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Asphalt Pavement Materials

Civil EngineeringFourth Year

Dr Hozayen Ahmed Hozayen

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Dr. Hozayen Ahmed HozayenProfessor of Highway and Traffic Engineering

Course Notes

Pavement Materials1. Asphalt Cement (Bitumen)

Asphalt CementLiquid AsphaltLiquid Asphalt

Asphalt Emulsions2. Aggregate and soil

Aggregate TypesAggregate EvaluationAggregate BlendingBase and Subgrade MaterialsBase and Subgrade MaterialsSoil Compaction and Classification

3. Mix DesignAsphalt mix TypesMarshall MethodSuperpave Mix Design

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Pavement Structure

Flexible pavement

Wearing Surface (AC) Tack Coat (Li id

(Asphalt Concrete Mix)

Base Course

t1

t2

Pavement Thickness

g ( )(Liquid Asphalt)

Binder Course (A.C)Prime Coat (Liquid Asphalt)

( p )

(Granular materials)

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Subgrade

t3 SubBase course (Granular materials)

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Make-Up Crude Petroleum

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Asphalt Cement

(bitumen)(Asphalt Binders)

(Asphalt)

• Paving Asphalt cement is a black, sticky, semisolid and highly viscous material.

• Asphalt cement (A.C.) is composed primarily of complex hydrocarbon molecules, but it also contains other atoms such as Oxygen, Nitrogen and Sulfur.

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• Asphalt cement softens as it is heated and hardens as it is cooled and its properties change dramatically with temperature and rate of loading. It can behave as elastic, visco-elastic or plastic material.

Asphalt Cement (Bitumen)( )

Resins

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AsphaltinesOil

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Tests for Asphalt Cement Evaluation:1- Viscosity Test: - To measure the viscosity of A.C. at certain

temperatures, 60 and 135 °C.- Kinamatic viscosity (135 °C): A.C. Flow time

under gravity. Viscosity = Time x Constant = Centistoke

(1 stoke = 100 centistoke)- Saybolt Furol viscosity (60 °C): A.C. Flow time

under vacuum pressure.Viscosity = Time x Constant = Poises

Absolute viscosity in Poises = Kinematic viscosity in stokes x specific gravity

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135 °C simulates mixing and laying down temp.60 °C simulates the max. pavement temp.

Vacuum Viscometer

Penetration Test

• Sewing machine needle

• Specified load, time, temperature (25 °C)

100 gPenetration in 0.1 mm

Initial After 5 seconds

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2- Penetration Test : - To measure consistency of A.C.

- The distance a needle penetrates on an A.C. container (at 25 °C)

- Asphalt Grades: Pen. 40 – 50 , Pen. 60 – 70

Pen. 85 – 100 , Pen. 120 – 150

3- Flash Point Test: - To indicate safe heating temperature i.e.,the temperature

at which volatiles can cause flash under a passing flame.4- Thin Film Oven Test: - To measure resistance of A.C. to changes under

hardening (heating – cooling) conditions simulatingplant operation.

5- Ductility Test: - To measure how much the A.C. can be elongated under certain conditions.

- Higher ductility means higher A.C. adhesion (to aggregates).

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g y g ( gg g )

6- Solubility Test: - To measure the purity of A.C.- The soluble portion of A.C. (in carbon disulfide) represents the

active cementing constituents. (inert materials are not soluble).

7- Softening point test: - To measure the temperature required to reach a certain degree of softening.

- (more important for non-paving applications).

Elastic BehaviorDelayed or Retarded

Elastic BehaviorSca

le)

Asphalt Cement Response

Viscous Behavio(1) At Short Loading Times S=E

PS

I or

Kg/

cm2

( Lo

g

•10

vior(1) At Short Loading Times S E

(2) At Intermediate Loading Times S=E(t)(3) At Long Loading Times S=ƛ / t

Were ƛ= Viscous Traction = 3 ȝȝ Measure of Viscous Deformation

Time ( Log Scale)

Stif

fnes

s ,S

,P

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Aging (Hardening) of asphalt binders

Short term aging: during processing (plant heating, construction)(Thin Film Oven Test, TFOT)

Long term aging: after construction during service lifeg g g g(Pressure aging Vessel test) - - Superpave method

Penetration of Aged asphalt%Retained Penetration = X100

Penetration of original asphalt

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Where:Penetration of Aged asphalt = Penetration After TFOT

Penetration of original asphalt = Penetration before TFOT

The higher % RP, The better the asphalt, i.e., asphalt didn’t loose much of its flexibility during processing (plant heating)

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Liquid Asphalt (L.A.)

