Thermal performance of precast concrete sandwich walls with a double-layer insulation system

Abstract

The advances in technology and design principles have required the development of wall systems with superior thermal performance in cold climate regions. This paper aims to develop a thermal-efficient precast concrete sandwich wall (PCS wall) for engineering utilization and investigate its thermal performance under the conditions of steady heat conduction using experimental tests and finite element analysis. The innovative precast concrete sandwich wall was incorporated with a double-layer insulation system (PCS-DLI wall) which consisted of autoclaved aerated concrete (AAC) board and polyurethane (PU) insulation layer. In the experimental program, twelve PCS-DLI specimens were tested using the calibrated hot box method. The tested parameters included the insulation layer thickness, concrete type, steel material property, and connector number. In the modeling program, 3D nonlinear finite element models of the PCS-DLI walls were built and validated against the test results. Subsequently, the validated models were further utilized to analyze the heat-transferring mechanism of the PCS-DLI wall and conduct parametric studies that evaluated the effects of critical structural parameters on the thermal performance of the PCS-DLI wall. The results indicated that the PCS-DLI wall incorporating AAC board and stainless-steel connections exhibited superior thermal performance with a significant decrease in thermal transmittance in comparison to traditional PCS wall with lightweight aggregate concrete panels with carbon steel connectors. In addition, the utilization of AAC board as the inner wall effectively improved the thermal performance of the PCS wall and mitigate the effects of thermal bridges among the connectors. The optimization analysis was also performed to achieve the desired thermal performance of the PCS-DLI wall while minimizing the insulation layer thickness and connector number. The thermal transmittance of the PCS-DLI wall was 0.241 W/(m²·K), which was significantly less than the traditional PCS wall. These results provided design and application suggestions for the innovative PCS-DLI wall in diverse climatic regions.