Method for testing strength of concrete beam after steam curing based on twin test blocks

Abstract

The invention relates to a method for testing the strength of a concrete beam after steam curing based on twin test blocks, which comprises the following steps of: placing a first temperature sensor in each plate of the concrete beam, and pouring concrete; meanwhile, a second temperature sensor is placed in the test block mold, concrete is poured into the test block mold, and the twin test block is obtained. The method comprises the following steps: collecting real-time temperature data of each plate on a concrete beam from the beginning of steam curing to the end of natural cooling of the concrete beam, adjusting the temperature of a twin test block to enable the temperature of the twin test block to be consistent with the temperature of the concrete beam, ensuring that the test strength of the twin test block is consistent with the concrete strength of the plates, and then carrying out a twin test block strength test to obtain a twin test block strength test result. And data support is provided for subsequent tensioning work of the concrete beam. Compared with the prior art, the steam curing temperature of each part of the concrete beam and the twin test block is collected, compared, regulated and controlled in real time, it is guaranteed that the maturity of the co-cured test block and the concrete beam is consistent, accurate strength re-carving is achieved, and the prefabrication quality of the concrete beam is improved.

Description

Technical Field

[0001] The invention relates to the technical field of bridge engineering, and in particular to a method for testing the strength of a concrete beam after steam curing based on twin test blocks. Background Art

[0002] The production process of prefabricated concrete beams generally includes: steel bar binding, concrete mixing, concrete transportation, concrete pouring, concrete vibration, initial setting demoulding, concrete steam curing, prestressing, prefabricated beam transportation and storage, etc. In order to speed up the prefabrication production speed, a steam curing shed is generally used for steam curing. The existing technical solutions have the following defects: (1) The existing concrete beams are generally placed on a bearing platform for fixed steam curing, which easily leads to uneven steam curing at the bottom of the beam and the web and top plate, thereby causing shrinkage deformation, shrinkage cracks and other phenomena in the concrete beam structure, and then leading to uneven strength of the concrete beam; (2) The existing same-condition curing test blocks and concrete beams only have the same external steam curing environment temperature, and cannot ensure that the maturity of the same-curing test blocks is consistent with the actual beam body, which will lead to misjudgment of the strength of the concrete beam, and is not conducive to ensuring the quality of the beam body, reducing construction efficiency.

[0003] Therefore, it is urgent to build a twinning technology of test blocks and concrete beams and slabs to achieve accurate replication of the strength of concrete beams. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method for testing the strength of concrete beams after steam curing based on twin test blocks. By real-time collection and regulation of the steam curing temperature of each part of the concrete beam, the steam on the surface of the concrete beam is uniform and the strength of each part of the concrete beam is consistent.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The present invention provides a method for testing the strength of a concrete beam after steam curing based on twin test blocks, comprising the following steps:

[0007] S1: placing a first temperature sensor in each plate of the concrete beam and pouring concrete to obtain a concrete beam with a temperature sensor; at the same time, placing a second temperature sensor in a test block mold and pouring concrete into the test block mold to obtain a twin test block;

[0008] S2: Steam curing is performed on the concrete beam in S1, and real-time temperature data of each plate on the concrete beam is collected from the start of steam curing to the end of natural cooling;

[0009] Put the twin test block into the temperature control box, obtain the temperature data, and compare it with the temperature data of the concrete beam, adjust the temperature of the twin test block to make it consistent with the temperature of the concrete beam; by comparing the difference between the temperature of the concrete beam plate and the test block temperature test data, adjust the heating heat of the temperature control box in real time to make the change of the test block temperature and the plate temperature consistent over time, so as to ensure the consistency of the maturity of the test block and the plate;

[0010] S3: Perform a strength test on the twin test blocks whose temperature has been controlled in S2, and judge the prestressed tensile strength of the concrete beam based on the strength test results of the twin test blocks, so as to improve the prefabrication quality of the concrete beam.

[0011] Furthermore, in S1, each plate component of the concrete beam includes a flange plate, a top plate, a web plate and a bottom plate, and each plate component of the concrete beam is provided with a twin test block.

[0012] Furthermore, the twin test blocks are provided in several groups, and the temperatures of the twin test blocks in the several groups correspond one by one to the temperatures of the flange plate, the top plate, the web plate and the bottom plate respectively.

