Because of its effectiveness, crack treatment has long been a popular preventative measure to keep moisture out of the pavement, preventing potholes from forming and extending pavement life. However, cracks that are not properly cleaned prior to repair simply cannot protect a pavement over the long term.
As the busy summer season begins to wind down, contractors should be encouraging crack sealing to their customers as a preventative maintenance service that must be completed before winter. Cracks sealed before winter help ensure the pavement is in the best possible state to endure the freeze/thaw cycles of the upcoming season and help to prevent further pavement damage.
Spring and fall are ideal times to crack seal as temperatures during these seasons are moderate and tend not to reach the extremes of winter and summer months. However, contractors must be sure cracks are fully cleaned before starting a repair. Aside from choosing the correct crack sealant, this is the single most crucial determinant of success in a crack seal operation.
Many contractors begin with a general sweeping of the area with a sweeper or hand broom before crack sealing, but crack cleaning shouldn’t stop there. It is necessary to blow debris out of individual cracks with an air compressor, or even better, use a hot air lance. Each speck or crumb of dust, gravel or similar debris in the crack weakens the ability of the crack sealant to make the best bond with the surface. Further, if the bond between the sealant and crack walls isn’t tight, the slightest droplets of moisture seriously degrade the quality of the repair.
Below are a few crack preparation objectives to complete prior to crack sealing to help provide an optimal environment for adhesion of crack repair materials.
If a pavement has been left unattended for a long period of time, vegetation will likely have taken root in the cracks. It’s essential to remove those plants from the root up before completing any crack repair efforts.
Remove Dirt and Debris
After vegetation has been killed, the crack needs to be cleaned out. It is essential to provide a clean, dry crack channel and remove any loose material from the crack. Cracks that contain debris, vegetation, loose aggregate or sand will fail prematurely because the sealant won’t stick to the crack walls. Cleaning consists of high-pressure dry, clean, compressed air blown into the crack. A minimum of 90 PSI is recommended to achieve the appropriate cleanliness.
The operator should hold the nozzle about 2-in. from the surface and make slow, repeated passes, blowing the debris forward of the nozzle. The final pass should move across the general surface area to remove debris from the vicinity that might re-contaminate the joints.
If heavy clay or debris is present, wire brushing can be used to break up the debris. Brushing should be done to adequately clean pavement that is excessively dirty or areas that contain oil spots and other contaminants. After brushing, cracks still need to be blown clean by an air compressor.
Dry the Crack
Any moisture present in the pavement or crack will prevent adhesion of the material to the crack walls, increasing the likelihood of failure. Conditions such as moist climates, performing crack treatments at night, or when temperatures are below the dew point can result in moisture being present in cracks.
Moisture in cracks during these conditions may be hard to identify, therefore it is recommended to use a hot air lance during crack treatments to ensure that any moisture present may be removed. When performing crack treatments at night, it is important to assure that dew is not forming on the crack surfaces. Also, if the temperature during the crack treatment is below the dew point, there is an increased chance of moisture being present, and operations to dry the cracks are needed.
It is common for surfaces to become moist again shortly after drying in these conditions so crack sealing operations should be performed immediately following hot air lancing operations.