Is there an overall guide to spec'ing structural adhesives 1

[samdamon]

I am looking for up-to-date articles or any other publications written by third parties (not the adhesive manufacturers) on how to choose and specify structural adhesives for use in attaching dowels and anchors to concrete and masonry.

I have current catalogs and manufacturer's data for many types of adhesives, but would like to hear about the qualities, relative strengths and weaknesses of each type from disinterested third parties. My chemistry is very rusty but would also be interested in learning more about the molecules now used in structural adhesives.

Third party data I have on hand at present on this topic is outdated and limited. A lot has changed in the last ten years.

Have a project coming up that is going to require an overhead attachment to concrete with a high demand on the anchors. Would also generally like to be more knowledgable when specifying and reviewing installation of these adhesives. Hope to avoid repeat of problems that occurred in Boston.

Any references or links highly appreciated.

 

[STR04]

This comes from Masterspec:

Epoxy Bonding Adhesive: ASTM C 881, two-component epoxy resin, capable of humid curing and bonding to damp surfaces, of class suitable for application temperature and of grade to suit requirements

 

[haynewp]

I think the ICC evaluations would be a good reference and to help substantiate your calcs.

http://www.strongtie.com/ftp/coderpts/esr1772.pdf

http://www.simpsonanchors.com/pdf/systems-specs/SST-Anchor-Systems-Specifications.pdf

 

[oldrunner]

I would suggest that you look at Covert undercut anchors. They have a extensive ICBO report that I believe you can download.

 

[samdamon]

Thanks you for the links and suggestions. They aren't quite what I was seeking, though. Perhaps it does not exist. I was hoping that an adhesives industry expert or very knowledgeable engineer who uses adhesives a lot has written something that would provide an overall guide on how to choose anchoring systems, not oriented to any one specific system or manufacturer. Thanks again anyway.

 

[dik]

epoxybot provided a bunch of information on Big Dig collapse... perhaps he's lurking.

Dik

 

[FSS]

Check out the last few issues of ACI's "Structural Journal." They recently had an article on epoxy anchors with all kinds of technical info.

 

[mitchelon]

Check ACI503R-93 and ACI503.1-92.

 

[wjsd]

I have never heard of anyone digging any further in to qualitative or side by side comparisons of adhesives by a third party. Hilti seems to be "the" concrete anchor system of choice of Engineers I have worked with. What were they using in Bean Town ?

 

[epoxybot]

Maybe better late than never.
Mind you, I cannot recommend the use of epoxy for overhead work. Having said that, if you want a more stringent evaluation than ICC; then a perusal of the Caltrans QPL for anchors grouted with epoxy is a good 3rd party read.

Cartridge Epoxies (10-23)

http://www.dot.ca.gov/hq/esc/approved_products_list/usmixpropoxy.doc

(Augmentations to ICBO-AC58)

http://www.dot.ca.gov/hq/esc/approved_products_list/Augmentation.pdf

Something to bear in mind is that the HDT of an epoxy is just an ASTM D-648 test value. Below the HDT (~20°F) epoxies can withstand substantial loads without deformation (creep). THATS 20°F BELOW THE HDT! As the temperature rises the properties can change dramatically. Think cheesy elastomer at 20°F over the HDT. For anchoring applications there is no room for brief excursions into the the "HDT ZONE".

Since epoxies thicken and set (vitrify) by a chemical reaction, the temperature at which the reaction takes place defines the properties of the cured material. Storage, installation and curing at temperatures lower that the lab test value (usually @68-75°F) can all result in lower strengths and HDT. Depending on the formulation the the effect can vary quite a bit. In other words the published HDT might not be your job conditions HDT or compressive strength, etc.

Consider a chemical reaction "rule of thumb" for every 18°F change in temperature, the rate of reaction either doubles in speed(warmer) or takes twice as long(cooler). For cooler add in 2x to 10x higher viscosity and the bulkiness of the epoxy molecule, the thin nature of the bond line and the end product might vitrify before all the molecules find a dance partner, dosy-doe and join in the middle.

Regarding ICC evaluations, I am saddly uninformed about the
actual test procedure for elevated temperature sensitivity. As I understand the procedure, the test is run once the entire specimen has reached the desired test temperature. This includes the concrete. If the concrete is substantial, it could take some time to heat up the entire block to an ambient test temp. It is likely that heat would travel more quickly through the dowel. I am only speculating but at the higher test temperatures, the time required to heat the concrete could induce a post-cure effect that could skew the values a bit higher.

Add in lack of jobber experience and hopefully you will consider other ways of attaching something overhead.

 

[epoxybot]

Here's a comprehensive report from CalTrans regarding their testing.

SEISMIC, CREEP, AND TENSILE TESTING OF VARIOUS EPOXY BONDED REBAR PRODUCTS IN HARDENED CONCRETE

http://www.dot.ca.gov/research/researchreports/reports/2006/epoxy_bonded_dowel-final_report.pdf

 

[samdamon]

Epoxybot- Many thanks for the valuable comments and links. Regards.