CN103323380A - Concrete in-situ non-destructive gas permeability measurement device as well as method - Google Patents

Abstract

The invention provides a concrete in-situ non-destructive gas permeability measurement device as well as a method. The device comprises a gas collecting hood, a gas pressure transmitter, a gas quality and flow rate controller, a vacuum pump, a plurality of valves and a controller, wherein the gas collecting hood is used for being bonded on the surface of to-be-tested concrete so as to form a sealed space; the gas pressure transmitter is installed on the outer surface of the gas collecting hood, and is used for collecting the pressure in the gas collecting hood when the gas collecting hood is at the negative pressure state; the gas quality and flow rate controller is installed on a pipeline between the gas collecting hood and the vacuum pump, and is used for detecting and controlling the current gas flow rate; the vacuum pump is used for extracting gases in the gas collecting hood, passing through the gas quality and flow rate controller; the plurality of valves are installed on the pipeline, and are used for controlling the gas on the pipeline to pass through; the controller is connected with the gas pressure transmitter and the gas quality and flow rate controller, and determines the gas permeability of concrete through parameters sensed by the gas pressure transmitter and the gas quality and flow rate controller. According to the device and the method, the permeability can be measured under the negative pressure state; the surface of concrete is not damaged; the measurement process is simple.

Description

The harmless measuring device for gas permeability of concrete in-situ and method

Technical field

The present invention relates to concrete test, in particular to the harmless measuring device for gas permeability of a kind of concrete in-situ and method.

Background technology

The perviousness of class concrete material (rock, concrete and brick etc.) is one of key factor that affects its permanance.The permeability survey mode is distinguished by the permeating medium of choosing at present, can be divided into liquid, gas two classes, and corresponding method of testing is respectively hydraulic pressure, air pressure method of testing.

Distinguish according to metering system, can be divided into sampling, two classes of not taking a sample.1. all be to be sampled as prerequisite at present, in the laboratory, detect the perviousness of concrete sample.This experimental technique generally belongs to destructive test, and for intact concrete sample, sampling method has destroyed the integrality of concrete component; For damaging concrete component, such as containing crack etc., sampling process can change concrete original faulted condition, even probably destroys the integrality of sample.This method can be brought larger measuring error.2. sampling and testing not.Do not need at present the in-situ test system of taking a sample, be mainly used in measuring the concrete surface layer gas permeability.This mode is not suitable for concrete component internal penetration rate to be measured, and reason is as follows: 1) in order to guarantee the sealing of measuring equipment and test surfaces, need to design anchor bolt around test zone, cause the test section peripheral concrete to destroy; 2) this measurement device principle is by increase air pressure in the sealing gas hood, and according to the permeability of the decline of pressure rule reckoner layer concrete in the sealing gas hood, measured zone is difficult to assess.

Summary of the invention

The present invention aims to provide the harmless measuring device for gas permeability of a kind of concrete in-situ and method, is not suitable for the problem that concrete component internal penetration rate is measured to solve above-mentioned metering system.

In an embodiment of the present invention, provide a kind of concrete in-situ to can't harm measuring device for gas permeability, having comprised:

Gas skirt is used for being bonded in concrete surface to be measured, forms the space of sealing;

Gas pressure transmitter is installed in the outside surface of described gas skirt, is used at described gas skirt gathering the pressure in the described gas skirt under negative pressure state;

Gas mass flow controller is installed on the pipeline between described gas skirt and the vacuum pump, for detection of the gas flow current with control;

Vacuum pump is used for extracting out the gas through in the described gas skirt of described gas mass flow controller;

Be installed in a plurality of valves on the described pipeline, the gas that is used for controlling on the described pipeline passes through;

Controller is connected with described gas pressure transmitter, described gas mass flow controller, by the two parameter of sensing, determines described concrete gas permeability.

The present invention also provides a kind of harmless gas permeability measuring method of concrete in-situ that comprises said apparatus, comprising:

Described gas skirt is placed on concrete surface, and the edge of described gas skirt and described concrete surface are bonded with sealant;

Adopt vacuum pump to take out gas in the described gas skirt, form negative pressure, gather the gas flow of pressure in the described gas skirt that described gas pressure transmitter measures, described pipeline that described gas mass flow controller is measured;

Determine described concrete permeability k by following formula;

$k=\frac{2\mathrm{\&mu;}{Q}_{\mathrm{sc}}{p}_{\mathrm{sc}}L}{\mathrm{GA}({\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="HDA00003334102800011.png"\; state="\{\{state\}\}">p</figure-callout>}}_1^2-p_0^2)}$

Wherein, G is modifying factor, be the gas that extracts in the gas skirt the ratio of the corresponding volume of concrete of projection under the concrete volume of process and the gas skirt inside; Q _ScIt is gas flow under the standard state; p _ScIt is the standard state gaseous tension; μ is the aerodynamic force viscosity under the current environmental temperature; L is described concrete thickness; A is described gas skirt sectional area; p ₁It is the outer atmospheric pressure of gas skirt; p ₀It is the gas skirt internal pressure.

