Self-compacting concrete and preparation method thereof

Abstract

The invention relates to self-compacting concrete and a preparation method thereof, and belongs to the technical field of concrete materials. Raw materials of the self-compacting concrete comprise carbonized steel slag aggregate, a solid waste-based cementing material and an auxiliary agent, the carbonized steel slag aggregate is approximately spherical and has multi-stage grain size distribution, and the carbonized steel slag aggregate comprises steel slag fine aggregate and steel slag coarse aggregate; wherein the self-compacting concrete comprises the following raw materials in parts by weight: 10-30 parts of the solid waste-based cementing material, 0-50 parts and more than 0 of the steel slag fine aggregate, and 0-50 parts and more than 0 of the steel slag coarse aggregate. The self-compacting concrete prepared by the invention meets at least one of the following indexes: the slump expansion degree is 550-700mm, and the expansion time is T500lt; the separation rate SR2 is smaller than or equal to 15% in 2s, the porosity is 1%-3%, the water permeability coefficient is lower than 1 * 10 <-12 > m / s, and the 28d compressive strength meets the strength grade of C30-C50.

Description

Technical Field

[0001] This application relates to the technical field of concrete materials, and particularly to a self-compacting concrete and a preparation method thereof. Background Art

[0002] With the rapid development of social industrialization, the demand for mineral resources is increasing. The accumulation and discharge of tailings, waste rocks, and industrial metallurgical waste residues have also caused many environmental problems such as environmental pollution and land occupation. Making full use of solid waste resources has become an urgent problem to be solved.

[0003] Traditional concrete is made by mixing raw materials such as clinker cement, coarse and fine aggregates, admixtures, and water. However, due to problems related to the compatibility of cementitious materials, aggregates, or admixtures, problems such as low fluidity, poor filling performance, and poor bonding performance often occur during the pouring process, resulting in poor self-compacting performance of the concrete. At the same time, the costs of clinker cement, waste rock coarse aggregates, and river sand fine aggregates required for traditional concrete are increasing year by year. Summary of the Invention

[0004] This application provides a self-compacting concrete and a preparation method thereof to solve the following technical problems: how to improve the self-compacting performance of concrete.

[0005] In a first aspect, an embodiment of this application provides a self-compacting concrete. The raw materials of the self-compacting concrete include carbonized steel slag aggregates, solid waste-based cementitious materials, and additives. The carbonized steel slag aggregates are nearly spherical and have a multi-level particle size distribution. The carbonized steel slag aggregates include steel slag fine aggregates and steel slag coarse aggregates; wherein,

[0006] By weight, in the raw materials of the self-compacting concrete, the solid waste-based cementitious material is 10 parts to 30 parts, the steel slag fine aggregate is 0 to 50 parts and greater than 0, and the steel slag coarse aggregate is 0 to 50 parts and greater than 0.

[0007] Optionally, the multi-level particle size distribution includes: 10 mm to 20 mm, 5 mm to 10 mm, and 0 to 5 mm.

[0008] Optionally, the surface area of the solid waste-based cementitious material is 450 m 2 / kg to 650 m 2 / kg.

[0009] Optionally, the steel slag fine aggregate meets the following indicators: the particle diameter is 0.15 mm ≤ d1 < 5 mm, the fineness modulus is 2.3 to 3.0, and the mud content is < 1 part; and / or,

[0010] The steel slag coarse aggregate particles meet the following indicators: the particle diameter is 5 mm ≤ d2 < 20 mm, the content of needle-shaped and flaky particles is < 10 parts, the void ratio is < 40 parts, and the mud content is < 1 part.

[0011] Optionally, the auxiliary agent includes water, water reducing agent and thickening agent.

[0012] Optionally, based on parts by weight, in the raw materials of the self-compacting concrete, water is 5 to 9 parts, the water reducing agent is 0 to 1 part and greater than 0, and the thickening agent is 0 to 0.5 part and greater than 0.

[0013] Optionally, the raw materials of the solid waste-based cementitious material include: slag, hot metal desulfurization slag, steel slag, gypsum, fly ash, iron tailings and red mud; wherein, based on parts by weight, in the raw materials of the solid waste-based cementitious material,

[0014] slag is 30 to 60 parts, hot metal desulfurization slag is 0 to 30 parts, steel slag is 0 to 40 parts, gypsum is 5 to 30 parts, fly ash is 0 to 15 parts, iron tailings is 0 to 10 parts, and red mud is 0 to 10 parts.

[0015] Optionally, the self-compacting concrete meets at least one of the following indexes: the slump flow is 550 mm to 700 mm, the spread time T500 < 2 s, the segregation rate SR2 ≤ 15%, the porosity is 1% to 3%, and the water permeability coefficient is lower than 1×10 -12 m / s, and the 28-day compressive strength meets the strength grades of C30 to C50.

[0016] In a second aspect, an embodiment of the present application provides a preparation method of the self-compacting concrete provided in any one of the embodiments of the first aspect, and the method includes:

[0017] Pretreat the steel slag to obtain steel slag particles with a multi-level particle size distribution;

[0018] Carry out carbonization treatment on the steel slag particles with the multi-level particle size distribution;

[0019] Carry out near-spheroidization and screening on the carbonized steel slag particles in sequence to obtain steel slag fine aggregate and steel slag coarse aggregate;

[0020] Mix the steel slag fine aggregate, the steel slag coarse aggregate, the solid waste-based cementitious material and the auxiliary agent to obtain a mixed slurry;

[0021] Pour and mold the mixed slurry and cure it to obtain self-compacting concrete.

