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Life Cycle Analysis

ShapeMaterial

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EnvironmentalIndicators

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ISMD

Evaluation

This project is focused on enhancing the design of infrastructure by integrating materials engineering, civil engineering, and life cycle analysis.Approach: By pairing a novel Integrated Structures and Materials Design (ISMD) approach with life cycle analysis (LCA) tools, an integrated life cycle design framework is formed (Figure 1). Incorporating sustainable design principles from nano-scale materials development, through kilometer-scale infrastructure performance, this framework uses social, economic, and environmental indicators to elevate overall infrastructure sustainability.

Results: Using LCA feedback, new “green” Engineered Cementitious Composites (ECC) contain 74% industrial waste, reducing burdens, but still exhibiting exceptional material performance (Figure 2). Applied in an innovative bridge system, significant improvements in environmental, social, and economic performance are seen over a 60 year service life (Table 1).

Figure 1. IntegratedLife Cycle Design

Figure 2. Bending of Green ECC Material

Developed using ISMD

Table 1. Performance Comparison

Framework for Integrated Life Cycle Design

Sustainable Concrete Infrastructure Materials and Systems:Developing an Integrated Life Cycle Design Framework

Gregory A. Keoleian, Victor C. Li, Stephen E. Kesler, Stuart A. Batterman, Gloria E. HelfandUniversity of Michigan, Ann Arbor http://sci.umich.edu CMS MUSES – 03294

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Indicator

Current Bridge System

New ECC Bridge System

Total Primary Energy (GJ) 78,000 46,000Global Warming Potential (tonnes CO2 equiv) 5200 3500

Sulfur Oxides (kg SOx) 4700 2600

Total Life Cycle Cost (million $) 21.0 18.5

http://www.sci.umich.edu/

Definition: Life Cycle Assessment (LCA) accounts for all material and energy inputs and waste outputs from a system for all life cycle phases including raw material acquisition, processing, construction, use, and end-of-life.

Conclusions: The sustainability of a concrete bridge deck, evaluated from the perspective of energy consumption, greenhouse gas emissions, and criteria air pollution can be improved through incorporation of advanced materials and designs. • Accounting for traffic related impacts is a key factor in assessing transportation infrastructure sustainability.

Bridge Deck Life Cycle

Construction Related Traffic Congestion

Materials Extraction & Processing

Construction processes & traffic delay

Use normal traffic

conditions

End of Lifedeck

demolition

Bridge Repair Recycling

Concrete Bridge Deck Case Study: Bridges and highway infrastructure are long-lived and capital intensive. A project that looks preferable in the near term, can prove to be suboptimal in the long term.

LCA is applied to two concrete bridge deck designs. One, a conventional expansion joint design and the other, an engineered cementitious composite (ECC) link slab design. ECC is a high-performance, fiber-reinforced, ductile composite.

Link

sla

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Conventional design

Life Cycle Model: The life cycle model includes a traffic flow model, an EPA emissions model (MOBILE6.2) and an equipment emissions model (NONROAD).

0.0E+001.0E+072.0E+073.0E+074.0E+075.0E+076.0E+077.0E+078.0E+079.0E+07

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End of LifeDistributionMaterialsConstructionTraffic

Results: The ECC Link Slab Design results in 40% less primary energy consumption, and 39% less carbon dioxide emissions.

85%

80%

17%

13%

Life Cycle Assessment of Concrete Infrastructure



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The sustainability of constructed facilities is becoming increasingly important, prompting the development of “greener” environmentally-preferable construction materials.

Approach: Cement-based materials development focuses both on replacing energy and resource intensive components using wastes (Table 1) but also engineering greener materials to improve material properties, such as ductility, strength, and resistance to large cracks or deterioration. These properties are important for durability and long service life. This design is guided by sustainability metrics (social, environmental, and economic) and has been termed material “smart greening”.

Results: New greener forms of Engineered Cementitious Composites (ECC) retain properties such as strength, ductility, and fine cracking (Figures 1 and 2). These properties are critical to keeping corrosives out, while reducing energy and resource intensity per liter (Table 2) through waste material substitution. Increased material energy intensity is overcome by using less high performance ECC material when compared to concrete over the full infrastructure life cycle.

