A method for evaluating the light transmission performance of cement-based materials

Abstract

The invention discloses a method for evaluating the light transmission performance of cement-based materials. The method comprises the following steps: firstly preparing a series of cement-based materials with different light-transmitting aggregate contents and cement-based materials without aggregate, measuring light reflectance and light transmittance by means of an integrating sphere; fitting a linear equation according to the transmittance and the aggregate contents, wherein the intercept of the ordinate is the light transmittance of cement without aggregate; substituting the reflectance and transmittance of the cement into an IAD algorithm to iteratively calculate the light absorption coefficient and the light scattering coefficient of the cement; building a structural model of the cement-based material by means of CT imaging or spherical particle accumulation, simulating the transmission of light in the cement-based medium by means of a Monte Carlo algorithm on the basis of the model, finally representing the light flux distribution in the cement-based material by a three-dimensional matrix containing light flux data information, and evaluating the light transmission performance of the cement-based material by means of the light flux distribution.

Description

Technical Field

[0001] The invention relates to a method for evaluating the light transmission performance of cement-based materials. Background Art

[0002] With the increase of population and the intensification of industrialization, environmental pollution is becoming more and more serious. Photocatalytic concrete makes the photocatalytic phenomenon occur in the building material itself and has great potential to reduce pollutants in the air such as sulfur dioxide, particulate matter, volatile organic compounds and nitrogen oxides.

[0003] There are two main methods for preparing photocatalytic cement-based materials: external doping and internal doping. The external doping method is to coat the reagent containing the photocatalyst on the finished cement-based material. Although the material will have a high photocatalytic performance in the initial stage of this method, the photocatalytic activity of the material will show a sharp decline over time. This is because there is only a very poor binding force between the suspension containing the photocatalyst and the cement matrix. Under the combined physical and mechanical effects of the external environment, the photocatalytic attachment material will gradually detach, and the photocatalytic performance of the cement-based material will quickly be lost. The internal doping method is to directly add the photocatalyst into the cement-based material, and the prepared photocatalytic cement-based material has a certain photocatalytic property. However, the general practice is to dope a large amount of photocatalyst, which is easy to cause waste. Experiments have found that when the cement-based material doped with photocatalyst reaches a certain thickness, increasing the thickness will not help improve the photocatalytic performance, and excessive doping of expensive photocatalysts is likely to cause a large cost waste.

[0004] If the transmission range of light in cement-based materials is clear, it can be used as a basis for doping photocatalysts, which can not only maximize the photocatalytic effect of photocatalytic cement-based materials, but also effectively avoid the cost increase caused by excessive or deep doping of photocatalysts. In general, the light distribution in the measurement medium can be measured in situ with the help of devices such as optical fiber sensors, and the field of biological tissue optics is also involved. However, due to the strength and deformation limitations of cement itself, it is difficult to directly assemble optical sensors to obtain the in-situ light intensity distribution inside cement-based materials. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a method for evaluating the light transmission performance of cement-based materials, which method can obtain the spatial distribution of light intensity inside cement-based materials under non-destructive conditions;

[0006] Technical solution: The method for evaluating the light transmission performance of cement-based materials according to the present invention comprises the following steps:

[0007] (1) Cement powder and water are mixed and stirred to form a cement paste with a water-cement ratio of W, and then multiple portions of cement paste with a water-cement ratio of W are taken, and different masses of aggregates are added to each portion of the cement paste to obtain a cement-based mixed material with an aggregate content of 0% and any value of 1 to 99%; the thickness of each portion of the cement-based mixed material is not greater than 0.5 mm;

[0008] (2) First, the reflectivity R of the cement-based mixed material with an aggregate content of 0% is measured using an ultraviolet spectrophotometer, and then the transmittance of the cement-based mixed material with different aggregate contents is measured using an integrating sphere. The aggregate content and transmittance are linearly fitted to obtain the transmittance T of the cement-based mixed material with an aggregate content of 0%;

[0009] (3) Substitute the measured reflectivity R and transmittance T of the cement-based mixed material and the sample thickness into the IAD algorithm, and obtain the light absorption coefficient μ through multiple iterations. a and light scattering coefficient μ′ s ;