[0022] Optionally, the process parameters of the carbonization treatment include: the temperature is 20°C to 70°C, and the time is 36 h to 100 h.

[0023] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0024] The self-compacting concrete provided by the embodiments of the present application. In the raw materials of the self-compacting concrete, the steel slag aggregate is carbonated, which can convert the free calcium oxide (f-CaO) and magnesium oxide (f-MgO) in the steel slag into carbonates, thereby reducing the occurrence of volume expansion problems of the steel slag aggregate; the steel slag aggregate is nearly spherical, which can improve the fluidity of the steel slag aggregate; the steel slag aggregate has a multi-level particle size distribution, which can improve the compactness and mechanical properties of the concrete; the solid waste-based cementitious material has high activity, ensures compatibility with additives, and can replace cement as a cementitious component, reducing carbon emissions; under the combined action of the carbonated steel slag aggregate, the solid waste-based cementitious material and the additives, and satisfying that the solid waste-based cementitious material is 10 parts to 30 parts, the fine steel slag aggregate is 0 to 50 parts and greater than 0, and the coarse steel slag aggregate is 0 to 50 parts and greater than 0, the void ratio of the concrete is reduced, the compactness is enhanced, high fluidity and anti-segregation are achieved, and self-compacting molding can be realized without vibration. Therefore, the self-compacting performance of the concrete is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings herein are incorporated into the specification and form a part of the specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is a schematic flow chart of a preparation method of a self-compacting concrete provided by an embodiment of the present application;

[0028] Figure 2 It is a schematic actual flow chart of a preparation method of a self-compacting concrete provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0030] Various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within the range, such as 1, 2, 3, 4, 5, and 6, and this applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0031] In the present application, unless otherwise stated, the orientation terms such as "upper" and "lower" specifically refer to the drawing direction in the drawings. Additionally, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural. In this document, "at least one" means one or more, and "a plurality" means two or more. "At least one kind", "at least one of the following items (pieces)" or similar expressions refer to any combination of these items, including any combination of single items (pieces) or plural items (pieces). For example, "at least one of a, b, or c", or, "at least one of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively. The "parts representation method" such as parts by weight, parts by mass, etc. represents the proportional relationship between each component. In the proportional relationships involved in this document, the parameters that need to be described by proportion should be understood as the antecedents of the proportional formula in the order of description, and the proportional numbers should be understood as the consequents of the proportional formula. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one by one with the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0032] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present application can be obtained through market purchases or can be prepared by existing methods.

[0033] First aspect, an embodiment of the present application provides a self-compacting concrete. The raw materials of the self-compacting concrete include carbonized steel slag aggregate, solid waste-based cementitious material, and additives. The carbonized steel slag aggregate is nearly spherical and has a multi-level particle size distribution. The carbonized steel slag aggregate includes steel slag fine aggregate and steel slag coarse aggregate; wherein,

[0034] In terms of parts by weight, in the raw materials of the self-compacting concrete, the solid waste-based cementitious material is 10 parts to 30 parts, the steel slag fine aggregate is 0 to 50 parts and greater than 0, and the steel slag coarse aggregate is 0 to 50 parts and greater than 0.

[0035] Free calcium oxide (f-CaO) and magnesium oxide (f-MgO) in steel slag will undergo a hydration reaction when encountering water, generating products such as calcium hydroxide and magnesium hydroxide. These products will cause volume expansion during the hardening process, resulting in problems such as cracks in the concrete structure. Through carbonization treatment, f-CaO and f-MgO are converted into carbonates, such as calcium carbonate and magnesium carbonate, etc. Carbonates have high stability and are not prone to volume expansion, thus effectively reducing the volume expansion problem of steel slag aggregate caused by f-CaO and f-MgO, and improving the stability and durability of the concrete. The nearly spherical steel slag aggregate has a smaller rolling friction coefficient in the concrete mixture compared to aggregates of other shapes. When the concrete flows under its own weight or other external forces, the nearly spherical steel slag aggregates are more likely to roll over each other, reducing the resistance between the aggregates, improving the overall fluidity of the concrete mixture, and facilitating the self-filling of all corners of the formwork during the pouring process of the concrete to achieve the self-compacting function. The steel slag aggregate with a multi-level particle size distribution allows particles of different particle sizes to fill each other. The small particle size aggregates can fill the voids between the large particle size aggregates, while the large particle size aggregates form the skeleton structure of the concrete. This filling method makes the internal structure of the concrete more compact, reduces the porosity, and thus improves the density of the concrete. The increase in density further enhances the mechanical properties of the concrete, such as compressive strength and flexural strength, because a more compact structure can better transmit and withstand external forces.

[0036] The solid waste-based cementitious material has high activity, which means that after contacting with water, it can quickly undergo a hydration reaction to generate substances with cementitious properties, such as ettringite and calcium silicate hydrate. These hydration products can firmly bond particles such as steel slag aggregate together to form a stable concrete structure. At the same time, the high activity also helps the solid waste-based cementitious material to be better compatible with additives, enabling them to work together in the concrete system to jointly improve the performance of the concrete. A large amount of carbon dioxide is emitted during the traditional cement production process, causing great pressure on the environment. The solid waste-based cementitious material can replace cement as the cementitious component, reducing the amount of cement used, thus reducing the carbon emissions during the concrete production process and having significant environmental benefits.

