Two types of pavement maintenance are generally recognized (Figure 1.1): preventive and corrective (or reactive). Preventive maintenance is used to arrest minor deterioration, retard progressive failures, and reduce the need for corrective maintenance. It is performed before the pavement shows significant distress to provide a more uniform performing pavement system. Corrective maintenance is performed after a deficiency occurs in the pavement; i.e., loss of friction, moderate to severe rutting, or extensive cracking. Although there are many different definitions for these terms, these are the ones used in this report.
Although each type of maintenance is needed in a comprehensive pavement preservation program, the emphasis should be placed on preventing a pavement from reaching the condition where corrective maintenance is required, since the cost associated with this approach can be substantial (4). This situation is often depicted as shown in Figure 1.2, which compares different treatments at different times. What is really needed is a determination of the cost effectiveness of the preventive maintenance (PM) approach compared with standard practices of rehabilitation when the pavement wears out (see Figure 1.3).