RHEOLOGICAL AND MECHANICAL PROPERTIES OF FIBER SELF-COMPACTING CONCRETE UNDER HIGH TEMPERATURE

Use of common bers, in addition to increasing ductility, toughness, rst point cracking, and ultimate strain, plays a major role in preventing shrinkage and thermal cracks. The role of temperature in ber bridging and change of material structure has been investigated in previous studies. Use of waste materials in structural materials can decrease further pollution of ecosystem. On the other hand, increase in oil and polymer-based waste materials, caused some concern in the international community because of the adverse environmental impact of this material. For this reason, in this research, steel ber (0.4, 0.5 and 0.6), Polypropylene ber (0.03, 0.05 and 0.1), and recycled Polyethylene terephthalate (PET) ber (0.2, 0.3 and 0.4) percent of the concrete mixture volume were used. The results of the rheological (V-funnel, T50, Slump and L-Box), mechanical properties (e.g., compressive, exural, and splitting tensile strength) and Ultrasonic Pulse Velocity (UPV) Test of self-compacting concrete exposed to temperatures of 20, 200, 300, 400, and 600 showed that high contents of bers did not satisfy some rheological and mechanical aspects of self-compacting concrete. Steel bers increased the compressive, exural, and splitting tensile strengths of concrete with maximum amount of 9.8% and two other bers cause 15% decrease in strength of unheated specimens at most. Fiber reinforced specimens had an increase in resistance in the range of 8 to 21% by heating specimens to600 . The exural strength of steel ber reinforced specimens had an increase of maximum 30% for unheated ones. PET and P.P. ber reinforced specimens had 9 to 20% increase in exural strength. The presence of bers increases the mechanical strength, toughness, and ductility of concrete and prevents loss of strength and spalling phenomenon at high temperatures, as well as having a fundamental role in the reduction of heat, microcracks, and retaining fundamental structure of concrete.