The field test for air and water permeability of concrete using the Figg technique.
Tests the air and water permeability of concrete - at the surface and beneath
Poroscope™ Plus measures the time it takes for air to flow into a known volume of a sealed, evacuated chamber in the concrete. While the vacuum reduces from -55 Kpa to -50 Kpa, a measure of air permeability is determined. For water permeability, Poroscope™ Plus uses the same chamber filled with water, and measures the total time in seconds for a volume of 0.01 ml of water to escape. Surface porosity is determined in like manner using a specially designed surface chamber.
Features & Benefits:
Both air and water permeability are measured by the same instrument.
Permeability both at the concrete surface as well as within the concrete mass can be determined.
Porosity in sealants and surface mortars can be checked.
The test is non-destructive (only a small plugged hole required) and can be completely carried out on site.
Each test can be completed in only a few minutes and gives reliable reproducible results.
The test enables meaningful concrete durability predictions to be made.
INTERNAL TEST; A hole 10 mm diameter x 40 mm deep is drilled and plugged leaving a cylindrical test void 10 mm diameter x 20 mm high situated 20 mm below the concrete surface. The time required for air and water to permeate through the test material to the void is used as an index to determine the quality of the con-crete under test.
AIR PERMEABILITY; The air permeability test is always done first since moisture has a large effect on permeability. Connect the air outlet tube on the instrument to the Luer connector on the top of the hypodermic needle. Connect the hand operated vacuum pump to the air connection on the top of the instrument and evacuate to greater than 55 kPa. The instrument timer and manometer will automatically show the time in seconds for the vacuum to fall from a – 55 kPa to a – 50 kPa. This time is the Figg number and is a measure of the air permeability of the concrete.
WATER PERMEABILITY; Connect the water outlet tube to the Luer socket on the top of the hypodermic and ensure that the fine plastic inner tube is of sufficient length to reach the bottom of the test cavity. After filling the syringe with distilled water connect it to the water inlet on top of the instrument. The water is then forced into the cavity and the air displaced out through the outer tube through the overflow tube which is 4 inches (100 mm) above the surface of the concrete. The cavity is filled when water starts to flow out the overflow tube. The instrument flow sensor and timer then automatically measures the time taken for the water meniscus to travel a distance of 50 mm and this time in seconds is displayed on the LCD display of the instrument. The time in seconds is the Figg number for water permeability.
SURFACE PERMEABILITY TEST; Measurements are carried out at the surface by clamping a stainless steel chamber on the smooth surface of the concrete. An exactly dimensioned cup grinding wheel is used to smooth the sealing surface of the concrete if necessary. A measurement of the time required for related amounts of air and water to permeate through the concrete is used as an index of the surface conditions. This time can then be used to determine the condition of any concrete sealant or surface mortar.
SURFACE TEST DETAILS; A stainless steel surface chamber with the same surface area and exactly twice the volume of the hole used in the internal test is now used as the void for this test.
The method of sealing the surface chamber to the concrete eliminates the possibility of variation in the test due to sealants seeping into the chamber, or voids along the sealing surface. The surface chamber is sealed to the concrete by grinding a smooth donut in the surface with the cup wheel provided. This cup wheel is sized to exactly match the dimensions of the surface chamber. A pair of o-rings mounted concentrically in the surface testers’ flange is then used to seal the chamber to the surface. The two o-rings eliminate the possibility of a surface void in the material being tested defeating the test. After clamping the surface chamber to the surface a strong seal is now provided with no variation in volume.
This surface chamber is now used as the void for testing porosity of the surface. Rather than the walls of the hole being the tested surface the surface that the chamber is sealed against is now the surface tested. This provides a check for water and air penetration through concrete sealants, surface mortars and any other methods used to seal construction material surfaces.
The surface chamber has been designed to easily accommodate attachment to the instrumentation. By first performing the air test as outlined in the internal test and then the water test the instrumentation will provide the time required for the chamber to lose 5 kPa vacuum or once filled with water, 0.01 ml water.
With the surface tester attached to the instrument both a Figg number and direct indices for air and water surface permeability can be established.
TECHNICAL; The ingress of air and moisture into the concrete can cause corrosion of the steel reinforcement and lead to a deterioration in concrete strength. Therefore, a measure of the ease of movement of liquids and gases through the surface layer of the concrete is a better method of assessing the soundness and expected life of concrete than strength alone. Permeability is recognized as being the most important parameter in assessing concrete durability.