[0013] Furthermore, in S1, the concrete poured in the test block mold is made of the same material as the concrete used to pour the concrete beam, and is from the same batch of concrete.

[0014] Furthermore, in S1, the twin test blocks include a temperature measurement test block and a strength test block, and a temperature sensor is provided in the temperature measurement test block.

[0015] Further, in S1, the first temperature sensor is connected to an external first wireless acquisition chassis, the first temperature sensor is connected to an external first wireless acquisition chassis, and the first temperature sensor includes a flange plate temperature sensor, a top plate temperature sensor, a web plate temperature sensor, and a bottom plate temperature sensor;

[0016] The second temperature sensor is connected to an external second wireless acquisition chassis.

[0017] Further, in S3, after the temperature of the temperature measuring test block in the twin test block is adjusted, the strength test block in the twin test block is used to perform a strength test.

[0018] Further, in S3, the temperature of each plate of the concrete beam is adjusted to be within ±1°C of the temperature of the twin test block.

[0019] Further, in S2, a temperature control box is used to increase or decrease the temperature of the twin test blocks;

[0020] The heating process is as follows: the heating amount of the temperature control box during the heating period is calculated according to the temperature difference between the target temperature and the naturally cured test block, and is dynamically adjusted. The calculation formula is:

[0021]

[0022] Among them, Q(t0) is the total heat provided by the temperature control box up to time t0; T1 is the temperature equation of the concrete beam and slab; T3 is the temperature equation of the natural curing specimen; T0 is the ambient temperature equation; h is the convection heat release coefficient between the temperature control box and the environment.

[0023] Furthermore, the cooling process is as follows: the cooling period is mainly based on heat dissipation, and the heat flow inside and outside the control box is balanced. The temperature of the temperature control box is calculated as follows:

[0024]

[0025] Among them, T c is the temperature of the temperature control box; h c is the convection heat release coefficient between the temperature control box and the twin test blocks.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0027] 1. When pouring concrete beams, the present invention embeds temperature sensors in the flange plate, top plate, web plate and bottom plate respectively to collect and regulate the steam curing temperature of each part of the concrete beam in real time, thereby ensuring uniform steam on the surface of the concrete beam and consistent strength of each part of the concrete beam.

[0028] 2. In the process from the beginning of steam curing to the end of natural cooling, the present invention collects, compares and regulates the steam curing temperature of each part of the concrete beam and the twin test block in real time, ensures that the maturity of the co-cured test block and the concrete beam is consistent, realizes accurate strength replication, and improves the prefabrication quality of the concrete beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a flow chart of the working method of a twin test block forming device for steam curing of concrete beams;

[0030] Figure 2 is a schematic diagram of a concrete beam in Example 1;

[0031] Figure 3 This is a schematic diagram of embedding temperature sensors at various locations of a concrete beam in Example 1;

[0032] Figure 4 This is a schematic diagram of steaming of twin test blocks in Example 1;

[0033] Figure 5 Schematic diagram of temperature control of the concrete beam and the twin test block in Example 1;

[0034] Figure 6 Schematic diagram of temperature changes of concrete beams and naturally cured test blocks in Example 1.

[0035] Figure 2 Description of the mark in:

[0036] 1-concrete beam, 11-flange plate, 12-top plate, 13-web plate, 14-bottom plate;

[0037] Figure 3 Description of the mark in:

[0038] 21-flange plate temperature sensor, 22-top plate temperature sensor, 23-web plate temperature sensor, 24-bottom plate temperature sensor, 25-first wireless temperature collection box;

[0039] Figure 4 Description of the mark in:

[0040] 31 - temperature measuring test block, 32 - strength test block, 41 - temperature control box, 42 - second temperature sensor, 43 - second wireless acquisition chassis. DETAILED DESCRIPTION

[0041] The specific implementation methods of the present invention are described in detail below through examples. These examples are implemented on the premise of the scheme described in the present invention, and provide detailed implementation methods and specific operating processes, but the protection scope of the present invention is not limited to the following examples.

[0042] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. Any features such as component models, material names, connection structures, preparation methods, materials, structures or composition ratios not clearly described in this technical solution are deemed to be common technical features disclosed in the prior art.

