Comprehensive Condition Assessment of ASR Affected Pier Cap and Pier Shaft from Montreal's Champlain Bridge

Abstract

Alkali-Silica Reaction (ASR) is amongst the most harmful damage mechanisms affecting concrete infrastructure in Canada and worldwide. Among ASR affected structures in Canada the Champlain Bridge (CB), a six-lane highway bridge which crossed the St. Lawrence River and St. Lawrence Seaway in the province of Quebec, is a prime example with deterioration leading to closure of the bridge in 2019 after only 57 years in service. During decommissioning of the CB, a number of sections from its structural members (i.e., pier shaft – PS, pier cap – PC) were stored for further coring and analysis. This work presents a comprehensive investigation of an ASR affected PC and PS from the CB including a thorough external appraisal (i.e., comprehensive visual inspection and non-destructive testing) accompanied by laboratory investigation of extracted concrete cores using a multi-level assessment protocol (i.e., microscopic and mechanical test procedures). Microscopic investigations were conducted primarily using the damage rating index and supplemental image analysis while mechanical assessment was conducted through resonant frequency, the stiffness-damage test and compressive testing. This assessment identified ASR as the primary damage mechanism with cores exhibiting high to very high levels of deterioration in both members. Image analysis identified distinct crack orientations in extracted cores corresponding to expected expansion occurring preferentially to the least restrained directions of both the PC and PS members. Finally, a strong correlation between microscopic damage features and mechanical performance of the affected core specimens was observed; induced deterioration was found to be strongly associated to direction, depth and environment of the specimens.