Multi-parameter collaborative evaluation method for interface transition area of composite cementing material system based on backscattered electron image

Abstract

The invention discloses a multi-parameter collaborative evaluation method for an interface transition area of a composite cementing material system based on a backscattered electron image, and belongs to the technical field of material structure analysis and image processing. In the prior art, a structure-activity relationship between a pore structure and the macroscopic performance of concrete is difficult to systematically reveal when a concrete interface transition area is represented by using a single parameter. The method comprises the following steps: acquiring a plurality of backscattered electron images of a to-be-detected test block, and dividing the to-be-detected test block into a plurality of strips at equal intervals towards a matrix side by taking the boundary of aggregate and the matrix as a reference; determining the position of an interface transition region by utilizing the porosity distribution characteristics of the strip; then acquiring pore structure parameters of an interface transition area and chemical composition parameters of a test block to be detected; and evaluating the interface transition area by using the pore structure parameters and the chemical composition parameters. The method is mainly used for evaluating the interface transition area of the composite cementing material system.

Description

Technical Field

[0001] This invention relates to the field of materials structure analysis and image processing technology, specifically to an evaluation method for the interface transition zone of composite gel materials. Background Technology

[0002] Concrete is a typical multiphase composite gel material composed of cementitious materials, aggregates, and an interfacial transition zone. The interfacial transition zone in a composite cementitious material system serves as a key microstructural unit connecting the aggregates and the cement matrix; its composition, porosity, and microcrack distribution directly determine the mechanical properties, volumetric stability, and durability of the concrete. During concrete pouring, the edge-wall effect and the slurry-flooding effect significantly increase the local water-cement ratio in the interfacial transition zone, leading to coarse crystals, enhanced orientation, and a loose structure in the hydration products. This forms a weakened layer with high porosity, becoming a critical area for the deterioration of the concrete's internal properties.

[0003] Existing methods for characterizing the interfacial transition zone structure in concrete generally employ single-parameter evaluation models, such as using porosity or interfacial thickness as the sole quantitative indicator. However, the interfacial transition zone is a complex and coupled structural system, and single-parameter evaluation methods cannot comprehensively and systematically reveal the structure-property relationship between pore structure and the macroscopic properties of concrete. Therefore, there is an urgent need to establish a statistically representative quantitative characterization method for the interfacial transition zone that enables multi-dimensional parameter synergistic analysis, in order to achieve a comprehensive assessment of the interfacial microstructure and provide a scientific basis for optimizing concrete interfacial performance. Summary of the Invention

[0004] To overcome the technical problem that existing technologies, which use single parameters to characterize the transition zone of concrete interfaces, are unable to systematically reveal the structure-property relationship between pore structure and macroscopic properties of concrete, this invention provides a multi-parameter synergistic evaluation method for the transition zone of composite cementitious material systems based on backscattered electron imaging.

[0005] This invention is achieved through the following technical solution:

[0006] A multi-parameter collaborative evaluation method for the interfacial transition zone of a composite cementitious material system based on backscattered electron imaging includes:

[0007] S1: Prepare the composite gel material sample to be evaluated, cure it to the preset age, cut off the initial cut block containing the complete interface transition zone, and obtain the test block to be tested after pretreatment;

[0008] S2: Acquire multiple backscattered electron images of the test block to be inspected, and divide it into several strips at equal intervals towards the matrix side, based on the boundary between the aggregate and the matrix; calculate the porosity of each strip, and determine the strip where the interface transition zone is located based on the porosity distribution characteristics;

[0009] S3: Collect the pore structure parameters in the strip where the interface transition region is located, and at the same time collect the chemical composition parameters based on the backscattered electron image of any of the test blocks to be tested.

[0010] S4: The interface transition region of the composite gel material sample to be evaluated is evaluated using the pore structure parameters and chemical composition parameters.

[0011] By acquiring multiple backscattered electron images of the test block under test, the aggregate and matrix boundary is divided into several strips at equal intervals towards the matrix side. The porosity distribution characteristics of the strips are used to determine the location of the interface transition zone. Then, the pore structure parameters of the interface transition zone and the chemical composition parameters of the test block under test are acquired. The interface transition zone is evaluated using the pore structure parameters and chemical composition parameters.

