[TowerTalk] Welding re-bar, preventing corrosion
Red
RedHaines at centurytel.net
Fri Jul 7 17:34:34 EDT 2006
An earlier post included information from Hank Lonberg, P.E./ S.E., KR7X that addressed welding
rebar. Among many points Mr. Lonberg made, ASTM A 706 is a weldable reinforcing bar. A major
redi-mix firm near here stocked it. I found it easy to weld with E7018 electrodes. I designed a
rebar structure that provided both the reinforcing required for my tower base and complied with
the requirements for a Ufer ground. It was very easy to lower that welded assembly into the
hole with the loader on my tractor. Alternatively, I believe two persons could have lowered
it into the hole.
Good welds ensure low resistance connections among the members, which is essential for the
Ufer cage and any connections from it to the outside.
Another point that should be observed in building a tower base:
It is important that no steel penetrate the concrete below grade. A penetration provides a path
for the natural alkalinity of concrete to leach out, thus losing some of the anti-corrosion
protection that concrete provides to steel. Bring grounding terminals out of the concrete above
grade. To prevent penetration, place concrete "pills" at least 3" thick under the steel at the
bottom before pouring the concrete.
An easy way to level the bottom of the hole for those pills is with limestone screenings from
a crushed limestone supplier. In this area, the screenings are sold for about 1/2 the price
of road rock. They level easily and pack firmly with very little tamping.
73 de WOØW
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