Effect of alkali-silica treatments of miscanthus fibres on chemical and micro-morphological modifications

Chemical treatments can remove waxes and sugar components from the surface of bio-fibres, increasing their compatibility with mineral binders. This paper investigates the effects of alkali solutions treatments on miscanthus shives. For 8, 24, and 48 h, fibres were immersed in NaOH solutions at 1.5, 2.5, and 5.0% concentrations, with and without a 2.5% sodium silicate solution, having a silica modulus (SiO₂/Na₂O) of 2.0. SEM and Fourier Transform Infrared Spectroscopy (ATR-FTIR) were used to investigate the effect of different treatments on the microstructure and surface chemistry of miscanthus. The SEM results show that the morphologies of miscanthus fibres were significantly altered in the case of 5.0% NaOH treatment, with a weakening of the inner cell structures in some locations. Furthermore, the ATR-FTIR patterns of raw and treated shives were analysed, suggesting that treating miscanthus with 2.5% NaOH and 2.5% sodium silicate results in the required chemical modifications while retaining the cellular structure of miscanthus fibres. For all treatments, the absorbance was reduced by 31 to 77% at 450 cm⁻¹ and 48–80% at 1035 cm⁻¹.