CN205262878U - Bending test machine in concrete material high temperature - Google Patents

Abstract

The utility model provides a concrete material high-temperature medium-bending test machine, which includes loading equipment for applying pressure to concrete test pieces, heating equipment for heating the concrete test pieces, and displacement acquisition devices for measuring the deformation of the concrete test pieces. The utility model concrete material bending test machine at high temperature combines the heating equipment and loading equipment of the concrete test ingeniously together, and is supplemented by a displacement acquisition device to form a comprehensive test system that can be used for the bending test of concrete specimens at high temperatures. Loading synergy, loading and measurement synchronization, can simulate the real environment of concrete in high-temperature fire, the test results obtained by the concrete material test through the high-temperature bending test machine for concrete materials are very close to the actual bending performance of concrete in high-temperature fire, for Research on the high temperature and fire resistance of concrete materials provides a guarantee.

Description

Concrete material high temperature bending test machine

technical field

The utility model relates to a concrete material mechanical performance testing machine, in particular to a testing machine for high-temperature flexural strength and bending toughness of common concrete, fiber concrete, recycled concrete, high-strength concrete and other materials.

Background technique

Concrete is the most widely used and most used building material in engineering construction. In recent years, with the in-depth application of concrete materials in special conditions such as high-rise, high-rise, long-span and harsh environments, new requirements have been put forward for the high-temperature fire resistance of concrete materials, and corresponding high-temperature test equipment is urgently needed to develop the high-temperature performance of concrete materials. Fire resistance. The heating system and loading system of the existing concrete high-temperature bending test equipment are often separated, and the bending performance test of concrete at high temperature and medium cannot be carried out in the strict sense. Only the bending performance test of concrete after high temperature and the approximate bending performance test of concrete at high temperature can be carried out. The bending performance test of concrete after high temperature is to heat the concrete material in the heating equipment, stop heating after reaching the target value, and load it on the loading equipment after the concrete material cools down. The approximate bending performance test of concrete at high temperature is to load the concrete material in a high temperature state on the bending test machine with special high temperature clamps and other tools immediately after the temperature of the concrete in the heating equipment reaches the target value. In practical application, it is found that whether it is the post-high temperature bending test or the approximate high temperature bending test, the results of the high temperature bending test of concrete are quite different from the actual bending properties of the concrete in the high temperature fire.

In order to solve the above existing problems, people have been seeking an ideal technical solution.

Utility model content

After a long period of technical research, technicians finally discovered the cause of the above problems. The reason for the large difference between the results of high-temperature bending tests of concrete and the actual bending properties of concrete in high-temperature fires is that the heating system of the bending test equipment in high-temperature concrete is separated from the loading system, and the coordination of heating and loading cannot be realized. The temperature of the concrete specimen will always be lower than the target temperature during heating to varying degrees. During the cooling process of the concrete specimen, the external cooling is fast and the internal cooling is slow, thereby generating a thermal stress gradient and causing stress damage to the concrete material. The actual flexural properties of concrete at high fire temperatures produce differences. For the bending performance test of concrete after high temperature, the temperature of the concrete specimen has dropped to normal temperature during loading, and the thermal stress damage is very obvious. For the approximate bending performance test of concrete at high temperature, although the concrete specimen is loaded immediately after it is taken out of the heating equipment, the temperature drops less, but because the ambient temperature during loading is much lower than the temperature in the heating equipment, the heat of the concrete specimen The stress gradient is large, and thermal stress damage cannot be ignored. In addition, during the research and development process, the technicians also encountered a technical problem, that is, the displacement gauge used to measure the deformation of concrete would burn out when placed in the heating device.

In addition, according to the current relevant test method standards and specifications in our country, the properties of concrete materials (such as compressive strength) are determined according to the test results of three concrete specimens under the same conditions. Problems with heating and loading in high temperature environments.

