slag mentioned above differs from that in Example 1 in that the low-speed stirring in step (4) is 25 rpm for 65 s and the high-speed stirring is 45 rpm for 150 s, while the rest is the same as in Example 1.

[0026] Example 3 A high-performance cement composite material containing steel slag comprises the following components in parts by weight: 95 parts sulfoaluminate cement, 18 parts modified steel slag, 17 parts modified fly ash, 13 parts mineral powder, 2.5 parts silica, 4 parts carboxylated styrene-butadiene emulsion, 1.3 parts polypropylene fiber, 0.06 parts boric acid, 2 parts polycarboxylate superplasticizer, and 32 parts mixing water. The method for preparing the modified steel slag is as follows: Step S1: Crush and grind the steel slag to a particle size < 0.075 mm and a specific surface area ≥ 450 m². 2 / kg, treated with saturated steam at 100℃ and normal pressure for 5.5h, and dried at 80℃ to constant weight to obtain activated steel slag; Step S2: The mixed silane solution is atomized and sprayed onto activated steel slag stirred at 8°C at a rotation speed of 20 rpm. Then, it is transferred to a planetary ball mill jar with zirconia balls, 5 mm in diameter, and a ball-to-material mass ratio of 8:1. The ball milling program is as follows: 300 rpm for 10 min, intermittent cooling for 5 min, 350 rpm for 10 min, intermittent cooling for 5 min, and 300 rpm for 10 min. During ball milling, the material temperature is controlled to be ≤55°C to obtain spray-treated steel slag. The mixed silane solution is composed of KH560, KH570 and deionized water in a mass ratio of 2.3:1.2:3.5. The mass ratio of activated steel slag to mixed silane solution is 100:7. Step S3: The spray-treated steel slag is sequentially kept at 80℃ for 2 hours, 120℃ for 1.5 hours, and 140℃ for 30 minutes, and then naturally cooled to room temperature to obtain modified steel slag.

[0027] The modified fly ash is prepared as follows: Step a: Dry mix fly ash, calcium hydroxide, and anhydrous gypsum to obtain a mixture. Add water in three stages and atomize and ball mill. Use zirconia balls with a diameter of 10 mm and a ball-to-material mass ratio of 6:1. The first addition of water accounts for 12% of the mass of the mixture, and ball milling is carried out at 300 rpm for 10 minutes. The second addition of water accounts for 10% of the mass of the mixture, and ball milling is carried out at 350 rpm for 15 minutes. The third addition of water accounts for 8% of the mass of the mixture, and ball milling is carried out at 300 rpm for 10 minutes. During ball milling, control the material temperature to ≤60℃. Dry at 80℃ until the moisture content is <1% to obtain activated fly ash. The mass ratio of fly ash, calcium hydroxide, and anhydrous gypsum is 100:6:3. Step b: Atomize and spray the KH550 solution onto the activated fly ash, mix for 17 minutes, and then keep it at 80℃ for 60 minutes and 110℃ for 60 minutes in sequence to obtain modified fly ash. The solvent of the KH550 solution is a mixture of anhydrous ethanol and water with a volume ratio of 95:5. The mass fraction of KH550 in the KH550 solution is 35%, and the mass ratio of activated fly ash to KH550 is 100:2.5.

[0028] The preparation method of the high-performance cement composite material containing steel slag mentioned above differs from that in Example 1 in step (4) by stirring at low speed for 60 seconds at 20 rpm and at high speed for 135 seconds at 40 rpm, while the rest is the same as in Example 1.

