Principles of computerised X-ray tomography and applications to building materials

This paper reviews the physical principles of conventional X-ray radiography and computerised X-ray tomography (CT). It also mentions the various instrumentation and calibration techniques, and illustrates the power of CT with examples of applications of non-destructive research in the field of geology and material characterisation (scanning of core material, correlation of cores with well logs, measurement of compressibility and compaction, multiphase fluid or gas flow experiments, measurement of bulk density and moisture content, porosity and permeability studies, and sedimentary structures). The paper exemplifies the applicability of the CT-method for the study of building materials by characterisation of a Belgian porous calcareous sandstone of Middle Eocene (Tertiary) age, and an Italian metamorphic non-porous Carrara marble. Technical problems like sample positioning, tomographic density value error distribution and data transfer and conversion are discussed in detail.