Precision Monitoring Device for the Flow Process of Cementitious Materials and Characterization Method for the Flow Performance of Cementitious Materials

Abstract

The present invention belongs to the technical field of workability testing of cement-based materials, and in particular discloses a precision monitoring device for the flow process of cement-based materials. By using a translucent platform as the work platform for the fluidity of cement-based materials and arranging a camera below it to record the entire process of the flow expansion of cement-based materials after removing the test mold, the present invention can avoid the inability to monitor the flow performance of cement-based materials in the initial stage and the inaccurate results caused by using the diameter parameter to characterize the fluidity. The present invention also provides a method for characterizing the flow performance of cement-based materials based on the above precision monitoring device, which combines image processing and fitting calculation to evaluate the flow process parameters of cement-based materials. The precision monitoring device and its corresponding characterization method provided by the present invention can accurately analyze the changes in the flow performance of the slurry caused by factors such as cementitious materials, chemical admixtures, and water-cement ratio, and can be used for the accurate testing of the rheological properties of cement-based materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of workability testing of cement-based materials. Specifically, it relates to a precision monitoring device for the flow process of cement-based materials and a method for characterizing the flow performance of cement-based materials based on this precision monitoring device. Background Art

[0002] A significant feature of modern concrete is that it has high durability, high volume stability, and excellent workability while meeting the requirements of engineering structures for mechanical properties. Workability is the unity of fluidity, water retention, and cohesiveness, and is a prerequisite for ensuring the quality of concrete projects. Concrete is a three-phase material composed of solid, liquid, and gas. Along with the hydration process of cement in it, the workability of concrete also shows a time-related characteristic. Therefore, accurately and quickly evaluating the workability of concrete is of great significance for concrete construction. In engineering practice, the workability of concrete is mainly characterized by the fluidity or spread of neat cement paste, mortar, or concrete. However, with the application of mineral admixtures and polycarboxylate water reducers, the viscosities and workabilities of neat cement paste, mortar, or concrete with fluidity vary greatly. Therefore, there are obvious deficiencies in evaluating the workability of concrete only from the final fluidity or spread.

[0003] Therefore, only by providing real-time and precise monitoring of the flow process of concrete and providing performance characterization during the flow process can the workability of the concrete be evaluated more accurately. Summary of the Invention

[0004] The inventors of the present invention found during a large number of experimental operations that the flow process of cement-based materials is closely related to the rheological properties of the paste itself. The flow process of cement paste is a flow process under the action of gravity shear. Its flow rate is controlled by shear force and viscosity, and it is a process in which the shear force gradually decreases. The shear force is the largest in the initial stage (within 5 s), and the flow velocity differences of different types of pastes are most obvious in this stage. Therefore, accurately measuring the flow velocity in the initial stage is of great significance and can scientifically evaluate the rheological characteristics of the paste. However, in the process of testing the fluidity of cement-based materials, the test mold needs to be lifted manually, and this process takes about 3 s to 10 s. Existing technical means cannot completely record the flow process in this stage. In addition, it is difficult to avoid the test mold tilting during the operation, and the paste flow shows an irregular non-circular expansion. Therefore, there is a problem of inaccurate fluidity measurement by the method of measuring the diameter.

[0005] To solve the problems existing in the above-mentioned prior art and summarized from test experience, the present invention provides a precision monitoring device for the flowability of cement-based materials. This precision monitoring device can monitor the flow process of cement-based materials in real time and still monitor the flow state very close to the initial moment, and can more accurately reflect the change trend of the flow process of cement-based materials over time.

[0006] To achieve the above-mentioned invention purpose, the present invention adopts the following technical solutions:

[0007] A precision monitoring device for the flow process of cement-based materials, which includes a workbench for carrying a fluidity test mold and a detection component located below the workbench; wherein, the workbench includes a semi-transparent platform, an adjustment bracket for supporting and regulating the semi-transparent platform to be horizontal, and a level for detecting the levelness of the semi-transparent platform; the detection component includes a camera located under the semi-transparent platform and a lifting platform for supporting and adjusting the height of the camera; the adjustment ranges of the adjustment bracket and the lifting platform are such that the recording range of the camera completely includes the semi-transparent platform.

