Relationship between microstructure and performance of polypropylene fibre reinforced cement composites subjected to elevated temperature

Abstract

This article presents the investigation on mechanical and transport properties of polypropylene (PP) fibre reinforced cement composites with varying fibre volume (0.05–0.30%). Fresh property of the fibre reinforced concrete was evaluated through the flow table test, while hardened properties including compressive strength (1, 3, 7 and 28-day), and modified flexural strength, ultrasonic pulse velocity and water absorption were assessed at the 28-day. The effects of fibre addition on mechanical properties were evaluated at room temperature and 200 °C. Microstructural characterizations were performed using field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray spectroscopy (EDX). Micrographs of the failed PP fibre reinforced composites indicated that the increase in flexural strength at room temperature was attributed to the crack bridging and fibre debonding at the fibre/matrix interface. Higher water absorption value was achieved for PP reinforced composites subjected to elevated temperature compared to control mortar. FESEM/EDX analyses on the elevated temperature samples indicated that the increment was due to the growing of macro-pores from the empty space left behind by fibre settlement. In conclusion, the addition of PP fibres in the cement mortar adversely affect the strength when the composite is subjected to elevated temperature, but resulted in improved durability.