Steel slag cement composition and preparation method thereof
The steel slag cement composition with silicate cement and latex, combined with CO2 treatment, addresses pollution and stability issues, enhancing mechanical properties and sustainability in cement production.
Patent Information
- Application Number
- CN202510564617.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-30
- Publication Date
- 2025-07-15
Smart Images
Figure BDA0005385595260000141 
Figure BDA0005385595260000142 
Figure BDA0005385595260000151
Abstract
Description
Technical Field
[0001] This application relates to the field of waste residue utilization, and particularly to a steel slag cement composition and a preparation method thereof. Background Art
[0002] In today's world, climate change and the greenhouse effect are significant, which strongly drive people to accelerate the sustainable development process of "low-carbon environmental protection". China actively responds and puts forward the grand development goals of achieving "carbon peak" by 2030 and "carbon neutrality" by 2060, and is fully promoting all industries to make great strides towards the direction of "green low-carbon, energy conservation and emission reduction". However, the ongoing infrastructure construction across the country has exposed a series of severe problems. On the one hand, it consumes a large amount of non-renewable resources; on the other hand, it generates tens of thousands of C&D waste. At the same time, the cement production process is characterized by high energy consumption and high emissions, which poses a sharp obstacle to the realization of China's "dual carbon" goal. Thus, it can be seen that if the research and production of green, low-carbon and environmentally friendly ecological concrete are not actively carried out, it will be extremely difficult for the construction industry and building materials industry to smoothly achieve the goals of "carbon peak and carbon neutrality".
[0003] Steel slag is an inevitable by-product of iron and steel production. About 15% of steel slag is produced for every 1t of crude steel produced. Most of the unutilized steel slag is directly buried and landfilled, which not only occupies a large amount of land resources, but also pollutes the soil, water body and air. Therefore, for the huge stock of steel slag, it is necessary to accelerate its safe, efficient and environmentally friendly resource utilization. China has a huge annual consumption of concrete. There have been many studies and practices on using steel slag powder as an auxiliary cementitious material and replacing part of the cement and aggregates with fine and coarse aggregates respectively. However, due to the presence of free CaO and free MgO in the steel slag powder, the volume expansion after hydration will cause stability problems and pose potential safety hazards. Summary of the Invention
[0004] In view of the above technical problems, the specific technical solutions of this application are as follows:
[0005] A steel slag cement composition, which includes portland cement, steel slag powder, latex and water.
[0006] Further, in terms of mass parts, the dosage of the portland cement is greater than 0 parts and less than 100 parts, the dosage of the steel slag powder is greater than 0 parts and less than or equal to 40 parts, the dosage of the latex is greater than 0 parts and less than or equal to 2 parts, and the dosage of the water is greater than or equal to 20 parts and less than or equal to 40 parts.
[0007] Further, in terms of mass parts, the dosage of the steel slag powder is 20 - 40 parts, and the dosage of the latex is 0.5 - 2 parts.
[0008] Further, the composition of the steel slag powder includes C2S and C3S.
[0009] This application also provides a preparation method of a steel slag cement composition, including:
[0010] Mixing portland cement, steel slag powder, latex and water proportionally and stirring to obtain a premix; carbonizing and curing the premix with CO2 to obtain the steel slag cement composition.
[0011] Further, by mass, the dosage of the portland cement is 60 - 100 parts, the dosage of the steel slag powder is 0 - 40 parts, the dosage of the latex is 0 - 2 parts, and the dosage of the water is 20 - 40 parts.
[0012] Further, the dosage of the steel slag powder is 20 - 40 parts, and the dosage of the latex is 0.5 - 2 parts.
[0013] Further, before carbonizing and curing the premix with CO2, it also includes:
[0014] Performing pre-curing on the premix.
[0015] Further, the pre-curing includes:
[0016] Pre-curing the premix in a standard curing environment for 23 - 25 h, the temperature of the pre-curing is 18 - 22 °C, and the relative humidity of the pre-curing is ≥ 95%.
[0017] Further, the temperature of the carbonizing and curing is 45 - 55 °C, and the time of the carbonizing and curing is greater than or equal to 2 h.
[0018] This application combines portland cement with steel slag powder to realize the consumption of steel slag powder, converts the waste that originally needed to be stockpiled into high-performance building material raw materials, effectively inhibits the soil, water body and atmospheric pollution caused by the stockpiling of steel slag powder, and provides a technical solution that is both economical and sustainable for the consumption of steel slag powder. The latex polymer chains can effectively fill the pores between the steel slag powder and the portland cement matrix, enhance the interfacial bonding force, and inhibit the propagation of microcracks caused by the hydration of free CaO and MgO in the steel slag powder, thereby significantly improving the volume stability and durability of the material; the toughening effect of the latex and the synergistic effect of the active components of the steel slag powder can significantly improve the compressive strength and splitting strength, while avoiding material softening caused by excessive addition. Specific embodiments
[0019] The present application will be described in detail below in conjunction with the described embodiments. Although specific embodiments of the present application are shown, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present application can be more thoroughly understood and the scope of the present application can be fully conveyed to those skilled in the art.
