Thermally Insulated Concrete Pavements: Life-Cycle Cost Analysis Methods and Preliminary Results...

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Thermally Insulated Concrete Pavements:Life-Cycle Cost Analysis Methods and

Preliminary Results

January 10, 2011

John HarveyNick Santero

Lev Khazanovich

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Background

• Compare thermally insulated concrete pavements (TICP) with conventional concrete designs using life-cycle cost analysis (LCCA)– Use net present value (NPV) to calculate life-cycle costs– Develop model to compare various alternatives and test

variable sensitivity• Identify situations/circumstances where TICP offers

potential cost savings, for example:– Construction type (new, rehab, etc.)– Desired service life– Location/Region/Agency

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Tasks and Status

• Create TICP/JPCP LCCA tool– First version tool created– Tool will need updating based on feedback from initial studies

and to better reflect non-California practices• Survey TICP agencies for input data

– California information taken from LCCA manual and knowledge, not yet discussed with Caltrans

– Initial data collected from WSDOT and MnDOT• Perform preliminary comparisons

– Two California cases analyzed using conceptual performance data

– Additional studies should be performed after performance analyses are completed

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Data Collection and Sources

• Surveyed three states for data– California (Caltrans)– Minnesota (MnDOT)– Washington (WSDOT)

• Current analysis uses California data– Maintenance schedules, annual maintenance costs and

LCCA protocol adapted from Caltrans’ LCCA Manual– Unit material and construction costs for contract

maintenance and rehabilitation estimated from Caltrans’ Construction Cost Database, LCCA Manual and UCPRC studies

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Model Development

• LCCA model based in Excel– Focuses exclusively on agency cost

• Calculates NPV and Crossover Points– NPV: establishes life-cycle costs over a specified analysis

period– Crossover points: identifies the future year when one

alternative (e.g., TICP) becomes economically rational decision• All inputs are user-defined

– Users can specify agency- or project-specific values for every parameter

– Additional parameters (e.g., specific material and unit costs) can be added as necessary

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Model Screenshots (1 of 3)Design and Maintenance Inputs

Jointed Plain Concrete Pavement - Design and Costs Parameters

Initial Construction Maintenance and Rehabilitation ln-mi= 0.6212 ln-km

Initial Construction Design Maintenance and Rehabilitation Summary

Value Unit Schedule Year Life Cost Annual MtceMainline Init Const. 0 45 $8,145,496 $8,945truck lane length 18 lane-km M&R #1 45 5 $995,182 $33,545PCC thickness 300 mm M&R #2 50 10 $1,185,273 $16,773base thickness 150 mm M&R #3 0 0 $0 $0base density 2.4 Mg/m3 M&R #4 0 20 $774,030 $26,091lane width 3.9 m M&R #5 20 20 $774,030 $26,091average joint length 4.1 m M&R #6 40 15 $774,030 $26,091dowels per joint 12 M&R #7 0 0 $0 $0design life 45 years M&R #8 0 0 $0 $0pass lane length 14 lane-km M&R #9 0 0 $0 $0

M&R #10 0 0 $0 $0Shoulder 60shoulder width 0 mPCC thickness 0 mmAC thickness 0 mmAC density 2.4 Mg/m3 Year: 45

truck lanes Life: 5 yearsAnnual Maintenance Cost $497 /yr/ln-km Maintenance and Rehabilitation #1 Annual Mtce: $1,864 /yr/ln-km

Length: 18 ln-kmTraffic Handlingcost factor 0.15 Activity/Material Unit Unit Cost No. Units Subtotal Costconstruction duration 74 days CPR-C ln-km $55,288 18 $995,182

