Advanced investigation of water sorption isotherms measured on raw earth construction blocks

Abstract This study offers a detailed analysis of water sorption isotherms in raw earth materials, which are increasingly recognized as sustainable alternatives to traditional building materials. The water retention behavior of Compressed Earth Blocks (CEBs) was examined under steady-state conditions using sorption isotherms, which do not fully capture transient moisture buffering performance at the building scale. In this context, we focus on their ability to adsorb and desorb moisture as a measure of their potential to help control indoor humidity. The Dynamic Vapor Sorption (DVS) device was employed to compare the adsorption and desorption isotherms of 1 cm 3 cubic samples and powder fragments (2650 mg) of CEBs. Several factors were also investigated, including temperature (15, 23, and 35 °C), repeated wet/dry cycles, and the effects of time on sorption behavior. Using appropriate isotherm modeling, the isosteric heat of water sorption was calculated for the CEB. Results indicated that cubic samples adsorbed up to 23% more water than powder fragments, highlighting the significance of sample form in assessing hygric properties. Three consecutive adsorption/desorption cycles did not significantly affect the adsorption capacity, whereas higher temperatures led to decreased moisture uptake. Remarkably, even after nine months, the CEB’s adsorption and desorption performance shifted only slightly. The isosteric heat was 56.9 kJ.mol −1 . These findings demonstrate that CEBs have stable and effective moisture buffering abilities, making them promising materials for enhancing indoor environmental quality in sustainable construction. Understanding the effects of sample state, cycling, temperature, and time is crucial for accurately evaluating their hygric performance.