FIELD INVESTIGATION FOR REHABILITATION OF SEVERELY DETERIORATED CRCP ON BAN-ETSU EXPRESSWAY IN JAPAN

A 7 km section of CRCP was constructed on the Ban-Etsu Expressway, which was opened in October 1990, in heavy snowy region of the Japan main island. Transverse cracks had opened wide and the crack spacing had become shorter just after 9 year service, resulting in punchout on the surface. The deteriorated part of the CRCP section had been repaired with the partial depth patching using SFRC and double layer asphalt overlay. However , the similar severe deterioration has appeared on the other parts of the section recently. Therefore, in 2018, comprehensive investigations including material tests, excavation of the slabs and joints, FWD tests and ground penetrator radar (GPR) survey were conducted to establish the rehabilitation strategy for the CRCP section. In the investigations, horizontal cracks were found at a depth of the reinforcement bar, which started from the transverse crack. Also, some extracted bars were severely corroded. The material tests revealed high chloride ion concentration in the upper part of the concrete slab. Based on those investigation results, it was assumed that the expansion of the corroded reinforcement bars initiated and developed the horizontal cracks at the position of reinforcement bars, which divided the CRC slab into two layers, resulting in severe punchout.