Asphalt Cement + Solvent Liquid Asphalt (L .A .)

Naphtha

Kerosene

Light Oil R.C. M.C.S.C.

Asphalt Cement

Solvent

• Rapid cure (RC) (Naphtha or Gasoline)– High volatility of solvent– Used for Tack coats

• Medium cure (MC) (Kerosene)– Moderate volatility of solvent– Used for Prime coat

• Slow cure (SC) (Low viscosity oil)

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p

Example :(MC 0) or (MC 30) means Medium Curing liquid asphalt Degree (0)or Medium Curing liquid asphalt with viscosity (from 15 to 30).

Used for prime coat (applied temperature 170 °C)

– Low volatility of solvent– Used for dust control

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Asphalt EmulsionsAsphalt Emulsions consist of Asphalt Cement mixed with water in existence of

emulsifying agent to keep asphalt molecules suspended in water.

AsphaltAsphalt

WaterEmulsion

emulsifying agent

Slow Setting(S.S.)

Medium Setting(M.S.)

Rapid Setting(R.S.)

According to type And portion of emulsifying agent

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Mixed with fine materials (sand)

M.S.1 M.S.2 R.S.1 R.S.2Cold mixIn mixer

Cold mix In site

low Vis. High Vis.Used in Macadam and surface treatment

Asphalt EmulsionsRS-----RS-0 to RS-5MS----MS-0 to MS-5SS----SS-0 to SS-5

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Aggregate Types-According to Aggregate Source

Natural Aggregate Manufactured(Artificial)Aggregate

Aggregate

- Steel Slag- Blast furnace Slag- Electric furnace slag

Pit. (Non-Processed Agg.)-Gravel-Sand

Quarry(Processed Agg.)

Crushing Machine (Crusher)

Crusher Run Agg.or Crushed Agg.

DenseG

-According to Aggregate Gradation

1- Dense (well) graded agg. 2- Open graded Agg.3- Gap graded Agg.4- one-size Agg.

%Pass

Sieve Size

Gap

Open

Aggregate EvaluationPhysical Requirements1- Cleanliness:

Free from organic materials, Clay dust or any foreign substances.

2- Toughness:Resistance to abrasive wear during processing, placing, and compaction.

3- Soundness:Durability measures, resistance to weather action.

4- Particle shape:Minimum flat and elongated particles

5- Surface texture:Rough surface texture provides better friction between particles.

6- Absorption:more absorption would improve adhesion between agg. And asphalt.

7- Affinity:Resistance to separation of asphalt from agg. Due to water.Agg. Sensitive to water are called Hydrophilic (water loving) material.Agg. Not sensitive to water are called Hydrophobic (Water Hating) materials.

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Laboratory Tests for Aggregate Physical Requirements

A P t T t U dAgg. Property Test UsedCleanliness Washed sieve size Analysis or sand-equivalent test.Toughness Loss Angles Abrasion Test. Soundness Magnesium Sulphate Test (Soaking-Drying cycles)Particle shape %Flat and Elongated particles.Absorption Absorption test.Affi it f A h lt M h l l ti St bilit T tAffinity for Asphalt Marshal relative Stability Test.Specific Gravity Specific gravity testStrength California Bearing Ration ( CBR ) test

Aggregate BlendingExample:Neither agg. A or Agg. B meets the specification requirements.It is required to blend (or mix) a certain percent of agg. A with another percent of agg. B in order to obtain an aggregate

Specification limits %pass

Agg.(A) %pass

Sieve size

80-100981”

60-9070½”

45-6520# 4

p gg gg ggradation that meets the specifications.

