Tensile Properties of Straw Fibres for Rammed Earth Reinforcement

The use of bio-based and locally available materials in construction is an effective approach to reducing embodied energy and supporting circular economy principles. In the earthen construction, the cereal straw fibres have traditionally been used as a natural reinforcement. However, their tensile properties and interspecies variability remain insufficiently documented. This study investigates the tensile behaviour of the straw fibres from four cereal species, wheat, rye, oat, and barley, to evaluate their suitability for rammed earth construction. The straw samples were collected during the 2020/2021 growing season and prepared under controlled laboratory conditions. Single-fibre tensile tests were performed using a Zwick/Roell Z600 universal testing machine under displacement-controlled loading at 0.5 mm/min. Tensile strength and modulus of elasticity were derived from the load–displacement data and specimen geometry. The results indicate systematic interspecies variations in the tensile behaviour. Wheat fibres exhibited the highest average tensile strength (39.61 MPa) and stiffness, indicating a favourable crack-bridging capacity. Rye and oat fibres showed comparable tensile strengths of 33.50 MPa and 33.72 MPa, respectively, accompanied by a greater variability. Barley fibres recorded the lowest average tensile strength (25.32 MPa), suggesting a limited structural suitability. These findings confirm the mechanical potential of cereal straw fibres, particularly wheat, as natural micro-reinforcement for the rammed earth. The study supports the valorisation of the agricultural by-products in sustainable, low-carbon construction.