Figure 1. Ductility or “bendability” of green ECC materials

Figure 2. Green ECC resistance to large cracks

Table 2. Selected Material Properties and Sustainability Indicators

Table 1. Industrial Waste Materials Tested

Design of Green Cement-based Materials

Material PropertyOrdinary Concrete

Green ECC

ECC Improvement

Strength (MPa) 28-40 60-70 2 XDuctility (%) 0.01 4.0 400 XMaximum Crack Width (mm) 0.3 0.05 6 XSustainability IndicatorPrimary Energy (MJ/L) 2.84 4.7 -1.65 XWaste Generated (kg/L) 0.32 -1.22 4.8 XCO2 Released (kg/L) 407.2 324.7 1.2 X

Fly Ash Municipal Waste AshCement Kiln Dust Post-consumer Carpet FiberWaste Foundy Sand Aluminum Pot AshWastewater Sludge Banana Fibers



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Life Cycle Costs of Bridge DecksBridge Deck Case Study: LCCA is applied to two concrete bridge deck designs. One, a conventional expansion joint design and the other, an engineered cementitious composite (ECC) link slab design. ECC is a high-performance, fiber-reinforced, ductile composite.

•The ECC link slab design approximately doubles the durability of the concrete bridge deck by eliminating the expansion joints, meaning longer deck life and fewer repairs. • Agency costs account for material, labor and equipment rental and operation. • User costs account for time lost to motorists in construction related traffic delay, increased vehicle operating costs in the construction zone, and increased risk of vehicle crash in the construction zone.• Environmental costs account for air pollution damage costs from increased morbidity and mortality costs due to criteria air pollution, and the cost of climate change due to greenhouse gases.• A 4% discount rate is applied to all costs.

• Despite that the ECC link slab design is initially more costly than the conventional design, it resulted in 14% less total cost and a 30% decrease in agency costs over the total 60-year life cycle.• User costs comprise more than 98% of total costs.• Results are driven by the number and timing of construction events for repair and rehabilitation.

Alternative Bridge Deck Designs

Definition: Life Cycle Cost Analysis (LCCA) is a full-cost accounting method. Here, applied to highway infrastructure, it accounts for costs to the funding agency, users, and society throughout the life cycle of the application.

Life Cycle Analysis of Concrete Bridge Deck Designs



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$10,000

$100,000

$1,000,000

$10,000,000

$100,000,000

2000 2010 2020 2030 2040 2050 2060

ECC-User Conv-User

ECC-Agency Conv-Agency

ECC-Environmental Conv-Environmental

Arrows show when the conventional design becomes more costly than the ECC link slab design

Note log

scale


Predicting infrastructure service life is critical to creating accurate life cycle models to assess total infrastructure costs far into the future. Yet complex infrastructure systems can fail in countless ways making development of accurate infrastructure deterioration models very important, particularly when implementing new and innovative materials or construction systems.

Approach: To examine the consequences of new materials infrastructure service life, a material deterioration model is combined with a structure deterioration model (Figure 1). This captures the dual impact of improved materials along with the overall effect these materials have on a structure’s path to failure. It combines numerical predictions of material performance with real structure performance records for greater accuracy.

Results: Predicting the service life and maintenance schedule of a jointless bridge deck which uses new ductile Engineered Cementitious Composites (ECC) (Figure 2), maintenance such as deck repairs and resurfacing is reduced by as much as 50% over the 90 year bridge service life (Figure 3).

Figure 1. Bridge deterioration models for typical concrete (left) and jointless ECC bridges (right)

Figure 2. Jointless bridge deck system

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Figure 3. Comparison of bridge maintenance closings

Service Life Modeling of Bridge Infrastructure Systems Incorporating New Materials

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Prediction of infrastructure service life is critical for creating accurate life cycle models to assess social, environmental, and economic sustainability far into the future. These predictions must be rooted in deterioration models which estimate how long a structure will last, and are particularly important for new materials which have yet to be proven over decades of use, such as ductile concretes (ECC).

Approach: By combining various numerical models that predict migration of corrosives through concrete, crack formation due to expanding rust, and rust buildup on rebar, the length of time from initial construction (using regular or ductile concretes) until large cracks form due to rusting steel reinforcement can be calculated. This is based on material properties, such as strength or ductility, along with structural geometry, and exposure conditions.

Results: In bridge decks that often fail due to rebar rusting (Figure 1), this modeling shows that new ductile concretes can last decades longer than typical concrete by forming microcracks which absorb expanding rust (Figure 2) rather than cracking like concrete and forming bridge deck potholes.

Figure 1. Deteriorated bridge due to concrete chloride exposure and steel rebar oxidation

Figure 2. Model of steel rebar corrosion and large crack formation in concrete (left) and corrosion and deterioration suppression through microcracking in ECC (right).

