Freeze-thaw-chloride ion intrusion coupled multi-scale thermohydraulic model

Abstract

The invention relates to the technical field of concrete durability, in particular to a freeze-thaw-chloride ion intrusion coupled multi-scale thermohydraulic model, which comprises the following steps of: establishing a volume equilibrium equation of capillary pores by considering phase change during freeze-thaw, local migration of pore water and capillary pore deformation; an entrained air gap volume balance equation considering phase change during freezing and thawing, local water migration, dissolution-diffusion and entrained air gap deformation; a constitutive model of a concrete volume shell unit; a solution transmission control equation of solution overall migration under pressure driving; and obtaining a chloride ion mass balance control equation. The method is mainly suitable for describing chloride ion migration in freeze-thaw cycle and chloride ion migration experiments, an interpretation model can be provided for the acceleration phenomenon of the freeze-thaw cycle on chloride ion permeation, and a basis is provided for researching the coupling influence of the freeze-thaw cycle and chloride ion migration.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete durability, and in particular to a multi-scale thermohydraulic model for freeze-thaw - chloride ion intrusion coupling. Background Art

[0002] Chloride ion corrosion and freeze-thaw damage are the most destructive factors affecting the durability of concrete. The simulation of chloride diffusion is based on Fick's law, which was first proposed by Collepardi. Subsequently, the effects of hydration, temperature, load, and adsorption and carbonation coupling on diffusion have been widely studied.

[0003] Regarding the mechanism of freeze-thaw damage, since the classical hydraulic theory and osmotic pressure theory, many theories have been proposed, such as critical saturation based on hydrostatic theory, migration obstruction mechanism, and micro ice lens based on the stability criterion of the non-frozen water, ice, and steam three-phase system. For the coupling effect of freeze-thaw cycles and chloride ion penetration, many experimental studies have shown that the damage caused by an increase in the number of freeze-thaw cycles will significantly increase the diffusion coefficient, thereby increasing the transport of chloride ions in concrete.

[0004] However, in rapid freeze-thaw cycle tests, although chloride ions hardly diffuse at such low temperatures and short time scales, chloride ion migration was still found in the experiments, and the migration of chloride ions in rapid freeze-thaw cycles is related to the number of cycles rather than time. In addition, with the increase in the number of freeze-thaw cycles, the chloride distribution on the surface layer increases sharply, and this phenomenon cannot be explained by the increase in the diffusion coefficient caused by freeze-thaw damage. A recent study on the alternation of chloride ion intrusion and freeze-thaw also found that the acceleration of chloride ion penetration cannot be simply explained by the increase in the chloride ion diffusion coefficient induced by freeze-thaw cycles. Therefore, this application proposes a new convective effect mechanism model caused by the phase change of pore solution under freeze-thaw cycles to explain the above phenomena. Summary of the Invention

[0005] The purpose of this application is to provide a multi-scale thermohydraulic model for freeze-thaw - chloride ion intrusion coupling, aiming to solve the problems in the prior art.

[0006] The embodiments of this application provide a multi-scale thermohydraulic model for freeze-thaw - chloride ion intrusion coupling, including the following steps:

[0007] S1. Establish an external temperature change field, and at the same time calculate the total porosity of the concrete specimen through the following formula; the total porosity includes capillary pores and entrained air voids;

[0008] φ = φ cap + φ void

[0009] φ cap is the porosity of capillary pores and its initial value is φcap,0 , φ void is the porosity of the entrained air gap and the initial value is φ void,0 ;

[0010] S2. Calculate the water pressure on the air gap surface through the following formula;

[0011] p l = p void - p A

[0012] where p void is the air pressure in vacuum and the initial value is equal to zero atmospheric pressure; p A is the crystallization pressure;

[0013] S3. Assume that the capillary pores are initially saturated and only liquid phase and ice crystal phase exist therein, and calculate the porosities of the undeformed liquid phase and ice crystal phase in the capillary pores through the following formula respectively;

[0014]

[0015] In the formula, φ l,cap is the porosity of the liquid phase in the capillary pores, φ c,cap is the porosity of the ice crystal phase in the capillary pores, S cap is the saturation of the capillary pores and the value is 1, ρ l is the mass density of the liquid phase, ρ c is the mass density of the ice crystal phase, m l,cap is the mass ratio of the liquid phase in the capillary pores, m c,cap is the mass ratio of the ice crystal phase in the capillary pores;

