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ACCELERATED AGING TEST
A simple test based on accelerated aging methodology was used for predicting the long-term
mechanical properties of vinyl sheet pile (VSP) materials. The test is based on the Arrhenius
principle and was used by Litherland et al. in 1981 and by Vijay and GangaRao in 1991.
Litherland et al. have correlated their data with naturally weathered samples of about 10 years.
Their testing involved exposing a sample to a higher temperature for a short time and then
relating the resulting degradation in mechanical properties to the equal degradation resulting from
natural exposure over a longer time. Thus, they determined that the natural exposure of 18 days in
UK produced the same degradation as 1 day of their chamber exposure. Vijay and Ganga Rao
used the value of 17 days for Morgantown, West Virginia, for 1 day of chamber exposure. The
timetemperature superposition Arrhenius equation as determined by Vijay and Ganga Rao is
given by
ND/CD = 0.098 e 0.0558T
where
T = temperature (F)
ND = Natural day
CD = Chamber day.
The theory is explained graphically in Figure 43. This figure shows that an exposure at 120F
for a day will cause the same degradation as 98 days natural weather exposure. If the chamber
temperature is raised to 150F, then one day of chamber test will be equivalent of 400 days of
natural weather test. Using the same approach we concluded that at 212F, the boiling
temperature of water, an exposure of 1, 2, 10, and 20 hours would show a progressive aging
effect (Figure 44). In fact, according to the above equation, an exposure at 212F for 20 hours
would be equivalent to 36 years of exposure.
Figure 43. Theory of accelerated aging test.
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