In order to solve the above-mentioned technical problems, the technical solution adopted by the utility model is: a high-temperature bending test machine for concrete materials, including loading equipment for applying pressure to concrete specimens, heating equipment for heating concrete specimens, and for measuring Displacement acquisition device for bending deformation of concrete specimens;

The loading device includes a base, a column fixed on the base, a crossbeam arranged on the upright and moving up and down along the upright and positioned, an upper platen fixed on the bottom of the beam, and a high-temperature resistant plate fixed on the bottom of the upper platen. The pressure head, the lower pressure plate on the base, the high temperature resistant lower pressure head on the lower pressure plate, the high temperature resistant pad on the lower pressure head, and the upper pressure plate for applying upward pressure on the lower pressure plate. The loading power source of the action force, the lower end of the high-temperature-resistant upper pressure head is provided in parallel with two strip-shaped convex parts for applying pressure downward to the middle of the concrete specimen, and the upper end of the high-temperature-resistant cushion block is provided with two strip-shaped protrusions in parallel. For the strip-shaped protrusions that apply pressure upwards to the two ends of the concrete specimen, the strip-shaped protrusions on the high-temperature-resistant upper pressure head and the strip-shaped protrusions on the high-temperature-resistant pad are arranged in parallel and jointly form a Four fulcrums that exert force on the concrete specimen;

The heating equipment includes a high-temperature furnace support frame, a high-temperature furnace arranged on the high-temperature furnace support frame, and a heating element arranged in the high-temperature furnace. The high-temperature furnace is located between the upper platen and the lower platen. The top plate of the high-temperature furnace is provided with the upper piercing hole for the high-temperature-resistant upper pressure head to penetrate downward into the interior of the high-temperature furnace, and the bottom plate of the high-temperature furnace is provided with the lower piercing hole for the high-temperature-resistant lower pressure head to penetrate upward into the interior of the high-temperature furnace. The upper perforation and the lower perforation are vertically opposite to each other;

The displacement acquisition device includes three displacement gauges arranged on the high temperature resistant upper pressure head, a displacement gauge collection box for collecting information of the three displacement gauges, two end guide rod structures and a middle guide rod structure, The high temperature resistant guide rod of the middle guide rod structure slides through the center hole of the high temperature resistant upper pressure head in the vertical direction and goes deep into the high temperature furnace, and the high temperature resistant guide rods of the two end guide rod structures respectively slide The two sides of the high-temperature-resistant upper pressure head go deep into the high-temperature furnace downwards, and the top of the high-temperature furnace is provided with guide holes for each of the high-temperature-resistant guide rods to pass through, and the displacement gauges arranged on both sides of the high-temperature-resistant upper pressure head The pressure fit with the corresponding end guide rod structure is used to measure the deformation at both ends of the concrete specimen, and the displacement gauge arranged on the upper pressure plate is press fit with the middle guide rod structure to measure the deformation of the concrete specimen. Deformation in the middle of the specimen.

Preferably, the high temperature resistant upper pressure head includes an upper pressure head support fixed on the upper pressure plate and an upper pressure head body fixed on the upper pressure head support, and the high temperature resistant lower pressure head It includes a lower pressing head support fixed on the lower pressing plate and a lower pressing head body fixed on the lower pressing head support, and the corresponding strip-shaped protrusion is located on the upper pressing head body.

Preferably, the upper part of the column is provided with threads, the two ends of the beam are rotated with nuts, the beam is provided with a motor for driving the two nuts to rotate, and the beam is matched with the thread of the column Realize moving up and down and positioning.

Preferably, the heating device further includes a temperature control system and a temperature sensor installed in the high-temperature furnace, the heating element is a silicon carbide rod, the temperature control system is connected to the temperature sensor for sampling, and the temperature control The system is electrically connected to the silicon carbide rods.

Preferably, the end guide rod structure includes a spring seat provided on the bottom surface of the upper pressure head support and has a compression spring, and the high-temperature-resistant guide rod whose top is provided at the bottom end of the compression spring, and the spring The outer side of the seat is provided with a guide slot along the axial direction, and the upper end of the high-temperature-resistant guide rod is provided with a transverse pressure plate, which is slidably inserted in the guide slot and used for detection with the corresponding displacement gauge. The two high-temperature-resistant guide rods are respectively arranged to face the strip-shaped protrusions on the high-temperature-resistant lower pressure head; the structure of the middle guide rod includes the lever, the high-temperature-resistant guide rod and extension spring located at the inner end of the lever, the upper and lower ends of the extension spring are respectively fixed on the outer end of the lever and the upper pressure plate, and the outer end of the lever is Correspondingly, the detection part of the displacement meter is press-fitted.