[0010] (4) obtaining microstructure data, specifically as follows: using CT imaging means and image segmentation technology to determine the three-dimensional structural model of cement-based materials, i.e., the position information of each component; or using spherical particle stacking means to obtain the three-dimensional position information of cement-based materials;

[0011] (5) Generate a 500×500×500 three-dimensional matrix with the help of MATLAB. According to the microstructure position information obtained in step (4), the different components of the cement-based material are distinguished by assigning a value to each position of the three-dimensional matrix. After determining the distribution position information of each component, a data structure containing position information and optical parameter information is generated in combination with the optical parameters calculated in step (3). Finally, the matrix coordinates and optical parameter data are integrated to generate a binary file containing the name, position information, and optical parameter information of each component of the cement-based material.

[0012] (6) The binary file obtained in step (5) is read into the binary file containing the information required for calculation using the Monte Carlo algorithm written in C language to perform Monte Carlo simulation. The random number generation function is used to determine the absorption and scattering effects of each photon at the action position and the step length of movement to the next position. By tracking the entire transmission process of each photon, a large number of photon samples are counted to generate another 500×500×500 three-dimensional matrix containing the light flux distribution information.

[0013] The generated three-dimensional matrix representing the spatial distribution of light is saved as a new binary file. Finally, the matrix information contained in the binary file is read out with the help of MATLAB tools. The three-dimensional spatial distribution of light is converted into a quasi-one-dimensional distribution along the incident direction of the light beam, and the transmission process of photons in real cement-based materials is obtained.

[0014] Wherein, in step (2), the reflectivity R of the cement-based mixed material with an aggregate content of 0% is obtained by the following method: the wavelength range of the ultraviolet spectrophotometer measurement is 300nm to 800nm, firstly, a standard glass slide with good light transmittance is placed as a reference, and the reflectivity R of the standard glass slide is obtained. 0 , then place the cement-based mixed material with 0% aggregate content, and measure the reflectivity R' of the cement-based mixed material with 0% aggregate content. R' minus R 0 The real reflectivity R of cement-based mixed materials with an aggregate content of 0% is obtained.

[0015] Among them, in step (2), the transmittance measurement of the cement-based mixed material with an aggregate content of 0% requires the use of an integrating sphere, and the incident light source is a blue-violet point laser module provided by Linsen Laser. First, the transmittance of at least three groups of cement-based mixed materials with aggregate content ranging from 1% to 99% is calculated using calculation formula (I) to obtain T 1 , T 2 and T 3 ,

[0016]

[0017] Wherein, Ts is the light intensity when the sample is placed, Tr is the light intensity when the reference sample is placed (the reference sample refers to the standard glass slide), and D represents the light intensity when no light source is emitted; different aggregate contents and their corresponding transmittance T are fitted to obtain the equation: y=0.295x+2.02; the transmittance T corresponding to the aggregate content x being 0% is obtained.

[0018] Wherein, in step (1), the aggregate includes glass, plastic or sand having light transmission properties.

[0019] Among them, in step (3), the inverse addition method (IAD) is the reverse process of the addition method, which is an iterative algorithm. By guessing the initial optical parameters and calculating the reflectivity and transmittance by the addition method for multiple times, the light absorption coefficient μ of the material is finally obtained. a and light scattering coefficient μ′ s .

[0020] The inverse doubling method specifically refers to: first guessing a set of light absorption coefficients and light scattering coefficients, using the doubling method to calculate the reflectivity R' and transmittance T' under the light absorption coefficients and light scattering coefficients, comparing the reflectivity R and transmittance T measured and calculated in step (2) with the calculated R' and T', if the error is less than the threshold, it indicates that the calculation is successful, otherwise, the optical parameters are continued to be changed on the basis of the previous guess to perform calculations, and the measured values ​​are compared until the error meets the threshold requirement, and finally the light absorption coefficient μ that meets the calculation accuracy requirement is obtained through multiple iterations. aand light scattering coefficient μ′ s .

