High albedo surfaces for thermal stabilisation of road embankment built on permafrost Simon Dumais1, Guy Doré, Department of Civil Engineering and Centre for Northern Studies, Université Laval, 1 simon.dumais.2@ulaval.ca

•  Micro texture •  British pendulum (BPN) •  Low speed skid resistance

•  Macro texture •  Sand patch test (MTD) •  High speed skid resistance and

water management •  Provides durability and thermal

benefits

Skid resistance

Methodology Test section in Beaver Creek, Yukon along the Alaska Highway •  Four surfaces with different albedos

•  Bituminous surface treatment with light coloured aggregates •  Asphalt cold mix •  Lafrentz (white coating) •  Nippo (grey coating with high infrared reflection)

•  Surface temperatures recorded from august 2012

Model for surface temperature calculation Introduction Heat absorbed by dark pavement can increase thaw penetration within a road embankment and can induce instability caused by thaw settlement of the underlying permafrost. High albedo road surfaces (HAS) can reduce the heat absorbed by the pavement thus increasing stability of the embankment. Past experiments with HAS have shown that they can efficiently reduce thaw penetration but that they present some technical flaws mainly regarding skid resistance.

Conclusion Solar reflectivity and skid resistance properties of high albedo surfaces have been evaluated on the Beaver Creek test section.

Beaver Creek test section August 2012

Albedo measurement May 2013

Incident  solar  

radia.on  

Reflected  solar  

radia.on  

Wind  

Convec.on  Emi6ed  FIR  

radia.on  

Absorbed  FIR  

radia.on  

Conduc.on  

Pavement  Embankment  

Energy balance at the surface

Albedo   Cold  mix   L-­‐BST   Nippo   Lafrentz  

August  2012   0,04   0,23   0,40   0,60  

Mai  2013   0,14   0,23   0,29   0,55  

0=𝑞↓𝑟 + 𝑞↓𝑐 + 𝑞↓𝑒 + 𝑞↓𝑔 

Solar radiation 𝑞↓𝑟 =(1−𝑎)𝑞↓𝑖   

Convection 𝑞↓𝑐 = ℎ↓𝑐 ( 𝑇↓𝑠 − 𝑇↓𝑎 )

FIR radiation 𝑞↓𝑒 =𝜎(𝜀↓𝑠  𝑇↓𝑠↑4 −

𝜀↓𝑠𝑘𝑦 𝑇↓𝑎↑4 )

Conduction 𝑞↓𝑔 =−0,11 𝑞↓𝑟_𝑚𝑎𝑥 

𝑠𝑖𝑛((𝑛−2)𝜋/6 )

Objectives •  Evaluate skid resistance and solar reflectivity of HAS •  Quantify the effect of albedo on pavement’s temperature

0  

5  

10  

15  

20  

25  

30  

0   50   100   150   200   250  

Surface  tempe

rature  [°C]  

Absorbed  solar  radiaIon  qr  [W/m2]    

Monthly  average  surface  temperature  

Model  Ta=5°C  Model  Ta=10°C  Model  Ta=15°C  BC  May  Ta=6°C  BC  September  Ta=7°C  BC  August  Ta=11°C  BC  July  Ta=14°C  BC  June  Ta=15°C  

For  Ta>0°C  with  U=1,5  m/s,  ε=0,85  and  εsky=0,70  

Skid resistance testing

A model has been developed to predict surface temperature of pavements in function of their albedo based on energy balance at the surface of the pavement. The model has been validated using data from the test section in Beaver Creek, Yukon.

Skid  resistance   Cold  mix   L-­‐BST   Nippo   Lafrentz  

BPN   94   97   74   59  

MTD  (mm)   0,746   1,910   0,702   0,589  

Solar reflectivity •  Albedo •  Measured with pyranometer