FIREPROOF
Modern residential, and
commercial uses, as well as marinas, demand a non-combustible and
explosion-proof system. The IMF marina system eliminates combustible
structural wooden whalers.
MAINTENANCE-FREE
The floating platforms
never require expensive haul-out for painting or scraping below the
water-line.
ONE PIECE CONSTRUCTION
Floating foundation
platforms must be one piece to allow construction to meet local building
codes. Typical infrastructure and marina sections are one piece, 60'
long.
MASS or WEIGHT
To provide a safe, gentle
ride, a quality floating platform must be heavy, with a low centre of
gravity.
DURABLE
The floating platform
must last longer than the structure built on it.
RIGID
The floating platform is
built on land with the rigidity to withstand launching stresses,
particularly when buildings are included.
INSULATED
The floating platform is
completely insulated for variations in water temperature, including ice
conditions.
INSURABLE
International Marine
Floatation Systems Inc. floats qualify for standard insurance as they
are permanent, fireproof and unsinkable.
PORTABLE
The IMF system is
engineered to allow production of floating platforms and marina systems
in remote and foreign locations without expensive facilities.
Furthermore, these floating systems are designed with delivery options
of trucking or towing. To date, IMF floating platforms have been towed
over 400km on the North American coastline, and trucked across the
United States.
FLEXIBLE
Services such as
waste-water drainage, tankage, storage, electrical, etc. are
incorporated within the float to accommodate local building codes.
In-slab heating systems are another popular option.
ENVIROMENTALY SAFE
All materials in the IMF floating system are non-toxic.
CONNECTOR
IMF's structural concrete
design and patented "Danbuoy" connector eliminate dependance
on structural wooden whalers and through-rods.
ENGINEERING
The engineers at IMF provide complete services, from conceptual to working drawings, for your
specific floating projects and marinas.
International Marine
Floatation Systems Inc. considers these requirements essential for modern
floating developments. IMF has supplied superior floating structures to
waterfront developers and industry, in both salt and fresh water locations
since 1982.
The following is a
testament to the benefits of concrete.
GORDON
S P R A T T & ASSOCIATES LTD.
CONSULTING PROFESSIONAL ENGINEERS
2348 Yukon Street, Vancouver
British Columbia V5Y 3T6
Phone: (604) 872-1211
Fax: (604) 872-1274
February 22, 2000
I.M.F.S. International Marine Flotation Systems Inc.
3473 River Road West
Delta, B.C.
V4K 3N2
Fax: 946-6796
Attention: Mr. Dan Wittenberg
Dear Sir:
Re: Marine Floating Concrete
Structures - Durability.
In response to your request I have
carried out a technical review on the durability of concretes exposed to
marine environments over long periods of time. Much of my reporting to you
is based upon personal experience, working as one of Canada’s most
experienced Concrete Consulting Engineer. My Curriculum Vitae is attached
as Appendix ”A”.
1. CONCRETE - A BRIEF HISTORY
1.1.
Concrete has been around for about 7,000 years, first used as a mixture of
gravel and gypsum, in the floors of mud and straw huts in Central Europe.
1.2.
The Romans developed their own type of corncrete, utitizing a mixture of
lime and volcanic ash, as the binder. Aggregates included natural
materials, crushed brick, and pumice / scoria. Examples of 2,000 year plus
Roman concrete abound throughout Europe. My research on a section that I
took from Hadrian’s wall in Great Britain showed very well developed
calcium silicate structure, in spite of 2,000 years of weathering.
Compressive strength of that sample was over 3,000 psi.
1.3.
Portland cements are hydraulic, that is, they set and harden by reacting
with water. This is a chemical reaction, called hydration, that combines
cement and water to form a stonelike mass.
The invention of portland cement is
generally credited to Joseph Aspdin, an English mason. In 1824 he
obtained a patent for his product, which he named portland cement because
it produced a concrete that was the colour of the excellent natural
limestone queried on the Isle of Portland, a limestone peninsula in the
english Channel west of the Isle of Wright. The name has endured and is
used throughout the world, with many manufacturers adding their own trade
or brand names.
1.4.
Many examples of concrete, more than 150 years old, and still in service,
exist today.
1.5.
Because Portland Cement is a true "hydraulic" cement, it could be used to
con-struct underwater, without negatively affecting the properties of the
hardened concrete. Further, because concrete doesn't dissolve when
continuously immersed, it was found to be a good material for marine
structures, in both fresh and salt water.
