A method for rapidly detecting the activity of metakaolin using XRD

Abstract

The invention discloses a method for rapidly detecting the activity of metakaolin using XRD, comprising the following steps: placing a metakaolin sample in an X-ray diffractometer and performing an XRD slow scan; importing the data measured by the XRD diffractometer into an XRD analysis software, performing peak search and back-sampling to obtain peak search data; calculating the ratio R of the diffraction peak height to the corresponding half-peak width based on the obtained peak search data; summing the areas of all diffraction peaks with R values ​​below 1000 to obtain ∑S 衍射峰 Finally, the same test and analysis conditions were used to calculate the ∑S of different metakaolin powders. 衍射峰 , according to ∑S 衍射峰 The activity of different metakaolin powders is evaluated by measuring the value of XRD. This invention proposes for the first time a method for rapidly detecting and evaluating the activity of metakaolin using XRD. This method is simple and efficient and can provide a new approach for the efficient detection of metakaolin activity.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic non-metallic material property analysis and evaluation, and particularly relates to a method for rapidly detecting metakaolin activity by utilizing XRD. Background Art

[0002] Metakaolin is a volcanic ash material formed by thermally activating kaolin at temperatures between 500-900°C. As a high-quality cement substitute, it significantly improves the strength and durability of cement concrete. Metakaolin's activity primarily stems from its amorphous active silicon and aluminum, which react with calcium hydroxide to form gels such as CSH and CASH, which enhance cement strength and durability. Due to the quality differences between kaolins from different origins, the activity of the calcined metakaolin varies significantly, resulting in varying optimal activation conditions. Therefore, accurately evaluating metakaolin's activity is crucial for selecting appropriate activation conditions.

[0003] Currently, metakaolin activity testing methods primarily fall into two categories: instrumental analysis and physicochemical methods. Instrumental analysis methods include XRD, IR, and comprehensive thermal analysis, while physicochemical methods include active aluminum content determination, calcium absorption, alkali absorption, compression strength measurement, and mortar strength measurement. Existing instrumental analysis methods primarily provide simple qualitative analysis of changes in kaolin phase and crystallinity under different calcination conditions, but they do not provide a basis for determining metakaolin activity. Active aluminum content determination only considers the contribution of changes in active aluminum content to metakaolin activity, ignoring the influence of changes in active silicon content, resulting in inaccurate test results. Calcium absorption, alkali absorption, and compression strength measurement methods generally only indicate whether metakaolin is active; the measured amount lacks a clear correlation with the actual activity level, and therefore cannot quantify the activity level. The mortar strength method is the most direct method for determining metakaolin activity and is currently recognized as the most accurate method for determining clay mineral activity. However, it typically takes 28 days to produce results, significantly impacting industrial production efficiency. Therefore, there is an urgent need to find a fast, simple and accurate detection method to guide industrial production practice.

[0004] Kaolin contains a variety of minerals, including kaolinite, illite, muscovite, feldspar, quartz, and pyrite, which are the most common phases among clay minerals. When kaolin is calcined to form metakaolin, the primary contributors to its activity are active aluminum oxide and silicon oxide, generated by the amorphization of aluminosilicate minerals. However, due to the large variety and complex composition of metakaolin phases, most of which are aluminosilicate minerals with identical or similar chemical elements and crystal structures, and similar XRD characteristic peak positions, neither traditional chemical analysis nor XRD quantitative analysis can accurately determine the content of each phase in metakaolin. Therefore, there is currently no effective method for quantitatively analyzing the content of substances such as active aluminum and active silicon in metakaolin. Summary of the Invention

[0005] The main purpose of the present invention is to address the limitations of existing metakaolin activity detection technology and to propose for the first time a method for rapidly detecting metakaolin activity using XRD. This method is simple, easy to use, low in cost, has little human error, and is highly accurate, providing a new idea for the efficient detection of metakaolin activity.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for rapidly detecting the activity of metakaolin using XRD comprises the following steps:

[0008] 1) Place the metakaolin sample in an X-ray diffractometer and perform an XRD slow scan;

[0009] 2) Importing the data measured by the XRD diffractometer into the XRD analysis software, searching for peaks and deducting the background to obtain peak-finding data;

[0010] 3) Calculate the ratio R of the diffraction peak height to the corresponding half-peak width based on the obtained peak search data;

[0011] 4) Sum the areas of all diffraction peaks with R values ​​below 1000 to obtain ∑S 衍射峰 ;

[0012] 5) Using the same test and analysis conditions as above, calculate the ∑S of different metakaolin powders 衍射峰 , according to ∑S 衍射峰 The activity of different metakaolin powders is evaluated by the high and low values ​​of

[0013] In the above scheme, the XRD slow scan rate in step 1) is 0.02-0.05° / step, and the scanning range is 5-70°.

