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.
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.
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
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
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.
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.
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?
