Section 19: Opening to Traffic
Introduction
Traffic should be kept off the fresh seal coat as long as
possible. This section discusses the various factors that can affect
when it is appropriate to open the seal coat to traffic.
Traffic Volume
Roadways with a low-traffic volume may be opened to traffic
sooner than high-traffic volume roadways.
Truck Traffic
On roadways with a high volume of truck traffic, hot asphalt
needs longer to cool (and stiffen) and emulsions need longer to
cure so that trucks will not damage the surface.
Traffic Speed
When sealing roadways where traffic speeds are high, it is
best to allow additional time for asphalt to bond to the aggregate
securely prior to opening to traffic. This not only prevents damage
to the freshly placed seal coat but also reduces the potential for
vehicle damage.
Allowing slow-moving traffic on a new seal coat after final
rolling is one of the best means to reduce premature aggregate loss.
Slowly moving vehicles seem to provide a level of aggregate orientation
not achievable by conventional pneumatic rollers. One method to
assure the traffic will move slowly is to use pilot vehicles.
Asphalt Type and Weather Conditions
The type of asphalt binder used will affect the amount of
time prior to opening the lane to traffic.
Asphalt Cement
.
Asphalt
cements stiffen sooner and bind the aggregate with greater tenacity
than asphalt emulsions, and thus may be opened to traffic sooner.Asphalt Emulsions
.
Emulsions
are typically shot at about 150°F which is near
the pavement temperature during the summer, so there is little loss
of binder temperature. However, high humidity requires more time
for emulsions to break. When humidity is greater than 50 percent, traffic
should be kept off the seal as long as possible.If it rains and emulsions are in use, traffic must be kept
off the fresh seal or it is likely that most of the aggregate and
much of the binder will be lost.
Changing Lanes
When a lane is finished and it is time to turn traffic onto
the fresh seal, extreme care must be taken to avoid confusion and
ensure the safety of motorists and construction personnel. The critical
issue is that complete and positive control is exercised over the
traffic, movement of equipment onto the opposite side, and the resetting
of traffic cones.