Transcript Materials - Florida A&M University

Material Properties
Material Types
• Unbound (soil)
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
Natural (i.e., subgrade)
Select (i.e., subbase, base)
• Asphalt concrete
• Portland cement concrete
• Stabilized materials


Cement stabilized
Bituminous stabilized
• Bedrock
• Recycled
Material Properties Needed for Design
• Pavement response model material inputs
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Modulus (stiffness)
Poisson’s ratio
• Materials-related pavement distress criteria
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Permanent deformation resistance
Fatigue resistance
Strength
• Other materials properties
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Density
Permeability
Thermal expansion coefficient
Material Models
(Yoder and Witczak, 1974)
Material Models
• Linear elasticity

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Asphalt
Stabilized layers
Unbound layers
• Linear viscoelasticity
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Asphalt
• Nonlinear (all materials, to some extent)
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Nonlinear elasticity
Plasticity
Nonlinear viscoelasticity
Viscoplasticity
Soil Classification
Systems
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
Soil Classification Systems
• MIT
• AASHTO
• USCS
• FAA
MIT Classification
Material
Boulder
Gravel
Sand
Silt
Clay
Size (mm)
> 60
Fine
2–6
Medium
6 – 20
Coarse
20 – 60
Fine
0.06 – 0.2
Medium
0.2 – 0.6
Coarse
0.6 – 2
Fine
0.002 – 0.006
Medium
0.006 – 0.02
Coarse
0.02 – 0.06
< 0.002
AASHTO Classification
• AASHTO: American Association of State Highways
and Transportation Officials
• Used mainly for subgrade rating for highway
purposes.
• Requires:
Gradation
 LL
 PI

AASHTO Classification (Granular Materials)
AASHTO Classification (Fine Materials)
AASHTO Classification
(Coduto, 1999)
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 = %P#200 – 35
(0 to 40)
b = %P#200 – 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)
USCS Classification
• USCS: United Soil Classification
System
• Used mainly for geotechnical purposes
• Requires:
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

Gradation
LL
PI
USCS Classification
Soil
Symbol Property
Symbol
Gravel
G
Well Graded
W
Sand
S
Poor Graded
P
Clay
C
High LL (High Plasticity)
H
Silt
M
Low LL (Low Plasticity)
L
Peat
Pt
Clay
C
Organic soil
O
silt
M
EX: SC  Clayey Sand
GW  Well Graded Gravel
CL  Clay with low plasticity
EX: Dual Symbol: SP-SM
poorly graded sand
with silt
Computing CU and CC
D 60
CU 
D10
CC 
2
D30
D10  D60
Coefficient of Uniformity
High Values Indicate WellGraded Soil
Coefficient of Curvature
Values Between 1-3 Indicate
Well-Graded Soil
A-Line Chart
Separates Clays and Silts
60
PLASTICITY INDEX
50
CH
40
30
CL
MH
OH
&
MH
20
CL-ML
10
ML
ML &
OL
0
0
10
20
30
40
50
LIQUID LIMIT
60
70
80
90
100
USCS Classification
USCS Classification (Coarse-Grained)
CoarseGrained
Soils
50% or
less pass
#200
% P #4 <
50%
(Gravel)
% P #4 >
50%
(Sand)
Less than
5% Fines
Cu>4, Cc = (1-3)
GW
Not satisfying GW
GP
More than
12% Fines
Below A-Line
GM
PI>7& Above ALine
GC
Less than
5% Fines
Cu>6, Cc = (1-3)
SW
Not satisfying GW
SP
More than
12% Fines
Below A-Line
SM
PI>7& Above ALine
SC
USCS Classification (Fine-Grained)
ML
LL<50%
More
than 50%
LL>50%
pass
#200
PLASTICITY INDEX
FineGrained
Soils
60
CL
50
40
OL
CH
30
CL
20
MH
OH
MH & MH
CL-ML
10
CH
ML
ML
&
OL
0
0
20
40
60
LIQUID LIMIT
Highly Organic Soils
80
100
OH
Pt
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
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 %P#200 SI sieve.
• AASHTO:
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%P#200 < 35%  Coarse grained
%P#200 > 35%  Fine grained
• Unified:
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%P#200 < 50%  Coarse grained
%P#200 > 50%  Fine grained
Comparison between the AASHTO and
Unified Systems (Cont’d)
• 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
(NCHRP 1-37A. 1999)
(Das, 1990)
FAA Classification
• FAA: Federal Aviation Administration
• Used mainly for soil classification for airport
construction.
• Requires:
Gradation
 LL
 PI

FAA Classification
Soil
Group
% R#10 %P#10,
R#60
(Yoder & Witczak 1975)
%P#60,
R#270
%P#270
LL
PI
E-1
0-45
40+
60-
15-
25-
6-
E-2
0-45
15+
85-
25-
25-
6-
E-3
0-45
-
-
25-
25-
6-
E-4
0-45
-
-
35-
35-
10-
E-5
0-55
-
-
45-
40-
15-
E-6
0-55
-
-
45+
40-
10-
E-7
0-55
-
-
45+
50-
10-30
E-8
0-55
-
-
45+
60-
15-40
E-9
0-55
-
-
45+
40+
30-
E-10
0-55
-
-
45+
70-
20-50
E-11
0-55
-
-
45+
80-
30+
E-12
0-55
-
-
45+
80+
-
E-13
Muck and Peat – Field Examination
FAA Classification Chart for Fine-Grained
Soils
Plasticity Index
100
0
10
20
30
40
50
10
60
70
90
E-12
80
liquid Limit
E-11
70
E-9
E-10
60
E-8
50
E-7
40
30
20
10
E-6
(Yoder & Witczak 1975)
It is Hard to be
an engineer!