The concretes with C-LWA had lower density in the hardened state of about 12% and 14% for the C-LWA presaturated and C-LWA dry, respectively, compared to the reference concrete (Table ). The concretes with the C-LWA contained about 20% vol-% of the LWA with their water-accessible porosity of 45% (see Table ), hence the porosity of concretes should nominally increase by about 9%. In addition to this extra porosity, a further reduction of concrete density was due to the fact that the solid part of the pellets is less dense than the normal-weight aggregates that are replaced. These effects can be accounted for in the mix design based on the known densities of the components. Finally, additional porosity may be due to entrapped air bubbles that may originate both from the LWA and from the reduced workability of the mix -this was the case for the C-LWA dry concrete with over 6% air content in fresh state (about 3% more compared to the other concretes, see Table ).