[0012] By utilizing the changes in pore space characteristics and the chemical modification rules of the C–(A)–S–H gel structure in ITZ, a physical-chemical dual-dimensional evaluation of the ITZ structure optimization effect under the composite cementitious material system was achieved.

[0013] Furthermore, the preprocessing procedure described in S1 includes:

[0014] (1) The initial cut pieces are dried using a drying method;

[0015] (2) Use sandpaper to polish the initial cut blocks;

[0016] (3) Use ultrasonic cleaning to remove surface debris from the initial cut pieces;

[0017] (4) Place the initial cut pieces in a vacuum drying oven and dry until the mass is constant;

[0018] (5) Place the initial cut block in a cylindrical silicone mold and vacuum embed the blast furnace slag concrete sample in a 70 kPa vacuum environment by circulating epoxy resin and curing agent.

[0019] (6) Use sandpaper to sand the surface of the initial cut block until the substrate of the initial cut block is exposed;

[0020] (7) Polishing is performed using polishing fluid.

[0021] By employing a 70 kPa vacuum circulation process during the mounting stage, epoxy resin can fully penetrate into the micropores inside the sample, thereby effectively avoiding edge damage and structural distortion caused by pore exposure during polishing, and improving the clarity and structural integrity of the microscopic imaging of the interface area.

[0022] Furthermore, determining the strip containing the interface transition zone based on porosity distribution characteristics includes:

[0023] (1) Calculate the porosity value of each strip and determine the porosity distribution range;

[0024] (2) Select target strips whose porosity distribution range is wider than all other strips;

[0025] (3) Calculate the extreme value of porosity of the target strip. If the difference between the maximum porosity value of the target strip and the porosity value of the adjacent strip on the aggregate side is less than a preset threshold A, the difference between the minimum porosity value and the porosity value of the adjacent strip on the matrix side is less than a preset threshold B, and the average porosity value is greater than or equal to 1.2 times the matrix porosity value, then it is determined that the interface transition zone between the aggregate and the matrix is ​​located in the current target strip.

[0026] This invention utilizes the law of porosity variation with spatial location to automatically identify and divide ITZ regions and non-ITZ matrix regions. The division results have a higher degree of agreement with the actual microstructure boundaries, improving the objectivity and repeatability of subsequent characterization.

[0027] Furthermore, the pore structure parameters include: porosity, number of pores, average pore area, maximum pore area, average shape factor, fractal dimension, and probability entropy.

[0028] This invention extracts multidimensional parameters such as porosity, number of pores, maximum / average pore area, shape factor, fractal dimension, and probability entropy to achieve systematic quantification of the pore structure characteristics of ITZ.

[0029] Furthermore, the average shape factor is the average of all pore shape factors within the target range, used to describe the degree of deviation of the pore shape from the ideal geometry; the value of the shape factor is... ,in, Represents the pore area. This indicates the perimeter of the pore.

[0030] Furthermore, the fractal dimension is used to characterize the relationship between the pore perimeter and pore area as a function of the pore's characteristic spatial scale, and this relationship satisfies the formula: In the formula, Indicates the circumference of the pore. Denotes the fractal dimension. Represents the spatial scale of pore characteristics. Represents a constant.

[0031] Furthermore, the probability entropy quantitatively reflects the uniformity and disorder of the pore distribution. In the formula, This indicates the percentage of pore size within a graded range based on pore size.

[0032] Furthermore, the optimization effect of the interface transition region of the composite gel material sample to be evaluated is evaluated using the pore structure parameters and chemical composition parameters, including: evaluating the compactness of the interface transition region using the pore structure parameters and chemical composition parameters; evaluating the spatial structure characteristics of the interface transition region using the pore structure parameters; and evaluating the composition and degree of reaction of the hydration products in the interface transition region using the chemical composition parameters.

