How Asphalt Paving Works: Why Brookhaven Pavement Cracks First
A driveway looks like one solid layer, but the asphalt is only a skin. Under it sits a bed of crushed rock that runs four to eight inches deep, while the asphalt on top is three to five inches thick. When water softens that bed, the skin flexes under every tire and splits along the lines of greatest stress.
Brookhaven ground makes the problem likelier. Large areas are mapped as urban land. Nearby soil series include Pacolet, Madison, Cecil, Gwinnett and Appling, many with clay subsoil near 30 to 47 percent. Wet clay is weak, and fill placed during past development can settle unevenly. A base laid without checking for either one fails early. Compact lots add a wrinkle, since trucks and rollers have little room to turn, and the crew plans the order of work so the equipment never traps itself.
Weather finishes the work. Rain totals near 50 inches a year with none of it skipping a month, and the thermometer reaches freezing on about 36 nights. Water slips into any gap, freezes, pushes the gap wider and repeats after every cold snap. For that reason a careful crew spends more effort below the surface than on top of it.