Natural fibers reinforcement for earthen building components: Mechanical performances of a low quality sheep wool (“Valle del Belice” sheep)

The paper proposes the use of Sheep wool fibers (SWF) deriving from the fleece of domestic sheep (“Valle del Belice” from Sicily) as reinforcement for rammed earth building components. Addition of natural fibers to the mix design of earth-based building materials allows to improve their tensile strength, ductility, impact resistance, toughness, and to reduce drying shrinkage. To this aim, an experimental campaign on more than 180 fibers has been carried out, determining the main mechanical properties of interest for their use as reinforcement. Since wool is highly hydrophilic, three different conditioning programs (wet, dry and an intermediate condition) were compared, in order to get useful information about the preservation of the mechanical properties in wet environments like those present in lime mixes. The dependency of the properties from the fibers’ diameter was investigated, and the results were statistically analyzed using a modified Weibull distribution as function of the fiber diameters, finding a strong correlation with the mechanical properties. The use of natural fibers as reinforcement could enhance the environmental sustainability of the building components, especially when natural fibers are obtained from agricultural wastes deriving from sheep of low-quality wool not used in the textile industry and that must be disposed of in landfills.