[TowerTalk] Pre-rebared concrete

[Lonberg, Hank]

Hakan:
Indeed the fibers are introduced into the concrete mix to reduce hairline
cracking due to temperature and shrinkage effects on the concrete. They
provide an enhanced durability to the concrete. I've seen plastic and other
materials as fiber, but not steel or other ferrous alloys used due to
rusting. You will still need the reinforcing bar as the fibers do not really
contribute to the load carrying strength of the concrete.

Hank Lonberg P.E. / KR7X


	-----Original Message-----
	From:	Hakan Linderhed [SMTP:sm5jbm@swipnet.se]
	Sent:	Tuesday, July 04, 2000 2:20 AM
	To:	towertalk@contesting.com
	Subject:	[TowerTalk] Pre-rebared concrete


	Hi

	While pouring the base for my new tower yesterday, the concrete
	truck driver told me about a new type of "pre-rebared concrete"
	that he said is going to revolutionize the concrete industry.
	Instead of using the normal steel bars, they mix lots of small
	pieces of steel wire with the concrete, which supposedly should
	do the same job as the traditional bars.
	He showed me one "mini-bar". It was about 7 cm (3") long and
	about 1 mm (0.04") in diameter.

	Has anyone any experience from this type of concrete? Does it mean
	we don't have to mess with unwieldy rebar cages any more?

	Intuitively the idea seems pretty sound and I guess you could say
	that the concrete is reinforced at a "lower level" than when using
	large sized bars. But will this type of concrete hold up for 
	demanding structural applications?

	The driver also mentioned that he brought some of this concrete home
	(a fringe benefit in his profession ;-) to do some stairs at his
house,
	and (no surprise...) discovered that all superficial wires in the
concrete
	rusted in a very short time. Since the wire bits are not connected
to any
	other wires, this is probably more of an aestetical than a
structural issue.

	Can someone in the "concrete business" enlighten us?

	73, Hawk SM5JBM (SM5G)




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