Preparation method of modified coal gangue ceramic aggregate and high-strength lightweight concrete

Abstract

This invention relates to a method for preparing modified coal gangue ceramsite aggregate and high-strength lightweight concrete. The preparation method includes: Step 1, mixing alkaline solution, water glass, and coal gangue ceramsite, and then soaking under pressure to obtain mixture A. The pH of the alkaline solution is ≥13. The pressurization process includes two stages: pressurization and constant pressure. Step 2, adding composite mineral powder to mixture A, and letting it stand for 48 hours to obtain mixture B. The composite mineral powder is a mixture of S95 mineral powder and S105 mineral powder in a certain mass ratio. Step 3, after mixture B is clarified, retaining the clarified liquid, filtering, and washing the precipitate to obtain solid particles, which are the modified coal gangue ceramsite aggregate. This modified coal gangue ceramsite can be used in high-strength lightweight concrete. This invention, by modifying coal gangue ceramsite, reduces the porosity of the ceramsite, thereby weakening its water absorption and storage capacity, and increasing its compressive strength and apparent density. It also solves the problem of ceramsite aggregate floating in concrete due to its low density.

Description

Technical Field

[0001] This invention relates to the field of concrete, specifically to a method for preparing modified coal gangue ceramsite aggregate and high-strength lightweight concrete. Background Technology

[0002] The wastewater from concrete mixing plants mainly comes from the washing water of mixing equipment and vehicles. This wastewater contains a large amount of unhydrated cement, fly ash and other gel materials, is highly alkaline and has a large amount of harmful residues. Random discharge will cause soil and water pollution.

[0003] Currently, the common method for treating wastewater from concrete mixing plants is to use inorganic acids to adjust the pH value of the wastewater to the discharge standard before discharge. However, the large-scale use of inorganic acids introduces excessive harmful ions back into the wastewater, making it impossible to recycle the wastewater. Furthermore, the treatment process is slow, energy-intensive, and ineffective.

[0004] Coal gangue is a solid waste generated during coal mining and washing. It contains large amounts of alkaline earth metals and sulfides, which can be leached by rainwater, causing harmful components to enter the atmosphere, soil, and water bodies, resulting in environmental pollution. However, landfill remains the primary method for disposing of coal gangue, but it also poses serious risks to the soil and water bodies in the landfill areas.

[0005] Existing technologies use coal gangue as raw material to produce coal gangue ceramsite, but coal gangue ceramsite has problems such as high porosity, strong water absorption, and low cylinder compressive strength, which prevents it from being widely used. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing modified coal gangue ceramsite aggregate and high-strength lightweight concrete. By modifying the coal gangue ceramsite, the porosity of the coal gangue ceramsite is reduced, its water absorption and storage capacity is weakened, its compressive strength is increased, and the application range of coal gangue ceramsite is expanded.

[0007] The technical objective of this invention is achieved through the following technical solution:

[0008] A method for preparing modified coal gangue ceramsite aggregate, the method comprising:

[0009] Step 1: Mix alkaline solution, water glass, and coal gangue ceramsite, then sieve out the solid particles floating on the water surface. Soak under pressure to obtain mixture A. The pH of the alkaline solution is ≥13. The pressurization process includes two stages: pressurization and constant pressure.

[0010] Step 2: Add composite mineral powder to mixture A, and after standing for 48 hours, mixture B is obtained. The composite mineral powder is composed of S95 mineral powder and S105 mineral powder in a certain mass ratio.

[0011] Step 3: After the mixture B is clarified, retain the clarified liquid and filter and wash the precipitate to obtain modified coal gangue ceramsite aggregate, keep it saturated and surface dry for later use.

[0012] Furthermore, the alkaline solution is the supernatant from the sedimentation tank of the concrete mixing plant wastewater. After adding water glass to the supernatant and mixing it evenly, coal gangue is immediately added and stirred.

[0013] Furthermore, in step 1, during the first stage of pressurization, the air pressure is increased to 2 atmospheres within 5 minutes.

[0014] Furthermore, in step 2, before adding the composite mineral powder, the mixture A is stirred until the coal gangue ceramsite is in a suspended state. During the addition of the composite mineral powder, stirring is continued, and after the composite mineral powder is added, stirring is continued for no less than 5 minutes.