[0016] S4. The air gap water saturation increases with the migration of the solution from the capillary pores to the air gap under the dissolution-diffusion action of hydraulic pressure and air. Calculate the air gap water saturation through the following formula;

[0017]

[0018] where S void is the air gap water saturation and the initial value is 0; Q 1 is the solution flow rate of the capillary pores; Q 2 is the flow rate of water flowing into the air gap through a slow air dissolution-diffusion process;

[0019] S5. Assume that air is sealed in the entrained air gap, and the inflow or formation of ice crystals of water will generate pressure in the air gap; combining S3 and S4, calculate the porosities of the undeformed gas phase, liquid phase and ice crystal phase in the air gap through the following formulas respectively;

[0020] φ g,void = φ void (1 - S void)

[0021]

[0022] Among them, φ g,void is the porosity of the gas phase in the entrained air void, φ l,void is the porosity of the liquid phase in the entrained air void, φ c,void is the porosity of the ice crystal phase in the entrained air void, m l,void is the mass ratio of the liquid phase in the entrained air void, m c,void is the mass ratio of the ice crystal phase in the entrained air void;

[0023] S6. Combining with Darcy's law, calculate the overall migration velocity of the solution under the drive of the volume-averaged hydraulic gradient through the following formula;

[0024]

[0025] Among them, u g is the overall velocity of the pore solution under the drive of the freeze-thaw pressure, with the unit of m / s, k con is the concrete permeability; is the average pressure on the shell;

[0026] S7. Describe the solution transport control equation for the overall migration of the solution under pressure drive through the following formula;

[0027]

[0028] Among them, φ l is the total volume of the liquid-phase pore solution, φ c is the total volume of the ice crystals;

[0029] S8. Establish a macroscopic diffusion model. The total chloride ions in the concrete include free chloride ions and bound chloride ions in the liquid-phase pore solution. Describe the chloride ion mass balance control equation through the following formula;

[0030]

[0031] Among them, C f is the concentration of free chloride ions in the liquid-phase pore solution, with the unit of mol / m 3 , C b is the concentration of bound chloride ions in the concrete, with the unit of mol / m 3 , D f is the diffusion coefficient of free chloride ions in the pore solution, with the unit of m 2 / s;

[0032] S9. Establish the heat transfer field of the concrete microscopic model and describe the phase change caused by heat transfer through the following formula;

[0033]

[0034] In the above formula, T is the absolute temperature in K, ρ con is the mass density of concrete in kg / m 3 , c q is the specific heat of concrete and takes an average value of 1100 J / kg·K, λ is the thermal conductivity of concrete and takes an average value of 1.74 W / m·K, L is the latent heat of fusion of water, and M c is the total mass of ice crystals.

[0035] Furthermore, in S2, the specific calculation method of p void and p A is as follows: Since ice forms in air voids, the thermodynamic equilibrium between ice and water makes the pressure of water less than that of ice, and the magnitude is the crystallization pressure p A , which is calculated by the following formula;

[0036] p A = p c - p l = S f (T 0 - T);

[0037] where p c is the ice crystal pressure in the air voids, p l is the water pressure on the surface of the air voids, S f is the melting entropy of crystals per unit volume, T 0 is the initial temperature in K, and T is the crystallization temperature in K;

[0038] Since ice is in contact with air, the pressure of ice is equal to the air pressure in the air voids, that is;

[0039] p c = p void .

[0040] Furthermore, m c,cap and m l,cap are calculated by the following formulas respectively;

[0041] m c,cap = m c,void × f(poresize) × f(T)

[0042] m l,cap = 1 - m c,cap

[0043] where f(poresize) is the influence factor of the most probable pore size and the total capillary porosity, and f(T) is the temperature influence factor, both of which depend on the specific material.

[0044] Furthermore, in S4, Q 1and Q 2 The specific calculation method is as follows: Assuming that the flux of the outer boundary is zero and the air gap is not always filled with air, the solution flow rate through the capillary pores is calculated by the following formula;

[0045]

[0046] After a slow air dissolution-diffusion process, the water flow rate into the air gap is calculated by the following formula;

[0047]

[0048] where ρ air is the mass density of air, with the unit of kg / m 3 , and q' is the air flux, with the unit of kg / s.

