Low-pressure concrete preparation device and concrete freeze injury evaluation method

Abstract

The invention discloses a low-pressure concrete preparation device and a concrete freeze injury evaluation method, and belongs to the field of concrete. The low-pressure concrete preparation device comprises a stirring cabin body, a stirring assembly, a vacuum pump, a refrigeration assembly and a plurality of sampling pieces, at least part of the stirring assembly extends into the stirring cabin body, and the stirring assembly is used for stirring materials placed in the stirring cabin body to form concrete; the vacuum pump is communicated with the stirring cabin body and is used for pumping out gas in the stirring cabin body, so that the air pressure in the stirring cabin body is reduced; the refrigeration assembly is communicated with the stirring cabin body, and the refrigeration assembly is used for refrigerating materials in the stirring cabin body; the plurality of sampling pieces are detachably connected with the stirring cabin body, at least part of the sampling pieces extend into the stirring cabin body, and the sampling pieces are used for taking out prepared concrete from the stirring cabin body for detection.

Description

Technical Field

[0001] This application belongs to the field of concrete, and specifically relates to a low-pressure concrete preparation device and a method for evaluating concrete frost damage. Background Art

[0002] Water conservancy projects in alpine and high-altitude regions face problems such as low temperature, low humidity, low air pressure, and frost damage, posing a severe challenge to the durability of hydraulic concrete. These regions usually have characteristics such as low temperature, large temperature difference between day and night, and low air pressure. Especially in winter, hydraulic concrete structures are extremely vulnerable to early frost damage in low-temperature and low-air-pressure environments. Early frost damage of hydraulic concrete is a complex problem caused by the synergistic action of multiple factors such as low temperature, low pressure, salt erosion, and strong radiation. Frost damage is usually triggered by the expansion stress generated by the freezing of internal pore water, resulting in the expansion of microcracks inside the concrete, a decrease in strength, and surface spalling. Therefore, it is necessary to evaluate hydraulic concrete, and thus it is necessary to first prepare hydraulic concrete in a low-temperature and low-pressure environment. However, in related technologies, the equipment for preparing concrete cannot accurately simulate a low-temperature and low-pressure environment, making it difficult to simulate concrete in a low-temperature and low-pressure environment, and further resulting in inaccurate evaluation of hydraulic concrete. For example, the freeze-thaw box used in related technologies cannot control air pressure parameters. Summary of the Invention

[0003] The purpose of the embodiments of this application is to provide a low-pressure concrete preparation device and a method for evaluating concrete frost damage, which can at least solve the problem that the equipment for preparing concrete cannot accurately simulate a low-temperature and low-pressure environment, making it difficult to simulate concrete in a low-temperature and low-pressure environment, and further resulting in inaccurate evaluation of hydraulic concrete.

[0004] In a first aspect, the embodiments of this application provide a low-pressure concrete preparation device, which includes: a stirring chamber body, a stirring component, a vacuum pump, a refrigeration component, and multiple sampling components; At least part of the stirring component extends into the stirring chamber body, and the stirring component is used to stir the materials placed in the stirring chamber body to form concrete; The vacuum pump is connected to the stirring chamber body, and the vacuum pump is used to pump out the gas in the stirring chamber body to reduce the air pressure in the stirring chamber body; The refrigeration component is connected to the stirring chamber body, and the refrigeration component is used to refrigerate the materials in the stirring chamber body; Multiple sampling components are detachably connected to the stirring chamber body, and at least part of the sampling components extends into the stirring chamber body. The sampling components are used to take out the prepared concrete from the stirring chamber body for testing.

[0005] Optionally, the multiple sampling pieces are divided into at least two groups of sampling pieces, each group of the sampling pieces includes at least two sampling pieces, each of the sampling pieces in each group partially extends into the stirring chamber, and at least two of the sampling pieces in each group are circumferentially spaced apart along the stirring chamber; At least two groups of the sampling pieces are axially spaced apart along the stirring chamber, among the at least two groups of the sampling pieces, the depths at which multiple sampling pieces in one group of the sampling pieces extend into the stirring chamber are different, and the depths at which multiple sampling pieces in the other group of the sampling pieces extend into the stirring chamber are the same.

[0006] Optionally, the sampling piece includes a sampling tube, one end of the sampling tube is a closed end, and sampling holes are provided on the sampling tube, and the sampling holes and the sampling holes are located inside the stirring chamber.

[0007] Optionally, scale lines are provided on the outer wall of the sampling tube.

[0008] Optionally, a sampling valve is provided on the sampling tube, the sampling valve is located outside the stirring chamber, and the sampling valve has an open state and a closed state; When the sampling valve is in the open state, the material in the sampling tube can flow out from the sampling tube; when the sampling valve is in the closed state, the material in the sampling tube is blocked by the sampling valve.

[0009] Optionally, the low-pressure concrete preparation device further includes a gas-liquid separator, the gas-liquid separator is connected to the stirring chamber, and the gas-liquid separator is used to prevent water and concrete from flowing out of the stirring chamber.

[0010] Optionally, the refrigeration component includes a nitrogen pump and a circulation pipe; The nitrogen pump is located outside the stirring chamber, the circulation pipe is located inside the stirring chamber, the nitrogen pump is connected to the circulation pipe, and the nitrogen pump is used to inject nitrogen into the circulation pipe so that the circulation pipe cools the inside of the stirring chamber.

