Research and Development
Test
Results Show Superior Performance of Connolly Key Joint
In July, August and September of 2001, at the request of Connolly
Key Joint, the Australian Centre for Construction Innovation
(ACCI) undertook tests of tongue and groove type construction
joints in reinforced concrete slabs formed using a range of
profiles. The purpose of this testing was to investigate the
strength capabilities of joints constructed using various
profiles of keyed joints. The joints were established using
strips folded from galvanised steel sheet and are intended
to transmit some vertical shear across a construction or control
joint in a slab on ground. The tests conducted by the ACCI
sought to compare the ultimate shear strengths of 150mm thick
concrete slab specimens joined across their widths using a
variety of joint profiles provided by Connolly - no attempt
was made to simulate the interaction between the slab and
sub grade on which it is supported.
Among
the six different profiles tested were samples of the existing
products produced by both Connolly Key Joint and Danley Construction
Products. The average of all tests conducted using these two
profiles, with a joint opening of 5mm, can be depicted by
the following graph. The configurations of the other profiles
that were tested cannot be disclosed at this time as they
form part of planned new product releases in the near future.
Results
of the comparative tests between the Danley product and the
Connolly product proved what many people have believed in
the past. The profile of the joint formed by the Connolly
Key Joint is far stronger under loading situations than that
of the Danley product. Now scientific testing has proved these
beliefs, and comparisons can be made using the quantifiable
results obtained. The loads achieved by joints constructed
using the Connolly product exceeded those produced using the
Danley product by 35%.
To
gain an understanding of the reasons why the two products
perform so differently it is best to consider an extract from
the report as follows:
"The test programme has shown that when opened to 5mm,
joint type D consistently shows less shear resistance than
others. In elevation, its deep tongue geometry leads to a
greater cantilever length for the top lobe with a consequently
greater bending stress under a given load. The nearly horizontal
tongue slope creates a sharper re-entrant corner at the root
of the top lobe - it is likely that this causes a local stress
concentration. Although profile E also has a deep tongue,
the steeper tongue slope appears to have improved its load
resistance when compared with the type D joints."
These
results clearly show that under a vertical loading situation
Connolly Key Joint is far superior to the Danley product.
In fact, of all six profiles tested, the Danley product had
the worst performance of all. The conclusion to the ACCI report
stated;
"Joints
of profile type D have a lower shear resistance than all others
tested."
For
some time now, Danley Construction Products has openly criticised
the slope of the Connolly Key Joint tongue, indicating that
it results in poor deflection characteristics at the surface
of the slab. As part of the ACCI testing process carried out
for Connolly Key Joint the vertical deflection properties
of the joints were also investigated using actual test slabs.
The results of these deflection tests showed that "no
trend could be seen". So in fact the tongue slope of
the Connolly product could not be shown to adversely affect
joint deflection but it was shown to provide joints capable
of carrying far greater loads.
These
are only some of the reasons why Connolly Key Joint performs
better and is the most accepted key joint on the market today.
If your customers are concerned about providing a long lasting
quality finish to their slabs they cannot ignore the results
of these tests. Connolly Key Joint really is the key to a
better job.
