The relationship between conctere composition and structural stability in case of fire

Abstract

A series of disasters caused by fire have made engineers aware that understanding the consequences of fire is essential, as human lives depend on it, and it can also cause significant material damage. The structural integrity of structures during and after a fire, including their stability, can be better ensured if we accurately understand the effects of fire. Of course, the effects of fire do not always lead to significant damage, but in many cases they do. Fire protection is intended, on the one hand, to ensure that buildings remain stable under fire for a certain period, which is necessary to enable occupants to escape safely and, on the other hand, to minimize damage to building structures. The concrete composition, i.e., the structure's microstructure, significantly influences the stability of reinforced concrete structures in the event of fire or heat. In the case of concrete, in addition to changes in the internal material structure in the event of fire, spalling has also appeared recently, largely due to the denser concrete structure. In summary, the higher strength of concrete and the concomitant change in the test strength will lead to spalling, which will have a major impact on the stability of structures under fire. Both small-element (fiber efficiency, aggregate efficiency) and large-element tests have been carried out to verify this. The small-element tests were carried out in an electric furnace to monitor possible concrete surface delamination and strength loss. The small-element tests can be used to select concrete compositions for the large-element tests. Based on their experimental results, an increase in the fire resistance limit of a structural element can be achieved by reducing the delamination of the concrete surface when plastic fibers are added to the concrete. However, if a further increase in the fire resistance limit is required, a change in the type of cement or a modification of the supplementary material may be necessary to increase the residual strength value. Overall, the microstructure of concrete has a significant impact on the stability of structures in the event of a fire.