[0029] Comparative Example 1 A high-performance cement composite material containing steel slag comprises the following components in parts by weight: 90 parts of sulfoaluminate cement, 10 parts of modified steel slag, 10 parts of modified fly ash, 10 parts of mineral powder, 2 parts of silica, 3 parts of carboxylated styrene-butadiene emulsion, 1.0 part of polypropylene fiber, 0.05 parts of boric acid, 1.5 parts of polycarboxylate superplasticizer, and 30 parts of mixing water. The method for preparing the modified steel slag is as follows: Step S1: Crush and grind the steel slag to a particle size < 0.075 mm and a specific surface area ≥ 450 m². 2 / kg, treated with saturated steam at 60℃ and normal pressure for 5h, and dried at 80℃ to constant weight to obtain activated steel slag; Step S2: The mixed silane solution is atomized and sprayed onto activated steel slag stirred at 5°C at a rotation speed of 20 rpm. Then it is transferred to a planetary ball mill jar with zirconia balls, 5 mm in diameter, and a ball-to-material mass ratio of 8:1. The ball milling program is as follows: 300 rpm for 10 min, intermittent cooling for 5 min, 350 rpm for 10 min, intermittent cooling for 5 min, and 300 rpm for 10 min. The material temperature is controlled to be ≤55°C during ball milling to obtain spray-treated steel slag. The mixed silane solution is composed of KH560, KH570 and deionized water in a mass ratio of 1:1:3. The mass ratio of activated steel slag to mixed silane solution is 100:1. Step S3: The spray-treated steel slag is sequentially kept at 50℃ for 1.5h, 70℃ for 1h, and 90℃ for 20min, and then naturally cooled to room temperature to obtain modified steel slag.

[0030] The modified fly ash is prepared as follows: Step a: Dry mix fly ash, calcium hydroxide, and anhydrous gypsum to obtain a mixture. Add water in three stages and atomize and ball mill. Use zirconia balls with a diameter of 10 mm and a ball-to-material mass ratio of 6:1. The first addition of water accounts for 8% of the mass of the mixture, and the ball milling is carried out at 300 rpm for 10 min. The second addition of water accounts for 7% of the mass of the mixture, and the ball milling is carried out at 350 rpm for 15 min. The third addition of water accounts for 5% of the mass of the mixture, and the ball milling is carried out at 300 rpm for 10 min. During ball milling, control the material temperature to ≤60℃. Dry at 80℃ until the moisture content is <1% to obtain activated fly ash. The mass ratio of fly ash, calcium hydroxide, and anhydrous gypsum is 100:1:1. Step b: Atomize and spray the KH550 solution onto the activated fly ash, mix for 5 minutes, and then keep it at 30℃ for 50 minutes and 60℃ for 50 minutes in sequence to obtain modified fly ash. The solvent of the KH550 solution is a mixture of anhydrous ethanol and water with a volume ratio of 1:1. The mass fraction of KH550 in the KH550 solution is 30%, and the mass ratio of activated fly ash to KH550 is 100:1.

[0031] The preparation method of the high-performance cement composite material containing steel slag mentioned above differs from that in Example 1 in step (4) low-speed stirring is 10 rpm for 10 s and high-speed stirring is 100 rpm for 180 s, the rest is the same as in Example 1.

[0032] Comparative Example 2 The high-performance cement composite material containing steel slag differs from Example 1 in that the modified steel slag is replaced with commercially available steel slag, while the rest is the same as Example 1.

[0033] Comparative Example 3 The high-performance cement composite material containing steel slag differs from Example 1 in that the modified fly ash is replaced with commercially available fly ash, while the rest is the same as Example 1.

[0034] Comparative Example 4 The high-performance cement composite material containing steel slag differs from Example 1 in that the modified steel slag is replaced with commercially available steel slag, and the modified fly ash is replaced with commercially available fly ash; otherwise, it is the same as Example 1.

[0035] Performance testing: Compressive strength (3d, 7d, 28d) and flexural strength (3d, 7d, 28d): tested according to the requirements of GB / T 50081-2019 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The test results are shown in Table 1. Water penetration resistance, chloride ion penetration resistance, 28-day drying shrinkage rate, and crack resistance were tested according to the requirements of GB / T 50082-2024 "Standard for Test Methods of Physical Long-Term Performance and Durability of Ordinary Concrete". The water penetration resistance test was conducted using the water penetration height method, the chloride ion penetration resistance test was conducted using the rapid chloride ion migration coefficient method (RCM method), and the 28-day drying shrinkage rate test was conducted using the contact method. The test results are shown in Table 2.

