High-temperature-resistant and radiation-resistant concrete and preparation method thereof

Abstract

The present application relates to a kind of high-temperature resistant radiation-proof concrete and its preparation method, the components of the concrete are as follows by mass ratio (kg / m 3 ): serpentine 600-700, serpentine sand 1000-1100, cementing material 500-600, water 200-230, water reducing agent 8-9.The high-temperature resistant radiation-proof concrete is optimized and designed, and the anti-neutron transmission performance and long-term mechanical properties of the shielding concrete after high-temperature damage are considered.The concrete is optimized and designed at the beginning of mix design, which effectively improves the comprehensive performance of the in-pile wall and near-core concrete in the emergency situation of core melting, and cooperates with the bottom plate sacrificial concrete, which can effectively improve the radiation shielding performance of the material after thermal damage, reduce the threat of nuclear radiation, and protect the ecological environment safety and personnel health.

Description

Technical Field

[0001] This invention belongs to the field of radiation-resistant concrete preparation technology, and specifically relates to a high-temperature resistant radiation-resistant concrete and its preparation method. Background Technology

[0002] Currently, the global energy industry is transitioning towards clean energy, and low-carbon emission energy sources such as nuclear power will become an important solution for future global electricity demand growth. During the construction of nuclear power plants, radiation-shielding concrete is mainly used in safety structures such as prestressed containment vessels and nuclear island base plates to shield against radiation, requiring high performance. Unlike ordinary concrete, radiation-shielding concrete not only has requirements for mechanical and construction properties, but also for high-temperature performance and homogeneity. In current fourth-generation nuclear reactors, such as molten salt reactors, the concrete operating temperature is consistently above 150°C, placing high demands on the performance of the crater wall concrete and near-core concrete. Furthermore, in the event of a core meltdown accident, the high-temperature performance requirements for radiation-shielding concrete structures such as containment vessels are even higher, necessitating a comprehensive consideration of the thermal and radiation effects.

[0003] Neutron radiation, particularly in nuclear radiation, has strong penetrating power. Neutrons scatter and collide with hydrogen nuclei, losing most of their energy. In engineering, materials with high water content and high density are typically used to moderate neutrons and absorb radiation. Aggregates such as barite, serpentine, and limonite are commonly selected; these aggregates generally have high density, large mass, and high water content, thus providing good radiation shielding capabilities. However, under long-term neutron radiation and core thermal irradiation, concrete aggregates and cementitious materials experience moisture loss, material decomposition, and thermal stress accumulation, leading to a significant decrease in radiation shielding capabilities and mechanical properties, thus posing safety risks.

[0004] Therefore, it is necessary to optimize the design of radiation-shielding concrete for high-temperature operating conditions to meet the new core protection requirements. Summary of the Invention

[0005] This invention provides a high-temperature resistant radiation-shielding concrete and its preparation method. Starting from the requirements of radiation shielding performance and mechanical properties of radiation-shielding concrete at high temperatures, it optimizes the design of high-temperature radiation-shielding concrete, providing a new path for performance optimization of radiation shielding structural materials, thereby effectively ensuring the safety of nuclear facilities. This method will promote research on the composition, structure, and performance relationship of radiation shielding materials, providing a corresponding theoretical basis for the design and construction of concrete radiation shielding structures, and solving the needs of large-scale application in nuclear facilities.

[0006] To solve the above technical problems, the present invention includes the following technical solutions:

[0007] A high-temperature resistant and radiation-proof concrete, wherein the components of the concrete are in the following mass ratio (kg / m³). 3 ):

[0008] Serpentine 600-700, serpentine sand 1000-1100, cementitious material 500-600, water 200-230, water-reducing agent 8-9.

[0009] A method for preparing high-temperature resistant and radiation-proof concrete, the method comprising the following steps:

[0010] Step S1: Prepare radiation-proof concrete that meets the design requirements of nuclear facilities at room temperature, make concrete specimens, and embed temperature sensors in the concrete specimens. The temperature sensors are used to monitor and display the internal temperature of the concrete. After demolding, the concrete specimens are placed in a standard curing room for curing for 28 days. The concrete specimens are then taken out and placed in a dry and ventilated place to dry to constant weight. The mass is recorded as m0.

[0011] Step S2: Place the concrete specimen in a muffle furnace and heat it from room temperature to the target temperature at a certain heating rate. The target temperature, the constant temperature fixation time, and the constant temperature duration are all determined by the concrete working conditions. A CO2 sensor is installed on the muffle furnace to detect changes in CO2 concentration in the environment in real time.

