Method for modifying coal gangue with volcanic ash activity, concrete and preparation method thereof

Abstract

The application relates to the technical field of concrete, and particularly discloses a modification method of fly ash active coal gangue. The coal gangue fly ash active modification method comprises the following steps: (1) crushing and screening the coal gangue after high-temperature calcination, and reserving the coal gangue; (2) preparing an iron-reducing bacteria liquid: after the iron-reducing bacteria strain is activated, centrifuging the bacteria liquid with a good growth trend at 4000-5000 r / min for 5-10 min, washing the bacteria liquid with sterile normal saline for 3 times, and then adding sterile normal saline to resuspend and reserve the bacteria liquid; (3) impregnation: mixing the coal gangue crushed and screened in the above step with the iron-reducing bacteria liquid, stirring the mixture uniformly, and impregnating the mixture for 30-40 min; taking out the impregnated coal gangue, and cleaning and drying the coal gangue to obtain the modified coal gangue. The method can be used for the modification treatment of the coal gangue, and the application range of the coal gangue is expanded.

Description

Technical Field

[0001] This application relates to the field of concrete technology, and more specifically, to a method for active modification of coal gangue pozzolanic and concrete preparation method. Background Technology

[0002] As a common industrial waste, coal gangue has seen increasing attention in recent years regarding its pozzolanic activity enhancement. Highly active coal gangue has potential applications in concrete admixtures, effectively improving concrete strength and durability. However, some components in coal gangue, such as sulfides, pose a serious threat to concrete durability. Sulfides in coal gangue typically exist in the form of iron sulfide, etc. These compounds may be gradually released during concrete hardening, reacting chemically with moisture and oxygen in the concrete to generate corrosive substances such as sulfates. These corrosive substances erode the interior of the concrete, leading to deterioration and severely impacting its service life.

[0003] Therefore, in order to fully activate 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 pozzolanic activity of coal gangue while avoiding the potential adverse effects of sulfides in coal gangue, this application provides a method for modifying the pozzolanic activity of coal gangue and a concrete preparation method.

[0005] In a first aspect, this application provides a method for the active modification of coal gangue pozzolanic, employing the following technical solution:

[0006] A method for reactive modification of coal gangue pozzolanic includes the following steps:

[0007] (1) The coal gangue is calcined at high temperature, then crushed and screened for later use;

[0008] (2) Preparation of iron-reducing bacteria culture: After activating the iron-reducing bacteria, take the well-growing culture and centrifuge it at 4000-5000 r / min for 5-10 min. After washing it 3 times with sterile physiological saline, add sterile physiological saline to resuspend it and store it for later use.

[0009] (3) Impregnation: The coal gangue that has been calcined, crushed and screened at high temperature is mixed with iron-reducing bacteria solution and impregnated for 30-40 minutes. The impregnated coal gangue is then taken out, washed and dried to obtain modified coal gangue.

[0010] By adopting the above technical solution, the activity of coal gangue pozzolanic is improved through high-temperature calcination, while some sulfides and alkali metal ions are removed, reducing the harm of harmful substances inside the coal gangue. Crushing and screening yield coal gangue with a uniform particle distribution, which is beneficial for subsequent modification treatment. With the metabolic activity of iron-reducing bacteria, the residual sulfides in the coal gangue are gradually consumed, thereby inhibiting the oxidation of pyrite and further suppressing acidification and the migration and transformation of pollutants.

[0011] During the impregnation process, iron-reducing bacteria attach to the surface of the coal gangue and begin metabolic activity. In this process, the bacteria utilize sulfides in the coal gangue as electron donors and insoluble iron as electron acceptors, resulting in a reduction reaction. During this process, sulfides are gradually consumed, while soluble ferrous ions are generated. These ferrous ions can chemically react with silicates, carbonates, and other components in the coal gangue to form highly stable mineral phases such as ferrous silicate and ferrous carbonates. This improves the activity and strength of the coal gangue while reducing the potential harm of sulfides in the coal gangue to concrete.

