Thermal Properties
Thermal properties of concrete to
understand the behavior of concrete to heating and cooling.The study of thermal
properties of concrete is an important aspect while dealing with the durability
of concrete.
Concrete is a material used in
all climatic regions for all kinds of structures.The important properties that
will be discussed are:
ü Thermal
conductivity
ü Thermal
diffusivity
ü Specific
heat
ü Coefficient
of thermal expansion
1Thermal Conductivity
This measures the ability of
material to conduct heat. Thermal conductivity is measured in joules per second
per square meter of are conductivity of concrete depends on type of aggregate a
of body when the temperature difference is 1degree C per meter thickness of the
body.
The conductivity of concrete
depends on type of aggregate moisture content, density and temperature of
concrete. When the concrete is saturated, the conductivity ranges generally
between about 1.4 to 3.4 J/S/m2
2 Thermal Diffusivity
Diffusivity represents the rate
at which temperature changes within the concrete mass. Diffusivity is simply
related to the conductivity by the following equation:
Diffusivity=Conductivity/CP
Where C is the specific heat, and
P is the density of Concrete. The range of diffusivity of concrete is between
0.002 to 0.006m2/h
3Specific heat
It is defined as the quantity of
heat, required to raise the temperature of a unit mass of a material by one
degree centigrade. The common range of values for concrete is between 840 to
1170 j/kg3/C
4Coefficient Thermal Expansion
It is defined as the change in
unit length per degree change of temperature. In concrete, it depends upon the
mix proportions. The coefficient of thermal expansion of hydrated cement paste
varies between 11x10^-6 and 20x10^-6 per degree C. The coefficient of thermal
expansion of aggregates varies between 5x10^6 and 12x10^-6 per degree C
Limestone and Gabbros will have low values and gravel and Quartzite will have
high values of coefficient of thermal expansion.
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