NSAR in Concrete Slabs

June 29, 2008
Publication: Concrete Construction p 15-17
Author(s): Matthew Sherman Dennis J. Pinelle Mauro Scali

Over the years, we have had a number of call-backs on projects where our epoxy coating applications had developed fluid-filled blisters. When we had these problems investigated, we found that osmosis was most likely the cause. Lately, a number of the forensic experts who have viewed similar troubled projects have suggested that alkali silica reaction (ASR) in the near-surface region of the concrete could be the cause of the blistering. Conventional understanding has always dictated that when potentially reactive aggregates are present, ASR should take many years to develop. Yet these blistering conditions have developed in a relatively short period of time. Can ASR develop in the near-surface region of a concrete slab and contribute to the blistering of polymer coatings applied to a concrete slab surface?