Modification method of volcanic ash active coal gangue, concrete and preparation method

Abstract

The invention relates to the technical field of concrete, and particularly discloses a modification method of volcanic ash active coal gangue. The invention relates to a coal gangue volcanic ash activity modification method, which comprises: (1) calcining coal gangue at a high temperature, crushing, and screening for spare; (2) preparing an iron reducing bacteria solution, namely activating an iron reducing bacteria strain, centrifuging the bacteria solution with good transfer growth vigor under the condition of 4000-5000r / min for 5-10 minutes, washing with sterile normal saline for 3 times, adding the sterile normal saline, resuspending and preserving for later use; and (3) dipping: mixing and uniformly stirring the crushed and screened coal gangue with an iron reducing bacteria solution, dipping for 30-40 minutes, taking out the dipped coal gangue, cleaning, and drying to obtain the modified coal gangue. The method can be used for coal gangue modification treatment, and the application range of coal gangue is widened.

Description

Technical Field

[0001] The present application relates to the technical field of concrete, and more specifically, to a method for modifying the activity of gangue volcanic ash and concrete, and a preparation method thereof. Background Art

[0002] As a common industrial waste, coal gangue has gradually received attention in recent years in terms of how to stimulate its volcanic ash activity. Coal gangue with high volcanic ash activity has potential application value in the field of concrete admixtures, and can effectively improve the strength and durability of concrete. However, some components in coal gangue, such as sulfides, pose a serious threat to the durability of concrete. Sulfides usually exist in coal gangue in the form of iron sulfide, etc. These compounds may be gradually released during the hardening process of concrete, and react chemically with moisture and oxygen in the concrete to generate corrosive substances such as sulfates. These corrosive substances will corrode the interior of the concrete, causing concrete deterioration and seriously affecting its service life.

[0003] Therefore, in order to fully stimulate the pozzolanic activity of coal gangue while avoiding its potential adverse effects, it is particularly important to develop an effective modification method. Summary of the invention

[0004] In order to improve the volcanic ash activity of coal gangue while avoiding the potential adverse effects of sulfides in the coal gangue, the present application provides a method for modifying the volcanic ash activity of coal gangue and concrete, and a preparation method.

[0005] In the first aspect, the present application provides a method for modifying the activity of gangue volcanic ash, which adopts the following technical solution: A method for modifying the activity of gangue volcanic ash comprises the following steps: (1) calcining the coal gangue at high temperature, crushing it, screening it and setting it aside; (2) Preparing a bacterial solution of iron-reducing bacteria: After activating the iron-reducing bacteria, take a bacterial solution with good growth and centrifuge it at 4000-5000 r / min for 5-10 min, wash it with sterile saline for 3 times, add sterile saline to resuspend it and store it for later use; (3) Impregnation: The coal gangue that has been calcined, crushed and screened at high temperature is mixed with the iron-reducing bacteria solution and evenly stirred, and the mixture is impregnated for 30-40 minutes. The impregnated coal gangue is taken out, washed and dried to obtain the modified coal gangue.

[0006] By adopting the above technical scheme, the volcanic ash activity of coal gangue is improved through high-temperature calcination, and a part of sulfide and alkali metal ions are removed at the same time, reducing the harm of harmful substances in coal gangue. Coal gangue with uniform particle distribution is obtained through crushing and screening, which is conducive to subsequent modification. With the metabolic activity of iron-reducing bacteria, the residual sulfide in the coal gangue is gradually consumed, thereby inhibiting the oxidation of pyrite, and further inhibiting acidification and the migration and transformation of pollutants.

[0007] During the impregnation process, iron-reducing bacteria attach to the surface of coal gangue and start metabolic activities. During the metabolic process, iron-reducing bacteria use sulfide in coal gangue as electron donor and insoluble iron in coal gangue as electron acceptor to cause reduction reaction. In this process, sulfide is gradually consumed and soluble ferrous ions are generated. These ferrous ions can react chemically with silicate, carbonate and other components in coal gangue to form highly stable mineral phases such as ferrous silicate and ferrous carbonate, thereby improving the activity and strength of coal gangue, while reducing the potential harm of sulfide in coal gangue to concrete.

