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Stripping of Seals in South Africa:
Gerrie van Zyl, G Fourie, D Rossmann
Mycube Asset Management Systems (Pty) Ltd.
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SUMMARY OF ASPECTS ADDRESSED IN THE PAPER Seal strength
(resistance to stripping)
Seal geometry (structure), Cohesive strength of the binder
Adhesive bond strength between the binder and the aggregate
External influences, with the main factors being Climatic
conditions (temperature and moisture) and Traffic
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DESIGN
Too low application rates – design curves Over-estimation of
embedment Under-estimation of existing texture Compensation for
shape and micro texture Average values Binder
split/distribution
No penetration expected
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DESIGN
Too low application rates Over-estimation of embedment
Under-estimation of existing texture Compensation for shape and
micro texture Average values Binder split/distribution Current
conflict
in TRH3J Anochie-Boateng
Smooth micro texture requires extra binder
How much extra binder ?
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DESIGN Too low application rates Over-estimation of embedment
Under-estimation of existing texture Compensation for shape and
micro texture Average values for texture (Danger using averages for
design) Binder split/distribution
No specifications for existing crushed
stone base texture
Result
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DESIGN
Too low application rates Over-estimation of embedment
Under-estimation of existing texture Compensation for shape and
micro texture Average values Binder split/distribution
Double seals Cover spray
Emulsion S-E1 S-R1
Run-in dependent on viscosity
S-R1
Bonds created by cover spray
Difference between 60/40 split and 50/50 split + cover
spray
Effect of run-in
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CONSTRUCTION
Climatic conditions Aggregate over application Rolling Bond
strength development Traffic compaction
Stripping in low temperature area
< 25 oC > 25 oC
Why we need 25oC and rising
Note the temp drop after spray
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CONSTRUCTION
Climatic conditions Aggregate over application Rolling Bond
strength development Traffic compaction
Voids required for orientation
Aggregate cannot orientate
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CONSTRUCTION
Climatic conditions Aggregate over application Rolling Bond
strength development Traffic compaction
Rubber padded vibrating
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CONSTRUCTION
Climatic conditions Aggregate over application Rolling Bond
strength development
Precoating Testing
High paraffin content No paraffin
Emulsion not cured
Adhesion only at shoulders
Immediate full adhesion
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CONSTRUCTION
Climatic conditions Aggregate over application Rolling Bond
strength development Traffic compaction
Binder stiffness & volume Road temperature Aggregate spread
Embedment
After traffic compaction
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CONSTRUCTION
Climatic conditions Aggregate over application Rolling Bond
strength development Traffic compaction
Opening to traffic Result of traffic compaction
Constructed 27/04 and trafficked for 1 warm day
Constructed 29/04
Temperature drop 30/04
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SUMMARY
Paper #94: "Stripping of Seals in Southern Africa: Case Studies
and Guidelines for an improved approach to mitigate it“
Focus – minimising risk of stripping Design Construction Opening
to traffic
Author Contact details: GD VAN ZYL - Mycube, Cell +27 83 656
7187; E-mail: [email protected] HG Fourie - SANRAL, Tel: +27 78
893 6262; Email: [email protected] Dennis Rossmann – Tel: +27 83
283 6013; Email: [email protected]
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