DIGEST 2006 - Sabita

Figure 2: “Pick-up” on truck tyres
"Clean"emulsions
During the developmental stage of
the Colnet system, Colas in France
performed comparative tests in
the laboratory with conventional
and “clean” emulsions to evaluate
the development of the bond
strength over time. The emulsion
was applied in an even layer on
aluminium trays and small glass
cylinders were positioned on the
emulsion layer. In the case of the
“clean” emulsion, the breaking
agent was
first evenly
sprayed over
the emulsion
layer before
positioning
the glass
cylinders. The
strain
required to
debond the
cylinders was
then
determined
over time
(See Figure
3).
Conclusion
Tack coats and bond
coats are critical to the
successful performance
of hot mix asphalt
surfacings. Although the
design and construction
of hot mix asphalt layers
always receive detailed
attention, the selection
and application of tack
and bond coats often do
not receive the attention
they deserve despite
their influence on the overall
performance of the new paved
surface. Hand application of tack
coat is still common practice in
South Africa, but is forbidden in
most developed countries. Should
the use of calibrated binders
distributors eventually become
compulsory for the application of
tack coats, the emulsion producers
will have greater incentives to
produce innovative binders for this
market sector.
Figure 3: Bond strength – Conventional vs “clean"emulsion
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