[0008] Optionally, the impregnation temperature is maintained between 20-40°C during the impregnation step.

[0009] By adopting the above technical solution, maintaining the temperature of the impregnation process between 20-40°C is conducive to the full reaction between iron-reducing bacteria and coal gangue. Iron-reducing bacteria are highly active and have vigorous metabolic activity at 20-40°C, and can better play their role, promote the conversion of sulfides in coal gangue, and improve the modification effect.

[0010] Optionally, the weight ratio of the coal gangue to the iron-reducing bacteria solution is 1:1.5-2, and the biomass in the iron-reducing bacteria solution is 10 g / L.

[0011] By adopting the above technical scheme, the appropriate mixing ratio helps to provide sufficient coal gangue surface for the attachment and growth of reducing bacteria, ensure that the number of microorganisms in the bacterial solution is sufficient for efficient biochemical reactions, improve the modification effect of coal gangue, remove harmful components inside the coal gangue, and convert the difficult-to-use components inside the coal gangue into a more usable form, thereby improving the utilization rate of coal gangue.

[0012] Optionally, biochar may be added during the impregnation process, and the weight ratio of the biochar to the coal gangue is 0.2-0.4:1.

[0013] By adopting the above technical solution, biochar can act as an electron transfer medium to promote the electron transfer process of iron-reducing bacteria, help completely consume the sulfides in the gangue, and improve the modification effect. On the other hand, during the calcination process, the gangue will release a large amount of volatiles and gases, resulting in voids, and biochar can fill these voids to further improve the strength of the gangue.

[0014] Optionally, the particle size of the coal gangue after crushing and screening is 0.15-0.30 mm.

[0015] By adopting the above technical solution, within a suitable range, the smaller the particle size of the gangue particles is, the larger its surface area is, thereby providing more reaction sites, so that the iron-reducing bacteria can be more evenly attached to the surface of the gangue, promoting their reaction with harmful substances such as sulfides in the gangue, thereby improving the volcanic ash activity of the modified gangue.

[0016] Optionally, in the high temperature calcination step, the calcination temperature is 600-700° C. and the calcination time is 1.5-3 h.

[0017] By adopting the above technical solution, high temperature calcination at 600-700℃ can effectively remove some organic matter and volatile matter in coal gangue, reducing its interference with the subsequent modification process. Calcining coal gangue under high temperature conditions can make the minerals therein form glassy substances, effectively improve the physical and chemical properties of coal gangue, and be beneficial to the formation of higher volcanic ash activity of coal gangue.

[0018] In a second aspect, the present application provides a concrete prepared from coal gangue modified by volcanic ash activity, using the following technical solution: A concrete prepared from coal gangue modified by volcanic ash activity, comprising the following raw materials in parts by weight: 10-16 parts of coal gangue, 20-30 parts of cement, 8-10 parts of quartz sand, 0.2-0.4 parts of polycarboxylic acid water reducer, 8-10 parts of crushed stone, and 25-30 parts of water. The coal gangue is volcanic ash activated coal gangue obtained by the modification method described in any one of claims 1 to 6.

[0019] By adopting the above technical solution, the interface area between the aggregate quartz sand and cement has a larger porosity and more calcium hydroxide crystals, so it is the weakest area in the concrete. The addition of coal gangue with high volcanic ash activity can consume a large amount of calcium hydroxide crystals in the interface to generate CSH gel with higher stiffness and hardness, thereby improving the interface strength between the aggregate and the cement gel body, and then improving the overall strength of the concrete.

[0020] In a third aspect, the present application provides a method for preparing volcanic ash active modified coal gangue concrete, which adopts the following technical solution: A method for preparing volcanic ash active modified coal gangue concrete comprises the following steps: According to a certain mix ratio, coal gangue, crushed stone, cement and quartz sand modified by volcanic ash activity are weighed, stirred and mixed evenly, and then water and polycarboxylic acid water reducer are added and stirred continuously to form a uniform slurry. The obtained slurry is poured into a test mold, dried and cured to obtain the finished product.

