Cement-based material salt erosion damage detection method based on CT (Computed Tomography) technology

Abstract

The invention relates to the technical field of detection and identification of damage of a cement-based material subjected to salt erosion, in particular to a method for detecting salt erosion damage of a cement-based material based on a CT (Computed Tomography) technology, which comprises the following steps: extracting. Dcm file data obtained by CT scanning, identifying volume deformation, porosity change and mortar density change of the cement-based material subjected to salt erosion, and calculating the damage of the cement-based material subjected to salt erosion. The damage and degradation characteristics of the cement-based material under the action of salt erosion are reflected. According to the detection method disclosed by the invention, under the action of salt erosion, the volume deformation, porosity change and mortar density change of the cement-based material subjected to the action of salt erosion are identified by adopting a CT technology according to the principle, and the damage and degradation characteristics of the cement-based material subjected to the action of salt erosion are reflected; the method is suitable for the deterioration characterization of the cement-based material at the initial stage of salt erosion, overcomes the attenuation effect of X rays during CT scanning, is not limited by the resolution ratio of CT detection equipment, and provides a new method for the detection and identification technology of the damage of the cement-based material under the action of salt erosion.

Description

Technical Field

[0001] This invention relates to the field of detection and identification technology for damage to cement-based materials subjected to salt erosion, specifically a method for detecting salt erosion damage to cement-based materials based on CT technology. Background Technology

[0002] In marine or saline-alkali areas, cement-based materials in buildings can be corroded by salts such as sulfates, chlorides, and magnesium salts, which can damage the cement matrix, reduce the strength of the materials, and even cause cracks that lead to the destruction of the building.

[0003] Currently, the main methods for assessing damage to cement-based materials caused by salt erosion are macroscopic testing methods such as strength testing and volume stability testing. These methods are highly destructive and can only be used to study the overall performance of cement-based materials, failing to characterize localized erosion characteristics. Therefore, people have turned their attention to microscopic detection techniques. These techniques can not only characterize the damage and deterioration phenomena caused by salt erosion but also facilitate the study of damage mechanisms. Due to the heterogeneity of cement-based materials, and because coarse aggregates and pores can interfere with wave propagation, some microscopic detection methods, such as ultrasonic testing, often cannot capture localized damage.

[0004] Since the early 1980s, CT technology has been used in research on cement-based materials. CT scans have been successfully applied to the durability studies of cement-based materials. Currently, many scholars use CT technology to characterize cracks or pores to reflect the damage and deterioration characteristics of cement-based materials under salt erosion. However, due to the slow rate of salt erosion, this method cannot characterize the changes in the properties of cement-based materials in the early stages of salt erosion, i.e., before cracks appear or before significant changes in identifiable pores. Consequently, it is impossible to further analyze the failure mechanism. Furthermore, during CT scans, when X-rays pass through cement-based materials, they interact with atoms in the material, resulting in energy loss and absorption or scattering of some rays. Current research rarely considers the attenuation effect of X-rays, which affects detection accuracy. With the innovation of CT technology, high-resolution equipment has gradually been applied to the damage detection and identification of cement-based materials. However, the high cost often deters researchers, greatly limiting the pace of scientific research. Summary of the Invention

[0005] The purpose of this invention is to provide a method for detecting salt erosion damage in cement-based materials based on CT technology, so as to solve the problem that the detection methods proposed in the background art all have certain limitations.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for detecting salt erosion damage in cement-based materials based on CT technology, comprising:

[0007] Extracting .dcm file data from CT scans, identifying volumetric deformation, porosity changes, and mortar density changes in cementitious materials affected by salt erosion, and reflecting the damage and deterioration characteristics of cementitious materials under salt erosion, the following scheme is employed:

[0008] 01) Based on the pore distribution in the CT value 2D image, the CT value threshold of mortar and identifiable pores can be determined. Based on the mix ratio, the volume ratio of coarse aggregate in concrete can be calculated. Adding the CT value pixel ratio, the CT value threshold of coarse aggregate and mortar in concrete can be determined. The length (pixel) and resolution of each pixel can be determined based on the CT equipment.

