445
4201.011
Rhodes, J.A.
STP-169-B
Article
1973
After 1973
242-261
Y
The thermal characteristics of concrete covered in this chapter are: thermal conductivity, specific heat, thermal expansion (or contraction), thermal diffusivity, and heat of hydration of cementitious materials. This last property is included because of its significant influence on the thermal and physical behavior of concrete in most of its uses.The mineralogical differences among such aggregates as generally used have little effect on specific heat of the concrete, with values at normal temperatures ranging between 0.22 and 0.24 cal/g.°C (BTU/lb.°F). Increased water content, according to the Boulder Canyon studies, tended to increase the specific heat of the concrete. The actual values found were 0.22 cal/g.°C. at 4 percent of mixing water by weight of concrete and 0.24 cal/g.°C at 7 percent mixing water by weight and higher.
Specific heat varies directly with concrete temperatures. These values represent mass concrete mixes and several aggregate types. Specific heats of most rock types tend to increase up to at least 400°C (750°F), and hydrated cement pastes up to 1000°C (1830°F). Investigations by Harmathy and Allen indicate the specific heat of expanded aggregate lightweight concrete differs little from that of normalweight concrete at ordinary temperatures and also increases up to at least 600°C (1110°F).