Post-Fire Mechanical Degradation of Lightweight Concretes and Maintenance Strategies with Steel Fibers and Nano-Silica

Currently, the growth of building construction and the need for lighter but more sustainable materials are of interest. Additionally, recent fire incidents highlight the insufficient knowledge of the properties of materials after a fire. Common materials such as concrete should, to minimize their adverse environmental effects and expenses, be maintained in such a way as to increase their resistance and preserve their mechanical properties when subjected to high temperatures. Hence, in this research, the post-fire mechanical degradation of lightweight concrete (LWC) has been investigated. Moreover, the addition of steel fiber and nano-silica have been studied in terms of their ability to reduce the mechanical degradation of LWC subjected to high temperatures. For this purpose, different samples were considered in four mixture designs: the LWC samples, samples with steel fibers, samples with nano-silica, and samples with a combination of steel fibers and nano-silica. All samples were subjected to temperatures of 200, 400 and 600 degrees Celsius and compared with the control samples. The results show that, as the temperature increased, the tensile and compressive resistances of LWC decreased. The samples without fibers and nano-silica showed a greater decrease in mechanical properties with increasing temperature. The addition of steel fibers and nano-silica, individually or as a combination, can improve the compressive and tensile strength of the concrete both at room temperature and at higher temperatures.