Water, Sewage & Effluent March April 2019 | Page 34

It is vital that building contractors and consulting engineers specify the correct
chemical anchors for the application in hand to avoid potential disaster.
By Tarren Bolton
A
vailable in South Africa
exclusively from leading
distributor Upat, fischer
anchoring
systems
represent the epitome of
German engineering and innovation.
However, specifying the correct product
is essential for the ultimate effectiveness
of the technology, notes Upat fischer
technical manager, Kevin Owen.
Highlighting a local example of
incorrect anchor specification, Owen
points to a South African case study.
Several years ago, the Midvaal Water
Company upgraded a water-treatment
plant in Orkney in North West Province
to increase the quantity of water that
could be processed by raising the height
of the launder channels.
Additional tie beams were added to
strengthen the channels, placed into the
concrete using the correct selection of
chemical anchors. However, polyester
was used as the fixing agent, which
loses bonding strength with continual
exposure to moisture. “The contractor
made the incorrect selection of
chemical fixing because polyester is
sensitive to moisture, so should never
have been used here. Either a vinyl
ester or epoxy mortar should have been
used,” explains Owen.
It appears that the tie beams were
shorter than the critical dimension
required, which was at least 60mm
of grout packing on either side. This
reduced the effective depth of the
anchors. “It is essential to ensure
32
Critical function of
chemical anchors
Building contractors and consulting engineers should be better educated about product
specification and proper installation requirements.
that the minimum anchorage depth is
attained,” Owen stresses.
Owen says that there is no standard
in South Africa for defining critical
dimensions and anchorage depths;
therefore, it is left up to the supplier to
specify these, depending on the applied
loads. “The strength of an anchor is
directly proportional to its embedment
depth. Unfortunately, not all installers
or contractors understand this,”
says Owen. He explains that a typical
example is where reinforcing steel is
encountered in the concrete. “We have
Water Sewage & Effluent March/April 2019
seen many cases of the contractor
simply shortening the anchor so as not
to clash with the reinforcing steel. The
correct practice is then to move the
anchor to a different position to avoid the
reinforcing steel,” says Owen.
In this case, polyester was used,
which is only suitable for use in indoor
applications, emphasising not only the
importance of specifying the correct
product for the correct application,
but also the proper installation. “The
specification of what type of anchor to
be used rests with the consultant, who
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