WHAT IS GNEISS?
Gneiss is a monolithic mineral in the Estonian basement found beneath sedimentary bedrock layers. It has parameters similar to granite. The crystalline basement layers are closer to the ground on the northern coast, whereas in southern Estonia, they lie deeper.
Since hydropower storage in Estonia has to be underground, approximately 38 million tons of gneiss will be extracted from the Pakri Peninsula during construction. Estonia’s road construction sector could benefit significantly from replacing traditional limestone aggregates with gneiss in road pavement.
Gneiss offers significant advantages compared to limestone as a construction material, including high abrasion- resistant, lower long-term costs, and a much smaller environmental footprint than commonly used materials such as limestone and imported granite. Find out how TalTech has assessed the benefits of gneiss used as road construction aggregates in the pumped hydro storage project by clicking HERE.
Benefits of Gneiss
High abrasion resistance
Laboratory tests show that gneiss has 5–6 times greater resistance to mechanical abrasion than the commonly used limestone in Estonia. As a result, road base layers built with gneiss aggregates have a significantly longer life cycle—at least 50 years, which is about twice as long as roads built with limestone aggregates.
Economic Advantage
Using highly abrasion resistant construction materials in roads reduces total lifecycle costs and decreases the carbon footprint, especially in the long term. The longer lasting the road, the less frequent and extensive repairs are needed, postponing significant reconstruction . Over 50 years, the cost savings from using gneiss aggregates are estimated at 10–30%, depending on the road type—resulting in annual savings of €17–20 million.
Environmental Benefits
Since gneiss does not need to be imported, its transportation requires less fossil fuels. Additionally, because roads built with gneiss last longer, its use significantly reduces CO₂ emissions over the road’s life cycle compared to limestone.
Preserving Natural Landscapes
Using gneiss helps slow the expansion of limestone quarries—potentially reducing their growth by over 400 hectares over 50 years. This minimises environmental impact and improves conditions for local communities. As gneiss is extracted from deep underground, the resulting openings can be repurposed/reused? for other industries. In addition to hydropower facilities, these spaces could be used for underground datacentres or secure storage facilities for strategic national reserves.