[0020] It should be noted that certain terms are used in the specification and claims to refer to particular components. Those skilled in the art should understand that technicians may use different terms to refer to the same component. The specification and claims do not use the difference in terms as a way to distinguish components, but rather use the difference in the functions of components as the criterion for distinction. As used throughout the specification and claims, the terms "comprising" or "including" are open-ended terms and should be construed as "including but not limited to". The following description of the specification is a preferred embodiment for implementing the present application, but the description is for the purpose of the general principles of the specification and is not intended to limit the scope of the present application. The scope of protection of the present application shall be determined by the scope defined by the appended claims.
[0021] The present application provides a steel slag cement composition, which includes Portland cement, the steel slag powder, latex, and water.
[0022] Specifically, the Portland cement is the main active component of the steel slag cement composition, providing early strength and long-term stability; the steel slag powder is used as an auxiliary cementitious material to replace part of the cement, realizing the high-value utilization of industrial solid waste; the latex is used as a polymer modifier to improve the fluidity and water retention of the paste and form a three-dimensional network structure to enhance the interfacial bonding.
[0023] In a specific embodiment, by mass fraction, the dosage of the Portland cement is greater than 60 parts and less than 100 parts, and can be, for example, one of 60 parts, 63 parts, 65 parts, 68 parts, 70 parts, 73 parts, 75 parts, 78 parts, 80 parts, 83 parts, 85 parts, 88 parts, 90 parts, 93 parts, 95 parts, 98 parts, 100 parts or any range value between any two of them. Through the synergistic effect with the steel slag powder, latex, and CO2 curing process, it has a systematic impact on the cementitious system construction, mechanical properties, and durability of the steel slag cement composition. The above range of the Portland cement dosage, through the synergistic matching with the steel slag powder, latex, and curing process, not only realizes the efficient resource utilization of the steel slag powder but also takes into account the mechanical properties and low-carbon environmental protection requirements of the cement-based material, providing a flexible and adjustable formulation space for the engineering application of the steel slag cement composition.
[0024] In a specific embodiment, by mass parts, the dosage of the steel slag powder is greater than 0 part and less than or equal to 40 parts. For example, it can be one of 1 part, 3 parts, 5 parts, 8 parts, 10 parts, 13 parts, 15 parts, 18 parts, 20 parts, 23 parts, 25 parts, 28 parts, 30 parts, 33 parts, 35 parts, 38 parts, 40 parts or the range value of any two of them, and preferably 20 - 40 parts.
[0025] Specifically, when the dosage of the steel slag powder is 1 - 10 parts, the steel slag powder forms a composite system with the Portland cement as an auxiliary cementitious material. Active substances such as C2S and C3S in the steel slag powder slowly hydrate in an alkaline environment. At the same time, CO2 carbonation curing promotes the formation of dense CaCO3 crystals from free CaO / MgO, improving the density of the system while reducing the dosage of the Portland cement. The interfacial modification effect of the latex enhances the adhesion between the steel slag powder and the Portland cement matrix, enabling the steel slag cement composition to possess basic compressive strength and crack resistance. As the dosage of the steel slag powder increases to 13 - 30 parts, the active components of the steel slag powder gradually play a dominant role, forming a "hydration - carbonation" dual cementitious mechanism with the hydration products C - S - H gel and Ca(OH)2 of the Portland cement: The vitreous structure in the steel slag powder fully exposes the reaction sites under the dispersion effect of the latex. CO2 diffuses through the pores and reacts with free oxides to form cementitious carbonates. At the same time, the unhydrated steel slag powder is embedded in the cement matrix as a rigid skeleton, significantly enhancing the compressive strength of the steel slag powder composition with the increase of the dosage, and the splitting strength is synchronously enhanced due to the optimization of the interfacial transition zone. When the dosage is in the preferred range of 20 - 40 parts, the proportion effect of the steel slag powder replacing the Portland cement and the activation effect of the activity reach the best balance: When the dosage is 20 parts, the steel slag powder begins to play a large - scale replacement role. When the dosage is 40 parts, the dosage of the Portland cement drops to 60 parts. The system wraps the steel slag powder particles with a flexible film layer of the latex, inhibiting the interfacial defects caused by the high dosage. At the same time, CO2 curing converts more than 90% of the free CaO in the steel slag powder into CaCO3, solving the volume expansion problem, and the generated calcite crystals and C - S - H gel are intertwined to form a high - strength network structure, enabling the steel slag cement composition to still maintain a compressive strength ≥28.35 MPa and a splitting strength ≥0.46 MPa when the dosage of the steel slag powder is 40 parts, achieving the dual goals of "replacing clay with slag" and performance improvement.