Specification limits %pass

Agg.(B) %pass

Sieve size

80-1001001”

60-90100½”

45-6592# 445 6520# 4

30-508# 16

20-305# 30

15-254# 50

8-152# 100

0-91# 200

45 6592# 4

30-5060# 16

20-3050# 30

15-2535# 50

8-1520# 100

0-912# 200

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Two-aggregate Blending1- Graphical Method

2- Analytical Method % pass of mix

Aggregate Blending

a.PA + b.PB = Pmix% of Ain mix % pass of

agg.A% of BIn mix

% pass of Bin mix

a + b = 100 or a + b = 1

Three aggregate BlendingThree-aggregate Blending1- Analytical Method

a.PA + b.PB + c.Pc = Pmix

a + b + c = 1

2- Graphical Method

Three-aggregate Blending

Agg

rega

te Specification limits %pass

Pblend =

a .Pa + b.Pb +c.Pc

Agg.(C) %pass

Agg.(B) %pass

Agg.(A) %pass

Sieve Opening

(mm)

Sieve size

100100100100193/4”

Pa Pb Pc

Coa

rse

80 - 10010010090131/2”

70 - 90100100599.43/8”

50 - 7010096164.75# 4

35 - 50100823.22.36# 8

26 - 38100772 51 18# 16gate

26 - 38100772.51.18# 16

18 -29100511.10.6# 30

13 - 23963600.3# 50

8-16932100.15# 100

4 - 10829.200.075# 200

Fin

e A

ggre

g

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Base Layer : is granular material treated or untreated.

Treated : Stabilized or cemented with lime, Portland

cement, asphalt cement,…….etc.

Base and Subbase Materials

Untreated: Only aggregate (without additives).

Subgrade : is the natural soil (or foundation) under the

permanent layers.

**Both base and subgrade materials are characterized by:

) S il Cl ifi i h da) Soil Classification methods.

b) Aggregate Evaluation Tests (LOA, Soundness, ….etc).

c) California Bearing Ratio (CBR).

d) Plate Bearing Test.

Types of Base Course

Untreated Base Courses treated Base Courses

Cement treated bases

Asphalt treated Bases

Chemical treated bases

Granular Base CoursesThe most common type(Pure agg. with gradation

requirements)

Macadam Base Courses(one size agg.)

PenetrationMacadam

Water-BoundMacadam

Dry-BoundMacadam

Water Li id A h l

(Dust interlock and Friction) (Friction + Cementation) (Cementation)

Crushed Rock multi-layersLos Angles Abrasion < 50%

Water Liquid Asphalt

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Requirements for Granular Base Course :a) Gradation Requirements

b) LOA < 50 % (after 500 cycle).

) L L < 25 %c) L.L. < 25 %

d) P.I. < 6 %

e) CBR > 60 % or 80 %

f) Absorption < 10 %

g) Swelling < 5% (or according to code )

Soil Classification Methods

Purposes of soil classification is to be able to predict subgrade performance

of a given soil based on results of few simple tests (Routine Tests) ,

Gradation Aterberg limits (L L P I )Gradation, Aterberg limits (L.L., P.I.)

1-AASHTO Classification Method:

AASHTO: American Association of State Highway and Transportation

Officials.

1-FAA Classification Method:

FAA: Federal Aviation Administration

(Developed for Airfield Pavements)

3- Unified Classification Method:

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Soil ClassificationAASHTO Classification FAA Classification

%P #200 = (x) %P #200 = (x)

X < 35%1-Granular soil

A1 A3

X > 35%1- Fine soil

A4 A7

X < 45%1-Granular soil

E1 E5

X > 45%1- Fine soil

E6 E13A1 ---A32- Use table 2-1By the use of :1) %P# 200 =2) %P# 40 =3) %P# 10 =4) L.L.5) P I

A4---A72- Use figure 2-

2By the use of:• L.L 2)P.I.

E1 ---E52- Use table 2-2By the use of :1) P.I.2) L.L.2) %P# 200 =4) %P# 40 - %P# 200 =3) %P %P

E6---E132- Use figure 2-3By the use of:• L.L 2)P.I.

