[TowerTalk] Re: Concrete an insulator???

[Jim Smith]

    It's normal for freshly poured concrete to have a very high resistance.
It drops over a long period of time. This is why building departments don't
check the ground resistance on ufer grounds. They know that the readings
they get in new construction will be worthless. Therefore, they have to rely
on proven techniques, and trust that the resistance will come down.
    As to whether concrete is an insulator, or conductor, the National
Electrical Code defines concrete walls as a grounded surface.
Jim Smith
KQ6UV

-----Original Message-----
From: Edward W. Sleight <k4sb@mindspring.com>
To: Peter Larsen <larsenp@cadvision.com>
Cc: Ted Leaf <tleaf@hotmail.com>; towertalk@contesting.com
<towertalk@contesting.com>
Date: Tuesday, October 13, 1998 8:17 PM
Subject: Re: [TowerTalk] Re: Concrete an insulator???


>
>OK guys, I happen to be in a very unique position. The base was poured
>for my new 89 footer yesterday. It's 5.5 x 6 x 7.5 feet. This evening,
>I measured the resistance between one of the ground rods (4) and the
>center of the base. At that time, the concrete was 36 hours old. The
>resistance was 1.47 Meg Ohms.
>
>I believe keeping the exposed section as wet as possible strengthens
>the concrete, so earlier today, I flooded the top with 2" of water.
>
>I'll flood it again tomorrow and repeat the test ( before and after )
>At that resistance, it won't even blow a .1 amp fuse.
>
>73
>
>Ed
>
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