ABSTRACT
L.A. Qureshi University of Engineering & Technology Taxila, Pakistan
M. Ilyas Sh. Bahauddin Zakariya University, Multan, Pakistan
ABSTRACT: In this paper, the performance of structural concrete members in actual fire situations is discussed. The fire resistance properties of a structural concrete member was improved by adding polypropylene fibres of special characteristics, manufactured in China. An experimental program was designed, in which 12 beams in 4 groups A, B, C and D were cast. In group A, no fibres were added, in B, PP fibres were added in 0.9 Kg/m3 ratio, while in group C, PP fibres were added as 1.8 Kg/m3. In the last group, D, local nylon fibres were tried with 0.9 kg/m3 ratio. After curing and drying, 8 beams (2 from each group) were subjected to standard fire conditions. The temperature during the fire was measured with a digital infrared thermometer at different time intervals. Spalling was the most critical phenomenon that occurred in structural concrete members during the fire. PP fibres prevented spalling in the beam samples of group B and C. Significant spalling was observed in the beams having no fibres and those with local nylon fibre. A two point loading test was carried out on all unfired and fired beam samples. Deflections of these beams were measured at incremental loads. It was found that by adding PP fibres with the ratio of 0.9 Kg/m3 the fire resistance of beams improved with a loss of 4 to 5% in cracking and failure loads after being exposed to fire. By adding PP fibres brittle behavior of the concrete also transited towards ductile.
