Ultra Thin PCC Overlays, HR-559, Construction Report, 1995

A 11.6 km (7.2 mi.) portion of IA 21 in Iowa County from the junction of US 6 north to the junction of IA 212, was selected for the research project. The project was divided into 65 different test sections of a PCC overlay of an existing asphalt concrete (AC) surface with thicknesses of 50 mm (2 in.), 100 mm (4 in.), 150 mm (6 in.), and 200 mm (8 in.). The joint spacings for these sections were 0.6 m (2 ft.), 1.2 m (4 ft.), 1.8 m (6 ft.), 3.7 m (12 ft.), and 4.6 m (15 ft.). Joints were sealed if the thickness of the pavement was over 100 mm (4 in.), unless specified. Two types of polypropylene fibers, monofilament and fibrillated, were added to the conventional PCC mix for designated sections. Three additional sections consisted of an asphalt overlay for comparison with the concrete overlay. Three different base preparations were used on the project, consisting of: patching and scarifying, patching only, and cold-in-place recycling. Sensors were placed in various test sections to measure the temperature and strain during and after construction of the overlay. Pullout tests were also conducted at various locations. Beams cylinders were made for each of the PCC mixes and tested for flexural and compressive strengths. Evaluation of the performance will be conducted through December 31, 1999.