Whats up with “fresh oil” on roads?
Dear Straight Dope: I was driving into work today and passed a sign that said “fresh oil.” The sign was on a street that had been freshly stripped of its blacktop and was down to what looked like concrete. The question occurred to me: Why do we put oil on streets like this? Does it dry out otherwise? Does it help a fresh layer of asphalt adhere somehow? I am sure that this will be a chip shot for you to answer, hopefully just the question for a lazy summer day. — Eric From your description, it sounds like the street in question was concrete with an asphalt overlay, which was being outfitted with something like Petromat. Petromat is a synthetic polypropylene fabric (the trade name is owned by BP/Amoco), which is placed between the road base and the asphalt-concrete upper surface to provide a water barrier, strengthen the road, and prevent cracking of the overlay. When used during resurfacing, it’s almost always soaked with an oily-looking asphalt sealer (sometimes called an asphalt emul
