Chip Seals (or seal coating, BST, Bituminous Surface Treatment) is the application of a special protective wearing surface to an existing pavement.
A dump truck full of chips (gravel) locks on to the chip spreader and is pulled backwards.
A thin layer of liquid asphalt is sprayed down in front of the chip spreader.
Why chip seal?
- To keep water from penetrating the road structure on paved surfaces.
- To fill and seal cracks and raveled surfaces of old pavement.
- To provide an anti-glare surface during wet weather and an increased reflective surface for night driving.
- To seal the pavement surface-minimizing the effects of aging.
- To provide a highly skid-resistant surface, particularly on wet pavements.
- The cost of chip seals is 15%-20% of the cost of pavement overlays.
The Chip Seal Process
1. First, asphalt is mixed with about 30% water. This emulsified mixture is then applied to the road using a special spray truck. As soon as the liquid asphalt meets the road surface, the water starts to evaporate.
2. Immediately after spraying this asphalt, a layer of crushed gravel is applied by a spreader. The gravel (or chips) has a maximum size of 3/8 inch.
3. Next, the gravel is compacted and embedded into the asphalt by rubber-tired rollers. However, even with the high pressure rolling, some gravel will not become embedded in the asphalt.
4. The new chip-seal surface can require up to two days to cure properly. Hot, dry weather helps speed up this process in which all of the remaining water in the emulsion evaporates and the asphalt hardens. Traffic can pass over this surface at reduced speeds during the curing process. The recommended speed is 15-20 mph.
5. After curing, the loose gravel is swept off the surface. This may take several sweepings.
As with any highway construction project, motorists must exercise caution. Reduced speeds ensure your safety and minimize the chance of damaging your vehicle.
During the chip seal process, from the time the gravel is placed on the road to when the excess is swept away, the speed limit is 15-20 mph. At that speed, vehicles should not be damaged by flying rocks.
Traffic moving at higher speeds can create dust, limit visibility, and cause an inconvenience to local residents. Increased speeds can also cause gravel to break loose from a fresh chip seal creating the risk of flying rock. Rocks thrown from your tires may crack or break a windshield. Flying rocks might also injure pedestrians, bicycle riders, or motorcyclists.
By driving 15-20 mph, you protect your vehicle from unnecessary damage that can be caused by the sprayed asphalt and loose gravel. The slower speed also decreases the chance of damage from rocks which may be thrown up from other vehicles. Additionally, by driving slow you help to compact the new surface.
We appreciate your patience.
Throughout the Summer and Fall, we will be making improvements to town highways which may cause some traffic delays. Please be patient. Traveling at the posted construction speed limit in construction zones will ensure your safety and the safety of highway workers. Obeying warning signs and flagging personnel instructions benefits all those who share the roadway with you, too.