Influence of Straw Incorporation on the Sorption Properties and Moisture Buffer Value of Plaster

¹ Applied Sciences Laboratory (LSA), National School of Applied Sciences (ENSAH), at Abdelmalek Essaadi University, M’hanneche II, Al Hoceima, 32000 Tangier North, Morocco
² Applied Sciences and Advanced Technologies - Higher School of Technology Nador, at Mohammed First University - BV Mohamed VI, Mohamed, Oujda, 60000, Oriental, Morocco

Abstract

This study investigates the influence of straw incorporation on the hygroscopic behavior of plaster-based composites for sustainable building applications. Two formulations were prepared using plaster with 0% and 3% straw content by mass in order to evaluate the effect of lignocellulosic fibers on moisture-related properties. Sorption tests were carried out under controlled hygrothermal conditions at relative humidity levels of 20%, 40%, 60%, and 80% using a climatic chamber. In addition, the Moisture Buffer Value (MBV) was determined according to the NORDTEST protocol to assess the ability of the materials to regulate indoor humidity fluctuations. The results showed that the incorporation of straw significantly enhanced the hygroscopic performance of the plaster composite. The equilibrium moisture content increased progressively with relative humidity for both samples, while the composite containing 3% straw exhibited higher moisture adsorption capacity at all humidity levels. Moreover, the MBV increased considerably from approximately 0.6 g/(m²•%RH) for the reference plaster to about 2.9 g/(m2•%RH) for the straw-based composite. These findings highlight the potential of straw-plaster composites as bio-based materials for passive indoor humidity regulation and improved hygrothermal comfort in buildings.