A method for calculating the specific surface area of ​​coarse aggregate based on sieving curve

Abstract

The present invention relates to the field of building materials, and discloses a method for calculating the specific surface area of ​​coarse aggregate based on a screening curve, comprising the following steps: the first step: conducting a screening test, screening out coarse aggregates of different sizes, and obtaining sample one; the second step: adopting a quarter sampling method to sample sample one, obtaining an aggregate sample that is easy to count and representative, and determining its screening curve at the same time; the third step: using a slurry coating method to determine the specific surface area, and numerically fitting the sample surface area, volume and diameter to obtain the mathematical relationship between the specific surface area, volume and diameter of the aggregate; the fourth step: using image analysis software to analyze the aggregate sample to obtain the geometric size parameters of the aggregate; the fifth step: firstly, it is necessary to define the test parameters, and then establish a mathematical formula based on the screening curve; the sixth step: error analysis. The present invention obtains the specific surface area of ​​the coarse aggregate by calculation, and uses it as a sufficient condition for calculating the slurry film thickness of the concrete specimen, and it is also an important technical parameter for analyzing the effect of the coarse aggregate on the performance of concrete. The present invention provides a new design idea for the mix design of high-performance concrete.

Description

Technical Field

[0001] The invention relates to the field of building materials, and in particular to a method for calculating the specific surface area of ​​coarse aggregate based on a screening curve. Background Art

[0002] Coarse aggregate is one of the important components of concrete, and its volume proportion is generally 40-60%, mainly playing the role of skeleton support and filling. Coarse aggregate is made of natural rock, pebbles or mine waste rock through mechanical crushing and screening, and has an irregular shape. There are many parameters used to characterize the shape of coarse aggregate, such as specific surface area, roundness, particle size and screening characteristics. Among them, specific surface area is an important parameter for determining the thickness of concrete cementitious materials, but it is difficult to obtain using traditional experimental methods. In addition, the screening curve of coarse aggregate can well describe the gradation of coarse aggregate, which is easy to obtain in the laboratory. Properly graded coarse aggregate can make concrete denser and have lower porosity. This dense stacking state is closely related to the gradation and specific surface area of ​​coarse aggregate. The specific surface area of ​​coarse aggregate directly affects the workability, mechanical properties and durability of concrete. Therefore, the quantitative analysis of the specific surface area of ​​coarse aggregate is not only the key to the design of high-performance concrete, but also the key to the improvement and optimization of the performance of traditional concrete.

[0003] At present, the main methods for determining specific surface area are the BET method and the laser diffraction method. However, the specific surface area determined by the above methods takes into account the internal pores of the material, and the particle size of the sample is generally below 4.75 mm, which is not suitable for coarse aggregates larger than 5 mm. CT scanners are also used to determine the specific surface area of ​​coarse aggregates. Although this method can restore the irregular shape of the aggregate to the greatest extent, the original CT image has uneven lighting and blurred boundaries, requires a lot of post-image processing, and is costly, so its adaptability is low. In addition, cement paste or paraffin is used as a wrapping material, and the specific surface area of ​​coarse aggregate can also be calculated using the mass relationship. However, the amount of coarse aggregate is large, and the determination of the specific surface area using this method requires a lot of experiments, which does not meet the actual engineering needs. For this reason, we propose a method for calculating the specific surface area of ​​coarse aggregate based on the screening curve. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies in the prior art, the present invention provides a method for calculating the specific surface area of ​​coarse aggregate based on a screening curve to solve the above-mentioned problems.

