COMPRESSIVE BEHAVIOR OF FIBER REINFORCED HIGH-PERFORMANCE CONCRETE SUBJECTED TO ELEVATED TEMPERATURES

Abstract In this paper, the effects of elevated temperatures on the compressive strength stress–strain relationship (stiffness) and energy absorption capacities (toughness) of concretes are presented. High-performance concretes (HPCs) were prepared in three series, with different cementitious material constitutions using plain ordinary Portland cement (PC), with and without metakaolin (MK) and silica fume (SF) separate replacements. Each series comprised a concrete mix, prepared without any fibers, and concrete mixes reinforced with either or both steel fibers and polypropylene (PP) fibers. The results showed that after exposure to 600 and 800 °C, the concrete mixes retained, respectively, 45% and 23% of their compressive strength, on average. The results also show that after the concrete was exposed to the elevated temperatures, the loss of stiffness was much quicker than the loss in compressive strength, but the loss of energy absorption capacity was relatively slower. A 20% replacement of the cement by MK resulted in a higher compressive strength but a lower specific toughness, as compared with the concrete prepared with 10% replacement of cement by SF. The MK concrete also showed quicker losses in the compressive strength, elastic modulus and energy absorption capacity after exposure to the elevated temperatures. Steel fibers approximately doubled the energy absorption capacity of the unheated concrete. They were effective in minimizing the degradation of compressive strength for the concrete after exposure to the elevated temperatures. The steel-fiber-reinforced concretes also showed the highest energy absorption capacity after the high-temperature exposure, although they suffered a quick loss of this capacity. In comparison, using PP fibers reduced the energy absorption capacity of the concrete after exposure to 800 °C, although it had a minor beneficial effect on the energy absorption capacity of the concrete before heating.

[1]  P. Aitcin.  High Performance Concrete , 1998 .

[2]  Salman Azhar,et al.  Performance of metakaolin concrete at elevated temperatures , 2003 .

[3]  Chi Sun Poon,et al.  Effect of Fly Ash and Silica Fume on Compressive and Fracture Behaviors of Concrete , 1998 .

[4]  Daniel Quenard,et al.  Spalling and pore pressure in HPC at high temperatures , 2000 .

[5]  Binsheng Zhang,et al.  Residual Fracture Toughness of Normal- andHigh-Strength Gravel Concrete after Heating to 600 °C , 2002 .

[6]  Luc Taerwe,et al.  Influence of Steel Fibers on Design Stress-Strain Curve for High-Strength Concrete , 1996 .

[7]  Pierre Kalifa,et al.  High-temperature behaviour of HPC with polypropylene fibres: From spalling to microstructure , 2001 .

[8]  M. C. Nataraja,et al.  STRESS-STRAIN CURVES FOR STEEL-FIBER REINFORCED CONCRETE UNDER COMPRESSION , 1999 .

[9]  Raymond J. Connolly,et al.  The spalling of concrete in fires , 1995 .

[10]  J. Bai,et al.  Metakaolin and calcined clays as pozzolans for concrete: a review , 2001 .

[11]  Wei Sun,et al.  Compressive strength and pore structure of high-performance concrete after exposure to high temperature up to 800°C , 2000 .

[12]  Chi Sun Poon,et al.  Impact of high temperature on PFA concrete , 2001 .

[13]  Mohamed Heikal.  Effect of temperature on the physico-mechanical and mineralogical properties of Homra pozzolanic cement pastes , 2000 .

[14]  Z. Bažant,et al.  Concrete at High Temperatures: Material Properties and Mathematical Models , 1996 .

[15]  L. Taerwe.  Influence of Steel Fibers on Strain-Softening of High-Strength Concrete , 1993 .

[16]  Hui Li,et al.  Effect of High Temperature on Residual Mechanical Properties of Confined and UnconfinedHigh-Strength Concrete , 2002 .

[17]  T. H. Wee,et al.  STRESS-STRAIN RELATIONSHIP OF HIGH-STRENGTH FIBER CONCRETE IN COMPRESSION , 1999 .

[18]  Chunxiang Qian,et al.  Development of hybrid polypropylene-steel fibre-reinforced concrete , 2000 .

[19]  Salman Azhar,et al.  Comparison of the strength and durability performance of normal- and high-strength pozzolanic concretes at elevated temperatures , 2001 .

[20]  Wei Sun,et al.  Effect of heating and cooling regimes on residual strength and microstructure of normal strength and high-performance concrete , 2000 .