Red mud-humus synergistic pyrolysis modified multifunctional ecological concrete and preparation method thereof

Abstract

The invention discloses red mud-humus synergistic pyrolysis modified multifunctional ecological concrete and a preparation method thereof. The ecological concrete comprises the following components in parts by weight: 390-410 parts of coarse aggregate, 140-180 parts of a cementing material, 30-40 parts of a modified material obtained by synergistic pyrolysis of red mud and humus according to a mass ratio of 1: 1, 60-70 parts of water and 6-8 parts of a polycarboxylate superplasticizer, wherein the cementing material is formed by mixing silica fume and cement. According to the invention, by fully utilizing the synergistic effect of two solid wastes, namely the red mud and the humus, in-situ compounding of a mineral-carbon interface is realized in a high-temperature pyrolysis process, so that the mechanical property, the ecological vegetation performance and the environmental restoration capability of the concrete are remarkably improved, and meanwhile, high-valued utilization of industrial solid wastes and organic wastes is realized.

Description

Technical Field

[0001] This invention belongs to the field of concrete technology, specifically relating to a multifunctional ecological concrete modified by synergistic pyrolysis of red mud and humus, and its preparation method. Background Technology

[0002] Eco-concrete, as a green material with potential, partially replaces cement with solid waste, which not only reduces cement usage and alleviates resource pressure but also achieves a unity between ecological landscape and structural function. Its surface is naturally covered with vegetation, combining aesthetics with ecological restoration benefits. However, the following key technical bottlenecks still exist in the engineering applications of eco-concrete: (1) Limited mechanical strength: High porosity design is beneficial to vegetation growth, but at the same time weakens the density and mechanical properties of concrete; (2) Poor vegetation effect: Ecological concrete lacks the key nutrients necessary for the healthy growth of vegetation, which directly affects the vegetation performance and its ecological restoration and beautification functions; (3) Limited functional perspective: Existing research focuses on mechanical and vegetation performance, and pays less attention to its potential value in environmental restoration, especially in the treatment of heavy metal pollution. Summary of the Invention

[0003] This invention aims to overcome the problems of insufficient strength, poor vegetation performance, and limited environmental remediation capacity of existing ecological concrete based on the resource utilization of solid waste, and proposes a multifunctional ecological concrete modified by synergistic pyrolysis of red mud and humus and its preparation method.

[0004] The technical solution of this invention is as follows: A multifunctional eco-concrete modified by synergistic pyrolysis of red mud and humus, comprising the following components in parts by weight: 390-410 parts coarse aggregate; 140-180 parts of cementitious material; 30-40 parts of synergistic pyrolysis modified material; 60-70 parts water; 6-8 parts of polycarboxylate superplasticizer; The cementitious material is mainly composed of silica fume and cement, with a mass ratio of silica fume to cement of (1~1.5):15; Synergistic pyrolysis modified materials are produced by mixing red mud and humus at a mass ratio of 1:1 and then heating under an inert atmosphere at 500-800 °C. oIt is prepared by pyrolysis of C for 1-4 hours. During this process, the pyrolysis products of humic substances have a reducing and activating effect on iron and aluminum oxides in red mud, promoting their valence state transformation and enhancing their reactivity; the mineral components of red mud have a catalytic and pore-forming effect on the carbonization process of humic substances, thereby forming a porous mineral-carbon composite structure. The introduction of this modified material can significantly improve the pore structure stability of concrete, enhance the interfacial bonding performance, and improve the overall mechanical properties, vegetation performance, and heavy metal ion fixation capacity.

[0005] The ratio of red mud to humus is 1:1, which is based on maximizing the material balance and synergistic effect of the two during pyrolysis. If the ratio is too low, there will be insufficient carbon source, resulting in weak pore-forming and reduction effects; if the ratio is too high, there will be too many mineral phases, which will easily agglomerate and will not be conducive to uniform compounding.

[0006] On the one hand, red mud is a large-scale industrial solid waste generated during the extraction of alumina from bauxite. It is rich in active oxides such as iron, aluminum, and calcium, and has good potential for ion exchange and heavy metal adsorption. However, its dense pore structure and poor interfacial reactivity limit its application performance. On the other hand, humus is a complex organic waste formed by the decomposition of animal and plant remains by microorganisms. It is rich in carbon, nitrogen, phosphorus, and various oxygen-containing functional groups, and has the ability to complex, reduce, and fix heavy metals. However, when used alone, it has insufficient thermal stability and poor mechanical support.

[0007] To fully leverage the advantages of both components and overcome their respective limitations, this invention achieves deep integration and structural optimization of the mineral and carbon phases through synergistic compounding and pyrolysis modification. During pyrolysis, the H2, CO, and volatile organic compounds generated from the pyrolysis of humic substances can partially reduce Fe(III) (such as hematite Fe2O3) in red mud to more reactive Fe(II) (such as magnetite Fe3O4 or aragonite FeO) at 500-800℃, and promote the formation of amorphous Al2O3. This process enhances the reactivity and specific surface area of ​​the minerals. Iron and aluminum oxides in the red mud catalyze and pore-forming reactions of the humic substances, promoting the ordered graphitic microcrystal formation of pyrolyzed carbon and inhibiting secondary coking of tar, thereby forming abundant mesopores and macropores on the carbon skeleton. Simultaneously, the molten red mud silicate components can encapsulate carbon particles, forming a robust "mineral-carbon core-shell structure," improving the mechanical strength and chemical stability of the composite material. The pyrolysis process does not completely destroy the oxygen-containing functional groups (such as -COOH, -OH) of humic substances. Instead, they are partially preserved and transformed within a specific temperature range (such as 500-800℃). They interact strongly with the newly formed OH- on the surface of red mud minerals, thus constructing a synergistic adsorption / complexation center of "organic functional group-metal active site".

