A formula for all-solid-waste non-combustion low-carbon concrete and carbonation curing process

Abstract

This invention discloses a non-fired, low-carbon concrete made entirely from solid waste, composed of a solid mixture and additives. The solid mixture comprises the following raw materials by weight percentage: 25-55% red mud, 20-45% carbide slag, 5-18% fly ash, 3-20% industrial gypsum, and 10-25% waste concrete powder. The additives include: alkali activator, foaming agent, water-reducing agent, and reinforcing fiber. The invention further discloses a carbonization curing process for this non-fired, low-carbon concrete. This technology achieves deep carbon reduction through a dual pathway of non-fired process and carbonization curing. Compared to traditional cement requiring high-temperature calcination (carbon emissions of approximately 800-900 kg / t), the non-fired, solid waste cementitious material does not require calcination, reducing carbon emissions to below 75 kg / t, a reduction of over 90%. Simultaneously, the carbonization curing process actively absorbs CO₂, resulting in a carbon sequestration of over 15 kg per cubic meter of concrete.

Description

Technical Field

[0001] This invention relates to the field of all-solid-waste non-fired concrete technology, specifically to an all-solid-waste non-fired low-carbon concrete formula and carbonation curing process, applicable to fields such as building engineering, road engineering, and filling engineering. Background Technology

[0002] With the rapid development of the construction industry, the demand for concrete as a basic building material continues to rise. However, its production process relies on a large amount of natural mineral resources, and traditional silicate cement production releases a large amount of carbon dioxide, exacerbating resource depletion and the greenhouse effect. Against this backdrop, solid waste-based low-carbon concrete technology has become a research hotspot, and several technological achievements have already been industrialized.

[0003] Existing technologies utilize industrial solid waste such as fly ash, slag, and red mud as primary raw materials to prepare cementitious materials through alkali-activated reactions, replacing traditional cement and reducing carbon emissions by 60%-80%. For example, some technologies use red mud, carbide slag, fly ash, and industrial gypsum to prepare foamed concrete, achieving solid waste resource utilization and exhaust gas utilization through tail gas carbonization curing; other technologies use steel slag, desulfurized gypsum, and tailings as raw materials to prepare all-solid-waste cementitious materials with strength exceeding C30 cement, while production costs are only 20% of cement. Simultaneously, recycled aggregate concrete technology is gradually maturing, obtaining recycled aggregates from crushed construction waste for use in non-load-bearing structures and roadbed filling, reducing the consumption of natural aggregates.

[0004] Current technologies face several challenges: First, balancing solid waste utilization with performance is difficult. Most technologies only address the resource utilization of single or a few types of solid waste, and the amount of solid waste added is limited to ensure the mechanical properties of concrete, making it impossible to achieve efficient utilization of all solid waste components. Some high-volume solid waste concrete exhibits slow strength development, high drying shrinkage, and insufficient durability, failing to meet the requirements of load-bearing structures. Second, carbonation curing processes are imperfect. Existing carbonation curing technologies often use high-concentration carbon dioxide gas sources, resulting in high costs. Furthermore, the precision of temperature, humidity, and carbon dioxide concentration control during the curing process is insufficient, leading to uneven carbonation reactions and the formation of pores and cracks within the concrete, affecting strength and durability. Simultaneously, exhaust gas pretreatment and recycling technologies are immature, and impurities in the exhaust gas can negatively impact concrete performance. Third, formulation adaptability is poor. The composition of solid waste varies significantly across different regions, and existing formulations lack universality. Formulations optimized for specific solid wastes cannot be directly applied to other types of solid waste, increasing the difficulty of technology promotion. Furthermore, some technologies rely on specific alkali activators or admixtures, leading to increased production costs and hindering large-scale industrial applications. From the above analysis, it is clear that existing all-solid-waste concrete materials require improvement in the following areas: First, develop concrete formulations with all-solid-waste components to further improve solid waste utilization, while optimizing raw material blending and admixtures to ensure the mechanical properties and durability of the concrete; second, optimize the carbonation curing process to reduce carbon dioxide source costs, achieve efficient utilization of industrial exhaust gas, improve the automation and precision control of the curing process, and ensure uniform carbonation reaction; third, enhance the universality of the formulation, developing adaptable solutions for different types of solid waste to reduce dependence on specific raw materials and control production costs. Summary of the Invention

[0005] This invention addresses the aforementioned problems by proposing a non-combustible, low-carbon concrete formula and carbonization curing process based on solid waste, thereby resolving the problems described above.

