Structural ultra-lightweight concrete – from laboratory research to field trials

This article presents the laboratory development and subsequent field trials of a novel structural ultra-lightweight concrete. The concrete is developed aiming at the application in monolithic buildings (i.e. no insulation layer required), which would facilitate the construction and recycling processes, as well as provide new opportunities to architects and structural engineers. The development of the ultra-lightweight concrete presented in this study includes the optimization of its composition (ultra-lightweight aggregates, binders, admixtures) and is targeted on the concrete properties such as the compressive strength, density and thermal conductivity. In order to reduce the risk of an excessive overheating of concrete during its early hydration process caused by its self-insulating properties, the binder composition and amount was further investigated and optimized. Finally, a material of an ultra-low density (< 800 kg/m3), ultra-low thermal conductivity (as low as 0.14 W/(m·K)) and a compressive strength of 10 MPa was developed. Subsequently, several batches of 2 m3 of concrete were produced in a ready-mix concrete plant and a L-shaped test-wall was cast. The temperature development as well as hardened concrete properties were monitored. The field tests show that, although there still are some issues to overcome (e.g. workability), the developed material has a very good potential to enter the concrete market and find new applications