Pavement Materials
Pavement Materials
Pavement Materials
ENGINEERING II
Modern Pavements
Sheet Asphalt
1876
Sheet asphalt placed on a concrete base
(foundation)
Bitulithic Pavements
1901-1903 (Frederick J. Warren)
First step towards HMA
Pavement Layers-UK, PAK
Wearing Course
Bituminous Base Course
Subbase
Subgrade
Pavement Layers-USA
Surface Course
Binder Course
Subbase
Subgrade
Overview of Pavement Infrastructure Life-Cycle
Pavement Pavement
Network- Pavement Pavement
Network- Constructio Preservation Pavemen
level Paveme Constructio Preservation
level Paveme n Pavemen
t
Programmin nt Constructio
n Rehabilitati
Programmin nt n on
t
Monitorin
g and Design
g and Design Preventive Monitorin
g
Planning
Planning Inspectio Maintenanc g
n/Supervi e
sion
Corrective
Maintenanc
e
LEGEND
Pavement
Construction 11
Asset Operations
Pavement Design, Maint & Rehab
What Is DESIGN ?
Conceive/Develop Plans for Something to Serve a
Specific Function
Economy
Safety
Serviceability
Load-Carrying Capacity
Aesthetics
13
Pavement Performance Concerns
Repeated & Dynamic Loading
Different Load Magnitudes & Configurations:
Characteristics
Different Types of Failure:
Structural
Functional
14
Philosophy of Pavements
Pavements are alive structures
They are subjected to moving traffic loads that are
repetitive in nature.
Each traffic load repetition causes a certain
amount of damage to the pavement structure that
gradually accumulates over time and eventually
leads to the pavement failure.
Thus, pavements are designed to perform for a
certain life span before reaching an unacceptable
degree of deterioration.
In other words, pavements are designed to fail.
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Pavement Types
Flexible
Hot-Mix Asphalt
Surface Treatments
Rigid
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Conventional Flexible Pavement
20
Distribution of Wheel Load (Flexible)
21
Rigid Pavement
PCC Is Much Stiffer Than HMA and Distributes
the Load over a Much Wider Area
22
Jointed Plain Concrete Pavement
(JPCP)
23
Jointed Reinforced Concrete
Pavement (JRCP)
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Continuously Reinforced Concrete Pavement (CRCP)
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Typical Rigid Pavement Details
15 30 ft 30 100 ft
26
300 700 ft
Portland Cement Concrete Pavements (PCCP)
Joints
To Prevent Premature Cracking due to
Temperature and Moisture Changes
Pavement Joint Types
Contraction (Transversal)
Expansion (Transversal)
Construction (Transversal)
Longitudinal
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Pavement Design Concept / Principle
The tensile and compressive stresses induced in a
pavement by heavy wheel loads decrease with
increasing depth. This permits to use gradation of
materials, relatively strong and expensive materials
being used for the surfacing and less strong and
cheaper ones for base and sub-base.
The pavement as a whole limit the stresses in the sub-
grade to an acceptable level, and the upper layers must
in a similar manner protect the layers below.
Pavement design is the process of developing the most
economical combination of pavement layers (in relation
to both thickness and type of materials) to suit the soil
foundation and the traffic to be carried during the
design life in a given climate 28
Functions of the Base and Subbase
Flexible Pavement:
Structural Support
Subsurface drainage & Prevent
Pumping
Rigid Pavement:
Swelling
TYPES OF SURFACE (New Constructions)
Jointed Jointed
Plain Reinforce
Concrete d Concrete
Pavement Pavement
(JPCP) (JRCP) Often touted as a perpetual
pavement (CALTRANS, ILDOT, etc.)
30
TYPES OF SURFACE (Existing/Rehabilitated Pavements)
Continuous Asphaltic
Jointed AC-on- Composi PCC-on-
ly- Concrete
Concrete Pavement AC te PCC
Paveme reinforced
(ACP)
nt (JCP) Concrete
Pavement
(CRCP)
Jointed Jointed AC-on-PCC PCC-on-AC
Plain Reinforce
(blacktoppin (whitetoppin
Concrete d Concrete
g) g)
Pavement Pavement
(JPCP) (JRCP)
Traditiona Rubblized Crack&Se
l at 31
Surface Types
Flexible pavement (Asphaltic
concrete)
Rigid pavement
(Portland cement
concrete)
New Composite 32
Pavement
(new AC-over-new
New Flexible Pavement on Crushed-Stone 33
Aggregate Base
Reinforced Rigid pavement 34
35
Portland Cement Concrete (PCC)
37
Portland Cement Concrete (PCC)
38
Portland Cement Concrete (PCC)
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www.ci.champaign.il.us
40
Reinforced Rigid Pavement on unbound base
(Here, the concrete is cast on site)
www.fhwa.dot.gov
Reinforced Rigid Pavement on unbound base with thin
drainage layer
41
(Here, the concrete is pre-cast elsewhere and laid on site)
Continuously-reinforced Rigid Pavement
42
Non-traditional materials for the subbase, base,
or surface layers
http://www.highwaysmaintenance.com/Rcycling/srfchipcyc.jpg
Steel slag
(a by-product from steel mills)
45
Non-traditional materials for the subbase, base,
or surface layers
www.engineering.ualb www.targetrecycling.bc.c
erta.ca/.../tires1.jpg a/images/product_med/.
