Common Failures. Asphalt, if designed, installed and maintained correctly should last indefinitely. Asphalt can fail in a number of ways. The most common failures are caused by the following:
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asphalt oils breaking down from sun exposure;
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inadequately designed asphalt thickness and base substrate to handle traffic loads (failures often occur around trash enclosures where heavy trash trucks maneuver); and
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uncontrolled irrigation run-off or asphalt with inadequate slope to drain water.
Definitions. Following are common terms related to asphalt.
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Remove and Replace: The process for completely removing and replacing existing pavement. This is the most expensive and intrusive form of repair.
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Resurface: The process of installing a new layer of asphalt over the existing pavement. The new layer is typically 1.5 inches to 2 inches thick.
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Seal Coat: Application of an asphalt emulsion over the asphalt to avoid oxidation or breakdown of the asphalt oil due to UV rays.
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Crack Sealing: The injection of hot liquid like rubberized sealant into isolated cracks. This prevents water from making its way to the substrate below the asphalt. Crack sealing should be used in conjunction with seal coating.
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Slurry Seal: Similar to a seal coat but with more aggregate mix in the emulsified asphalt.
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CONDITION #1
New asphalt surface which is smooth and crack free. Streets look new and well maintained.
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CONDITION #2
Oxidation starting (black to grey), small shrinkage cracks appear and allow surface water to penetrate below surface.
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CONDITION #3
Shrinkage cracks are getting longer and
wider. Surface oxidation pronounced. More surface water penetrating to
base. This is a good time to apply a seal coat.
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CONDITION #4
Reaching critical point where increasing
moisture penetration is damaging base. Surface fines are being abraded
and being blown off. Surface color is light and surface is getting
rough. It is not too late yet to apply a seal coat.
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CONDITION #5
Oxidation, cracking, abrading, raveling, and
base damage occurring at increasing rate. Surface stones are socketing
and being dislodged by traffic. The surface texture is open and rough.
By this time you may be able to prolong the life of the asphalt without
expensive repairs by crack sealing and slurry coating.
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CONDITION #6
General disintegration rate begins to
accelerate due to previous base and surface damage. Shrinkage at Curb
lines creating large gaps. Too late, save your repair money for
resurfacing or in extreme cases removal and replacement of the asphalt.
Start thinking of excuses as to how this was not your fault.
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CONDITION #7
Base failure hastened by water penetration. Affected area settles and cracks in “alligator” patterns. Failure rapidly spreads from this
point. Once asphalt reaches this
stage, plan on removal and replacement of the affected area or all asphalt if this condition is systemic (over 50% of the surface area).
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CONDITION #8
“Alligatored” areas are breaking up. Loose
blocks are rocking and can be dislodged. General surface condition is
very poor. Large amounts of stone and fines are evidence. Unsupported
edges are cracked and broken.
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CONDITION #9
Pot holes developing and large pieces of
pavement are breaking off edges. Surface heaved and generally bad.
Traffic forced to slow down to avoid large holes. The pot holes enlarge
and base material is free to wash away. Surface is heaved and
generally broken. Traffic forced to slow down because of
over-all-location of holes.
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MAINTENANCE TIPS
- Plan to seal
coat every 3 to 6 years. Hot inland areas will need to
seal coat more often than communities along the coast.
- Plan to resurface the asphalt every 12 to 15 years.
- Do
not let cracks go untreated. Cracks between the asphalt and curb and
gutter, or long continuous cracks, can be sealed. Alligator cracks
cannot be sealed. These areas of asphalt must be replaced.
- For new communities, plan on seal coating within a year of the completion of construction when the asphalt is fully cured.
- If
you continue to have failure problems (alligatoring or spalling) with
your asphalt, consider the use of a soils engineer to help design the
asphalt section and substrate.
Information submitted by Jeff Smith of Smith Architects, a firm that specializes in architectural services to common interest developments.
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