Wood-microorganism synergistic eco-concrete and preparation method thereof

Abstract

This invention discloses an eco-friendly concrete with synergistic effects between wood and microorganisms and its preparation method. The concrete comprises cementitious materials, modified wood-based materials, a symbiotic microbial community of wood functional microorganisms, and auxiliary additives. The microbial community is a symbiotic system of white-rot fungi and nitrogen-fixing bacteria. The modified wood-based material consists of alkali-treated and carbonized wood fibers and sawdust with a porosity of 60-80%. This eco-friendly concrete composite material can be applied to building structures, slope restoration, or marine engineering.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a high-performance ecological concrete composite material utilizing the synergistic symbiosis of wood-functional microorganisms and its preparation method, applicable to the fields of green building, ecological restoration and sustainable building materials. Background Technology

[0002] Concrete, as the most critical building material, traditionally uses silicate cement as its core binder. To overcome the shortcomings of traditional concrete, such as its susceptibility to cracking and lack of self-healing properties, the industry has developed microbial concrete technology. This technology typically involves introducing a single microorganism, such as Bacillus pasteurellii, to induce the production of calcium carbonate, thereby repairing cracks. Furthermore, the large amounts of sawdust and wood fibers generated during wood processing are also valuable solid waste resources that can be utilized in the building materials sector.

[0003] However, the existing technological systems still have significant shortcomings. On the one hand, the single bacterial species relied upon in microbial concrete cannot effectively interact within the concrete. This results in unstable self-healing performance, high costs, and a function limited to crack sealing, making it difficult to actively optimize the matrix microenvironment. On the other hand, the highly promising wood processing waste is only recycled at a low value in current technologies. Its natural porous structure, as a carrier for microorganisms, has not yet been fully explored to synergistically enhance concrete, and efficient integration with microbial remediation technologies has not been achieved. Therefore, developing a new material that can synergistically utilize waste biomass resources, overcome the environmental adaptability limitations of bacterial species, and improve the overall performance of concrete has become a crucial direction that the industry urgently needs to address. Summary of the Invention

[0004] In view of the above-mentioned problems in the existing technology, the purpose of this invention is to improve the mechanical properties, self-healing ability and ecological benefits of concrete through the synergistic symbiosis of wood functional microorganisms and wood-based materials, so as to realize the high-value utilization of waste resources.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A wood-microbial synergistic eco-concrete, comprising the following components (by weight percentage):

[0007] Cementing materials: 43-52% silicate cement, 13-15% fly ash; Wood-based materials: 8-11% modified wood fiber, 5-7% carbonized wood chips; Functional microbial community: a symbiotic community of wood-decaying fungi (white rot fungi) and nitrogen-fixing fungi loaded in the wood-based materials, the content of the functional microbial community is 1-4%; Auxiliary additives: 14-16% lightweight aggregate (expanded perlite), 3-4% nano silica, 1-2% activator (calcium lactate).

[0008] Functional Microbial Synergistic Mechanism: This invention constructs a highly efficient and synergistic composite system: In the cementitious material, the pozzolanic reaction of fly ash continuously consumes the highly alkaline calcium hydroxide produced by cement hydration, not only improving later-stage strength but also creating a gradually milder microenvironment for microbial survival; the modified wood-based material forms a multi-level porous carrier, providing physical shelter and calcium ion enrichment sites for microorganisms, while the white-rot fungi-nitrogen-fixing bacteria symbiotic community it supports also achieves efficient colonization and targeted repair through metabolism. Specifically, the white-rot fungi degrade lignin to provide a carbon source and locally buffer alkalinity for the nitrogen-fixing bacteria, while the nitrogen-fixing bacteria utilize nutrients to induce calcium carbonate deposition and feed back nitrogen, achieving efficient colonization and targeted repair; simultaneously, the auxiliary additives, such as nano-silica, refine the pores to enhance matrix density, calcium lactate acts as a multifunctional activator to simultaneously provide calcium source and pH buffer, and lightweight aggregates construct a continuous water-air transport network to ensure the long-term activity of deep-layer microorganisms. All components are closely coupled through material exchange, environmental regulation, and functional complementarity.

