Wicking Forces in Concrete
Wicking action is the movement of water by forces of attraction (both capillary and chemical) between the water and the adsorbing material. For example, capillary forces are seen in a glass where the water edge rises slightly above the surface. If the diameter of the glass is reduced to the size of a small tube, the force of attraction will become stronger than the gravitational force, causing the water to move up the tube.
Wicking Effects of Different Materials
|
Material |
Description |
Height of action |
|---|---|---|
|
Gravel |
Large spaces between rocks and pebbles prevent wicking forces from acting on the water. |
Zero |
|
River sand |
Small, compacted sand particles will induce wicking forces on the water. |
From ½' to 2' depending on compaction |
|
Clay |
Small particle size creates strong wicking forces. |
Tens of feet |
|
Concrete |
Very small cement particles create strong wicking forces. |
Tens of feet |
An
excellent example of
wicking action and rising damp is the flow of water in a Redwood tree
rising over 375 feet above the ground:
-
The roots soak up water from the ground, similar to the concrete footing;
-
The trunk transfers the water vertically, similar to the concrete wall above the footing;
-
The leaves evaporate the water to the air, just as the water evaporates from the interior concrete wall surface.