[0014] In the above scheme, the XRD analysis software described in step 2) is Jade. Right-click the "Find Peaks" button to set the peak search parameters, and set the Points variable between 9 and 13; left-click the "Find Peaks" button to search for peaks, double-click the "Fit BG" button to fit the background, click the "Peak Search Report" submenu under the "Report" menu, and then click the "Copy" button to obtain the peak search data.

[0015] In the above scheme, the calculation steps for obtaining R in step 3) are: paste the peak search data into an Excel spreadsheet, and the ratio R of the diffraction peak height to the corresponding half-peak width is equal to the ratio of the Height cell value to the FWHM cell value in the corresponding row.

[0016] In the above scheme, the summation calculation step in step 4) is: sort the data in the Excel spreadsheet in ascending order of R value, and for data with R value less than or equal to 1000, use the sum function to sum the "Area" column to obtain ∑S 衍射峰 .

[0017] In the above scheme, during the evaluation process, ∑S 衍射峰 The higher the value of the metakaolin powder, the more active it is.

[0018] In the above solution, the metakaolin powder is obtained by calcining kaolin as raw material at 600-900°C.

[0019] In the above scheme, the metakaolin sample is obtained by mixing metakaolin powder and water in proportion, grinding, drying, and adding the mixture into a sample tank.

[0020] In the above scheme, the particle size of the metakaolin powder obtained after grinding (ball mill grinding) and drying is less than 6.5 μm.

[0021] In the above solution, the mass ratio of the mixed metakaolin powder and deionized water is 4 to 7:1.

[0022] In the above scheme, the drying temperature is 100-110° C. and the drying time is 2-4 hours.

[0023] In the above scheme, the ground and dried metakaolin powder is poured into the sample holder of the XRD diffractometer, the sample holder is placed on an oscillator and shaken to make it evenly spread in the sample slot in the sample holder, and then flattened with a glass slide;

[0024] In the above scheme, the mass of the metakaolin powder laid in the sample tank per unit volume is 0.5-0.6 mg / mm 3 .

[0025] According to the above method, a batch of metakaolin samples prepared under different activation process conditions can be selected according to the highest ∑S 衍射峰 Value, quickly screen out the most active metakaolin sample; and according to ∑S 衍射峰 The activity of metakaolin is quickly sorted in the order of increasing or decreasing values ​​(the activity of metakaolin increases with ∑S 衍射峰 increases with the increase of the value).

[0026] Furthermore, for a batch of metakaolin samples (comparison samples) to be tested, data must be collected under the same experimental conditions, that is, the XRD diffractometer sample holder must be the same sample holder, the particle size and amount of powder must be the same, the XRD diffractometer used must be the same diffractometer, the same target material must be used, the XRD tube voltage and tube current must be the same, and the XRD slow scan rate and scanning range must also be the same.

[0027] Furthermore, when using Jade software for data processing, it is necessary to ensure that the peak search variable Points is set between 9 and 13, and only the diffraction peak areas corresponding to the data with a ratio R of the diffraction peak height to the corresponding half-peak width less than or equal to 1000 are summed.

[0028] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) The present invention proposes for the first time to regulate and optimize the XRD diffraction peak area sum function that can be effectively linked to the amorphous phase content in metakaolin (the sum function corresponding to the diffraction peak area when the peak search variable Points is set between 9 and 13 and the ratio R is below 1000), thereby establishing a relationship between this function and the activity of metakaolin. This fully considers the effects of substances such as active silicon and active aluminum on the activity of metakaolin, thereby achieving efficient and rapid detection of metakaolin activity.

[0031] 2) The sample preparation method used in the present invention is relatively simple and easy to operate, and can quickly and accurately establish the relationship between the evaluation index after XRD optimization and the activity of metakaolin. The analysis, testing and comparison of the activity of multiple groups of metakaolin samples can be completed within one day;

[0032] 3) The present invention avoids the influence of human operation errors on the experimental results to the greatest extent, and the evaluation results are more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 ∑S obtained from the metakaolin prepared at different calcination temperatures obtained in Example 1衍射峰 The relationship with calcination temperature;

[0034] Figure 2 The figures are comparative diagrams showing the results of activity analysis of metakaolin using the method described in Example 1 of the present invention and the mortar strength activity test method.

