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Section 19: Opening to Traffic

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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.

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Traffic Volume

Roadways with a low-traffic volume may be opened to traffic sooner than high-traffic volume roadways.

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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.

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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.

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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.

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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.

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