CHAIN DRAG

Well, it's as simple as it sounds. In order to identify areas of hollow sounding delaminated concrete, a chain is dragged across the surface of the concrete. An inspector, who drags the chain, delineates these hollow areas in order to map out the limits of each delamination, typically for future repairs. This practice is historically considered as the accepted practice for assessing the condition of concrete bridge decks without asphalt overlays. With some training, chain drag can be performed by most able-bodied workers... However, there are drawbacks to this traditional means of concrete evaluation. In the application of bridge deck evaluation, chain drag testing requires a lane closure and disruption of normal traffic patterns. Depending on the size of the deck and the number of inspectors performing chain drag, these closures could last for a significant amount of time. Lane closures are expensive and can cause major traffic delays... There is also the question of the accuracy..