Architects and engineers have, for a long time, broadly specified concrete by default. Decisions mainly focused on strength class, finish, reinforcement, exposure class, and cost. Even though varied mixes, depending on the previously mentioned factors, are commonly used within the same project, both regulations and markets have developed a need for a more nuanced approach. This is because material choice is not just important for its structural properties anymore, but also for its environmental impact.

Today’s field includes developments within Carbon Capture and Storage (CCS) cement, Supplementary Cementitious Materials (SCMs), biochar-enhanced mixes, Ultra-High-Performance Concrete (UHPC), self-healing systems, circular recovery pathways, and more. Each strategy prioritizes a different technical aspect. Some reduce process emissions. Others store carbon. Some extend span and slenderness. Some focus on crack control, repair cycles, or material recovery. While "Concrete” still sounds like one category, it no longer acts like one in practice.

The market has already moved beyond pilot language. Heidelberg sold out its 2025 evoZero production from Brevik¹. Northern Lights has started storing captured carbon dioxide from the Brevik cement plant beneath the North Sea². CRH paid $2.1 billion for Eco Material, a company centered on supplying Supplementary Cementitious Materials³. The interesting thing is that despite their individual success, these actions follow different industry logics. One relies on capture and storage infrastructure, while the other depends on byproduct streams and alternative binders. Their coexistence tells a larger story: the material sector is expanding rather than settling on a single concrete formula.

Regulation influences the current shift. The revised Energy Performance of Buildings Directive, EPBD⁴, and the European Commission’s 2025 life-cycle global warming potential framework promote low-carbon materials, carbon storage, reuse, and recycling, bringing them closer to mainstream building practices. Material choice now carries more importance early in the project. What used to be a late-stage substitution decision is increasingly influencing the project from the beginning. How has this influence started to affect the construction industry?

Global regulatory shifts, climate, and economic challenges are creating a market for high specialization, where researchers and companies develop various methods to address future concrete viability in construction. This leads to the previous monolithic material branching into multiple families, each with its own purpose, advantages, and disadvantages.

One family reduces emissions upstream. Carbon Capture and Storage (CCS) cement fits here. The chemistry of concrete can stay familiar at the project level while carbon reduction occurs through capture, transport, and deep geological storage. At Brevik, they capture carbon dioxide, liquefy it, and ship it to Øygarden. At Øygarden, the liquified carbon dioxide is sent through a pipeline and injected about 2,600 meters below the seabed⁵. This approach suits projects that prefer conventional structural logic with a lower process-emissions profile.

A second family incorporates alternatives to clinker into the binder. Here, Supplementary Cementitious Materials (SCMs) such as fly ash, slag, silica fume, calcined clays, and similar materials⁶ partially replace clinker in the binder system, which modifies the cementitious matrix itself. They can reduce emissions and may enhance workability or durability depending on the mix and curing process. This family has contributed significantly to practical decarbonization efforts in concrete so far. However, it also faces a serious supply challenge because the most well-known SCM sources are linked to shrinking industries⁷.

A third family stores carbon within the material itself. Biochar-enhanced systems and carbon-curing or mineralization routes fall into this category. Holcim and ELEMENTAL have showcased biochar concrete as both a carbon-storage solution and an architectural material⁸. The research literature demonstrates why this approach is technically compelling yet challenging. Biochar can influence hydration, moisture behavior, workability, and strength, depending on factors such as dosage, particle size, feedstock, water-to-biochar ratio, and mixing method⁹. Both strong and weak mixes are achievable. Architects who view this as simply "greener concrete” overlook the core point. This family alters the internal behavior of the concrete, not just its emissions profile, which means precision is important for consistent performance, and the properties ought to be monitored to ensure they persist over time.

A fourth family enhances structural performance and longevity. Ultra-High-Performance Concrete, UHPC, fits into this category. UHPC achieves its high strength and low permeability through dense particle packing, very low water-binder ratios, admixtures, and often fibers¹⁰. It typically includes Supplementary Cementitious Materials such as silica fume, which contribute to its packing and reaction processes. Architects favor UHPC because it can reduce section sizes, span longer distances, refine details, and boost durability. While not a new material (it’s been used since the 1990s), its significance now depends on context. It’s recently been used in Snøhetta’s Shanghai Grand Opera House. Expected to be completed in a couple of months, it's already garnered praise for the open spaces and long, cantilevered stair spans made possible by UHPC¹¹.

A fifth category is emerging around durability and circularity. Self-healing systems are part of this group, as is the recovery of cement fines and aggregates from demolished concrete. The growth of self-healing strategies partly stems from the fact that some lower-carbon concrete systems tend to be more brittle or prone to cracking than traditional Portland cement mixes under certain formulations. Lower-carbon concrete is not inherently weaker, but some formulations involve different durability trade-offs, and self-healing offers a way to manage these¹². Circular recovery addresses another issue entirely: how to lessen dependence on virgin inputs. When these groups are considered together, a more complex question arises¹³. If some overlap already exists, why would they not eventually combine into a single, super-concrete?

Some overlap between concrete families is already occurring. UHPC often incorporates Supplementary Cementitious Materials¹⁴. Low-carbon mixes can include self-healing strategies¹⁵. Biochar can serve as a carbon-storage additive while also influencing internal curing¹⁶. Carbon-curing can enhance early strength while sequestering carbon. The field is not confined to separate categories, and future hybrid approaches are likely, but unlikely to become a unified standard.