[0033] Synchronous acquisition of pore structure parameters in the interface transition zone, as well as chemical composition parameters of the specimen, avoids the limitations of single-parameter characterization and achieves dual-dimensional, multi-parameter collaborative characterization of pore structure characteristics and chemical composition characteristics, thus more accurately capturing the core characteristics of the interface transition zone. Based on the comprehensive evaluation of the interface transition zone using pore structure parameters and chemical composition parameters, it is possible to systematically link the microstructure and chemical composition of the interface transition zone with the macroscopic properties of concrete, clearly revealing the structure-property relationship between pore structure and macroscopic properties of concrete.

[0034] Furthermore, the chemical composition parameters include Ca, Si, Al, Ca / Si molar ratio, and Al / Si molar ratio.

[0035] Furthermore, the trend of decreasing Ca / Si molar ratio and increasing Al / Si molar ratio is used to characterize the densification of the pore structure.

[0036] This invention systematically evaluates the improvement effect and interface optimization mechanism of various supplementary cementitious materials on the microstructure of ITZ by examining the density, uniformity, complexity, and chemical composition variation of the pore structure of ITZ in the cementitious material system.

[0037] The beneficial effects of this invention are:

[0038] This invention acquires multiple backscattered electron images of the test block, dividing it into strips at equal intervals towards the matrix, using the aggregate-matrix boundary as a reference. The porosity distribution characteristics of these strips determine the location of the interface transition zone. Then, the pore structure parameters of the interface transition zone and the chemical composition parameters of the test block are acquired. These parameters are used to evaluate the interface transition zone. This forms a complete evaluation system from sample preparation, interface transition zone location, multi-parameter acquisition to comprehensive evaluation. By comprehensively evaluating the interface transition zone based on pore structure and chemical composition parameters, it systematically correlates the microstructure and chemical composition of the interface transition zone with the macroscopic properties of concrete, clearly revealing the structure-property relationship between pore structure and macroscopic concrete properties. This overcomes the limitations of traditional single-index judgments, providing a scientific basis and technical support for improving the interface performance and optimizing the structure of composite cementitious material systems. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the process for preparing the test block in one embodiment of the method of the present invention;

[0041] Figure 2 This is a schematic diagram of the image with aggregate removed from the backscattered electron image in one embodiment of the method of the present invention;

[0042] Figure 3 This is a schematic diagram of backscattered electron image segmentation in one embodiment of the method of the present invention;

[0043] Figure 4 This is a schematic diagram of a binarized backscattered electron image segmentation strip in one embodiment of the method of the present invention;

[0044] Figure 5 This is a schematic diagram illustrating the determination of the initial grayscale threshold in one embodiment of the method of the present invention;

[0045] Figure 6 This is a schematic diagram of the porosity distribution of cement concrete strips in one embodiment of the method of the present invention;

[0046] Figure 7 This is a schematic diagram of the porosity distribution of blast furnace slag cement concrete strips in one embodiment of the method of the present invention;

[0047] Figure 8 This is a schematic diagram comparing the pore structure parameters of cement concrete and blast furnace slag cement concrete in one embodiment of the method of the present invention.

[0048] Figure 9 This is a schematic diagram comparing the elemental distribution around the ITZ of cement concrete and blast furnace slag cement concrete in one embodiment of the method of the present invention.

[0049] Figure 10 This is a schematic diagram comparing the macroscopic parameters of cement concrete and blast furnace slag cement concrete in one embodiment of the method of the present invention. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Specific Implementation Method 1

[0052] Step S100: Prepare the composite gel material sample to be evaluated. After curing to the preset age, cut off an initial block containing the complete interfacial transition zone (ITZ). After pretreatment, obtain the test block to be tested. (Reference) Figure 1 Specifically, this includes S101-S102:

[0053] Step S101: Prepare the composite gel material sample to be evaluated and cure it to the preset age. Specifically:

[0054] In this embodiment, blast furnace slag cement concrete is used as the composite gel material to be evaluated. The admixture parameters of the blast furnace slag cement concrete are as follows:

[0055] The mix proportion of blast furnace slag cement concrete is: 478 parts by weight of cementitious materials, 606 parts by weight of sand, 987 parts by weight of coarse aggregate, and 215 parts by weight of water. When preparing blast furnace slag cement concrete, a specific surface area of ​​[missing information] is used. Blast furnace slag is used to replace 40% of the cement in cement concrete. The cement is P·O 42.5 ordinary Portland cement; the sand is natural river sand with a fineness modulus of 2.7; and the stone is natural crushed stone of 5–20 mm.