[0021] In summary, this application has the following beneficial effects: 1. Since the present application removes harmful components in coal gangue through calcination and the action of iron-reducing bacteria, and significantly improves the volcanic ash activity of coal gangue, the modified coal gangue can better play its advantages when used as a concrete admixture, thereby improving the strength and durability of concrete.

[0022] 2. The present application improves the utilization value of coal gangue through modification treatment of coal gangue. When used as concrete admixture, it can better play an active role, improve the strength and durability of concrete, and help promote the resource utilization of coal gangue and reduce environmental pollution. DETAILED DESCRIPTION

[0023] The present application is further described in detail below with reference to the embodiments.

[0024] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0025] The loose bulk density of the carbonaceous coal gangue selected in this application is 1200-1400kg / m 3 , crushing value 10.0%; iron-reducing strain (TACC 53774) was purchased from China General Microbiological Culture Collection Management Center; silicate cement was purchased from Jidong Cement Tongchuan Co., Ltd., with a strength grade of 42.5. Example

[0026] Example 1 A kind of coal gangue modified by volcanic ash activity, the preparation comprises the following steps: (1) Put the coal gangue into a calcining furnace and calcine it at 650° C. for 2 h, then put it into a crusher and crush and sieve it, and select the coal gangue with a particle size range of 0.15-0.30 mm for use; (2) Prepare the bacterial solution of iron-reducing bacteria: Take the strain out of the refrigerator and place it on a sterile operating table that has been sterilized under ultraviolet light for half an hour in advance. After it reaches room temperature, pour the strain into the LB medium and culture it at 28°C and 120r / min for 9h. After the bacterial solution becomes turbid, take the bacterial solution and inoculate it into fresh LB medium on the sterile operating table to activate it again. After the activation is completed, transfer the bacterial solution with good growth to a centrifuge and centrifuge it at 4000r / min for 10 minutes. Add an appropriate amount of sterile saline to the bacterial solution. The amount of saline should be enough to cover the bacteria. Use a sterile pipette to gently blow the centrifuge tube to resuspend the bacteria in the saline. Centrifuge the resuspended bacterial solution again. Repeat 3 times, add sterile saline to resuspend it for use. The biomass in the bacterial solution is 10g / L; (3) Take 20 kg of the crushed and screened coal gangue and 40 kg of the iron-reducing bacteria solution, mix them evenly, and keep the temperature at 20° C. to soak for 30 minutes. Take out the soaked coal gangue, wash it, and dry it to obtain coal gangue modified by volcanic ash activity.

[0027] A concrete prepared from coal gangue modified by volcanic ash activity, the preparation comprising the following steps: Weigh 10kg of the prepared coal gangue modified by volcanic ash activity, 8kg of crushed stone, 30kg of silicate cement and 9kg of quartz sand, stir and mix them evenly, then add 25kg of water and 0.2kg of polycarboxylate water reducer (model: DH-4005) and continue stirring to form a uniform slurry, pour the obtained slurry into a test mold, dry and cure to obtain a finished product. The quartz sand has a particle size of 0.5-2mm, and the crushed stone has a particle size of 5-10mm.