[0009] 02) Read the .dcm file and input the CT value of each pixel;

[0010] 03) Determine the concrete scanning section area of ​​the CT scan window and calculate the total number of pixels N in the concrete scanning section area;

[0011] 04) Calculate the maximum CT value MaxCT and minimum CT value MinCT of the concrete scanning section area;

[0012] 05) Based on the salt erosion path, the concrete scanning section area is divided into layers. The more layers, the more accurate the calculation results. For example, for a two-dimensional erosion path, the circular section is divided into multiple rings, or the rectangular section is divided into multiple rectangular rings. For a one-dimensional erosion path, the rectangular section is divided into multiple sections.

[0013] 06) Calculate the maximum CT value MaxCT_i and minimum CT value MinCT_i of the i-th layer in the concrete scanning section region after reassignment;

[0014] 07) To overcome the attenuation effect of X-rays during CT scanning, the CT values ​​of each layer in the concrete scanning section are reassigned proportionally, as shown in the following formula:

[0015] CT_RE=(MaxCT-MinCT) / (MaxCT_i-MinCT_i)*(CT-MinCT_i)+Min CT;

[0016] 08) Calculate the porosity, mortar ratio, aggregate ratio, and average CT value of the entire concrete scanning section area;

[0017] 09) Calculate the porosity, mortar ratio, aggregate ratio, and average CT value of each layer in the concrete scanning section area;

[0018] 10) Calculate the area and minimum radius of the entire concrete scanned section. The calculation formula for the area of ​​the entire concrete scanned section is as follows:

[0019] Area = N * Pixel 2;

[0020] 11) The calculated cross-sectional area of ​​the concrete reflects the change in concrete volume under salt erosion; the calculated change in porosity reflects the change in concrete porosity under salt erosion; and the calculated CT value of the mortar reflects the change in mortar density in the concrete under salt erosion.

[0021] Preferably, the mortar contains smaller pores, a paste, and fine aggregates below resolution.

[0022] Preferably, the CT value is in the range of -1024 to 3071 HU.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] Under salt erosion, the density of cement-based materials changes significantly, whether due to the filling of pores by byproducts or the formation of cracks. Since the attenuation of CT scan rays through a medium is proportional to the medium's density, this invention utilizes CT technology to identify volumetric deformation, porosity changes, and mortar density changes in cement-based materials subjected to salt erosion. This reflects the damage and deterioration characteristics of cement-based materials under salt erosion. This invention is suitable for characterizing the deterioration of cement-based materials in the early stages of salt erosion, overcomes the attenuation effect of X-rays during CT scans, and is not limited by the resolution of CT equipment. It provides a new method for detecting and identifying damage to cement-based materials subjected to salt erosion. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the window concrete scanning section area of ​​the present invention;

[0026] Figure 2 This is a schematic diagram of the multi-layered circular ring of the present invention;

[0027] Figure 3 This is a schematic diagram of the multi-layer rectangular ring of the present invention;

[0028] Figure 4 This is a schematic diagram of the multi-layer cross-section of the present invention.

[0029] In the diagram: 1. Concrete scan section area; 2. Non-concrete scan section area. Detailed Implementation

[0030] 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.

[0031] Please see Figure 1-4 One embodiment of the present invention is a method for detecting salt erosion damage in cement-based materials based on CT technology.

[0032] This includes: extracting .dcm file data from CT scans, identifying volumetric deformation, porosity changes, and mortar density changes in cement-based materials affected by salt erosion, reflecting the damage and deterioration characteristics of cement-based materials under salt erosion, as follows:

[0033] 01) Based on the pore distribution in the 2D CT value map, the CT value threshold of mortar and identifiable pores can be determined. Based on the mix ratio, the volume ratio of coarse aggregate in concrete can be calculated. Adding the CT value pixel ratio, the CT value threshold of coarse aggregate and mortar in concrete can be determined. Based on the CT equipment, the length (pixel) and resolution of each pixel point are determined. Mortar is a building bonding material made by mixing inorganic cementitious materials, fine aggregate and water in proportion. It is mainly used for masonry, plastering and decorative fixing. Its core feature is that it does not contain coarse aggregate.