[0037] Therefore, under the combined action of carbonized steel slag aggregate, solid waste-based cementitious material, and additives, and ensuring that the solid waste-based cementitious material is 10 parts to 30 parts, excellent cementitious properties and mechanical properties of the concrete are ensured; the fine steel slag aggregate is 0 to 50 parts and greater than 0, and the coarse steel slag aggregate is 0 to 50 parts and greater than 0. An appropriate amount of fine steel slag aggregate can fill the tiny voids between the coarse steel slag aggregate and the cementitious material, improve the compactness of the concrete, improve the microscopic structure of the concrete, and enhance the interfacial bonding performance of the concrete. An appropriate amount of coarse steel slag aggregate can support the overall structure of the concrete, bear the main load, and provide basic mechanical properties for the concrete. At the same time, the dosages of the fine steel slag aggregate and the coarse steel slag aggregate also consider the fluidity of the concrete, realizing excellent self-compacting performance of the concrete. In summary, the void ratio of the concrete is reduced, the compactness is enhanced, high fluidity and anti-segregation performance are achieved, and self-compacting molding can be realized without vibration. Exemplarily, the solid waste-based cementitious material can be 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, etc.; the fine steel slag aggregate can be 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50, etc.; the coarse steel slag aggregate can be 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, etc.

[0038] In some embodiments, the multi-level particle size distribution includes: 10 mm to 20 mm, 5 mm to 10 mm, and 0 to 5 mm.

[0039] Function of particle size (10 mm to 20 mm): This part of the steel slag aggregate with a larger particle size mainly plays a skeletal role in the concrete and can form the basic support framework of the concrete structure. Function of medium particle size (5 mm to 10 mm): The steel slag aggregate of 5 mm to 10 mm can fill the voids formed by the 10 mm to 20 mm aggregate, further reducing the pore size inside the concrete and improving the compactness of the concrete. They play a role of transition connection between the large particle size aggregate and the small particle size aggregate, making the internal structure of the concrete more uniform and improving the integrity of the concrete. Function of small particle size (0 to 5 mm): The steel slag aggregate of 0 to 5 mm can fill into smaller pores, including the tiny gaps between the large and medium particle size aggregates and the pores in the cement paste, minimizing the voids inside the concrete to make the concrete structure more dense, thereby improving durability indexes such as the impermeability and frost resistance of the concrete. Therefore, the multi-level particle size distribution enables the aggregates in the concrete to interlock with each other to form a stable structure. The steel slag aggregates with different particle sizes interact with the solid waste-based cementitious material to improve the overall performance of the concrete.

[0040] In some embodiments, the surface area of the solid waste-based cementitious material is 450 m 2 / kg to 650 m2 / kg.

[0041] The surface area of the solid waste-based cementitious material can be 450 m 2 / kg to 650 m 2 / kg. The solid waste-based cementitious material has sufficient contact area with the additives, enabling more complete hydration reactions. The solid waste-based cementitious material particles are uniformly dispersed in the system with a large specific surface area, which can better wrap and lubricate other components such as steel slag aggregates, promoting the interfacial bonding between the solid waste-based cementitious material and steel slag aggregates, etc., and fully improving the self-compacting performance of the concrete. Exemplarily, the surface area of the solid waste-based cementitious material can be 450 m 2 / kg, 500 m 2 / kg, 550 m 2 / kg, 600 m 2 / kg, 650 m 2 / kg, etc.

[0042] In some embodiments, the fine steel slag aggregate meets the following indicators: the particle diameter is 0.15 mm ≤ d1 < 5 mm, the fineness modulus is 2.3 to 3.0, and the mud content is < 1 part; and / or,

[0043] The coarse steel slag aggregate particles meet the following indicators: the particle diameter is 5 mm ≤ d2 < 20 mm, the content of needle-like and flaky particles is < 10 parts, the void ratio is < 40 parts, and the mud content is < 1 part.

[0044] The appropriate fine aggregate particle size helps to adjust the fluidity and cohesiveness of the concrete mixture. The fineness modulus reflects the fineness degree and particle gradation of the fine aggregate. A fineness modulus of 2.3 to 3.0 indicates that the particle gradation of the fine steel slag aggregate is relatively reasonable, with proper matching of coarse and fine particles. A low mud content can ensure good bonding between the fine steel slag aggregate and the cementitious material.

[0045] The coarse steel slag aggregate with 5 mm ≤ d2 < 20 mm can work better synergistically with the fine steel slag aggregate and the cementitious material. The content of needle-like and flaky particles < 10 parts can ensure that the shape of the coarse steel slag aggregate is relatively regular and can be evenly distributed in the concrete, which is beneficial to improving the workability of the concrete mixture and making it easier to pour and form. The void ratio < 40 parts means that the accumulation of the coarse steel slag aggregate is relatively compact, forming fewer pores and channels in the concrete. Similar to the requirement for the mud content of the fine steel slag aggregate, the mud content of the coarse aggregate < 1 part can ensure good bonding performance between the coarse aggregate and the cementitious material.

[0046] In some embodiments, the additives include water, water reducer, and thickener.

[0047] In some embodiments, in the raw materials of the self-compacting concrete by weight, water is 5 to 9 parts, the water reducing agent is 0 to 1 part and greater than 0, and the thickening agent is 0 to 0.5 part and greater than 0.

