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RE: Concrete Problem

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Just what IS the 28 day compressive strength??    Did rain hit the wet concrete?? (I assume no frozen temps were encountered)
By all means core the slab in at least 3 places and observe,  plus I think that I would do a cylinder test on these cores.
If at this point you get at least 3000 psi, mesh or rebar was Properly placed, then consult with Master Builders or Sika or similar floor hardener people.          I'm a little skeptical about trying to "harden" an existing WEAK material as you've described.  You may want to make the contractor post a bond in the case that it all fails 2 years (or so) down the road; and if he won"t do this, then just RIP IT OUT and start over. 
-----Original Message-----
From: T. Eric Gillham PE [mailto:teric(--nospam--at)]
Sent: Monday, February 26, 2001 1:47 AM
To: seaoc list
Subject: Concrete Problem

I would appreciate anyone who can give me some help on this one:
How does one go about hardening and strengthening a layer of concrete that has already been cast and cured, without removing the concrete entirely?  In other words, is there a product that can be added to the surface of the concrete to harden it?
The concrete in this particular case would be difficult to remove because of embedded piping.  The hardened surface would then have tile set on it, and would form the floor of a hot water wading pool.  The layer of concrete which needs to be hardened was poured over 2 months ago, and is quite sandy in color with hardly any hint of gray.  This would seem to me to indicate a low cement content.
Anybody have any ideas on this one?
T. Eric R. Gillham PE
PO Box 3207 Agana Guam 96932
Ph:   (671) 477-9224
Fax: (671) 477-3456
Cel  (671) 687-7115