[0021] The method of the present invention first prepares a series of cement-based materials with different light-transmitting aggregate content and without aggregate, and measures light reflectance and light transmittance by means of an integrating sphere; a linear equation is obtained by fitting according to the transmittance and aggregate content, and the intercept of the ordinate is the transmittance of cement without aggregate; the reflectance and transmittance of the cement are substituted into an IAD algorithm to iteratively calculate the light absorption coefficient and light scattering coefficient of the cement; a cement-based material structure model is built by means of CT, and the transmission of light in the cement-based medium is simulated by a Monte Carlo algorithm on the basis of the model, and finally the light flux distribution in the cement-based material is represented by a three-dimensional matrix containing light flux data information, and the light transmission performance of the cement-based material is evaluated by the light flux distribution.

[0022] Beneficial effects: The present invention can study the transmission of light inside cement-based materials to measure the light transmission range in cement-based materials, and then study the factors affecting the transmission of light in cement-based materials and regulate the transmission effect of light in cement-based materials, filling the gap that the prior art cannot measure the light transmission range inside cement-based materials; in the process of measuring parameters, the present invention adopts the method of measuring the transmittance of aggregate-doped samples and then linear fitting to overcome the problem of being unable to accurately measure the transmittance of pure cement samples due to the inability to prepare thinner cement samples; the present invention provides theoretical support for the internal doping method of photocatalytic cement-based materials, obtains the real transmission behavior of light inside cement-based materials, and provides theoretical reference and data support for the doping amount of photocatalyst, the doping depth of photocatalyst and the subsequent improvement of photocatalytic cement-based performance, thereby effectively controlling the cost waste problem of the internal doping method of photocatalytic cement-based materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of reflectivity of cement-based material sample of the present invention;

[0024] Figure 2 Schematic diagram of light transmittance of cement-based material samples of the present invention;

[0025] Figure 3 This is a schematic diagram of the XZ plane of light distribution in the cement-based material of Example 1;

[0026] Figure 4 Schematic diagram of quasi-one-dimensional light distribution along the incident direction of the light beam in Example 1;

[0027] Figure 5 is a sample CT slice data obtained by X-ray tomography;

[0028] Figure 6 This is a schematic diagram of the XZ plane of light distribution in the cement-based material of Example 2;

[0029] Figure 7 Schematic diagram of quasi-one-dimensional light distribution along the incident direction of the light beam in Example 2. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0031] Example 1

[0032] The method for evaluating the light transmission performance of cement-based materials of the present invention comprises the following steps:

[0033] Step 1, mixing cement powder and water to form cement paste, the cement powder is Jiangnan Onoda P.II52.5 grade, and the water-cement ratio of the cement paste is 0.4; taking out multiple groups of pastes and adding quartz sand thereto respectively to prepare cement-based material samples with aggregate contents of 0%, 30%, 40%, and 50%, respectively, and the sample thickness of each group is 0.5 mm;

[0034] Step 2: For the sample obtained in step 1, the reflectance is measured by using a Cary 5000 UV spectrophotometer, and the wavelength range of the measurement is 300nm to 800nm; first, a group of standard glass slides with good light transmittance are placed for scanning as a reference to obtain the reflectance R 0 Then place a cement sample without aggregate to measure the reflectivity R', R' minus R 0 The actual reflectivity of the sample is R = 80%, such as Figure 1 As shown; the measurement of transmittance requires the use of an integrating sphere. The incident light source is a blue-violet point laser module provided by Linsen Laser, model HB540580D-AL01A. The transmittance T of samples with aggregate content of 30%, 40%, and 50% is calculated using calculation formula (I): 1 =3.48%, T 2 =3.23%, T 3 =2.89%, such as Figure 2 As shown:

[0035]

[0036] Wherein, Ts is the light intensity when the sample is placed, Tr is the light intensity when the reference sample is placed, and D represents the light intensity when no light source is emitted; the aggregate content and transmittance are linearly fitted to obtain the transmittance T of the cement-based mixed material with an aggregate content of 0%; the aggregate content and transmittance are fitted to obtain the equation: y = 0.295x + 2.02; the intercept is the transmittance (y) T = 2.02% of pure cement with an aggregate content x of 0%;

