Gangue-based biological self-repairing brick based on synergistic modification of tannic acid-waste rubber and mineralization of basophilic bacteria and preparation method of gangue-based biological self-repairing brick

Abstract

The invention relates to the technical field of mixed modified coal gangue, in particular to a coal gangue-based biological self-repairing brick based on tannic acid-waste rubber synergistic modification and basophilic bacteria mineralization and a preparation method thereof. Comprising the following steps: firstly, crushing coal gangue, steel slag and waste rubber by using a rock crusher, and sieving; calcining and cooling the coal gangue powder; the preparation method comprises the following steps: drying grape skin, crushing, carrying out Soxhlet extraction, filtering, carrying out rotary evaporation on filtrate, removing ethanol to obtain a tannic acid crude product, and recrystallizing and purifying; mixing and stirring the heat-treated coal gangue powder, steel slag, fly ash, lime, water glass, waste rubber powder, porous fly ash microspheres and tannic acid according to a certain proportion to obtain green brick mud; and pouring the green brick mud into a mold, pressing by using a hydraulic brick press, and then putting into a concrete curing box for standard curing. The self-repairing brick disclosed by the invention can be used for self-repairing when cracks are generated.

Description

Technical Field

[0001] The present invention relates to the technical field of mixed modified coal gangue, in particular to a coal gangue-based biological self-repairing brick based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization and a preparation method thereof. Background Art

[0002] Gangue is solid waste generated during coal mining and washing. Large amounts of gangue accumulation not only occupy land resources but also can cause environmental pollution, such as soil and water contamination. Traditional treatment methods have limitations, necessitating the exploration of new and efficient approaches for its utilization.

[0003] With the development of the industrial and automotive sectors, the production of waste rubber continues to increase. Waste rubber is difficult to degrade naturally, its accumulation also takes up a lot of space, and poses a fire hazard. Therefore, the proper reuse of waste rubber has become a pressing issue.

[0004] Furthermore, traditional masonry structures are prone to developing microscopic cracks due to long-term exposure to temperature fluctuations, humidity changes, and load pressure. If these cracks are not repaired promptly, they can accelerate the penetration of water and chemicals, leading to corrosion of steel bars, a decrease in structural strength, and even safety hazards.

[0005] At the same time, the construction industry is experiencing a growing demand for sustainable building materials. Traditional building materials often rely on the extensive extraction of natural resources, such as stone and clay, which places significant pressure on the environment. The development and utilization of waste materials to create building materials aligns with the concept of sustainable development. Furthermore, traditional building materials have shortcomings in certain performance areas, such as freeze-thaw resistance and toughness. New materials or additives are needed to improve the overall performance of building materials to meet the requirements of building structures in diverse environments. Summary of the Invention

[0006] The present invention considers that coal gangue after high-temperature activation contains a large amount of silicon and aluminum, which can react and complex with steel slag and tannic acid under alkaline conditions to produce a gelling reaction. At the same time, the waste rubber powder can improve the toughness and impact resistance of the material, reduce the porosity of the material, and enhance the freeze-thaw cycle resistance of the recycled brick. At the same time, the metabolism and secretion of exopolysaccharides by extreme alkaliphilic actinomycetes can promote the secondary hydration of the aluminosilicate network and repair microcracks. Therefore, the following technical solution is provided: coal gangue-based bio-self-repairing bricks based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization and their preparation method.

[0007] The specific technical solution of the present invention is as follows: a coal gangue-based bio-self-repairing brick based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization, the preparation method of which includes the following steps:

[0008] Step 1: First, the gangue, steel slag and waste rubber are crushed with a rock crusher, and then screened with a mesh screen to obtain gangue powder, steel slag powder and waste rubber powder of appropriate particle size, wherein the particle size of the gangue powder, steel slag powder and waste rubber powder meets the requirements of cementitious materials;

[0009] Step 2: Use a crucible to fill the coal gangue powder, put it into a muffle furnace for calcination, then cool it down and take it out, and keep it at room temperature for 24 hours;

[0010] Step 3: The grape skins are dried and crushed, and the crushed grape skins are placed in a Soxhlet extractor. An appropriate amount of ethanol is added, and the mixture is heated under reflux for several hours. After the extraction is completed, the solid residue is removed by filtration, and the filtrate is subjected to rotary evaporation to remove the ethanol to obtain crude tannic acid, which is then further purified by recrystallization.

