Fire Safety Science Digital Archive

Tests have been carried out to investigate the effect of temperature on the crushing strength of concrete using 2 in. diameter by 4 in. long specimens manufactured with normal Portland cement, River sand and gravel aggregate using mix proportions by weight of 1 : 3, 1 : 4.5 and 1 : 6 and various water/cement ratios. Tests were performed at a) constant temperatures and b) constant temperature-constant stress as well as to determine the residual strength after heating. It is shown that crushing strength of concrete up to 600c is independent of the water/cement ratio used but is influenced by the cement/aggregate ratio. Concrete specimens loaded to produce normal design compressive stress during the period of heating showed less reduction in strength than specimens without imposed load. The residual strength after heating to a given temperature in the range 200 to 450 C was approximately 20 per cent less than the corresponding strength at that temperature.