2. EXAMPLE AT POWELL RIVER, B.C.
2.1.
The breakwater at Powell River is constructed of partially sunken concrete
shipping vessels. Some of the vessels have been in service or in the
breakwater, i.e., in saltwater, for more than 70 years.
2.2.
Approximately 15 years ago I was retained by the then owner of the
breakwater, MacMillan Bloedel Ltd., to evaluate the condition of the
concrete in the breakwater vessels. Observing, core drilling, measuring
in-situ strength, confirmed the undeniable durability of concrete in a
marine service condition.
3. WORLD WAR I SHIPS (for more
information see www.concreteships.org)
3.1.
When the USA entered in World War I in 1917 there was shortage of high
grade pipe steel. Small ships, barges, and a tanker had already been
designed and built using concrete.
3.2.
The Selma, a tanker, weighed 7500 tons, and had a length of 434 feet, a
beam of 54 feet, and a draft with full cargo of 26 feet. The full cargo
displacement was 13,000 tons. The concrete hull was 5 inches thick on the
bottom and 4 inches on the sides.
3.3.
After the war, The Selma went into service transporting crude oil from
Tampico, Mexico to Texas Gulf Coast Refinery Ports.
3.4.
After 3 years of service The Selma ran aground at Tampico and a crack
occurred in the hull near the bow. It was towed to Galviston, but because
no on cold guarantee a permanent repair, the Owners towed her out into
the bay and sank her in 1923.
3.5.
Thirty-four years later (1966) Engineer's Testing Laboratory Inc. of
Houston Texas conducted tests of the hull. The concrete 1/4 inch beneath
the sufface was found to be dry with no discoloration form absorbed water.
An examination of the interior of the hull showed no visible cracks; it
was deemed to be in excellent condition.
3.6.
Comparison of the properties of the concrete in 1953 with what was known
about the hull when it was placed, showed beyond doubt that the concrete
had successfully withstood the action of sea water without damage. The
reinforcing steel, with only 5/8 inch of concrete cover was adequately
protected.
4. CONCRETE DURABILITY – EUROPE
4.1.
I attended at an international conference on concrete durability at
Odense, Denrnark in 1994. For four days I listened to authors from a
variety of countries describing their research into durability of concrete
for marine structures.
4.2.
Many of the authors referred to Building Codes in their own countries,
which require 100 year durability for any concrete used in a marine
environment. Many of the papers discussed technologies and construction
practices which would safely ensure this durability goal being achieved.
4.3.
The requirement for the Chunnel between England and France was for 120
year durability.
4.4.
Reinforced concrete marine structures in Scandinavia have traditionally
performed well. A greet number of harbours and bridges exist today,
mainly constructed in reinforced concrete. Some of these are now more
than 60 years old. Their performance has in generally been exemplary.
4.5.
The deterioration mechanisms included carbonation, chloride ingression,
oxidation, and saturation. To achieve a 100 year service life in the
presence of the above, requires special mix designs, which include use of
low water / cement ratios and combinations of pozzolans, such as, fly
ash, silica fume, granulated blast furnace slag, and ground metakaloin.
5. THE FUTURE
5.1.
The Romans were successful in developing extremely durable concrete. They
did not have to deal with corrosion of reinforcement, nor the
environmental problems that we have today.
5.2.
Today's expert engineers can comfortably design marine based structures,
with 100 plus year expected durability, subject to proper research and
testing.
5.3.
Construction of floating marine structures, as proposed and tested by you,
for use as part of a floating tank farm, and wave attenuator are
considered by the writer to be of viable use of concrete.
5.4.
Most researchers have shown, for strength levels above 40 MPa, concretes
made with blended cements appear to offer significant advantages in terms
of longer corrosion onset periods than those provided by portland cement
concretes. From a specifications standpoint, such findings, important as
they are, still involve the setting of prescriptive binder requirements.
5.5.
High performance concrete, with strength in excess of 60 MPa, can be
obtained by careful selection and control of ingredients, the use of
admixtures, and superplasticizers.
Yours truly
GORDON SPRATT & ASSOCIATES LTD.
Per:
G.W. Spratt, M.Eng., P.Eng.,
GWS/op
Notice! Remember to include
your IMF floating assets in your will -- to your grandchildren.
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