DIGEST 2006 - Sabita

Conclusions
MC 30 cutback bitumen’s
performance as a prime is, apart
from granular base type and
density, very dependent on
temperature, since temperature
has the most direct influence on
its viscosity. The viscosity
influences the ability of the
product to penetrate the base
material and any MC 30 cutback
bitumen which does not penetrate
in the first day will lie on top of
the base for more than a week, if
not more.
There are a number of actions
from suppliers which may in future
solve some of the penetration and
drying time of cutback bitumen
primes. True invert bitumen
emulsions will increase success
rate, but be careful, conventional
emulsions cannot be used as
primes.
From this study it is evident that
temperature and other weather
conditions will play a significant
role in the success of prime
applications.
The following should be considered
to ensure successful prime
applications on site:
• During winter and early
spring, prime applications are
more sensitive to climatic
conditions regardless which
prime is used;
• It is preferable to dampen the
base with water the night
before to achieve the desired
moisture content;
• Surface tension may be
broken with a light
application of water on the
day the prime product is to
be sprayed;
• Temperature must be
measured on site and the
road temperature must be
Figure 6: The viscosity-temperature relationship for MC30 cutback bitumen
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