[0008] When this synergistic pyrolysis material is incorporated into concrete, it not only promotes the generation of hydration products and improves pore structure and interfacial bonding, thereby significantly enhancing mechanical strength, but also provides a "nutrient pool-carbon source" system for plant growth and microbial reproduction by slowly releasing nutrients such as carbon, nitrogen, and phosphorus, thus enhancing vegetation performance and ecological restoration capabilities. Simultaneously, the synergistic effect of active oxides and organic functional groups in the material can effectively immobilize heavy metal ions through mechanisms such as adsorption, complexation, co-precipitation, and reduction fixation, achieving in-situ remediation and stabilization of polluted environments.

[0009] Furthermore, the cement is sulfoaluminate cement.

[0010] Furthermore, the silica fume has a particle size of 0.15~0.3 μm. It is mainly used to fill the gaps between cement particles, and its highly reactive SiO2 reacts with the cement hydration product Ca(OH)2 to generate more CSH gel. When compounded with sulfoaluminate cement, it can synergistically promote early strength development and optimize pore structure.

[0011] Furthermore, the coarse aggregate is gravel with a particle size of 20-30 mm. This can improve the pore structure and permeability while ensuring mechanical properties.

[0012] Furthermore, the inert atmosphere is a nitrogen atmosphere, the flow rate is 100~300 mL / min, and the heating rate is 5~10℃ / min.

[0013] A method for preparing a multifunctional eco-concrete modified by synergistic pyrolysis of red mud and humus includes the following steps: (1) Preparation of synergistic pyrolysis modified materials: After drying the humic substance to constant weight, it is mixed and ground with red mud at a mass ratio of 1:1. The mixture is placed in a tube furnace and heated to 500-800℃ at 5-10℃ / min under an inert atmosphere and kept at the temperature for 1-4 hours to obtain mineral-carbon composite modified materials. When the pyrolysis temperature is below 500℃, the carbonization of the humic substance is incomplete and the activation of the red mud is insufficient. When the temperature is above 800℃, the carbon skeleton is excessively graphitized and a large number of functional groups are lost. Furthermore, the red mud may be excessively sintered, leading to a decrease in activity and pore closure.

[0014] (2) Concrete batching and mixing: Mix the synergistic pyrolysis modified material with cementitious materials, water and polycarboxylate superplasticizer evenly, then add coarse aggregate and mix into a uniform mixture; (3) Molding and curing: The mixture is put into the mold and compacted by vibration. After being covered with plastic film and left to stand for 24 hours, it is demolded and cured in an environment with a temperature of 18~22℃ and a relative humidity of ≥95% for 5~8 days. The selected curing conditions can ensure that the hydration reaction is fully carried out, which can effectively avoid drying shrinkage and cracking, and also help the strength to grow steadily.

[0015] Furthermore, the inert atmosphere described in the preparation method is a nitrogen atmosphere, and the flow rate is 100~300 mL / min.

[0016] The application of multifunctional ecological concrete modified by red mud-humus synergistic pyrolysis in ecological slope protection, ecological bank protection or polluted soil remediation projects can achieve synergistic functions of structural load-bearing, vegetation restoration and heavy metal pollution environmental remediation, while also demonstrating the comprehensive benefits of solid waste resource utilization.

[0017] The eco-concrete of this invention is not a simple superposition of multiple functions, but rather achieves internal coupling and synergistic enhancement of functions through the core component of red mud-humus synergistic pyrolysis modified material. Its porous structure provides planting space while optimized pore morphology (such as reduced interconnected pores and enhanced pore walls) and mineral-carbon interfaces enhance matrix density, thereby synergistically improving mechanical strength while ensuring high vegetability. Simultaneously, this porous structure and abundant surface sites serve as both slow-release carriers of nutrients and efficient traps for heavy metal ions, enabling the planting and environmental remediation processes to mutually promote each other: organic matter secreted by plant roots further activates the fixation sites on the material surface, while the heavy metals fixed by the material reduce plant toxicity, forming a synergistic remediation chain of material fixation-plant absorption-microbial transformation.

[0018] A red mud-humic synergistic pyrolysis modified material is prepared by mixing red mud and humic substances at a mass ratio of 1:1 and pyrolyzing them at 500-800℃ for 1-4 hours under a nitrogen atmosphere at a temperature of 5-10℃ / min.

[0019] An inert atmosphere is a necessary condition to ensure that red mud and humus undergo "mutual catalytic activation reactions" at high temperatures (such as the reduction of metal oxides by organic matter and the catalytic formation of pores by metal oxides). In an aerobic environment, the reaction pathway will be completely changed, mainly becoming their respective oxidation processes, and the "mineral-carbon composite interface structure" cannot be formed.

[0020] Application of a red mud-humus synergistic pyrolysis modified material as a concrete reinforcing agent, soil conditioner, or heavy metal adsorbent.

