High-cold region hydraulic concrete natural curing and quick freezing method damage mapping method and system

Abstract

The application relates to the technical field of durability evaluation of hydraulic concrete materials, and discloses a high-cold-region hydraulic concrete natural curing and quick freezing method damage mapping method and system. Real temperature change data of the hydraulic concrete under the natural curing environment is obtained through a buried temperature sensor, the defects that the traditional standard quick freezing test is greatly different from the natural environment condition, the empirical equivalent coefficient is rough, and the prediction deviation is large due to the dependence on only macro weather data are overcome, and the technical problem that the service life of the hydraulic concrete under the actual working condition cannot be accurately determined according to the anti-freezing grade determined through the indoor test is solved.

Description

Technical Field

[0001] This invention relates to the field of durability assessment technology for hydraulic concrete materials, specifically to a method and system for mapping damage caused by natural curing and rapid freezing of hydraulic concrete in cold regions. Background Technology

[0002] Freeze-thaw damage to hydraulic concrete is a major durability problem faced by hydraulic and other concrete structures in cold regions. Currently, the indoor rapid freeze-thaw method (GB / T 50082-2024) is mainly used to evaluate the freeze-thaw resistance of concrete. The freeze-thaw resistance level is determined by measuring the number of cycles required for the relative dynamic modulus of elasticity to drop to 60% or the mass loss to reach 5%.

[0003] However, the freeze-thaw cycle of the standard rapid freezing method (e.g., cooling rate of 15.3 ℃ / h, minimum negative temperature of -18 ℃) differs significantly from the actual natural environment. In real-world environments, concrete experiences fewer freeze-thaw cycles, a slower cooling rate, and greater variations in the minimum negative temperature. Directly equating the number of indoor freeze-thaw cycles with the number of outdoor freeze-thaw cycles leads to significant deviations in lifespan prediction. While some existing technologies have proposed equivalent models based on fatigue damage, most rely on fixed empirical equivalence coefficients (e.g., 6 outdoor cycles equivalent to 1 indoor cycle) or only use macroscopic temperature data from environmental meteorological stations. These methods fail to accurately reflect the true freeze-thaw process within the hydraulic concrete at the project site, resulting in low prediction accuracy. Therefore, existing methods struggle to establish an accurate correlation between the freeze-thaw resistance level determined by indoor tests and the service life of hydraulic concrete under actual working conditions. This leads to freeze-thaw durability assessment results deviating from engineering realities, limiting the guidance for durability design, operation and maintenance decisions, and lifespan assessment of hydraulic concrete. Therefore, there is an urgent need to develop an assessment method that can accurately map the damage equivalence between natural freeze-thaw cycles and indoor rapid freezing, so as to achieve reliable prediction of the freeze-thaw durability life of hydraulic concrete in cold regions. Summary of the Invention

[0004] This invention aims to overcome the shortcomings of existing technologies and provide a model mapping the damage relationship between natural curing and rapid freezing of hydraulic concrete in high-altitude and cold regions. The method uses standard rapid freezing tests as a benchmark and acquires real temperature change data inside the hydraulic concrete under natural curing conditions through embedded temperature sensors. Based on hydrostatic pressure theory and damage mechanics theory, an equivalent coefficient function is constructed, including the cooling rate of the natural curing environment, the minimum negative temperature, the duration of the negative temperature, and the saturation coefficient. The equivalent coefficient of a single natural environment freeze-thaw cycle relative to a standard rapid freezing cycle is calculated, and the equivalent damage of all natural environment freeze-thaw cycles is accumulated. When the accumulated total equivalent damage reaches the limit damage measured by indoor rapid freezing tests, the hydraulic concrete structure is determined to have reached the end of its service life. This solves the technical problem of not being able to accurately determine the service life of hydraulic concrete under actual working conditions based on the freeze-thaw resistance level determined by indoor tests.