[0006] (II) Technical solution

[0007] In order to achieve the above-mentioned purpose, the present invention provides the following technical solutions:

[0008] A method for calculating the specific surface area of ​​coarse aggregate based on a screening curve comprises the following steps:

[0009] Step 1: Conduct a sieving test, using seven square sieves with different apertures to sieve out coarse bones of different sizes to obtain sample 1;

[0010] Step 2: Use the quarter sampling method to sample sample 1, obtain an aggregate sample that is easy to count and representative, and determine its screening curve at the same time;

[0011] Step 3: Prepare a sample with a regular shape as a reference, use the paste coating method to determine the specific surface area, and obtain the mathematical relationship between the specific surface area, volume and diameter of the aggregate by numerically fitting the sample surface area, volume and diameter;

[0012] Step 4: Use image analysis software to analyze the aggregate sample to obtain the geometric size parameters of the aggregate;

[0013] Step 5: First, you need to define the test parameters, and then establish a mathematical formula based on the screening curve;

[0014] Step 6: Error analysis.

[0015] Preferably, in the first step, the square sieve is 2.36-31.5 mm, the screening vibration time is 10 minutes, the maximum diameter of the aggregate is 26.5 mm, and the apparent density is 2.699 g / cm 3 , 12.0 kg of coarse aggregate was used for the screening test.

[0016] Preferably, the process of the quarter sampling method in the second step is as follows: randomly select the same batch of aggregates and mix them for 3 minutes to ensure that the aggregates are randomly distributed, then spread the aggregates into a round cake shape, divide them into four parts in two orthogonal directions, randomly select one part, and then repeat the above operation until a sufficient number is obtained and easy to count;

[0017] The sieving curve was obtained as follows: the diameter of each sample, the minimum diameter and mass of the aggregate that can pass through the sieve were measured and recorded using a ±0.02 mm vernier caliper and a ±0.001 g electronic scale. All samples were numbered from small to large particle size, and the volume was the ratio of the aggregate mass to the apparent density. The sieving curve was then obtained.

[0018] Preferably, the specific surface area in the third step is obtained as follows: immerse the aggregate sample in cement paste with a water-cement ratio of 0.50 for 5 seconds, then take out the aggregate sample, weigh its mass, calculate the mass of the cement paste wrapping the aggregate, and then calculate the specific surface area of ​​the aggregate by the formula.

[0019] Preferably, the steps for obtaining the geometric size parameters in the fourth step are as follows: place a ruler as a reference size, photograph all aggregates and the ruler, use software to set the color threshold of the image, binarize the image to obtain a black and white image, and finally use software to calculate the pixel information in the image to finally obtain the size parameters of the aggregate sample.

[0020] Preferably, the contents of defining the test parameters and establishing the mathematical formula in the fifth step are as follows:

[0021] S1: Set d1-d7 as the square sieve aperture used in the first step for different screening tests, and f1-f6 as the mass distribution content of aggregate remaining on the sieve;

[0022] S2: Set the diameter interval to d a -d a+1 The aggregate is divided into m equal parts, and the mass distribution content of each aggregate is f a-m ;

[0023] S3: In summary In conclusion, f a is the mass distribution content of aggregate on sieve a after the screening test, Δd a is the diameter increment of aggregate;

[0024] S4: Based on the above formula, the diameter of each aggregate is d a to d a +(m-1)Δd a between;

[0025] S5: The total surface area of ​​the aggregate is calculated by cumulative addition, and then the ratio of the total surface area of ​​the aggregate to the total mass is calculated to obtain the specific surface area of ​​the aggregate;

[0026] The formula is:

[0027] Preferably, the formula in S5 can be simplified to:

[0028] Preferably, the content of the sixth step error analysis is as follows:

[0029] S1: Substitute the mathematical relationship between the specific surface area, volume and diameter of the aggregate obtained in the third step into the mathematical formula in the fifth step;

[0030] S2: calculated specific surface area;

[0031] S3: Perform numerical comparison.

