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the moisture susceptibility of the conventional mixture (Lum and Tay 1992). A similar
result, of reduced moisture susceptibility, was found by Fwa and Aziz, when incinerator
ash was used to replace the mineral filler portion of hot-mix asphalt mixtures (Fwa and
Aziz 1995). One study in Japan successfully utilized incinerator ash as a partial
aggregate replacement for both base course and hot-mix asphalt mixtures in a commercial
haul road pavement (Kouda 1996). The incinerator fly ash produced in these plants may
have uses similar to those detailed under Coal ash by-products, but the exact properties
of the incinerator fly ash produced need to be evaluated. One investigation found that
combining 15 percent incinerator fly ash with tropical fine-grained soils increased the
shear strength and decreased the plasticity of the soils evaluated (Nicholson and Ding
1997). Some incinerator ash has been shown to possess substantial pozzolanic behavior
Prior to using incinerator ash in any application the environmental effects must be
considered. Analysis has shown that most incinerator ashes are classified as
nonhazardous under U.S. regulatory standards; however, each case should be evaluated
for the application planned (Rivard-Lentz et al.1997 and NaQuin 1998).
d. Plastics. The amount of plastic waste materials generated increases each year.
The plastic materials can be classified into 6 major types:
(1) LDPE - Low Density Polyethylene (film and trash bags)
(2) PVC - Polyvinyl Chloride (pipes, siding, and flooring)
(3) HDPE - High Density Polyethylene (milk jugs)
(4) PP - Polypropylene (battery casings and luggage)
(5) PS - Polystyrene (egg cartons, plates, and cups)
(6) PET - Polyethylene Terepthalate (soda bottles)
LDPE has been used for many years as an asphalt modifier in hot-mix asphalt mixes and
other asphalt paving applications. At least seven states have used LDPE which is
normally recycled into pellets for adding to hot asphalt cement (Collins and Ciesielski
1994). LDPE has been shown to be effective in reducing low temperature cracking and
reducing rutting at high temperatures (Liang 1993). At low temperatures LDPE mixtures
may be more susceptible to fatigue problems; however, the high temperature performance
has usually been exceptional (Little 1993). HDPE has also been used to make signs and
posts. The Florida DOT has had extensive experience with this material (Smith and
Ramer 1996). PET bottles have been used to produce geotextiles and, when chemically
modified to a thermoset polyester, they have been used to produce a polymer concrete.
Direct references indicating use of the remaining plastic materials was not found.
A large part of the plastic waste is commingled; meaning it is a mixture of two or more
plastics. These materials have been used to produce signs and posts and in granulated
form have been used as a lightweight sand replacement in a PCC bridge deck.