Engineering properties of historic brick – variability considerations as a function of stationary versus nonstationary kiln type

Brick produced prior to the mid-twentieth century exhibit high levels of variability in appearance, geometry, and mechanical properties. Understanding historic brick variability is important for accurate performance prediction of existing structures, and for the selection of appropriate replacement units. A lack of uniformity amongst historic brick can be caused by the molding and firing methods, as well as the composition of their raw materials. This paper focuses on one aspect of production-induced disparities: kiln type. Tremendous variance can be shown from this alone, between both kiln type and even within a single firing. Although kilns of past eras were constantly improved for energy efficiency, their products continued to be highly inconsistent in appearance and performance. This paper presents the mechanics of heat distribution in kilns and demonstrates its direct impact on the variability of engineering properties due to inconsistent heat application.