Material Properties

1
Material Properties
2
Material Types

• Unbound (soil)
• Natural (i.e., subgrade)
• Select (i.e., subbase, base)
• Asphalt concrete
• Portland cement concrete
• Stabilized materials
• Cement stabilized
• Bituminous stabilized
• Bedrock
• Recycled

3
Material Properties Needed for Design

• Pavement response model material inputs
• Modulus (stiffness)
• Poissons ratio
• Materials-related pavement distress criteria
• Permanent deformation resistance
• Fatigue resistance
• Strength
• Other materials properties
• Density
• Permeability
• Thermal expansion coefficient

4
Material Models
(Yoder and Witczak, 1974)
5
Material Models

• Linear elasticity
• Asphalt
• Stabilized layers
• Unbound layers
• Linear viscoelasticity
• Asphalt
• Nonlinear (all materials, to some extent)
• Nonlinear elasticity
• Plasticity
• Nonlinear viscoelasticity
• Viscoplasticity

6
Soil Classification Systems
7
Soil Classification

• The separation of soil into classes or groups
  each having similar characteristics and
  potentially similar behaviour
• Few simple (routine) tests are used to classify
  soils.
• Gradation
• Atterberg Limits

8
Soil Classification Systems

• MIT
• AASHTO
• USCS
• FAA

9
MIT Classification
10
AASHTO Classification

• AASHTO American Association of State Highways
  and Transportation Officials
• Used mainly for subgrade rating for highway
  purposes.
• Requires
• Gradation
• LL
• PI

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AASHTO Classification (Granular Materials)
12
AASHTO Classification (Fine Materials)
13
AASHTO Classification
(Coduto, 1999)
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Group Index (GI)

• GI is used to classify the fine grained soils
  within one group and for judging their
  suitability as subgrade materials.
• GI 0.2 a 0.005 a.c 0.01 b.d ?(0 to 20)
• a P200 35 ?(0 to 40)
• b P200 15 ?(0 to 40)
• c LL 40 ?(0 to 20)
• d LL 10 ?(0 to 20)
• GI to the nearest whole number (integer)
• High GI ? low quality material
• EX A-7-6(5), A-7-6(18)

15
USCS Classification

• USCS United Soil Classification System
• Used mainly for geotechnical purposes
• Requires
• Gradation
• LL
• PI

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USCS Classification
EX SC ? Clayey Sand EX
Dual Symbol SP-SM GW ? Well Graded
Gravel poorly graded sand
CL ? Clay with low plasticity with
silt
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Computing CU and CC
Coefficient of Uniformity
High Values Indicate Well-Graded Soil
Coefficient of Curvature
Values Between 1-3 Indicate Well-Graded Soil
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A-Line Chart
Separates Clays and Silts
OH MH
ML OL
19
USCS Classification
20
USCS Classification (Coarse-Grained)
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USCS Classification (Fine-Grained)
OH MH
ML OL
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Dual Symbols
USCS

• For the following conditions a dual symbol should
  be used
• a) Coarse grained soils with fines between 5
  and 12
• The first symbol is indicative of the gradation
  (W or P), the second symbol is indicative of the
  fines.
• EX SP-SM poorly graded sand with silt
• b) Fine grained soils within the shaded zone in
  the A-line chart (PI between 4 and 7, LL between
  12 and 25).
• EX CL-CM, Silty clay with Low LL

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Comparison between the AASHTO and Unified Systems

• Both systems are based on the texture and
  plasticity of the soil.
• Both systems divide the soils into two major
  categories Coarse grained and Fine grained based
  on P200 SI sieve.
• AASHTO
• P200 lt 35 ? Coarse grained
• P200 gt 35 ? Fine grained
• Unified
• P200 lt 50 ? Coarse grained
• P200 gt 50 ? Fine grained

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Comparison between the AASHTO and Unified Systems
(Contd)

• AASHTO 10 sieve separates gravels and sand
• Unified 4 sieve separates gravels and sand
• AASHTO There is no organic soil
• Unified There is organic soil
• AASHTO gravely and sandy soils are not clearly
  separated
• Unified gravely and sandy soils are clearly
  separated

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(NCHRP 1-37A. 1999)
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(Das, 1990)
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FAA Classification

• FAA Federal Aviation Administration
• Used mainly for soil classification for airport
  construction.
• Requires
• Gradation
• LL
• PI

28
FAA Classification (Yoder Witczak 1975)
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FAA Classification Chart for Fine-Grained Soils
(Yoder Witczak 1975)
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