The Civil Engineering Contractor June 2018 | Page 26

TECHNOLOGY
With its superior engineering skills,
South Africa has been able to position
itself at the cutting edge of the
impervious membrane (geosynthetics)
technology, says Dr Kevin Gast,
principal engineer and consultant for
Thusanang Gast, whose Geosynthetics
Division is one of the oldest and most
experienced in Africa.
The Gast Group patented its first
impervious membrane system back
in 1981, which involved the actual
plasticisation of in situ soils, followed
by the world’s first inland blue lagoon
in 1984. Gast himself is a leading
global engineering authority on
water and impervious membranes,
having served on a commission
chaired by former US Vice-president
Al Gore, while chairing several local
committees for various SABS codes,
and was the past president of the
Waterproofing Federation of South
Africa and the African Waterproofing
Institute.
The company’s expertise extends
to having completed some 11 281
projects in 34 countries in Africa.
Gast’s own forensic work of more
than 2 000 impervious membrane
installations in six countries revealed
that “the largest cause of failure was
in workmanship, and the second-
largest was attributable to design
fault. Materials, in fact, when
specified correctly, were almost
never the cause,” Gast says.
Geosynthetics are a highly
competitive industry, with major
international players such as Atarfil,
GSE, and Solmax manufacturing to
the international standards GRI GM
13-17. These dictate the quality of
the product as well as the installation
requirements. Gast stated that
“Notwithstanding these standards,
one does still see failures in design
and installation, especially where
concomitant materials and activities
are present. One must remember that
in order to be able to accommodate
thermodynamic movement, these
materials inherently need to be
pliable, which then renders them
susceptible to damage and abuse.”
Gast described three major
elements in achieving a waterproof
impervious membranes project, at
each of which things can go wrong
and each of which require specialised
skills and is a science in its own right:
design; installation; and maintenance.
“In the design phase, the selection
of materials, followed by the election
of substrata and the potential for
extraneous factors, are the most
critical issues.
“In implementation, most critical
is adherence to quality assurance
and quality control procedures and
following OEM manuals for the
materials,” Gast says. The purpose
of impervious membranes is to
extend the life of the asset before
it needs intervention in the form of
the third element, maintenance. A
project cannot be seen in isolation:
impervious membranes have multiple
components, and impervious
membranes (geosynthetic) itself is
typically part of a broader project’s
objective.
“For instance, a geosynthetic
project typically has one of two
objectives: environmental protection
or asset protection, though in many
cases these will be symbiotic. A gold
mine wanting to protect against
leachate will both be protecting
the environment from toxic waste
entering water courses, while
protecting its asset: the pregnant
solution contained in the pond at the
mine,” Gast says.
We’re on top of the world
Dr Kevin Gast, principal engineer and
consultant for Thusanang Gast.
It would seem that technology in
impervious membranes has advanced
enormously in recent years, with
installations particularly being far
more mechanised than they were
before, as Gast elaborated: “Our
advance drone technology with
artificial intelligence can analyse the
surface before a project commences
in a fraction of the time it would
have taken a civil engineer and land
surveyor to inspect the s