Floating Castle Made With Low-Carbon Concrete Draws Attention on Eindhoven's Dommel River

Yvonne Mak's Sandbag Castle is a floating concrete installation on the Dommel River in Eindhoven, next to the Van Abbemuseum Cafe. The five-meter-wide, three-meter-high structure stacks sandbag-shaped concrete modules to look like a castle, with red flags that reference beach safety warnings and a coat of arms tied to water, bridges, flora, and hands. The project is also a materials demonstration. It uses over ten low-carbon concrete formulations, including calcined clay, alternative binders, geopolymer concrete, recycled aggregates, and self-healing concrete. Developed with main partner TBI and material specialists, the installation shows how concrete construction could cut CO2 emissions while keeping structural form. For anyone tracking low-carbon building materials, this is a compact example of what is technically possible today.