High albedo surfaces for thermal stabilisation of road...
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Skid resistance • Micro texture • British pendulum • ASTM E303 • Low speed skid resistance • Macro texture • Sand patch test • ASTM E965 • High speed skid resistance and water management • Provides durability and thermal benefits Durability • Samples • High albedo coating applied on asphalt plate • Abrasion resistance • Sand blast method • Measured mass loss of coating after each cycle • Adhesion to substrate • Direct tension test • Indicate adhesion force of coating to substrate • Resistance to freeze/thaw cycles • ASTM C666 • Thawing in water at 4°C • Freezing in air at -18°C • Visual evaluation of degradation Technical properties of HAS The following properties and test methods are proposed to evaluate the skid resistance and the durability of HAS. High albedo surfaces for thermal stabilisation of road embankment built on permafrost Simon Dumais 1 , Guy Doré,, Department of Civil Engineering and Centre for Northern Studies, Université Laval, 1 [email protected] Methodology Test section in Beaver Creek, Yukon along the Alaska Highway • Four surfaces with different albedos • Bituminous surface treatment using light coloured aggregates • Asphalt cold mix • Lafrentz (white coating) • Nippo (grey coating with high infrared reflection) • Surface temperatures recorded from august 2012 • Albedo (a) measured using pyranometer (ASTM E1918) 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 regarding skid resistance and durability. Conclusion 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 a test section in Beaver Creek, Yukon. A method to evaluate the technical properties of HAS regarding durability and skid resistance has been proposed. Beaver Creek test section - August 2012 Albedo measurement May 2013 Incident solar radiation Reflected solar radiation Wind Convection Emitted FIR radiation Absorbed FIR radiation Conduction Pavement Embankment Energy balance at the surface of the pavement 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= + + + Solar radiation = 1 − Convection = ℎ ( − ) FIR radiation = 4 − 4 Conduction = −0,085 _ −2 6 Objectives The main objective of this project is to provide a way to evaluate the relevance of using HAS and especially to: • Quantify the effect of a pavement’s albedo on its surface temperature • Provide methods to evaluate technical properties of HAS 0 5 10 15 20 25 30 0 50 100 150 200 250 Surface temperature [°C] Absorbed solar radiation q r [W/m 2 ] 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 ε sky =0,70 Skid resistance evaluation Abrasion resistance Direct tension test
Transcript of High albedo surfaces for thermal stabilisation of road...
Skid resistance • Micro texture • British pendulum • ASTM E303 • Low speed skid resistance
• Macro texture • Sand patch test • ASTM E965 • High speed skid resistance and water management • Provides durability and thermal benefits
Durability • Samples • High albedo coating applied on asphalt plate • Abrasion resistance • Sand blast method • Measured mass loss of coating after each cycle
• Adhesion to substrate • Direct tension test • Indicate adhesion force of coating to substrate
• Resistance to freeze/thaw cycles • ASTM C666 • Thawing in water at 4°C • Freezing in air at -18°C • Visual evaluation of degradation
Technical properties of HAS The following properties and test methods are proposed to evaluate the skid resistance and the durability of HAS.
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 [email protected]
Methodology Test section in Beaver Creek, Yukon along the Alaska Highway • Four surfaces with different albedos
• Bituminous surface treatment using light coloured aggregates • Asphalt cold mix • Lafrentz (white coating) • Nippo (grey coating with high infrared reflection)
• Surface temperatures recorded from august 2012 • Albedo (a) measured using pyranometer (ASTM E1918)
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 regarding skid resistance and durability.
Conclusion 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 a test section in Beaver Creek, Yukon. A method to evaluate the technical properties of HAS regarding durability and skid resistance has been proposed.
Beaver Creek test section - August 2012
Albedo measurement May 2013
Incident solar
radiation
Reflected solar
radiation
Wind
Convection Emitted
FIR radiation
Absorbed FIR
radiation
Conduction
Pavement Embankment
Energy balance at the surface of the pavement
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 = 𝑞𝑟 + 𝑞𝑐 + 𝑞𝑒 + 𝑞𝑔
Solar radiation 𝑞𝑟 = 1 − 𝑎 𝑞𝑖
Convection 𝑞𝑐 = ℎ𝑐(𝑇𝑠 − 𝑇𝑎)
FIR radiation 𝑞𝑒 = 𝜎 𝜀𝑠𝑇𝑠4 − 𝜀𝑠𝑠𝑠𝑇𝑎4
Conduction 𝑞𝑔 = −0,085𝑞𝑖_𝑚𝑎𝑚𝑠𝑠𝑠𝑛−2 𝜋6
Objectives The main objective of this project is to provide a way to evaluate the relevance of using HAS and especially to:
• Quantify the effect of a pavement’s albedo on its surface temperature
• Provide methods to evaluate technical properties of HAS
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5
10
15
20
25
30
0 50 100 150 200 250
Surf
ace
tem
pera
ture
[°C]
Absorbed solar radiation qr [W/m2]
Monthly average surface temperature
Model Ta=5°CModel Ta=10°CModel Ta=15°CBC May Ta=6°CBC September Ta=7°CBC August Ta=11°CBC July Ta=14°CBC June Ta=15°CFor Ta>0°C with U=1,5 m/s, ε=0,85 and εsky=0,70
Skid resistance evaluation
Abrasion resistance
Direct tension test