[0049] Furthermore, the calculation method of q 1 in S3 is as follows: When ice forms in the capillary pores, the volume expansion of ice crystals will generate hydraulic pressure in the capillary pores, so the pore water will be discharged from the capillary pores to the entrained air gap; The local migration of capillary pore water calculated by the following formula according to Darcy's law;

[0050]

[0051] where q 1 is the seepage velocity of the liquid-phase solution in the capillary pores, k is the permeability of the porous material, with the unit of m 2 , η is the viscosity of the liquid-phase solution, with the unit of Pa·s, and p cap is the hydraulic pressure in the capillary pores.

[0052] Furthermore, m c,void and m l,void in step S5 are calculated by the following formulas respectively;

[0053]

[0054] m l,void =1 - M c,void

[0055] where N 0 is the initial mass concentration of the volume solution, with the unit of %wt, and T t is the current temperature, with the unit of °C.

[0056] Furthermore, representing the average pressure on the concrete volume shell is calculated by the following formula;

[0057]

[0058] Further, in S7, φ l and φ c are calculated as follows;

[0059] φ l = φ l,cap + φ l,void

[0060] φ c = φ c,cap + φ c,void .

[0061] Further, in S9, M c is calculated by the formula M c = ρ c V c .

[0062] The beneficial effects of the present invention are as follows: The model provided by the present invention can explain the accelerating effect of freeze-thaw cycles on chloride ion penetration in concrete. By establishing the balance of capillary pore volume and entrained air void volume in concrete during phase change, the variation laws of their porosities are obtained. Combining the constitutive model of concrete shell, the solution migration law, and the heat transfer equation, a mass balance control equation of chloride considering freeze-thaw phase change is constructed. Due to the differences in porosity and heat transfer of concretes prepared under different experimental conditions, different mix ratios, and admixtures, the present invention is mainly applicable to describe the migration of chloride ions in freeze-thaw cycle and chloride ion migration experiments. The present invention can provide an explanatory model for the accelerating phenomenon of chloride ion penetration caused by such freeze-thaw cycles, and provide a basis for studying the coupled influence of freeze-thaw cycles and chloride ion migration. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 is the calculation flow chart of the present invention.

[0064] Figure 2 is a schematic diagram of capillary pores and entrained air voids in concrete.

[0065] Figure 3 is the boundary condition diagram of local solution migration in capillary pores.

[0066] Figure 4 is the variation of water-containing porosity with time within 20 temperature cycles.

[0067] Figure 5 is the variation of the overall solution migration velocity with time within 20 temperature cycles.

[0068] Figure 6 is a schematic diagram of the macroscopic diffusion model.

[0069] Figure 7 is the concentration change along the analysis path C f after different cycles.

[0070] Figure 8 The concentration of C at different analysis points f changes with time. Specific embodiments

[0071] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0072] As Figure 1 shown, a multi-scale thermohydraulic model of freeze-thaw - chloride ion intrusion coupling includes the following steps:

[0073] S1. Establish an external temperature change field and describe the temperature change with time through the following formula;

[0074]

[0075] where f T is the external temperature and T 0 is the initial temperature value.

[0076] S2. The schematic diagram of the concrete micro-unit model is shown in Figure 2 . Considering a concrete specimen with a total porosity of φ, including capillary pores and entrained air voids, calculate the concrete porosity through the following formula;

[0077] φ = φ cap + φ void

[0078] where φ cap is the porosity of capillary pores and the initial value is φ cap,0 , taking 0.12, and φ void is the porosity of entrained air voids and the initial value is φ void,0 , taking 0.08;

[0079] The calculation formulas of m c,void and m l,void are as follows;

[0080]

[0081] m l,void = 1 - m c,void

[0082] where m c,void is the mass ratio of ice crystal phase in the entrained air voids, and m l,void is the mass ratio of liquid phase in the entrained air voids, and N 0The initial mass concentration of the volumetric solution is taken as 10%.

[0083] m c,cap and m l,void can be calculated by the following formula;

[0084]

[0085] m l,cap = 1 - m c,cap

[0086] m l,cap is the mass ratio of the liquid phase in the capillary pores, and m c,cap is the mass ratio of the ice crystal phase in the capillary pores.