Preferably, the pushing device also includes a high-temperature-resistant guide rail arranged on the inner surface of the bottom plate of the high-temperature furnace and perpendicular to the furnace door, a push rod slidingly inserted on the side wall of the high-temperature furnace, and driving the push rod to reciprocate The power source, the bottom of the high temperature resistant block is provided with a chute that slides with the high temperature resistant guide rail, and the push rod is used to push the high temperature resistant block to slide on the high temperature resistant slide rail.

Preferably, the power source includes a motor bracket and a motor arranged on the motor bracket, the motor bracket includes two horizontally arranged lead screws arranged on the rear side of the high-temperature furnace, and the motor and the lead screw on the lead screw The female drive is connected, and there is a scale beside the lead screw.

Preferably, it also includes a computer, the computer is connected with the displacement meter collection box for collecting the displacement signal of the displacement meter collection box, and the computer is connected with the control box of the testing machine so as to control the loading power source through the control box of the testing machine Apply an upward force to the lower platen and receive a load signal fed back from the control box of the testing machine.

Compared with the prior art, the utility model has substantive features and progress. Specifically, the high-temperature bending test machine for concrete materials skillfully combines the heating equipment and loading equipment of the concrete test, and is supplemented by a displacement acquisition device, forming a usable A comprehensive test system for bending tests of concrete specimens at high temperatures. The high-temperature furnace is supported between the upper and lower pressure plates by the high-temperature furnace. Upper and lower perforations and guide holes are set on the high-temperature furnace to make the high-temperature-resistant The indenter and the high-temperature-resistant guide rod can go deep into the high-temperature furnace, realizing the synchronization of heating and loading, and can truly simulate the real environment of concrete in high-temperature fires. It solves the problem of not being able to use displacement measurement to measure the deformation of concrete specimens in a high-temperature environment; the test results obtained from the high-temperature bending test of concrete materials by this high-temperature bending test machine for concrete materials are consistent with the actual bending of concrete in high-temperature fires The properties are very close, which provides a guarantee for the study of high temperature and fire resistance of concrete materials.

Furthermore, the upper part of the column is provided with threads, and the crossbeam can move up and down and be positioned by cooperating with the threads of the column. The structure is simple and the use is very convenient.

Furthermore, the heating equipment also includes a temperature control system and a temperature sensor installed in the high-temperature furnace, which can set the temperature according to the demand and automatically maintain the set temperature.

Furthermore, the push device enables the high-temperature-resistant block in the high-temperature furnace to move back and forth, so as to achieve the purpose of heating up three concrete specimens at a high temperature in turn, which meets the requirements of Group 1 specified in the standard for concrete mechanical performance test methods. Requirements for 3 specimens for bending test.

Furthermore, the guide rod structure cleverly converts the movement of the high-temperature-resistant guide rod into the movement of the detection part of the displacement gauge, so that the displacement gauge can be installed outside the high-temperature furnace, preventing the displacement gauge from being damaged or affected by high temperature and affecting the measurement accuracy .

Further, the power source includes a motor bracket and a motor arranged on the motor bracket, the motor bracket includes two horizontally arranged lead screws arranged on the rear side of the high-temperature furnace, and the motor is drivingly connected to the screw nut on the lead screw , It is very convenient for the motor to move on the lead screw, and there is a scale beside the lead screw to monitor the distance moved by the motor and the push rod.

Furthermore, the information connection between the computer and the displacement meter collection box is used to collect the displacement signal of the displacement meter collection box, and the computer is connected with the control box of the testing machine so that the loading power source is controlled by the control box of the testing machine to apply an upward force to the lower platen and receive The load signal fed back by the control box of the testing machine.

Description of drawings

Fig. 1 is a front structural schematic diagram of a high-temperature medium-bending testing machine in an embodiment of the utility model.

Fig. 2 is a side view structural schematic diagram of the high-temperature medium bending testing machine in the embodiment of the utility model.