[0048] Water undergoes a hydration reaction with the solid waste-based cementitious material, causing the cementitious material to set and harden, binding particles such as coarse and fine steel slag aggregates together to form a concrete structure with certain strength and properties. The water reducing agent can adsorb on the surfaces of cement particles and steel slag aggregates, making the particle surfaces carry the same charge, thereby generating an electrostatic repulsion force, dispersing the cementitious material and aggregates from each other, and releasing the water wrapped by the flocculated structure. Without increasing the water consumption, it effectively improves the fluidity of the concrete mixture, ensuring that the concrete can flow smoothly under its own weight and achieving self-compaction. This high-performance water reducing agent is one or a combination of a melamine-based high-performance water reducing agent, an amino sulfonate-based high-performance water reducing agent, a polycarboxylic high-performance water reducing agent, and a naphthalene-based high-performance water reducing agent. The thickening agent can increase the viscosity of the concrete mixture and improve its cohesiveness.

[0049] Water can be 5 to 9 parts, which can ensure the ratio of water to the solid waste-based cementitious material, thereby ensuring the strength of the concrete. The water reducing agent can be 0 to 1 part, and can better adjust the fluidity of the concrete under different raw materials and construction conditions. The thickening agent can be 0 to 0.5 part, making the concrete system have appropriate cohesiveness. Exemplarily, water can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, etc.; the water reducing agent can be 1 part, 0.9 part, 0.8 part, 0.7 part, 0.6 part, 0.5 part, etc.; the thickening agent can be 0.5 part, 0.4 part, 0.3 part, 0.2 part, etc.

[0050] In some embodiments, the raw materials of the solid waste-based cementitious material include: slag, hot metal desulfurization slag, steel slag, gypsum, fly ash, iron tailings, and red mud; wherein, by weight, in the raw materials of the solid waste-based cementitious material,

[0051] slag is 30 to 60 parts, hot metal desulfurization slag is 0 to 30 parts, steel slag is 0 to 40 parts, gypsum is 5 to 30 parts, fly ash is 0 to 15 parts, iron tailings is 0 to 10 parts, and red mud is 0 to 10 parts.

[0052] Raw materials such as slag, hot metal desulfurization slag, steel slag, gypsum, fly ash, iron tailings, and red mud are combined in different weight portions, which can cooperate with each other, give play to their respective advantages, and jointly constitute a solid waste-based cementitious material with good performance. For example, slag, steel slag, etc. provide the main cementitious properties, gypsum adjusts the setting time, fly ash improves the workability, and iron tailings and red mud play a role in filling and auxiliary strengthening. By reasonably adjusting the dosage of each raw material, a solid waste-based cementitious material that meets different engineering requirements can be prepared, realizing the resource utilization of solid waste, reducing production costs at the same time, and having good economic and environmental benefits. Exemplarily, the slag can be 30 parts, 40 parts, 50 parts, 60 parts, etc.; the hot metal desulfurization slag can be 10, 15 parts, 20 parts, 25 parts, 30 parts, etc.; the steel slag can be 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, etc.; the gypsum can be 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, etc.; the fly ash can be 2 parts, 5 parts, 8 parts, 10 parts, 12 parts, 15 parts, etc.; the iron tailings can be 10 parts, 8 parts, 6 parts, 4 parts, 2 parts, etc.; the red mud can be 10 parts, 8 parts, 6 parts, 4 parts, 2 parts, etc.

[0053] In some embodiments, the self-compacting concrete satisfies at least one of the following indicators: the slump flow is 550 mm to 700 mm, the spread time T500 < 2 s, the segregation rate SR2 ≤ 15%, the porosity is 1% to 3%, and the water penetration coefficient is lower than 1×10 -12 m / s, and the 28-day compressive strength meets the strength grades of C30 to C50.

[0054] In a second aspect, the embodiments of the present application provide a preparation method for the self-compacting concrete provided in any one of the embodiments of the first aspect. Figure 1 It is a schematic flow chart of a preparation method for the self-compacting concrete provided in the embodiments of the present application; please refer to Figure 1 The method includes:

[0055] S1. Pretreat the steel slag to obtain steel slag particles with a multi-level particle size distribution;

[0056] The original state of steel slag is usually lumps of different sizes, and impurities may also be mixed in it. Through pretreatment operations such as crushing and grinding, the steel slag is processed into particles with a multi-level particle size distribution. The steel slag particles with a multi-level particle size distribution can form a good gradation in the subsequent concrete, and the small particles fill the voids between the large particles, improving the compactness and performance of the concrete.

[0057] S1 may include: graded crushing and multiple magnetic separation: using a jaw crusher to crush the original steel slag with a particle size of 0-50 mm into particles with a particle size of 10-20 mm and 5-10 mm, and then using a cone crusher or an impact crusher to crush a portion of the steel slag into particles with a particle size of 0-5 mm; and using a belt iron remover or a plate iron remover for multiple circulation magnetic separation in each crushing process.

[0058] S2, carbonizing the steel slag particles having a multi-level particle size distribution;

[0059] Steel slag contains free calcium oxide (f-CaO) and magnesium oxide (MgO), which will undergo hydration reaction when in contact with water, resulting in volume expansion, which may cause cracks in the concrete structure and affect durability. Carbonation treatment is to allow steel slag particles to react with carbon dioxide to convert f-CaO and MgO into carbonates such as calcium carbonate and magnesium carbonate. These carbonates are stable in nature and are not prone to volume expansion, thereby reducing the occurrence of volume expansion problems in steel slag aggregates.

[0060] S2 may include: placing the steel slag particles of 10-20 mm, 5-10 mm and 0-5 mm obtained by the above crushing into a carbonization box for carbonization for 36-100 hours respectively, and then placing the carbonized steel slag in a drying box at 105° C. with forced air to dry it to constant weight.

[0061] In some embodiments, the process parameters of the carbonization treatment include: a temperature of 20° C. to 70° C. and a time of 36 h to 100 h.