[0087] S4. For the concrete specimen in contact with the solution, assuming that the capillary pores are initially saturated and only the liquid phase and the ice crystal phase exist therein, the porosities of the undeformed liquid phase and the ice crystal phase in the capillary pores are calculated respectively by the following two equations;

[0088]

[0089] where, φ l,cap is the porosity of the liquid phase in the capillary pores, with the initial value of φ cap,0 ; φ c,cap is the porosity of the ice crystal phase in the capillary pores, with the initial value of 0, S cap is the saturation of the capillary pores and the initial value is taken as 1, ρ l is the mass density of the liquid phase, taken as 1000 kg / m 3 ; ρ c is the mass density of the ice crystal phase, taken as 920 kg / m 3 ;

[0090] S5. Since ice forms in the air voids, the thermodynamic equilibrium between ice and water makes the pressure of water less than the pressure of ice, and the magnitude of which is the crystallization pressure, described by the following equation;

[0091] p A = p c - p l = S f (T 0 - f T )

[0092] where, p c is the ice crystal pressure in the air voids, with the initial value of 0 Pa, p l is the water pressure on the surface of the air voids, S f is the melting entropy of the unit volume crystal, taken as 1.2 MPa / K, and T is the crystallization temperature (K);

[0093] Since ice is in contact with air, the pressure of the ice is equal to the air pressure in the air gap, denoted as p c = p void , and the water pressure on the air gap surface is calculated by the following formula;

[0094] p l = p void - p A

[0095] where p void is the air pressure in the air gap and is calculated by the following formula;

[0096]

[0097] p void0 is the initial air pressure in the air gap, taking 0 atmospheres, and K g is the air bulk modulus, taking 101.3 kPa.

[0098] S6. Calculate the local migration of capillary pore water according to Darcy's law by the following formula;

[0099]

[0100] where q 1 is the seepage velocity of the liquid-phase solution in the capillary pores, k is the permeability of the porous material, taking 10 -19 m 2 , η is the viscosity of the liquid-phase solution, taking 1.79×10 -3 Pa·s, and p cap is the hydraulic pressure inside the capillary pores and is equal to the liquid-phase pressure p l of the entrained air gap, see Figure 3 ;

[0101] S7. Calculate the solution flow rate through the capillary pores by the following formula;

[0102]

[0103] where R E is the radius of the concrete model unit, taking 0.04762 mm, and r E is the radius of the entrained air gap, taking 0.02 mm.

[0104] Through the slow air dissolution-diffusion process, calculate the amount of water flowing into the air gap by the following formula,

[0105]

[0106] where ρ air is the mass density of air, taking 1.25 kg / m 3 , and q' is the air flux and is calculated by the following formula;

[0107] q 2 = 1 -33 (m 2 ) × Pv / q 1

[0108] where P v is one atmosphere, with a value of 1.01325 × 10 5 Pa.

[0109] The air-gap water saturation increases with the migration of the solution from the capillary pores to the air gap under the dissolution-diffusion action of hydraulic pressure and air, and is calculated by the following formula;

[0110]

[0111] where, S void is the air-gap water saturation and the initial value is 0;

[0112] S8. Assuming that air is sealed in the entrained air gap, the inflow of water or the formation of ice crystals will generate pressure in the air gap. The porosity of the undeformed gas phase, liquid phase, and ice crystal phase in the air gap is calculated by the following three formulas respectively;

[0113] φ g,void = φ void (1 - S void )

[0114]

[0115] where, φ g,void is the porosity of the gas phase in the entrained air gap, with an initial value of 1, φ l,void is the porosity of the liquid phase in the entrained air gap, with an initial value of 0, φ c,void is the porosity of the ice crystal phase in the entrained air gap, with an initial value of 0.

[0116] S9. The average pressure on the concrete volume shell is calculated by the following formula;

[0117]

[0118] where, is the average pressure on the shell;

[0119] S10. Combining Darcy's law, the overall migration of the solution driven by the volume-averaged hydraulic gradient is calculated by the following formula;

[0120]

[0121] where, u g is the overall flow velocity of the pore solution driven by the freeze-thaw pressure, k con is the concrete permeability, with a value of 10 -19 m2 .