The air permeability test involves measuring the time taken for air to flow into a known volume of a sealed, evacuated chamber in the concrete, reducing the vacuum from—55 kPa to—50 kPa. This time is a measure of the air permeability of the concrete.
The water permeability test utilizes the same sealed chamber in the concrete which is completely filled with water and the total time in seconds for a volume of 0.01 ml of water to escape is taken as a measure of the water permeability of the concrete.
The moisture content of the concrete has a major effect on permeability. For example, fully saturated concrete is almost impermeable to air and results in extremely long times in the water permeability test.
For effective testing the concrete should be dry and the near surface moisture content measured. Permeability test results have show that there is a good correlation with both water/cement ratio and compressive strength of the concrete.
Specifications
Weight, complete in carrying case
12.0 lbs. (5.4kg)
Dimensions
17 x 12 x 6 inches 43 x 30 x 15 cm
Power Supply
Standard 9V Battery
Grinding Wheel Rpm
12000 max
Sales Numbers
C-P-6000
Poroscope™ original system for internal permeability
C-P-6060
Pack of twenty-five test plugs
C-P-6040
Surface Chamber Kit for Poroscope™ Plus
C-P-6050
Poroscope™ Plus complete system
Instructions OPERATING INSTRUCTIONS I. PREPARATION OF TEST HOLE Drill a series of test holes 10 mm diameter and exactly 40 mm deep using a masonry drill fitted with a tungsten carbide bit (See Figures 2a-2b). At least 3, preferably 6, test holes (arranged in a compact group) should be tested and the mean value of the cluster taken as an indication of concrete air or concrete air or water permeability.
Holes must not be less than 30 mm (1-1/4”) apart or less than 30 mm from the edge of the concrete. Blow out all loose dust from the holes with the rubber bulb blower. Insert a molded silicon rubber plug into each test hole, making sure that the top flange of the plug is seated securely on the concrete surface. Insert the hypodermic needle through the silicon rubber plugged hole so that the hollow needle just protrudes through the bottom of the plug. Clear the hole with a steel wire to ensure needle bore is free from obstructions.
The end result should be a cylindrical void exactly 20 mm high and 10 mm in diameter with a hypodermic needle connecting it to atmosphere.
Vertical Surfaces For testing vertical surfaces, the following procedures should be adopted: Drill a horizontal test hole, as in Figure 2a, to the standard dimensions. From the top of this test hole, measure a distance vertically upward of 6” (152 mm).
From this position, measure horizontally a distance of approximately 3” (75 mm); at this point drill a ¼” (6 mm) diameter anchor hole. Set expansion anchor in the hole and screw in the #8 screw.
Hang instrument on this anchor screw using the slotted hole at the top of the instrument base.
II. TEST PROCEDURE Check Instrument Function Switch on power. Reset timer display to zero using reset button. Always test air permeability before testing water permeability. Even when air permeability is not required, the air test procedure should be done so that all dust within the void is vacuumed out.
Air Permeability Fit male Luer taper end of filter on air line into female socket of hypodermic needle.
Connect flexible tube with male connector from hand vacuum pump to right hand fitting marked air, on top of the instrument.
Turn vacuum valve on the instrument to position marked open.
Using slow, steady hand strokes, exhaust system to a vacuum in excess of 55 kPa (16.24 in Hg) below atmospheric pressure. (During this operation the red-50 kPa LED – then the red -55 kPa LED should light up.)
Close vacuum valve on the instrument.
Confirm that the clock timer is not running and that the display still reads 00.00 (if not, reset accordingly.)
Verify that both -50 kPa LED and -55 kPa LED remain illuminated.
When vacuum is reduced to -55 kPa by infiltration of air into the test cavity, the left LED will go out and the timer will commence to run. When vacuum is reduced to -50 kPa, the right LED will go out and timer will stop.
Note timer reading (minutes:seconds) and convert to seconds. This is the time for a 5 kPa pressure change within the test hole from a -55 kPa to -50 kPa below atmospheric pressure.
Repeat test, which should give the same elapsed time in seconds, + 2% of the reading.
