CN206656946U - Concrete gas testing permeability device - Google Patents

Abstract

The utility model provides a kind of concrete gas testing permeability device, sample container including piston container and placement sample, sample container upper end connects top cover, piston container is connected by conduit and air intake valve with top cover, sample container lower ending opening, sample periphery is cased with latex film, the sample container lower end is connected with gas container, gas container side is connected by conduit with vavuum pump, operated pneumatic valve is set between gas container and vavuum pump, gas container opposite side connects pressure transmitter, and the pressure transmitter is connected with computer.The gas permeability experiment to concrete can be realized using the device, solves the technical problem of the uncontrollable gas volume of existing instrument and sealing.

Description

Concrete Gas Permeability Test Device

technical field

The utility model relates to the technical field of concrete permeability testing, in particular to a concrete gas permeability testing device and method.

Background technique

Concrete is a complex porous material and a permeable body. Many properties of concrete are to some extent related to the pore volume, pore structure and permeability of the concrete. As an important index to evaluate the durability of hydraulic concrete, permeability mainly includes water permeability and air permeability. As the main transmission medium of aggressive media (Cl ^- , SO ₄ ^2- , etc.), water permeability is the main index to evaluate the permeability of concrete. Gas permeability mainly includes the carbonation effect of CO ₂ and other gases on concrete structures, and is also an important index for evaluating the permeability of concrete.

Numerous studies have shown that for ordinary concrete, rapid permeability tests can be carried out with water as the penetration medium, and then the relationship model between water permeability and carbonation performance can be established. For high-performance concrete, due to the low water-binder ratio and the effect of active admixtures, its permeability is very small and basically impermeable (the impermeability level is often above S40), so the commonly used water permeability test method has been unable to Measuring the permeability of high performance concrete. At present, the chloride ion conductivity method or gas permeation method is usually used in the world to measure the permeability of high-performance concrete. Compared with the chloride ion conductivity method, the gas permeation method has the advantages of accurately reflecting the micropore structure and not being affected by the chemical composition of the concrete pore liquid. . However, because the gas permeation method has high requirements on the airtightness and the control of the gas volume during the test, many existing devices cannot meet the test requirements, resulting in relatively insufficient research on the gas permeation test of concrete.

Contents of the invention

The technical problem to be solved by the utility model is to provide a concrete gas permeability test device and method to realize the gas permeability test of concrete and solve the technical problem that the existing instruments cannot control the gas volume and sealing performance.

In order to solve the above technical problems, the technical solution adopted by the utility model is: a concrete gas permeability testing device, including a piston container and a sample container for placing samples, the upper end of the sample container is connected to the top cover, and the piston container passes through a conduit and an air inlet valve. Connected to the top cover, the lower end of the sample container is open, and the sample is covered with a latex film. The lower end of the sample container is connected to the air container. One side of the air container is connected to the vacuum pump through a conduit. A pneumatic valve is set between the air container and the vacuum pump. One side is connected with a pressure transmitter, and the pressure transmitter is connected with a computer.

In a preferred solution, the height of the sample is lower than that of the sample container.

Further, the distance between the upper end of the sample and the lower end of the top cover is 5mm.

In a preferred solution, the sample container, sample, and gas container are cylindrical.

In a preferred solution, the sample container and the gas container are made of transparent PVC material.

The utility model provides a concrete gas permeability test device, compared with the prior art, has the following advantages and effects:

1. The test is carried out by means of negative pressure pumping, which solves the difficulty of sealing between the concrete sample and the latex film in the way of air injection and pressurization, and only needs to paint a layer of thin film water on the surface of the concrete sample (the viscosity of water is relatively Gas viscosity is relatively large), and the concrete sample is tightly connected with the latex film by the suction of negative pressure, and there is no need to apply other materials to seal;

2. Adopt the principle of gas mass conservation in the process of permeation test, without considering the influence of pressure on gas density;

3. The closed volume variable pressure gradient test method is adopted, which is similar to the variable water head test method of the concrete water permeability test. It not only has the advantages of shortening the test cycle and saving costs, but also eliminates the need for supplementary air pressure when using a constant pressure gradient test in the past. interference from external factors;

4. The utility model can test different types of gas mixtures or one of the gases. It only needs to replace the gas in the piston container with a single gas (such as _CO2 , etc.), and its operation method is simple and fast;

5. The utility model can monitor the pressure change in the gas container in real time through the pressure transmitter and the computer acquisition program, so as to realize the real-time conversion of the concrete permeability coefficient, and more truly reflect the gas permeation process.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the utility model is further described.

Fig. 1 is a schematic diagram of the overall structure of the utility model.

In the figure: piston container 1, intake valve 2, top cover 3, bolt 4, sample container 5, sample 6, latex film 7, air container 8, pneumatic valve 9, vacuum pump 10, pressure transmitter 11, computer 12.

detailed description

As shown in Figure 1, a concrete gas permeability test device includes a piston container 1 and a sample container 5 for placing a sample 6, the upper end of the sample container 5 is connected to the top cover 3, and the piston container 1 passes through the conduit and the air inlet valve 2 and the top cover 3 The connection is characterized in that the lower end of the sample container 5 is open, and the outer periphery of the sample 6 is covered with a latex film 7. The lower end of the sample container 5 is connected to the gas container 8, and one side of the gas container 8 is connected to the vacuum pump 10 through a conduit, and the gas container 8 is connected to the vacuum pump. A pneumatic valve 9 is arranged between 10, and the other side of the gas container 8 is connected to a pressure transmitter 11, and the pressure transmitter 11 is connected to a computer 12.

