Page 239 - Materials Chemistry, Second Edition

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Sustainable Industrial Design and Waste Management
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Until World War II breakwater armoring was typically either made of
rock or of parallel-epipedic concrete units (cubes) (Bakker et al., 2003). Armor
units were typically either randomly or uniformly placed in single or double
layers. The governing stability factors are the units’ own weight and their inter-
locking. Breakwaters were mostly designed with gentle slopes and relatively
large armor units that were mainly stabilized by their own weight. A large vari-
ety of concrete armor units has been developed in the period 1950 –1970.

Floating breakwater
Floating breakwaters are usually made of HDPE, recycled plastic, or rejects
without sand content resulting in the following (Ibrahim, 2006):

• The zero percent sand content rejects float over water and have a very
low absorption rate compared to other mixing ratios, 67% less than
the following absorption rate of the 30% sand mix.
• The density of the zero percent sand content rejects is higher than the
HDPE by 2%.
• The zero percent MSW reject mix is less stiff by 59% thus reacting
better to sudden loads.
• The ultimate strength of the zero percent sand content rejects is higher
than the lower limit of HDPE by 23%.

Accordingly, usage of rejects with zero percent sand mix in the production
of a floating breakwater is recommended. However, foam injection could be
investigated and might be utilized due to its superior properties for floating
breakwater.

Breakwater
Breakwaters or armor units used in breakwaters as mentioned before are made
of concrete and new improvements include the usage of HDPE in particular
designs, so the following concerns were noticed while comparing MSW rejects
with the concrete properties (Ibrahim, 2006):

• This usage requires higher specific gravity as illustrated in the 50%
sand mix which is 33% higher than the 40% sand mix and 65% higher
than the 30% sand mix.
• The modulus of elasticity of the 50% sand mix is 6% higher than
the 40% sand mix and 8% higher than the 30% sand mix; tempera-
ture negatively impacts this property as the 40% sand mix modulus
decreases by 9.5 and 11.5% respectively at 160 and 180°C.
• In regards to strength, the 40% mix is found to be 19% higher than
the 50% sand mix and only 5% higher than the 30% sand mix; but
temperature did not add much to this property.