[0032] (III) Beneficial effects

[0033] Compared with the prior art, the method for calculating the specific surface area of ​​coarse aggregate based on the screening curve provided by the present invention has the following beneficial effects:

[0034] 1. The method for calculating the specific surface area of ​​coarse aggregate based on the screening curve. The aggregate screening curve is obtained based on the screening test and is usually used to characterize the particle size and grading of the aggregate. Compared with the BET method, laser diffraction method, CT scanning image analysis method or slurry coating method, the screening test is simpler and easier to complete. Based on this, the present invention establishes a numerical relationship between the screening characteristics and the specific surface area of ​​coarse aggregate, and with the help of image analysis technology, derives a calculation formula for calculating the specific surface area of ​​coarse aggregate based on the screening curve. Compared with the results calculated by the slurry coating method or the image analysis method, the specific surface area error calculated by this method is within 2%, which shows that the calculation method provided by the present invention is a simple and efficient method for determining the specific surface area of ​​coarse aggregate.

[0035] 2. The method for calculating the specific surface area of ​​coarse aggregate based on the screening curve is not only the key to the design of high-performance concrete, but also the key to the improvement and optimization of the performance of traditional concrete. The specific surface area of ​​coarse aggregate obtained by calculation is a sufficient condition for calculating the slurry film thickness of the concrete specimen, and is also an important technical parameter for analyzing the effect of coarse aggregate on the performance of concrete. The present invention provides a new design idea for the mix design of high-performance concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Aggregate screening curve of the embodiment of the present invention;

[0037] Figure 2 is the relationship between the surface area and diameter of the aggregate sample measured by the paste coating method in the embodiment of the present invention;

[0038] Figure 3 is the relationship between the volume and diameter of the aggregate sample measured by the paste coating method in the embodiment of the present invention;

[0039] Figure 4 The shape parameters of the aggregate samples obtained by image analysis in the embodiment of the present invention;

[0040] Figure 5 Specific surface areas of aggregate samples calculated by different shape models according to the embodiments of the present invention.

[0041] Figure 6 is the relationship between the surface area and Feret diameter of the aggregate sample measured by the image analysis method (M4) in the embodiment of the present invention;

[0042] Figure 7 is the relationship between the aggregate sample volume and the Feret diameter measured by the image analysis method (M4) in the embodiment of the present invention;

[0043] Figure 8 The specific surface area data of aggregate samples measured by the paste coating method and different models in the embodiments of the present invention;

[0044] Fig. 9 is the distribution content curve of the aggregate in the embodiment of the present invention;

[0045] Fig.10 is the relationship between the specific surface area and the number m of the divided parts in the embodiment of the present invention; DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] Example

[0048] See also Figure 1-10 The method for calculating the specific surface area of ​​coarse aggregate based on the screening curve provided in an embodiment of the present invention comprises the following steps:

[0049] 1. Coarse aggregate screening characteristics

[0050] In this embodiment, the apertures of the square sieves used in the screening test are 2.36 mm, 4.75 mm, 9.50 mm, 16.00 mm, 19.00 mm, 26.50 mm and 31.5 mm respectively. The maximum diameter of the granite coarse aggregate used is 26.5 mm, and the apparent density is 2.699 g / cm 3 12.0 kg of coarse aggregate was used for the screening test, and the screening vibration time was 10 minutes to ensure that the aggregate was fully screened. The specific screening curve is as follows Figure 1 shown.

[0051] 2. Sample preparation

[0052] In the screening test, the number of coarse aggregate samples is usually too large to be analyzed and counted in detail. Therefore, the quartering method is used to obtain aggregates that are easy to count and representative. The quartering method process is as follows: First, randomly select aggregates from the same batch and mix them for 3 minutes to ensure that the aggregates are randomly distributed. Then, the aggregates are spread out into a round cake shape and divided into four parts in two orthogonal directions. One part is randomly selected and the above operation is repeated until a sufficient number is obtained and easy to count.

