BEHAVIOR AND PERFORMANCE OF UTW ON THIN ASPHALT PAVEMENT

Abstract

During the 1999 spring, two sections of ultra-thin whitetopping (UTW) were built in an urban street in São Paulo City over a thin 45 mm asphalt layer. The UTW was constructed at a bus stop within the University campus, defining two panels of squared 0.6 and 1.0 m and 95 mm slabs. A high strength concrete was applied and the test sections were fully instrumented with top and bottom thermal resistors and strain gages. The instrumentation allowed the analysis of temperatures and thermal gradients on slabs as well as the curling deformation induced by these gradients. Temperature measurements showed daytime thermal gradients up to 11.7o C and nighttime gradients up to –4.2o C. Concrete stresses due uniquely to curling reached very low values in all seasons and were deemed negligible. Open to traffic since November 1999, 19 months later no cracks or faulting were observed on UTW sections submitted to a daily traffic of 120 buses and trucks making it possible, on the basis of measured flexural stresses on slabs, to predict a good performance of the UTW even over a thin 45 mm asphalt layer once no distresses have been verified as yet.