Concrete gas permeability testing system

Abstract

The invention relates to the technical field of concrete testing, and discloses a concrete gas permeability testing system which comprises a placement base, a fixed seat arranged on one side of one end of the top of the placement base, and a testing container shell arranged on the top of the fixed seat, the limiting ring seats are arranged on the two sides of the testing container shell, and one end of each limiting ring seat extends to an inner cavity of the testing container shell. According to the concrete gas permeability testing system, the buffer gas tank is used for providing pressure intensity and detecting the gas pressure of the test piece penetrating through the test piece, so that the gas permeability rule of the large concrete centimeter-level test piece under different confining pressures and gas pressures is accurately obtained, and meanwhile, the operation steps and time cost of an experiment are greatly saved; therefore, the working efficiency is improved, and more test tasks can be completed in a shorter time in practical application, so that the progress of an engineering project is accelerated.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete testing, and particularly to a concrete gas permeability testing system. Background Art

[0002] Concrete, as a commonly used building material, is widely used in fields such as construction and transportation. Its cumulative usage amount increases year by year. The durability and sealing problems of concrete are both caused by the transfer and exchange of harmful substances through its pore structure. Therefore, it is necessary to conduct in-depth research and exploration on the mass transfer performance of concrete, that is, the permeability of concrete, in order to seek fundamental measures to improve the durability and sealing of concrete. As one of the external corrosive media, gases such as oxygen (O2) and carbon dioxide (CO2) have an impact on the durability of cement-based materials. At the same time, when using inert gases such as nitrogen (N2) as the seepage medium, since it does not react chemically with concrete, the permeability of concrete can be effectively maintained constant throughout the test process. This seepage process and the measured permeability can more accurately reflect the resistance of the pore structure of cement-based materials to the intrusion of external media. Therefore, gas permeability is an important parameter for measuring the durability of cement-based materials.

[0003] However, the current laboratory operation methods generally use the constant pressure test method or the variable pressure test method. The current methods have relatively complex test procedures, take a long time to obtain data, have a large experimental difficulty, and a large investment cost. Summary of the Invention

[0004] In view of the problems of the current laboratory operation methods generally using the constant pressure test method or the variable pressure test method, with relatively complex test procedures, taking a long time to obtain data, having a large experimental difficulty, and a large investment cost, the present invention is proposed.

[0005] Therefore, the object of the present invention is to provide a concrete gas permeability testing system, which aims to: accurately obtain the gas permeability law of large concrete specimens with centimeter-level dimensions under different confining pressures and gas pressures, while saving the experimental operation steps and time costs, and improving work efficiency.

[0006] To solve the above technical problems, the present invention provides the following technical solution: A concrete gas permeability testing system, including a placement base, further including a fixing base provided on one side of one end of the top of the placement base, a testing container housing provided on the top of the fixing base, limiting ring seats provided on both sides of the testing container housing, and one end of the limiting ring seat extending into the inner cavity of the testing container housing, a testing cylinder provided in the inner cavity of the testing container housing, and the testing cylinder being connected to one end of the two groups of limiting ring seats close to each other, a snap-in plug provided in the inner cavity of one group of the limiting ring seats, and one end of the snap-in plug extending into the inner cavity of the testing cylinder, a free-end plug provided in the inner cavity of the other group of the limiting ring seats, and one end of the free-end plug extending into the inner cavity of the testing cylinder, and a test piece provided in the inner cavity of the testing cylinder and located between the snap-in plug and the free-end plug.

[0007] As a preferred solution of the concrete gas permeability testing system of the present invention, wherein: a plug lengthening pad is provided in the inner cavity of the testing cylinder between the test piece and the free-end plug, and a seventh connecting pipe is provided on one side of the plug lengthening pad, and the seventh connecting pipe penetrates through the plug lengthening pad.

[0008] As a preferred solution of the concrete gas permeability testing system of the present invention, wherein: a buffer gas tank is provided on one side of one end of the top of the placement base far from the testing container housing, a buffer gas tank intake end is provided on the top of the buffer gas tank, a buffer gas tank exhaust end is provided on the bottom of the buffer gas tank, a gas storage tank is provided on one side of one end of the top of the placement base close to the buffer gas tank, and a gas storage tank exhaust end is provided on the bottom of the gas storage tank.

