Effect of macro polypropylene, polyamide and steel fibers on the residual properties of SCC at ambient and elevated temperatures

This paper considers the effect of equivalent macro size fibers of polypropylene (PP), polyamide (PA) and steel (ST) on the properties of reinforced self-compacting concrete (FRSCC) exposed to normal and elevated temperatures. Different fiber concentrations of 0%, 0.3%, 0.6% and 1% were investigated under temperatures of 20 degrees C, 300 degrees C, 500 degrees C and 800 degrees C. Mass loss, residual compressive strength (RCS), residual flexural strength (RFS), toughness indices (TI), residual strength factors (RSF) and residual toughness (RT) capacities of FRSCCs were studied at hardened state based on their initial results at ambient curing. Meanwhile, slump-flow diameter, T500 time and L-box parameters were also tested at fresh state. In addition, the microstructural changes due to the use of various fibers and temperatures were examined by scanning electron microscope (SEM) analysis. The effect of macro PA and PP was comparable in terms of their minor influence on the mass loss, RCS and RFS of FRSCC compositions. However, macro PA presented greater contribution than PP in preserving the toughness capacity, particularly in the post-peak stage. Unlike PA and PP, the use of macro ST fibers caused noticeable increments in RFS and RT capacities. The superior outcome of using macro ST was confirmed through its higher effect in mitigating the crack formation of FRSCC, especially under elevated temperatures of 500 degrees C and 800 degrees C. (C) 2021 Elsevier Ltd. All rights reserved.