[0015] Furthermore, in step 2, after the composite mineral powder is added, the mixture is intermittently stirred no less than 3 times during the standing period, with a stirring interval of no less than 8 hours. Each stirring session lasts 3-5 minutes, and the stirring speed should ensure that all the ceramsite particles are in a suspended state. No stirring is performed during the last 4 hours of standing.

[0016] Furthermore, the water glass is industrial liquid sodium silicate with a modulus of 2.30-2.40, a Na₂O content of not less than 12%, and a SiO content of not less than 29%; the coal gangue ceramsite has a particle size of 1-6 mm and an apparent density of 1500 kg / m³. 3 The bulk density is 900 kg / m³. 3 The mass ratio of supernatant to water glass is 20:1-25:1, and the volume ratio of supernatant to coal gangue ceramsite is 2:1-3:1.

[0017] Furthermore, the mass ratio of S95 mineral powder to S105 mineral powder in the composite mineral powder is 4:1-5:1, and the mass ratio of the supernatant to the composite mineral powder is 5:1-10:1; the specific surface area of ​​S95 mineral powder is 430 m² / kg, and the 28-day activity index is 95%; the specific surface area of ​​S105 mineral powder is 510 m² / kg, and the 28-day activity index is 105%.

[0018] Furthermore, during step 3 filtration, the precipitate from step 2 should be poured into a flat-bottomed, round-hole sieve with a pore size of 0.6 mm. The precipitate in the sieve should be rinsed with the clarified liquid, and the precipitate should be stirred until clean during rinsing.

[0019] This invention also provides a modified coal gangue ceramsite high-strength lightweight concrete, wherein a single cubic meter of concrete comprises, by weight, the following components:

[0020] 280-450 parts cement, 70-110 parts S95 mineral powder, 900-1200 parts modified coal gangue ceramsite, 40-90 parts cenospheres, 10-50 parts liquid silica fume, 70-140 parts mixing water, and 3.5-7 parts admixtures; the modified coal gangue ceramsite is modified according to the above method, and the compressive strength of the coal gangue ceramsite before modification is 15.1 MPa;

[0021] The cement used is P·Ⅱ52.5 cement with a specific surface area of ​​340 m² / kg; the S95 mineral powder has a specific surface area of ​​430 m² / kg and a 28-day activity index of 95%; the cenospheres have a bulk density of 420 kg / m³. 3 The liquid silica fume contains 50% solids; the additive is a polycarboxylic acid additive, which contains 0.5% by mass of a thickening component.

[0022] Furthermore, the mixing water includes tap water and the clarified liquid of mixture B in step 3, with a mass ratio of tap water to clarified liquid of 7:3-8:2, the storage time of the clarified liquid is ≤20h, and it is stored in a sealed container.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. This invention modifies coal gangue ceramsite, reduces the porosity of the ceramsite to weaken its water absorption and storage capacity, and increases its apparent density. This solves the problem that ceramsite may float in concrete due to its low density. At the same time, it improves the phenomenon of concrete segregation and stratification caused by excessive water absorption of coal gangue ceramsite leading to the release of free water.

[0025] 2. The preparation method of the present invention improves the compressive strength of coal gangue ceramsite, thereby expanding the application range of coal gangue ceramsite in concrete, breaking through the dosage bottleneck, and enabling the preparation of high-strength lightweight concrete.

[0026] 3. In this invention, the supernatant from the sedimentation tank of concrete mixing plant wastewater is used as the base mother liquor for the modification of coal gangue ceramsite. This supernatant contains OH... - The ions are largely consumed during the modification process, which gradually reduces the alkalinity of the supernatant. The reaction conditions are mild and there is no secondary pollution. The resulting clarified liquid can be reused in the subsequent modification of coal gangue ceramsite or in the preparation of high-strength concrete made from modified coal gangue ceramsite, achieving closed-loop utilization. This can reduce the harm and treatment cost of wastewater and improve the performance of coal gangue ceramsite. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to specific embodiments:

[0028] A method for preparing modified coal gangue ceramsite aggregate, the method comprising:

[0029] Step 1: Take an alkaline solution, add water glass to the alkaline solution and mix well, then immediately add coal gangue ceramsite and stir. Sieve out the impurities and particles floating on the surface of the alkaline solution, and soak under pressure to obtain mixture A. The pH of the alkaline solution is ≥13. The pressurization process includes two stages: the first stage is to continuously increase the pressure until the air pressure reaches 2 atmospheres within 5 minutes, and the second stage is to maintain 2 atmospheres for no less than 24 hours.