[0009] As a preferred solution of the concrete gas permeability testing system of the present invention, wherein: one end of the gas storage tank exhaust end is connected to a first connecting pipe, a first valve is provided at one end of the first connecting pipe far from the gas storage tank exhaust end, and the output end of the first valve is connected to the buffer gas tank intake end;

[0010] A second connecting pipe is provided at one end of the buffer gas tank exhaust end, a second valve is provided at one end of the second connecting pipe far from the buffer gas tank exhaust end, a third connecting pipe is provided at the output end of the second valve, a third valve is provided at one end of the third connecting pipe far from the second valve, and a pressure display is provided on the surface of the second connecting pipe.

[0011] As a preferred embodiment of the concrete gas permeability testing system of the present invention, one end of the snap-in plug is provided with a fourth connecting pipe, and the fourth connecting pipe penetrates through the snap-in plug. One end of the fourth connecting pipe is connected to the output end of the third valve. A fifth connecting pipe is arranged in the inner cavity of the free-end plug, and the fifth connecting pipe is formed in an L shape. Both ends of the fifth connecting pipe extend to the outside of the free-end plug. A fifth valve is arranged at one end of the fifth connecting pipe.

[0012] As a preferred embodiment of the concrete gas permeability testing system of the present invention, an installation sleeve is arranged on one side of the outer shell of the test container. One end of the free-end plug extends into the inner cavity of the installation sleeve. A limiting through hole is arranged at the top of the installation sleeve, and the limiting through hole is in communication with the inner cavity of the installation sleeve. One end of the fifth connecting pipe extends to the outside of the installation sleeve through the limiting through hole;

[0013] A threaded rod is arranged on the side of the free-end plug away from the limiting ring seat, and one end of the threaded rod away from the free-end plug extends to the outside of the installation sleeve. A rotating handle is arranged on the threaded rod outside the installation sleeve.

[0014] As a preferred embodiment of the concrete gas permeability testing system of the present invention, an oil pump is arranged at one end of the top of the placement base away from the gas storage tank. An output end of the oil pump is arranged on one side of the oil pump. A fourth valve is arranged at one end of the output end of the oil pump. A sixth connecting pipe is arranged at the output end of the fourth valve. One end of the sixth connecting pipe away from the fourth valve is inserted into the top of the outer shell of the test container and is in communication with the outer shell of the test container.

[0015] As a preferred embodiment of the concrete gas permeability testing system of the present invention, the test result is mainly based on the change of the inlet-end pressure, and the effective permeability of the gas is obtained according to Darcy's law. The formula for the effective permeability is:

[0016]

[0017] Among them, \(k_{gas}\) is the effective permeability, \(\mu\) is the gas viscosity coefficient, \(V_0\) is the volume of the buffer cylinder, \(A\) is the cross-sectional area of the specimen, \(h\) is the height of the specimen, and \(\Delta P\) is the change in the inlet-end pressure; the average pressure in the buffer bottle Among them, \(P_1\) is the pressure in the buffer bottle, and \(P_0\) is the atmospheric pressure.

[0018] To achieve the above object, the present invention provides the following technical solution: A testing method for a concrete gas permeability testing system, including the following steps:

[0019] Step 1, use a vernier caliper to measure the diameter \(d\) and height \(h\) of the rock specimen;

[0020] Step 2: Then install the test container housing, connect the connecting pipes, and ensure that all valves are closed.

[0021] Step 3: Open the sixth connecting pipe to allow the oil pump to provide the confining pressure Pc inside the test container housing.

[0022] Step 4: Open the first valve to fill the buffer gas tank with nitrogen gas and provide a pressure (less than Pc), and then close the first valve.

[0023] Step 5: Open the second valve to allow nitrogen gas to fill the second and third connecting pipes. After the air pressure stabilizes, open the third and fifth valves. After the air pressure reduction value stabilizes regularly, record the air pressure P and time t of the air pressure display.

[0024] Step 6: Continuously record the air pressure P and time t of the air pressure display until the recording is stopped and the second valve is closed.

[0025] Step 7: When there is no gas pressure in the second, third, fourth, and fifth connecting pipes, close the third and fifth valves, and at the same time open the fourth valve to unload the confining pressure.

[0026] Step 8: After the confining pressure inside the test container housing recedes, the snap-in plug can be opened to take out the test piece.