[0026] When the dosage of the steel slag powder is increased to 33 - 40 parts, the steel slag powder forms a complement with the Portland cement as the main cementitious component: The calcium ferrite aluminate minerals in the steel slag powder are evenly distributed under the dispersion effect of the latex. The carbonates generated by CO2 carbonation fill the pores of the cement stone, improving the density. At the same time, the toughening effect of the latex offsets the decrease in splitting strength caused by the brittleness of the steel slag powder, enabling the composition to have both high volume stability and excellent durability.
[0027] In a specific embodiment, the amount of the latex added is greater than 0 and less than or equal to 2 parts by mass, for example, it can be 0.1, 0.3, 0.5, 0.8, 1.0, 1.3, 1.5, 1.8, 2.0 parts or any two of the range values, preferably 0.5 to 2 parts. The latex polymer chain can effectively fill the pores between the steel slag powder and the silicate cement matrix, enhance the interfacial adhesion, and inhibit the microcrack extension caused by the hydration of free CaO and MgO in the steel slag powder, thereby significantly improving the volume stability and durability of the material; the toughening effect of the latex and the synergistic effect of the active components of the steel slag powder can significantly improve the compressive strength and splitting strength, while avoiding the softening of the material caused by excessive addition. The rheological properties of the latex match the water demand of the slurry, ensuring the uniformity and molding density of the slurry, and overcoming the problem of decreased fluidity caused by the addition of the steel slag powder.
[0028] In a specific embodiment, the water content is greater than or equal to 20 parts and less than or equal to 40 parts by mass, for example, it can be 20 parts, 23 parts, 25 parts, 28 parts, 30 parts, 33 parts, 35 parts, 38 parts, 40 parts or any two of the range values. When the water content is 20 parts, it can ensure that each component forms a premix with a suitable consistency during the mixing process, which can avoid uneven dispersion and insufficient hydration reaction due to insufficient water, and maintain structural stability during CO2 carbonization curing, so that the active ingredients in the steel slag powder are fully in contact with the silicate cement and undergo synergistic hydration and carbonization reactions to form a dense gel network and carbonate cementation structure. As the water content increases, the fluidity of the premix gradually improves, which is conducive to the uniform distribution of latex in the system and the role of interface modification, reducing the agglomeration of the steel slag powder and cement particles, and thus improving the splitting strength and bonding properties of the cement paste. At the same time, the problem of increased porosity due to excessive water is avoided. Water, as a reaction medium, accelerates the carbonation reaction of free CaO and MgO during the carbonation curing process. At the same time, the film-forming effect of latex inhibits the shrinkage defects caused by the evaporation of excess water, so that the steel slag cement composition has excellent durability and crack resistance while maintaining good construction performance. The above water content range achieves the performance optimization of the steel slag cement composition from the construction stage to the hardening stage through the synergistic effect of latex, the steel slag powder and the curing process, meeting the requirements of different application scenarios for material workability, strength and durability.
[0029] In a specific embodiment, the composition of the steel slag powder includes C2S and C3S. The main components of the steel slag powder are C2S and C3S. C3S undergoes rapid hydration reaction with water at normal temperature to generate C-S-H (hydrated silicate gel) and calcium hydroxide, providing early strength for the steel slag cement composition. The crystal structure of C2S is stable, making its hydration rate relatively slow, but its hydration products continuously form and fill the voids, making a key contribution to the long-term durability of the steel slag cement composition.
[0030] The present application also provides a method for preparing a steel slag cement composition, which includes:
[0031] Stir and mix portland cement, steel slag powder, latex and water in proportion to obtain a premix; subject the premix to carbonation curing with CO2 to obtain the steel slag cement composition.
[0032] Specifically, in the process of stirring and mixing the portland cement, the steel slag powder, the latex and water in proportion, each component can be evenly dispersed and fully contacted to form a premix with a stable structure. Among them, the addition of the latex can improve the interfacial adhesion between the steel slag powder and the portland cement through physical entanglement and chemical adsorption during the stirring process, reduce the phenomenon of particle agglomeration, thereby optimizing the microstructure of the premix and laying a foundation for the full progress of the gelling reaction during the subsequent curing process. When the premix is carbonation-cured with CO2, CO2 reacts with active components such as free CaO and MgO in the steel slag powder to form dense carbonate minerals, which not only effectively solves the volume stability problem caused by the hydration expansion of free oxides in the steel slag powder, but also further enhances the density of the steel slag cement composition through the cementing action of the carbonate. At the same time, the carbonation process promotes the synergistic reaction between active substances such as C2S and C3S in the steel slag powder and the hydration products of portland cement to form a more complex gel network structure, significantly improving the compressive strength and splitting strength of the steel slag cement composition.