[0053] The present invention obtains a total of 20 aggregate samples by the quarter sampling method. The diameter (d0, the minimum diameter of the aggregate that can pass through the sieve) and mass (m0) of each sample are measured and recorded using a vernier caliper (±0.02 mm) and an electronic scale (±0.001 g). All samples are numbered from small to large particle size. The volume is the ratio of the aggregate mass to the apparent density. Table 1 lists the characteristics of all 20 samples such as diameter, weight and volume.

[0054] Figure 1 The sieving curves of 20 samples are listed in Figure 2. It can be seen that the sieving curves of the 20 samples are relatively consistent with the sieving curve of 12 kg aggregate, which shows that these samples can be used to represent the particle size distribution of aggregate.

[0055] Table 1. Dimensions and weights of aggregate samples and paste test results.

[0056]

[0057]

[0058] 3. Determination of specific surface area by batter coating method

[0059] Since the coarse aggregate in concrete is always coated by cement paste, the cement paste coating method is used to determine the surface area of ​​the above 20 aggregate samples. The use of cement paste can well simulate similar aggregate-paste interfaces in concrete, ensuring the accuracy of the coating method. Before conducting the coating method test, it is necessary to prepare a sample with a regular shape as a reference. The reference sample mass, shape and size, and surface area parameters are shown in Table 1. The test steps of the coating method are as follows: immerse each aggregate in cement paste with a water-cement ratio of 0.50 for 5 seconds, then take out the aggregate and weigh its mass m1. Through Δm 1-i =m1-m0 can be used to calculate the mass of the cement paste wrapping the aggregate, and then the surface area of ​​the aggregate can be calculated using formula 1.

[0060]

[0061] Among them, S 0-i is the surface area of ​​aggregate number i measured by the paste coating method, Δm 1-i is the mass of cement paste for aggregate with package number i, Δm R is the mass of cement paste wrapping the reference sample, S R is the surface area of ​​the reference sample.

[0062] The surface area data of each sample measured by the batter coating method are shown in Table 1. From the table, we know that the total surface area of ​​20 samples is 5823.95mm 2The total mass is 14.781 g, and the total specific surface area is the ratio of the total surface area to the total mass, which is calculated to be 394.02 mm 2 / g.

[0063] By numerically fitting the sample surface area, volume and diameter, the mathematical relationship between the surface area, volume and diameter of the aggregate is obtained. The fitting formulas are shown in Formula 2 and Formula 3, and the fitting curve is shown in Figure 2 and Figure 3 shown.

[0064]

[0065] 4. Determination of specific surface area by image analysis

[0066] The present invention uses the image analysis software Image Pro Plus 6.0 (IPP) to analyze the aggregate sample to obtain the geometric size parameters of the aggregate. The detailed process of image analysis is as follows: First, place a ruler as a reference size. Secondly, take pictures of all aggregates and the ruler. Use the IPP software to set the color threshold of the image, perform binarization on the image, and obtain a black and white image. Finally, use the IPP software to calculate the pixel information in the image, and finally obtain the size parameters of the aggregate sample. The geometric size of the sample is as follows: Figure 4 shown.

[0067] like Figure 4 As shown, the IPP software can export the size parameters of 8 samples. The cross-sectional parameters include the cross-sectional area A1, the cross-sectional perimeter P1. The longest diameter D1 through the center, the shortest diameter D2, and the average diameter D3. The outer frame rectangle parameters, such as the length L1, the width W1. The Feret diameter F1.

[0068] It is worth noting that the Feret diameter is the average distance between the parallel lines of the two boundaries of the particle projection contour measured clockwise / counterclockwise at intervals of 2°.

[0069] In order to calculate the surface area of ​​irregularly shaped aggregates, assumptions were made about the shapes of the aggregate samples. There are 10 models in total, and the model height is equal to the ratio of the sample volume to its cross-sectional area. Models 1 to 4 are cylindrical, and the corresponding cross-sectional diameters of the models are D1, D2, D3 and F1, respectively. Models 5-8 are prism models, and the cross-sectional side lengths are D1, D2, D3 and F1, respectively. Model 9 is a cuboid model, and its cross-sectional length is L1 and width is W1. Model 10 is an irregular cross-sectional cylinder, with a cross-sectional area of ​​A1 and a cross-sectional perimeter of P1.

