Petrographic Investigation into the Influence of Chopped Basalt Fibers on the Microstructure of Portland Cement Mortars at Elevated Temperatures

Abstract

This research investigated the effects of usage of basalt fiber (BF) in cement mortars at elevated temperatures. Compressive strength, mass loss, and microstructure characteristics, including petrographic analyses and scanning electron microscopy (SEM) images of cement composites, were investigated. BF was added in the mortars at five different ratios: 0%, 0.5%, 1%, 1.5%, and 2% by volume of the mix. The mortars were subjected to temperatures of 23°C, 200°C, 400°C, 600°C, and 800°C. The mixture with 1% BF had the best residual compressive strength at high temperatures, so that is considered to be the optimum dosage. The lowest amount of mass loss at each temperature was for specimens with 2% BF. The results indicate that adding BF to the mixes decreased the mass loss. Petrographic and SEM images showed that with increasing temperature, the part of the microstructure which began to deteriorate first was the interfacial transition zone between cement matrix and fiber. BF has a significant function in spreading the cracks, and acts like bridge between two parts of cement paste.