Wednesday, January 21, 2009

RE: Bond Strength of Portland Grouts

This is correct.  In the old ACI 318-63, there was a bond strength for plain bar.  This proved to be HIGHLY variable to zero bond with some smooth cold rolled bars.  Stick with the tested information. 

Regards, Harold Sprague




To: seaint@seaint.org
Subject: Re: Bond Strength of Portland Grouts
From: Tom.Hunt@fluor.com
Date: Wed, 21 Jan 2009 15:22:58 -0800


Thor,

It is a lot more complicated than simple "bond" strength.  The "bond" strength of your grout to the rod will be different depending on whether you are using smooth bar, threaded rods, or deformed rebar and the different values you see for each in a HILTI catalog are based on testing.  If my memory is correct, in the "good old days", we use to use 60 psi actual bond of concrete to steel rods but I suspect it would be much higher for a treaded rod.  If your client does not like the epoxy suggest a proprietary cementitious grout which again would have an ICC report with values you can fall back on otherwise you are left holding the bag if anything goes wrong.  You would also have to come up with your own written installation, curing, testing, and inspection guidelines instead of being able to just reference an appropriate ICC ES Report number.

Thomas Hunt, S.E.
Fluor




"Thor Tandy" <vicpeng@telus.net>
01/21/2009 02:36 PM
Please respond to seaint
To
"SEAINT" <seaint@seaint.org>
cc
Subject
Bond Strength of Portland Grouts





I've been asked by the Client to review substituting Hilti RE-500 SD epoxy
with "Portland Expanding (no-shrink) Grout".  I'm anchoring a cable support
post, using baseplate and threaded ASTM 193 rods, to conglomerate bedrock

To do that I need to have an idea of the available bond strength.  The
supplier I was able to contact said that it isn't normal to have BS for
grouts.  I don't think it's doable but before I cause a frown on my client's
face, does anyone have a reasonable value for the bond strength of this
grout.

The RE-500-SD has up to 12.4MPa (1800psi) but I don't think the grout is
anywhere near this.

TIA


Thor A. Tandy P.Eng, C.Eng, Struct.Eng, MIStructE
Victoria, BC
Canada



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