[0021] Compared with the prior art, the beneficial effects of the present invention are: This invention fully utilizes the synergistic effect of red mud and humic substances, two types of solid waste, to achieve in-situ composite formation at the mineral-carbon interface during high-temperature pyrolysis. This significantly improves the mechanical properties, ecological vegetation performance, and environmental remediation capabilities of concrete, while simultaneously realizing the high-value utilization of industrial solid waste and organic waste. This technology not only improves the microstructure and interfacial compactness of concrete but also endows the material with excellent heavy metal adsorption and fixation properties, combining sustainability, economy, and environmental protection advantages, demonstrating significant application potential and innovative value.

[0022] This invention achieves efficient resource utilization of industrial solid waste and organic waste through the synergistic pyrolysis of red mud and humus, and constructs a multifunctional ecological concrete system with high strength, excellent ecological properties and environmental restoration capabilities, providing a new technical path for green building materials and ecological environment governance. Attached Figure Description

[0023] Figure 1 Photographs of the ecological concrete specimens prepared for this invention; Figure 2 The images shown are scanning electron microscope (SEM) images of representative embodiments and comparative examples of the present invention, including a comparison of the microstructures of Examples 2, 5, and 7 and Comparative Examples 1, 3, and 7. Figure 3 These are the compressive strength diagrams for Examples 1-7 and Comparative Examples 1-7 of the present invention; Figure 4 This is a diagram showing the plant biomass of Examples 1-7 and Comparative Examples 1-7 in this invention; Figure 5 The diagram shows the heavy metal removal efficiency of Examples 1-7 and Comparative Examples 1-7 in this invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0025] Example 1: This example provides a multifunctional ecological concrete modified by synergistic pyrolysis of red mud and humus. The proportions of each component by weight are as follows: 400 kg of gravel (particle size 20~30 mm), 145 kg of cementitious material (including 13 kg of silica fume (particle size 0.15~0.3 μm) and 132 kg of cement), 30 kg of synergistic pyrolysis modified material, 65 kg of water, and 7 kg of polycarboxylate superplasticizer.

[0026] The preparation steps are as follows: (1) After drying the humus to constant weight, grind it evenly with red mud at a mass ratio of 1:1 to obtain a mixture; (2) The mixture is placed in a quartz tube furnace and heated at 700°C under nitrogen protection. o Under C conditions, synergistic pyrolysis was carried out for 2 hours to obtain red mud-humus synergistic pyrolysis modified material; (3) After the synergistic pyrolysis modified material and the cementitious material are mixed evenly, a specified amount of water is added and stirred to form a mixed slurry I; (4) Add polycarboxylate superplasticizer and stir evenly to obtain mixed slurry II; (5) Mix the mixed slurry II with the coarse gravel thoroughly to obtain a uniform mixture; (6) Fill the mold with the mixture and shake it to form the shape. Cover it with plastic film and let it stand for 24 hours before demolding. (7) After demolding, at 20 o C. Cure in an environment with a relative humidity of 95% or higher for 5 days.

[0027] Example 2: The difference between this example and Example 1 is that the preparation steps, other components and dosages remain the same, but the dosage of the synergistic pyrolysis modified material is increased from 30 kg to 35 kg.

[0028] This embodiment provides a multifunctional ecological concrete modified by synergistic pyrolysis of red mud and humus. The proportions of each component by weight are as follows: 400 kg of gravel (particle size 20~30 mm), 145 kg of cementitious material (including 13 kg of silica fume (particle size 0.15~0.3 μm) and 132 kg of cement), 35 kg of synergistic pyrolysis modified material, 65 kg of water, and 7 kg of polycarboxylate superplasticizer.

[0029] The prepared concrete samples are as follows Figure 1 As shown.

[0030] Example 3: The difference between this example and Example 1 is that the preparation steps, other components and dosages remain the same, but the dosage of the synergistic pyrolysis modified material is increased from 30 kg to 40 kg.

[0031] This embodiment provides a multifunctional ecological concrete modified by synergistic pyrolysis of red mud and humus. The components are mixed in the following proportions by weight: 400 kg of gravel (particle size 20~30 mm), 145 kg of cementitious material (including 13 kg of silica fume (particle size 0.15~0.3 μm) and 132 kg of cement), 40 kg of synergistic pyrolysis modified material, 65 kg of water, and 7 kg of polycarboxylate superplasticizer.

[0032] Example 4: The difference between this example and Example 2 is that, while keeping the preparation conditions and dosage of the synergistic pyrolysis modified material consistent, the proportions of other components have been adjusted, while the preparation method remains unchanged.

[0033] This embodiment provides a multifunctional ecological concrete modified by synergistic pyrolysis of red mud and humus. The proportions of each component by weight are as follows: 390 kg of gravel (particle size 20~30 mm), 160 kg of cementitious material (including 10 kg of silica fume (particle size 0.15~0.3μm) and 150 kg of cement), 35 kg of synergistic pyrolysis modified material, 60 kg of water, and 6 kg of polycarboxylate superplasticizer.

[0034] Example 5: The difference between this example and Example 2 is that, while keeping the preparation conditions and dosage of the synergistic pyrolysis modified material consistent, the proportions of other components have been adjusted, while the preparation method remains unchanged.

[0035] This embodiment provides a multifunctional ecological concrete modified by synergistic pyrolysis of red mud and humus. The components are mixed in the following proportions by weight: 410 kg of gravel (particle size 20~30 mm), 180 kg of cementitious material (including 14 kg of silica fume (particle size 0.15~0.3 μm) and 166 kg of cement), 35 kg of synergistic pyrolysis modified material, 70 kg of water, and 8 kg of polycarboxylate superplasticizer.

