Diagnosis and Prognosis Assessment of an Alkali-Silica Reaction (ASR) Affected Bridge Structure in Montreal

The footings of a bridge structure crossing the St. Lawrence River in Montreal were subjected to a diagnosis and prognosis study for ASR. The Damage Rating Index (DRI) and the Stiffness Damage Test (SDT) were used to evaluate the damage in the footings while the expansion tests on concrete cores (>95% R.H. at 38 ℃) and the water-soluble alkali content test were used to establish their expansion potential. Two types of concrete were identified in the footings. Even though both concretes showed extensive damage, higher damage was found in Concrete B with both the DRI and SDT results. Both concretes showed a similar (high) expansion potential even though a much higher water-soluble alkali content was measured in Concrete A. The lower damage and the higher water-soluble alkali content in Concrete A are due to the presence of a significant proportion of non-reactive volcanic rock type in the coarse aggregate. It is believed that an alkali-rich (feldspathoid) mineral in the volcanic rock type in the coarse aggregate of Concrete A has contributed to the high water-soluble alkali content measured on that concrete.