ASPHALT 101 | Your asphalt pavement education resource.
ASPHALT: WHAT IS IT?
Blacktop, asphalt pavement, parking lot, roadway, driveway – there are a lot of terms for the same product. Engineering firms and construction companies sometimes call it “asphalt concrete pavement,” or “AC” for short. AC is a hard, rolled surface that is constructed from a slate black product called asphalt.
Road surfaces and such like, account for about 85% of all the asphalt used in the United States. Typically, this pavement material is composed of 5% asphalt material and 95% of a mixture of stone, sand, and gravel. It is laid down in layers over a bed of compacted, crushed rock. The use of the asphalt bitumen binds the aggregates together and gives it that nice black appearance.
ASPHALT'S WORST ENEMIES
Otherwise know as the weather. The weather is a natural enemy to asphalt pavement because the heating/cooling cycle causes expansion and contraction of the substrate. When water seeps into the pavement and freezes, or the water begins to disturb the crushed rock fill, sinking and lifting or cracks and potholes become evident.
Original Construction Quality
This includes the grade of asphalt used to initially construct the pavement, the quality of base materials and prep, and how it was installed. The drainage system is also crucial to the overall lifespan of the pavement. Keeping the drains and vaults clear of debris helps shed the water quickly of the seasonal rains and extend the lifespan of the product.
Constant patterns of traffic over the same areas and the weight of that traffic can exponentially affect the condition of the blacktop. Wheels actually cause the pavement to flex, causing small fractures in the surface. Over time, these small fractures can turn into big repair bills if left unaddressed.
Motor oil, gasoline spills, antifreeze, and diesel fuel are all solvents that can cause considerable damage to the asphalt. These should be cleaned and/or neutralized at regular intervals to prevent long-term damage.
STAGES OF ASPHALT DETERIORATION
After the first year, asphalt begins to lose the binding oils that keep the mixture flexible and resilient. This happens through the normal cycle of the weather (rain, freeze/thaw cycle, wind, etc) and evaporation.
The asphalt begins to oxidize and turn grayish in color and appearance. This is the ideal time to sealcoat. At this point, the surface is still in great condition and is ready for a sealcoat to preserve its integrity and appearance.
At this point, the surface of the pavement begins to lose its integrity. The aggregate materials on the top of the pavement are exposed. The surface appears rough, or rougher than the original application. The sand that is used to help seal and keep a smooth finish is working its way out with the help of the weather. Sealcoating at this stage will return integrity to the pavement and return the condition of the pavement to original application.
Loose rock begins to appear on the surface of your asphalt. The common conception is that vehicles or traffic is bringing this in and depositing it. Actually, this is your pavement beginning to unravel and detach itself from the top layer. In addition, you may begin to notice small cracks along seams. This is asphalt’s worst enemy! Through these cracks, water now has an entry point into the base and sub base of your pavement. Heaving (due to freezing and thawing) and disruption and washing away of the base materials can now occur. Sealcoating, along with some other materials, will be needed to get your pavement back to Stage One.
Loose rock is now collecting in “puddles” on the pavement. Larger cracks (1/4” and larger) are now appearing with small cracks leading out from them, like a spider web. These large cracks require a crack sealer to prevent water and debris from filling them and causing more damage. Finally, a sealcoat over the whole investment should be done to prevent further deterioration.
At this point, deterioration of the pavement escalates at a rapid pace. The cracked areas begin to look like an alligator’s skin. Repair at this level now requires removal of the “gatored” areas and the asphalt replaced. Depending on the condition of the rest of the pavement, asphalt skin patching may be required.
Small pieces of asphalt begin breaking off around the larger cracks. Potholes, or chuckholes begin appearing. At this point, the pavement will need non-stop patching to keep it in presentable condition.
At this point, the pavement has deteriorated to the point that a fresh overlay of asphalt is the only logical and long-term solution.
ASPHALT PREVENTATIVE MAINTENANCE
Just like a vehicle or a house, asphalt preventative maintenance will save thousands of dollars long term. Sealcoating prevents the asphalt from absorbing water by sealing the porous top layer of the pavement. This prevents damage from the freeze/thaw cycle, sleet, snow, and frost. It also provides a protective top layer from the sun, which will oxidize and dry out the asphalt, leading to deterioration of the aggregate.
Minimal Investment. Exponential Return.
Sealcoating your investment and applying crack filler is usually 10% of the cost to repair and/or resurface. If an owner sealcoats the pavement every 3-5 years, you can expect a 300% increase in the lifespan of the pavement. Plus, it will look maintained and new at all times!
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