[0033] In a specific embodiment, the CO2 curing is based on the reaction between the internal components of the material and CO2. When there are reactive alkaline substances in the material that can react with carbon dioxide, such as free calcium oxide, calcium hydroxide, etc., when CO2 is introduced under specific temperature and pressure conditions, it will react with the reactive alkaline substances to undergo a carbonization reaction, generating carbonates such as calcium carbonate. The carbonate has high strength and density, can fill the internal pores of the material, and thus improve the microstructure of the material. From the perspective of the impact on the properties of the material, CO2 curing can improve the compressive strength and flexural strength of the material. At the same time, for materials that expand in volume due to the presence of substances such as free CaO in the material, CO2 curing can cause such substances to react quickly to form stable carbonates, avoid the problem of unstable material volume, enhance the stability of the material, and because the microstructure of the material becomes dense, harmful substances from the outside, such as water and chloride ions, are difficult to enter the interior of the material, enhancing the durability of the material.
[0034] In a specific embodiment, before mixing the portland cement, steel slag powder, latex and water in proportion and stirring to obtain a premix, the process of grinding the steel slag powder into steel slag powder and removing impurities is also included.
[0035] Specifically, the blocky steel slag powder is coarsely crushed by equipment such as a crusher to initially reduce its particle size for subsequent grinding operations. The particle size of the coarsely crushed steel slag powder is still uneven and needs to be further finely ground by a ball mill. During the ball milling process, the steel slag powder particles collide and rub against the grinding medium and are gradually crushed into fine particles. The particle size of the steel slag powder can be controlled by adjusting parameters such as the rotation speed of the ball mill, the grinding time, and the ratio of the grinding medium.
[0036] During or after the process of grinding the steel slag powder into powder, an impurity removal operation is required. Since the steel slag powder may contain metal impurities such as iron filings and non-metal impurities such as unreacted slag. For metal impurities, a magnetic separation method can be used to adsorb and separate the ferromagnetic metal impurities in the steel slag powder by using a magnetic field. For other non-metal impurities, a screening method can be used to screen the steel slag powder through a sieve with an appropriate mesh number to remove impurity particles with particle sizes that do not meet the requirements and larger ones. A water washing method can also be used. The steel slag powder is placed in water, stirred and precipitated to dissolve the soluble impurities in the water, and then the impurity solution is removed by pouring and filtering to further purify the steel slag powder.
[0037] In a specific embodiment, by mass fraction, the dosage of the portland cement is greater than 60 parts and less than 100 parts. For example, it can be any one or the range value of any two of 60 parts, 63 parts, 65 parts, 68 parts, 70 parts, 73 parts, 75 parts, 78 parts, 80 parts, 83 parts, 85 parts, 88 parts, 90 parts, 93 parts, 95 parts, 98 parts, 100 parts. Through the synergistic effect with the steel slag powder, latex and CO2 curing process, it has a systematic impact on the gel system construction, mechanical properties and durability of the steel slag cement composition. The above-mentioned dosage range of portland cement, through the synergistic matching with the steel slag powder, latex and curing process, not only realizes the efficient resource utilization of steel slag powder, but also takes into account the mechanical properties and low-carbon environmental protection requirements of cement-based materials, providing a flexible and adjustable formula space for the engineering application of steel slag cement composition.
[0038] In a specific embodiment, by mass fraction, the dosage of the steel slag powder is greater than 0 part and less than or equal to 40 parts. For example, it can be any one or the range value of any two of 1 part, 3 parts, 5 parts, 8 parts, 10 parts, 13 parts, 15 parts, 18 parts, 20 parts, 23 parts, 25 parts, 28 parts, 30 parts, 33 parts, 35 parts, 38 parts, 40 parts, and is preferably 20 - 40 parts.
[0039] Specifically, when the dosage of the steel slag powder is 1-10 parts, the steel slag powder forms a composite system with the portland cement as an auxiliary cementitious material. Active substances such as C2S and C3S in the steel slag powder slowly hydrate in an alkaline environment. At the same time, CO2 carbonation curing promotes the formation of dense CaCO3 crystals from free CaO / MgO, improving the system density while reducing the dosage of the portland cement. The interfacial modification effect of the latex enhances the adhesion between the steel slag powder and the portland cement matrix, enabling the steel slag cement composition to possess basic compressive strength and crack resistance. As the dosage of the steel slag powder increases to 13-30 parts, the active components of the steel slag powder gradually play a dominant role, forming a "hydration-carbonation" dual cementitious mechanism with the hydration products C-S-H gel and Ca(OH)2 of the portland cement: The vitreous structure in the steel slag powder is fully exposed to reaction sites under the dispersion action of the latex, and CO2 diffuses through the pores to react with free oxides to form cementitious carbonates. At the same time, the unhydrated steel slag powder is embedded in the cement matrix as a rigid skeleton, significantly increasing the compressive strength of the steel slag powder composition with the increase in dosage, and the splitting strength is synchronously enhanced due to the optimization of the interfacial transition zone. When the dosage is in the preferred range of 20-40 parts, the proportion effect of the steel slag powder replacing the portland cement and the activation effect of activity reach the best balance: At 20 parts, the steel slag powder begins to play a large-scale replacement role, and at 40 parts, the dosage of the portland cement is reduced to 60 parts. The system wraps the steel slag powder particles with a flexible film layer of the latex, inhibiting the interfacial defects caused by high dosage. At the same time, CO2 curing converts more than 90% of the free CaO in the steel slag powder into CaCO3, solving the volume expansion problem, and the generated calcite crystals and C-S-H gel are intertwined to form a high-strength network structure, enabling the steel slag cement composition to still maintain a compressive strength ≥28.35 MPa and a splitting strength ≥0.46 MPa when the dosage of the steel slag powder is 40 parts, achieving the dual goals of "replacing clay with slag" and performance improvement.