[0011] In a second aspect, an embodiment of the present application provides a method for evaluating concrete frost damage, which is used to evaluate the concrete prepared by the low-pressure concrete preparation device according to any one of the above first aspects. The method for evaluating concrete frost damage includes: Two groups of concrete samples are provided. Among the two groups of concrete samples, the first group of concrete samples is the concrete samples obtained by the vacuum pump in the low-pressure concrete preparation device pumping the air pressure in the mixing chamber to a preset air pressure and the refrigeration component refrigerating the mixing chamber, and the second group of concrete samples is the concrete samples obtained by the vacuum pump in the low-pressure concrete preparation device pumping the air pressure in the mixing chamber to a preset air pressure and the refrigeration component not refrigerating the mixing chamber. The second group of concrete samples serves as the control samples, and the first group of concrete samples serves as the test samples; Both the control samples and the test samples are subjected to a first test and a second test. The first test is a test for measuring the CH content in the concrete samples, and the second test is a test for measuring the Vickers hardness of the concrete samples, so as to obtain the control test results of the control samples and the test test results of the control samples; Compare the test test results with the control test results to obtain the evaluation results of the test samples.

[0012] Optionally, both the control samples and the test samples are subjected to a first test and a second test, including: Obtain at least two first sample blocks from the control samples and at least two second sample blocks from the test samples; Remove the free water from one of the first sample blocks to obtain a first dried sample block, and remove the free water from one of the second sample blocks to obtain a second dried sample block. Polish another first sample block to obtain a first polished sample block, and polish another second sample block to obtain a second polished sample block; Place the first dried sample block and the second dried sample block in a thermogravimetric analyzer, and respectively record the mass curves corresponding to the first dried sample block to determine the CH content in the first dried sample block, and the mass curve corresponding to the second dried sample block to determine the CH content in the second dried sample block. Analyze the first polished sample through a hardness tester to obtain the Vickers hardness of the first polished sample, and analyze the second polished sample through the hardness tester to obtain the Vickers hardness of the second polished sample.

[0013] Optionally, comparing the test test results with the control test results to obtain the evaluation results of the test samples includes: Compare the test test results with the control test results, and the deviation value of the test test results relative to the control test results; According to the deviation value and the evaluation relationship, obtain the evaluation results of the test samples. Among them, the evaluation relationship includes multiple evaluation deviation values, and one evaluation deviation value corresponds to one evaluation result.

[0014] In an embodiment of the present application, the stirring assembly at least partially extends into the stirring chamber. Therefore, once the materials are added to the stirring chamber, the materials in the stirring chamber can be stirred by the stirring assembly to form concrete. In addition, the vacuum pump is connected to the stirring chamber, and the refrigeration assembly is connected to the stirring chamber. Thus, the gas in the stirring chamber can be pumped out by the vacuum pump, causing the air pressure in the stirring chamber to drop, simulating a low-pressure environment, and enabling the refrigeration assembly to cool the stirring chamber, simulating a low-temperature environment. Furthermore, a low-pressure and low-temperature environment can be better simulated, such that the concrete is in a low-temperature and low-pressure environment. In addition, a plurality of sampling members are detachably connected to the stirring chamber, and at least a part of the sampling members extends into the stirring chamber. Thus, the prepared concrete can be taken out from the stirring chamber through the sampling members, facilitating the evaluation of the concrete. That is to say, in the embodiment of the present application, by providing a vacuum pump and a refrigeration assembly, a low-temperature and low-pressure environment can be better simulated during the preparation of concrete, so that the prepared concrete is in the required low-temperature and low-pressure environment. Furthermore, it is convenient to subsequently take out the concrete through the sampling members to evaluate the concrete, and the evaluation results are relatively accurate. Description of the Drawings

[0015] Figure 1 A schematic diagram showing a low-pressure concrete preparation device provided by an embodiment of the present application; Figure 2 A schematic diagram showing a sampling member provided by an embodiment of the present application; Figure 3 A flowchart showing a method for evaluating concrete frost damage provided by an embodiment of the present application.

[0016] Reference Numerals: 10: Stirring chamber; 20: Stirring assembly; 30: Vacuum pump; 40: Refrigeration assembly; 41: Nitrogen pump; 42: Circulation pipe; 50: Sampling member; 51: Sampling pipe; 52: Scale line; 53: Sampling valve; 60: Gas-liquid separator. Detailed Embodiments

[0017] The terms "first" and "second" in the description and claims of the present application may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, the meaning of "a plurality" is two or more. In addition, "and / or" in the description and claims indicates at least one of the connected objects, and the character " / " generally indicates an "or" relationship between the associated objects before and after.

[0018] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0019] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0020] As Figures 1 to 2 shown, the low-pressure concrete preparation device includes: a stirring tank body 10, a stirring assembly 20, a vacuum pump 30, a refrigeration assembly 40, and a plurality of sampling members 50.

