Section 2: Pavement Deterioration Cycle
It is important to note that even if a pavement is properly designed for the expected traffic it receives and is constructed according to specifications, it will still start the deterioration process within a year. However, the better the design, the longer it will take to progress through each phase of the cycle. Annual preventive maintenance and repair procedures can delay each phase of the cycle thus saving the property manager greater expense in the long run.
Governments rate roadways using a standardized numerical system to evaluate the phase in the life cycle of a pavement. Engineers use these ratings to determine the extent of maintenance and repair required each year to maximize return on investment. There are several systems used by various public agencies but these are fairly complex and, in many instances, are not appropriate for parking lot pavements. Carolina Asphalt has produced its own rating scale to analyze the condition of a pavement. This rating system is a convenient reference for the estimator and property manager to talk about a particular parking lot condition.
Property Manager hint: Some property managers choose not to do any preventive maintenance or repair work and this accelerates the deterioration cycle. When the pavement needs to be completely replaced, it can be a significant capital expense for the owner. Annual maintenance and repair procedures can often be charged to the tenants (who did the damage) in the form of common area maintenance (CAM charges).
For each level of deterioration on our scale, Carolina Asphalt has developed an appropriate solution. These solutions are discussed in the last section of the seminar.
Carolina Asphalt Pavement Rating Scale
Level 1: Separation or "Raveling" of surface aggregate
Level 2: Isolated cracking along pavement seams
Level 3: Water in the sub-grade or stone layer
Level 4: Minor "alligator" cracking (5- 35% of total area)
Level 5: Widespread "alligator" cracking (> 35% of total area)
Level 6: Complete pavement failure
Level One: Raveling
Definition: Raveling is the separation of the surface aggregate in the pavement mix. As some of the surface aggregate rolls out of the mix, the surface becomes rougher in texture. The surface aggregate that has rolled out of the surface is most evident in the gutter pans and close to drains. (although this may not be seen if a pavement is cleaned regularly) Occurs within 6 months on new asphalt installation.
Cause: The liquid asphalt binder that holds the surface together is broken down by oxidation, which causes the rocks to separate from each other. This is the best point to start preventive maintenance.
Solution: Sealcoating
Level Two: Isolated Cracking
Definition: Pavement breaking at its weakest point. Cracks are random and not (yet) connected into a networked pattern.
Cause: As a new pavement expands and contracts during weather cycles, it forms cracks at the weakest points in the asphalt structure, the pavement "seams." Seams are created during the initial paving by the application process. The better the initial installation, the better the seams will hold up over time. However, regardless of the installation, it is only a matter of time before cracks in the pavement begin forming. Water finds its way to the base layer through these cracks and saturates the base immediately under the crack which can accelerate the cracking process.
Solution: Cracksealing
Level Three: Water in the sub-grade or stone layer
Definition: Water that penetrates the stone layer or sub-grade and creates an unstable structure under the pavement.
Cause: Often caused by leaking irrigation systems located under landscaping islands. Irrigation systems are usually made of plastic pipes and heads, which are easily broken. Whenever a break occurs in the water system, the water will travel through dirt and around the curb structure. Other sources of water include: broken roof drain lines, broken sewer lines, and underground springs. Once the water finds the sub-grade and stone layers, it penetrates these 2 layers and channels up to the asphalt surface. This same water can saturate the sub-grade causing it to become unstable.
Solution: French Drain
Level Four: Minor alligator cracking, 5-35 % of total area
Definition: The asphalt layer of the pavement system can no longer support the load and breaks in a series of networked areas.
Cause: Water has infiltrated and saturated the base of the pavement structure decreasing its structural capability. Pavement system was under-designed or under-constructed for current traffic conditions. Pavement system is severely oxidized from age and has become brittle. Loads that could be absorbed at one time now cause pavement to break.
Solution: Patching
Level Five: Widespread alligator cracking, over 35% of area
Definition: The pavement system is network-cracked throughout. It is difficult to clearly define localized areas of repair.
Cause: Minor isolated cracks, minor block cracks and water problems have not been addressed. Water is saturating the sub-grade and damage is accelerating. Entire pavement system is under-designed or under-constructed for current traffic conditions. Pavement system has reached its design life and can no longer support the loads it used to.
Solution: Rehabilitation
Level Six: Complete failure of the pavement
Definition: Pavement has reached the end of its service life. The cost to repair is higher than the cost to replace.
Cause: Age of pavement structure, radical change of use
Solution: Complete removal and replacement. Best to contact a soils engineer.
Property Manager hint: With a copy of the site plan in hand, walk the property and make notes about the pavement condition. Label each section with the level of deterioration and share this information with your estimator. Take digital pictures and print them for the estimator so you can be sure to address each of your concerns. Whenever possible, spend the time to walk the lot with the estimator in order to eliminate any ambiguity. Remember, it will take more of your time if the estimator has to come back to the site to redo a bid that does not address your needs!
The lower the level of deterioration, the easier and more economical the solution will be. A pavement lot in Levels 1 or 2 is a candidate for general maintenance operations. A pavement in Levels 3 or 4 is a candidate for repair operations. A pavement in Levels 5 or 6 is a candidate for rehabilitation operations.
Problems in Levels 1 – 4 are fairly routine, and a solution can be proposed. Once a pavement reaches Level 5, a professional geo-technical engineer should be used to evaluate existing soil conditions and design a solution that meets the needs of the property owner.
It is important to practice regular maintenance of your property in order to prevent future costly problems.
In Summary:
| Level | Name | Cause | Solution | |
| Maintanence Operations | Level 1 | Raveling | Oxidation | Sealcoating |
| Level 2 | Isolated Cracking | Expansion/contraction | Cracksealing | |
| Repair Operations | Level 3 | Water in the sub-grade | Irrigation leak | French drain |
| Level 4 | Minor alligator cracking | Local base failure | Patching | |
| Rehabilitation Operations | Level 5 | Widespread alligator cracking | Base failures not addressed soon enough | Rehabilitation |
| Level 6 | Complete failure | Neglect or age | Remove and replace |