Transcript New Binder Specification SUPERPAVE

Pavement Types
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
Vehicle loads



Typical vehicle weighs about 1588 kg, tire
pressures around 241 kN/m2
Truck can weigh up to 3.628 tonne with tire
pressure of 690 kN/m2
Trucks and busses present a much more
significant load on the pavement.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
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.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
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
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
4
What is a Pavement?

A multi layer system that distributes the vehicular
loads over a larger area
CE 2020: Construction Materials
Dr. B. Munwar Basha
5
IIT Hyderabad
Load Distribution

Want to distribute the load to avoid permanent deformation
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
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

CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
7
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 material should be non-frost
susceptible
Pavement surface should be skid resistant
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
8
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
9
Types of Pavement
PAVEMENTS
Flexible Pavements
Rigid Pavements
Asphalt concrete
Concrete Pavements
CE 2020: Construction Materials
Dr. B. Munwar Basha
10IIT Hyderabad
Pavement Condition
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
Pavement Condition
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
Pavement Condition
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
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
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
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.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
Flexible Pavements
Asphalt Concrete
Aggregate Base Course
Natural Soil (Subgrade)
Aggregate Subbase Course
CE 2020: Construction Materials
Dr. B. Munwar Basha
16 IIT Hyderabad
Flexible Pavements
Given Wheel Load
150 psi
Wearing C.
Base
3 psi
Sub-base
Sub-grade
Load Distribution in Flexible Pavements
CE 2020: Construction Materials
Dr. B. Munwar Basha
17 IIT Hyderabad
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”
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.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
Flexible Pavement

Structure




Surface course
(waterproof, anti-skid)
Base course
Subbase course
Subgrade
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
Flexible Pavement

Flexible pavements are so named because the total
pavement structure deflects, or flexes, under loading. A
flexible pavement structure is typically composed of
several layers of different materials.
Flexible pavements
 Elastic
 Three main layers




Surfacing
 Wearing course
 Base course
Road base
Sub base
Supported by Sub-grade
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
20
Load Distribution in Flexible Pavements


Each layer receives the loads from the above layer, spreads them out, then
passes on these loads to the next layer below.
Thus, the further down in the pavement structure a particular layer is, the less
load (in terms of force per unit area) it must carry.
CE 2020: Construction Materials
Dr. B. Munwar Basha
21IIT Hyderabad
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.
 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.
 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.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
22
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.
In addition, it serves to prevent the entrance of
excessive quantities of surface water into the underlying
base, sub-base and sub-grade. This top structural layer
of material is sometimes subdivided into two layers.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
23
Wearing Course

This is the layer in direct contact with traffic loads. It is
meant to take the brunt of traffic wear and can be
removed and replaced as it becomes worn. A properly
designed (and funded) preservation program should be
able to identify pavement surface distress while it is still
confined to the wearing course. This way, the wearing
course can be rehabilitated before distress propagates into
the underlying intermediate/blinder course
Intermediate/Binder Course

Intermediate/Binder Course: This layer provides the bulk of
the HMA structure. It's main purpose is to distribute load.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
24
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.
HMA: In certain situations where high base stiffness is
desired, base courses can be constructed using a variety of
HMA mixes. In relation to surface course HMA mixes,
base course mixes usually contain larger maximum
aggregate sizes, are more open graded and are subject to
more lenient specifications.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
25
Sub-base Course

The sub-base course is between the base course and the subgrade. 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.
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.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
26
Sub-base Course

However, a pavement constructed over a low quality soil
such as a swelling clay may require the additional load
distribution characteristic that a sub-base course can
offer. In this scenario the sub-base course may consist of
high quality fill used to replace poor quality sub-grade.
Sub-grade


Although a pavement's wearing course is most prominent, the
success or failure of a pavement is more often than not dependent
upon the underlying sub-grade , the material upon which the
pavement structure is built.
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.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
27
Sub-grade Preparation
CE 2020: Construction Materials
Sub-grade Failure Crack
Dr. B. Munwar Basha
28IIT Hyderabad
Types of Flexible Pavement
Dense-graded
Open-graded
CE 2020: Construction Materials
Gap-graded
Dr. B. Munwar Basha
IIT Hyderabad
Flexible Pavement – Construction
CE 2020: Construction Materials
Dr. B. Munwar Basha
30IIT Hyderabad
Rigid Pavements

Introduction
Rigid pavements are so named because the pavement
structure deflects very little under loading due to the high
modulus of elasticity of their surface course. A rigid
pavement structure is typically composed of a PCC
surface course built on top of either




the sub-grade or
an underlying base course.
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.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad31
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’
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
32
Basic Components of Concrete Pavement
CE 2020: Construction Materials
Dr. B. Munwar Basha
33IIT Hyderabad
Rigid Pavement
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
Rigid Pavements
Load Distribution in Rigid Pavements
CE 2020: Construction Materials
Dr. B. Munwar Basha
35 IIT Hyderabad
Rigid Pavement

Structure




Surface course
Base course
Subbase course
Subgrade
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
Types of Rigid Pavement

Jointed Plain Concrete Pavement (JPCP)
Joints accommodate shrinkage during drying.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
Types of Rigid Pavement

Continuously Reinforced Concrete Pavement
(CRCP)
Photo from the Concrete Reinforcing
Steel Institute
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
Pavements Comparison
• Heavy vehicles consume less fuel on rigid pavements
• Rigid pavements more economic when considering
environmental / life-cycle costing
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
39
Concrete paver
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
40
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.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
41
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.
PCC Surface
CE 2020: Construction Materials
Rigid Pavement Slab
(Surface Course) Thickness
Dr. B. Munwar Basha
42
IIT Hyderabad
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.
CE 2020: Construction Materials
Dr. B. Munwar Basha
43 IIT Hyderabad
Base Course
 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.
CE 2020: Construction Materials
Dr. B. Munwar Basha
44 IIT Hyderabad
Base Course



Lean concrete. Contains less Portland cement paste than a typical
PCC and is stronger than a stabilized aggregates.
Lean concrete bases (LCB s) can be built to as much as 25 - 50
percent of the surface course strength.
A lean concrete base, functions much like a regular PCC surface
course and therefore, it requires construction joints and normally
cracks over time. These joints and cracks can potentially cause
reflection cracking in the surface course.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
45
Completed CTB with Curing Seal
CE 2020: Construction Materials
Lean Concrete Base Material
Dr. B. Munwar Basha
46IIT Hyderabad
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.
CE 2020: Construction Materials
Dr. B. Munwar Basha
47
IIT Hyderabad
Sub-grade


Sub grade provides support to the overlying concrete slab. If it is of
good quality then slab can be laid over it without providing sub-base
otherwise if it is extremely poor then a sub-base layer should be
incorporated .
For design purpose the only thing to know about sub-grade is its
classification and the unit pressure coming from slab to sub-grade
should be calculated for its selection. However, it must be resistant to
moisture damages.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
48
96% of Paved Roads are Asphalt
• Today, 96% of all paved roads and streets in India almost 45 lakhs kms - are surfaced with asphalt.
• Almost all paving asphalt used today is obtained by
processing crude oils. After everything of value is
removed, the leftovers are made into asphalt cement for
pavement.
• Man-made asphalt (Coal Tar) consists of compounds of
hydrogen and carbon with minor proportions of nitrogen,
sulfur and oxygen.
• Natural forming asphalt, or brea, also contains mineral
deposits.
• The first road use of asphalt occurred in 1824, when
asphalt blocks were placed on the Champs-Élysées in Paris.
CE 2020: Construction Materials
Dr. B. Munwar Basha
IIT Hyderabad
49