[0021] At least part of the stirring assembly 20 extends into the stirring tank body 10, and the stirring assembly 20 is used for stirring the materials placed in the stirring tank body 10 to form concrete; the vacuum pump 30 is communicated with the stirring tank body 10, and the vacuum pump 30 is used for pumping out the gas in the stirring tank body 10 to reduce the air pressure in the stirring tank body 10; the refrigeration assembly 40 is communicated with the stirring tank body 10, and the refrigeration assembly 40 is used for refrigerating the materials in the stirring tank body 10; the plurality of sampling members 50 are detachably connected to the stirring tank body 10, and at least part of the sampling members 50 extends into the stirring tank body 10, and the sampling members 50 are used for taking out the prepared concrete from the stirring tank body 10 for detection.

[0022] In the embodiment of the present application, the stirring assembly 20 at least partially extends into the stirring chamber 10. Therefore, once the materials are added to the stirring chamber 10, the materials in the stirring chamber 10 can be stirred by the stirring assembly 20 to form concrete. In addition, the vacuum pump 30 is communicated with the stirring chamber 10, and the refrigeration assembly 40 is communicated with the stirring chamber 10, so that the gas in the stirring chamber 10 can be pumped out by the vacuum pump 30, the air pressure in the stirring chamber 10 can be reduced to simulate a low-pressure environment, and the refrigeration assembly 40 can refrigerate the stirring chamber 10 to simulate a low-temperature environment. Furthermore, a low-pressure and low-temperature environment can be better simulated, and the concrete can be located in a low-temperature and low-pressure environment. In addition, a plurality of sampling members 50 are detachably connected to the stirring chamber 10, and at least part of the sampling members 50 extends into the stirring chamber 10, so that the prepared concrete can be taken out from the stirring chamber 10 through the sampling members 50, which is convenient for evaluating the concrete. That is to say, in the embodiment of the present application, by setting the vacuum pump 30 and the refrigeration assembly 40, a low-temperature and low-pressure environment can be better simulated during the preparation of concrete, so that the prepared concrete is in the required low-temperature and low-pressure environment. Furthermore, it is convenient to take out the concrete through the sampling members subsequently, evaluate the concrete, and the evaluation result is relatively accurate.

[0023] It should be noted that in the embodiment of the present application, a pressure gauge is connected to the vacuum pump 30, and the pressure gauge is used to indicate the air pressure value in the stirring chamber 10. Specifically, when the gas in the stirring chamber 10 is pumped out by the vacuum pump 30, the pressure gauge displays the value in real time, and this value represents the air pressure value in the stirring chamber 10. For example, once the vacuum pump 30 is turned on and the vacuum pump 30 pumps out the gas in the stirring chamber 10, at this time, the reading of the pressure gauge is 80 KPa, indicating that the air pressure in the stirring chamber 10 is 80 KPa.

[0024] In addition, in the embodiment of the present application, a temperature detection device can be connected to the stirring chamber 10. By detecting the temperature inside the stirring chamber 10 in real time through the temperature detection device, when the refrigeration assembly 40 refrigerates the inside of the stirring chamber 10, the temperature detection device can determine the temperature inside the stirring chamber 10 in real time, and further ensure that the temperature inside the stirring chamber 10 is within the set temperature range.

[0025] In addition, in the embodiment of the present application, the stirring assembly 20 includes a stirring rod and a stirring member connected to the stirring rod. The stirring rod at least partially extends into the stirring chamber 10, and the stirring member is located in the stirring chamber 10. The stirring rod is connected with a driving motor. The driving motor drives the stirring rod to rotate, and the stirring rod drives the stirring member to rotate, and the materials in the stirring chamber 10 are stirred by the stirring member.

[0026] In addition, in the embodiments of the present application, the mixing chamber 10 may include a receiving chamber and an upper cover. The upper cover is closed on the receiving chamber, and the upper cover is sealingly connected to the receiving chamber. When it is necessary to add materials to the mixing chamber 10, the upper cover can be opened to add materials to the receiving chamber. Among them, the vacuum pump 30 may be connected to the upper cover. Thus, when the vacuum pump 30 operates, the gas in the receiving chamber can be pumped out, so that the air pressure in the receiving chamber decreases.

[0027] In addition, in the embodiments of the present application, the mixing ratio of the materials for preparing concrete may be as shown in FIG. 1, that is, according to the mixing ratio of each material in Table 1, each material can be added to the mixing chamber 10 and stirred by the stirring assembly 20 to prepare concrete.

[0028] Table 1

[0029] In addition, in the embodiments of the present application, the vacuum pump 30 and the refrigeration assembly 40 can be adjusted so that the air pressure in the mixing chamber 10 is at different air pressures and the temperature in the mixing chamber 10 is at different temperatures, and a more complex environment can be simulated in the mixing chamber 10.

[0030] In addition, in some embodiments, the multiple sampling members 50 are divided into at least two groups of sampling members 50. Each group of sampling members 50 includes at least two sampling members 50. Each sampling member 50 in each group of sampling members 50 partially extends into the mixing chamber 10, and at least two sampling members 50 in each group of sampling members 50 are spaced apart along the circumferential direction of the mixing chamber 10; at least two groups of sampling members 50 are spaced apart along the axial direction of the mixing chamber 10. Among at least two groups of sampling members 50, the depths at which multiple sampling members 50 in one group of sampling members 50 extend into the mixing chamber 10 are different, and the depths at which multiple sampling members 50 in the other group of sampling members 50 extend into the mixing chamber 10 are the same.