[0005] To achieve the above objectives, this invention provides a method for mapping damage caused by natural curing and rapid freezing of hydraulic concrete in cold regions, comprising the following steps: S1. Obtain internal temperature change data of hydraulic concrete under natural freeze-thaw cycles; S2. Based on the data of internal temperature change of hydraulic concrete under natural environment curing, calculate the equivalence coefficient between the damage caused by one natural environment freeze-thaw cycle and the damage caused by one standard rapid freezing and thawing cycle. S3. Determine the predicted life of hydraulic concrete based on the equivalent coefficient and the number of extreme freeze-thaw cycles measured by the standard rapid freezing method.

[0006] Preferably, S2 includes: Based on the data on internal temperature changes of hydraulic concrete under natural environmental curing, the cooling rate, minimum negative temperature and duration of negative temperature were determined. The equivalent coefficient is determined based on the cooling rate, minimum negative temperature, duration of negative temperature, and saturation coefficient.

[0007] Preferably, the specific method for determining the equivalent coefficient includes: , Where, k i R is the equivalent coefficient; lab T min,lab and t neg,lab These represent the cooling rate, minimum internal negative temperature, and duration of negative temperature for hydraulic concrete in the standard rapid freezing method, respectively. i T min,i and t neg,i α, β, and γ represent the cooling rate, minimum negative temperature, and duration of negative temperature of hydraulic concrete under natural environmental curing conditions, respectively; α, β, and γ represent the sensitivity of hydraulic concrete to the three factors of cooling rate, minimum negative temperature, and duration of negative temperature, respectively; θ i The value ranges from 0.5 to 1.5.

[0008] Preferably, S3 includes: The equivalent total number of freeze-thaw cycles in the natural environment is determined based on the equivalence coefficient and the total number of freeze-thaw cycles in the natural environment. When the equivalent total number of freeze-thaw cycles in the natural environment is greater than or equal to the limit number of freeze-thaw cycles measured by the standard rapid freezing method, the predicted lifespan is determined based on the total number of freeze-thaw cycles in the natural environment.

[0009] Preferably, when the equivalent total number of natural environmental freeze-thaw cycles N eq ≥N lab When the hydraulic concrete reaches the end of its service life, the predicted service life L is calculated as follows: , Where, N lab The value of n represents the maximum number of freeze-thaw cycles using the standard rapid freezing method, and n represents the number of natural freeze-thaw cycles per year. This represents the average equivalent coefficient.

[0010] This invention also provides a damage mapping system for natural curing and rapid freezing of hydraulic concrete in high-altitude and cold regions. The system is used to implement the above method and includes: The temperature measurement module is used to acquire data on the internal temperature changes of hydraulic concrete under natural freeze-thaw cycles. The calculation module is used to calculate the equivalence coefficient between the damage caused by a natural freeze-thaw cycle and the damage caused by a standard rapid freeze-thaw cycle, based on internal temperature change data. The prediction module is used to determine the predicted life of hydraulic concrete based on the equivalent coefficient and the number of extreme freeze-thaw cycles measured by the standard rapid freezing method.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention acquires real temperature change data inside hydraulic concrete under natural curing conditions using embedded temperature sensors. It overcomes the shortcomings of traditional methods, such as large differences between standard rapid freezing tests and natural environmental conditions, coarse empirical equivalence coefficients, and large prediction errors due to reliance solely on macroscopic meteorological data. It also solves the technical problem of not being able to accurately determine the service life of hydraulic concrete under actual working conditions based on the frost resistance level determined by indoor tests. Based on hydrostatic pressure theory and damage mechanics, an equivalent coefficient function is constructed, including cooling rate, minimum negative temperature, duration of negative temperature, and saturation coefficient. The equivalent damage from each natural freeze-thaw cycle is accumulated, and the end of the service life is determined when the total equivalent damage reaches the limit damage measured by the standard rapid freezing method. This method can accurately reflect the actual freeze-thaw damage evolution process inside hydraulic concrete, significantly improving the accuracy and reliability of predicting the frost resistance and durability of hydraulic concrete in cold regions, and providing a scientific basis for the durability design, operation and maintenance, and service life assessment of hydraulic concrete. Attached Figure Description

[0012] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the method flow according to an embodiment of the present invention; Figure 2 This is a schematic diagram (shaded side) of a natural environment curing test of hydraulic concrete specimens from a hydropower station in a certain region of my country, as an embodiment of the present invention. Figure 3 This is a schematic diagram (sunny side) of a natural environment curing test of hydraulic concrete specimens from a hydropower station in a certain region of my country, as an embodiment of the present invention. Figure 4 This is a schematic diagram illustrating the natural environmental curing temperature monitoring of hydraulic concrete specimens from a hydropower station in a certain region of my country, as an embodiment of the present invention. Detailed Implementation

[0014] 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.

