Coal gangue-biomass ash-based micro-mineral cementitious material and alkali-free dry method base preparation method

Abstract

The present application relates to waste utilization technical field, particularly relates to a coal gangue-biomass ash-based micro-mineral cementing material and alkali-free dry method base preparation method, the present application embodiment provides a coal gangue-biomass ash-based micro-mineral cementing material, raw material includes: dry material: coal gangue, fly ash, mineral powder, biomass ash, the mass fraction of coal gangue in dry material is 50-65%, the mass fraction of fly ash in dry material is 15-20%, the mineral powder includes calcium oxide, the mass fraction of mineral powder in dry material is 10-15%, the biomass ash includes K2O, P2O5 and SiO2, the mass fraction of biomass ash in dry material is 5-8%, wet material: bacteria liquid, the present application embodiment provides a coal gangue-biomass ash-based micro-mineral cementing material and alkali-free dry method base preparation method, and can utilize coal gangue waste.

Description

Technical Field

[0001] This invention relates to the field of waste utilization technology, and in particular to a coal gangue-biomass ash-based micro-mineral adhesive material and an alkali-free dry method for preparing a base layer. Background Technology

[0002] Coal gangue is a solid waste generated during coal mining and washing. It is mainly composed of minerals such as carbonaceous shale, mudstone, and sandstone, and usually contains small amounts of residual coal as well as sulfides and heavy metals. Long-term accumulation not only occupies a large amount of land resources, but can also cause serious pollution to the surrounding ecological environment, such as soil pollution, water pollution, and air pollution.

[0003] To address the aforementioned shortcomings, there is an urgent need for a coal gangue-biomass ash-based micro-mineral adhesive material that can utilize coal gangue waste. Summary of the Invention

[0004] This invention provides a coal gangue-biomass ash-based micro-mineral adhesive material and an alkali-free dry-process base layer preparation method, which enables the utilization of coal gangue waste.

[0005] In a first aspect, embodiments of the present invention provide a coal gangue-biomass ash-based micromineral adhesive material, the raw materials of which include:

[0006] Dry materials: coal gangue, fly ash, mineral powder, biomass ash, wherein the coal gangue comprises 50-65% by mass, the fly ash comprises 15-20% by mass, the mineral powder includes calcium oxide and comprises 10-15% by mass, and the biomass ash includes K2O, P2O5 and SiO2 and comprises 5-8% by mass.

[0007] Wet substrate: bacterial solution.

[0008] In one possible design, the particle size of the coal gangue is no greater than 5 mm.

[0009] In one possible design, the porosity of the coal gangue is 30-45%.

[0010] In one possible design, the mineral powder contains at least 40% calcium oxide by mass.

[0011] In one possible design, the biomass ash comprises 8-12% by weight of K2O, 4-6% by weight of P2O5, and 45-55% by weight of SiO2.

[0012] In one possible design, the bacterial strain in the bacterial solution includes Bacillus pasteurellii, and the concentration of the bacterial solution is not less than 10. 7 CFU / mL.

[0013] In one possible design, the wet material also includes urea.

[0014] Secondly, embodiments of the present invention also provide an alkali-free dry-process base layer preparation method, based on any of the above-mentioned coal gangue-biomass ash-based micro-mineral adhesive materials, the preparation method comprising:

[0015] Mix all the raw materials in the dry material evenly to obtain a mixture;

[0016] The bacterial strain was cultivated to obtain a bacterial solution;

[0017] The bacterial solution is sprayed into the mixture;

[0018] After curing with a film, a base layer of coal gangue-biomass ash-based micro-mineral adhesive material is obtained.

[0019] In one possible design, the amount of bacterial solution sprayed is determined based on a liquid-to-solid ratio of 0.1 for the bacterial solution dry material.

[0020] In one possible design, the wet material further includes urea, and after the bacterial solution is sprayed into the mixture and before mulching, it also includes:

