Improving the Resistance of Self Compacting Concrete exposed to Elevated Temperatures by Using Steel Fiber

Abstract

Elevated high temperatures due to fire represents one of the most severe risks to buildings and structures, which negatively affects on the engineering properties for constituent members of these buildings. The study aims to investigate the role of  steel fiber to improve of  properties of self compacting concrete (SCC) at elevated temperature (25, 200, 400 and 600°C) with two different exposure durations of (0.5 and 1.5 hours). Specimens were exposed to temperature and tested at age (7, 28 and 90 days) .The slump flow and T_500mm, L-box, and Sieve segregation resistance were conducted to investigate the fresh properties of SCC. Whereas the properties of hardened concrete were inspected using compression test, splitting tensile test, and flexural , as well as modulus of elasticity tests.

The results indicate that Elevated temperatures and increasing of exposure duration had  passively influenced on hardened properties of both plain and reinforced SCC, hardened properties of two type of SCC decreased with increased temperatures and increasing of exposure duration. Also the results indicate that steel fiber used in self-compacting concrete reduced the amount of deterioration of properties of Self compacting fiber-reinforced concrete (SCFRC) at high temperature. The percentage change ( improvement ) for mixes with steel fiber (0.5 and 1%) with respect to mixes without steel fiber , where compressive strength ranged between (0.3-20.9%) at 200 ^o C, (-3.1-31.3%) at 400 ^o C and (-3.9-31.5%) at 600 ^o C. Also the best percentages of increase were in splitting tensile strength and flexural strength , the percentages of increase in splitting tensile ranged between (27-94%) at 200 ^o C, (39-121%) at 400 ^o C and (38-109%) at 600 ^o C. and the percentage of increase in flexural strength ranged between (68-146%)  at 200 ^o C, (75-122%) at 400 ^o C and (45-109%) at 600 ^o C. Also the percentage of increase in static modulus of elasticity ranged between (4.3-15.5%) at 200 o C and (6.1-18.3%) at 400 ^o C for mixes with steel fiber (0.5 and 1%) with respect to reference mixture. It had also emerged the spalling phenomenon at parts of cylinders and prisms specimens  at exposed to high temperatures (400 ^oC), at  the duration of exposure was 1.5 hours, and the temperature (600 ^oC) at duration of exposure 0.5 and 1.5 hours.

Keywords: Self compacting concrete , elevated  temperature , Steel Fiber , Compressive strength, Splitting tensile , Flexural strength , modulus of elasticity, spalling phenomenon .