www.asphaltinstitute.org
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Pavement cracking caused Subgrade Preparation
by subgrade failure
Subgrade Characteristics and Properties
48
Soil Investigation
Preliminary investigation
This may include the identification of soil types from
topographical maps, geological maps, soil maps, aerial
photos and satellite images, ground water conditions
and examination of existing roads
The visual investigation coupled with small amount of
sampling and testing
Elements of investigation
Existing topography
Drainage pattern
Erosion and vegetation
49
Soil Investigation
Detailed investigation - Field and lab investigation
1. Field investigation
. It includes geophysical exploration , test pits and
boring sampling of soil and rocks and ground water
conditions
. Two geophysical methods used for investigation are
the electric resistivity and seismic refraction method
Electric resistivity mainly depends on clay minerals ,
moisture content and type of concentration of
electrolytes in water.
Seismic refraction method mainly relies upon that
velocity of sound is different for different materials.50
Soil Investigation
Detailed investigation
2. Lab investigation
Representative samples
The depth of test pit and boring should be at least
one meter below the purposed subgrade elevation
Where soft soil is encountered, go down to
denser strata
It is advisable to take a greater no of samples in
the field that can be tested in lab
51
Soil Investigation
Lab Testing/ Terminologies in the Context of Pavement Engg
Particle size distribution important since many properties
such as internal friction, void content, wear resistant and
permeability etc can be ascertained. The PSD of a material can
be important in understanding its physical and chemical
properties. It affects the strength and load-bearing properties of
rocks and soils
Moisture content- for strengths and deformation characteristics
Specific gravity is used in the equations expressing the phase
relation of air, water and solids in a given volume of material
Plasticity use to estimate the engineering behavior of clayey
soils
Free swell
Used to verify swelling tendencies
Calculated as the increase of volume as a %age of initial
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volume
Soil Investigation
Lab Testing (continued)
Density - Influence on bearing capacity and
potential for settlement
Compaction- standard and modified compaction
test
California bearing ratio, CBR
Dynamic cone penetrometer test, DPC
Consolidation test Employed to estimate the
settlement of soil under embankment or other
structures
Tri-axial compression test is used to examine the
structural strength of soil as foundation of structure
53
Soil Characteristics:
1. Grain Size:
The most important!.. Behavior varies greatly when
comparing coarse (gravels and sands) to fine-grained
(silts and clays) soils
2. Shape and Texture:
Coarse grained - gravel and sand: rounded and
angular
Fine grained - silts: rounded and plate shaped
Fine grained - clays: plates and elongated crystals
54
Subgrade Characteristics and Properties
Clays
Silts
Top Sizes
55
Subgrade Characteristics and
Properties
Soil Physical Properties:
1. Permeability - Ability of water to flow through soil
the best: high or low ?
2. Capillarity - Ability to draw water above water
table
the best: high or low ?
3. Compressibility - Ability to consolidate (compress)
under load the best: high or low ?
4. Elasticity - Ability of soil to "'rebound" when
unloaded
the best: high or low ?
5. Strength - Ability to withstand deformation and
movement under load 56
Gap
Graded
Uniform
ly Well
Graded Graded
58
Analysis of Soil Properties (cont.)
Moisture and Fine Grained Soils
States of moisture (Atterberg limits: ASTM D4318
or AASHTO T-89/90)
59
Analysis of Soil Properties (cont.)
Shrinkage Limit (SL):
Water content where no further soil
volume change takes place upon drying
(Volume = 0)
62
Characterization of Highway Subgrade Material
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Characterization of Highway Subgrade Material
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Soil Classification: AASHTO
Example: LL = 53%, PI = 22% , % Passing #200 =
71% and % Passing #10 = 100%
(Notes: Final classification is the best possible
grouping, F = % Passing #200)
AASHTO: Since > 35% passes #200, LL > 40 and PI
> 11 then soil is A-7
For A-7-5 (see note on bottom of chart) PI = LL - 30;
22 < 23 ok
So, soil is A-7-5
Group Index: GI = (F-35) [0.2 + 0.005 (LL-40)] +
0.01 (F-15)(PI-10)
F = 71%, LL = 53, PI = 22 then, GI = 16.26, say 16.
