Study on Spalling of Extremely Heated FRC by Free Hexagons

Fiber reinforced concrete (FRC) exposed to extremely elevated temperature is of great concern in tunnel structures, for example. In the paper a study on spalling on the face of FRC block being subjected to fire of 1200 degrees C in duration of 2 hours is to be presented from both theoretical and experimental views. The experiments have been conducted in a furnace its dimensions are to be specified in the paper and the theoretical considerations start with a discrete element method based on free hexagons. The latter method assumes a "soft contact" between hexagonal particles, i.e. springs simulate either tensile and shear contacts in the normal concrete or FRC, where fibers over-bridge possible cracks appearing during cooling process after removing the source of fire. Since the experimental blocks are loaded only by change of temperature and no other type of loading is considered (volume weight of the block is neglected), the "soft contact" is fully sufficient to describe the mechanical behavior of the material. The results from numerical procedure and experimental are compared and the mechanical properties of the material are tuned accordingly.