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