P.I.

5) P.I.

From table soil is ( )P.I.

From chart soil is ( )

3) %P# 10 - %P# 40 =

From table soil is ( )

Group Index (GI) (GI = 0……20)

GI = 0.2a + 0.005ac + 0.01bdExample:Soil is A-5(8) or A-6(15.2)

Note: 1) For Table 2-2 - maximum+ minimum

2) GI is not required for FAA classificationExample: Soil is E5 or E11

California Bearing Ratio (CBR) Test

W.s

Base

Subgrade

h1

h2

p

Piston (area = 3 in2)

Standard soil

Surcharge

Penetration (inch) Load (ib) Pressure (psi)

0.1 3000 1000

0.2 4500 1500

•Any sample p0 1 = load that causes a penetration equal to 0.1 inch.

6”

(Crushed Stone)

y p p0.1 p q

p0.2 = load that causes a penetration equal to 0.2 inch.

3000CBR 0.1 = * 100 = %

p 0.1

4500CBR 0.2 = * 100 = %

p 0.2

Choose the bigger value

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1000CBR 0.1 = * 100 = % ,

P 0.1

1500CBR 0.2 = * 100 = %

P 0.2

Note: P = pressure

Load

(or pressure)

Penetration

P 0.2

P 0 1

CBR 0.2

CBR

Load or pressure

Note:

Penetration0.0 0.1 0.2 0.3 0.4 0.5

0.0 0.1 0.2 0.3 0.4 0.5

P 0.1CBR 0.1 Soaked vs. unsoaked test.Swelling soil consideration

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Compaction Methods and Equipment(Roller Compaction)

1- Pressure Types(S i bl f h i il )

Smooth-Wheeled Rollers

Pneumatic-tired Roller(Suitable for cohesive soils) Sheep’s Foot Roller

2- Vibratory Roller Types(Suitable for gravel and sand soils)

3- Impact Types3 Impact Types(Plate Compaction)

(γd)(γd)

ququUnconfined Strength

Laboratory Compaction

Road Soil CompactionDefinition: Reduction in voids ratio by mechanical means

(air is forced out or dissolved in soil water)

W/C

Field Compaction

(γd)Heavy Roller

Light Roller

Density Requirements:

Relative Compaction (R.C.)

y p(Proctor Test)

No. of passes

g

R.C. =γd field

γd laboratory* 100

p ( )

> 95% or98% or 100%

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(Proctor Test)

hHummer (weight = w)

Volume = 1/30 ft3

Laboratory Compaction

Water Content W/C =W water

W solid, Bulk Density γm =

W total

V total

Dry Density γd =γm

1 / ( d )Dry Density γd 1 + w/c

W/C

(γd)(γd max)

O.M.C.

95% γd max

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Dry Density (γd)

Line of optimums

Higher Compaction effort

W/CTo increase the max. dry density

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1- Increase the No. of passes of roller.

2- Increase the weight of roller.

3- Modify water content (probably increase the (w/c)).

4- Decrease the thickness of layers (20 to 30 cm).

5- Change the roller type.

Pavement Rutting ?

• Permanent deformation on the Wheel Path

Vehicle Turnover

Pavement Surface

Asphalt Layer

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Design of Asphalt MixturesAggregate + Cementing Material

(bitumen) (Asphalt cement)

% bit or %A.C.Aggregate:

Percentage Sp. Gr. (S)C A % C A SCoarse Agg. % C.A. S C.A.

Fine Agg. % F.A. S F.A.

Mineral Filler %M.F. S M.F.

S A.V.

S A.V . =100 or ( Σ percentages)

% C.A. + S C.A.

% F.A. +S f.A.

% M.F.S M.F.

=

S =γ wγ

Or γ = S . γ w

Agg.

Bit. (A.C.)Air

Vagg.

Vb

VA

W agg.

W bVt

wb = vb . γ b = vb ( Sb. γ w)

γ w = 1 gm /cm3

= 62.4 Ib /ft3

Asphalt Cement

%A.C. =Wt

* 100 (T.W.B.) total weight basisor (by weight of mix)

W bit

%A.C. =W agg.

