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- Thread starterRobert222
- Start dateOct 17, 2010
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- Oct 17, 2010
- #1
Robert222
Structural
- Mar 2, 2010
- 24
Could someone help me understand when to use epoxy and when to use expansion anchors for masonry or concrete?
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- Oct 17, 2010
- #2
ooox
Structural
- Jun 22, 2009
- 95
Hilti's Manual provides some guidance when you can and cannot use certain types of anchors plus the theory behind them. I've found eopxy anchors to be suitable for the majority of installations. Expansions anchors have the advantage in that there's no waiting time until you can load, some are suitable for use in the tension zone and they have smaller edge distance requirements however they tend to be more expensive. They also have advantages for overhead installations.
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- Oct 17, 2010
- #3
rscassar
Structural
- Jul 29, 2010
- 631
I would always prefer the use of epoxy anchors over expansion anchors except for the following situations:
1. Overhead applications. You can google the Boston Big Dig Tunnel collapse for information regarding epoxy creep when subject to a constant tension load.
2. Where the anchors need to be installed immediately. Epoxy anchors need some time to set. However, you can get epoxy which sets in less than 1 hour.
3. Where fire-protection is paramount such as steel frame structures which are fixed to and prevent concrete wall panels from falling outwards. I am yet to see a compliance certificate for epoxy used in post-installed anchor situations where it has been shown that the epoxy can withstand exposure to high temperatures for a prolonged period of time.
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- Oct 17, 2010
- #4
msquared48
Structural
- Aug 7, 2007
- 14,745
When retrofitting an anchor into the top of a concrete or masonry stemwall, as for an anchor bolt or a holddown, always use an epoxy anchor, never an expansion anchor, due the spalling issue.
I agree with the other comments above too.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
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- Oct 18, 2010
- #5
rowingengineer
Structural
- Jun 18, 2009
- 2,464
Epoxy is great if you have a trusty labourer, some mechanical anchors are good also, however concrete shrinkage will reduce effectiveness over time, so your spec needs to cover these possibles, mechincal is torque settings and retightening spec, while epoxy is testing at % capacity for a % number. I prefer something solid, aka castin or similar for major connections.
A clear conscience is usually the sign of a bad memory
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- Oct 18, 2010
- #6
SLTA
Structural
- Aug 11, 2008
- 1,641
Don't forget too that epoxy is only as strong as the hole it goes into, meaning epoxy bonded to dust and dirt does no good at all. Be sure to clean the holes properly.
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- Oct 18, 2010
- #7
rscassar
Structural
- Jul 29, 2010
- 631
slta,
Good point. I know of some engineers who are specify pull-tests for epoxy anchors (say 1 in every 10).
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- Oct 18, 2010
- #8
RHTPE
Structural
- Jun 11, 2008
- 702
Keep in mind the method for drilling the holes - core-drilled holes have smoother walls and will affect the effectiveness of the anchor.
Ralph
Structures Consulting
Northeast USA
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- Oct 18, 2010
- #9
ATSE
Structural
- May 14, 2009
- 594
One more benefit to epoxy over expansion ("wedge"):
With epoxy, you can use 316 stainless steel threaded rod. Some of the wedge anchors that have been certified for "cracked concrete" are 304, but not 316.
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- Oct 19, 2010
- #10
keenaseng
Structural
- Jul 11, 2010
- 26
Kikflip,
Further to your point about epoxy + high temperatures, what are your thoughts on welding to chemset bolts (ie. column baseplate welded to chemset hold down bolts) assuming the hold down bolts are low carbon steel that can be welded.
The temperature passed through the epoxy during the welding process is high, but over short period. Would you consider this to ruin the epoxy?
I have seen this done on site before.
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- Oct 19, 2010
- #11
csd72
Structural
- May 4, 2006
- 4,574
Most mechanical anchors have poor performance under oscillating loads.
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