[0012] Step S3: First, measure the total mass of CO2 in the muffle furnace before heating, and record it as m1. After the constant temperature is reached, use a CO2 sensor to measure the total mass of CO2 in the muffle furnace at a fixed temperature, and record it as m2. Then, the mass of CO2 produced by the decomposition of CaCO3 in the concrete during the heating process is recorded as m3. Then, m3 = m2 - m1.

[0013] Step S4: After the experiment, immediately remove the concrete specimen from the muffle furnace and weigh it, recording the weight as m4. The formula for calculating the water loss m during the high-temperature process is: m = m0 - m4 - m3.

[0014] Therefore, the formula for calculating the high-temperature water loss L of a single cubic meter of concrete is:

[0015] L = m / V; m is in kg; V is the volume of the cylindrical concrete specimen in m³. 3 ;

[0016] Step S5: A is the long-term mechanical property degradation coefficient after 112 days of high-temperature damage, A = G / S, where G is the 112-day strength of concrete at high temperature (in MPa); S is the 112-day strength of concrete at room temperature; calculate the undamaged strength Cz of concrete at room temperature, Cz = Gz / A, where Gz is the expected target value of concrete strength at high temperature.

[0017] Step S6: Obtain the mapping relationship between the strength fc and M of concrete at different ages at room temperature using a fitting method: f c= a·log M)+b, where fc is the compressive strength at maturity M; a and b are constants obtained by fitting; M is the maturity calculated by the Nurse-Saul equation;

[0018] Step S7: When the design strength of the concrete is less than C60, the concrete mix design strength is determined by the following formula:

[0019] f cu，0 ≥f cu，k +1.645δ;

[0020] When the design strength of concrete is greater than or equal to C60, the concrete mix design strength is determined by the following formula:

[0021] f cu，0 ≥1.15f cu，k ;

[0022] In the formula, δ is the standard deviation of concrete strength;

[0023] Step S8: Determine the water-cement ratio R of concrete at high temperature. 高温 , In the formula, a a and a b All are regression coefficients, f b The compressive strength of the cementitious mortar after 28 days;

[0024] Step S9: Adjust the mix proportion while keeping the quality of the main aggregates in the radiation-proof concrete unchanged at room temperature. 高温 =W 常温 +L,C 高温 =W 高温 / R 高温 In the formula, W 高温 Water consumption for high-temperature radiation-proof concrete; W 常温 Water consumption for room temperature radiation-proof concrete; C 高温 The dosage of cementitious materials for high-temperature radiation-proof concrete;

[0025] Step S10: Increase the amount of water-reducing agent in the concrete. The water-reducing agent is increased at intervals of 0.1% of the amount of cementitious material, thereby obtaining the final mix proportion of the high-temperature radiation-proof concrete.

[0026] Furthermore, the Nurse-Saul equation is as follows: In the formula, M represents maturity (°C·h or °C·d); T represents the average concrete temperature (°C) within the time interval Δt; and T0 represents the reference temperature (°C). The reference temperature refers to the temperature at which the concrete strength no longer increases with age, i.e., the temperature at which the hydration reaction inside the concrete stops. In the calculation, -10°C is used. Substituting the undamaged concrete strength Cz at room temperature into the logarithmic model, the corresponding standard value of the 28-day compressive strength f of the concrete can be obtained.cu,k .

[0027] Furthermore, the concrete specimen is a molded cylindrical concrete specimen.

[0028] Furthermore, the concrete specimen dimensions are φ60×80mm. In this case, the volume of the cylindrical concrete specimen is (π×0.03). 2 ×0.08).

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] This invention provides a high-temperature resistant and radiation-proof concrete, wherein the components of the concrete are in the following mass ratio (kg / m³). 3 ): Serpentine 600-700, serpentine sand 1000-1100, cementitious material 500-600, water 200-230, water-reducing agent 8-9.

[0031] The high-temperature radiation-resistant concrete was optimized, taking into account both the neutron transmission protection performance and long-term mechanical properties of the shielding concrete after high-temperature damage. The concrete was optimized from the initial mix design stage, which effectively improved the comprehensive performance of the crater wall and near-core concrete under emergency conditions such as core meltdown. When combined with the sacrificial concrete of the bottom slab, it can effectively improve the radiation shielding performance of the material after thermal damage, reduce the threat of nuclear radiation, and ensure the safety of the ecological environment and the health and safety of personnel. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a high-temperature thermal damage experiment on high-temperature resistant radiation-proof concrete according to an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram illustrating high-temperature thermal damage to high-temperature resistant and radiation-proof concrete according to an embodiment of the present invention.

