Performance of Ultra-Thin Bituminous Overlays

Ultra-thin bonded bituminous surface (UBBS or Novachip) is a preventive maintenance or thin surface treatment that consists of a thin, gap-graded hot-mix asphalt (HMA) layer applied over a thick polymer-modified emulsion layer. The Kansas Department of Transportation (KDOT) has been using UBBS since 2002 and some of these projects are now being rehabilitated. The main objective of this study was to evaluate the performance of UBBS projects in Kansas using distress data from the Pavement Management Information System (PMIS). It was found that pavements treated with UBBS showed high variability in service life with majority serving six years. Before and after (BAA) studies showed that UBBS reduces pavement roughness, transverse and fatigue cracking one year after the treatment. A sharp drop-off in effectiveness for mitigating transverse and fatigue cracking was observed after a couple of years in service. The analysis of variance shows that service life, cumulative traffic and existing pavement thickness are not significant determinants of progression of distresses.