[0021] The urea was sprayed in three stages: 0.5M, 1.0M, and 1.5M, with an interval of 8 hours between sprayings. The amount of urea used in each stage was determined based on a urea dry material liquid-to-solid ratio of 0.1.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] The main aggregate is coal gangue, whose porous structure provides space for microbial colonization and calcium carbonate precipitation. Fly ash and mineral powder, as active components, can form C-(A)-SH gel through a pozzolanic effect in an alkaline hydration environment. The phosphorus, potassium, and silicon elements in the biomass ash can continuously release potassium. + PO4 3-The presence of active silica satisfies the metabolic needs of bacterial proliferation, achieving mineralization without the addition of external nutrient solutions. The bacterial solution in the wet material rapidly multiplies under the nutrients provided by the biomass ash, and a large number of bacteria can generate mineralized calcium carbonate cement. The calcium source of the calcium carbonate cement comes from the mineral powder, eliminating the need for additional calcium sources. The main component of the mineral powder is calcium oxide, which undergoes hydration and hydrolysis in the early stages of material forming (0–12 h), slowly releasing calcium ions at a dissolution rate of 0.025 mol / (L·h), reaching a cumulative concentration of 0.6 mol / L by 24 h, which is just sufficient to meet the needs of the bacteria. The silica and alumina in the fly ash and biomass ash react with the water in the wet material to generate a weakly alkaline environment (pH 9–10), providing an alkaline environment with a pozzolanic effect without excessive alkalinity that could inhibit bacterial activity. In summary, this application, through the coupling effect of mineral powder, biomass ash, and fly ash, provides a reaction system that requires neither calcium nor nutrient sources. Within this system, the slowly released calcium ions provide the material basis for bacteria to produce calcium carbonate, and the biomass ash can continuously release potassium. + PO4 3- The active silicon in biomass ash and mineral powder can meet the metabolic needs of microbial growth. The silicon and aluminum oxides in biomass ash and mineral powder can provide an alkaline environment and can also be used as reaction raw materials for the volcanic ash effect. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a SEM scan image of CaCO3 crystal deposition on the surface of coal gangue provided in an embodiment of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] like Figure 1 As shown, this embodiment of the invention provides a coal gangue-biomass ash-based micromineral binder material, the raw materials of which include:

[0028] Dry materials: coal gangue, fly ash, mineral powder, biomass ash. Coal gangue accounts for 50-65% of the dry materials by mass, fly ash accounts for 15-20% of the dry materials by mass, mineral powder includes calcium oxide and accounts for 10-15% of the dry materials by mass, and biomass ash includes K2O, P2O5 and SiO2 and accounts for 5-8% of the dry materials by mass.

[0029] Wet substrate: bacterial solution.

[0030] In this embodiment, coal gangue is selected as the main aggregate, whose porous structure provides space for microbial colonization and calcium carbonate precipitation. Fly ash and mineral powder, as active components, can generate C-(A)-SH gel through the pozzolanic effect in an alkaline hydration environment. The phosphorus, potassium, and silicon elements in the biomass ash can continuously release potassium. + PO4 3- The presence of active silica satisfies the metabolic needs of bacterial proliferation, achieving mineralization without the addition of external nutrient solutions. The bacterial solution in the wet material rapidly multiplies under the nutrients provided by the biomass ash, and a large number of bacteria can generate mineralized calcium carbonate cement. The calcium source of the calcium carbonate cement comes from the mineral powder, eliminating the need for additional calcium sources. The main component of the mineral powder is calcium oxide, which undergoes hydration and hydrolysis in the early stages of material forming (0–12 h), slowly releasing calcium ions at a dissolution rate of 0.025 mol / (L·h), reaching a cumulative concentration of 0.6 mol / L by 24 h, which is just sufficient to meet the needs of the bacteria. The silica and alumina in the fly ash and biomass ash react with the water in the wet material to generate a weakly alkaline environment (pH 9–10), providing an alkaline environment with a pozzolanic effect without excessive alkalinity that could inhibit bacterial activity. In summary, this application, through the coupling effect of mineral powder, biomass ash, and fly ash, provides a reaction system that requires neither calcium nor nutrient sources. Within this system, the slowly released calcium ions provide the material basis for bacteria to produce calcium carbonate, and the biomass ash can continuously release potassium. + PO4 3- The active silicon in biomass ash and mineral powder can meet the metabolic needs of microbial growth. The silicon and aluminum oxides in biomass ash and mineral powder can provide an alkaline environment and can also be used as reaction raw materials for the volcanic ash effect.

[0031] In this invention, the final material is a nano- to micro-level filler: C-(A)-SH gel serves as the binder phase, and calcite / aragonite crystals serve as the reinforcing phase, forming a "soft-hard" composite structure with a compressive strength of 8–12 MPa (150% higher than pure MICP material). CaCO3 is distributed in various forms, with the amorphous phase (≤100 nm) sealing gel cracks and micron-sized crystals (1–5 μm) reinforcing the aggregate interface, ultimately reducing the porosity to 8%–12%. In the mineral adhesive material, the total solid waste content is ≥85%, eliminating the need for external activators and reducing material costs by 35% compared to traditional alkali-activated systems; the chloride ion content is ≤0.05%, eliminating the risk of steel reinforcement corrosion; the bacterial survival rate is >90% (72 h), and the urease activity remains stable at 2.5–3.0 U / mL.

