Material PropertiesMaterial Properties

Material Types 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

Material Properties Needed for DesignMaterial Properties Needed for Design

• Pavement response model material inputs Modulus (stiffness) Poisson’s ratio

• Materials-related pavement distress criteria Permanent deformation resistance Fatigue resistance Strength

• Other materials properties Density Permeability Thermal expansion coefficient

Material ModelsMaterial Models

(Yoder and Witczak, 1974)

Material ModelsMaterial Models

• Linear elasticity Asphalt Stabilized layers Unbound layers

• Linear viscoelasticity Asphalt

• Nonlinear (all materials, to some extent) Nonlinear elasticity Plasticity Nonlinear viscoelasticity Viscoplasticity

Soil Classification Soil Classification SystemsSystems

Soil ClassificationSoil 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 SystemsSoil Classification Systems

• MIT

• AASHTO

• USCS

• FAA

MIT ClassificationMIT ClassificationMaterial Size (mm)

Boulder > 60

Gravel

Fine 2 – 6

Medium 6 – 20

Coarse 20 – 60

Sand

Fine 0.06 – 0.2

Medium 0.2 – 0.6

Coarse 0.6 – 2

Silt

Fine 0.002 – 0.006

Medium 0.006 – 0.02

Coarse 0.02 – 0.06

Clay < 0.002

AASHTO ClassificationAASHTO 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 (Granular Materials)

AASHTO Classification (Fine Materials)AASHTO Classification (Fine Materials)

AASHTO ClassificationAASHTO Classification

(Coduto, 1999)

Group Index (GI)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 ClassificationUSCS Classification

• USCS: United Soil Classification System

• Used mainly for geotechnical purposes

• Requires: Gradation LL PI

USCS ClassificationUSCS 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 EX: Dual Symbol: SP-SM GW Well Graded Gravel poorly graded sand CL Clay with low plasticity with silt

Computing CU and CCComputing CU and CC

Coefficient of Uniformity

Coefficient of Curvature

High Values Indicate Well-Graded Soil

Values Between 1-3 Indicate Well-Graded Soil

10

60

D

DCU

6010

230

DD

DCC

A-Line ChartA-Line Chart

Separates Clays and Silts

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70 80 90 100

LIQUID LIMIT

PL

AS

TIC

ITY

IND

EX CH

CL

ML

MH

CL-ML

ML & OL

OH & MH

USCS ClassificationUSCS Classification

USCS Classification (Coarse-Grained)USCS Classification (Coarse-Grained)

Coarse- Grained

Soils

50% or less pass

#200

% P #4 < 50%

(Gravel)

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 A-Line

GC

% P #4 > 50%

(Sand)

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 A-Line

SC

USCS Classification (Fine-Grained)USCS Classification (Fine-Grained)

Fine- Grained

Soils

More than 50%

pass #200

LL<50%

ML

CL

OL

LL>50%

MH

CH

OH

Highly Organic Soils Pt

0

10

20

30

40

50

60

0 20 40 60 80 100LIQUID LIMIT

PLAS

TICI

TY IN

DEX CH

CL

ML

MH

CL-ML

OH & MH

ML & OL

USCSDual SymbolsDual Symbols

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 Comparison between the AASHTO and Unified SystemsUnified 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: %P#200 < 35% Coarse grained %P#200 > 35% Fine grained

• Unified: %P#200 < 50% Coarse grained %P#200 > 50% Fine grained

Comparison between the AASHTO and Comparison between the AASHTO and Unified Systems (Cont’d)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 ClassificationFAA Classification

• FAA: Federal Aviation Administration

• Used mainly for soil classification for airport construction.

• Requires: Gradation LL PI

FAA Classification FAA Classification (Yoder & Witczak 1975)(Yoder & Witczak 1975)

Soil Group

% R#10 %P#10, R#60

%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 FAA Classification Chart for Fine-Grained SoilsSoils

80

70

60

50

40

30

20

10

0 10 20 30 40 50 10 60 70

E-12

E-9 E-10

E-8

E-7

E-6

Plasticity Indexli

qu

id L

imit

E-11

100

90

(Yoder & Witczak 1975)(Yoder & Witczak 1975)

It is Hard to be an engineer!