[0062] The temperature of the carbonization treatment can be 20℃~70℃, and the carbonization reaction can be carried out at a suitable rate to ensure the carbonization effect. The time can be 36h~100h, and the carbonization reaction needs a certain time to fully proceed so that the f-CaO and f-MgO in the slag are fully converted into carbonates. In addition, industrial flue gas can be used for carbonization treatment, and the CO2 concentration can be 10wt%~20wt%, and the reaction pressure is 0.5~2.0MPa; or the carbonization treatment can use high-purity CO2 concentration>90wt%, and the reaction pressure is 0.1~0.5MPa; the humidity of both is 5%~10%; for example, the temperature of the carbonization treatment can be 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, etc.; the time can be 36h, 40h, 45h, 50h, 55h, 60h, 70h, 80h, 90h, 100h, etc.

[0063] S3, sequentially performing near-spheroidization and screening on the steel slag particles after the carbonization treatment to obtain steel slag fine aggregate and steel slag coarse aggregate;

[0064] The steel slag particles after carbonization treatment are spheroidized to make the steel slag aggregate nearly spherical. The nearly spherical steel slag aggregate has a small rolling friction coefficient in the concrete mixture, which can effectively improve the fluidity of the steel slag aggregate, facilitate the better flow and filling of the formwork by the concrete under its own weight, and achieve self-compaction. The spheroidized steel slag particles are screened through sieves with different apertures and divided into steel slag fine aggregate (particle diameter 0.15mm ≤ d1 < 5mm) and steel slag coarse aggregate (particle diameter 5mm ≤ d2 < 20mm) to meet the requirements of self-compacting concrete for aggregates with different particle sizes.

[0065] S3 may include: the steel slag particles obtained from the above carbonization are spheroidized (shaped) by a sand and stone shaping machine and then classified by a rotary screen or a vibrating screen, and various steel slag aggregates in the form of nearly spherical particles are obtained.

[0066] S4. Mix the steel slag fine aggregate, the steel slag coarse aggregate, the solid waste-based cementitious material and the additives to obtain a mixed slurry;

[0067] Mix the steel slag fine aggregate, the steel slag coarse aggregate, the solid waste-based cementitious material and the additives (such as water, water reducer, thickener, etc.) in a certain proportion to obtain a uniform mixed slurry.

[0068] The acquisition method of the solid waste-based cementitious material includes: (1) Crushing and magnetic separation: For massive iron-containing raw materials such as steel slag and hot metal desulfurization slag, they need to be first crushed by a jaw crusher to a particle size less than 2.36mm, and then magnetic separation is carried out to remove metallic iron impurities; Grinding: The treated slag, hot metal desulfurization slag, steel slag, gypsum, pulverized coal, iron tailings, red mud raw materials are ground to a specific surface area of 450m 2 / kg~650m 2 / kg to produce the solid waste-based cementitious material.

[0069] S5. Pour and mold the mixed slurry and cure it to obtain self-compacting concrete.

[0070] Pour the mixed slurry into a pre-prepared formwork. Due to the good fluidity and segregation resistance of self-compacting concrete, it can fill every corner of the formwork under its own weight and form a dense structure without vibration. Curing can ensure that the hydration reaction of the cementitious material in the concrete can continue, making the concrete strength continuously increase, and finally obtaining self-compacting concrete.

[0071] The preparation method of this self-compacting concrete is realized based on the above self-compacting concrete. The specific raw materials of this self-compacting concrete can refer to the above embodiments. Since the preparation method of this self-compacting concrete adopts some or all of the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated one by one here.

[0072] A self-compacting concrete and its preparation method provided by an embodiment of this application have the following advantages:

[0073] (1) Through crushing, carbonization, shaping and screening, the volume expansion problems of free calcium oxide (f-CaO) and magnesium oxide (f-MgO) in steel slag are solved (stable carbonates are generated by the carbonization reaction). At the same time, the aggregate particle shape and gradation are optimized to improve the density and mechanical properties. The carbonization process is used for the modification of steel slag aggregate. By fixing f-CaO with CO2, the volume stability and carbon fixation problems are solved synchronously, combining environmental protection and performance improvement;

[0074] (2) In the acquisition of solid waste-based cementitious materials, metal iron impurities are removed by magnetic separation, and the material activity is improved by grinding (such as the latent hydraulicity of steel slag powder), ensuring compatibility with water reducers, and replacing cement as the cementitious component to reduce carbon emissions;

[0075] (3) The water-binder ratio is reduced by water reducers, and the viscosity is adjusted by thickeners. Combining with the continuous gradation formed by the shaped and screened solid waste steel slag aggregate, the void ratio is reduced, the compactness is enhanced, and high fluidity and anti-segregation are achieved, and self-compacting molding can be realized without vibration;

[0076] (4) The solid waste-based self-compacting concrete has high fluidity, anti-segregation, stable physical properties, and fully utilizes solid waste resources, taking into account both economy and environmental protection.

[0077] In summary, the carbonization process is used for the modification of steel slag aggregate. By fixing f-CaO with CO2, the volume stability and carbon fixation problems are solved synchronously, combining environmental protection and performance improvement; the all-solid waste cementitious system completely replaces cement with industrial solid wastes such as steel slag powder and slag, activates its hydraulicity through magnetic separation and grinding, reduces the dependence on cement and carbon emissions; the solid waste collaborative design of self-compacting concrete is to replace natural sand and gravel with steel slag fine / coarse aggregate (the maximum proportion is 50%), reduce resource consumption, and complete performance regulation through the synergistic effect of additives and solid waste gradation, realizing self-compaction without vibration, taking into account construction efficiency and structural compactness. In addition, the solid waste utilization rate is high (the proportion of cementitious materials + aggregate reaches more than 80%), reducing the cost of concrete, and at the same time reducing the pollution of steel slag stacking.