[0036] Example 6: The difference between this example and Example 2 is that only the pyrolysis temperature and / or pyrolysis time of the synergistic pyrolysis modified material are adjusted, while the proportions of other components are the same as in Example 2.

[0037] This embodiment provides a multifunctional ecological concrete modified by synergistic pyrolysis of red mud and humus. The proportions of each component by weight are as follows: 400 kg of gravel (particle size 20~30 mm), 145 kg of cementitious material (including 13 kg of silica fume (particle size 0.15~0.3 μm) and 132 kg of cement), 35 kg of synergistic pyrolysis modified material, 65 kg of water, and 7 kg of polycarboxylate superplasticizer.

[0038] The preparation steps are as follows: (1) After drying the humus to constant weight, grind it evenly with red mud at a mass ratio of 1:1 to obtain a mixture; (2) The mixture is placed in a quartz tube furnace and heated at 500°C under nitrogen protection. o Under C conditions, synergistic pyrolysis was carried out for 1 hour to obtain red mud-humus synergistic pyrolysis modified material; (3) After the synergistic pyrolysis modified material and the cementitious material are mixed evenly, a specified amount of water is added and stirred to form a mixed slurry I; (4) Add polycarboxylate superplasticizer and stir evenly to obtain mixed slurry II; (5) Mix the mixed slurry II with the gravel thoroughly to obtain a uniform mixture; (6) Fill the mold with the mixture and shake it to form the shape. Cover it with plastic film and let it stand for 24 hours before demolding. (7) After demolding, at 20 o C. Cure in an environment with a relative humidity of 95% or higher for 5 days.

[0039] Example 7: The difference between this example and Example 2 is that only the pyrolysis temperature and / or pyrolysis time of the synergistic pyrolysis modified material are adjusted, while the proportions of other components are the same as in Example 2.

[0040] This embodiment provides a multifunctional ecological concrete modified by synergistic pyrolysis of red mud and humus. The proportions of each component by weight are as follows: 400 kg of gravel (particle size 20~30 mm), 145 kg of cementitious material (including 13 kg of silica fume (particle size 0.15~0.3 μm) and 132 kg of cement), 35 kg of synergistic pyrolysis modified material, 65 kg of water, and 7 kg of polycarboxylate superplasticizer.

[0041] The preparation steps are as follows: (1) After drying the humus to constant weight, grind it evenly with red mud at a mass ratio of 1:1 to obtain a mixture; (2) The mixture is placed in a quartz tube furnace and heated at 800°C under nitrogen protection. o Under C conditions, synergistic pyrolysis was carried out for 4 hours to obtain red mud-humus synergistic pyrolysis modified material; (3) After the synergistic pyrolysis modified material and the cementitious material are mixed evenly, a specified amount of water is added and stirred to form a mixed slurry I; (4) Add polycarboxylate superplasticizer and stir evenly to obtain mixed slurry II; (5) Mix the mixed slurry II with the gravel thoroughly to obtain a uniform mixture; (6) Fill the mold with the mixture and shake it to form the shape. Cover it with plastic film and let it stand for 24 hours before demolding. (7) After demolding, at 20 o C. Cure in an environment with a relative humidity of 95% or higher for 5 days.

[0042] Comparative Example 1: This comparative example provides a common ecological concrete, which differs from Example 1 in that it does not contain any synergistic pyrolysis modifier. The proportions of each component by weight are as follows: 400 kg of gravel (particle size 20~30 mm), 145 kg of cementitious material (including 13 kg of silica fume (particle size 0.15~0.3 μm) and 132 kg of cement), 65 kg of water, and 7 kg of polycarboxylate. The cementitious material is a mixture of silica fume and cement.

[0043] (1) Mix the cementitious material with water to form mixed slurry I; (2) Add water-reducing agent and stir evenly to obtain mixed slurry II; (3) Mix the mixed slurry II with the gravel thoroughly, pack it into the mold and compact it, cover it with plastic film and let it stand for 24 hours before demolding; (4) After demolding, at 20 o C. Cure in an environment with a relative humidity of 95% or higher for 5 days.

[0044] Comparative Example 2: This comparative example provides an eco-concrete modified with only pyrolytic humic substances. The difference from Example 2 is that only pyrolytic humic substances are added. The proportions of each component by weight are as follows: 400 kg of gravel (particle size 20~30 mm), 145 kg of cementitious material (including 13 kg of silica fume (particle size 0.15~0.3 μm) and 132 kg of cement), 35 kg of pyrolytic humic substances, 65 kg of water, and 7 kg of polycarboxylate superplasticizer. The cementitious material is a mixture of silica fume and cement.

[0045] The preparation method of pyrolysis humus-modified eco-concrete in this comparative example includes the following steps: (1) Dry and grind the humus evenly to obtain pretreated humus; (2) The pretreated humus is placed in a quartz tube furnace and heated at 700°C under nitrogen protection. o Synergistic pyrolysis was carried out under C conditions for 2 hours to obtain a single humic pyrolysis modified material; (3) After the single humic pyrolysis modified material and the cementitious material are mixed evenly, a specified amount of water is added and stirred to form a mixed slurry I; (4) Add polycarboxylate superplasticizer and stir evenly to obtain mixed slurry II; (5) Mix the mixed slurry II with the gravel thoroughly to obtain a uniform mixture; (6) Fill the mold with the mixture and shake it to form the shape. Cover it with plastic film and let it stand for 24 hours before demolding. (7) After demolding, at 20 o C. Cure in an environment with a relative humidity of 95% or higher for 5 days.