[0034] Figure 3 This is a schematic diagram illustrating the strength growth law of concrete at room temperature according to an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of a neutron shielding test of high-temperature radiation-resistant concrete according to an embodiment of the present invention. Detailed Implementation

[0036] The following detailed description, in conjunction with specific embodiments and accompanying drawings, provides a high-temperature resistant radiation-proof concrete and its preparation method according to the present invention. The advantages and features of the present invention will become clearer from the following description.

[0037] Design concept: Descriptions of key indicators such as crystal water content, material composition, thermal stability, and density are the basis for accurately analyzing the evolution of the shielding capacity of radiation-proof concrete, and also a powerful means to optimize the design of new radiation-proof concrete.

[0038] (1) Prepare radiation-resistant concrete that meets the design requirements of nuclear facilities at room temperature, and mold cylindrical concrete specimens (φ60×80mm). Embed a temperature sensor in the concrete specimen to monitor and display the internal temperature of the concrete. After demolding, place the specimen in a standard curing room for 28 days. Remove the specimen and place it in a dry and ventilated place to dry to constant weight. The mass of the concrete specimen is recorded as m0.

[0039] (2) See Figure 1 The prepared concrete specimens were placed in a muffle furnace and heated from room temperature to target temperatures (100℃, 200℃, 300℃, 400℃, 500℃, 600℃, 700℃, and 800℃) at a controlled rate. The target temperature, the holding time, and the duration of holding the temperature were all determined by the concrete working conditions. A CO2 sensor was installed on the muffle furnace to monitor changes in the CO2 concentration in the environment in real time.

[0040] (3) First, measure the total mass of CO2 in the muffle furnace environment before heating, and record it as m1. After the constant temperature is reached, use a CO2 sensor to measure the total mass of CO2 in the muffle furnace at a fixed temperature, and record it as m2. Then, the mass of CO2 generated by the decomposition of CaCO3 in the concrete during the heating process is recorded as m3, which can be calculated by the following formula:

[0041] m3 = m2 - m1

[0042] (4) After the experiment, the concrete specimen was immediately removed from the muffle furnace and weighed, and the mass was recorded as m4. Therefore, the water loss m during the high-temperature process can be calculated by the following formula:

[0043] m = m0 - m4 - m3

[0044] Therefore, the high-temperature water loss L of a single cubic meter of concrete can be calculated using the following formula:

[0045] L = m / V, where V is the volume of the cylindrical concrete specimen, i.e., L = m / (π × 0.03). 2 ×0.08)

[0046] (5)Reference Figure 3 At normal temperatures, the strength growth of concrete exhibits a clear regularity: rapid early-stage strength growth followed by slow, medium- to long-term strength growth, conforming to a logarithmic model. However, under high-temperature conditions, the internal structure of concrete is damaged by evaporating water vapor and CO2, and the decomposition of hydration products weakens the interfacial bond between aggregates, leading to a decline in the mechanical properties of concrete—a condition known as thermal damage. (Typical reference) Figure 2 .

[0047] Let S be the 112-day strength of concrete at room temperature and G be the 112-day strength of concrete at high temperature, both in MPa. Based on the engineering requirements for radiation-proof concrete, the long-term mechanical property attenuation coefficient A after 112 days of high-temperature damage can be calculated using the following formula: In this embodiment, the 112-day strength of concrete is used as the main criterion for identifying thermal damage. In actual engineering projects, a suitable age is selected according to actual needs.

[0048] A = G / S

[0049] Given a fixed variety of radiation-shielding aggregates and cementitious materials, the undamaged strength Cz of concrete at room temperature can be calculated from the expected target value of concrete strength at high temperature, Gz. The calculation formula is as follows:

[0050] Cz = Gz / A

[0051] (6) The mapping relationship between the strength fc and M of concrete at different ages under normal temperature can be obtained by fitting method, which is very close to the logarithmic function model relationship. a and b are fitting parameters. The formula is shown below:

[0052] f c =a·log M)+b, where fc is the compressive strength at maturity M; a and b are constants obtained by fitting; and M is the maturity calculated by the Nurse-Saul equation.

[0053] The Nurse-Saul equations are as follows: In the formula, M represents maturity, measured in °C·h or °C·d; T represents the average concrete temperature over the time interval Δt, measured in °C; and T0 represents the reference temperature, measured in °C. The reference temperature refers to the temperature at which the concrete strength no longer increases with age, i.e., the temperature at which the hydration reaction inside the concrete stops. In the calculation, -10 °C is used. Substituting the undamaged concrete strength Cz at room temperature into the logarithmic model yields the corresponding standard value f of the 28-day compressive strength of the concrete. cu,k .

