Influence of polypropylene fibers on high-strength concrete at high temperatures

Abstract

In this study, the effect of incorporating polypropylene fibers (PF) into high-strength concrete (HSC) at elevated temperatures was investigated, and an analysis of potential spalling, residual compressive strength, tensile strength, static modulus of elasticity, water absorption, weight loss, electrical resistivity, ultrasonic pulse velocity, and microstructure, utilizing scanning electron microscopy (SEM), was conducted. A series of tests was performed on cylindrical specimens under progressive heating from 100 °C to 750 °C at a constant rate of 1 °C/min, maintaining the temperature for 60 minutes, and then cooling at 1 °C/min. Subsequently, several tests were executed. The results revealed the absence of spalling in any of the tests. They indicated that the PF addition enhanced the CAR's residual compressive strength and electrical resistivity (up to 500 °C) and tensile strength and compactness (up to 250 °C). At higher temperatures (750 °C), PF inclusion caused the development of channels and escalation in microcracks and the degradation of the connection between the cement paste and aggregate, ultimately resulting in a decline in compressive strength.