[0056] Blast furnace slag cement concrete samples were prepared according to the above mixing method. After molding, the samples were allowed to stand and cure under standard conditions for 24 hours before demolding. Subsequently, they were placed in an environment of 20℃ and 95% humidity for 28 days for curing. After curing, the blast furnace slag cement concrete samples were placed in an environment of 20±2℃ and 70±5% humidity for one year.

[0057] Step S102: Cut out an initial block containing the complete interface transition area, and obtain the test block to be inspected after preprocessing:

[0058] A preliminary blast furnace slag cement concrete block with a side length of 10 mm and a thickness of 2 mm, containing the complete ITZ, was cut from the blast furnace slag cement concrete sample. The following processing was performed on the preliminary blast furnace slag cement concrete block to be cut:

[0059] (1) The blast furnace slag cement concrete pre-cut blocks were dried using the D-dry drying method for 48 hours to terminate the hydration reaction inside the blast furnace slag cement concrete pre-cut blocks.

[0060] (2) Use 800-grit sandpaper to pre-grind the blast furnace slag cement concrete blocks to remove the surface damage layer and initially level them.

[0061] (3) Use ultrasonic cleaning to remove surface debris from the initial cut blocks of blast furnace slag cement concrete.

[0062] (4) Place the blast furnace slag cement concrete pre-cut blocks in a 40℃ vacuum drying oven and dry them until the quality is constant.

[0063] (5) Place the blast furnace slag cement concrete pre-cut blocks into In the cylindrical silicone mold, In a vacuum environment, epoxy resin and curing agent are cyclically used to vacuum embed blast furnace slag cement concrete samples.

[0064] (6) Use 800-grit and 1200-grit sandpaper to grind the surface of the blast furnace slag cement concrete initial cut block until the matrix of the blast furnace slag cement concrete initial cut block is exposed.

[0065] (7) Polishing was performed sequentially using 9μm, 3μm and 1μm diamond suspension polishing slurries under a pressure of 20N. The sample was thoroughly cleaned before each change to a finer particle size polishing medium.

[0066] This embodiment employs a 70 kPa vacuum circulation process during the mounting stage to treat the initial cut blast furnace slag cement concrete blocks. This allows the epoxy resin to fully penetrate the micropores within the blast furnace slag cement concrete sample, effectively preventing edge damage and structural distortion caused by exposed pores during polishing. This optimization improves the clarity and structural integrity of the microscopic imaging of the interface region (especially the ITZ) of the initial cut blast furnace slag cement concrete blocks.

[0067] Step S200: Acquire multiple backscattered electron (BSE) images of the test block under test, and obtain a pore structure distribution map after binarization; divide the sample radially at equal intervals to obtain multiple strips and calculate the porosity of each strip; determine the strip containing the interface transition zone based on the strip porosity distribution characteristics. Specifically, this includes:

[0068] Step S201: Acquire backscattered electron images of the test block under test and perform binarization processing to obtain a pore structure distribution map. Specifically: First, the test block under test is treated with carbon spraying to form a uniform conductive layer, which can avoid charge accumulation and signal interference; then, at a working voltage of 15kV and BSE mode, different observation areas are randomly selected at the aggregate-slurry interface of the test block under test at a magnification of 1000x, and 36 backscattered electron images of the ITZ region are taken. The boundary between the aggregate and the matrix in the image is identified, and the image portion of the aggregate is removed. The backscattered image of the matrix after removing the aggregate is shown below. Figure 2 As shown.

