Research of the Processes of High Temperature Influence on Cementitous Concrete

The paper focuses on analysis of behaviour of cement composite materials (concrete) exposed to high temperatures. Experimental work was focused on designing and verification of mix-design with higher resistance to action of high temperature. Concrete specimens were exposed to thermal load at the temperatures 200 °C, 400 °C, 600 °C and 900 °C with isothermal dwell 60 minutes. After exposition to high temperature, physicalmechanical properties were tested and compared to reference specimens, which were not exposed to high temperature. Surface of testing specimens was analyzed and percent damage of surface was defined. Concrete mix-designs with components aimed at increasing fire resistance showed the least drop of compressive strength. Concrete with quartz sand and greywacke aggregate with no components enhancing fire resistance showed the most significant changes of compressive strength and appearance. Combination of fibers and basalt aggregate had positive effect compared to using only basalt aggregate.