Estimating Expansion in Aged Structures Using Visual, Non-destructive and Microscopic Techniques

Internal swelling reactions (ISR), such as the alkali-aggregate reaction, are an ongoing threat to concrete infrastructure. ISR can cause significant reductions in the mechanical properties of the concrete such as reductions in compressive/tensile strength and stiffness at relatively low expansion. Visual assessment, including the use of the cracking index (CI), is useful in assessing structures affected by ISR. However, determining the diagnosis (cause and extent of deterioration) of a concrete affected by ISR relies heavily on assessment of cores extracted from the structure using microscopic (i.e. the damage rating index - DRI) and mechanical (i.e. the stiffness damage test - SDT) assessments. In this work visual, non-destructive, microscopic and mechanical assessments are utilized on two elements from a reinforced concrete structure constructed in the early 1960’s. The two elements represent a variety of exposure conditions: a pier cap which was exposed to chlorides with the east side in close proximity to a water body, and the dry and semi-submerged sections of a pier shaft which is located in the waterbody. Data collected from visual, non-destructive testing and assessment of cores suggests high damage with the presence of mixed mechanisms, the alkali-aggregate reaction, freeze-thaw, and reinforcement corrosion.