[0069] The matrix backscattered electron image was then binarized to obtain a clear and identifiable pore structure distribution map. In backscattered imaging, the different atomic numbers of different components result in a significant grayscale contrast between the two images: aggregates typically appear as brighter areas, while the slurry and interface transition zones exhibit lower grayscale. Simultaneously, aggregates appear as smooth, non-porous areas in the image, while the matrix appears as porous, non-smooth areas.

[0070] Step S202: Divide the pore structure distribution map radially at equal intervals to obtain multiple stripes:

[0071] The pore structure distribution map is divided into several strips at equal intervals towards the matrix side, using the boundary between the aggregate and the matrix as a reference. In this embodiment, the fixed step size is set to 10 μm, resulting in 5 strips, as shown below. Figure 3 As shown.

[0072] In practical applications, a reasonable analysis range can be set based on factors such as research objectives, material type, and microscopic image resolution. For example, multi-point analysis can be performed using a range of 5–20 μm or layer distances (such as 5 μm, 10 μm, 15 μm, etc.) to obtain more comprehensive ITZ gradient feature information. Therefore, 10 μm is not the only limiting value, but rather a preferred parameter in this embodiment.

[0073] The initial grayscale threshold is determined based on the inflection point of the cumulative frequency curve of the processed image and the intersection of the fitted straight lines at the two inflection points of the cumulative frequency curve. Figure 5 As shown, the initial grayscale threshold is multiplied by a correction coefficient to obtain the grayscale correction threshold. The correction coefficient is set within the range of (0.85, 0.95), and in this embodiment, the correction coefficient is set to 0.9. The image being processed can be a striped binarized image or a whole binarized image divided into strips. Figure 4 shows the overall binarized image and the binarized striped regions.

[0074] This invention reduces the risk of pores being incorrectly identified as pores due to surface depressions by correcting the initial grayscale threshold, thereby improving the conservatism and reliability of pore identification.

[0075] Step S203: Identify pores using a grayscale correction threshold, then calculate the porosity of each strip, and determine the strip containing the interface transition zone based on the porosity distribution characteristics. Specifically:

[0076] (1) Using the grayscale correction threshold, the pores in each strip image are identified, and then the porosity value of each strip is calculated to determine the porosity distribution range;

[0077] (2) Select target strips whose porosity distribution range is wider than all other strips;

[0078] (3) Calculate the extreme porosity of the target strip. If the difference between the maximum porosity value of the target strip and the porosity value of the adjacent strip is less than a preset threshold A, the difference between the minimum porosity value and the porosity value of the non-adjacent strip is less than a preset threshold B, and the maximum porosity value is greater than or equal to 1.2 times the matrix porosity value, then it is determined that the interface transition zone between the aggregate and the matrix is ​​located in the current target strip. In this embodiment, the preset thresholds A and B are both 5%.

[0079] The porosity is calculated by dividing the sum of the pixels of all pores in the target strip image by the sum of the pixels of all pixels in the strip image.

[0080] Step S300: Collect the pore structure parameters of the strip containing the interface transition region, and collect the chemical composition parameters of the test block to be tested. Specifically, this includes steps S301-S302:

[0081] Step S301: Collect pore structure parameters in the strip containing the interface transition region. These pore structure parameters include: porosity, number of pores, average pore area, maximum pore area, average shape factor, fractal dimension, and probability entropy. These parameters are used to characterize the compactness and spatial structure features of the interface transition region.

[0082] The number of pores is the sum of the number of all pores on the strip image. For ease of statistical comparison, the number of pores is expressed as the number of pores per 1000 square micrometers.

[0083] The average pore area is the sum of the pore areas on the strip image divided by the number of pores.

[0084] The maximum pore area is the largest pore area of ​​a single pore on the strip image.

[0085] The average shape factor is the average of all pore shape factors within the target range, used to describe the degree of deviation of the pore shape from the ideal geometry (usually circular or spherical); the value of the shape factor is... Where A represents the pore area and C represents the pore perimeter.

[0086] The fractal dimension is used to characterize the relationship between the pore perimeter and pore area as a function of the spatial scale of pore features, reflecting the autocorrelation of pore structure, describing the relationship between the perimeter or pore boundary complexity and the pore area as a function of the spatial scale of pore features, thereby quantifying the irregularity and heterogeneity of pore networks.

