Life Cycle Cost and Pavement Preservation Issues

Prepared by: Douglas D Carlson

Vice President

Asphalt Products

Presenter: Mark Belshe

Crude Oil, Gas and Asphalt Costs Oil, Asphalt and Gas

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$/G

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Asphalt Crude Oil Gasoline

Life Cycle Costs Analysis for

Asphalt Rubber Paving Materials

by

R. Gary Hicks and Ding Cheng

CP2 Center prepared for

RPA Annual Meeting

San Antonio Texas

February 8, 2011

Background

• Asphalt rubber used since 1960s

• Primary uses include: – Chip seals

– Interlayers

– Hot mix applications

• Other uses – Crack sealants

– Membranes

Chip Seals

• Use began in 1960s

• Used for preventive

maintenance

• Now used by many

agencies

Chip Seals

Interlayers

• Used to prevent reflection

cracking

• Used in two or three layer

systems

• Used by several agencies

Rubberized Hot Mix Asphalt

• Used in gap-, open-, and

dense-graded mixes

• Used primarily in Arizona,

California, and Texas

• Reduced thickness is

allowed by some

agencies

LCCA Process

• Establish strategies for analysis period

• Establish M&R activity timing

• Estimate agency costs

• Estimate user and non-user costs

• Develop expenditure streams

• Compute net-present value

• Analyze results

Establish Strategies & Timing

• What?

• When?

• How long?

Analysis Period P

ave

me

nt

Co

nd

itio

n

Pavement

Life Analysis Period

Include at least one Rehab.

30-40 yrs

Agency Costs

• Design & engineering

• Initial construction

• Rehabilitation and maintenance

User and Non-User Costs

• Vehicle operating

• User delay

• Accident

• Impacts to adjacent businesses

• Disruptions to local residents

Develop Expenditure Streams

• Agency costs

• User and non-user costs

• Salvage value

Calculate Net Present Value (NPV)

NPV = Initial Cost + Future Cost

where

i = discount rate

n = year of expenditure

N

K=1 (1 + i)n

1 [ ]

Typical Expenditure Stream

Initial

Construction Rehabilitations

Analysis Period

TIME Salvage Value

Net Present Value

0

$325

Rehab #1

15 30

Costs

($1,0

00)

Time (years) Salvage Value $217

$1,100

Initial Cost

$300

User Costs

$269 User Cost

$361 User Cost

$325

Rehab #2

Analyze Results

• Deterministic approach

(w/o variability)

• Probabilistic approach (w/

variability)

Summary

• LCCA is a

– Decision support tool

– Results are not decisions

– Used to improve M&R strategies

LCCA Example Calculations

• System preservation - chip seals

• System preservation - thin hot overlays

• Structural overlay - reduced thickness

Inputs

• Discount rate, % 2.5, 4.0, 5.5

• Analysis period, yrs 40

• Average expected life Conv. AR

– Chip seals 5 10

– Thin HMA overlay 3 7

– Thick HMA overlay 10 15

1995 Agency Costs - Average

Treatment Conv. AR

Chip Seals ($/yd2) 1.00 2.00

HMA overlays ($/ton) 35 50

Routine maintenance 0.15 0.15

($/yd2 per year )

Scenarios Investigated

System Preservation Alternates

- Chip Seals Conventional chip seal followed by 100mm

HMA-DG.

AR chip seal followed by 50mm RHMA-GG over

50mm HMA-DG.

- Thin Hot Overlays 25mm HMA-DG followed by 100mm

HMA-DG.

25mm RHMA-GG followed by 50 mm RHMA-GG

over 50mm HMA-DG.

Scenarios Investigated (cont.)

System Preservation Alternates

Structural Overlays 100mm HMA-DG followed by 100mm

HMA-DG.

100mm RHMA-GG followed by 50mm

RHMA-GG.

User Costs Considerations

• Only consider delays costs due to interruption

• Other user and non-user cost are assumed

equal

• Concept of lane rental fees used as surrogate

for delay costs

Results - Deterministic Approach

Scenario Present Worth ($/yd)

Preservation – Chip Seal

• Conventional 18.39

• AR 15.87 2.25

Preservation – Thin HMA

• Conventional 20.69

• AR 17.33 3.36

Structural Overlay

• Conventional 21.97

• AR 14.63 7.34

Results - Probabilistic Model

Percentage of times

Scenario savings result using AR

Preservation - chip seal 86

Preservation - thin HMA 82

Structural Overlay 86

Summary-LCCA

• Asphalt rubber is cost effective for the scenarios

evaluated

• When variability in the inputs is considered, the AR

alternate would be the best choice over 80% of the time

• Asphalt rubber may not be cost effective in all situations.

LCCA allows one to determine when and where it will be

cost effective.