Traffi c handling ls 149,277.27 0 $0$0

Initial Construction Costs $0$0

Activity/Material Unit Unit Cost No. Units Subtotal Cost Total Cost $995,182PCC material (mainline) m3 $190 21060 $4,001,400PCC material (shoulder) m3 $168 0 $0AC material (shoulder) Mg $98 0 $0base material m3 $192 10530 $2,021,760dowels each $0 52682.9268 $0 Year: 50PCC placement (mainline) m3 $0 21060 $0 truck lanes Life: 10 yearsshoulder placement m3 0 $0 Maintenance Rehabilitation #2 Annual Mtce: $932 /yr/ln-kmbase placement Mg 25272 $0 Length: 18 ln-kmdowel placement each 52682.9268 $0joint preparation joint 4390.2439 $0 Activity/Material Unit Unit Cost No. Units Subtotal Costsubgrade preparation m2 $2 140400 $280,800 CPR-B ln-km $65,848 18 $1,185,273remove concrete pavement m3 $12 31590 $379,080 Traffi c handling ls $177,791 0 $0traffi c handling % 7,083,040 74 $1,062,456 $0mobilization project $400,000 1 $400,000 $0diamond grinding m2 $0 $0

$0 Total Cost $1,185,273$0$0$0

Total Cost $8,145,496Year:Life: years

Maintenance Rehabilitation #3 Annual Mtce: /yr/ln-kmLength: ln-km

Activity/Material Unit Unit Cost No. Units Subtotal Cost$0$0$0$0$0

Total Cost $0

Year: 0pass lanes Life: 20 years

Maintenance Rehabilitation #4 Annual Mtce: $1,864 /yr/ln-kmLength: 14 ln-km

Activity/Material Unit Unit Cost No. Units Subtotal CostCPR-C passenger lanes ln-km $55,288 14.0 $774,030Traffi c handling ls $116,105 0 $0

$0$0$0

Total Cost $774,030




$0$0$0

Total Cost $774,030




$0$0$0

Total Cost $774,030

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Net Present Value Calculations

LCCA Inputs

Discount Rate 4.0%Analysis Period 55 years

Net Present Value Results

Pavement NPV TICP JPCP thickness 153JPCP $10,500,878TICP $10,500,878

LCCA Calculations: JPCP LCCA Calculations: TICP

Schedule Year Life Activity Ann. Mtce Salvage Schedule Year Life Activity Ann. Mtce SalvageInit Const. 0 45 $8,145,496 $185,350 $0 Init Const. 0 50 $8,178,774 $2,109,564 $0M&R #1 45 5 $170,374 $25,566 $0 M&R #1 0 0 $0 $0 $0M&R #2 50 10 $166,783 $10,507 -$68,542 M&R #2 0 0 $0 $0 $0M&R #3 0 0 $0 $0 $0 M&R #3 50 8 $143,181 $4,903 -$44,132M&R #4 0 20 $774,030 $354,584 $0 M&R #4 0 0 $0 $0 $0M&R #5 20 20 $353,257 $161,827 $0 M&R #5 50 15 $182,364 $26,151 -$99,926M&R #6 40 15 $161,222 $60,422 $0 M&R #6 0 0 $0 $0 $0M&R #7 0 0 $0 $0 $0 M&R #7 0 0 $0 $0 $0M&R #8 0 0 $0 $0 $0 M&R #8 0 0 $0 $0 $0M&R #9 0 0 $0 $0 $0 M&R #9 0 0 $0 $0 $0M&R #10 0 0 $0 $0 $0 M&R #10 0 0 $0 $0 $0

Net Present Value Net Present Value

Model Screenshots (2 of 3)NPV Results

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0 10 20 30 40 50 60 70 80 90 100$0

$1,000,000

$2,000,000

$3,000,000

$4,000,000

$5,000,000

$6,000,000

Series1

Cumulative NPV

JPCPCompositeCrossover Point

Year

Net

Pre

sent

Val

ueModel Screenshots (3 of 3)

Time Series and Crossover Points

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LCCA Approach

• Solve for two key unknowns:

1. Maximum PCC thickness for TICP in order to be cost effective compared to JPCP

2. Minimum extension of life needed by TICP design in order to be cost effective compared to JPCP

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California Case Studies

Case 1: Lane replacement of truck lanes in Southern California as TICP instead of JPCP. This project is based on the scope of a real project on I-15 near Devore (District 8).

Case 2: Convert multi-lane highway in Northern California into divided highway by adding new direction with TICP instead of JPCP. This project is roughly based on the scope of a real project on State Route 70 near East Nicholas (District 3).

