When a pavement section is opened up, the story is almost always the same. The asphalt on top is fine. Underneath it is a base that has been sitting in water, or a subgrade that was never compacted, or a low spot that has been collecting runoff since the day the lot was built. The surface just reported the problem. If you replace the surface and leave the problem, you get the same failure back in the same place, usually faster.
Asphalt is a flexible pavement
Concrete is rigid; it spans small weaknesses beneath it. Asphalt bends. Every truck that rolls across it pushes the surface down slightly and the layers below have to push back evenly. If the base is uniform and dry and the subgrade under it is compacted, the load spreads out and nothing moves. If there is a soft spot, the asphalt flexes more there, over and over, until it cracks in the interlocking pattern everyone calls alligatoring. That pattern is not a surface defect. It is a map of where the support failed.
The three things that fail below the surface
- Water in the base. Base rock works because the stones lock together. Saturated base loses that interlock and behaves more like mud. Water gets there through open cracks, through joints against curbs and drains, and from below when a lot sits low. Almost every base failure we dig up is a drainage failure first.
- Uncompacted or inconsistent subgrade. The native soil under the base has to be graded and compacted before anything goes on top of it. Fill that was dumped and driven over, old trench backfill that was never compacted, and organic soil left in place all settle later and take the pavement with them.
- Too little section for the load. A lot designed for cars that becomes a truck route, a dumpster pad, or a delivery lane is carrying loads its base was never built for. The heavy-traffic areas rut and alligator while the rest of the lot looks fine.
What we do before a single ton goes down
On a full-depth repair or a new section, the paving is the last and fastest part. Most of the schedule is underneath. We saw cut the failed area back to sound pavement, remove the asphalt and the wet base, and look at the subgrade. If it is soft, it gets over-excavated and either recompacted or replaced. Then new base rock goes in and gets compacted in lifts and checked, not just driven over. The grade is set so water leaves the area toward a drain or an edge instead of collecting where the old low spot was. Only then does the paver show up.
- Proof-roll the subgrade. A loaded truck across the prepared subgrade shows soft spots before they are buried under base rock. Anything that pumps or deflects gets fixed then, when it is cheap.
- Compact base in lifts. Base placed in one thick pass compacts on top and stays loose underneath. Thinner lifts, each compacted, give a uniform layer that supports the asphalt evenly.
- Grade for drainage. Every section gets checked for slope toward an outlet. Flat spots that hold water become next year's alligator patch, so we fix the grade while the section is open.
- Compact the mix while it's hot. Hot-mix asphalt densifies only within a temperature window. Rolling happens right behind the paver, in a pattern, so edges and joints get the same density as the middle.
What this means for the quote you're reading
Two bids for the same failed area can be far apart, and the gap is usually what is being done below grade. A quote that says "remove and replace asphalt" without mentioning base, subgrade, or compaction is pricing the surface. A quote that lists saw cut, excavation depth, base rock, compaction, and grading is pricing the repair. They are not the same job, and only one of them stays fixed. Ask what happens if the subgrade is soft when it's opened up, and how that gets priced. You want that answer before the section is open, not after.
Paragon runs the whole sequence with one crew: saw cut, demo, excavation, base, compaction, and paving. That is why we start every asphalt estimate by asking what is under the surface, and why our sections stay flat after the trucks come back.