Determining in-place concrete strengths is particularly important for the seismic evaluation of existing buildings. Underestimating the concrete strength in a seismic rehabilitation design by adopting a lower-bound estimate of the in-place concrete strength can undervalue component resistances, potentially triggering inappropriate rehabilitation solutions. The objective of this article is to review assessment requirements and guidelines and identify ways of setting core sampling requirements appropriate for seismic evaluation. Recommendations are based on a review of statistical methods to select sample size for an acceptable error level and assessment of outlier data.

During the construction of a wastewater treatment facility in 2007, the wet wells and other basins were coated with a coal tar epoxy. Within a year and a half after commissioning, the plant operators noticed that the coating was delaminating from the walls of several clarifier wet wells. Yet, inspections of the clarifier basins showed no coating failures. This article presents a field and laboratory investigation of coating deterioration as well as repair recommendation.