Rigid Pavements By Fasih
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Presented By: M. Fasih-ur-Rehman Presented To: Dr. Sajjad Maqbool
Rigid Pavement
Those which are surfaced with Portland Cement Concrete (PCC).
These types of pavements are called “Rigid" because they are substantially stiffer than flexible pavements due to PCC's high stiffness.
Surfaces of a Typical Rigid Pavement Surface •
course
This is the top layer, which consists of the PCC slab.
Surfaces of a Typical Rigid Pavement Base
course
This is the layer directly below the PCC layer and generally consists of aggregate or stabilized subgrade. •
Lean Concrete Base Material
Surfaces of a Typical Rigid Pavement:
Sub-base course
•
The base course is immediately beneath the surface course. It:
•
Minimizes the intrusion of fines from the sub-grade into the pavement structure. Improves drainage. Minimizes frost action damage. Provides a working platform for construction.
• • •
Why Rigid Pavement is Constructed?
Load distribution is on wider area.
So additional base and sub-base layers are not necessarily required.
Why Rigid Pavement is Constructed?
Due to higher strength it carries more load and undergoes less wear and tear. The chemical and mechanical resistance of rigid pavements is excellent, making them ideal for high traffic loading and container terminals etc. Initial cost of rigid pavement is high but its lesser maintenance cost and long life with more load carrying capacity make it economical.
Types of Rigid Pavement
Rigid pavements are differentiated into three major categories by their means of crack control. •
•
•
Jointed Plain Concrete Pavement (JPCP) Jointed Reinforced Concrete Pavement (JRCP) Continuously Reinforced Concrete Pavement (CRCP)
Types of Rigid Pavement
Jointed Plain Concrete Pavement (JPCP)
•
JPCP controls cracks by dividing the pavement up into individual slabs separated by contraction joints. Slabs are typically one lane wide and between 3.7 m (12 ft.) and 6.1 m (20 ft.) long. It does not use any reinforcing steel but does use dowel bars and tie bars.
•
•
Jointed Plain Concrete Pavement (JPCP)
Jointed Plain Concrete Pavement (JPCP)
Types of Rigid Pavement
Jointed Reinforced Concrete Pavement (JRCP)
•
JRCP uses contraction joints and reinforcing steel to control cracking. Transverse joint spacing is longer than that for JPCP and typically ranges from about 7.6 m (25 ft.) to 15.2 m (50 ft.). Temperature and moisture stresses are expected to cause cracking between joints, hence reinforcing steel is used to hold these cracks tightly together.
•
•
Jointed Reinforced Concrete Pavement (JRCP)
Jointed Reinforced Concrete Pavement (JRCP)
Types of Rigid Pavement
Continuously Reinforced Concrete Pavement (CRCP)
•
CRCP does not require any contraction joints.
•
Transverse cracks are allowed to form but are held tightly together with continuous reinforcing steel.
Continuously Reinforced Concrete Pavement (CRCP)
Continuously Reinforced Concrete Pavement (CRCP)
Types of Rigid Pavement
Fiber Reinforced Concrete:
•
In FRC, the amount and location of reinforcement is not governed by loading and tensile stresses. Fibers are randomly dispersed to increase the strength of concrete. They may be steel, polypropylene, polyethylene or nylon.
•
•
Steel Fibers
Synthetic Fibers
Joints in Rigid Pavement Joints are purposefully placed discontinuities in a rigid pavement surface course. Concrete pavements are subjected to volumetric changes due to temperature changes, shrinkage and change in moisture content. To minimize the affect of these stresses, joints are provided.
Types of Joints
The most common types of pavement joints, defined by their function, are • • • • •
Contraction Joints Expansion Joints Construction Joints Longitudinal Joints Isolation Joints
Types of Joints
Contraction Joints:
•
Temperature changes cause contraction in the concrete which induces tensile stresses and slab cracks. A contraction joint is a sawed, formed, or tooled groove in a concrete slab that creates a weakened vertical plane.
•
Typical Contraction Joint
Contraction Joints
Rigid Pavement Showing The middle lane contraction joint Contraction Joints was not sawed resulting in a transverse slab crack. The outer lanes have proper Contraction Joints and therefore, no cracking
Contraction Joints
Function of Dowel Bar:
Contraction Joints
Skewed Contraction Joint: •
•
•
Skewed joints are cut at obtuse angles to the direction of traffic flow to help with load transfer. If the joint is properly skewed, the left wheel of each axle will cross onto the leave slab first and only one wheel will cross the joint at a time. which results in lower load transfer stresses
Skewed Contraction Joint
Types of Joints
Expansion Joints:
•
Expansion takes place when the temperature of the slab rises above the value when it was laid.
