In the previous post we have an overall idea about thermal properties of concrete. Of those parameters we will discuss not about specific heat. Specific heat is a basic term of physics, we will not go through the definition. We will now learn about influences of specific heat of concrete.
Specific heat is found to be increased with the increase in moisture content of concrete. But mineralogical properties of aggregate have no influence on specific heat. This property increased with the increment of temperature of concrete. But an opposite response is observed with density of concrete i.e. it increases with the decrease in concrete density.
For ordinary concrete, specific heat may vary from 0.20 to 0.28 Btu/lb per 0F. A term named thermal absorptivity is used in quantify the fire effects on concrete.
The expression is
Thermal absorptivity= √(Kρc)
Where K=thermal conductivity of concrete
ρ=density of concrete
C=specific heat of concrete
Form this expression, we can conclude, this thermal property is both depend on specific heat and thermal conductivity. So both thermal conductivity and specific heat are important to determine behavior of concrete in extreme temperature like fire and explosion generated heat.
Thermal absorptivity of normal weight concrete is 6.44 Btu/ft2h1/2per0F
Thermal absorptivity of light weight concrete is 2.73 Btu/ft2h1/2per0F for concrete of density 90.5 lb/ft3