[0040] When the dosage of the steel slag powder is increased to 33-40 parts, the steel slag powder forms a complementarity with the portland cement as the main cementitious component: The calcium ferrite mineral in the steel slag powder is evenly distributed under the dispersion action of the latex, and the carbonates generated by CO2 carbonation fill the pores of the cement stone, improving the density. At the same time, the toughening effect of the latex offsets the decrease in splitting strength caused by the brittleness of the steel slag powder, enabling the composition to have both high volume stability and excellent durability.
[0041] In a specific embodiment, based on parts by mass, the dosage of the latex is greater than 0 part and less than or equal to 2 parts. For example, it can be any one or the range value of any two of 0.1 part, 0.3 part, 0.5 part, 0.8 part, 1.0 part, 1.3 part, 1.5 part, 1.8 part, and 2.0 parts, and is preferably 0.5 - 2 parts. The latex polymer chains can effectively fill the pores between the steel slag powder and the Portland cement matrix, enhance the interfacial bonding force, and inhibit the propagation of microcracks caused by the hydration of free CaO and MgO in the steel slag powder, thereby significantly improving the volume stability and durability of the material; the toughening effect of the latex and the synergistic effect of the active components of the steel slag powder can significantly improve the compressive strength and splitting strength, while avoiding the softening of the material caused by excessive addition. The rheological properties of the latex match the water demand of the paste, ensuring the uniformity of the paste and the molding density, and overcoming the problem of decreased fluidity caused by the incorporation of the steel slag powder.
[0042] In a specific embodiment, based on parts by mass, the dosage of the water is greater than or equal to 20 parts and less than or equal to 40 parts. For example, it can be any one or the range value of any two of 20 parts, 23 parts, 25 parts, 28 parts, 30 parts, 33 parts, 35 parts, 38 parts, and 40 parts. When the dosage of water is 20 parts, it can ensure that a premix with appropriate consistency is formed during the mixing process of each component, avoiding both uneven dispersion and insufficient hydration reaction caused by insufficient water, and maintaining the structural stability during CO2 carbonation curing, enabling the active components in the steel slag powder to come into full contact with the Portland cement and undergo synergistic hydration and carbonation reactions to form a dense gel network and carbonate cementation structure. As the dosage of water increases, the fluidity of the premix gradually improves, which is beneficial to the uniform distribution of the latex in the system and the exertion of the interfacial modification effect, reducing the agglomeration of the steel slag powder and cement particles, and thus improving the splitting strength and bonding performance of the cement stone. At the same time, the problem of increased porosity caused by excessive water is avoided. Water acts as a reaction medium during the carbonation curing process to accelerate the carbonation reaction of free CaO and MgO, and at the same time inhibits the shrinkage defects caused by the evaporation of excess water through the film-forming effect of the latex, enabling the steel slag cement composition to have excellent durability and crack resistance while maintaining good workability. The above water dosage range realizes the performance optimization of the steel slag cement composition from the construction stage to the hardening stage through the synergistic effect with the latex, the steel slag powder, and the curing process, meeting the requirements of workability, strength, and durability of the material in different application scenarios.
[0043] In a specific embodiment, before using CO2 to carbonize and cure the premixture, it also includes: a step of pre-curing the premixture. The step of pre-curing the premixture is to promote the initial hydration reaction between the silicate cement and the steel slag powder before CO2 carbonization curing to form a gel skeleton with a certain strength, providing a stable microstructural basis for the subsequent carbonization reaction. After pre-curing, the semi-rigid gel network formed inside the premixture can effectively fix the steel slag powder, avoid particle displacement caused by CO2 diffusion during carbonization curing, and provide an orderly diffusion channel for CO2 gas, so that the carbonization reaction can penetrate deeper into the material more evenly. The hydration product formed by pre-curing acts as a precursor for the carbonization reaction. After contacting with CO2, it quickly generates CaCO3, forms a dense carbonate cementing layer on the surface of the steel slag powder and in the pores of the silicate cement, further fills the pores and improves the overall density. In addition, during the pre-curing process, the film-forming effect of the latex is gradually enhanced as the water evaporates, forming a flexible transition zone at the interface between the steel slag powder and the cement, alleviating the volume change stress generated by the carbonization reaction and reducing the generation of microcracks, thereby improving the crack resistance and durability of the steel slag cement composition.
