11
©
Germann Instruments, Inc.
Test Smart – Build Right
©
Figure 7
The PR-1070 Vacuum desiccator for
saturating 16 specimens (dia. 100 mm x 50 mm) and
the PR-1081 vacuum pump with hose with <10 mm
Hg vacuum.
4.
Conditioning the specimens
For moistening the samples, boiled (cooled down) or de-
aerated tap water is required. Boil the required amount of
water for half an hour to make sure the water is free of air.
De-aerated water will permeate the concrete specimen
more easily. Should the tap-water contain chlorides it is
recommended to use destilled or de-ionized water. Allow
the water to cool off before pouring it into a separate
container or bucket.
Place the specimen(s) in the empty vacuum desiccator (
see
figure 7
), preferably positioned on a floor close to a water
drainage outlet. Keep the desiccator at this same position
all the time, also during final drainage of the solutions. A
maximum of 6 specimens can be placed in one PR-1069
plastic desiccator and 18 in the PR-1070 desiccator. Clean
the edge of the lid and oil slightly with silicone oil. Make
sure the valves are closed and place the top lid on the
desiccators. Connect the hose from the vacuum pump to
one of the valve nipples in the lid. Open the valve and turn
on the pump. After running the vacuum pump for the
required 3 hours, close the valve and then turn off the pump.
Attach another hose to the second valve of the desiccator´s lid and place the end of the hose in the
container with the prepared boiled water (make sure that the amount is enough for all the specimens to
be fully submerged). For NT BUILD 492, a saturated CaOH solution is needed. Allow the water or solution
to flow into the desiccator by opening the valve slowly until the specimens are completely covered. No air
should be allowed to enter the desiccator.
Close the valve, start the vacuum pump and open the valve leading to the pump. Run the vacuum pump
for another hour.
Turn off the vacuum pump, close the valve to the pump and then remove the hoses from the valve
nipples. Open one of the valves slowly, allowing air to enter the desiccator. Let the specimens soak in the
container for another 18 hours. Remove the lid together with the moistened specimens and blot them
dry.
Finally, a hose is connected to the bottom (red) valve and the water or solution is drained completely
from the desiccator.
When moulded cylinders are required (e.g. for ASTM C1760), cure them in a moist room or in water
storage tanks for 28 days.
