at Auburn University

Strategies for Design and Construction of High-Reflectance

Asphalt Pavements

Nam Tran, Buzz Powell, Howard Marks, Randy West and Andrea

Kvasnak

at Auburn University

Outline

• Urban heat island (UHI) effects

• Cool pavements and LEED credits

• SRI and how to measure

at Auburn University

Background

Source: EPA – Cooling Summertime Temperatures

What Causes Heat Islands?

Source: www.DigitalWorldTokyo.com

Trap hot air and reduce wind flow

Replace trees with buildings & infrastructures

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How to Reduce UHI?

• More trees

• Reflective and green roofs

• Cool pavements

• Efficient cooling systemsU of Washington

ACROS Fukuoka, JP

Ennis Paint

at Auburn University

How to be “Cool” and Get Awards

• According to LEED, cool pavement strategies include: – Shading hard surfaces– Using high-reflectance materials– Using open grid or porous pavements

• LEED awards:– 1 credit for “New” and “School” projects for

50% coverage using cool pavements– 1 credit for 25%, 2 credits for 50%, and 3

credits for 75% coverage for “Retail” projects

at Auburn University

Solar Reflectance Index (SRI)• A function of reflectance and emittance –

– SRI = 100 for standard white surface– SRI = 0 for standard black surface– Reflectance has profound effect on SRI– More information in ASTM E 1980

• Higher SRI, lower surface temperature

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How to Measure Reflectance

• Field – ASTM E 1918– Equip.: ~ $2,000– Mat: 10 ft x 10 ft

• Laboratory– ASTM C 1549– Equip.: ~ $30,000– Core: 6 in. dia

at Auburn University

0

10

20

30

40

New Old (~ 7 years)Pavement Surface

SR

I (%

)

HMA PCC

Asphalt vs. Concrete

Have similar SRI as they

get older

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Thank You