The embodiment of the invention, owing to adopting vacuum pump, the metering system that metering system is different from the past is not destroying in the concrete situation, measures permeability; In addition, the method for all the time measuring permeability all is malleation; Adopt device of the present invention to realize measuring permeability by negative pressure, adopt the sealing effectiveness that can guarantee gas skirt and concrete surface contact area than simple measures.

Description of drawings

Accompanying drawing described herein is used to provide a further understanding of the present invention, consists of the application's a part, and illustrative examples of the present invention and explanation thereof are used for explaining the present invention, do not consist of improper restriction of the present invention.In the accompanying drawings:

Fig. 1 shows the structural drawing of embodiment;

Fig. 2 shows the schematic diagram of the computation model of the coefficient G among the embodiment.

Embodiment

Below with reference to the accompanying drawings and in conjunction with the embodiments, describe the present invention in detail.

Referring to Fig. 1, Fig. 1 is the structural drawing of embodiment, comprises with lower member:

1-concrete component, 2-gas skirt, 3-air-outlet valve, 4-gas pressure transmitter, 5-drying agent, 6-filtrator, 7,8,11 and 12-valve, 9 and 10-different span gas mass flow controllers, 13-vacuum pump, 14-gas mass flow controller data line in parallel, 15-gas mass flow controller data line, 16-gas pressure transmitter data line, 17-data acquisition controller, 18-sealant coating zone;

A kind of concrete in-situ among the embodiment can't harm measuring device for gas permeability, comprising:

Gas skirt 2 is used for being bonded in concrete surface to be measured, forms the space of sealing;

Gas pressure transmitter 4 is installed in the outside surface of described gas skirt 2, is used at described gas skirt 2 gathering the pressure in the described gas skirt 2 under negative pressure state;

Gas mass flow controller 9, gas mass flow controller 10 are installed on the pipeline between described gas skirt 2 and the vacuum pump 13, for detection of with control the current corresponding pipeline that links to each other gas flow;

Vacuum pump 13 is used for extracting out the gas through in the described gas skirt 2 of described gas mass flow controller 9, gas mass flow controller 10;

Be installed in a plurality of valves on the described pipeline, the gas that is used for controlling on the described pipeline passes through;

Controller 17 also can be described as data acquisition controller, is connected with described gas pressure transmitter 4, described gas mass flow controller 9,10, by the two parameter of sensing, determines described concrete gas permeability.

Preferably, in the above-mentioned device, the quantity of described gas mass flow controller comprises different two of measuring accuracy scope, and on the pipeline of two parallel connections, every pipeline is installed one;

Wherein, the range of two described gas mass flow controllers is different, and the scope of a range is: 10 ^-16～10 ^-13m ²The scope of another range is: 10 ^-15～10 ^-12m ²Can adopt the gas mass flow controller of a plurality of different accuracies, to obtain the measuring device for gas permeability of multiple different ranges.

Can find out from measure equation, the factor that affects this measuring method range mainly contains: factor of influence G, gas mass flow controller range and pressure unit range.It is as follows that this method is measured range computation process:

Factor of influence G is subjected to gas skirt and measures the sample physical dimension to affect.Here the radius of measuring for example sample is 20cm, highly is 20cm; Use the bottom inside radius of gas skirt to be 5cm, external radius is 10cm; Calculative determination coefficient G is 5.56.1＜G under the general measure condition＜10.

The effective range of gas mass flow controller control is typically chosen in 5%～95% of its range.

5%～95% of effective its range of measurement measurement range selection of pressure unit.The pressure unit that this experiment is used is 0-100kPa, so the pressure effective range is 5-95kPa.The setting measurement environment atmospheric pressure is 90kPa, and the measurement minimum pressure is 5kPa, and maximum pressure is 89kPa.