The sample container 5 and the top cover 3 as well as the sample container 5 and the gas container 8 are connected by bolts 4 .

The sample container 5 and the gas container 8 are made of transparent PVC material. Intensity can be satisfied, and it is easy to observe.

In a preferred solution, the height of the sample 6 is lower than that of the sample container 5 .

The distance between the upper end of the sample 6 and the lower end of the top cover 3 is 5mm. In the air seepage test, the gas can be evenly distributed on the top surface of the concrete sample 6 .

In a preferred solution, the sample container 5, the sample 6, and the gas container 8 are cylindrical. Processing is relatively simple.

The specific operation method includes the following steps:

1) prepare

a. To inject gas, first remove the air intake valve 2 and the piston container 1 connected to the top cover 3, open the air intake valve 2, push the piston rod to discharge the gas in the piston container 1, and then use the pressure tank and the piston container 1 Connect the gas guide tube, inject the test gas into the piston container 1, close the intake valve 2, and finally connect the tube to the top cover 3 of the sample container 5;

B, measure the volume V of the gas container 8, measure the height of the gas container 8 and the diameter of the bottom plate, and calculate the volume of the gas container 8, or by filling the gas container 8 with water at a constant temperature, by measuring the weight difference before and after the gas container 8 is filled with water Get the volume of gas container 8;

c. To detect air tightness, connect the concrete gas permeability test device as required, close the intake valve 2, use the vacuum pump 10 to evacuate the air container 8, and close the pneumatic valve 9. If the pressure in the concrete gas permeability test device is within If there is no rise for an hour, proceed to the next test, otherwise, use soapy water to detect the connection of each component to find the leak point and reconnect;

2) Test the gas permeability of concrete

a. When filling the sample, first brush a thin layer of water on the surface of the sample 6, and then put the latex film 7 on the sample 6. The viscosity of water is greater than that of air, which can ensure that the latex film 7 is closely attached to the surface of the sample 6 .

b. After starting the test, close the intake valve 2, and use the vacuum pump 10 to evacuate the gas container 8. After closing the pneumatic valve 9, the pressure in the gas container 8 has been stabilized for more than 1 hour, and the pressure in the container is recorded by the pressure transmitter 11. Initial pressure P ₀ ; then open the intake valve 2, and record the pressure value P in the gas container through the computer 12 in real time.

3) End the test, and stop the test when the air pressure in the gas container 8 rises to 1/2 of the initial air pressure.

The gas permeability coefficient of sample 6 was calculated based on the above experimental results.

Because it changes with the change of pressure during the gas volume flow process, the inflow and outflow of gas mass are equal. Therefore, this method uses the mass change of gas as the test basis. The pressure of the gas container 8 monitored at any time t during the test can be recorded as P, after the time dt, the pressure in the container increases by dP, then the amount and quality of the gaseous substance flowing from the sample into the gas container 8 within the time dt are respectively :

In the formula: R is the ideal gas constant 8.314J/mol k; T represents the absolute temperature, T=Celsius+273.15, unit: k; V represents the volume of the gas container 8, unit: m ³ ; M represents the molar mass of the gas, the unit : g/mol; dn means the amount of increased substance, unit: mol; means increased mass, unit: g.

According to Darcy's law, the mass of gas flowing from piston container 1 into sample 6 within dt time is:

In the formula: A represents the cross-sectional area of sample 6, unit: ^m2 ; L represents the length of sample 6, unit: m; P represents the pressure at time t, because the monitored pressure is negative pressure, the pressure gradient needs to add a negative sign before the symbol P , unit: N/m ² ; g means acceleration due to gravity, unit: N/kg.

According to the principle of continuity, there should be dm _e =dm ₀ , that is,

Integrate both sides of the formula, where the initial pressure is P ₀

Above-mentioned embodiment is only the preferred technical scheme of the present utility model, and should not be considered as the restriction to the present utility model, and the protection scope of the present utility model should be the technical solution described in the claims, including the technology in the technical solution described in the claims. An equivalent alternative to the feature is the scope of protection. That is, equivalent replacement and improvement within this scope are also within the protection scope of the present utility model.

Claims (5)

1. a kind of concrete gas testing permeability device, including piston container（1）With placement sample（6）Sample container（5）, Sample container（5）Upper end connects top cover（3）, piston container（1）Pass through conduit and air intake valve（2）With top cover（3）Connection, its It is characterised by：Sample container（5）Lower ending opening, sample（6）Periphery is cased with latex film（7）, the sample container（5）Lower end and gas Container（8）Connection, gas container（8）Side passes through conduit and vavuum pump（10）Connection, gas container（8）With vavuum pump（10）Between set Put operated pneumatic valve（9）, gas container（8）Opposite side connects pressure transmitter（11）, the pressure transmitter（11）Connect with computer Connect（12）.

2. concrete gas testing permeability device according to claim 1, it is characterised in that：The sample（6）Highly Less than sample container（5）.

3. concrete gas testing permeability device according to claim 2, it is characterised in that：The sample（6）Upper end With top cover（3）The distance of lower end is 5mm.

4. concrete gas testing permeability device according to claim 1, it is characterised in that：The sample container（5）、 Sample（6）, gas container（8）For cylindrical type.

5. concrete gas testing permeability device according to claim 1, it is characterised in that：The sample container（5） Gentle container（8）Using clear PVC material.