Analysis of chloride threshold from laboratory and field experiments in marine atmosphere zone

• Lower water to cement ratio means higher chloride threshold.
• Pozzolanic addition means lower chloride threshold.
• Field chloride thresholds are lower than laboratory chloride thresholds.
• There is a linear relationship between laboratory and field chloride thresholds.

Studies focusing on chloride threshold analysis based on field experiments are still scarce. Although taking longer than laboratory experiments, they can help on setting chloride thresholds closer to realistic conditions. The present work analyses results from reinforced concrete specimens exposed in a marine atmosphere zone of the northeast coast of Brazil and also from specimens subjected to wetting and drying cycles in sodium chloride solution. After the process of corrosion had just been initiated, the concrete specimens were broken and the total and free chloride contents at the rebar level were measured and assumed as the chloride thresholds for starting corrosion. Results show that average total chloride threshold varies in a range between 1.82 and 2.45 (% cement weight) and between 0.88 and 1.58 (% cement weight) for laboratory and field exposure experiments, respectively. Environmental interaction contributes for these differences. On the other hand, a good correlation could be obtained between both experimental conditions, helping on transporting laboratory results to field conditions.