Development of Improved Guidelines and Designs for Thin Whitetopping: Construction and Initial Environmental Response of Full-Scale BCOA Sections

Thin bonded concrete overlay of asphalt (BCOA) is a rehabilitation alternative consisting of a 100 to 175 mm (0.33 to 0.58 ft) thick portland cement concrete (PCC) overlay of an existing flexible or composite pavement. Fifteen BCOA sections were built at the Davis facilities of the University of California Pavement Research Center in February 2016. Eleven of these full-scale sections were tested under accelerated loading, while four of them were used for monitoring the response of BCOA to the ambient environment and cement hydration. This full-scale experiment is part of a research project whose primary goal is to develop recommendations and guidance on the use of thin BCOA as a rehabilitation alternative in California. The design and construction of these sections is presented in this report, together with results from the quality control/quality assurance testing that was conducted. This testing was focused on the four early high-strength mixes that were used in the construction. The concrete mixes included Type II/V and Type III portland cements and calcium sulfoaluminate cement, and they were designed to provide 2.8 MPa (400 psi) flexural strength after either 4 or 10 hours. Concrete overlays were built either on top of old asphalt pavements that had been tested for another research project or on top of a new gap-graded rubberized hot mix asphalt (RHMA-G) layer. Three slab sizes were built: 1.8x1.8 m (6x6 ft), 2.4x2.4 m (8x8 ft), and 3.6x3.6 m (12x12 ft). This report also describes the instrumentation of the sections and evaluates the engineering reasonableness of the initial data collected by the sensors up to August 2016. There are no recommendations presented in this report. Recommendations regarding implementation of BCOA will be included in the final report of this project.