•
Expansion joints are intended to provide space in the pavement for expansion of the slab.
•
These are omitted altogether.
Typical Expansion Joint
Types of Joints
Construction Joints:
•
A construction joint is between slabs that results when concrete is placed at different times.
•
These joints can be longitudinal as well as transverse.
Construction Joints
Longitudinal and Transverse Construction Joints
Types of Joints
Longitudinal Joints: •
When the pavement width is more than, say 5m,
•
Stresses are produced in longitudinal direction
•
It is necessary to provide a longitudinal joint with some form of load transferring device.
Typical Longitudinal Joints
Types of Joints
Isolation Joints:
•
An isolation joint is used to lessen compressive stresses that develop between the pavement and a structure (or another existing pavement)
•
They are typically filled with a joint filler material to prevent water and dirt infiltration.
Isolation Joints
Roofing Paper Used for an Isolation Joint
Design of Rigid Pavement
There are mainly four design techniques for rigid pavements, which are • • •
•
Indian Design Guidelines Design by Westergaard Method AASHTO Method of Rigid Pavement Design UK Design Curve (By Road Note)
Design of Rigid Pavement
Indian Design Guidelines: •
These guidelines are not used internationally.
•
This method is not used world wide and is practiced only in India.
Indian Design Guidelines Charts
Design of Rigid Pavement
Design by Westergaard Method: Inputs
Wheel Load Heaviest single axle load Flexural Stress of Concrete Mod. of Rupture Mod. Of Sub-grade Reaction it is determined by Plat Load Test and is expressed as k=p/δ where p = applied pressure to soil δ = is corresponding deflection
Design by Westergaard Method
Design of Rigid Pavement
AASHTO Method of Rigid Pavement Design: Inputs
Calculation of Design Load(W18) for design life Reliability “R” in (%) Overall Standard Deviation, So Design Serviceability Loss (▲PSI) Modulus of Sub-grade Reaction Modulus of Elasticity of Concrete
After these calculation use the following graph
AASHTO chart for Rigid Pavement
AASHTO chart for Rigid Pavement
Design of Rigid Pavement
UK Design Curve (By Road Note)
•
After calculation of W18, the design chart for rigid pavement by Road Note is used to find the thickness.
Rigid Pavement
Those which are surfaced with Portland Cement Concrete (PCC).
These types of pavements are called “Rigid" because they are substantially stiffer than flexible pavements due to PCC's high stiffness.
Surfaces of a Typical Rigid Pavement Surface •
course
This is the top layer, which consists of the PCC slab.
Surfaces of a Typical Rigid Pavement Base
course
This is the layer directly below the PCC layer and generally consists of aggregate or stabilized subgrade. •
Lean Concrete Base Material
Surfaces of a Typical Rigid Pavement:
Sub-base course
•
The base course is immediately beneath the surface course. It:
•
Minimizes the intrusion of fines from the sub-grade into the pavement structure. Improves drainage. Minimizes frost action damage. Provides a working platform for construction.
• • •
Why Rigid Pavement is Constructed?
Load distribution is on wider area.
So additional base and sub-base layers are not necessarily required.
Why Rigid Pavement is Constructed?
Due to higher strength it carries more load and undergoes less wear and tear. The chemical and mechanical resistance of rigid pavements is excellent, making them ideal for high traffic loading and container terminals etc. Initial cost of rigid pavement is high but its lesser maintenance cost and long life with more load carrying capacity make it economical.
Types of Rigid Pavement
Rigid pavements are differentiated into three major categories by their means of crack control. •
•
•
Jointed Plain Concrete Pavement (JPCP) Jointed Reinforced Concrete Pavement (JRCP) Continuously Reinforced Concrete Pavement (CRCP)
Types of Rigid Pavement
Jointed Plain Concrete Pavement (JPCP)
•
JPCP controls cracks by dividing the pavement up into individual slabs separated by contraction joints. Slabs are typically one lane wide and between 3.7 m (12 ft.) and 6.1 m (20 ft.) long. It does not use any reinforcing steel but does use dowel bars and tie bars.
•
•
Jointed Plain Concrete Pavement (JPCP)
Jointed Plain Concrete Pavement (JPCP)
Types of Rigid Pavement
Jointed Reinforced Concrete Pavement (JRCP)
•
JRCP uses contraction joints and reinforcing steel to control cracking. Transverse joint spacing is longer than that for JPCP and typically ranges from about 7.6 m (25 ft.) to 15.2 m (50 ft.). Temperature and moisture stresses are expected to cause cracking between joints, hence reinforcing steel is used to hold these cracks tightly together.