Fig. 3 is an enlarged view of Fig. 1A.

detailed description

The technical solutions of the present invention will be further described in detail through specific implementation methods below.

High-temperature bending test machine for concrete materials, as shown in Figures 1 to 3, includes loading equipment for applying pressure to concrete specimens, heating equipment for heating concrete specimens, and displacement for measuring the deformation of concrete specimens The collection device and the pushing device used to push the concrete specimen to move toward the furnace mouth; the loading device includes a base 6, a column 7 fixed on the base 6, a crossbeam 9 arranged on the column 7 and moving up and down along the column 7 and positioned , the upper pressure plate 10 fixed on the bottom of the beam, the high temperature resistant upper pressure head fixed on the bottom of the upper pressure plate, the lower pressure plate 11 located on the base 6, the high temperature resistant lower pressure head located on the lower pressure plate 11, and the lower pressure head located on the lower pressure plate The high temperature-resistant pad 18 on the indenter and the loading power source for applying upward force to the lower pressure plate 11, the lower end of the high-temperature-resistant upper indenter is provided in parallel with two strips for applying downward pressure on the middle of the concrete specimen. Convex portion 32, two strip-shaped convex portions 21 for applying upward pressure on the two ends of the concrete specimen are arranged in parallel on the upper end of the high-temperature resistant pad 18, the strip-shaped convex portion 32 on the high-temperature resistant upper pressure head and the high-temperature resistant pad The strip-shaped protrusions 21 on the block 18 are arranged in parallel and jointly form four fulcrums for applying force to the concrete specimen 20; the upper ends of the columns 7 are connected by a cross bar 8 to increase stability, and the top of the column 7 is provided with threads. The two ends of the beam 9 are rotated with nuts (not shown in the figure), and the beam 9 is provided with a motor for driving the two nuts to rotate (not shown in the figure), and the beam 9 moves up and down by threading with the column 7 and position. The high temperature resistant upper pressure head includes an upper pressure head support 16 fixed on the upper pressure plate 10 and an upper pressure head body 14 fixed on the upper pressure head support 16, and the high temperature resistant lower pressure head includes an upper pressure head support fixed on the lower pressure plate 11 The upper lower pressure head support 17, the lower pressure head body 15 fixed on the lower pressure head support 17, the strip-shaped convex parts are respectively located on the upper pressure head body 14 and the high temperature resistant pad 18, the high temperature resistant upper pressure head And the high-temperature resistant lower pressure head is made of silicon nitride combined with silicon carbide, which has excellent properties such as high hardness, high strength, high temperature resistance and high temperature creep resistance; the heating equipment includes a high temperature furnace support frame 2, which is located in the high temperature furnace The high-temperature furnace 1 on the support frame 2, the heating element arranged in the high-temperature furnace, the temperature control system 5 and the temperature sensor 4 arranged in the high-temperature furnace, the heating element is a silicon carbide rod, specifically a U-shaped silicon carbon rod in this embodiment Rod 3, temperature control system 5 is connected to temperature sensor 4 for sampling, temperature control system 5 is electrically connected to U-shaped silicon carbon rod, temperature sensor 4 is a corundum thermocouple, and the front end of the high-temperature furnace body has a furnace door 28 for taking , put concrete test piece 20, and furnace door has 2 small round holes, observes the situation in the furnace when being used for heating and testing. The high-temperature furnace 1 is located between the upper platen 10 and the lower platen 17. The top plate of the high-temperature furnace is provided for the high-temperature-resistant upper pressure head to penetrate downward into the upper perforation inside the high-temperature furnace, and the bottom plate of the high-temperature furnace is provided for the high-temperature-resistant lower pressure head to penetrate upward. The lower piercing hole inside the high temperature furnace, the upper piercing hole and the lower piercing hole are vertically opposite to each other; the displacement acquisition device includes three displacement gauges installed on the high temperature resistant upper pressure head, and the displacement gauge acquisition device for collecting the information of the three displacement gauges. The box 23, the two end guide rod structures and the middle guide rod structure, the high temperature resistant guide rod 35 of the middle guide rod structure slides through the center hole of the high temperature resistant upper pressure head in the vertical direction and goes deep into the high temperature furnace 1. The high-temperature-resistant guide rods 24 of the end guide-rod structure go deep into the high-temperature furnace 1 from both sides of the high-temperature-resistant upper pressure head respectively, and the top of the high-temperature furnace is provided with guide holes for the high-temperature-resistant guide rods 24, 35 to pass through. Displacement gauges 22 located on both sides of the high-temperature-resistant upper pressure head are press-fitted with corresponding end guide rod structures to measure the deformation at both ends of the concrete specimen. The press fit is used to measure the deformation in the middle of the concrete specimen. The end guide rod structure includes a spring seat 30 provided on the bottom surface of the upper pressure head support 16 and having a compression spring 29 and a high temperature resistant guide rod 24 whose top is located at the bottom of the compression spring. The outer side of the spring seat 30 is along the axis. Direction is provided with guide seam, and two high-temperature-resistant guide rods 24 are opposite to the strip-shaped protrusions on the high-temperature-resistant lower pressure head respectively. In the guide seam and the transverse pressure plate 31 is used to press fit with the detection part of the corresponding displacement gauge 22. Specifically, the displacement gauge is arranged on the side walls on both sides of the upper pressure head support 16; the middle guide rod structure includes a rotating connection The lever 34 on the high-temperature-resistant upper pressure head, the high-temperature-resistant guide rod 35 and the extension spring 36 located at the inner end of the lever, the upper and lower ends of the extension spring 36 are respectively fixed on the outer end of the lever and the upper pressing plate 10, The outer end of the lever is press-fitted with the detection part of the corresponding displacement gauge 33, and the displacement gauges 22 are all grating displacement gauges. The pushing device includes a high-temperature-resistant guide rail 19 arranged on the inner surface of the bottom plate of the high-temperature furnace 1 and perpendicular to the furnace door 28, a push rod 25 slidingly inserted on the side wall of the high-temperature furnace, and a power source for driving the push rod 25 to reciprocate. The bottom of the high-temperature-resistant pad 18 is provided with a chute that is slidably matched with the high-temperature-resistant guide rail 19. The push rod is used to promote the high-temperature-resistant pad 18 to slide on the high-temperature-resistant slide rail 19. The power source includes a motor bracket 27 and a The motor 26 on the 27, the motor support includes two horizontally arranged leading screws arranged on the rear side of the high-temperature furnace, the motor is connected with the screw nut on the described leading screw, and a scale is arranged beside the leading screw. The information connection between the computer and the displacement meter collection box is used to collect the displacement signal of the displacement meter collection box, and the computer 13 is connected with the control box 12 of the testing machine so that the loading power source is controlled by the control box 12 of the testing machine to apply an upward force to the lower platen 17 and receive The load signal fed back by the testing machine control box 12 is a hydraulic cylinder as the loading power source.

