All-solid-waste-based core-shell type carbonized artificial aggregate and preparation method thereof

Abstract

The invention discloses an all-solid-waste-based core-shell type carbonized artificial aggregate and a preparation method thereof, and relates to the technical field of artificial aggregates. The water-binder ratio is 0.15-0.25, and the water-binder comprises the following components in percentage by mass: 10%-30% of red mud, 10%-30% of steel slag, 35%-50% of granulated blast-furnace slag, 5%-15% of fly ash, 3%-7% of an alkali activator and 0.5%-1% of a water reducer, a mixed solution of the alkali activator and the water reducer is sprayed during granulation in the preparation process, a mixture of the red mud, the steel slag, the fly ash and 37%-60% of the granulated blast-furnace slag is granulated to obtain an inner core, and the inner core is prepared from the red mud, the steel slag, the fly ash and the granulated blast-furnace slag. And continuously granulating the residual granulated blast furnace slag on the basis of the inner core to obtain the shell. Under the condition of meeting the national standard, the environment problem caused by overuse of natural aggregate and accumulation of industrial solid waste is reduced, the cold bonding method is adopted for preparation, the process is simple, and the production energy consumption is low.

Description

Technical Field

[0001] The present invention relates to the technical field of artificial aggregates, in particular to a fully solid waste-based core-shell carbonized artificial aggregate and a preparation method thereof. Background Art

[0002] In recent years, with the expansion of infrastructure construction around the world, construction resources have been rapidly consumed, especially key materials such as sand and gravel. The discharge of bulk solid waste has also significantly aggravated global warming and had an adverse impact on the environment.

[0003] The preparation technologies of artificial aggregates mainly include high-temperature sintering technology and cold bonding technology. Among them, high-temperature sintering technology is accompanied by huge energy consumption and carbon dioxide emissions. It is also easy to cause the volatilization of pollutants such as heavy metals in industrial waste, thereby causing secondary pollution problems. Therefore, this technology is not suitable for the resource utilization of waste incineration fly ash; while cold bonding technology is based on different cementitious systems, using the hydration reaction or geopolymerization reaction of cementitious materials to achieve aggregate hardening, and through various physical and chemical mechanisms such as physical encapsulation, chemical adsorption and covalent bonding of reaction products, the endogenous pollutants of the raw materials are fixed, which has the advantages of low energy consumption and high environmental benefits.

[0004] The Chinese invention patent application with application number CN202110353517.9 discloses a sinter-free lightweight aggregate, a preparation method thereof, and lightweight concrete, which prepares an epoxy base material through epoxy resin, epoxy diluent, epoxy defoamer and reinforcing powder, adds epoxy curing agent to the epoxy base material to prepare epoxy preparatory liquid, places expanded polystyrene in the epoxy preparatory liquid to prepare preparatory lightweight aggregate, places the preparatory lightweight aggregate in construction waste powder for tumbling to prepare preparatory sinter-free lightweight aggregate, and then solidifies at room temperature to obtain sinter-free lightweight aggregate. The sinter-free lightweight aggregate of this patent can be used to prepare lightweight concrete, which has the advantage of reducing energy consumption, but the structure is made of a single lightweight aggregate inside and outside, and does not have the defect of an outer shell structure to enhance structural strength; the Chinese invention patent application with application number CN202011103873.7 discloses an artificial steel Slag aggregate and its preparation method, which promotes the precipitation of free calcium oxide in the low-activity mineral phase through admixtures, makes full use of steel slag to absorb CO2, solves the stability problem of steel slag and improves the working performance of steel slag aggregate. However, the use of cement in cementitious materials brings higher raw material costs and indirect carbon emissions. The Chinese invention patent application with application number CN202011103706.2 discloses a green and energy-saving artificial lightweight aggregate and its preparation method, which is low in cost and can fix CO2, but the cementitious material used is a steel slag mono-cementitious material, and the activity of the steel slag needs to be fully stimulated, and the synchronous carbonization equipment used needs to be specially customized, which has certain difficulties in large-scale industrial utilization. In addition, the CO2 used is high-concentration CO2 after enrichment, and the enrichment process will be accompanied by an increase in operation and construction costs.

