Long-Term Effects of Alkaline Environments on Basalt Fibres

In recent years, Fibre-Reinforced Cementitious Matrix (FRCM) composite materials have been increasingly utilised for the structural rehabilitation and strengthening of existing structures. These advanced solutions play a crucial role in restoration, seismic retrofitting, and the reinforcement of buildings and infrastructure, ensuring effective structural enhancement. However, ensuring their long-term performance and stability throughout their service life is essential. One key factor influencing the durability of FRCM systems is their exposure to highly alkaline environments. High alkalinity may lead to the degradation of the embedded fibers over time, potentially compromising the mechanical properties and reducing the overall effectiveness of the reinforcement. Among the various types of fibers used in FRCM systems, basalt fibers have demonstrated promising mechanical properties, but their resistance to alkaline conditions warrants further experimental investigation. To address this, the present study aims at evaluating the impact of an alkaline environment on the mechanical properties of basalt fibres, adopted as reinforcing material in a FRCM system. For the conditioning of the samples, given the absence of a standardised testing protocol, textile specimens and single fibre bundles were submerged in a saturated calcium hydroxide (Ca(OH)₂) solution at temperatures of 23 °C and 40 °C, with the higher temperature level applied with the aim to accelerate the conditioning process. Tensile tests were subsequently conducted after 1000, 2000, and 3000 h of exposure, following the setup outlined in the EAD-340275 guidelines. The study ultimately assessed the degradation effects of alkaline exposure on the mechanical properties of the basalt fibers, providing valuable insights into their long-term performance in FRCM applications.