Deterioration Modeling of Ductile Cement-based Materials

Cl-

Cl- Cl- Cl-Cl- Cl- Cl-Cl- Cl-Cl- Cl-

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Single concrete crack

ECCmicro-cracks



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Overlay ConstructionMinor Repair & MaintenanceMajor Repair & Maintenance

Analysis period Daily Traffic Lanes Length Discount Rate

40 years 70000 4 10 km 4%

To improve sustainability in pavement design, a new bendable concrete material (ECC) is explored. An integrated life cycle assessment and cost (LCA-LCC) model is developed to evaluate an unbonded concrete overlay, a hot mix asphalt (HMA) overlay, and an ECC overlay over a 40 year life cycle (Table 1).

Approach: Incorporating overlay design (Figure 1), maintenance schedule (Figure 2), traffic congestion, and pavement roughness effects, this LCA-LCC model evaluates the long-term sustainability of overlay systems by dynamically capturing the impacts of users, construction, and roadway deterioration.

Results: ECC overlay system reduces greenhouse gas (GHG) emission by 34%, primary energy consumption by 14% (Figure 3), and life cycle cost by 39% (Figure 4).

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Table 1 System Definition

Figure 1 Overlay Structure Figure 2 Timeline

Figure 3 Primary Energy Consumption & GHG Emission

Figure 4 Life Cycle Cost

1.2 m 3.6 m 3.6 m 2.7 m

Concrete Overlay

Existing Reinforced Concrete Pavement

Rubblize Existing Reinforced Concrete Pavement

HMA Overlay

ECC Overlay

Existing Reinforced Concrete Pavement

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Dynamic Life Cycle Modeling of Pavement Overlay Systems



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Service Life Modeling of Ductile Concrete Pavement Overlays

Service life prediction is an integral part of life cycle analysis of infrastructure incorporating new materials, such as ductile concrete (ECC) in pavement overlays. These predictions must be based on dominant deterioration mechanisms which govern how long the structure will last.

Approach: By combining experimental investigations that relate the traffic load to service life and numerical analysis that links the pavement response with pavement thickness, the service life can be predicted for given roadway overlay repair. This is based on material properties, such as bending strength, along with roadway geometry, and traffic loads.

Results: For pavement overlay repairs that fail due to cracks originating from old concrete through new overlay (Figure 1), this modeling shows that new ductile concrete pavement overlay repairs can double the service life of current roadway repairs with only half of the thickness (Table 1) by forming microcracks which blunt the pre-existing cracks rather than forming large potholes (Figure 1).

Table 1. Service life prediction of two overlay scenarios

Figure 1. Current (left) and future ECC (right) overlaid pavement performance through introduction of ECC

Material Ductility (%)

Bending Strength

(MPa)

Thickness(mm)

Service life(years)

Regular Concrete 0.01 4.6 200 20

Ductile Concrete 3.0 12.0 100 40

Future ECC overlay after

40 year service life

Current overlay after 20 year service life

Old concrete

Current overlayECC Overlay

Old concrete

Microcrack zone shielding Single

large crack

Old concretecrack

Old concretecrack



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Figure 1. Network Diagram Representing ASTM Concrete SpecificationsThe concrete industry is heavily reliant on consensus

standards writing organizations to ensure industry-wide quality and safety. The objective of this study is to identify institutional barriers and opportunities for sustainable concrete practice presented by industry standards.

Approach: Social Networking Theory was used to find the most heavily referenced industry standards to identify potential leverage points for sustainable practice. Standards related to concrete bridge decks were networked based on their references to each other (Figure 1). The networks were then evaluated to identify the most central specifications and provide a framework for case study analysis.

Results: Based on case study analysis of the three most heavily referenced standards, centrality (highest number of references) proves to be an indicator of the most significant levers and barriers to both sustainable practice and innovation. The most central standards prove to be the most difficult to change and generally the most significant barriers to innovation. Table 1 reflects the most heavily referenced standards among the American Society of Testing and Materials (ASTM) specifications evaluated.

Table 1. Most Central ASTM Standards

Designation

Network Analysis of Concrete Industry Standards



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Description DesignationPortland Cement C150Concrete Aggregates C33Blended Hydraulic Cements C595Chemical Admixtures C494Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture C618C09 Terminology C125Air Entraining Admixtures C260Std. Practice for Proportioning Normal, Heavyweight and Mass Concrete C211.1Specification for Ready Mixed Concrete C94C01 Terminology C219

Sustainability requires consideration of long-term economic, social, and environmental impacts, yet transportation departments in the US do not integrate environmental issues (non-user costs) into pavement-type decision making processes (Figure 1).

