Stacking Is Regional - How Concrete Supply Chains get to Zero

In Carbon: The Reason We Are Here, we established that no single technology will decarbonize concrete alone. The industry must stack multiple levers — SCMs, novel binders, carbon mineralization into SCMs and aggregates, carbon-cured additives, and CCS-produced cement — all layered together in the same ready-mix truck to reach 90%+ reduction. We introduced the "Ready Mix Truck Test" as the strategic filter: does a subject solution play well with others?

The ‘Ready Mix Truck Test’ addresses stacking at the product level — what goes into a single cubic yard of concrete. We now take on the harder question: how do you stack at the regional level? Or put another way: What combination of decarbonized cementitious production & distribution sites do I need to collectively deliver a fully decarbonized supply chain across all concrete needs in my region?

The ingredients available for stacking are not the same everywhere. They are dictated by geology, logistics, policy, and the physical infrastructure of a specific supply basin. They are also produced at different volumes and costs.

To answer that question, we need data. At CTC, we collect and synthesize supply chain intelligence across the national concrete ecosystem and publish some of it through the Concrete Atlas — our platform for mapping cement plants, ready-mix facilities, SCM availability, and regional emissions profiles.

Concrete is a hyper-local commodity. It is heavy, cheap, and perishable — a ready-mix truck must deliver within 90 minutes of batching. While some individual feedstocks like cement or slag are sometimes shipped, every region's concrete is fundamentally shaped by what is physically available within a short radius. And those inputs vary enormously and have knock on effects on logistics, regulation, & cost.

Here is where regional geology directly dictates decarbonization strategy. Southern California's aggregates — primarily alluvial deposits from the LA River basin and desert washes — are generally sub-optimal: poorly graded, high absorption, and often rounded rather than angular.

When local aggregate is sub-optimal in shape, grading, or absorption, mix designers are forced to use a higher cement factor — substantially more Portland cement per cubic yard — to achieve the required structural performance and workability. A typical LA mix uses 564–658 lbs/CY of cementitious material, compared to 470–520 lbs/CY in markets with excellent glacial aggregate like the Upper Midwest.

This means every cubic yard poured in Southern California starts with a carbon penalty. The region cannot simply optimize its way out of the problem — the geology dictates it. This is precisely why stacking must be regional: the constraint is literally in the earth.

This is the regional roadmap: build the SCM supply chain to displace 2.75 million additional tons of clinker, decarbonize the remaining kilns producing 1.5 million tons of OPC, and deploy CCU to capture and utilize ~40% of residual process CO₂ — mineralizing it into aggregates, curing concrete with captured carbon, and producing carbonate building products. All three must happen simultaneously. The City of LA, City of Long Beach, and County of Los Angeles — in partnership with USGBC California — have already begun this work through their LA28 Low-Carbon Concrete RFI, targeting 1 million tons of low-carbon alternatives per year by 2030, with findings to be published at Carbon Forward on September 17, 2026.