* 100 (A.W.B.) Agg. weight basisor (by weight of agg.)

W bit

γ m = γ bulk =

o (by we g o gg.)General Relationships

V tW t

W S.A. Weight of sample in air (Wt)W S.W. Weight of sample in water

W S A - W S WW S.A * γ wγ m =V t =

S.A S.W

γ w γ w, γ m =

W S.A - W S.W

γ theoretical= γ max =W t

V t – V air

V Air * 100, % Air voids =V t

= 1 - %A.V. orγ bulk

γ theoretical= 1 -

γ bulkγ theoretical

V Air

V t

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Volume of voids in Aggregate Mass = VAMOr Voids of Mineral Aggregate = VMA

VAM = V air + V bit = V t – V agg

* 100%VAM = V air + V bit

V t

% of Voids Filled with Bitumen = %VFB

Or (%VMA) V t

* 100 =%VFB = V air + V bit

V bit* 100

VAMV bit

Volumetric properties: % A V %VMAVolumetric properties: % A.V. , %VMA

Mechanical properties: Stability , Flow

Types of Hot Asphalt Concrete Mixes

Type Application1-1 Dense Graded Mix Wearing Course, A.V. 3-5%1-2 Gap Graded Mix To Resist FatigueGap G aded o es st at gue1-3 Stone-Mastic Asphalt Wearing Course, A.V. 3-5%1-4 Open Graded Friction - To Reduce Accidents.

Course (OGFC) - High drainage properties.- Air Voids = (10 to 12)%.

1-5 Porous Asphalt Mix - To Reduce Accidents.High drainage properties

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- High drainage properties.- Air Voids = (15 to 20)%.

1-6 Open Graded Mixes Binder Course 5-8%

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Marshall Method of Mix Design

Objective : To determine optimum Asphalt Content for a given agg. Blend.

Test Procedure:1- Heat aggregate to 170°C for a period of 6 hrs.2- Heat asphalt cement (A.C.)to about 150°C.3- Mix Agg. And A.C. at mixing temperature >140°C.gg g p4- Fabricate cylindrical samples D = 4” , h = 2.5” by applying hummer compaction

at compaction temperature>130°C.** No. of blows 35(low Traffic volume) or 50 (medium Traffic ) or 75 (high Traffic).

Testing conditions:- Test temperature = 60°C

- Rate of loading = 2”/min PTest Results:1- Stability Ib or Newton (load at failure).2- Flow 0.01 inch3- %Air Voids (A.V.). 4- % VMA.5- Bulk relative density (γ m).6- Repeat Test Results at (5) or more A.C. values. 7- Determine Optimum A.C.

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**Example

Variable 5 5.5 6 6.5 7Weight of sample in air = Wt 1211.9 1214.2 1221.4

Weight of sample in water =Ws 718.9 726.4 737.3V t = (W sA- W sw) /γ w

A.C. Content, %

W bit = (%A.C.) *WtV bit = (W bit) /(S bit * γ w)

W agg= W t - W bit

Vagg= W agg /( S agg *1)

V air= V t - V bit -Vagg

%A.V. = (V air/V t) *100( )VMA= V bit +V air

%VMA. = (VAM /Vt) *100γ bulk = (W t/V t)Stability (Ib) 1646 1755Flow 0.01” 10 12 13 ---- -----

Surface Mix

Mid rang for A.V.

Surface Mix3 < A.V. < 5

4

Binder Mix3 < A.V. < 8

5.5

OGFC Mix10 < A.V. < 12

Porous Asph. Mix15 < A.V. < 20

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Determining Optimum A.C.- Obtain x1 , x2 ,x3 as shown in the graph

- Optimum A.C. = X = (x1 + x2 + x3) /3 = %

- Determine mix properties at selected A.C. content (X) : Stability, Flow, A.V.,

VMA., γ at (X).VMA., γm at (X).