[0078] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. For the experimental methods without specific conditions in the following embodiments, they are usually determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions or the conditions recommended by the manufacturer.

[0079] Example 1

[0080] A self-compacting concrete, 1 m 3 The concrete comprises the following raw material components by mass fraction: 360 kg of solid waste cementitious material, with a specific surface area of 600 m 2 / kg, 930 kg of steel slag fine aggregate (0.15 - 5 mm), 186 kg of steel slag coarse aggregate (5 - 10 mm), 744 kg of (10 - 20 mm), 180 kg of water, 1.44 kg of water reducer, and 0.72 kg of thickening agent. Among them, the solid waste cementitious material comprises the following components by mass fraction: 45% of slag, 15% of hot metal desulfurization slag, 10% of steel slag, 10% of gypsum, 10% of fly ash, 5% of iron tailings, and 5% of red mud.

[0081] A preparation method of self-compacting concrete, Figure 2 is a schematic diagram of the actual process of a preparation method of self-compacting concrete provided by an embodiment of the present application; please refer to Figure 2 ; specifically, it includes the following steps:

[0082] Pretreatment and carbonization treatment of steel slag aggregate: Classification and crushing and multiple magnetic separations: The as-received steel slag with particles of 0 - 50 mm is crushed by a jaw crusher to particles with particle sizes of 10 - 20 mm and 5 - 10 mm, and then a part of the steel slag is further crushed by a cone crusher or an impact crusher to particles with a particle size of 0 - 5 mm; and in each crushing process, a belt-type iron remover or a plate-type iron remover is used for multiple cycle magnetic separations; Carbonization treatment: The crushed steel slag particles of 10 - 20 mm, 5 - 10 mm, and 0 - 5 mm are respectively put into a high-purity carbonization box (CO2 concentration 95 wt%) for carbonization at 20 °C for 36 h, the reaction pressure is 0.5 MPa, the humidity is 5%, and then the carbonized steel slag is placed in a drying oven at 105 °C for air drying to constant weight; Shaping and screening: The carbonized steel slag particles are shaped by a sand and stone shaping machine and then classified by a rotary screen or a vibrating screen, and the obtained various steel slag aggregates (steel slag fine aggregate and steel slag coarse aggregate) are nearly spherical particles; Finished product inspection: The particle diameter of the steel slag fine aggregate in the aggregate is 0.15 mm ≤ d1 < 5 mm, the fineness modulus is 2.3 - 3.0, and the mud content < 1%; the particle diameter of the steel slag coarse aggregate is 5 mm ≤ d2 < 20 mm, the needle and flake content < 10%, the void ratio < 40%, and the mud content < 1%.

[0083] Pretreatment of solid waste-based cementitious materials: Crushing and magnetic separation: For massive iron-containing raw materials such as steel slag and hot metal desulfurization slag, they need to be first crushed by a jaw crusher to a particle size less than 2.36 mm and then subjected to magnetic separation; Grinding: The treated slag, hot metal desulfurization slag, steel slag, gypsum, pulverized coal, iron tailings, and red mud raw materials are ground according to the process of first grinding each raw material separately and then mixing them together.

[0084] It is made by mixing steel slag fine aggregate, steel slag coarse aggregate, solid waste-based cementitious material, water, water reducer, and thickening agent.

[0085] The mixing ratios of various materials in Example 1 and various macroscopic properties of the steel slag aggregate solid waste-based self-compacting concrete prepared are shown in Tables 1 and 2.

[0086] Table 1 Concrete mix ratio of Example 1 (kg / m 3 )

[0087]

[0088] Table 2 Concrete properties of Example 1

[0089] Cementitious material / kg Slump flow / mm Slump flow time / s Segregation rate / % Porosity / % <![CDATA[Permeability coefficient / m·s -1 > 28-day compressive strength / MPa 360 650 0.5 10 2.2 <![CDATA[1×10 -13 > 36.5

[0090] Example 2

[0091] A kind of self-compacting concrete, 1 m 3 The concrete includes the following raw material components by mass fraction: 480 kg of solid waste cementitious material, with a specific surface area of 550 m 2 / kg, 700 kg of steel slag fine aggregate (0.15 - 5 mm), 525 kg of steel slag coarse aggregate (5 - 10 mm), 525 kg (10 - 20 mm), 170 kg of water, 2.88 kg of water reducer, and 1.44 kg of thickening agent. Among them, the solid waste cementitious material includes the following components by mass fraction: 50% of slag, 5% of hot metal desulfurization slag, 20% of steel slag, 12% of gypsum, 5% of fly ash, 5% of iron tailings, and 3% of red mud.