[0037] Step 3, first guess a set of light absorption coefficients μ a and light scattering coefficient μ′ s, the reflectivity R' and transmittance T' are calculated by the doubling method. The so-called doubling method is to subjectively divide a thick tissue sample into parallel thinner layers of tissue, determine the reflectivity and transmittance of light penetrating each thin layer of tissue, and on this basis, multiply the reflectivity and transmittance of each thin layer until the true thickness is obtained to obtain the reflectivity and transmittance of the true thickness; compare the reflectivity R and transmittance T calculated by step 2 with the calculated R' and T'. If the error is less than a certain threshold (such as 10 -4 ) indicates that the calculation is successful, otherwise the optical parameters are continuously changed based on the previous guess to perform calculations, and the measured values ​​are compared until the error meets the threshold requirement. The light absorption coefficient μ that meets the calculation accuracy requirement is obtained through multiple iterations. a =1.327 / cm, light scattering coefficient μ′ s =217 / cm;

[0038] Step 4, using MATLAB to generate a 500×500×500 three-dimensional matrix, and distinguish different components of cement-based materials by assigning values ​​to each position of the three-dimensional matrix. After determining the distribution position information of each component, a data structure containing position information and optical parameter information is generated in combination with the optical parameters calculated in step 3. Finally, the matrix coordinates and optical parameter data are integrated to generate a binary file containing the name, position information, and optical parameter information of each component of the cement-based material.

[0039] Step 5, use the Monte Carlo algorithm written in C language to read the binary file obtained in step 4 into the binary file containing the information required for calculation, perform Monte Carlo simulation, and use the random number generation function to determine the absorption and scattering effects of each photon at the corresponding position and the step length of movement to the next position. By tracking the entire "life cycle" of each photon, a large number of photon samples are counted to generate another 500×500×500 three-dimensional matrix containing the luminous flux distribution information.

[0040] The generated three-dimensional matrix representing the spatial distribution of light is saved as a new binary file. Finally, the matrix information contained in the binary file is read out with the help of MATLAB tools. The XZ section of the light distribution is as follows: Figure 3 As shown, along the incident direction of the light beam, the three-dimensional spatial distribution of light is transformed into a quasi-one-dimensional distribution, as shown in Figure 4 shown.

[0041] Example 2

[0042] Step 1, as in step 1 of Example 1;

[0043] Step 2, as in step 2 of Example 1;

[0044] Step 3, as in step 3 of embodiment 1;

[0045] Step 4, for the cement-based material sample with an aggregate content of 30% obtained in step 1, select a suitable scanning position for three-dimensional X-CT imaging to obtain three-dimensional grayscale image data. The X-CT imaging equipment used is an Xradia510 X-ray microscope. The X-CT scanning parameters are: scanning peak voltage 80 kV, power 7 watts, exposure time of each projection 1.2 seconds, resolution 13 microns, and each scan obtains a two-dimensional CT slice image (such as Figure 5 After obtaining the three-dimensional grayscale data of the cement-based material, the three-dimensional model of the cement-based material is segmented by using MATLAB tools with the help of image filtering, grayscale threshold method, circularity threshold method and area threshold method to obtain a three-dimensional matrix containing the type information and position information of each component, and the remaining steps of step 4 in Example 1 are continued; a 500×500×500 three-dimensional matrix is ​​generated with the help of MATLAB, and different components of the cement-based material are distinguished by assigning values ​​to each position of the three-dimensional matrix. After determining the distribution position information of each component, a data structure containing position information and optical parameter information is generated in combination with the optical parameters calculated in step 3, and finally the matrix coordinates and optical parameter data are integrated to generate a binary file containing the name, position information and optical parameter information of each component of the cement-based material;

[0046] Step 5, as in step 5 of embodiment 1, the XZ section of the light distribution is as follows: Figure 6 As shown, the quasi-one-dimensional distribution of light, such as Figure 7 shown.

[0047] from Figure 1 and Figure 2 From the experimental data, we can see that cement is a medium with strong scattering properties and poor light transmittance. Figure 4 and Figure 7 It can be found that the doping of translucent aggregate is beneficial to the transmission of photons and improves the light distribution effect inside cement-based materials. The present invention does not measure the light intensity of cement-based materials in situ, but can obtain the light distribution law inside the material, providing theoretical support and data reference for the doping amount and doping method of photocatalysts.

