CN111855527A - Device and method for detecting gas permeability of damaged concrete - Google Patents

Abstract

The invention discloses a damaged concrete gas permeability detection device, comprising a nitrogen tank connected by a first pressure-bearing hose and a damaged concrete gas penetration detector. The damaged concrete gas penetration detector is connected with a flowmeter through the pressure-bearing hose. The detection device of the invention solves the problem of the gas permeability after detecting the damage of the existing concrete, and can realize the gas permeability detection of the damaged concrete. The invention also provides a method for detecting the gas permeability of damaged concrete. Compared with the existing gas permeation method, the method of the invention can measure the air permeability of damaged concrete, requires small test specimens, and can detect the gas permeation performance of damaged concrete of various ages and strengths.

Description

Device and method for detecting gas permeability of damaged concrete

technical field

The invention belongs to the technical field of concrete durability detection devices, in particular to a damaged concrete gas permeability detection device, and also to a damaged concrete gas permeability detection method.

Background technique

Impermeability, as an important index for evaluating the durability of concrete, has produced test methods such as water permeation, gas permeation and ion permeation. For the realization of concrete structures, the secondary hydration will change the internal structure of concrete when using the water infiltration method to test, resulting in inaccurate measurement results, which cannot meet the needs of high-performance concrete quality control and evaluation; the ion infiltration method is mainly used for Detect chloride corrosion, but the test piece needs to be immersed in the solution, which will also be affected by secondary hydration, and at the same time it is difficult to simulate the real environmental characteristics of concrete structures; the gas permeation method is used to overcome the effects of hydration. It is not affected by the environment and is not limited by the environment, and the test can be completed by drilling core samples in the concrete structure. At present, the concrete gas infiltration detection technology based on the Cembureau method and the air pressure difference method at home and abroad has the advantages of high detection accuracy and convenient operation.

For the prior art, the general detection method for the gas permeability of concrete is non-destructive testing, that is, the concrete specimen is intact. However, during the long-term service of concrete, under the action of the external environment and load, cracks will occur on the surface and even the interior of the concrete, resulting in damage to the concrete. Therefore, this method is no longer suitable for testing the permeability of concrete with damage. Therefore, it is necessary to develop a new method. A set of devices suitable for testing the gas permeability of damaged concrete.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a gas permeability detection device for damaged concrete, which solves the problem of gas permeability after detection of existing concrete damage, and can realize the gas permeability detection of damaged concrete.

Another object of the present invention is to provide a method for detecting gas permeability of damaged concrete.

The technical scheme adopted in the invention is that a damaged concrete gas permeability detection device includes a nitrogen tank connected by a first pressure-bearing hose and a damaged concrete gas penetration detector, and the damaged concrete gas penetration detector passes through the pressure-bearing hose. A flow meter is connected.

The present invention is also characterized in that,

A pressure reducing valve, a first cut-off valve and a pressure gauge are sequentially arranged on the first pressure-bearing hose between the nitrogen tank and the damaged concrete gas penetration detector.

A second shut-off valve is arranged on the second pressure-bearing hose between the damaged concrete gas penetration detector and the flowmeter; a flowmeter support frame is also arranged under the second pressure-bearing hose to support the flowmeter.

The flowmeter is a digital gas flowmeter.

The damaged concrete gas permeation detector includes an annular sleeve, the top and bottom edges of the annular sleeve are provided with annular mounting plates; an upper cover is arranged above the annular sleeve, and the upper cover and the top of the annular sleeve are provided with annular mounting plates. The mounting plate is connected by high-strength bolts; a lower cover is arranged under the annular sleeve, and the lower cover and the mounting plate at the bottom end of the annular sleeve are connected by high-strength bolts; The shaped bump is installed toward the inside of the annular sleeve, the diameter of the cylindrical bump is the same as the inner diameter of the annular sleeve, and a rectangular parallelepiped groove is opened on the inner side of the cylindrical bump toward the inside of the annular sleeve; the center of the cylindrical bump is provided with There is an upper cover quick joint, one end of the upper cover quick joint is connected with the second pressure-bearing hose, and the other end of the upper cover quick joint is communicated with the inside of the annular sleeve through the cuboid groove; the lower cover has the same structure as the upper cover, and the lower cover The cylindrical protrusion of the lower cover is installed toward the inside of the annular sleeve, and the center of the cylindrical protrusion of the lower cover is provided with a lower cover quick connector, one end of the lower cover quick connector is connected with the first pressure-bearing hose, and the other end of the lower cover quick connector is connected. One end is communicated with the inside of the annular sleeve through the cuboid groove; a support base is also arranged under the lower cover, and the lower cover and the support base are welded together.

