Pakkasprojekti25 – developing the quality assurance of frost-resistant concrete
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A national frost project has been launched in Finland to renew the quality assurance of the frost resistance of concrete. The Pakkasprojekti25 (Frost Project 25) was implemented during 2025 and contained three subprojects. Subproject 1 examined the scaling of existing bridge structures in the slab test, revealing wide variability (300–22 000 g/m2) and rather unexpected carbonation effects. Subproject 2, the largest part of the project, identified critical error sources in the slab test through laboratory visits, surveys, and research, and produced a detailed national application guide (By 72, Part 5) to complement technical specification CEN/TS 12390-9:2016. A new round-robin test demonstrated that the coefficient of variation for reproducibility improved from 82 % to 34 % (P30 concrete) and 42 % (P50 concrete), both within the reference values. The improvement was achieved primarily through harmonisation of practices between laboratories. Subproject 3 proposed developments in quality assurance practices of frost resistance, including simplified limit values and removal of the spacing factor requirement for exposure class XF1.