[0046] Comparative Example 3: This comparative example provides an eco-friendly concrete modified with only pyrolytic red mud. The difference from Example 2 is that only pyrolytic red mud is added. The proportions of each component by weight are as follows: 400 kg of gravel (particle size 20~30 mm), 145 kg of cementitious material (including 13 kg of silica fume (particle size 0.15~0.3 μm) and 132 kg of cement), 35 kg of pyrolytic red mud, 65 kg of water, and 7 kg of polycarboxylate superplasticizer. The cementitious material is a mixture of silica fume and cement.

[0047] The preparation method of pyrolysis humus-modified eco-concrete in this comparative example includes the following steps: (1) Dry and grind the red mud evenly to obtain pretreated humus; (2) The pretreated red mud is placed in a quartz tube furnace and heated at 700°C under nitrogen protection. o Synergistic pyrolysis was carried out under C conditions for 2 hours to obtain a single humic pyrolysis modified material; (3) After the single red mud pyrolysis modified material and the cementitious material are mixed evenly, a specified amount of water is added and stirred to form a mixed slurry I; (4) Add polycarboxylate superplasticizer and stir evenly to obtain mixed slurry II; (5) Mix the mixed slurry II with the gravel thoroughly to obtain a uniform mixture; (6) Fill the mold with the mixture and shake it to form the shape. Cover it with plastic film and let it stand for 24 hours before demolding. (7) After demolding, at 20 o C. Cure in an environment with a relative humidity of 95% or higher for 5 days.

[0048] Comparative Example 4: The difference between this comparative example and Example 1 is that only the dosage of the synergistic pyrolysis modified material is adjusted, while the other components and dosages remain the same. The dosage of the synergistic pyrolysis modified material is reduced from 30 kg in Example 1 to 20 kg, making it lower than the 30-40 parts range specified in this invention, while the preparation method remains unchanged.

[0049] This embodiment provides a multifunctional ecological concrete modified by synergistic pyrolysis of red mud and humus. The proportions of each component by weight are as follows: 400 kg of gravel (particle size 20~30 mm), 145 kg of cementitious material (including 13 kg of silica fume (particle size 0.15~0.3 μm) and 132 kg of cement), 20 kg of synergistic pyrolysis modified material, 65 kg of water, and 7 kg of polycarboxylate superplasticizer.

[0050] Comparative Example 5: The difference between this comparative example and Example 1 is that only the dosage of the synergistic pyrolysis modified material is adjusted, while the other components and dosages remain the same. The dosage of the synergistic pyrolysis modified material is increased from 30 kg in Example 1 to 50 kg, making it higher than the 30-40 parts range specified in this invention, while the preparation method remains unchanged.

[0051] This embodiment provides a multifunctional ecological concrete modified by synergistic pyrolysis of red mud and humus. The proportions of each component by weight are as follows: 400 kg of gravel (particle size 20~30 mm), 145 kg of cementitious material (including 13 kg of silica fume (particle size 0.15~0.3 μm) and 132 kg of cement), 20 kg of synergistic pyrolysis modified material, 65 kg of water, and 7 kg of polycarboxylate superplasticizer.

[0052] Comparative Example 6: The difference between this comparative example and Example 2 is that the proportion of the synergistic pyrolysis modified material remains unchanged, and only the pyrolysis temperature and time are adjusted to be lower than the range defined in this invention; the remaining components and dosages are the same as in Example 2.

[0053] This embodiment provides a multifunctional ecological concrete modified by synergistic pyrolysis of red mud and humus. The proportions of each component by weight are as follows: 400 kg of gravel (particle size 20~30 mm), 145 kg of cementitious material (including 13 kg of silica fume (particle size 0.15~0.3 μm) and 132 kg of cement), 35 kg of synergistic pyrolysis modified material, 65 kg of water, and 7 kg of polycarboxylate superplasticizer.

[0054] The preparation steps are as follows: (1) After drying the humus to constant weight, grind it evenly with red mud at a mass ratio of 1:1 to obtain a mixture; (2) The mixture is placed in a quartz tube furnace and heated at 400°C under nitrogen protection. o Under C conditions, synergistic pyrolysis was carried out for 0.5 hours to obtain red mud-humus synergistic pyrolysis modified material; (3) After the synergistic pyrolysis modified material and the cementitious material are mixed evenly, a specified amount of water is added and stirred to form a mixed slurry I; (4) Add polycarboxylate superplasticizer and stir evenly to obtain mixed slurry II; (5) Mix the mixed slurry II with the gravel thoroughly to obtain a uniform mixture; (6) Fill the mold with the mixture and shake it to form the shape. Cover it with plastic film and let it stand for 24 hours before demolding. (7) After demolding, at 20 o C. Cure in an environment with a relative humidity of 95% or higher for 5 days.

[0055] Comparative Example 7: The difference between this comparative example and Example 2 is that the proportion of the synergistic pyrolysis modified material remains unchanged, and only the pyrolysis temperature and time are adjusted to be higher than the range defined in this invention; the remaining components and dosages are the same as in Example 2.