[0006] To achieve the above technical objectives, this invention employs a non-fired, low-carbon concrete made entirely from solid waste, which is composed of a solid mixture and additives. The solid mixture comprises the following raw materials by weight percentage: 25-55% red mud, 20-45% carbide slag, 5-18% fly ash, 3-20% industrial gypsum, and 10-25% waste concrete powder. The additives include: alkali activator, foaming agent, water-reducing agent, and reinforcing fiber.

[0007] The alkali activator is added at 3-12% of the mass of the solid mixture, the foaming agent is added at 0.3-1.5% of the mass of the solid mixture, the water-reducing agent is added at 0.3-0.8% of the mass of the solid mixture, and the reinforcing fiber is added at 0.2-1% of the mass of the solid mixture. The alkali activator is chemical waste, including one or more of the following: distillation waste liquid from the soda ash industry and red mud dealkalization waste liquid from the aluminum industry.

[0008] Preferably, the red mud is any one or more of the red mud produced by the Bayer process, sintering process, or combined process; the waste concrete powder is obtained by crushing and grinding waste concrete and then passing it through a 120-180 mesh square hole sieve.

[0009] More preferably, the reinforcing fiber is one or more of polypropylene fiber, polyvinyl alcohol fiber, and glass fiber, with a fiber length of 6-12 mm.

[0010] More preferably, the foaming agent is one or more of animal protein foaming agents, plant protein foaming agents, and synthetic foaming agents; the water-reducing agent is a polycarboxylate-based water-reducing agent.

[0011] Based on the above, the present invention further discloses a carbonation curing process for all-solid-waste non-combustion low-carbon concrete, comprising the following steps: S1. Weigh each raw material of the solid mixture according to the weight percentage, mix them evenly, add the additives and warm water, and stir to make concrete slurry. The temperature of the warm water is 25-55℃, and the water-cement ratio of the solid mixture to the warm water is 0.15-0.3. S2. Inject the concrete slurry into the mold, vibrate to form, and then pre-cur for 12-24 hours at a temperature of 20-30℃. S3. Place the pre-cured concrete billet into the carbonation curing equipment, introduce industrial exhaust gas for carbonation curing, the CO2 volume concentration in the industrial exhaust gas is 15-35%, the carbonation curing temperature is 30-60℃, the relative humidity is 40-70%, and the carbonation curing time is 24-72 hours. S4. After carbonization curing is completed, the concrete blank is removed and placed in a natural environment for curing for 7-14 days to obtain the finished product of all-solid waste non-fired low-carbon concrete.

[0012] Preferably, in step S3, the industrial exhaust gas is one or more of the exhaust gases emitted by thermal power plants, cement plants, and steel plants, and the exhaust gas undergoes dust removal and desulfurization pretreatment before being introduced.

[0013] In a further preferred embodiment, during the carbonization curing process in step S3, the CO2 concentration in the carbonization curing equipment is detected and exhaust gas is replenished every 6-12 hours to maintain the CO2 volume concentration within the set range.

[0014] In this invention, the carbonization curing equipment includes a carbonization chamber, an exhaust gas supply system, a temperature and humidity control system, and an exhaust gas recirculation system. The exhaust gas recirculation system can recycle the exhaust gas that has not been completely reacted in the carbonization chamber.

[0015] In this invention, concrete can be used to prepare non-load-bearing wall materials, thermal insulation boards, and roadbed filling materials.

[0016] In this invention, when used to prepare thermal insulation boards, 5-10% by weight of expanded perlite or vermiculite can be added to the concrete slurry.

