Dr. Anton HartmanAurecon, Pretoria, South Africa

Ass. Min. James ReynoldsMPW, Monrovia, Liberia

ALTERNATIVE SURFACINGS FOR LOW VOLUME ROADS IN GHANA, SIERRA LEONE AND LIBERIA

CONTENT• Background• Approach

Design lead thinking Design criteria Surfacing types

• Liberia experience• Outcome and key findings

https://www.6sqft.com/believe‐it‐or‐not‐the‐worlds‐entire‐population‐can‐fit‐inside‐new‐york‐city/

AIMTo find surfacing solutions that may be viable for low volume roads compared to traditional gravel surfacing.

Liberia

Ghana

SierraLeone

$GDP

Ghana

Liberia

Sierra Leone

42.69 Billion USD

3.67 Billion USD

2.10 Billion USD

South Africa 294.1 Billion USD

0 500 1000 1500 2000 2500 3000 3500

Sierra Leone

Ghana

Liberia

South Africa

Total Rainfall (mm)

Pretoria (660 mm)Monrovia (3160 mm)

Accra (994 mm)Freetown (2866 mm)

0

50

100

150

200

250

SierraLeone

Ghana Liberia SouthAfrica

Feed

er R

oad L

ength

('000

km)

4,152

km 24,10

0 km

5,702

km

222,9

00 km

Only Ghana has surfaced

Feeder Roads

Land Area

Liberia (99,067 km2)

Sierra Leone(71,740 km2)

Ghana(238,553 km2) South Africa

(1,210,090 km2)

Population

25.5 Million

Liberia

Ghana

Sierra Leone 6.1 Million

4.6 Million

South Africa 57.4 Million

COUNTRY COMPARISON

EXPLORING THE WHY OF THINGS…

WHAT IS?

WHAT IF?

WHAT WOWS?

WHAT WORKS?

FROMABSTRACT TO

NEW VALUEBUILD

UNDERSTANDING

SHAPE

HYPOTHESES

MAKE BETTER

DECISIONS

Understanding what is happening

and setting a design criteria

Test the ideas generated from the

design criteria

Providing the final alternative surfacing

options

Understand what’s going on today

Explore, experiment on what might be possible

for tomorrow

Test assumptions. Refine ideas. Test again.

Identify best solution.

Improve the solution and deliver.

Create new, more meaningful

value.

EXPLORING THE WHY OF THINGS…

WHAT IS?

WHAT IF?

WHAT WOWS?

WHAT WORKS?

FIRST WORKSHOP

SECOND WORKSHOP

THIRD WORKSHOP

Understand what’s going on today

Explore, experiment on what might be possible

for tomorrow.

Test assumptions. Refine ideas. Test again.

Identify best solution.

Improve the solution and deliver.

Create new, more meaningful

value.

INTERNAL WORKSHOP

CHALLENGES

High Rainfall

High Temperatures

Flooding of low lying areas

Steep Slopes

Skilled Labour

Resources

CHALLENGES

DESIGN CRITERIA• Require low maintenance• Resistant to environment• Labour intensive construction• Skill transfer to different industries• Locally available material• Low level of supervision required• Uncomplicated design• Low skilled contractor can construct

Surfa

cing

Optio

ns Bituminous Surfacing

Seals

Sand

Slurry

Single

Cape

Otta

Double

Inverted Double

Triple

ChokedAsphalt

Cold mix

Hot mixConcrete Surfacing

Plain Jointed

Dowel Jointed

Ultra thin

Roller Compacted

Continuously Reinforced

Strip Roads

Discrete elements

Concrete

Cobbles

Clay

Geocell

UNCONVENTIONAL ALTERNATIVES

BITUMEN/CEMENT MODIFICATION

RAW LATEX

BEESWAX

COCOA

SUGARCANE ASH

PALM OIL

TERMITE SALIVA

PLASTIC ROADS

BITUMEN RUBBER

SELF HEALING CONCRETE

INVERTED CONCRETE ROADS

SOLAR PANNELS

IMAGES FROM THE FOLLOWING SOURCES

http://blogs.discovermagazine.com/seriouslyscience/2014/07/22/can-guess-bees-make-hexagons-honeycomb/#.XUvo3GiFOUk

https://en.wikipedia.org/wiki/Natural_rubber#/media/File:Latex_-_Hevea_-_Cameroun.JPG

https://www.treehugger.com/natural-sciences/nature-blows-my-mind-miracles-termite-mounds.html

http://storage.googleapis.com/powop-assets/kew_profiles/Theobroma_cacao_STE_The_cac_20100413AM013_crop_web_fullsize.jpg

https://www.sciencefocus.com/nature/how-long-does-a-bacterium-live/

https://www.chinimandi.com/government-should-consider-scheme-to-purchase-sugarcane-harvesting-machine/

LIBERIAEXPERIENCE

DESIGN CRITERIA

LIBERIA TRIALS

LIBERIA TRIALS

Surfacing Length (m)Concrete strip road 80Hand packed stone 50Otta seal ‐ double crushed rock 100Otta seal ‐ double lateritic gravel 60Otta seal ‐ single crushed rock 670Otta seal ‐ single crushed rock + sand 100Single seal 700Single seal + sand 60

LIBERIA TRIALSCOMMENTSAPPEARANCEDESCRIPTION

OTTA SEAL WITH NATURAL LATERITE GRAVEL

VERY GOOD APPEARANCE. DIFFICULT TO SIEVE AND KEEP MOISTURE OUT.

