The influence of frost attack on chloride transport in concrete

Research on the durability of reinforced concrete structures is focusing ever more on the combined effect of degradation mechanisms. While most of the research has been directed at combined carbonation and chloride penetration, recently some attention has been given to emulate combined degradation conditions, especially those existing in Nordic countries (frost attack/chloride penetration), with regards to the harsh environmental conditions. Frost attack of concrete affects the chloride penetration by reducing the concrete cover, and more importantly, by changing the characteristics of the surface and internal concrete due to cracking. Recent research has shown there to be a synergetic effect, but no steps have been taken to characterize and comprehend the mechanisms involved, and to develop a procedure to transfer this knowledge to the industry and into practise. To address this need, a research project was set up with the objective of: ascertaining how ice formation in the concrete pore structure influences the transport properties of chloride ions in un-cracked concrete; to establish the characteristics of chloride ions transport in concrete subject to frost attack; and integrate the effect of combined degradation mechanism into a service life model. In this paper the, the preliminary result of this research project are presented.