[0012] Optionally, the impregnation temperature is maintained between 20-40°C during the impregnation step.

[0013] By adopting the above technical solution, maintaining the temperature of the impregnation process between 20-40℃ 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℃, which can better exert their role, promote the conversion of sulfides in coal gangue, and improve the modification effect.

[0014] Optionally, the weight ratio of the coal gangue to the iron-reducing bacteria solution is 1:1.5-2, and the biomass of the iron-reducing bacteria solution is 10 g / L.

[0015] By adopting the above technical solution, a suitable mixing ratio helps to provide sufficient coal gangue surface for the attachment and growth of reducing bacteria, ensuring that the number of microorganisms in the bacterial solution is sufficient to carry out efficient biochemical reactions, improving the modification effect of coal gangue, removing harmful components inside the coal gangue, and transforming the difficult-to-use components inside into more usable forms, thereby improving the utilization rate of coal gangue.

[0016] Optionally, biochar may be added during the impregnation process, wherein the weight ratio of biochar to coal gangue is 0.2-0.4:1.

[0017] By adopting the above technical solution, biochar can serve as an electron transfer medium, promoting the electron transfer process of iron-reducing bacteria, helping to completely consume sulfides in coal gangue, and improving the modification effect. On the other hand, coal gangue releases a large amount of volatiles and gases during calcination, creating voids, which biochar can fill to further improve the strength of coal gangue.

[0018] Optionally, the particle size of the coal gangue after crushing and screening is 0.15-0.30 mm.

[0019] By adopting the above technical solution, within a suitable range, the smaller the particle size of coal gangue, the larger its surface area, thereby providing more reaction sites. This allows iron-reducing bacteria to adhere more evenly to the surface of coal gangue, promoting their reaction with harmful substances such as sulfides in the coal gangue, thereby improving the pozzolanic activity of the modified coal gangue.

[0020] Optionally, the calcination temperature in the high-temperature calcination step is 600-700℃, and the calcination time is 1.5-3 hours.

[0021] By adopting the above technical solution, high-temperature calcination at 600-700℃ can effectively remove some organic matter and volatile matter from coal gangue, reducing their interference with subsequent modification processes. Calcination of coal gangue at high temperatures can cause the minerals within it to form glassy substances, effectively improving the physical and chemical properties of the coal gangue and promoting its high pozzolanic activity.

[0022] Secondly, this application provides a concrete prepared from coal gangue modified with pozzolanic activity, using the following technical solution:

[0023] A type of concrete prepared from coal gangue modified with volcanic ash, comprising the following raw materials in parts by weight: 10-16 parts coal gangue, 20-30 parts cement, 8-10 parts quartz sand, 0.2-0.4 parts polycarboxylate superplasticizer, 8-10 parts crushed stone, and 25-30 parts water, wherein the coal gangue is volcanic ash-modified coal gangue obtained by any one of the modification methods described in claims 1-6.

[0024] By adopting the above technical solution, the interface region between aggregate quartz sand and cement has a large porosity and a large number of calcium hydroxide crystals, making it the weakest area in concrete. Adding coal gangue with high pozzolanic activity can consume a large number of calcium hydroxide crystals in the interface to generate CSH gel with higher stiffness and hardness, thereby improving the interfacial strength between aggregate and cement gel, and thus improving the overall strength of concrete.

[0025] Thirdly, this application provides a method for preparing pozzolanic active modified coal gangue concrete, employing the following technical solution:

[0026] A method for preparing pozzolanic active modified coal gangue concrete includes the following steps:

[0027] Weigh out the volcanic ash-modified coal gangue, crushed stone, cement and quartz sand according to a certain mix ratio, mix them evenly, add water and polycarboxylate superplasticizer and continue mixing to form a uniform slurry. Pour the obtained slurry into a test mold, dry and cure to obtain the finished product.