[0008] Further, the semi-transparent platform is made of tempered glass with a thickness greater than 5 mm.

[0009] Further, the light transmittance of the semi-transparent glass is 60% - 80%.

[0010] Further, the camera is a digital video camera, a high-definition camera or a smart phone.

[0011] Another object of the present invention also lies in providing a method for characterizing the flowability of cement-based materials, which is carried out based on the above-mentioned precision monitoring device. The characterization method includes the following steps:

[0012] S1. Use the precision monitoring device described above to record the free-flow expansion process of cement-based materials to generate a flow expansion video;

[0013] S2. Process the flow expansion video by using binary processing combined with the flowability area mapping calculation method to obtain the flowability of the cement-based materials at different times, and draw the flow process curve of the cement-based materials;

[0014] S3. Fit the flow process curve to the equation shown in Formula 1 below:

[0015] R t -R0 = (R g -R0)[1 - exp(-kt n )] Formula 1

[0016] In Equation 1: t is time, with the unit of s; R0 is the outer diameter of the lower bottom surface of the test mold, with the unit of mm; R t is the value of the fluidity of the cement-based material at time t, with the unit of mm; R g is the fitted final fluidity of the cement-based material, with the unit of mm; k is the rheological property parameter, with the unit of s -n ; n is the spreading index, dimensionless;

[0017] S4. Obtain the values of the rheological property parameter k and the spreading index n from the said Equation 1, and calculate the ratio of n / k;

[0018] Among them, the smaller the ratio of n / k, the faster the flow rate of the said cement-based material in the initial stage, and the lower the viscosity of the said cement-based material.

[0019] Furthermore, the specific method of the said step S2 is as follows:

[0020] S21. Extract the images in the said flow expansion video at intervals of 0.1 s through a computer program;

[0021] S22. Perform binary processing on each obtained frame of image to obtain a clear binary image;

[0022] S23. Take the first frame of image when about to lift the fluidity test mold as the reference binary image at time 0, and calculate the areas of the parts with pixel values of zero in the reference binary image and the binary image at time t respectively, as the reference fluidity area and the fluidity area at time t of the said cement-based material;

[0023] S23. Perform linear mapping calculation on the fluidity area at time t and the reference fluidity area to obtain the fluidity of the said cement-based material at time t;

[0024] S24. Plot the change of fluidity with time at each moment to obtain the said flow process curve.

[0025] Furthermore, the specific method of the said step S1 is as follows:

[0026] S11. Support and adjust the height of the said semi-transparent platform with the said adjusting bracket, and use the said level to test until the said semi-transparent platform reaches a horizontal state;

[0027] S12. Adjust the height of the said lifting platform so that the recording range of the said camera exactly completely accommodates the size of the said semi-transparent platform into the picture;

[0028] S13. Turn on the camera and lift the flow table mold, record the process of the free flow and spread of the cementitious material after lifting the flow table mold until the cementitious material stops flowing, then end the recording to obtain the flow spread video.

[0029] In the present invention, a translucent platform is used as the operating platform for the fluidity of the cementitious material, and a camera is placed below it to record the entire process of the flow and spread of the cementitious material after removing the mold. This setup can, on the one hand, completely avoid the shadow caused when the operator is between the general camera equipment and the cementitious material during the manual removal of the mold, which affects the binarization processing of the fluidity state pictures. As a result, corresponding fluidity state pictures cannot be obtained during the process of removing the mold, and the fluidity performance of the cementitious material at this stage cannot be monitored. On the other hand, it can also avoid the occlusion problem caused by the aforementioned operator. During the process of removing the mold, only the diameter parameter of the circle formed by the flow and spread of the cementitious material can be collected, that is, only this data can be used to characterize the fluidity, and there are inevitably drawbacks such as inaccurate results.