A rubber gasket is arranged between the lower cover and the mounting plate at the bottom end of the annular sleeve; and a rubber gasket is arranged between the upper cover and the mounting plate at the top end of the annular sleeve.

The technical scheme adopted by the invention is that a method for detecting gas permeability of damaged concrete adopts the above-mentioned detection device, and the specific measurement steps are as follows:

Step 1: Before carrying out the gas permeability measurement, pre-treat the damaged concrete specimen, specifically: coating the surface of the damaged concrete specimen with white latex, and drying the damaged concrete specimen at 50°C for 12-24 hours After cooling to room temperature;

Step 2: Put the damaged concrete specimen into the damaged concrete gas penetration detector, the specific method is as follows:

Step 2.1: First place a silicone pad above the lower cover;

Step 2.2: Then place the damaged concrete specimen on the silicone pad;

Step 2.3: Connect the mounting plate at the bottom of the annular sleeve to the lower cover, place a layer of rubber gasket between the two, and connect with high-strength bolts;

Step 2.4: Then apply epoxy resin glue between the contact surface of the damaged concrete specimen and the inside of the annular sleeve, bond the damaged concrete specimen to the inner wall of the annular sleeve, and place a silicone pad on the damaged concrete specimen;

Step 2.5: Finally, connect the mounting plate at the top of the annular sleeve to the upper cover, place a layer of rubber gasket between the two, and connect with high-strength bolts;

Step 3: Start the measurement, first open the second stop valve and the first stop valve, then open the air pressure gauge and flowmeter and adjust to zero, and finally open the pressure reducing valve, and the air pressure is controlled within the range of 0.01-0.3MPa;

Step 4: When the value in the flow meter does not change with time, write down the flow rate measured at this time, and calculate the gas permeability coefficient of the damaged concrete specimen;

Step 5: After the test is over, first close the second stop valve and the first stop valve, then close the air pressure gauge and flowmeter, and wait for the end of the deflation to take out the damaged concrete specimen in the annular sleeve.

The present invention is also characterized in that,

In step 4, the gas permeability coefficient calculation formula used to calculate the gas permeability coefficient of the damaged concrete specimen is:

where: K—the permeability coefficient of the damaged concrete specimen, m ² ;

Q _out - the flow at the outlet end, that is, the indication measured by the flow meter, m ³ /s;

r—radius of the tested damaged concrete specimen, m;

P ₂ —Pressure at the outlet, atmospheric pressure, N/m ² ;

P ₁ —pressure at the inlet end, measured by a barometer, N/m ² ;

μ—the gas viscosity coefficient, depending on the ambient temperature during the detection, S·N/m ² ;

L—thickness of the tested damaged concrete specimen, m;

A—The area of the damaged concrete specimen to be tested is the average value of the front and back sides of the damaged concrete specimen, measured by CAD software.

The beneficial effects of the present invention are:

(1) A kind of damaged concrete gas permeability detection device of the present invention improves the existing gas permeability testing device. The upper and lower sides of the measurement specimen are coated with white latex, and the upper and lower sides are attached with silica gel pads. Between the side wall of the specimen and the sleeve It is sealed with epoxy resin, and a rubber gasket is added between the upper cover, the lower cover and the annular sleeve, which can strengthen the sealing effect between the test piece and the sleeve, and reduce the measurement error caused by gas leakage from the side wall;

(2) The gas permeability detection device for damaged concrete of the present invention can obtain the gas flow indication by changing the differential pressure conditions and measure multiple times, so as to further understand the gas permeability of the damaged concrete, and calculate the gas permeability coefficient based on the deduced Darcy's law. Expression, quantitative calculation of its concrete permeability coefficient, simple and convenient;

(3) The gas permeability detection device for damaged concrete of the present invention is simple and easy to carry, and can be used for on-site drilling core sampling detection;

(4) Compared with the existing gas permeation method, the method of the present invention can measure the gas permeability of damaged concrete, the required test specimen is small, and can detect various ages, various Strength impairs the gas permeability of concrete.