[0005] In summary, in view of the adverse effects of natural aggregate waste and solid waste emissions on the environment, there is an urgent need to provide a safe and environmentally friendly artificial aggregate, which is of great significance to the resource utilization of industrial waste and environmental protection. Summary of the Invention

[0006] To address the shortcomings of the background technology, the present invention provides a fully solid waste-based core-shell carbonized artificial aggregate and a preparation method thereof. While meeting national standards, it helps reduce the environmental problems caused by the excessive use of natural aggregates and the accumulation of industrial solid waste. It is prepared by a cold bonding method, which has a simple process and low production energy consumption.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A fully solid waste-based core-shell carbonized artificial aggregate has a water-to-binder ratio of 0.15-0.25 and comprises the following components by mass: 10%-30% red mud, 10%-30% steel slag, 35%-50% granulated blast furnace slag, 5%-15% fly ash, 3%-7% alkali activator, and 0.5%-1% water reducer. During the preparation process, a mixed liquid formed by the alkali activator and the water reducer is sprayed during granulation, and a mixture formed by red mud, steel slag, fly ash, and 37%-60% granulated blast furnace slag is granulated to obtain an inner core with a diameter of 4.75-8 mm. The remaining granulated blast furnace slag is further granulated on the basis of the inner core to obtain an outer shell with a thickness of 1-3 mm.

[0009] Furthermore, the red mud has a SiO2 content of 43.02% to 45%, an Al2O3 content of 14.5% to 15.7%, and an average particle size of 20 to 44 μm.

[0010] Furthermore, the steel slag has a SiO2 content of 48% to 52%, a CaO content of 20% to 23%, and an average particle size of 20 to 44 μm.

[0011] Furthermore, the strength ratio of the granulated blast furnace slag at 28 days is not less than 95%.

[0012] Furthermore, the fly ash is Class F, Grade I low-calcium fly ash, wherein the mass content of free CaO is less than 1%.

[0013] Furthermore, the alkaline activator is compounded by water glass solution and sodium hydroxide particles, the water content of the water glass solution is 52.77%, and the purity of the sodium hydroxide particles is greater than 90%.

[0014] Furthermore, the water reducer is a polycarboxylic acid water reducer with a solid content of ≥40% and a water reduction rate of ≥40%.

[0015] A method for preparing a fully solid waste-based core-shell carbonized artificial aggregate comprises the following steps:

[0016] S1. Mixed liquid configuration

[0017] Add sodium hydroxide particles to the water glass solution, adjust the modulus of the water glass solution to 1, then add the corresponding amount of water and let it stand for 24 hours. After cooling to room temperature, obtain the alkaline activator. Then add the water reducer to the alkaline activator and stir well to form a mixed solution for use;

[0018] S2. Granulation of aggregate

[0019] All red mud, steel slag, fly ash and 37% to 60% of granulated blast furnace slag are put into a mixer and mixed for 5 to 10 minutes to obtain a mixture. The disc inclination angle of the disc granulator is set to 45° to 50° and the disc speed is set to 35 to 55 rpm. 5% to 10% of the mixture is put into the disc granulator and the mixed liquid is continuously sprayed to form an initial sphere. Then, the remaining mixture is continuously added to the disc granulator while the mixed liquid is continuously sprayed for granulation. The granulation time is 15 to 20 minutes. After standing for 24 hours, the core is obtained. Thereafter, the mixed liquid is sprayed on the core until the surface is wet. The remaining granulated blast furnace slag is then put into the disc granulator while the mixed liquid is continuously sprayed to continue granulation. The granulation time is 8 to 10 minutes, so that the granulated blast furnace slag forms a shell on the surface of the coated core. Finally, carbonization curing is carried out for 1 day and then steam curing is carried out at 60°C to 85°C for 2 days to obtain a fully solid waste-based core-shell carbonized artificial aggregate.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention uses red mud, steel slag, fly ash, and granulated blast furnace slag as the core and granulated blast furnace slag as the shell, and adopts a cold bonding method to prepare core-shell artificial aggregate. This helps to consume a large amount of industrial solid waste and reduce the environmental problems caused by the accumulation of large amounts of red mud and steel slag. In addition, the density and cylinder compressive strength of the artificial aggregate after curing can meet the grade requirements of GB / T17431.1-2010, effectively alleviating the demand for natural aggregate and reducing the excessive use of natural aggregate.