Approach: A life-cycle assessment model was built to help evaluate & compare the environmental impact of asphalt and concrete pavement alternatives for 12 actual road projects managed by Michigan Department of Transportation. Impacts from material production and distribution, equipment use, and work-zone congestion were included. These were then monetized and compared with life-cycle agency and user costs currently taken into account in the MDOT LCCA procedure.

Results: Generally, asphalt pavements have lower life-cycle emissions for some air pollutants (e.g. CO2, NOx, SOx) but higher for others (e.g. VOC, CH4) than concrete alternatives (Table 1). Asphalt pavement also shows higher life-cycle primary energy consumption than concrete alternatives. However, the pollution damage costs of both alternatives contributed to less than 9% of total life-cycle cost, and did not alter the lowest-cost alternative in the 12 road projects studied.

Life-cycle Cost

AgencyCost

User Cost

Pollution Damage

Coste.g. pollution

Figure 1: Life-cycle cost analysis (LCCA)framework for pavement-type selection

Table 1: Life-cycle environmental impact and damage costs of pavement alternatives in projects studied

Incorporating Pollution Damage Costs into Michigan DOT Life Cycle Cost Analysis (LCCA)


Gregory A. Keoleian, Victor C. Li, Stephen E. Kesler, Stuart A. Batterman, Gloria E. Helfand

Part of aset of 12

University of Michigan, Ann Arbor http://sci.umich.edu CMS MUSES – 03294

(per dir-mile) Asphalt ConcreteTotal Primary Energy (TJ) 30-85 >> 10-25

GHG (tonne) 700-3,500 < 1,100-4,100VOC (tonne) 0.45-1.00 > 0.17-0.70NOx (tonne) 2.0-6.0 < 2.5-6.2SOx (tonne) 0.18-0.38 < 0.22-0.44PM (kg) 32-260 ~ 31-240

GHG 15-30% 22-60%VOC 5-20% 5-10%NOx -45-65% -40-55%SOx 10-30% 10-25%PM 5-20% 5-20%Others <1% <1%

Total $1,000-35,000 $5,000-30,000

Environmental Impacts

Damage Costs

Bendable Concrete Incorporating Ultra High Volumes of Fly Ash

In the development of high performance and high strength concretes, material sustainability is seldom a concern and high cement contents are commonly used. The production of cement is responsible for 5% of global greenhouse gas emissions. A high performance bendable concrete (ECC) has been developed taking into account environmental sustainability.

Approach: Sustainability is improved by incorporating large amounts of fly ash, a coal power plant waste product, to replace cement while maintaining/improving bendable concrete performance The interaction between material components – fiber, matrix, and fiber-matrix interface – is carefully controlled to turn wastes into beneficial material ingredients.

Results: Bendable concrete using ultra high volumes of fly ash has been developed with cement content 60% lower than high performance/ strength concretes (see chart). The resulting material has a tensile ductility over 300 times that of concrete (see photo) and tight crack widths about half the thickness of fine human hair. These properties promote infrastructure sustainability through simultaneous enhancement of material greenness and infrastructure durability.

High Performance/Strength Concrete

Cement

Coarse AggFine Agg

WaterSP

Microsilica

Ultra High Fly Ash Bendable Concrete

Cement

Fly ashSand

WaterSP

Fiber



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Life-Cycle Cost Analysis (LCCA) has become a common tool used by state Departments of Transportation in pavement-type selection. However, the usefulness of LCCA is dependent on estimating the pavement costs and performance accurately.

Approach: Application of LCCA in actual Michigan DOT road projects was reviewed. Ten highway sections were grouped into four case studies. Their estimated and actual accumulated costs and maintenance schedules were analyzed and compared.

Results: Case studies indicated that Michigan DOT LCCA procedures correctly predict the pavement type with lower initial construction cost, but actual construction costs are usually lower than estimated using LCCA (Figure 1). This is likely due to non-site specific cost estimation within the Michigan DOT LCCA. Refinements to pavement construction and maintenance cost estimating procedures would assist the Michigan DOT in realizing the full potential of LCCA in identifying the lowest cost pavement alternatives.

Figure 1 : Estimated vs. actual costs of pavement of two MDOT managed pavement projects

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* asphalt overlaid on rubblized concrete# asphalt overlaid on repaired concrete

Evaluating Michigan DOT Life-Cycle Cost Analysis Practices


Gregory A. Keoleian, Victor C. Li, Stephen E. Kesler, Stuart A. Batterman, Gloria E. Helfand

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University of Michigan, Ann Arbor http://sci.umich.edu CMS MUSES – 03294

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