[0009] As an improvement, the functional microbial community is a symbiotic system composed of white-rot fungi and nitrogen-fixing bacteria in a 1:1 ratio. Previous experimental optimization revealed that when the ratio of viable white-rot fungi to nitrogen-fixing bacteria is 1:1, their metabolic activities reach an optimal balance. The organic acids produced by the white-rot fungi during lignin degradation buffer the local microenvironment pH, providing suitable survival conditions for the nitrogen-fixing bacteria and supplying them with a carbon source; conversely, the nitrogen-fixing bacteria fix atmospheric nitrogen, providing a nitrogen source for the white-rot fungi, forming a stable mutually beneficial symbiotic relationship. Compared to other ratios (such as 2:1 or 1:2), the 1:1 ratio shows the highest calcium carbonate mineralization efficiency of the microorganisms and increases the survival rate by more than 30% in the alkaline environment of concrete.

[0010] As an improvement, the modified wood fiber is a porous material obtained by soaking wood fibers and sawdust in a 3-5% NaOH solution for 24 hours, followed by calcination at 300-400℃ under nitrogen protection for 1-3 hours or more. A NaOH concentration of 3-5% can effectively dissolve lignin and hemicellulose, exposing the internal pores of the fiber. If the concentration is too low, the modification effect will be insufficient; if it is too high, excessive degradation of cellulose will lead to a decrease in strength. The calcination temperature of 300-400℃ falls within the range of mild carbonization. At this temperature, residual volatiles can be removed and a stable microporous and mesoporous structure can be formed. If the temperature is below 300℃, carbonization will be incomplete and the porosity will be low; if it is above 400℃, the fiber skeleton may be damaged. The calcination time of 1-3 hours can be adjusted according to the material thickness to ensure sufficient pore development. Through the above modification, the porosity of the wood-based material can reach 60-80%, and the specific surface area is significantly increased, providing an ideal carrier for microbial attachment.

[0011] As an improvement, the activator is calcium lactate with a purity ≥99.5%. Lactate ions can serve as an auxiliary carbon source for microorganisms and slightly acidify the environment during metabolism, thus helping to buffer the pH inside the concrete; calcium ions are essential raw materials for microbial-induced calcium carbonate deposition.

[0012] As an improvement, the lightweight aggregate is expanded perlite with a particle size of 2-4 mm and a bulk density of 80-120 kg / m³. This specification of expanded perlite is chosen to construct a continuous water and air transport network: the 2-4 mm particle size forms macroscopic channels in the concrete, facilitating the transport of oxygen, water, and nutrients, thereby maintaining the long-term activity of internal microorganisms; the bulk density of 80-120 kg / m³ ensures the lightweight and porous characteristics of the aggregate, reducing the apparent density of the concrete without affecting the mechanical properties of the matrix due to excessively low strength.

[0013] The preparation method of wood-microorganism synergistic ecological concrete includes the following steps:

[0014] Step 1: Pretreatment of wood-based materials. Wood fibers and wood chips are treated with alkali (soaked in 5% NaOH solution for 24 hours) and then carbonized (calcined at 300-400℃ under nitrogen protection for 1 hour) to obtain porous modified wood-based materials, namely modified wood fibers.

[0015] Step 2: Loading of microbial community. White rot fungus (Phanerochaetechrysosporium) and nitrogen-fixing bacteria (Azotobacter vinelandii) are mixed in a 1:1 ratio and inoculated into modified wood-based material. The mixture is then cultured at 25-30℃ for 48 hours to form a microbial-wood carrier composite.

[0016] Step 3: Concrete mixture preparation: Dry mix cement, fly ash, lightweight aggregate, and nano-silica for 3-5 minutes; add microbial-wood carrier composite and activator, and slowly add water (water-cement ratio of 0.3-0.4, i.e., the mass ratio of water to cementitious material is 0.3:0.4) and stir until uniform;

[0017] Step 4: After casting and molding, cure for 7 days under conditions of humidity ≥90% and temperature 25℃ to promote microbial activity and mineralization reaction.

[0018] As an improvement, step S2 employs a vacuum-pressure cyclic impregnation process at a pressure of 0.08-0.1 MPa, repeated 2-3 times. This process aims to achieve deep microbial loading within the carrier: air is extracted from the carrier pores via vacuum, followed by pressure to allow the bacterial solution to permeate. Repeating this process 2-3 times ensures the bacterial solution fully fills the multi-level pores, increasing the viable bacterial load per unit carrier. Experiments show that using this process increases the viable bacterial load of modified wood fibers by approximately two times compared to atmospheric pressure impregnation, which is beneficial for the initial colonization of microorganisms in concrete.

