Paper presented at the 33rd Annual Southern African Transport Conference 7-10 July 2014 "Leading Transport into the Future", CSIR International Convention Centre, Pretoria, South Africa.
The application of seals as surfacing on South African roads has increased due to its dual
advantage in performance potential and sustainability. The field performance of spray
seals depends on a number of factors, and its defects measured predominantly by
bleeding and ravelling of the seals.
During construction, viscosity is controlled such that the binder is sprayable, but not too
low in viscosity as to run off the road surface. To avoid pavement distress resulting from
loss of the binder or from inconsistent binder thickness after application, it is important to
understand the run-off behaviour of seals.
Run-off tests were conducted in the laboratory by constructing surfacing seals with varying
texture depths. These seals were constructed on a surface that would allow the user to
change the angle of application in order to simulate the spraying of the seals on different
road gradients. A movable/mobile spraybar was used to simulate typical conditions as for
a spray tanker during construction. Run-off was measured through a gutter system where
the emulsions was collected and weighed.
An analysis of the run-off results obtained from these experiments, revealed that the spray
rate had the largest effect on run-off, followed by texture depth, and gradient.