[0027] Advantages of the present invention:

[0028] In the present invention, by providing pressure through the buffer gas tank and detecting the air pressure of the test piece passing through the test piece, not only can the gas seepage law of large concrete centimeter-level test pieces under different confining pressures and gas pressures be accurately obtained, but also the experimental operation steps and time costs are greatly saved, the work efficiency is improved. Furthermore, in practical applications, more test tasks can be completed in a shorter time, thus accelerating the progress of engineering projects. At the same time, the test system of the present invention selects inert gas nitrogen as the seepage medium. Since it does not chemically react with concrete, the permeability of concrete can be effectively maintained constant throughout the test process. This not only ensures the accuracy of the test results but also avoids the potential impact of chemical reactions on the environment. In contrast, traditional test methods may use other gases or chemical reagents, which may cause environmental pollution. Therefore, the test system of the present invention is more environmentally friendly. Description of the drawings

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings. Among them:

[0030] Figure 1 It is a schematic diagram of the main stereoscopic structure of the concrete gas permeability testing system of the present invention.

[0031] Figure 2 It is a side view stereoscopic structural schematic diagram of the concrete gas permeability testing system of the present invention.

[0032] Figure 3 It is a schematic diagram of the back view of the three-dimensional structure of the concrete gas permeability testing system of the present invention.

[0033] Figure 4 It is a schematic diagram of the cross-sectional three-dimensional structure of the concrete gas permeability testing system of the present invention.

[0034] Description of reference numerals:

[0035] 1. Gas storage tank; 2. First valve; 3. Buffer gas tank; 4. Air pressure display; 5. Second valve; 6. Third valve; 7. Oil pump; 8. Snap-on plug; 9. Plug extension pad; 10. Fourth valve; 11. Test piece; 12. Test container shell; 13. Fixed seat; 14. Placement base; 15. Free end plug; 16. Fifth valve; 17. Gas storage tank exhaust end; 18. First connecting pipe; 19. Buffer gas tank inlet end; 20. Buffer gas tank exhaust end; 21. Second connecting pipe; 22. Third connecting pipe; 23. Fourth connecting pipe; 24. Limiting ring seat; 25. Test tube; 26. Fifth connecting pipe; 27. Sixth connecting pipe; 28. Oil pump output end; 29. ​​Seventh connecting pipe; 30. Mounting sleeve; 31. Threaded rod; 32. Rotating handle; 33. Limiting port. DETAILED DESCRIPTION

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0037] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0038] Reference Figures 1-4, which is an embodiment of the present invention, provides a concrete gas permeability testing system. This concrete gas permeability testing system includes a placement base 14, and further includes a fixing base 13 fixedly installed on one side at one end of the top of the placement base 14, a test container housing 12 installed on the top of the fixing base 13, limiting ring seats 24 installed on both sides of the test container housing 12, and one end of the limiting ring seat 24 extends into the inner cavity of the test container housing 12. A test cylinder 25 is arranged in the inner cavity of the test container housing 12, and the test cylinder 25 is connected to one end of the two groups of limiting ring seats 24 that are close to each other. A snap-in plug 8 is sleeved in the inner cavity of one group of limiting ring seats 24, and one end of the snap-in plug 8 extends into the inner cavity of the test cylinder 25. A free-end plug 15 is sleeved in the inner cavity of the other group of limiting ring seats 24, and one end of the free-end plug 15 extends into the inner cavity of the test cylinder 25, and a test piece 11 is arranged in the inner cavity of the test cylinder 25 and located between the snap-in plug 8 and the free-end plug 15.

[0039] A plug lengthening cushion block 9 is arranged in the inner cavity of the test cylinder 25 between the test piece 11 and the free-end plug 15, and a seventh connecting pipe 29 is connected to one side of the plug lengthening cushion block 9, and the seventh connecting pipe 29 penetrates through the plug lengthening cushion block 9.

[0040] On one side at one end of the top of the placement base 14 far from the test container housing 12, a buffer gas tank 3 is fixedly installed. The buffer gas tank 3 is used to provide pressure for the permeability test. A buffer gas tank intake end 19 is installed on the top of the buffer gas tank 3, a buffer gas tank exhaust end 20 is arranged at the bottom of the buffer gas tank 3, a gas storage tank 1 is fixedly installed on one side at one end of the top of the placement base 14 close to the buffer gas tank 3. The gas storage tank 1 is used to provide nitrogen for the buffer gas tank 3 to provide stable and controllable air pressure for the gas test, and a gas storage tank exhaust end 17 is arranged at the bottom of the gas storage tank 1.