[0044] In a specific embodiment, the pre-curing step includes pre-curing the premix for 23 to 25 hours under a standard curing environment; the standard curing environment is an environment in which the pre-curing temperature is 18 to 22°C and the pre-curing relative humidity is ≥95%. The pre-curing step can accurately control the early hydration process of the silicate cement and the steel slag powder by placing the premix in a standard curing environment of 18 to 22°C and a relative humidity of ≥95% for 23 to 25 hours, thereby constructing an ideal microstructural foundation for subsequent CO2 carbonization curing. In this temperature range, the hydration reaction rate is moderate, which not only avoids hydration stagnation caused by low temperature, but also prevents the early hydration products caused by high temperature from crystallizing too quickly, ensuring that the CSH gel and Ca(OH)2 crystals grow in a uniform and dense form; the high humidity environment with a relative humidity of ≥95% effectively inhibits water evaporation, so that the active components in the steel slag powder are fully dispersed under sufficient moisture conditions, forming a preliminary bonding network with the silicate cement hydration products, and promoting the latex to form a continuous flexible film layer at the interface between the steel slag powder and the cement matrix, significantly enhancing the interfacial bonding between the two phases. After pre-curing, a semi-rigid skeleton structure with moderate strength is formed inside the premix: the CSH gel layer generated on the surface of the silicate cement particles and the Ca(OH)2 released by the hydration of the steel slag powder are bonded to the premix. 2+The interaction forms a "gel-film layer-particle" composite interfacial transition zone under the wrapping of the latex film layer. This structure not only provides an ordered channel for CO2 gas diffusion but also resists the structural deformation caused by gas pressure during carbonation curing. Meanwhile, the Ca(OH)2 crystals generated during the pre-curing process, as the direct precursor of the carbonation reaction, are rapidly converted into dense CaCO3 under the subsequent action of CO2, and the carbonate crystals grow directionally along the gel pores formed during pre-curing, thus significantly improving the density and volume stability of the steel slag cement composition.
[0045] In a specific embodiment, the temperature of the carbonation curing is 45 - 55 °C. By precisely regulating the chemical reaction kinetics and microstructural evolution of CO2 and the steel slag cement composition, the directional optimization of the carbonation reaction depth and product morphology is achieved. This temperature range is significantly higher than room temperature and avoids the adverse effects of high temperature on the latex film layer and cement hydration products, enabling the best match between the kinetic energy of CO2 molecules and the reaction activity of the active components in the steel slag powder: at 45 °C, the CO2 diffusion coefficient is increased by 20% - 30% compared with room temperature, accelerating its transmission in the pores of the premix and promoting the rapid reaction of free CaO / MgO in the steel slag powder with CO2 to form calcite-type CaCO3 crystals, which fill the pores of the cement stone and the interface of the steel slag powder in the form of needles or flakes; when the temperature rises to 55 °C, the carbonation reaction rate further accelerates, and the reaction depth can reach 30 - 50 μm inside the steel slag powder, eliminating the potential volume expansion hazard caused by the hydration of free oxides and promoting the secondary reaction of active substances such as C2S and C3S in the steel slag powder with the cement hydration product C-S-H gel to form an intertwined and dense composite gel network.
[0046] In a specific embodiment, the time of the carbonation curing is greater than or equal to 2 h. By prolonging the reaction duration of CO2 and the steel slag cement composition, the depth and sufficiency of the carbonation reaction can be significantly improved, thereby producing a progressive optimization effect on the volume stability, mechanical properties, and durability of the material. Under the synergistic action of a pressure of 0.5 MPa and a temperature of 45 - 55 °C, sufficient carbonation time ensures that CO2 gas can fully diffuse into the interior of the premix, and the generated carbonate crystals such as CaCO3 not only fill the pores of the cement stone but also form a dense modification layer with a uniform thickness on the surface of the steel slag powder particles, eliminating the potential volume expansion hazard caused by the hydration of free oxides.