[0122] S11, φ l is the total volume of the liquid-phase pore solution, φ c is the total volume of ice crystals, and they are calculated respectively by the following formulas;

[0123] φ l = φ l,cap + φ l,void

[0124] φ c = φ c,cap + φ c,void

[0125] S12. Establish the heat transfer field of the concrete microscopic model. The phase change caused by heat transfer is described by the following formula;

[0126]

[0127] where T is the absolute temperature (K), and the initial value is f T , ρ con is the mass density of concrete, taking 2500 kg / m 3 , c q is the specific heat of concrete, taking 1100 J / (kg·K), λ is the thermal conductivity of concrete, taking 1.74 W / (m·K), L is the latent heat of fusion of water, taking 3.33×10 5 J / kg, M c is the total mass of ice crystals and is calculated by the following formula;

[0128] M c = ρ l φ cap m c,cap

[0129] Calculate u g and φ l versus time over 20 cycles according to S1 - S12, as shown in Figure 4 and Figure 5 .

[0130] S13. Establish the macroscopic diffusion model. The schematic diagram is shown in Figure 6 . Assuming that the bound chloride ion concentration remains constant, solve for the free chloride ions in the liquid-phase pore solution of the concrete. The chloride ion mass balance control equation is described by the following formula;

[0131]

[0132] where D f is the diffusion coefficient of free chloride ions in the pore solution, taking 3×10 -12 m 2 / s; Cf is the concentration of free chloride ions in the liquid-phase pore solution (mol / m 3 ), calculate 20 temperature cycles, and the calculation results of the analysis path and different boundary points of the steel bar cross-section are shown in Figure 7 , Figure 8 . The model is constructed by combining microscopic phase change and macroscopic diffusion.

[0133] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A multi-scale thermal hydraulic model of freeze-thaw-chloride intrusion coupling, characterized in that: The following steps are involved: S1. Establish the external temperature change field, and calculate the total void ratio of the concrete specimen by the following formula; the total void ratio includes capillary voids and entrained air voids; f=f cap +φ void φ cap is the porosity of the capillary pores and the initial value is φ cap,0 ,φ void is the porosity of the entrained air voids and the initial value is φ void,0 ; S2. Calculate the water pressure on the air gap surface by the following formula; p l =p void -p A Among them, p void is the air pressure in a vacuum, and its initial value is equal to zero atmospheric pressure; p A is the crystallization pressure; S3. Assuming that the capillary pores are initially saturated and only contain liquid and ice crystal phases, the porosities of the undeformed liquid and ice crystal phases in the capillary pores are calculated by the following formulas, respectively; In the formula, φ l,cap is the porosity of the liquid phase in the capillary pores, φ c,cap Porosity of ice crystal phase in capillary pores, S cap is the saturation of the capillary pores and takes the value 1, m l,cap is the mass ratio of the liquid phase in the capillary pores, m c,cap is the mass ratio of ice crystal phase in capillary pores, ρ l is the liquid mass density, ρ c is the mass density of the ice crystal phase; S4, air gap water saturation increases as the solution migrates from the capillary pores to the air gaps under the dissolution-diffusion action of hydraulic pressure and air. The air gap water saturation is calculated by the following formula; Among them, S void is the air gap water saturation and its initial value is 0; Q1 is the solution flow rate in the capillary pores; Q2 is the flow rate of water flowing into the air gap through the slow air dissolution-diffusion process; S5. Assuming that air is sealed in the entrained air gap, the inflow of water or the formation of ice crystals will generate pressure in the air gap; combining S3 and S4, the porosity of the undeformed gas phase, liquid phase and ice crystal phase in the air gap is calculated by the following formulas respectively; f g,void =φ void (1-S void ) Among them, φ g,void is the porosity of the gas phase in the entrained air gap, φ l,void is the porosity of the liquid phase in the entrained air gap, φ c,void is the porosity of the ice crystal phase in the entrained air voids, m l,void is the mass ratio of liquid phase in the entrained air gap, m c,void is the mass ratio of ice crystal phase in the entrained air gap; S6. Combined with Darcy's law, the overall migration velocity of the solution driven by the volume average hydraulic gradient is calculated by the following formula: Among them, u g is the overall flow rate of the pore solution driven by freeze-thaw pressure, in m / s, k con is the concrete permeability; is the average pressure on the shell; S7, the solution transport control equation describing the overall migration of the solution under pressure drive is as follows; Among them, φ l is the total volume of the liquid pore solution, φ c is the total volume of the ice crystals; S8. Establish a diffusion macroscopic model. The total chloride ions in concrete include free chloride ions and bound chloride ions in the liquid pore solution. The chloride ion mass balance control equation is described by the following formula; Among them, C f is the concentration of free chloride ions in the liquid pore solution, in mol / m 3 , C b is the concentration of bound chloride ions in concrete, expressed in mol / m 3 , D f is the diffusion coefficient of free chloride ions in the pore solution, in m 2 / s; S9. Establish the heat transfer field of the concrete micromodel and describe the phase change caused by heat transfer by the following equation; In the above formula, T is the absolute temperature in K, ρ con is the mass density of concrete, in kg / m 3 , c q is the specific heat of concrete and takes an average value of 1100 J / kg·K, λ is the thermal conductivity of concrete and takes an average value of 1.74 W / m·K, L is the latent heat of fusion of water, M c is the total mass of the ice crystals.

