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Re: Epoxy type grout for anchor bolt

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Bob,
 
Yes the modulus of adhesives is typically lower than concrete, but looking at the overall flexibility of an anchorage assembly, the other components will usually have significantly more flexibility than the anchor itself.  The modulus of the products that we would typically recommend for anchoring range from equal to that of the concrete to about 1/4 of the modulus of concrete.  Even at only 1/4 Ec, that is still pretty rigid. 
 
Thanks,
 
Howard Silverman, PE
Covert Operations/USP Structural Connectors
Signal Hill, CA
hsilverman(--nospam--at)uspconnectors.com
(562) 986-4212
 
 
-----Original Message-----
From: Robert Kazanjy <rkazanjy(--nospam--at)gmail.com>
To: seaint(--nospam--at)seaint.org
Sent: Thu, 1 Sep 2005 21:06:59 -0700
Subject: Re: Epoxy type grout for anchor bolt

Howard-

What about the effect of bond line thickness?  

Isn't the modulus of the typical adhesive much lower than concrete?

Does a thicker bondline not increase flexibility of the system?

cheers
Bob

On 9/1/05, coengineer(--nospam--at)aol.com <coengineer(--nospam--at)aol.com> wrote:
 Sorry for the late response, but hopefully I can provide some info for you and others for future applications as this is a common question.  There are two main problems with using typical adhesive anchor products in oversize holes.  The first being shrinkage due to the evaporation of solvents present in the adhesive.  Some adhesives contain styrene, water, or other volatiles that evaporate out of the product as it cures.  The effect of this shrinkage is compounded with thick sections associated with oversize holes.  This shrinkage causes the product to try to delaminate from the hole as it cures. 
 
The second problem is the exotherm and associated heat expansion (and then contraction during cooling)that occurs during curing.  Anchoring adhesives typically cure due to a chemical reaction between the 2 or more components.  This may not be a problem in some instances because the concrete is generally a large heat sink, however some rapid curing products can develop extremely high temperatures during cure.  On the other hand, there are some epoxy products that use curing agents that are designed to cure slowly with a gentle exotherm.  One of the products manufactured by Covert Operations/USP will reach a peak exotherm of only 109 F on a 6" x 12" cylinder of epoxy grout at 75 F ambient temperature. 
 
In general, it is good idea to speak with the manufacturer regarding special applications (i.e. Hilti would not recommend using their HY 150 for this application, Covert/USP would not recommend using their CIA-EA for this application, etc.)
 
Best regards,
 
Howard Silverman, PE
Covert Operations/USP Structural Connectors
Signal Hill, CA
hsilverman(--nospam--at)uspconnectors.com
(562) 986-4212
 
 
-----Original Message-----
From: Rich Lewis <seaint03(--nospam--at)lewisengineering.com>
To: seaint(--nospam--at)seaint.org
Sent: Tue, 23 Aug 2005 13:54:54 -0500
Subject: Expoxy type grout for anchor bolt

Is there a product for grouting anchor bolts in large holes?    Typically, from what I've seen, most epoxy anchor holes are slightly bigger than the bolt diameter. 
 
I have a project where the anchor bolts were not installed correctly.  The contractor wants to core 2-3" diameter holes for installing new bolts.  I was wondering if there was a product that would bond to the bolts and a hole that big.  The anchor diameters are ¾" & 1".
 
Thanks.
 
Rich