lec 9_pavement design

Pavement Engineering

What is a Pavement?A structure built on existing ground to facilitate rapid, safe, reliable & comfortable traffic movement

Pavement engineering involve the study of:• Pavement Materials• Pavement Structural Analysis• Pavement Design• Pavement Maintenance and Rehabilitation• Pavement Management Systems

Pavements are designed based on “serviceability”

Serviceability is an indication of how good a ride the traveling public gets!

Pavement Structure

Types of Pavements

Flexible Pavements Rigid Pavements

Flexible Pavement Surfaces

Hot Mix Asphalt Surface

Hot Mix Asphalt Binder Course

Stabilized Base

Granular Subbase

Natural Subgrade

Prime Coat

Prime Coat

Tack Coat

Typical Flexible Pavement Configuration- High Traffic Volume

Hot Mix Asphalt Surface

Granular Base

Natural Subgrade

Prime Coat

Typical Flexible Pavement Configuration

- Low Traffic Volume

Typical Hot Mix Asphalt Concrete (HMAC) Paving Operation

Asphalt Concrete Paving

Seal Coat Pavement (a.k.a. Chip Seal, Surface Treatment)

Surface Treatment (or Seal Coat or Chip Seal)

Granular Base

Natural Subgrade

Typical Flexible Pavement Configuration

- Low Traffic Volume

Seal Coat Construction – Asphalt Spray

Seal Coat Construction – Aggregate Spread

Seal Coat Construction – Rolling

Rigid Pavement Surfaces

Portland Cement Concrete Surface Slab

Stabilized Base

Granular Subbase

Natural Subgrade

Prime Coat

Prime Coat

Typical Rigid Pavement Configuration- High Traffic Volume

Portland Cement Concrete Surface Slab

Granular Base

Natural Subgrade

Prime Coat

Typical Rigid Pavement Configuration- Low Traffic Volume

Paving of a Concrete Pavement

Types of Rigid Pavements

Jointed Plain Concrete Pavement (JPCP)

Jointed Reinforced Concrete Pavement (JRCP)

Continuously Reinforced Concrete Pavement (CRCP)

Pre-stressed Concrete Pavements (PCP)

Types of Rigid Pavements Jointed Plain Concrete Pavement (JPCP)

Types of Rigid Pavements Jointed Reinforced Concrete Pavement (JRCP)

Types of Rigid Pavements Continuously Reinforced Concrete Pavement (CRCP)

Types of Rigid Pavements Prestressed Concrete Pavement (PCP)

Use of Aggregates in Pavement Construction

Hot Mix Asphalt Concrete (HMAC)

Portland Cement Concrete (PCC)

Granular Base and Subbase Layers

Seal Coats

Classification of Aggregates Based on Origin (Natural & Artificial)

Based on Density of Particles

– Normal Weight (SG 2.5-2.8); Lightweight (SG 1.5-2.0) Based on Method of Processing (Crushed/uncrushed) Based on Affinity to Water

– Hydrophilic (siliceous); Hydrophobic (Carbonaceous) Based on Particle Size

– Coarse Aggregate (Larger than #4 sieve)– Fine Aggregate: #4(4.75mm) to #200 sieves (75 m)– Mineral filler (finer than #200 sieve)

Natural & Artificial Aggregate Types

Natural aggregates from:

Igneous Rocks (Granite) Metamorphic Rocks (Marble, Gneiss, Quartzite) Sedimentary Rocks (Limestone, Dolomite, Sandstone, Caliche)

Artificial aggregates from: Byproducts of Industrial Processes (Blast-furnace slag; Iron-

ore gravel) Manufactured Aggregates (Lightweight aggregate, Hydrated fly

ash)

Coarse & Fine Crystals - Igneous Rocks

Microstructure of Limestone & Marble- Sedimentary vs. Metamorphic

Excavation

Crushing

Transportation

Sizing

Stockpiling

Some Distinct AggregatesConcrete Sand

Screenings

¾” Crushed Limestone

1” Crushed Gravel

3/8” Pea Gravel

3/8” Crushed Trap Rock

Criteria for Selection of Aggregates

Stabilized (Bound) Materials

Compatibility with binder Durability -Resistance to freeze-thaw, degradation Stability (or strength) of the Mix

Unstabilized Materials

Strength Durability Drainability Low frost susceptibility

Important Aggregate Properties Gradation (ASTM C-33)

Specific Gravity & Absorption (ASTM C-127, C-128)

Hardness or Resistance to Wear (ASTM C-131)

Durability (Resistance to wet-dry, freeze-thaw, heat-cool)

Shape and Surface Texture

Deleterious Substances (ASTM C-40, C-142)

Surface Chemistry

Particle Crushing Strength

Standard Tests by ASTM, AASHTO, State DOTs

Los Angeles Abrasion Test

Before

After

Soundness Test

Before After

5 Cycles of Soaking and Oven Drying

Magnesium Sulfate or Sodium Sulfate Solution

Aggregate Gradations

Continuous GapUniform

* Uniformly graded- Few points of contact- Poor interlock (shape dependent)- High permeability

* Well graded- Good interlock- Low permeability

* Gap graded- Only limited sizes- Good interlock- Low permeability

Types of Gradations

Aggregate Size Definitions

Nominal Maximum Aggregate Size– one size larger than the first sieve to

retain more than 10%

Maximum Aggregate Size– one size larger than nominal maximum

size

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Aggregate Moisture States

Asphalt Concrete Mixes

Asphalt Concrete 3-phase system (aggregate, asphalt cement, air) Mix design to achieve maximum stability

– Aggregate type & gradation– Asphalt content (% by weight of total mix)– % Air voids

Mix design methods– Marshall Method– Hveem Method– Superpave Method

Marshall Mix Design Method Compaction Testing

SHRP (Superpave®) Gyratory Compactor

Design Parameters Six Mix Design Parameters

– Stability– Flow– Unit weight of compacted mix– Voids in mineral aggregate (VMA)– Percent voids in mix– Voids filled with asphalt (VFA)

Mix Design Method– Calculate asphalt content for maximum stability, maximum unit

weight and median air voids (4%)– Average the three asphalt contents above– Check 6 parameters for compliance with design criteria

Asphalt Concrete Phase Diagram

Aggregate Solids

Absorbed Asphalt

Effective(free) Asphalt

Air VoidsVAV

VEA

VAGG

VT

MAGG

MAA

MEA

MT

MTA

Distresses in Flexible Pavements

Pothole

Rutting

Alligator Cracking

Longitudinal Cracking

Transverse Cracking

Block Cracking & Edge Cracking

Flushing & Bleeding

Raveling in HMAC & Seal Coats

Failures

Airfield Pavement Failure

Airfield Pavement Failure

Distresses in Rigid Pavements

Longitudinal & Transverse Cracking

Corner Crack & Diagonal Crack

Spalling

Faulting

Punchout

Failures

Failed Crack

Shattered Slab

Pumping from Slab Edge

Polished Aggregate & Scaling

Blow-Ups (Buckling & Shattering)

Condition Assesement

PhotoLog Van

CT Photolog

Pavement Profiling

Laserand

Acceler-ometerin here

Pavement Profile

US24 Pavement Profile

WB High Freq.

The high frequency roughnessdoes not have a significantaffect on truck dynamics

US24 Pavement Profile

WB Low Freq.

Low frequency variationsare long bumps that canget trucks bouncing

US24 Pavement Profile

EB Low Freq.