(1) at first under the calculated examples condition, gas mass flow controller is the range of 500ml/min

Minimum range state: measuring flow minimum and pressure reduction is maximum

$k_{500\_\min }=\frac{2\&times;(1.85\&times;{10}^{-5})\&times;(1.01\&times;{10}^5)\&times;(500\&times;0.05\&times;1.667\&times;{10}^{-8})\&times;0.2}{5.65\&times;(3.1416\&times;{0.05}^2)({90}^2-5^2){10}^6}$

$=9.48\&times;{10}^{16}{m}^2$

Maximum range state: measuring flow maximum and pressure reduction is minimum

$k_{500\_\min }=\frac{2\&times;(1.85\&times;{10}^{-5})\&times;(1.01\&times;{10}^5)\&times;(500\&times;0.95\&times;1.667\&times;{10}^{-8})\&times;0.2}{5.65\&times;(3.1416\&times;{0.05}^2)({90}^2-{89}^2){10}^6}$

$=7.45\&times;{10}^{13}{m}^2$

(2) the Calculation of Gas mass flow controller is the range of 5000ml/min, and computing method are the same, and just flow enlarges an order of magnitude, so the Last range of range ratio enlarges an order of magnitude synchronously.Measurement range is 9.48 * 10 ^-15m ²～7.45 * 10 ^-12m ²

On every pipeline, between described gas mass flow controller and the described gas skirt 2, valve is installed.The for example valve among Fig. 17, valve 8.

Preferably, on the pipeline between the branch road that the pipeline of described two parallel connections converges and the described gas skirt 2, also be connected with drying agent 5 and air strainer 6.

Preferably, a valve 3 in described a plurality of valves is installed on the described gas skirt 2, for the gaseous tension (close with external atmospheric pressure) in the described gas skirt 2 behind the adjusting test, conveniently gas skirt 2 is removed from measuring the surface.

Measurement mechanism in the embodiment of the invention, owing to adopting vacuum pump, the metering system that metering system is different from the past is not destroying in the concrete situation, measures permeability; In addition, measure the permeability method all is malleation all the time; Adopt device of the present invention to realize measuring permeability by negative pressure, adopt the sealing effectiveness that can guarantee gas skirt and concrete surface contact area than simple measures.

Embodiments of the invention also provide a kind of measuring method, may further comprise the steps:

Step 1, cleaning class concrete surface layer attachment is determined measured zone;

Step 2 is coated the certain thickness sealant at the gas skirt bottom margin, places it on the measured zone; Such as the zone 18 among Fig. 1;

Step 3 is opened data acquisition controller, and preheating gas mass flow controller 9, gas mass flow controller 10 are about 20 minutes;

Step 4 is opened vacuum pump 13, slow control valve, and the flow of gas mass flow controller is set; Because the range of two gas mass flow controllers is different, therefore, need to pre-estimate the probable ranges of the gas permeability of tested object, selects the gas mass flow controller of corresponding range according to estimated value.

Open successively valve 7 or valve 8 and valve 11, measure and the control gas flow;

Wait for pressure and flow Simultaneous Stabilization, after not fluctuating, record data.

Step 5, successively valve-off 7(or 8) and 11, then close vacuum pump 13, open at last valve 12 and wait for after end gaseous tensions and the atmospheric pressure balance again valve-off 12.

Step 6 is opened valve 3, waits for after end gaseous tension and the atmospheric pressure balance again valve-off 3, removes gas skirt, finishes to test.

Step 7, utilize formula Calculation of Gas permeability k:

$k=\frac{2\mathrm{\&mu;}{Q}_{\mathrm{sc}}{p}_{\mathrm{sc}}L}{\mathrm{GA}({\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="HDA00003334102800011.png"\; state="\{\{state\}\}">p</figure-callout>}}_1^2-p_0^2)}$

Wherein, G is modifying factor, by the gas that extracts in the gas skirt the ratio of the corresponding volume of concrete of projection under the concrete volume of process and the gas skirt inside; Q _ScIt is the gas flow under the standard state; p _ScBe the standard state gaseous tension, equal 101325Pa; μ is the aerodynamic force viscosity under the current environmental temperature; L is described concrete thickness; A is described gas skirt sectional area; p ₁It is the outer atmospheric pressure of gas skirt; p ₀It is the gas skirt internal pressure.Owing to being negative pressure, there is p ₁P ₀Wherein, standard state refers to the state depressed at a normal atmosphere.

The below illustrates computation process with a concrete example:

The radius of for example measuring sample is 20cm, highly is 20cm; Use the bottom inside radius of gas skirt to be 5cm, external radius is 10cm; Calculative determination coefficient G is 5.56.Gas viscosity μ is taken as 1.86 * 10 according to temperature ^-5Pas.

Kinetic viscosity under other state of temperature can be chosen in such a way.

Aerodynamic force viscosity is relevant with temperature, and table 1 is aerodynamic force viscosity data under the different temperatures, and the state of temperature that mediates adopts interpolation method to calculate and obtains.

