Hi Anthony - great article, congratulations!
I think one thing to keep in mind is that EAF steel is not primary steel production, but rather recycled steel, so depending on demand blast furnace steel is hard to get away from. Of course hydrogen reduced steel is around the corner which will significantly reduce the impact of steel production and may lead to net 0 emission steel (not sure about the mining impacts, etc.). I particularly like that you’ve tied the emissions intensity back to the electricity grid, for most materials this will dominate… except for concrete.
Flyash SCM is a bug bear of mine, because it is producing a revenue stream for coal power plants, and the attribution of emissions is hidden by the assumption that this revenue is <1%, as coal power becomes less competitve with renewables the attribution will need to change, and even with very little attribution the emission intensity of flyash swamps OPC. In my opinion the very difficult emissions from cement may need to be dealt with by circular economy design.
Finally - I couldn’t agree more with this statement
A bigger lever is choosing to retrofit existing buildings, where the structure and envelope are repurposed, taking advantage of the carbon already expended.