High performance basalt-fibre modified cement for elevated temperature environments

Cementitious materials, defined by their brittle nature and specific composition, are typically susceptible to thermal attack in various engineering scenarios. Basalt fibre (BF), employed as an inorganic silicate additive in cement, has garnered significant attention due to its exceptional mechanical and thermal stability. However, there exists a shortage of essential experimental data regarding the performance of BF-modified cement at elevated temperatures, and, more importantly, a lack of understanding of the key mechanisms involved in the reinforcement processes. In this study, the mechanical behavior of cementitious composites with various contents of BF is investigated at both ambient and elevated temperature conditions (up to 200 °C) to determine the optimal dosage of BF in cement and crucially the role of BF in stability of cement paste at elevated temperatures. Microstructure and phase composition analyses are performed to reveal the mechanisms of reinforcement. The results indicate that the addition of 0.05–0.1 wt% BF to cement can significantly enhance overall mechanical strength of cement paste and crucially its crack resistance at elevated temperatures, i.e., flexural strength improved by up to 60 % at 200 °C. This was primarily attributed to multiple energy-consumption processes, including the bridging effect, breaking effect, pulling out effect, crack deflection effect, and adhesive effect. Notably, the adhesion between BF and cement matrix improved after subjected to elevated temperatures, owing to the increased formation of hydration products on BF surface. While needle-shaped hydration products were commonly observed at ambient conditions, contributing to a slight increase in the surface friction of BF, the accelerated growth of hydration products at higher temperature conditions as the result of BF addition to cement was found to be the most dominant factor for enhancement of mechanical strength and improved ductility of cement composite. The outcomes of this study provide further insights and promising future for the application of BF-modified cement composite where the structure is exposed to high temperatures, including deep geothermal wells, CO2 storage wells, radioactive waste disposal, and many other deep geo-energy applications.