[0019] As an improvement, in step S3, a planetary mixer is used to mix at a speed of 45-60 r / min for 8-10 min. The choice of a lower speed and a moderate time is to ensure that the components are mixed evenly while minimizing mechanical shear damage to the "microorganism-wood carrier composite" and avoiding structural damage or loss of microbial activity caused by high-speed mixing.

[0020] As an improvement, in step S4, the concrete is covered with a membrane to retain water for 48-72 hours after initial setting. This step creates a critical window of water activation for microorganisms: after the concrete has initially set, there is still a large amount of free water inside. Covering with a membrane to retain water can prevent surface moisture evaporation and ensure that sufficient water is provided for microorganisms to initiate metabolism and initial colonization in the early stages of curing. This is crucial for their long-term survival and function within the concrete.

[0021] Compared with the prior art, the present invention has at least the following advantages:

[0022] By constructing a micro-ecosystem centered on modified wood materials and a symbiotic system of white-rot fungi and nitrogen-fixing bacteria, this invention overcomes the limitations of single-species bacteria in concrete, achieving a triple synergy of "carrier customization, bacterial symbiosis, and matrix reinforcement." Under this technical approach, the material can achieve a designable strength of C30. Furthermore, this invention uses fly ash, sawdust, and other solid waste as primary raw materials, resulting in a high solid waste content and significantly reducing the carbon footprint. This represents a shift from "resource consumption" to "recycling," providing a high-performance, self-maintaining, and low-environmental-impact solution for green building and ecological restoration projects. Detailed Implementation

[0023] Example 1: This example provides an eco-friendly concrete with synergistic effect of wood and microorganisms and its preparation method. The components, calculated as a percentage of the total mass of all solid raw materials (i.e., cementitious materials, wood-based materials, functional microbial communities, and auxiliary additives), are as follows:

[0024] Silicate cement: 43.0%, fly ash: 15.0%, modified wood fiber: 11.0%, carbonized wood chips: 7.0%, functional microbial community composed of white-rot fungi and nitrogen-fixing bacteria in a 1:1 ratio of live bacteria: 4.0%, expanded perlite: 15.0%, nano silica: 4.0%, calcium lactate: 1.0%.

[0025] Preparation method:

[0026] Raw material pretreatment: Wood fibers were soaked in 5% NaOH solution for 24 hours, and then calcined at 350℃ for 1 hour under nitrogen protection to obtain modified wood fibers. Wood chips were calcined at 350℃ for 1 hour under nitrogen protection to obtain carbonized wood chips.

[0027] Microbial loading: White-rot fungi and nitrogen-fixing bacteria were mixed in a 1:1 ratio and inoculated into modified wood fibers using a vacuum-pressure cyclic impregnation process (0.08 MPa, 3 cycles). The mixture was then cultured at 28℃ and ≥95% humidity for 48 h to obtain a microbial-wood carrier composite.

[0028] Mixing and Molding: Weigh out silicate cement, fly ash, carbonized wood chips, expanded perlite, and nano-silica according to the above proportions, and dry mix them in a planetary mixer for 4 minutes. Then add the microbial-wood carrier composite and calcium lactate, followed by mixing water (water-cement ratio, 0.3), and mix at 45 r / min for 8 minutes until homogeneous to obtain the concrete mixture. Subsequently, pour and vibrate the mixture to form the final product.

[0029] Curing: After molding, cure for 7 days at a temperature of 25℃ and a humidity of ≥90%, and cover with a film to retain water for 72 hours after initial setting.

[0030] Performance testing: According to the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T 50081), the 28-day compressive strength of the material in this embodiment is 26.2 MPa.

[0031] The modified wood fibers prepared according to the method of Example 1 were characterized: the specific surface area was determined to be 180-250 m² / g by nitrogen adsorption-desorption method (according to GB / T19587), and the T2 NMR spectrum showed that there were a large number of micron-sized pores on the surface and inside, confirming the formation of a multi-level pore structure, which provided sufficient space for microbial loading.

[0032] Example 2: This example provides another eco-friendly concrete composite material, the composition of which is as follows:

[0033] Silicate cement: 48.0%, fly ash: 15.0%, modified wood fiber: 10.0%, carbonized wood chips: 6.0%, functional microbial community composed of white-rot fungi and nitrogen-fixing bacteria in a 1:1 ratio of live bacteria: 3.0%, expanded perlite: 14.0%, nano silica: 3.0%, calcium lactate: 1.0%.