[0028] In summary, this application has the following beneficial effects:

[0029] 1. Because this application removes harmful components from coal gangue through calcination and the action of iron-reducing bacteria, and significantly improves the pozzolanic activity of coal gangue, the modified coal gangue can better exert its advantages when used as a concrete admixture, thereby improving the strength and durability of concrete.

[0030] 2. This application improves the utilization value of coal gangue through modification treatment, enabling it to better exert its active effect when used as a concrete admixture, thereby enhancing the strength and durability of concrete and promoting the resource utilization of coal gangue while reducing environmental pollution. Detailed Implementation

[0031] The present application will be further described in detail below with reference to the embodiments.

[0032] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0033] The loose bulk density of the carbonaceous coal gangue selected in this application is 1200-1400 kg / m³. 3 Crushing value 10.0%; iron-reducing strain (TACC 53774) was purchased from China General Microbiological Culture Collection Center; silicate cement was purchased from Jidong Cement Tongchuan Co., Ltd., with a strength grade of 42.5.

[0034] Example

[0035] Example 1

[0036] A type of coal gangue modified with volcanic ash is prepared by the following steps:

[0037] (1) After calcining the coal gangue in a calcining furnace at 650℃ for 2 hours, put it into a crusher for crushing and sieving. Select coal gangue with a particle size range of 0.15-0.30mm for later use.

[0038] (2) Preparation of iron-reducing bacteria culture: The bacterial strain was removed from the refrigerator and placed on a sterile operating table that had been sterilized under ultraviolet light for half an hour beforehand. After reaching room temperature, the strain was poured into LB medium and cultured at 28℃ and 120 r / min for 9 hours. After the culture became turbid, the culture was inoculated into fresh LB medium on a sterile operating table for reactivation. After activation, the well-growing culture was transferred to a centrifuge and centrifuged at 4000 r / min for 10 minutes. An appropriate amount of sterile physiological saline was added to the culture, enough to cover the bacteria. The centrifuge tube was gently blown with a sterile pipette to resuspend the bacteria in the physiological saline. The resuspended culture was centrifuged again, and this process was repeated 3 times. After resuspending in sterile physiological saline, the culture was kept for later use. The biomass in the culture was 10 g / L.

[0039] (3) Take 20 kg of the crushed and screened coal gangue and mix it with 40 kg of iron-reducing bacteria solution. Keep the temperature at 20℃ and soak for 30 min. Take out the soaked coal gangue, wash and dry it to obtain coal gangue modified by pozzolanic activity.

[0040] A type of concrete prepared from coal gangue modified with pozzolanic activity includes the following steps:

[0041] Weigh 10 kg of pozzolanic-modified coal gangue, 8 kg of crushed stone, 30 kg of silicate cement, and 9 kg of quartz sand. Mix them thoroughly, then add 25 kg of water and 0.2 kg of polycarboxylate superplasticizer (model: DH-4005) and continue mixing to form a homogeneous slurry. Pour the resulting slurry into a mold, dry, and cure to obtain the finished product. The quartz sand has a particle size of 0.5-2 mm, and the crushed stone has a particle size of 5-10 mm.

[0042] Example 2

[0043] A type of coal gangue modified with volcanic ash is prepared by the following steps:

[0044] (1) After calcining the coal gangue in a calcining furnace at 600℃ for 3 hours, put it into a crusher for crushing and sieving. Select coal gangue with a particle size range of 0.15-0.30mm for later use.

[0045] (2) Preparation of iron-reducing bacteria culture: The bacterial strain was removed from the refrigerator and placed on a sterile operating table that had been sterilized under ultraviolet light for half an hour beforehand. After reaching room temperature, the strain was poured into LB medium and cultured at 28℃ and 120 r / min for 9 h. After the culture became turbid, the culture was inoculated into fresh LB medium on a sterile operating table for reactivation. After activation, the well-growing culture was transferred to a centrifuge and centrifuged at 5000 r / min for 5 min. An appropriate amount of sterile physiological saline was added to the culture, enough to cover the bacteria. The centrifuge tube was gently blown with a sterile pipette to resuspend the bacteria in the physiological saline. The resuspended culture was centrifuged again, and this process was repeated 3 times. After resuspending in sterile physiological saline, the culture was kept for later use. The biomass in the culture was 10 g / L.