[0056] This embodiment provides a multifunctional ecological concrete modified by synergistic pyrolysis of red mud and humus. The proportions of each component by weight are as follows: 400 kg of gravel (particle size 20~30 mm), 145 kg of cementitious material (including 13 kg of silica fume (particle size 0.15~0.3 μm) and 132 kg of cement), 35 kg of synergistic pyrolysis modified material, 65 kg of water, and 7 kg of polycarboxylate superplasticizer.

[0057] The preparation steps are as follows: (1) After drying the humus to constant weight, grind it evenly with red mud at a mass ratio of 1:1 to obtain a mixture; (2) The mixture is placed in a quartz tube furnace and heated at 900°C under nitrogen protection. o Under C conditions, the material was subjected to synergistic pyrolysis for 5 hours to obtain red mud-humus synergistic pyrolysis modified material; (3) After the synergistic pyrolysis modified material and the cementitious material are mixed evenly, a specified amount of water is added and stirred to form a mixed slurry I; (4) Add polycarboxylate superplasticizer and stir evenly to obtain mixed slurry II; (5) Mix the mixed slurry II with the gravel thoroughly to obtain a uniform mixture; (6) Fill the mold with the mixture and shake it to form the shape. Cover it with plastic film and let it stand for 24 hours before demolding. (7) After demolding, at 20 o C. Cure in an environment with a relative humidity of 95% or higher for 5 days.

[0058] The component content and process conditions of each embodiment and comparative example are shown in Table 1 below.

[0059] Table 1 Examples and Comparative Examples

[0060] Performance testing: Comparison of Examples 1-7 and Comparative Examples 1-7. (1) SEM Analysis: To more intuitively compare the effects of different modification methods on the microstructure of concrete, this study selected six representative samples for SEM testing. Examples 2, 5, and 7 represent typical states of synergistic pyrolysis modified materials under appropriate dosages, different matrix ratios, and different pyrolysis conditions, respectively; Comparative Examples 1, 3, and 7 are used to demonstrate the microstructure of unmodified materials, single-component modified materials, and materials whose pyrolysis conditions deviate from the optimal range. This combination can comprehensively reflect the microstructure regulation law of synergistic pyrolysis materials, and the results are as follows: Figure 2 As shown.

[0061] from Figure 2 It can be seen that the hydration products in Comparative Example 1 are unevenly distributed, the matrix porosity is high, and there are many irregular pores and microcracks inside. In Comparative Examples 2 and 3, the number of pores is slightly reduced due to the filling effect of the modified components, but local loose areas are still visible. In contrast, the slurry structure of Examples 1-3 is significantly denser, the C-S-H gel distribution is more continuous, and the pores are significantly reduced. This indicates that the material obtained by the synergistic pyrolysis of red mud and humic substances can promote the generation and accumulation of hydration products, thereby improving the density and overall structural stability of the slurry.

[0062] Example 7 and Comparative Example 7 also showed significant differences in microstructure. Example 7 used a suitable pyrolysis temperature and time, resulting in a more complete surface structure of the material, uniform distribution of fine pores, and continuous growth of hydration products in the slurry to form a relatively dense structure. In contrast, Comparative Example 7, due to pyrolysis conditions deviating from the optimal range, experienced localized sintering or excessive shrinkage on the material surface, leading to uneven distribution of hydration products, relatively more pores, and significantly weaker overall density than Example 7.

[0063] (2) Concrete compressive strength: In accordance with the relevant provisions of the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T 50081-2019), the compressive strength of each group of concrete specimens was tested, and the results are shown in Table 2 and... Figure 3 As shown.

[0064] Table 2 Comparison of Concrete Compressive Strength

[0065] From Table 2 and Figure 3 It can be seen that the 28-day compressive strength of ordinary ecological concrete without the addition of modified materials (Comparative Example 1) is 8.9 MPa, which is the lowest among all samples. When a single humic pyrolysis material (Comparative Example 2) or a single red mud pyrolysis material (Comparative Example 3) is added, the 28-day compressive strength increases to 9.7 MPa and 9.5 MPa, respectively, which are approximately 9.0% and 6.7% higher than those in Comparative Example 1, indicating that a single modified material can improve the mechanical properties of concrete to a certain extent.

[0066] When the modified material obtained by the synergistic pyrolysis of red mud and humus was used (represented by Example 2), the 28-day compressive strength was significantly increased to 13.6 MPa, an increase of approximately 52.8% compared to Comparative Example 1, and an increase of 40.2% and 43.2% compared to Comparative Examples 2 and 3, respectively. This result indicates that red mud and humus produce a significant synergistic effect during the synergistic pyrolysis process. The mineral-carbon composite structure formed can more effectively promote the hydration reaction of cementitious materials, improve the morphology of the interfacial transition zone, and increase the density of the overall structure, thereby significantly enhancing the compressive strength of concrete.

[0067] When the dosage of the modified material deviates from the recommended range of this invention (Comparative Examples 4 and 5), its 28-day compressive strength is only 8.3 MPa and 8.6 MPa, respectively, both significantly lower than that of the embodiments of this invention. The main reason is that when the dosage is too low, the active components are insufficient, making it difficult to form an effective hydration promoting and filling effect; while when the dosage is too high, it will destroy the uniformity of the slurry structure and increase the porosity, thereby weakening the overall reinforcing effect.

[0068] Furthermore, when the pyrolysis conditions deviated from the recommended range of this invention (Comparative Example 6 and Comparative Example 7), the compressive strength of the samples decreased significantly, with the 28-day strength being only 7.8 MPa and 7.9 MPa, further verifying the importance and rationality of the pyrolysis temperature and time range defined in this invention.

