ETH Zurich researchers predict service life of reinforced concrete using weather data in Zurich; climate drives rust, enabling broader low-carbon use
Low-carbon concrete put to the climate test | ETH Zurich
Low-carbon concrete put to the climate test
Researchers at ETH have developed a new approach that enables the service life of reinforced concrete to be predicted based on weather conditions. This could enable engineers to use low-carbon concrete more widely without creating tomorrow’s maintenance problems.
ETH researchers use weather data to show how moisture affects the service life of reinforced concrete.
The same concrete can have extremely different lifespans depending on the climate, even though, under current standards, the sites studied are classified identically.
This approach assesses the service life more realistically and thus could promote the wider use of low-carbon concrete in construction.
It is hard to imagine the modern world without concrete. Enormous quantities are used in construction worldwide, and the production of cement – its main ingredient – generates a great deal of CO₂, a greenhouse gas that accelerates climate change. Lower carbon cements are therefore a key factor in more climate-friendly construction.
However, this type of concrete often carbonates more quickly than conventional concrete: CO₂ from the air penetrates the concrete and alters its chemical composition. As a result, the steel inside, which contributes significantly to the load-bearing capacity of the structure, can begin to rust.
For this reason, today’s building standards aim to protect the steel from corrosion for as long as possible. However, this approach puts modern, environmentally friendly types of concrete at a disadvantage compared with traditional concrete, which hinders their adoption in practice. Researchers consider the current approach taken by the standards too narrow: according to Cristhiana Albert of the Institute of Building Materials at ETH Zurich, what really matters is how quickly the steel actually rusts afterwards.
Four locations in the climate test
Moisture, in particular, determines how quickly the steel in the concrete rusts. According to Albert, if the concrete is wet, this process can take place up to a hundred times faster than when it is dry. In comparison, the composition of the concrete mixes examined made a significantly smaller difference.
The researchers investigated three concrete mixes at four locations with different climatic conditions: Zurich, Bergen, Manaus and Huailai. They fed detailed weather data into a model that simulates fluctuations in moisture levels within the concrete over time, thereby showing how quickly the steel inside rusts.
For Ueli Angst, Professor of Durability of Engineering Materials at ETH Zurich, one of the findings was particularly surprising: “The climate plays a much bigger role than we expected. The same concrete can behave completely differently in a different climate.” Nevertheless, current European standards classify all four sites in the same category, “alternating wet and dry”.
Rainfall alone does not tell the whole story
This is particularly evident in both Bergen and Manaus, where rainfall levels are around 2,500 millimetres per year. Nevertheless, the calculations show that the steel corrodes at different rates. This is because concrete absorbs water quickly but only dries out slowly. The key factor, therefore, is the pattern of alternating wet and dry periods. The model calculations also show that certain types of low-carbon concrete examined can last for 50 years or more, depending on the location, but may suffer damage sooner under different conditions. Annual rainfall or average humidity alone say little about the extent to which the steel in the concrete corrodes.
Low-carbon concrete is not necessarily worse
The results do not mean that low-carbon concrete is, as a rule, less durable or even unsafe. In terms of strength, such concrete can match conventional concrete. The crucial question is rather how it behaves over the course of decades. It may lose its natural protective effect on the steel more quickly, but if the concrete is not continuously wet, the steel will then rust only very slowly over a long period of time.
“We need to gain a better understanding of how environmentally-friendly types of concrete behave over the long term under different weather conditions,” says Albert. Instead of using the same concrete everywhere according to the same rules, in future, greater consideration must be given to a structure’s location and its climatic conditions. There will no longer be a single solution that works equally well everywhere. In particularly damp regions, for example, additional measures may be needed to reduce water ingress.
The new approach could also help overcome a barrier to the use of lower-carbon building materials. Many of today’s testing methods were developed for conventional cements and increasingly fail to take account of the specific properties of environmentally-friendly types of concrete. “As a result, the current standards can become an obstacle to new and more environmentally friendly materials,” says Angst.
The approach developed is not yet suitable for use in practice: the calculations are complex and need to be further tested on real structures.
In the long term, the researchers aim to develop a simpler method for assessing new types of concrete more quickly, without having to wait decades for experience from real structures.
This is also important in the context of climate change: if the frequency and duration of rainy and dry periods change, the rate at which steel rusts within concrete may also change. In the future, such a “climate test” could reveal which type of low-carbon concrete is best suited to each location in the long term.
Albert C, Schmid T, Zhang Z, Angst U. “Rethinking Concrete Durability for Low-Carbon Concretes through Climate-Informed Corrosion Modelling” Nature Communications, August 21, 2026, DOI: external page 10.1038
07.09.2026 by Carmen Raggenbass, Corporate Communications