[0031] Since the depths at which multiple sampling members 50 in one group of sampling members 50 among at least two groups of sampling members 50 extend into the mixing chamber 10 are different, and the depths at which multiple sampling members 50 in the other group of sampling members 50 extend into the mixing chamber 10 are the same, therefore, when sampling is performed through at least two groups of sampling members 50, samples of the sampling members 50 at different depths extending into the mixing chamber 10 can be obtained, so that different samples can be studied, and thus the concrete can be evaluated more accurately.

[0032] It should be noted that a plurality of sampling holes are provided on the stirring chamber body 10, and the sampling holes penetrate through the chamber wall of the stirring chamber body 10. A plurality of sampling members 50 are respectively inserted into the plurality of sampling holes, and each sampling member 50 at least partially extends into the stirring chamber body 10. Among them, the low-pressure concrete preparation device further includes a plurality of plugs, and the plurality of plugs and the plurality of sampling tubes are alternately inserted into the sampling holes. Specifically, during the process of preparing concrete, if sampling is not required, the plurality of plugs are respectively inserted into the plurality of sampling holes to block the plurality of sampling holes; if sampling is required, the plurality of sampling tubes are respectively inserted into the plurality of sampling holes, and sampling is performed through the plurality of sampling tubes.

[0033] In addition, in the embodiments of the present application, the number of the sampling members 50 can be set according to actual needs. For example, the number of the sampling members 50 is 6, and the 6 sampling members 50 are divided into 2 groups of sampling members 50. Each group of sampling members 50 includes 3 sampling members 50. The first group of sampling members 50 and the second group of sampling members 50 are spaced apart along the axial direction of the stirring chamber body 10. The depths of the 3 sampling members 50 in the first group of sampling members 50 extending into the stirring chamber body 10 are 30 mm, 60 mm, and 90 mm respectively, and the depths of the 3 sampling members 50 in the second group of sampling members 50 extending into the stirring chamber body 10 are all 60 mm. For another example, the number of the sampling members 50 is 8, and the 8 sampling members 50 are divided into 2 groups of sampling members 50. Each group of sampling members 50 includes 4 sampling members 50. The first group of sampling members 50 and the second group of sampling members 50 are spaced apart along the axial direction of the stirring chamber body 10. The depths of the 4 sampling members 50 in the first group of sampling members 50 extending into the stirring chamber body 10 are 30 mm, 60 mm, 90 mm, and 120 mm respectively, and the depths of the 4 sampling members 50 in the second group of sampling members 50 extending into the stirring chamber body 10 are all 60 mm. The specific number of the sampling members 50 is not limited in the embodiments of the present application.

[0034] In addition, in some embodiments, the sampling member 50 includes a sampling tube 51. One end of the sampling tube 51 is a closed end, and sampling holes are provided on the sampling tube 51. The sampling holes and the sampling holes are located inside the stirring chamber body 10. Through such a setting, when the sampling tube 51 is inserted into the stirring chamber body 10, the concrete formed in the stirring chamber body 10 can flow into the sampling tube 51 through the sampling holes, facilitating the sampling tube 51 to perform sampling.

[0035] It should be noted that in one embodiment, the sampling hole is located on the closed end of the sampling tube 51, and in another embodiment, the sampling hole is located on the tube wall of the sampling tube 51.

[0036] In addition, in the embodiments of the present application, the material of the sampling tube 51 is a metal material. For example, the material of the sampling tube 51 is an alloy, and for another example, the material of the sampling tube 51 is steel. The specific material of the sampling tube 51 is not limited in the embodiments of the present application.

[0037] In addition, in some embodiments, scale lines 52 are provided on the outer wall of the sampling tube 51. Through such a setting, when the sampling tube 51 is inserted into the stirring chamber 10, the depth of the sampling tube 51 extending into the stirring chamber 10 can be accurately known through the scale lines 52, and it is convenient to determine the depth of the sampling tube 51 extending into the stirring chamber 10.

[0038] In addition, in some embodiments, a sampling valve 53 is provided on the sampling tube 51. The sampling valve 53 is located outside the stirring chamber 10 and has an open state and a closed state; when the sampling valve 53 is in the open state, the material in the sampling tube 51 can flow out from the sampling tube 51; when the sampling valve 53 is in the closed state, the material in the sampling tube 51 is blocked by the sampling valve 53.

[0039] Since the sampling valve 53 is provided on the sampling tube 51 and the sampling valve 53 is located outside the stirring chamber 10, when the sampling tube 51 is inserted into the stirring chamber 10 for sampling, the sampling valve 53 can be in the closed state to prevent the material flowing into the sampling tube 51 from flowing out of the sampling tube 51; after sampling is completed, when the material in the sampling tube 51 needs to be taken out, the sampling valve 53 can be in the open state, so that the material in the sampling tube 51 can flow out from the sampling tube 51. That is, by providing the sampling valve 53, it is convenient to sample with the sampling valve 53 and it is convenient for the material in the sampling tube 51 to flow out of the sampling tube 51.

