A method for distinguishing genuine fly ash from fake fly ash impersonated by solid waste

Abstract

The invention discloses a method for distinguishing genuine fly ash from fake fly ash posing as solid waste, comprising the following steps: a. taking a trace amount of dried ash sample to be tested and evenly spreading it on a conductive tape on a sample stage to obtain a single-layer powder material layer; b. placing the sample stage in a scanning electron microscope sample chamber, taking at least 5 fields of view within each field of view, and obtaining a clear image of ash sample particles; c. converting the image into a gray image, performing binarization processing, and measuring the particle size, area and roundness of the ash sample particles in the binary image; d. using data processing software to count the total area value of particles with a roundness of more than 0.8 and the total area value of particles with a roundness of more than 0.5, and dividing the two to obtain a criterion S R>0.8 / S R>0.5 Value: When it is higher than 5%, it is real fly ash; when it is between 2%-5%, it is inferior fly ash mixed with some fake ash; when it is lower than 2%, it is fake fly ash disguised as solid waste. It can quickly, efficiently and accurately identify real and fake fly ash.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering material identification methods, and in particular to a method for identifying real fly ash and fake fly ash pretending to be solid waste. Background Art

[0002] Fly ash is an artificial volcanic ash material, which comes from the powder produced by coal burning in power plants. Its main chemical components are silicon oxide, aluminum oxide, iron oxide, calcium oxide and unburned carbon. It has potential volcanic ash activity and can undergo chemical reactions in a normal temperature alkaline environment with water to produce a gelling substance. Fly ash has a ball effect, a filling effect and an activity effect in concrete, which can improve the workability of concrete, improve construction performance, improve concrete microstructure and improve the later strength and durability of concrete. At the same time, it can also reduce the amount of cement, reduce the heat of hydration, and achieve the environmental effect of energy saving and environmental protection, so it is widely used in engineering construction.

[0003] However, due to the huge economic and environmental benefits generated by the application of fly ash in mortar concrete, the high-quality fly ash in the market is in short supply. Fake fly ash or adulterated fly ash disguised as solid waste such as coal gangue, furnace slag, metallurgical waste slag, waste stone powder, etc. has flowed into the market, causing the concrete mixture in the project to have poor workability and rheology, seriously affecting the quality of the project.

[0004] On September 28, 2021, the China Patent Office published "A method and device for identifying glass beads in fly ash". By identifying glass beads in fly ash particle images, the percentage of the number of glass beads in the total number of particles and the volume percentage of the total particle volume are obtained, and the authenticity of the fly ash is judged in combination with the pre-set threshold. The main problems with this method are: the principle and method of the controller to identify and calculate the percentage of the number and volume of glass beads are unclear; in addition, the threshold for identifying glass beads is not disclosed, and the reasonable range of the threshold range is unclear, so quantitative judgment cannot be made.

[0005] On September 5, 2017, the Chinese Patent Office announced a "quick on-site identification method for fly ash for concrete". The photo of the fly ash sample to be tested is magnified and observed, and the percentage of the fly ash glass is obtained through microscope image observation to determine whether the fly ash is qualified, unqualified or needs comprehensive testing. This method uses the percentage of glass as a criterion, but the microscope magnification is low, the sample particles are stacked, and counting the glass by observation is labor-intensive, with high errors and low detection efficiency. Summary of the invention

[0006] The present invention aims to provide a rapid, efficient and accurate method for distinguishing genuine fly ash from fake fly ash impersonated by solid waste.

[0007] To this end, the technical solution adopted by the present invention is: a method for distinguishing true fly ash from fake fly ash impersonated by solid waste, comprising the following steps:

[0008] a. Take a small amount of dried ash sample to be tested and spread it evenly on the conductive tape on the sample table. Use an ear-cleaning bulb to blow away the excess powder covering the powder layer to obtain a single layer of powder material;

[0009] b. Place the sample stage into the SEM sample chamber and start vacuuming. At the same time, open the SEM software and image analysis software on the computer. Take at least 5 fields of view in each field of view to obtain a clear image of the gray sample particles.

[0010] c. Use image analysis software to convert the image into a gray image and perform binarization processing, and use image analysis software to measure the shape factor value of the gray sample particles in the binary image. The shape factor value includes the particle size, area and roundness of a single gray sample particle in the field of view;

[0011] d. Use the data processing software to use the formula = SUMIF (roundness column: roundness column, "> = roundness value", area column: area column), and calculate the total area of ​​particles with a roundness of more than 0.8 and the total area of ​​particles with a roundness of more than 0.5. Divide the two to obtain the criterion SR>0.8 / SR>0.5 value:

[0012] When the SR>0.8 / SR>0.5 value is higher than 5%, the ash sample is true fly ash;

[0013] When the SR>0.8 / SR>0.5 value is between 2% and 5%, the ash sample is low-quality fly ash mixed with some fake ash;

[0014] When the SR>0.8 / SR>0.5 value is lower than 2%, the ash sample is fake fly ash disguised as solid waste.

