No abstract

In this paper, an experimental work was carried out to study the effect of high temperatures on the strength of high-performance self compacting concrete (HPSCC). Four concrete mixes were investigated. The first mix represented HPSCC without fibers. The second mix represented HPSCC including steel fibers. The third mix represented HPSCC including steel and micropolypropylene fibers. The fourth mix represented HPSCC including steel, polypropylene and polyolefin fibers. Compressive, tensile and flexural strengths were measured at room temperature (RT) and after exposure to high temperatures of 200 o C, 400 o C, 600 o C and 750 o C for 2 hours. The residual unstressed test method was followed. Microscopic examination was performed on concrete samples from the four mixes at RT and after exposure to high temperatures. The results showed that incorporating hybrid fibers seems to be a promising way to enhance the resistance of HPSCC to thermally induced explosive spalling and increase the residual strengths.

This work analyses the structural behavior of high performance self compacting reinforced concrete (RC) beams under direct fire. Concrete strength of about 130 MPa was investigated. Six reinforced concrete beams represents three types of concrete mixes were investigated. The first mix was high performance self compacting concrete (HPSCC) without fibers. The second mix was HPSCC with the presence of steel fibers (SF). The third mix was HPSCC with hybrid fibers, SF and two types of polypropylene fibers (micro-polypropylene and polyolefin). Three beams representing the three mixes were tested at room temperature without exposure to fire. The other corresponding three beams were tested under direct fire, while they were loaded at 45% from the fracture load of the corresponding three beams tested at room temperature to failure. All beams were tested under 3-points bending. Experimental results clearly indicated the superior effect of adding hybrid fibers to such concrete in reducing explosive spalling and increasing flexural capacity of RC beams when exposed to direct fire.