TOPIC:- PAVEMENT DESIGN

SUBMITED TO: ASSISTANT PROF. GAJENDRA RAGHUWANSHI

SUBMITED BY: RANJAN KUMAR 0531CE111035

What is a Pavement?

A multi layer system that distributes the vehicular loads over a larger area

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What is a Pavement?

OR Highway pavement is a structure

consisting of superimposed layers of selected and processed materials whose primary function is to distribute the applied vehicle load to the sub grade.

OR It can also be defined as “structure

which separates the tires of vehicles from the under lying foundation.”

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What is a Pavement?

Pavement is the upper part of roadway, airport or parking area structure

It includes all layers resting on the original ground

– It consists of all structural elements or layers, including shoulders

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Functions of the Pavement Reduce and distribute the traffic loading so

as not to damage the subgrade – Provide vehicle access between two

points under all-weather conditions – Provide safe, smooth and comfortable

ride to road users without undue delays and excessive wear & tear

– Meet environmental and aesthetics requirement

– Limited noise and air pollution – Reasonable economy

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Requirements of pavement structure

Sufficient thickness to spread loading to a pressure intensity tolerable by subgade

Sufficiently strong to carry imposed stress due to traffic load

Sufficient thickness to prevent the effect of frost susceptible subgade

Pavement material should be impervious to penetration of surface water which could weaken subgade and subsequently pavement

Pavement mat. shd be non-frost susceptible

Pavement surface shd. be skid resistant

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Classification of Pavements

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Types of Pavement

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Flexible Pavements

PAVEMENTS

Rigid Pavements

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Natural Soil (Subgrade)

Aggregate Subbase Course

Aggregate Base CourseAsphalt Concrete

Flexible Pavements

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Given Wheel Load

Load Distribution in Flexible Pavements

Flexible Pavements

150 psi

3 psi

Wearing C.

Base

Sub-base

Sub-grade

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Rigid Pavements

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Rigid Pavements

Load Distribution in Rigid Pavements

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Pavements Comparison

Flexible pavements:• Deep foundations / multi layer construction• Energy consumption due to transportation of materials • Increasing cost of asphalt due to high oil prices

Rigid pavements• Single layer • Generally last longer• May require asphalt topping due to noise / comfort

issues

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Pavements Comparison

• Heavy vehicles consume less fuel on rigid pavements

• Rigid pavements more economic when considering environmental / life-cycle costing

Flexible Pavement

“A flexible pavement is a structure that maintains intimate contact with and distributes load to the sub grade and depends on aggregate interlock, particle friction and cohesion for stability”

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OR

It is a structure which distributes the traffic loading stresses to the soil (sub grade) at a magnitude that will not shear or distort the soil i.e., from 150 psi to 3 psi

OR

Pavement which reflects deformation of sub grade & the subsequent layers on to the surface” i.e.; load is transmitted from grain to grain through contact points of granular material, i.e. in a compressive way.

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Flexible Pavement

Flexible Pavement

Flexible pavements

Elastic

Three main layers

Surfacing Wearing course

Base course

Road base

Sub base

Supported by Sub-grade

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Load Distribution In Flexible Pavements

Structure of Flexible Pavement In order to take maximum advantage of

this property, material layers are usually arranged in order of descending load bearing capacity with the highest load bearing capacity material (and most expensive) on the top and the lowest load bearing capacity material (and least expensive) at the bottom.

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– Surface Course: This is the top layer and the layer that comes in contact with traffic.

– Base Course: This is the layer directly below the surface course and generally consists of aggregates (either stabilized or un-stabilized).

– Sub-base Course: This is the layer (or layers) under the base layer. A sub-base is not always needed.

Structure of Flexible Pavement

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– Sub-grade Course: The "sub-grade" is the material upon which the pavement structure is placed. Although there is a tendency to look at pavement performance in terms of pavement structure and mix design alone. The sub-grade can often be the overriding factor in pavement performance.

Structure of Flexible Pavement

Surface Course

The surface course is the layer in contact with traffic loads and normally contains the highest quality materials.  It provides characteristics such as friction, smoothness, noise control, rut and shoving resistance and drainage.

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Base Course

The base course is immediately beneath the surface course.  It provides additional load distribution and contributes to drainage and frost resistance.  Base courses are usually constructed out of:

Aggregates: Base courses are most typically constructed from durable aggregates that will not be damaged by moisture or frost action.  Aggregates can be either stabilized or un-stabilized. 

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24Lime rock Base Course Undergoing Final Grading

Sub-base Course

The sub-base course is between the base course and the sub-grade.  It functions primarily as structural support but it can also:

Minimize the intrusion of fines from the sub-grade into the pavement structure.

Improves drainage.

Minimize frost action damage.

Provides a working platform for construction.

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Sub-base Course

The sub-base generally consists of lower quality materials than the base course but better than the sub-grade soils. 

A sub-base course is not always needed or used. 

For example, a pavement constructed over a high quality, stiff sub-grade may not need the additional features offered by a sub-base course so it may be omitted from design. 