[0030] As a preferred option, the alkaline solution is the supernatant from the sedimentation tank of concrete mixing plant wastewater.

[0031] The water glass is industrial liquid sodium silicate with a modulus of 2.30-2.40, a Na₂O content of not less than 12%, and a SiO content of not less than 29%; the coal gangue ceramsite has a particle size of 1mm-6mm and an apparent density of 1500kg / m³. 3 The bulk density is 900 kg / m³. 3 The mass ratio of supernatant to water glass is 20:1-25:1, and the volume ratio of supernatant to coal gangue ceramsite is 2:1-3:1.

[0032] Step 2: Add composite mineral powder to mixture A. The composite mineral powder is a mixture of S95 mineral powder and S105 mineral powder. The mass ratio of S95 mineral powder to S105 mineral powder in the composite mineral powder is 4:1-5:1, and the mass ratio of supernatant to composite mineral powder is 5:1-10:1. The specific surface area of ​​S95 mineral powder is 430㎡ / kg, and the 28-day activity index is 95%. The specific surface area of ​​S105 mineral powder is 510㎡ / kg, and the 28-day activity index is 105%.

[0033] Before adding the composite mineral powder, mix A until the coal gangue ceramsite is in a suspended state. Continue stirring during the addition of the composite mineral powder, and after the powder is added, continue stirring for at least 5 minutes. After stirring, let it stand for 48 hours to obtain mix B. During the 48-hour standing period, intermittent stirring is required, with each stirring interval at least 8 hours, and at least 3 stirrings in total. Do not stir during the last 4 hours. Each stirring should ensure the coal gangue ceramsite is in a suspended state, and each stirring time should be 3-5 minutes.

[0034] Step 3: Allow the mixture to stand to obtain a clarified liquid. Remove the clarified liquid, seal it, and store it for later use. The clarified liquid can be used for subsequent preparation of modified coal gangue ceramsite aggregate and for washing the ceramsite, as well as for the preparation of lightweight aggregate concrete. Remove the precipitate obtained from the supernatant and pour it into a sieve for filtration. Use the clarified liquid to wash the precipitate in the sieve. The sieve is a flat-bottomed round-hole sieve with a mesh size of 0.6 mm. After washing and cleaning, modified coal gangue ceramsite aggregate is obtained. The addition of composite mineral powder reacts with the sodium silicate absorbed in the coal gangue ceramsite and the alkaline solution to generate low-calcium silicate and other solid reactants, increasing the density of the coal gangue ceramsite. Ultimately, this results in increased compressive strength, increased apparent density, and reduced water absorption of the coal gangue ceramsite.

[0035] This invention also provides a modified coal gangue ceramsite high-strength lightweight concrete, wherein the modified coal gangue ceramsite obtained by the above method is used to prepare high-strength concrete, and the concrete per cubic meter comprises, by weight, the following proportions:

[0036] 280-450 parts cement, 70-110 parts S95 mineral powder, 900-1200 parts modified coal gangue ceramsite, 40-90 parts cenospheres, 10-50 parts liquid silica fume, 70-140 parts mixing water, and 3.5-7 parts admixtures.

[0037] The cement is P·Ⅱ52.5 cement with a specific surface area of ​​340 m² / kg; the S95 mineral powder has a specific surface area of ​​430 m² / kg and a 28-day activity index of 95%; the cenosphere bulk density is 420 kg / m³. 3 The liquid silica fume has a solid content of 50%; the additive is a polycarboxylate additive, which contains a thickening component with a mass fraction of 0.5%; the compressive strength of the coal gangue ceramsite before modification is 15.1 MPa. The mixing water can be tap water. In this embodiment, the mixing water includes tap water and the clarified liquid of mixture B in step 3 above. The mass ratio of tap water to clarified liquid is 7:3-8:2, and the storage time of the clarified liquid is ≤20h.

