[TowerTalk] Concrete-Rock cracking compound - one brand - Betonamit circa 1998

[Kimo Chun]

I haven’t followed the thread closely. I used a compound, I believe, made in
Germany called Betonamit  (sp?) over ten years ago. It is a powder you mix
with water then pour into the bore holes you made in the concrete or rock.
I am sure there are competing products as it appears on the links someone
posted. If memory serves it generated something like 12K psi. My limitation
was only having a regular electric ¾ or perhaps 1 inch rotary hammer and a
12 inch long bit. Making holes in Basalt is difficult at best as it is
highly compressed powder and laughed at my drill.  I had a premade cage and
didn’t want to incorporate the boulder into my tower base. Perhaps I should
have. I could only make a series of short holes as chord cuts across the
face of the boulder, pour in the slurry and pick up the sheared off pieces
in the morning – then back to drilling. This was a very slow process. If you
can bore deeper you can crack off more at one time. But, at that point you
probably are using something or could use something that can drive clear
through the boulder and make short work of it already.

 

Before that point I had rented a back-hoe at around $600 for a day and only
got down 3 feet or so before hitting the 4 x 3 x 6 foot boulder. I could
have rented the hydraulic hammer head to replace the shovel but that would
have been another $600 plus another day of the hoe, let alone whether I
could figure out how to change the implements by myself. I had more time
than money (meaning poor common sense) and spent the next few months on
weekends busting out the boulder. Dumb idea, ultimately, though I did
finish. The last third of the boulder was lifted out by a back-hoe using a
wirer-rope cable I rigged to two 3/4 inch drop-in anchors I had placed in
the boulder. A case of beer to the crew using the hoe for a water project
nearby and the thing went away.

 

I could have modified my steel cage and epoxied it to the boulder. One note
about epoxy: My first experience with bulk quantity epoxy was with a
standard caulking gun size cartridge. It required hand mixing to activate –
later an interface bit for a drill was available. The hand mixing was a
bust. The epoxy wasn’t mixed well enough and never set up properly. A much
newer version from another supplier, Rawl, used a mixing method through the
tip that worked well. During the construction of a freeway here years ago a
worker was killed because of improperly applied epoxy. I don’t know if
mixing was the problem but my experience goes to show that it is a critical
requirement.

 

Good luck.

 

Kimo KH7U