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This report presents the initial performance of the Woodland SR 113 thin concrete overlay on asphalt (COA) project built in 2018-2019.The project comprises approximately four miles of a two-lane highway. The COA had 6 ft. transverse joint spacing, a slab thickness of 6in., and an asphalt base that was overall in very poor condition. The performance of the project between the date of construction andOctober 2020 is presented in this report. The performance was evaluated by different means, including periodic visual inspections andlongitudinal profiler evaluations; falling weight deflectometer (FWD) testing; real load testing (RLT), where the concrete strains undertruck loading were recorded; and continuous monitoring of slab temperatures and drying shrinkage deformations. Overall, the projectperformed as expected. Visual inspection of the COA did not indicate any cracking, faulting, or other structural distress. FWD and RLTevaluations indicate that the COA structure has remained stable since the construction. While the smoothness varied considerably during the period evaluated in this report, the variation was caused by changes in slab curvature due to thermal gradients through the slab depthand concrete drying shrinkage.

This report documents the design and construction of a concrete overlay on asphalt (COA) pavement on State Route 113 in Woodland, California, one of the first COA projects in the Caltrans road network. The project site extended over approximately 4 mi. of a two-lane secondary road. The concrete slabs were a half-lane wide (6×6 ft.) and 6 in. thick. The transverse joints were undoweled, but tie bars were installed at all the longitudinal joints. The outside slabs were 2 ft. wider than the interior slabs to provide a concrete shoulder. The project included a section with newly placed, rubberized, gap-graded asphalt mix base. A rapid-strength concrete mixture with Type II/V portland cement designed to be opened to traffic in 24 hours was used for construction of the overlay. The northern part of the project (PM 14.760 to PM 17.580) was built in October and November 2018, while the southern part (PM 11.860 to PM 12.890) was built in April and May 2019. The concrete mixture was produced in a fixed plant and transported in ready-mix trucks 25 mi. to the construction site. A slipform paver was used to consolidate and finish the concrete. A number of the quality control/quality assurance (QC/QA) tests and evaluations summarized in this report were conducted before, during, and after the construction of the concrete overlay. These QC/QA tests and evaluations revealed no major design or construction issues with the concrete overlay, but they did show that the condition of the asphalt base was very poor, particularly in the northern part of the project.

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.