Effect of matrix modification on the durability of cementitious composites reinforced with aligned Ensete fibre

Abstract

Researchers are looking for new eco-friendly products to preserve non-renewable and non-biodegradable re sources. Fibres obtained from natural sources offer indisputable advantages over synthetic reinforcement ma terials, including low density, low cost, abundance, comparable strength, non-toxicity and minimum environmental impact. However, when using natural fibres in a pure Portland cement matrix, the mechanical strength is significantly reduced due to the alkalinity of the cement. To date, there has been no study on the durability and mitigation of Ensete ventricosum (Ev) fibres in cementitious matrices. Therefore, in this study, the effects of partial replacement of Portland cement with different supplementary cementitious materials (SCM) including metakaolin (MK), fly ash (FA) and scoria (SC) were investigated. The composites, varying in matrix composition and reinforced by aligned Ev fibres, were subjected to 0 and 25 wet-dry cycles before being tested in a four-point bending configuration. A detailed investigation of the cracking behaviour was carried out using optical Digital Image Correlation techniques. The microstructure of the Ev fibres was next examined using scanning electron microscopy. The flexure tests showed that after 25 wet/dry cycles, Ev fibre reinforced com posites with 100% Portland cement matrix had completely lost their ductility and strength while ternary matrices of 70% FA and 10% MK exhibited minimal degradation, demonstrating that partial replacement of Portland cement by SCMs can reduce the degradation of natural fibres in cement-based composites.