Chemically they are net-neutral only if they are non-hydraulic lime, but hydraulic mortars do continue to absorb some CO2 over time. Separately, they are nearl

Chemically they are net-neutral only if they are non-hydraulic lime, but hydraulic mortars do continue to absorb some CO2 over time. Separately, they are nearly always heated with fossil fuels, but, unlike steel, it's not chemically helpful to do so.