Method for calculating crystallization pressure of salt in pores of porous material

Abstract

The invention is suitable for the field of porous material salt crystallization damage, and provides a porous material pore salt crystallization pressure calculation method, which comprises the following steps: S1, establishing a porous material pore salt crystallization model, and determining the type of a pore salt crystal; s2, acquiring pore size parameters and salt crystal material parameters; s3, salt crystal strain parameters are solved; and S4, calculating the crystallization pressure in the pores of the porous material according to a salt crystallization pressure CDC calculation formula. The salt crystallization pressure calculation formula (CDC formula) is invented according to the crystal elastic deformation coordination theory, the method for calculating the salt crystallization pressure in the pores of the porous material is provided, the method has the advantages of being high in calculation speed, high in calculation efficiency, easy in parameter obtaining and the like, the defect that parameters are difficult to obtain in a traditional calculation method is overcome, and the calculation efficiency is improved. And a theoretical basis is provided for salt crystallization damage analysis of the porous material in the salt corrosion process.

Description

Technical Field

[0001] The invention belongs to the field of salt crystallization damage of porous materials, and in particular relates to a method for calculating the salt crystallization pressure in pores of porous materials. Background Art

[0002] Salt crystallization plays an important role in the physical weathering process of porous materials and is generally considered to be one of the main problems affecting the durability of materials. Most of the weathering damage of porous materials is related to salt crystallization. Taking concrete, a typical porous material, as an example, concrete has become the most widely used building material in modern buildings due to its excellent performance and low cost. With the increasing demand for the expansion of human living space, concrete has been widely used in harsh environments such as marine environments, high-cold environments, and saline-alkali areas. However, concrete in salt corrosion environments often suffers from severe damage due to crystallization pressure, which brings a heavy economic burden to society. Therefore, studying the crystallization pressure inside porous materials is of great value for the study of material durability in the fields of construction engineering, historical building protection engineering, transportation engineering, underground and geotechnical engineering, and is of great significance for improving the disaster prevention and mitigation capabilities of historical buildings and infrastructure, and for reasonably predicting the service life of structures.

[0003] Crystallization pressure plays a decisive role in the crystallization failure behavior of porous materials. The existing crystallization pressure calculation method is mainly based on the Correns formula ([1] Naillon, Antoine, Pierre Joseph, and Marc Prat. Ion transport and precipitation kinetics as key aspects of stress generation on pore walls induced by salt crystallization [J]. Physical review letters 120.3 (2018): 034502.), and the supersaturation of the salt solution is the core parameter in the formula. Since the nucleation and crystallization process of salt crystals is extremely short and difficult to observe and measure, the supersaturation of the salt solution is difficult to measure, which makes it difficult to quickly and easily apply the formula to the calculation of crystallization pressure, which limits the prediction and evaluation of the salt damage resistance of porous materials.

[0004] Therefore, in response to this situation, it is necessary to propose a method for calculating the salt crystallization pressure in the pores of porous materials to achieve the purpose of quickly, conveniently and accurately calculating the crystallization pressure of porous materials, so as to overcome the shortcomings in current practical applications. Summary of the invention

[0005] The purpose of the present invention is to provide a method for calculating the salt crystallization pressure in the pores of a porous material, aiming to solve the problems mentioned in the above background technology.

[0006] The present invention is implemented as follows: a method for calculating the salt crystallization pressure in the pores of a porous material comprises the following steps:

[0007] S1. Establish a pore salt crystallization model for porous materials and determine the types of salt crystals in the pores;

[0008] S2, obtaining pore size parameters and salt crystal material parameters;

[0009] S3, solving the salt crystal strain parameters;

[0010] S4. Calculate the crystallization pressure in the pores of porous materials based on the salt crystallization pressure CDC calculation formula.

[0011] A further technical solution is that in step S1, the model can at least show the phenomenon that the salt crystal crystallization process is restricted by the pore wall, and the pore size in the porous material pore salt crystallization model is in the micron level; the type of salt crystal is determined based on the salt crystal that applies crystallization pressure to the pore wall in the pore.

[0012] According to a further technical solution, in step S2, the size parameter of the pore is the pore diameter; the salt crystal is regarded as a homogeneous material, and its material parameters include the elastic modulus and the minimum unit cell size of the salt crystal.

