Concrete and Steel Account for About 11% of Global Greenhouse Gas Emissions

Concrete and steel account for about 11% of global greenhouse gas emissions. I'm curious, knowing that these materials take a lot of energy to produce and manufacture, do we know how good we can be? We've already talked about net zero being the goal, but let's say there's no technology improvements and it's just a practice improvement. How low can we reasonably get that number? It's a hard number to quantify.