Causes of Pavement Deterioration
Heat from direct sunlight and ultra-violet rays cause the liquid asphalt in pavement to oxidize and become brittle. The weight of vehicles causes the surface to crumble at the point of contact between the tires and the pavement. Water then washes away the dry, crumbled aggregate, diminishes pavement thickness, and reveals a rough, rocky appearance.
Variations in temperature and expansive soils cause pavement to expand and contract. Cracking causes the pavement surface to divide into rectangular pieces. Longitudinal (expansion) cracks run parallel to the roadway or along curb lines. These are quite common in California and can be kept in check through regular pavement maintenance. Transverse cracks (block cracking) run perpendicular to centerline and are a sign of age. These cracks indicate that the pavement has lost its flexibility and needs major reconstruction.
When it rains, or when irrigation overflows the landscaping, water enters the cracks and over time slowly carries away the "fines" of the sub-grade. This causes unstable, unsupported pavement. The weight of vehicles combined with this moisture can cause the pavement to crack like pieces of a puzzle or alligator skin, which is referred to as "alligatoring" or "alligator cracking."
Alligatoring will spread through the pavement like cancer, breaking the pavement into even smaller pieces and eventually forming potholes as the loose pieces are thrown off to the side. Just like a leaky roof left unrepaired, the costs increase rapidly at this stage. Immediate response is highly recommended.