[0015] As a preferred embodiment of the above scheme, in step a, the drying temperature is 105-110° C. and the drying time is 1-2 h.

[0016] More preferably, in step a, a thin needle is used as a sampling tool for the ash sample to be tested.

[0017] More preferably, in step b, the acceleration voltage of the scanning electron microscope is 15 kV and the magnification is 400 times.

[0018] More preferably, in step b, 1000-30000 ash particles are obtained in each field of view of each sample.

[0019] More preferably, the threshold selected during the binarization process in step c is between 100-110.

[0020] The method for distinguishing true fly ash from false fly ash posing as solid waste provided by the present invention is based on the following: the false fly ash posing as solid waste such as coal gangue, furnace bottom slag, metallurgical waste slag, waste stone powder, etc. is characterized in that its particle shape is irregular and multi-faceted, while the particle shape of fly ash is basically spherical based on its formation mechanism. For non-independent particles that are stuck together, their roundness is low but they occupy a large area. In order to eliminate their influence on the area ratio, particles with roundness R>0.5 are selected as single particles, and their area sum is used as the denominator; particles with roundness R>0.8 are selected as near-spherical particles, and their area sum is the area sum of true fly ash particles, which is used as the denominator.

[0021] The invention has the beneficial effects of directly measuring the shape factor of a powder particle group based on the range of the roundness of a single particle by an image analysis method, wherein the single particles of real fly ash are all spherical (roundness R>0.8), the single particles of fake fly ash are irregular and multi-prism (roundness 0.5<R<0.8), and the non-independent particles that are stuck together (roundness R≯0.5) are excluded, and the appropriate particle group shape characteristic parameters are calculated, and the calculated SR>0.8 / SR>0.5 value can reflect the shape characteristics of the powder particle group, and a high SR>0.8 / SR>0.5 value indicates that there are many high-roundness particles, and vice versa; the method does not require chemical treatment, and the required parameters can be obtained by using an electron microscope and image analysis software, so as to quantitatively distinguish between real and fake fly ash, and has the advantages of simple operation, reliable judgment, rapidity and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Comparison of 400x scanning electron microscope images of real fly ash, inferior fly ash mixed with some solid waste powder, and fake fly ash that is entirely solid waste powder. DETAILED DESCRIPTION

[0023] The present invention will be further described below by way of embodiments and in conjunction with the accompanying drawings:

[0024] Example 1: The ash sample is real fly ash, and its microscopic image is as follows Figure 1 (a), the specific steps are:

[0025] a. Stick a conductive tape of appropriate size on the sample table, then use a fine needle to take a small amount of dried ash sample (real fly ash) to be evenly spread on the conductive tape, use an ear-cleaning bulb to blow away the excess powder covering the powder layer, and if there are too dense areas, use a fine needle to gently poke to obtain a single layer of powder material. The drying temperature of the ash sample to be tested is 105-110℃, and the drying time is 1-2h.

[0026] b. After the sample preparation is completed, the sample stage is placed in the SEM sample chamber and vacuum is started. At the same time, the SEM software and image analysis software on the computer are opened. After the sample chamber reaches vacuum, 5 fields of view are taken within each field of view to obtain a clear image of the ash sample particles. Preferably, the acceleration voltage of the SEM is 15 kV and the magnification is 400 times.

[0027] c. Use image analysis software to convert the image into a gray image, select a threshold of 102 for binarization, and use image analysis software to measure the shape factor value of the gray particles in the binary image. The shape factor value includes the particle size, area and roundness of a single gray particle in the field of view.

[0028] d. Use data processing software to use the formula = SUMIF (roundness column: roundness column, "> = roundness value", area column: area column) to calculate the total area of ​​particles with a roundness of more than 0.8 and the total area of ​​particles with a roundness of more than 0.5, and divide the two to obtain the criterion SR>0.8 / SR>0.5 value.

[0029] The data of the five viewing fields of the gray sample are shown in Table 1.

[0030] Table 1 Five viewing field data of grade Ⅰ gray sample

[0031]

[0032] The SR>0.8 / SR>0.5 values ​​of the real fly ash samples are both above 5%.

[0033] Example 2: The ash sample is low-quality ash mixed with some solid waste powder, and its microscopic image is as follows Figure 1 (b), the specific steps are:

[0034] a. Stick a conductive tape of appropriate size on the sample table, then use a fine needle to take a small amount of dried ash sample to be tested (low-quality ash mixed with some solid waste powder) and spread it evenly on the conductive tape, and use an ear-cleaning bulb to blow away the excess powder covering the powder layer. If there are too dense areas, use a fine needle to gently poke to obtain a single layer of powder material. The drying temperature of the ash sample to be tested is 105-110℃, and the drying time is 1-2h.

[0035] b. After the sample preparation is completed, the sample stage is placed in the SEM sample chamber and vacuum is started. At the same time, the SEM software and image analysis software on the computer are turned on. After the sample chamber is vacuumed, 5 fields of view are taken in each field of view to obtain a clear image of the ash particles. Preferably, the acceleration voltage of the SEM is 15 kV and the magnification is 400 times. 1,000 to 30,000 ash particles are obtained in each field of view of each sample.