[0034] Preparation method:

[0035] Raw material pretreatment: Wood fibers were soaked in 3% NaOH solution for 24 hours, and then calcined at 350℃ for 1 hour under nitrogen protection to obtain modified wood fibers. Wood chips were calcined at 350℃ for 1 hour under nitrogen protection to obtain carbonized wood chips.

[0036] Microbial loading: White-rot fungi and nitrogen-fixing bacteria were mixed in a 1:1 ratio and inoculated into modified wood fibers using a vacuum-pressure cyclic impregnation process (0.08 MPa, 3 cycles). The mixture was then cultured at 28℃ and ≥95% humidity for 48 h to obtain a microbial-wood carrier composite.

[0037] Mixing and Molding: Weigh out silicate cement, fly ash, carbonized wood chips, expanded perlite, and nano-silica according to the above proportions, and dry mix them in a planetary mixer for 4 minutes. Then add the microbial-wood carrier composite and calcium lactate, followed by mixing water (water-cement ratio, 0.35), and mix at 45 r / min for 8 minutes until homogeneous to obtain the concrete mixture. Subsequently, pour and vibrate the mixture to form the final product.

[0038] Curing: After molding, cure for 7 days at a temperature of 25℃ and a humidity of ≥90%, and cover with a film to retain water for 72 hours after initial setting.

[0039] Performance testing: According to the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T 50081), the 28-day compressive strength of the material in this embodiment is 32.9 MPa, which meets the requirements of C30 grade.

[0040] Example 3: This example provides another eco-friendly concrete composite material, the composition of which is as follows:

[0041] Silicate cement: 52.0%, fly ash: 13.0%, modified wood fiber: 8%, carbonized wood chips: 5.0%, functional microbial community composed of white-rot fungi and nitrogen-fixing bacteria in a 1:1 ratio of live bacteria: 2%, expanded perlite: 16.0%, nano-silica: 2%, calcium lactate: 2%.

[0042] Preparation method:

[0043] Raw material pretreatment: Wood fibers were soaked in 4% NaOH solution for 24 hours, and then calcined at 350℃ for 1 hour under nitrogen protection to obtain modified wood fibers. Wood chips were calcined at 350℃ for 1 hour under nitrogen protection to obtain carbonized wood chips.

[0044] Microbial loading: White-rot fungi and nitrogen-fixing bacteria were mixed in a 1:1 ratio and inoculated into modified wood fibers using a vacuum-pressure cyclic impregnation process (0.08 MPa, 3 cycles). The mixture was then cultured at 28℃ and ≥95% humidity for 48 h to obtain a microbial-wood carrier composite.

[0045] Mixing and Molding: Weigh out silicate cement, fly ash, carbonized wood chips, expanded perlite, and nano-silica according to the above proportions, and dry mix them in a planetary mixer for 4 minutes. Then add the microbial-wood carrier composite and calcium lactate, followed by mixing water (water-cement ratio, 0.4), and mix at 45 r / min for 8 minutes until homogeneous to obtain the concrete mixture. Subsequently, pour and vibrate the mixture to form the final product.

[0046] Curing: After molding, cure for 7 days at a temperature of 25℃ and a humidity of ≥90%, and cover with a film to retain water for 72 hours after initial setting.

[0047] Performance testing: According to the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T 50081), the 28-day compressive strength of the material in this embodiment is 36.8 MPa, which meets the requirements of C30 grade.

[0048] Examples 4 to 10 use the same process steps as Example 1, the difference being the proportions of the raw materials (Table 1) and the process parameters for each step (Table 2).

[0049] Table 1

[0050] The following ingredients are listed as a percentage by weight.

[0051]

[0052] Table 2

[0053]

[0054] Table 3 shows the performance test results of the wood-microbial synergistic ecological concrete obtained in Examples 4-10.