- Check design criteria (Specifications):

Stability > Smin

fmin < Flow < fmax

3 < A.V. < 5 for Surface mix ,

3 < A.V. < 8 for Binder mix. Note; For OGFC or PA3 < A.V. < 8 for Binder mix. Note; For OGFC or PA

VMA min

Max. agg. Size(¾) or 1”

VMA > VMA min

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Adjust mix properties if necessary

- Low Stability -------- increase coarse aggregate.

- Low Voids -------- decrease mineral filler , use clean sand.

- High Voids ----------increase fine Agg. Or filler.

- Low Flow ----------use absorptive agg. (Dolomite agg.)

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Mix Property Distress

Low Stability Deformation, Rutting

Low A.V. Bleeding, low skid resistance, RuttingLow A.V. Bleeding, low skid resistance, Rutting

High A.V. Densification under traffic,moisture

damage

Low Flow Difficult to Compact (harsh mix)

High Flow Difficult to Compact (Tender mix)

Low VMA Less Durable mix

Mix Design AlternativesSieve

Size or No.Percent Passing by Weight

MixA

MixB

MixC

Job mixformula

Tolerances

Specs. limits

1 –in. 100 100 100 5 + 100

3/4-in 83.6 82.1 83.6 5 + 80-100

1/2-in 68.1 67.6 68.1 4 + 65-100

No. 4 48.4 42 48.4 4 + 40- 60

No. 8 39.7 38.0 39.7 3 + 25- 50

No. 40 22.5 23 22.5 3+ 15- 25

No. 200 9.5 5 9.5 2+ 5- 10

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Agg. TypeStability

FlowA.V.A.C.

Limestone Limestone Dolomite

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Superpave Binder Test Purpose

Advanced Mix Design Methods (Superpave Design) USA in 1993

by SHRP: Strategic Highway Research Program.

Superpave Binder Test Purpose

Dynamic Shear Rheometer (DSR)

Measure properties at high and intermediate temperatures.

Rotational Viscometer (RV)Measure properties at high

temperatures

Bending Beam Rheometer (BBR) M ti t l

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Bending Beam Rheometer (BBR)

Direct Tension Tester (DTT) Measure properties at low

temperatures

Rolling Thin Film Oven (RTFO)

Pressure Aging Vessel (PAV) Simulate hardening (durability)

characteristics.

PG 52-28

PG 58-3450 %

98 %

SuperPave Asphalt Binder Grade

-40 -30 -20 -10 0 10 20 30 40 50 60 c

PG 58 34

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PG 58-34Minimum Pavement Temperature

Average 7 DayMax. Pavement Temperature

Performance Grade

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SuperPave Asphalt Binder Specifications

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Superpave Compaction• Gyratory compactor

– Axial and shearing action– 150 mm diameter molds

• Aggregate size up to 37.5 mmgg eg e s e up o 37.5• Height measurement during compaction

– Allows densification during compaction to be evaluated

•ram pressure•600 kPa

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•1.25 degrees

•30 gyrations•per minute

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Quality Control Tests- For Soil, Agg. Layers:

1-Sand cone test (γd )2- Core-Cutter test (γd )3- Volumenometer test (γd )4- Aggregate Gradation5- Core samples (for thickness)6- Straight Edge

Material Characterization Tests

1- California Bearing Ratio (CBR)(strength)

2- Proctor test (γlab. )

- For Asphalt mix layers:

1- Extraction Test (%A.C.)2- Aggregate Gradation3- Core samples (for thickness)4- Bulk density (γm ) 5- Straight Edge

2- Aggregate Evaluation Tests3- Plate Bearing Test

Elastic modulus of a layer (E) and Modulus of Subgrade Reaction (K)

During Construction to ensure quality Before construction to provide

design data

• A quality Control Test used to separate asphalt cement from an asphalt mix and to determine :

A C t t

Extraction Test

- A.C. content

- Aggregate gradation

• Samples are taken as :

1- Core Samples after construction.

2- Loose mix during construction.

3- Loose mix from asphalt mix plant.

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Extraction Test

A h lt Mi ( )

Solvent + Bitumin

Asphalt Mix (w total)

Aggregate (w agg. )Solvent

W bit = W total - W agg

% A.C. = (W bit / W total )* 100

Pas

s%

Sieve Size