[0046] (3) Take 20 kg of the crushed and screened coal gangue and mix it with 30 kg of iron-reducing bacteria solution. Keep the temperature at 30℃ and soak for 35 min. Take out the soaked coal gangue, wash and dry it to obtain coal gangue modified by pozzolanic activity.

[0047] A type of concrete prepared from coal gangue modified with pozzolanic activity includes the following steps:

[0048] Weigh 13 kg of pozzolanic-modified coal gangue, 10 kg of crushed stone, 25 kg of silicate cement, and 8 kg of quartz sand. Mix them thoroughly, then add 27.5 kg of water and 0.3 kg of polycarboxylate superplasticizer (model: DH-4005) and continue mixing to form a homogeneous slurry. Pour the resulting slurry into a mold, dry, and cure to obtain the finished product. The quartz sand has a particle size of 0.5-2 mm, and the crushed stone has a particle size of 5-10 mm.

[0049] Example 3

[0050] A type of coal gangue modified with volcanic ash is prepared by the following steps:

[0051] (1) After calcining the coal gangue in a calcining furnace at 700℃ for 1.5h, put it into a crusher for crushing and sieving. Select coal gangue with a particle size range of 0.15-0.30mm for later use.

[0052] (2) Preparation of iron-reducing bacteria culture: The bacterial strain was removed from the refrigerator and placed on a sterile operating table that had been sterilized under ultraviolet light for half an hour beforehand. After reaching room temperature, the strain was poured into LB medium and cultured at 28℃ and 120 r / min for 9 h. After the culture became turbid, the culture was inoculated into fresh LB medium on a sterile operating table for reactivation. After activation, the well-growing culture was transferred to a centrifuge and centrifuged at 5000 r / min for 5 min. An appropriate amount of sterile physiological saline was added to the culture, enough to cover the bacteria. The centrifuge tube was gently blown with a sterile pipette to resuspend the bacteria in the physiological saline. The resuspended culture was centrifuged again, and this process was repeated 3 times. After resuspending in sterile physiological saline, the culture was kept for later use. The biomass in the culture was 10 g / L.

[0053] (3) Take 20 kg of the crushed and screened coal gangue and mix it with 35 kg of iron-reducing bacteria solution. Keep the temperature at 40℃ and soak for 40 min. Take out the soaked coal gangue, wash and dry it to obtain coal gangue modified by pozzolanic activity.

[0054] A type of concrete prepared from coal gangue modified with pozzolanic activity includes the following steps:

[0055] Weigh out 16 kg of pozzolanic-modified coal gangue, 9 kg of crushed stone, 20 kg of silicate cement, and 10 kg of quartz sand. Mix them thoroughly, then add 30 kg of water and 0.4 kg of polycarboxylate superplasticizer (model: DH-4005) and continue mixing to form a homogeneous slurry. Pour the resulting slurry into a mold, dry, and cure to obtain the finished product. The quartz sand has a particle size of 0.5-2 mm, and the crushed stone has a particle size of 5-10 mm.

[0056] Example 4

[0057] A type of coal gangue modified with volcanic ash, differing from Example 1 in that 4 kg of biochar was added during the impregnation process in this example, and the preparation includes the following steps:

[0058] Steps (1) and (2) are the same as in Example 1;

[0059] (3) Take 20 kg of crushed and screened coal gangue and mix it with 30 kg of iron-reducing bacteria solution. Add 4 kg of biochar and keep the temperature at 30℃ for 35 min. Take out the impregnated coal gangue, wash and dry it to obtain coal gangue modified with volcanic ash.