The soil is A-7-5(16) 65
Soil Compaction
Soil compaction increases soil density, strength (stability)
and reduces the amount of water that can be absorbed in
service (swelling, softening)
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Highway Compaction Requirements
Control of Soil Compaction in Field
Table 18.7: Commonly Used Minimum Requirement for
Compaction of Embankments and Subgrades
AASHTO Class Maximum Relative Density
of Soil
Embankments Subgrade
A1, A3 95 95
A2-4, A2-5 95 95
71
Soil Engineering for Highway Design
Field Density Example Problem: Sand Cone
A sand cone holds 851.0 g. The loose density of the sand is
1.430 g/cc.
Field test results:
Total weight of soil: 639.5 g
Dry Weight of soil: 547.9 g
Initial weight of the sand-cone apparatus: 4527.8 g
Final weight of the sand-cone apparatus: 3223.9 g
Determine the Field Dry Density and Water Content.
SOLUTION:
Mass of Sand Used:
Mass in Test Hole:
Volume of Test Hole:
Field Dry Density:
72
Field Water Content:
Field Density Example Problem: Balloon Densometer
73
California Bearing Ratio (CBR) - AASHTO T193, ASTM D1883
Early 1940's U.S. Army Corps of Engineers developed for
airfield design
Procedure:
Compact soil sample at opt. moisture using standard or modified
Proctor,
Soak for 4 days, and then perform the CBR test
Record loads to cause 0.1-in., 0.2-in. up to 0.5 in. penetrations
in the soil sample @ penetration rate of 1.25 mm/min.
Compare soils strength in punching shear to that of Standard
Crushed Stone, expressed as a %
(1) CBR (%) at 0.1-in. penetration = [Psoil (psi) / 1,000 psi] * 100
(2) CBR (%) at 0.2-in. penetration = [Psoil (psi) / 1,500 psi] * 100
74
If (2) is greater than (1), compute CBR using 0.2-in. penetration
results
Resilient (Elastic) Behavior Resilient
Modulus
Contact Pressure
100 psi
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Bearing Capacity
10 psi
Subgrade Characteristics and Performance
Subgrade Characteristics:
1. Load bearing capacity
2. Moisture content
Moisture tends to affect a number of subgrade
properties including load bearing capacity, shrinkage
and swelling
Moisture content can be influenced by a number of
things such as drainage, groundwater table elevation,
infiltration, or pavement porosity (which can be
assisted by cracks in the pavement)
Generally, excessively wet subgrades will deform
excessively under load 77
Subgrade Characteristics and Performance
Subgrade Characteristics:
1. Load bearing capacity
2. Moisture content
3. Shrinkage and/or swelling
Some soils shrink or swell depending upon their
moisture content
Soils with excessive fines content may be
susceptible to frost heave in cold climates
Shrinkage, swelling and frost heave will tend to
deform and crack any pavement type constructed
over them
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Subgrade Characteristics and Performance
Subgrade stability
refers to soil strength influences
pavement construction operations
Prevent excessive
rutting and shoving
during construction
Subgrade stability
influences long-term
pavement performance 79
Improve Subgrade Performance
1. Increase strength
2. Reduce plasticity (PI)
3. Decrease volume change potential
4. Improve workability (Compactability)
5. Increase durability(long term effects)
80
Stabilization Objectives
1. Increase strength/stiffness
2. Decrease soil response to environmental changes
(improve durability), Moisture, temperature &
freeze/thaw
3. Construction expediency,
Economics (cost reduction)
increase density of engineered pavement layers
4. Subgrade modification
Reduction of PI, control volume changes and
moisture susceptibility, etc.
81
Stabilization Objectives
82
Subgrade Stability Solutions
Considers stabilization for all subgrade soils with CBR < 6
4. Mechanically stabilize
Geosynthetics and coarse aggregate
Geogrids or high strength geotextiles 83
Improve Subgrade Performance
Poor subgrade should be avoided if possible, but when
it is necessary to build over weak soils there are
several methods available to improve subgrade
performance:
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Granular Bases and Subbases (Ballast and Sub-ballast)
Purposes:
Drainage - open graded ballast
Load Distribution - flexible pavements
Stability - greater angularity, greater stability
Raise pavement or track structure (over the subgrade)
Moisture
o Pavements are susceptible to water
o Sources of Water:
(1) Joints and cracks (rigid and flexible pavements)
(2) Shoulders and ditches
(3) Surface permeability (AC & PCC)
(4) Upward movement of ground water table (or capillary
action)
(5) Seepage from high ground 90
91
Suitable Materials for Cement Stabilization
Minimum of 55% passing #4 sieve
PI < 30
Less than 1% sulfate
Non-reactive aggregates
93
Mechanically Stabilized Surfaces
Fiber Reinforcement
Materials that have been
used for fiber reinforcement
include metallic,
polypropylene, glass, wire,
straw, and hemp fibers.