[0028] Example 2 A kind of coal gangue modified by volcanic ash activity, the preparation comprises the following steps: (1) Put the coal gangue into a calcining furnace and calcine it at 600° C. for 3 hours, then put it into a crusher for crushing and sieving, and select the coal gangue with a particle size range of 0.15-0.30 mm for standby use; (2) Prepare the bacterial solution of iron-reducing bacteria: Take the strain out of the refrigerator and place it on a sterile operating table that has been sterilized under ultraviolet light for half an hour in advance. After it reaches room temperature, pour the strain into the LB medium and culture it at 28°C and 120r / min for 9 hours. After the bacterial solution becomes turbid, take the bacterial solution and inoculate it into fresh LB medium on the sterile operating table for reactivation. After the activation is completed, transfer the bacterial solution with good growth to a centrifuge and centrifuge it at 5000r / min for 5 minutes. Add an appropriate amount of sterile saline to the bacterial solution. The amount of saline should be enough to cover the bacteria. Use a sterile pipette to gently blow the centrifuge tube to resuspend the bacteria in the saline. Centrifuge the resuspended bacterial solution again. Repeat 3 times, add sterile saline to resuspend for use. The biomass in the bacterial solution is 10g / L; (3) Take 20 kg of the crushed and screened coal gangue and 30 kg of the iron-reducing bacteria solution, mix them evenly, and keep the temperature at 30° C. for 35 minutes. Take out the impregnated coal gangue, wash it, and dry it to obtain coal gangue modified by volcanic ash activity.

[0029] A concrete prepared from coal gangue modified by volcanic ash activity, the preparation comprising the following steps: Weigh 13kg of the prepared coal gangue modified by volcanic ash activity, 10kg of crushed stone, 25kg of silicate cement and 8kg of quartz sand, stir and mix them evenly, then add 27.5kg of water and 0.3kg of polycarboxylate water reducer (model: DH-4005) and continue stirring to form a uniform slurry, pour the obtained slurry into a test mold, dry and cure to obtain a finished product. The quartz sand has a particle size of 0.5-2mm, and the crushed stone has a particle size of 5-10mm.

[0030] Example 3 A kind of coal gangue modified by volcanic ash activity, the preparation comprises the following steps: (1) Put the coal gangue into a calcining furnace and calcine it at 700° C. for 1.5 hours, then put it into a crusher for crushing and sieving, and select the coal gangue with a particle size range of 0.15-0.30 mm for standby use; (2) Prepare the bacterial solution of iron-reducing bacteria: Take the strain out of the refrigerator and place it on a sterile operating table that has been sterilized under ultraviolet light for half an hour in advance. After it reaches room temperature, pour the strain into the LB medium and culture it at 28°C and 120r / min for 9 hours. After the bacterial solution becomes turbid, take the bacterial solution and inoculate it into fresh LB medium on the sterile operating table for reactivation. After the activation is completed, transfer the bacterial solution with good growth to a centrifuge and centrifuge it at 5000r / min for 5 minutes. Add an appropriate amount of sterile saline to the bacterial solution. The amount of saline should be enough to cover the bacteria. Use a sterile pipette to gently blow the centrifuge tube to resuspend the bacteria in the saline. Centrifuge the resuspended bacterial solution again. Repeat 3 times, add sterile saline to resuspend for use. The biomass in the bacterial solution is 10g / L; (3) Take 20 kg of the crushed and screened coal gangue and 35 kg of the iron-reducing bacteria solution, mix them evenly, and keep the temperature at 40° C. to soak for 40 minutes. Take out the soaked coal gangue, wash it, and dry it to obtain coal gangue modified by volcanic ash activity.

[0031] A concrete prepared from coal gangue modified by volcanic ash activity, the preparation comprising the following steps: Weigh 16kg of the prepared coal gangue modified by volcanic ash activity, 9kg of crushed stone, 20kg of silicate cement and 10kg of quartz sand, stir and mix them evenly, then add 30kg of water and 0.4kg of polycarboxylate water reducer (model: DH-4005) and continue stirring to form a uniform slurry, pour the obtained slurry into a test mold, dry and cure to obtain a finished product. The quartz sand has a particle size of 0.5-2mm, and the crushed stone has a particle size of 5-10mm.

[0032] Example 4 A kind of coal gangue modified by volcanic ash activity, which is different from Example 1 in that 4 kg of biochar is added during the impregnation process in this embodiment, and the preparation includes the following steps: Steps (1) and (2) are the same as in Example 1; (3) 20 kg of crushed and screened coal gangue was mixed with 30 kg of iron-reducing bacteria solution, and 4 kg of biochar was added to maintain the temperature at 30°C and soaked for 35 minutes. The soaked coal gangue was taken out, washed, and dried to obtain coal gangue modified by volcanic ash activity.

