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RE:waterstoppers in concrete

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I am not a fan of rubber waterstops.  I prefer
creating a good construction joint where the new
concrete bonds to the existing with reinforcement to
keep any cracks small.  To this you should apply an
exterior membrane that can bridge the small cracks. 
Consider also xypex as an admixture in the concrete to
help seal the cracks.

Since concrete cracks do not always occur at the
construction joints we need a solution that also deals
with the random cracks.  Waterstops do not satisfy
this criteria.

Waterstops get in the way of the reinforcing steel and
make it hard to get good consolidation.  This is
doubly so if the waterstop is placed in a key.  I
believe that this makes the concrete even more porous.

The bentonite strips placed in the construction joint
seem to work and can be accomodated by the concrete.

The one application that I have found where I think
rubber waterstops are appropriate is where the
concrete structures on both sides will move
independently up to an inch or possibly more and where
the inevitable leaking can be drained away on the
inside. One example of this is the joints between
segments in a subway tunnel.

Mark Gilligan

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