Description of drawings

Fig. 1 is the structural representation of a kind of damaged concrete gas permeability detection device of the present invention;

Fig. 2 is a kind of test schematic diagram of the damaged concrete gas permeability detection device of the present invention;

3 is a schematic structural diagram of a damaged concrete gas permeability detector of a damaged concrete gas permeability detection device of the present invention;

4 is a schematic diagram of the test of a damaged concrete gas permeability detector equipped with a damaged concrete test piece of a damaged concrete gas permeability detection device of the present invention;

5 is a top view of the upper cover or the lower cover of the damaged concrete gas permeation detector in the detection device of the present invention;

Figure 6 is a schematic diagram of the calculation of the damaged location area of the damaged concrete specimen.

In the figure, 1. Quick connector for upper cover, 2. High-strength bolt, 3. Upper cover, 4. Ring sleeve, 5. Silicon pad, 6. Damaged concrete specimen, 7. Lower cover, 8. Quick connector for lower cover, 9. Support base, 10. Nitrogen tank, 11. Pressure reducing valve, 12. First stop valve, 13. Air pressure gauge, 14. First pressure hose, 15. Flowmeter, 16. Flowmeter support frame, 17 . Second globe valve, 18. Second pressure hose, 19. Cuboid groove, 20. Circular through hole, 21. High-strength bolt hole, 22. Cracks that damage the concrete specimen.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

A gas permeability detection device for damaged concrete of the present invention, as shown in FIGS. 1-6 , includes a nitrogen tank 10 connected by a first pressure-bearing hose 14 and a gas permeability detector for damaged concrete, and the gas permeability detector for damaged concrete passes through The flowmeter 15 is connected to the pressure hose 18 .

A pressure reducing valve 11 , a first shut-off valve 12 and a barometer 13 are sequentially arranged on the first pressure-bearing hose 14 between the nitrogen tank 10 and the damaged concrete gas penetration detector.

A second shut-off valve 17 is provided on the second pressure-bearing hose 18 between the damaged concrete gas permeation detector and the flowmeter 15 ; a flowmeter support frame 16 is also arranged below the second pressure-bearing hose 18 to support the flowmeter 15.

The flow meter 15 is a digital display gas flow meter.

The damaged concrete gas permeation detector includes an annular sleeve 4, the top and bottom edges of the annular sleeve 4 are provided with annular mounting plates; an upper cover 3 is arranged above the annular sleeve 4, and the upper cover 3 is connected to the annular sleeve 4. The mounting plate at the top end of the sleeve 4 is connected by high-strength bolts 2; a lower cover 7 is provided below the annular sleeve 4, and the lower cover 7 is connected with the mounting plate at the bottom end of the annular sleeve 4 through high-strength bolts 2; The upper cover 3 includes a Bottom plate, the center of the bottom plate is provided with a cylindrical protrusion, the cylindrical protrusion is installed toward the inside of the annular sleeve 4, the diameter of the cylindrical protrusion is the same as the inner diameter of the annular sleeve 4, and the cylindrical protrusion faces the inside of the annular sleeve 4. There is a cuboid groove 19 on the side; the center of the cylindrical bump is provided with an upper cover quick connector 1, one end of the upper cover quick connector 1 is connected with the second pressure-bearing hose 18, and the other end of the upper cover quick connector 1 passes through The cuboid groove 19 is communicated with the inside of the annular sleeve 4; the structure and size of the lower cover 7 and the upper cover 3 are the same, the cylindrical protrusion of the lower cover 7 is installed toward the inside of the annular sleeve 4, and the cylindrical protrusion of the lower cover 7 is installed. The center of the block is provided with a lower cover quick connector 8, one end of the lower cover quick connector 8 is connected with the first pressure-bearing hose 14, and the other end of the lower cover quick connector 8 communicates with the inside of the annular sleeve 4 through a cuboid groove 19; A support base 9 is also provided below the lower cover 7 , and the lower cover 7 and the support base 9 are welded together.