The concrete material bending test machine at high temperature in this embodiment cleverly combines the heating equipment and loading equipment of the concrete test, and is supplemented by a displacement acquisition device to form a comprehensive test system that can be used for the bending test of concrete specimens at high temperature. The furnace is erected between the upper platen and the lower platen through the support of the high-temperature furnace. Upper and lower perforations and guide holes are set on the high-temperature furnace, so that the high-temperature-resistant upper and lower pressure heads and high-temperature-resistant guide rods can go deep into the interior of the high-temperature furnace. The synchronization of heating and loading can simulate the real environment of concrete in high-temperature fire, and the test results obtained from the high-temperature bending test of concrete materials by this concrete material high-temperature bending test machine are very close to the actual bending performance of concrete in high-temperature fire. It provides a guarantee for the study of high temperature and fire resistance of concrete materials. Threads are provided on the upper part of the column, and the beam can move up and down and be positioned by cooperating with the thread of the column. The structure is simple and the use is very convenient. The heating equipment also includes a temperature control system and a temperature sensor installed in the high-temperature furnace, which can set the temperature according to the demand and automatically maintain the set temperature. The push device enables the high-temperature-resistant block in the high-temperature furnace to move back and forth, so as to achieve the purpose of loading three concrete specimens at a high temperature in sequence at one time, and meets the requirements of one set of bending tests and three specimens specified in the standard for concrete mechanical performance test methods. Test piece requirements. The guide rod structure cleverly converts the movement of the high-temperature-resistant guide rod into the movement of the detection part of the displacement gauge, so that the displacement gauge can be installed outside the high-temperature furnace to prevent the displacement gauge from being damaged or affected by high temperature and affecting the measurement accuracy. The power source includes a motor bracket and a motor arranged on the motor bracket. The motor bracket includes two horizontally arranged lead screws arranged on the rear side of the high-temperature furnace. The motor is driven and connected to the nut on the lead screw. It is very convenient to move on the rod, and there is a scale next to the lead screw to monitor the distance moved by the motor and the push rod. The information connection between the computer and the displacement meter acquisition box is used to collect the displacement signal of the displacement meter acquisition box, and the computer is connected with the control box of the testing machine so that the loading power source can be controlled by the control box of the testing machine to exert an upward force on the lower platen and receive the control box of the testing machine Feedback load signal.