[0035] Figure 3 The following is a comparison chart showing the results of activity analysis of metakaolin using the method described in the comparative example and the mortar strength activity test method. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] In the following examples, the amount of powder to be tested is 550 mg. The XRD diffractometer used is a German Bruker X-ray diffractometer D8 Advance diffractometer with a Cu target, λ = 0.154178 nm, an XRD tube voltage of 40 kV, a tube current of 40 mA, and an XRD slow scan rate of 0.02° / step to increase the intensity of each diffraction peak in the sample and reduce the influence of background noise on the test results. The scanning range is 5-70° to identify the various phases contained in the sample as much as possible and make the measured diffraction peak area more accurate and comparable.

[0038] The metakaolin samples used were prepared by calcining the same batch of kaolin at 700°C, 750°C, 800°C and 850°C for 2h and 6h respectively, followed by rapid cooling.

[0039] Example 1

[0040] A method for rapidly detecting the activity of metakaolin using XRD is provided. The main components of a batch of kaolin are (wt%): SiO2 64.25%, Al2O3 14.58%, Fe2O3 4.20%, K2O 2.76%, CaO 1.83%, MgO 1.83%, TiO2 0.66%, and Na2O 0.21%. The specific detection steps are as follows:

[0041] 1) Using an agate mortar, mix and grind metakaolin powder prepared by calcining at 700°C with deionized water at a mass ratio of 5:1, pass through a 2000 mesh sieve, and then dry at 105°C for 2 h.

[0042] 2) Pour 550 mg of dried metakaolin powder into the sample holder of an XRD diffractometer, place the sample holder on an oscillator and oscillate it evenly, flatten it with a glass slide, and perform an XRD slow scan at a rate of 0.02° / step over a scanning range of 5-70°.

[0043] 3) Import the data measured by the XRD diffractometer into the XRD analysis software Jade6.5, right-click the "FindPeaks" button, set the peak search variable Points to 13 (except for the peak search variable Points value, other parameters are set according to the default standard parameters of the XRD analysis software; the same below), left-click the "Find Peaks" button to search for peaks, double-click the "Fit BG" button to fit the background, click the "Peak Search Report" submenu under the "Report" menu, and then click the "Copy" button to obtain the peak search data;

[0044] 4) Import the peak search data into the Excel spreadsheet, calculate the ratio R of the diffraction peak height to the corresponding half-peak width, and use the sum function to sum the "Area" column with R less than or equal to 1000 to obtain ∑S 衍射峰 ;

[0045] 5) Repeat steps 1)-4) to calculate the corresponding ∑S of the XRD spectra of the metakaolin powders prepared at other calcination temperatures (750℃, 800℃ and 850℃, respectively). 衍射峰 ;

[0046] 6) The ∑S prepared at different calcination temperatures 衍射峰 Import Origin spreadsheet, draw the graph, and see the result Figure 1 ; According to ∑S 衍射峰 The activity of different metakaolin powders is evaluated by the high and low values ​​of

[0047] Depend on Figure 1 It can be seen that when the calcination temperature is 800℃, the total XRD diffraction peak area of ​​the amorphous phase of metakaolin is the largest, indicating that the contents of active silicon and active aluminum in metakaolin are the highest and the activity of metakaolin is the highest.

[0048] Example 2

[0049] A method for rapidly detecting the activity of metakaolin using XRD is provided. The main components of a batch of kaolin are (wt%): SiO2 46.08%, Al2O3 38.4%, Fe2O3 0.59%, K2O 0.13%, CaO 0.01%, MgO 0.06%, TiO2 0.06%, and Na2O 0.06%. The specific detection steps are as follows:

[0050] 1) Using an agate mortar, mix and grind metakaolin powder prepared by calcining at 700°C with deionized water at a mass ratio of 5:1, pass through a 2000 mesh sieve, and then dry at 105°C for 2 h.

[0051] 2) Pour 550 mg of dried metakaolin powder into the sample holder of an XRD diffractometer, place the sample holder on an oscillator and oscillate it evenly, flatten it with a glass slide, and perform an XRD slow scan at a rate of 0.02° / step over a scanning range of 5-70°.

