I guess I might as well jump in here on the subject of concrete exploding under
lightning stresses.
First of all I am a certified concrete technician with nearly 30 years
experience and have designed numerous concrete structures, including tower
bases and water tank foundations.
Concrete is a hydrated crystalline material. The crystal structure combines
several inorganic elements with water molecules. When concrete hardens it does
not ?dry? it becomes rigid as the crystal structure forms. None of the water in
the concrete mixture is lost. The crystallization process is very slow. About
60% will be completed in a week and nearly 90% in a month. Theoretically it
never reaches completion.
The point is, concrete contains water; a lot of it, in the crystal structure.
It also contains metallic elements. When a sufficiently powerful electric
field is imposed on the crystal structure it begins to break down and becomes
conductive. The water molecules in its structure begin to be released and will
flash into water vapor. As one person stated, this can happen in 40 year old
concrete that is as dry as a bone.
The final analysis is that you must not, under any circumstance, permit an
electric current to run through the concrete. Even if a good conductor is
embedded in the concrete, a lightning strike will cause current to flow in the
concrete immediately in contact with the conductor and the degradation process
will take place.
Ground rods and conductors should always be placed outside the concrete
foundation. QED
---------------------------------
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