64
CONSTRUCTION FIXINGS
Resin bonded anchors –
recent developments
In the 32 years that Mark Salmon of Independent Fixing Consultants has been involved
in the construction fi xings industry he has witnessed some remarkable developments
in fi xings technology - from the introduction of thick walled sleeve anchors through
self drilling and tapping plasterboard fi xings to self tapping concrete screws. Each one
has revolutionised a different application area - but none has been so remarkable or
unrelenting as the continuous development in resin anchoring.
There are developments in three areas that I feel are important. These capsules are therefore not yet available for use with
Making resin anchors work in cracked concrete, reducing curing conventional resin studs. Both components are also substantially
times and reducing their environmental impact. more expensive than conventional items so their usage will be
Of these the one which probably appeals most to users is the adopted only very slowly. Even so, the fact that the faster cure
reduction in curing times, as one of the biggest drawbacks of resin technology exists is a good thing and we can only hope that it
systems is the time we have to wait before we can tighten or will soon be made available for use with standard resin studs, and
load an anchor. Currently the fastest curing times, with standard at lower prices.
resin types, are offered by capsule systems. They generally cure The application of resin anchoring technology to cracked concrete
about three to four times faster than equivalent injection systems is not actually that new – I explained the mechanism behind it
with curing times of as little as 20 – 30 minutes at 10ºC and 10 to in an article on behalf of the Construction Fixings Association
20 minutes at 20ºC for the fastest types. By comparison injection as long ago as November 2005 (Issue 36) - but the recognition
systems, which are undoubtedly the more commonly used systems, of cracked concrete as the normal condition by more and more
take between 60 and 90 minutes
at 10ºC and 45 to 50 minutes at
20ºC. For many applications this
sort of delay can be coped with
but for some it is inconvenient -
while for others it makes using a
resin system a non-starter.
Special fast curing capsule. Slim, dark and different.
Sometimes impatience on the part of the installer may lead engineers means that we should be seeing more specifi cations
to the anchor being tightened too soon and the resin bond being for resin anchors with European Technical Approvals for use in
broken. This is not always obvious but the anchor may fail later on. cracked concrete so demand will increase. I should point out here
Industrial chemists, though, are a resourceful breed and faster curing that special anchor rods designed to work in cracked concrete
systems are becoming available in both formats. One manufacturer are available from other manufacturers and for use with injection
has introduced a capsule system capable of curing in as little as systems so the technology is not restricted to use with capsules.
4 minutes at 10ºC and just 2 minutes at 20ºC. Admittedly in my So what about curing times for injection systems? Well there is
experience these times are a bit mean. I would always give them good news here too. The same manufacturer who has introduced the
an extra minute before tightening or loading them. But even so, fast curing capsules has also introduced a “Winter” grade of injection
4 minutes, let’s say 5, is as close to immediate loading as most resin. This does not cure as fast as the fast curing capsule system but
applications need. Brilliant! does cure as fast as many standard capsules. And they are right to
One slight irony with this development is that it is part of refer to it as a Winter grade because, while it may take 30 minutes
this manufacturer’s solution to another problem - that of cracked to cure at 10ºC compared to 60 for their standard version, the resin
concrete - which means the capsules have to be used with specially cures in the nozzle quickly enough to become too stiff to pump
shaped studs necessary to function in the cracks that affect most after only a few minutes at temperatures above 10ºC. So, unless
sections of concrete. the installer can work in such a way as to keep injecting on a near
continuous basis, the rate of nozzle usage becomes uneconomic, not
to say wasteful.
Which brings us neatly enough to the other new development,
that of foil or soft skin cartridges. We’ve seen foil capsules for quite
a while now with their advantage of not breaking if dropped or
inadvertently put into a pocket. However, up to now most injection
Special anchor rods for cracked concrete.
cartridges have been constructed of a hard plastic, which is not only
wasteful of resources but can only be disposed of via landfi ll,
Use with capsules or cartridges. Cool eh?
Fastener + Fixing Magazine • Issue 61 January 2010
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