[0070] In this embodiment, the surface area of ​​model 1-10 is calculated as shown in formula 4-13.

[0071]

[0072] The surface area calculation results of model 1-10 are as follows Figure 5 shown.

[0073] Compared with the total surface area data measured by the batter coating method, the total surface area measured by model 4 is closest, which is 5887.39mm 2 , which is 1.08% higher than the total specific surface area measured by the paste coating method. Model 4 uses the Feret diameter. By numerically fitting the surface area, volume and Feret diameter obtained by Model 4, the mathematical relationship between the surface area, volume and Feret diameter of the aggregate is obtained. The fitting formulas are shown in Formula 14 and Formula 15, and the fitting curve is shown in Figure 6 and Figure 7 shown.

[0074]

[0075] The specific surface area results calculated by the batter coating method and model 1-10 are as follows Figure 8 As shown in the figure, it can be seen that the specific surface area calculated by the cylinder model with Feret diameter is closest to the specific surface area measured by the paste coating method.

[0076] 5. Establish a mathematical formula based on the screening curve

[0077] Before building the mathematical formula, several test parameters need to be defined. Fig. 9 As shown, in this embodiment, the apertures of the square sieves used in the screening test are 2.36mm, 4.75mm, 9.50mm, 16.00mm, 19.00mm, 26.50mm and 31.5mm, respectively, corresponding to d1-d7. After the screening test, f1-f6 are the mass distribution content of the aggregate remaining on the sieve. For example, f1 represents the mass distribution content of the aggregate remaining in the stone diameter of 2.36-4.75mm.

[0078] like Fig. 9 As shown, in order to improve the calculation accuracy, according to the idea of ​​mathematical integration, the diameter interval is set in d a -d a+1 (a is the sieve sequence number) the aggregate is divided into m equal parts. Taking the aggregate interval d2-d3 as an example, the aggregate in this interval is divided into m equal parts, and the diameters of the aggregates are d 2-0 (d2), d 2-1 , d 2-2 ,…d 2-n , d 2-(n+1) , …d 2-(m-1) The mass distribution content of each aggregate is f a-m , as shown in Formula 16, and the diameter difference of each aggregate is shown in Formula 17.

[0079]

[0080] Among them, f a-m is the mass distribution content of each aggregate, f a is the mass distribution content of aggregate on sieve a after the screening test, Δd a is the diameter increment of aggregate.

[0081] After the aggregate is classified, the diameter interval d a -d a+1 The aggregate is divided into m parts, and the diameter of each part is d a , d a +Δd a , d a +2Δd a , …, d a +(m-1)Δd a Then, the total surface area of ​​the aggregate is calculated by accumulation, and then the ratio of the total surface area of ​​the aggregate to the total mass is calculated to obtain the specific surface area of ​​the aggregate. The specific derivation process is shown in Formula 18.

[0082]

[0083] In formula 18, SSA' is the specific surface area of ​​the aggregate, S is the total surface area of ​​the aggregate, M is the total mass of the aggregate, a is the number of sieves with different mesh sizes, k is equal to the number of sieves in the screening test minus one, n is the number of aggregates that did not pass through the sieve, m is the number of aggregates that did not pass through the sieve, and f a-m is the average mass distribution content of aggregate on sieve number a after the screening test, d a-n is the diameter of aggregate numbered n on sieve numbered a, SSA(d a-n ) is the functional relationship between the specific surface area of ​​aggregate numbered n on sieve numbered a and its diameter.

[0084] It is worth noting that d a-n Calculate according to formula 19.

