Study of modifications on the chemical and mechanical compatibility between cement matrix and oil palmfibres

Nowadays, the substitution of the traditional reinforcements of cement-based composite materials by natural fibres is more and more common. However, some problems remain, mostly because the addition of natural fibres to cement can delay its hydration due to the high concentration of polysaccharide in the fibres’ leachates. Many studies have shown the effectiveness of alkaline treatments in order to improve the natural fibre/cement compatibility but the mechanical compatibility, i.e. the bonding strength between the cement and the fibres has never been characterized. Therefore, this study aims to fully understand the natural fibre/cement interface. Oil palm fibre is chosen as reference fibre because of its very low compatibility with cement. NaOH treatments and superplasticizer are used, in order to modify the surface of the fibre and the viscosity of the matrix. Both chemical and mechanical compatibilities are characterized, by various methods such as isothermal calorimetry, FTIR, tensile tests on single fibres and pull-out tests. Results show that alkali-treatments are very effective since it can improve both compatibilities, while a more fluid matrix allows to further enhance the properties of the interface, by limiting the amount of sugar at the fibre’s surface without hindering the cement hydration.