I designed a reinforced masonry wall with instructions that the grout be mechanically vibrated. The contractor wanted to consolidate the grout by puddling instead. I agreed that this was acceptable so long as the reinforcing bars were in place when the grout was placed and that a separate bar be used for puddling. Later I learned that the contractor had poured the grout, then puddled using a bar that was then left in place as part of the reinforcement. There are bar positioners in the block cells, and the contractor assures me he got bars into all the positioners. I am not confident, though, that the bars are in the right place or that the consolidation is adequate. Some of the walls are designed close to their real strength (not overdesigned). How can I be sure that the rebars are in place and the grout is consolidated?

The position of the reinforcement can be determined with a metal detector. There are several types of metal detectors available. Some metal detectors can be used to estimate the depth of the reinforcing if the diameter of the bar is known. After locating the bars, you can confirm the size of the reinforcing by making exploratory openings. Determining whether the grout has been properly consolidated is more difficult. There are several nondestructive tests available, including pulse echo, impact echo, ultrasound, and x-ray. These methods are rather expensive, though, for verifying consolidation over the entire wall surface. We have had reasonable success finding voids in grouted concrete masonry using a sounding hammer to locate voids and then confirming these voids by drilling a small hole. With this approach, it is also important to make some openings by removing face shells to confirm your findings.