Effect of coupled deterioration mechanisms on concrete durability in cold environments

The durability of concrete is traditionally assessed based on the deterioration of a single mechanism. Yet in practice, as a result of varying environmental exposure, concrete is typically affected by several deterioration mechanisms, possibly with synergetic effect on the degradation rate of concrete. Concrete infrastructure located in cold climates has to perform in rather difficult conditions due to the extremely harsh winters. This results in unique combinations of degradation mechanisms. Commonly occurring deterioration mechanisms are freeze-thaw, carbonation and chloride induced corrosion. In light of recent research more attention is now being drawn to assessing coupled deterioration mechanisms. For instance, evaluating how cracks resulting from freeze-thaw influence chloride ingress, or how carbonation changes the surface properties and thereby influencing frost-salt scaling and chloride penetration. In this paper, the results of research projects at VTT based on assessing coupling deterioration mechanisms are presented. These research projects have built on several decades of concrete durability research at VTT, including 15 years of field station studies. Durability performance has been assessed both by accelerated laboratory testing and from in situ exposure results from field stations. This research provides the background for development of service life prediction tools, and supports a holistic approach for deterioration assessment.