read all about it

With the growing interest in non-metallic reinforcements, one of the biggest questions has been: Are these materials ready for standard construction use?

The answer is now a confident yes. In 2024, the German Institute for Building Technology (DIBt) granted general technical approval Z-1.6-308 for carbon reinforcement grids, supported by a newly published national guideline from the German Committee for Reinforced Concrete (DAfStb).

This is a major step forward for engineers, designers, and planners who want to build lighter, longer-lasting, and corrosion-free structures—without the need for special permits or complex custom approvals.

To better understand the significance of this milestone, we spoke with Dr. Marcus Hinzen, Head of Product Development at solidian, who has been directly involved in the approval and guideline development process.

In this interview, he explains what the approval covers, how it impacts design freedom, and what’s next for non-metallic reinforcements in Germany and beyond.

Can you briefly explain what the German national technical approval (Z-1.6-308) covers and why it is significant for non-metallic reinforcements?

Non-metallic reinforcements are a highly innovative construction product, but until recently, they were not yet regulated. There are also no product standards that define the requirements for non-metallic reinforcements in the same way as we are familiar with for reinforcing steel or steel fibers. The reason for this is not a lack of interest from standardization committees but rather the fact that the reinforcements currently available on the market are highly individualized and cannot be generally described in terms of geometry and properties. This situation necessitates the issuance of individual product approvals by the DIBt (German Institute for Building Technology), which legally serve as a full substitute for the product standards that do not yet exist. Therefore, obtaining a product approval is the key requirement for construction without additional regulatory approvals.

The content of such a product approval includes, on the one hand, a definition of application limits, as not all areas of everyday construction can be covered at once. For example, various geometric variations of carbon grids are already covered by the approval for use in bending-stressed, predominantly static applications. This means that most applications can already be addressed. On the other hand, the product approval provides all the design parameters necessary for structural planning.

But how can structures be designed? All relevant design guidelines refer to steel reinforcement.

That is a valid question. After all, product approvals—just like an ETA (European Technical Assessment) at the European level—only include design parameters but not the design rules. For this reason, it was necessary to close this gap as well. Therefore, the German Committee for Reinforced Concrete (DAfStb) began early on to establish a working group for the development of a German guideline. Such a guideline typically follows the structure of the Eurocode and supplements the missing regulations for new construction methods or innovative building products.

Solidian actively participated in this process and contributed to the development of the guideline. The first edition of the guideline, titled "Concrete Structures with Non-Metallic Reinforcement," was published in 2024. In combination with a product approval, it now enables the completely approval-free use of non-metallic reinforcement in the previously mentioned application areas.

What are the main technical requirements and performance standards that non-metallic reinforcements must meet under these regulations?

The great thing about the current regulations is that while we have precisely defined which parameters are important and how they must be tested, we have set very few limits or minimum values. For example, all material combinations of high-performance fibers and polymers can generally be approved. However, they must undergo standardized performance tests, which can result in either very good or weaker design values. The only requirements are that the reinforcement must be impregnated with a polymer and that both the fiber material and the polymer must be harmless in interaction with concrete.

How does the approval affect the design and dimensioning of concrete elements using solidian GRID carbon reinforcement?

The General Building Approval (abZ) for solidian GRID offers users a wide range of benefits. Engineers and designers can now use solidian GRID without the need for costly individual approvals or extensive testing. Since carbon reinforcement does not corrode, the concrete cover for corrosion protection is no longer required. This allows for the design of thinner and lighter concrete elements, reducing material consumption, weight, and CO₂ emissions. At the same time, carbon reinforcement maintains its exceptionally high tensile strength for over 100 years. Ideal application areas include facades, bridges, precast elements, thin-walled panels, and shell structures. The General Building Approval eliminates many barriers to the use of solidian GRID carbon reinforcement. Designers and engineers can now work more easily and efficiently with non-metallic reinforcement without the need for additional approvals. The ability to design slimmer and more durable concrete structures without corrosion risk offers both economic and ecological benefits for the construction industry.

What are the key differences between carbon reinforcement grids and traditional steel reinforcements from a regulatory and application perspective?

From a regulatory perspective, thanks to the DAfStb guideline and our approval, there are fortunately no significant differences between steel and carbon reinforcement anymore. As long as projects remain within the application limits defined by the guideline and approval, carbon reinforcement can be planned just as freely as steel reinforcement. I have already addressed the differences in application potential. The corrosion resistance of carbon reinforcement, which enables a 100-year service life, and the ability to design slimmer, more resource-efficient structures are key advantages of building with carbon reinforcement. However, we have not yet discussed another crucial aspect:
The cement industry, as a major CO₂ emitter, has been working for years on innovative and alternative binder concepts. These efforts are often limited by the fact that the passivation of steel reinforcement can no longer be ensured under certain conditions.The use of non-metallic reinforcements opens up entirely new possibilities for the cement industry, as there is no longer any need to consider the protection of steel reinforcement.

What are the restrictions or limitations imposed by the approval that designers and engineers should be aware of?

As previously mentioned, the product approval includes certain limitations that structural engineers must currently take into account. The following list highlights some key points:

• Steel and carbon reinforcements must not be used together in tensile-stressed areas to avoid contact corrosion.
• Forming on-site is not yet possible with our current carbon reinforcements based on epoxy resin. However, we are actively working on a suitable solution.
• Fatigue loading is not yet covered—the approval currently applies only to quasi-static, predominantly non-dynamic loads.
• The use of solidian GRID as shear reinforcement was not included in the first edition of the approval.

What are the next steps in the development of regulations for non-metallic reinforcements in Germany and the EU? How do you see the future of these materials in construction?

Some of the limitations in the first edition of the German guideline are not technically justified but were simply not addressed in time due to scheduling constraints. Other restrictions were not yet fully developed at the time of publication. We are therefore already working intensively on a second edition of the guideline, which will allow for significantly expanded application possibilities. Key additions include:

• The fatigue behavior of carbon reinforcement, enabling its use in bridge construction.
• Prestressing with carbon tendons, which is particularly important as the high tensile strength of carbon fibers can be leveraged very efficiently in prestressing applications.
• Fire design, i.e., the assessment of load-bearing capacity at high temperatures.
• The use of solidian GRID carbon reinforcement for shear reinforcement.

This second edition of the guideline is expected to be published in 2026 and will be the most comprehensive guideline for non-metallic reinforcement—far more extensive than the current provisions in the new Eurocode. For this reason, efforts are underway to incorporate the guideline’s content into Germany’s National Annex to the Eurocode. Looking even further ahead, we hope that other European countries will align with the German regulations and adopt the guideline’s content.