[0033] A concrete prepared from coal gangue modified by volcanic ash activity. The coal gangue modified by volcanic ash activity used is prepared in this embodiment, and the specific preparation steps are the same as those in Example 1.

[0034] Example 5 A coal gangue modified by volcanic ash activity, which is different from Example 1 in that 8 kg of biochar is added during the modification process in this embodiment, and the preparation includes the following steps: Steps (1) and (2) are the same as in Example 1; (3) 20 kg of crushed and screened coal gangue was mixed with 30 kg of iron-reducing bacteria solution, and 8 kg of biochar was added to maintain the temperature at 30°C and soaked for 35 minutes. The soaked coal gangue was taken out, washed, and dried to obtain coal gangue modified with volcanic ash activity.

[0035] A concrete prepared from coal gangue modified by volcanic ash activity. The coal gangue modified by volcanic ash activity used is prepared in this embodiment, and the specific preparation steps are the same as those in Example 1.

[0036] Example 6 A coal gangue modified by volcanic ash activity, which is different from Example 1 in that the particle size range of the coal gangue in this example is 0.35-0.50 mm.

[0037] A concrete prepared from coal gangue modified by volcanic ash activity. The coal gangue modified by volcanic ash activity used is prepared in this embodiment, and the specific preparation steps are the same as those in Example 1.

[0038] Example 7 A coal gangue modified by volcanic ash activity, which is different from Example 1 in that the particle size range of the coal gangue in this example is 0.05-0.15 mm.

[0039] A concrete prepared from coal gangue modified by volcanic ash activity. The coal gangue modified by volcanic ash activity used is prepared in this embodiment, and the specific preparation steps are the same as those in Example 1.

[0040] Example 8 A coal gangue modified by volcanic ash activity, which is different from Example 1 in that the impregnation temperature in the impregnation step in this embodiment is 50°C.

[0041] Comparative Example Comparative Example 1 A coal gangue modified by volcanic ash activity, which is different from Example 1 in that it is not calcined in this comparative example.

[0042] Comparative Example 2 A kind of coal gangue modified by volcanic ash activity, which is different from Example 1 in that no iron-reducing bacteria liquid is added in this comparative example, and the preparation comprises the following steps: (1) Put the coal gangue into a calcining furnace and calcine it at 600° C. for 3 hours, then put it into a crusher for crushing and sieving, and select the coal gangue with a particle size of 0.15-0.30 mm for standby use; (2) 20 kg of the crushed and sieved coal gangue was mixed with 40 kg of sterile physiological saline and stirred evenly, and the mixture was immersed at 20° C. for 30 min. The immersed coal gangue was taken out, washed and dried to obtain coal gangue modified with volcanic ash activity.

[0043] A concrete prepared from coal gangue modified by volcanic ash activity. The coal gangue modified by volcanic ash activity is prepared in this comparative example, and the specific preparation steps are the same as those in Example 1.

[0044] Performance testing Test method / test method Compressive strength: According to GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", the compressive strength of concrete at 28 days and 98 days was tested. The results are shown in Table 1. Evaluation of the activity of coal gangue: The strength activity index of coal gangue was tested according to GB / T 1596-2017 "Fly ash used in cement and concrete". The test mortar and the comparison mortar were prepared according to the standard requirements (using silicate cement purchased from Lingshou County Qianfu Mineral Products Processing Plant, with a strength grade of 42.5), and calculated by the following formula: Where: H28—intensity activity index, %; R—28d compressive strength of test mortar, in megapascals (MPa); R 0 —Compare the 28d compressive strength of mortar, in megapascals (MPa).

[0045] Table 1 Performance test results Combining Examples 1-3 and Comparative Example 1 and Table 1, it can be seen that the test data of Examples 1-3 are better than those of Comparative Example 1, indicating that the calcined coal gangue can effectively remove some organic matter and volatile matter in the coal gangue, which is beneficial to subsequent modification, and the strength of the calcined coal gangue is improved, thereby further improving the strength of the coal gangue modified by volcanic ash activity.