95
Aggregates: Definitions and Functional
Requirements
Granular material that comprises the largest
quantity of material used in most pavement and
railroad track structures
Functional Requirements:
Strength
Distribute Load, Reduce Stresses in
Underlying layers via thickness and modulus
Aid Drainage
Reduce Damage from Frost (Increase depth to 96
Subgrade), Filler
Aggregates: Definitions and Functional
Requirements
Functional Requirements:
When aggregates are used as an ingredient in
asphalt and PCC, additional functional
requirements and tests are needed:
skid/polish resistance, angularity
requirements, freeze/thaw durability, etc.
Description of the Best Aggregate for
Transportation Uses:
CRUSHED
ANGULAR
ROUGH, TEXTURED SURFACE
99
Wearing Course
The surface course is the layer in contact with
traffic loads and normally contains the highest
quality materials.
Wearing Course.
Intermediate/Binder Course.
Wearing Course - Gradation
HMA mix types differ from each other mainly in
maximum aggregate size, aggregate gradation
and asphalt binder content/type
Air voids 15 20 %
Bituminous Materials
Asphalts -Natural or fractional distillation of
petroleum
Tars Destructive distillation of bituminous
coal, wood having distinct odor (high temp
susceptibility, health hazards)
Pitches -Fractional distillation of tar
Barrel of
Crude Oil
103
Production of Asphalt Concrete
Mixing & placing at low viscosity
hot asphalt cement
liquid asphalts
o cutback asphalts
o emulsified asphalts
Cannot cast -use compaction, Three stage
process (vibratory, pneumatic, steel)
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Petroleum-Based Asphalt Binders
10
5
Asphalt Binders
Background
History of
Specifications
1. Penetration Grading System
2. Viscosity Grading System
3. Aged-Residue Viscosity Grading
System
4. Superpave Grading System
10
6
Early Specifications
Lake Asphalts
Appearance
Solubility in carbon disulfide
Petroleum asphalt binders (early 1900s)
Consistency
Chewing
Penetration machine
10
7
Penetration Testing
No. 2 sewing
machine needle
1
.5
.3 Compaction Range
.2 Mixing Range
.1
100 110 120 130 140 150 160 170 180 190 200
11
2
Temperature, C
Comparison of Pen, Viscosity & AR
Penetration Grades
AC 40 AR
Viscosity, 60C (140oF)
40 16000
100 50 AC 20
AR 8000
60
50 AC 10
70 AR 4000
85
100 AC 5
AR
120 2000
150 AC 2.5
200 AR
10
300 1000
5
11
3
Ductility
Evaluates the ability of an asphalt binder
sample to stretch at a rate of 5 cm/min at
25oC
Centimeter
Scale
Mold
Asphalt
Sample
11
4
Typical Penetration Specifications
Penetration 40 50 200
- 300
Flash Point, F 450+ 350+
Ductility, cm 100+ 100+
Solubility, % 99.0+ 99.0+
Ductility, cm NA 100+
11
*Table Provided as Handout 5
Advantages
11
6
Disadvantages
Empirical test
Shear rate
High
Variable
Mixing and compaction temp. information
not available
Similar penetrations at 25oC (77oF) do not
reflect wide differences in asphalts
11
7
Flash Point (Safety)
Thermometer
Wand attached
to gas line
11
8
Solubility (Purity)
Asphalt binder is
dissolved in a solvent
either carbon-
disulfide or
Trichloroethylene
then filtered through a
vacuum flask.
The amount of
insoluble material
retained on the filter
represents the
impurities in the
asphalt binder. 11
9
Outside of Oven
Thin Film Oven (durability)
TFO simulating the
change in asphalt binder
properties which occur
during tank storage,
mixing and construction
processes.
Pan Thermometer
Three containers with 50
g Asphalt in each.
Rotated/kept in oven at
163 oC oven for 5 hours.
Rotating Shelf
12
0
Superpave Asphalt Binder
Specifications
121
Superpave Asphalt Binder Specification
PG 64 - 22
Min pavement
Performance temperature
Grade
Average 7-day max
pavement temperature
The PG Binder designation is based on expected extremes of hot and cold
pavement temperatures. 122
Tests Used in Superpave PG Specifications
Construction
Fatigue Thermal
Rutting Cracking Cracking
RV DSR BBR
+ve Temp -ve
PAV
No Aging Long Term Aging
RTFO (Short Term
Aging) 123
Tests Used in Superpave PG Specifications
Heavy Trucks
> Early part of
pavement
service life
125
Fatigue Cracking
Addressed by intermediate
temperature stiffness
G*sin on RTFO & PAV aged asphalt binder < 5000
kPa