[0087] The relationship between the changes satisfies the formula: In the formula, Indicates the circumference of the pore. Denotes the fractal dimension. Represents the spatial scale of pore characteristics. Represents a constant.

[0088] The probability entropy quantitatively reflects the uniformity and disorder of pore distribution. The larger the entropy value, the more complex and dispersed the pore structure. The smaller the entropy value, the more concentrated the pore size and the simpler the structure.

[0089] The probability entropy In the formula, This indicates the percentage of pore size within a graded range based on pore size.

[0090] Multiple pore structure parameters can reflect the compactness, complexity, and spatial distribution characteristics of the ITZ pore structure. Compared with traditional evaluation methods based solely on single indicators such as porosity or thickness, multiple pore structure parameters significantly improve structural resolution and information dimensions, enabling precise capture of detailed structural differences and local defect characteristics in the ITZ.

[0091] Step S302: Acquire the chemical composition parameters of the test block to be tested: Select the backscattered electron image of any of the test blocks to be tested, perform energy dispersive spectroscopy (EDS) line scanning, extract the Ca, Si, and Al elemental content curves along the aggregate-slurry direction, and calculate the changes in the Ca / Si and Al / Si molar ratios at each point to obtain the elemental gradient distribution characteristics. This is used to characterize the composition and reaction degree of hydration products in the interfacial transition zone. By identifying the chemical modification rules of the C–(A)–S–H gel structure in the ITZ, the densification degree and evolution characteristics of the silicon-aluminum skeleton in the interfacial region are systematically characterized, providing a scientific basis for optimizing the interfacial performance of the composite cementitious system.

[0092] Step S400: Evaluate the optimization effect of the interface transition zone of the composite gel material sample to be evaluated using the pore structure parameters and chemical composition parameters, including: evaluating the compactness of the interface transition zone using the pore structure parameters and chemical composition parameters; evaluating the spatial structure characteristics of the interface transition zone using the pore structure parameters; and evaluating the composition and reaction degree of the hydration products in the interface transition zone using the chemical composition parameters.

[0093] The compactness of the interfacial transition region is evaluated using the pore structure parameters and chemical composition parameters, wherein the trend of decreasing Ca / Si molar ratio and increasing Al / Si molar ratio is used to characterize the compaction of the pore structure.

[0094] This invention utilizes BSE images to extract pore parameters, quantitatively reflecting the compactness, uniformity, and complexity of ITZ from a physical perspective. Simultaneously, it combines energy dispersive spectroscopy (EDS) line scanning analysis of Ca / Si and Al / Si molar ratio changes to reveal the C–(A)–S–H structural modification laws and interfacial chemical densification mechanisms induced by supplementary cementitious materials. This achieves a simultaneous quantitative description of the physical structural evolution and chemical reaction processes of ITZ, systematically revealing the optimization paths and modification mechanisms of interfacial structures by different supplementary cementitious materials. It overcomes the limitations of traditional single-indicator or empirical judgments, providing a scientific basis and technical support for improving the interfacial performance and optimizing the structure of composite cementitious material systems. Compared to X-ray CT, mercury intrusion porosimetry, and nanoindentation techniques, this invention achieves a good balance between cost, representativeness, and spatial resolution. It can be widely applied to comparative studies and structural optimization design of ITZ microstructures in various supplementary cementitious material systems, providing an efficient and economical characterization method for improving concrete durability and performance.

[0095] To verify the beneficial effects of the present invention, the following experiments were conducted:

[0096] Blast furnace slag cement concrete and cement concrete with the same mix proportions were prepared using the method of the present invention, and the same subsequent treatment was performed according to Specific Embodiment 1.

