Warm Mix AsphaltObservations from the WSDOT I-90 Job (June 2008)

1. Where are we with WMA?

2. What do we know and not know?

3. Life cycle assessment

4. I-90 Observations

Where are we at with WMA technology?

WMA has been around in its current iteration since about the mid 1990s but has existed in some for or another for at least 30 years.

1995 2009

current WMA starts

1970s

Older WMA-like productsBoeing and others

WMA standard use starts in some places

Plant foaming methods

MAXAM AquaBlack Foaming attachment

Terex Roadbuilding

Warm mix asphalt sys.

Foaming attachment

Astec Industries Double Barrel Green Foaming attachment

Gencor Industries Green Machine Foaming attachment

Kolo Veidekke WAM Foam Foaming process

Material foaming

Aspha-min Aspha-min Zeolite powder

PQ Corporation Advera Zeolite powder

Additives

Sasol Wax Sasobit Wax pellets

McConnaughay Low energy asphalt Chemical process

LEA CO Low energy asphalt Chemical process

Akzo Nobel Rediset WMX Surfactant pellets

Arkema Group CECABASE RT Surfactant chemicals

Meadwestvaco Evotherm Surfactant chemicals

The classic WMA benefits are enticing.

1. Reduced plant fuel consumption2. Reduced emissions

– At the plant– Fugitive emissions

3. Reduced viscosity during construction– Better compaction– Longer haul distances– Cold weather paving

4. Same viscosity during operation– Some have greater viscosity

What do we know and not know?

Based on published reports and presentations, here’s what we think we know.

Item Evidence Results

FieldPerformance

Older jobs: Europe (some > 10 yrs)Newer jobs: Europe and U.S.APT: NCAT, Caltrans PRC, others

≥ HMA(not positive yet)

Laboratory Performance

NCAT, State DOTs, Europe •Some moisture issues•Can be overcome

Energy Use Europe, U.S. trials 10-30% less

Emissions Europe, U.S. trials(far fewer data points)

10-70% reduction depending upon compound

Fumes/smell Europe (experiment)U.S. (mostly visual)

30-50% PAH reduction

Compaction EuropeNumerous U.S. trials

≥ HMA

Aging Some lab work, some speculation

Less aging

What do we not yet know to our satisfaction?

Item Unknown Help

FieldPerformance

Long-term performance APT (NCAT, Caltrans PRC)NCHRP Project 09-47

Laboratory Performance

Mix designCharacterization tests

NCHRP Project 09-43NCHRP Project 09-47

Energy Use Good protocol for quantification Life cycle assessment (LCA)NCHRP Project 09-47

Emissions Good protocol for quantification Life cycle assessment (LCA)NCHRP Project 09-47

Fumes/smell Quantification is very complex Simple method neededNCHRP Project 09-47

Compaction EuropeNumerous U.S. trials

≥ HMANCHRP Project 09-47

Aging Aging effects of WMA Less aging

Specification Best way(s) of doing it TWGLeader states (e.g., TX)

A “life cycle assessment” can help assess the energy, environmental and materials picture.

Life cycle assessment (LCA) is a good tool to assess the overall life cycle impact of WMA.

Life cycle assessment (LCA)A protocol to assess the environmental, economic, and social impacts of an industrial system.

The life cycle of the industrial system extends from cradle-to-grave: from materials acquisition and production, through manufacturing, system use and maintenance, and finally through the end of the system’s life.

Essentially an accounting tool.

oil extraction

Aggregate Quarry

transport refinery transport

transport

placement transport

emissions waste hazardouswaste

other outputs

water fuel

other inputs

hma plant

An example of LCA processes, inputs and outputs to consider for

HMA paving.

For a given unit of production (e.g., 1 lane-mile of pavement) a typical LCA gives a range of outputs.

• Amount of materials used (tonnes)• Total energy use (MJ)• Water consumption (kg)• Emissions

– Global warming potential (tonnes of CO2 equivalent)– Nitrogen oxides – NOx (kg)– Sulfur dioxide – SO2 (kg) – Particulate matter – PM10 (kg)– Carbon Monoxide – CO (kg)

• Toxic things– Human toxicity potential – Mercury – Hg (g)– Lead – Pb (g)– Hazardous waste (kg)– Polycyclic aromatic hydrocarbons (PAHs)

0 1 2 3 4

CRCP

HMA

Pav

emen

t

Total Energy Consumed (TJ)

Raw Materials Extraction

Manufacturing

Placement

Amount of energy consumed by 100 US households in a year (4 TJ) - On average, a US household consumes 11,000 KWh of energy per year - Does not include anything outside of the house (e.g., cars, fuel, etc.)

An example of a LCA output relating to energy consumption in pavement construction.

Data from: Zapata and Gambatese, Energy Consumption of Asphalt and Reinforced Concrete Pavement Materials and Construction, J. of Inf. Sys., vol. 11, issue 1, p. 9-20.

Amount of Energy Required to Build 1 Lane-Mile of Pavement

Notes:•90%+ from manufacturing•Numbers change a lot depending on assumption

9-inch CRC Pavement(6 inches base material)

12-inch HMA Pavement(6 inches base material)

94%3% 3%

91%7% 2%

3.7 TJ

3.0 TJ

4.0 TJ

An example of a LCA output relating to the contribution of different processes to environmental outcomes.