[0041] One end of the gas storage tank exhaust end 17 is connected to a first connecting pipe 18, a first valve 2 is arranged at one end of the first connecting pipe 18 far from the gas storage tank exhaust end 17, and the output end of the first valve 2 is connected to the buffer gas tank intake end 19;

[0042] A second connecting pipe 21 is arranged at one end of the buffer gas tank exhaust end 20, a second valve 5 is arranged at one end of the second connecting pipe 21 far from the buffer gas tank exhaust end 20, a third connecting pipe 22 is arranged at the output end of the second valve 5, a third valve 6 is arranged at one end of the third connecting pipe 22 far from the second valve 5, and a gas pressure display 4 is arranged on the surface of the second connecting pipe 21. The gas pressure display 4 is used to test the gas pressure of the buffer gas tank.

[0043] One end of the snap-in plug 8 is provided with a fourth connecting pipe 23, and the fourth connecting pipe 23 penetrates through the snap-in plug 8. One end of the fourth connecting pipe 23 is connected to the output end of the third valve 6. A fifth connecting pipe 26 is arranged in the inner cavity of the free-end plug 15, and the fifth connecting pipe 26 is formed in an L shape. Both ends of the fifth connecting pipe 26 extend to the outside of the free-end plug 15. A fifth valve 16 is arranged at one end of the fifth connecting pipe 26, which is used to provide confining pressure to the specimen 11, limit the horizontal movement, and prevent a large gap between the snap-in plug 8 and the free-end plug 15 and the specimen 11.

[0044] An installation sleeve 30 on one side of the test container housing 12. One end of the free-end plug 15 extends into the inner cavity of the installation sleeve 30. A limit through-port 33 is arranged at the top of the installation sleeve 30, and the limit through-port 33 is in communication with the inner cavity of the installation sleeve 30. One end of the fifth connecting pipe 26 extends to the outside of the installation sleeve 30 through the limit through-port 33;

[0045] A threaded rod 31 is arranged on the side of the free-end plug 15 away from the limit ring seat 24, and one end of the threaded rod 31 away from the free-end plug 15 extends to the outside of the installation sleeve 30, and a rotary handle 32 is arranged on the threaded rod 31 outside the installation sleeve 30.

[0046] One end of the placement base 14 at the top away from the gas storage tank 1 is provided with an oil pump 7. The oil pump 7 is used to provide confining pressure Pc in the test container housing 12. An oil pump output end 28 is arranged on one side of the oil pump 7. A fourth valve 10 is arranged at one end of the oil pump output end 28. A sixth connecting pipe 27 is arranged at the output end of the fourth valve 10, and one end of the sixth connecting pipe 27 away from the fourth valve 10 is inserted into the top of the test container housing 12 and is in communication with the test container housing 12.

[0047] The test results are mainly based on the change of the inlet-end pressure, and the effective permeability of the gas is obtained according to Darcy's law. The effective permeability formula:

[0048]

[0049] Among them, k_gas is the effective permeability, μ is the gas viscosity coefficient, V0 is the volume of the buffer steel cylinder, A is the cross-sectional area of the specimen, h is the height of the specimen, and ΔP is the change amount of the inlet-end pressure; the average pressure in the buffer bottle Among them, P1 is the pressure in the buffer bottle, and P0 is the atmospheric pressure.

[0050] A test method for a concrete gas permeability test system includes the following steps,

[0051] Step 1, use a vernier caliper to measure the diameter d and height h of the rock specimen;

[0052] Step 2: Then install the test container housing 12 and connect the connecting pipes, and ensure that all valves are closed.

[0053] Step 3: Open the sixth connecting pipe 27 to allow the oil pump 7 to provide the confining pressure Pc inside the test container housing 12.

[0054] Step 4: Open the first valve 2 to fill the buffer gas tank 3 with nitrogen gas and provide a pressure less than Pc, and then close the first valve 2.

[0055] Step 5: Open the second valve 5 to allow the nitrogen gas to fill the second connecting pipe 21 and the third connecting pipe 22. After the air pressure is stable, open the third valve 6 and the fifth valve 16. After the law of the air pressure decrease value is stable, record the air pressure P1 and the time t1 of the air pressure display 4.

[0056] Step 6: Continuously record until the air pressure P2 and the time t2 of the air pressure display 4, stop recording and close the second valve 5.

[0057] Step 7: When there is no gas pressure in the second connecting pipe 21, the third connecting pipe 22, the fourth connecting pipe 23 and the fifth connecting pipe 26, close the third valve 6 and the fifth valve 16, and at the same time open the fourth valve 10 to unload the confining pressure.

