Thermal performance of variable density wall panels made using Portland cement or inorganic polymer concrete

Structural concrete has poor insulation when used as building facades but does have the potential to provide significant thermal mass benefits. The concept of a variable density wall panel was proposed that incorporates both exterior insulation and interior thermal mass. This is achieved by stratifying concrete where a concrete mix containing different density aggregates is subjected to controlled segregation using high frequency vibration. These precast panels are designed to have the lightweight insulating layer on the outside while the heavyweight layer on the inside contributes strength and thermal mass that is 'connected' to the building interior. The thermal properties and structural performance of variable density wall panels was investigated made with a range of Portland cement (PC) and inorganic polymer concrete mixes and using different light and heavyweight aggregates. Results from this study found that inorganic polymer concrete produces lower thermal conductivity and volumetric heat capacity compared with PC concrete. The overall thermal performance of stratified concrete panels was superior to that of lightweight panels having similar insulation resistance. Variable density panels exposed to dynamic ambient conditions showed considerably better thermal performance than that predicted from steady-state U-factors.