On 1/4/14 8:47 AM, Ray, W4BYG wrote:
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.
I understand that they used to set parking meters with sulfur..When the
meter was damaged, they could replace it by melting out the sulfur.
These days, one uses epoxy as a "chemical anchor". The epoxy is
specifically designed to have the right amount of resilience to avoid
cracks, etc.
BTW, silicon, germanium, gallium, Antimony, and Bismuth expand when
solidfying. I don't know that sulfur does. Iron might also (I found
several references with varying density numbers. it's a pretty close thing).
It has to do with whether the crystal lattice is spaced farther apart
than the atoms in liquid. There's a bunch of compounds that expand on
freezing: most salts, acetic acid, but not sulfuric or nitric acid
(something to keep in mind when you're making your own blasting supplies
for that really tough rock)
(not that pouring molten silicon to hold in a bolt is something you're
likely to be doing..<grin>)
Sulfur, though, is an example of something that forms an amorphous
non-crystalline solid (like glass). However, I seem to recall from 40
years ago that a lump of molten sulfur that is cast eventually turns
into powdered sulfur. But maybe there's some annealing or heat profile
that's important.
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