[0047] Through the collaborative innovation of replacing the portland cement with the steel slag powder, latex modification and CO2 curing process, this application forms systematic technical advantages in aspects such as low-carbon environmental protection, mechanical properties, volume stability and durability: the large-scale incorporation of steel slag powder realizes the high-value utilization of industrial solid waste, reduces cement consumption and carbon emissions at the same time, and CO2 curing promotes the conversion of free CaO / MgO in the steel slag powder into dense carbonate crystals, fundamentally eliminating the hidden danger of volume expansion and fixing CO2, forming the dual environmental protection benefits of "solid waste consumption - carbon sequestration"; the addition of the latex forms a flexible film layer between the steel slag powder and the cement matrix, improves the interfacial bonding force, and constructs a composite cementitious network with the rigid carbonate crystals generated by CO2 curing. The synergistic effect of the pre-curing and CO2 carbonation curing promotes the interwoven growth of hydration products and carbonation products, refines the pore structure, improves the density, increases the impermeability and the number of freeze-thaw cycles of the steel slag cement composition; no water reducer is required in the whole preparation process, and through the precise matching of component ratios and curing parameters, the balance between construction fluidity and post-hardening performance is achieved, providing a solution with both high performance and environmental protection for the engineering application of steel slag powder in fields such as low-carbon cementitious materials and ecological concrete, effectively promoting the resource utilization of steel slag powder and the green transformation of building materials.
[0048] Example
[0049] Example 1
[0050] Mix 100 g of portland cement (cement grade: Lafarge, PC425R), 2 g of latex (rubber powder from Shandong Jinnait Environmental Protection Technology Co., Ltd.) and 40 g of water and stir to obtain a premix;
[0051] After pre-curing the premix in an environment of 20 °C and a relative humidity of 98% for 28 days, carbonize and cure the premix with CO2 for 2 h to obtain the steel slag cement composition, and the curing temperature is 50 °C and the pressure is 0.5 MPa.
[0052] Example 2
[0053] Mix 60 g of portland cement (cement grade: Lafarge, PC425R), 40 g of steel slag powder (Leshan steel slag powder), 1 g of latex (rubber powder from Shandong Jinnait Environmental Protection Technology Co., Ltd.) and 40 g of water and stir to obtain a premix;
[0054] After pre-curing the premix in an environment of 20 °C and a relative humidity of 98% for 28 days, do not carbonize and cure the premix with CO2 to obtain the steel slag cement composition.
[0055] Example 3
[0056] Mix 60 g of Portland cement (cement grade: Lafarge, PC425R), 40 g of steel slag powder (Leshan steel slag powder) and 40 g of water, stir and mix to obtain a premix;
[0057] After pre-curing the premix for 28 days in an environment at 20 °C with a relative humidity of 98%, carbonize and cure the premix with CO2 for 2 h to obtain the steel slag cement composition, the curing temperature is 50 °C and the pressure is 0.5 MPa.
[0058] Example 4
[0059] Mix 80 g of Portland cement (cement grade: Lafarge, PC425R), 20 g of steel slag powder (Leshan steel slag powder), 2 g of latex (rubber powder from Shandong Jinnait Environmental Protection Technology Co., Ltd.) and 40 g of water, stir and mix to obtain a premix;
[0060] After pre-curing the premix for 28 days in an environment at 20 °C with a relative humidity of 98%, do not carbonize and cure the premix with CO2 to obtain the steel slag cement composition.
[0061] Example 5
[0062] Mix 60 g of Portland cement (cement grade: Lafarge, PC425R), 40 g of steel slag powder (Leshan steel slag powder), 2 g of latex (rubber powder from Shandong Jinnait Environmental Protection Technology Co., Ltd.) and 40 g of water, stir and mix to obtain a premix;
[0063] After pre-curing the premix for 28 days in an environment at 20 °C with a relative humidity of 98%, carbonize and cure the premix with CO2 for 1 h to obtain the steel slag cement composition, the curing temperature is 50 °C and the pressure is 0.5 MPa.
[0064] Example 6
[0065] Mix 80 g of Portland cement (cement grade: Lafarge, PC425R), 20 g of steel slag powder (Leshan steel slag powder), 1 g of latex (rubber powder from Shandong Jinnait Environmental Protection Technology Co., Ltd.) and 40 g of water, stir and mix to obtain a premix;
[0066] After pre-curing the premix for 28 days in an environment at 20 °C with a relative humidity of 98%, carbonize and cure the premix with CO2 for 2 h to obtain the steel slag cement composition, the curing temperature is 50 °C and the pressure is 0.5 MPa.
[0067] Example 7
[0068] Mix 100 g of Portland cement (cement grade: Lafarge, PC425R), 1 g of latex (rubber powder from Shandong Jinnait Environmental Protection Technology Co., Ltd.) and 40 g of water, stir and mix to obtain a premix;
[0069] After the premix is pre-cured for 28 days in an environment at 20°C and a relative humidity of 98%, the steel slag cement composition is obtained by carbonizing and curing the premix with CO2 for 1 h, with the curing temperature being 50°C and the pressure being 0.5 MPa.
[0070] Example 8
[0071] 80 g of Portland cement (cement grade: Lafarge, PC425R), 20 g of steel slag powder (Leshan steel slag powder) and 40 g of water are stirred and mixed to obtain a premix;
[0072] After the premix is pre-cured for 28 days in an environment at 20°C and a relative humidity of 98%, the steel slag cement composition is obtained by carbonizing and curing the premix with CO2 for 1 h, with the curing temperature being 50°C and the pressure being 0.5 MPa.