A rubber gasket is arranged between the lower cover 7 and the mounting plate at the bottom end of the annular sleeve 4 ; a rubber gasket is arranged between the upper cover 3 and the mounting plate at the top end of the annular sleeve 4 .

The bottom plate of the upper cover 3 has a diameter of 200mm and a thickness of 10mm, the diameter of the cylindrical bump is 100mm and a thickness of 30mm, and six high-strength bolt holes 21 (diameter of the high-strength bolt holes 12mm) are arranged at a radius of 75mm from the center of the bottom plate.

The size of the cuboid groove 19 is 80x20x20mm (length x width x height), and a circular through hole 20 with a diameter of 10mm is set at the center of the lower cover 7 and the upper cover 3 for installing the upper cover quick connector 1 and the lower cover quick connector 8, As shown in Figure 5.

The specification of the pressure hose is

(1) Place the damaged concrete specimen 6 to be inspected on the lower cover 7, seal with epoxy resin glue between the side wall of the damaged concrete specimen 6 and the sleeve, and increase the space between the upper cover 3, the lower cover 7 and the annular sleeve 4 The rubber gasket can strengthen the sealing effect between the damaged concrete specimen 6 and the annular sleeve 4, and reduce the measurement error caused by the gas leakage of the side wall;

The test principle of the damaged concrete gas permeability detection device of the present invention is as follows: the nitrogen tank 10 provides a constant pressure for the damaged concrete gas permeability detector, the damaged concrete specimen 6 infiltrates under the action of constant air pressure, the air flow passes through the cracks and collects In the second pressure-bearing hose 18, the flow meter 15 is used to read the stable flow rate indication to achieve the test purpose, and further calculation is performed by the gas permeability coefficient calculation formula proposed by the present invention.

When testing the present invention, a concrete material with damaged cracks was selected, as shown in FIG. 4 .

The present invention also provides a method for detecting the gas permeability of damaged concrete, which adopts the above-mentioned detection device, and the specific measurement steps are as follows:

Step 1: Before carrying out the gas permeability measurement, the damaged concrete specimen 6 is pretreated, specifically: coating the surface of the damaged concrete specimen 6 with white latex, and drying the damaged concrete specimen 6 at 50° C. for 12 hours - Cool to room temperature after 24 hours;

Step 2: Put the damaged concrete specimen 6 (diameter 100mm, thickness 50mm) into the damaged concrete gas penetration detector. The specific method is as follows:

Step 2.1: First place the silicone pad 5 above the lower cover 7;

Step 2.2: Then place the damaged concrete specimen 6 on the silicone pad 5;

Step 2.3: Connect the mounting plate at the bottom of the annular sleeve 4 to the lower cover 7, place a layer of rubber gasket between the two, and connect with high-strength bolts 2;

Step 2.4: Then apply epoxy resin glue between the contact surface of the damaged concrete specimen 6 and the inside of the annular sleeve 4, bond the damaged concrete specimen 6 to the inner wall of the annular sleeve 4, and place it above the damaged concrete specimen 6 Place the silicone pad 5;

Step 2.5: Finally, connect the mounting plate at the top of the annular sleeve 4 to the upper cover 3, place a layer of rubber gasket between the two, and connect with high-strength bolts 2;

Step 3: Start the measurement, first open the second stop valve 17 and the first stop valve 12, then open the air pressure gauge 13 and the flow meter 15 and adjust to zero, and finally open the pressure reducing valve 11, and the air pressure is controlled within the range of 0.01-0.3Mpa ;

Step 4: When the value in the flow meter 15 does not change with time, write down the flow rate measured at this time, and calculate the gas permeability coefficient of the damaged concrete specimen 6;

Step 5: After the test, first close the second stop valve 17 and the first stop valve 12, then close the air pressure gauge 13 and the flow meter 15, wait for the end of the deflation, and then take out the damaged concrete specimen 6 in the annular sleeve 4.