[0034] 02) Read the .dcm file and input the CT value for each pixel. The CT value is a numerical value used in computed tomography (CT) imaging to quantify tissue density, and the unit is Henry's units. Using the absorption coefficient of water as a benchmark, the density differences are reflected by comparing the absorption capacity of different tissues to X-rays.

[0035] 03) Determine the concrete scanning section area of ​​the CT scan window and calculate the total number of pixels N in the concrete scanning section area;

[0036] 04) Calculate the maximum CT value (MaxCT) and minimum CT value (MinCT) of the concrete scan section. CT value is a numerical value used in computed tomography (CT) imaging to quantify tissue density, expressed in Henry units. Using the absorption coefficient of water as a benchmark, the density differences are reflected by comparing the absorption capacity of different tissues to X-rays.

[0037] 05) Based on the salt erosion path, the concrete scanning section area is divided into layers. The more layers, the more accurate the calculation results. For example, for a two-dimensional erosion path, the circular section is divided into multiple rings, or the rectangular section is divided into multiple rectangular rings. For a one-dimensional erosion path, the rectangular section is divided into multiple sections.

[0038] 06) Calculate the maximum CT value MaxCT_i and minimum CT value MinCT_i of the i-th layer in the concrete scan section after reassignment. The CT value is a numerical value used in computed tomography imaging to quantify tissue density, and the unit is Henry's units. Using the absorption coefficient of water as a benchmark, the density differences are reflected by comparing the absorption capacity of different tissues to X-rays.

[0039] 07) To overcome the attenuation effect of X-rays during CT scanning, the CT values ​​of each layer in the concrete scanning section are reassigned proportionally, as shown in the following formula:

[0040] CT_RE=(MaxCT-MinCT) / (MaxCT_i-MinCT_i)*(CT-MinCT_i)+Min CT;

[0041] 08) Calculate the porosity, mortar ratio, aggregate ratio, and average CT value of the entire concrete scanning section area;

[0042] 09) Calculate the porosity, mortar ratio, aggregate ratio, and average CT value for each layer of the concrete scan section. The CT value is a numerical value used in computed tomography (CT) imaging to quantify tissue density, expressed in Henry units. Using the absorption coefficient of water as a benchmark, the density differences are reflected by comparing the absorption capacity of different tissues to X-rays.

[0043] 10) Calculate the area and minimum radius of the entire concrete scanned section. The calculation formula for the area of ​​the entire concrete scanned section is as follows:

[0044] Area = N * Pixel 2 ;

[0045] 11) The calculated cross-sectional area of ​​the concrete reflects the change in concrete volume under salt erosion; the calculated change in porosity reflects the change in concrete porosity under salt erosion; the calculated CT value of the mortar reflects the change in mortar density in the concrete under salt erosion. Mortar is a building bonding material made by mixing inorganic cementitious materials, fine aggregates and water in proportion. It is mainly used for masonry, plastering and decorative fixing. Its core characteristic is that it does not contain coarse aggregates.

[0046] Furthermore, mortar contains smaller pores, paste, and fine aggregates below resolution. Mortar is a building bonding material made by mixing inorganic cementitious materials, fine aggregates, and water in a certain proportion. It is mainly used for masonry, plastering, and decorative fixing. Its core characteristic is that it does not contain coarse aggregates.

[0047] Furthermore, the CT value ranges from -1024 to 3071 HU. The CT value is a numerical value used in computed tomography (CT) imaging to quantify tissue density, and its unit is Henle units. Using the absorption coefficient of water as a benchmark, the density differences are reflected by comparing the absorption capacity of different tissues to X-rays.