[0097] The porosity of cement concrete and blast furnace slag cement concrete were obtained using the method of this invention. The porosity of cement concrete varies with the strip distance as follows: Figure 6 As shown, the porosity of blast furnace slag cement concrete varies with the strip distance as follows: Figure 7 As shown, the porosity increases gradually from the matrix towards the aggregate surface. In cement concrete, the porosity distribution in the 20-30 micrometer band is wider than in other bands, while in blast furnace slag cement concrete, the porosity distribution in the 10-20 micrometer band is wider than in other bands. Therefore, the ITZ (intermediate zone) of cement concrete and blast furnace slag cement concrete can be determined to be within the 10-20 micrometer and 20-30 micrometer ranges, respectively.

[0098] Comparing the pore parameters of the two types of concrete ITZ, such as Figure 8As shown, blast furnace slag cement concrete exhibits significant densification characteristics in the ITZ region, with an overall lower porosity than ordinary cement concrete. The introduction of supplementary cementitious material (blast furnace slag) effectively reduces the number and area of ​​macropores. Simultaneously, changes in pore morphology parameters further validate the structural optimization effect. The average shape factor of pores in the blast furnace slag cement concrete ITZ is higher than that in cement concrete, indicating a more regular pore profile and a significant reduction in fissure-like irregular pores. Fractal dimension results show that the complexity and tortuosity of the pore structure in the blast furnace slag cement concrete ITZ increase, while probability entropy analysis indicates that the pore distribution in the blast furnace slag cement concrete ITZ is more concentrated and ordered, indicating a more uniform pore size distribution and a more stable pore structure. This ITZ densification and structural homogenization characteristic, reflected by multiple parameters, directly improves the macroscopic performance of the material, such as… Figure 10 As shown, the reduction in porosity and the concentration of pore size distribution decrease the number of interconnected channels and capillary suction effect, thereby effectively suppressing the non-uniform infiltration of water and ions; the regularization of pore morphology and the increase in fractal dimension enhance the geometric resistance and energy dissipation capacity of the interface region, increase the threshold for microcrack propagation, and manifest as higher interfacial bonding strength and overall compressive strength.

[0099] EDS line scans were performed on BSE images of cement concrete and blast furnace slag cement concrete to obtain chemical elements. The elemental distributions are shown in Table 1 and 2. Figure 9 As shown, the Ca / Si molar ratio of the cement concrete (OPCC) matrix is ​​approximately 1.0 to 2.6, while that of BFSC is reduced to approximately 0.6–1.5. This reduction reflects the fact that the incorporation of BFS reduces the Ca / Si ratio by consuming limestone and generating Si-rich calcium silicate hydrated calcium silicate gel (C–S–H). Meanwhile, BFSC has a higher Al content (Al / Si ≈ 0.25–0.6), which further modifies the C–S–H structure. Al substitution at silicate bridging sites elongates the chain length, enhances crosslinking, and thus strengthens the interlayer bonding of C–(A)–S–H. Furthermore, Al incorporation may cause a transformation of the C–(A)–S–H morphology from fibrous to lamellar, which contributes to a denser arrangement and finer pore distribution, thereby optimizing the ITZ structure.

[0100] Table 1. Ca / Si and Al / Si molar ratios based on EDS linear scan analysis

[0101]

[0102] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0103] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-parameter synergistic evaluation method for the interfacial transition zone of a composite cementitious material system based on backscattered electron imaging, characterized in that, include: S1: Prepare the composite gel material sample to be evaluated, cure it to the preset age, cut off the initial cut block containing the complete interface transition zone, and obtain the test block to be tested after pretreatment; S2: Acquire multiple backscattered electron images of the test block to be inspected, and divide it into several strips at equal intervals towards the matrix side, based on the boundary between the aggregate and the matrix; calculate the porosity of each strip, and determine the strip where the interface transition zone is located based on the porosity distribution characteristics; S3: Collect the pore structure parameters in the strip where the interface transition region is located, and at the same time collect the chemical composition parameters based on the backscattered electron image of any of the test blocks to be tested. S4: The interface transition region of the composite gel material sample to be evaluated is evaluated using the pore structure parameters and chemical composition parameters.

