Materials Characterization

Want to know the original mortar composition so that you can make repair recommendations? Curious whether the specified mix was used in a new installation? Our scientists use ASTM C1324 to reverse engineer historical and modern mortars. We regularly encounter complex materials that require a comprehensive understanding of construction practice and history. Our staff also lecture and write on this subject. Currently, we are working on an appendix to ASTM C1324 that shares our extensive experience in historical mortars and their accurate analysis.

Behind an otherwise unassuming gray surface of all concrete lies a rich diversity of materials. Locked inside is evidence of the original construction and interaction of the concrete with the environment. We use petrography to identify rocks used for aggregate and observe whether they have reacted with the cement paste. We can see forensic evidence of excessive bleed, retempering, or overfinishing. By characterizing secondary phases and their spatial distribution we identify reactions such as aggressive carbonation or thaumasite sulfate attack.

Most construction materials contain microtextural or chemical evidence that we use to help determine their geographic sources or approximate manufacturing period. Trace minerals or microstructures we observe petrographically in building stone can assist in identifying a particular geological formation or even a quarry district. When routine mortar analysis cannot be used to distinguish periods of construction, we measure the concentrations of trace elements in the binder to connect samples to one another.

Petrography derives from the geological sciences, and the tools and approaches are effective for most building materials made from mineral resources. Sliced thinly enough, we can study the mineralogy and microtexture of brick, terra cotta, self-leveling compound, terrazzo, and many other mineral-based construction products. By preserving the microstructural context, we can investigate potential causes of any visible distress.

When inquiries about material composition or potentially damaging contaminants require specialized instrumental analysis, our scientists tailor the sample preparation and methods of analysis to address your specific questions. Through our partnerships with universities and research laboratories, we have access to numerous technologies including x-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), and pyrolysis gas chromatography/mass spectrometry (py-GCMS).

A salt study can be as simple as identifying an efflorescence on a new brick wall or as complex as generating a three-dimensional diagram of salt contaminants and concentrations in the structural masonry of a historic landmark. We use x-ray diffraction to identify assemblages of salt species either directly or through extraction. We use wet chemical techniques to quantify specific groups of salts such as chlorides, sulfates, and nitrates.