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13.44 MATERIAL-SPECIFIC FORENSIC ANALYSES
FIGURE 13.36 Infrared thermogram showing masonry structure with grouted cells and ungrouted cells clearly
indicated. (Courtesy of Greg Stockton, Stockton Infrared Thermographic Services, Inc., Randleman, NC.)
thermogram showing grouted and ungrouted cells in a concrete masonry wall. Stockton 59
describes the technique.
Hardness testing of units and mortar are useful for comparing masonry at various loca-
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tions within a construction. Transue describe hardness testing of mortar.
Other nondestructive test methods for masonry include examination of facial separation
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cracks, low-frequency ultrasonics, gamma radiography, and pachometrics. Some of these
techniques may be very expensive and are frequently unnecessary.
Interviews
After site reconnaissance, the investigating engineer may conduct interviews with the
architect, engineer, and general contractor. In cases of structural collapse, interviews with
eyewitnesses and survivors may be useful. Meetings may be helpful with craftsmen
employed during the original construction of masonry as well as with the masonry con-
tractor and her or his foreman and superintendent. Without demolition or bore scope exam-
ination, no one better knows what is in the wall than the person who built it. The client’s
consent should be obtained for all such interrogations.
If craftsmen are to be interviewed, seek meetings with masonry foremen, working
masons, and mortar makers. Ask permission to tape-record the interview. Make written
notes of pertinent answers. Be informal in dress, speech, and conduct. Make small talk. Ask
about family, sports. Find something in common. Only one respondent and no more than
two interrogators should be present during the interview. The craftsman’s employer should
not be present. If answers are vague, pause and rephrase a question.
Document Discovery
If litigation is pending or is in progress, it may be advisable for the forensic engineer to read
all discovery documents relating in any way to masonry. This may include the following:
