Abstract
Petrography is a microscopy method providing a revealing view of inorganic materials. Hydraulic cements rarely react completely and telltale residuals are detected by the petrographer. Combined with accurate chemical analysis, the petrographic examination not only identifies the original components but often allows for a quantitative assessment of material proportions. Such data are crucial for the proper conservation and rehabilitation of historic masonry structures. Portland cement, lime, and natural cement in any combination may be present in historic American masonry construction. A comprehensive petrographic examination serves as the basis for the successful creation and implementation of an historically accurate project specification. This paper provides insight into how various binders are properly distinguished. While technical data will be offered, the goal is to provide the architect or conservator with a general understanding of the methods employed by the petrographer and to demystify the often complicated mortar analysis report.
