19 June 2001
Foams. Foams are used at the waterfront as filler material for
sandwich construction, to provide buoyancy for buoys; landing floats; and floating
brows, and in foam-filled fenders to absorb the energy of berthing ships. Foams
are resistant to deterioration in the marine environment if encased in an
impermeable, durable material.
The common foams are polyurethane, polystyrene, polyethylene, and
foams formed of ionomer resins. Polyurethane foams can be foamed on-site.
However, before the foam hardens it is unstable in direct sunlight and is
Polystyrene foams are relatively inexpensive compared to
polyurethane. They can be purchased in large quantities and cut to shape.
Polystyrene foams are used in decks for buoyancy of small boat moorings in
Closed cell cross-linked polyethylene foams are used in foam-filled
fenders. The foam, encased in an elastomer cover, absorbs the impact energy of
berthing ships. Ionomer foams have been used in buoys and fenders. The outer
skin of the products is a denser version of the low-density encased foam.
Rubber and Elastomers. Numerous natural and synthetic rubbers
and elastomers are used at the waterfront in hose lines, gaskets, fender system
components, and other specialized applications. These materials are resistant to
the marine environment provided the appropriate rubber or elastomer is used.
The more common material is a urethane elastomer as used for the shell of
foam-filled fenders. The elastomer ethylene propylene dimonomer (EPDM) is
used in arch-type rubber fenders.
Other Synthetic Materials. Synthetic materials are also used at the
waterfront for pile wraps, piping, and as adhesives. Pile wraps are made of
flexible polyvinyl chloride (PVC) or polyethylene (PE) films and prevent growth of
wood boring organisms. PVC piping is widely used for numerous applications, as
it is lightweight and corrosion resistant. Some degradation of the piping will occur
if exposed to sunlight and other weathering factors. Normally, PVC pipe becomes
brittle as it ages.
Adhesives, coatings, and putties made from epoxy have been
developed for bonding to damp and underwater surfaces. They are used to bond
structures or components, connections, joints, and other metal configurations
susceptible to corrosion; to fill voids; and to protect surfaces. They can also be
used to patch holes above the water or underwater.
SOIL FILL FOR QUAYWALLS AND MOLES. Soil is the most
common backfill material behind quaywalls, shoreline walls, and solid fill/mole
piers; dikes; and levees. Refer to MIL-HDBK 1007/3, Soil Dynamics and Special
Design Aspects, NAVFAC Textbook DM 7.01, Soil Mechanics, and NAVFAC