[0030] The method for characterizing the fluidity performance of the cementitious material provided by the present invention can obtain the flow process curve of the cementitious material by analyzing the flow spread video of the cementitious material recorded by the precision monitoring device of the present invention, and combining binarization processing and the flow area mapping calculation method. Then, through numerical analysis and fitting, an equation for the change of the fluidity of the paste with time can be obtained, and the equation parameters can be used to quantitatively characterize the rheological characteristics of the cementitious material. Based on the complete recording of the free expansion process by the aforementioned precision monitoring device, this characterization method can, on the one hand, obtain the initial free expansion data and precisely characterize the process performance of different cementitious materials. On the other hand, the flow area mapping calculation method is used to obtain the fluidity data, which also avoids the measurement inaccuracy problem existing in the existing circular diameter / radius measurement method. This measurement and characterization method overcomes the adverse effects caused by unbalanced force during the lifting process of the flow table mold.

[0031] Based on the precision monitoring device and its corresponding characterization method provided by the present invention, the changes in the fluidity performance of the paste caused by factors such as cementitious materials, chemical admixtures, and water-cement ratio can be accurately analyzed, and it can be used for the accurate testing of the rheological properties of cementitious materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Through the following description in conjunction with the drawings, the above and other aspects, features, and advantages of the embodiments of the present invention will become clearer. In the drawings:

[0033] Figure 1 is a schematic structural diagram of the precision monitoring device according to the present invention;

[0034] Figure 2It is the image of the fluidity of the slurry collected by the precision monitoring device according to the present invention;

[0035] Figure 3 is Figure 2 the binary image of the fluidity image in

[0036] Figure 4 It is the flow process curve graph when the characterization method of the flow performance of the cement-based material according to the present invention is applied to mortars with different water-cement ratios;

[0037] Figure 5 It is the flow process curve graph when the characterization method of the flow performance of the cement-based material according to the present invention is applied to neat cement pastes containing different mineral admixtures;

[0038] Figure 6 It is the flow process curve graph when the characterization method of the flow performance of the cement-based material according to the present invention is applied to mortars containing different admixtures;

[0039] Figure 7 It is the flow process curve graph when the characterization method of the flow performance of the cement-based material according to the present invention is applied to self-compacting concrete. Detailed implementation manners

[0040] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention can be implemented in many different forms, and the present invention should not be construed as limited to the specific embodiments set forth herein. On the contrary, these embodiments are provided to explain the principles of the present invention and its practical applications, so that other technical personnel in the art can understand various embodiments of the present invention and various modifications suitable for specific intended applications. In the drawings, for clarity, the shapes and sizes of the elements may be exaggerated, and the same reference numerals will always be used to represent the same or similar elements.

[0041] It should be noted that the terms "including" and "having" and any variations thereof in the description and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0042] In this application, the orientation or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. are based on the orientation or positional relationships shown in the drawings. These terms are mainly used to better describe the present invention and its embodiments, and are not used to limit that the indicated devices, elements or components must have a specific orientation, or be constructed and operated in a specific orientation.

[0043] Moreover, in addition to being used to represent orientation or positional relationships, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0044] In addition, the terms "mounted", "arranged", "provided with", "connected", "coupled", "socketed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or there is internal communication between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] Specifically referring to Figure 1 , the precision monitoring device for the flow process of the cement-based material provided by the present invention includes a workbench 1 for carrying the fluidity test mold a and a detection assembly 2 located below the workbench 1.

[0046] Specifically, the workbench 1 includes a translucent platform 11, an adjustment bracket 12 for supporting and regulating the translucent platform 11 to be horizontal, and a level 13 for detecting the levelness of the translucent platform 11; while the detection assembly 2 includes a camera 21 located below the translucent platform 11 and a lifting platform 22 for supporting and adjusting the height of the camera 21.

[0047] The camera 21 is used to record the complete free-flow expansion process of the cement-based material after removing the test mold a. Therefore, the adjustment range requirements for the adjustment bracket 12 and the lifting platform 22 are such that the recording range of the camera 21 completely includes the translucent platform 11.

