In the design of the concrete mix, the water absorption of the C-LWA respect to the cured mass of 0.19 g/g was used (see Table ). Considering that water in the pores of the C-LWA in their cured state is at equilibrium with ~90% RH, it can be assumed that the water contained in this state is not released into the concrete if the concrete itself stays at >90% RH and hence does not contribute to the effective w/c.