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RE: Fiber-reinforced concrete (was: Control joints in elevated slabs)

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OK Harold:
   The California Department of Water Resources has about
400 miles or more of 4-inch concrete lined (paved) open
channels. This has served the State very well for 20 to 30
years without any steel.
   These canals transverse the coastal range including
regions of landslides, thrust blocks, quicksand, holes,
faults, rock, mud, springs, and whatever else the geologist
may encounter through that career choice.
   During emergency liner repair these were cleaned,
re-leveled, covered with a waterproofing membrane, and then
covered with 2-inches of 4,500 psi shotcreted mixture with
roller screeding for consolidation. Some of this cover
mixture included  polypropylene fibers.
   Those panels that did not have the polypropylene fibers
demonstrated shrinkage cracking outside of the crack control
joints, which were located over existing control joints.
Where the polypropylene fibers were used the crack control
joints appeared to serve their purpose. These joints were
sealed with
   No reinforcing steel was installed due to the
availability of moisture.
   The 2-inches of concrete cover is an anchor and an
abrasive resistance surface to the "potable" water delivered
from the "biomass" of the Sacramento Delta region.

-----Original Message-----
From: Michael Hemstad [mailto:mlhemstad(--nospam--at)yahoo.com]
Sent: Friday, November 30, 2001 8:21 AM
To: seaint(--nospam--at)seaint.org
Subject: Fiber-reinforced concrete (was: Control joints in
elevated
slabs)


>... cracking in concrete slabs on metal deck is an
issue.
>
>Number one, never use polypropylene fibers.  Use mesh
or rebar.  This
is
>another topic.

OK, Harold, you opened this can.  Tell us about
polypropylene fibers.

I've got a bunch of outdoor slabs on grade (not
elevated slabs-I changed the subject) that I pulled
all the steel out of due to concerns about de-icing
salts.  In the slabs I put poly fibers.  The slabs
have substantial edge beams which I couldn't make
myself believe would be all right without steel, so I
used epoxy bars.  Good, bad, or indifferent?

Mike Hemstad
TKDA
St. Paul, Minnesota


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