Comparative study of natural and accelerated ageing of basalt fibres under alkaline and mildly acidic conditions

This paper investigates the durability of basalt fibres (BF) in a model environment of synthetic pore solutions of ordinary Portland cement, alkaline environment, and magnesium phosphate cement (MPC), mildly acidic environment, under natural (21 ± 2°C) and accelerated (60 ± 2°C) ageing conditions. The mechanical properties (tensile strength, initial modulus of elasticity and elongation at break) and the morphology of the BF surface were determined before and after exposure. The results show that the residual BF properties are strongly dependent on the environment and exposure time, with an alkaline environment being a harsher environment for BF than an mildly acidic one. Among the mechanical properties analyzed, tensile strength and elongation at break proved to be the most susceptible to deterioration in both mildly acidic and alkaline environments. BF became increasingly brittle and prone to breakage, especially when exposed to natural aging in an alkaline environment, where BF experienced a complete loss of mechanical properties within 90 days. In contrast, fibers subjected to accelerated aging in an MPC environment retained 31% of their original strength after 180 days. The behavior of the BF fibres under accelerated test conditions is very similar to the behavior observed under natural exposure, highlighting the relevance of the accelerated test. The relationship between BF properties under both ageing conditions was determined by a two-parameter Weibull analysis together with acceleration factors for a faster future assessment of BF long-term properties.