Investigation of the Impact Resistance, Microstructure and Weight Loss in Fibrous Pozzolanic Concrete Containing Fibers, Under High Temperatures

Today, the construction of highly critical structures (such as military and nuclear structures, hospitals and infrastructures), with high resistance to impact loads and high temperatures, is of particular importance in the field of passive defense. In this regard, the production of high-strength and nature-friendly concrete as the main material used in these types of structures plays a significant role. In this paper, the laboratory properties of the slag geopolymer concrete containing 0 to 8% nanosilica and 1 to 2% polyalphin fibers have been investigated. The concrete samples made at 90 days of curing age at 25 and 500 °C Celsius underwent weightlifting, weight loss, scanning electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy, and X-ray fluorescence (XRF) at 25 °C. At the age of seven days, the processing was performed on the concrete samples. The results indicate the weakening of the microstructure of concrete exposed to high temperatures. Also, the improvement of test results in the geopolymer concrete compared to ordinary concrete is evident. The best and worst performance in the weight loss test of the samples belonged to the geopolymer concrete containing 8% nanosilica and the geopolymer concrete containing 8% nanosilica and 2% fibers, by 0.061% and 0.12% weight loss of the sample, respectively. The best performance in the energy absorption of falling weight at 25 and 500 degrees Celsius belongs to the geopolymer concrete (containing 8% nanosilica and 2% fiber) at 2928.25 and 773.44 joules, respectively. The highest and lowest energy loss of concrete samples at 500 °C compared to 25 °C belong to the ordinary concrete and the geopolymer concrete (containing 8% nanosilica) by 83.33% and 53.33%, respectively.