Contribution of Main Processes on Environmental Impacts of HMA

Hassan, M.M. (2009). Life-Cycle Assessment of Warm-Mix Asphalt: An Environmental and Economic Perspective. Presentation at the 88th Annual Meeting of the Transportation Research Board, Washington, D.C., 11-15 January, 2009.

0 500 1,000 1,500 2,000 2,500 3,000

Waste Generated (Tons)

Extraction Manufacturing Construction End of Life

Waste from 1,000 average US households/yr- On average 2 tons/household/yr

An example of a LCA output relating to waste production in roadways.

Data from: Rajendran and Gambatese, Solid Waste Generation in Asphalt and Reinforced Concrete Roadway Life Cycles, J. of Inf. Sys., vol. 13, issue 2, p. 88=96.

Waste Generated by 1 Lane-Mile of PavementNotes:•Most from manufacturing and EOL•Numbers change a lot depending on assumption

9-inchCRC Pavement(6 inches base)

10-inch HMA Pavement(15 inches base)

41% 52%6%1%

38% 59%2%1% 2,852 tons

2,225 tons

2,000 tons

0.200.64

1.801.48

2.782.88

1.99

2.05

1.68

0.05

0.970.78

1.05

2.17

2.21

0

1

2

3

4

5

6

7

Zapata, Gambetese (2005) Mroueh, et al. (1999) Hoang et al. (2005) Athena (2006) Athena (2006) 20% RAP

Tota

l Ene

rgy

(TJ)

maintenance

placement

manufacturing

extraction

3.03

3.85

5.37

6.02

4.46

Total Energy Use for 1 lane-mile of HMA pavementSt

ruct

ure

(inch

es)

0

12

24

= HMA= Base= Subbase

LCAs are a defensible protocol for quantifying the energy, environmental and materials aspects of WMA.

• Account for all processes associated with HMA– Include WMA additive production/transport– Include human health benefits beyond criteria pollutants

• Isolate improvements attributable to WMA

But…there are issues with the way we do LCA.

• Functional unit– describes the function and performance of the

subject of the product or process being studied – Example: 1 lane-mile of pavement capable of

supporting 100 million ESALs over 50 years

Implies1.Structural design2.Traffic measurement3.Defining maintenance/rehabilitation methods4.Performance standard

And…we are missing a good chunk of the data we need to calculate a good LCA and it is expensive to get this data.

Process Data Source

Issues

Fuel/Energy GREET Generic vehicle types

Transport GREET Generic vehicle types

Asphalt Production Eurobitume Dated European data

Aggregate Production

Eurobitume Dated European data

HMA Production EPA AP-42Eurobitume

Only data for average plantCannot differentiate by process

Laydown EPA NONROAD

Uses generic engine hp sizes

WMA Additive None No good information

GREET: Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation Model from Argonne National LaboratoriesEurobitume: LCI report for Eurobitume (European-type Asphalt Institute)EPA NONROAD: EPA emissions model for non-road vehiclesEPA AP-42: EPA emissions factors (emissions tied to quantity of material)

The I-90 Sasobit WMA job (June 2008)

12,500 tons½-inch Superpave0.25-ft mill-and-fill

Right lane only

Key ParametersHMA Class ½-inch WMA Class ½-inch

Binder content

5.2% 5.2%

Binder type PG 76-28 PG 76-28 (83-28 w/Sasobit)

Gyrations 100 100

RAP content 20% 20%

Tonnage 7,781 tons 4,724 tons

Sasobit 0 2% by binder weight

Cost/ton $58.00 $64.10

Production temp

340-350°F 300°F

Laydown temp

300-330°F 270-300°F

CPF 1.03 1.04

Compaction PF

1.02-1.05 1.03-1.05

Average density

93.60% of Rice 93.67% of Rice

Fuel usage 1.4 gal/ton (diesel) 1.07 gal/ton (diesel)23.5% less

Roller pattern 5-8 passes in 30 min

same

HMA: 12 June 2008

HMA: 12 June 2008

WMA: 23 June 2008

WMA: 23 June 2008

Open Path FTIR

Preliminary LCA results from I-90

Grant County power mix. This is one of the cleanest mixes in the nation.

Other (Solar, Wind,Biomass, etc.)

1.35%

Nuclear5.52%

Natural Gas3.06%

Coal8.21%

Hydro82.84%

A few observations.

• Mix temperature drives everything– We can gather less data and get same value

• How to simplify– Report mix temperature

• Temperature vs. criteria pollutants for types of plants• Temperature vs. vapor pressure for HMA compounds• Temperature vs. vapor pressure is NOT linear• The first 50°F is bigger than the second 50°F

– Report burner performance– Report fuel usage

Summary

• We have learned a lot about WMA• LCA can provide a defensible protocol for

analyzing environmental/energy factors• Need to gather a few pieces of information

to reduce the environmental data needed– HMA temperature vs. criteria pollutants– HMA temperature vs. asphalt fumes