The effects of high temperature on mechanical properties of cementitious composites reinforced with polymeric fibers

Polymeric fibers are cheap and popular materials used in the concrete industry, and they may improve the mechanical properties of cementitious composites under high temperature. In this study, three different types of polymeric fibers - Copolymer Polypropylene/polyethylene (CPP), Homopolymer Polypropylene (HPP), and Aramid (AR) - are added to cement mortars with the aim to investigate their mechanical contributions to mortars under high temperature, comparatively. These fibers are added into mortars in five different ratios (0.0%, 0.3%, 0.6%, 0.9% and 1.2%) by volume. The mortars are subjected to following temperatures: 21 °C (normal conditions), 100 °C (oven dry), 450 °C, 650 °C and 850 °C. It is concluded that polymeric fibers used in this study contribute to the flexural strength of mortars under normal dry conditions (100 °C). This effect continues clearly up to 450 °C and polymeric fibers show effects on flexural strength especially at 450 °C. Each fiber shows the best performance different addition ratio when flexural and compressive strength are taken into consideration at the same time under high temperature. The highest increase in flexural strength and the lowest decrease in compressive strength are at 0.3-0.9% fiber addition ratio for HPP, at 0.3-0.6% fiber addition ratio for CPP and at 0.9% fiber addition ratio for AR for every temperature.