[0038] To further illustrate the solution of the present invention, the present invention also provides the following four sets of embodiments:

[0039] Example 1

[0040] A method for preparing modified coal gangue ceramsite aggregate, the method comprising the following steps:

[0041] Step 1: Take 30 kg (30 L) of supernatant from the sedimentation tank of the concrete mixing plant wastewater, add 1.5 kg of water glass to the alkaline supernatant and mix well. Immediately add 10 L of coal gangue ceramsite and stir. Sieve out the impurities and particles floating on the surface of the liquid to obtain mixture A. The pH of the supernatant is 13.6. The pressurization process includes two stages: the first stage is to continuously increase the pressure until the air pressure reaches 2 atmospheres within 5 minutes. The second stage is to maintain 2 atmospheres for no less than 24 hours.

[0042] The water glass is industrial liquid sodium silicate with a modulus of 2.30, a Na₂O content of 12%, and a SiO content of 29%. The coal gangue ceramsite has a continuous gradation of 1mm-6mm and an apparent density of 1500kg / m³. 3 The bulk density is 900 kg / m³. 3 The cylinder compressive strength is 15.1 MPa.

[0043] Step 2: Add 6 kg of composite mineral powder to mixture A. The composite mineral powder is a mixture of S95 mineral powder and S105 mineral powder, with a mass ratio of 4:1. The specific surface area of ​​S95 mineral powder is 430 m² / kg, and its 28-day activity index is 95%. The specific surface area of ​​S105 mineral powder is 510 m² / kg, and its 28-day activity index is 105%.

[0044] Before adding the composite mineral powder, mix A is stirred until the coal gangue ceramsite is in a suspended state. Stirring continues during the addition of the composite mineral powder, and after the addition is complete, stirring continues for at least 5 minutes. After stirring, the mixture is allowed to stand for 48 hours to obtain mix B. During the 48-hour standing period, the mixture is stirred intermittently four times, with each stirring interval of 10 hours. No stirring is performed during the last four hours. Each stirring session ensures the coal gangue ceramsite remains in a suspended state, and each stirring session lasts 3-5 minutes.

[0045] Step 3: Let the mixture stand to obtain a clear liquid. Remove the clear liquid, seal it, and store it for later use. The clear liquid can be used for the subsequent preparation of modified coal gangue ceramsite aggregate or for the preparation of lightweight aggregate concrete. Take the sediment obtained from the supernatant and pour it into a sieve for filtration. Use the clear liquid to wash the sediment in the sieve. After rinsing and cleaning, the modified coal gangue ceramsite aggregate is obtained, denoted as A1.

[0046] Example 2

[0047] A method for preparing modified coal gangue ceramsite aggregate, the method comprising the following steps:

[0048] Step 1: Take 30 kg (30 L) of supernatant from the sedimentation tank of the concrete mixing plant wastewater. Add 1.5 kg of water glass to the alkaline supernatant and mix well. Immediately add 15 L of coal gangue ceramsite and stir. Sieve out the impurities and particles floating on the surface of the liquid to obtain mixture A. The pH of the supernatant is 13.6. The pressurization process includes two stages: the first stage is to continuously increase the pressure until the air pressure reaches 2 atmospheres within 5 minutes. The second stage is to maintain 2 atmospheres for no less than 24 hours.

[0049] The water glass is industrial liquid sodium silicate with a modulus of 2.30, a Na₂O content of 12%, and a SiO content of 29%. The coal gangue ceramsite has a continuous gradation of 1mm-6mm and an apparent density of 1500kg / m³. 3 The bulk density is 900 kg / m³. 3 The cylinder compressive strength is 15.1 MPa.

[0050] Step 2: Add 6 kg of composite mineral powder to mixture A. The composite mineral powder is a mixture of S95 mineral powder and S105 mineral powder, with a mass ratio of 4:1. The specific surface area of ​​S95 mineral powder is 430 m² / kg, and its 28-day activity index is 95%. The specific surface area of ​​S105 mineral powder is 510 m² / kg, and its 28-day activity index is 105%.