[0015] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] Example 1: like Figure 1 The diagram shown is a schematic representation of the method flow in this embodiment, and the steps include: S1. Obtain internal temperature change data of hydraulic concrete under natural freeze-thaw cycles.

[0017] A high-precision temperature sensor with an accuracy of ±0.1℃ was pre-embedded in the core of a 100 mm × 100 mm × 400 mm prismatic hydraulic concrete specimen. The specimen was then naturally cured on-site. Temperature data inside the hydraulic concrete was continuously measured and recorded using a data acquisition device at a set sampling frequency (sampling interval no greater than 15 minutes) to obtain a complete temperature-time test sequence. This measurement process covered the entire natural freeze-thaw cycle, ensuring the accuracy of test parameters such as cooling rate, minimum negative temperature, and duration of negative temperature, which are crucial for subsequent damage equivalence coefficient calculations.

[0018] S2. Based on the internal temperature change data, calculate the equivalence coefficient between the damage caused by one natural environment freeze-thaw cycle and the damage caused by one standard rapid freezing freeze-thaw cycle.

[0019] Let the damage from one natural freeze-thaw cycle be D. i The damage from one standard indoor cycle is D. lab Then the equivalent coefficient k i The function of multiple temperature characteristic parameters, such as cooling rate, minimum negative temperature, and duration of negative temperature, is shown in equation (1): (1) Among them, R iThe cooling rate is the average rate at which the temperature drops from 0°C to the lowest temperature, expressed in °C / h; T min,i The lowest sub-zero temperature inside hydraulic concrete, unit: °C; t neg,i The duration of negative temperature inside hydraulic concrete, in hours; θ i The saturation coefficient is determined based on the environment in which the hydraulic concrete is located (underwater, wet-dry cycle, above water).

[0020] Based on hydrostatic pressure theory and damage mechanics, an equivalent coefficient k is constructed. i The function is as follows (2): (2) Among them, R lab T min,lab and t neg,lab The values ​​are the cooling rate, the lowest negative temperature inside the hydraulic concrete, and the duration of negative temperature, respectively, in the standard rapid freezing method; R is 15.3 ℃ / h, -18 ℃, and 2h. i T min,i and t neg,i The values ​​are 0.8 ℃ / h, -6 ℃, and 11h, respectively, for the cooling rate, minimum negative temperature, and duration of negative temperature of hydraulic concrete under natural environmental curing. α, β, and γ represent the sensitivity of hydraulic concrete materials to the cooling rate, minimum negative temperature, and duration of negative temperature, which are related to factors such as the mix proportion and air content of the hydraulic concrete. i The values ​​are taken as 0.5 to 1.5 based on the environment in which the hydraulic concrete is located. The values ​​of α, β, and γ are shown in Table 1-3.

[0021] Table 1: .

[0022] Table 2: .

[0023] Table 3: .

[0024] S3. Determine the predicted life of hydraulic concrete based on the equivalent coefficient and the number of extreme freeze-thaw cycles measured by the standard rapid freezing method.

[0025] When the equivalent total number of natural environment freeze-thaw cycles N eq ≥N lab When the hydraulic concrete reaches the end of its service life, the predicted service life L should be calculated according to the following formula (3): (3) Where, N lab The value of n represents the maximum number of freeze-thaw cycles using the standard rapid freezing method, and n represents the number of natural freeze-thaw cycles per year. This represents the average equivalent coefficient.

[0026] Example 2: The following will describe in detail, with reference to this embodiment, how the present invention solves the technical problems in practical work.