2. The multi-scale thermal hydraulic model of freeze-thaw-chloride intrusion coupling according to claim 1 is characterized in that: The S2 p void With p A The specific calculation method is as follows: Since ice forms in the air gap, the thermodynamic equilibrium between ice and water makes the pressure of water less than the pressure of ice, and its magnitude is the crystallization pressure p A , calculated by the following formula; p A =p c -p l =S f (T0-T); Among them, p c is the ice crystal pressure in the air gap, p l is the water pressure on the air gap surface, S f is the melting entropy of the crystal per unit volume, T0 is the initial temperature, unit is K, T is the crystallization temperature, unit is K; Since the ice is in contact with the air, the pressure of the ice is equal to the pressure of the air in the air gap, i.e.; p c =p void 。 3. The multi-scale thermal hydraulic model of freeze-thaw-chloride ion intrusion coupling according to claim 1 is characterized in that: The m c,cap and m l,cap Calculated by the following formulas respectively; m c,cap =m c,void ×f(poresize)×f(T) m l,cap =1-m c,cap Among them, f (pore size) is the most likely pore size and total capillary porosity influencing factor, and f (T) is the temperature influencing factor, both of which depend on the specific material.

4. The multi-scale thermal hydraulic model of freeze-thaw-chloride intrusion coupling according to claim 1, characterized in that: The specific calculation method of Q1 and Q2 in S4 is as follows: Assuming that the flux at the outer boundary is zero and the air gap is not always filled with air, the solution flow through the capillary pores is calculated by the following formula; After a slow air dissolution-diffusion process, the flow rate of water into the air gap is calculated by the following formula; Among them, ρ air is the mass density of air in kg / m 3 ,q' is the air flux in kg / s.

5. The multi-scale thermal hydraulic model of freeze-thaw-chloride intrusion coupling according to claim 4, characterized in that: The calculation method of q1 in S3 is as follows: when ice forms in the capillary pores, the volume expansion of ice crystals will generate hydraulic pressure in the capillary pores, so the pore water will be discharged from the capillary pores into the entrained air gaps; the local migration of capillary pore water is calculated by the following formula according to Darcy's law; Where q1 is the seepage velocity of the liquid solution in the capillary pores, and k is the permeability of the porous material, in m 2 , η is the viscosity of the liquid phase solution, the unit is Pa·s, p cap is the hydraulic pressure within the capillary pores.

6. The multi-scale thermal hydraulic model of freeze-thaw-chloride intrusion coupling according to claim 1, characterized in that: m in step S5 c,void and m l,void Calculated by the following formulas respectively; m l,void =1-m c,void Where N0 is the initial mass concentration of the volume solution, in %wt, T t is the current temperature in °C.

7. The multi-scale thermal hydraulic model of freeze-thaw-chloride intrusion coupling according to claim 1, characterized in that: The S6 The average pressure on the shell representing the concrete volume is calculated by the following formula; 8. The multi-scale thermal hydraulic model of freeze-thaw-chloride intrusion coupling according to claim 1, characterized in that: The S7 φ l With φ c The calculation formula is as follows; f l =φ l,cap +φ l,void f c =φ c,cap +φ c,void 。 9. The multi-scale thermal hydraulic model of freeze-thaw-chloride intrusion coupling according to claim 1, characterized in that: The S9M c By formula M c =ρ c V c calculate.

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