[TowerTalk] concrete fiber vs. rebar

SGTOKIE at aol.com SGTOKIE at aol.com
Sat Sep 13 03:13:23 EDT 2008

Dan, in my previous tower base as well as the 3 basses I currently have & 1 
planned, I used rebar cages AND the course fiber with #4000 concrete. Let me 
explain why “I did it this way” 
The reason I use fiber fill is to help prevent cracks and fractures in the 
concrete when it cures. I also use reduced water in the mixture and exchange 20% 
of the sand for pea gravel to further reduce the water required in the mix 
(has to do with surface area of sand/surface area of pea gravel)……the less 
water in the mix means lesser shrinkage during curing. Expansion and contracting 
in the concrete will induce cracking. HOWEVER, reduced water (less slump) means 
the concrete wont “flow”. It will me harder to move around the rebar, will 
reduced curing times and more difficult to finish the top. 

The rebar cage is electrically bonded to the tower section planted in the 
concrete with #4 solid copper in 3 places on the tower faces to the rebar 
(covered in concrete). I have also tied my tower above the concrete level to ground 
rods about 16’ (2x ground rod lengths to prevent the electrical saturation of 
the grounds) 

The rebar cage and the concrete base is called a UFER ground (google it). Dr. 
Ufer found out that concrete absorbs moisture fairly quickly and releases it 
slowly. The releasing of the moisture to the sourrounding soil improves the 
conductivity of the soil from electrolytes in the concrete mix. Even though the 
concrete base is not a perfect conductor-it will conduct “some” of the strike 
energy. My theory is if I can dissipate any portion of the strike energy, USE 
IT to my advantage. 

Ufer grounding is required in many local building codes per NEC. I don’t have 
a NEC book with me but google “NEC UFER”…….there should be no reason to NOT 
use all available sources to decrease the possible damage due to a lightning 
strike…..ie air terminals, ground rods, salt wells,  Ufer ground, spark gaps 
on window line and open wire feeders, arrestors for coax and rotor cable 

If you ask 10 hams their opinion on the subject of grounding you will get 11 
different responses (somebody will give you 2 answers). Im not saying we are 
all 100% correct or we are 100% wrong…..we are just hams enjoying our hobby and 
trying to give information to someone else since most of us had an elmer to 
advise us at one time or another. Im not paying for your damaged equipment and 
your not paying for mine…I got a few pics to send if you want to see

de david, k5qwo, el2rl, yi9qwo (ex: kd5qwo)

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