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Pavement Design

CEE 320Anne Goodchild

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Dictionary.com

• Pavement: Noun– a paved road, highway, etc. – a paved surface, ground covering, or floor.– material used for paving– Sidewalk

• Pave: Verb– to cover or lay (a road, walk, etc.) with

concrete, stones, bricks, tiles, wood, or the like, so as to make a firm, level surface.

– noun 2.Southern Louisiana. a paved road

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What is Pavement: Wikipedia

• Pavement (material), the durable surfacing of roads and walkways ("road surface" in British English)

• Sidewalk, a walkway along the side of a road, in American English ("pavement" in British English and Philadelphia dialect)

• Pavement (architecture), a floor-like stone or tile structure • Pavement (band), an indie rock band from Stockton, California • Pavement (magazine), a youth culture magazine, published in New Zealand • Pavement Records, a record label • Portuguese pavement, the traditional paving used in most pedestrian areas

in Portugal ("Calçada Portuguesa" in Portuguese) • Road surface marking, highway surface markings intended to convey

information • Limestone pavement, a naturally occurring level outcrop • Tessellated pavement, a rare sedimentary rock formation that occurs on

some ocean shores

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Outline

1. Pavement Purpose

2. Pavement Significance

3. Pavement Condition

4. Pavement Typesa. Flexible

b. Rigid

5. Pavement Design

6. Example

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Pavement Purpose

• Load support• Smoothness• Drainage• All weather

operation• Direction and

guidance

DC to Richmond Road in 1919 – from the Asphalt Institute

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Pavement Significance

• How much pavement?– 4 million centerline miles in U.S.– 2.5 million miles (63%) are paved– 8.37 million lane-miles total– Largest single use of HMA and PCC

• Costs– $20 to $30 billion spent annually on pavements– Over $100 million spent annually in WA– Many states over billion dollar budgets

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Interstate Highway System

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Interstate Highway System

• Largest highway system in the world• Largest public works project in history• Started construction in 1956• 90% federal, 10% state funding• Owned built and operated by states• Construction and maintenance costs

primarily provided by fuel tax

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Resources

• Pavement Interactive

• State DOTs• AASHTO

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Pavement Design Procedures

• Asphalt Institute method• National Stone Association procedure• Shell procedure• AASHTO Guide for Design of Pavement

Structures – American Association of State Highway and Transportation Officials– First published in 1972

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What makes it difficult

• Construction process control• Material variations• Exposed environment

– Temperature and weather variability

• Transportation of materials• Cost of materials• Unkown traffic loads

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Pavement Types

• Flexible pavements– Asphalt

• Rigid pavements– Concrete

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Pavement Types

• Want to distribute the load to avoid permanent deformation

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Vehicle loads

• Typical vehicle weighs about 3500 lb, tire pressures around 35 lb/in2

• Truck can weigh up to 80,000 lb with tire pressure of 100 lb/in2

• Trucks and busses present a much more significant load on the pavement.

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Vehicle Volume

• Pavements have a design life, and fail after cumulative vehicle exposure.

•Volume of vehicles and prediction of vehicle volume is fundamental to pavement design.

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Pavement Condition

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Pavement Condition

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Pavement Condition

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Pavement Condition

• Defined by users (drivers)• Develop methods to relate physical

attributes to driver ratings• Result is usually a numerical scale

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Serviceability Concept

• Pavements degrade over time due to– Exposure to traffic– Time– Exposure to elements

• Different for different materials and different construction methods

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What pavement thickness is required to sustain X vehicle loads of Y weight?

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Pavement Types

• Flexible Pavement– Hot mix asphalt (HMA) pavements– Called "flexible" since the total pavement structure

bends (or flexes) to accommodate traffic loads – About 82.2% of paved U.S. roads use flexible pavement

• Rigid Pavement– Portland cement concrete (PCC) pavements– Called “rigid” since PCC’s high modulus of elasticity

does not allow them to flex appreciably – About 6.5% of paved U.S. roads use rigid pavement

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Flexible Pavement

Base: higher strength material than subbase, often a cementing material is used.Cementing material can be portland cement or asphaltic cement, or other material.

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Flexible Pavement

• Structure– Surface course

(waterproof, anti-skid)– Base course– Subbase course– Subgrade

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Types of Flexible Pavement

Dense-graded

Open-graded Gap-graded

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Rigid Pavement

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Rigid Pavement

• Structure– Surface course– Base course– Subbase course– Subgrade

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Types of Rigid Pavement

• Jointed Plain Concrete Pavement (JPCP)

Joints accommodate shrinkage during drying.

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Types of Rigid Pavement

• Continuously Reinforced Concrete Pavement (CRCP)

Photo from the Concrete Reinforcing Steel Institute