In other embodiments, different from the above embodiments, the beam can also be fixed by jacking screws, the high temperature resistant upper pressure head and the high temperature resistant lower pressure head have a columnar integrated structure, and the end guide rod structure is a high temperature resistant guide rod. The detection parts of the displacement gauges on both sides of the high-temperature-resistant upper pressure head are directly connected to the high-temperature-resistant guide rods; in other embodiments, different from the above-mentioned embodiments, the power source can also be an electric push rod or a pneumatic cylinder.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present utility model and not limit it; although the utility model has been described in detail with reference to the preferred embodiment, those of ordinary skill in the art should understand that: still The specific implementation of the utility model can be modified or some technical features can be equivalently replaced; without departing from the spirit of the technical solution of the utility model, all of them should be included in the scope of the technical solution claimed by the utility model.

Claims (8)

1. Bending test machine in concrete material high temperature, it is characterized in that: comprise the loading equipment that is used to apply pressure to concrete specimen, be used for heating the temperature rise equipment of concrete specimen and be used to measure the displacement collecting device of concrete specimen bending deformation amount ; The loading device includes a base, a column fixed on the base, a crossbeam arranged on the upright and moving up and down along the upright and positioned, an upper platen fixed on the bottom of the beam, and a high-temperature resistant plate fixed on the bottom of the upper platen. The pressure head, the lower pressure plate on the base, the high temperature resistant lower pressure head on the lower pressure plate, the high temperature resistant pad on the lower pressure head, and the upper pressure plate for applying upward pressure on the lower pressure plate. The loading power source of the action force, the lower end of the high-temperature-resistant upper pressure head is provided in parallel with two strip-shaped convex parts for applying pressure downward to the middle of the concrete specimen, and the upper end of the high-temperature-resistant cushion block is provided with two strip-shaped protrusions in parallel. For the strip-shaped protrusions that apply pressure upwards to the two ends of the concrete specimen, the strip-shaped protrusions on the high-temperature-resistant upper pressure head and the strip-shaped protrusions on the high-temperature-resistant pad are arranged in parallel and jointly form a Four fulcrums that exert force on the concrete specimen; The heating equipment includes a high-temperature furnace support frame, a high-temperature furnace arranged on the high-temperature furnace support frame, and a heating element arranged in the high-temperature furnace. The high-temperature furnace is located between the upper platen and the lower platen. The top plate of the high-temperature furnace is provided with the upper piercing hole for the high-temperature-resistant upper pressure head to penetrate downward into the interior of the high-temperature furnace, and the bottom plate of the high-temperature furnace is provided with the lower piercing hole for the high-temperature-resistant lower pressure head to penetrate upward into the interior of the high-temperature furnace. The upper perforation and the lower perforation are vertically opposite to each other; The displacement acquisition device includes three displacement gauges arranged on the high temperature resistant upper pressure head, a displacement gauge collection box for collecting information of the three displacement gauges, two end guide rod structures and a middle guide rod structure, The high temperature resistant guide rod of the middle guide rod structure slides through the center hole of the high temperature resistant upper pressure head in the vertical direction and goes deep into the high temperature furnace, and the high temperature resistant guide rods of the two end guide rod structures respectively slide The two sides of the high-temperature-resistant upper pressure head go deep into the high-temperature furnace downwards, and the top of the high-temperature furnace is provided with guide holes for each of the high-temperature-resistant guide rods to pass through, and the displacement gauges arranged on both sides of the high-temperature-resistant upper pressure head The pressure fit with the corresponding end guide rod structure is used to measure the deformation at both ends of the concrete specimen, and the displacement gauge arranged on the upper pressure plate is press fit with the middle guide rod structure to measure the deformation of the concrete specimen. Deformation in the middle of the specimen. 