[0058] Step 8: After the confining pressure inside the test container housing 12 recedes, the snap-in plug 8 can be opened to take out the test piece 11.

[0059] During the use process, first, the snap-in plug 8 can be removed by canceling the fixation. Then, the test piece 11 can be placed into the inner cavity of the test cylinder 25. Then, the snap-in plug 8 can be put back into the test cylinder 25 and fixed, so as to block and limit the test piece 11. Then, the rotating handle 32 can be rotated to drive the threaded rod 31 to rotate, and then the horizontal end of the free-end plug 15 can be made, so as to drive the plug extension pad 9 to approach the test piece 11, which can limit the horizontal movement of the test piece 11 and prevent a large gap between the snap-in plug 8 and the plug extension pad 9 and the test piece 11.

[0060] Then start the oil pump 7 and open the fourth valve 10. The confining pressure Pc can be provided to the inside of the test container housing 12 through the sixth connecting pipe 27. Then, open the first valve 2. Then, the nitrogen gas in the gas storage tank 1 enters the buffer gas tank 3 through the first connecting pipe 18. When the pressure is continuously provided in the buffer gas tank 3 and is less than Pc, close the first valve 2. Then, open the second valve 5 to allow the nitrogen gas to fill the second connecting pipe 21 and the third connecting pipe 22 from the buffer gas tank 3. Then, when the air pressure is stable, open the third valve 6 and the fifth valve 16. At this time, the nitrogen gas will pass through the fourth connecting pipe 23, then pass through the test piece 11, and then pass through the seventh connecting pipe 29 and be transferred to the fifth connecting pipe 26, and then be discharged from one end of the fifth connecting pipe 26. When the law of the air pressure decrease value is stable, record the air pressure P1 of the air pressure display 4 and the time t1;

[0061] After the recording is completed, close the second valve 5. Then, when there is no air pressure in the third connecting pipe 22, the fourth connecting pipe 23, the seventh connecting pipe 29, and the fifth connecting pipe 26, close the third valve 6 and the fifth valve 16, and at the same time open the fourth valve 10 to unload the confining pressure inside the test container housing 12. When the confining pressure is completely removed, the buckle plug 8 can be opened to take out the test piece 11.

[0062] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A concrete gas permeability testing system, comprising a placement base (14), characterized in that: It further includes a fixing seat (13) arranged on one side at one end of the top of the placing base (14), a test container housing (12) arranged on the top of the fixing seat (13), limiting ring seats (24) arranged on both sides of the test container housing (12), and one end of the limiting ring seat (24) extends into the inner cavity of the test container housing (12), a test cylinder (25) arranged in the inner cavity of the test container housing (12), and the test cylinder (25) is connected to one end of the two groups of limiting ring seats (24) close to each other, a snap-in plug (8) arranged in the inner cavity of one group of the limiting ring seats (24), and one end of the snap-in plug (8) extends into the inner cavity of the test cylinder (25), a free-end plug (15) arranged in the inner cavity of the other group of the limiting ring seats (24), and one end of the free-end plug (15) extends into the inner cavity of the test cylinder (25), and a test piece (11) arranged in the inner cavity of the test cylinder (25) and located between the snap-in plug (8) and the free-end plug (15).

2. The concrete gas permeability test system according to claim 1, wherein: A plug lengthening cushion block (9) arranged in the inner cavity of the test cylinder (25) and located between the test piece (11) and the free-end plug (15), and a seventh connecting pipe (29) arranged on one side of the plug lengthening cushion block (9), and the seventh connecting pipe (29) penetrates through the plug lengthening cushion block (9).

3. The concrete gas permeability testing system according to claim 2, wherein: A buffer air tank (3) is arranged on one side at one end of the top of the placing base (14) far from the test container housing (12), a buffer air tank air inlet end (19) is arranged on the top of the buffer air tank (3), a buffer air tank air outlet end (20) is arranged on the bottom of the buffer air tank (3), an air storage tank (1) is arranged on one side at one end of the top of the placing base (14) close to the buffer air tank (3), and an air storage tank air outlet end (17) is arranged on the bottom of the air storage tank (1).