[0046] Combining Examples 1-3 and Comparative Example 2 and Table 1, it can be seen that the various test data of Examples 1-3 are better than those of Comparative Example 2, indicating that the coal gangue that has not been modified by the iron-reducing bacteria liquid contains a large amount of sulfides that are difficult to remove. During the long-term use of concrete, it overflows, resulting in a decrease in the performance of the concrete and affecting the normal use of the concrete.

[0047] Combining Examples 1-5 and Table 1, it can be seen that the test data of Examples 4-5 are better than those of Examples 1-3, indicating that adding biochar during the impregnation process is beneficial to improving the modification effect and activity, and biochar can fill and remove the pores caused by harmful components inside the coal gangue, thereby improving the strength of the concrete.

[0048] Combining Example 1 with Examples 6-7 and Table 1, it can be seen that the various test data of Example 1 are better than those of Examples 6-7, indicating that the particle size of coal gangue affects the final modification result of coal gangue. Controlling the particle size of coal gangue between 0.15-0.30 mm can increase its reaction points, thereby improving the modification effect.

[0049] Combining Example 1 with Example 8 and Table 1, it can be seen that the various test data of Example 1 are better than those of Example 8, indicating that the impregnation temperature during the impregnation process affects the final modification of the coal gangue. The appropriate impregnation temperature is conducive to improving the activity of iron-reducing bacteria, which can better play its role, promote the conversion of sulfides in coal gangue, and improve the modification effect.

[0050] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for modifying the activity of gangue volcanic ash, characterized in that: The steps include: (1) After calcining the coal gangue at high temperature, crushing and screening it for later use; (2) Preparation of iron-reducing bacteria culture: After activating the iron-reducing bacteria, take the culture solution with good growth and centrifuge it at 4000-5000 r / min for 5-10 min, wash it with sterile saline for 3 times, add sterile saline to resuspend it and store it for later use; (3) Impregnation: The coal gangue that has been calcined, crushed and screened at high temperature is mixed with the iron-reducing bacteria solution and impregnated for 30-40 minutes. The impregnated coal gangue is taken out, washed and dried to obtain modified coal gangue.

2. The method for modifying the activity of gangue volcanic ash according to claim 1, characterized in that: The impregnation temperature is maintained between 20-40°C during the impregnation step.

3. The method for modifying the activity of gangue volcanic ash according to claim 1, characterized in that: The weight ratio of the coal gangue to the iron-reducing bacteria liquid is 1:1.5-2, and the biomass in the iron-reducing bacteria liquid is 10 g / L.

4. The method for modifying the activity of gangue volcanic ash according to claim 1, characterized in that: Biochar may also be added during the impregnation process, and the weight ratio of the biochar to the coal gangue is 0.2-0.4:

1.

5. The method for modifying the activity of gangue volcanic ash according to claim 1, characterized in that: The particle size of the coal gangue after crushing and screening is 0.15-0.30 mm.

6. The method for modifying the activity of gangue volcanic ash according to claim 1, characterized in that: In the high temperature calcination step, the calcination temperature is 600-700° C. and the calcination time is 1.5-3 hours.

7. A concrete prepared from coal gangue modified by volcanic ash activity, comprising the following raw materials in parts by weight: 10-16 parts of coal gangue, 20-30 parts of cement, 8-10 parts of quartz sand, 0.2-0.4 parts of polycarboxylic acid water reducer, 8-10 parts of crushed stone, and 25-30 parts of water. The coal gangue is the coal gangue obtained by the volcanic ash active modification method according to any one of claims 1-6.

8. A method for preparing concrete according to claim 7, characterized in that: The steps include: According to a certain mix ratio, coal gangue, cement and quartz sand modified by volcanic ash activity are weighed, stirred and mixed evenly, and then water and polycarboxylic acid water reducer are added and stirred continuously to form a uniform slurry. The obtained slurry is poured into a test mold, dried and cured to obtain the finished product.

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