Schmidt hammer rebound hardness tests for the characterization of ancient fired clay bricks

This article presents results of non-destructive Schmidt hammer tests performed on ancient fired clay bricks sampled from historical masonry. These tests were carried out in order to evaluate, and compare, the different degrees of degradation, depending on the bricks’ specific exposures and locations within a wall. The results indicate that this technique is sensitive enough to distinguish sample locations and measure weathering differences, even for different surfaces of a particular sample. For each case study, referenced surfaces were tested for bricks from a facade or interior wall. Each surface was tested with a Schmidt hammer type LB at ten different points of measurement, and these measurements were repeated ten times. For each impact at a particular point, a mean rebound value was calculated to provide an index of the degree of brick-surface microweathering.