Md Azree Othuman Mydin and Sara Soleimanzadeh
The impacts of volume fraction of polypropylene fiber (PF) on the bending behavior of lightweight foamed concrete (LFC) before and during exposing it to high temperature is experimentally studied. Five mixes of LFC with 600, 800, 1000, 1200 and 1400 kg/m³ densities were made in current investigation. Then, the effect of adding PF with volume fraction of 0.1, 0.2, 0.3, 0.4, 0.45 and 0.5% on the flexural strength and pore structure of each considered density at ambient and elevated temperatures up to 600 °C was examined. The outcomes demonstrated that an increasing temperature had a detrimental influence on LFC property especially in a temperature range of 200 to 600 °C degrees in which flexural resistance was reduced by about 15 to 60% due to the micro diffusion of bound water molecules, detachment of the C-S-H gel and CH, weakness in chemical bond structure of cement paste and suppresses of the cohesive forces in the micropores. At each predetermined temperature, LFC with higher density achieved higher bending resistance as it had smaller and more uniform voids compared to LFC with lower density and higher loads were required to break it down. Adding PF by 0.1-0.4% of mix volume enabled LFC to resist high temperatures better than control plain concrete and the improvement percentage was directly correlated with PF content and LFC density. However, adding PF with volume fraction more than 0.4% reduced the flexural strength considerably. At ambient temperature, the larger content of PF led to an increased amount of pores in concrete structure and at elevated temperature a larger number of cracks were induced due to evaporation of more fibers and replacement of them by air voids led to significant reduction in flexural strength of LFC.