OTTA SEAL WITH CRUSHED AGGREGATE

SOME BLEEDING OBSERVED.

LIBERIA TRIALSDESCRIPTION

HAND PACKED STONE (COBBLES)

VERY ROUGH SURFACE, SOME STONE LOSS/POTHOLES ALREADY PRESENT. DIFFICULT TO SHAPE AND LAY.

DUAL STRIPS

CONSTRUCTED ON STEEPEST ROAD SECTION.SOME EDGE DROPS OBSERVED. MOTORCYCLES TRAVELLING ON SHOULDER. EROSION OF SIDE DRAIN OBSERVED. VERY EASY TO CONSTRUCT.

COMMENTSAPPEARANCE

LIBERIA TRIALSDESCRIPTION

SINGLE SEAL (16mm WITH CAT 72 EMULSION)

ROUGH SURFACE, BLEEDING IN THE WHEELTRACKS.

SINGLE SEAL WITH SAND SEAL

SMOOTH SURFACE, LIGHT BLEEDING WITH SLIGHT DEFORMATION.

COMMENTSAPPEARANCE

OUTCOME AND KEY FINDINGS

DESIGN CRITERIA

0.0

1.0

2.0

3.0

4.0

5.0

Low designskill levelrequired

Skill transferto differentindustries

Low skillcontractor can

construct

Labourintensive

construction

Low level ofsupervision

required

Resilient toenvironment

Require lowmaintenance

Locallyavailablematerials

Weig

hting

Ghana Sierra Leone Liberia Experts

SURFACING SELECTION

0%

5%

10%

15%

20%

25%

30%

35%

Single Seal Double Seal Cape Seal Otta Seal Triple seal ColdAsphalt

ConcreteBlocks

Geo Cells Cobble PlainJointed

Concrete

Doweljointed

concrete

ConcreteStrip Roads

RCC UTRCP

% V

otes

Ghana Sierra Leone Liberia Experts

CONSTRUCTION COST (USD)

0.000.100.200.300.400.500.600.700.80

Sing

le Se

al

Doub

le Se

al

Tripl

e Sea

l

Cape

Sea

l

Otta

Seal

Cold

Asph

alt

Plain

Joint

ed C

oncre

te

Dowe

l Join

ted C

oncre

te

Ultra

-Thin

Con

crete

Rolle

r Com

pacte

d Con

crete

Conc

rete

Strip

Roa

ds

Geo C

ells

Cobb

les

Conc

rete

Bloc

k Pav

ing

Millio

ns

GhanaSierra LeoneLiberia

DISCOUNTED LIFE CYCLE COST

0.000.100.200.300.400.500.600.700.800.90

Sing

le Se

al

Doub

le Se

al

Tripl

e Sea

l

Cape

Sea

l

Otta

Seal

Cold

Asph

alt

Plain

Joint

ed C

oncre

te

Dowe

l Join

ted C

oncre

te

Ultra

-Thin

Con

crete

Rolle

r Com

pacte

d Con

crete

Conc

rete

Strip

Roa

ds

Geo C

ells

Cobb

les

Conc

rete

Bloc

k Pav

ing

Millio

ns

Liberia

With MaintenanceWithout Maintenance

RANKING OF SURFACING OPTIONS

ASPHALT

0.0

0.1

0.3

0.4

0.5

0.6

0.0

0.1

0.0

0.1

0.0

0.1 0.1

0.20.2

0.30.2

0.3

0.4

0.7

0.8

0.9

1

CONSTRUCTION COSTLIFE CYCLE COST

(WITHOUT MAINTENANCE)

LIFE CYCLE COST (WITH MAINTENANCE)

TECHNICAL ANALYSIS (IN COUNTRY)

TECHNICAL ANALYSIS (EXPERTS)

Σ W = 1

RANKING OF SURFACING OPTIONSMonte Carlo Simulation

Σ (Weight x Ranking)

Cold Asphalt

Double Seal

Triple Seal

Cape Seal

Otta Seal

Plain Jointed Concrete

Ultra Thin Concrete

Roller Compacted Concrete

Dowel Jointed Concrete

Concrete Block Paving

Single Seal

Geo Cells

Dual Strips

Determine the number of times

a certain surfacing is

ranked under the top 3

A total of 352 combinations were checked

Prevents bias towards either of

the rankings

TOP 5 SURFACING OPTIONS

TOP 5 SURFACING OPTIONSLIBERIASIERRA LEONEGHANA

12345

OTTA SEAL

PLAIN JOINTED CONCRETE

ULTRA-THIN CONCRETE

CONCRETE BLOCK PAVING

CONCRETE STRIP ROADS

OTTA SEAL

ULTRA-THIN CONCRETE

PLAIN JOINTED CONCRETE

CONCRETE BLOCK PAVING

CONCRETE STRIP ROADS OTTA SEAL

CONCRETE STRIP ROADS

DOUBLE SEAL

CONCRETE BLOCK PAVING

PLAIN JOINTED CONCRETE