Influence of an Impregnation Treatment on the Morphology and Mechanical Behaviour of Flax Yarns Embedded in Hydraulic Lime Mortar

Giuseppe Ferrara,Enzo Martinelli,Marco Pepe,Romildo Dias Tolêdo Filho

doi:10.3390/fib7040030

Abstract

The increasing attention toward environmental aspects has led, also in the sector of construction materials, to the need for developing more eco-friendly solutions. Among several options, the employment of low energy raw materials appears as an efficient solution intended to enhance the sustainability of building structures. One of the applications moving in this direction is the use of plant fibers as a reinforcement in cement-based composites, hence named as natural textile reinforced mortar (NTRM) composites. Although representing a promising technique, there are still several open issues concerning the variability of plant fibers properties, the durability, and the mechanical compatibility with the mortar. This study aims at investigating the influence of an impregnation process on the thread’s morphology and on the mechanical response. Therefore, the geometry of dry and impregnated flax threads is identified by using scanning electron microscope (SEM) images analysis, and their mechanical response in tension is assessed. In addition, the fibers-to-mortar bond behavior is investigated by means of pull-out tests. The proposed results show that the impregnation procedure employed, although not improving the fibers-to matrix bond, leads to a standardisation of the threads morphology and reduces the thread’s deformability in tension, and paves the way for further investigations on a larger scale.

Highlights

The reduction of environmental impact represents one of the major challenges of our time that interests all the industrial sectors of our society [1]
This study aims to investigate the effect of flax fibers impregnation on their morphology, tensile strength, and mortar-to-fibers adherence behavior
The impregnation creates a weak layer between the fibers and the mortar that reduces the adhesion of the reinforcement-to-mortar system

Summary

Introduction

The reduction of environmental impact represents one of the major challenges of our time that interests all the industrial sectors of our society [1]. As for building materials, several strategies have been implemented with the aim of promoting life cycle assessment methodologies [3], the use of recycled sources [4,5], and, more generally, the adoption of “low embodied energy” raw materials [6] With respect to the latter aspect, the use of plant fibers instead of industrial ones as reinforcement in composite systems appears to be an efficient solution to increase the sustainability [7]. Physical, and economical properties [8], the so-called bio-composites materials have gained a broad application field [9,10,11] in several sectors, such as the automotive [12], packaging [13], biomedical [14], infrastructural [15], and civil engineering fields [16].

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