[0069] (3) Concrete vegetation performance: The plant growth experiment was conducted in a greenhouse with a light duration of approximately 16 hours and a temperature of approximately 28 degrees Celsius. o C; Darkroom time is approximately 8 hours, temperature is approximately 18 degrees Celsius. oC; Ambient relative humidity approximately 75%. The pores on the surface of the eco-concrete bricks prepared in the example were filled with a mixture of natural soil and nutrient soil, and covered with an approximately 8 cm thick layer of the mixture. Grass seeds were then evenly sown on top. Biomass was measured periodically during plant growth, and the results are shown in Table 3 and... Figure 4 As shown.

[0070] Table 3 Comparison of Plant Biomass

[0071] From Table 3 and Figure 4 It can be seen that different modification methods have a significant impact on the vegetation performance of ecological concrete. Ordinary ecological concrete (Comparative Example 1) has the lowest plant biomass, at 2.5 g and 4.2 g after 15 and 30 days, respectively. After modification with pyrolytic humus alone (Comparative Example 2), the plant biomass increased to 2.7 g and 5.5 g, respectively, an increase of approximately 8% and 31% compared to Comparative Example 1; after modification with pyrolytic red mud alone (Comparative Example 3), the plant biomass further increased to 2.9 g and 5.8 g, an increase of approximately 16% and 38%.

[0072] When modified materials obtained from the synergistic pyrolysis of red mud and humus were used (Examples 1-3), the vegetation performance was optimal, with plant biomass reaching 3.4-3.7 g and 6.7-7.1 g after 15 and 30 days, respectively. Taking Example 2 as an example, the biomass was increased by approximately 48% and 69% compared to ordinary ecological concrete (Comparative Example 1), respectively. The results indicate that red mud and humus produce a synergistic effect during pyrolysis, and the resulting modified materials effectively improve the moisture retention and nutrient supply environment of the concrete surface, significantly promoting root growth and aboveground biomass accumulation, thereby improving the overall vegetation performance of the ecological concrete.

[0073] To further verify the applicability of the modification conditions of this invention, experiments were conducted with different dosages and different pyrolysis conditions (Examples 4-7 and Comparative Examples 4-7). It can be seen that when the dosage of the modified material or the pyrolysis temperature and time deviated from the conditions set by this invention, the control group (Comparative Examples 4-7) all exhibited lower vegetative growth performance; while Examples 4-7, although still within the scope of this invention, showed slight fluctuations in plant biomass compared to Examples 1-3, indicating that the modification effect is affected by changes in dosage and pyrolysis process.

[0074] Overall, all embodiments within the scope of this invention are superior to the corresponding comparative examples that deviate from the scope, further demonstrating that the modified material composition and pyrolysis process range defined by this invention are reasonable and necessary.

[0075] (4) Concrete Remediation of Heavy Metal Pollution in the Environment: The heavy metal removal experiment was conducted using a simulated contaminated soil environment. First, contaminated soil samples were collected to determine the initial heavy metal concentration. Then, the prepared ecological concrete bricks were laid in the soil, and samples were taken after 15 and 30 days of curing to determine the residual heavy metal concentration. The heavy metal removal efficiency was calculated based on the initial and residual concentrations, and the results are shown in Table 4. Figure 5 As shown.

[0076] Table 4 Comparison of Heavy Metal Removal Efficiency

[0077] From Table 4 and Figure 5 It can be seen that different modifying materials have a significant impact on the heavy metal removal efficiency of eco-friendly concrete. Ordinary eco-friendly concrete (Comparative Example 1) has the lowest removal efficiency, at 12% and 23% after 15 and 30 days, respectively. After adding a single pyrolytic humic material modifier (Comparative Example 2), the removal efficiency increased to 16% and 30%, respectively, which is about 33% and 30% higher than Comparative Example 1. After adding a single pyrolytic red mud modifier (Comparative Example 3), the removal efficiency was 15% and 28%, respectively, which is also a significant improvement over Comparative Example 1.

[0078] Examples 1-3 using red mud-humic synergistic pyrolysis modified materials showed the best performance, with removal efficiencies of 22%-24% and 37%-40% after 15 and 30 days, respectively. These figures represent improvements of approximately 83%-100% and 61%-74% compared to ordinary ecological concrete (Comparative Example 1), approximately 38%-50% and 23%-33% compared to pyrolysis humic material alone (Comparative Example 2), and approximately 47%-60% and 32%-43% compared to red mud alone (Comparative Example 3). The results indicate that red mud and humic substances can form a mineral-carbon composite interface structure with high specific surface area and abundant functional groups during synergistic pyrolysis, significantly enhancing the material's heavy metal adsorption and stabilization capabilities, thereby improving the in-situ remediation performance of ecological concrete for polluted environments.

[0079] To verify the rationality of the parameter range defined in this invention, Examples 4-7 with different dosages and different pyrolysis conditions, as well as corresponding comparative examples deviating from the range, were further established. The results show that although Examples 4-7 still maintained a certain removal capacity, their efficiency was slightly lower than that of Examples 1-3; conversely, the comparative examples 4-7, which deviated from the condition range of this invention, had even lower removal efficiency, and even showed significant attenuation. This comparative result indicates that the synergistic pyrolysis material composition and pyrolysis condition range set in this invention are key to achieving stable and efficient heavy metal removal performance.