[0013] According to a further technical solution, the pore diameter refers to the straight-line distance between two planes corresponding to the contact constraint of the crystal growth surface and the pore wall, and the diameter of the pore is in the micron level.

[0014] In a further technical solution, in step S3, the strain calculation formula of the salt crystal is:

[0015]

[0016] Where: d uni is the minimum unit cell size of a salt crystal D por is the pore diameter (um).

[0017] A further technical solution is that in step S4, a salt crystallization pressure calculation formula (Crystal deformation coordination equation, CDC formula) is invented based on the crystal elastic deformation coordination theory, and the salt crystallization pressure CDC calculation formula in the pores of the porous material is:

[0018]

[0019] Where: cryis the salt crystallization pressure (MPa); E cry is the elastic modulus of the salt crystal (GPa).

[0020] The present invention provides a method for calculating the salt crystallization pressure in the pores of a porous material, which has the following beneficial effects:

[0021] The present invention invents a salt crystallization pressure calculation formula (CDC formula) based on the crystal elastic deformation coordination theory, and provides a method for calculating the salt crystallization pressure in the pores of porous materials. The method has the advantages of fast calculation speed, high calculation efficiency and easy parameter acquisition, which makes up for the difficulty of parameter acquisition in traditional calculation methods and provides a theoretical basis for salt crystallization destruction analysis of porous materials during salt corrosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic flow chart of a method for calculating the salt crystallization pressure in the pores of a porous material provided by an embodiment of the present invention;

[0023] Figure 2 This is a diagram of the porous salt crystallization model of the porous material involved in the embodiments of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0026] like Figure 1 As shown, a method for calculating the salt crystallization pressure in the pores of a porous material provided by an embodiment of the present invention includes the following steps:

[0027] S1. Establish a pore salt crystallization model for porous materials and determine the types of salt crystals in the pores.

[0028] Among them, the model can at least show the phenomenon that the salt crystal crystallization process is restricted by the pore wall. The pore size in the porous material pore salt crystallization model is in the micron level; the type of salt crystal is determined based on the salt crystal that applies crystallization pressure to the pore wall in the pore.

[0029] S2. Obtain pore size parameters and salt crystal material parameters.

[0030] Among them, the size parameter of the pore is the pore diameter; the salt crystal is regarded as a homogeneous material, and its material parameters include the elastic modulus and the minimum size of the unit cell of the salt crystal.

[0031] The pore diameter refers to the straight-line distance between two planes corresponding to the contact constraint of the crystal growth surface and the pore wall, and the diameter of the pore is in the micron level.

[0032] S3. Solve the strain parameters of salt crystals.

[0033] Wherein, in step S3, the strain calculation formula of the salt crystal is:

[0034]

[0035] Where: d uni is the minimum unit cell size of a salt crystal D por is the pore diameter (um).

[0036] S4. Calculate the crystallization pressure in the pores of the porous material according to the salt crystallization pressure CDC calculation formula invented.

[0037] Among them, a salt crystallization pressure calculation formula (Crystal deformation coordination equation, CDC formula) is invented based on the crystal elastic deformation coordination theory, and the salt crystallization pressure CDC calculation formula in the pores of porous materials is:

[0038]

[0039] Where: cry is the salt crystallization pressure (MPa); E cry is the elastic modulus of the salt crystal (GPa). Specific embodiment:

[0041] The following uses two kinds of corrosive salts, sodium chloride and sodium sulfate, as examples to illustrate a method for calculating the crystallization pressure of salt in the pores of porous materials. The model is as follows: Figure 2 The method for calculating the salt crystallization pressure in the pores of the porous material comprises the following steps:

[0042] S1: Establish a salt crystallization model in the pores of porous materials and determine the types of salt crystals in the pores.

[0043] The model can at least show the phenomenon that the salt crystal crystallization process is restricted by the pore wall, and the pore size in the porous material pore salt crystallization model is micron-level.

[0044] The type of salt crystal is determined based on the crystallization pressure exerted by the salt crystal on the pore walls within the pores.

[0045] S2: Obtain pore size parameters and salt crystal material parameters.

[0046] Among them, the size parameter of the pore is the pore diameter; the salt crystal is regarded as a homogeneous material, and its material parameters include the elastic modulus and the minimum size of the unit cell of the salt crystal, which can be obtained by referring to the literature.

