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Project ID: G5RD-CT-2000-00346
Finanziato nell'ambito di: FP5-GROWTH
Paese: Sweden

Laboratory test results - HPC under chloride attack

The results include laboratory and field studies of resistance of HPC to chloride attack. More than 22 mixtures of HPC, manufactured in Norway, Germany and Italy, have been investigated in the studies. The Nordic standardised rapid test method NT BUILD 492 was employed in the laboratory study for determination of chloride migration coefficient in different types of HPC cured at different ages (28 days, 6 months and 2 years). The specimens were also exposed in the seawater of different geographic zones from southern to northern European coasts. Chloride penetration profiles in the specimens were examined after one and two years field exposure.

Overall, the results from the CTH method showed that the concrete blended with 7% silica fume reveals an excellent resistance to chloride ingress at both 28 days and 6 months ages. Blending with fly ash or slag results in a good resistance at the older age (e.g. 6 months), but not at the younger age (28 days), due to the slower hydration process. It should be noticed that the chloride diffusivity is just an indicator of chloride penetration and that chloride penetration itself does not make any damage of concrete, but induce corrosion of reinforcement steel, the chloride threshold value for corrosion must be taken into account when evaluating the resistance of concrete to chloride attack.

Both the chloride migration coefficient from the laboratory rapid test and the chloride penetration profiles from the field exposure have supplied very useful information about the influence of the wide range of different constituents on the resistance of HPC to chloride attack.

The chloride ingress data from such a wide range of different mixtures of HPC covering different geographic zones of chloride attack environments are of greatest interest for concrete consumers and suppliers. With these data it was possible to develop a feasible model for prediction of chloride ingress in HPC, so as to be able to assess the resistance of HPC to chloride attack in advance and to avoid therefore the corrosion of reinforcement steel in HPC structures in practice. The experimental results received by different partners have been already partly published and have been included within the final manual with recommendations for optimal use of HPC in different chloride attack environments (Deliverable D10 Report).

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Luping TANG
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