Meglio, Emilia (2025) Novel plasters reinforced with hemp fibers for seismic retrofit of existing buildings. [Tesi di dottorato]

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Abstract

The construction industry is one of the largest contributors to global resource depletion, energy consumption, and greenhouse gas emissions. In response to the urgent need for sustainable building materials, natural fiber-reinforced composites have gained increasing attention for their ability to reduce environmental impact while maintaining high mechanical performance. This research explores the potential of hemp fiber-reinforced plasters as an eco-friendly and effective solution for the seismic retrofitting of existing buildings. The study focuses on two different reinforcement strategies: (i) lime-based plasters incorporating short hemp fibers randomly distributed within the matrix and (ii) a Fiber-Reinforced Cementitious Matrix (FRCM) system that employs a hemp mesh as reinforcement. The first experimental campaign analyzes the effect of hemp fiber addition on the fresh and hardened properties of lime-based plasters, including workability, flexural and compressive strength, and failure mechanisms. Results indicate that the incorporation of hemp fibers enhances the ductility of the plaster while maintaining adequate mechanical resistance, making it a viable alternative to traditional reinforcement materials. The second experimental phase focuses on the development and characterization of the Hemp-FRCM system, where a hemp mesh is embedded within a lime-based matrix. The mechanical properties of both the reinforcement and the matrix are evaluated separately before the composite system is subjected to direct tensile testing. The results demonstrate that the Hemp-FRCM system exhibits satisfactory effective stress distribution, with a progressive failure mechanism typical of FRCM systems. To complement the experimental findings, a numerical investigation is conducted using a Finite Element Model (FEM) to simulate the single-lap shear test between the hemp FRCM and a clay brick substrate. A parametric analysis is performed to explore the influence of different material properties and interface conditions on the shear strength and failure mechanisms of the composite system, providing valuable insights into the adhesion characteristics and mechanical response of hemp-based reinforcements in lime-based matrices. Overall, this research highlights the potential of hemp fiber-reinforced composites as a sustainable and effective solution for seismic retrofitting and structural reinforcement of structures. The findings demonstrate that hemp fibers not only offer mechanical benefits, but also contribute to reducing the environmental footprint of construction materials. The study provides a foundation for further research and development in bio-based reinforcement systems, paving the way for their broader implementation in structural engineering applications.

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