[0054] (7) According to the national standard "Specification for Mix Proportion Design of Ordinary Concrete" (JGJ 55-2011):

[0055] When the design strength of concrete is less than C60, the concrete mix design strength is determined by the following formula:

[0056] f cu，0 ≥f cu，k +1.645δ;

[0057] When the design strength of concrete is greater than or equal to C60, the concrete mix design strength is determined by the following formula:

[0058] fcu，0 ≥1.15f cu，k ;

[0059] In the formula, δ is the standard deviation of concrete strength.

[0060] (8) Based on the national standard "Specification for Mix Proportion Design of Ordinary Concrete" (JGJ 55-2011), determine the water-cement ratio R of concrete at high temperature. 高温 , In the formula, a a and a b All are regression coefficients, f b The compressive strength of the cementitious material mortar after 28 days.

[0061] (9) Since the main water loss in concrete at high temperatures is caused by the dehydration of calcium silicate gel, a product of cement hardening, the mix proportion is adjusted while maintaining the original mass of the main aggregates in the radiation-proof concrete at room temperature. Because the undamaged strength Cz of concrete at room temperature is higher than the strength prepared by the mix proportion at room temperature, the calculated water-cement ratio is too low. Therefore, the total amount of concrete paste is adjusted to avoid situations such as insufficient slurry coverage on the surface of concrete aggregates and water loss cracking, thereby improving the stability of the high-temperature radiation-proof concrete. The adjustment method is as follows:

[0062] W 高温 =W 常温 +L,C 高温 =W 高温 / R 高温 In the formula, W 高温 Water consumption for high-temperature radiation-proof concrete;

[0063] W 常温 Water consumption for room temperature radiation-proof concrete; C 高温 This refers to the amount of cementitious material used in high-temperature radiation-proof concrete.

[0064] (10) Given the known high-temperature water consumption W of high-temperature radiation-proof concrete. 高温 High-temperature cementitious material usage C 高温 Based on the original aggregate dosage (using the same mix proportions at room temperature), the water-reducing agent dosage was increased. Trial mixes were conducted to ensure the concrete's flowability met specific construction requirements, thus yielding the final mix proportion for high-temperature radiation-proof concrete. The water-reducing agent was increased at intervals of 0.1% of the cementitious material dosage, resulting in the final mix proportion for high-temperature radiation-proof concrete.

[0065] During the design of nuclear-related structures, key design optimization parameters such as the high-temperature water loss L of concrete at the design temperature and the long-term mechanical property decay coefficient A can be obtained from basic experiments, thereby deriving an optimized design scheme for high-temperature resistant and radiation-proof concrete.

[0066] All 28-day performance data for concrete were obtained after the specimens underwent heat damage and were cooled to room temperature in a dry, ventilated place. The heating rate was 4℃ / h, and the holding time was 2h.

[0067] Neutron flux after concrete shielding is measured in the following ways:

[0068] refer to Figure 4 The neutron shielding experiment used the cylindrical concrete specimen of this embodiment.

[0069] A neutron source with the same energy range as the inner surface of the molten salt reactor is generated by an electron accelerator neutron source to irradiate a concrete sample. The receiver can count the collected neutron energy, and the neutron shielding performance of the concrete can be calculated by using the ratio of the neutron flux after shielding to the neutron flux before shielding.

[0070] Example 1: The mix proportion of radiation-shielding concrete at room temperature is as follows: (kg / m³) 3 )

[0071] cementing materials Serpentine Snake-patterned sand water Water reducing agent 400 690 1060 200 5.4

[0072] The mechanical properties and radiation shielding properties of concrete at room temperature are as follows:

[0073]

[0074] The mechanical properties and radiation shielding performance of concrete after high-temperature damage at 600℃ are as follows:

[0075]

[0076] The optimized mix design of the radiation-shielding concrete is as follows: (kg / m³) 3 )

[0077] cementing materials Serpentine Snake-patterned sand water Water reducing agent 532 690 1060 218 8.2

[0078] The mechanical properties and radiation shielding performance of concrete after high-temperature damage are as follows:

[0079]

[0080] The mechanical properties and radiation shielding performance of concrete after high-temperature damage at 400℃ are as follows:

[0081]

[0082] The optimized mix design of the radiation-shielding concrete is as follows: (kg / m³) 3 )