[0055] Table 3

[0056]

[0057] As shown in Table 3, a systematic analysis of the 28-day compressive strength of 10 examples with different mix proportions indicates that the white-rot fungus-nitrogen-fixing bacteria symbiotic system constructed in this invention can achieve good compatibility with the matrix within a reasonable mix proportion range. The influence of microbial content exhibits a clear regularity: under the premise of cement content ≥48%, C30 grade strength can be achieved with microbial community content ranging from 1% to 3%, and the strength increases with increasing cement proportion, indicating that the white-rot fungus-nitrogen-fixing bacteria symbiotic system has good compatibility with the high-cementing material matrix, and its metabolic activity does not significantly weaken the strength. When the microbial content is 2% and the cement content reaches 52% (Example 3), the strength reaches a peak of 36.8 MPa, while the strength is 34.4 MPa with 1% microbial content at the same cement content (Example 8), indicating that an appropriate amount of microorganisms can positively contribute to the later strength through degradation and mineralization deposition of the woody carrier. However, when the cement content is ≤45% and the microbial content is too high (Examples 1 and 7), the strength drops to 26-28 MPa, revealing that microbial metabolism exacerbates the increase in matrix porosity when the cementing material is insufficient. Therefore, the microbial content needs to be matched with the amount of cement used. It is recommended to use 1% to 3% microorganisms and 48% to 52% cement to ensure that the C30 strength meets the standard and to give full play to the self-repair and ecological functions of microorganisms, which reflects the core technology of "carrier-microbial community-matrix" triple synergy.

Claims

1. A wood-microbial synergistic eco-concrete, characterized in that, Includes the following components, by weight percentage: Cementitious materials: 43-52% silicate cement, 13-15% fly ash; Wood-based materials: 8-11% modified wood fiber, 5-7% carbonized wood chips; Functional microbial community: including a symbiotic community of wood-decaying fungi and nitrogen-fixing bacteria loaded on wood-based materials, wherein the weight percentage of the functional microbial community is 1-4%; Auxiliary additives: 14-16% lightweight aggregate, 3-4% nano-silica, 1-2% activator.

2. The eco-concrete with synergistic effect of wood and microorganisms according to claim 1, characterized in that, The functional microbial community is a symbiotic system composed of white-rot fungi and nitrogen-fixing bacteria in a 1:1 ratio.

3. The wood-microbial synergistic ecological concrete according to claim 1, characterized in that, The modified wood fiber is a porous material obtained by soaking wood fiber and wood chips in 3-5% NaOH solution for 24 hours and then calcining them at 300-400℃ under nitrogen protection for 1-3 hours.

4. The wood-microbial synergistic ecological concrete according to claim 1, characterized in that, The activator is calcium lactate with a purity of ≥99.5%.

5. The wood-microbial synergistic ecological concrete according to claim 1, characterized in that, The lightweight aggregate is expanded perlite with a particle size of 2-4 mm and a bulk density of 80-120 kg / m³.

6. A method for preparing the wood-microbial synergistic ecological concrete according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Wood-based material pretreatment: Wood fibers and wood chips are modified to obtain modified wood fibers; The modification method involves soaking the sample in 3-5% NaOH solution for 24 hours, followed by calcination at 300-400℃ under nitrogen protection for 1-3 hours. S2: Microbial community loading: White rot fungi and nitrogen-fixing bacteria were mixed in a 1:1 ratio and inoculated into modified wood fibers. The mixture was cultured at 25-30℃ for 48-72h to obtain a microbial-wood carrier composite. S3: Weigh each component according to the weight percentage specified in claim 1, dry mix the cementitious material, lightweight aggregate, and nano-silica for 3-5 minutes, add the microbial-wood carrier composite and activator, add water and stir until uniform to obtain concrete mixture, wherein the water-cement ratio is 0.3-0.

4. S4: Curing: After the concrete mixture is poured and formed, it shall be cured for 7 days under conditions of humidity ≥90% and temperature 20-25℃.

7. The method for preparing eco-concrete with synergistic effect of wood microorganisms according to claim 6, characterized in that, In step S2, a vacuum-pressure cyclic impregnation process is used, with a pressure of 0.08-0.1 MPa and 2-3 cycles.

8. The method for preparing eco-concrete with synergistic effect of wood microorganisms according to claim 6, characterized in that, In step S3, a planetary mixer is used to mix at a speed of 45-60 r / min for 8-10 minutes.

9. The method for preparing eco-concrete with synergistic effect of wood microorganisms according to claim 6, characterized in that, In step S4, after initial setting, cover with a membrane to retain water for 48-72 hours.

10. The application of the wood-microorganism synergistic ecological concrete according to any one of claims 1-5 in green building and ecological restoration projects.

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