Should a second layer of asphalt be placed over an older layer of asphalt?

Question

I have an asphalt driveway. It has its fair share of cracks, etc. However, most troublesome is that "ruts" have formed from the weight of cars driving on it. This means there is a high spot in the middle that is taking a fair amount of abuse when I plow the driveway in the winter.

It has been suggested that I should put another layer of asphalt on top. If current asphalt and whatever is under it is not hard enough to stand up to weight of car traffic, doesn't really seem like another layer of asphalt is what I need, but if I knew what I was talking about I wouldn't be here...

Should I have another layer of asphalt put down on top? If not, what should be done?

Answer 1

Another layer of blacktop asphalt, usually a finer "grit", will fill the low spots and get you through another year -- but it sounds like your driveway is under-engineered for the weight you're regularly driving/parking on it. So, you've got a few choices:

• Another layer of blacktop every year or two, and probably mopping tar on it every summer.

• Tear it up and put in a new asphalt driveway, which will probably have the same problems. I would make sure you consult an engineer and have a few soil cores/studies done before you pursue this angle... you will want to have the substrate rebuilt from the soil on up, and you will want to have had some soil studies for expansion ratios and whatnot done and an appropriate base engineered before you pursue this angle. This will PROBABLY include digging up everything that is there -- the blacktop, crushed gravel, and all, re-tilling the soil with some additives to improve it's compressibility for your climate, and then re-laying everything... probably a bit thicker.

• Tear it up and put in a concrete driveway with a high PSI load concrete, which will occasionally have problems due to the freeze/thaw cycle, but won't sag due to vehicle weight and where you can have any lippage that appears ground down and then can cover it with blacktop again when it does finally blow out or get too thin to grind. See notes above about soil+engineering study, plus tearing out all the base layers and digging deeper/re-packing them.

The last is the pattern that will last the longest, but is obviously going to cost most.

Answer 2

Your problem is the ground under asphalt is not strong enough to sustain load. If you put a new layer of asphalt over the existing driveway it will get the same rut very quickly. Asphalt is highly flexible and once the ground under asphalt sags asphalt sags too.

The real solution would be to tear the driveway up and put proper ballast. If there's any flexible earth beneath (like fertile soil) it should be removed and replaced with sand. Then you have to put crushed stone ballast and ram it thoroughly. Once you have rigid base you can put either concrete or asphalt.

Also see this answer to a question about repairing concrete driveways.

Answer 3

Your existing asphalt is an excellent base for a second layer of asphalt. Not so good for macadam , chip and seal , and some other asphalt pavement substitutes. Assuming you do not have a serious problem like some peat deposits. In the past , asphalt concrete was promoted to governments as a base for cement concrete pavement. ( The higher price of oil has made this too costly.)