Effect of Sisal fiber's treatment on hydration and thermophysical properties of cement biocomposite

Cement-based biocomposites are a current area of construction research. Plant fibres retard the setting times of cement due to their hydrophilic nature and the thermal properties of raw cement mortar containing plant fibres can be problematic. This aim of this work was to study the effect of fibre treatment to reduce the hydrophilicity of natural fibres while enhancing the thermal properties of the cementitious matrix. The first part of this study focused on structural and morphological aspects. Scanning electron microscopy showed a tiny calcium layer around the sisal fibre treated with sodium hydroxide and paraffin oil on the adhesion surface. Fourier transform infrared spectroscopy revealed a disparity in the peaks of the absorption bands of calcium carbonate and calcium hydroxide. The treatment slowed the alkaline hydrolysis and mineralisation of the fibre cell walls in the interfacial transition zone, thus promoting cement hydration. The second part of this work was a thermophysical study of the composites. The inclusion of sisal fibres led to remarkable decreases in thermal conductivity and heat capacity. The best thermal properties were obtained for the composite with sisal fibre immersed in paraffin oil. Biomortars with treated sisal fibre are thus promising from an insulation point of view.