CONCRETE
32
A healthy market
RCC in Tennessee
US contractor switched to concrete after years of asphalt work
R
oller-compacted concrete (RCC) is a heavy-duty cement mix that can be poured as
quickly as asphalt. This product has been in use for decades, but it hasn’t caught
on in many parts of the US because of a traditional prefernce for asphalt and
poured-in concrete.
Consisting of the same basic ingredients as standard concrete, the material can be
placed with conventional or high-density asphalt paving equipment. But unlike conventional
concrete, RCC is a drier mix – stiff enough to be compacted by vibratory rollers.
Typically, RCC is constructed without joints and does not require forms or finishing, nor
does it contain dowels or steel reinforcing. This makes RCC relatively simple, fast, and
economical to place.
It is also less damaging to the environment than oil-derrived asphalt, which was one
aspect that was key to US whiskey producer Jack Daniels opting to use this concrete
instead of asphalt to repave its distillery site in Lynchburg, Tennessee.
Contractor Robert Smith was tasked with the job. It had been in the asphalt paving
business for 40 years before it began using RCC. Now this material accounts for more than
90% of its workload.
The contractor used a Volvo CE ABG7820 to pave more than 49,000 m
2
of compacted
concrete for the project, replacing old asphalt roads which were breaking down because of
the weight of trucks carrying products to and from the warehouse.
Volvo said its tracked pavers were particularly suitable for paving a wide range of
materials from the wearing course down to the base courses on diversified paving
contracts
About 92 m
2
of concrete was laid every hour on the project by the ABG7820 paver, with
130 mm of compacted concrete placed over 152 mm of compacted aggregate base.
Contractor Formsite used equipment from RMD Australia
to support construction of a new seven story Global
Switch Data Centre in Pyrmont, Sydney. Alform beams,
Superslim Soldiers, Slimshor props and the Rapidshor
shoring system were used to construct 5.5 m long soffits
for each of the 1,600 m
2
floors.
610 tonnes of steel will be installed in the slabs, the floors and
underground walls.
A production plant automatically assembles the bars for
the project according to the plans via CAM-files. The bars are
automatically selected, cut and welded to separate elements for
each of the two reinforcement directions.
Each element is then rolled up when finished and supplied to
the construction site where they are simply positioned and rolled
out. This technology is said to remove the resource-intensive
process of arranging and wiring single bars together, leading to
time and cost savings.
“Thanks to fully automated production, the steel bars can be
staggered in a very precise way, which would hardly be possible
with a normal loose bar reinforcement, or if so only with a huge
effort,” said Franz Häussler, CEO of Häussler Innovation GmbH
and son of the inventor of the technology.
A new kind of lifting system was also tested to position the wall
reinforcement that enabled components measuring up to 100 m²
to be moved into position safely and swiftly.
“The principle involved here is that elements can be rolled
out on the device, pre-assembled and secured before being
lifted into position as complete sections of internal or external
reinforcement“, explained Mr Häussler.
“This could in future cut installation time
by about -60%, relieving the workers
from the awkward and partly dangerous
process of steel fixing on the scaffolding.”
From
innovations
in
rebar
reinforcement to new remote monitoring
and diagnostics systems, change is
coming to every aspect of the concrete
construction industry.
It will be interesting to see
how quickly emerging markets adopt
the latest technology, as well as how
manufacturers tailor and adapt new
designs to their specific target markets.
iC
internationalconstruction
december 2013