In step 4, the gas permeability coefficient calculation formula used to calculate the gas permeability coefficient of the damaged concrete specimen 6 is formula (2), which is as follows:

First of all, after the test specimen is damaged, it is in the form of micro-cracks. The gas permeability calculation formula derived from Darcy's law is:

Therefore, when the damaged concrete specimen 6 is detected, the surface is coated with white latex, and the damaged concrete specimen 6 is placed on top and bottom with silicone pads. Therefore, gas seepage occurs at the damaged crack during detection, and the gas permeability coefficient is calculated as follows:

In the formula: K ₀ - the permeability coefficient of the concrete specimen damaged by no white latex coating on the surface, m ² ;

K—the permeability coefficient of the damaged concrete specimen 6, m ² ;

Q _out —flow at the outlet end, that is, the indication measured by the flow meter 15, m ³ /s;

r—the radius of the tested damaged concrete specimen 6, m;

P ₂ —Pressure at the outlet, atmospheric pressure, N/m ² ;

P ₁ —pressure at the inlet, that is, measured by the barometer 13, N/m ² ;

μ—the gas viscosity coefficient, which depends on the ambient temperature during the detection, S·N/m ² ;

L—thickness of the measured damaged concrete specimen 6, m;

A—The area of the damaged concrete specimen 6 to be tested is the average value of the front and back sides of the damaged concrete specimen 6, measured by CAD software, as shown in Figure 6 for the crack 22 of the damaged concrete specimen.

A gas permeability detection device for damaged concrete of the present invention has the following characteristics:

(1) It can realize the detection of gas permeability of damaged concrete

The invention can realize the gas permeability detection of damaged concrete, evaluate the permeability of concrete with damaged cracks, and then evaluate the durability of concrete structural parts.

(2) The size of the test piece is small, the production cost is low, and the test process is simple

The gas permeability detection device for damaged concrete of the invention has low cost when making a test piece, is not limited by age and maintenance conditions, and has a simple and easy test process.

(3) The measured pressure gradient is low, which reduces the secondary damage to the internal structure of the material

In the test process of the damaged concrete gas permeability detection device of the present invention, only nitrogen acts, without interference from other external effects, and will not cause damage to the internal structure of the material.

Claims (8)

1. The utility model provides a damage concrete gas permeability detection device, its characterized in that, is including nitrogen gas jar (10) and damage concrete gas permeability detector of connecting through first pressure-bearing hose (14), and damage concrete gas permeability detector is connected with flowmeter (15) through pressure-bearing hose (18).

2. The damaged concrete gas permeability detection device according to claim 1, wherein a pressure reducing valve (11), a first stop valve (12) and a barometer (13) are sequentially arranged on a first pressure-bearing hose (14) between the nitrogen tank (10) and the damaged concrete gas permeability detection instrument.

3. A damaged concrete gas permeability detection apparatus according to claim 1, characterized in that a second stop valve (17) is provided on a second pressure-bearing hose (18) between the damaged concrete gas permeability detection apparatus and the flow meter (15); and a flowmeter support frame (16) is arranged below the second pressure-bearing hose (18) and is used for supporting the flowmeter (15).

4. A damaged concrete gas permeability detection apparatus according to claim 1, characterized in that the flow meter (15) is a digital display gas flow meter.

5. The damaged concrete gas permeability detection device according to claim 1, wherein the damaged concrete gas permeability detection device comprises an annular sleeve (4), and annular mounting plates are arranged at the top end edge and the bottom end edge of the annular sleeve (4); an upper cover (3) is arranged above the annular sleeve (4), and the upper cover (3) is connected with a mounting plate at the top end of the annular sleeve (4) through a high-strength bolt (2); a lower cover (7) is arranged below the annular sleeve (4), and the lower cover (7) is connected with a mounting plate at the bottom end of the annular sleeve (4) through a high-strength bolt (2); the upper cover (3) comprises a bottom plate, a cylindrical bump is arranged in the center of the bottom plate, the cylindrical bump is arranged towards the inside of the annular sleeve (4), the diameter of the cylindrical bump is the same as the inner diameter of the annular sleeve (4), and a cuboid groove (19) is formed in one side of the cylindrical bump, which faces the inside of the annular sleeve (4); an upper cover quick connector (1) is arranged at the center of the cylindrical bump, one end of the upper cover quick connector (1) is connected with a second pressure-bearing hose (18), and the other end of the upper cover quick connector (1) is communicated with the inside of the annular sleeve (4) through a cuboid groove (19); the structure of the lower cover (7) is the same as that of the upper cover (3), a cylindrical bump of the lower cover (7) is installed towards the inside of the annular sleeve (4), a lower cover quick connector (8) is arranged at the center of the cylindrical bump of the lower cover (7), one end of the lower cover quick connector (8) is connected with a first pressure-bearing hose (14), and the other end of the lower cover quick connector (8) is communicated with the inside of the annular sleeve (4) through a cuboid groove (19); a supporting base (9) is arranged below the lower cover (7), and the lower cover (7) and the supporting base (9) are welded together.