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Sub-grade

• Sub-grades be composed of a wide range of materials although some are much better than others.  This subsection discusses a few of the aspects of sub-grade materials that make them either desirable or undesirable and the typical tests used to characterize sub-grades.

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Sub-grade Preparation Sub-grade Failure Crack

Types of Flexible Pavement

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Dense-graded

Open-graded Gap-graded

Flexible Pavement – Construction

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Types of Pavements

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Types of Pavements

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Types of Pavements

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Types of Pavements

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Wheel Load

Sub-grade

Bituminous Layer

Typical Load Distribution in Flexible Pavement

Rigid Pavement

Rigid pavements are those, which contain sufficient beam strength to be able to bridge over the localized sub-grade failures and areas of in adequate support.

OR

Load is transmitted through beam action of slab in rigid pavements.

OR

Rigid pavements are those, which reduces the stress concentration and distributes the reduced stresses uniformly to the area under the slab.

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Rigid Pavement

Rigidity – does not deform under stress Concrete – air entrained increases resistance

to frost damage and de-icing salt corrosion Reinforcement – may be bars or mesh.

Continuous rigid pavements have heavy reinforcement

Joints – used in non-continuous pavements to allow for thermal movement. Includes a ‘filler’ and surface sealant

Rigid pavements – laid as single layer by ‘concrete paver’

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Rigid Pavements

Basic Components of Concrete Pavement

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Concrete paver

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Rigid Pavements

Load Distribution in Rigid Pavements

Rigid Pavements

Because of its relative rigidity, the pavement structure distributes loads over a wide area with only one, or at most two, structural layers. 

There are other types of surfaces also i.e.; reinforced, continuously reinforced etc.

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Structure of Rigid Pavement

Surface course.  This is the top layer, which consists of the PCC slab, reinforced or continuously reinforced slabs .  

Base course.  This is the layer directly below the PCC layer and generally consists of aggregate or stabilized sub-grade.

Sub-base course.  This is the layer (or layers) under the base layer.  A sub-base is not always needed and therefore may often be omitted.

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Surface Course

• The surface course is the layer in contact with traffic loads and is made of PCC or RCC. It provides characteristics such as friction, smoothness, noise control and drainage. In addition, it serves as a waterproofing layer to the underlying base, sub-base and sub-grade.

• The surface course can vary in thickness but is usually between 150 mm (6 inches for light loading) and 300 mm (12 inches for heavy loads and high traffic). Figure shows a 300 mm (12 inch) surface course.

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PCC Surface

Rigid Pavement Slab (Surface Course) Thickness

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Base Course

• The base course is immediately beneath the surface course. It provides

• Additional load distribution, • Contributes to drainage and frost resistance, • Uniform support to the pavement and • A stable platform for construction equipment. Bases also

help and prevent sub grade soil movement due to slab pumping. Base courses are usually constructed out of:

– Aggregates base. A simple base course of crushed aggregates has been a common option since the early 1900s and is still appropriate in many situations.

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– Stabilized aggregate or soil. Stabilizing agents are used to bind otherwise loose particles to one another, providing strength and cohesion. Cement treated bases (CTB s) can be built to as much as 20 - 25 percent of the surface course strength.

– Dense-graded HMA. In situations where high base stiffness is desired base courses can be constructed using a dense-graded HMA layer.

– Permeable HMA. In certain situations where high base stiffness and excellent drainage is desired, base courses can be constructed using an open graded HMA.

Base Course

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Completed CTB with Curing Seal Lean Concrete Base Material

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Sub-base Course

• The sub-base course is the portion of the pavement structure between the base course and the sub-grade. It functions primarily as structural support but it can also:

– Minimize the intrusion of fines from the sub-grade into the pavement structure.

– Improves drainage. – Minimizes frost action damage.

– Provides a working platform for construction. • The sub-base generally consists of lower quality

materials than the base course but better than the sub-grade soils. Appropriate materials are aggregates and high quality structural fill.

Types of Rigid Pavement Jointed Plain Concrete Pavement (JPCP)

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Types of Rigid Pavement

Continuously Reinforced Concrete Pavement (CRCP)

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Photo from the Concrete Reinforcing Steel Institute

Rigid Pavement – Construction

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Slipform

Fixed form

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Pavements Comparison

Flexible pavements:• Deep foundations / multi layer construction• Energy consumption due to transportation of materials • Increasing cost of asphalt due to high oil prices

Rigid pavements• Single layer • Generally last longer• May require asphalt topping due to noise / comfort

issues

Pavements Comparison

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Types of Pavement Failure

Failure criteria Flexible Pavements Fatigue Cracking, Rutting, Thermal Cracking, Rigid Pavements Fatigue Cracking, Pumping or Erosion Others: Faulting, spalling, joint

deterioration

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Flexible vrs. Rigid Pavements

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Flexible vrs. Rigid Pavements

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Airport-Highway Pavements

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THANKS