[0048] In order to ensure the stiffness of the translucent platform 11 and thus ensure the accuracy of the test, the translucent platform 11 is preferably made of tempered glass with a thickness greater than 5 mm, and its light transmittance should be between 60% and 80% to reduce the influence of the operator and the environment on the image. At the same time, a smooth and wet glass surface is more beneficial for the expansion.

[0049] Figure 1 The removal process of the trial mold a is shown in the figure, where b represents the cement-based material that has started to expand.

[0050] In this precision monitoring device, the camera 21 can be any electronic device capable of clear recording, such as a digital camera, a high-definition camera, or a smartphone.

[0051] Based on the aforementioned precision monitoring device provided by the present invention, it can test and characterize the fluidity of the cement-based material. Specifically, refer to the following method:

[0052] In the first step, use the precision monitoring device provided by the present invention to record the free-flow expansion process of the cement-based material to generate a flow expansion video.

[0053] Specifically, refer to the following steps: 1) Support 12 through the adjustable bracket and adjust the height of the translucent platform 11, and use the level 13 to test whether the translucent platform 11 reaches the horizontal state; at the same time, adjust the height of the lifting table 22 so that the recording range of the camera 21 exactly accommodates the size of the translucent platform 11 into the picture; 2) Turn on the camera 21 and lift the flow table mold a, and record the process of the free-flow expansion of the cement-based material b inside the flow table mold a after it is lifted until the cement-based material b stops flowing, and end the recording to obtain the flow expansion video of the cement-based material.

[0054] The above method for lifting the trial mold can be adopted as described in any existing test method for the fluidity of cement paste or cement mortar, so that the paste of the cement-based material can freely flow and expand under the action of gravity.

[0055] In the second step, process the recorded flow expansion video to obtain a flow process curve.

[0056] Specifically, first, extract the images in the video at intervals of 0.1 s through a computer program; then perform binary processing on each obtained frame of image (see Figure 2 shown), adjust the contrast of the image by changing the binary threshold to obtain a clear binary image (see Figure 3 shown); in the third step, use the first frame of image when the trial mold is about to be lifted as the reference binary image at time 0, and calculate the areas of the parts with pixel values of zero in the reference binary image and the binary image at time t respectively as the reference fluidity area and the fluidity area at time t of the cement-based material; in the fourth step, perform a linear mapping calculation on the fluidity area at time t and the reference fluidity area to obtain the fluidity at time t of the cement-based material; finally, plot the change of fluidity over time at each moment to obtain the flow process curve of the cement-based material.

[0057] In the third step, fit the flow process curve to the equation shown in Equation 1 below to obtain the values of the rheological property parameters k and the spreading index n, and evaluate the viscosity of the cement-based material by the magnitude of n / k.

[0058] Specifically, the smaller the ratio of n / k, the faster the flow rate of the cement-based material in the initial stage, indicating that the viscosity of the cement-based material is lower.

[0059] R t -R0 = (R g -R0)[1 - exp(-kt n )] Equation 1

[0060] In Equation 1: t is the time, with the unit of s; R0 is the outer diameter of the lower bottom surface of the test mold, with the unit of mm; R t is the value of the fluidity of the cement-based material at time t, with the unit of mm; R g is the final fitted fluidity of the cement-based material, with the unit of mm; k is the rheological property parameter, with the unit of s -n ; n is the spreading index, dimensionless.

[0061] The following will illustrate the characterization method of the flow properties of cement-based materials based on the above-mentioned precision monitoring device of the present invention through several embodiments.

[0062] Example 1

[0063] In this example, the fluidity of mortars with different water-cement ratios was tested using the precision monitoring device provided by the present invention.

[0064] First, mortars with different water-cement ratios but basically the same final fluidity were prepared using Onoda cement, standard sand, and polycarboxylate superplasticizer PCA-I; then, the mortar flow process was tested using the above method.

