Unless your driveway is literally crumbling from a bad base, it should be able to be repaired. Since the base is hidden under the asphalt, it is impossible to inspect it. If it continues to deteriorate even after you make proper repairs, a bad base is the most likely cause. In that case, the driveway must be replaced again.
With an unstable gravel base, for whatever reason, there probably isn’t a “permanent” repair for the current cracks. This doesn’t mean you cannot make repairs that last several years, but smaller cracks through the repair are probable. Smaller cracks are easier to fix, and if you are lucky, they may get small enough that they are not an aesthetic issue.
Another problem you may have had with the repair is you did not follow the repair material manufacturer’s instructions. People typically don’t read the instructions thoroughly and just start filling in the crack. One common problem is to fill the crack when the temperature is too cold for the repair material. It may be warm enough during the day, but it gets too cold the first night before it sets. This results in poor adhesion.
The repair material instructions may also recommend a maximum thickness for the repair. Filling the entire depth of a deep crack can result in too much shrinkage. If there is a deep crack, it should first be filled with a foam backer rod. The ideal depth of the repair material should not be more than twice the width of the crack.
Don’t give up and assume things are hopeless, because it is important to keep those cracks as filled and closed as possible. Wherever there is a crack, water can seep through it into the ground. This will make the base even more unstable.
This is a particularly serious problem in cold climates. Water expands as it freezes. If it rains during the daytime, and then the temperature drops below freezing at night, the water in the crack can freeze. This expanding ice will force your previous repair compounds out of the crack.
No matter what type of repair material you select, clean out the crack as thoroughly as possible. This is important because the repair material needs a solid surface to which to adhere. Use a screwdriver to dig out any big chunks. Then, use a stiff brush followed by a wet/dry vacuum to remove the fine particles.
There are many types of crack repair materials available. When repairing a smaller crack during warm weather, a pourable type of material works well. Repair material in a tube that fits a standard caulking gun works well anytime and makes it easier to eliminate voids. Once the repair material is installed, sprinkle it with sand, place a piece of plywood over it, and drive the car over it to level the surface.
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