[0052] 3) Import the data measured by the XRD diffractometer into the XRD analysis software Jade6.5, right-click the "FindPeaks" button, set the peak search variable Points to 9, left-click the "Find Peaks" button to search for peaks, double-click the "Fit BG" button to fit the background, click the "Peak Search Report" submenu under the "Report" menu, and then click the "Copy" button to obtain the peak search data;

[0053] 4) Import the peak search data into the Excel spreadsheet, calculate the ratio R of the diffraction peak height to the corresponding half-peak width, and use the sum function to sum the "Area" column with R less than or equal to 1000 to obtain ∑S 衍射峰 ;

[0054] 5) Repeat steps 1)-4) to calculate the corresponding ∑S of the XRD spectra of the metakaolin powders prepared at other calcination temperatures (750℃, 800℃ and 850℃, respectively). 衍射峰 ;

[0055] 6) The ∑S in the metakaolin prepared at different calcination temperatures 衍射峰 Import Origin spreadsheet, draw a graph, and use ∑S 衍射峰 The activity of different metakaolin powders is evaluated by the high and low values ​​of

[0056] To further verify the detection effect of the present invention, the activity of the above samples was tested using a traditional mortar strength method, and the specific steps included:

[0057] The cementitious material composition consisted of 90 wt% ordinary silicate cement and 10 wt% metakaolin (the metakaolin described in Example 1). The total amount of cementitious material was mixed with standard sand in a mass ratio of 1:3, and the mortar had a water-binder ratio of 0.5. The mortar was cured in the formwork for one day, then removed from the formwork and placed in a curing room for standard curing for 28 days. The compressive strength of the mortar was measured in accordance with "Test Method for Strength of Cement Mortar (ISO Method)" GB / T17671-1999.

[0058] Import the 28-day compressive strength value obtained by the mortar strength method and the XRD diffraction peak area obtained by the present invention into the Origin spreadsheet and draw a graph in Stack mode, as shown in the following example: Figure 2 As shown in the figure, it can be seen that the variation pattern of the total XRD diffraction peak area of ​​metakaolin at different calcination temperatures is basically the same as the variation pattern of mortar strength. The greater the intensity, the larger the total XRD diffraction peak area of ​​the amorphous phase, indicating that the content of active silicon and active aluminum in the metakaolin is higher and the activity of the metakaolin is greater. This shows that the method described in the present invention can accurately reflect the activity of metakaolin.

[0059] In addition, the metakaolin sample in Example 2 was further tested by the mortar strength method and compared with the test results described in Example 2, and the results with the same rules as those in Example 1 were obtained.

[0060] The above results show that the method of the present invention can accurately reflect the activity of metakaolin, solving the problem of long time consumption or low accuracy in the prior art.

[0061] Comparative Example

[0062] A method for rapidly detecting the activity of metakaolin using XRD, the specific steps are roughly the same as those in Example 1, except that the peak search variable Points is set to 15, or the R value is set to 1100; the comparison diagrams of the corresponding detection results of the two detection methods and the test results of the traditional mortar strength method are shown in FIG. Figure 3 .

[0063] The above results show that when the set peak-finding variable Points or R value does not meet the corresponding requirements of the present invention, the above two situations will lead to a large difference between the detection effect and the detection law of the mortar strength method, which will significantly affect the accurate judgment of the activity of kaolin, and it is impossible to establish an effective connection between the "XRD" detection method and the activity of kaolin.

[0064] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for rapidly detecting the activity of metakaolin using XRD, characterized in that: The steps include: 1) Place the metakaolin sample in an X-ray diffractometer and perform XRD slow scan; 2) Import the data measured by the XRD diffractometer into the XRD analysis software, search for peaks, and remove the background to obtain peak search data; 3) Based on the obtained peak search data, calculate the ratio R of the diffraction peak height to the corresponding half-peak width; 4) Sum all diffraction peak areas with R values ​​below 1000 to obtain the diffraction peak area ∑S 衍射峰 ; Set the Points variable in the peak search parameters to 9-13; 5) Using the same testing and analysis conditions as above, calculate the diffraction peak area ∑S of different metakaolin powders 衍射峰 , according to ∑S 衍射峰 The activity of different metakaolin powders is evaluated by the value of The metakaolin powder is obtained by calcining kaolin as a raw material at 600-850°C.

2. The method according to claim 1, characterized in that The XRD slow scan rate in step 3) is 0.02-0.05 o / step, scan range 5-70 o .

3. The method according to claim 1, characterized in that During the evaluation process, ∑S 衍射峰 The higher the value of the metakaolin powder, the more active it is.

4. The method according to claim 1, wherein The metakaolin sample is obtained by mixing metakaolin powder and water in proportion, grinding, drying, and adding the mixture into a sample tank.

5. The method according to claim 4, characterized in that After grinding and drying, the particle size of the metakaolin powder is less than 6.5 μm.

6. The method according to claim 4, characterized in that The sample loading steps include: pouring the ground and dried metakaolin powder into the sample holder of the XRD diffractometer, placing the sample holder on an oscillator and shaking it so that it is evenly spread in the sample slot of the sample holder, and flattening it with a glass sheet.

7. The method according to claim 4, characterized in that The mass of metakaolin powder per unit volume of the sample tank is 0.5-0.6 mg / mm 3 .

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