The obstacle is not imagination or possibility, but rather conflicting optimization. Carbon Capture and Storage (CCS) in cement addresses process emissions through industrial infrastructure but does not resolve crack-healing, creep compatibility, or fire behavior at the material level. Supplementary Cementitious Materials (SCMs) reduce clinker demand, but the traditional SCM supply base is tightening¹⁷. Biochar can lower net emissions and support some mixed properties, though higher dosages may reduce workability or compressive strength. Ultra-High-Performance Concrete (UHPC) provides exceptional strength and durability, but its dense matrix and low permeability require careful fire and curing design¹⁸. Self-healing systems enhance crack management and service life, but they introduce biological, chemical, and cost constraints¹⁹. These priorities overlap and do not fit neatly into one cheapest, strongest, lowest-carbon, easiest-to-build, universally available solution.

Supply chains further widen the gap. Fly ash and slag are decreasing as coal power and blast-furnace steel decline. Calcined clays, natural pozzolans, recovered fines, and alternative binders can replace some of that volume, but they depend on geology, transportation, processing, and regional industry. Biochar depends on feedstock quality and pyrolysis. Carbon Capture and Storage, CCS, depends on highly specialized capture, shipping, storage, and monitoring infrastructure. Ultra-High-Performance Concrete, UHPC, depends on specialized mix design and quality control. The chemistry alone does not determine the outcome; geography, logistics, and industrial structure add layers of practical challenges that one producer is unlikely to solve. Yet, progress within the material branches might still be revolutionary in terms of producing safer, stronger, more sustainable and durable buildings. It might be easy to be swept away by the potential upsides and what this means for the future of the industry, but there are, at the same time, reasons to be careful, especially about getting caught up in the idea of a single, universal solution.

The Carbon Capture and Storage (CCS) route warrants caution rather than default approval. Northern Lights has started operating, and current evidence indicates that deep geological storage is viable when reservoir selection, pressure management, well integrity, and monitoring are properly maintained. Independent reviews still identify risks, including leakage pathways, caprock integrity, pressure buildup, geochemical changes, and induced seismic activity. Marine concerns focus on potential leakage and its effects on sediments and seawater chemistry. Long-term success relies on effective containment and monitoring over decades²⁰.

Supplementary Cementitious Materials, SCMs, raise a different question. A decarbonization path built too heavily around fly ash and slag would rely on feedstocks that are declining for structural reasons, not temporary ones. That does not necessarily render low-carbon concrete a dead end, but it does mean some of today’s most familiar routes are transitional rather than permanent. Calcined clay and other alternatives may scale well in some regions, but they do not offer the same ease everywhere²¹.

Ultra-High-Performance Concrete, UHPC, requires a careful approach as well. Concrete is often considered fire-resistant, but UHPC requires more attention in this regard. Its low permeability can trap vapor pressure and increase the risk of explosive spalling unless mitigation measures, such as polypropylene fibers, are included. Tests and reviews indicate that these strategies can be effective²². They also show that UHPC should not be specified as if it performs exactly like ordinary concrete in heat; the material benefits from precise handling.

This is where the architectural opportunity starts. A project doesn't have to choose one specific family and apply it throughout the entire building.

Recent research on composite elements made from Ultra-High-Performance Concrete, UHPC, and normal-strength concrete shows that hybrid use is technically feasible. The main concern is the interface: casting interval, surface preparation, curing conditions, and bond behavior²³. Researchers are examining these interfaces because combining different types of concrete within one element, retrofit, or prefabricated assembly is already a genuine engineering challenge. This matters for architects because it raises another design question. Which parts of the project truly require the same concrete logic?

As the concrete branches out, it opens up the architectural possibility of another, more practical approach: concrete purpose zoning. Use Ultra-High-Performance Concrete, UHPC, where thin sections, long spans, sharp cantilevers, or highly stressed connections justify it. Rely on lower-carbon conventional systems where volume is more important than extreme performance. Implement durability-focused or self-healing systems in façade zones, wet zones, or areas prone to repairs. Choose circular-recovery pathways when they are supported by the supply chain and quality control. A single project can include more than one concrete type. The interfaces require careful design intent from the start.

The frictions are in those respective interfaces and their logistics. Different families can creep, shrink, cure, and respond to heat in different ways. Fire design may need special attention in UHPC zones. Multiple suppliers might mean multiple approval processes, quality-control routines, and sequencing constraints. The specifications need to explain why one family is in one zone and another is in the next. None of that makes zoning impossible. It makes zoning a design challenge rather than a procurement shortcut. If you know the respective properties and their performance well enough, it might help you create slender, more generous spaces with less structural volume, that are durable and have a lower carbon footprint, by deliberately placing the families where they matter most. Mastering such an orchestration would put you ahead of the competition, as you could deliver more with a rational and commonly used material.

A progress-adapted concrete strategy begins with functional priorities. Which parts of the project require lower process emissions within a familiar structural system? Where does section thickness justify the use of Ultra-High-Performance Concrete, UHPC? Where does long service life or crack control outweigh the lowest initial material cost? Where does feedstock recovery take precedence over peak strength? Once the project is viewed this way, a generic concrete schedule from an outdated phase of the material market seems shorthanded.

As an exercise, review the next concrete-heavy project by zone, rather than using a single default mix:

The exercise will not create a miracle material. It will clarify the specification logic. Concrete has stopped acting like a single broad category. The design process now needs to catch up.

That’s all from this week’s deep dive! It’s been really rewarding to research, but heavy work! If you enjoyed it, share it with someone who also might, and make sure the knowledge reaches further!

-Johan

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