[0043] Example 1

[0044] This embodiment provides a method for testing the strength of concrete beams after steam curing based on twin test blocks. Figure 1 As shown, the following steps are included:

[0045] S1: Place flange plate temperature sensor 21, top plate temperature sensor 22, web plate temperature sensor 23 and bottom plate temperature sensor 24 in flange plate 11, top plate 12, web plate 13 and bottom plate 14 of the concrete beam respectively, connect them to the external first wireless acquisition chassis 25, and pour concrete to obtain a concrete beam with temperature sensors, such as Figure 2 and Figure 3 As shown; at the same time, a second temperature sensor 42 is placed in the test block mold, and concrete is poured into the test block mold to obtain a twin test block. The twin test block includes a temperature test block 31 and a strength test block 32. The temperature test block 31 is provided with a temperature sensor, such as Figure 4As shown. The concrete poured in the test block mold is made of the same material as the concrete used to pour the concrete beam, that is, the same batch of concrete, and the second temperature sensor 42 is connected to the external second wireless acquisition chassis 43. The twin test blocks are provided in several groups, and the temperatures of the several groups of twin test blocks correspond to the temperatures of the flange plate 11, the top plate 12, the web plate 13 and the bottom plate 14, respectively.

[0046] S2: Steam curing is performed on the concrete beam in S1, and real-time temperature data of each plate on the concrete beam is collected from the start of steam curing to the end of natural cooling;

[0047] A group of twin test blocks are placed in a temperature control box 41, temperature data is obtained, and compared with the temperature data of the concrete beam, and the temperature of the twin test blocks is adjusted so that the temperature of the twin test blocks is consistent with the temperature of the concrete beam, and the temperature difference is within ±1°C.

[0048] The temperature control box 41 is used to heat up or cool down the twin test blocks. The heating process is as follows: the heating amount of the temperature control box during the heating period is calculated according to the temperature difference between the target temperature and the naturally cured test block, and is dynamically adjusted. The calculation formula is:

[0049]

[0050] Among them, Q(t0) is the total heat provided by the temperature control box up to time t0; T1 is the temperature equation of the concrete beam and slab; T3 is the temperature equation of the natural curing specimen; T0 is the ambient temperature equation; h is the convection heat release coefficient between the temperature control box and the environment.

[0051] The cooling process is as follows: the cooling period is mainly based on heat dissipation, and the heat flow inside and outside the control box is balanced. The temperature calculation formula of the temperature control box is:

[0052]

[0053] Among them, T c is the temperature of the temperature control box; h c is the convection heat release coefficient between the temperature control box and the twin test blocks.

[0054] S3: After the temperature of the temperature measuring test block 31 in the twin test block is adjusted, the strength test block 32 in the twin test block is used for strength test. The specific process of the strength test is: the strength test block 32 is placed on the lower pressure plate or pad of the testing machine, so that the pressure-bearing surface of the strength test block 32 is perpendicular to the top surface during molding, the center of the strength test block 32 is aligned with the center of the lower pressure plate of the testing machine, and the load is applied until the strength test block 32 is destroyed. The prestressed tensile strength of the concrete beam is judged by the strength test result of the twin test block, thereby improving the prefabrication quality of the concrete beam. In addition, during prestressing, the strength of the concrete should meet the preset requirements. If there is no preset requirement, the concrete strength shall not be less than 75% of the design strength.

[0055] The measured internal temperature of the concrete beam and slab is T1, and the measured temperature of the natural curing test block is T3, where t1 = 0, t2 = 20d, h c =8.33e -7 J / (m 3 ·℃), the temperature of the temperature control box Tc can be obtained according to formula (2).

[0056] Substituting the known measured ambient temperature constant T0 into equation (3) can obtain the convection heat release coefficient h between the temperature control box and the environment;

[0057] Given the measured temperatures T1, T3 and the ambient temperature constant T0, the total amount of heat that the temperature control box needs to provide, Q(t0), can be obtained according to formula (1), so that the required temperature and heat can be dynamically adjusted in the time period of 0 to t0, as follows: Figure 5 and Figure 6 As shown, Figure 5 It is a schematic diagram of temperature control of the concrete beam and the twin test block of the present invention, wherein the solid line is the temperature curve of the concrete beam, the dotted line is the temperature curve of the twin test block, and the temperature difference between the two is basically controlled within ±1°C; the area integral between the temperature curve of the concrete beam and the natural curing temperature curve is the heat required for steam curing.

