Appropriate Road Pavement Technologies in a

Developing Changing World

Kim Jenkins

tellenbosch

Masters in Public Infrastructure Management MPIM in PACBPSANRAL HO: 25 th March 2013

Challenging areas in RoadsWhere can biggest difference be made?

• Material response models

• Damage models• Recursive analysis• Specs / QC• Constructability• Lab “simulating reality”

• Skills training• Education and

Mentoring• Resistance to Change• Scope for Innovation

TechnicalGeneral

Research versus practice?In pavement engineering

RESEARCHERSPRACTITIONERS

Where does the SANRAL Chair fit in?

Organigram of Academic Structures in the Roads Indu stry

Asphalt Academy

CSIR

C&CI

etc

Research Centres

TRAC (School)

SETA(Civ Eng)

etc

Training Programmes

Cape Tech

Pentech

etc

Technikons

Maties

Tukkies

UCT

etc

Universities

Tertiary Education

SANRAL ChairType title here

SANRAL

SabitaInternational

Partners

Industry Institutes

PG Programme : Courses

1. Pavement Materials I (granular, cemented)

2. Pavement Materials II (asphalt)

3. Pavement Materials III (bitumen stabilised mat’s)

4. Advanced Binder Technology5. Flexible Pavement Design6. Pavement Evaluation & Rehabilitation7. Rigid Pavement Design8. Pavement Construction9. Pavement Management Systems

Co-operation with Overseas Universities

• Overseas experts on our PG courses and research (25 in 10 years):– Molenaar, van de Ven ( TU Delft ), Zollinger

(Texas A&M), van Niekerk ( KOAC), Francken (BRRC), Bahia ( Wisconsin )

• Many local experts• Co-operation: CSIR• Sabita etc

Pavement Students

0

20

40

60

80

100

120

140D

ELE

GAT

ES

PE

R Y

EA

R

YEAR

Non students

PG Students

Specialist Research Apparatus

Need for research and innovation in SA

• Low Volume Roads (cost-effective)• Pre-coating fluids (no tar)• Energy and emissions (Enviro )• Recycled building materials (Enviro )• Surface seals (design and modelling)• Material performance, granular, BSM,

asphalt, polymers, nano (lab eval)• Etc

Closing the loop

Acquire knowledge

Develop tools

Implement

Response Damage

Awareness

Reality

check

Variability

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

0 1 2 3 4 5

Strain Ratio ε/εε/εε/εε/εb

Num

ber

of L

oad

App

licat

ions

Effective fatigue

εεεε

ε ε ε ε

100 120 140 160 180 200µεµεµεµε

Enormous variation in life

Log N

Cracked area (%)100 50 0

Can get a good idea from δδδδ0-δδδδ300

Variable h, tyre-pressure, load etc

h

?

SYSTEM

COMPONENT

!

CSIR, de Beer

Tyre

Load

Tyre Inflation Pressure

Axle load interval (kN)

0 to

10

Frequency

10 to

20

20 to

40

40 to

60

60 to

80

80 to

100

TrafficTyre-Pavement Interaction

Stress in Motion SIM

Pavement Materials & Behaviour

Greater flexibility

Greater rut resistance

Bitumen binder 6% 4%

Active F

iller

BSM

flexural

brittle

HMA

Time, temp dependent

granular Vis

co-e

last

cemented

“Linear-elastic”

Lean Mix Concrete

Lightly cemented

UnboundCrushed stone / gravel / soil

Stress dependent

Less economical mixes

Recycled Materials

RAP

CrushedAggregateWeathered

Gravels

CDW/RCM

Patches

?

Resilient Modulus of Recycled Base

• Granular Type Behaviour: BSM-foam BC = 2%

150

350

550

750

950

1150

1350

0.0 200.0 400.0 600.0 800.0 1000.0

Sum of Principal Stresses q (kPa)

Res

ilien

t Mod

ulus

Mr

(MP

a)

12kPa24kPa48kPa72kPa

s3

Univ Stell , Jenkins

θθθθ

Granular Structural Layers• Effective stress

– Stress caused by the wheel-load– Suction pressure – Overburden stress– Residual compaction stress

σvo

σhr

Residual compaction and

overburden stress+

σvo

σhr

σvo

σhr

Residual compaction and

overburden stress+

Internal suction

pressure

σS

+Internal suction

pressure

σSσS

+ External stress

External stress

Effective stress= Effective stress=

SAPDM,

Theyse

3.0

5.0

7.0

9.0

0 0.2 0.4 0.6 0.8 1

log

(N)

SR*S/VD

S-N model - 19 % plastic strain

Observed

Predicted

R2 = 0.727

SEE = 0.476

New “Simple triaxial”

Univ Stell , Mulusa

Density ± 80%

(Fluffed up)

Construction

+90% +90%± 80%

+90% +90%± 80%

+90% +90%± 80%

“BRIDGING”

2164 kg/m³

2013 kg/m³

± 7% difference

100%

93%

Cause: Grader before primary compaction

“TRAFFIC COMPACTION”

CUT 1CUT 2

Seals

BASE

Visco -Elastic Numerical Modelling

Uni StellTUD, Milne

Seal FatigueCreating a composite beam of

road seal and polyurethane

Uni Stell, Cloete

FIELD LAB

Uni Stell, Cloete

Flexural Stiffness (MPa)

Repetitions

0

500

1000

1500

0.5x106 1x106

Four Point Beam Fatigue

Seal Model

Embedment

Uni Stell, Gerber

Loading

Bleeding

Fatigue

CT scans

Closing remarks

• Education and training– Structured programme (courses)– Laboratory facilities– International cooperation (2 way)

• Appropriate research (LVRs, Seals, Gran)

• CLOSE THE LOOP! - requires – Sustained effort over long period– Sound data, good models & calibration

• Construction (QC, variability)

Not really

Are we heading the right direction?

Mmm…promising!

Mmm…tasty!