4. The concrete gas permeability testing system according to claim 3, wherein: One end of the air storage tank air outlet end (17) is connected with a first connecting pipe (18), a first valve (2) is arranged at one end of the first connecting pipe (18) far from the air storage tank air outlet end (17), and the output end of the first valve (2) is connected with the buffer air tank air inlet end (19); A second connecting pipe (21) is arranged at one end of the buffer air tank air outlet end (20), a second valve (5) is arranged at one end of the second connecting pipe (21) far from the buffer air tank air outlet end (20), a third connecting pipe (22) is arranged at the output end of the second valve (5), a third valve (6) is arranged at one end of the third connecting pipe (22) far from the second valve (5), and a pressure display (4) is arranged on the surface of the second connecting pipe (21).

5. The concrete gas permeability test system according to claim 4, wherein: One end of the snap-in plug (8) is provided with a fourth connecting pipe (23), and the fourth connecting pipe (23) penetrates through the snap-in plug (8). One end of the fourth connecting pipe (23) is connected to the output end of the third valve (6). A fifth connecting pipe (26) is arranged in the inner cavity of the free-end plug (15), and the fifth connecting pipe (26) is in an L shape. Both ends of the fifth connecting pipe (26) extend to the outside of the free-end plug (15). A fifth valve (16) is arranged at one end of the fifth connecting pipe (26).

6. The concrete gas permeability testing system according to claim 5, characterized in that: An installation sleeve (30) on one side of the test container housing (12). One end of the free-end plug (15) extends into the inner cavity of the installation sleeve (30). A limit through-hole (33) is arranged at the top of the installation sleeve (30), and the limit through-hole (33) is in communication with the inner cavity of the installation sleeve (30). One end of the fifth connecting pipe (26) extends to the outside of the installation sleeve (30) through the limit through-hole (33); A threaded rod (31) is arranged on the side of the free-end plug (15) away from the limit ring seat (24), and one end of the threaded rod (31) away from the free-end plug (15) extends to the outside of the installation sleeve (30), and a rotary handle (32) is arranged on the threaded rod (31) outside the installation sleeve (30).

7. The concrete gas permeability test system according to claim 6, wherein: One end of the top of the placement base (14) away from the gas storage tank (1) is provided with an oil pump (7). An oil pump output end (28) is arranged on one side of the oil pump (7). A fourth valve (10) is arranged at one end of the oil pump output end (28). A sixth connecting pipe (27) is arranged at the output end of the fourth valve (10), and one end of the sixth connecting pipe (27) away from the fourth valve (10) is inserted into the top of the test container housing (12) and is in communication with the test container housing (12).

8. The concrete gas permeability testing system according to claim 7, wherein: The test results are mainly based on the change of the inlet-end pressure, and the effective permeability of the gas is obtained according to Darcy's law. The formula for effective permeability: Among them, k_gas is the effective permeability, μ is the gas viscosity coefficient, V_0 is the volume of the buffer cylinder, A is the cross-sectional area of the specimen, h is the height of the specimen, and ΔP is the change in pressure at the inlet end; the average pressure in the buffer cylinder where P_1 is the pressure in the buffer cylinder and P_0 is the atmospheric pressure.

9. A testing method for a concrete gas permeability testing system, which is applied to the concrete gas permeability testing system described in claim 8, and is characterized in that: It includes the following steps Step 1: Use a vernier caliper to measure the diameter d and height h of the rock specimen; Step 2: Then install the test container housing (12), connect the connecting pipes, and ensure that all valves are closed; Step 3: Open the sixth connecting pipe (27) to let the oil pump (7) provide the confining pressure Pc inside the test container housing (12); Step 4: Open the first valve (2) to fill the buffer gas tank (3) with nitrogen gas and provide a pressure (less than Pc), and then close the first valve (2); Step 5: Open the second valve (5) to let the nitrogen gas fill the second connecting pipe (21) and the third connecting pipe (22). After the air pressure is stable, open the third valve (6) and the fifth valve (16). After the air pressure reduction value is stable and regular, record the air pressure P1 and time t1 of the air pressure display (4); Step 6: Continuously record until the air pressure P2 and time t2 of the air pressure display (4), stop recording and close the second valve (5); Step 7: When there is no gas pressure in the second connecting pipe (21), the third connecting pipe (22), the fourth connecting pipe (23), and the fifth connecting pipe (26), close the third valve (6) and the fifth valve (16), and at the same time open the fourth valve (10) to unload the confining pressure; Step 8: After the confining pressure in the outer shell (12) of the test container has retreated, the snap plug (8) can be opened to take out the test piece (11).

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