Experimental investigations of sandwich panels using high performance concrete thin plates exposed to fire

Structural sandwich panels using thin high performance concrete (HPC) plates offer a possibility to address the modern environmental challenges faced by the construction industry. Fire resistance is a major necessity in structures using HPC. This paper presents experimental studies at elevated temperatures for panels with 30 mm thick plates stiffened by structural ribs, thick insulation layers, and steel shear connecting systems. Parametric variation assessing the role of each component of the sandwich structure was performed on unloaded specimens of reduced size. Full size walls were tested with load. Tests were performed in standard furnaces, following the conditions of REI certification tests. Unloaded specimens successfully passed tests. Loaded specimens met the R and I requirements, failing E due to sustained flaming of the insulation. They exhibited multiple cracking of their exposed plate and one of them experienced heavy heat-induced spalling. Results highlighted insulation shear failure from differential thermal expansion at the interface with concrete. It suggests the existence of a high bond level between the two materials which might allow structural applications at early age. Cracks resulted from buckling and thermal bowing, present in the upper and lower parts of the panel. Shear connectors created stress concentrations leading to local failure. Only ribs were found to have a structural role, the plate being largely negligible and solely protecting the insulation from heat. Performance could be enhanced by using thicker plates (50 mm).