Title: Managing ASR and DEF in Concrete Bridge Columns
Author(s): Mark E. Williams
Publication: Symposium Paper
Appears on pages(s): 101-112
Keywords: alkali-silica reaction (ASR), delayed ettringite formation (DEF), concrete bridge columns, premature concrete deterioration
In recent years concrete bridge structures in the USA have been experiencing varied levels of premature concrete deterioration due to alkali-silica reaction (ASR) and related condition delayed ettringite formation (DEF). While these deleterious reactions can affect various concrete bridge members under the right conditions, bridge columns can be notably more susceptible due to their unique exposure conditions and aggressive environments. The degree of deleterious reactions in concrete bridge columns is dependent on susceptibility of the aggregate, and on environmental factors, such as temperature, moisture, and external sources of alkalis. Temperature gradients are known to affect the rate and severity of the ASR expansion. Moisture gradients can be facilitated by high atmospheric humidity, exposure to weather, proximity to water spray from adjacent roadways, malfunctioning joint systems, and/or failed drainage systems, which collectively can provide sufficient conditions for ASR and DEF expansion. This paper suggests that a review of the aggressive environmental conditions at the bridge site can provide valuable insight into the occurrence and progression of premature concrete deterioration and provide direction as to a future course of action for maintenance and repair for concrete bridge columns. Repair procedures are provided dependent on the severity of premature concrete deterioration.