Infrastructure Transportation Research Record 2019, Vol. 2673(2) 404–414 Ó National Academy of Sciences: Transportation Research Board 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0361198119825645 journals.sagepub.com/home/trr Accelerated Testing of Full-Scale Thin Bonded Concrete Overlay of Asphalt Angel Mateos 1 , John Harvey 2 , Fabian Paniagua 2 , Julio Paniagua 2 , and Rongzong Wu 2 Abstract A research study was conducted with the goal of determining the expected performance life of thin bonded concrete overlay of asphalt (BCOA) in California. Eleven thin BCOA sections were built and tested with the Heavy Vehicle Simulators (HVS) in Davis, California. The performance of the sections in the HVS testing provided insight into the mechanics of the thin BCOA structures and the effects the different rapid-strength concrete materials, traffic, jointing, and base factors on their performance, including testing in both very wet and very dry conditions. Overall, the performance of the thin BCOA sections in the HVS testing was excellent. The eleven sections resisted the predefined HVS loading without cracking. In five of the sec- tions, that loading was equivalent to 6 million single-axle loads and included load levels more than twice the legal limit in California, channelized traffic at the shoulder edge of the slabs, and a continuous water supply that simulated flooded condi- tions. The main conclusion from this research study is that a well-designed, well-built thin bonded concrete overlay with half- lane width slabs placedon top of an asphalt base that is in fair to good condition can provide 20 years of good serviceability on most of California’s non-interstate roadways. Thin bonded concrete overlay of asphalt (BCOA), for- merly known as thin white topping, is a pavement rehabi- litation technique that consists of the placement of a 100–175 mm (4–7 in.) thick concrete overlay on an exist- ing asphalt pavement. Thin BCOA differs from conven- tional concrete overlay of asphalt in several ways, with the structural contribution of the existing asphalt acting as a bonded base being the most critical. In conventional overlays, the asphalt base is primarily intended to serve as a flexible, nonerodible base to provide support for the concrete slabs. In the conception of the thin BCOA tech- nique the asphalt base makes a greater contribution to the pavement’s bearing capacity by bonding to the con- crete to form a composite system where both layers work together to resist bending. While thin BCOA has been used on highways and conventional roads in several US states as well as in other countries for at least 20 years (1, 2), its use has been very limited in California. The interest in the use of this rehabilitation technique led the California Department of Transportation (Caltrans) to sponsor a research proj- ect, in 2014, with the primary goal of developing recom- mendations and guidance for the use of thin BCOA as a rehabilitation alternative for California based on the adoption of, and improvements to, the technology devel- oped in other US states. Thin BCOA technology has steadily improved since the mid-1990s and could be regarded as a mature tech- nique by the time the research presented in this paper began. However, there were still key gaps in knowledge of the technique that required further research, and the need existed to address some unique conditions for BCOA in California. Among the gaps found in the previ- ous research were the essentially unknown role and per- formance of the concrete-asphalt interface; the mechanics of the asphalt base, which was systematically oversimpli- fied in BCOA design approaches; and the lack of a BCOA faulting model (3). In addition to those gaps in knowledge, thin BCOA practice regarding important design features—such as slab dimensions, shoulder type, and the need for asphalt milling before placing the overlay—differed from state to state. Further research was also needed because the California climate, with its distinct seasons alternating between periods that are 1 University of California Pavement Research Center, Institute of Transportation Studies, University of California, Berkeley, Richmond, CA 2 Department of Civil and Environmental Engineering, University of California Pavement Research Center, University of California, Davis, Davis, CA Corresponding Author: Address correspondence to Angel Mateos: angel-mateos@berkeley.edu