Exploring the impact of elevated temperature on the mechanical properties of concrete reinforced with Kevlar fibres

The study aimed to assess the effects of elevated temperatures on Kevlar fibre-reinforced concrete with varying fibre percentages. After curing for 7 and 28 days, the specimens were annealed at 200°C for 2 h, as this temperature is considered to be critical, leading to the deterioration of the cementitious matrix as was observed in the images obtained from SEM and a subsequent decline in performance. To further investigate the behaviour of Kevlar fibre-reinforced concrete beyond 200°C, where sample degradation makes it difficult to evaluate mechanical properties, an analytical model was developed to predict the behaviour up to 900°C and the model results were found to be in agreement with the experimental findings. Results demonstrated that Kevlar fibre-reinforced concrete exhibited reduced susceptibility to high temperatures compared to the control specimen, maintaining mechanical properties even after exposure. Early strength was observed, gradually strengthening over 28 days, suggesting that incorporating Kevlar fibres enhanced structural stability. Test results provided compelling evidence that integrating Kevlar fibres significantly enhances the resistance of concrete to elevated temperatures, rendering it more resilient in high-temperature environments. The study explored different fibre percentages, revealing positive effects on compressive, flexural, and split tensile stress compared to the control sample. Notably, a fibre content of 0.25% to the volume of concrete proved effective for reinforcing compressive strength, while higher percentages heightened flexural and split tensile stress. Higher fibre content resulted in a reduction in mechanical properties, highlighting the importance of selecting an appropriate fibre amount. Observations showed no spalling or explosive failure in Kevlar-reinforced concrete specimens due to high temperatures, with all specimens undergoing a yellowish colour change after 2 h of exposure. The research indicated that integrating Kevlar fibres offers potential benefits including increased residual strength, improved crack inhibition, and enhanced resistance to spalling at moderately elevated temperatures. The insights from the study could be valuable in the design and construction of structures like tunnel linings, airport runways, and pavements exposed to moderately higher temperatures.