A novel biocomposite material for sustainable constructions: Metakaolin lime mortar and Spanish broom fibers

The use of natural fibers as a main component in biocomposite materials for structural strengthening is a field of growing interest in the scientific community. This interest arises from the opportunity to recycle vegetable residues and use low-cost materials, which can contribute to reduce greenhouse gas emission. In this research paper, a novel biocomposite material for structural strengthening of masonry structures is proposed. It is made of hydraulic lime mortar enhanced with metakaolin and mixed with Spanish broom fibers. Metakaolin is employed to improve the resistance to water and harsh environments, while Spanish broom fibers are used to improve the mechanical performance (i.e. tensile and compressive strength), strain capacity and toughness of the lime mortar. Two types of Spanish broom fibers are used for reinforcing the mortar: raw fibers and thrums. Three different fiber length were used: 15 mm, 30 mm and a combination of 15 and 30 mm. Two different fiber concentrations were used for the raw fibers (0.5 % and 1.0 %) and a single concentration was used for the thrums (0.5 %). The specimens mechanical characteristics are experimentally investigated using three point bending tests and uniaxial compression tests. Different results are obtained depending on the fiber type, length and concentration used to reinforce the mortar. Indeed, the specimens reinforced with raw fibers show that some mechanical properties, such as tensile and compressive strength, are similar to those of the unreinforced specimens. However, differences are observed in other mechanical characteristics, notably maximum strain before failure and ductility, when compared to the unreinforced specimens.