[0085] <h2 style=";text-align:left;direction:ltr"><![CDATA[d <h2 style=";text-align:left;direction:ltr"> a-n <h2 style=";text-align:left;direction:ltr"> =d<h2 style=";text-align:left;direction:ltr"> a <h2 style=";text-align:left;direction:ltr"> +nΔd<h2 style=";text-align:left;direction:ltr"> a <h2 style=";text-align:left;direction:ltr"> ]]><h2 style=";text-align:left;direction:ltr"> Formula 19

[0086] Among them, d a is the mesh diameter of the sieve numbered a.

[0087] In Formula 18, SSA(d a-n ) can be simplified to the ratio of the surface area to the mass of the aggregate, so Formula 18 can be simplified to Formula 20:

[0088]

[0089] In formula 20, S(d a-n) is the quadratic function of the surface area of ​​aggregate numbered n on sieve numbered a with respect to the diameter, V(d a-n ) is the cubic function relationship between the volume of aggregate numbered n on the sieve numbered a and the diameter. In this embodiment, the number of sieves used in the screening test is 7, so k is 6.

[0090] It should be noted that the method of improving the calculation accuracy in formula 20 is derived from the principle of integration. Therefore, the aggregate is evenly divided into m parts according to the size of the diameter. When m is large enough, the numerical accumulation result calculated by formula 20 will converge and eventually reach the limit.

[0091] 6. Error analysis

[0092] From the image analysis, it can be seen that the specific surface area result of model 4 (assuming that the aggregate is a cylindrical model and the cross-sectional diameter is the Feret diameter) is closest to the specific surface area data measured by the paste coating method. Therefore, this embodiment is analyzed based on the calculation results of model 4 and the paste coating method.

[0093] By substituting Formula 2 and Formula 3 into Formula 20 and substituting different values ​​of m, the specific surface area SSA'0 can be calculated. When the value of m is greater than 20, the value of the specific surface area tends to be stable. Therefore, in this embodiment, m is 100.

[0094] By calculation, SSA'0 is stable at 390.9cm 2 / g This value is only slightly higher than the test result of the batter coating method (SSA0 = 394.0 cm 2 / g) is 0.78% lower. The specific calculation results are as follows Fig.10 shown.

[0095] In Model 4, the aggregate diameter is defined as the Feret diameter, so the sieve diameter in Equation 20 also needs to be corrected to the Feret diameter, the Feret diameter d' a With the sieve hole diameter d a The relationship is shown in Formula 21.

[0096] <h2 style=";text-align:left;direction:ltr"><![CDATA[d' <h2 style=";text-align:left;direction:ltr"> a <h2 style=";text-align:left;direction:ltr"> <1.215d<h2 style=";text-align:left;direction:ltr"> a <h2 style=";text-align:left;direction:ltr"> ]]><h2 style=";text-align:left;direction:ltr"> Formula 21

[0097] By substituting formula 14 and formula 15 into formula 20, and converting the diameter of the sieve according to formula 21, and taking m as 100, the specific surface area SSA' can be calculated. M4 388.9cm 2 / g, which is very close to the result obtained by image analysis calculation (SSA M4 =398.3cm 2 / g).

[0098] Table 2 summarizes the results calculated by the paste coating method or model 4 and the results calculated by the numerical formula, and also lists the errors between the test results and the results calculated by the numerical formula, all of which are within 2%. This shows that the mathematical formula proposed in the present invention is a reliable calculation method for determining the specific surface area of ​​coarse aggregate.

[0099] Table 2. Comparison of experimental results and numerical calculation results (m = 100)

[0100] type <![CDATA[SSA0(mm 2 / g)]]> <![CDATA[SSA M4 (mm 2 / g)]]> Test results 394.0 - Model 4 - 398.3 Numerical calculations 390.9 388.9 error -0.78％ -2.36％

[0101] In the above embodiment of the present invention, the specific surface area of ​​the coarse aggregate is obtained by calculation and used as a sufficient condition for calculating the slurry film thickness of the concrete specimen, and is also an important technical parameter for analyzing the effect of the coarse aggregate on the performance of concrete. The present invention provides a new design idea for the mix design of high-performance concrete.

