Epoxy anchors use and problems

Hello Poobear,

We have been using them for the last 20 years or so with good success, the hold and the fastener must be sized appropriatly, the concrete drill hold needs to have the dust blow out of it and folks need to read the directions on the epoxy.

if you google epoxy and fastners I am sure you will get a more thorough answer.

rick

As stated above, it is important to blow the holes out with air, and air compressor is the best one that can provide and constant volume flow rate. If using the hand pumps you should always use the cylindrical wire brushes as well, in order to remove the dust that is ground into the wall of the hole whilst drilling. When cleaning the holes with air you should wear a face shield to protect from flying particles.

Google: Hilti or Ramset Redhead for information; Hilti requires registration, that is free to do, before you can access data.

It is important to consider setting and working times when selecting your epoxies. The higher the ambient temperature the shorter the working and setting times. When using the Hilti HT 150 in high temperatures I have experienced cases where I was unable to drive or twist the anchors into the epoxied hole before the epoxy set preventing full insertion, I now prefer RedHead over the Hilti, which I have used on several projects where in the region of 2000 anchors have been installed and when testing 10% received no failures.

If installing large quantities of anchors it is best to use a pneumatic gun, they cost around $700, but increase your productivity substantially and can reduce wastage. When using the manual guns I have seen many broken when guys have approched the expiry time of the epoxy.

It is also important to plan any rebar and anchor locations to avoid each other, when hitting rebar whilst drilling concrete will stop you dead. This will cause the drill unit to kick or rotate, which could cause serious injury. The rebar can be drilled through with either a HSS drill bit or a rebar cutting bit (Relton Rebar Cutter), do not use the rebar cutter in a hammer drill it will chip the tungsten carbide teeth. Drilling rebar is not productive and it also damages your reinforcement.

thanks your comments are very helpful

would you recomend epoxy for an overhead application and if so what safety factor would you use?

do you know of any issues with creep based on loading overhead and if so does ICC ES take that into account for certain epoxies?

I have used epoxy on overheads for duct work and piping supports, where mechanical anchors were not approved. In these conditions safety factors were well above the loading.

If you are using epoxies for ceiling mounted applications, you must consider your application. Is it a static or a live load, will there be any fatigue cycles? Although I never been requested to perform fatigue analysis on epoxy anchors, it is always something you have trusted the manufactures testing and investigations on. Some engineers I have worked with have prefered to use epoxies for items subject to cyclic wind loads, as they have said in their experience the epoxy has had more give in it and has reduced anchor fatigue.

If I am designing for a duct support or something similar I like over engineer and allow for it to support a mans weight as well as the object and a SF of 2, this is usually higher than a SF of 4-5 for a light object like a duct alone. It is just a preference, as you know what accidents can happen when installing and what extra forces the installers insert. Guys will tie off to supports sometimes, although they should not, but when there is nothing else available, it may save someones life. A real lifeline support/eye should hold 5000lbs or 2268kg per person.

I have worked on many projects where there is no allowance for sub contractors to tie off to and the Safety officers have expected the sub-contractor to provide a tie off point, and have provided no solutions in a very dificult situation, forcing the guy to tie off to sprinkler pipes and duct supports. As further advice please consider tie off points for safety if conducting difficult elevated work.

All what "rickiniraq" said plus spin and set times.

Poobear: Google "epoxy anchor big dig". DickL

Or check the failures at the Pittsburgh Convention Center. Most all you will see does not include the anchors, but sliding brackets. The epoxy anchors failed also.

The Big Dig is the most dramatic to date, resulting in death.

Clean, clean, and do not be afraid to use water with the cleaning process to flush out determined and clinging dust.

I know a lot of these anchors have been used sucessfuly, but do not hesitate to have the manufacturer and your engineering group to provide instructions.

And hire a reliable, competent, and professional 3rd party inspection agency, not the usual government authorized inspectors.

This is a little off subject, but I think it will be helpful. We used to wait around for the testing service to send a technician out to validate the fasteners that we install. As you know, besides being inconvenient, it is expensive. We purchased a tester from www.com-ten.com , and life is a lot easier. The tester is expensive, but it has paid for itself in less than 6 months.

thanks for your comments it is very helpful

Epoxy anchors were failing on the Big Dig also. However, it is usually found that neither the anchor or the epoxy weren't the problem, but poor installation practice. Frequently the epoxy and anchors are much stronger then the concrete they are bonded to. Poor cleaning of the boreholes and improper placement of the epoxy are common errors. Not a bad idea to consider these types of contractor installation errors in design.