[0051] Before adding the composite mineral powder, mix A is stirred until the coal gangue ceramsite is in a suspended state. Stirring continues during the addition of the composite mineral powder, and after the addition is complete, stirring continues for at least 5 minutes. After stirring, the mixture is allowed to stand for 48 hours to obtain mix B. During the 48-hour standing period, the mixture is stirred intermittently four times, with each stirring interval of 10 hours. No stirring is performed during the last four hours. Each stirring session ensures the coal gangue ceramsite remains in a suspended state, and each stirring session lasts 3-5 minutes.

[0052] Step 3: Let the mixture stand to obtain a clear liquid. Remove the clear liquid, seal it, and store it for later use. The clear liquid can be used for the subsequent preparation of modified coal gangue ceramsite aggregate, or for the preparation of lightweight aggregate concrete. Take the sediment obtained from the supernatant and pour it into a sieve for filtration. Use the clear liquid to rinse the sediment in the sieve. After rinsing and cleaning, the modified coal gangue ceramsite aggregate is obtained, denoted as A2.

[0053] Example 3

[0054] A method for preparing modified coal gangue ceramsite aggregate, the method comprising the following steps:

[0055] Step 1: Take 30 kg (30 L) of supernatant from the sedimentation tank of the concrete mixing plant wastewater, add 1.2 kg of water glass to the alkaline supernatant and mix well. Immediately add 15 L of coal gangue ceramsite and stir. Sieve out the impurities and particles floating on the surface of the liquid to obtain mixture A. The pH of the supernatant is 13.6. The pressurization process includes two stages: the first stage is to continuously increase the pressure until the air pressure reaches 2 atmospheres within 5 minutes. The second stage is to maintain 2 atmospheres for no less than 24 hours.

[0056] The water glass is industrial liquid sodium silicate with a modulus of 2.30, a Na₂O content of 12%, and a SiO content of 29%. The coal gangue ceramsite has a continuous gradation of 1mm-6mm and an apparent density of 1500kg / m³. 3 The bulk density is 900 kg / m³. 3 The cylinder compressive strength is 15.1 MPa.

[0057] Step 2: Add 6 kg of composite mineral powder to mixture A. The composite mineral powder is a mixture of S95 mineral powder and S105 mineral powder, with a mass ratio of 4:1. The specific surface area of ​​S95 mineral powder is 430 m² / kg, and its 28-day activity index is 95%. The specific surface area of ​​S105 mineral powder is 510 m² / kg, and its 28-day activity index is 105%.

[0058] Before adding the composite mineral powder, mix A is stirred until the coal gangue ceramsite is in a suspended state. Stirring continues during the addition of the composite mineral powder, and after the addition is complete, stirring continues for at least 5 minutes. After stirring, the mixture is allowed to stand for 48 hours to obtain mix B. During the 48-hour standing period, the mixture is stirred intermittently four times, with each stirring interval of 10 hours. No stirring is performed during the last four hours. Each stirring session ensures the coal gangue ceramsite remains in a suspended state, and each stirring session lasts 3-5 minutes.

[0059] Step 3: Let the mixture stand to obtain a clear liquid. Remove the clear liquid, seal it, and store it for later use. The clear liquid can be used for the subsequent preparation of modified coal gangue ceramsite aggregate, or for the preparation of lightweight aggregate concrete. Take the sediment obtained from the supernatant and pour it into a sieve for filtration. Use the clear liquid to wash the sediment in the sieve. After rinsing and cleaning, the modified coal gangue ceramsite aggregate is obtained, which is denoted as A3.

[0060] Example 4

[0061] A method for preparing modified coal gangue ceramsite aggregate, the method comprising the following steps:

[0062] Step 1: Take 30 kg (30 L) of supernatant from the sedimentation tank of the concrete mixing plant wastewater, add 1.2 kg of water glass to the alkaline supernatant and mix well. Immediately add 15 L of coal gangue ceramsite and stir. Sieve out the impurities and particles floating on the surface of the liquid to obtain mixture A. The pH of the supernatant is 13.6. The pressurization process includes two stages: the first stage is to continuously increase the pressure until the air pressure reaches 2 atmospheres within 5 minutes. The second stage is to maintain 2 atmospheres for no less than 24 hours.