[0058] Figure 6 The actual test temperature change curve of the precast concrete beam and the natural curing test block of the present invention shows that the actual steam curing temperature of the concrete beam can be as high as 80°C, and the actual temperature of natural curing without steam curing can reach 35°C.

[0059] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for testing the strength of concrete beams after steam curing based on twin test blocks, characterized in that: The following steps are involved: S1: placing a first temperature sensor in each plate of a concrete beam and pouring concrete to obtain a concrete beam with a temperature sensor; at the same time, placing a second temperature sensor (42) in a test block mold and pouring concrete into the test block mold to obtain a twin test block; S2: Steam curing is performed on the concrete beam in S1, and real-time temperature data of each plate on the concrete beam is collected from the start of steam curing to the end of natural cooling; Put the twin test block into a temperature control box (41), obtain temperature data, compare it with the temperature data of the concrete beam, and adjust the temperature of the twin test block so that the temperature of the twin test block is consistent with the temperature of the concrete beam; S3: Perform a strength test on the twin test blocks whose temperature has been controlled in S2, and judge the prestressed tensile strength of the concrete beam based on the strength test results of the twin test blocks, so as to improve the prefabrication quality of the concrete beam.

2. A method for testing the strength of concrete beams after steam curing based on twin test blocks according to claim 1, characterized in that: In S1, each plate component of the concrete beam includes a flange plate (11), a top plate (12), a web plate (13) and a bottom plate (14), and each plate component of the concrete beam is correspondingly provided with a twin test block.

3. A method for testing the strength of concrete beams after steam curing based on twin test blocks according to claim 2, characterized in that: The twin test blocks are provided in a plurality of groups, and the temperatures of the twin test blocks in the plurality of groups correspond one to one with the temperatures of the flange plate (11), the top plate (12), the web plate (13) and the bottom plate (14).

4. The method for testing the strength of concrete beams after steam curing based on twin test blocks according to claim 1, characterized in that: In S1, the concrete poured in the test block mold is made of the same material as the concrete used to pour the concrete beam, and is from the same batch of concrete.

5. The method for testing the strength of concrete beams after steam curing based on twin test blocks according to claim 1, characterized in that: In S1, the twin test blocks include a temperature measurement test block (31) and a strength test block (32), and a second temperature sensor (42) is provided in the temperature measurement test block (31).

6. The method for testing the strength of concrete beams after steam curing based on twin test blocks according to claim 1, characterized in that: In S1, the first temperature sensor is connected to an external first wireless acquisition chassis, and the first temperature sensor includes a flange plate temperature sensor (21), a top plate temperature sensor (22), a web plate temperature sensor (23) and a bottom plate temperature sensor (24); The second temperature sensor (42) is connected to an external second wireless acquisition chassis (43).

7. The method for testing the strength of concrete beams after steam curing based on twin test blocks according to claim 1, characterized in that: In S3, after the temperature of the temperature measuring test block (31) in the twin test block is adjusted, a strength test is performed using the strength test block (32) in the twin test block to obtain the concrete strength of the twin test block and the concrete strength of the slab.

8. The method for testing the strength of concrete beams after steam curing based on twin test blocks according to claim 1, characterized in that: In S3, the temperature of each plate of the concrete beam is adjusted to be within ±1°C of the temperature of the twin test block.

9. The method for testing the strength of concrete beams after steam curing based on twin test blocks according to claim 1, characterized in that: In S2, a temperature-controlled box is used to increase or decrease the temperature of the twin test blocks; The heating process is as follows: the heating amount of the temperature control box during the heating period is calculated according to the temperature difference between the target temperature and the naturally cured test block, and is dynamically adjusted. The calculation formula is: Among them, Q(t0) is the total heat provided by the temperature control box up to time t0; T1 is the temperature equation of the concrete beam and slab; T3 is the temperature equation of the natural curing specimen; T0 is the ambient temperature equation; h is the convection heat release coefficient between the temperature control box and the environment.

10. A method for testing the strength of concrete beams after steam curing based on twin test blocks according to claim 9, characterized in that: The cooling process is as follows: the cooling period is mainly based on heat dissipation, and the heat flow inside and outside the control box is balanced. The temperature calculation formula of the temperature control box is: Among them, T c is the temperature of the temperature control box; h c is the convection heat release coefficient between the temperature control box and the twin test blocks.

Images