[0047] The pore diameter refers to the straight-line distance between two planes corresponding to the contact constraint of the crystal growth surface by the pore wall, and the diameter of the pore is in the micron level.

[0048] S3: Solve for the salt crystal strain parameters.

[0049] Among them, the strain calculation formula of salt crystal is:

[0050]

[0051] Where: d un i is the minimum unit cell size of the salt crystal D por is the pore diameter (um).

[0052] S4: Calculate the crystallization pressure in the pores of the porous material according to the invented salt crystallization pressure CDC calculation formula.

[0053] Among them, the calculation formula of salt crystallization pressure CDC in the pores of porous materials is:

[0054]

[0055] Where: cry is the salt crystallization pressure (MPa); E cry is the elastic modulus of the salt crystal (GPa).

[0056] The elastic modulus of sodium chloride is 24 GPa ([2] De Jong M, Chen W, Angsten T, et al. Charting the complete elastic properties of inorganic crystalline compounds [J]. Scientific data, 2015, 2 (1): 1-13.), and the minimum unit cell size is ([3] Sun XW, Wang XG, Song T, et al. Comparative investigations of the P–V–T relationship of NaCl at high pressure and temperature [J]. Physica B: Condensed Matter, 2008, 403(18):3255-3260.).

[0057] The elastic modulus of sodium sulfate is 43 GPa ([2] De Jong M, Chen W, Angsten T, et al. Charting the complete elastic properties of inorganic crystalline compounds [J]. Scientific data, 2015, 2 (1): 1-13.), and the minimum unit cell size is ([4]Chen Q, Yang

[0058] According to the calculation method of salt crystallization pressure in the pores of porous materials, the crystallization pressure is calculated using the CDC calculation formula and compared with the crystallization pressure calculated by the Correns formula. The comparison of the calculation results of salt crystallization pressure is shown in Table 1.

[0059] Table 1 Comparison of calculation results of salt crystallization pressure

[0060]

[0061] The above embodiment of the present invention provides a method for calculating the salt crystallization pressure in the pores of a porous material. A salt crystallization pressure calculation formula (CDC formula) is invented based on the crystal elastic deformation coordination theory, and a method for calculating the salt crystallization pressure in the pores of a porous material is provided. This method has the advantages of fast calculation speed, high calculation efficiency and easy parameter acquisition, which makes up for the difficulty of parameter acquisition in traditional calculation methods and provides a theoretical basis for the analysis of salt crystallization destruction of porous materials during salt corrosion.

[0062] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for calculating the salt crystallization pressure in the pores of a porous material, characterized in that: The steps include: S1. Establish a pore salt crystallization model for porous materials and determine the types of salt crystals in the pores; S2, obtaining pore size parameters and salt crystal material parameters; S3, solving the salt crystal strain parameters; S4. Calculate the crystallization pressure in the pores of porous materials based on the salt crystallization pressure CDC calculation formula.

2. The method for calculating the salt crystallization pressure in the pores of porous materials according to claim 1, characterized in that: In step S1, the model can at least show the phenomenon that the salt crystal crystallization process is restricted by the pore wall, and the pore size in the porous material pore salt crystallization model is micron-level; The type of salt crystal is determined based on the crystallization pressure exerted by the salt crystal on the pore walls within the pores.

3. The method for calculating the salt crystallization pressure in the pores of porous materials according to claim 2, characterized in that: In step S2, the size parameter of the pore is the pore diameter; The salt crystals are considered as homogeneous materials, and their material parameters include the elastic modulus and the minimum unit cell size of the salt crystals.

4. The method for calculating the salt crystallization pressure in the pores of porous materials according to claim 3, characterized in that: The pore diameter refers to the straight-line distance between two planes corresponding to the contact constraint of the crystal growth surface and the pore wall, and the diameter of the pore is in the micron level.

5. The method for calculating the salt crystallization pressure in the pores of porous materials according to claim 4, characterized in that: In step S3, the strain calculation formula of the salt crystal is: Where: d uni is the minimum unit cell size of the salt crystal; D por is the pore diameter.

6. The method for calculating the salt crystallization pressure in the pores of porous materials according to claim 5, characterized in that: In step S4, according to the crystal elastic deformation coordination theory, the calculation formula of the salt crystallization pressure CDC in the pores of the porous material is obtained as follows: Where: cry is the salt crystallization pressure; E cry is the elastic modulus of the salt crystal.

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