[0040] In addition, in some embodiments, the low-pressure concrete preparation device further includes a gas-liquid separator 60. The gas-liquid separator 60 is connected to the stirring chamber 10, and the gas-liquid separator 60 is used to prevent water and concrete from flowing out of the stirring chamber 10.

[0041] It should be noted that the gas-liquid separator 60 is connected to the bottom of the stirring chamber 10 to prevent water and concrete from flowing out of the stirring chamber 10.

[0042] In addition, in some embodiments, the refrigeration component 40 includes a nitrogen pump 41 and a circulation pipe 42; the nitrogen pump 41 is located outside the stirring chamber 10, the circulation pipe 42 is located inside the stirring chamber 10, the nitrogen pump 41 is connected to the circulation pipe 42, and the nitrogen pump 41 is used to inject nitrogen into the circulation pipe 42 to cool the inside of the stirring chamber 10 through the circulation pipe 42.

[0043] Since the nitrogen pump 41 is located outside the stirring chamber 10, the circulation pipe 42 is located inside the stirring chamber 10, and the nitrogen pump 41 is connected to the circulation pipe 42. Therefore, once the nitrogen pump 41 operates, the nitrogen pump 41 can inject low-temperature nitrogen into the circulation pipe 42, so that the low-temperature nitrogen can cool the nitrogen pipe in the stirring chamber 10, and then cool the inside of the stirring chamber 10. That is, by setting the nitrogen pump 41 and the circulation pipe 42, it is convenient to cool the inside of the stirring chamber 10.

[0044] It should be noted that the circulation pipe 42 can be spirally distributed along the inner wall of the stirring chamber 10. Thus, when the nitrogen pump 41 injects low-temperature nitrogen into the circulation pipe 42, the spirally distributed nitrogen pipe can better cool the inside of the stirring chamber 10 and avoid the problem that the temperature in a local area of the inside of the stirring chamber 10 drops while the temperature in other positions does not drop or drops less. That is, by setting the circulation pipe 42 to be spirally distributed along the inner wall of the stirring chamber 10, the temperature in the stirring chamber 10 can drop more evenly, better simulating a low-temperature environment.

[0045] In addition, in one embodiment, the refrigeration assembly 40 includes a heat exchange assembly and the circulation pipe 42. The circulation pipe 42 is connected to the heat exchange assembly, and there is a coolant in the circulation pipe 42. The coolant exchanges heat in the heat exchange assembly and continuously cools down, so that the low-temperature coolant can reduce the temperature inside the stirring chamber 10.

[0046] The embodiment of the present application provides a method for evaluating concrete frost damage, which is used to evaluate the concrete prepared by the low-pressure concrete preparation device in any one of the above embodiments, as Figure 3 shown. This method for evaluating concrete frost damage includes: Step 301: Provide two groups of concrete samples. Among them, in the two groups of concrete samples, the first group of concrete samples is the concrete samples obtained by the vacuum pump in the low-pressure concrete preparation device pumping the air pressure in the stirring chamber to a preset air pressure and the refrigeration assembly cooling the stirring chamber, and the second group of concrete samples is the concrete samples obtained by the vacuum pump in the low-pressure concrete preparation device pumping the air pressure in the stirring chamber to a preset air pressure and the refrigeration assembly not cooling the stirring chamber. The second group of concrete samples serves as a control sample, and the first group of concrete samples serves as a test sample.

[0047] Among them, when preparing concrete with a low-pressure concrete preparation device, first use a plug to seal the sampling pipe on the mixing chamber to prevent the concrete material from flowing out. Then pour the weighed coarse aggregate, fine aggregate, cement, and fly ash into the mixing chamber from the feed port for mixing, and make the mixing component perform preliminary mixing to obtain a uniformly mixed solid mixture. Specifically, the mixing component can be made to mix for 1 minute to obtain a uniform solid mixture. Then pour water into the mixing chamber from the feed port, and turn on the vacuum pump to make the vacuum pump evacuate the mixing chamber. Observe the reading on the vacuum gauge of the vacuum pump. After the reading on the vacuum gauge reaches the preset air pressure of 80 KPa - 50 KPa, turn off the vacuum pump to stop the evacuation. Among them, the preset air pressure can be any value between 80 KPa and 50 KPa. For example, the preset air pressure is 80 KPa, or for another example, the preset air pressure is 75 KPa, or for another example, the preset air pressure is 60 KPa, or for another example, the preset air pressure is 50 KPa.

[0048] Then prepare the first group of concrete. Specifically, make the refrigeration component cool the inside of the mixing chamber so that the temperature inside the lowering plate chamber reaches the predetermined temperature of -40°C - 0°C. Remove the plug on the mixing chamber, and insert the sampling piece into the mixing chamber for sampling. Before inserting the sampling piece into the mixing chamber, first evenly coat a layer of mineral oil on the inner wall of the sampling pipe to prevent the material in the mixing chamber from adhering to the inner wall of the sampling pipe. The sample taken out by the sampling piece is the first group of concrete samples, that is, the first group of samples is the concrete sample obtained when the vacuum pump in the low-pressure concrete preparation device evacuates the air pressure in the mixing chamber to the preset air pressure and the refrigeration component cools the mixing chamber.

