Civil Engineering Reference
In-Depth Information
0
100
BS 1881 minimum air drying period
Drying temperature
10
20°C
99
N4
Mix
20°C
20
98
N55
20°C
30
N7
97
50°C
40
96
N4
50°C
50
50°C
N55
95
BS 1881
minimum
period for
105°C oven
drying
60
N7
105°C
105°C
N4
N55
N7
94
70
105°C
93
80
1
2
4
7
14
21
50
100
Drying Period - Day (log scale)
Figure 5.3
Moisture loss under various conditions. (From Dhir, R. K. et al.,
Mag. Concrete
Res
., 39, 141, 1987.)
mineral admixtures did not vary as much as other transport properties and
appeared unaffected by the initial moisture condition.
Under steady-state conditions, the diffusion coefficient can be calculated
using Fick's first law of diffusion:
F
= -
D
× (
dc
/
dx
)
where
F =
mass flux (kg/m²s)
D
= diffusion coefficient (m²/s)
c
= concentration (kg/m³)
5.3.6 Wick action
Wick action is the transport of water through a concrete element from a
face in contact with water to a drying face as occurs in basements, tunnels,
slabs on grade, and hollow offshore structures. The term “wick action” to
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