Claims

1. A method for evaluating the light transmission performance of cement-based materials, It is characterized in that The steps include: (1) Cement powder and water are mixed and stirred to form a cement paste with a water-cement ratio of W, and then multiple portions of cement paste with a water-cement ratio of W are taken, and different masses of aggregates are added to each portion of the cement paste to obtain a cement-based mixed material with an aggregate content of 0% and any value of 1 to 99%; (2) First, the reflectivity R of the cement-based mixed material with an aggregate content of 0% is measured using an ultraviolet spectrophotometer, and then the transmittance of the cement-based mixed material with different aggregate contents is measured using an integrating sphere. The aggregate content and transmittance are linearly fitted to obtain the transmittance T of the cement-based mixed material with an aggregate content of 0%; (3) Substitute the measured reflectivity R and transmittance T of the cement-based mixed material and the sample thickness into the inverse addition method, and obtain the light absorption coefficient μ through multiple iterations. a and light scattering coefficient μ′ s ; Among them, the inverse doubling method is the reverse process of the doubling method. It is an iterative algorithm that calculates the reflectivity and transmittance by guessing the initial optical parameters and repeatedly approximating them, and finally obtains the light absorption coefficient μ of the material. a and light scattering coefficient μ′ s The inverse doubling method specifically means: first guess a set of light absorption coefficients and light scattering coefficients, use the doubling method to calculate the reflectivity R' and transmittance T' under the light absorption coefficients and light scattering coefficients, compare the reflectivity R and transmittance T measured and calculated in step (2) with the calculated R' and T', if the error is less than the threshold, it indicates that the calculation is successful, otherwise, continue to change the optical parameters based on the previous guess to calculate, compare the measured values ​​until the error meets the threshold requirement, and finally obtain the light absorption coefficient μ that meets the calculation accuracy requirement through multiple iterations. a and light scattering coefficient μ′ s ; (4) obtaining microstructure data, specifically as follows: using CT imaging means, with the help of image segmentation technology to determine the three-dimensional structural model of cement-based materials, and obtain the position information of each component; or using spherical particle stacking means to obtain the three-dimensional position information of cement-based materials; (5) Generate a three-dimensional matrix with the help of MATLAB, and distinguish different components of the cement-based material by assigning a value to each position of the three-dimensional matrix according to the microstructure position information obtained in step (4). After determining the distribution position information of each component, generate a data structure containing position information and optical parameter information in combination with the optical parameters calculated in step (3). Finally, integrate the matrix coordinates and optical parameter data to generate a binary file containing the name, position information, and optical parameter information of each component of the cement-based material; (6) The binary file obtained in step (5) is read into the binary file containing the information required for calculation using the Monte Carlo algorithm, and a Monte Carlo simulation is performed. The absorption and scattering effects of each photon at the action position and the step length of the movement to the next position are determined using a random number generation function. By tracking the entire transmission process of each photon, a large number of photon samples are counted to generate another three-dimensional matrix containing the light flux distribution information.

2. The method for evaluating the light transmission performance of cement-based materials according to claim 1, Features: In step (1), the aggregate includes glass, plastic or sand having light transmission properties.

3. The method for evaluating the light transmission performance of cement-based materials according to claim 1, Features: In step (2), the reflectivity R of the cement-based mixed material with an aggregate content of 0% is obtained by the following method: the wavelength range of the ultraviolet spectrophotometer measurement is 300nm to 2000nm, firstly a standard glass slide with good light transmittance is placed as a reference, and the reflectivity R of the standard glass slide is obtained. 0 Then, a cement-based mixed material with 0% aggregate content is placed, and the reflectivity R' of the cement-based mixed material with 0% aggregate content is measured. R' minus R 0 The real reflectivity R of cement-based mixed materials with an aggregate content of 0% is obtained.

4. The method for evaluating light transmission performance of cement-based materials according to claim 1, Features: In step (2), the transmittance measurement of cement-based mixed materials with an aggregate content of 0% requires the use of an integrating sphere. The incident light source is a blue-violet point laser module provided by Linsen Laser. First, the transmittance of at least three groups of cement-based mixed materials with aggregate content ranging from 1% to 99% is calculated using calculation formula (I) to obtain T 1 , T 2 and T 3 , Among them, T s is the light intensity when the sample is placed, T r is the light intensity when the reference sample is placed, and D represents the light intensity when no light source is emitted; different aggregate contents and their corresponding transmittance T are fitted to obtain a linear equation: y=kx+b; the corresponding transmittance T is obtained when the aggregate content x is 0%.

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