Concrete must at times resist the effects of artificially induced high temperatures such as might be encountered near furnace or in atomic reactors, in pavement subjected to jet engine blast, and in areas exposed to fire. Applications of concrete involving extremely high temperatures, such as landing pads for missiles, are considered expendable, but in most instances it is desired to avoid deterioration of the concrete's physical properties as much as possible. A number of factors will enter into a decision regarding the type of concrete to use under condition of elevated temperatures. These include the following: length of exposure, rate of temperature rise, temperature to which the concrete mass will be raised, temperature of concrete at initiation of exposure to high temperature, degree of water saturation of the concrete, age of the concrete, and type of aggregate used. Other factors: cement- preliminary studies indicate that the amount of calcium hydroxide in concrete is great importance in the resistance to high temperatures. Cements which release least amounts of calcium hydroxide during hydration and hardening of the concrete are certainly to be favored. Aggregates- studies of concrete heated to high temperatures indicate that the type of aggregate employed is critical. Nevertheless, no standard specifications have been developed. Water- the effect of quality of water used in concrete has not been studied in relation to performance of concrete under high temperatures. However, it is assumed that the relationship would not extend beyond the effect of water quality on strength of the concrete at room temperature. The study reported in the August 1956 Magazine of Concrete Research indicated that the effect of temperature on the compressive strength is independent of the water/cement ratio.