- Monolithic structure
- Load bearing (up to around 25-30MPa) and non
load bearing applications
- Approximately 50% of the density
of conventional concrete
- Durable surface suitable for external applications
without additional surface protection
- Very low thermal conductivity
- Very high fire resistance
To our knowledge, there is no equivalent
product available or being developed anywhere else in the
world. The exhaustive
patent process has also produced strong evidence that the technology
is unique.There is a range of pre-cast products known as autoclaved
aerated concrete (AAC), commonly seen in Australia
under the Hebel brand name. This is a very lightweight, low strength
(non load bearing,
less than 5 MPa) product which cannot
be used in external applications without a protective surface
treatment.
There are also a whole range of non autoclaved concrete products
which utilise chemical foams or
polystyrene filler. To date, these products have not been able to
achieve a compressive strength rating
of anywhere near that of HySSIL™.
There
is also a lightweight concrete technology which utilises lightweight
aggregates.
This is more commonly
seen in higher
strength concrete
mixes (greater than 40MPa) and
typically poured in-situ. The weight saving
against conventional
concrete is
typically only
around 25%,
and the high strength lightweight
aggregate concrete mixes are relatively
expensive.
The application
of lightweight aggregate concrete
is typically for “in-situ” pours
and not for pre-cast panels.
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Is
HySSIL™ cost competitive with conventional
precast concrete and
other building materials?
Yes, HySSIL™ is very cost competitive
with conventional precast concrete
and other building
materials.
Compared to conventional pre-cast
concrete panels, HySSIL™ is price
competitive ex-factory.
However, when an overall design
and construction view is considered,
the HySSIL™ cost advantage
increases significantly
due to:
- Reduced cartage costs
- Reduced cranage and installation costs
- Reduced structural
member costs
The CSIRO is also investigating various
component materials in order to further optimise costs and
performance. The costing studies will be an ongoing CSIRO task which
will review the HySSIL™ formula
depending
on the availability and
costs of
component materials
in various locations
around Australia and the
world. Consequently, there is a real potential to reduce costs.
We
have also carried out costing comparisons for HySSIL™ in the housing
industry in Australia
and found that HySSIL™ offers significant cost
advantages compared to
brick veneer and solid brick and, particularly given that the use
of HySSIL™ will halve the
time required to
get to lock-up stage.
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Why
couldn’t HySSIL™ be
mixed on site?
Pre-cast concrete
components have gained
increasing
popularity with
the building industry
over
the past 20 years
due to superior quality
control in the overall
building process and the lower onsite
impacts of adverse
weather conditions
and
the highly unionised
on-site labour
force. As a result
we would see HySSIL™ remaining
as
a pre-cast product in the long
term, built
under a
controlled factory
environment and
requiring less onsite
time than
in-situ concrete.
Technically,
at this stage, HySSIL™ needs
to be produced
as a flat
panel in a controlled
factory
environment,
such as
a conventional
precast concrete
factory. This is
due to the
liquid nature of
the mix and the way
in
which the cellular
structure
is formed
in the mix
by a chemical reaction.
Whilst
this means that HySSIL™ cannot
at this
stage be
carted to sites
in agitator trucks
and poured
in-situ, it does
not necessarily
prevent the development of
small scale transportable
production
facilities
for HySSIL™ to create
HySSIL™ panels on
site.
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What
are the current test results for
fire-rating
and waterproofing
for HySSIL™?
The fire tests
carried out
by CSIRO in accordance
with the
fire curve
of AS 1530.4
demonstrated
that a 75mm
thick HySSIL™ panel,
at an elemental
level, provides
in
excess of two
hours of fire
isolation.
For conventional
concrete,
an equivalent
rating normally
requires
a 100mm thick
panel.
The term ‘durability’ is
often used
in a very general
sense to cover
the
performance
of
a product or system
over its
intended design
life. There are many different aspects
to durability,
with varying
causes and
having a myriad
of consequences.
In
the context of its potential
use
in a
building
wall panel system, the major factor
influencing
the durability
of HySSIL™ relates to
the ease
with which water
can penetrate
the bulk
material. This has direct
implications
for the
intrinsic
waterproofing properties
of
HySSIL™ as
well as the potential
for
the cellular
mortar
to offer protection to steel
reinforcement.
HySSIL™ panels show excellent
resistance
to water
ingress
by capillary
sorption
under
a 50mm
hydrostatic pressure
head. From
tests it
is evident
that
the
depth of
water
sorption
increases
with
time, but
at a decreasing
rate,
levelling
off at
about 9mm
to 13mm
at
24 hours
(d24 value).
These
relatively
low sorptivity
values
more
than satisfy
the durability
requirements
for structures
in service
under
severe exposure
conditions
nominated
by the
AS 3600
classifications
of B1
and B2. For
instance,
the Roads
and
Traffic
Authority
of New
South
Wales
specifies a d24 value
of 17mm
for exposure
classification
B2
which
includes several
categories
of construction
in a
coastal environment.
Put into
context,
the
sorptivity results
for
HySSIL™ panels
are
similar to
or
better than
those
of
60 MPa concretes.
As
an example,
d24
values for a
60
MPa
structural precast
concrete
is
approximately 15mm
(compared
to
9-13mm for
HySSIL™).
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