Ten Years of Good Performance of Ultra-Thin Whitetopping Experiment in Brazil – Summary of Main Learnings

During the 1999 spring, two sections of ultra-thin whitetopping (UTW) were built in an urban street at a bus stop within the University of São Paulo campus, over a thin 45 mm asphalt layer. The UTW was constructed, defining two square panels of 0.6 and 1.0 m in size and a slab thickness of 95 mm. A high strength concrete was applied and the test sections were fully instrumented with top and bottom thermal resistors and strain gages. Temperature measurements in slabs indicated daytime thermal differentials up to 11.7oC and nighttime thermal differentials up to – 4.2oC. Concrete stresses due uniquely to curling reached very low values in all seasons and were deemed negligible. Open to traffic since November 1999, 10 years later no cracks or faulting were observed on UTW sections subjected to daily traffic of 120 buses. This paper aims to bring more details and practical insights learnt along ten years of excellent performance of such an experimental UTW. These details comprise thermal differentials, thermal stresses, fatigue and permeability of the high strength concrete and mechanical responses of the pavement structures.