DIGEST 2006 - Sabita

Alternatives to coal tar products:
The influence of weather on
prime applications
Johan Muller
Assistant Technical Manager
Tosas (Pty) Ltd
At the Conference on
Asphalt Pavements for
Southern Africa (CAPSA)
2004, the decision was made,
in line with global best
practice, to discourage the use
of coal tar products in road
construction in South Africa.
This decision resulted in Sasol
CarboTar closing its operations in
June 2006, which drastically
reduced the availability of coal tar
products in the market and left
only one source of coal tar
products, namely that from Mittal
Steel. The result was a significant
reduction in the range of prime
products available for the road
construction industry.
In the second half of 2006, Sabita
launched a series of seminars
under the auspices of the Society
for Asphalt Technology (SAT) in
the Gauteng, KwaZulu Natal and
Western Cape regions to promote
the discontinuation of coal tar
usage. The seminars were well
attended and suppliers were given
the opportunity to promote
alternative products and
techniques to coal tar for priming
granular bases and precoating
surfacing stone.
Contractor problems
Contractors complained that tar
products such as RTL 1/4P, RTH
1/4P and Sasol Quick Drying
primes wetted and cured quicker
in practice than cutback bitumen
primes such as MC 30.
Table 1 compares properties of the
different materials.
In general, it has been found that
invert bitumen primes work better
than cutback bitumen primes.
Yet, despite the properties of the
primes, other factors such as the
density and type of base material,
also create havoc for the
contractor. The moisture content
and temperature begin affecting
the performance of the prime in
the application, and the end result
is an undesirable primed surface
which causes delays in
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