[0102] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for calculating the specific surface area of ​​coarse aggregate based on screening curves, characterized in that: The following steps are involved: Step 1: Conduct a sieving test, using seven square sieves with different apertures to sieve out coarse bones of different sizes to obtain sample 1; Step 2: Sample 1 is sampled by the quartering method. Aggregates from the same batch are randomly selected and mixed for 3 minutes to ensure random distribution of aggregates. Then the aggregates are spread into a round cake shape and divided into four parts in two orthogonal directions. One part is randomly selected and the sampling operation of the quartering method is repeated until a sufficient number of representative aggregate samples are obtained, which are easy to count. At the same time, the diameter of each sample, the minimum diameter and mass of the aggregate that can pass through the sieve are measured and recorded with a ±0.02mm vernier caliper and a ±0.001g electronic scale. All samples are numbered from small to large according to the particle size. The volume is the ratio of the aggregate mass to the apparent density, and the screening curve is obtained; Step 3: Prepare a sample of regular shape as a reference, immerse the aggregate sample in cement paste with a water-cement ratio of 0.50 for 5 seconds, then take out the aggregate sample, weigh its mass, calculate the mass of cement paste wrapping the aggregate, and then calculate the specific surface area of ​​the aggregate through the formula. By numerically fitting the sample surface area, volume and diameter, the mathematical relationship between the specific surface area, volume and diameter of the aggregate is obtained; Step 4: Use image analysis software to analyze the aggregate sample to obtain the geometric size parameters of the aggregate; Step 5: First, you need to define the test parameters, and then establish a mathematical formula based on the screening curve: S1: Set d1-d7 as the square sieve aperture used in the first step for different screening tests, f1-f6 as the mass distribution content of aggregate remaining on the sieve, S2: Set the diameter interval to d a -d a+1 The aggregate is divided into m equal parts, and the mass distribution content of each aggregate is f a-m , S3: In summary In conclusion, f a is the mass distribution content of aggregate on sieve a after the screening test, Δd a is the diameter increment of aggregate, S4: Based on the above and The formula content is to obtain the diameter of each aggregate in d a to d a +(m-1)Δd a between, S5: The total surface area of ​​the aggregate is calculated by accumulating, and then the ratio of the total surface area of ​​the aggregate to the total mass is calculated to obtain the specific surface area of ​​the aggregate. The formula is: Step 6: Error analysis.

2. The method for calculating the specific surface area of ​​coarse aggregate based on the screening curve according to claim 1, characterized in that: In the first step, the square sieve used is 2.36-31.5 mm, and the screening vibration time is 10 minutes; the weight of the aggregate used for the screening test is 12.0 kg, the maximum diameter is 26.5 mm, and the apparent density is 2.699 g / cm 3 .

3. The method for calculating the specific surface area of ​​coarse aggregate based on the screening curve according to claim 1, characterized in that: The steps for obtaining the geometric size parameters in the fourth step are as follows: place a ruler as a reference size, take pictures of all aggregates and the ruler, use software to set the color threshold of the image, binarize the image to obtain a black and white image, and finally use software to calculate the pixel information in the image to finally obtain the size parameters of the aggregate sample.

4. The method for calculating the specific surface area of ​​coarse aggregate based on the screening curve according to claim 1, characterized in that: The formula in S5 can be simplified to:

5. The method for calculating the specific surface area of ​​coarse aggregate based on the screening curve according to claim 1, characterized in that: The contents of the sixth step error analysis are as follows: S1: Substitute the mathematical relationship between the specific surface area, volume and diameter of the aggregate obtained in the third step into the mathematical formula in the fifth step; S2: calculated specific surface area; S3: Perform numerical comparison.

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