[0011] Step 4: Use porous fly ash microspheres to encapsulate the spores of extremely alkaliphilic actinomycetes, and add magnesium phosphate cement (MPC) as a slow-release phosphorus source to maintain the nutrients required for microbial metabolism and ensure its survival in the high alkaline environment of the material.

[0012] Step 5: Mixing the heat-treated coal gangue powder, steel slag, fly ash, lime, water glass, waste rubber powder, porous fly ash microspheres and tannic acid in a certain proportion to obtain brick mud;

[0013] Step 6: Pour the brick mud into the mold, press it with a hydraulic brick press, and then place it in the concrete curing box for standard curing.

[0014] In the above-mentioned coal gangue-based biological self-repairing brick based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization, in step 1, the waste rubber is waste tires.

[0015] In the above-mentioned coal gangue-based biological self-repairing brick based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization, in step 1, the particle size is 0.06-1.0 mm.

[0016] In the above-mentioned gangue-based biological self-repairing brick based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization, in step 2, the calcination is carried out at a high temperature of 800° C. for 2 hours.

[0017] In the above-mentioned gangue-based biological self-repairing brick based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization, in step 4, the preparation method of the porous fly ash microspheres encapsulating the spores of extremely alkaliphilic actinomycetes is as follows: the fly ash is acid-leached to remove impurities and alkali-excited to form a viscous gel; at the same time, 1% glucose is added to the spore suspension as an organic carbon source, and then sucrose and gelatin are added to protect the spores; the above-mentioned gel is then mixed with the spore suspension, and ammonium bicarbonate pore-forming agent is added, and the molded product is formed by spray drying (the inlet air temperature is controlled at 80-100°C); after drying, the pore-forming agent is removed by washing with water to obtain porous fly ash microspheres with a multi-level pore structure and a spore embedding rate ≥90%.

[0018] In the above-mentioned gangue-based biological self-repairing brick based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization, in step 4, the alkali excitation is an alkali excitation liquid made from a sodium silicate solution with a solid content of 40%.

[0019] The above-mentioned gangue-based biological self-repairing bricks based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization, in step 5, include, in parts by mass, 30-40 parts of gangue powder, 20-25 parts of steel slag, 6-10 parts of fly ash, 10-15 parts of lime, 40-45 parts of water glass, 3-7 parts of waste rubber powder, 3-8 parts of porous fly ash microspheres and 1-3 parts of tannic acid.

[0020] In the above-mentioned gangue-based biological self-repairing bricks based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization, in step 5, the gangue powder and fly ash are first mixed and stirred for 1 min to 1.5 min to ensure uniform distribution of the active ingredients, and then lime and steel slag are added and stirred for 1 min to 1.5 min, and then water glass, waste rubber powder and porous fly ash microspheres are added and stirred. Tannic acid is added in the final stage of stirring, and disodium hydrogen phosphate accounting for 0.5% to 1% of the total mass of the solid material is added as a buffer, and the stirring time is 0.5 to 1 min. After stirring is completed, brick mud is obtained.

[0021] Tannic acid is rich in phenolic hydroxyl structures and can react with metal ions (Al3+, Ca 2+ The activated products of coal gangue and tannic acid catechol groups can enhance the interfacial bonding strength. Tannic acid phenolic hydroxyl groups can bind to metal ions (Fe 3+ , Al3+) complexation, changing the chemical environment of metal ions, increasing reaction activity and promoting gelation reaction. Tannic acid can 3+ ) is reduced to a low valence state (such as Fe 2+ ), enhance solubility and reactivity, and make low-valent metal ions more likely to participate in the gelation reaction to generate more gelled substances.

[0022] Waste rubber powder can improve the toughness and impact resistance of materials. The flexible network structure it forms can absorb and disperse stress, prevent crack expansion, and enhance freeze-thaw resistance. Its irregular shape and elasticity can form closed pores inside the material to accommodate the water that expands due to freezing and reduce internal pressure to improve freeze-thaw resistance. It can also increase the cohesion and plasticity of the system, improve workability, and facilitate construction compaction.

