Rehabilitation of Jointed Portland Cement Concrete Pavements: SPS-6, Initial Evaluation and Analysis

Chapter 4. MONITORING FREQUENCY

The frequency of the collection of monitoring data at each site is critical to identifying the unique performance trends specific to a particular rehabilitation alternative. For each monitoring type, the frequency of the collection of monitoring data is evaluated below, including pre- and post-monitoring collection and long-term testing after rehabilitation.

DATA COLLECTION DIRECTIVES

During the lives of these pavement sections, multiple directives have been issued regarding the testing frequency for each type of monitoring data collected. These directives are rules published by the FHWA-LTPP Division to ensure that consistent data are collected, monitored, and stored. Some of these directives slightly adjusted the testing intervals during the life of the program. All of the known directives as of the time of this report that reference the SPS-6 data collection monitoring frequency are listed in table 18. This table also identifies directives that supersede the previous directives.

These directives were used to identify all previous testing frequencies for each type of monitoring data collected and are summarized in table 19. The testing frequencies are listed chronologically from the oldest to the most recent within each cell of the table. Therefore, the current-as of the time of this report-testing frequency is listed at the bottom of each cell within the table. This allows for easy review of all previous SPS-6 testing frequencies that had been specified during the data collection process. Table 20 lists the current-again, as of the time of this report-monitoring frequencies for data collection.

*For supplemental sections, the frequencies are every 3 years for manual distress, every 2 years and responsive for PASCO, and every 5 years and responsive for FWD testing.

*For supplemental sections, the frequencies are every 3 years for manual distress, every 2 years and responsive for PASCO, and every 5 years and responsive for FWD testing.

In addition, closeout monitoring (FWD, profile, and manual distress surveys) should be conducted on each section. According to Directive GO-21, this is "when it is determined that the test section will be taken out-of-study (due to a construction event or at the option of the highway agency) or at the end of the field monitoring portion of the LTPP program, whichever comes first."

MONITORING FREQUENCIES AS COLLECTED

Appendix C provides a tabular listing for all of the monitoring activity dates at each SPS-6 section. These dates were used to determine the monitoring interval of each data collection type for each SPS-6 section. These testing frequencies were then summarized in tables 21 through 29 for each SPS-6 site. Each of these monitoring tables evaluates the monitoring interval prior to rehabilitation, immediately after rehabilitation, and throughout the long-term monitoring of these sections. These tables also include an additional column listing the number of sections without long-term monitoring data. It should be noted that most of the sections without long-term monitoring are a result of long-term monitoring data not having been entered or collected for the supplemental pavement sections. For easy comparison of the actual testing frequencies and the frequencies specified in the directives, the periods prior to and immediately after rehabilitation were assessed in terms of months and long-term monitoring was assessed in terms of years.

All of the testing intervals are assumed to originate from the end of the construction date. This date was determined by evaluating various SPS-6 rehabilitation tables. The rehabilitation dates were then compared, and the date that rehabilitation was completed was determined. Based on the intervals specified in the directives listed in table 19, it was assumed that the testing interval immediately after construction should have occurred within the first 12-month interval after construction, except for friction that was limited to an 18-month interval. These monitoring intervals are slightly greater than those specified in the directives to allow for a reasonable margin of error within the desired testing interval. It was assumed that if a section was not tested within the 12- or 18-month interval immediately after construction, then the monitoring for the interval immediately after construction was not conducted. Therefore, any testing that exceeds the 12- or 18-month interval immediately after construction was then included as part of the long-term monitoring.

The directives for the fractured PCC pavement states that testing must be conducted prior to fracturing the PCC; immediately after fracturing the PCC, but prior to seating; and immediately after seating, but before placement of the AC overlay. Because it is very difficult to identify the monitoring activities of the fractured sections that were tested immediately before and then after seating, this information was not assessed at this time. Monitoring activities conducted before rehabilitation (before cracking) and after rehabilitation (after placement of the AC overlay) were included in table 23.

The long-term monitoring interval begins immediately following the initial monitoring after rehabilitation and, therefore, does not include any testing prior to or immediately after rehabilitation, and ends at the test date prior to the deassign date. The long-term monitoring portion of the tables also provides a more detailed summary of the testing interval, including the minimum, maximum, and mean testing intervals that occurred during the long-term monitoring of each section.

The directives do not limit the interval when closeout tests must be performed. It can be assumed that the last test conducted during the long-term monitoring of each section is the closeout test. Therefore, closeout monitoring was not evaluated during this analysis.

Based on these assumptions, the frequency of the monitoring data is summarized for each site in tables 21 through 29. For each of these tables, the number of sections tested before and after construction is given in terms of the total number of sections. For example, in table 21, Alabama had 11 of 11 sections that had received longitudinal profile monitoring immediately before and after rehabilitation. In addition, all of these sections have had long-term monitoring ranging from an interval of 0.9 to 3.0 years. Most of the sites have received the required testing.

The more recently rehabilitated sections, including Alabama, Arkansas, Missouri (A), and Tennessee may have received all of the initial monitoring immediately before and after construction as specified in the directives. However, this information may be in the process of being entered into the regional IMS databases and, therefore, had not yet reached the IMS database as of the August 1999 or January 2000 IMS downloads.

Figures 3 through 11 visually show the long-term monitoring intervals that were graphically presented in tables 21 through 29 for each of the data monitoring types. Each figure shows the long-term monitoring intervals for all sections of a particular site. This includes the minimum and maximum testing interval, and the average monitoring frequency that occurred at each site. Typically, all of the sections within a site were tested within a 3-year period.

Figure 3. Profile testing intervals for each site.

Figure 4. Nonfractured FWD testing intervals for each site.

Figure 5. Fractured FWD testing intervals for each site.

Figure 6. Manual distress testing intervals for each site.

Figure 7. PASCO testing intervals for each site.

Figure 8. Combined manual distress and PASCO testing intervals for each site.

Figure 9. Faulting testing intervals for each site.

Figure 10. Rutting testing intervals for each site.

Figure 11. Friction testing intervals for each site.

In addition, because the data collection monitoring for the manual distress and PASCO surveys is used to identify the same information (surface distress), these dates were combined in figure 8. Using the combination of manual distress and PASCO survey dates, almost all of the sites have an average survey time of between 1 and 2 years. This interval is very good and it is vital information that will be used later to evaluate each pavement section. Surface distress may be a key parameter in identifying and recommending appropriate rehabilitation techniques for future projects.