[0017] After adopting the above-described technical improvements and preparation methods, the new technology of the present invention has the following advantages: 1. The technology of this invention achieves deep carbon reduction through a dual approach of "non-calcination process" and carbonization curing. Compared with traditional cement, which requires high-temperature calcination (carbon emissions of approximately 800-900 kg / t), the all-solid-waste non-calcination cementitious material does not require calcination, and carbon emissions can be reduced to below 75 kg / t, a reduction of over 90%. Simultaneously, the carbonization curing process can actively absorb CO2, with a carbon sequestration rate of over 15 kg per cubic meter of concrete. 2. The technology of this invention completely abandons natural limestone and clay, and instead uses bulk industrial solid waste such as steel slag, ore slag, desulfurization gypsum, carbide slag, and construction waste as raw materials. This not only reduces the exploitation of natural resources, but also solves the environmental pollution problem caused by solid waste stockpiling. There are 1 billion tons of industrial solid waste available for use in China every year. The raw materials are widely available and inexpensive, and have the potential for promotion and application at the 100 million ton level. 3. The material of this invention has stable mechanical properties, with a compressive strength of over 47.4 MPa after 28 days and a strength exceeding that of traditional cement concrete after 90 days. It also exhibits outstanding durability, excellent resistance to chloride ion penetration and freeze-thaw resistance, making it suitable for harsh environments such as marine engineering, tunnels, and water conservancy projects. Furthermore, it has low heat of hydration, making it suitable for large-volume concrete construction and effectively preventing temperature cracks. In addition, it has strong heavy metal solidification capabilities and can be used to co-process high-risk solid wastes such as fly ash and hazardous waste, thus expanding its environmental protection functions.

[0018] 4. The material of this invention is free from firing and steam curing, requiring no high-temperature calcination or steam curing, which significantly reduces energy consumption and equipment investment; and has obvious cost advantages, with the cost of cementitious materials being less than 50% of that of traditional cement, and does not rely on expensive chemical activators; at the same time, it can be adapted to industrial exhaust gas, and carbonization curing can directly utilize CO2-containing exhaust gas emitted by power plants, steel plants, etc., reducing gas capture costs. 5. The concrete prepared by this invention can be used for non-load-bearing walls, floors, permeable pavements, roadbed filling, mine filling, and precast components. By adjusting the formula and process, functional products with low shrinkage, high toughness, and thermal insulation can also be derived to meet the needs of multiple fields such as green building, sponge city, and ecological restoration. Attached Figure Description

[0019] Figure 1 The diagram shows the preparation steps of this invention; Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0021] A type of all-solid-waste non-fired low-carbon concrete is composed of a solid mixture and additives. The solid mixture comprises the following raw materials by weight percentage: 25-55% red mud, 20-45% carbide slag, 5-18% fly ash, 3-20% industrial gypsum, and 10-25% waste concrete powder. The additives include: alkali activator, foaming agent, water-reducing agent, and reinforcing fiber. The amount of alkali activator added is 3-12% of the mass of the solid mixture, the amount of foaming agent added is 0.3-1.5% of the mass of the solid mixture, the amount of water-reducing agent added is 0.3-0.8% of the mass of the solid mixture, and the amount of reinforcing fiber added is 0.2-1% of the mass of the solid mixture. The alkali activator is chemical waste, including one or more of the following: distillation waste liquid from the soda ash industry and red mud dealkalization waste liquid from the aluminum industry.

[0022] In this invention, the preferred red mud is any one or more of the red mud produced by the Bayer process, sintering process, or combined process; the waste concrete powder is obtained by crushing and grinding waste concrete and then passing it through a 120-180 mesh square hole sieve.

[0023] In this invention, the preferred reinforcing fiber is one or more of polypropylene fiber, polyvinyl alcohol fiber, and glass fiber, with a fiber length of 6-12 mm.

[0024] In this invention, the preferred foaming agent is one or more of animal protein foaming agents, plant protein foaming agents, and synthetic foaming agents; the water-reducing agent is a polycarboxylate-based water-reducing agent.

[0025] Combination Figure 1 As can be seen, based on the above, the present invention further discloses a carbonation curing process for all-solid-waste non-combustible low-carbon concrete, including the following steps: S1. Weigh each raw material of the solid mixture according to the weight percentage, mix them evenly, add the additives and warm water, and stir to make concrete slurry. The temperature of the warm water is 25-55℃, and the water-cement ratio of the solid mixture to the warm water is 0.15-0.3. S2. Inject the concrete slurry into the mold, vibrate to form, and then pre-cur for 12-24 hours at a temperature of 20-30℃. S3. Place the pre-cured concrete billet into the carbonation curing equipment, introduce industrial exhaust gas for carbonation curing, the CO2 volume concentration in the industrial exhaust gas is 15-35%, the carbonation curing temperature is 30-60℃, the relative humidity is 40-70%, and the carbonation curing time is 24-72 hours. S4. After carbonization curing is completed, the concrete blank is removed and placed in a natural environment for curing for 7-14 days to obtain the finished product of all-solid waste non-fired low-carbon concrete.