To avoid leakage between holes in the same vicinity, complete air permeability tests for all holes before starting water tests.
Water permeability Carefully insert fine central cannula tube of water connection through bore of hypodermic needle and then, firmly seat male Luer taper end of outer tube into hypodermic needle.
Attach stopcock to syringe and open stopcock. Fill syringe with water at approximately 20° C (70° F). Use filtered tap or distilled water completely free from soap or detergent.
Depress the syringe plunger steadily until water emerges from the fine nylon capillary tube at the side of the instrument.
60 seconds after the test hole has been filled with water, adjust the meniscus position in the nylon capillary by gentle manipulation of the syringe plunger to bring the meniscus close to the outside of the instrument case. Close the stopcock.
Check that both LED indicators are lit and that the timer display is not running and that it reads 00.00 (If not, reset.)
When the water meniscus passes sensor #1, the LED on the left will go out and the timer will start to run.
When the water meniscus passes sensor #2, the infra-red detector system will go out – and the timer will stop.
Note timer reading (minutes:seconds) and convert to seconds. This is the time required for 0.01 ml water to be absorbed by the concrete.
If air bubbles become trapped in the inner tube, the LED lights will switch on and off irregularly. When this occurs, the syringe plunger should be depressed with a firm, continuous pressure until the bubbles are expelled from the overflow tube.
If inner tube becomes blocked with dust particles, it should be replaced with a new water tube assembly according to the following instructions:
Instructions to Replace Water Tube Assembly DISASSEMBLY 1. Turn off the on-off switch. 2. Open Poroscope™ case by removing the 4 screws at the corners of the base of the case. 3. Separate top cover from base, being careful not to break plastic tubes. 4. Disconnect water tube at the inside of the dark grey plastic base by pulling the 1/8” (approx. 3 mm) ID plastic tube from plastic nipple. 5. Remove black strain relief fitting on the outside of the dark grey base by gripping with pliers and pulling away from base (you can cut water tube off at outside of strain relief to facilitate easy removal of strain relief fitting.) 6. Pull out and remove the overflow water tube from the side of the case and the aluminum block attached to the PC Board from the side of the case. 7. Remove complete water tube assembly from the case.
ASSEMBLY 1. Feed the new water tube assembly through the hole in the dark grey instrument base. 2. Feed water overflow tube through the aluminum block and out through the water overflow hole in the side of the instrument case. 3. Connect the nipple inside the case at the end of the water tube assembly to the 1/8” (3 mm) ID plastic leading to water inlet. 4. Place black strain relief fitting on tube near the outside base and push and lock it into place in the hole through the dark grey plastic base. 5. Carefully, without pinching or kinking any of the plastic tubes, fit the light plastic case top to the dark grey base; insert and tighten the four screws.
III. RESULTS Permeability times are influenced by the moisture content of concrete. The wetter the concrete, the longer the permeability times. Completely saturated concrete will give extremely long times (theoretically, infinity for water: for air, the time would reflect the rate of dissolution of atmospheric air in the concrete pore fluid.)
The Air Exclusion Rating for concrete may be calculated from the formula: Note: Where t = measured time(s) V = volume of apparatus, including test hole (ml) : for the standard Poroscope™, V = 77.1 ml; AER = 0.247 t. The water absorption rate is given by: WAR = (t/10) x 103 s/ml Note: Where t = measured time(s)
RESULTS The following table gives the tentative values for air and water permeability times and calculated AER ratings for concrete of varying protective quality for embedded reinforcement:
REFERENCES 1. Figg, J. W. Methods of Measuring the air and Water Permeability of Concrete. Magazine of Concrete Research, Vol. 36, No. 129 December 1973, pp 213-219. United Kingdom. 2. Cather R.Figg, J. W. Marsden, A. F., and O’Brien, T.P. Improvements to the Figg Method for Determining the Air Permeability of Concrete. Magazine of Concrete Research, Vol. 36, No. 129 December, 1984, pp 241-245. United Kingdom 3. Figg, John Concrete Surface Permeability: Measurement and Meaning. Chemistry and Industry (London), 6 November 1989, pp 714-719. United Kingdom
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( FORE CO. reserves the right to alter specifications to equipments to any time. )
(J16;CORROSION1) AIR and WATER PERMEABILITY of CONCRETE FIELD TEST with Figg Technique
