ACI 122R-14 Guide to Thermal Properties of Concrete and Masonry Systems

ACI 122R-14 Guide to Thermal Properties of Concrete and Masonry Systems. 2.2—Defnitions ACI provides a comprehensive list of defnitions through an online resource, “ACI Concrete Terminology,” http:// www.concrete.org/Tools/ConcreteTerminology.aspx. Def- nitions provided herein complement that resource. heat capacity––measure of the amount of heat required to change by one degree a specifed object. moist density––density of a material where moisture is present. overall coeffcient of thermal transmittance, U–– heat transfer of a construction assembly is determined by combining the thermal resistance of the interior and exterior surface-air-flms with the combined thermal resistance of the total construction materials. solar refectance—surface property of a material deter- mined as the ratio of the refected solar radiation, or electro- magnetic fux, to the incident solar radiation measured on a scale of 0.0 to 1.0: from not refective at 0.0 to 100 percent refective at 1.0. solar refectance index—calculated representation of a material’s surface solar refectance and emittance using temperature rise to represent the ability of a surface to refect solar heat. specifc heat––measure of the amount of heat required to change by one degree a specifed unit of mass of a gas, liquid, of solid. thermal conductance––of a gas, liquid, or solid is a measure of the rate at which heat (energy) passes perpendic- ularly through a unit area of material of specifed thickness for a temperature difference of one degree. thermal conductivity––measure of the rate at which heat (energy) passes perpendicularly through a unit area of ther- mally homogeneous gas, liquid, or solid of unit thickness for a temperature difference of one degree under steady-state conditions. 3.1—Introduction Many factors infuence the thermal conductivity of concrete and concrete products. The thermal properties of concrete are infuenced by the thermal properties and amounts of cement paste and aggregates, and the pres- ence of moisture. Further, the overall thermal conductance of nonmonolithic concrete elements is infuenced by the product confguration. 3.2—Thermal conductivity of concrete The measured thermal conductivity of a material, such as concrete or insulation, is usually determined in accor- dance with ASTM C177 or C1363. Results of many such measurements have been tabulated by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE 2009). Several methods for calculating concrete thermal conductivity have been developed. These calculated estimates are useful because the nearly infnite combina- tions of ingredients in concrete make it nearly impossible to generate test data for all concrete and concrete products.ACI 122R pdf...