Traveter Grupp renewed the protective coating of the concrete in the digester gas zone at the Oisu Biogaas OÜ biogas plant. The upper part of a digester, where the concrete is in constant contact with biogas, is one of the most aggressive environments for concrete: biogenic sulphuric acid, formed through the combined action of moisture and hydrogen sulphide, quickly degrades unprotected concrete.

The works included roughening of the substrate and application of the Sika protective coating system Sikagard®-7000 CR, consisting of Sikagard® P 770 primer and Sikagard® M 790 protective coating. The coating was applied in two layers – a grey first coat and a red second coat.

Sikagard®-7000 CR is a highly chemical-resistant, crack-bridging system based on Xolutec® technology, designed specifically for protecting concrete structures in wastewater treatment plants, sludge treatment facilities and biogas tanks. The system resists biogenic sulphuric acid attack, remains flexible to accommodate structural movement, and its primer can be applied even to damp concrete. The system is approved by the German Institute for Building Technology (DIBt) for use on concrete in biogas facilities.

The works were carried out in July 2025.