Seismic Retrofitting of Corroded Reinforced Concrete Columns Using Ultra-High-Performance Concrete Jacketing

This paper investigates the efficacy of ultra-high-performance concrete (UHPC) jacketing as an option for seismic retrofit (repair or strengthening) of structural components that have been damaged by reinforcement corrosion. Previous work has illustrated that UHPC cover fully mitigates corrosion in the absence of service cracks and significantly reduces the corrosion rate in the case of preexisting cracks. In the present experimental study, cover replacement by UHPC is used to repair and strengthen corroded columns. Six lap-spliced columns designed based on pre-1970s design standards were constructed and subjected to artificial corrosion. Parameters of the investigation were: a) the aspect ratio of the specimens; b) the bar size (to account for the effect of bar diameter loss on bond); and c) the condition of the specimen (repair or strengthening after damage due to application of simulated seismic load to assess the effectiveness of retrofitting corroded components, even after having endured earthquake damage). The results show that thin UHPC jackets replacing conventional concrete cover suffice to impart a significant increase in strength and ductility of the columns. The jackets also endow the corroded and unconfined lap splices with significant force and deformation development capacity, thus alleviating a source of excessive column flexibility in existing construction.