Hamburg Wheel-Tracking Database Analysis (0-1707-7)

This report outlines statistical analyses done to investigate whether the Hamburg wheel-tracking device (HWTD) can be used to validate durability tests such as the magnesium sulfate soundness (MSS) and Micro-Deval tests. Researchers manipulated and merged the Hamburg test database and aggregate properties database of the Texas Department of Transportation (TxDOT) to provide the basis for statistical analysis. The Qualitative visual examinations of plots of aggregate properties and Hamburg wheel-tracking device performance, based on soundness resistance, suggest that MSS and Micro-Deval tests do not correlate well with Hamburg tests results. However, single variable correlations between aggregate properties and Hamburg test performance indicate that both soundness and Deval tests have weak correlation with Hamburg test performance in that appropriate trends could be observed with final Hamburg results (deformation or number of wheel passes). These findings suggest that aggregate durability has some influence on the performance of the bituminous mix in the Hamburg test. The effects of aggregate, binder grade, mix type, and additive on HWTD results were also evaluated. The HWTD test parameters investigated included rutting, slope of the rutting curve, and the area beneath the rutting curve at specific cycles. Based on the results of the analysis, it was observed that the dominant factors influencing Hamburg test performance are those that stiffen the mix, particularly stiffer performance grades (PG) and additives such as lime.