Hygrothermal properties of historic bricks: An international characterisation and correlation analysis

This paper shows some preliminary results of an international collaboration, set up with the aim to compile a large worldwide dataset of hygrothermal brick and mortar properties. Currently, the work focuses on brick properties and includes data from Belgium, China, Ireland, Italy, the Netherlands, UK and USA. The study includes information on the variety in porosity, density, capillary and saturated moisture content. For some countries also the thermal conductivity is shown. Correlations between the bulk density and the other properties are evaluated. A clear correlation is found between bulk density, porosity and saturated moisture content. As for the capillary absorption coefficient and thermal conductivity, the correlation with the bulk density is less pronounced. Though, overall, a high bulk density suggests a low capillary absorption coefficient and a higher thermal conductivity. Finally, the dataset is compared with the database of the hygrothermal software Delphin. The measured properties in our dataset show more extreme values than found in Delphin. The work is extremely valuable in the heritage context, as in this context the number of samples for hygrothermal property characterisation is often scarce and in many cases only samples with small dimensions are available. The correlations achieved within the study are of interest for practitioners to get a first idea of the hygrothermal properties, which is of outmost importance to make hygrothermal assessment and modelling studies more reliable.