[0026] The industrial exhaust gas mentioned in step S3 is one or more of the exhaust gases emitted by thermal power plants, cement plants, and steel plants. The exhaust gas undergoes dust removal and desulfurization pretreatment before being introduced.

[0027] During the carbonization curing process in step S3, the CO2 concentration in the carbonization curing equipment is detected and exhaust gas is added every 6-12 hours to maintain the CO2 volume concentration within the set range.

[0028] In this invention, the carbonization curing equipment includes a carbonization chamber, an exhaust gas supply system, a temperature and humidity control system, and an exhaust gas circulation system. The exhaust gas circulation system can recycle the exhaust gas that has not been completely reacted in the carbonization chamber.

[0029] The concrete of this invention can be used to prepare non-load-bearing wall materials, thermal insulation boards, and roadbed filling materials.

[0030] When used to prepare thermal insulation boards, 5-10% by weight of expanded perlite or vermiculite can be added to the concrete slurry.

[0031] Example 1: Basic Formulation Validation Experiment (a) Experimental equipment Electronic balance (accuracy 0.01g), forced concrete mixer, standard concrete test mold (100mm×100mm×100mm), carbonation test chamber, pressure testing machine, constant temperature and humidity curing chamber, laser particle size analyzer.

[0032] (II) Experimental Materials Red mud (Bayer process, particle size distribution D50=25μm), carbide slag (particle size distribution D50=30μm), fly ash (Grade II, 12% residue on 45μm sieve), industrial gypsum (desulfurized gypsum, moisture content 5%), waste concrete powder (passed through 150-mesh square hole sieve), alkali activator (red mud dealkali desulfurization waste liquid, pH=13.5), animal protein foaming agent, polycarboxylate superplasticizer, polypropylene fiber (9mm in length), warm water (temperature 40℃).

[0033] (III) Formulation composition (by weight) Solid mixture: 35% red mud, 30% carbide slag, 10% fly ash, 8% industrial gypsum, 17% waste concrete powder; Additives: alkali activator (8% of solid mixture mass), foaming agent (0.8% of solid mixture mass), water-reducing agent (0.5% of solid mixture mass), polypropylene fiber (0.6% of solid mixture mass); water-cement ratio 0.22.

[0034] (iv) Experimental Procedure Weigh each ingredient according to the formula, pour the solid mixture into a forced mixer, and dry mix for 2 minutes until uniform.

[0035] Add warm water, alkali activator, and water-reducing agent, and stir for 3 minutes to make a uniform slurry. Then add foaming agent and polypropylene fiber, and continue stirring for 1 minute.

[0036] The slurry was injected into a standard mold, vibrated to form the mold, and then placed in a 25°C environment for pre-curing for 18 hours.

[0037] The pre-cured test blocks were placed in a carbonization test chamber, and exhaust gas from a thermal power plant (CO2 volume concentration of 25%) that had undergone dust removal and desulfurization pretreatment was introduced. The curing temperature was set at 45℃, the relative humidity at 55%, and the curing time was 48 hours. During this period, the exhaust gas was tested and replenished every 8 hours to maintain a stable CO2 concentration.

[0038] After carbonization curing, the test block is placed in a constant temperature and humidity curing chamber at 20℃ and 95% relative humidity for 10 days to obtain the finished test block.

[0039] (v) Experimental Data

[0040] Example 2: Optimization Experiment with High Solid Waste Content (a) Experimental equipment Same as Example 1.

[0041] (II) Experimental Materials Red mud (sintering method, particle size distribution D50=28μm), carbide slag (particle size distribution D50=32μm), fly ash (Grade I, 8% residue on 45μm sieve), industrial gypsum (phosphogypsum, moisture content 6%), waste concrete powder (passed through 120-mesh square hole sieve), alkali activator (distillation waste liquid from soda ash industry, pH=13.2), plant protein foaming agent, polycarboxylate superplasticizer, polyvinyl alcohol fiber (length 8mm), warm water (temperature 50℃).

