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Low Voltage Heating Material Promises an End to De-icing
Salts
A new low-voltage heating material already being used in the medical and
processing industries in the UK is now being developed for use in the bridge and
construction industries. The product, manufactured by UK firm Inditherm is being
promoted as a reliable and corrosion-free alternative to de-icing salts for
bridge decks, and one that is cheaper to run than existing deck heating
systems.
The material consists of a flexible polymer that can produce a uniform heat
output over its entire surface with no hot or cold patches, when operated using
a low power supply, typically 24v. It is already being used in the medical and
processing industries - for example to maintain patients body temperature during
operations, or to keep ingredients at the right temperature during food
processing - and has recently been installed for use as sports pitch
heating.
But the company has now formed a new division - Inditherm Construction
Products - to target the enormous market in precast concrete production and also
to develop de-icing solutions for bridge decks. Proposed applications include
use of the material in precasting formwork to ensure fast and even curing of the
concrete, saving the cost of the steam-curing or ambient heating systems that
are usually used in cold conditions.
Since the polymer requires a low power supply and can be run off batteries,
it can also be used to enable in situ concreting to be carried out throughout
winter in areas such as north and central Europe and North America .
It potential for use as frost protection on bridge decks is being
developed in conjunction with Sheffield Hallam University in the UK. Inditherm's product
can be cast in to concrete decks across the whole width of the roadway, and be
set up to come into operation when the temperature of the deck falls below a
certain level. It is simply laid across the top of the reinforcement and cast
into the concrete.
Alterations to the composition of the material, or the spacing between the
electrodes, can alter the temperature to which the material heats, so it can be
tailored to any particular need. One of its biggest benefits is that it can be
simply cut to fit round any ducts or box outs, this does not affect the
temperature or cause the creation of any hot or cold spots.
Existing heating systems in bridge decks have proven to be expensive and
difficult to maintain for example a system on a bridge in the USA which has to
heat an area of 13m by 36m consists of 3km of steel pipe filled with ammonia.
The system cost 27% of the total bridge construction.
Any refurbishment work or excavation that has to be carried out on the deck
could effect this type of heating system; in the case of an Inditherm system ,
however holes can be cut through the material without causing any problem. The
main benefit of the system is its ability to eliminate the need for de-icing
salts, removing the main cause of chloride attack and reinforcement
corrosion.
Inditherm is currently in discussions with industry partners to identify
projects where its technology can be trialled, both in pre-casting and
deck-heating applications.
Helen Russell
Bridge Design & Engineering, Second
Quarter 2004
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