[0032] It should be noted that the above reaction system can only be obtained by the organic combination of each raw material and its proportion. If any raw material is missing or the mass fraction of any raw material is not within the above range, the reaction system cannot be obtained.

[0033] In some embodiments of the present invention, the particle size of the coal gangue is no greater than 5 mm.

[0034] In some embodiments of the present invention, the porosity of the coal gangue is 30–45%. This porosity range is suitable for the directional growth of gels and bacteria.

[0035] In some embodiments of the present invention, the mass fraction of calcium oxide in the mineral powder is not less than 40%.

[0036] In some embodiments of the present invention, the biomass ash comprises 8-12% by mass of K2O, 4-6% by mass of P2O5 and 45-55% by mass of SiO2.

[0037] In some embodiments of the present invention, the bacterial strain in the bacterial solution includes Bacillus pasteurellii, and the concentration of the bacterial solution is not less than 10. 7 CFU / mL.

[0038] In some embodiments of the present invention, the wet material also includes urea.

[0039] This invention also provides an alkali-free dry-process base layer preparation method, based on any of the above-mentioned coal gangue-biomass ash-based micro-mineral adhesive materials, the preparation method comprising:

[0040] Mix all the ingredients in the dry material evenly to obtain the mixture;

[0041] The bacterial strain was cultivated to obtain a bacterial solution;

[0042] Spray the bacterial solution into the mixture;

[0043] After curing with a film, a base layer of coal gangue-biomass ash-based micro-mineral adhesive material is obtained.

[0044] In this embodiment, the spraying of wet material can be divided into two stages. The stage after the bacterial solution is sprayed (0-24h): under weakly alkaline conditions (pH 9-10), the bacterial cells proliferate rapidly (biomass reaches 10). 8 CFU / g) synchronously activates mineral powder and fly ash to generate nano C-(A)-SH gel (size 10-50nm), forming an initial gel network.

[0045] In some embodiments of the present invention, the amount of bacterial solution sprayed is determined based on a ratio of 0.1 between the dry and solid components of the bacterial solution.

[0046] In some embodiments of the present invention, the wet material further includes urea, and after the bacterial solution is sprayed into the mixture and before film curing, it further includes:

[0047] The urea was sprayed in three stages: 0.5M, 1.0M, and 1.5M, with an interval of 8 hours between spraying. The amount of urea used in each stage was determined based on the ratio of urea dry material to liquid solids of 0.1.

[0048] 24 hours after spraying the bacterial solution, urea was sprayed. After the urea was sprayed, the CaCO3 was directionally transformed from amorphous to calcite (70%–80%) and aragonite (20%–30%), with a grain size of 1–5 μm, preferentially filling pores of 20 nm–5 μm.

[0049] Specifically, the process flow is as follows:

[0050] Step 1: Dry-mix preforming: Solid waste raw materials (coal gangue, fly ash, mineral powder, biomass ash) are dry-mixed in proportion until uniform (moisture content ≤5%), and spread to the designed thickness (15cm per layer);

[0051] Step 2: Layered spraying: First spray with bacterial suspension (bacterial concentration 10). 7 CFU / mL, liquid-to-solid ratio 0.1), and then spray urea solution twice at 6-hour intervals (concentration gradient 0.5-1.5M, liquid-to-solid ratio 0.1);

[0052] Step 3: Temperature-controlled curing with membrane covering: Cover with a breathable membrane (oxygen permeability ≥ 5000g / (m²)). 2 • Maintain an ambient temperature of 25-35℃ and humidity of ≥90% for 24 hours. Open to traffic after 72 hours of curing.

[0053] This application has advantages in engineering adaptability:

[0054] Efficient construction: The single paving thickness reaches 16cm (traditional wet methods require 3-4 layers), shortening the construction period from 7 days to 3 days; abandoning traditional alkali activators, it utilizes the weak alkalinity (pH 8.0-9.5) of biomass ash and mineral powder to maintain the activity of the microbial community and reduce the risk of equipment corrosion.

[0055] Homogeneous and stable: standard deviation of compressive strength within the layer ≤ 0.5 MPa, 28-day shrinkage rate < 0.02%, meeting the technical requirements of road base course in JTG / T F20-2015;

[0056] Low carbon emission reduction: Production energy consumption < 0.2t CO 2 / The material reduces carbon emissions by 40% compared to cement-based materials and produces no alkaline wastewater.

