Adapting asphalt pavements to climate change challenges

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Adapting Asphalt Pavements to Climate Change Challenges :

Refiloe Mokoena, Georges Mturi, Johan Maritz, Johan Malherbe, Johan O’Connell CSIR

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ACKNOWLEDGEMENTS

Co-Authors: Department: Organization:

Georges Mturi Bitumen expert

Johan Maritz Geospatial processing Johan Malherbe Climate scientist

Johan O’Connell Bitumen expert

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BACKGROUND

climate.nasa.gov

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BACKGROUND

Temperature vs

solar activity

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BACKGROUND

Findings from IPCC report SR1.5

 Southern Africa identified as a hotspot for global climate change

 Temperature increases in sub-Saharan Africa are projected to be higher than the global mean temperature increase

 Particularly South Africa and parts of Namibia and Botswana

 Projections include increase in hot nights and heatwaves

 Climate extremes becoming more frequent and more intense over the past decades

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EFFECTS ON ROAD INFRASTRUCTURE

There is a NEED to investigate the effects of climate change on road infrastructure:

US Department of Transportation

Federal Highway Administration

NCHRP Report 750

Local Transport Strategy and

Funding Division UK Department

of Transport

Report on CC effects on highways

ReCAP

AfCAP Programme

Climate Adaptation Guidelines

United Nations

Importance of Adaptation

Planning

Reactive Approach- US$183.6

billion

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Temperature Precipitation Sea-level rise Increased storm events

EFFECTS ON ROAD INFRASTRUCTURE

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Temperature Precipitation Sea-level rise Increased storm events

EFFECTS OF RISING AIR TEMPERATURES

Weather change Impact on infrastructure Impact on

operations/serviceability

Higher and more frequent extreme temperatures

 Damage due to buckling and rutting

 Increased stresses from thermal expansion

 Premature deterioration

 Safety

 Maintenance

 Restricted transport operations

 Increased transportation costs

 Construction activities Larger temperature

ranges

 Change in freeze-thaw cycles

 Temperature related cracking

(Adapted from Meyer et al., 2014)

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EFFECTS OF RISING TEMPERATURES

Global

Warming Increased global temperatures

Adaptation Change in practice

Design

Process Binder selection

Source:

Pavementinteractive.org

Effects on asphalt pavements:

 Ageing of bituminous binders

 Bitumen softening in asphalt

 Permanent deformation

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CLIMATE TEMPERATURE MODEL

Representative Concentration Pathway (RCP)

CO₂ equivalent in 2100 (ppm)

2.6 453

4.5 586

6 779

8.5 1396

(Meyer et al., 2014)

Low mitigation model

Near-surface (2 m) air temperature 8 x 8 km spatial resolution over South Africa

Climate change models should not be

interpreted as forecasts

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PAVEMENT TEMPERATURE MODEL

Williamson

et al. Kennedy

et al. Everittet al. Viljoen Denneman O’Connell

et al.

1970-1975

Temperature measurement and prediction

1994

Superpave Temperature

models SHRP

1999

Calibration of Superpave for

South African application

2001

Development of temperature algorithms for South African

pavements

2012

Evaluation of South African binders for PG

specifications

 Permanent deformation at high temperatures

 Fatigue cracking at intermediate service temperatures

 Brittle fracture at low service temperatures PG specifications for asphalt bitumen

2007

Application of Viljoen equations for

use in South Africa/

ThermalPADS

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PAVEMENT TEMPERATURE MODEL

Variable Default value Surface absorptivity 0.9

Air-transmission coefficient 0.78

Zenith angle -

Air- emissivity 0.7

Asphalt- emissivity 0.9

Heat transfer coefficient (W/m²°C) 19.88 Conductivity (W/m²°C) 1.38

T_s(max)= T_air(max)+24.5(cosZ_n)².C

T_s(min)= 0.89T_air(min)+5.2 Minimum surface temperature Maximum surface temperature

Williamson

et al. Kennedy

et al. Everittet al. Viljoen Denneman O’Connell

et al.

2001

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MAP DEVELOPMENT PROCESS

Diurnal temperature profile Max/min pavement temperatures

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MAP DEVELOPMENT PROCESS

Air

• RCP 8.5

• >20 000 points

Viljoen

• 97.5% CL for maximum and

minimum pavement temperatures

ArcGIS • Kriging interpolation

Maps

• Warm temperature maps

• Cold temperature maps

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MAXIMUM TEMPERATURE OUTPUTS

1980-2000 2000-2020 2020-2040 2040-2060

A B C D

2.57 2.29

-0.1 -0.18 -0.29

3.71

2.19

0.53 1.43 0.67

0.19

1.05

0.65

-0.53

1.09

-2 -1 0 1 2 3 4 5 6 7 8 9

JHB PTA CPT DBN PMZB

AIR TEMPERATURE CHANGES (°C)

B C D

2.88 2.96

0.88 -0.34 0.14

3.74

2.13

0.35 1.3 0.75

1.02

1.4

0.86

-0.74

0.99

-2 -1 0 1 2 3 4 5 6 7 8 9

PAVEMENT TEMPERATURE CHANGES (°C)

B C D

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MINUMUM TEMPERATURE OUTPUTS

1980-2000 2000-2020 2020-2040 2040-2060

A B C D

0.86 0.31 0.71 1.52

0.71

-0.55 -0.48 -0.34

-2.55

0.11 2.43

1.47 1.11

-0.4

0.62

-4 -3 -2 -1 0 1 2 3 4

AIR TEMPERATURE CHANGES (°C)

D C B

0.76 0.27 0.63 1.35

0.64

-0.49 -0.42 -0.31

-2.27

0.1 2.16

1.31 0.99

-0.35

0.55

-4 -3 -2 -1 0 1 2 3 4

PAVEMENT TEMPERATURE CHANGES (°C)

D C B

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PAVEMENT TEMPERATURE MAPS

Warm pavement

temperatures

1980-2000 Period A

2000-2020 Period B

2020-2040 Period D 2040-2060

Period C

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PAVEMENT TEMPERATURE MAPS

1980-2000 2040-2060

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PAVEMENT TEMPERATURE MAPS

Cold pavement

temperatures

1980-2000

2000-2020 2020-2040

2040-2060

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INTERPRETATION OF MAPS

 “The amplitudes of warming are generally underestimated”- Engelbrecht et al. 2015

 Demonstrates changes in average air temperatures

 Not for prediction of future PG requirements

 Rather as an indication of change in PG requirements Climate models for pavement temperature prediction

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INTERPRETATION OF MAPS

A B C D

1980-2000 2000-2020 2020-2040 2040-2060

Historical? Future?

 Measured temperatures

 Actual weather station readings

 Incomplete datasets

 Sparsely situated

 Predicted temperatures

 Use of climate models

 Complete datasets

 High resolution Up to 7.64°C

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ADAPTATION MEASURES

“Adaptation consists of actions to reduce the vulnerability of natural and human systems or to increase system resiliency in

light of expected climate change or extreme weather events”- NCHRP Report 750, 2014

1. Impact reduction 2. Consequence reduction

Material selection

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RECOMMENDATIONS

Vulnerability

assessment Adaptation

options Adaptation

planning Implementation Review

DEA National Climate Change Adaptation Strategy

Design, construction and maintenance Engineering Guidelines

Transportation Planning

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“Essentially all models are wrong, but some are useful”

George E.P. Box

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Thank you

[email protected]

Adapting asphalt pavements to climate change challenges