3D documentation and analysis of porosity in deteriorated historic brick

April 22, 2020

Chandra L. Reedy - Center for Historic Architecture and Design, University of Delaware, Newark, DE, USA

Studies in Conservation, 22 April 2020. DOI: 10.1080/00393630.2020.1752426


Porosity; Micro-computed tomography; Micro-CT; Thin-section petrography; 3D image analysis; Historic brick; Pore systems; Thin sections


Bricks used in historic built heritage were often fired to a lower peak temperature than modern bricks, so tend to be porous and susceptible to deterioration. Long term exposure in an outdoor environment gives many deterioration mechanisms (moisture infiltration,crystallization and movement of salts, atmospheric pollutants,oil spills, polluted floodwaters, etc.). Better methods of imaging and quantifying pore structures and networks can help conservation practitioner sassess and document the depth and extent of deterioration before and after treatment and indicate the most appropriate treatment choices by highlighting potential avenues of future deterioration.This paper explores the use of high-resolution micro-computed tomography (HR micro-CT), extended with 3D image analysis, to enhance characterizations of pore systems in historic brick including overall porosity,range of pore size and shape, degree and type of pore network connections, and distribution patterns of pores including variation from surface to interior. This work builds on porosity studies by 2D thin-section petrographic image analysis. A next logical step is to extend 2D capabilities to 3D by incorporating HR micro-CT. This provides better characterization of the distribution of pores of various sizes and shapes and makes the nature of pore networks available for transport more visible, while the 2D thin-section petrography permits identification of the phases present. Examples are shown of how the 3D images can highlight location of pores within the brick matrix, as well as comparing the location of large-volume pores versus small ones. Results are discussed in relation to standard methods of porosity analysis.

How Our Software Was Used

Dragonfly was used for processing the results of HR micro-CT on deteriorated historic brick samples.