[0049] Prepare the second group of concrete again. The specific preparation process refers to the process of preparing the first group of concrete and will not be elaborated here. Among them, when preparing the second group of concrete, the refrigeration component is in the off state, that is, the refrigeration component does not cool the mixing chamber, and the temperature of the mixing chamber is normal temperature. Among them, normal temperature refers to a temperature of 20 ± 5. By preparing the second group of concrete, the second group of samples is obtained. The second group of samples is the concrete sample obtained when the vacuum pump in the low-pressure concrete preparation device evacuates the air pressure in the mixing chamber to the preset air pressure and the refrigeration component does not cool the mixing chamber.

[0050] Step 302: Conduct the first test and the second test on both the control sample and the test sample. The first test is a test for measuring the CH content in the concrete sample, and the second test is a test for measuring the Vickers hardness of the concrete sample to obtain the control test result of the control sample and the test test result of the control sample.

[0051] Among them, before the first test and the second test are carried out on the control sample and the test sample, the control sample and the test sample can be first cured under the room temperature conditions of 20°C and 95% humidity for 28 days, and then the first test and the second test are carried out. By curing the control sample and the test sample, the test results of subsequent tests can be made more accurate.

[0052] It should be noted that CH refers to calcium hydroxide, and the CH content refers to the calcium hydroxide content.

[0053] In addition, in some implementation manners, the implementation manner of step 402 can be: obtain at least two first sample blocks from the control sample, and obtain at least two second sample blocks from the test sample; remove the free water of one first sample block to obtain a first dried sample block, and remove the free water of one second sample block to obtain a second dried sample block, and polish another first sample block to obtain a first polished sample block, and polish another second sample block to obtain a second polished sample block; place the first dried sample block and the second dried sample block in a thermogravimetric analyzer, and respectively record the mass curve corresponding to the first dried sample block to determine the CH content in the first dried sample block, the mass curve corresponding to the second dried sample block to determine the CH content in the second dried sample block, analyze the first polished sample through a hardness tester to obtain the Vickers hardness of the first polished sample, and analyze the second polished sample through a hardness tester to obtain the Vickers hardness of the second polished sample.

[0054] Specifically, drill or cut two first sample blocks from the control sample, place one first sample block in an oven at 105°C for 24 hours to remove free water to obtain a first dried sample block, then grind the first dried sample block into powder, and pass the powder through a 100-200 mesh sieve to ensure that the particle size of the powder is less than or equal to 100um. Then, spread the powder evenly on a crucible, place the crucible with the powder in a thermogravimetric analyzer, and make the thermogravimetric analyzer run and display the mass curve, then the mass curve corresponding to the first dried sample block can be recorded. Among them, the mass curve includes a mass change curve and a differential thermogravimetric curve. Through the values shown in the mass curve, the CH content can be determined.

[0055] Among them, the CH content can be determined by the following formula: ; In the above formula, CH (%) is the content of the hydration product; ML is the mass loss rate in the corresponding temperature range; K is the molar mass ratio of the hydration product to water. . The hydration product is calcium hydroxide.

[0056] By determining the CH content, it is equivalent to carrying out the first test on the control sample.

[0057] Similarly, drill or cut two second sample blocks from the test sample. Place one second sample block in an oven at 105°C and dry it for 24 hours to remove free water, obtaining a second dried sample block. Then grind the second dried sample block into powder and sieve the powder through a 100 - 200 mesh sieve to ensure that the particle size of the powder is less than or equal to 100um. After that, evenly spread the powder in a crucible, place the crucible with the powder in a thermogravimetric analyzer, run the thermogravimetric analyzer to display the mass curve, and then the mass curve corresponding to the second dried sample block can be recorded. Among them, the mass curve includes a mass change curve and a differential thermogravimetric curve. Through the values shown by the mass curve, the CH content can be determined.

[0058] Grind the other first sample block drilled or cut from the control sample successively with sandpapers of different grits, and finally polish it to a mirror surface with diamond polishing fluid. Then use a microhardness tester to verify the accuracy of the load and indentation size. Among them, there is cement paste and aggregate in the concrete, and the first sample contains cement paste and aggregate. Determine the hardness at the interface between the cement paste and the aggregate to determine the hardness of the first sample.

[0059] Among them, when determining the hardness at the interface between the cement paste and the aggregate, deviate the measuring point 50um along the interface transition line between the aggregate and the cement paste, and then determine the hardness at the interface between the cement paste and the aggregate. The measuring point refers to the pressing point where the microhardness tester presses on the first sample.

[0060] Specifically, when determining the hardness value, it is determined according to the following formula: ; ; ; Among them, HV is the Vickers hardness, MPa; F is the test load, 0.0981N; d is the arithmetic mean of the indentation diagonals, mm. HV(paste) represents the Vickers hardness of the cement paste, HV(ITZ) represents the Vickers hardness at the interface between the cement paste and the aggregate, and HV(average) represents the Vickers hardness of the first sample.

[0061] Grind the other second sample block drilled or cut from the test sample successively with sandpapers of different grits, and finally polish it to a mirror surface with diamond polishing fluid. Then use a microhardness tester to verify the accuracy of the load and indentation size. Among them, there is cement paste and aggregate in the concrete, and the second sample contains cement paste and aggregate. Determine the hardness at the interface between the cement paste and the aggregate to determine the hardness of the second sample.

