Cement decarbonization will not come from one breakthrough technology. Instead, the sector needs a layered approach: using less concrete through better design, substituting clinker with calcined clays and other materials, and applying carbon capture only where necessary. Portland cement remains dominant because it is cheap and standardized, but its emissions come from both kiln heat and limestone chemistry. Practical wedges include lower clinker blends, mass timber for buildings, recycled concrete aggregate, and selective CCS for residual emissions. Each wedge is bounded by regional supply, standards, and cost. The credible path is many small improvements compounding over time, not a single magic cement.
