Nondestructive testing of the concrete roof shell at the Seattle Kingdome

As part of major rehabilitation and repair of the 360,000 square foot reinforced concrete shell roof of the Kingdome in Seattle, a comprehensive nondestructive testing program employing Infrared Thermographic and Impact Echo techniques was performed to evaluate various insitu concrete conditions. Questions had developed regarding the extent and significance of areas that exhibited honeycomb or paste voiding near reinforcing steel on the underside of the roof shell following removal of acoustical ceiling tile. The objective of the nondestructive testing program was to identify locations of large, planar-type regions of deep voiding of delamination associated with the consolidation and reinforcement placement conditions. The combined use of Infrared Thermography and Impact Echo techniques allowed for efficient and effective scanning of the large roof shell structure entirely from the interior. Anomalous areas identified by the testing were verified by additional nondestructive testing, visual inspection, local exploratory openings and core samples. Based on results of the nondestructive testing, a broad-based repair program was implemented to correct conditions of near surface voiding and through-thickness honeycomb. Repairs consisted of the application of structural shotcrete to restore integrity in thickened, key load transfer zones of the shell and the overall treatment of the entire underside of the shell with sprayed mortar. This paper present an overview of Infrared Thermographic testing theories and discusses the specific applications, logistics, and results from testing of the concrete shell of the Seattle Kingdome.