Suitability of Surface-Treated Flax and Hemp Fibers for Concrete Reinforcement

Abstract

The use of vegetable fibres as a sustainable alternative to non-natural sources of fibres applied for concrete reinforcement has been studied for over three decades. The main issues about plant-based fibres pointed out by other authors are the variability in their properties and concerns about potential high biodegradability in the alkaline pH of the concrete matrix. Aiming to minimise the variability of flax and hemp fibres, this research compares a range of chemical surface treatments, analysing their effects on the behaviour of the fibres and the effects of their addition to concrete. Corroborating what has been found by other authors, the treatment using NaOH 10% for 24 h was able to enhance the properties of hemp fibre-reinforced concrete and reduce the degradability in alkaline solution. For flax fibres, a novel alternative stood out: treatment using 1% of stearic acid in ethanol for 4 h. Treatment using this solution increased the tensile by 101%, causing a minor effect on the elastic modulus. Concrete mixes reinforced with the treated flax fibres presented reduced thermal conductivity and elastic modulus and increased residual tensile strength and fracture energy.

Impact of Oat Husk Extracts on Mid-Stage Cement Hydration and the Mechanical Strength of Mortar

“…Considering agricultural by-products, the studies are divided into investigations into residues as fillers or aggregate [14][15][16], exploring crushed stalks from different crops such as wheat straw [17] and rice straw [18], and the use of husks and hulls as in the case of rice [19] and hazelnut [20], and their use in the form of fibrous reinforcement [7,21], for example, flax [21,22], hemp [21] and jute [23].…”

Exploring Oat Husks as Aggregates in Limestone-Based Composites: Effects of Surface Treatments and Binder Selection on Mechanical Performance

“…The linseed oil coating treatment involves covering the oat husks with a film formed by linseed oil, which undergoes hardening upon contact with air due to the autoxidation of unsaturated fatty acids in its composition [ 42 ]. This treatment, proven effective in limiting extractive leaching and isolating the fibre from the alkaline environment of the matrix [ 29 , 43 ], is executed by initially drying the oat husks at 50 ± 0.1 °C, followed by mixing them with linseed oil in a planetary mixer for 3 min using an oil/fibre ratio of 0.25 in mass, and subsequent drying at 50 ± 0.1 °C for 14 days [ 27 ]. The husks subjected to this treatment are named linseed oat husks (LOHs).…”

“…While coating with linseed oil [ 27 ], a fatty acid oil, and stearic acid [ 29 ], a component of its composition, have demonstrated favourable results, improving its compatibility with the cementitious matrix [ 27 , 29 ], some authors have also investigated the pre-exposure to an alkaline environment [ 9 , 29 ], even similar to that found in the cement matrix, by coating the particles using Portland cement and pozzolanic agents [ 27 ].…”

Enhancing the efficiency of hemp fiber dyeing with natural dyes: Indigo and lac

“…The fibers have a low density of approximately 1.25 g⸳cm -1 [11] and less shrinkage but are strong with a strength of 210-750 MPa [12]. Hemp fibers can be used as a raw material for manufacturing a wide range of products, including composite materials [13][14][15], and textiles [16][17][18], which will be the focus of this research.…”