Ultra-lightweight foamed concrete for an automated facade application

The present study deals with the development and characterisation of ultra-lightweight foamed concrete (ULFC) that can be automatically sprayed onto bare walls to allow for sustainable facade refurbishments with a smaller workload and extended design possibilities. Since heat insulation and wall adhesion increase with reduced density, the objective of the development was to strive for ultra-low densities below 150 kg/m 3 that can be produced consistently and applied onto vertical walls by robots. For this purpose, rapid-setting binders based on Portland cement, calcium aluminate cement and calcium sulfate as well as protein- and surfactant-based foaming agents, were investigated to stabilise the foam structure initially. The results of this study demonstrate a foamed concrete mixture and a generator that allow for plastic densities below 150 kg/m 3 . The developed ULFC was examined in terms of thermal conductivity, microstructure, vertical applicability, compressive strength and durability. The results indicate excellent heat-insulation potential with the disadvantage that the material loses strength over time due to carbonation and the precipitation of ettringite.