Cement curing time.... (fwd)

[Frank Donovan]

---------- Forwarded message ----------
Date: Wed, 25 Sep 1996 22:25:39 -0700
From: Dan Keefe <KS6Z@Sprynet.com>
To: Frank Donovan <donovanf@sgate.com>
Subject: Re: Cement curing time....

More background on "Concrete" curing time.

Some years ago I worked for a company that made huge steel reinforced
concrete pipe for water/sewer transmission purposes.

Concrete curing time and conditions were a big source of concern for
this company because the hardness and other qualities were tested with
core samples and other methods before the product could be shipped.

Concrete continues to gain strength as long as it exists.  It gains
strength with decreasing momentum, i.e. most of it's strength is gained
early on in the curing period.

If you have a proper mix of "Cement", sand and gravel and not too much
water (this is a strength killer) the majority of the strength will
occur in the first ten days or so.

Strength Killers:

1. Sun beating on freshly poured concrete.  Keep it covered with plastic
or tar paper.
2. Excessive heat.  Don't pour concrete when the temperature is high.
3. pouring concrete into a hole that is dry.  Wet the bottom and sides
of the hole prior to pouring concrete otherwise the dry soil will suck
the water out of the concrete and you will surely have a weak mix when
it cures.
4. Don't fool with it or rock the tower base for at least a week or
better two weeks.  This is of course the road to the river and if the
concrete cracks you will wish you never heard of ham radio. It actually
takes many weeks (months) for concrete to approach it's full strength
but 
you can work with it in about ten days safely.
5. Don't let the surface get dry while it is curing. Give it a spray
with water as often as possible to keep it wet because it WON'T CURE IF
IT GETS DRY, IT WILL ONLY GET DRY.

Good luck,

Dan Keefe  KS6Z



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