Cracks are how asphalt tells you something is wrong. The shape, location and pattern of a crack usually point straight to its cause, whether that is water in the base, an unsupported edge or simple age. Once you know the cause, you know which fix will actually hold.
Here are the six crack types we see most often on New Jersey driveways and parking lots, what each one means and how it gets fixed.
1. Alligator Cracks
These look like the scales on an alligator’s back: a web of small, connected pieces, usually in the wheel paths or where trucks turn. Alligator cracking means the pavement has lost support from below. Most often the base got wet and weak, or the asphalt was too thin for the loads it carries.
The fix: A surface treatment will not help, because the problem is underneath. The damaged area needs to be cut out down through the asphalt, the base checked and recompacted or rebuilt, and the area filled with new hot mix and rolled. This full-depth repair is done as part of repaving, and when the cracking covers much of the surface, a full replacement with a new base is the better answer.
2. Edge Cracks
Edge cracks run parallel to the side of a driveway or lot, usually within a foot or two of the edge. They form when the soil next to the pavement washes away or when vehicles repeatedly drive on the edge. Without side support, the asphalt bends and breaks.
The fix: Restore support by backfilling the soil along the side and compacting it, and rebuild the broken edge with new asphalt when the driveway or lot is repaved. If water runs along that edge, correct the grading or redirect the downspout causing it. Otherwise the crack will come right back.
3. Block Cracks
Block cracking divides the surface into large rectangles, often a foot or more across. It is usually a sign of aging. Over time the binder in the asphalt oxidizes and stiffens, and the pavement can no longer expand and contract with temperature changes. It tends to appear on surfaces that do not see much traffic, such as the back of a parking lot.
The fix: Because block cracking reflects the condition of the whole top layer, spot fixes only go so far. If the base is still sound, milling off the worn surface and repaving is typically the long-term answer.
4. Transverse and Longitudinal Cracks
These are single, straight-ish cracks running across the pavement (transverse) or along its length (longitudinal). Temperature swings cause many of them, and New Jersey’s freeze-thaw winters make them common. Longitudinal cracks can also follow a poorly bonded seam between two paving passes.
The fix: A few isolated cracks on a sound surface are a warning sign rather than an emergency. Keep water moving off the pavement and watch them. If they widen, start to branch, or the edges begin to break apart, the pavement is losing ground. When these cracks are spread across the whole surface, milling and repaving is the more economical fix.
5. Slippage Cracks
Slippage cracks are crescent-shaped and often appear where vehicles brake, turn or accelerate. They happen when the top layer does not bond properly to the layer below and gets pushed out of position.
The fix: The poorly bonded area has to be removed and repaved with a proper tack coat between layers so the new asphalt grips what is underneath. Simply filling the crack leaves the loose layer in place.
6. Reflection Cracks
When new asphalt is laid on top of an old, cracked surface without proper preparation, the old cracks tend to show up again in the new layer. These are called reflection cracks. They mirror the pattern of whatever is underneath.
The fix: Prevention is the best cure. Before repaving, the old surface should be milled off, failed areas in the existing pavement should be removed and rebuilt down to a sound base, and badly broken surfaces should be fully replaced rather than covered. If reflection cracks have already appeared, the solution depends on how widespread they are, from milling and repaving to a full replacement.
Getting the Right Fix
The common thread is that the visible crack is a symptom. The lasting fix addresses the cause: water, support, bonding or age. You can read more about how we remove worn asphalt on our milling page, or see how we rebuild from the base up on our asphalt driveway paving and parking lot paving pages. Our post on signs your driveway needs to be repaired covers more warning signs. For other warning signs beyond cracking, see three problems to look for with asphalt.
If you are not sure which type you are looking at, we are glad to take a look and give you a free estimate.
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Dan The Paver handles asphalt driveway paving across Monmouth, Ocean (Toms River and north) and southern Middlesex counties. Free on-site estimates.