6. A damaged concrete gas permeability detection apparatus according to claim 5, characterized in that a rubber gasket is provided between the lower cover (7) and the mounting plate at the bottom end of the annulus (4); and a rubber gasket is arranged between the upper cover (3) and the mounting plate at the top end of the annular sleeve (4).

7. A method for detecting gas permeability of damaged concrete by using the detection device of any one of claims 1 to 6, which is characterized by comprising the following specific steps:

step 1, before gas permeability measurement, preprocessing a damaged concrete test piece (6), specifically: coating white latex on the surface of the damaged concrete test piece (6), drying the damaged concrete test piece (6) at 50 ℃ for 12-24 hours, and cooling to room temperature;

step 2: putting the damaged concrete test piece (6) into a damaged concrete gas permeation detector, wherein the specific method comprises the following steps:

step 2.1: firstly, a silica gel pad (5) is placed above a lower cover (7);

step 2.2: then placing the damaged concrete test piece (6) on the silica gel pad (5);

step 2.3: connecting the mounting plate at the bottom end of the annular sleeve (4) with the lower cover (7), placing a layer of rubber gasket between the mounting plate and the lower cover, and then connecting the mounting plate and the lower cover by using the high-strength bolt (2);

Step 2.4: then coating epoxy resin glue between the damaged concrete test piece (6) and the contact surface inside the annular sleeve (4), bonding the damaged concrete test piece (6) and the inner wall of the annular sleeve (4), and placing a silica gel pad (5) above the damaged concrete test piece (6);

step 2.5: finally, connecting the mounting plate at the top end of the annular sleeve (4) with the upper cover (3), placing a layer of rubber gasket between the mounting plate and the upper cover, and connecting the mounting plate and the upper cover by using a high-strength bolt (2);

and step 3: the measurement is started, the second stop valve (17) and the first stop valve (12) are opened, then the air pressure meter (13) and the flow meter (15) are opened and adjusted to zero, finally the reducing valve (11) is opened, and the air pressure is controlled within the range of 0.01-0.3 MPa;

and 4, step 4: when the numerical value in the flowmeter (15) does not change any more along with the time, recording the measured flow at the moment, and calculating the gas permeability coefficient of the damaged concrete test piece (6);

and 5: after the test is finished, the second stop valve (17) and the first stop valve (12) are closed, then the air pressure meter (13) and the flow meter (15) are closed, and after the air release is finished, the damaged concrete test piece (6) in the annular sleeve (4) is taken out.

8. The damaged concrete gas permeability detection method according to claim 7, wherein in the step 4, a gas permeability coefficient calculation formula for calculating the gas permeability coefficient of the damaged concrete specimen (6) is as follows:

In the formula: k-permeability coefficient, m, of damaged concrete specimen (6)²；

Q_{Go out}-flow at the outlet end, i.e. reading, m, measured by the flowmeter (15)³/s；

r-radius of the tested damaged concrete test piece (6), m;

P₂pressure at the outlet, atmospheric pressure, N/m²；

P₁Pressure at the inlet end, i.e. measured by a barometer (13), N/m²；

Mu-viscosity coefficient of gas, determined by ambient temperature at the time of detection, S.N/m²；

L is the thickness m of the tested damaged concrete test piece (6);

a-the area of the damage position of the detected damaged concrete sample (6), which is the average value of the front surface and the back surface of the damaged concrete sample (6), is detected by CAD software.

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