SU759958A1 - Method of determining air permeability of concrete - Google Patents

Description

The invention relates to the field of construction and can be used to determine the permeability of concrete and other porous materials.

There is a known method for determining the air permeability of concrete, consisting in installing working chambers on two opposite surfaces of a concrete element, sealing chambers, creating an increased pressure in one of the "0 chambers" and measuring the pressure drop in it.

This method is used to determine the permeability of small concrete samples and is not suitable for determining the 15 permeability of concrete in a structure.

The closest technical solution to the invention is a method for determining the air permeability of a b-20 tone, including installing concrete on the surface and sealing the working chamber, creating a pressure difference between the internal cavity of the chamber and the external medium, measuring pressure 25 in the chamber [2}.

According to a known method on

the surface of the sample of porous material set the working chamber

and seal it on the surface with 30

2

using a prigruz, cover the surface of the sample around the chamber with an airtight paint, supply air to the chamber at an overpressure and maintain this pressure at a constant level, measure the pressure established in the chamber with air flow from its peripheral holes through the layer of porous material to its central hole, steady-state pressure is indirectly evaluated by the air permeability of the material.

The known method cannot be used to measure the air permeability of concrete in structures, since the studied material layer for concrete is small, measurement of air permeability on the vertical planes of structures is impossible, air insulation of the surface of the structure around the working chamber and application of a special load for sealing it on the sample is required.

The aim of the invention is to provide the possibility of determining the air permeability of concrete directly in the structures, as well as simplifying and accelerating the work.

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759958

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This goal is achieved by the fact that in the proposed method of determining the air permeability of concrete, including installing the concrete surface on the concrete surface and sealing the working chamber, creating a pressure difference between the internal cavity of the chamber and the external environment, measuring the pressure in the chamber, using a working chamber with a supporting flange, and creating a differential pressure vacuum in the working chamber in the range (-0.98) - (0.6) atm, and simultaneously with the measurement of pressure Time is counted, after which air breathing is calculated-. concrete bridge according to the formula

(one)

where a is the air permeability parameter;

P _about - the pressure in the working chamber

at the beginning of the determination of air permeability;

P - the same at the end; .

V is the volume of the working chamber; _: . dî - the length of time during

whose pressure in the working chamber increased from P _o to P <.

The drawing shows a diagram of the device for implementing the described method. \

This device contains a working chamber 1 with a flange 2 and a vacuum meter 3 mounted on the surface of the structure 4. The sealing of the working chamber on the surface of the structures is carried out with the help of a sealant 5. The working chamber 1 is connected with a vacuum manifold 8 through hose в 7. The valves 9 and 10 are connected, the vacuum manifold with the hoses of the other working chambers .. The hose 11 with the valve 12 connects the vacuum manifold to the vacuum pump 13.

The determination of air permeability according to the described method is carried out in the following order. The flange 2 of the working chamber 1 is covered with a sealant 5, the vacuum pump 13 is turned on, the valve 12 and the valve 7 are opened, the camera is applied with a flange 2 to the concrete surface of the structure 4, limiting the connection between the internal space of the chamber and the surrounding medium. The vacuum pump 13. creates a vacuum in the working chamber, and due to the vacuum it is sealed on the surface. socks of construction 4, ensure uniform distribution of sealant 5 over the area of flange 2. After creating a certain initial vacuum level in the working chamber, valve 7 shut off and stop the flow of air through hose 6. Then, initial pressure P ₀₁ in the working chamber is fixed at vacuum gauge 3 and a stopwatch is started countdown Similarly, the following surface IDs are sequentially sealed by

.rabochie chamber vacuum is adjusted values in them until a certain level of overlap valves 9 and 10, fixed initial pressure level P ₀ - _s in these chambers and starts counting time measurements. Air permeability of concrete in construction sites is measured by the values of the parameter · air permeability by the formula. (one).

After the determination of air permeability at some site

»0 of the surface of the structure, the released working chamber is installed on the new surface of the surface and measurements are continued. To speed up measurements

. while maintaining the linear dependence of 15 pressure in the chamber from time to time

create a vacuum in the working chambers in the range (-0.98) - (-0.6) atm. .

The size of the concrete layer, the air permeability of which is determined, and

20 The length of the air filtration path depends on the width of the chamber flange and can be adjusted by changing this width. To ensure the required size of the concrete layer under study, the width of the flange should be at least 25 mm. The radial flow of air from the atmosphere through the layer of concrete into the working chamber begins from a narrow strip of the surface of the structure along the outer edge.

__ working chamber. Therefore, air insulation of the concrete surface outside the chamber in order to streamline the area of filtration. Air is not required.

The optimal number of working chambers simultaneously used when

4- * measurement is 5-7 cameras.

Using the described method provides the ability to determine the air permeability of concrete. directly in the designs and increases the reliability of the performance ratings of the latter. Measurement on. several sections of the surface of structures at the same time / lack of devices and

D5 means to maintain consistency _; . pressure and determine the flow of air in the measurements accelerate and upro. spawn them.

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Claims (1)

Claim The method for determining the air permeability of concrete, including the installation on the surface of concrete and sealing -. > Tion of the working chamber, creating raznos55 hee pressures between the interior chamber and the environment, the measurement of the pressure in the ^chamber: on TLIchayu conductive c i in that, in order to allow determination 60 air permeability of concrete directly in the structures, as well as simplifying and accelerating the work, and the use-. They have a working chamber with a support flange, and the pressure difference is equalized by я 5 in the working chamber in the range five 759958 (-0.98) - (-0.6) atm, and at the same time. Time is measured with pressure measurement, after which air permeability ^{1 is} calculated. ET'-E'R concrete according to the formula O- ζ where a is the parameter breathable. ti; Pp is the pressure in the working chamber at the beginning of the determination of breathability; ten (¾ - the same at the end; V is the volume of the working chamber; d - the length of time during whose pressure in the working chamber has increased from Р _о до. «Р ^.