[0063] The water glass is industrial liquid sodium silicate with a modulus of 2.30, a Na₂O content of 12%, and a SiO content of 29%. The coal gangue ceramsite has a continuous gradation of 1mm-6mm and an apparent density of 1500kg / m³. 3 The bulk density is 900 kg / m³. 3 The cylinder compressive strength is 15.1 MPa.

[0064] Step 2: Add 3 kg of composite mineral powder to mixture A. The composite mineral powder is a mixture of S95 mineral powder and S105 mineral powder, with a mass ratio of 4:1. The specific surface area of ​​S95 mineral powder is 430 m² / kg, and its 28-day activity index is 95%. The specific surface area of ​​S105 mineral powder is 510 m² / kg, and its 28-day activity index is 105%.

[0065] Before adding the composite mineral powder, mix A is stirred until the coal gangue ceramsite is in a suspended state. Stirring continues during the addition of the composite mineral powder, and after the addition is complete, stirring continues for at least 5 minutes. After stirring, the mixture is allowed to stand for 48 hours to obtain mix B. During the 48-hour standing period, the mixture is stirred intermittently four times, with each stirring interval of 10 hours. No stirring is performed during the last four hours. Each stirring session ensures the coal gangue ceramsite remains in a suspended state, and each stirring session lasts 3-5 minutes.

[0066] Step 3: Let the mixture stand to obtain a clear liquid. Remove the clear liquid, seal it, and store it for later use. The clear liquid can be used for the subsequent preparation of modified coal gangue ceramsite aggregate or for the preparation of lightweight aggregate concrete. Take the sediment obtained from the supernatant and pour it into a sieve for filtration. Use the clear liquid to wash the sediment in the sieve. After rinsing and cleaning, the modified coal gangue ceramsite aggregate is obtained, denoted as A1.

[0067] Apparent density, water absorption rate, and cylinder compressive strength of each embodiment were tested according to the "Lightweight Aggregates and Their Test Methods" (GB / T17431-2010). The test results are shown in Table 1 (A0 in Table 1 represents unmodified coal gangue ceramsite):

[0068] Table 1 Test Results

[0069]

[0070]

[0071] The above-mentioned five groups of coal gangue ceramsite (saturated surface-dry state) A0-A4 were used to prepare high-strength lightweight concrete. The mixing water was a mixture of clarified liquid obtained from modified coal gangue ceramsite and tap water in a 7:3 ratio. The specific ratio is shown in Table 2 below.

[0072] Table 2. Mix proportions of high-strength lightweight concrete made from coal gangue ceramsite (kg / m³) 3 )

[0073]

[0074] The concrete obtained from the five component ratios in Table 2 above was subjected to performance tests, as shown in Table 3 below:

[0075] Table 3. Experimental results of coal gangue ceramsite concrete.

[0076] Group Compressive strength (MPa) <![CDATA[Dry density (kg / m 3 )]]> 1 36.7 1680 2 61.3 1630 3 53.8 1610 4 54.6 1630 5 44.7 1650

[0077] As shown in Table 1, the apparent density of the modified coal gangue ceramsite increased, and the water absorption rate decreased after 1 hour. This indicates that the density of the modified coal gangue ceramsite increased after modification using the method of this invention, and the compressive strength was increased by more than 40%. When the modified coal gangue ceramsite is introduced into concrete as aggregate, it exhibits excellent high-strength and lightweight properties, as shown in Table 3. The compressive strength can reach over 60 MPa, and the dry density is controlled at 1650 kg / m³. 3 .