[0080] In summary, the eco-friendly concrete of the present invention has the following beneficial effects: (1) Improve mechanical strength The material obtained from the synergistic pyrolysis of red mud and humus possesses both a porous structure and the characteristics of active minerals. Its surface contains abundant functional groups such as carboxyl and phenolic hydroxyl groups, which can promote cement hydration and optimize the pore structure. Humus forms a colloidal support network in the composite system, partially compensating for the strength loss caused by high porosity, thereby significantly improving the matrix density, compressive strength, and structural stability of eco-concrete. Simultaneously, this process achieves the stable reuse of red mud, a highly alkaline industrial solid waste, demonstrating good environmental safety.

[0081] (2) Enhance plant growth performance Synergistic pyrolysis modified materials are rich in essential plant nutrients such as carbon, nitrogen, and phosphorus, and their slow-release properties help plants to quickly establish themselves and grow continuously. Humic acid and organic acids in the pyrolysis products of humus can improve the ecological environment of the concrete surface; while the mineral components and trace elements provided by red mud promote the symbiosis of plant roots and microorganisms, constructing a synergistic mechanism of "microorganisms-plants-humus-red mud", thereby significantly improving the vegetative performance and ecological restoration capacity of concrete.

[0082] (3) Improve the environmental heavy metal remediation capacity During pyrolysis, red mud-humus synergistic pyrolysis materials form porous mineral-carbon composite structures rich in oxygen-functional groups. These structures can effectively immobilize heavy metal ions in the soil through multiple mechanisms such as adsorption, complexation, and co-precipitation, reducing their mobility and bioavailability. Simultaneously, the humus carbon skeleton provides carbon sources and growth sites for soil microorganisms, promoting the biostabilization and transformation of metal ions, significantly enhancing the environmental remediation function and sustainable application value of eco-concrete.

[0083] (4) It has both economic and environmental benefits. Red mud and humus are both renewable or recyclable solid waste resources, widely available and inexpensive to obtain. This invention achieves the synergistic high-value utilization of these two types of waste, partially replacing cement components, reducing concrete production costs by approximately 20%, and decreasing carbon dioxide emissions. Each cubic meter of eco-concrete can utilize approximately 70 kg of red mud and humus, achieving the goal of "treating waste with waste" through recycling, thus balancing both economic and ecological benefits.

[0084] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A multifunctional ecological concrete modified by red mud-humus synergistic pyrolysis, characterized in that, The components include the following weight parts: Coarse aggregate 390-410 parts; Cementitious material 140-180 parts; Synergistic pyrolysis modified material 30-40 parts; Water 60-70 parts; Polycarboxylic acid water reducer 6-8 parts; The cementitious material is mainly composed of silica fume and cement, and the mass ratio of silica fume to cement is (1-1.5):

15. The synergistic pyrolysis modification material is a mixture of red mud and humus at a mass ratio of 1:1, and the mixture is pyrolyzed at 500-800 o C pyrolysis for 1-4 hours.

2. The multifunctional ecological concrete modified by red mud-humus synergistic pyrolysis according to claim 1, characterized in that, The cement is sulphoaluminate cement.

3. The multifunctional ecological concrete modified by red mud-humus synergistic pyrolysis according to claim 1, characterized in that, The particle size of the silica fume is 0.15-0.3 μm.

4. The multifunctional ecological concrete modified by red mud-humus synergistic pyrolysis according to claim 1, characterized in that, The coarse aggregate is gravel with a particle size of 20-30 mm.

5. The multifunctional ecological concrete modified by red mud-humus synergistic pyrolysis according to claim 1, characterized in that, The inert atmosphere is a nitrogen atmosphere, the flow rate is 100-300 mL / min, and the heating rate is 5-10℃ / min.

6. The application of the red mud-humus synergistic pyrolysis modified multifunctional ecological concrete in ecological slope protection, ecological bank protection or contaminated soil remediation engineering according to any one of claims 1-5.

7. A method for preparing the multifunctional ecological concrete modified by red mud-humus synergistic pyrolysis according to any one of claims 1-5, characterized in that, The steps include: (1) Preparation of synergistic pyrolysis modified material: After drying the humus to constant weight, mix and grind it with red mud at a mass ratio of 1:1, place it in a tube furnace, and heat it to 500-800℃ at a rate of 5-10℃ / min under an inert atmosphere, and keep it at this temperature for 1-4 hours to obtain a mineral-carbon composite modified material; (2) Concrete batching and mixing: Mix the obtained synergistic pyrolysis modified material with cementitious material, water and polycarboxylic acid water reducer uniformly, then add coarse aggregate and mix into a uniform mixture; (3) Molding and curing: Fill the mixture into a mold and shake it to form, cover it with plastic film and let it stand for 24 hours, then demold it and cure it in an environment with a temperature of 18-22℃ and a relative humidity of ≥95% for 5-8 days.

8. The method for preparing the multi-functional ecological concrete modified by bauxite residue-humus synergistic pyrolysis according to claim 7, characterized in that, The inert atmosphere is a nitrogen atmosphere, the flow rate is 100-300 mL / min.

9. A red mud-humus synergic pyrolysis modified material, characterized by, The red mud and humus are mixed at a mass ratio of 1:1, pyrolyzed at a rate of 5-10℃ / min to 500-800℃ under a nitrogen atmosphere for 1-4 hours.

10. The application of the red mud-humus synergistic pyrolysis modified material as a concrete reinforcing agent, soil conditioner or heavy metal adsorbent according to claim 9.

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