•
•
Jointed Reinforced Concrete Pavement (JRCP)
Jointed Reinforced Concrete Pavement (JRCP)
Types of Rigid Pavement
Continuously Reinforced Concrete Pavement (CRCP)
•
CRCP does not require any contraction joints.
•
Transverse cracks are allowed to form but are held tightly together with continuous reinforcing steel.
Continuously Reinforced Concrete Pavement (CRCP)
Continuously Reinforced Concrete Pavement (CRCP)
Types of Rigid Pavement
Fiber Reinforced Concrete:
•
In FRC, the amount and location of reinforcement is not governed by loading and tensile stresses. Fibers are randomly dispersed to increase the strength of concrete. They may be steel, polypropylene, polyethylene or nylon.
•
•
Steel Fibers
Synthetic Fibers
Joints in Rigid Pavement Joints are purposefully placed discontinuities in a rigid pavement surface course. Concrete pavements are subjected to volumetric changes due to temperature changes, shrinkage and change in moisture content. To minimize the affect of these stresses, joints are provided.
Types of Joints
The most common types of pavement joints, defined by their function, are • • • • •
Contraction Joints Expansion Joints Construction Joints Longitudinal Joints Isolation Joints
Types of Joints
Contraction Joints:
•
Temperature changes cause contraction in the concrete which induces tensile stresses and slab cracks. A contraction joint is a sawed, formed, or tooled groove in a concrete slab that creates a weakened vertical plane.
•
Typical Contraction Joint
Contraction Joints
Rigid Pavement Showing The middle lane contraction joint Contraction Joints was not sawed resulting in a transverse slab crack. The outer lanes have proper Contraction Joints and therefore, no cracking
Contraction Joints
Function of Dowel Bar:
Contraction Joints
Skewed Contraction Joint: •
•
•
Skewed joints are cut at obtuse angles to the direction of traffic flow to help with load transfer. If the joint is properly skewed, the left wheel of each axle will cross onto the leave slab first and only one wheel will cross the joint at a time. which results in lower load transfer stresses
Skewed Contraction Joint
Types of Joints
Expansion Joints:
•
Expansion takes place when the temperature of the slab rises above the value when it was laid.
•
Expansion joints are intended to provide space in the pavement for expansion of the slab.
•
These are omitted altogether.
Typical Expansion Joint
Types of Joints
Construction Joints:
•
A construction joint is between slabs that results when concrete is placed at different times.
•
These joints can be longitudinal as well as transverse.
Construction Joints
Longitudinal and Transverse Construction Joints
Types of Joints
Longitudinal Joints: •
When the pavement width is more than, say 5m,
•
Stresses are produced in longitudinal direction
•
It is necessary to provide a longitudinal joint with some form of load transferring device.
Typical Longitudinal Joints
Types of Joints
Isolation Joints:
•
An isolation joint is used to lessen compressive stresses that develop between the pavement and a structure (or another existing pavement)
•
They are typically filled with a joint filler material to prevent water and dirt infiltration.
Isolation Joints
Roofing Paper Used for an Isolation Joint
Design of Rigid Pavement
There are mainly four design techniques for rigid pavements, which are • • •
•
Indian Design Guidelines Design by Westergaard Method AASHTO Method of Rigid Pavement Design UK Design Curve (By Road Note)
Design of Rigid Pavement
Indian Design Guidelines: •
These guidelines are not used internationally.
•
This method is not used world wide and is practiced only in India.
Indian Design Guidelines Charts
Design of Rigid Pavement
Design by Westergaard Method: Inputs
Wheel Load Heaviest single axle load Flexural Stress of Concrete Mod. of Rupture Mod. Of Sub-grade Reaction it is determined by Plat Load Test and is expressed as k=p/δ where p = applied pressure to soil δ = is corresponding deflection
Design by Westergaard Method
Design of Rigid Pavement
AASHTO Method of Rigid Pavement Design: Inputs
Calculation of Design Load(W18) for design life Reliability “R” in (%) Overall Standard Deviation, So Design Serviceability Loss (▲PSI) Modulus of Sub-grade Reaction Modulus of Elasticity of Concrete
After these calculation use the following graph
AASHTO chart for Rigid Pavement
AASHTO chart for Rigid Pavement
Design of Rigid Pavement
UK Design Curve (By Road Note)
•
After calculation of W18, the design chart for rigid pavement by Road Note is used to find the thickness.
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