2. The high temperature medium bending test machine for concrete materials according to claim 1, characterized in that: the high temperature resistant upper indenter includes an upper indenter support fixed on the upper platen and an upper indenter fixed on the upper platen. The upper pressure head body on the pressure head support, the high temperature resistant lower pressure head includes the lower pressure head support fixed on the lower pressure plate and the lower pressure head body fixed on the lower pressure head support , and the corresponding strip-shaped convex portion is located on the upper indenter body. 3. The bending testing machine for concrete material at high temperature according to claim 1, characterized in that: the upper part of the column is provided with threads, the two ends of the beam are rotated with nuts, and the beam is provided with screws for driving two The nut is rotated by a motor, and the crossbeam moves up and down and is positioned through the threaded cooperation with the column. 4. The bending testing machine for concrete material at high temperature according to claim 1, characterized in that: the heating device also includes a temperature control system and a temperature sensor arranged in the high temperature furnace, and the heating element is a silicon carbide rod , the temperature control system is connected to the temperature sensor for sampling, and the temperature control system is electrically connected to the silicon carbide rod. 5. The bending test machine for concrete material at high temperature according to claim 1, characterized in that: the end guide rod structure includes a spring seat provided on the bottom surface of the upper pressure head support and has a compression spring and a top The high-temperature-resistant guide rod arranged at the bottom end of the pressure spring, the outer side of the spring seat is provided with a guide seam along the axial direction, and the upper end of the high-temperature-resistant guide rod is provided with a transverse pressure plate, and the transverse pressure plate is slidably inserted In the guide slot and the transverse pressure plate is used to press fit with the detection part of the corresponding displacement gauge, and the two high-temperature-resistant guide rods are respectively arranged opposite to the strip-shaped protrusions on the high-temperature-resistant lower pressure head; The middle guide rod structure includes a lever that is rotatably connected to the high-temperature-resistant upper pressure head, the high-temperature-resistant guide rod and a tension spring arranged at the inner end of the lever, and the upper and lower ends of the tension spring are respectively fixed on the The outer end of the lever is on the upper pressing plate, and the outer end of the lever is press-fitted with the detection part of the corresponding displacement gauge. 6. The bending testing machine for concrete material at high temperature according to claim 1, characterized in that: it also includes a pushing device including a high-temperature-resistant guide rail, a sliding insert, which is arranged on the inner surface of the bottom plate of the high-temperature furnace and is perpendicular to the furnace door. The push rod provided on the side wall of the high-temperature furnace and the power source for driving the push rod to reciprocate, the bottom of the high-temperature resistant pad is provided with a chute that slides and fits with the high-temperature-resistant guide rail, and the push rod is used for Push the high-temperature-resistant pad to slide on the high-temperature-resistant slide rail. 7. The bending testing machine for concrete material at high temperature according to claim 6, characterized in that: the power source includes a motor bracket and a motor mounted on the motor bracket, and the motor bracket includes a motor mounted on the rear side of the high-temperature furnace. There are two horizontally arranged lead screws, the motor is driven and connected to the screw nut on the lead screws, and a scale is arranged beside the lead screws. 8. The high-temperature bending testing machine for concrete material according to claim 7, characterized in that: it also includes a computer, and the computer is connected with the displacement meter collection box information to collect the displacement signal of the displacement meter collection box. The computer is connected to the control box of the testing machine so as to control the loading power source to exert upward force on the lower platen through the control box of the testing machine and receive the load signal fed back by the control box of the testing machine.