REPORT ON THE FIRST JACKSBORO MMLS TESTS

This report outlines the two accelerated pavement tests completed in Jacksboro, Texas, using the 1/3-scale Model Mobile Load Simulator (MMLS3). The MMLS3 tests were initially commissioned to investigate the stripping phenomenon evident under conventional trafficking of the outside lane adjacent to the TxMLS testing in the region. To achieve this goal, the MMLS3 was used in the field to test a pavement section on the northbound carriageway of US 281 near Jacksboro. During trafficking of the first MMLS3 test, water flowed over the pavement surface to accelerate the effects of stripping. Subsequent testing with the MMLS3 was used to investigate and compare the relative rutting of the 1/3-scale machine to that of the full-scale TxMLS without the use of water. In addition to the technical goals described, further development of the prototype MMLS3 was of particular interest. The mean combined operational productivity of the MMLS3 for the wet and dry tests was 79%, 13%, and 8% for run, maintenance, and data collection time, respectively. For both the wet and dry tests, data collection included hourly asphalt layer temperature monitoring, frequent transverse surface profiling, Surface Analysis of Spectral Waves (SASW) analyses, and relative asphalt surface deformation measurements. It was found that the temperature gradient of the asphalt concrete layer with water flowing over the surface (the wet test) ranged from 24 deg C to 27 deg C. For the dry test, the gradient ranged from 33 deg C to 38 deg C. The SASW modulus ratios (trafficked versus control sections) determined at the termination of the wet and dry MMLS3 tests were 38% and 90%, respectively, indicating that the asphalt surfacing (overlay) on the northbound carriageway of US 281 is potentially susceptible to moisture damage. For this reason, additional wet MMLS3 testing is recommended on the southbound carriageway of US 281 to ascertain whether this overlay is also susceptible, given that it performed relatively well under dry conditions.