2. The method for multi-parameter synergistic evaluation of the interfacial transition zone of a composite cementitious material system based on backscattered electron imaging according to claim 1, characterized in that, The preprocessing process described in S1 includes: (1) The initial cut pieces are dried using a drying method; (2) Use sandpaper to polish the initial cut blocks; (3) Use ultrasonic cleaning to remove surface debris from the initial cut pieces; (4) Place the initial cut pieces in a vacuum drying oven and dry until the mass is constant; (5) Place the initial cut block in a cylindrical silicone mold and vacuum embed the blast furnace slag concrete sample in a 70 kPa vacuum environment by circulating epoxy resin and curing agent. (6) Use sandpaper to sand the surface of the initial cut block until the substrate of the initial cut block is exposed; (7) Polishing is performed using polishing fluid.

3. The method for multi-parameter synergistic evaluation of the interfacial transition zone of a composite cementitious material system based on backscattered electron imaging according to claim 2, characterized in that, The determination of the interface transition zone based on porosity distribution characteristics includes: (1) Calculate the porosity value of each strip and determine the porosity distribution range; (2) Select target strips whose porosity distribution range is wider than all other strips; (3) Calculate the extreme value of porosity of the target strip. If the difference between the maximum porosity value of the target strip and the porosity value of the adjacent strip on the aggregate side is less than a preset threshold A, the difference between the minimum porosity value and the porosity value of the adjacent strip on the matrix side is less than a preset threshold B, and the average porosity value is greater than or equal to 1.2 times the matrix porosity value, then it is determined that the interface transition zone between the aggregate and the matrix is ​​located in the current target strip.

4. The method for multi-parameter synergistic evaluation of the interfacial transition zone of a composite cementitious material system based on backscattered electron imaging according to claim 3, characterized in that, The pore structure parameters include: porosity, number of pores, average pore area, maximum pore area, average shape factor, fractal dimension, and probability entropy.

5. The method for multi-parameter synergistic evaluation of the interfacial transition zone of a composite cementitious material system based on backscattered electron imaging according to claim 4, characterized in that, The average shape factor is the average of all pore shape factors within the target range, used to describe the degree of deviation of the pore shape from the ideal geometry; the value of the shape factor is... ,in, Represents the pore area. This indicates the perimeter of the pore.

6. The method for multi-parameter synergistic evaluation of the interfacial transition zone of a composite cementitious material system based on backscattered electron imaging according to claim 5, characterized in that, The fractal dimension is used to characterize the relationship between the pore perimeter and pore area as a function of the pore's characteristic spatial scale, and this relationship satisfies the formula: In the formula, Indicates the circumference of the pore. Denotes the fractal dimension. Represents the spatial scale of pore characteristics. Represents a constant.

7. The method for multi-parameter synergistic evaluation of the interfacial transition zone of a composite cementitious material system based on backscattered electron imaging according to claim 6, characterized in that, The probability entropy quantitatively reflects the uniformity and disorder of the pore distribution. In the formula, This indicates the percentage of pore size within a graded range based on pore size.

8. The method for multi-parameter synergistic evaluation of the interfacial transition zone of a composite cementitious material system based on backscattered electron imaging according to claim 7, characterized in that, The optimization effect of the interface transition region of the composite gel material sample to be evaluated is evaluated using the pore structure parameters and chemical composition parameters, including: evaluating the compactness of the interface transition region using the pore structure parameters and chemical composition parameters; evaluating the spatial structure characteristics of the interface transition region using the pore structure parameters; and evaluating the composition and degree of reaction of the hydration products in the interface transition region using the chemical composition parameters.

9. The method for multi-parameter synergistic evaluation of the interfacial transition zone of a composite cementitious material system based on backscattered electron imaging as described in claim 8, characterized in that, The chemical composition parameters include Ca, Si, Al, Ca / Si molar ratio, and Al / Si molar ratio.

10. The method for multi-parameter synergistic evaluation of the interfacial transition zone of a composite cementitious material system based on backscattered electron imaging according to claim 9, characterized in that, The trend of decreasing Ca / Si molar ratio and increasing Al / Si molar ratio is used to characterize the densification of the pore structure.

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