[0073] Comparative Example 1
[0074] 100 g of Portland cement (cement grade: Lafarge, PC425R) and 40 g of water are stirred and mixed to obtain a premix;
[0075] After the premix is pre-cured for 28 days in an environment at 20°C and a relative humidity of 98%, the steel slag cement composition is obtained without carbonizing and curing the premix with CO2.
[0076] The steel slag cement compositions obtained in the above examples are subjected to characterization experiments, and the results are shown in Tables 1 and 2.
[0077] Table 2
[0078]
[0079] Table 3 Splitting Strength of Cement Paste Specimens
[0080]
[0081]
[0082] In the above embodiments, when the content of steel slag powder increases from 0 part to 40 parts, the compressive strength of Comparative Example 1 with pure cement is 76.42 MPa, while the compressive strength of Example 5 with 40 parts of steel slag powder, without adding latex and without CO2 curing, decreases to 18.65 MPa. However, the compressive strength of Example 2 with the addition of 1 part of latex and 2-hour CO2 curing increases to 48.14 MPa, indicating that latex and CO2 curing can effectively alleviate the problem of strength decline caused by replacing cement with steel slag powder. In terms of splitting strength, the splitting strength of Example 3 reaches 1.09 MPa, which is 137% higher than that of Comparative Example 1 (0.46 MPa), and further increases to 1.18 MPa in Example 6, showing that the combined action of latex modification and CO2 curing significantly improves the flexibility and interfacial bonding force of cement stone. By comparing different CO2 curing durations, it is found that for the 2-hour curing in Example 1, Example 3, and Example 6, their compressive / splitting strengths are generally higher than those of 0 hour or 1 hour. Among them, Example 3 still maintains the advantage of splitting strength under a high content of steel slag powder. When the latex content is 0 - 2 parts, the splitting strength of Example 1 is 0.70 MPa and that of Example 7 is 0.90 MPa, showing a trend of first increasing and then stabilizing with the increase of the content, indicating that an appropriate amount of latex can optimize the microstructure through film-forming action, while excessive addition does not significantly improve the strength. Although Comparative Example 1 with blank control has the highest compressive strength, its splitting strength is the lowest. The overall data shows that within the parameter range of 20 - 40 parts of steel slag powder, 0.5 - 2 parts of latex, and 1 - 2 hours of CO2 curing, the steel slag powder cement paste can achieve a compressive strength ≥ 28.35 MPa and a splitting strength ≥ 0.86 MPa, which not only meets the mechanical property standards of building materials but also realizes low carbonization through high content of steel slag powder and CO2 carbon sequestration.
[0083] The above are only the preferred embodiments of the present application, and do not limit the present application in other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes. However, as long as it does not depart from the technical solution content of the present application, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present application still belong to the protection scope of the technical solution of the present application.
Claims
1. A steel slag cement composition, characterized in that, It includes Portland cement, steel slag powder, latex and water.
2. The composition according to claim 1, wherein By mass fraction, the dosage of the Portland cement is greater than 60 parts and less than 100 parts, the dosage of the steel slag powder is greater than 0 part and less than or equal to 40 parts, the dosage of the latex is greater than 0 part and less than or equal to 2 parts, and the dosage of the water is greater than or equal to 20 parts and less than or equal to 40 parts.
3. The composition according to claim 2, wherein By mass fraction, the dosage of the steel slag powder is 20 - 40 parts, and the dosage of the latex is 0.5 - 2 parts.
4. The composition according to claim 1, wherein The composition of the steel slag powder includes C2S and C3S.
5. A method for preparing a steel slag cement composition, characterized in that, It includes: Stir and mix the Portland cement, steel slag powder, latex and water in proportion, and then obtain a premix; Use CO2 to carry out carbonation curing on the premix to obtain the steel slag cement composition.
6. The method according to claim 5, characterized in that By mass fraction, the dosage of the Portland cement is greater than 60 parts and less than 100 parts, the dosage of the steel slag powder is greater than 0 part and less than or equal to 40 parts, the dosage of the latex is greater than 0 part and less than or equal to 2 parts, and the dosage of the water is greater than or equal to 20 parts and less than or equal to 40 parts.
7. The method according to claim 6, wherein The dosage of the steel slag powder is 20 - 40 parts, and the dosage of the latex is 0.5 - 2 parts.
8. The method according to claim 5, characterized in that, Before using CO2 to carry out carbonation curing on the premix, it also includes: Carry out pre-curing on the premix.
9. The method according to claim 8, wherein The pre-curing includes: Pre-cure the premix in a standard curing environment for 23 - 25 h, the temperature of the pre-curing is 18 - 22 °C, and the relative humidity of the pre-curing is ≥95%.
10. The method according to claim 5, wherein The temperature of the carbonation curing is 45 - 55 °C, and the time of the carbonation curing is greater than or equal to 2 h.