[0027] This embodiment takes a project in a certain region of my country as an example. The hydraulic concrete in the high-altitude and cold region includes the following components by mass: cementitious material 240 kg / m³ 3 Aggregate 1601 kg / m³ 3 Water-reducing agent 1.32 kg / m 3 0.018 kg / m³ of entraining agent 3 120kg / m 3 .

[0028] The aggregate consists of sand and gravel, with sand accounting for 31% of the total aggregate mass. The gravel has a three-stage gradation of 5-20 mm, 20-40 mm, and 40-80 mm, with a mass ratio of 3:3:4 for 5-20 mm, 20-40 mm, and 40-80 mm gravel.

[0029] The ultimate freeze-thaw cycle number N was determined by the standard rapid freezing method (the rapid freezing test method in this embodiment is GB / T 50080-2024). lab =250, and at the same time, the hydraulic concrete is placed in the shaded side and partially submerged in water under natural curing conditions, and temperature sensors are embedded inside to continuously collect temperature data. According to equations (2) and (3), the equivalent coefficient of the freeze-thaw cycle in the natural environment and the predicted life can be obtained.

[0030] The above is a schematic diagram of the natural environment curing test of hydraulic concrete specimens from a hydropower station in a certain region of my country. Figure 2 , Figure 3 As shown; the monitoring results of the natural environmental curing temperature of hydraulic concrete specimens from a hydropower station in a certain region of my country are as follows. Figure 4 As shown.

[0031] In addition, this embodiment provides data from seven other different regions to illustrate the effectiveness of the invention in practical work, and the results are shown in Table 4: Table 4: .

[0032] Example 3: This embodiment also provides a damage mapping system for natural curing and rapid freezing of hydraulic concrete in cold regions, including a temperature measurement module, a calculation module, and a prediction module.

[0033] First, a temperature measurement module is used to continuously measure the internal temperature changes of hydraulic concrete under natural freeze-thaw cycles using an embedded temperature sensor. In this embodiment, the temperature measurement module is a high-precision temperature sensor pre-embedded in the core of a 100 mm × 100 mm × 400 mm prism-shaped hydraulic concrete specimen, which is naturally cured on-site. The internal temperature data of the hydraulic concrete is continuously monitored and recorded using a data acquisition device, with sampling intervals not exceeding 15 minutes.

[0034] The calculation module uses internal temperature change data to calculate the equivalence coefficient between the damage caused by one natural freeze-thaw cycle and the damage caused by one standard rapid freezing freeze-thaw cycle.

[0035] Let the damage from one natural freeze-thaw cycle be D. i The damage from one standard indoor cycle is D. lab Then the equivalent coefficient k i The function of multiple temperature characteristic parameters, such as cooling rate, minimum negative temperature and duration of negative temperature, is shown in equation (4): (4) Among them, R i The cooling rate is the average rate at which the temperature drops from 0°C to the lowest temperature, expressed in °C / h; T min,i The lowest sub-zero temperature inside hydraulic concrete, unit: °C; t neg,i The duration of negative temperature inside hydraulic concrete, in hours; θ i The saturation coefficient is determined based on the environment in which the hydraulic concrete is located (underwater, wet-dry cycle, above water).

[0036] Based on hydrostatic pressure theory and damage mechanics, an equivalent coefficient k is constructed. i The function is as follows (5): (5) Among them, R lab T min,lab and t neg,lab These represent the cooling rate, the lowest negative temperature inside the hydraulic concrete, and the duration of the negative temperature in the standard rapid freezing method, respectively, with values ​​of 15.3 ℃ / h, -18 ℃, and 2h; R i T min,i and t neg,i α, β, and γ represent the cooling rate, minimum negative temperature, and duration of negative temperature of the hydraulic concrete during natural environmental curing, respectively; α, β, and γ represent the sensitivity of the hydraulic concrete material to the three factors of cooling rate, minimum negative temperature, and duration of negative temperature, respectively, which are related to factors such as the mix proportion and air content of the hydraulic concrete. In this embodiment, the values ​​are taken as 1.0, 0.4~0.6, and 0.2~0.3, respectively; θ iThe values ​​are taken as 0.5 to 1.5 based on the environment in which the hydraulic concrete is located; the values ​​of α, β and γ are shown in Tables 1-3.