[0042] (III) Formulation composition (by weight) Solid mixture: 30% red mud, 25% carbide slag, 12% fly ash, 10% industrial gypsum, 23% waste concrete powder; Additives: alkali activator (10% of solid mixture mass), foaming agent (0.6% of solid mixture mass), water-reducing agent (0.4% of solid mixture mass), polyvinyl alcohol fiber (0.8% of solid mixture mass); water-cement ratio 0.20.

[0043] (iv) Experimental Procedure Similar to Example 1, the carbonization curing time is extended to 60 hours, and the CO2 volume concentration in the exhaust gas is adjusted to 30%.

[0044] (v) Experimental Data

[0045] Example 3: Comparative Experiment of Replacing C40 Concrete (a) Experimental equipment Similar to Example 1, but with the addition of a flexural testing machine and a freeze-thaw cycle test chamber.

[0046] (II) Experimental Materials Red mud (combined method, particle size distribution D50=26μm), carbide slag (particle size distribution D50=31μm), fly ash (Grade I, 7% residue on 45μm sieve), industrial gypsum (desulfurized gypsum, moisture content 4%), waste concrete powder (passed through 180-mesh square hole sieve), alkali activator (compound of red mud dealkali desulfurization waste liquid and soda ash distillation waste liquid, pH=13.8), synthetic foaming agent, polycarboxylate superplasticizer, glass fiber (length 10mm), warm water (temperature 45℃).

[0047] (III) Formulation composition (by weight) Solid mixture: 28% red mud, 22% carbide slag, 15% fly ash, 12% industrial gypsum, 23% waste concrete powder; Additives: alkali activator (12% of solid mixture mass), foaming agent (0.5% of solid mixture mass), water-reducing agent (0.3% of solid mixture mass), glass fiber (1.0% of solid mixture mass); water-cement ratio 0.18.

[0048] (iv) Experimental Procedure Similar to Example 1, the carbonization curing temperature was adjusted to 55°C, the relative humidity to 45%, and the curing time to 72 hours. Simultaneously, flexural strength and freeze-thaw cycle durability were tested.

[0049] (v) Experimental Data

[0050] Example 4: Compatibility Verification Experiment with Different Solid Wastes (a) Experimental equipment Same as Example 1.

[0051] (II) Experimental Materials Red mud (Bayer process, particle size distribution D50=27μm), carbide slag (particle size distribution D50=33μm), fly ash (Grade II, 15% residue on 45μm sieve), industrial gypsum (fluorogypsum, moisture content 7%), waste concrete powder (passed through 150-mesh square hole sieve), alkali activator (red mud dealkali desulfurization waste liquid, pH=13.4), animal protein foaming agent, polycarboxylate superplasticizer, polypropylene fiber (length 12mm), warm water (temperature 35℃).

[0052] (III) Formulation composition (by weight) Solid mixture: 40% red mud, 28% carbide slag, 8% fly ash, 7% industrial gypsum, 17% waste concrete powder; Additives: alkali activator (7% of solid mixture mass), foaming agent (1.0% of solid mixture mass), water-reducing agent (0.6% of solid mixture mass), polypropylene fiber (0.5% of solid mixture mass); water-cement ratio 0.25.

[0053] (iv) Experimental Procedure Similar to Example 1, the exhaust gas used is cement plant exhaust gas (CO2 volume concentration 20%), and the carbonization curing time is adjusted to 36 hours.

[0054] (v) Experimental Data

[0055] In the four specific embodiments described above, Embodiment 1 is a basic formula verification. Through reasonable raw material compounding and process parameter settings, it achieves full utilization of solid waste, and the concrete performance meets the requirements of C30 concrete, with a significant reduction in carbon emissions. Embodiment 2 further improves the concrete strength by adjusting the solid waste ratio and curing parameters, while maintaining 100% solid waste utilization and achieving an even greater reduction in carbon emissions. After formula and process optimization in Embodiment 3, the concrete strength reaches the C40 grade, while possessing excellent flexural strength and durability, and can replace traditional high-grade concrete, reducing carbon emissions by more than 80%, fully demonstrating the advanced nature of this technology. Embodiment 4 verifies the adaptability of the technology to different types of solid waste. Even when using fly ash and fluorogypsum of slightly lower quality, concrete that meets engineering requirements can still be prepared, providing a feasible solution for the resource utilization of solid waste in different regions.