Update to LCCA

• Include current initial costs

• Real life performance data

• Compare more materials, Conventional, Rubber,

Polymer, and Soluble Rubber (Recycled TR

Polymers) binders

30

Example of Survey Data – Estimated Pavement Life (AR

Chip Seal, RHMA-G, RHMA-O)

Development of Scenarios

• Consider the following for the modified binders

– Extended life between treatments

– Reduced overlay thickness

– Reduced maintenance

– More variable lives

Caltrans LCCA Analysis Period

Objective Approach Needed

• Variables affecting performance include

– Traffic and Climate

– Quality control

– Existing pavement condition

Timing of Treatments Affect

Performance

• Good- minor distress (< 5% cracking)

• Fair-minor to moderate distress (5-20%

cracking)

• Poor- moderate to severe distress (>20%

cracking)

Cost Data Being Collected

• In-place construction costs

• Maintenance costs

• User costs

In-place Construction Costs

• All modified binders cost more than un

modified asphalt

• As such, they must last longer or be used in

reduced thickness

• Typical costs in $/ton are being determined for

– AR ($115/ton Gap graded, $90/ton Open graded)

– Conventional ($89/ton large, $96/medium)

Maintenance Cost Comparisons

User Costs

• Fuel consumption-about the same

• Safety costs-about the same

• Vehicle maintenance-about the same

• User delay costs-about the same

• Do we need to include user costs-only if the agencies do

• Realcost software has the capability to include user costs.

Questions to be Addressed with

Real Cost Calculations

• What life extension is needed to make the following cost effective? – AR

– PMA

– Terminal blends

• How much does the thickness need to be reduced to make these products cost effective?

• How does the variability in pavement performance impact the cost effectiveness?

Summary

• AR is cost effective assuming it produces greater lives or can be used in reduce thickness

• Later this year, we will have updated results on the cost effectiveness of AR and modified binders

In 20 years, 3 surface

treatments and 19008

gallons

In 20 years, 2 surface

treatments and 16896

gallons

TEXAS

Treatment Performance Capacity – A tool to

predict the Effectiveness of Maintenance

Strategies

By

Dr. Jorge B. Sousa

and George Way

Study Approach-estimating

Treatment Lives

• How to Bring in the Effect of Climate in Life

of Treatments?

• How to Bring in the Effect of Traffic in Life of

Treatments?

• How to Bring in the Effect of Existing

Pavement Condition?

• How to Bring in the Intrinsic Maintenance

Material Properties?

Treatments Should Perform

Better if they have:

• More binder

• Better

binder

• Thicker

layers

Traffic Index

• Low TI < 6 • [Less than 33,000 ESAL’s]

• Intermediate 6 < TI < 12 • [Between 33,000 and 1.1 million ESAL’s]

• Heavy TI >12 • [Greater than 1.1 million ESAL’s]

Existing Pavement Condition

Affects Treatment Life

• Good- Minor distress (< 5 % cracking).

– Expected life of 8-10 years or more

• Fair- minor to moderate distress (5-20%

cracking).

– Expected life of 4-6 years

• Poor condition (>20 % cracking). Moderate to

severe distress and with structural problems.

– Expected life of 1-3 years

Effect of Binder

• Quantity of binder,

• Aging characteristics of the binder used in

treatments

• Elastic characteristics of binder,

• Strain energy at break of the binder,

• Types of additives (none, polymer, rubber,

others),

• Mix stiffness (if applicable)

Effect of Type of Binder

TPF-5(019) Accelerated Loading Facility Status Report Jan. 2005

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25000 50000 75000 100000 125000 150000 175000 200000 225000 250000 275000 300000

Number of Load Passes

Cum

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rack

Length

(m

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Control L2 SBS LG L4 CR-AZ L1

ALF - FHWA Test Results 2004

Control SBS Polymer

Asphalt Rubber

ASPHALT RUBBER

“Can undergo about five times

the strain before rupture than can

asphalt”

1977 ADOT Research Report

By Green and Tolonen

TPC

TREATMENT PERFORMANCE CAPACITY

(TPC) (mm*l/m2) = BC * SE * T

BC - BINDER CONTENT PER METER SQUARE

(LITER/M2) *

SE - STRAIN ENERGY AT FRAILURE ratio *

T - THICKNESS OF TREATMENT (mm)”

CONCLUSIONS

• This research made clear that better treatments are

those that have higher Treatment Performance Capacity

(TPC), which indicates, what is intuitively known from all

pavement engineers, that treatments perform better if

they have more binder, are made with better binder and

are thicker (i.e. more long lasting and more

waterproofing).

• Currently most cost effective treatments (i.e. highest

TPC/$) are those with asphalt rubber.

COST SAVINGS

Three Ways To Save

1. Reduce Thickness

2. Substitute Virgin Polymers

3. Less Maintenance Over Time

Any questions?