[0048] Working principle: During use, the .dcm file data obtained from CT scans is extracted to identify the volume deformation, porosity changes, and mortar density changes of cement-based materials affected by salt erosion. Based on the pore distribution in the 2D CT value map, the CT value threshold for mortar and identifiable pores can be determined. The volume ratio of coarse aggregate in concrete can be calculated based on the mix proportion. Adding the CT value pixel ratio, the CT value threshold for coarse aggregate and mortar in concrete can be determined. The length (pixel) and resolution of each pixel are determined according to the CT equipment. The .dcm file is read, and the CT value of each pixel is entered. The concrete scanning section area in the CT scan window is determined, and the total number of pixels N in the concrete scanning section area is calculated. The maximum CT value MaxCT and minimum CT value MinCT of the concrete scanning section area are calculated. Based on the salt erosion path, the concrete scanning section area is layered. The more layers, the more accurate the calculation results. The maximum CT value MaxCT_i and minimum CT value MinCT_i of the i-th layer of the concrete scanning section area are calculated after reassignment. The CT values ​​of each layer of the concrete scanning section area are reassigned proportionally, as shown in the following formula:

[0049] CT_RE=(MaxCT-MinCT) / (MaxCT_i-MinCT_i)*(CT-MinCT_i)+Min CT;

[0050] Calculate the porosity, mortar ratio, aggregate ratio, and average CT value of the entire concrete scanning section area. Calculate the porosity, mortar ratio, aggregate ratio, and average CT value of each layer in the concrete scanning section area. Calculate the area and minimum radius of the entire concrete scanning section area. The calculation formula for the entire concrete scanning section area is as follows:

[0051] Area = N * Pixel 2 ;

[0052] The calculated cross-sectional area of ​​the concrete reflects the volume change of the concrete under salt erosion; the calculated porosity change reflects the porosity change of the concrete under salt erosion; and the calculated mortar CT value reflects the density change of the mortar in the concrete under salt erosion. This is the complete working principle of the present invention.

[0053] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for detecting salt erosion damage in cement-based materials based on CT technology, characterized in that, include: Extracting .dcm file data from CT scans, identifying volumetric deformation, porosity changes, and mortar density changes in cementitious materials affected by salt erosion, and reflecting the damage and deterioration characteristics of cementitious materials under salt erosion, the following scheme is employed: 01) Based on the pore distribution in the CT value 2D image, the CT value threshold of mortar and identifiable pores can be determined. Based on the mix ratio, the volume ratio of coarse aggregate in concrete can be calculated. Adding the CT value pixel ratio, the CT value threshold of coarse aggregate and mortar in concrete can be determined. The length (pixel) and resolution of each pixel can be determined based on the CT equipment. 02) Read the .dcm file and input the CT value of each pixel; 03) Determine the concrete scanning section area of ​​the CT scan window and calculate the total number of pixels N in the concrete scanning section area; 04) Calculate the maximum CT value MaxCT and minimum CT value MinCT of the concrete scanning section area; 05) Based on the salt erosion path, the concrete scanning section area is divided into layers. The more layers, the more accurate the calculation results. For example, for a two-dimensional erosion path, the circular section is divided into multiple rings, or the rectangular section is divided into multiple rectangular rings. For a one-dimensional erosion path, the rectangular section is divided into multiple sections. 06) Calculate the maximum CT value MaxCT_i and minimum CT value MinCT_i of the i-th layer in the concrete scanning section region after reassignment; 07) To overcome the attenuation effect of X-rays during CT scanning, the CT values ​​of each layer in the concrete scanning section are reassigned proportionally, as shown in the following formula: CT_RE=(MaxCT-MinCT) / (MaxCT_i-MinCT_i)*(CT-MinCT_i)+Min CT; 08) Calculate the porosity, mortar ratio, aggregate ratio, and average CT value of the entire concrete scanning section area; 09) Calculate the porosity, mortar ratio, aggregate ratio, and average CT value of each layer in the concrete scanning section area; 10) Calculate the area and minimum radius of the entire concrete scanned section. The calculation formula for the area of ​​the entire concrete scanned section is as follows: Area=N*Pixel 2 ; 11) The calculated cross-sectional area of ​​the concrete reflects the change in concrete volume under salt erosion; the calculated change in porosity reflects the change in concrete porosity under salt erosion; and the calculated CT value of the mortar reflects the change in mortar density in the concrete under salt erosion.

2. The method for detecting salt erosion damage in cement-based materials based on CT technology according to claim 1, characterized in that: The mortar contains smaller pores, slurry, and fine aggregates below resolution.

3. The method for detecting salt erosion damage in cement-based materials based on CT technology according to claim 1, characterized in that: The CT value ranges from -1024 to 3071 HU.

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