[0022] 2. Compared with the traditional sintering process for preparing artificial aggregates, the core-shell artificial aggregate prepared by the present invention is not only simple in process, but also does not require high-temperature calcination throughout the entire process, resulting in low energy consumption and can be used for large-scale production;

[0023] 3. The core of the core-shell type artificial aggregate of the present invention is prepared using red mud and steel slag from industrial solid waste, and the fly ash and granulated blast furnace slag have high alkali activation activity to provide strength. The outer shell of the core-shell type artificial aggregate uses granulated blast furnace slag alone to reduce the precipitation rate of heavy metal ions in red mud and steel slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic flow chart of the method for preparing artificial aggregate of the present invention;

[0025] Figure 2 It is a trend diagram of the test results of each embodiment. DETAILED DESCRIPTION

[0026] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] A fully solid waste-based core-shell carbonized artificial aggregate, having a water-binder ratio of 0.15-0.25, comprises the following components by mass: 10%-30% red mud (RM), 10%-30% steel slag (SS), 35%-50% granulated blast furnace slag (GGBS), 5%-15% fly ash (FA), 3%-7% alkali activator, and 0.5%-1% water reducer. The following components are included:

[0028] The red mud has a SiO2 content of 43.02% to 45%, an Al2O3 content of 14.5% to 15.7%, and an average particle size of 20 to 44 μm.

[0029] The SiO2 content of the steel slag is 48% to 52%, the CaO content is 20% to 23%, and the average particle size is 20 to 44 μm.

[0030] The strength ratio of the granulated blast furnace slag at 28 days is not less than 95%.

[0031] The fly ash is Class F, Grade I low-calcium fly ash, wherein the mass content of free CaO is less than 1%.

[0032] The alkaline activator is compounded by water glass solution and sodium hydroxide particles. The water content of the water glass solution is 52.77%, and the purity of the sodium hydroxide particles is greater than 90%. The prepared alkaline activator needs to be left to stand for 24 hours before use.

[0033] The water reducer is a polycarboxylic acid water reducer with a solid content of ≥40% and a water reduction rate of ≥40%.

[0034] During the preparation process, a mixture formed by an alkali activator and a water reducer is sprayed during granulation, and a mixture formed by red mud, steel slag, fly ash and 37% to 60% of granulated blast furnace slag is granulated to obtain an inner core with a diameter of 4.75 to 8 mm. The remaining granulated blast furnace slag is further granulated on the basis of the inner core to obtain an outer shell with a thickness of 1 to 3 mm.

[0035] A method for preparing all-solid waste-based core-shell carbonized artificial aggregate, the process of which is combined with Figure 1 As shown, the following steps are included:

[0036] S1. Mixed liquid configuration

[0037] Add sodium hydroxide particles to the water glass solution, adjust the modulus of the water glass solution to 1, then add the corresponding amount of water and let it stand for 24 hours. After cooling to room temperature, obtain the alkaline activator. Then add the water reducer to the alkaline activator and stir well to form a mixed solution for use;

[0038] S2. Granulation of aggregate

[0039] All red mud, steel slag, fly ash and 37% to 60% of granulated blast furnace slag are put into a mixer and mixed for 5 to 10 minutes to obtain a mixture. The disc inclination angle of the disc granulator is set to 45° to 50° and the disc speed is set to 35 to 55 rpm. 5% to 10% of the mixture is put into the disc granulator and the mixed liquid is continuously sprayed to form an initial sphere. Then, the remaining mixture is continuously added to the disc granulator while the mixed liquid is continuously sprayed for granulation. The granulation time is 15 to 20 minutes. After standing for 24 hours, the core is obtained. Thereafter, the mixed liquid is sprayed on the core until the surface is wet. The remaining granulated blast furnace slag is then put into the disc granulator while the mixed liquid is continuously sprayed to continue granulation. The granulation time is 8 to 10 minutes, so that the granulated blast furnace slag forms a shell on the surface of the coated core. Finally, carbonization curing is carried out for 1 day and then steam curing is carried out at 60°C to 85°C for 2 days to obtain a fully solid waste-based core-shell carbonized artificial aggregate. Among them, the role of carbonization is to form a three-dimensional network structure after the raw materials are activated by alkali, which makes it easier to enhance the absorption and storage capacity of CO2 in artificial aggregates.

