The Identification of Corrosion-Related Damage from Cramp Anchors in a Limestone-Clad Building Facade Using NDE Techniques

A recent restoration project on a 100-year-old, limestone-clad building provided an opportunity to evaluate the efficacy of certain non-destructive evaluation (NDE) techniques in identifying corrosion-related distress of embedded cramp anchors. After decades of service, progressive corrosion of the anchors had caused limestone delaminations and spalls, and presented a life-safety risk when fragments of limestone became dislodged and fell from the facade. Adding to this risk, it became clear early in the investigation that for certain areas of corrosion damage, stone cracking was not apparent on the surface or was otherwise difficult to detect. In an attempt to identify these pre-emergent cracks and delaminations, a range of NDE methods was considered to supplement the traditional techniques of visual identification and sounding. Of the NDE techniques implemented (i.e., ultrasonic pulse velocity surveys, infrared thermographic scans), infrared thermographic scans proved to be the more effective diagnostic tool to locate pre-emergent cracking and delamination sites, and showed promise as an early detection technique for similar buildings.