Comparison between timber-concrete and steel-concrete composite slabs. Where are we now?

Timber combined with other traditional building materials – concrete and steel – results in innovative solutions for slabs, which generally represent the most impactful structural members in terms of carbon emissions. The comparison outlined in this paper highlights the benefits arisen by composites, where each material properties – both structural and environmental – are exploited and optimised. Timber in particular is light and characterised by a very low value of embodied carbon, while concrete is well known for its cost-effectiveness and excellent compressive strength and steel allows for section’s optimisation and high level of prefabrication. On the other hand, steel is characterised by very high tensile strength, which allows for thin decks, generally coupled with concrete to provide adequate stiffness. These positive characteristics are coupled with some undesirable features for each material, which are sensibly smoothed in case composite sections are adopted: in this way a wider perspective is considered, where not just the material itself is taken into account, but the whole member is studied both according to environmental and structural requirements. Effective bending stiffness of each analysed slabs is calculated, then Life Cycle Assessment with current End-of-Life scenarios is performed. Finally, Stiffness Warming Potential parameter – previously assessed by the authors of this paper – is computed, such that real benefits of combining structural materials is captured in a single value.