[0023] The exopolysaccharides secreted by extremely alkaliphilic actinomycetes have high adhesion and ion chelation capabilities. They form a three-dimensional gel network in an alkaline environment, wrapping particles such as coal gangue and fly ash, increasing the contact area of ​​the reaction interface, and can also chelate Ca through functional groups such as carboxyl and hydroxyl groups. 2+ , Al3+ ions, promote the nucleation and growth of aluminosilicate gel (C-(A)-SH). At the same time, extreme alkaliphiles maintain an alkaline microenvironment (pH 10-12) through ammoniation and carbonate metabolism: promoting the dissolution of inert minerals such as β-C2S in steel slag, releasing active SiO2 and CaO. It drives the Si-O-Si bond on the surface of fly ash glass to break, increasing the reaction sites; the CO3 produced 2 -With Ca 2+ Calcite microcrystals are generated to fill the pores and enhance the mechanical properties of the material. DETAILED DESCRIPTION

[0024] Example 1

[0025] Step 1: First, crush the coal gangue, steel slag and waste tires with a rock crusher, and then screen with a mesh screen to obtain coal gangue powder (particle size ≤ 0.25mm), steel slag powder (particle size ≤ 0.5mm) and waste rubber powder of appropriate particle size. The particle size of coal gangue powder, steel slag powder and waste tire rubber powder meets the requirements of cementitious materials;

[0026] Waste tire rubber is mainly made of vulcanized rubber, including natural rubber (NR), styrene-butadiene rubber (SBR) and a small amount of butadiene rubber (BR). The tread rubber has strong wear resistance and the carcass rubber has good toughness. It can be mechanically crushed to remove steel wire and fiber cords to make rubber powder (the particle size can be processed from 0.06 to 0.5 mm, of which 0.06 to 0.25 mm particles should account for no less than 70%).

[0027] Step 2: Fill a crucible with coal gangue powder, place it in a muffle furnace and keep it at 800℃ for 2 hours, then cool it down and take it out, and keep it at room temperature for 24 hours;

[0028] Step 3: The grape skins are dried and crushed. The crushed grape skins are placed in a Soxhlet extractor, an appropriate amount of ethanol is added, and the mixture is heated under reflux for several hours. After extraction, the solid residue is removed by filtration, and the filtrate is rotary evaporated to remove the ethanol, yielding crude tannic acid. Finally, the tannic acid is further purified by recrystallization.

[0029] Step 4: Use porous fly ash microspheres to encapsulate the spores of extremely alkaliphilic actinomycetes, and add magnesium phosphate cement (MPC) as a slow-release phosphorus source to maintain the nutrients required for microbial metabolism and ensure its survival in the high alkaline environment of the material.

[0030] The method for preparing porous fly ash microspheres encapsulating spores of extremely alkaliphilic actinomycetes is as follows: first, fly ash is subjected to acid leaching to remove impurities, and then alkali-activated using a mixture of NaOH and sodium silicate with a solid content of 40% to prepare a viscous gel; simultaneously, 1% glucose is added to the spore suspension as an organic carbon source, followed by the addition of sucrose and gelatin to protect the spores; then, the gel is mixed with the spore suspension, and ammonium bicarbonate pore-forming agent is added, and the resulting particles are spray-dried (with the air inlet temperature controlled at 80-100°C) to form the particles; and after drying, the pore-forming agent is removed by washing with water to prepare porous fly ash microspheres having a multi-level pore structure and a spore encapsulation rate of 90% or higher.

[0031] The preparation method of fly ash microspheres with multi-level pore structure is as follows:

[0032] Acid leaching and impurity removal: 100g fly ash was mixed with 1000mL 2mol / L hydrochloric acid, and acid leached at 60℃ with magnetic stirring for 2 hours. After the reaction was completed, centrifugation was performed, and the precipitate was washed with deionized water until neutral, and dried for later use;

[0033] Then, the alkali-stimulated solution made of sodium silicate solution with a modulus of 3.3 and a solid content of 40% was mixed at a mass volume ratio of 1:1.2 (treated fly ash and alkali-stimulated solution) and stirred into a viscous gel; then 5% sucrose and 3% gelatin were dissolved in sterile water to prepare a protective agent solution, and extremely alkaliphilic actinomycete spores were added to prepare a solution with a concentration range of 10 8 -10 9 A spore suspension of 100 CFU / mL is mixed with a viscous gel, a spore suspension, and an ammonium bicarbonate pore former in a mass ratio of 100:10:20. Magnesium phosphate cement (MPC) is then added in a ratio of 20 g MPC to 100 g fly ash. The mixture is spray-dried at a temperature of 90° C., a pressure of 12 bar, and a feed rate of 40 mL / min. The dried sample is completely immersed in deionized water and immersed for 1-2 hours with low-speed stirring or ultrasound assistance. The sample is washed 3-5 times until the conductivity of the washing solution approaches that of deionized water (<10 μS / cm) and the pH is neutral. The sample is then dehydrated and dried at low temperature to obtain fly ash microspheres with a spore embedding efficiency of 90% or more and a hierarchical pore structure.

