Roger Green

Long-Term Performance of Broken and Seated Pavements

A study was developed to evaluate the effectiveness of breaking and seating (B/S) as a rehabilitation strategy for retarding reflective cracking in asphalt concrete (AC) overlays on jointed reinforced concrete pavements (JRCP). Several test sections were constructed by milling the original AC layer, breaking and seating the concrete slabs, and constructing new AC overlays. Control sections were constructed adjacent to the B/S sections in the same way, but without breaking the underlying concrete slabs. Two types of pavement breakers were used in this study: guillotine and pile hammer. The majority of the concrete slabs were broken into 0.46-m (18-in.) segments. Performance of the test sections was monitored for a total period of 9 years. Breaking the concrete slabs into smaller pieces resulted in a reduction in the flexural strength, an increase in the surface deflection (50% to 100%), and a decrease in area and spreadability (20% to 30%). Within 2 to 4 years, reflection cracks developed over more than 80% of the joints in all the control sections. The B/S sections were relatively free of cracks after 9 years. This result clearly indicates that breaking and seating has been extremely effective in minimizing and delaying reflection cracking. Based on the results of this study, it was concluded that breaking and seating is an effective technique for the rehabilitation of composite pavements (AC over JRCP). It provides an effective solution for the maintenance and rehabilitation of in-service composite pavements.

INSTRUMENTING OHIO TEST PAVEMENT

The Ohio Department of Transportation (ODOT) constructed a test pavement on US-23 in Delaware County, Ohio. Of the nine Specific Pavement Studies (SPS) formulated by the Strategic Highway Research Program (SHRP), four (SPS-1, SPS-2, SPS-8, and SPS-9) were included at the OH-SHRP DEL-23 site. Sensors were carefully selected and installed to monitor structural response and seasonal parameters on the basis of prior field experiences accumulated in the United States and Canada. Criteria used to select the sensors were cost, accuracy, sensitivity, longevity, and level of success in previous pavement research projects, especially projects in Ohio. Described here is the development of the Ohio test pavement in terms of objectives, overall instrumentation plan, and selection of sensors as well as typical instrumentation plans for asphalt concrete and portland cement concrete sections.

Rutting resistance of asphalt mixes containing highly modified asphalt (HIMA) binders at the Accelerated Pavement Load Facility in Ohio

Highly modified asphalt (HiMA) mixes have been proposed as a stronger alternative to standard asphalt concrete mixes that will enable thinner perpetual pavements in Ohio. HiMA uses a polymer-enhanced binder has a higher unit cost, but has the potential to reduce the thickness of perpetual pavements, resulting in savings compared to conventional HMA perpetual pavement projects. Test sections containing HiMA in the surface, intermediate, and base layers were constructed with total thicknesses of 20, 23, and 25 cm, created by varying the depth of the AC treated base, in the Accelerated Pavement Load Facility (APLF) at Ohio University in Lancaster, Ohio. An additional 28 cm section was installed as a control with a non-HiMA base layer and HiMA surface and intermediate layers to compare with the experimental sections. Each pavement was subjected to 10,000 passes with a single axle load of 40 kN while the pavement was held at each of two pavement temperatures of 21.1 and 37.8 °C. Rutting on the surface of the pavement was measured using a rolling wheel profilometer after 100, 300, 1000, 3000, and 10,000 wheel passes at each temperature. The four sections showed no significant rutting damage after being subjected to a total of over 20,000 passes, and remained well below ODOT’s “low rutting” threshold of 3.2 mm. Extrapolating the rutting data indicated the worst-performing section would reach the low rutting threshold after more than a million passes of the load. The rutting data were compared to those obtained in a previous perpetual pavement study in the APLF that had surface courses including Aspha-min warm mix asphalt and a conventional hot mix asphalt, which crossed the low rutting threshold well before 10,000 passes at the high temperature.