[0065] The mortar mix ratios are shown in Table 1, where the dosage of PCA-I is the percentage relative to the mass of cement.

[0066] Table 1 Mix ratios and fluidities of mortars with different water-cement ratios

[0067]

[0068] From the final fluidities of the three different water-cement ratios in Table 1, it can be seen that although the water-cement ratios are different, the final fluidities of the three are not significantly different, that is, the yield stresses of the three are not much different.

[0069] Figure 4 Shows the flow process curve of the mortar fluidity changing with time.

[0070] According to Equation 1 above for Figure 4The flow process curves in it were fitted, and the fitting results obtained are shown in Table 2.

[0071] Table 2 Fitting Results

[0072]

[0073] It can be seen from Table 2 that the correlation coefficient R 2 is close to 1, indicating that the fitting result of Equation 1 is reasonable.

[0074] Comparing the mortars obtained with three different water-cement ratios in this embodiment, it can be seen that as the water-cement ratio increases, the n / k ratio gradually decreases, indicating that under the mixing ratio conditions adopted in this embodiment, the greater the water-cement ratio, the lower the viscosity of the corresponding mortar and the faster its early flow. This is also confirmed by Figure 4 the curvature of the change curve of the fluidity of each mortar with time in it; obviously, among the three, the mortar with a water-cement ratio of 0.36 obtains the maximum fluidity in the same time, that is, it shows the fastest flow and the lowest viscosity.

[0075] Example 2

[0076] In this embodiment, the flow process of the neat cement with different cementitious material compositions was tested using the precision monitoring device provided by the present invention.

[0077] First, neat cement with basically the same final fluidity was prepared using Onoda cement, standard sand, fly ash, slag powder, silica fume, and polycarboxylate superplasticizer PCA-I; then, the flow process of the neat cement was tested using the above method.

[0078] The mix proportion of the neat cement is shown in Table 3, where the dosage of PCA-I is the percentage relative to the total mass of the cementitious materials.

[0079] Table 3 Mix Proportion and Fluidity of Neat Cement with Different Types of Mineral Admixtures

[0080]

[0081] It can be seen from the final fluidity of the neat cement obtained from the four different types of mineral admixtures in Table 3 that although the types of mineral admixtures are different, there is no significant difference in the final fluidity of the four, that is, the yield stresses of the four are not very different.

[0082] Figure 5 shows the flow process curve of the fluidity of the neat cement changing with time.

[0083] According to Equation 1 above, Figure 5 the flow process curves in it were fitted, and the fitting results obtained are shown in Table 4.

[0084] Table 4 Fitting Results

[0085]

[0086] As can be seen from Table 4, the correlation coefficient R 2 is close to 1, indicating that the fitting result of Equation 1 is reasonable.

[0087] Comparing the neat pastes obtained from the four groups of mixing ratios in this example, it can be seen that the n / k ratio corresponding to the neat paste with the components of cement and fly ash in one group is the smallest, indicating that under different mixing ratio conditions in this example, the viscosity of the neat paste in Group 2 is the lowest and its early flow is the fastest. This is also verified from the Figure 5 curvature of the variation curves of the fluidity of each neat paste with time; obviously, among the four, the neat paste with the simultaneous addition of cement and fly ash obtains the largest fluidity within the same time, that is, it shows the fastest flow and the lowest viscosity.

[0088] Example 3

[0089] In this example, the provided precision monitoring device of the present invention is used to test the influence of different water reducers and their dosages on the mortar flow process.

[0090] First, mortars with basically the same fluidity are prepared by using Onoda cement, standard sand, and polycarboxylate superplasticizers with different molecular structures; then, the above method is used to test the mortar flow process.

[0091] The mortar mixing ratio is shown in Table 5, where the dosage of PCA-I is the percentage relative to the mass of cement.

[0092] Table 5 Mixing ratio and fluidity of mortars with different water reducers and dosages

[0093]

[0094] From the final fluidity of the mortars obtained from the three different water reducers and their dosages in Table 5, it can be seen that although the types and dosages of the water reducers are different, the final fluidities of the three do not show significant differences, that is, their yield stresses are not very different.