[0036] Table 1 Compressive strength and flexural strength test results

[0037] Table 2. Tests on water penetration resistance, chloride ion penetration resistance, 28-day drying shrinkage rate, and crack resistance.

[0038] As shown in Tables 1 and 2, compared with the examples, Comparative Example 1 not only significantly reduced the amount of modified steel slag and modified fly ash, but also deviated significantly from the process parameters defined in this invention. Ultimately, this resulted in a significant decrease in the compressive and flexural mechanical properties of the composite material at all ages, a coarse internal pore structure, an increase in interconnected pores, a significant increase in water permeability height and chloride ion migration coefficient, an aggravated drying shrinkage deformation of the hardened system, a large number of microcracks initiating and expanding, a simultaneous increase in the 28-day drying shrinkage rate and crack area, and a significant deterioration in overall durability and volume stability.

[0039] As shown in Tables 1 and 2, compared with the examples, Comparative Example 2, by replacing the modified steel slag with commercially available steel slag, completely lost the functional modification effects brought about by steps S1, S2, and S3. The f-CaO in the commercially available steel slag was not steam-activated, and during the later stages of cement hydration, it slowly hydrated to generate Ca(OH)2, causing volume expansion. This led to expansion stress within the cement stone, triggering microcracks and even macroscopic cracking, resulting in reduced compressive and flexural strength, and increased 28-day shrinkage and crack area. Simultaneously, the surface of the commercially available steel slag lacked the active hydroxyl groups generated by steam activation and was not grafted with KH560 and KH570. Therefore, it could not form chemical crosslinks with the carboxylated styrene-butadiene emulsion. The steel slag and cement paste relied solely on physical friction and weak van der Waals forces, resulting in weak interfacial adhesion. Under external forces, the steel slag easily escaped from the system, leading to a particularly significant decrease in flexural strength. Increased interfacial porosity resulted in a simultaneous increase in permeability height and chloride ion migration coefficient.

[0040] As shown in Tables 1 and 2, compared with the examples, Comparative Example 3, by replacing the modified fly ash with commercially available fly ash, lost the activation and grafting effects brought about by steps a and b. Commercially available fly ash has a smooth surface and low pozzolanic activity, hardly participating in the reaction in the early stages of cement hydration, acting only as an inert filler and unable to provide CSH seed crystals to induce hydration. Therefore, the compressive and flexural strengths decreased significantly in the early stages (3d, 7d). Because the surface of fly ash lacks amino functional groups, it cannot react with the carboxyl groups of the carboxylated styrene-butadiene emulsion or with the Ca in the system. 2+ The lack of chemical bonding at the fly ash-polymer-cement stone interface resulted in a more significant loss in flexural strength than in compressive strength. Furthermore, commercially available fly ash cannot effectively fill the micropores in the interfacial transition zone, leading to increased water penetration height and chloride ion migration coefficient. The 28-day drying shrinkage and crack area also increased due to weak interfacial adhesion.

[0041] As shown in Tables 1 and 2, compared with the examples, Comparative Example 4 used both commercially available steel slag and commercially available fly ash, meaning that neither component underwent any modification treatment, resulting in the most severe performance degradation. The combined effects of the f-CaO hydration expansion in the commercially available steel slag and the low activity, smooth surface, and lack of chemical bonding ability of the commercially available fly ash caused the compressive and flexural strengths of the composite material at all ages to reach their lowest values, while the water penetration height and chloride ion migration coefficient reached their highest values. The 28-day shrinkage rate and crack area were also the largest. Compared with the examples, Comparative Example 4 completely lost the stabilization treatment and chemical grafting of steel slag in steps S1, S2, and S3, as well as the seed activation of fly ash in step a and the amino grafting of fly ash in step b. Both steel slag and fly ash existed in the form of traditional inert fillers, with only physical contact at the interface, making it impossible to form a multi-scale synergistic reinforcing network. Therefore, all properties were significantly degraded.

