Lime-Based Plaster Reinforced with Hemp Braids as Sustainable Building Product

Sustainability is of fundamental importance for the construction industry: in recent decades researchers focused on supplementing building components with multiple natural fibres, evaluating their mechanical performance and application fields. In this field, the common plasters are usually equipped with glass fibre mesh to avoid crack patterns due to shrinkage. Natural fibres, thanks to their high tensile resistance, can represent a green solution to solve this problem. In particular, this work investigates the properties and the mechanical characteristics of a biocompound obtained with hemp fibres. The first phase aims at identifying the ideal mixture between hemp fibres and mortar to improve workability and avoid altering the water/lime ratio. The performed physical tests provide useful information for the evaluation of the consistency and the workability of the compound. Based on these preliminary results, 10 combinations of 3 parameters, namely fibre diameter, percentage of hemp fibre in the mortar and length of the hemp braid fragments, are tested. Among the mechanical properties, bending, compressive and tensile behaviours are evaluated. For each test, the performances of fibre-reinforced samples are compared to reference specimens. From compressive tests it is noted that the best performances were obtained from fibres with diameter of 1 mm and length of 2 cm. On the other hand, from flexural tests, it is seen that braids with a length of 2 cm provide an average bending stress about 13% less than that of the control specimen. Contrarily, braids with a length of 3 cm give a mean increase of bending stress of about 8% compared to the control specimen.