[0092] A preparation method of a kind of self-compacting concrete, Figure 2 is the actual process schematic diagram of a preparation method of a kind of self-compacting concrete provided by an embodiment of this application; please refer to Figure 2 ; specifically includes the following steps:

[0093] Steel slag aggregate pretreatment and carbonization treatment: Classification crushing and multiple magnetic separation: The original steel slag with particle size of 0 - 50 mm is crushed by a jaw crusher into particles with particle sizes of 10 - 20 mm and 5 - 10 mm, and then a part of the steel slag is further crushed by a cone crusher into particles with particle size of 0 - 5 mm; and multiple cyclic magnetic separation is carried out by a belt-type iron remover in each crushing process; Carbonization treatment: The crushed steel slag particles with particle sizes of 10 - 20 mm, 5 - 10 mm and 0 - 5 mm are respectively put into a carbonization box with a concentration of 20 wt% and carbonized at 50 °C for 72 h, the reaction pressure is 1.0 MPa, the humidity is 5%, and then the carbonized steel slag is dried to constant weight in a drying oven at 105 °C with air blowing; Shaping and screening: The carbonized steel slag particles are shaped by a sand and stone shaping machine and then classified by a drum screen, and various steel slag aggregates (steel slag fine aggregate and steel slag coarse aggregate) in the shape of nearly spherical particles are obtained; Finished product inspection: The particle diameter of the steel slag fine aggregate in the aggregate is 0.15 mm ≤ d1 < 5 mm, the fineness modulus is 2.3 - 3.0, and the mud content < 1%; The particle diameter of the steel slag coarse aggregate is 5 mm ≤ d2 < 20 mm, the content of needle-shaped and flaky particles < 10%, the void ratio < 40%, and the mud content < 1%.

[0094] Pretreatment of solid waste-based cementitious material: Crushing and magnetic separation: For massive iron-containing raw materials such as steel slag and hot metal desulfurization slag, they need to be first crushed by a jaw crusher to a particle size less than 2.36 mm and then subjected to magnetic separation; Grinding: The treated slag, hot metal desulfurization slag, steel slag, gypsum, pulverized coal, iron tailings, and red mud raw materials are ground according to the process of first separately and then mixing each raw material.

[0095] It is made by mixing steel slag fine aggregate, steel slag coarse aggregate, solid waste-based cementitious material, water, water reducer, and thickener.

[0096] The material ratios of each component in Example 2 and various macroscopic properties of the steel slag aggregate solid waste-based self-compacting concrete prepared are shown in Table 3 and Table 4.

[0097] Table 3 Concrete mix ratio of Example 2 (kg / m 3 )

[0098]

[0099] Table 4 Concrete properties of Example 2

[0100] Cementitious material / kg Slump flow / mm Slump flow time / s Segregation rate / % Porosity / % <![CDATA[Permeability coefficient / m·s -1 > 28-day compressive strength / MPa 480 600 0.8 7 1.8 <![CDATA[0.5×10 -13 > 47.7

[0101] Example 3

[0102] A self-compacting concrete and its preparation method, 1 m 3 The concrete includes the following raw material components by mass fraction: 600 kg of solid waste cementitious material, with a specific surface area of 500 m 2 / kg, 574 kg of fine steel slag aggregate (0.15 - 5 mm), 492 kg of coarse steel slag aggregate (5 - 10 mm), 574 kg of (10 - 20 mm), 160 kg of water, 6.0 kg of water reducer, and 3.0 kg of thickening agent. Among them, the solid waste cementitious material includes the following components by mass fraction: 55% of slag, 20% of hot metal desulfurization slag, 10% of steel slag, 15% of gypsum, 0% of fly ash, 0% of iron tailings, and 0% of red mud.

[0103] A preparation method of self - compacting concrete Figure 2 is the actual process schematic diagram of a preparation method of self - compacting concrete provided by an embodiment of the present application; please refer to Figure 2 ; The specific steps are the same as those in Example 1.

[0104] The material ratios of Example 3 and various macroscopic properties of the steel slag aggregate solid - waste - based self - compacting concrete prepared are shown in Table 5 and Table 6.

[0105] Table 5 Concrete mix ratio of Example 3 (kg / m 3 )

[0106]

[0107] Table 6 Concrete properties of Example 3

[0108] Cementitious material / kg Slump flow / mm Slump flow time / s Segregation rate / % Porosity / % <![CDATA[Permeability coefficient / m·s -1 > 28-day compressive strength / MPa 600 550 1.0 5 1.3 <![CDATA[1×10 -14 > 58.3

[0109] Comparative Example 1

[0110] Based on the content disclosed in Example 1, the difference between Comparative Example 1 and Example 1 is that the steel slag aggregate has no carbonation and no shaping treatment.

[0111] The material ratios of Comparative Example 1 and various macroscopic properties of the steel slag aggregate solid - waste - based self - compacting concrete prepared are shown in Table 7 and Table 8.

[0112] Table 7 Concrete mix ratio of Comparative Example 1 (kg / m 3 )

[0113]

[0114] Table 8 Concrete properties of Comparative Example 1

[0115] Cementitious material / kg Slump flow / mm Slump flow time / s Segregation rate / % Porosity / % <![CDATA[Permeability coefficient / m·s -1 > 28-day compressive strength / MPa 360 600 0.8 17 2.8 <![CDATA[5×10 -12 > 33.5

[0116] Comparative Example 2

[0117] Based on the content disclosed in Example 1, the difference between Comparative Example 2 and Example 1 is that the cementitious material is ordinary Portland cement, slag powder, and fly ash.

[0118] The material ratios of Comparative Example 2 and the various macroscopic properties of the steel slag aggregate solid waste-based self-compacting concrete prepared are shown in Tables 9 and 10 as follows.