[0042] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-performance cement composite material containing steel slag, characterized in that, The composition includes the following components in parts by weight: 90-100 parts sulfoaluminate cement, 15-20 parts modified steel slag, 15-20 parts modified fly ash, 10-15 parts mineral powder, 2-3 parts silica, 3-5 parts carboxylated styrene-butadiene emulsion, 1.0-1.5 parts polypropylene fiber, 0.05-0.08 parts boric acid, 1.5-2.5 parts polycarboxylate superplasticizer, and 30-35 parts mixing water. The method for preparing the modified steel slag is as follows: Step S1: Crush and grind the steel slag to a particle size < 0.075 mm and a specific surface area ≥ 450 m². 2 / kg, treated with saturated steam at 95-105℃ and normal pressure for 5-6 hours, and then post-treated to obtain activated steel slag; Step S2: Atomize the mixed silane solution and spray it onto activated steel slag that is stirred at 5-10℃, then ball mill it in stages to obtain spray-treated steel slag; Step S3: The spray-treated steel slag is sequentially kept at 75-85℃ for 1.5-2.5h, 115-125℃ for 1-2h, and 135-145℃ for 20-40min, and then cooled to room temperature to obtain modified steel slag.

2. The high-performance cement composite material containing steel slag according to claim 1, characterized in that, The mixed silane solution in step S2 is composed of KH560, KH570 and deionized water in a mass ratio of 2-2.5:1-1.5:3-4.

3. The high-performance cement composite material containing steel slag according to claim 1, characterized in that, The mass ratio of activated steel slag and mixed silane solution in step S2 is 100:6-8.

4. The high-performance cement composite material containing steel slag according to claim 1, characterized in that, The modified fly ash is prepared as follows: Step a: Dry mix fly ash, calcium hydroxide, and anhydrous gypsum, add water in batches and ball mill, controlling the material temperature to ≤60℃ during ball milling, and obtain activated fly ash after post-treatment; Step b: Atomize and spray the KH550 solution onto the activated fly ash, mix for 15-20 minutes, and then keep it at 75-85℃ for 50-70 minutes and 105-115℃ for 50-70 minutes in sequence to obtain modified fly ash.

5. The high-performance cement composite material containing steel slag according to claim 4, characterized in that, The mass ratio of fly ash, calcium hydroxide, and anhydrous gypsum in step a is 100:5-8:2-4.

6. The high-performance cement composite material containing steel slag according to claim 4, characterized in that, The solvent of the KH550 solution mentioned in step b is a mixture of anhydrous ethanol and water with a volume ratio of 93-97:5, and the mass fraction of KH550 in the KH550 solution is 30-40%.

7. The high-performance cement composite material containing steel slag according to claim 4, characterized in that, The mass ratio of activated fly ash to KH550 in step b is 100:2-3.

8. A method for preparing a high-performance cement composite material containing steel slag as described in any one of claims 1-7, characterized in that, Includes the following steps: Sulfoaluminate cement, modified steel slag, modified fly ash, mineral powder, silica, and boric acid are dry-mixed, and then polypropylene fiber is added and stirred evenly to obtain a dry mix. Then, carboxylated styrene-butadiene emulsion, polycarboxylate superplasticizer, and mixing water are mixed to obtain a liquid mixture. The liquid mixture is added to the dry mix and stirred at low speed first, then at high speed. Finally, it is molded and cured to obtain the final product.

9. The method for preparing high-performance cement composite material containing steel slag according to claim 8, characterized in that, The low-speed stirring is 15-25 rpm for 55-65 seconds, and the high-speed stirring is 35-45 rpm for 120-150 seconds.

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