Claims

1. A type of all-solid-waste, non-fired, low-carbon concrete, characterized in that, It is composed of a solid mixture and additives. The solid mixture includes the following raw materials by weight percentage: 25-55% red mud, 20-45% calcium carbide slag, 5-18% fly ash, 3-20% industrial gypsum, and 10-25% waste concrete powder. The additives include: alkali activator, foaming agent, water-reducing agent, and reinforcing fiber. The amount of alkali activator added is 3-12% of the mass of the solid mixture, the amount of foaming agent added is 0.3-1.5% of the mass of the solid mixture, the amount of water-reducing agent added is 0.3-0.8% of the mass of the solid mixture, and the amount of reinforcing fiber added is 0.2-1% of the mass of the solid mixture. The alkali activator is chemical waste, including one or more of the following: distillation waste liquid from the soda ash industry and red mud dealkali removal waste liquid from the aluminum industry.

2. The all-solid-waste, non-fired, low-carbon concrete according to claim 1, characterized in that, The red mud is any one or more of the red mud produced by the Bayer process, sintering process, or combined process; the waste concrete powder is obtained by crushing and grinding waste concrete and then passing it through a 120-180 mesh square hole sieve.

3. The all-solid-waste, non-fired, low-carbon concrete according to claim 1, characterized in that, The reinforcing fiber is one or more of polypropylene fiber, polyvinyl alcohol fiber, and glass fiber, with a fiber length of 6-12 mm.

4. The all-solid-waste, non-fired, low-carbon concrete according to claim 1, characterized in that, The foaming agent is one or more of animal protein foaming agents, plant protein foaming agents, and synthetic foaming agents; the water-reducing agent is a polycarboxylate water-reducing agent.

5. A carbonation curing process for all-solid-waste non-fired low-carbon concrete as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Weigh each raw material of the solid mixture according to the weight percentage, mix them evenly, add the additives and warm water, and stir to make concrete slurry. The temperature of the warm water is 25-55℃, and the water-cement ratio of the solid mixture to the warm water is 0.15-0.

3. S2. Inject the concrete slurry into the mold, vibrate to form, and then pre-cur for 12-24 hours at a temperature of 20-30℃. S3. Place the pre-cured concrete billet into the carbonation curing equipment, introduce industrial exhaust gas for carbonation curing, the CO2 volume concentration in the industrial exhaust gas is 15-35%, the carbonation curing temperature is 30-60℃, the relative humidity is 40-70%, and the carbonation curing time is 24-72 hours. S4. After carbonization curing is completed, the concrete blank is removed and placed in a natural environment for curing for 7-14 days to obtain the finished product of all-solid waste non-fired low-carbon concrete.

6. The carbonization curing process according to claim 5, characterized in that, The industrial exhaust gas mentioned in step S3 is one or more of the exhaust gases emitted by thermal power plants, cement plants, and steel plants. The exhaust gas undergoes dust removal and desulfurization pretreatment before being introduced.

7. The carbonization curing process according to claim 5, characterized in that, During the carbonization curing process in step S3, the CO2 concentration in the carbonization curing equipment is detected and exhaust gas is added every 6-12 hours to maintain the CO2 volume concentration within the set range.

8. The carbonization curing process according to claim 5, characterized in that, The carbonization curing equipment includes a carbonization chamber, an exhaust gas supply system, a temperature and humidity control system, and an exhaust gas recirculation system. The exhaust gas recirculation system can recycle the exhaust gas that has not been completely reacted in the carbonization chamber.

9. An application of the all-solid-waste non-fired low-carbon concrete as described in any one of claims 1-4, characterized in that, The concrete can be used to prepare non-load-bearing wall materials, thermal insulation boards, and roadbed filling materials.

10. The application according to claim 9, characterized in that, When used to prepare thermal insulation boards, 5-10% by weight of expanded perlite or vermiculite can be added to the concrete slurry.

Images