Table 1

Temperature/℃	0	10	20	40	60	80
							Kinetic viscosity/10 -5Pa.s	1.75	1.81	1.86	1.96	2.05	2.14

Geometric corrections factor G in the measure equation is the correction to the plane one-dimensional model, can be applied to the non-one-dimensional model in plane by revising measure equation.The physical meaning of this parameter is to measure the ratio of effective coverage I, II and standard one dimension effective coverage I, the example of Fig. 2 for showing.This model is axisymmetric model, and gas skirt is placed on top, and this figure is velocity vector field and the calculation of streamlines result who adopts finite difference method to calculate.The top shade is gas skirt, and length is dimensionless variable among the figure, and the gas skirt external radius is 1.4, and the gas skirt inside radius is 1, and the specimen radius is 4, highly is 4.The zoning is divided into three districts, I: the one-dimensional model zone, and I+II: the in site measurement effective coverage, III: inactive area, the numerical value of modifying factor G equal the volume of the volume/I of effective coverage (I+II), and this is worth greater than 1.Can find out from numerical result, this factor and gas skirt size, specimen size are relevant.

Referring to Fig. 2, Fig. 2 is the sectional view of gas skirt and test concrete sample, and has only shown half zone along central axis.The black square at concrete sample top represents the gas collection wall among Fig. 2.

Use the range of one of them gas mass flow controller to be 500ml/min, the control flow is 60% of its range; After waiting for that gas flow and pressure reach steady state (SS) simultaneously, the pressure in the record set gas hood is 45.230kPa; The measuring state external atmospheric pressure is 90.124kPa.The steady state (SS) here refers to the error of fluctuation of pressure and flow in certain threshold range, and for example fluctuating error is within 0.2%.

According to above initial and measurement data, the gas permeability that can be calculated measured zone by formula is 2.0 * 10 ^-15m ²

Method of the present invention by above-mentioned step, has realized measuring concrete permeability under negative pressure state, compares with traditional malleation mode, neither destroys concrete surface, can realize again the measurement of permeability,

The above is the preferred embodiments of the present invention only, is not limited to the present invention, and for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (6)

1. the harmless measuring device for gas permeability of concrete in-situ is characterized in that, comprising:

Gas skirt is used for being bonded in concrete surface to be measured, forms the space of sealing;

Gas pressure transmitter is installed in the outside surface of described gas skirt, is used at described gas skirt gathering the pressure in the described gas skirt under negative pressure state;

Gas mass flow controller is installed on the pipeline between described gas skirt and the vacuum pump, for detection of the gas flow current with control;

Vacuum pump is used for extracting out the gas through in the described gas skirt of described gas mass flow controller;

Be installed in a plurality of valves on the described pipeline, the gas that is used for controlling on the described pipeline passes through;

Controller is connected with described gas pressure transmitter, described gas mass flow controller, by the two parameter of sensing, determines described concrete gas permeability.

2. device according to claim 1 is characterized in that, the quantity of described gas mass flow controller comprises different two of measuring accuracy scope, on the pipeline of two parallel connections, installs one for every;

Wherein, the range of two described gas mass flow controllers is different;

On every pipeline, between described gas mass flow controller and the described gas skirt, valve is installed.

3. device according to claim 2 is characterized in that, on the pipeline between the branch road that the pipeline of described two parallel connections converges and the described gas skirt, also is connected with drying agent and air strainer.

4. device according to claim 1 is characterized in that, in described a plurality of valves one installs on the described gas skirt, is used for that the gaseous tension in the described gas skirt is adjusted to external atmospheric pressure close after the test.

5. the harmless gas permeability measuring method of concrete in-situ that comprises the described device of claim 1 is characterized in that,

Described gas skirt is placed on concrete surface, and the edge of described gas skirt and described concrete surface are bonded with sealant;

Adopt vacuum pump to take out the interior gas of described gas skirt, form negative pressure, gather the gas flow that described gas pressure transmitter is measured the described pipeline of the pressure in the described gas skirt, the measurement of described gas mass flow controller;

Determine described concrete permeability k by following formula;

$k=\frac{2\mathrm{\&mu;}{Q}_{\mathrm{sc}}{p}_{\mathrm{sc}}L}{\mathrm{GA}(p_1^2-p_0^2)}$

Wherein, G is modifying factor, be the gas that extracts in the gas skirt the ratio of the corresponding volume of concrete of projection under the concrete volume of process and the gas skirt inside; Q _ScIt is gas flow under the standard state; p _ScIt is the standard state gaseous tension; μ is the aerodynamic force viscosity under the current environmental temperature; L is described concrete thickness; A is described gas skirt sectional area; p ₁It is the outer atmospheric pressure of gas skirt; p ₀It is the gas skirt internal pressure.

6. method according to claim 5 is characterized in that, before the pressure in the described collection gas skirt, the gas flow, also comprises:

The undulating quantity that determines described gas flow by controller is carried out described acquisition operations again in threshold range.

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