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Frequently Asked RCC Questions
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FAQs > SRI of RCC
What is the Solar Reflectance of Roller-Compacted
Concrete?
 Until
recently, no testing had been performed to determine the solar reflectance
index (SRI) of roller-compacted concrete (RCC) pavements. However,
a recent report prepared by CTLGroup, Skokie, Ill. shows that the
SRI of RCC pavements is similar to SRI of conventional concrete.
Both conventional concrete and RCC pavements provide high solar
reflectance, which help mitigate the urban heat island effects.
The SRI of conventional concrete pavements decreases with age from
about 38 when new to about 30 at ages beyond 10 years. Whereas,
the SRI of asphalt pavements increases with age from about 7 when
new to about 20 at the age of 8 years. Asphalt surface layers are
typically replaced with new materials every 6 to 9 years, which
results in an SRI of 20 or less during the entire service life of
an asphalt pavement.
 To
determine the SRIs of two RCC parking area pavements in Tennessee,
three core specimens were obtained from each pavement. At the time
of sampling, Pavement 1 and Pavement 2 were about 2 and 10 years
old, respectively. Both RCC mixes contained #57 stone, manufactured
limestone sand, 400 lbs/yd3 portland cement, and about
125 lbs/yd3 Class F fly ash. The cores surfaces were
tested in accordance with ASTM C1549-04, Standard Test Method
for Determination of Solar Reflectance near Ambient Temperature
Using a Portable Solar Reflectometer. The SRI of each set of
3 specimens was calculated in accordance with ASTM E1980-01, Standard
Practice for Calculating Solar Reflectance Index of Horizontal and
Low-Sloped Opaque Surfaces. The SRIs for Pavement 1 and Pavement
2 were 36 and 38, respectively, which are very similar to the SRI
of new conventional concrete pavements.
Although the data is limited and additional SRI evaluations of
RCC pavements covering different regions of the country and different
applications are needed, it is believed that the SRI of all new
RCC pavements would meet the minimum of 29 needed to earn a point
toward the sustainable sites credit of the LEED rating system.
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