Jones, David, Bor-Wen Tsai, John T. Harvey (2008) Reflective Cracking Study: First-Level Report on HVS Testing on Section 590RF - 90 mm MB4-G Overlay. Institute of Transportation Studies, University of California, Davis, Research Report UCPRC-RR-2006-04
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 first HVS reflective cracking testing section,
designated 590RF, carried out on a 90-mm full-thickness MB4-G overlay. The test forms part of Partnered
Pavement Research Center Strategic Plan Element 4.10: “Development of Improved Rehabilitation Designs for
HVS trafficking on the section commenced on January 13 and was completed on June 16, 2004. A temperature
chamber was used to maintain the pavement temperature at 20°C±4°C. A dual tire (720 kPa pressure) and
bidirectional loading with lateral wander configuration was used. A total of 1,981,365 load repetitions, equating to
37 million ESALs and a Traffic Index of 14, was applied during this period. Findings and observations based on the
data collected during this HVS study include:
• No reflective cracking from the underlying severely cracked DGAC layer was observed on the MB4-G overlay
after almost two million HVS repetitions. The MB4-G overlay thus appeared to successfully prevent any
cracking in the underlying layer from reflecting through to the surface, despite final-to-initial deflections
indicating that considerable damage had occurred in the asphalt layers under loading.
• The average maximum rut depth across the entire test section at the end of the test was 12.7 mm, equivalent to
the Caltrans (and experiment) failure criteria of 12.5 mm. The maximum rut depth measured on the section
was 19.0 mm, with a maximum rut depth of 12.5 mm reached after about 1.17 million repetitions, soon after
the load increase from 60 to 90 kN.
• Ratios of final-to-initial elastic surface deflections under a 60 kN wheel load increased by between 1.9 and 3.0
times along the length of the section. The ratios for in-depth deflections show that damage increased at all
depth in the pavement structure (between 1.9 and 2.2 times) by the end of trafficking. Loss of stiffness was
highest in the area of most severe cracking in the underlying DGAC layer.
• Analysis of surface profile and in-depth permanent deformation measurements indicates that most of the
permanent deformation (between 67 [at MDD6] and 88 percent [at MDD10]) occurred in the asphalt-bound
surfacing layers (overlay and cracked DGAC) with marginal deformation in the base layer and negligible
deformation in the subgrade.
No recommendations as to the use of MB4-G 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