Impact of elevated temperature on the mechanical properties of cement mortar reinforced with rope waste fibres

The exposure of concrete or cement mortars to fire or other elevated temperatures negatively affects the mechanical properties, and a change may also occur in the pore structures, leading to cracking and spalling. In order to hinder or reduce the negative impact of elevated temperature on cement mortar, as well as to promote reuse of waste in the concrete industry to improve the environment, this study aims to investigate the effect of elevated temperature on the mechanical properties of cement mortar reinforced with rope waste fibres (RWF). The fibres were obtained by cutting a used polymeric rope (0.034 mm in diameter) into small fibres with average lengths of 12 mm. Four mortar mixtures, including one reference mixture (without fibres) and three mixtures containing RWF in proportions of 0.25%, 0.5% and 0.75% (by mortar weight), were cast. After 28 days of curing, the hardened specimens were air dried for at least two weeks, and some specimens were exposed to a controlled temperatures of 300 and 600 °C for two hours, while the others were placed at ambient temperature. All specimens were then examined via compressive strength, flexural strength, mass loss, ultrasonic pulse velocity and visual inspection tests. The results indicated that RWF can prevent cracks appearing at 600 °C; however, the RWF had a negative impact on the compressive strength of the mortar under elevated temperatures, despite the flexural strength and UPV properties being improved significantly.