[0062] Step 303: Compare the test results with the control test results to obtain the evaluation result of the test sample.

[0063] By comparing the test results with the control test results, the deviation between the two can be determined, and evaluation can be carried out to obtain the evaluation result of the test sample.

[0064] In addition, in some implementation manners, the implementation manner of step 403 can be: comparing the test results with the control test results, and obtaining the deviation value of the test results relative to the control test results; obtaining the evaluation result of the test sample according to the deviation value and the evaluation relationship, where the evaluation relationship includes multiple evaluation deviation values, and one evaluation deviation value corresponds to one evaluation result.

[0065] Specifically, by comparing the test results with the control test results, the deviation value of the test results relative to the control test results can be obtained. After determining the deviation value, the evaluation result corresponding to the deviation value can be determined in the evaluation relationship, so as to obtain the evaluation result of the test sample.

[0066] For example, the evaluation relationship is shown in Table 2 below: Table 2

[0067] If the decrease amount of the hydration products in the test sample relative to the hydration products in the control sample is less than 10%, and the decrease amount of the hardness of the test sample relative to the hardness of the control sample is less than 20%, it is determined that the test sample has mild frost damage; if the decrease amount of the hydration products in the test sample relative to the hydration products in the control sample is between 10% - 20%, and the decrease amount of the hardness of the test sample relative to the hardness of the control sample is between 20% - 35%, it is determined that the test sample has moderate frost damage; if the decrease amount of the hydration products in the test sample relative to the hydration products in the control sample is between 20% - 30%, and the decrease amount of the hardness of the test sample relative to the hardness of the control sample is between 35% - 50%, it is determined that the test sample has severe frost damage; if the decrease amount of the hydration products in the test sample relative to the hydration products in the control sample is greater than 30%, and the decrease amount of the hardness of the test sample relative to the hardness of the control sample is greater than 50%, it is determined that the test sample has serious frost damage.

[0068] It should be noted that in the embodiments of the present application, if the reduction rates of the hydration product CH and the average Vickers hardness do not belong to the same grade, the higher grade shall prevail. For example, if the decrease amount of the hydration products in the test sample relative to the hydration products in the control sample is less than 10%, and the decrease amount of the hardness of the test sample relative to the hardness of the control sample is between 20% - 35%, it should be determined as mild frost damage according to the decrease amount of the hydration products, and it should be determined as moderate frost damage according to the decrease amount of the hardness. Mild frost damage and moderate frost damage do not belong to the same grade, and the result of the higher grade shall prevail, that is, it is determined that the test sample has moderate frost damage.

[0069] In addition, in the embodiments of the present application, it is possible to evaluate the concrete samples obtained by sampling pieces inserted at different depths in the mixing cabin, and the evaluation results are shown in Tables 3 and 4 below: Table 3

[0070] Table 4

[0071] Table 3 shows the CH content in concrete samples at different depths, and Table 4 shows the hardness of concrete samples at different depths. The paste represents the cement paste, and the ITZ represents the position at the interface between the cement paste and the aggregate.

[0072] It can be seen from Tables 3 and 4 that as the depth of the sampling piece inserted into the mixing cabin increases, the CH content of the concrete sample increases, and the Vickers hardness of the paste and ITZ increases. The early frost damage of the concrete sample compared with the non-frost-damaged concrete, that is, the reduction rate of CH content relative to the control sample is less than 10%, and the average reduction rate of Vickers hardness is less than 20%, belonging to mild frost damage.

[0073] In addition, in the embodiments of the present application, it is possible to evaluate the concrete samples obtained at different sampling times, and the evaluation results are shown in Tables 5 and 6 below: Table 5

[0074] Table 6

[0075] Table 5 shows the CH content of concrete samples at different sampling times, and Table 6 shows the hardness of concrete samples at different sampling times. Among them, the depth of the sampling piece inserted into the mixing cabin in Tables 5 and 6 is the same. D represents the number of days. For example, 7d represents 7 days. It can be seen from Tables 5 and 6 that as the sampling time increases, the CH content of the concrete sample decreases, and the Vickers hardness of the paste, ITZ, and aggregate all decreases, and the reduction rate of CH in the early frost damage of the concrete sample compared with the non-frost-damaged concrete is less than 10%, and the average reduction rate of Vickers hardness is less than 20%, belonging to mild frost damage.

[0076] In the embodiments of the present application, two groups of concrete samples are provided; both the control sample and the test sample are subjected to a first test and a second test. The first test is a test for measuring the CH content in the concrete sample, and the second test is a test for measuring the Vickers hardness of the concrete sample, so as to obtain the control test results of the control sample and the test results of the test sample; the test results are compared with the control test results to obtain the evaluation results of the test sample. That is, in the embodiments of the present application, when evaluating the concrete, it is equivalent to evaluating according to two parameters, namely the CH content and the hardness, so that the evaluation results for the concrete evaluation are more accurate and more in line with the actual needs.

[0077] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0078] Although the embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of the present application. The scope of the present application is defined by the claims and their equivalents.

