Field Investigation of Spalling in Partial-Depth Precast Concrete Bridge Decks using Nondestructive Testing

This study involved field investigations of spalling in several partial-depth precast, prestressed concrete bridge decks through nondestructive testing. Ground penetrating radar (GPR) was used to assess the condition of concrete throughout the deck to identify areas of cracking and corrosion, as well as the condition of prestressing tendons in the precast, prestressed concrete panels. Particular techniques were used to identify areas of delamination at the interface between the panels and cast-in-place concrete topping. Core sampling and visual inspection were used to interpret and validate GPR data. Findings indicate that transverse reflective cracks at the panel joint locations played a key role in spalling. Combined data analyses showed that the spalling observed results from penetration of water and chlorides through reflective cracking in the cast-in-place concrete topping at the panel joints to the cast-in-place concrete topping and precast, prestressed concrete panel interface, then through the panels to the prestressing tendons. Concrete integrity increased with increased cast-in-place concrete topping reinforcement in the bridge longitudinal direction because such reinforcement serves as transverse crack control and thus delays the onset of spalling