Effect of sorption capacity on thermo-mechanical properties of unfired clay bricks

• Unfired clay bricks have a significant sorption capacity.
• Soils properties affect the hygroscopic capacity of unfired clay bricks.
• Thermal conductivity increases with the moisture content of earthen materials.
• Sorption capacity introduces a negative impact on mechanical and thermal properties.
• The sorption capacity improves slightly the thermal capacity.

The present work aims at studying the effect of sorption capacity on mechanical and thermal properties of three types of unfired clay bricks. They were industrially produced by the Briqueteries du Nord, a factory located in the north of France. This study has demonstrated that these green materials have a high sorption capacity, compared to other building materials such as concrete block or fired clay bricks. In fact, the moisture content of unfired clay bricks reached 3.5% at 95% of relative humidity. This quality of earthen materials enabled to balance the indoor building climate by adsorbing or releasing moisture according to changes in the relative humidity of the ambient air. This advantage however causes a decrease on compressive strength and thermal resistance of unfired clay bricks. An identification of physico-chemical properties of soils was done in this work to study the sorption capacity and its impact on brick properties.