In a following step, the C-LWA were used to replace part of the coarse aggregate (gravel) in concrete, where they made up about 20% of the total volume. The amount of the C-LWA in the concrete was calculated to compensate via negative emissions for the whole emissions of the concrete (originating mostly from the cement), thereby obtaining concrete with net zero emissions. In order to assess the integrity of the C-LWA during mixing, the microstructure of concrete and the embedded C-LWA were studied with X-ray tomography. We also investigated the mechanical properties of the concretes in order to assess their suitability for structural applications.