[0040] The following five examples are given to verify the superiority of the artificial aggregate prepared by the present invention:

[0041] Example 1

[0042] The water-binder ratio by weight is 0.2, and the mass percentages are: red mud is 23%, steel slag is 20%, granulated blast furnace slag is 47% (core 25%, shell 22%), Class F, Grade I low-calcium fly ash is 10%, alkali activator is 6%, and polycarboxylic acid water reducer is 0.75%.

[0043] Example 2

[0044] The water-binder ratio by weight is 0.2, and the mass percentages are: red mud is 20%, steel slag is 20%, granulated blast furnace slag is 50% (30% core, 20% shell), Class F, Grade I low-calcium fly ash is 10%, alkali activator is 5%, and polycarboxylic acid water reducer is 0.75%.

[0045] Example 3

[0046] The water-binder ratio by weight is 0.15, and the mass percentages are: red mud is 25%, steel slag is 10%, granulated blast furnace slag is 50% (core 28%, shell 22%), Class F I low-calcium fly ash is 15%, alkali activator is 7%, and polycarboxylic acid water reducer is 1%.

[0047] Example 4

[0048] The water-binder ratio by weight is 0.25, and the mass percentages are: red mud is 30%, steel slag is 30%, granulated blast furnace slag is 35% (13% inner core, 22% outer shell), Class F, Grade I low-calcium fly ash is 5%, alkali activator is 3%, and polycarboxylic acid water reducer is 0.5%.

[0049] Example 5

[0050] The water-binder ratio by weight is 0.2, and the mass percentages are: red mud is 10%, steel slag is 25%, granulated blast furnace slag is 50% (30% inner core, 20% outer shell), Class F, Grade I low-calcium fly ash is 15%, alkali activator is 7%, and polycarboxylic acid water reducer is 0.5%.

[0051] The raw materials of the above five examples were used to prepare all-solid waste-based core-shell carbonized artificial aggregates according to the method of the present invention. The cylinder compressive strength and 1-hour water absorption performance tests were performed, and the apparent density and bulk density were obtained. The cylinder compressive strength and water absorption tests were performed in accordance with the requirements of GB / T17431.2-2010, and the calculation formula is as follows:

[0052]

[0053] Where, f a Indicates the cylinder pressure strength, p1 indicates the pressure value when the stamping die is pressed into 20mm (N), p2 indicates the mass of the stamping die (N), and F indicates the area of the stamping die (F = 10000mm 2 ).

[0054]

[0055] Where, ω a represents the water absorption rate (%), m0 represents the mass of dry artificial aggregate (g), and m1 represents the mass of artificial aggregate in the surface dry saturated state (g).

[0056] Finally, the experimental data of each embodiment are shown in Table 1:

[0057] Table 1 Experimental data of each embodiment

[0058]

[0059] In order to clearly show the strength and strain variation trend of the all-solid waste-based core-shell carbonized artificial aggregate prepared in each embodiment, a trend graph of the test results was drawn. Figure 2 shown.

[0060] In summary, the innovation of the present invention compared with traditional aggregates is reflected in:

[0061] (1) Innovation in material system: Breaking through the traditional single-component solid waste utilization model, a composite system of red mud-steel slag-fly ash-granulated blast furnace slag is used to form the aggregate core, which forms a gradient activation structure with the granulated blast furnace slag shell, thus establishing a solid waste functionalization design of "calcium source supply-silicon-aluminum activation";

[0062] (2) Structural design innovation: A core-shell heterogeneous structure is constructed using a cold bonding process. The high calcium content of the steel slag in the core promotes the CO2 mineralization reaction. At the same time, a dense cementing layer is formed by the volcanic ash effect produced by the microcrystalline phase of granulated blast furnace slag in the shell, achieving synergistic effects of physical coating and chemical activation.

[0063] (3) Performance optimization mechanism: By regulating the ratio of core-shell components and particle size grading, an interpenetrating network structure of calcium aluminate and CSH gel is induced to form at the heterogeneous interface, which effectively improves the cylinder compressive strength of the aggregate and reduces the water absorption rate.