[0060] A concrete prepared from coal gangue modified with volcanic ash, wherein the coal gangue modified with volcanic ash is the same as that prepared in this embodiment, and the specific preparation steps are the same as in Embodiment 1.

[0061] Example 5

[0062] A type of coal gangue modified with volcanic ash, differing from Example 1 in that 8 kg of biochar was added during the modification process in this example, and the preparation includes the following steps:

[0063] Steps (1) and (2) are the same as in Example 1;

[0064] (3) Take 20 kg of crushed and screened coal gangue and mix it with 30 kg of iron-reducing bacteria solution. Add 8 kg of biochar and keep the temperature at 30℃ for 35 min. Take out the impregnated coal gangue, wash and dry it to obtain coal gangue modified with volcanic ash.

[0065] A concrete prepared from coal gangue modified with volcanic ash, wherein the coal gangue modified with volcanic ash is the same as that prepared in this embodiment, and the specific preparation steps are the same as in Embodiment 1.

[0066] Example 6

[0067] A type of coal gangue modified with volcanic ash differs from Example 1 in that the coal gangue particle size range in this example is 0.35-0.50 mm.

[0068] A concrete prepared from coal gangue modified with volcanic ash, wherein the coal gangue modified with volcanic ash is the same as that prepared in this embodiment, and the specific preparation steps are the same as in Embodiment 1.

[0069] Example 7

[0070] A type of coal gangue modified with volcanic ash, which differs from Example 1 in that the coal gangue particle size range in this example is 0.05-0.15 mm.

[0071] A concrete prepared from coal gangue modified with volcanic ash, wherein the coal gangue modified with volcanic ash is the same as that prepared in this embodiment, and the specific preparation steps are the same as in Embodiment 1.

[0072] Example 8

[0073] A type of coal gangue modified with volcanic ash differs from Example 1 in that the impregnation temperature in the impregnation step of this example is 50°C.

[0074] Comparative Example

[0075] Comparative Example 1

[0076] A type of coal gangue modified with volcanic ash activity differs from Example 1 in that it has not been calcined in this comparative example.

[0077] Comparative Example 2

[0078] A type of coal gangue modified with volcanic ash activity, differing from Example 1 in that iron-reducing bacteria solution was not added in this comparative example, and its preparation includes the following steps:

[0079] (1) After calcining the coal gangue in a calcining furnace at 600℃ for 3 hours, crush it in a crusher and sieve it to select coal gangue with a particle size of 0.15-0.30mm for later use;

[0080] (2) Mix 20 kg of the crushed and screened coal gangue with 40 kg of sterile saline solution, keep the temperature at 20℃ and soak for 30 min. Take out the soaked coal gangue, clean and dry it to obtain coal gangue modified by volcanic ash activity.

[0081] A concrete prepared from coal gangue modified with volcanic ash activity, wherein the coal gangue modified with volcanic ash activity is the same as that prepared in this comparative example, and the specific preparation steps are the same as in Example 1.

[0082] Performance testing

[0083] Test method / test method: Compressive strength: The compressive strength of concrete on the 28th day and the 98th day was tested according to GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The results are shown in Table 1.

[0084] Evaluation of coal gangue activity: The strength activity index of coal gangue was tested according to GB / T 1596-2017 "Fly Ash for Cement and Concrete". Test mortar and control mortar were prepared according to the standard requirements (using silicate cement purchased from Lingshou County Qianfu Mineral Products Processing Plant, strength grade 42.5). The activity index was calculated using the following formula:

[0085]

[0086] In the formula:

[0087] H28—Strength and activity index, %;

[0088] R—28-day compressive strength of the test mortar, in megapascals (MPa);

[0089] R0—Comparative mortar 28-day compressive strength, in megapascals (MPa).