[0119] Table 9 Concrete mix ratio of Comparative Example 2 (kg / m 3 )

[0120]

[0121] Table 10 Concrete properties of Comparative Example 2

[0122] Cementitious material / kg Slump flow / mm Slump flow time / s Segregation rate / % Porosity / % <![CDATA[Coefficient of water permeability / m·s -1 > 28-day compressive strength / MPa 360 550 1 20 3.4 <![CDATA[8×10 -12 > 35.0

[0123] It can be seen from Examples 1 to 3 and Comparative Examples 1 to 2 that by using solid waste-based cementitious materials to replace traditional portland cement, and at the same time, after the steel slag aggregate is pretreated by crushing, carbonization, shaping and screening, it can be used in concrete to improve the density and mechanical properties. And by using the carbonization process to modify the steel slag aggregate, the volume stability and carbon sequestration problems can be solved synchronously, with both environmental protection and performance improvement. In addition, by using a water reducer to reduce the water-binder ratio and a thickening agent to adjust the viscosity, combined with the continuous gradation formed by the shaped and screened solid waste steel slag aggregate, the void ratio can be reduced, the compactness can be enhanced, and high fluidity and anti-segregation can be achieved, and it can self-compact and form without vibration.

[0124] One or more technical solutions in the embodiments of the present application at least further have the following technical effects or advantages:

[0125] (1) The steel slag aggregate solid waste-based self-compacting concrete and its preparation method have the advantages of simple production process, wide material sources and low prices, and have better economic practicability;

[0126] (2) Make full use of the beneficial resources such as silicon, aluminum and calcium in steel slag, slag and desulfurized gypsum, and recycle harmful solid waste, which is in line with the concept of sustainable development;

[0127] (3) By adjusting the gradation of coarse and fine aggregates, the dosage of additives and solid waste cementitious materials, solid waste-based self-compacting self-leveling concrete suitable for different construction environments can be prepared;

[0128] (4) The flowability, macroscopic strength, anti-segregation performance and filling performance of the provided concrete meet the construction requirements of C30 - C50 self-compacting self-leveling concrete;

[0129] (5) The provided concrete has excellent construction properties such as high fluidity and high filling performance, can achieve one-time pouring and forming, the surface is smooth and flat, the color is uniform, and it shows good mechanical properties, providing a direction for the utilization of steel slag and solid waste-based cementitious materials.

[0130] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A self-compacting concrete, wherein the raw materials of the self-compacting concrete include carbonized steel slag aggregate, solid waste-based cementitious material and additives, wherein the carbonized steel slag aggregate is nearly spherical and has a multi-grade particle size distribution, and the carbonized steel slag aggregate includes steel slag fine aggregate and steel slag coarse aggregate; wherein: In parts by weight, among the raw materials of the self-compacting concrete, the solid waste-based cementitious material accounts for 10 to 30 parts, the steel slag fine aggregate accounts for 0 to 50 parts and greater than 0, and the steel slag coarse aggregate accounts for 0 to 50 parts and greater than 0.

2. The self-compacting concrete according to claim 1, characterized in that: The multi-level particle size distribution includes: 10mm-20mm, 5mm-10mm and 0-5mm.

3. The self-compacting concrete according to claim 1, characterized in that: The surface area of ​​the solid waste-based cementitious material is 450 m 2 / kg~650m 2 / kg.

4. The self-compacting concrete according to claim 1, characterized in that: The steel slag fine aggregate meets the following indicators: particle diameter is 0.15mm≤d1<5mm, fineness modulus is 2.3-3.0, mud content is <1 part; and / or, The steel slag coarse aggregate particles meet the following indicators: particle diameter is 5mm≤d2<20mm, needle-like content is <10 parts, void ratio is <40 parts, and mud content is <1 part.

5. The self-compacting concrete according to claim 1, characterized in that: The auxiliary agent includes water, a water reducing agent and a thickener.

6. The self-compacting concrete according to claim 5, characterized in that: In parts by weight, the raw materials of the self-compacting concrete include 5 to 9 parts of water, 0 to 1 part and greater than 0 of a water reducer, and 0 to 0.5 part and greater than 0 of a thickener.

7. The self-compacting concrete according to claim 1, characterized in that: The raw materials of the solid waste-based cementitious material include: slag, hot metal desulfurization slag, steel slag, gypsum, fly ash, iron tailings and red mud; wherein, in parts by weight, the raw materials of the solid waste-based cementitious material include: The slag is 30 to 60 parts, the molten iron desulfurization slag is 0 to 30 parts, the steel slag is 0 to 40 parts, the gypsum is 5 to 30 parts, the fly ash is 0 to 15 parts, the iron tailings is 0 to 10 parts, and the red mud is 0 to 10 parts.

8. The self-compacting concrete according to any one of claims 1 to 7, characterized in that: The self-compacting concrete meets at least one of the following indicators: slump expansion of 550 mm to 700 mm, expansion time T500 < 2 s, segregation rate SR2 ≤ 15%, porosity of 1% to 3%, water permeability coefficient less than 1×10 -12 m / s, and the 28d compressive strength meets the C30~C50 strength grade.

9. A method for preparing the self-compacting concrete according to any one of claims 1 to 8, the method comprising: Pre-treating the steel slag to obtain steel slag particles with multi-grade particle size distribution; Carrying out carbonization treatment on the steel slag particles having a multi-level particle size distribution; The carbonized steel slag particles are sequentially subjected to near-spheroidization and screening to obtain steel slag fine aggregate and steel slag coarse aggregate; The steel slag fine aggregate, the steel slag coarse aggregate, the solid waste-based cementitious material and the additive are mixed to obtain a mixed slurry; The mixed slurry is cast and cured to obtain self-compacting concrete.

10. The method according to claim 9, characterized in that The process parameters of the carbonization treatment include: temperature of 20° C. to 70° C. and time of 36 h to 100 h.

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