Identifying a masonry problem correctly is always the first step toward solving it. When troubleshooting an existing masonry structure, it is essential to understand the many investigative tools and techniques currently available before you can decide on the system that will both meet your objectives and stay within your budget.
A number of nondestructive evaluation (NDE) procedures have been developed for assessing masonry in place, many adapted from other fields such as concrete construction and mining.
As the most common cause of masonry performance failure, cracks must be taken seriously. To measure change in crack width over time, most investigators use a crack comparator, or visual crack gauge. To measure horizontal and vertical crack movement, consider using a two-piece crack monitor.
Before repairing or retrofitting an existing masonry building, it is necessary to know the loads applied to the masonry, its compressive strength, and its compressive deformability properties. Surface assessment tests, which show material property variations over large areas near the masonry surface, can be performed quickly and easily in place. Masonry shear strength, an important material property for resisting seismic and wind loads, is difficult to measure in place. Unreinforced masonry walls subjected to flexural loads can develop bed joint cracks because of tensile failure of mortar-unit bond. Pulse transmission techniques are among the most widely used methods for nondestructive evaluation.
Several additional techniques for evaluating masonry buildings in place are now available and are especially useful when wall access is limited, such as Impact-echo, Borescopic investigations, Infrared thermography, and Rebar locator.