[0036] c. Use image analysis software to convert the image into a gray image, select a threshold of 105 for binarization, and use image analysis software to measure the shape factor value of the gray particles in the binary image. The shape factor value includes the particle size, area and roundness of a single gray particle in the field of view.

[0037] d. Use data processing software to use the formula = SUMIF (roundness column: roundness column, "> = roundness value", area column: area column) to calculate the total area of ​​particles with a roundness of more than 0.8 and the total area of ​​particles with a roundness of more than 0.5, and divide the two to obtain the criterion SR>0.8 / SR>0.5 value.

[0038] The data of the five fields of view of the gray sample are shown in Table 2.

[0039] Table 2 Data of five viewing fields of inferior gray samples

[0040]

[0041] The SR>0.8 / SR>0.5 values ​​of inferior ash samples are both between 2% and 5%.

[0042] Example 3: The ash sample is fake fly ash disguised as solid waste powder, and its microscopic image is as follows Figure 1 (c), the specific steps are:

[0043] a. Stick a conductive tape of appropriate size on the sample table, then use a fine needle to take a small amount of dried ash sample to be tested (low-quality ash mixed with some solid waste powder) and spread it evenly on the conductive tape, and use an ear-cleaning bulb to blow away the excess powder covering the powder layer. If there are too dense areas, use a fine needle to gently poke to obtain a single layer of powder material. The drying temperature of the ash sample to be tested is 105-110℃, and the drying time is 1-2h.

[0044] b. After the sample preparation is completed, the sample stage is placed in the SEM sample chamber and vacuum is started. At the same time, the SEM software and image analysis software on the computer are turned on. After the sample chamber is vacuumed, 5 fields of view are taken in each field of view to obtain a clear image of the ash particles. Preferably, the acceleration voltage of the SEM is 15 kV and the magnification is 400 times. 1,000 to 30,000 ash particles are obtained in each field of view of each sample.

[0045] c. Use image analysis software to convert the image into a gray image, select a threshold of 110 for binarization, and use image analysis software to measure the shape factor value of the gray particles in the binary image. The shape factor value includes the particle size, area and roundness of a single gray particle in the field of view.

[0046] d. Use data processing software to use the formula = SUMIF (roundness column: roundness column, "> = roundness value", area column: area column) to calculate the total area of ​​particles with a roundness of more than 0.8 and the total area of ​​particles with a roundness of more than 0.5, and divide the two to obtain the criterion SR>0.8 / SR>0.5 value.

[0047] The data of the five viewing fields of the gray sample are shown in Table 3.

[0048] Table 3 Data of five viewing fields of fake fly ash

[0049]

[0050] The SR>0.8 / SR>0.5 values ​​of pseudo fly ash are both below 2%.

Claims

1. A method for distinguishing genuine fly ash from fake fly ash disguised as solid waste, characterized in that: The following steps are involved: a. Take a small amount of dried ash sample to be tested and spread it evenly on the conductive tape on the sample table. Use an ear-cleaning bulb to blow away the excess powder covering the powder layer to obtain a single layer of powder material; b. Place the sample stage into the SEM sample chamber and start vacuuming. At the same time, open the SEM software and image analysis software on the computer. Take at least 5 fields of view in each field of view to obtain a clear image of the gray sample particles. c. Use image analysis software to convert the image into a gray image and perform binarization processing, and use image analysis software to measure the shape factor value of the gray sample particles in the binary image. The shape factor value includes the particle size, area and roundness of a single gray sample particle in the field of view; d. Use the data processing software to use the formula =SUMIF(roundness column:roundness column,">=roundness value", area column:area column) to calculate the total area of ​​particles with a roundness of more than 0.8 and the total area of ​​particles with a roundness of more than 0.5, and divide the two to get the criterion S R>0.8 / S R>0.5 Value, R is roundness: When S R>0.8 / S R>0.5 When the value is higher than 5%, the ash sample is true fly ash; When S R>0.8 / S R>0.5 When the value is between 2% and 5%, the ash sample is low-quality fly ash mixed with some fake ash; When S R>0.8 / S R>0.5 When the value is less than 2%, the ash sample is fake fly ash posing as solid waste; The accelerating voltage of the scanning electron microscope in step b is 15 kV and the magnification is 400 times; The threshold selected during the binarization process in step c is between 100 and 110.

2. The method for distinguishing genuine fly ash from fake fly ash disguised as solid waste according to claim 1, characterized in that: In step a, the drying temperature is 105-110° C. and the drying time is 1-2 h.

3. The method for distinguishing genuine fly ash from fake fly ash disguised as solid waste according to claim 1, characterized in that: In the step a, a fine needle is used as a sampling tool for the ash sample to be tested.

4. The method for distinguishing genuine fly ash from fake fly ash disguised as solid waste according to claim 1, characterized in that: In the step b, 1000-30000 ash particles are obtained in each field of view of each sample.

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