[0090] Table 1 Performance test results

[0091]

[0092]

[0093] Combining Examples 1-3 and Comparative Example 1 with Table 1, it can be seen that the test data of Examples 1-3 are all better than those of Comparative Example 1. This indicates that calcined coal gangue can effectively remove some organic matter and volatiles from the coal gangue, which is beneficial for subsequent modification. Furthermore, the strength of calcined coal gangue is improved, thereby further enhancing the strength of coal gangue modified by pozzolanic activity.

[0094] Combining Examples 1-3 and Comparative Example 2 with Table 1, it can be seen that the test data of Examples 1-3 are all better than those of Comparative Example 2. This indicates that the coal gangue that has not been modified by iron-reducing bacteria solution contains a large amount of sulfides that are not easy to remove. During the long-term use of concrete, these sulfides overflow, causing a decline in concrete performance and affecting the normal use of concrete.

[0095] As can be seen from Examples 1-5 and Table 1, the test data of Examples 4-5 are all better than those of Examples 1-3, indicating that adding biochar during the impregnation process is beneficial to improving the modification effect and activity. Furthermore, biochar can fill the pores caused by the removal of harmful components inside coal gangue, thereby improving the strength of concrete.

[0096] Combining Examples 1 and 6-7 with Table 1, it can be seen that the experimental data of Example 1 are all 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 sites, thereby improving the modification effect.

[0097] Combining Examples 1 and 8 with Table 1, it can be seen that the experimental data of Example 1 are all better than those of Example 8, indicating that the impregnation temperature affects the final modification of coal gangue during the impregnation process. A suitable impregnation temperature is conducive to improving the activity of iron-reducing bacteria, enabling them to play a better role, promoting the conversion of sulfides in coal gangue, and improving the modification effect.

[0098] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for active modification of coal gangue pozzolanic, characterized in that, Includes the following steps: (1) After high-temperature calcination, the coal gangue is crushed and screened for later use; (2) Preparation of iron-reducing bacteria culture: After activating the iron-reducing bacteria strain, take the well-growing culture and centrifuge it at 4000-5000 r / min for 5-10 min. After washing it 3 times with sterile physiological saline, add sterile physiological saline to resuspend it and store it for later use. (3) Impregnation: Mix the coal gangue that has been calcined, crushed and screened at high temperature with iron reducing bacteria solution and stir well. Impregnate for 30-40 minutes. Take out the impregnated coal gangue, wash and dry it to obtain modified coal gangue. During the impregnation step, the impregnation temperature is maintained between 20-40°C; The weight ratio of the coal gangue to the iron-reducing bacteria solution is 1:1.5-2, and the biomass of the iron-reducing bacteria solution is 10 g / L. Biochar may also be added during the impregnation process, and the weight ratio of biochar to coal gangue is 0.2-0.4:

1.

2. The method for active modification of coal gangue pozzolanic according to claim 1, characterized in that: The particle size of the coal gangue after crushing and screening is 0.15-0.30 mm.

3. The method for active modification of coal gangue pozzolanic according to claim 1, characterized in that: The calcination temperature in the high-temperature calcination step is 600-700℃, and the calcination time is 1.5-3 hours.

4. A type of concrete prepared from coal gangue modified with volcanic ash, comprising the following raw materials in parts by weight: 10-16 parts coal gangue, 20-30 parts cement, 8-10 parts quartz sand, 0.2-0.4 parts polycarboxylate superplasticizer, 8-10 parts crushed stone, and 25-30 parts water, wherein the coal gangue is the coal gangue obtained by the volcanic ash active modification method according to any one of claims 1-3.

5. A method for preparing concrete according to claim 4, characterized in that, Includes the following steps: Weigh out coal gangue, crushed stone, cement, and quartz sand according to a specific mix ratio, and mix them thoroughly. Add water and polycarboxylate superplasticizer and continue stirring to form a uniform slurry. Pour the resulting slurry into a mold, dry and cure to obtain the finished product.

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