[0037] Finally, the prediction module determines the predicted life of hydraulic concrete based on the equivalent coefficient and the number of extreme freeze-thaw cycles measured by the standard rapid freezing method.

[0038] When the equivalent total number of natural environment freeze-thaw cycles N eq ≥N lab When the hydraulic concrete reaches the end of its service life, the predicted service life L should be calculated according to the following formula (6): (6) Where, N lab The value of n represents the maximum number of freeze-thaw cycles using the standard rapid freezing method, and n represents the number of natural freeze-thaw cycles per year. This represents the average equivalent coefficient.

[0039] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for mapping damage between natural curing and rapid freezing of hydraulic concrete in high-altitude and cold regions, characterized in that... Includes the following steps: S1. Continuously measure the internal temperature change data of hydraulic concrete under natural freeze-thaw cycles using an embedded temperature sensor to obtain a test curve of temperature change over time. S2. Based on the internal temperature change data, extract freeze-thaw test parameters and calculate the equivalence coefficient between the damage caused by one natural environment freeze-thaw cycle and the damage caused by one standard rapid freezing freeze-thaw cycle; the steps include: calculating the cooling rate, minimum negative temperature, and duration of negative temperature based on the measured internal temperature change data of the hydraulic concrete cured in the natural environment; determining the equivalence coefficient based on the cooling rate, minimum negative temperature, duration of negative temperature, and water saturation coefficient of the hydraulic concrete cured in the natural environment; the specific method for determining the equivalence coefficient includes: ， in, k i Equivalent coefficient; R lab , T min,lab and t neg,lab These represent the cooling rate, minimum internal negative temperature, and duration of negative temperature for hydraulic concrete in the standard rapid freezing method. R i , T min,i and t neg,i These are the cooling rate, minimum internal negative temperature, and duration of negative temperature of hydraulic concrete during natural environment curing. α , β , γ The sensitivity of hydraulic concrete to three factors: cooling rate, minimum negative temperature, and duration of negative temperature. θ i The saturation coefficient is 0.5 to 1.

5. S3. Determine the predicted life of hydraulic concrete based on the equivalent coefficient and the ultimate freeze-thaw cycle count obtained by the standard rapid freezing method. The steps include: determining the equivalent total natural environment freeze-thaw cycle count based on the equivalent coefficient and the total number of freeze-thaw cycles in the natural curing environment; when the equivalent total natural environment freeze-thaw cycle count is greater than or equal to the ultimate freeze-thaw cycle count obtained by the standard rapid freezing method, determine the predicted life based on the total number of freeze-thaw cycles in the natural environment.

2. The method for natural curing and rapid freezing damage mapping of hydraulic concrete in high-altitude cold regions according to claim 1, characterized in that, When the equivalent total number of natural environmental freeze-thaw cycles N eq ≥ N lab When the hydraulic concrete reaches the end of its service life, its lifespan is predicted. L The calculation method is as follows: ， in, N lab This indicates the number of limit freeze-thaw cycles in the standard rapid freezing method. n This indicates the number of natural freeze-thaw cycles per year. This represents the average equivalent coefficient.

3. A damage mapping system for natural curing and rapid freezing of hydraulic concrete in high-altitude and cold regions, the system being used to implement the method described in any one of claims 1-2, characterized in that, include: The temperature measurement module is used to continuously measure the internal temperature change data of hydraulic concrete under natural freeze-thaw cycles through an embedded temperature sensor. The calculation module is used to calculate the equivalence coefficient between the damage caused by a natural freeze-thaw cycle and the damage caused by a standard rapid freeze-thaw cycle, based on internal temperature change data. The prediction module is used to determine the predicted life of hydraulic concrete based on the equivalent coefficient and the number of extreme freeze-thaw cycles measured by the standard rapid freezing method.

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