Reflective Cracking Study: First-Level Report on the HVS Rutting Experiment

This report is the seventh in a series of first-level analysis reports that describe the results of HVS testing on a fullscale experiment being performed at the Richmond Field Station (RFS) to validate Caltrans overlay strategies for the rehabilitation of cracked asphalt concrete. It describes the results of the six HVS rutting testing sections, designated 580RF through 585RF, carried out on six different overlays. The test forms part of Partnered Pavement Research Center Strategic Plan Element 4.10: “Development of Improved Rehabilitation Designs for Reflective Cracking.†HVS trafficking on the first section (582RF) commenced on September 4, 2003 and was completed on the last section (583RF) on December 16, 2003. A temperature chamber was used to maintain the pavement temperature at 50°C±4°C. A dual tire (720 kPa pressure) and a channelized, unidirectional 60 kN loading configuration was used. Load repetitions to failure (12.5 mm) on each of the sections varied between 726 and 8,266. Findings and observations based on the data collected during this HVS study include: • The majority of the rutting occurred in the underlying DGAC layer. • The rutting was fairly uniform along the length of each test section. • Little or no deformation was measured in the base and subgrade materials. The ranking of rutting performance (keeping in mind that most damage occurred in the underlying DGAC layer) based on the number of repetitions to reach an average maximum rut depth of 12.5 mm, from best to worst was: 1. 90-mm AR4000-D (8,266 repetitions) 2. 45-mm MB4-G (3,043 repetitions) 3. 45-mm RAC-G (2,324 repetitions) 4. 90-mm MB4-G (1,522 repetitions) 5. 45-mm MB15-G (914 repetitions) 6. 45-mm MAC15-G (726 repetitions) No recommendations as to the use of the modified binders in overlay mixes are made at this time. These recommendations will be included in the second-level analysis report, which will be prepared and submitted on completion of all HVS and laboratory testing.