[0078] This embodiment is merely a further explanation of the present invention and is not intended to limit the present invention. Those skilled in the art can make non-inventive modifications to this embodiment as needed after reading this specification, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing a modified coal gangue ceramicite aggregate, characterized in that, The method includes: Step 1: Mix alkaline solution, water glass, and coal gangue ceramsite, then sieve out the solid particles floating on the surface of the alkaline solution. Soak under pressure to obtain mixture A. The pH of the alkaline solution is ≥13. The pressurization process includes two stages: pressurization and constant pressure. Step 2: Add composite mineral powder to mixture A, and after standing for 48 hours, mixture B is obtained. The composite mineral powder is composed of S95 mineral powder and S105 mineral powder in a certain mass ratio. Step 3: After the mixture B is clarified, retain the clarified liquid, and filter and wash the precipitate from which the clarified liquid is removed to obtain modified coal gangue ceramsite aggregate, keep it saturated and surface dry for later use; The alkaline solution is the supernatant from the sedimentation tank of the concrete mixing plant wastewater. Water glass is added to the supernatant and mixed evenly, and then coal gangue is immediately added and mixed. In step 2, after the composite mineral powder is added, the mixture is stirred intermittently at least 3 times during the settling period, with an interval of at least 8 hours between stirrings. Each stirring session lasts 3-5 minutes, and the stirring speed ensures that all the ceramsite particles are in a suspended state. No stirring is performed during the last 4 hours of settling.

2. The method for preparing modified coal gangue ceramic aggregate according to claim 1, characterized in that, In step 1, during the pressurization process, the air pressure is increased to 2 atmospheres within 5 minutes.

3. The method for preparing modified coal gangue ceramicite aggregate according to claim 1, characterized in that, In step 2, before adding the composite mineral powder, the mixture A is stirred until the coal gangue ceramsite is in a suspended state. During the addition of the composite mineral powder, stirring is continued, and after the composite mineral powder is added, stirring is continued for no less than 5 minutes.

4. The method for preparing modified coal gangue ceramsite aggregate according to claim 1, characterized in that, The water glass is industrial liquid sodium silicate with a modulus of 2.30-2.40, a content of not less than 12%, and a SiO2 content of not less than 29%; the coal gangue ceramsite has a particle size of 1-6 mm, an apparent density of 1500 kg / m³, and a bulk density of 900 kg / m³; the mass ratio of the supernatant to the water glass is 20:1-25:1, and the volume ratio of the supernatant to the coal gangue ceramsite is 2:1-3:

1.

5. The method for preparing modified coal gangue ceramsite aggregate according to claim 1, characterized in that, The mass ratio of S95 mineral powder to S105 mineral powder in the composite mineral powder is 4:1-5:1, and the mass ratio of the supernatant to the composite mineral powder is 5:1-10:1; the specific surface area of ​​the S95 mineral powder is 430 m² / kg, and the 28-day activity index is 95%; the specific surface area of ​​the S105 mineral powder is 510 m² / kg, and the 28-day activity index is 105%.

6. The method for preparing modified coal gangue ceramsite aggregate according to claim 1, characterized in that, In step 3, during filtration and washing, pour the sediment from which the clarified liquid has been removed into a flat-bottomed, round-hole sieve with a pore size of 0.6 mm. Use the clarified liquid to rinse the sediment in the sieve, stirring the sediment until it is clean.

7. A high-strength lightweight concrete made from modified coal gangue ceramsite, characterized in that, In a single cubic meter of concrete, the following are included by weight percentage: The mixture comprises 280-450 parts cement, 70-110 parts S95 mineral powder, 900-1200 parts modified coal gangue ceramsite, 40-90 parts cenospheres, 10-50 parts liquid silica fume, 70-140 parts mixing water, and 3.5-7 parts admixtures; the modified coal gangue ceramsite is modified according to any one of claims 1-6, and the compressive strength of the coal gangue ceramsite before modification is 15.1 MPa; The cement is P·Ⅱ52.5 cement with a specific surface area of ​​340㎡ / kg; the S95 mineral powder has a specific surface area of ​​430㎡ / kg and a 28-day activity index of 95%; the cenosphere bulk density is 420kg / m³, and the liquid silica fume has a solid content of 50%; the admixture is a polycarboxylate admixture, which contains a thickening component with a mass fraction of 0.5%.

8. The modified coal gangue ceramsite high-strength lightweight concrete according to claim 7, characterized in that, The mixing water includes tap water and the clarified liquid of mixture B in step 3. The mass ratio of tap water to clarified liquid is 7:3-8:

2. The clarified liquid is stored for ≤20 hours and is sealed.

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