[0064] The all-solid waste-based core-shell carbonized artificial aggregate of the present invention not only meets the technical indicators of high-strength lightweight aggregate in GB / T17431.1-2010, shortens the curing period by 82%-93% compared with the conventional 28-day curing period, but also realizes the comprehensive utilization of industrial solid waste while providing a new interface engineering path for the low-carbon preparation of building aggregates. Compared with the traditional sintering process, the preparation method has the advantages of easy operation, simple process, and energy saving.

[0065] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other configurations without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations coming within the meaning and range of equivalents of the claims are intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0066] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A fully solid waste-based core-shell carbonized artificial aggregate, characterized by: The artificial aggregate has a water-cement ratio of 0.15 to 0.25 and comprises the following components by mass percentage: 10% to 30% red mud, 10% to 30% steel slag, 35% to 50% granulated blast furnace slag, 5% to 15% fly ash, 3% to 7% alkali activator and 0.5% to 1% water reducer. During the preparation process, a mixed liquid formed by the alkali activator and the water reducer is sprayed during granulation, and a mixture formed by red mud, steel slag, fly ash and 37% to 60% granulated blast furnace slag is granulated to obtain an inner core with a diameter of 4.75 to 8 mm. The remaining granulated blast furnace slag is further granulated on the basis of the inner core to obtain an outer shell with a thickness of 1 to 3 mm.

2. The all-solid waste-based core-shell carbonized artificial aggregate according to claim 1, characterized in that: The red mud has a SiO2 content of 43.02% to 45%, an Al2O3 content of 14.5% to 15.7%, and an average particle size of 20 to 44 μm.

3. The all-solid waste-based core-shell carbonized artificial aggregate according to claim 1, characterized in that: The SiO2 content of the steel slag is 48% to 52%, the CaO content is 20% to 23%, and the average particle size is 20 to 44 μm.

4. The all-solid waste-based core-shell carbonized artificial aggregate according to claim 1, characterized in that: The strength ratio of the granulated blast furnace slag at 28 days is not less than 95%.

5. The all-solid waste-based core-shell carbonized artificial aggregate according to claim 1, characterized in that: The fly ash is Class F, Grade I low-calcium fly ash, wherein the mass content of free CaO is less than 1%.

6. The all-solid waste-based core-shell carbonized artificial aggregate according to claim 1, characterized in that: The alkaline activator is prepared by compounding water glass solution and sodium hydroxide particles. The water content of the water glass solution is 52.77%, and the purity of the sodium hydroxide particles is greater than 90%.

7. The all-solid waste-based core-shell carbonized artificial aggregate according to claim 1, characterized in that: The water reducer is a polycarboxylic acid water reducer with a solid content of ≥40% and a water reduction rate of ≥40%.

8. A method for preparing a core-shell carbonized artificial aggregate based on solid waste, characterized by: The artificial aggregate according to any one of claims 1 to 7, wherein the preparation method thereof comprises the following steps: S1. Mixed liquid configuration Add sodium hydroxide particles to the water glass solution, adjust the modulus of the water glass solution to 1, then add the corresponding amount of water and let it stand for 24 hours. After cooling to room temperature, obtain the alkaline activator. Then add the water reducer to the alkaline activator and stir well to form a mixed solution for use; S2. Granulation of aggregate All red mud, steel slag, fly ash and 37% to 60% of granulated blast furnace slag are put into a mixer and mixed for 5 to 10 minutes to obtain a mixture. The disc inclination angle of the disc granulator is set to 45° to 50° and the disc speed is set to 35 to 55 rpm. 5% to 10% of the mixture is put into the disc granulator and the mixed liquid is continuously sprayed to form an initial sphere. Then, the remaining mixture is continuously added to the disc granulator while the mixed liquid is continuously sprayed for granulation. The granulation time is 15 to 20 minutes. After standing for 24 hours, the core is obtained. Thereafter, the mixed liquid is sprayed on the core until the surface is wet. The remaining granulated blast furnace slag is then put into the disc granulator while the mixed liquid is continuously sprayed to continue granulation. The granulation time is 8 to 10 minutes, so that the granulated blast furnace slag forms a shell on the surface of the coated core. Finally, carbonization curing is carried out for 1 day and then steam curing is carried out at 60°C to 85°C for 2 days to obtain a fully solid waste-based core-shell carbonized artificial aggregate.

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