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California Designs

Case 1 – Lane Replacement(in mm) JPCP TICP #1 TICP #2AC surface 30, 45 75, 105PCC 300 300* 255*AC base 150 150 150

Case 2 – New ConstructionJPCP TICP # 1 TICP #2

AC surface 30, 45 75, 105PCC 255 255* 225*LCB base 150 150 150

• Two TICP designs are compared for each Case Study• Thinner versus thicker PCC slab thickness

• When solving for PCC thickness, asterisked (*) thickness are solved for rather than inputted

• AC surface is either conventional hot-mix asphalt (HMA) or rubberized hot-mix asphalt (RHMA)• Factorial considers price of both materials

• Future maintenance schedules adapted from Caltrans LCCA manual

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California Factorial

• Each case and design was evaluated by altering several key parameters– AC surface thickness and type (30, 45 for HMA and RHMA;

75 for RHMA and 105 mm for HMA)– AC unit cost ($154 or $192/m3 for HMA, $192 or $240/m3

for RHMA); unit cost for PCC was $190/m3

– Traffic handling costs (15%, 50% of construction costs)• Future factorials could be run for other design

uncertainties– Unit price for TICP concrete slab– Cost changes for smoothness requirements

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California ResultsExample for Thickness Solutions

Traffic Handling Cost on M&R (% pave cost)

TICP HMA/RHMA type, thickness

TICP Design No.

JPCP PCC thickness (mm)

TICP PCC thickness for equal NPV (mm)

15 HMA 105 mm 1 300 17115 RHMA 75 mm 1 300 18515 HMA 30 mm 2 255 21715 HMA 45 mm 2 255 19615 RHMA 30 mm 2 255 20715 RHMA 45 mm 2 255 18050 HMA 105 mm 1 300 17550 RHMA 75 mm 1 300 19050 HMA 30 mm 2 255 22950 HMA 45 mm 2 255 20850 RHMA 30 mm 2 255 21850 RHMA 45 mm 2 255 192

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Traffic Handling Cost on M&R (% pave cost)

HMA/RHMA type, thickness

TICP Design No.

JPCP PCC thickness

TICP PCC thickness

TICP % PCC life change for same NPV

15 HMA 105 mm 1 300 300 >70%15 RHMA 75 mm 1 300 300 >70%15 HMA 30 mm 2 300 255 24%15 HMA 45 mm 2 300 255 54%15 RHMA 30 mm 2 300 255 37%15 RHMA 45 mm 2 300 255 >70%50 HMA 105 mm 1 300 300 >70%50 RHMA 75 mm 1 300 300 >70%50 HMA 30 mm 2 300 255 17%50 HMA 45 mm 2 300 255 44%50 RHMA 30 mm 2 300 255 30%50 RHMA 45 mm 2 300 255 67%

California ResultsExample for Life Extension Solutions

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California ResultsSummary

• Results indicate that marginal PCC thickness reductions in TICP are needed to make the pavement cost effective compared with JPCP– Results are similar for both Case 1 (lane replacement) and Case 2 (new

construction)– Results are especially favorable to TICP when asphalt costs are lower

• Life extension results are mixed for the different cases– Case 1: some scenarios (e.g., shorter initial service lives and lower

asphalt costs) found minimal (<30%) life extension needed to be competitive with JPCP, others found unreasonably high life extensions needed

– Case 2: all scenarios required large life extensions in order to be competitive with JPCP

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Key Limitations and Assumptions• Cost of PCC assumed to be same for life extension cases, where PCC

layer has same thickness in both JPCP and TICP. May be conservative if specifications for TICP pavement PCC include relaxed smoothness and other surface characteristics requirements.

• For PCC thickness requirement cases, cost per volume of the PCC is assumed to be same for new JPCP and TICP pavements. PCC unit costs for TICP may be lower if mix specification changes regarding surface durability.

• Potential environmental benefits not considered through a Life Cycle Assessment (LCA). – PCC in TICP pavements may use higher percentages of supplementary

cementitious materials, recycled concrete aggregates, or lower cost local aggregates. Offsetting benefits are environmental costs of HMA.

• Analysis does not consider noise or ride quality over the life cycles.• No user delay costs caused by construction were included.

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