[0083] cementing materials Serpentine Snake-patterned sand water Water reducing agent 508 690 1060 224 8.7

[0084] The mechanical properties and radiation shielding performance of concrete after high-temperature damage are as follows:

[0085]

[0086] The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. The above embodiments only illustrate several implementations of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method of formulating a high temperature resistant radiation shielding concrete, characterized by, Comprising the following steps: Step S1, preparing the anti-radiation concrete meeting the design requirements of nuclear facilities at room temperature, making a concrete test piece, and embedding a temperature sensor in the concrete test piece, the temperature sensor is used for monitoring and displaying the internal temperature of the concrete, the concrete test piece is placed in a standard curing room after demolding and cured to 28d age, the concrete test piece is taken out and placed in a dry and ventilated place to dry to constant weight, and the mass is recorded as m0; Step S2, the concrete test piece is placed in a muffle furnace and heated from room temperature to a target temperature at a certain heating rate, the target temperature, constant temperature fixing time and constant temperature time are determined by the working condition of the concrete, a CO2 sensor is installed on the muffle furnace for real-time detection of the change of CO2 concentration in the environment; Step S3, first, the total mass of CO2 in the environment of the muffle furnace before heating is measured and recorded as m1, after constant temperature, the total mass of CO2 in the muffle furnace at the fixed temperature is measured by the CO2 sensor and recorded as m2, then the mass of CO2 generated by the decomposition of CaCO3 in the concrete during the heating process is recorded as m3, that is, m3= m2- m1; Step S4, after the experiment, the concrete test piece is immediately taken out from the muffle furnace and weighed, recorded as m4, then the calculation formula of the water loss m in the high temperature process is: m= m0- m4- m3, Therefore, the calculation formula of the high temperature water loss L of single concrete is: L = m / V; m is in Kg; V is the volume of the cylindrical concrete specimen in m 3 ; Step S5, A is the long-term mechanical property attenuation coefficient of high temperature damage 112d, A=G / S, G is the 112d strength of concrete at high temperature, unit: MPa; S is the 112d strength of concrete at room temperature; calculate the undamaged strength Cz of concrete at room temperature, Cz=Gz / A, Gz is the expected target value of the strength of concrete at high temperature; Step S6, mapping relationship between concrete strength fc at each age and M at normal temperature is obtained by fitting method: , wherein fc is the compressive strength when the maturity is M; a and b are constants obtained by fitting; and M is the maturity calculated by the Nurse-Saul equation. Step S7, when the design strength of the concrete is less than C60, the concrete preparation strength is determined according to the following formula: ； When the design strength of the concrete is greater than or equal to C60, the concrete preparation strength is determined according to the following formula: ； In the formula, δ is the standard deviation of the strength of the concrete; Step S8, determining the water-binder ratio R of the concrete at high temperature 高温 , ; wherein a a and a b are regression coefficients, f b is the 28d mortar compressive strength of the cementitious material Step S9, adjusting the mix proportion while keeping the quality of the main aggregate of the radiation-proof concrete unchanged at the original normal temperature, , , wherein W 高温 is the water quantity for the high-temperature radiation-proof concrete; W 常温 is the water quantity for the normal-temperature radiation-proof concrete; C 高温 is the quantity of the cementitious material for the high-temperature radiation-proof concrete; Step S10, adjusting the amount of water reducing agent of the concrete, the interval of the water reducing agent adjustment is 0.1% of the amount of cementitious materials, so as to obtain the final proportioning of the high-temperature radiation-proof concrete, the components of the concrete are as follows in kg / m 3 The mass ratio is: The serpentine is 600-700, the serpentine sand is 1000-1100, the cementitious material is 500-600, the water is 200-230, and the water reducing agent is 8-9.

2. The method of formulating according to claim 1, wherein, The Nurse-Saul equation is as follows: In the formula, M is maturity, in units of °C h or °C d; T is the average temperature of the concrete in the time interval Δt, in units of °C; T0 is the reference temperature, in units of °C, and the reference temperature refers to the temperature at which the strength of the concrete no longer increases with the age, i.e., the temperature at which the hydration reaction inside the concrete stops, and in the calculation, -10 °C is taken, and the undamaged strength Cz of the concrete at normal temperature is substituted into the logarithmic model, so that the corresponding standard value f of the 28d compressive strength of the concrete can be obtained cu,k .

3. The method of formulating according to claim 2, wherein, The concrete test piece is a shaped cylindrical concrete test piece.

4. The method of formulating according to claim 3, wherein, The size of the concrete test piece is φ60*80mm.

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