Residual compressive strength of plain and fiber reinforced concrete after exposure to different heating and cooling regimes

Abstract

The article investigated the impact of different cooling regimes on the response of both plain and fibre reinforced concrete (FRC) after heating. A total of 256 standard concrete cylinders of normal strength concrete (NSC) and high strength concrete (HSC) were tested in compression after heating at 200 °C, 400 °C, and 600 °C. For each concrete grade, 32 specimens were prepared without fibres while 96 cylinders had fibres (steel, polypropylene (PP) and their hybrid) in the concrete mixture. The cooling regimes adopted for cooling the test specimens were water quenching and natural ambient cooling. Effect of studied parameters was evaluated for tested cylinders in terms of stress-strain characteristics, residual strength, modulus of elasticity, and failure modes. For both NSC and HSC, the reduction in strength increased significantly when the temperature was increased from 400 to 600 °C. At 600 °C, the use of steel fibres caused lower loss in compressive strength, elastic modulus and energy absorption as compared to the use of PP and hybrid fibres. The residual strength of water quenched concrete was more than the air cooled concrete because the heated specimens were kept submerged in water for 24 h, which helped in the rehydration of anhydrous cement products.