[0057] To more clearly illustrate the technical solution and advantages of the present invention, several embodiments are described in detail below.

[0058] Example 1

[0059] 1. Raw material composition and pretreatment

[0060]

[0061] 2. Preparation process

[0062] Step 1: Dry Mixing

[0063] Add coal gangue, fly ash, mineral powder, and biomass ash into a forced mixer in proportion, and mix at 30 r / min for 15 min until uniformly mixed. The moisture content of the mixture should be ≤5%.

[0064] Step 2: Activation of bacterial culture

[0065] The strain of Bacillus pasteurellii (ATCC 11859) was inoculated into LB medium (pH 9.0) and incubated at 37°C for 24 hours until the bacterial concentration reached 10⁻⁶. 9 CFU / mL;

[0066] Step 3: Spray in multiple stages

[0067] First spray of bacterial solution: liquid-to-solid ratio 0.1 (100L of bacterial solution per ton of dry material), let stand for 6 hours to allow the bacteria to adsorb;

[0068] Secondary urea spraying: Spray urea solution of gradient concentration in three stages (0.5M→1.0M→1.5M), with an interval of 8 hours between each spraying and a liquid-to-solid ratio of 0.1;

[0069] Step 4: Covering and Curing

[0070] Covered with a high-polymer breathable membrane (oxygen permeability 5500g / (m²)) 2• Curing time: 24 hours, ambient temperature controlled at 30±2℃, humidity ≥90%, demolding after 7.2 hours.

[0071] 3. Performance Verification

[0072] Compressive strength: 40mm×40mm×160mm specimens were molded according to GB / T 50081-2016 standard, and the 28-day compressive strength was 10.2MPa;

[0073] Ca 2+ Leaching amount: Take a crushed sample (passed through a 0.15 mm sieve) after 24 hours of curing, soak it in deionized water at a solid-liquid ratio of 1:10, and determine the Ca content by ICP-OES. 2+ Concentration 0.58 mol / L;

[0074] Chloride ion content: Detection of Cl by silver nitrate titration - The content is 0.03%, which meets the Class I environmental requirements in GB / T 50476-2019;

[0075] Engineering application: Used for repairing the base course of a road in an open-pit mine (design thickness 15cm). After 72 hours of curing, the CBR value was ≥90%, and there was no cracking after 28 days.

[0076] Example 2

[0077] Example 2 is an optimization and adjustment based on Example 1:

[0078] 1. Raw material composition and optimization adjustment

[0079]

[0080] 2. Key Points of Process Optimization

[0081] Bacterial solution concentration control: Due to the increased amount of solid waste, the bacterial solution concentration was increased to 1.5 × 10⁻⁶. 9 CFU / mL, spraying volume adjusted to a liquid-to-solid ratio of 0.12 (120L per ton of dry material);

[0082] Gradient urea spraying optimization: The spraying time of 1.5M urea solution was extended to 12 hours to ensure the full development of calcite crystals;

[0083] Temperature adjustment during curing: adopt phased temperature increase (25℃→35℃ within 24 hours) to promote early gelation and mineralization synergy.

[0084] 3. Performance Verification

[0085] Compressive strength and porosity: 28-day compressive strength 8.5 MPa, total porosity 10.5% (mercury porosimetry), more suitable for non-load-bearing filling scenarios than Example 1;

[0086] Cl- Leaching with heavy metals: Cl - The content is 0.04%, and the Pb / Cr leaching concentrations are 0.08 mg / L and 0.12 mg / L respectively (GB5085.3-2007), which meets the Class III land use standard.

[0087] Comparative Example 1 (Conventional MICP): Using only coal gangue + 30% CaCl2, the strength after 28 days was 6.8 MPa, but Cl... - The content was 2.15%, verifying the dependence on exogenous calcium salts and high Cl content. - risk.

[0088] Comparative Example 2 (Alkali-activated system): Coal gangue + fly ash + mineral powder + NaOH activation, 28-day strength 7.3 MPa, but Ca 2+ The self-release concentration is only 0.02 mol / L, indicating no mineralization enhancement effect.

[0089] Solid waste utilization rate and gelling activity (GB / T 50081-2016 standard test)

[0090]

[0091] It can be seen that the multi-element solid waste system (Examples 1 and 2) releases Ca2+ through the self-release of mineral powder under conditions without external CaCl2. 2+ (0.55~0.58mol / L), 28d compressive strength reaches 8.5~10.2MPa, which is 16%~40% higher than the alkali-activated system (Comparative Example 2); chloride ion content <0.05%, far lower than the MIP system containing CaCl2 (Comparative Example 1), avoiding the risk of corrosion.