Claims

1. A low-pressure concrete preparation device, characterized in that The low-pressure concrete preparation device includes: a stirring chamber body, a stirring component, a vacuum pump, a refrigeration component, and multiple sampling components; At least a part of the stirring component extends into the stirring chamber body, and the stirring component is used for stirring the materials placed in the stirring chamber body to form concrete; The vacuum pump is communicated with the stirring chamber body, and the vacuum pump is used for pumping out the gas in the stirring chamber body to reduce the air pressure in the stirring chamber body; The refrigeration component is communicated with the stirring chamber body, and the refrigeration component is used for refrigerating the materials in the stirring chamber body; Multiple sampling components are detachably connected to the stirring chamber body, and at least a part of the sampling components extends into the stirring chamber body, and the sampling components are used for taking out the prepared concrete from the stirring chamber body for detection.

2. The low-pressure concrete preparation device according to claim 1, characterized in that, The multiple sampling components are divided into at least two groups of sampling components. Each group of sampling components includes at least two sampling components. Each sampling component in each group of sampling components partially extends into the stirring chamber body, and at least two sampling components in each group of sampling components are circumferentially spaced apart along the stirring chamber body; At least two groups of sampling components are spaced apart along the axis direction of the stirring chamber body. The depths at which multiple sampling components in one group of sampling components in at least two groups of sampling components extend into the stirring chamber body are different, and the depths at which multiple sampling components in the other group of sampling components extend into the stirring chamber body are the same.

3. The low-pressure concrete preparation device according to claim 2, characterized in that, The sampling component includes a sampling tube. One end of the sampling tube is a closed end, and a sampling hole is provided on the sampling tube, and the sampling hole and the sampling hole are located inside the stirring chamber body.

4. The low-pressure concrete preparation device according to claim 3, characterized in that, Scale lines are provided on the outer wall of the sampling tube.

5. The low-pressure concrete preparation device according to claim 3, characterized in that, A sampling valve is provided on the sampling tube. The sampling valve is located outside the stirring chamber body, and the sampling valve has an open state and a closed state; When the sampling valve is in the open state, the materials in the sampling tube can flow out from the sampling tube; when the sampling valve is in the closed state, the materials in the sampling tube are blocked by the sampling valve.

6. The low-pressure concrete preparation device according to any one of claims 1-5, characterized in that, The low-pressure concrete preparation device further includes a gas-liquid separator. The gas-liquid separator is connected to the stirring chamber body, and the gas-liquid separator is used to prevent water and concrete from flowing out of the stirring chamber body.

7. The low-pressure concrete preparation device according to any one of claims 1-5, characterized in that, The refrigeration component includes a nitrogen pump and a circulation pipe; The nitrogen pump is located outside the stirring chamber body, the circulation pipe is located inside the stirring chamber body, the nitrogen pump is connected to the circulation pipe, and the nitrogen pump is used to inject nitrogen into the circulation pipe to cool the inside of the stirring chamber body through the circulation pipe.

8. A method for evaluating concrete freeze-thaw damage, characterized in that, For evaluating the concrete prepared by the low-pressure concrete preparation device according to any one of claims 1-7, the concrete frost damage evaluation method includes: Two groups of concrete samples are provided. Among the two groups of concrete samples, the first group of concrete samples is the concrete sample obtained when the vacuum pump in the low-pressure concrete preparation device pumps the air pressure in the mixing chamber to a preset air pressure and the refrigeration component cools the mixing chamber. The second group of concrete samples is the concrete sample obtained when the vacuum pump in the low-pressure concrete preparation device pumps the air pressure in the mixing chamber to a preset air pressure and the refrigeration component does not cool the mixing chamber. The second group of concrete samples serves as a control sample, and the first group of concrete samples serves as a test sample; Both the control sample and the test sample are subjected to a first test and a second test. The first test is a test for measuring the CH content in the concrete sample, and the second test is a test for measuring the Vickers hardness of the concrete sample, so as to obtain the control test result of the control sample and the test test result of the control sample; The test test result is compared with the control test result to obtain the evaluation result of the test sample.

9. The concrete freeze-thaw damage evaluation method according to claim 8, wherein, Both the control sample and the test sample are subjected to a first test and a second test, including: At least two first sample blocks are obtained from the control sample, and at least two second sample blocks are obtained from the test sample; The free water of one of the first sample blocks is removed to obtain a first dried sample block, and the free water of one of the second sample blocks is removed to obtain a second dried sample block. Another first sample block is polished to obtain a first polished sample block, and another second sample block is polished to obtain a second polished sample block; The first dried sample block and the second dried sample block are placed in a thermogravimetric analyzer, and the mass curve corresponding to the first dried sample block is recorded respectively to determine the CH content in the first dried sample block, and the mass curve corresponding to the second dried sample block is determined to determine the CH content in the second dried sample block. The Vickers hardness of the first polished sample is obtained by analyzing the first polished sample with a hardness tester, and the Vickers hardness of the second polished sample is obtained by analyzing the second polished sample with the hardness tester.

10. The concrete frost damage evaluation method according to claim 8, characterized in that, The comparison of the test test result with the control test result to obtain the evaluation result of the test sample includes: The test test result is compared with the control test result, and the deviation value of the test test result relative to the control test result; According to the deviation value and the evaluation relationship, the evaluation result of the test sample is obtained, wherein the evaluation relationship includes a plurality of evaluation deviation values, and one evaluation deviation value corresponds to one evaluation result.

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