Originally published in 1998
Asphalt pavement cracks and deterioration often start in the joints between the paving lanes. Continuous highway traffic runs parallel to the joints and kneads the flexible pavement into the joints, thus preventing cracks from starting. On airport pavements, however, joint density is especially important because airport traffic flows randomly and crosses joints, unlike traffic following a highway lane.
Engineers can extend the life of the airport pavement and reduce the likelihood of cracks by ensuring high density, particularly in the area of the joints. When constructing pavement, engineers consider both the size of the grains of aggregate (usually lime rock) and the amount of liquid asphalt.
To understand the engineer’s challenge, imagine pouring water into a jar filled with marbles. If all the marbles are the same size, the large spaces between the marbles allow plenty of room for water. If the marbles vary in size, smaller marbles can fill spaces between large marbles thus increasing the density of the jar’s contents. In the same way, engineers use varying sizes of aggregate thus filling as many spaces as possible to increase overall pavement density.
SOURCE: Florida Flyer, Winter 1998