[0095] Figure 6 shows the flow process curve of the mortar fluidity varying with time.

[0096] According to Equation 1 above for Figure 6 each flow process curve in, the fitting results obtained are shown in Table 6.

[0097] Table 6 Fitting results

[0098]

[0099] As can be seen from Table 6, the correlation coefficient R 2Close to 1, indicating that the fitting result of Equation 1 is reasonable.

[0100] Comparing the neat pastes obtained from the three group ratios in this example, it can be seen that the n / k ratio corresponding to the mortar obtained using PCA3 as the water reducer is the smallest, indicating that under the ratio conditions in this example, the mortar using PCA3 has the lowest viscosity and the fastest early flow rate. This is also confirmed by Figure 6 the curvature of the variation curve of the fluidity of each mortar with time in; obviously, compared with the three, the mortar corresponding to using PCA3 as the water reducer obtains the largest fluidity within the same time, that is, it shows the fastest flow and the lowest viscosity.

[0101] Example 4

[0102] In this example, the provided precision monitoring device of the present invention is used to test the flow process of different self-compacting concretes.

[0103] First, self-compacting concrete is prepared using Onoda PII52.5 cement, fly ash, blast furnace slag, river sand with a fineness modulus of 2.8, limestone with a particle size of 5 mm to 20 mm, and water reducer PCAI according to the concrete mix ratio shown in Table 4; then, the above method is used to test the concrete flow expansion process.

[0104] The mortar mix ratio is shown in Table 7, where the dosage of PCA-I is the percentage relative to the mass of cement.

[0105] Table 7 Concrete mix ratio

[0106] Unit: kg / m 3

[0107]

[0108] It can be seen from the final spread of the concrete obtained from the two different mix ratios in Table 7 that although the mix ratios are different, the final spreads of the two are not significantly different, that is, their yield stresses are not very different.

[0109] Figure 7 The flow process curve showing the variation of the concrete spread with time is shown.

[0110] According to Equation 1 above for Figure 7 fitting each flow process curve in, the fitting results obtained are shown in Table 8.

[0111] Table 8 Fitting results

[0112]

[0113] It can be seen from Table 8 that the correlation coefficient R 2 is close to 1, indicating that the fitting result of Equation 1 is reasonable.

[0114] Comparing the concretes obtained from the two-group ratios in this embodiment, it can be seen that the n / k ratio of the concrete corresponding to Ratio 1 is smaller, indicating that the concrete under this ratio in this embodiment has the fastest initial flow. This is also confirmed by Figure 7 the curvature of the curves showing the change of the slump flow of each concrete over time; obviously, when compared, the concrete corresponding to Ratio 1 obtains the largest slump flow within the same time, that is, it shows the fastest flow and has the lowest viscosity.

[0115] As can be seen from the above embodiments, based on the precision monitoring device provided by the present invention and the characterization method for the flow performance of cement-based materials provided thereby, it is possible to quantitatively analyze the effects of water-cement ratio, cementitious material composition, and water reducers with different molecular structures on the flow process of the paste, and thus reflect the working performance and rheological characteristics of the cement-based material paste. Specifically, the device can record the entire flow expansion process of the paste from the moment of the initial flow of the whole paste, especially the flow process under the action of gravity shear at the initial stage when the paste starts to flow from rest. Figures 4 to 7 The test results show that although the final flowability or final slump flow of different pastes is basically the same, the flowability or slump flow within 5 s varies greatly, and the gap reaches the maximum at 10 s. Thereafter, as the shear force decreases, the gap between the flowability or slump flow gradually narrows and finally reaches a basically consistent state. It can be seen that the present device and the above-mentioned characterization method based on the device can precisely monitor the entire process of the flow of cement-based materials, especially the initial flow stage where the difference is most obvious.

