When drilling into concrete or stone for mounting bolts, I many years ago
learned a neat trick from an old time machinist, Grover Shank. He advised
me concrete injected around bolts or hardware store expansion devices will
vibrate and eventually come loose.
He suggested the way they would anchor bolts into concrete for heavy
equipments, was to drill the holes larger and deeper than needed for the
bolts. Then buy a bag or two of powdered sulfur (purchased at a local Drug
store, inexpensive) and melt it in a melting pot, with a butane torch. Set
the bolts in place and temporarily wire them to stay in position. Then pour
the melted sulfur into the holes. Let it cool.
The logic is there are only two natural substances that will expand when
cooled, water and sulfur. The sulfur expanded and locked the bolts in place
securely for years.
I did this for a 72' tower carrying a 2 element 40 meter beam on top and a 5
element tribander below, while living in Atlanta. Years later the tower has
was moved to another city, but I'm pretty sure the 2 bolt guy brackets which
were attached to granite rock at the surface, are still there. The bolts
showed no sign of loosening or cracking.
Since then, I understand hydraulic concrete in tubes has become available.
I have seen it used for metal fence rails and have noticed cracks in the
holes after just a short time. Therefore I wouldn't put much trust in it
for tower foundations.
But my experience with the sulfur even though it stank pretty bad while
being melted, worked so well I would use it again today "in a heartbeat" for
similar applications.
73,
Ray, W4BYG
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