As pavement progresses through its 20 year, average performance life cycle, it changes along the way.  Its appearance and functionality diminish over time.  This aging process begins immediately after construction even though these early changes are impossible to see.  After a while, the asphalt becomes noticeably more gray.  This is a chemical oxidation process that is often referred to as the aging or age-hardening process.  This chemical change at the asphalt binder makes the pavement more brittle and subject to wear and cracking.  In addition to hardening, the asphalt also begins a process known as raveling.  Raveling is the degradation of fines, or binder, that surround the aggregate and hold it in place. This could be best understood by comparing a very tight, smooth surface of new asphalt to a rough, deeply pitted, surface of old asphalt.  If preventative maintenance is not utilized, and the pavement is allowed to deteriorate past this point, the damage is irreversible.

NEW INSTALLATION  Smooth tight surface and rich dark appearance, give way to

OXIDATION  Chemical changes from environmental factors, leads to graying and age-hardening that results in mild cracking, giving way to

RAVELING Pavement becomes brittle and cannot expand and contract as well with changes in temperature.  Cracks grow and water is able to penetrate the surface, giving way to

SUB-GRADE EROSION Water from landscape irrigation, and weather, seeps into cracks and begins to wash away the sub-grade.  Pavement structure becomes less solid and can cause existing cracks to grow and new cracks to develop.  Once the cracks connect, chunks of asphalt can become dislodged, giving way to

IRREVERSIBLE DEGRADATION  Potholes, upheaval, shoving, rutting, etc. all causing the surface and structure of the pavement to become weakened and unstable.