2.3.2. Water permeability
Permeability as a unique ability for water to penetrate through
porous concrete was expressed in millimetres per second (mm/s).
Since porous concrete generally owns a much higher permeability
compared to the normal dense concrete, the permeability test
method for the latter one was not suitable for testing porous concrete.
As there is no Australian Standards for such testing, a testing
method which was similar to the falling head test method for soil
(AS1289.6.7.2-2001) was adopted in this research.
The testing apparatus has been gradually improved from our
previous research [16]. Instead of using a rigid perspex tube as previous
testing, the cylindrical plastic pipe was used in this test. With
inline steel wire and adjustable steel tie, the pipe was tight to inhibit
water leakage along the sides of the sample (see Fig. 2). Moreover,
the tiny gap between the specimen and the pipe at the
bottom was sealed with processed plasticene to prevent water
infiltration through the edge of pipe, which will affect the accuracy
of the permeability coefficient. Subsequently, the water permeability
rate of porous concrete was calculated by Eq. (1).
K ¼
aL
At ln
h1
h2