INVESTIGATION OF A SURFACING
PROBLEM
Messed up the seal? Read how to start
your investigation here:
Start by getting the background quality
control details (NB this is written in terms of Australian
standards, and other authorities use other tests - the same concept applies
irrespective of test method).
Aggregate Source and test results that
relate specifically to your works.
Old results are no good unless the traceability can be confirmed back to stockpiles
of material that were actually used on the works.
Test results should include:
Particle Size Distribution
Flakiness Index
Los Angeles Abrasion Value
Wet / Dry Strength Variation
Water Absorption
Particle Density
All testing should have been performed in
accordance with AS1141 under the guidelines of AS 2758 Part 5 Asphalt
Aggregates.
Bitumen Source and test results that
relate specifically to your works.
These results should include:
Viscosity @ 60C
Viscosity @ 135C
Penetration @ 25C
Flashpoint
Matter Insoluble in Toluene
Short Term effect of heat and air
Viscosity of residue as % of original after
heat and air effects
Long Term effect of Heat and Air
Density @ 15C
and I'd give some thought to doing extra
tests. Wax content if it looks like the bitumen has been flowing in hot
weather. If you smell diesel or tar, or you suspect contamination, then maybe
GC and HPLC testing is needed. I've got a paper on reverse engineering a
bleeding seal in my list of papers and another paper
on tracking bitumen quality.
All testing should have been performed in
accordance with AS 2341 under the requirements of Table 2 of AS2008
Residual Bitumen.
If it is asphalt and not a seal: it
should have been in accordance with AS 2150 Hotmix Asphalt and asphalt
laying should have been in accordance with AS 2734 Guide to Good Paving
Practice - Asphalt.
Hidden secrets of top investigators 
The hidden secrets are to go and look for:
- Delivery dockets (of stone, lime or
what-have-you)
- Test results from manufacturing on the
day
- Access to any retained samples of
aggregate, bitumen or asphalt held by the asphalt company or others (of
course since all bitumen looks alike, so if you ask for a sample from some suppliers
of the bitumen for NEXT year, they already have the sample
waiting for you plus the test certificate.
- Paving notes or plans detailed what was
laid, with what equipment where.
- For checking rolling, get the number of
hours from the hire dockets.
- For bitumen and asphalt, check delivery
dockets for: Date (PMB)
Grade,
Origin,
Sampling point,
Manufacturing certificate number or batch number,
Customer Customer order number, etc. Delivery details (delivery point, time
and temperature).
- Check the actual weather from Met Bureau vs stated
weather on dockets/spray sheets to catch them lying
- Check asphalt VMA calculation from fundamental
calculation in case they have fiddled to drop the b.c.
- Find the haul distance - cause it cools the mix and it
won't compact
Thanks to Lyndon White
who wrote most of this.
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Last updated 22 March 2008
