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Structure and distresses of rigid pavements

Atul Narayan, S. P.

IIT Madras

September 13, 2015

Outline

Introduction

Structure

Distresses

Rigid Pavement Types

Subordinate learning objectives

▸ To analyze the stress-strain distribution in pavements for givenloading conditions.

▸ To estimate pavement distresses based on stresses andstrains in pavement structure.

▸ To explain the effect of mechanical properties on pavementbehavior and performance.

▸ To analyze the stresses and distresses caused by vehicleloading.

▸ To estimate the expected volume of traffic in design life.

Outline

Introduction

Structure

Distresses


General Structure

Source:www.mto.gov.on.ca

▸ A rigid pavement mainly consists of portland cement concrete(PCC) slabs.

▸ Sometimes a base layer (cement-treated base or granularbase) may be used underneath the slab.

Components of Rigid Pavements

▸ Joints:▸ Longitudinal joints - separates pavement slabs in the

transverse direction▸ Transverse joints

▸ Expansion joints - provided to give room for concrete expansion▸ Contraction joints - provided to reduce stresses due to

contraction▸ Construction joints

▸ Reinforcements - provided to bear tensile stresses due tocontraction

▸ Tie bars - provided to hold slabs across longitudinal jointtogether

▸ Dowel bars - provided to transfer load across tranverse joints

Outline

Introduction

Structure

Distresses


Pumping

▸ It is the loss of subgrade material from underneath the slab.▸ It reduces support for the slab and in turn lead to other

distresses like linear cracking, corner breaks, edge punchoutand so on.

Source:pavementinteractive.org

Pumping (cont.)


Corner break

▸ Caused by a combination of fatigue and pumping


Edge punchout▸ Caused by a combination of fatigue and pumping


Blowup

▸ It is caused by inadequacy of expansion joints.


Faulting

▸ Mainly caused by pumping and the lack of support for the slab


Spalling▸ It is the loss of concrete material by chipping, breaking,

cracking, etc.▸ It is caused by excessive stresses at joints and cracks.


Linear/Longitudinal Cracking

▸ It is caused by a combination of different phenomena - trafficloading, curling, warping, etc.


Outline

Introduction

Structure

Distresses


Types of Rigid Pavements

▸ Jointed Plain Concrete Pavement (JPCP)

▸ Jointed Reinforced Concrete Pavement (JRCP)

▸ Continuous Reinforced Concrete Pavement (CRCP)

▸ Prestressed Concrete Pavement (PCP)

Types of Rigid Pavements (cont.)

Source: Huang (1993)

Jointed Plain Concrete Pavements

▸ It is used when thermal expansion/contraction is notsignificant.

▸ Dowel bars may or may not be provided▸ In case of undoweled slabs load transfer at the joint is through

aggregate interlock.▸ It needs closer joint spacing because of lack of reinforcement

and for aggregate interlock.▸ It is more susceptible to pumping, faulting and corner

breaking.

Jointed Reinforced Concrete Pavement

▸ It is the most common type of concrete pavement▸ Reinforcement is provided for concrete expansion/contraction.▸ Joint spacing can be higher because of the presence of

reinforcements.▸ Dowel bars are provided for transferring load amongst

adjoining slabs.▸ It is more susceptible to pumping and faulting type of failure.

Continuous Reinforced Concrete Pavement

▸ Constructed without transverse joints▸ Joints are viewed as the weekest part of concrete slab.▸ Thermal expansion/contraction stresses are relieved by

cracking of concrete slab.▸ Reinforcement is so provided as to limit the width of cracks

while increasing their number.▸ This type of pavement is more susceptible to edge punchout.

Prestressed Concrete Pavements

▸ Prestressing is used to increase the structural capacity of thepavements.

▸ PCPs require fewer transverse joints.▸ Thickness can be reduced because of prestressing.▸ PCPs are more commonly used as airport pavements.