​​​​​​​Safe and sustainable use of local aggregates for concrete. Effect of pyrrhotite on concrete durability (2020-2024)

Why?

If the pyrrhotite mineral is present in concrete aggregates, it can lead to expansion and cracking of the concrete, in the worst case to such an extent that concrete structures must be demolished and replaced after only a few years. In the last 10 years, this has happened in Canada and the USA, and led to claims for compensation from homeowners of several billion NOK. These damage cases have raised international awareness on the topic, also here in Norway. Limited knowledge of the damage mechanisms and uncertainty regarding the current European regulations and limit values ​​for the content of sulfur* in aggregates, poses a major challenge for the aggregate and concrete industry and creates uncertainty for construction owners. There is a need to revise the regulations, and it is important that the Norwegian industry gets involved, so that the interests of Norwegian aggregate and concrete producers and owners of Norwegian infrastructure are safeguarded.

*Pyrrhotite is a mineral consisting of iron and sulfur. In the absence of methods for direct quantification of pyrrhotite, the sulfur content is quantified.

What is the challenge?

In order to ensure sustainable and safe use of aggregate resources in concrete, there is a need to revise current analytical methods and limit values ​​for the sulfur content* in aggregates. As part of this, there is a need to develop reliable laboratory methods for accelerated testing of concrete in order to be able to predict potential damage development as a result of the use of aggregates with varying contents of pyrrhotite.

The objective of the project

Contribute to more sustainable and safe use of local aggregate resources for future concrete structures in Norway by improving our understanding of the issue and developing new regulations and test methods.

Main focus areas of the project

1. Develop reliable procedures for determining the critical content of sulfide minerals in aggregates. The entire process from sampling to analysis and reporting must be optimized to ensure reliable results.
2. Critical review and revision of the limit values ​​for sulfur* in the regulations. These limit values ​​must be fine-tuned so that they safeguard against long-term damage development, without excluding sustainable aggregate resources from the market.
3. Develop reliable testing methods for aggregates and concrete. The test methods must provide safety and predictability for the owners, aggregate and concrete manufacturers and contractors.

Project organization

The project is divided in 2 phases.

Phase I includes methods for characterizing aggregates and establishing methods for testing aggregates in concrete.

In Phase II, we will take a closer look at link lab fields, limit values ​​and function testing. Research partners in the project's Phase I are the Norwegian Public Roads Administration, NTNU and SINTEF. PhD candidate Nikolas Oberhardt and Senior Researcher Jan Lindgård are key players in Phase I. In addition, we have established collaboration with international universities and research institutions, e.g. in Canada and the United States.

Budget and financing

The total budget is 22 MNOK for the period 2020-2024. Phase I is fully funded with 12 MNOK through contributions from the following partners: the Norwegian Public Roads Administration, BaneNOR, Heidelberg-Cement Northern Europe, the Research Council and NTNU. An additional 10 MNOK is needed to be able to complete Phase II.