T05862020Test method for permeability coefficient of cement concrete

1Purpose, scope of application, and reference standards

This method specifies the test method for the permeability coefficient of cement concrete

This method is applicable for determining the permeability coefficient of porous concrete specimens under laminar flow conditions.

2Instruments and materials

21Penetrometer:Mainly composed of a water tank, specimen sleeve, sleeve cover, rubber sealing ring, micro differential pressure gauge, stopwatch, porous plate soft airbag, vacuum pump, valve, thermometer, balance, and connecting pipe(See figureT0586-1)

imageT0586-1Penetrometer(unit of measurement:mm)

22water tank:Made of organic glass,Beneficial for observing water surface height,Easy to control.

2.3Test piece sleeve:Made by integral casting of sand mold cast iron,The inner diameter of the sleeve is180mm

2.6perforated plate:Supporting the specimen and reducing the inflow of water

27Soft airbag:Long tube hollow airbag made of soft rubber,After inflation, the inner diameter is150mm,The outer diameter is182mmlength150mm,After inflating the airbag, the internal pressure generated by inflation can be used to seal the pores between the specimen wall and the specimen sleeve,Prevent water from passing through

28vacuum pump:Before pouring water into the test piece sleeve, it is necessary to evacuate it,Reduce the impact of closed bubbles in pores

29thermometer:The division value is1℃。

2.10graduated cylinder:The division value is0.1mL

2.11lstopwatch:The division value isls

22connecting pipe:Connecting pipe ① is used to connect the water tank and the test piece sleeve,Using a pipe diameter of20macrylic tube:Connecting tube ② is used to connect the specimen sleeve and the micro differential pressure gauge,Using an inner diameter of10mTransparent plastic pipe:Connecting tube ③ is used to connect the test piece sleeve and the vacuum pump,Using an inner diameter of10mmVacuum specialized tube.

3Experimental steps

3.1Cut both ends of the specimen before the experiment,Make the diameter of the specimen150mm,Height not less than150mm

3.2Check whether various components and instruments are connected properly,Ensure the airtightness of the entire system.

3.3Fill the water tank to a constant position and maintain a constant water head.

34Fix the soft airbag inside the test piece sleeve,Insert the test piece,Inflate the soft airbag to a certain pressure,Fill the soft airbag tightly with the specimen sleeve wall,Then fix and seal the sleeve cover.

35Close all other valves,Open the vacuum pump suction valve,Activate the vacuum pump to evacuate the interior of the sleeve,Vacuumize to90 kPa±1kPa,And maintain it30min

3.6While maintaining vacuum pumping,Open the inlet valve,The sample is in a permeable state,Wait for the sample to be completely soaked in water,And the water level is higher than the sample5mmtime,Close the exhaust valve,Stop vacuuming.

37After vacuuming,Open the water outlet valve,Wait a few minutes,After the water flow stabilizes,Adjust the inlet valve. Read and record the differential pressure gauge reading.

38Use a measuring cylinder to collect water from the outlet,Record time,Volume of outflow waterQ,Accurate to0mL

3.9repeat3.7、3.8Steps in total4time,Read and record experimental data

3.10A set of experiments has been completed,Remove the test piece,Replace with a new specimen for the next round of testing

4Result Calculation

Permeability coefficient,According to the formula(T0586-1)calculate:

(T0586-1)

in the formula

KOne water temperatureTPermeability coefficient at ℃(cms)

QtimetThe amount of exudate inside(m)

LDistance between pressure measuring holes(cm)

AThe cross-sectional area of the specimen(cm)

hAverage head difference(cm)Permeable time(s)

Usage formula(T0586-2)Translate into EnglishKconvert toK

T0586-2)

in the formula:K20-water temperature20Permeability coefficient at ℃(cms):

Kwater temperatureTPermeability coefficient at ℃(cms)

nrwater temperatureTDynamic viscosity coefficient of water at ℃(kPas)

water temperature20Dynamic viscosity coefficient of water at ℃(kPas)

nEarly constant value,Refer to the current 'Standard for Work Test Methods'(GBT023)

5Test Report

The test report should include the following contents

(1)Name and execution standards of the required testing items

(2)Variety, specifications, and place of origin of raw materials

(3)Test date and time

(4)Name, model and number of the instrument and equipment

(5)Environmental temperature and humidity

(6)Permeability coefficient

(7)Other content to be explained

provisions explanation

The specimen and sleeve wall of the general manufacturing instrument have a certain degree of tightness,Most of them use wax, latex, and oil for sealing,The water always flows in the direction of daring and large flow,Due to the unevenness of the outer surface of the concrete specimen,Fully integrate with the sidewall light method of the permeameter,The selection of water flow from the reverse direction seriously affects the authenticity of the obtained data. This method uses inflatable soft airbags made of soft rubber instead of expanding acid, sealing, or filling the holes between the inverted wall and the specimen. Cover the test piece with an inflatable soft airbag,I put in the permeameter,Then inflate it,Qi not only fills the pores on the sidewall, but also,Return the porosity of the outer wall of the test piece to Jin Ye,Solving the problem of lateral exhaustion directly affects the distribution and measurement accuracy of the internal water flow in the permeameter due to the cross-sectional size of the pressure tube. If the cross-sectional area is too large,Will cause the water flow inside the specimen to form a flow,Distribution of Shadow Logistics Field:The cross-section is too small,Will cause capillary effect in the pressure measuring tube,Impact test results,After repeated face tests, it was shown that the cross-sectional diameter of the pressure measuring tube is1cmIt is appropriate. Try to use transparent hoses as much as possible,In order to directly observe whether there are bubbles inside the pressure measuring tube, micro differential pressure gauges are generally inclined glass tubes,Sometimes the water head cover is only1-~3m,It is difficult to accurately read with the eyes at this time. Therefore, it can make

Differential pressure transmitter,The accuracy of a differential pressure gauge used to convert differential pressure into digital signals is approximately0.Imm