[0116] In this characterization method, the obtained test results are subjected to fitting analysis through Equation 1, and the rheological parameters k and n of the paste can be obtained, and the n / k ratio can be calculated. The above parameters have a significant response to the flow process of cement-based materials and can comprehensively and quantitatively reflect the rheological characteristics of cement-based materials.

[0117] Therefore, the present invention can be applied to the research on the rheological characteristics of cement-based material paste, and can also be used for the quantitative test of the influence on the rheological performance of the paste during the development of products such as chemical admixtures and mineral admixtures related to cement-based materials.

[0118] Although the present invention has been shown and described with reference to specific embodiments, those skilled in the art will understand that various changes in form and detail may be made herein without departing from the spirit and scope of the invention as defined by the claims and their equivalents.

Claims

1. A method for characterizing the flowability of a cement-based material, characterized in that, It is carried out based on a precision monitoring device, and the precision monitoring device includes a workbench for carrying a fluidity test mold and a detection component located below the workbench; wherein, the workbench includes a translucent platform, an adjustment bracket for supporting and regulating the translucent platform to be horizontal, and a level for detecting the levelness of the translucent platform; the detection component includes a camera located under the translucent platform and a lifting platform for supporting and adjusting the height of the camera; the adjustment ranges of the adjustment bracket and the lifting platform are such that the recording range of the camera completely includes the translucent platform. The characterization method includes the following steps: S1. Use the precision monitoring device to record the free flow expansion process of the cement-based material to generate a flow expansion video. S2. Process the flow expansion video by using binary processing combined with the flow area mapping calculation method to obtain the fluidity of the cement-based material at different times, and draw the flow process curve of the cement-based material. S3. Fit the flow process curve to the equation shown in Formula 1 below: R t -R0 = (R g -R0)[1 - exp(-kt n )] Equation 1 In Equation 1: t is time with the unit of s; R0 is the outer diameter of the lower bottom surface of the test mold with the unit of mm; R t is the value of the fluidity of the cement-based material at time t with the unit of mm; R g is the fitted final fluidity of the cement-based material with the unit of mm; k is the rheological property parameter with the unit of s -n ; n is the spreading index, dimensionless; S4. Obtain the values of the rheological property parameters k and the spreading index n from Formula 1, and calculate the ratio of n / k. Among them, the smaller the ratio of n / k, the faster the flow rate of the cement-based material in the initial stage and the lower the viscosity of the cement-based material.

2. The characterization method according to claim 1, wherein The translucent platform is made of tempered glass with a thickness greater than 5 mm.

3. The characterization method according to claim 2, wherein The light transmittance of the translucent platform is 60% - 80%.

4. The characterization method according to claim 1, wherein The camera is a digital camera, a high-definition camera or a smart phone.

5. The characterization method according to any one of claims 1 to 4, wherein The specific method of step S2 is as follows: S21. Extract the images in the flow expansion video at intervals of 0.1 s through a computer program. S22. Perform binary processing on each obtained frame image to obtain a clear binary image. S23. Take the first frame image when the fluidity test mold is about to be lifted as the reference binary image at the 0 moment, and calculate the areas of the parts with pixel values of zero in the reference binary image and the binary image at the t moment respectively, as the reference flow area and the flow area at the t moment of the cement-based material. S23. Perform linear mapping calculation on the flow area at the t moment and the reference flow area to obtain the fluidity of the cement-based material at the t moment. S24. Plot the change of fluidity with time at each moment to obtain the flow process curve.

6. The characterization method according to claim 5, wherein The specific method of step S1 is as follows: S11. Use the adjustment bracket to support and adjust the height of the translucent platform, and use the level to test until the translucent platform reaches a horizontal state. S12. Adjust the height of the lifting platform so that the recording range of the camera exactly accommodates the size of the translucent platform into the picture. S13. Turn on the camera and lift the fluidity test mold, record the process of the free flow expansion of the cement-based material after the fluidity test mold is lifted until the cement-based material stops flowing, end the recording, and obtain the flow expansion video.

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