[0034] Cultivation of Extremely Alkaliphilic Actinomycete Spores: After collecting a sample from alkaline soil (5-20 cm depth) with a pH ≥ 8.5, 10 g of soil was added to 90 mL of sterile saline solution. The sample was shaken with 50 glass beads for 30 minutes to release the spores, and then filtered through a 100-mesh sieve to remove impurities. The filtrate was heat-treated in a 60°C water bath for 10 minutes, passed through a cotton ball column, and centrifuged at 5000 rpm for 5 minutes. The precipitate was resuspended in 1 mL of sterile water to form a spore suspension. The suspension was graded and 100 μL was spread on an agar medium containing 10 g of soluble starch and 5 g of CaCO3, adjusted to a pH of 9.0-10.0 (with 50 mg / L potassium dichromate and nystatin). The sample was incubated at 30°C for 5-7 days. Dry, wrinkled colonies were streaked and purified, and spore morphology was confirmed under a microscope.

[0035] The specific confirmation method is as follows: the colonies can be dried and wrinkled, the hyphae branches have no septa and are Gram-positive, the spores are spiral or solitary, and they grow when inoculated into a culture medium with a pH of 9.0, but do not grow when the pH is ≤ 7.0. At the same time, a culture medium containing 10g soluble starch, 5g beef extract, 5g peptone, 5g NaCl and 15g agar is prepared, and the pH is adjusted to 9.0 with NaOH. After sterilization, the plate is poured, and the center of the colony is streaked for inoculation. The colony is cultured at 30°C for 5-7 days, and iodine solution is added dropwise. If a transparent circle appears around the colony, it indicates that the starch has been hydrolyzed. Then, a culture medium containing 12g gelatin and 5g peptone (pH 9.0) is prepared, and after sterilization, a test tube slope is made, and the test bacteria are punctured and inoculated. The culture medium is cultured at 22°C for 5 days. If the culture medium changes from a solidified state to a flowing and clear state, it is gelatin liquefaction positive. Finally, if it survives in an alkaline culture medium containing 10% NaCl and 50 U / mL penicillin, combined with the comparison of the morphological and physiological characteristics of the genus Alkaliphilic Actinomycetes in the Bergey's Manual of Systematic Bacteriology, it can be determined that it is a spore of extreme alkaliphilic actinomycetes.

[0036] Step 5: Cool the heat-treated coal gangue at room temperature for 24 hours, and then add 30g coal gangue powder, 24g steel slag, 6g fly ash, 10g lime, 40g water glass, 6g waste rubber powder, 3g porous fly ash microspheres and 2g tannic acid after heat treatment into a beaker and mix them with a stirrer at a speed of 600r / min. The coal gangue powder and fly ash need to be put into the beaker for stirring first, and the stirring time is 1min~1.5min to ensure that the active ingredients are evenly distributed. Then the lime and steel slag powder are poured into the beaker for stirring, and the stirring time is 1min~1.5min. Finally, water glass, waste rubber powder and porous fly ash microspheres are added for stirring. Tannic acid is added in the final stage of stirring, and 0.5%~1% of disodium hydrogen phosphate accounting for the total mass of the solid material is added as a buffer, and the stirring time is 0.5~1min. After stirring, brick mud is obtained;

[0037] Step 6: Pour the brick mud into the mold, press it with a hydraulic brick press, and then place it in the concrete curing box for standard curing.

[0038] Comparative Example 1

[0039] The preparation was carried out according to the method described in Example 1, but without adding porous fly ash microspheres to encapsulate the spores of extremely alkaliphilic actinomycetes.

[0040] Similar cracks were scratched on the surfaces of the two groups using a tool, and the two groups were placed in a warm place after being sprayed with water. Regular observation was conducted every day for 14-28 days. White precipitates appeared on the cracks in the experimental group and the cracks gradually narrowed or even closed, while the cracks in the control group remained unchanged. The biorepairing bricks obtained in Example 1 were effective in biorepairing.

