Period: 1.1.2024 - 31.12.2026

Content: The key themes in the Innovation and Skills in Finland 2021−2027 program are to achieve a carbon-neutral Finland and to encourage a transition to a circular economy. Due to climate change, the structure/infrastructure sector has recently paid more attention to more sustainable construction works/solutions, among others by using materials with a low carbon footprint. The structure/infrastructure sector has a need for more efficient ways/methods to decrease the environmental impact of acid sulfate soils and for better technical solutions to problems related to construction on acid sulfate soils. In current earthworks projects, mass transfers are usually required where soil materials are swapped out with sand or gravel and transported away. The re-use of acid sulfate soil materials can be challenging due to their potential acidity, corrosive properties and in some cases poor geotechnical properties.

The re-use of acid sulfate soil materials can be made feasible by neutralization and stabilization, after which the soil materials can be used safely as base materials, for example as noise barriers and other applied earthwork projects. Stabilization and neutralization of acid sulfate soil materials inhibit the acid formation in the soil materials and the subsequent environmental load and problems related to corrosion.

Stabilization and neutralization techniques currently use cement or lime, the use of these materials greatly increases the carbon footprint of the construction sector. In earthworks, the use of recycled materials is still uncommon, even though it has been shown that industrial side streams, such as ash and slag, may be used for stabilization and neutralization. The use of industrial side streams does not cause any new release of carbon dioxide, but in order to utilize them in an environmentally safe way, research in both laboratory and field scale is required. The re-use, instead of disposal, of soil materials is wise and beneficial both for the environment and the construction sector from a sustainability and economic point of view.

A prerequisite for the stabilization and neutralization, is that the properties of the excavated material is investigated properly so that the correct amount of additives is used. Time is often of the essence and information about the excavated material properties should be assessed rapidly since a proper investigation of the soil materials cannot always be performed before excavations start. Currently, acidifying soil materials can be characterized using quick identification and risk assessment methods, but the suitability of these methods for the assessment of neutralization, stabilization and corrosion have not been studied. Corrosion studies are currently performed according to guidelines by the Finnish Transport Infrastructure Agency. However, these guidelines do not consider the change in environmental conditions such as lower groundwater levels and changes in the redox potential, which considerably affect corrosion. In construction projects, acid sulfate soil assessment and corrosion studies are performed separately, even though samples are collected simultaneously, and acid sulfate soil materials greatly increase the risk of corrosion. Therefore, several analytical methods for acid sulfate soils may be used directly to assess corrosion risks, which will save resources and time. With the aid of analytical methods developed for acid sulfate soils, it is possible to consider environmental changes and their effect on corrosion.

The goal of this project is to develop research methods for acid sulfate soils from the perspective of corrosion risks and sustainable re-use of excavated soil materials. During the project, the use of industrial side streams for neutralization and stabilization of acid sulfate soil materials is also investigated, which would enable re-use of such soil materials; considering corrosion risks and if needed, update current guidelines.

Focus area: Hållbar energiteknik

Campus: Vasa Wolffskavägen 33

Financers: Europeiska regionala utvecklingsfonden (ERUF) 2021-2027, Fingrid Oy, Väylävirasto, Kiertokaari Oy

Project owner: Finnish Environment Institute

Project manager: Eva Högfors-Rönnholm

Partners: Finnish Environment Institute, Geological Survey of Finland, Åbo Akademi University, Novia University of Applied Sciences

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