THERMAL PROPERTIES OF CONCRETE

The main thermal properties required for the design of structures are thermal conductivity, thermal diffusivity, specific heat, and thermal expansion coefficient.

The thermal properties of concrete are a measure of the ability to conduct concrete heat and are measured when the temperature difference in British thermal units per hour per square foot area of ​​the body is 1 ° F per foot thickness.

Thermal conductivity depends on the composition of the concrete. Structural concrete, which has a normal composition, conducts heat more easily than lighter concrete. The lower the water content of the mixture, the greater the conductivity of hardened concrete.

The density of concrete does not significantly affect the conductivity of ordinary concrete. The variability of the thermal conductivity of concrete with temperature is shown in Fig. 8.28

Where D, k, S, and d are the thermal diffusivity, thermal conductivity, specific heat, and density of concrete, respectively.

The specific heat gives the heat capacity of the concrete. It increases with the moisture content of the concrete. The specific heat values ​​of common concrete are between 0.2 and 0.28 BTU / lb / ° F.

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The coefficient of thermal expansion of concrete depends on the composition of the mixture and the values ​​of the coefficient of expansion of cement paste and aggregate. The coefficient for normally treated concrete decreases slightly with age but it is not the case in processed concrete under high-pressure steam.

For common concrete, the value of the thermal expansion coefficient varies from 9 × 10-6 ° C to 12 × 10-6 ° C.

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