Nondestructive Evaluation: Structural Performance of Masonry

Masonry is one of the world’s most durable construction materials. Masonry structures can remain in service for hundreds or even thousands of years. Masonry structures often outlive their designers, their original design documents, and their original functions. When historic masonry structures are evaluated for preservation, adaptive use, or additions, there are numerous questions that may arise about the construction and the condition of the brick, stone, concrete block, and mortar. One of the first questions typically asked by the design or investigation team is “How is it performing?” It is important to understand observed distress, such as cracks, corrosion, and surface erosion. Often the cause and/or extent of distress can play a major role in rehabilitation work and in determining what other types of nondestructive evaluation are required. Another common question about masonry is “How strong is it?” In order to conduct a structural evaluation, an engineer must have at least some information about the strength of the masonry. A related question often asked next is “How was it constructed?” Masonry characteristics such as ties, voids, headers, and embedded items are often hidden from view, but these items are critical to understanding how the assembly will perform. Finally, in some cases it is important to ask “What is it doing right now?” It can be vital to understand what types of loads and stresses the masonry is currently experiencing, especially in order predict future performance under new or different loads. Other questions regarding moisture permeability, acoustic properties, or thermal behavior of masonry may also arise. This Practice Point focuses on these fundamental questions by providing a summary of current nondestructive-evaluation tools available for the assessment of historic masonry. While case studies and descriptions of specific nondestructive test methods are fairly common, this article provides an overview of numerous techniques, both listing the technologies available and helping in the selection of an appropriate method. A wide range of evaluation methods are available for use, and many claims are made regarding the accuracy of Practice Points NUMBER 09