[0041] The invention improves the recycling rate of waste rubber, makes up for the lack of calcium in the reaction process of coal gangue and steel slag, and provides a good alkaline environment, provides conditions for the further reaction of coal gangue and steel slag, and improves the reaction rate of steel slag and coal gangue. The coal gangue after thermal activation will produce a large amount of active silicon and aluminum, which will react with the calcium in the steel slag and lime in an alkaline environment to produce a gel structure, and combine with fly ash to form a dense matrix. At the same time, tannic acid is rich in phenolic hydroxyl structure and can react with metal ions (Al3+, Ca2+) in coal gangue, steel slag and lime. 2+ The chelate is formed to promote the cross-linking of the gel network, thereby enhancing the strength of the recycled bricks and achieving the purpose of recycling industrial waste.

Claims

1. Coal gangue-based bio-self-repairing bricks based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization, characterized in that: The preparation method comprises the following steps: Step 1: First, the gangue, steel slag and waste rubber are crushed with a rock crusher, and then screened with a mesh screen to obtain gangue powder, steel slag powder and waste rubber powder of appropriate particle size, wherein the particle size of the gangue powder, steel slag powder and waste rubber powder meets the requirements of cementitious materials; Step 2: Use a crucible to fill the coal gangue powder, put it into a muffle furnace for calcination, then cool it down and take it out, and keep it at room temperature for 24 hours; Step 3: The grape skins are dried and crushed, and the crushed grape skins are placed in a Soxhlet extractor. An appropriate amount of ethanol is added, and the mixture is heated under reflux for several hours. After the extraction is completed, the solid residue is removed by filtration, and the filtrate is subjected to rotary evaporation to remove the ethanol to obtain crude tannic acid, which is then further purified by recrystallization. Step 4: Use porous fly ash microspheres to encapsulate the spores of extremely alkaliphilic actinomycetes, and add magnesium phosphate cement (MPC) as a slow-release phosphorus source to maintain the nutrients required for microbial metabolism and ensure its survival in the high alkaline environment of the material; Step 5: Mixing the heat-treated coal gangue powder, steel slag, fly ash, lime, water glass, waste rubber powder, porous fly ash microspheres and tannic acid in a certain proportion to obtain brick mud; Step 6: Pour the brick mud into the mold, press it with a hydraulic brick press, and then place it in the concrete curing box for standard curing.

2. The gangue-based biological self-repairing brick based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization according to claim 1 is characterized in that: In step 1, the waste rubber is a waste tire.

3. The gangue-based bio-self-repairing brick based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization according to claim 1 is characterized in that: In step 1, the particle size is 0.06-1.0 mm, wherein the particle size of the waste rubber powder is 0.06-0.5 mm, and the proportion of particles of 0.06-0.25 mm is required to be ≥70%.

4. The gangue-based bio-self-repairing brick based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization according to claim 1, characterized in that: In step 4, the preparation method of the porous fly ash microspheres encapsulating the spores of extremely alkaliphilic actinomycetes is as follows: fly ash is acid-leached to remove impurities and alkali-excited to form a viscous gel, which is then spray-dried with an extremely alkaliphilic actinomycete spore suspension protected by sucrose and gelatin and an ammonium bicarbonate pore-forming agent (the inlet air temperature is controlled at 80-100° C.); after drying, the pore-forming agent is removed by water washing to obtain porous fly ash microspheres having a multi-level pore structure and a spore encapsulation rate of ≥90%.

5. The gangue-based biological self-repairing brick based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization according to claim 5, characterized in that: In step 4, the alkali excitation is an alkali excitation solution made of a sodium silicate solution with a solid content of 40%.

6. The gangue-based biological self-repairing brick based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization according to claim 1, characterized in that: In step 5, the ingredients, in parts by mass, include 30-40 parts of coal gangue powder, 20-25 parts of steel slag, 6-10 parts of fly ash, 10-15 parts of lime, 40-45 parts of water glass, 3-7 parts of waste rubber powder, 3-8 parts of porous fly ash microspheres and 1-3 parts of tannic acid.

7. The gangue-based bio-self-repairing brick based on tannic acid-waste rubber synergistic modification and alkaliphilic bacteria mineralization according to claim 1, characterized in that: In step 5, the gangue powder and fly ash are first mixed and stirred for 1 min to 1.5 min to ensure uniform distribution of the active ingredients, and then lime and steel slag are added and stirred for 1 min to 1.5 min. Finally, water glass, waste rubber powder and porous fly ash microspheres are added and stirred. Tannic acid is added in the final stage of stirring, and disodium hydrogen phosphate accounting for 0.5% to 1% of the total mass of the solid material is added as a buffer. The stirring time is 0.5 to 1 min. After the stirring is completed, brick mud is obtained.