Key Findings From LTPP Analysis 2000-2003

PAVEMENT MAINTENANCE

Accomplishing necessary maintenance with minimal disruption to traffic is important from the standpoints of customer satisfaction, the safety of both those doing the work and the traveling public, and overall productivity. The following are key findings from several LTPP pavement maintenance studies. These findings are grouped into two areas: maintenance of rigid pavements and maintenance of flexible pavements.

• Treatment Performance

• Treatment Performance
• Pothole Repair Treatment Performance and Repair Methods

Maintenance of Rigid Pavements

• There are no significant differences (either in spalling or in any other performance measure) between the control sections (unsealed) and the sealed-joint or undersealed (slab stabilization) sections. This observation is based on the 32 test sites constructed for the SPS-4 experiment (rigid pavement maintenance) in the United States and Canada between 1990 and 1995.
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• Based on 5 years of data collected in Arizona, Colorado, Nevada, and Utah, differences in initial pavement smoothness among the three treatments consisting of sealed, undersealed, and unsealed joints in the SPS-4 experiment are not significant. Neither does faulting analysis indicate significant differences among the three treatments.

Report Nos. FHWA-RD-97-155 and NCHRP 20-50(2)

• Based on 5 years of data collected at the five test sites built in Arizona, Colorado, and Utah (all in the dry region), the effects of sealed and unsealed joints on spalling are similar.

Report No. FHWA-RD-99-151

• Predominant among the SPS-4 State supplemental test sections built in Arizona, Colorado, Nevada, and Utah between 1990 and 1995 was a comparison of joint sealant types: silicone seals, compression seals, and hot pours. Silicone seals appeared to outperform the other two treatments for transverse joint seals.

Report No. FHWA-RD-99-153

• When comparing saw-and-patch and chip-and-patch procedures in 28 test sites in four climatic regions, the annual cost for chip-and-patch is lower than for sawand-patch. There are other considerations, in addition to cost, that make the chip-and-patch procedure preferable to saw-and-patch.

Maintenance of Flexible Pavements

• In terms of roughness, rutting, and fatigue cracking, the most effective of the four maintenance treatments investigated in the SPS-3 experiment (flexible pavement maintenance) is the thin (38-mm (1.5-inch)) AC overlay treatment, followed by the chip seal treatment, the slurry seal treatment, and then the crack seal treatment.
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• For the SPS-3 test sections, the thin (38-mm (1.5-inch)) AC overlay treatment is the only one of the four treatments (thin AC overlays, chip seals, slurry seals, and crack seals) under investigation that has shown a significant initial effect on rutting. Thin AC overlays also have the most significant effect on long-term rutting control.
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• In the SPS-3 thin overlay sections, age of pavement was the only one of the factors studied (traffic, climate, stiffness, thickness) found to be significantly correlated to the rate of rutting.
• In the SPS-3 crack sealed and chip sealed sections, average annual precipitation was the only one of the factors studied found to be significantly correlated to the rate of rutting.

Pothole Repair Treatment Performance and Repair Methods
Report No. FHWA-RD-99-168

• The two main elements of quality pothole patching in flexible pavements are material selection and repair procedures. For every combination of these two factors, the cost-effectiveness of the overall patching operation will be affected by material, labor, and equipment costs.

• Although pothole patches are intended to be temporary repairs, using the best materials available can provide patches that remain in service for several years and that reduce the need for re-patching.

Report No. FHWA-RD-99-143

• The most cost-effective treatments for crack seals are usually those consisting of rubberized asphalt placed in a standard or shallow-recessed band-aid configuration. The standard recessed band-aid method showed the longest estimated service life, followed very closely by the shallow recessed band-aid method.
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• For long-term crack-seal performance (5 to 8 years) under the condition where a 2.5 to 5.0 mm (0.1 to 0.2 inches) of horizontal crack movement occurred, a modified rubberized asphalt sealant should be installed in either a standard or shallow recessed band-aid configuration.

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