[0092] Further experimental analysis was conducted on the product obtained in Example 1:

[0093] Mineralization efficiency and microstructure analysis

[0094] 1. Dynamic monitoring of microbial community activity and mineralization process

[0095] parameter 0h 24h 48h 72h Urease activity (U / mL) 0.1 2.8 2.6 2.3 Microbial community survival rate (%) 100 95 92 88 <![CDATA[CaCO3 deposition amount (g / kg)]]> 0 62 128 185

[0096] 2. Porosity and crystal phase distribution (quantitative analysis using mercury porosimetry / XRD)

[0097]

[0098] It can be seen that the peak urease activity reached 2.8 U / mL and remained stable for 72 h (with only 18% decay), which is better than the 60% decay (48 h) of traditional MICP, achieving the advantage of dynamic regulation; the directional calcite / aragonite crystals (size 1-5 μm) and C-(A)-SH gel synergistically fill the pores, reducing the porosity by 67% compared with traditional MICP, achieving a graded filling effect; high-purity calcite (78%) significantly improves the compressive strength and water resistance of the material (softening coefficient ≥0.85), achieving crystal stability.

[0099] Engineering application performance testing (JTG / T F20-2015)

[0100] 1. Construction efficiency and interlayer bonding strength (field simulation test)

[0101] parameter This invention (dry process) Traditional wet process Single-layer paving thickness (cm) 16 5 Construction period (days) 3 7 Poor compressive strength (MPa) 0.4 1.8 28d resilient modulus (MPa) 2100 1500

[0102] 2. Durability test (GB / T 50082-2009)

[0103]

[0104] It can be seen that a single-layer 15cm paving + 72 hours to open to traffic shortens the construction period by 57% and enhances construction efficiency; CaCO3 mineralization products improve corrosion resistance, and the sulfate erosion strength loss rate is only 35% of that of cement-based materials, thus improving durability.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A coal gangue-biomass ash-based micromineral binder material, characterized in that, Raw materials include: Dry materials: coal gangue, fly ash, mineral powder, biomass ash, wherein the coal gangue comprises 50-65% by mass, the fly ash comprises 15-20% by mass, the mineral powder includes calcium oxide and comprises 10-15% by mass, and the biomass ash includes K2O, P2O5, and SiO2 and comprises 5-8% by mass. Wet substrate: bacterial solution; The particle size of the coal gangue is no greater than 5 mm; The porosity of the coal gangue is 30-45%; Process: Mix all the raw materials in the dry material evenly to obtain a mixture, and spray the bacterial solution into the mixture.

2. The coal gangue-biomass ash-based micromineral binder material according to claim 1, characterized in that, The mineral powder contains at least 40% calcium oxide by mass.

3. The coal gangue-biomass ash-based micromineral binder material according to claim 1, characterized in that, The biomass ash comprises 8-12% by mass of K2O, 4-6% by mass of P2O5, and 45-55% by mass of SiO2.

4. The coal gangue-biomass ash-based micromineral binder material according to claim 1, characterized in that, The bacterial strain in the bacterial solution includes Bacillus pasteurellii, and the concentration of the bacterial solution is not less than 10. 7 CFU / mL.

5. The coal gangue-biomass ash-based micromineral binder material according to claim 1, characterized in that, The wet material also includes urea.

6. A method for preparing an alkali-free dry base layer, characterized in that, Based on the raw materials of any one of the coal gangue-biomass ash-based micromineral adhesives according to claims 1-5, the preparation method includes: Mix all the raw materials in the dry material evenly to obtain a mixture; The bacterial strain was cultivated to obtain a bacterial solution; The bacterial solution is sprayed into the mixture; After curing with a film, a base layer of coal gangue-biomass ash-based micro-mineral adhesive material is obtained.

7. The method for preparing a base layer according to claim 6, characterized in that, The amount of the bacterial solution sprayed is determined based on a liquid-to-solid ratio of 0.1 for the bacterial solution and dry material.

8. The method for preparing a base layer according to claim 6, characterized in that, The wet material also includes urea, and after the bacterial solution is sprayed into the mixture and before mulching and curing, it also includes: The urea was sprayed in three stages: 0.5M, 1.0M, and 1.5M, with an interval of 8 hours between sprayings. The amount of urea used in each stage was determined based on a urea dry material liquid-to-solid ratio of 0.1.

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