Thermal Resistivity of Concrete 1

[steve1]

I have been asked by an electrical enginner in our firm to provide a value of the thermal resistivity of concrete. I have been unable to locate a reference that discuuses this topic. According to the EE "the lower the thermal resistivity (higher thermal conductivity) the better we are electrically speaking". Can anyone provide insight into this property?

 

[concretemasonry]

The thermal resistivity (R-value)will depend on the density of the concrete AND the chemical composition of the aggregates. Generally, lighter concrete has greater resistivity (insulation) than heavier concrete.

I don't have a specific reference handy, but normal weight concrete is in the range of 0.06 to 0.11 hr*sf*degree F/BTU/in (mKW) if I recall correctly. Lightweight concrete, which is less than 115 pcf would have a range of 0.11 to 0.19.

This is usually based on a guarded hor plate test with measurements under steady state conditions - my mind in failing on these details.

You should be able to find it in the ASHRAE manual.

I still do not know how this relates to electrical, but the amount of range in values should pose a problem unless someon wants to pay for and schedule an actual test.

Dick

 

[DRC1]

We have run into this quite a bit. The new 345 kV lines generate a considerable amount of heat and if it is not disapted properly, can cause the line to fail. Geotherm in Canada (and I believe in Arizona) provides testing and expertise in this field. Will have contact info next week.
They are definetely the guys to ask.

 

[Prepakt1]

The High density concretes were used in nuclear construction.
Made with limonite, magnatite and steal punchings as aggregates. A Complex and expensive proceedure

Intrusion Prepakt /marineconcrete.com